阅读说明：本技术 用于单电池的具有隔热层的壳体 (Housing for a single cell with a heat insulation layer ) 是由 张雅 王永 曹勇 林志宏 程骞 于 2019-05-22 设计创作，主要内容包括：本发明涉及用于单电池的具有隔热层的壳体。复合壳体包括基材和在所述基材上的双层结构涂层,其中所述双层结构涂层包括含有具有超低热导率的气凝胶材料的内层,以及含有可防止电解质溶剂渗透到所述内层中的阻隔材料的外层。根据本发明,复合壳体可以防止棱柱式或袋式电池中的壳体在电池发生热失控时熔化。(The invention relates to a housing for a single cell with a thermally insulating layer. A composite housing includes a substrate and a two-layer structure coating on the substrate, wherein the two-layer structure coating includes an inner layer comprising an aerogel material having an ultra-low thermal conductivity, and an outer layer comprising a barrier material that prevents electrolyte solvents from penetrating into the inner layer. According to the present invention, the composite case can prevent the case in the prismatic or pouch type battery from being melted when thermal runaway of the battery occurs.)

1. A case with a thermal insulating layer for a single cell, comprising:

a substrate and a two-layer structured coating on the substrate,

wherein the two-layer structure coating comprises:

an inner layer proximal to the substrate, the inner layer comprising an aerogel material having a thermal conductivity of 25mW/m-K or less, and

an outer layer distal to the substrate and coated on the inner layer, the outer layer comprising a barrier material that prevents penetration of electrolyte solvent into the inner layer.

2. The case with the insulating layer for a single cell according to claim 1, wherein the inner layer has a thickness of 300 μm or more.

3. The case for a single cell having a heat insulating layer according to claim 1 or 2, wherein the outer layer has a thickness of 100nm to 500 μm.

4. A casing for a single cell with a thermally insulating layer as claimed in any one of claims 1 to 3, wherein the outer layer comprises a barrier polymer such as polyethylene terephthalate (PET), Polytetrafluoroethylene (PTFE).

5. The case for a single cell with an insulating layer according to any one of claims 1 to 4, wherein the aerogel material contains an opacifier such as SiC, TiO₂Or carbon black, and a binder such as glass fiber.

6. The case for a single cell having an insulating layer according to any one of claims 1 to 5, wherein the shrinkage of the aerogel material after heating at 900 ℃ for 24 hours is less than 2%.

7. The case for a single cell having an insulating layer according to any one of claims 1 to 6, wherein the base material is a hard metal material such as aluminum or an alloy thereof, or a soft material such as an aluminum laminated film.

8. A cell, comprising:

a jelly-roll, the jelly-roll comprising:

the anode is provided with a positive electrode and a negative electrode,

a negative electrode, a positive electrode, a negative electrode,

a separator between the positive electrode and the negative electrode, and

an electrolyte, and

a case containing the jelly roll, the case being the case for a single cell having an insulating layer according to any one of claims 1 to 7.

9. The cell as claimed in claim 8, which is a pouch battery or a prismatic battery.

10. A battery pack comprising a plurality of single cells as claimed in claim 8 or 9.

Technical Field

The present invention relates to a case for a single cell having a heat insulating layer, and more particularly, to a heat insulating layer in a case for a single cell, which can prevent the case from melting in a prismatic or pouch type battery when thermal runaway of the battery occurs.

Background

Over the last two decades, lithium ion batteries have become a highly desirable power source for new energy vehicles. Lithium ion batteries currently on the market with graphite negative electrodes and layered structure LiMO (M ═ Ni, Co, Mn binary or ternary systems) positive electrodes have a gravimetric energy of more than 250Wh/kg at the battery level. The industry continues to strive for even higher energy densities (>300 Wh/kg).

High nickel lithium metal oxide, which may be an NCM-based battery in which the metal is nickel, cobalt, manganese or an NCA-based battery in which the metal is nickel, cobalt, aluminum, has a great advantage in terms of high energy density compared to lithium ion phosphate batteries having a relatively low energy density (160-180 Wh/kg). However, such batteries have a great safety problem due to the high composition of the chemically active substance. When a battery therein is exposed to high temperature, overcharge, or internal short circuit, thermal runaway may occur.

In this case, a pressurized atmosphere exists in the cell, which may cause thermal runaway. If the pressure inside the cell is too high, the battery may explode. Therefore, the direction of exhaust is generally designed in the unit cell to reduce the pressure when it thermally runaway. Generally, the exhaust direction refers to a safety valve provided at the top of the cell. When the pressure inside the battery is excessively high, the safety valve may be opened, so that the internal pressure may be reduced by discharging gas through the safety valve. The excessive heat in the cells can also be dissipated by exhausting the gas to the outside of the cells.

However, in high energy density batteries, the internal temperature of the single cell can rise to 700-800 ℃, which can melt and damage the aluminum housing before the safety valve opens and directly cause heat to propagate to adjacent cells. On the other hand, even if the safety valve is opened before the aluminum case is melted, a safety problem occurs in which the liquid electrolyte leaks through the safety valve.

