阅读说明：本技术 金属纤维的网络、生成金属纤维的网络的方法、电极和电池 (Network of metal fibers, method of producing a network of metal fibers, electrode and battery ) 是由 马克西米利安·哈克纳 蒂莫托伊斯·扬克 扎克利娜·布格哈德 亚历山大·米库莱 约阿希姆·P· 于 2019-07-16 设计创作，主要内容包括：本发明涉及一种金属纤维的网络,包括彼此固定的多个金属纤维；其中多个金属纤维中的至少一些具有1.0mm或更大的长度、100μm或更小的宽度和50μm或更小的厚度。本发明还涉及一种方法,该方法包括通过熔融纺丝生成多个金属纤维(2)的步骤1；提供在步骤1中生成的金属纤维(2)的松散网络的步骤2；和通过以下处理c1至c4中的一个处理将多个金属纤维彼此固定的步骤3。(The invention relates to a network of metal fibers comprising a plurality of metal fibers fixed to each other; wherein at least some of the plurality of metal fibers have a length of 1.0mm or more, a width of 100 μm or less, and a thickness of 50 μm or less. The invention also relates to a method comprising a step 1 of generating a plurality of metal fibers (2) by melt spinning; a step 2 of providing a loose network of metal fibers (2) generated in step 1; and a step 3 of fixing the plurality of metal fibers to each other by one of the following processes c1 to c 4.)

1. A network (6) of metal fibers (2) comprising:

a plurality of metal fibers (2) fixed to each other;

wherein at least some of the plurality of metal fibers (2) have a length of 1.0mm or more, a width of 100 μm or less, and a thickness of 50 μm or less.

2. The network (6) according to claim 1,

wherein the metal fibers (2) show an exothermic event when heated in a DSC measurement before and/or after fixing the metal fibers (2) to each other.

3. Network (6) according to claim 1 or 2,

wherein the metal fibers (2) are in electrical contact with each other.

4. Network (6) according to any one of the preceding claims,

wherein at least some of the metal fibers (2) of the plurality of metal fibers (2) are amorphous or wherein at least some of the metal fibers (2) of the plurality of metal fibers (2) are nanocrystalline.

5. Network (6) according to any one of the preceding claims,

wherein at least some of the metal fibers (2) of the plurality of metal fibers (2) are sintered to each other.

6. Network (6) according to any one of the preceding claims,

wherein the metal fibers (2) are capable of being melt spun, preferablySelective horizontal melt spinning, subjecting the molten material of the metal fibers (2) to 10²K·min^-1Or a higher cooling rate.

7. Network (6) according to any one of the preceding claims,

wherein each metal fiber (2) is in contact with one or more other metal fibers (2).

8. Network (6) according to any one of the preceding claims,

wherein the network (6) is an unordered or ordered network (6).

9. Network (6) according to any one of the preceding claims,

wherein the network (6) has open pores between the metal fibers (2) of the plurality of metal fibers (2).

10. Network (6) according to any one of the preceding claims,

wherein at least some of the metal fibers (2) of the plurality of metal fibers (2) are at least partially coated.

11. Network (6) according to any one of the preceding claims,

wherein the contact points (7) between the metal fibers are distributed in a disordered or ordered manner throughout the three-dimensional structure of the network (6).

12. A method of generating a network (6) of metal fibers (2) preferably according to any of the preceding claims,

wherein the method comprises

A step 1 of producing a plurality of metal fibers (2) by melt spinning;

a step 2 of providing a loose network of metal fibers (2) generated in step 1; and

step 3 of fixing the plurality of metal fibers to each other by one of the following processes c1 to c 4:

c 1: placing the plurality of metal fibers in a hot press (10) and subjecting the plurality of metal fibers (2) present in the hot press (10) to a predetermined pressure and temperature for a predetermined period of time to generate a network (6) by sintering the plurality of metal fibers (2) to each other forming contact points (7) between the metal fibers (2), wherein in process c1 the pressure is between 0 and 20GPa, preferably at least 20Mpa, and the temperature is between 10 and 95% of the melting temperature of the material of the metal fibers (2), wherein the melting temperature is determined by DSC measurement;

c 2: placing a loose network of metal fibers (2) between two heated plates and adjusting the distance between the two heated plates to 0.1mm to 1mm and heating the heated plates to a temperature of 10% to 95% of the melting temperature of the material of the metal fibers (2), wherein the melting temperature is determined by DSC measurement;

c 3: ultrasonic welding;

c 4: hammering.

13. The method of claim 12, wherein the first and second light sources are selected from the group consisting of,

wherein the treatment c3 or c4 serves to fix the metal fibers (2) to each other over the entire surface area of the network (6) or at a plurality of separate areas distributed over the surface area of the network (6).

14. The method according to claim 12 or 13, wherein the metal fibers (2) have a length of 1cm to 20cm or more, a width of 100 μ ι η or less and a thickness of 50 μ ι η or less.

15. The method of any one of claims 12 to 14,

wherein the method further comprises a step 4 of coating the metal fibers (2), wherein step 4 is preferably performed after step 3.

16. Network (6) of metal fibers (2), preferably according to any of claims 1 to 10,

wherein the network (6) of metal fibers (2) comprises a plurality of metal fibers (2) fixed to each other;

and wherein the network (6) of metal fibers (2) is obtainable by a process comprising the steps of:

by subjecting 10 the molten material from which the metal fibers are to be produced²K·min^-1A step 1 of generating a plurality of metal fibers (2) having a length of 1.0mm or more, a width of 100 μm or less, and a thickness of 50 μm or less at a cooling rate of 1 or more;

a step 2 of arranging the metal fibers (2) obtained in step (1) into a network of loose metal fibers (2);

step 3 of sintering the metal fibers (2) to each other by one of the following treatments c1 to c 4:

c 1: placing the plurality of metal fibers in a hot press (10) and subjecting the plurality of metal fibers (2) present in the hot press (10) to a predetermined pressure and temperature for a predetermined period of time to generate a network (6) by sintering the plurality of metal fibers (2) to each other forming contact points (7) between the metal fibers (2), wherein in process c1 the pressure is between 0 and 20GPa, preferably at least 20Mpa, and the temperature is between 10 and 95% of the melting temperature of the material of the metal fibers (2), wherein the melting temperature is determined by DSC measurement;

c 2: placing a loose network of metal fibers (2) between two heated plates and adjusting the distance between the two heated plates to 0.2mm to 1mm and heating the heated plates to a temperature of 10% to 95% of the melting temperature of the material of the metal fibers (2), wherein the melting temperature is determined by DSC measurement;

c 3: ultrasonic welding;

c 4: hammering.

17. Network (6) of metal fibers (2) according to claim 16,

wherein in step 2 the metal fibers (2) are arranged using carding, sedimentation or sedimentation from a liquid dispersion or from a gas stream or by spraying.

18. An electrode comprising the network (6) according to any one of claims 1 to 11, 16 and 17, preferably as a collector electrode (14).

19. A cell, half-cell (13a) or a plurality of half-cells separated by a membrane comprising an electrode according to claim 18.

Technical Field

The present invention relates to a network of metal fibers, a method of manufacturing a network of metal fibers, an electrode comprising a network of metal fibers, and a battery comprising such an electrode.

Background

The network of metal fibers may improve the performance of the secondary electrode, as described below. Such a network of metal fibers may also contribute to the performance in catalytic materials, fuel cells, hydrolysis, as a component in electromagnetic shielding materials, as filters, in polymer composites or as tissue materials and tissue hybrid materials, which may also be included as additives, such as cotton, silk or wool.

In lithium ion batteries, the active electrode material is deposited on a metal foil that serves as the current collector. Typically, the negative electrode is made of Li on copper foil_xC_nPositive charge of graphite intercalation compoundThe pole is composed of a Co-, Ni-, Mn-, or Fe compound into which lithium cations can be doped, and an aluminum foil is used as a collector. Upon discharge, electrons are transferred to the copper collector and lithium cations travel from the graphite intercalation compound to the cathode. The mobility of Li cations is promoted by the aprotic electrolyte. Many current research and development efforts are focused on the development of new anode and cathode materials.

Since the above reaction occurs in the active electrode material, electrons must travel through the active electrode material to reach the collector. The low electrical conductivity of the active electrode material imposes a limit on the capacity of the lithium ion battery. Thus, the long distance or path length of electrons from their free position in the active material to the collector is also detrimental to the efficient charge and discharge process.

Therefore, attempts have been made to reduce the resistance of the active electrode material by incorporating conductive materials (such as carbon nanotubes). These additives are loosely dispersed in the active electrode material, and there is a risk that these materials do not sufficiently connect the active electrode material with the current collector. As a result, there is a risk that the capacity of the battery in which the carbon nanotubes are doped in the active electrode material is not sufficiently improved.

To enhance connectivity between such conductive additives, composites of active materials with copper or aluminum foil are pressed together with high mechanical forces. This increases the conductivity of the composite material and its mass density. However, mass density is critical for the diffusion of lithium ions from the anode to the cathode and vice versa. An overly dense composite limits the diffusion of lithium ions and compromises the performance of the battery.

In addition, since a conductive additive and a binder are used in the active electrode material, i.e., a material in which electrochemical reactions occur, is reduced, which is detrimental to the performance of the battery.

It is also known that charge/discharge processes are accompanied by changes in the volume of the active material, which leads to structural degradation and loss of capacity of the battery during use. Similarly, mechanical deformation can compromise the performance of such cells, and thus the manufacture of flexible lithium ion battery components remains a challenge. Improving the flexibility of the electrode without affecting the performance of the electrode would open new applications but would also be advantageous to the manufacturing process itself.

Disclosure of Invention

It is a primary object of the present invention to provide a current collector material suitable for improving battery performance. It is another object of the present invention to provide an electrode material suitable for providing a flexible electrode and a battery, which electrode material utilizes a material suitable for improving the battery capacity, while showing a high resistance to degradation due to flexible deformation, and having improved battery charging kinetics and lifetime.

These objects are met by a network according to each of claims 1 and 16 by a method for producing a network of metal fibers, an electrode and a battery according to the independent claims.

A disadvantage of using a metal foil, such as copper foil, as current collector is described in WO2017/222895 a1 is that such current collector makes the battery rigid and prone to damage due to bending and folding. To provide a flexible battery assembly, WO2017/222895 a1 discloses a porous substrate, onto which a suitable electrode material slurry can then be coated. Suitable electrode material slurries include an active material, such as lithium iron phosphate for producing a lithium ion cathode or lithium titanate for producing a lithium ion anode, and a conductive additive and binder in an organic solvent.

Another electrode for a secondary battery is disclosed in WO 2018/048166 a 1. The electrode is produced by introducing an electrode mixture containing an active electrode material into pores of a current collector having a three-dimensional network structure. As an example of this three-dimensional structure, conductive metal felt is mentioned in WO 2018/048166 a1 as being suitable for use in flexible batteries.

In the invention described herein, a metal current collector material exhibiting an ultra-fine electron conducting network of metal fibers is utilized according to claim 1. The invention also relates to a method of producing a metal fiber web, an electrode and a battery according to the independent claims. Surprisingly, the invention also allows a significant increase in the charge/discharge current without damaging the battery.

Description of the network and preferred embodiments of the metal fibers:

according to a first aspect of the present invention, there is provided a network of metal fibers, wherein a plurality of metal fibers are fixed to each other, and wherein said metal fibers have a length of 1.0mm or more, a width of 100 μm or less and a thickness of 50 μm or less. The fibers may optionally have a circular or elliptical cross-sectional area with a diameter of less than 100 μm, preferably less than 10 μm. In the case of an elliptical cross-section, the diameters mentioned are mean diameters. For example, the elliptical cross-section has the shape of an ellipse.

The network according to the invention is flexible and can be repeatedly deformed without causing degradation of the network, i.e. without separating individual metal fibers from the network of metal fibers due to deformation. The metal fibers are fixed to each other such that the metal fibers are in contact with each other, i.e. the contact points are immovable with respect to the metal fibers, as is the case with non-woven agglomerates of entangled metal fibers, such as metal felts. The metal fiber web according to the invention is therefore mechanically stable but flexible. Mechanically stable in this context means that the metal fiber network is not a loose agglomerate of metal fibers, i.e. the network does not disintegrate into isolated metal fibers when small forces act on the network. Thus, such a network of metal fibers can be flexibly deformed without breaking. The network of metal fibers is able to recover its form after deformation. However, if the network of metal fibers is folded, it is also possible to permanently reshape it.

With metal fibers having a length of 1.0mm or more, a width of 100 μm or less and a thickness of 50 μm or less, it is possible to generate a network with the metal fibers fixed to each other without heating the metal fibers to a temperature close to their melting point. Traditionally, higher temperatures are required to make a network of metal fibers. Such higher temperatures are typically located near or above the melting temperature of the metal and thus may melt or at least soften the material of the metal fibers to such an extent that the metal fibers may form a metal foil rather than the claimed network. Since the network of metal fibers is not a metal foil, i.e. the structure of the metal fibers used for making the network of metal fibers can still be identified in the network of metal fibers. Thus, in a cross-sectional view of the metal fiber web, there are voids not being part of the metal fibers but between the metal fibers of the network fibers.