The molten aluminum case may cause problems such as leakage and splashing of the liquid electrolyte at high temperatures, which may cause direct heat propagation. Typically, insulation may be provided between the cells in the battery pack, which may aid in venting and prevent adjacent cells from thermal runaway. However, when the aluminum case is melted, the heat insulator cannot effectively prevent heat from spreading.

On the other hand, pouch batteries without a hard metal case generally do not have a safety valve because the internal pressure is difficult to control, which makes it more difficult to prevent the melting of the outer case and the propagation of heat when the battery is thermally out of control.

Many attempts have been made in the prior art to provide a battery case having a multi-layered structure with flame retardancy. For example, CN 102328779 a discloses a soft battery case with multiple layers, which has high temperature resistance and barrier properties. Although the soft battery case has good barrier properties against an electrolyte inside the battery, it can withstand only a high temperature of about 200 c, and thus cannot be used in a battery with a high energy density.

Therefore, it is important to prevent the case in the cell from melting when thermal runaway occurs in the battery, particularly in high energy density batteries.

Disclosure of Invention

The present invention has been made in view of the above-mentioned problems. The present invention is uniquely designed to address the problem of heat propagation between cells. In one aspect, it is an object of the present invention to provide a casing for a single cell having a thermal insulating layer/coating on a duralumin substrate/aluminum laminated film, wherein the coating can effectively act as a thermal insulator to protect the single cell.

In another aspect, it is an object of the present invention to provide a single cell including the case with a heat insulating layer of the present invention, which can prevent melting when thermal runaway of the cell occurs.

To achieve the above object, in one aspect, there is provided a case for a single cell having a thermal insulating layer, comprising a base material and a two-layer structure coating on the base material, wherein the two-layer structure coating comprises an inner layer containing an aerogel material having an ultra-low thermal conductivity (e.g., 25mW/m-K or less) at a proximal end of the base material, and an outer layer coated on the inner layer at a distal end of the base material, the outer layer containing a barrier material that prevents an electrolyte solvent from penetrating into the inner layer.

Preferably, the substrate comprises or consists of a hard aluminium shell or a soft aluminium laminated film.

Preferably, the inner layer is comprised of an aerogel material having a thermal conductivity of 25mW/m-K or less.

Preferably, the outer layer has a barrier material, such as polyethylene terephthalate (PET) or Polytetrafluoroethylene (PTFE).

The present invention also provides a single cell comprising a jelly-roll comprising a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte, and a case containing the jelly-roll, wherein the case is the case defined in the present invention.

The invention also provides a battery pack comprising a plurality of single cells according to the invention.

According to the present invention, the case of a single cell having a double-layer structure coating on a base material such as an aluminum case or an aluminum laminated film can avoid melting when thermal runaway occurs in the single cell, and can solve the problem of heat propagation between the single cells.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:

fig. 1 is a schematic view showing a case for a pouch-type cell of the present invention, in which fig. 1(a) is a plan view of the pouch-type cell, fig. 1(b) is a sectional view of the pouch-type cell taken along a section X-X shown in fig. 1(a), and fig. 1(c) is a sectional view of the pouch-type cell taken along a section Y-Y shown in fig. 1 (a).

Fig. 2 is a schematic view showing a case for a prismatic battery cell of the present invention, in which fig. 2(a) is a plan view of the prismatic battery cell, fig. 2(b) is a sectional view of the prismatic battery cell taken along a section X-X shown in fig. 2(a), and fig. 2(c) is a sectional view of the prismatic battery cell taken along a section Y-Y shown in fig. 2 (a).

Fig. 3 is a perspective view schematically showing the structure of a battery pack including the pouch type battery for test in comparative example 2 and examples 3 to 4.

Fig. 4 is a perspective view schematically showing the structure of a battery pack including the prismatic battery for test in comparative example 4 and examples 7 to 8.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the technical idea of the present invention. It is to be understood that the present invention is not limited to the following embodiments, and may be variously embodied.

As described above, in one aspect, there is provided a housing for a single cell having a thermal insulating layer comprising a base material and a two-layer structure coating on the base material, wherein the two-layer structure coating comprises an inner layer proximal to the base material comprising an aerogel material having an ultra-low thermal conductivity (e.g., 25mW/m-K or less, preferably 5mW/m-K or less), and an outer layer distal to the base material and coated on the inner layer, the outer layer comprising a barrier material that prevents penetration of electrolyte solvents into the inner layer.

Hereinafter, the housing of the present invention may also be referred to as a "composite housing".

According to the present invention, the case having the heat insulating layer can be used for a single cell having a hard metal case (prismatic battery) or a soft case (pouch battery). In other words, the substrate of the case may be a hard metal material such as an aluminum case, or a soft material such as an aluminum laminated film.

Fig. 1 and 2 show the composite case for a single cell of the present invention in a pouch type battery and a prismatic battery, respectively.

Referring to fig. 1(a), as seen from an external view thereof, a pouch type battery 100 is provided with a composite case 170 of the present invention, and a negative electrode tab 150 and a positive electrode tab 160. The case 170 contains a jelly-roll, which includes a negative electrode, a positive electrode, a separator, and an electrolyte therein. Here, as shown in fig. 1(b) and 1(c), the battery includes a jelly-roll 140. The pouch type battery 100 may have a size commonly used in the art, for example, when used in a medium-and-large sized device, the pouch type battery 100 may have a length of about 261mm and a width of about 216 mm.