Preferably the metal fibers show an exothermic event when heated in a DSC measurement before and/or after fixing the metal fibers to each other. An example of such a heat release event is shown in figure 6 d. In other words, the metal fibers are not in their thermodynamic equilibrium at ambient temperature. During heating in DSC measurements, the metal fiber may transition from a metastable state to a thermodynamically more stable condition, e.g. by crystallization, recrystallization or other relaxation processes that reduce defects in the metal atom lattice. When heated, an exothermic event of the metal fiber (fig. 6d), e.g. observed during DSC measurements, indicates that the metal fiber is not in its thermodynamic equilibrium, e.g. the metal fiber may be in an amorphous or nanocrystalline state comprising defect energy and/or crystallization energy, which is released during heating of the metal fiber due to crystallization or recrystallization taking place. For example, DSC measurements can be used to identify these events (fig. 6 d). Surprisingly, it was found that a network of metal fibers showing such exothermic events has improved strength and electrical conductivity after the metal fibers are fixed to each other, e.g. by sintering or welding. In the context of the present disclosure, the terms "sintering" and "welding" may be used interchangeably, i.e. these terms have the same meaning.

It should be understood that the network according to the invention may be obtained by the method described below.

In order to ensure high electrical conductivity throughout the network, it is preferred that the metal fibers are in electrical contact with each other at their fixed positions (i.e. contact points) even if the network is deformed. In order to achieve an electrically conductive but mechanically stable fixation of the metal fibers to each other, it is further preferred that in the network of the invention at least some of the plurality of metal fibers are sintered to each other, i.e. the connections between the metal fibers are formed from the material of the metal fibers. This provides a strong connection between the metal fibers as a result of the bonding between the metal atoms formed by the two contacting metal fibers and thus results in a durable but flexible network with good electrical conductivity. In this respect, it is particularly preferred to sinter the metal fibers onto other metal fibers, most preferably directly onto other metal fibers, without the need for additional binders, such as polymeric binders. Most preferably, the fixation of one metal fiber to another metal fiber is achieved by the material of the metal fibers. It is therefore further preferred that the metal fibers are fixed to each other without polymeric binders, since such polymeric binders generally have poor electrical conductivity and high temperature properties. By sintering the metal fibers directly to each other, it is also possible to omit soldering material or the like in the network according to the invention.

It is also preferred to use ultrasonic welding or hammering to fix the metal fibers to each other. Ultrasonic welding and peening are simple processes that can be used to quickly secure metal fibers to one another. When ultrasonic welding or hammering is used to fix the metal fibers to each other, a metal fiber network can be produced in which the fixing of the metal fibers is not uniform over the entire surface of the network, but is limited to areas that are separated from each other and distributed over the metal fiber network. For this purpose, it is particularly preferred to configure the compacting tool for ultrasonic welding or hammering. For example, a compaction tool for ultrasonic welding or peening may have a plurality of protrusions, such as needle-like tips or rims. With such a plurality of protrusions, a separate region in which the metal fibers are fixed to each other can be generated with one motion. Between these separate areas, the metal fibers may have contact points, but are not fixed to each other. As mentioned above, this may improve the overall flexibility of the network of metal fibers. Therefore, it is preferred that the network comprises areas where the metal fibers have contact points but are not fixed to each other, and that the network comprises areas where the metal fibers have contact points where the metal fibers are fixed to each other.

According to one embodiment, at least some of the plurality of metal fibers are amorphous. According to another embodiment, at least some of the plurality of metal fibers are nanocrystalline. Amorphous and nanocrystalline metal fibers may also be combined in a metal fiber network. Nanocrystalline metal fibers contain crystalline domains. Upon heating to a temperature of about 20-60% of the melting temperature of the nanocrystalline metal fiber, these domains recrystallize, resulting in an increase in the average size of the domains compared to the average size of the original domains in the nanocrystalline metal fiber prior to heating. It is also possible to mix non-equilibrium (e.g. nanocrystalline or amorphous fibres) with equilibrium (e.g. annealed) fibres.

As mentioned above, it is preferred that the metal fibers before and/or after fixing the metal fibers to each other show an exothermic event when heated in a DSC measurement. The extent of the exothermic event observed when heating the metal fibers is not particularly limited. Preferably, the amount of energy released by the exothermic event is 0.1kJ/g or greater, more preferably 0.5kJ/g or greater, even more preferably 1.0kJ/g or greater, and most preferably 1.5kJ/g or greater. The absolute amount depends very much on the metal or metal alloy used. The extent of the exothermic event can be determined by comparing DSC measurements of the metal fibers before and after thermal equilibrium.

Amorphous and nanocrystalline metal fibers may be manufactured by melt spinning using an apparatus and a method for manufacturing metal filaments by melt spinning, for example as described in the examples disclosed in european patent applications with application numbers EP19175749.1, WO2016/020493a1 and WO2017/042155a1, the contents of which are hereby incorporated by reference with respect to the method of forming and thus obtaining metal fibers. Thus, the metal fibers may be, for example, Cu₉₉Si1、Cu₉₆Si₄Aluminum, Al₉₉Si₁、Fe₄₀Ni₄₀B₂₀Au, Ag, Pb, Si or stainless steel V2A.

The metal fibers are preferably produced by melt spinning. Such metal fibers produced by melt spinning may contain spatially confined regions of high energy states due to the rapid cooling applied in the melt spinning process. It is thus possible to sinter such metal fibers together while keeping the temperature well below the melting temperature of the metal fibers when activating the structural transformation of such high-energy domains, by which the domains loose the energy used to activate the sintering process. It is thus possible to sinter such metal fibers together even at temperatures below the crystallization temperature and well below the melting temperature of the material of the metal fibers. This is particularly advantageous if the metal fibers are coated with a coating that is sensitive to high temperatures. Since higher temperatures will cause the crystallization of the fibers to destroy the amorphous or nanocrystalline state of such fibers, there is a risk that these fibers lose their special mechanical properties of high elasticity and low brittleness. The domains in the high energy state may release energy when heated or mechanically compressed by a press, hammer or ultrasonic welding device. The release of energy from these regions can be observed in the form of an exothermic event.

The metal fibers are made of metal or at least comprise metal. In the present invention, it is not particularly limited which metal is contained in the metal fiber or which metal the metal fiber is made of. Preferably, however, the metal fibers of the plurality of metal fibers in the network comprise one of the elements selected from the group consisting of copper, silver, gold, nickel, palladium, platinum, cobalt, iron, chromium, vanadium, titanium, aluminum, silicon, lithium, combinations thereof and alloys comprising one or more of the foregoing. It is further preferred that the metal fibers of the plurality of metal fibers in the network comprise one of the elements selected from the group consisting of copper, silver, gold, nickel, palladium, platinum, iron, vanadium, aluminum, silicon, lithium, combinations thereof and alloys comprising one or more of the foregoing.

It is particularly preferred that the metal fibers are made of copper or aluminum or stainless steel alloys. Different types of metal fibers may be combined with each other such that the network may comprise metal fibers made of, for example, copper, one or more stainless steel alloys, and/or aluminum. Networks of metal fibers, wherein the metal fibers are copper, aluminum, cobalt, copper-containing alloys, aluminum, silicon and/or cobalt are particularly preferred. An example of an alloy of aluminum and cobalt is Al₉₉Si₁And Co₆₆Fe₄Mo₂B₁₂Si₁₆. An example of a copper alloy is CuSi₁、CuSi₄Or CuSi1₂。

Preferably the metal fibers have a length of 2.0mm or more, more preferably 10mm or more, even more preferably 20mm or more, even more preferably 70mm or more. With a length of the metal fibers that meets the above-mentioned length specification, the mechanical stability of the network of metal fibers is improved, because each metal fiber may have, due to the increased length of the metal fiber, a plurality of contact points with other metal fibers of the network, at which contact points the metal fiber is fixed to the respective other metal fibers, so as to form a mechanically strong and electrically conductive connection between these metal fibers. Thus, when one connection between the metal fibers is broken, this does not compromise the overall structural integrity of the network, nor does it separate the metal fibers from the network, as several other connections between the fibers are available to hold the network together and provide the desired electrical conductivity. Preferably, the fiber length should be in the range of 1 to 20cm, more preferably in the range of 3 to 15cm, even more preferably in the range of 4 to 8cm, since it is easy to arrange the fibers by carding.

It is also preferable if the width of the metal fibers is 80 μm or less, more preferably 70 μm or less, even more preferably 40 μm or less, and most preferably 5 μm or less. Further, it is preferable that the thickness of the metal fiber is 50 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, and most preferably 5 μm or less. Instead of a rectangular cross section of the fibers, it is also possible to have a circular or elliptical cross section of the dimensions as described above. With metal fibers that show an exothermic event when heated or mechanically pressed, a network can be created with the metal fibers fixed to each other without the need to heat the metal fibers to a temperature close to the melting point, i.e. a temperature sensitive coating can be preserved on top of the metal fibers when the fibers are fixed to each other, e.g. by sintering. Furthermore, since high temperatures for fixing the fibers to each other can be avoided, the risk of metal fibers being transformed into metal foil during the production of the network can be reduced.

There is no particular lower limit on the width and thickness of the metal fibers. However, the metal fibers may have a width of not less than 1 μm, preferably not less than 3 μm, and a thickness of not less than 1 μm.

In the metal fiber network according to the invention it is also preferred that in the network a majority of the metal fibers are in contact with one or more other metal fibers. This ensures that high electrical conductivity is provided throughout the network. It is further preferred that the network is an unordered network. Such disordered networks have good electrical conductivity in each direction. Furthermore, it is easier to create a network of disordered metal fibers than an ordered network of fibers. It is further preferred that the fibers in the network are carded in different directions to provide directionality of the individual fibers, but still allow conductivity through the network to be equal in all possible directions. It is therefore preferred that some or all of the fibres in the network have an orientation, i.e. that the lengths of the fibres are not randomly oriented but have a predominant orientation in one or more spatial directions.

It is particularly preferred if the network of metal fibers according to the invention are fixed to each other at contact points randomly distributed throughout the metal fiber web. According to another inventive aspect, it is preferred that the contact points are not randomly distributed, but for example distributed in the peripheral area of the network of metal fibers, or that the metal fibers are ordered such that the contact points are also ordered. It is further preferred that the contact points where the metal fibers are fixed to each other are positioned in specific areas and are not uniformly arranged on the complete network of metal fibers. With the presence of contact points where the metal fibers are fixed to each other only in separate regions, the fibers between these regions can have a high flexibility while ensuring mechanical stability and good electrical conductivity.

It is further preferred if in the metal fiber network according to the invention the metal fibers are fixed to each other at contact points, wherein the metal fibers are in contact with each other. Preferably, each metal fiber has at least two contact points with the other metal fibers, more preferably at least three contact points, even more preferably at least four contact points.

It is particularly preferred if in the metal fiber network according to the invention the metal fibers are fixed to each other at contact points, wherein the contact points are distributed throughout the network such that there are contact points throughout the three-dimensional structure of the network of metal fibers. Thus, the contact points are not only arranged in a specific area of the network of metal fibers, for example in the center or in the circumference of the mesh. The contact points may be evenly distributed throughout the network. It is also possible that the density of contact points throughout the network has a gradient, i.e. areas of the network having a higher density of contact points and areas having a lower density of contact points. There may also be an ordered or random spatial distribution of contact points.

The network according to the invention preferably has open pores between the metal fibers. The porosity of the network is preferably up to 95 vol%. It is also preferred that the porosity of the network is greater than 80 vol%. When the porosity is in the range of 80 vol% to 95 vol%, it is even more preferable. Active materials can be incorporated into the open pores, such as active electrode materials or active catalyst materials. It is further preferred that in the network according to the invention at least some of the plurality of metal fibers are at least partially coated. The coating may be, for example, an active material, such as an electrode active material that interacts with lithium ions in the battery or converts CO to CO₂Or catalytically active materials that are active in hydrolysis. It is also possible to apply a coating on the metal fibers, which improves the fixation of the metal fibers to each other, thereby increasing the mechanical strength of the network.

By way of example, such active electrode materials for batteries are: for the anode: graphite, silicon carbide (SiC) and tin oxide (SnO), tin oxide (SnO)₂) And lithium titanium oxide (Li)₄Ti₅O₁₂) (ii) a For the cathode: lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LiCoO)₂) And lithium iron phosphate (LFP).

It is particularly preferable if the coating layer contains an active material for an electrode of a secondary battery. Such a metal fiber mesh is provided with a coating layer containing an active material for a secondary battery electrode, and can be used to provide a flexible secondary battery having an increased capacity. Furthermore, the use of a metal foil as a current collector can be omitted, which not only improves the flexibility of the battery, but also reduces the weight of the battery.

In a further preferred embodiment of the invention, the network of metal fibers has metal fibers coated with a coating comprising at least one catalytically active material. Such a network may be used as a catalyst. In particular, if the network has open pores and the metal fibers are coated with a coating comprising at least one transition metal, a gaseous or liquid fluid can flow through the network, so that compounds contained in the fluid can come into contact with the coating provided on the metal fibers, so that a catalytic reaction can take place. Suitable metal alloys may also be used as the catalytic material itself, such as nickel fibers.

The catalytically active material may be any material capable of catalyzing a chemical reaction. It is particularly preferred that the catalyst material comprises one or more transition metals.

It is further preferred if in the network according to the invention a plurality of metal fibers form a network of interconnected pores.

It is further preferred if the coating provided on the plurality of metal fibers is in electrical contact with the plurality of metal fibers. This is particularly advantageous if the network is used as an electrode material for a fuel cell in hydrolysis or batteries. A network comprising metal fibers coated with a coating capable of transporting electrons to or from a reaction site, the coating comprising an element suitable for catalyzing an electrochemical reaction occurring at an electrode of a fuel cell or battery. Thus, such a network can be used to improve the performance of a fuel cell or battery.