Typically, a plurality of pouch cells, such as those of the sizes described above, may be secured in a metal frame as a module, such as a module comprising 2 to 10 pouch cells. Furthermore, a battery pack is typically made up of several such modules. Pouch batteries are characterized by higher gravimetric energy density due to their lighter packaging material. The shape design of the bag-type battery is also flexible.

As shown in fig. 1(b) and 1(c), the housing 170 of the present invention comprises a substrate 110, an inner layer 120 at a proximal end of the substrate, and an outer layer 130 at a distal end of the substrate and coated on the inner layer. As described above, the inner layer 120 and the outer layer 130 form a two-layer structure coating in the present invention.

Similarly, referring to fig. 2(a), as seen from an external view thereof, the prismatic battery 200 is provided with the composite case 270 of the present invention, as well as the negative and positive electrode tabs 250 and 260. As shown in fig. 2(b) and 2(c), a battery jelly-roll is accommodated in the case 270. The prismatic battery 200 may have dimensions common in the art, for example, it may have a length of about 148mm, a width of about 91mm, and a thickness of about 26.5 mm.

The prismatic battery is characterized by high reliability due to protection of a hard case such as an aluminum case, and a high cell-to-pack ratio (cell-to-pack ratio) generally reaching 40% or more when a battery pack is formed. In addition, since the prismatic battery is provided with the safety valve through which hot air can be transferred, improved safety is obtained even for the entire battery pack. However, prismatic batteries also have the disadvantage of a lower gravimetric-volumetric energy density, in particular a lower gravimetric-energy density, due to the greater weight and volume of the aluminum casing.

In addition, as shown in fig. 2(b) and 2(c), the housing 270 of the present invention includes a substrate 210, an inner layer 220 at a proximal end of the substrate, and an outer layer 230 at a distal end of the substrate and coated on the inner layer. The inner layer 220 and the outer layer 230 form a two-layer structure coating in the present invention.

According to the present invention, as shown in fig. 1 and 2, the two-layer structure coating layer is not necessarily applied on the entire surface (inner surface) of the substrate. For example, it may be coated on a portion of the inner surface of the cell based on different thermal management designs. Preferably, the two-layer structure coating is applied to all vertical walls, while the top and bottom surfaces are not. For example, as shown in fig. 1 and 2, a two-layer structure coating is applied on four vertical walls of a pouch-type or prismatic battery case. However, in pouch cells, a double layer structure coating is particularly important because it is not possible to control the venting direction, and the double layer structure coating can prevent direct melting of the aluminum substrate and further prevent thermal runaway of adjacent pouch cells in the battery pack caused by hot gases escaping from one cell melted from the aluminum substrate.

In addition to the two-layer structure coating, additional layers such as an adhesive layer may be present on the substrate. In embodiments of the invention, an adhesive layer may be disposed between the two-layer structure coating and the substrate to improve adhesion of the inner layer to the substrate. The adhesive layer may comprise an adhesive that can be bonded to the substrate via heat or pressure. There is no particular limitation on the adhesive used in the adhesive layer, as long as it can ensure satisfactory adhesion between the inner layer and the substrate. For example, specific examples of thermally bonded adhesives include polyolefins such as polyethylene or polypropylene, while pressure sensitive adhesives may be acrylic adhesives, rubbers, or silicones.

Next, the composite casing of the present invention will be described in detail with reference to fig. 1 and 2. As described above, the composite shell includes a substrate and a two-layer structural coating on the substrate.

As to the substrate, it may be a relatively soft substrate 110 in a pouch battery, or a hard metal substrate 210 in a prismatic battery. The hard metal substrate 210 is not particularly limited in the present invention, but any hard metal material, such as aluminum or an alloy thereof, SUS, or Fe, may be used as long as it can satisfy the requirements of the prismatic battery. Similarly, the soft base material 110 is also not particularly limited in the present invention, but any soft material such as an aluminum laminated film may be used as long as it can satisfy the requirements for the pouch type battery. Typically, an aluminum laminated film comprises a thin aluminum substrate, such as an Al (or Al alloy) foil, and one or more layers of polymeric material on one or both sides of the substrate. For example, the aluminum laminated film may have a multi-layer structure in which an upper layer is composed of nylon having a thickness of 12 μm, an intermediate layer is composed of Al-Fe alloy having a thickness of 40 μm, and a lower layer is composed of cast polypropylene (CPP) having a thickness of 14 μm.

Next, a two-layer structure coating may be formed on the substrate as a thermal insulator and an electrolyte-solvent barrier. The two-layer structure coating may be formed by applying an inner layer having an ultra-low thermal conductivity on a substrate and then applying an outer layer to the inner layer. Optionally, the two-layer structure coating may be applied to the substrate by bonding the inner layer of the two-layer structure coating via an adhesive layer.

The inner layer is proximal to the substrate and contains aerogel material, and thus may be referred to herein as an "aerogel layer". Aerogel materials refer to highly porous solid materials composed of colloidal particles or organic polymer molecules connected to one another to form a nanoporous spatial network structure having pores that are typically filled with a gas. Therefore, it has a special continuous irregular network structure. Aerogel materials have very low thermal conductivity because they have nanoparticles and a large number of pores dispersed therein. The reason is considered as follows. It is known that heat conduction operates primarily by three means, gas conduction, solid conduction and radiative conduction. Wherein the gas conduction has the least amount of heat that can be transferred, since most gases have very low thermal conductivity. Therefore, generally most of the thermal insulation materials have a porous structure in which air occupies a part of the volume of the solid material, so that the overall thermal conductivity of the material can be reduced.

Aerogel materials of the present invention have a high porosity, which can be expressed as a volume percent (%) of air. In some embodiments, the aerogel material can have a volume percent of air greater than 95%, preferably greater than 97%, and more preferably greater than 99%. In some embodiments, the aerogel material can have a pore size of 100nm or less, more preferably 50nm or less, and most preferably 10nm or less.

The aerogel layer of the present invention can have a thickness of about 100 μm or more, preferably about 300 μm or more, and more preferably about 500 μm or more. If the thickness is less than 100 μm, a desired insulation effect may not be obtained. The upper limit of the thickness is not particularly limited, but in view of its compatibility with the single cell, it is preferably 1500 μm or less, more preferably 1000 μm or less.

As noted above, aerogel materials of the present invention have a thermal conductivity of 25mW/m-K or less, preferably 5mW/m-K or less. If the thermal conductivity is more than 25mW/m-K, the desired insulation effect cannot be obtained.

In some embodiments, aerogel materials can be made from nano-sized materials selected from silica, titanium oxide, chromium oxide, iron oxide, vanadium oxide, neodymium oxide, samarium oxide, holmium oxide, carbon (including carbon nanotubes), or any other metal oxide, or any combination thereof. More preferably, the aerogel material is made of silica, titania, carbon, or any combination thereof. Most preferably, the aerogel material is made of silica. Here, the term "nano-sized" means that the material has a particle size of the order of nanometers, for example, a particle size of 500nm or less, preferably 100nm or less, and more preferably 50nm or less.

In other embodiments, the aerogel material contains the aerogel-forming materials listed above as the main components and additives. Where additives are included, the aerogel material can contain about 60 wt% to 90 wt% aerogel-forming material, based on the total weight of the aerogel material. Additives may be used to enhance the structural stability or cohesiveness of the aerogel material, or to provide other physical benefits. For example, aerogel materials can contain glass fibers as a binder to provide a composite material with suitable mechanical strength, such as glass fibers having a length of 10 μm to 2 mm. Furthermore, radiative heat conduction may occur, especially at high temperatures. Thus, aerogel materials can generally include opacifiers such as SiC, TiO₂Or carbon black to block heat radiation. The opacifier may be in the form of a single crystal or a polycrystalline. The sunscreen agent may be in particulate form and may have a particle size of 1 μm to 50 μm. Particle size can be measured by a laser particle size analyzer such as HORIBA LA-960. Here, the particle size may refer to two of polycrystalline particlesThe secondary particle size.

In some embodiments, aerogel materials of the invention can contain about 60 to 90 weight percent aerogel-forming material (e.g., SiO with a particle size of 10 nm) based on the total weight of the aerogel material₂Or nano-sized SiO₂With nano-sized TiO₂Combinations of (a) and (b) 5 to 30 wt% of SiC having a particle diameter of, for example, 20 μm, and 2 to 10 wt% of glass fibers having a length of 100 μm.

Aerogel materials of the present invention not only can provide ultra-low heat transfer at low thickness, but also have advantages such as low light weight and high thermal stability, and are therefore useful in the present invention.

Aerogels are typically made by sol-gel polymerization, wherein the monomers used to form the aerogel framework react with each other to form a sol, which consists of bound cross-linked macromolecules, and a deposit of liquid solution fills the pores within the macromolecules.

Then, the resultant was subjected to supercritical drying under supercritical conditions. The supercritical conditions are not particularly limited, and supercritical drying may be performed under conditions commonly used in the art. For example, the aged gel may be incubated at a supercritical temperature that is higher than the critical temperature of the supercritical drying medium to obtain an aerogel. The supercritical drying medium may be selected from carbon dioxide, methanol or ethanol, and may preferably be carbon dioxide. The supercritical drying may be carried out at a supercritical temperature of 30 to 60 ℃, preferably 40 to 45 ℃, under a pressure of 1.01MPa or more (preferably 5.06MPa or more, more preferably 7.38MPa or more) for a holding time of 2 to 5 hours, preferably 2 to 3 hours.

During supercritical drying, the liquid solution is evaporated and leaves behind the bound cross-linked macromolecular framework. To have low solid conductivity, the resultant should have a small particle size (5 to 20nm) which enables high contact resistance and a tortuous thermal path through the solid matrix. This reduces the rate at which heat can flow by conduction through the solid. With respect to gas conduction, due to nanomaterials (e.g. pyrogenic SiO)₂) Is smaller than the mean free transport path (74nm) of air molecules, so it can have low convective heat transfer.