The thickness of the network of the present invention is not particularly limited. However, it is preferred that the network has a thickness of 0.01mm or greater. More preferably the thickness of the network is 0.03mm or more, even more preferably 0.05mm or more, even more preferably 0.07mm or more, most preferably 0.1mm or more. If the thickness of the network is less than 0.01mm, there is a risk that the mechanical stability of the network is insufficient. The upper limit of the network thickness is not particularly limited. However, depending on the application, the upper limit may be 3.0mm or less, or 2.5mm or less. For battery applications, the most preferred thickness of the network is in the range from 0.1mm to 0.5 mm. A network having a thickness in this range is advantageous for stacking and rolling of the active material coated network for producing a battery. This also facilitates Li ion diffusion in a reasonable time.

The invention also relates to a network of metal fibers comprising a plurality of metal fibers fixed to each other; wherein the network of metal fibers is obtainable by a process comprising the steps of: in the first step, the first step is that,by subjecting 10 the molten material from which the metal fibers are to be produced²A cooling rate of K x min-1 or more to generate a plurality of metal fibers having a length of 1.0mm or more, a width of 100 μm or less, and a thickness of 50 μm or less; a step 2 of arranging the metal fibers obtained in the step into a loose network of metal fibers; step 3 of sintering the metal fibers to each other by one of the following processes c1 to c 4: c 1: placing a plurality of metal fibers in a hot press and subjecting the plurality of metal fibers present in the hot press to a predetermined pressure and temperature for a predetermined period of time to form contact points by sintering the plurality of metal fibers to each other, at which contact points the metal fibers are fixed to each other between the metal fibers, wherein in process c1 the pressure is between 0-20GPa, preferably at least 20MPa, and the temperature is between 10-95% of the melting temperature of the material of the metal fibers, wherein the melting temperature is determined by DSC measurement; c 2: placing a loose network of metal fibers between two heated plates, adjusting the distance between the two heated plates to 0.1mm to 1mm, and heating the heated plates to a temperature of 10% to 95% of the melting temperature of the material of the metal fibers, wherein the melting temperature is determined by DSC measurement; c 3: ultrasonic welding; c 4: hammering.

In step 1, metal fibers are produced from the melt with a controlled length of 1mm or greater. In the case of entangled fibres or fibres of insufficiently uniform length, they are further processed by developing techniques for recovering carbon fibres (Henrik Dommes, "Vom Faseralbure zum Hochwertigen Leichtbbau Halbzeug", Light weight Design 2010, 3, 23-27; doi: 10.1007/BF 03223621). They can therefore be cut to the desired length, separated and partially oriented by means of a mechanical cutter or by means of a laser.

In step 2, the metal fibers produced in step 1 are formed into a liquid dispersion by precipitation or are randomly arranged by an air flow ((fig. 27, step 2, b 2)). An ordered array of metal fibers was formed by carding (fig. 27, step 2, b 1). In this way, a felt-like structure is produced, as is standard in the textile processing of nonwovens, for example by carding.

Thus, as a further aspect, the invention relates to a method for producing a network of metal fibers having welded or sintered contacts between the fibers. The invention comprises steps 1 and 2 of providing a plurality of metal fibers and webs and step 3 for interconnection of the filaments to form a consolidated porous non-woven felt-like structure.

In step 3 (fig. 27, step 3), the loose mat of disordered wires (also called loose network of metal fibers) obtained by steps 1 and 2 is subjected to one of the treatments c1 to c 4. For example, it is placed in a hot press (fig. 27, step 3, c1, c2) and subjected to a predetermined pressure and temperature for a predetermined period of time to generate a network by welding the metal fibers at their points of contact to form a network of crosslinked metal fibers. The plurality of metal fibers present in the hot press are subjected to a predetermined pressure and temperature for a predetermined period of time to generate a network by sintering the plurality of metal fibers to each other forming contact points between said metal fibers, wherein the pressure is between 0 and 2GPa, preferably at least 20MPa, and the temperature is between 10% and 95% of the melting temperature of the material of the metal fibers, wherein the melting temperature is determined by DSC measurement, e.g. by monitoring the recrystallization temperature. Based on DSC measurements, the person skilled in the art is able to determine the appropriate temperature at which the metal fibers are sintered to each other in step 3. The person skilled in the art understands that the features relating to steps 1 to 3 may be combined with the features relating to steps 1 to 3 described below and in the claims as well as with all the features described above, the features relating to the metal fiber network described below and in the claims.

In process c2 of step 3, when adjusting the distance between the heating plates, it is preferred to compact the loose network of metal fibers to create contact points between the metal fibers.

In a further embodiment of step 3, if the compaction tool is equipped with a structured contact surface, e.g. protrusions such as needle-like tips as opposed to a flat surface or edge pattern, the network structure can be customized in different length scales (fig. 27, step 3, c3, c 4; protrusions not shown in fig. 27). In this case the distance between the fibre chains is controlled by the density of the fibres in the region where the tool or its protrusions compress the mat, but where the compression tool is not applied to the network at the contact points of the metal fibres or where the compaction tool has no protrusions, no weld will be formed at the contact points of the metal fibres. With this tool structure, the average porosity and flexibility of the network of metal fibers can be improved.

Preferably, the fiber length should be in the range of 1cm to 20cm, more preferably in the range of 3cm to 15cm, even more preferably in the range of 4cm to 8 cm. For fibers having a length as described above, the fibers can be easily arranged by carding.

In a modified procedure, if the wire is welded by hammer impact rather than continuously compressing the wire, the temperature at which the wire is welded to the consolidated mat (i.e., the network according to the present invention) can be reduced, where the shock wave can reach a significantly higher peak pressure in conjunction with localized heating (fig. 27, step 3, c 4). This hammering impact can be applied in the form of ultrasound, i.e. ultrasonic welding, with oscillation in the direction perpendicular to the mat (fig. 27, step 3, c 3). In the case of welding by hammer impact or by ultrasound, as mentioned above, the compaction tool is preferably equipped with a structured surface having a plurality of protrusions, such as needle-like points or edges. As mentioned above, such structured compaction tools may be used to create a network according to the present invention in which the contact points at which the metal fibers are fixed to each other are only in a plurality of discrete regions, such that between such discrete regions the metal fibers may have contact points that are not, however, fixed to each other. The regions where the metal fibers are not fixed to each other may improve the porosity and may also increase the flexibility of the metal fiber network.

It is further preferred that each region where the metal fibers are fixed to each other and/or each region where the metal fibers are not fixed to each other has at least 1mm²More preferably at least 2mm²And even more preferably at least 5mm²The size of (c). It is further preferred, in particular, for each region in which the metal fibers are fixed to one another and/or each region in which the metal fibers are not fixed to one another to have a thickness of at least 1mm²Wherein the region where the metal fibers are fixed to each other is formed in an island shapeA structure, the island-like structure being surrounded by a sea-like region in which the metal fibers are not fixed to each other. Alternatively, it is also preferred, in particular when each region where the metal fibers are not fixed to each other and/or each region where the metal fibers are fixed to each other has at least 1mm²In the case of (3), the region where the metal fibers are not fixed to each other forms an island-like structure surrounded by a sea-like region where the metal fibers are fixed to each other.

Common to all treatments c1 to c4 is that the fibers as a whole remain significantly below the melting temperature and are sintered only at the points of contact between them. This ensures that the fibre structure does not collapse. In all cases, the fact that the rapidly cooled fibres obtained by, for example, melt spinning are not in their thermal equilibrium and contain amorphous and/or nanocrystalline domains, where atoms can rearrange more easily than the equilibrium crystalline domains, improves and mitigates welding of the contact between the different filaments.

In the method according to the invention, the pressure applied in process c1 allows to maintain a temperature significantly below the melting temperature of the metal fiber material, while at the same time creating a strong bond between the metal fibers to create a stable metal fiber network. In all treatments c1 to c4 of the method according to the invention, the diffusion of atoms by thermal energy remains low, while the diffusion of atoms by mechanical pressure increases. This mechanism allows it to produce a stable network of metal fibers that are permanently sintered together at low cost and without the need for careful control of the applied temperature. If the temperature is above 95% of the melting temperature of the metal fiber material, there is a risk that the metal fibers are transformed into a metal foil. On the other hand, if the temperature is below 10% of the melting temperature of the metal fiber material, the mobility of the atoms is so low that in this process the metal fibers are not sintered together sufficiently to provide a stable network of metal fibers or take too much time.

In the context of the description of the present invention, "a%" of the melting point "refers to the melting point of ° c. Thus, if the melting point is 1000 ℃, then in the context of the description of the present invention 20% of the melting point is 200 ℃, 50% of the melting point is 500 ℃ and 95% of the melting point is 950 ℃.

It is understood that all aspects of the metal fiber network described above, in particular in connection with metal fibers, constitute preferred embodiments which also allow for the method according to the invention.

In the method according to the invention it is preferred if the metal fibers provided have a length in the range of 1cm to 20cm, more preferably in the range of 3cm to 15cm, even more preferably in the range of 4cm to 8cm, have a width of 100 μm or less, have a thickness of 50 μm or less, or have a circular or elliptical cross-section. With regard to the length, width and thickness of the metal fibers, it is to be understood that the same dimensions indicated above for describing the network are also preferred in the method according to the invention. It was observed that such fibers can be used to create a stable network of metal fibers without the need to heat the metal fibers to their melting temperature.

In the method according to the invention, the temperature applied depends on the material of the metal fibers. In order to avoid crystallization of the amorphous metal fibers during the soldering process, it is preferred to keep the applied temperature below the crystallization temperature of these fibers. For the metal fibers to be measured, the crystallization temperature can be determined by Differential Scanning Calorimetry (DSC). DSC measurements were performed using the following conditions: the initial temperature is 30 ℃, and the heating rate is 10K min^-1Cooling at a rate of 10K min to 1200 deg.C^-1Up to room temperature. At a constant argon flow of 100 ml min^-1In a zirconium-oxygen-trap system in an argon atmosphere and in a completely oxygen-free atmosphere (STA 449F3 Jupiter, Netzsch Bj.2017).

In the method according to the present invention, the time for which the metal fiber is subjected to the predetermined temperature and pressure is not particularly limited, and depends on the material of the metal fiber, the applied pressure and temperature. However, in order to ensure sufficient sintering together of the metal fibers, it is preferable that the predetermined time in the treatments c1 and c2 is 10 seconds or longer, more preferably 1 minute or longer, even more preferably 2 minutes or longer, even more preferably 3 minutes or longer, and most preferably 5 minutes or longer. The upper limit of the temperature and pressure to which the metal fibers in step b) are subjected is not particularly limited. However, from an economic point of view, it is preferred if the time is 60 minutes or less, even more preferably 45 minutes or less, most preferably 30 minutes or less.

In order to ensure a stable connection between the metal fibers throughout the network, it is preferred if the pressure and heat in process c1 are applied for at least one minute.

Preferably the pressure applied in processes c1 and c2 is 20MPa or higher, more preferably 30MPa or higher, even more preferably 100MPa or higher, most preferably 120MPa or higher. Depending on the metal alloy and the melt spinning process, the applied pressure can also be reduced. The upper limit of the pressure is not particularly limited. However, in order to avoid converting the metal fibers into metal foil, the pressure is preferably 1000MPa or less, more preferably 750MPa or less, even more preferably 500MPa or less, and most preferably 300MPa or less.

In order to produce a network comprising coated metal fibers, it is in principle possible to provide the coated metal fibers after step 1 or 2 or to carry out step 4 of coating the metal fibers, wherein step 4 is preferably carried out after step 3. Performing step 4 after sintering in step 3 allows the creation of a basic network for many applications. In a subsequent step 4, the network may then be modified for the intended application by providing a suitable coating on the metal fibers. Furthermore, performing step 4 after step 3 allows to provide a coating on the metal fibers which will be easy to apply during sintering and/or welding in step 3. This is the case, for example, if the coating has a low melting point such that subjecting the coating to the conditions in step 3 melts the coating.

In the process according to the invention it is further preferred if the metal fibers are produced by melt spinning. Such metal fibers produced by melt spinning may contain spatially restricted domains of high energy states due to the rapid cooling applied during melt spinning. In this connection, rapid cooling means a cooling rate of 102 K.min^-1Or higher, preferably 104 K.min^-1Or higher, more preferably a cooling rate of 105 K.min^-1Or higher. Therefore, the temperature in the step 3 can be kept much lower than the melting temperature of the metal fibersWhile sintering the metal fibers together. Such metal fibers may even be sintered together at a temperature below the crystallization temperature of the metal fiber material. This is particularly advantageous if the metal fibers are coated with a coating that is sensitive to high temperatures. In view of the above, it is preferable that the metal fibers of the metal fiber net according to the present invention may be subjected to 102K · min with a molten material of the metal fibers by melt spinning^-1Or a higher cooling rate.

It is preferred if in the process according to the invention the temperature applied in step 3 is 80% or less, more preferably 70% or less, even more preferably 60% or less, most preferably 50% or less of the melting temperature of the metal fiber material. It is even possible that the temperature applied in step 3 is 25% or less of the melting temperature of the metal fiber material. By keeping the temperature in step 3 below these limits, the risk of converting metal fibers into metal foil is reduced. The temperature is preferably 10% or more, more preferably 20% or more, even more preferably 25% or more, most preferably 30% or more of the melting temperature of the metal fiber material. If the temperature in step 3 is below these limits, the risk of not sintering the metal fibers together sufficiently to provide a stable network of metal fibers is increased due to the reduced mobility of the atoms of the metal fibers. However, the lower limit depends on the metal or metal alloy and may therefore even be below 20% of the melting temperature.