In addition, the aerogel materials of the present invention have very low shrinkage at high temperatures. For example, aerogel materials can have a shrinkage of less than 0.5%, preferably less than 0.1%, and more preferably about 0% after heating at 600 ℃ for 24 hours. Furthermore, the aerogel material can have a shrinkage of less than 2%, preferably less than 1.5%, and more preferably less than 1%, after heating at 900 ℃ for 24 hours.

In accordance with the present invention, aerogel materials can deform when the aerogel materials are subjected to compressive forces exerted by adjacent cells due to thermal expansion during operation of the cells. Specifically, 10kg (5X 5 mm) of the total weight of the composition is added²) Is applied to a size of 3X 3mm²And a test piece having a thickness of 1mm has a compression set of 10% or more, preferably 10% to 15% in a compression test for 1 hour.

The formation of aerogel materials involves a solution for forming aerogel materials containing monomers for forming an aerogel framework, a solvent, and optionally the above-described additives.

The solvent for forming the aerogel material is not particularly limited, and any solvent commonly used in the art for forming aerogels may be used. For example, the solvent may be an aqueous liquid such as water or a water/ethanol mixture, or an organic solvent such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, or an ionic liquid such as 1-ethyl-3-methylimidazolium bis [ (trifluoromethyl) sulfonyl ] amide.

Aerogel materials can be formed in a process comprising the steps of:

(1) forming a stable solution of precursors for forming an aerosol, wherein the solution may be a stable solution of precursors, optional opacifier and binder as described above;

(2) gelling the solution via a polycondensation reaction, for example, changing the pH of the solution to 3 to 4 with an alkaline solution such as NaOH or KOH;

(3) aging the sol obtained in step (2) at a predetermined temperature; and is

(4) The aged gel is subjected to supercritical drying under supercritical conditions and is shaped into a desired form or shape.

Through the above steps (1) to (4), an aerogel material having a desired porosity and thickness can be obtained, and can be applied to a substrate through a common process to form an aerogel layer. Alternatively, the aerogel layer may be first combined with an outer layer described below, and the combined coating may then be applied to the substrate in a single cell.

Next, the outer layer may be coated over the aerogel layer as a barrier that prevents the electrolyte solvent from penetrating into the inner layer. In the present invention, the outer layer may also be referred to as an "electrolyte-solvent barrier layer".

The barrier material in the outer layer is not particularly limited as long as it can prevent the electrolyte solvent from penetrating into the inner layer. Typically, the barrier material comprises a polymeric material that will not dissolve in the solvent of the electrolyte and will not swell too much upon contact with the electrolyte. Specific examples thereof include barrier polymers such as polyethylene terephthalate (PET), Polytetrafluoroethylene (PTFE), polypropylene, polyethylene, polyimide, or polyisobutylene, which may be used alone or in combination of two or more thereof. Among them, PET and PTFE are preferable in terms of the effect of preventing the electrolyte solvent from penetrating into the inner layer.

In addition, the polymeric material serves to ensure that the solvent does not come into contact with the porous aerogel material during its operation under normal conditions. It is also important that the polymer material is not affected in its thermal insulation properties when thermal runaway occurs in the battery. Thus, in some embodiments, if a better effect is desired, it is preferred to use a polymeric material having a Melting Point (MP) above 150 ℃, preferably above 200 ℃, more preferably above 300 ℃.

Further, as for the electrolyte in the battery, it generally includes a solvent and a lithium salt dissolved in the solvent. The electrolyte solvent is not particularly limited, but any solvent commonly used in the art may be used in the present invention. For example, the solvent may be an organic solvent such as an ether, an ester, an amide, a linear carbonate, a cyclic carbonate, or the like, which may be used alone or in combination of two or more thereof. For example, the electrolyte solvent may contain a mixture of a linear carbonate (e.g., diethyl carbonate) and a cyclic carbonate (e.g., ethylene carbonate).

The lithium salt in the electrolyte is not particularly limited, but any lithium salt commonly used in the art may be used in the present invention. For example, in some embodiments of the invention, the lithium salt may be LiPF₆。

The electrolyte-solvent barrier layer can be coated on the aerogel layer by conventional coating methods (e.g., spray coating, spin coating, thermal evaporation, etc.). For example, raw materials of a barrier polymer such as PET or PTFE may be uniformly mixed, coated on the aerogel layer, and dried, thereby obtaining an electrolyte-solvent barrier layer. If a curing process is involved, an optional cross-linking agent may be added to obtain the barrier polymer.

The thickness of the electrolyte-solvent barrier layer in the present invention is not particularly limited as long as the barrier layer can prevent the electrolyte solvent from penetrating into the inner layer. However, the thickness of the electrolyte-solvent barrier layer may be 100nm to 500 μm, preferably 1 to 50 μm, from the viewpoint of sufficient barrier effect and easy manufacturing.

With the above configuration, by providing the aerogel layer as a heat insulator on the inside of the case base material to significantly reduce the amount of heat transferred to the case base material, and providing the electrolyte-solvent barrier layer for protecting the functional heat insulator from being damaged by the organic solvent in the battery, the composite case for the unit cell can avoid melting when thermal runaway of the unit cell occurs.

Further, on the other side (i.e., the outer side) of the case base material opposite to the side on which the two-layer structure coating is formed, an additional layer such as a protective layer may be formed. Of course, the outer side may not be subjected to any coating process to improve heat conduction.

According to the present invention, in another aspect, there is provided a single cell comprising a jelly-roll comprising a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte, and a case containing the jelly-roll, wherein the case is as defined in the present invention.

In particular, the present invention provides a pouch-type single cell comprising a jelly roll as defined above and a soft case containing the jelly roll, wherein the case is a composite case as defined in the present invention and the substrate is a relatively soft material, such as an aluminum laminated film.

In addition, the present invention provides a prismatic cell comprising a jelly-roll as defined above and a hard case containing the jelly-roll, wherein the case is a composite case as defined in the present invention and the substrate is a hard metal material, such as an aluminum case.

The positive electrode, the negative electrode, and the separator in the single cell are not particularly limited in terms of their shapes and materials, but any composition and configuration commonly used in the art may be used in the present invention.

According to the present invention, there is provided a battery pack including a plurality of the electric cells of the present invention.

According to the present invention, there is provided a battery pack including the battery pack of the present invention. Further, a device comprising the battery pack of the invention is provided. The battery pack is used as a power source of the device. For example, the device may be one or more of an electric vehicle, including an Electric Vehicle (EV), a Hybrid Electric Vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV).

Examples

Hereinafter, embodiments are described in detail using examples, but not limited to the examples.

< measurement of shrinkage >

Sample 1

_{2 2}Preparation of SiO/TiO aerogels

SiO is produced by the following steps (1) to (4)₂/TiO₂Aerogel:

(1) first, 4g of Na having a nano size was weighed₄SiO₄(Sigma Aldrich) and 3g Na₂Ti₃O₇(Sigma Aldrich) and added to 100ml of distilled water with stirring well to prepare Na₄SiO₄And Na₂Ti₃O₇The stable aqueous solution of (1).

(2) An alkaline solution (1M KOH, Sigma Aldrich) was slowly added to the stabilizing solution to adjust the pH of the stabilizing solution to 3.5, thereby forming SiO₂/TiO₂And (3) sol.

(3) The resulting SiO₂/TiO₂The sol was aged in water for 10 hours to form a gel.

(4) Subjecting the aged gel to supercritical CO₂Incubation in medium at supercritical temperature of 50 ℃ for 2 hours to form SiO₂/TiO₂An aerogel.

Through the above steps (1) to (4), a SiO solid containing 72% by weight was obtained₂/TiO₂The aerogel of (1). In addition, 25% by weight of SiC (sunscreen, Sigma Aldrich, 378097) and 3% by weight of glass fibers (binder, Asashi Kasei, PA66) were also added in step (1). The resulting SiO₂/TiO₂The aerogel was formed to have a thickness of 0.3 mm.

Sample 2

SiO was prepared in the same manner as in sample 1₂/TiO₂Aerogel, except that aerogel contains 63 wt% SiO₂/TiO₂34% by weight of SiC and 3% by weight of glass fibers.

Testing

The resulting aerogels, samples 1 and 2, were tested for shrinkage according to ASTM C356 and the proprietary "in-house" technique. In this "full soak" exposure method, the test material is fully soaked and heated to 100 ℃, 600 ℃, 900 ℃ respectively for a period of 24 hours, after which the dimensional change is measured. The results for samples 1 and 2 are shown in table 1.

TABLE 1 shrinkage results for samples 1 and 2

As shown in Table 1, SiO for samples 1 and 2₂/TiO₂Aerogels exhibit very low shrinkage at high temperatures. For example, in samples 1 and 2, the aerogel was at 100No shrinkage (0%) was exhibited after heating at 600 ℃ for 24 hours. The aerogel in sample 2 after heating for 24 hours exhibited a shrinkage of at most 1.7% even at an elevated temperature of 900 ℃. It is well known that SiO increases with temperature₂/TiO₂The particles begin to sinter and fuse together, changing the properties of the structure and increasing the solid conductive component of heat transfer. However, very low shrinkage can be obtained using the microporous insulation structure of the present invention, which will have hardly any effect on the effective performance when used in a pouch battery.

Comparative example 1

Thermal runaway occurred in a pouch battery (250Wh/kg,550Wh/L) having only an aluminum laminate film (SPALF manufactured by Showa Denko, whose outside-to-inside structure was: nylon 25 μm-adhesive 4 μm-aluminum foil 40 μm-adhesive 4 μm-CPP 30 μm) as its case. The behavior of the aluminum laminated film during thermal runaway was observed.

A pouch-type battery having a shape as shown in FIG. 1(a) with dimensions of 261mm in length and 216mm in width and 1M LiPF in a mixed solvent of EC: DEC (3:7) was prepared₆The electrolyte solution of (1). Here, EC means ethylene carbonate and DEC means diethyl carbonate. The results of comparative example 1 are shown in table 2.

Example 1

SiO was prepared in the same manner as in sample 1₂/TiO₂Aerogels, i.e. SiO₂/TiO₂The aerogel contained 72 wt% SiO₂/TiO₂25% by weight of SiC and 3% by weight of glass fibers. The obtained SiO₂/TiO₂The aerogel was formed to have a thickness of 0.3 mm.