In the method of the present invention, amorphous metal fibers may be used. If amorphous metal fibers are used, the temperature in step b) is preferably kept below the crystallization temperature. The crystallization temperature can be determined by Differential Scanning Calorimetry (DSC). It is further preferred that if amorphous metal fibers are used, the temperature is preferably 50% or less of the crystallization temperature of the metal fiber material, more preferably 35% or less of the crystallization temperature of the metal fiber material, even more preferably 30% or less of the crystallization temperature of the metal fiber material, most preferably 20% or less of the crystallization temperature of the metal fiber material. However, it is possible that if amorphous metal fibers are used, the temperature is preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, most preferably 80% or less of the crystallization temperature of the metal fiber material.

In the context of the description of the present invention, "a%" of crystallization temperature refers to the crystallization temperature in degrees celsius as determined by Differential Scanning Calorimetry (DSC) measurements. Thus, if the crystallization temperature is 1000 ℃, in the description of the present invention, 20% of the crystallization temperature is 200 ℃, 50% of the crystallization temperature is 500 ℃, and 95% of the crystallization temperature is 950 ℃.

It is further preferred that in the method of generating a metal fiber network, a step of filling the interstices between the metal fibers in the network at least partially with an active material, in particular with an active electrode material or a catalyst material, is performed. The step of filling the voids between the metal fibers is schematically shown in fig. 27.

After the network of metal fibers has been produced by the process of the invention, it is particularly preferred to cut the metal fiber web into a shape suitable for the desired application. The cutting may be performed before or after the coating step, and also if the coating step is not intended at all. If the cutting is performed after the metal fiber web is formed, the cutting facilitates the production of the metal fiber web in a desired shape.

Description and preferred embodiments of an electrode comprising a network of metal fibers:

another aspect of the invention relates to an electrode comprising a network as described above, preferably manufactured according to or obtained by the above-described method. It is particularly preferred that the network of metal fibers forming part of the electrode has been separated from the network as described above, for example by cutting.

It is particularly preferred if the electrode comprises a network as collector electrode.

In the electrode according to the invention, it is further preferred if the interstices between the metal fibers in the network are at least partially filled with an active material, in particular an active electrode material or a catalyst material.

Description and preferred embodiments of a battery comprising an electrode comprising a network of metal fibers:

another aspect of the invention relates to a battery comprising an electrode, such as described above. At least one electrode in the cell is a cathode (positive electrode) and/or at least one electrode is an anode (negative electrode). The terms anode and cathode refer to the electrodes when the battery is discharged.

The porous structure of the network of metal fibers provides a relatively large volume that can be occupied by the active electrode material and is not present in, for example, common metal foils. Therefore, the amount of the electrode active material can be significantly increased without impairing the capacity due to the increase in resistance caused by the high amount of the active electrode material. Furthermore, by using a network of metal fibers as described above, the active material is distributed throughout the current collector. Therefore, the electrons must overcome only the short distance between the active material and the collector. Since the conductivity and connectivity of the active material and the electrode are generally high, it is not necessary to press the electrode material as much as in the case of a metal foil used as an electrode, and thus diffusion of lithium ions is enhanced. As a result, the charge time of the battery can be significantly reduced, and the use of additives such as carbon black and a binder can also be reduced, so that more active materials can be incorporated into the electrode of the battery, further improving the performance of the battery. The flexibility and stability of the network of metal fibers allows the manufacture of durable electrodes and thus allows the battery to have an increased lifetime. Furthermore, batteries using the electrode according to the present invention have improved battery charging kinetics due to the three-dimensional nature of the metal network penetrating the active electrode material. This results in a short migration distance of electrons and charge carriers from their origin within the active material to the metal collector, from where they are distributed in the circuit.

It is preferred if the battery according to the invention is a secondary battery, more preferably a lithium ion battery. The network being a network of copper metal fibres or copper alloy fibres, e.g. Cu₉₉Si₁、Cu₉₈Si₂、Cu₉₆Si₄、Cu₈₈Si₁₂Or Cu₉₂Sn₈Or a network of aluminium metal or aluminium alloy fibres, e.g. Al₉₉Si₁And is also preferable. Copper alloys and aluminum alloys have better manufacturing conditions for melt-spun fibers than pure metals, while they exhibit nearly equal conductivity.

It is also preferable to provide a network of metal fibers, wherein the metal fibers are made of aluminum for a cathode of a secondary battery or made of copper for an anode of a secondary battery. This network can be infiltrated with a lithium active material and used in an electrode. Also in this case, the distance between the current collector and the active material can be reduced, which is advantageous for the performance of the battery.

It is therefore particularly preferred if the battery according to the invention comprises an electrode comprising a network of metal fibers of copper or a copper alloy. It is also particularly preferred if the battery according to the invention comprises an electrode comprising a network of metal fibers of aluminum or an aluminum alloy. It is also particularly preferred if the battery according to the invention comprises a first electrode comprising a network of metal fibers of copper or copper alloy and a second electrode comprising a network of metal fibers of aluminum or aluminum alloy. It is also possible to use two or more electrodes of the same or different metal fiber material.

In the present disclosure, emphasis is placed on the network of metal fibers and their use as electrode materials. However, it is also preferred to use the metal fiber networks as described herein in catalytic materials, in fuel cells, in hydrolysis, as a component in electromagnetic shielding materials, as a filter, in polymer composites or as tissue materials and tissue hybrid materials which may also include as additives (e.g. cotton, silk or wool).

Drawings

The invention will now be described in further detail by way of example only with reference to the accompanying drawings and figures and by way of various examples of the network and method of the invention. Shown in the figure are:

FIG. 1a) is a schematic illustration of a vertical melt spinning apparatus.

FIG. 1b) is a schematic illustration of a horizontal melt spinning apparatus.

FIG. 1c) is from Al₉₉Si₁Photographic images taken of the images of the alloy fused deposited onto the rotating wheel.

Figure 2a) is a photographic image of copper metal fibers.

Fig. 2b) is a photographic image of cobalt metal fibers.

FIG. 2c) is Al₉₉Si₁Photographic image of metal fibers of the alloy.

FIG. 2d) is Co₆₆Fe₄Mo₂B₁₂Si₁₆Photographic image of metal fibers of the alloy.

FIG. 3a) i) Co manufactured at a wheel speed of 50m/s₆₆Fe₄Mo₂B₁₂Si₁₆Photographic image of the alloy metal fibers, ii) showing Co₆₆Fe₄Mo₂B₁₂Si₁₆Average thickness of alloy metal fibers, iii) Co₆₆Fe₄Mo₂B₁₂Si₁₆Average width of the alloy metal fibers.

FIG. 3b) i) Co manufactured at a wheel speed of 25m/s₆₆Fe₄Mo₂B₁₂Si₁₆Photographic image of the alloy metal fibers, ii) showing Co₆₆Fe₄Mo₂B₁₂Si₁₆Average thickness of alloy metal fibers, iii) Co₆₆Fe₄Mo₂B₁₂Si₁₆Average width of the alloy metal fibers.

Fig. 4a) is an X-ray diffraction pattern of copper metal fibers.

FIG. 4b) is Al₉₉Si₁X-ray diffraction pattern of the alloy metal fiber.

FIG. 4c) is Co₆₆Fe₄Mo₂B₁₂Si₁₆X-ray diffraction pattern of the alloy metal fiber.

Fig. 5a) is a Scanning Electron Micrograph (SEM) of copper metal fibers.

Fig. 5b) is an enlarged view of fig. 5 a).

FIG. 5c) is Al₉₉Si₁Scanning electron micrographs of the alloy metal fibers.

Fig. 5d) is an enlarged view of fig. 5 c).

FIG. 5e) is Al₉₉Si₁Further scanning electron micrographs of the alloy metal fibers.

FIG. 5f) is a scanning electron micrograph of gold metal fibers

FIG. 5g) is Cu₉₂Sn₈Scanning electron micrographs of the alloy metal fibers.

FIG. 5h) is Cu₉₆Si₄Scanning electron micrographs of the alloy metal fibers.

FIG. 6a) 527 Al pieces produced at a wheel speed of 25m/s₉₉Si₁Thickness and width of the alloy metal fibers.

FIG. 6b) 527 Al produced at a wheel speed of 25m/s₉₉Si₁Distribution of the thickness of the alloy metal fibers.

FIG. 6c) 527 Al produced at a wheel speed of 25m/s₉₉Si₁Distribution of the width of the alloy metal fibers.

FIG. 6d) CuSn after melt spinning (Curve I) and after thermal equilibration of the same microfibers (Curve II)₈DSC measurements of microfibers, which demonstrate exothermic treatment with heated melt spun fibers compared to equilibrium metal fibers.

FIG. 7 shows sintered Co₆₆Fe₄Mo₂B₁₂Si₁₆SEM image of a network according to the invention (network of example 2) of alloyed metal fibers.

FIG. 8 is sintered Co prior to deformation₆₆Fe₄Mo₂B₁₂Si₁₆Photographic image of a network according to the invention of alloyed metal fibers.

Fig. 9 is a photographic image of the network of fig. 8 in a deformed state.

Fig. 10 is a photographic image of a network according to the invention (network of example 9) of copper metal fibers sintered at a temperature of 300 ℃ and a pressure of 177MPa for 5 minutes.

Fig. 11 is a photographic image of a network according to the invention (network of example 10) of copper metal fibers sintered at a temperature of 300 ℃ and a pressure of 177MPa for 3 minutes.

Fig. 12 is a SEM image of the network shown in fig. 11.

Fig. 13 magnified SEM images of the networks shown in fig. 11 and 12.

FIG. 14a) Cu sintered for 3 minutes at a temperature of 300 ℃ and a pressure of 78MPa₉₂Sn₈Photographic image of a network according to the invention of alloyed metal fibers (network of example 11).

Fig. 14b) SEM image of the network of fig. 14 a.

Fig. 14c) an enlarged SEM image of the network shown in fig. 14 b.

Fig. 15 is a schematic illustration of a hot press.

Fig. 16a) is a schematic view of a battery according to the invention.

Fig. 16b) is a schematic view of a reference cell according to the prior art.

Fig. 17 is a comparison of the capacity of a battery according to the present invention and a reference battery according to the prior art.

Fig. 18 is a charge-discharge graph of a reference battery obtained by chronopotentiometry (chronopotentiometry).

Fig. 19 is a graph of the charge-discharge distribution of the inventive network battery obtained by chronopotentiometry.

Fig. 20a) a graph of the second and last charge-discharge profiles of the reference cell obtained by chronopotentiometry as shown in fig. 18.

Fig. 20b) a graph of the second and last charge-discharge profiles of the network battery of the invention obtained by chronopotentiometry as shown in fig. 19.

Fig. 21a) is a graph of the charge-discharge profile of a network battery of the invention and a reference battery with current normalized time obtained by chronopotentiometry.

Fig. 21b) is an enlarged view of the graph of fig. 21a showing the first cycle.

Fig. 21c) is an enlarged view of the graph of fig. 21a showing the area around the last cycle of the reference cell.

Fig. 22 is a graph of the capacity of the network cell and reference electrode of the present invention over the number of cycles.

Fig. 23a) is an SEM image of an electrode of the present invention showing graphite flakes within the fiber network.

Fig. 23b) is an EDX map of copper for the electrode of the invention shown in fig. 23 a.

Fig. 23c) is an EDX map of the carbon of the electrode of the invention shown in fig. 23 a.

FIG. 24 is a version of an exemplary carding machine for the formation of metal wool.

Fig. 25 is a photographic image of a manufacturing process according to the present invention, in which metal fibers are formed into fluff and combined with cotton fluff.

Fig. 26 is a copper-based fluff mechanically stabilized by ultrasonic treatment.

Fig. 27 is a schematic representation of a process according to the present invention.

Detailed Description

For clarity reasons, reference numerals are not shown in some or all of the figures.

Fig. 1a) shows a schematic view of a melt spinning apparatus 1 that can be used to generate metal fibers 2 suitable for forming a network according to the invention. The melt spinning apparatus 1 has a vertically rotating wheel 3 rotatable about an axis Z. Above the rotating wheel 3, a micro-structured nozzle 4 is arranged, by means of which micro-structured nozzle 4 molten droplets 5 of the material producing the metal fibers 2 can be deposited onto the rotating wheel 3. Alternatively, a horizontal melt spinning machine may be used (fig. 1 b; a horizontal melt spinning machine is disclosed in the european patent application with application number EP19175749.1, the content of which is incorporated herein by reference.

Fig. 1b) shows a schematic view of a horizontal melt spinning device 1 that can also be used for forming metal fibers 2. In contrast to the melt-spinning apparatus 1 shown in fig. 1a), the melt-spinning apparatus 1 shown in fig. 1b) has a horizontally rotating wheel 3. Similar to the melt-spinning apparatus 1 shown in fig. 1a), in the melt-spinning of fig. 1b) a wheel 3 is rotatable about an axis Z, above which wheel 3a microstructure nozzle 4 is arranged, by means of which microstructure nozzle 4 droplets 5 of the material melt produced by the metal fibers 2 can be deposited onto the wheel 3.

FIG. 1c) shows Al₉₉Si₁Photographic image of the generation of the alloy metal fibers. The photographic image showsAl₉₉Si₁The alloy melt is deposited onto the rotating wheel 3 and separated from the image taken at 40000fps of the deposition of the metal melt onto the rotating wheel 3 of the melt spinning device 1. The rotating wheel 3 is located at the bottom and the microstructured nozzle 4 is located at the top of the photographic image shown in fig. 1C. The temperature of the melt is set in the range of 50 to 300 c above the melt temperature (higher processing temperatures are possible). The melt forms a stream of metal which wets the rotating wheel 3 and is rapidly cooled to form metal fibers 2 from the metal stream 5.