PET polymer from Sigma Aldrich (429252) was used as received. PET polymer was coated on SiO by thermal spraying at 300 deg.C₂/TiO₂A PET layer having a thickness of 10 μm was formed on the aerogel layer.

The resulting two-layer structure coating was coated on the inner surface of an aluminum laminated film in a pouch cell (250Wh/kg,550Wh/L) via an adhesive layer, as shown in fig. 1. The pouch cell had a size of 261mm in length and 216mm in width and was contained in a mixed solvent of EC: DEC (3:7)With 1M LiPF₆The electrolyte solution of (1).

Causing thermal runaway of the pouch cell. The behavior of the composite shell during thermal runaway was observed. The results of example 1 are shown in table 2.

Example 2

A two-layer structure coating was prepared by the same method as described in example 1, except that SiO was prepared₂/TiO₂The aerogel may have a thickness of 0.5 mm.

The resulting two-layer structure coating was coated on the surface of the interior of a pouch-type cell (250Wh/kg,550Wh/L) via an adhesive layer, as shown in fig. 1. The pouch cell had a size of 261mm in length and 216mm in width, and had 1M LiPF in a mixed solvent of EC: DEC (3:7)₆The electrolyte solution of (1).

Causing thermal runaway of the pouch cell. The behavior of the composite shell during thermal runaway was observed. The results of example 2 are shown in table 2.

TABLE 2 results of the melting test for comparative example 1, example 1 and example 2

Examples	Thickness of multilayer composite	Case of aluminum laminated film
			Comparative example 1	0mm	Melting occurs
Example 1	0.31mm	Without melting
			Example 2	0.51mm	Without melting

As can be seen from table 2, the use of the two-layer structure coating of the present invention in examples 1 and 2 can prevent the aluminum laminated film from melting during thermal runaway, as compared to comparative example 1 having only the aluminum laminated film. Therefore, it can be concluded that the composite case of the present invention can prevent the aluminum laminated film in the pouch battery from melting during thermal runaway and help to stop heat propagation between batteries.

Comparative example 2

The single cell prepared as in comparative example 1 was used. Fig. 3 is a perspective view schematically illustrating the structure of a battery pack including a test pouch battery. As shown in FIG. 3, a battery pack 300 having 4 pouch cells (250Wh/kg,550Wh/L) was used as the test vehicle. Battery 1, battery 2, battery 3, and battery 4 are designated 310, 320, 330, and 340 in fig. 3, and are arranged in parallel. No separator is provided between adjacent pouch cells.

In the test, thermal runaway of the battery 1 was caused. The thermal runaway latency for the remaining batteries was recorded. The 4 pouch cells were placed in an open space large enough so that the hot gases from the heat-loss controlled cells did not affect the adjacent cells. As a result, adjacent cells can only be ignited by direct heat transfer from cells with thermal runaway. The results of comparative example 2 are shown in table 3.

Example 3

A two-layer structure coating was prepared by the same method as described in example 1. The resulting two-layer structure coating was coated on the surface of the inside of a pouch-type battery (250Wh/kg,550Wh/L) to obtain a composite case for a pouch-type battery as shown in fig. 1.

The composite casing was subjected to a thermal runaway test as described in comparative example 2. Causing thermal runaway of the battery 1. The thermal runaway latency for the remaining batteries was recorded. The results of example 3 are shown in table 3.

Example 4

A two-layer structure coating was prepared by the same method as described in example 1, except that SiO was prepared₂/TiO₂The aerogel may have a thickness of 0.5 mm.

The resulting two-layer structure coating was coated on the surface of the inside of a pouch-type battery (250Wh/kg,550Wh/L) via an adhesive layer to obtain a composite case as shown in fig. 1. Pouch cells with 1M LiPF in EC: DEC (3:7) mixed solvent₆The electrolyte solution of (1).

The composite casing was subjected to a thermal runaway test as described in comparative example 2. Causing thermal runaway of the battery 1. The thermal runaway latency for the remaining batteries was recorded. The results of example 4 are shown in table 3.

TABLE 3 results of thermal runaway test for comparative example 2, example 3 and example 4

As can be seen from table 3, example 3 including the double-layer structure coating can significantly improve the waiting time for thermal runaway of the batteries 2, 3 and 4, as compared to comparative example 2. The use of aerogel materials as thermal insulation has proven to be effective in substantially reducing thermal propagation between cells. When the aerogel layer has a thickness of 0.5mm or more, as shown in example 4, thermal runaway of the battery 4 over time can be prevented. Therefore, as can be seen from table 3, the composite case of the present invention can have an excellent heat insulating effect and prevent heat propagation between batteries during thermal runaway in a battery pack.

Comparative example 3

Thermal runaway was caused for a prismatic battery (230Wh/kg, 560Wh/L) having only an aluminum case as its case. The behavior of the aluminum shell during thermal runaway was observed. The prismatic cell has dimensions of 148mm in length, 91mm in width and 26.5mm in thickness and has 1M LiPF in a mixed solvent of EC: DEC (3:7)₆The electrolyte solution of (1). The results of comparative example 3 are shown in table 4.