In fig. 2a) to d), photographic images of copper metal fibers (fig. 2a)), cobalt metal fibers (fig. 2b), Al are shown after the metal fibers 2 are produced and collected using the melt spinning apparatus 1 as shown in fig. 1a) and b)₉₉Si₁Photographic image of alloyed Metal fibers (FIG. 2c) and Co₆₆Fe₄Mo₂B₁₂Si₁₆Photographic image of the alloy metal fibers. The metal fibers 2 form an entangled network of metal fibers 2, wherein the metal fibers 2 are not fixed to each other, so that the individual metal fibers 2 can be easily separated from the entangled network of metal fibers 2.

Co₆₆Fe₄Mo₂B₁₂Si₁₆Further photographic images of the alloy metal fibers are shown in fig. 3a) and b). Co generated from wheel speeds of 50m/s and 25m/s respectively₆₆Fe₄Mo₂B₁₂Si₁₆Photographic images were taken of the alloy metal fibers 2. From the corresponding thickness and width distributions as also shown in fig. 3a) and b), it can be seen that a higher wheel speed of 50m/s results in a metal fiber 2 with a reduced thickness and width (see fig. 3a)) compared to a metal fiber 2 produced with a wheel speed of 25m/s (see fig. 3 b).

Bruker D8 forward XRD using Brugg-Bretano mode of a cobalt source with 30mA and 40kV anode current and acceleration voltage recorded the x-ray diffraction spectra shown in fig. 4a to 4 c. Data were collected with a Bruker VANTEC-1 detector and measurements were made in air. Metallic copper fibers 2 (see fig. 4a)) and Al₉₉Si₁Alloy metal fibers 2 (see fig. 4b)) indicate that these metal fibers are visible at a particular angle as a sharp peak 202 is polycrystalline, and Co₆₆Fe₄Mo₂B₁₂Si₁₆Alloy metal fibers 2 (see fig. 4c)) over a relatively large angular range of extending peaks 22, i.e. the absence of such sharp peaks 20, indicates that these metal fibers 2 are amorphous.

Scanning electron micrographs of the metallic copper fibers 2 are shown in fig. 5a) and b). Micrographs were recorded on a Zeiss Ultra 55 at an acceleration voltage of 3 kV. The scale in the lower left corner of fig. 5a) indicates a length of 100 μm and the scale in the lower left corner of fig. 5b) indicates a length of 2 μm. As can be seen from the photomicrograph of fig. 5a), the metal fibers 2 are not fixed to each other and form an entangled network, wherein the metal fibers 2 can be moved relative to each other such that the individual metal fibers 2 can be easily separated from the entangled network. It can also be appreciated from the photomicrograph of fig. 5a) that the metal fibers 2 have a substantially constant width over a length of millimeters. In fact, the width and thickness of the metallic copper fibers are substantially constant over a length of a few centimeters, although not visible in fig. 5a) and b). In Al in a manner analogous to the scanning electron micrographs shown in FIGS. 5a) and b)₉₉Si₁Further scanning electron micrographs as shown in fig. 5c) and d) were recorded on the alloy metal fiber 2. The scale bar in the lower left corner of fig. 5c indicates a length of 100 μm, while the scale bar in the lower left corner of fig. 5d indicates a length of 10 μm. As can be appreciated, Al₉₉Si₁The alloy metal fibers 2 form an entangled network in which the metal fibers 2 are not fixed to each other. The thickness and width of these metal fibers 2 are also substantially constant over the length of a millimeter. In fact, Al, although not visible from FIGS. 5c) and d), is present₉₉Si₁The width and thickness of the alloy metal fiber 2 are also substantially constant over a length of a few centimeters. FIG. 5e shows Al₉₉Si₁Another scanning electron micrograph of the alloy metal fiber 2. The scale bar in the lower left corner of fig. 5e indicates a length of 3 μm. In the micrograph shown in fig. 5e, the nano-crystalline domains can be identified as a grain structure. A scanning electron micrograph of the gold metal fiber 2 is shown in fig. 5 f). The scale bar in the lower left corner of fig. 5f) indicates a length of 10 μm. In the micrograph shown in FIG. 5f), the nano-crystalline domains can be identified as grainsAnd (5) structure. In FIG. 5g), Cu is shown₉₂Sn₈Scanning electron micrographs of the alloy metal fiber 2. The scale bar at the lower left corner of FIG. 5g indicates a length of 1 μm. Also in the micrograph shown in fig. 5g), the nanocrystalline domains can be identified. The nano-crystalline domain may also be in Cu produced by melt spinning₉₆Si₄Alloy metal fibers 2, as can be seen from the scanning electron micrograph of such fibers 2 shown in fig. 5 h). The scale bar in the lower left corner of fig. 5h) indicates a length of 1 μm.

527 pieces of Al produced with a wheel speed of 25m/s₉₉Si₁The thickness and width of the alloy metal fiber 2 are shown in the diagram of fig. 6 a). The corresponding thickness and width distributions are shown in the diagrams of fig. 6b and 6c, respectively. As can be seen from FIGS. 6a) and 6b), Al₉₉Si₁The thickness of the alloy metal fibers ranges between 3 and 17 μm with an average thickness of 8.5 μm. The thickness distribution follows a narrow gaussian function, such as indicated by the lines in fig. 6 b). The width of the metal fibers is in the range of 5 to 80 μm, with an average width of 39.5 μm and a median width of 35.0 μm. Fig. 6d) shows two DSC measurements. Curve I in FIG. 6d) is a plot directly from CuSn after melt spinning₈Microfibers were obtained and curve II in fig. 6d) was obtained after thermal equilibration of the same microfibers. This demonstrates the exothermic treatment in the case of heating the melt spun fibers as compared to the equilibrium metal fibers.

A scanning electron micrograph of a network 6 of metal fibers 2 according to the invention is shown in fig. 7. The scale bar in the lower left corner of fig. 7 indicates a length of 20 μm. The metal fibres 2 in the network 6 of fig. 7 are Co₆₆Fe₄Mo₂B₁₂Si₁₆Amorphous metal fibers 2 of the alloy. In contrast to the entangled network of metal fibers 2, as shown for example in the scanning electron micrographs of fig. 5a) or c), in the network 6 of metal fibers 2 as shown in fig. 7, the metal fibers 2 are fixed to each other at contact points 7, wherein the metal fibers 2 are sintered to each other. The metal fibers 2 are fixed to each other due to the sintering of the metal fibers to each other, so that it is not possible to move these metal fibers 2 relative to each other and to break the contact point 7 and to one of the metal fibers 2Separated from the network 6.

As can be seen from fig. 7 to 9, the network 6 of metal fibers 2 according to the invention has voids 9 in the form of pores between the metal fibers 2. For a better overview, only some of the metal fibers 2, contact points 7 and voids 9 are indicated with reference numerals in fig. 7. Reference numerals of the voids 9 and the contact points 7 are omitted in fig. 8 and 9, and only a part of the metal fibers 2 is denoted by the reference numerals.

In FIGS. 8 and 9, Co is shown₆₆Fe₄Mo₂B₁₂Si₁₆Photographic image of another network 6 of amorphous metal fibers 2 of the alloy. As can be seen from these photographic images, the network 6 can be held with tweezers 8 without separating the metal fibers 2 from the network 6 of metal fibers 2, and the network 6 is a disordered network 6, i.e. the metal fibers 2 do not have a preferred orientation, but are randomly oriented.

Fig. 8 and 9 show photographic images of the same network 6 of metal fibers 2. In fig. 8, the network 6 obtained after production is held by tweezers 8. As can be seen from fig. 9, the network 6 can be bent and the metal fibers 2 are still fixed to each other and not separated from the network 6 of metal fibers 2.

Furthermore, as can be seen from fig. 8 and 9, the network 6 of metal fibers 2 has a porous structure, wherein interconnected pores extend through the network of metal fibers. The contact points 7 between the metal fibers 2 are randomly distributed throughout the network 6 of metal fibers 2.

Photographic images of the network 6 of copper metal fibers 2 are shown in fig. 10 and 11. The generation of the network 6 shown in fig. 10 is described below as example 9, and the generation of the network 6 shown in fig. 11 is described below as example 10. Therefore, the network 6 shown in fig. 10 is generated at a higher temperature than the network 6 shown in fig. 11. Although both networks 6 show voids 9 in the form of pores distributed throughout the entire network 6, in the network 6 shown in fig. 10, the density of pores, i.e. the number of pores per surface area, is lower at the center of the network 6 and increases towards the edges of the network 6. For a better overview, the reference numerals of the metal fibers 2, the contact points 7 and the voids 9 are omitted in fig. 10 and 11.

In the network 6 shown in fig. 11, the distribution of the voids 9 in the form of pores is more uniform throughout the network 6 of metal fibers 2 than the distribution of the voids 9 in the network 6 shown in fig. 10. The fracture of the metal fibers 6 is transformed into a metal foil, possibly due to the higher processing temperatures used to create the network 6 shown in fig. 10. This is almost completely avoided by lowering the process temperature, as found in the network 6 shown in fig. 11.

Scanning electron micrographs of the network shown in fig. 11 are shown in fig. 12 and 13. The recording of the scanning electron micrographs is performed similarly to the recording of the other scanning electron micrographs described above. The scale bar in the lower left corner of fig. 12 indicates a length of 200 μm, and the scale bar in the lower left corner of fig. 13 indicates a length of 100 μm. From these scanning electron micrographs it can be recognized that the structure of the metallic copper fibers 2 is conserved, while the metallic fibers 2 are sintered together at the contact points 7, so that they no longer merely form an entangled network but are fixed to each other, so that it is no longer possible to easily separate the individual metallic fibers 2 from the network 6 of metallic fibers 2. It will also be appreciated that the voids 9 in the form of pores extend through the network 6 of metal fibers 2 and that the contact points 7 are randomly distributed throughout the network 6. The striations visible in the scanning electron micrographs of fig. 12 and 13 result from the thermal alloy disks used to create the network 6 of metal fibers 2, as described in the following example. These hot-melt metal discs are cut and therefore have very fine grooves (not shown) on their surface, which are embossed onto the network of metal fibers during production using a hot press 10 as schematically shown in fig. 15.

Fig. 14a) shows another photographic image of a network 6 of metal fibers 2 according to the invention. In the network 6 of metal fibers 2, the metal fibers consist of Cu₉₂Sn₈Is made of alloy. The generation of the network 6 shown in fig. 14a) is described below as example 11. In the network 6 shown in fig. 14a, the voids 9 in the form of pores are distributed throughout the network 6. The network 6 is a disordered network 6, i.e. the metal fibers 2 do not have a preferred orientation, but are randomly oriented, wherein the metal fibers 2 are fixed to each other at contact points 7, wherein the metal fibers 2 are sintered to each other. To is coming toTo better summarize, the reference numerals of the contact points 7 and the interstices 9 are omitted in fig. 14a), and only part of the metal fibers 2 are indicated by reference numerals in fig. 14 a. The metal fibers 2, the contact points 7 and the voids 9 can be identified from the SEM images of fig. 14b) and 14c), which were taken from the network 6 shown in fig. 14 a). The scale in the lower left corner of fig. 14b indicates a length of 100 μm, and the scale in the lower left corner of fig. 14c indicates a length of 20 μm. The enlarged view provided in fig. 14c) is right-hand, and at the contact point 7 more than two metal fibers 2 can be sintered together, so that at a single contact point 7 a plurality of metal fibers 2 can be fixed to each other due to sintering. For a better overview, in fig. 14b and 14c only some of the metal fibers 2, the contact points 7 and the interstices 9 are indicated by reference numerals.

Fig. 15 shows a schematic view of a hot press 10 which can be used for producing the network 6 of metal fibers 2 according to the invention. The hot press 10 is provided with an upper part 11 and a lower part 11, which upper part 11 and lower part 11 can exert a force on the discs 12, the metal fibers 2 being placed between the discs 12. In the hot pressing, the temperature of the place where the metal fiber 2 is located can be controlled. It is also possible to omit the disc 12 and place the metal fibers 2 directly between the upper part 11 and the lower part 11. To produce the network 6 of metal fibers 2 (scanning electron micrographs are shown in fig. 12 and 13), the disc 12 is made of a hot melt alloy with fine grooves (not shown) on its surface. The fine grooves have a width in the range of 30 to 60 μm.

Schematic views of a half-cell 13a according to the invention and a cell 13b according to the prior art are shown in fig. 16a) and 16b), respectively. In the two half cells 13a, 13b, a collector electrode 14 is provided as a first electrode. The current collector 14 is coated with an active electrode material 15. Lithium 16 is provided as the electrolyte. In the half cells 13a and 13b, an electrolyte is provided, which impregnates all the components of the cells 13a and 13b and transports lithium ions. In the half-cell 13a schematically shown in fig. 16a) the current collector 14 is a network 6 of metal fibers 2 according to the invention, whereas in the cell 13b schematically shown in fig. 16b the current collector 14 is a copper foil. In the context of describing examples, the structure and composition of the batteries 13a and 13b are described in more detail below.

Fig. 17 shows the results of the capacity measurement of the half cells 13a and 13 b. The battery according to the invention comprising a network of metal fibers has an increased capacity of about 50% compared to a reference battery comprising a copper foil instead of a network of metal fibers, while keeping the composition and amount of active material of both half-cells 13a and 13b constant.

Using Cu alloyed with copper₉₆Si₄The network of constituent metal fibers forms the other electrode. The network was infiltrated with a dispersion of 90% graphite and 10% binder, as described further below. As reference electrode, a copper foil was coated with the same dispersion in 50 μm layers using a doctor blade. Fig. 18 and 19 show graphs of the discharge profiles of the electrode of the invention with a metal fiber network and a reference cell obtained by chronopotentiometry.