Example 5

Bilayers were prepared by the same method as described in example 1And (5) structural coating. The resulting two-layer structure coating was coated on the surface of the interior of the prismatic battery (230Wh/kg, 560Wh/L) to obtain a composite case for the prismatic battery as shown in fig. 2. The prismatic cell has dimensions of 148mm in length, 91mm in width and 26.5mm in thickness and has 1M LiPF in a mixed solvent of EC: DEC (3:7)₆The electrolyte solution of (1).

Causing thermal runaway of the prismatic battery. The behavior of the composite shell during thermal runaway was observed. The results of example 5 are shown in table 4.

Example 6

A two-layer structure coating was prepared by the same method as described in example 1, except that SiO was prepared₂/TiO₂The aerogel may have a thickness of 0.5 mm.

The resulting two-layer structure coating was coated on the surface of the inside of the prismatic battery (230Wh/kg, 560Wh/L) via the adhesive layer to obtain a composite case as shown in fig. 2. The prismatic cell has dimensions of 148mm in length, 91mm in width and 26.5mm in thickness and has 1M LiPF in a mixed solvent of EC: DEC (3:7)₆The electrolyte solution of (1).

Causing thermal runaway of the prismatic battery. The behavior of the composite shell during thermal runaway was observed. The results of example 6 are shown in table 4.

TABLE 4 results of the melting test for comparative example 3, example 5 and example 6

Examples	Thickness of multilayer composite	Case of aluminum laminated film
			Comparative example 3	0mm	Occurrence of meltingTransforming
Example 5	0.31mm	Without melting
			Example 6	0.51mm	Without melting

As can be seen from table 4, the use of the two-layer structure coating of the present invention in examples 5 and 6 can prevent the aluminum case from melting during thermal runaway, as in the case of the pouch battery. It can therefore be concluded that the composite casing of the present invention can prevent the aluminum case in the prismatic battery from melting during thermal runaway and help to stop the thermal propagation between the batteries.

Comparative example 4

The single cell prepared as in comparative example 3 was used.

Fig. 4 is a perspective view schematically illustrating the structure of a battery pack including a test prismatic battery. As shown in fig. 4, a battery pack 300 having 4 prismatic batteries (230Wh/kg, 560Wh/L) was used as a test vehicle. Battery 1, battery 2, battery 3, and battery 4 are designated 410, 420, 430, and 440 in fig. 4, and are arranged in parallel. No separator is provided between adjacent prismatic batteries.

In the test, thermal runaway of the battery 1 was caused. The thermal runaway latency for the remaining batteries was recorded. The 4 prismatic cells were placed in an open space large enough so that the hot gases from the heat-loss controlled cells did not affect the adjacent cells. As a result, adjacent cells can only be ignited by direct heat transfer from cells with thermal runaway. The results of comparative example 4 are shown in table 5.

Example 7

A two-layer structure coating was prepared by the same method as described in example 1. Coating the obtained two-layer structure coating layer on a prismatic battery via an adhesive layer (230Wh/kg, 560Wh/L) to obtain a composite casing for prismatic batteries as shown in fig. 2. The prismatic cell has dimensions of 148mm in length, 91mm in width and 26.5mm in thickness and has 1M LiPF in a mixed solvent of EC: DEC (3:7)₆The electrolyte solution of (1).

The composite casing was subjected to a thermal runaway test as described in comparative example 4 herein. Causing thermal runaway of the battery 1. The thermal runaway latency for the remaining batteries was recorded. The results of example 7 are shown in table 5.

Example 8

A two-layer structure coating was prepared by the same method as described in example 1, except that SiO was prepared₂/TiO₂The aerogel may have a thickness of 0.5 mm.

The resulting two-layer structure coating was coated on the surface of the inside of the prismatic battery (230Wh/kg, 560Wh/L) via the adhesive layer to obtain a composite case as shown in fig. 2. The prismatic cell has dimensions of 148mm in length, 91mm in width and 26.5mm in thickness and has 1M LiPF in a mixed solvent of EC: DEC (3:7)₆The electrolyte solution of (1).

The composite casing was subjected to a thermal runaway test as described in comparative example 4 herein. Causing thermal runaway of the battery 1. The thermal runaway latency for the remaining batteries was recorded. The results of example 8 are shown in table 5.

TABLE 5 results of thermal runaway test for comparative example 4, example 7 and example 8

As can be seen from table 5, example 7 containing the two-layer structure coating can significantly improve the waiting time for thermal runaway of the batteries 2, 3 and 4, as in the case of the pouch battery. The use of aerogel materials as thermal insulation has proven to be effective in substantially reducing thermal propagation between cells. When the aerogel layer has a thickness of 0.5mm or more, as shown in example 8, thermal runaway of the battery 4 over time can be prevented. Therefore, as can be seen from table 5, the composite case of the present invention can have an excellent heat insulating effect and prevent heat propagation between batteries during thermal runaway in a battery pack.

While particular embodiments of the present invention have been described above, various applications and modifications will become apparent to those skilled in the art without departing from the scope of the present invention.