In fig. 20a) the second and last charge-discharge profiles of the curve of fig. 18 of the reference cell obtained by chronopotentiometry are shown, and in fig. 20b the second and last charge-discharge profiles of the network cell of the invention obtained by chronopotentiometry are shown. To better demonstrate the variation of the charge-discharge profile during cyclization, fig. 21a shows a plot of the charge-discharge profile versus current normalized time for the network cell of the invention and the reference cell obtained by chronopotentiometry. Enlarged views are provided in fig. 21b) and 21 c). Fig. 22 shows the development of the capacity of the electrode of the invention and the reference electrode with the number of cycles.

In FIG. 23a, a copper alloy Cu is provided₉₆Si₄SEM images of the electrodes of the invention comprising a network of metal fibers. From the SEM image it can be seen that the graphite flakes are within the network of metal fibers, i.e. between the metal fibers. Fig. 23b) shows the EDX mapping of copper for the electrode of the invention shown in fig. 23a), and fig. 23c shows the EDX mapping of carbon for the electrode of the invention shown in fig. 23 a. EDX mapping demonstrated graphite between the metal fibers.

The following experiments were performed:

production of metal fibers:

a melt spinning apparatus using a series of experimental parameters was used to form the metal fibers. On the one hand, the device consists of a large wheel 3 (copper alloy) 200mm in diameter, placed in a chamber with argon at atmospheric pressure at 300mbar (all typical experimental settings). On the other hand, the wheel speed is increased to 60 m/s. A pressure differential of up to 2000 mbar (or less) between the crucible with the nozzle and the surrounding chamber atmosphere triggers the ejection of molten metal or metal alloy onto the rotating wheel surface. As a result, for droplets of different metals deposited on the spinning wheel, molten droplets are formed by rapid quenching (see fig. 1a) and b)) and shaped into metal fibers in the form of micro-strips. Details of the melt spinning apparatus used are disclosed in EP19175749.1, WO2016/020493a1 and WO2017/042155a 1.

Each individual droplet 5 is converted into a single metal fiber 2 or a plurality of metal fibers 2. The deposition rate of the molten alloy on the rotating wheel 3 is reduced to 1.0 to 10.0 mg-s^-1Or even lower. With this deposition rate, the metal fibers 2 are formed in the crucible in the form of micro-strips in a large amount of up to 90-95% of the initial mass of the molten alloy. The resulting optical image of the metal fibers 2 is shown in fig. 2a to d) after rapid quenching and collection, the metal fibers 2 form an entangled network in which the metal fibers easily slide relative to each other, so that one single metal fiber is easily isolated from the network.

Typical initial masses of the melt are in the range of 5 to 12g (but can be increased to 100 g). The distance between the nozzle 5 and the wheel surface is set in the range of 50 to 3000 μm, see fig. 1b), which shows the mixing of Al at 40000fps₉₉Si₁The alloy melt is deposited onto a photographic image taken of the rotating wheel with image separation. The temperature of the melt is set in the range of 50 to 300 ℃ higher than the melting temperature (higher processing temperatures are possible). The photographic images shown in fig. 2a) to d) and 3a) and b) are taken from the correspondingly produced metal fibers.

Structure of metal fiber:

the metal fibers 2 in the form of micro-strips are made of Co, Cu, Al and alloys of these elements with other elements such as Co₆₆Fe₄Mo₂B₁₂Si₁₆、Al₉₉Si₁(no comprehensive list) is generated. With pure Cu or alloyed Al₉₉Si₁The metal fiber 2 produced has a crystalline polycrystalline structure with a maximum dimension of up to 8 μm, such as copper metal fiber 2 (FIG. 4a) and Al₉₉Si₁The X-ray diffraction spectrum of the alloy metal fiber 2 (fig. 4b) shows. From Co₆₆Fe₄Mo₂B₁₂Si₁₆The metal fibers 2 made of the alloy have a typical structure of glassy metals, i.e. the metal fibers 2 are amorphous metal fibers 2, such as Co depicted in fig. 4c₆₆Fe₄Mo₂B₁₂Si₁₆The X-ray diffraction spectrogram of the alloy metal fiber 2 can be seen.

When more complex Cu and Al alloys are used and experimental parameters such as wheel speed and melting temperature are adjusted, metal fibers 2, which may be composed primarily of Al or Cu, may be fabricated to have nanocrystalline or glassy metal structures (e.g., Co for Co alloys)₆₆Fe₄Mo₂B₁₂Si₁₆Observed).

Size of metal fiber:

for Co alloy Co₆₆Fe₄Mo₂B₁₂Si₁₆The metal fibers 2 have the following typical dimensions: a width of 2.0 to 25.0 μm, a thickness of 1.0 to 7.0 μm, and a length of 2.0 to 100.0mm (see fig. 3a) and 3 b)). The band thickness distribution is a narrow gaussian distribution with a standard deviation as small as 0.4 μm, i.e. 68% (correspondingly 95%) of the metal fibers 2 have a thickness within a spacing (centered on the average thickness) as narrow as 0.8 μm (correspondingly 1.6 μm). The average thickness of the band was 5.80 μm at a wheel speed of 25m/s (see FIG. 3 b)). When the wheel speed is doubled, it decreases to 3.22 μm (see fig. 3 a)). The fiber width distribution is gaussian or lognormal. At a wheel speed of 25m/s, the average width of the fibers was 14.2 μm and the median width was 13.2 μm, i.e. 50% of the fibers had a width below 13.2 μm. When the wheel speed doubled, the average and median widths were reduced to 9.4 μm, i.e. 50% of the fibers had a width below 9.4 μm.

For Al alloy Al₉₉Si₁The average and median thickness is 8.5 ± 0.1 μm, i.e. 68% (respectively 95%) for the fibre, and the fibre 2 hasA thickness between 6.6 and 10.4 (4.8 and 12.2, respectively) μm. The mean width was 39.5 ± 1.0 μm and the median width was 35.0 ± 1.0 μm, i.e. 50% of the fibers had a width below 35.0 μm (fig. 6a to c)). Al (Al)₉₉Si₁SEM images of the alloy metal fibers 2 are shown in fig. 5c) and 5d), respectively.

The size of the metallic copper fibers 2 is similar to that of the Al alloy metal fibers (or smaller). SEM images of the metallic copper fibers 2 are shown in fig. 5a) and 5 b). These SEM images demonstrate that the width of the metal fiber 2 remains constant over a length of at least 1mm (even for a length of 1 cm). These bands have a crystalline structure: observing the top side (which is the liquid-gas interface) prior to rapid quench solidification allows direct observation of the grains. The maximum size of these crystals is estimated to be in the range of 5-8 μm.

The metal fibers 2 are used to create a network 6 of metal fibers 2.

Generation of metal fiber network:

determining Co alloy Co by using Differential Scanning Calorimetry (DSC) before producing the network 6 of metal fibers 2₆₆Fe₄Mo₂B₁₂Si₁₆Having a crystallization temperature of 560 ℃ and a melting temperature of 1021 ℃.

Example 1:

co to be produced by the above melt spinning process₆₆Fe₄Mo₂B₁₂Si₁₆Is placed between two discs 12 of alumina having a diameter of 45 mm. The disc 12 with 45mm of a delightful alumina and the main components of the metal fibers 2 are then placed in a 400 c preheated hot press 10 and the fibers 2 are pressed for a predetermined time of 30 minutes at a predetermined pressure of 377MPa to avoid the effect of thermal expansion due to heating.

Example 2:

the network 6 of example 2 was prepared identically to the network 6 of example 1, except that the pressure was reduced to 277 MPa. An SEM image of the network 6 of example 2 is provided in fig. 7, as can be seen, the metal fibers 2 are sintered together and form a stable network 6. The SEM image shows that the material and appearance of the metal fibers 2 are retained except for the contact surface with the alumina disc 12.

Example 3:

the network 6 of example 3 was prepared identically to the network 6 of example 1 except that an alumina disk 12 of Thermax superalloy having a diameter of 60mm was used instead of the disk 12. The applied pressure was 283 MPa.

Example 4:

the network 6 of example 4 was prepared identically to the network 6 of example 3, except that the time was reduced to 20 minutes.

Example 5:

the network 6 of example 5 was prepared identically to the network 6 of example 3, except that the time was reduced to 10 minutes.

Example 6:

the network 6 of example 6 was prepared identically to the network 6 of example 3, except that the time was reduced to 5 minutes.

Example 7:

the network 6 of example 7 was prepared identically to the network 6 of example 3, except that the temperature was lowered by 300 ℃.

Comparative example 1:

for comparative example 1, Co₆₆Fe₄Mo₂B₁₂Si₁₆Is placed in an oven and heated to 600 c for 30 minutes without applying external pressure. The fibers crystallize but do not sinter together.

Comparative example 2:

the network of comparative example 2 was prepared identically to the network 6 of example 1, except that the pressure was reduced to 157 MPa.

The network disintegrates when removed from the hot press 10, which indicates that the metal fibers 2 are not sufficiently sintered together.

Comparative example 3:

the network of comparative example 3 was prepared identically to network 6 of example 3, except that the pressure was reduced to 177 MPa.

Comparative example 4:

the network of comparative example 4 was prepared identically to the network 6 of example 4, except that the temperature was reduced to 100 ℃.

Comparative example 5:

the network of comparative example 5 was prepared identically to the network 6 of example 4, except that the temperature was reduced to 200 ℃.

Table 1 summarizes the time, pressure and temperature used to prepare the networks of examples 1 to 7 and comparative examples 1 to 5.

In comparative example 2, the time and temperature were the same as in examples 1 and 2. However, the network of comparative example 2 is disassembled when it is moved again from the press 10. This indicates that the pressure is not sufficient to sinter the amorphous Co₆₆Fe₄Mo₂B₁₂Si₁₆The metal fibers 2 are alloyed to provide fixation of the metal fibers 2 to each other. It can be concluded that the pressure is the driving force for sintering of the metal fibers 2. Since amorphous materials have a lower density than crystalline materials, atoms at the phase interface start to move when pressure is applied. This causes the atoms to transform into an energetically preferred state in view of the applied pressure. As a result of the movement of the atoms, the metal fibers 2 are permanently sintered together.

The network 6 of metal fibers of examples 3 to 5 does not show a significant difference. When the time was shortened to only 5 minutes in example 6, the fibers 2 were not fixed to each other as strongly as in examples 3 to 5. This proves that Co is mixed with₆₆Fe₄Mo₂B₁₂Si₁₆The process of fixing the metal fibers 2 of the alloy to each other has a certain time dependence, but is completed within a few minutes.

It can be seen that although the temperature to which the metal fibers 2 are subjected is only about Co, respectively₆₆Fe₄Mo₂B₁₂Si₁₆40% or 30% of the melting temperature of the alloy, but a process takes place in which the metal fibers 2 are sintered together, such as is demonstrated by examples 4 and 7 in which the temperatures are 400 ℃ and 300 ℃, respectively. Comparative examples 4 and 5 show that if the temperature is lowered to 100 ℃ or 200 ℃, respectively, the movement of atoms is too low to provide fixation of the metal fibers 2 to each other by sintering.

Example 8:

the network 6 of example 8 was prepared identically to the network 6 of example 3, however, the temperature was set to 500 ℃ and the time was set to 20 minutes. Furthermore, in the network 6 of example 8, more fibers 2 were used to obtain a network 6 having a thickness of 0.7 mm. After 20 minutes at a temperature of 500 ℃ and a pressure of 283MPa, the network 6 of example 8 was fully sintered, i.e. the stability of the network 6 was comparable to that of example 3.

An image of the network 6 of example 8 before deformation is shown in fig. 8, and an image of the network 6 of example 8 in a deformed state is shown in fig. 9. Therefore, as can be seen from fig. 9, even when the network 6 is highly deformed, no metal fibers 2 are separated from the network 6. This indicates that a highly stable network 6 is formed which is not easily damaged by deformation.

Example 9:

the network 6 of example 9 was prepared identically to the network 6 of example 3, however, instead of Co₆₆Fe₄Mo₂B₁₂Si₁₆The amorphous metal fiber 2 of (2) was a polycrystalline wire fiber 2 of copper (Cu) as described above, the time was set to 5 minutes, the pressure was set to 177MPa, and the temperature was set to 300 ℃.

Example 10:

the same network 6 of example 10 as the network 6 of example 9 was prepared, however, the time was set to 5 minutes.

Comparative example 6:

the network 6 of comparative example 6 was prepared identically to the network of example 9, however, the time was set to 30 minutes and the temperature was set to 500 ℃.

Table 2 summarizes the time, pressure and temperature used to prepare the networks of examples 9 and 10 and comparative example 6.

TABLE 2

In comparative example 6, the metal fiber could not be identified in the sintered product, and the obtained product was a copper foil. If the light source is placed behind the copper foil, some non-uniformity can be identified. The network 6 of examples 9 and 10 has a thickness of from 0.15mm up to 0.25 mm.

To produce the network 6 of example 9, the time and temperature were reduced to 5 minutes and 300 ℃, while the pressure was the same as the pressure applied in comparative example 6. The metal fibers 2 and the porous structure can be identified in the resulting product, i.e. voids 9 can be observed at least in some areas. Thus, to produce the network 6 of example 10, the time was further reduced to 3 minutes while maintaining the time and pressure at the same values as in example 9. It was found that the porous structure, i.e. the voids 9, existed substantially uniformly throughout the entire sample.

Images of the network 6 of examples 9 and 10 are shown in fig. 10 and 11, respectively. As can be seen from fig. 10, the network 6 of example 9 has some regions of reduced porosity. Particularly near the edge of the network 6 of example 9, many holes can be observed. By reducing the time from 5 minutes to 3 minutes, the porosity increases as can be seen by the image of the network 6 of example 10 provided in fig. 11.

SEM images of the network 6 of example 10 are shown in fig. 12 and 13. The SEM image shows that the porous structure of the network 6 and the metal fibers 2 are sintered together. The striations visible in fig. 12 and 13 are produced by the surface of the disc 12 of Thermax superalloy used for pressing the metal fibers 2. The striations in the disk of the Thermax superalloy are the result of cutting the Thermax superalloy.

Without being bound by theory, it is hypothesized that metallic copper fibers 2 exhibit improved sintering capability due to the high energy stored due to the rapid cooling rate resulting from the melt spinning process used to make the fibers. The melt spinning process provides up to 106 K.min^-1Which freezes the movement of the atoms of the system before they can be arranged into an energetically favorable state. Of course, copper specific effects associated with atomic diffusion may also play a role.

The network 6 of the above example can be bent without permanently deforming them. If these networks 6 are folded, they can be provided with a stable new shape.

Using Cu alloy Cu₉₂Sn₈Further experiments were carried out on the metal fibers of (2). Cu alloy Cu₉₂Sn₈The metal fibers of (3) are prepared similarly to the other metal fibers described above. Mixing Cu alloy Cu₉₂Sn₈The metal fibers of (2) were dispersed in 200mL of demineralized water containing 50mg of SDS (sodium dodecyl sulfate), vacuum-filtered, and dried. In the entangled network of metal fibers obtained in this way, the metal fibers are uniformly distributed but are not oriented.

Example 11:

cu prepared by the above melt spinning method and treated with an aqueous SDS solution₉₂Sn₈Is placed between the discs 12 of hot melt alloy having a diameter of 60mm (also as described above). The disc 12 of hot-melt alloy having a diameter of 60mm and the main component of the metal fiber 2 are then placed in a hot press 10 preheated at 300 c and the fiber 2 is pressed for a predetermined time of 3 minutes at a predetermined pressure of 78MPa in order to avoid the effect of thermal expansion due to heating. Thus, Cu was obtained₉₂Sn₈A stable network 6 of metal fibers having a deformation stability similar to the network 6 of examples 1 to 10 above. The network 6 of example 11 has a thickness in the range from 0.15mm up to 0.25 mm. Cu₉₂Sn₈A photographic image of the network 6 of metal fibers is shown in fig. 14 a). Cu₉₂Sn₈SEM images of the network of metal fibers are shown in fig. 14b) and 14 c).

Comparative example 7:

the network 6 of comparative example 7 was prepared identically to the network 6 of example 11, however, the temperature was maintained at room temperature, i.e., about 20 ℃. The metal fibers are not sintered together and only weak mechanical stability is observed. The mechanical stability is a result of the deformation of the metal fibers due to the applied pressure, and not due to the sintering of the metal fibers.

Comparative example 8:

the network 6 of comparative example 8 was prepared identically to the network 6 of example 11, however, only a weak pressure of about 2kPa was applied. The metal fibers obtained are not fixed to each other.

Example 11 and comparative examples 7 and 8 demonstrate that a combination of pressure and temperature is required to sinter the metal fibers to each other so that the metal fibers 2 are fixed to each other. Without being bound by theory, it is likely that the metal fibers 2 are brought into close contact with each other due to the pressure and that a matching contact surface is formed between the metal fibers 2 due to the mechanical deformation. The increased temperature promotes the movement of atoms in the direction of the pressure and thus leads to sintering of the metal fibers 2, so that the metal fibers 2 are fixed to each other.

Example 12

Preparation of fluff by carding

Carding is a mechanical process of disentangling, cleaning and mixing the fibers 2 to produce a continuous fluff 26. The solution of the carding machine 24 is shown in figure 24. The continuous pile 26 is obtained by passing the fibres 3 between different moving surfaces, such as drums 28, covered with a card cloth 30. The card cloth 30 breaks up the yarn pieces and the unorganized lumps of the fibers 2 and then aligns the respective fibers 2 in parallel with each other. Although carding is well known for fluff, it has not been used to organize the metal fibers 2 to form the fluff 26.

Fig. 25 shows an example of the nap after combing. Here, brass fibers about 10cm long, 30 μm wide and 2 μm thick as prepared by melt spinning are disentangled by a carding device. Forming two layers stacked on top of each other. It may also be stacked between layers of cotton to form cotton/metal hybrid fluff or weave. The combination of cotton and metal fiber web can also be detangled by a carding step and form cotton/metal fiber hybrid fluff.

Fig. 25 shows a photographic image of a manufacturing method according to the present invention. First, the metal fibers are disentangled by a carding device, as shown in the upper left drawing of fig. 25. For a better overview, reference numerals are not shown in fig. 25. The next layer 1 and layer 2 of differently oriented fibers as shown in the two middle photographs in line on fig. 25 are stacked on top of each other to provide a double layer of fluff as shown in the upper right image of fig. 25. As an intermediate material, cotton wool (such as the cotton wool shown in the lower right drawing of fig. 25) may be integrated in the metal fibers to provide a layered wool, the upper and lower sides of which are shown in the lower left and lower middle drawing of fig. 25.

Example 13:

ultrasonic welding is applied to mechanically fix all the fibres 2 in the metal network 6 or only the fibres 2 at different positions. In principle, longitudinal and vertical ultrasonic welding are possible. Corresponding machines are commercially available. Vertical ultrasound is the preferred technique. Here, the hammer moves up and down at a high frequency. In principle, this is also possible by hammering a suitable object onto the pile made of metal fibers 2. An example of a copper-based fluff is shown in fig. 26. In fig. 26, reference numerals are not shown for better overview. The left part of fig. 26 shows a photographic image of the network 6 of metal fibers 2 according to the invention. The square portion clearly visible in the middle of the photographic image on the left side is the region in which the metal fibers 2 are fixed to each other via ultrasonic welding as described above. The images numbered 1 to 3 in fig. 26 are enlarged views of the portions indicated by the corresponding boxes and numbers in the photographic image on the left side of fig. 26. The image below the enlarged view 1 is another enlarged view corresponding to the frame indicated in the enlarged view 1, and shows that the metal fibers 2 are fixed to each other due to the applied ultrasonic welding.

Preparing an electrode and a lithium ion battery:

the electrode of the present invention:

disks of 6mm diameter were cut from the network 6 of example 10 and infiltrated with a dispersion of 80% SnO, 10% carbon black and 10% binder. In the electrode of the invention, a network 6 of sintered metal fibers 2 of copper is used as the current collector 14.

Electrode not of the invention:

a copper foil was coated with a dispersion of 80% SnO, 10% carbon black and 10% binder to obtain a copper foil having a coating layer of an active material on the surface thereof. The thickness of the coating was adjusted to 50 μm by using tape casting. Copper foil is used as the collector 14.

The following materials were used to prepare the dispersions:

SnO: tin (II) oxide, 99.9 wt%, trace metal base (AlfaAesar (Art. Nr.11569))

Carbon black: (carbon nanopowder < 100nm, SigmaAldrich, P-code: 633100-25)

Adhesive: polyvinylidene fluoride (PVDF) (AlfaAesar (Art. Nr.44080))

A battery:

as schematically shown in fig. 16a), a half cell 13a comprising electrodes 14 and 15, separator 17 and Li foil 16 is assembled. In this half cell 13a, the electrode described above as the electrode of the present invention, i.e., the network 6 of example 10, coated with the active electrode material 15 was used.

For reference, the other half cell 13b is assembled, as schematically shown in fig. 16 b). In this half cell 13b, the above-described electrode as a non-inventive electrode, i.e., the copper foil coated with the 50 μm active electrode material as described above, was used.

If the amount of active electrode material 15 in the reference half cell 13b is increased, i.e. a layer thicker than 50 μm is tape cast, the capacitance decreases, since the electrons have to pass through a thicker layer of active electrode material. It was found that by using the assembly shown in 13a, the amount of active electrode material can be increased by a factor of 60 by incorporating it into the conductive network compared to the standard assembly shown in 13 b. Furthermore, a uniform charge distribution throughout the electrode can be obtained by using a metal fiber network, and the capacity per mass unit can be further significantly increased.

A comparison of the capacities of the two half-cells 13a, 13b is provided in fig. 17. As can be seen, the capacity of the half-cell 13a (according to the invention) is increased by almost 50% compared to the reference half-cell 13 b.

Capacity measurements were performed using a Metrohm M204 electrochemical measurement system, which was run in a software NOVA cell 1.0. The battery is in Swagelok^TMAssembled in a cell type, using lithium foil (Sigma Aldrich (99.8 wt%) as the counter electrode, polymer vlie beta (Sigma Aldrich,a glass microfiber filter, which is composed of a glass microfiber,stage) as a separator, and 1M LiClO₄(Sigma Aldrich) was dissolved in 1:1EC/DMC (ethyl carbonate/dimethyl carbonate (ALFAAESAR)) as the electrolyte.

To measure the capacity of the half-cell, a constant current of 100mAh/g was applied, normalized to the amount of active material used for the respective electrode. The potential was measured simultaneously and the eddy current points of the potential were measured at 0.0125V (lower eddy current point) and 2.2V (higher eddy current point). The resulting set of data points includes the value of the potential at any given point in time. Since a constant current is supplied, the capacity can be calculated by multiplying the time between the lower (fully discharged) and higher eddy current points (fully charged) by the applied current.

In addition to the above-described half cell 13a, other electrodes were prepared and assembled with a counter electrode, a separator and an electrolyte, and analysis was performed. The method comprises the following specific steps:

from copper alloy Cu₉₆Si₄Is dispersed, vacuum filtered and then pressed between two 60mm diameter Thermax alloys at 300 c and a pressure of 300kN for 3 min. From the resulting sintered network (mechanically stable) 10mm diameter discs were punched and infiltrated with a dispersion of 90% graphite and 10% binder. Here, the copper alloy network acts as a collector. For reference, a copper foil was coated with the same dispersion in 50 μm layers using a doctor blade.

The graphite and binder used were as follows:

graphite: powder, < 20 μm, synthesized (SigmaAldrich (Art. Nr.282863)

Adhesive: polyvinylidene fluoride (PVDF) (AlfaAesar art. Nr.44080)

Capacity measurements were performed using a Metrohm M204 electrochemical measurement system, which was run in a software NOVA cell 1.0. Battery assembly Swagelok^TMIn the cell type, a lithium foil (Sigma Aldrich (99.8 wt%) was used as a counter electrode, a glass fiber (Sigma Aldrich,a glass microfiber filter, which is composed of a glass microfiber,stage) as separator, EC: DMC (1M LiPF6) as electrolyte (EC: ethylene carbonate; DMC:dimethyl carbonate).

To measure the capacity of the half-cell, a constant current of 382mA/g was applied, normalized to the amount of active material used for the respective electrode. The potential was measured simultaneously and the eddy current points of the potential were measured at 0.0125V (lower eddy current point) and 2.2V (higher eddy current point). The resulting set of data points includes the value of the potential at any given point in time. Since a constant current is supplied, the capacity can be calculated by multiplying the time between the lower (fully discharged) and higher eddy current points (fully charged) by the applied current.

For the reference cell with the reference electrode, a 76% reduction in capacity (from 1183mAh/m2 to 289mAh/m2) was noted after 50 cycles. For the batteries with the network electrodes of the present invention, a reduction in capacity of only 9% was noted (from 1492mAh/m2 to 1381mAh/m 2). This demonstrates that the network electrode of the present invention is electrochemically more stable over 50 cycles than a common reference electrode with nearly constant capacity when the same active material is used. This relates to a 3D network of the inventive electrode that supports an efficient distribution of the stress created within the active material due to expansion during ion intercalation. Upon intercalation of lithium ions, the active material undergoes expansion (up to 8 vol% for graphite), which results in a decrease with cycling capacity in the reference cell.

Furthermore, these results indicate that the electron conductivity is improved by the metal fiber network of the present invention acting as a current collector. This network improves electrode conductivity by shortening the electron conduction path compared to a reference electrode in which there is a conductivity gradient across the electrode. Thus, for the case of the electrode of the invention, the half-cell can be charged and discharged 50 times in 6 hours compared to the reference electrode charged 50 times in 16 hours. Furthermore, as mentioned above, the capacity of the network electrode of the invention (1492 mAh/m) can be preserved²→1381mAh/m²) This is for the reference electrode (1183 mAh/m)²→289mAh/m²) This is not the case.

Fig. 18 and 19 present graphs of the charge-discharge profiles of the reference cell and the network cell of the present invention, respectively. Fig. 20a) and 20b) present the first and last cycles of the same measurement. Fig. 21a) to 21c) present a charge-discharge characteristic profile with current normalized time in order to better observe the change upon cyclization. Fig. 22 presents the capacity over a cycle.

The first cycle of each measurement is excluded for all calculations.

Fig. 23a) presents a cross-sectional SEM image of the network electrode of the invention, which visualizes the graphite flakes between the copper fibers. The same points of the mapping study by EDX (EDAX model ZEISS Ultra 55,132-10) are shown in FIGS. 23b) and 23 c).

Microstructure of the metal fiber:

to investigate the effect of the microstructure of the metal fibers in the network of metal fibers, CuSi was generated using the above method₄、Al₉₉Si₁、Cu₉₂Sn₈、Co₆₆Fe₄Mo₂B₁₂Si₁₆And fibers of FeNiB. The alloys listed in table 3 were thermally pre-treated with the parameters listed in table 3 to reduce the stored defect energy, but without causing a change in grain structure caused by recrystallization. The amorphous/nanocrystalline fibers were also heat treated above the crystallization temperature to study differences in microstructure state.

TABLE 3

Part of the fibers in each state (before thermal pretreatment, after thermal pretreatment and after crystallization) were melted twice under an argon atmosphere using Netzsch STA449F 3. Thermal pretreatment was also performed using the parameters described in table 3, using Netzsch STA449F 3. In Al₉₉Si₁In the case of (2), all samples were heated from 30 ℃ to 1200 ℃ or 900 ℃ and then cooled again to 30 ℃ at constant heating and cooling rates of 10K/min, respectively. The sample was then heated to 1200 ℃ or 900 ℃ respectively. The temperature is maintained at 30 ℃ for 1 hour between the individual melting steps or, where applicable, between heat treatment and melting. By subtracting the second thermal period from the first thermal period, the measurement can be adjusted such that only the fiber is measuredThe amount of pure energy of. The difference in area integrals between measurements with and without thermal pretreatment corresponds to the stored defect energy or crystallization energy. The amount of energy stored is shown in table 4 as defect energy and crystallization energy. Not to determine CuSi₄Because during thermal pretreatment the fibers are transferred to a thermodynamically stable phase having a two-phase structure. Due to the resulting two-phase structure, a correct measurement of the stored defect energy is not possible.

TABLE 4

Material	Defect energy [ kJ/g ]]	Crystallization energy [ kJ/g ]]
			Cu96Si4	-	-
Al99Si1	1.7	-
			Cu92Sn8	1.8	-
Co66Fe4Mo2B12Si16	0.1	2.6
			Fe40Ni40B20	2.8	3.8

From the results of table 4 it can be seen that the metal fibers obtained by melt spinning as described above have a significant amount of stored energy in the form of defect energy and/or crystallization energy, i.e. the fibers are not in their thermodynamic equilibrium. Even for alloy Cu₉₆Si₄Without indicating any value, it is noted that the metal fibers of this alloy also have a significant amount of defect energy; however, it was not possible to make meaningful quantification of this, as the material was transferred to a thermodynamic equilibrium state when subjected to the thermal pretreatment conditions specified in table 3. Cu₉₆Si₄Is estimated to be about 2.3 kJ/g.

The fibers were then weighed against the values given in table 5 and wet-laid to form a uniform nonwoven structure thereof. These were then sintered using pressure induced low temperature sintering, as described above for example 1, with the parameters also listed in table 5. The electrical conductivity of the nonwoven structure of copper and aluminum alloy fibers was determined by 4-point measurement and impedance measurement prior to sintering. These measurements were repeated after sintering. The measured values before and after sintering are listed in table 6.

Table 5: initial weight and pressure sintering parameters.

Material	Weight [ g ]]	Temperature [ deg.C ]]	Pressure [ MPa ]]	Duration [ min ]]
					Cu96Si4	1	300	35	5
Al99Si1	0.7	200	35	5
					Cu92Sn8	1	300	35	5
Co66Fe4Mo2B12Si16	1	400	140	5
					Fe40Ni40B20	0.7	400	140	5

Table 6: electrical conductivity.

It can clearly be seen that the electrical conductivity of the sintered samples is many times higher than that of the unsintered samples. It is worth mentioning that in the case of loose fibres (before sintering), the distance between the contacts used for measuring the electrical conductivity of the material is only 5 mm. Increasing the distance between these contacts increases the resistance by a factor of more than 100. This is because the unsintered fibers do not form stable conductivity between the fibers. In contrast, in the case of a sintered network, when the distance between contacts is increased, the conductivity hardly depends on the distance. This is because of the high conductivity between the fibers due to sintering.

To investigate the mechanical stability of the samples, strips 10mm wide were cut from each sample and examined by means of a tensile test at a tensile rate of 0.01 mm/s. The results of the tensile measurements are presented in table 7. The same number of fibers per cross-section was selected for standardization of the samples, as all samples were made from the same resulting uniform fibers with the same basis weight. Thus, the samples from the network of metal fibers (in which the fibers were subjected to a thermal pretreatment as described in table 3) had the same density of fibers as compared to the samples from the network of metal fibers (in which the fibers were not subjected to such a thermal pretreatment).

Table 7: mechanical stability of sintered fiber networks

It can clearly be seen that the mechanical properties of the sintered network are negatively affected by the heat treatment of the sample and the associated degradation of the storage defects. In other words, the use of metal fibers having a structure that is not in thermodynamic equilibrium improves the strength of the resulting sintered network. This is for Co subjected to thermal pretreatment₆₆Fe₄Mo₂B₁₂Si₁₆The sample becomes particularly clear. Thermally pretreated Co compared to untreated samples₆₆Fe₄Mo₂B₁₂Si₁₆The sample was not sintered at all. Amorphous/nanocrystalline alloy Co₆₆Fe₄Mo₂B₁₂Si₁₆And Fe₄₀Ni₄₀B₂₀The crystalline sample of (2) is completely incapable of sintering; the samples were annealed prior to the sintering process. They decompose into fine fiber particles during pressing without any mechanical cohesion.

It can be concluded that only fibers produced by melt spinning can be mechanically strongly bonded to each other by pressure induced low temperature sintering if the sample is not annealed before sintering. The results presented here show how much the defect energy introduced by the manufacturing process affects the degree of sintering and thus the mechanical and electrical properties of the 3D mesh. In order to use the 3D mesh as a current collector, it is necessary that these fibers are firmly connected to each other to ensure constant electrical conductivity across the entire battery electrode. However, it is required that the structure of the fibers is maintained during sintering, i.e. that the fibers are not pressed onto the metal foil without holes.

Hereinafter, the present invention is further described with respect to a method of manufacturing a battery. Battery generation consists of 7 processing steps:

1. production of Metal fibers (step 1 in FIG. 27)

2. Carding the web to lay down the fiber fluff (step 2, b1 in fig. 27); alternatively, the fibers are deposited by liquid dispersion or air flow (step 2, b2 in fig. 27).

3. Sintering of the metal fibers for the formation of the metal fiber mesh electrode (step 3 in fig. 27); in a hot press (c1, c2), by ultrasonic welding (c3) or peening (c 4).

4. Formation of anodes and cathodes by loading a metal fiber mesh with an electrode active material (step 4 in FIG. 27)

5. Rolling of electrode (step 5 in FIG. 27)

6. Ultrasonic welding of a conductive wire to an electrode as a connector (step 6 in FIG. 27)

7. Assembly of battery (step 7 of FIG. 27)

A schematic of these processing steps is provided in fig. 27, where step 1 shows the production of metal fibers, step 2 shows the arrangement of the fiber web for the layer fiber fluff, and step 3 shows the different sintering methods of the metal fibers for forming the mechanically stable metal fiber web. Sintering may be performed by pressure induced low temperature sintering (part c1) or by thermal sintering (part c2), ultrasonic welding (part c3) or peening (part c 4). In part d, the anode and cathode are formed by loading a network of metal fibers with active material (step 4). The electrode was densified in part e using calendering (step 5). As a next step, a conductive foil is attached to the network of metal fibers in step 6. The battery assembly is shown in step 7 of fig. 27. These processing steps are also described below.

Step 1. production of Metal fibers

The metal fibers are prepared by melt spinning. Two main different melt spinning techniques can be used to produce metal fibers: a) a vertical melt spinning machine, b) a horizontal melt spinning machine; vertical melt spinners have technical limitations that make the product more expensive and less efficient than production using horizontal melt spinners. Therefore, a horizontal melt spinning machine is preferably used in the present invention.

Step 2, paving the fiber fluff

For textiles, the metal fibers are treated much like cotton for textiles, which is why the resulting web can be called a metal textile. First, the metal "wool" is disentangled and the fibers aligned by carding, as shown schematically in fig. 24. This step requires microfibers of considerable length. By using melt spinning as described herein, fibers having a length of a few centimeters can be produced; due to the significant length of the fibers, a liquid dispersion step is not necessary or possible. This treatment produces a three-dimensional web for subsequent processing. In step 2, bl, the fibers are carded by a carding comb, as is known in the art of cotton processing, to obtain a uniform fibrous network, and such ordered layers are stacked on top of each layer. To do this, the fibers preferably have a length of 5-18cm and no connections between them before carding. In this step, no liquid dispersion step is required. Due to the elongation of the fibres it is possible to avoid liquid dispersions.

Alternatively, the random web is generated by deposition from a liquid dispersion or from an air stream (step 2, b 2).

Step 3 sintering of metal fibers for formation of 3D metal fiber mesh

Two heating plates (adjustable distance between 0.2 and 1mm, in this case 0.5 mm; Al)₉₉Si₁At 650 ℃ for 1.5 h; cu₉₆Si₄At 950 ℃ for 2h), such as schematically shown in step 3, c2 of fig. 27.

This results in a strong mechanical connection between the fibers at their crossing points. Once the metal fibers are mechanically connected and sintered, the electrical conductivity increases significantly.

Alternatively, the 3D metal fiber web is pressure sintered between 2 hot plates. For this purpose, the fibers were placed on two polished hot plates and pressed in a preheated uniaxial press at a pressure of 10GPa at 150 ℃ against Al₉₉Si₁Pressing and applying Cu at 300 deg.C₉₆Si₄Pressurization is carried out for 1 minute, as schematically shown in step 3, c1 of FIG. 27, for example. After this, the mechanically stable 3D fiber network can be easily pulled away from the substrate.

Alternatively, the metal fibers are locally fixed by ultrasonic welding (fig. 27, step 3, c3) or hammering (fig. 27, step 3, c 4).

Step 4. formation of anode and cathode by loading 3D metal fiber mesh with electrode active material

The active used in the examples is commercially available as a slurry from CustomCell. Graphite is used for the anode side and NMC _111 is used for the cathode side.

Next, the 3D metal web was loaded with the active material slurry using a standard doctor blade process (from Rakel blade), as shown in FIG. 27, step 4, D. A siliconized PMMA foil was placed on the plate and then wetted with ethanol/acetone. After flattening the foil, the sintered fiber network is placed on the foil. A rather liquid slurry of the active material is then drop cast onto the 3D metal web. The 3D metal fiber web structure provides capillary forces that pull the slurry into the network and evenly coat the slurry. The more viscous slurry was poured onto the network and the residual slurry (height 0.650mm) was removed using a gap knife. Subsequently, the samples were dried (anode at Room Temperature (RT) and cathode at 30 ℃).

The 3D metal fiber network is formed without contact with the active material, i.e. after sintering of these networks is completed, the active material is applied to the network of metal fibers.

Lamination/post-treatment of electrodes

Step 5. calendering of the electrode

After drying the electrodes, they were laminated using a calendering process with a gap of 0.2mm and a weight limit of 40kg per roll. Additional experiments with the following parameters were also performed:

gap of-0.4 mm, 40kg

40kg without gap

120kg without gaps

112kg, 160 ℃ without gaps

A schematic of this calendering process is shown in step 5, e of figure 27.

Step 6, conducting foil is welded on the electrode in an ultrasonic mode

Finally, the Ni foil was attached to the electrode side by ultrasonic welding. These Ni foils are the contact electrodes of the cell. Ultrasonic welding of the contact electrodes to the network 6 is schematically illustrated in step 6, f of fig. 27.

Step 7. assembling the battery

Encapsulation of the 3D metal fiber network begins with stamping out the active material loaded electrodes in the desired size/geometry. The sample was placed in a uniaxial press and punched in the desired form. Subsequently, these samples were glued in acetone using PVDF adhesive on the respective sides of a separator (PP/PE drawn) that was punched out beforehand with an overlap of 1-2mm in order to avoid internal short-circuiting of the electrodes. Then, they were put into a laminate bag and dried in an oven at 110 ℃ for 48 hours. After 48h, willThe samples were transferred to a glove box and filled with electrolyte (EC/DMC, 1M LIPF)₆) And sealed to ensure an airtight package. After wetting the sample for 3h, excess electrolyte was removed using a syringe and vacuum pump with a liquid filter and again sealed tightly directly under the electrode.

As a result:

the battery of the invention obtained by the above-described method was compared with a comparative battery not comprising a metal fiber mesh as current collector but comprising a planar foil. The results are provided in tables 8 and 9 below.

Table 8: gravimetric capacity and gravimetric energy density

	Battery of the invention	Comparative battery
			Weight capacity	140Ah/kg(0.1C)	63Ah/kg(0.1C)
	135Ah/kg(0.5C)	52Ah/kg(0.5C)
				67Ah/kg(1C)	29Ah/kg(1C)
Gravimetric energy density	519Wh/kg(0.1C)	233Wh/kg(0.1C)
				499Wh/kg(0.5C)	196Wh/kg(0.5C)
	249Wh/kg(1C)	107Wh/kg(1C)

Table 9: volumetric capacity and volumetric energy density

	Battery of the invention	Comparative battery
			Volumetric capacity	87Ah/l(0.1C)	28Ah/l(0.1C)
	81Ah/l(0.5C)	24Ah/l(0.5C)
				41Ah/l(1C)	18Ah/l(1C)
Volumetric energy density	320Wh/l(0.1C)	106Wh/l(0.1C)
				301Wh/l(0.5C)	89Wh/l(0.5C)
	150Wh/l(1C)	67Wh/l(1C)

In the above tables 8 and 9, the C-rates for determining the values of the weight and volume capacity and the energy density are represented as 0.1C, 0.5C and 1C, respectively.

Reference numerals

1 melt spinning apparatus

2 Metal fiber

3 rotating wheel

4 microstructure nozzle

5 liquid droplet

6 network

7 contact point

8 tweezers

9 gap

10 hot press

11 upper and lower parts

12 disks

13a battery

13b prior art battery

14 collector electrode

15 active electrode material

16 lithium

17 separator

20 peak of

22 peak

24 carding machine

26 fluff

28 rotating drum

30 comb fitting