阅读说明：本技术 一种金属锂电池用集流体、负极及其制备和应用 (Current collector and negative electrode for metal lithium battery, and preparation and application of current collector and negative electrode ) 是由 赖延清 范海林 覃昭铭 洪波 张治安 张凯 于 2018-08-29 设计创作，主要内容包括：本发明公开了一种用于高能二次锂电池的金属锂负极。所述的金属锂负极包括平面金属集流体,所述的平面金属集流体带有第一表面和第二表面；所述的平面金属集流体上设置有多个贯穿第一表面和第二表面且彼此独立的孔道,孔道的横截面呈矩形；平面金属集流体第一表面和/或第二表面的金属上复合有绝缘层A,孔道中的任意相对的两个表面的金属上复合有绝缘层B。覆盖在矩形微米孔道长面的绝缘层有利于金属锂在微米孔道的宽面沉积,有利于保证在金属锂沉积和溶解过程中SEI膜在宽面上下浮动,从而避免在锂沉积溶解过程中发生SEI膜的挤压和破裂。如此设计的金属锂负极可以实现超稳定和超长时间的循环。(The invention discloses a metallic lithium cathode for a high-energy secondary lithium battery. The lithium metal negative electrode comprises a planar metal current collector, and the planar metal current collector is provided with a first surface and a second surface; the planar metal current collector is provided with a plurality of independent pore passages which penetrate through the first surface and the second surface, and the cross sections of the pore passages are rectangular; an insulating layer A is compounded on the metal of the first surface and/or the second surface of the planar metal current collector, and an insulating layer B is compounded on the metal of any two opposite surfaces in the pore passage. The insulating layer covering the long surface of the rectangular micron pore canal is beneficial to the deposition of metal lithium on the wide surface of the micron pore canal, and is beneficial to ensuring that an SEI film floats up and down on the wide surface in the processes of deposition and dissolution of the metal lithium, so that the extrusion and the cracking of the SEI film in the process of deposition and dissolution of the lithium are avoided. The lithium metal cathode designed in such a way can realize ultra-stable and ultra-long-time circulation.)

1. A kind of metal lithium battery uses the mass flow body, characterized by: the current collector comprises a planar metal current collector, wherein the planar metal current collector is provided with a first surface and a second surface;

the planar metal current collector is provided with a plurality of independent pore passages which penetrate through the first surface and the second surface, and the cross sections of the pore passages are rectangular;

an insulating layer A is compounded on the metal of the first surface and/or the second surface of the planar metal current collector,

and insulating layers B are compounded on the metal of any two opposite surfaces in the pore channel.

2. The current collector for a lithium metal battery as claimed in claim 1, wherein: the planar metal current collector is a metal foil made of at least one of copper, titanium, nickel, iron and chromium;

preferably, the thickness of the planar metal current collector is 5-500 μm; preferably 15 to 100 μm;

preferably, the porosity is 10-90%; preferably 30-80%; more preferably 40 to 60%.

3. The current collector for a lithium metal battery as claimed in claim 1, wherein: the pore canal is vertical to the surface of the plane metal current collector.

4. The current collector for a lithium metal battery as claimed in claim 1, wherein: the pore canal has a smooth surface;

preferably, the metal of the two surfaces with large area in the pore channel is compounded with an insulating layer B.

5. The current collector for a lithium metal battery as claimed in claim 1, wherein: the width of the pore channel is 1-30 μm, and the length is 3-50 μm;

preferably, the length-width ratio of the pore channel is 1-5: 1; preferably 1.5-3: 1.

6. The current collector for a lithium metal battery as claimed in any one of claims 1 to 5, wherein: the insulating layer A, B is made of at least one of polyvinyl alcohol, polytetrafluoroethylene, polyethylene, polypropylene, polybutylene, polyisobutylene, polyvinylidene chloride, polyvinylidene fluoride, polyethylene terephthalate and polystyrene;

the thickness of the insulating layer A is 0.0001-0.006 time of that of the planar current collector; preferably 0.02-3 μm; preferably 0.05 to 2 μm; further preferably 0.1 to 0.5 μm;

the thickness of the insulating layer B is 0.001-0.05 times smaller than the width of the pore channel, and preferably 0.02-1.5 mu m; preferably 0.05 to 1.2 μm; more preferably 0.1 to 0.5 μm.

7. A method of preparing a current collector for a lithium metal battery as claimed in any one of claims 1 to 6, wherein: etching the planar metal current collector to form the pore passage by a focused ion beam etching method; subsequently coating the polymer of the insulating layer to form insulating layers A and B; preparing the current collector for the metal lithium battery;

preferably, the etching voltage is 3-40 kV; preferably 5-30 kV;

preferably, the etching time is 0.2-10 h; preferably 0.5-7 h; further preferably 1 to 4 hours.

8. A metallic lithium negative electrode for a secondary lithium battery, characterized by: the current collector comprises the current collector of any one of claims 1 to 6 or the current collector prepared by the method of claim 7, and metallic lithium filled in the current collector pore canal;

the content of the metal lithium is 12-88 vol.%, preferably 32-78 vol.%.

9. A method of preparing a metallic lithium negative electrode for a secondary lithium battery as claimed in claim 8, characterized in that: filling metal lithium into the current collector pore canal by an electrodeposition or melting method to prepare the metal lithium cathode;

preferably, the pore is filled with metallic lithium by electrodeposition;

preferably, the electrodeposition step is: performing electrodeposition in an organic solvent containing a lithium salt by using the current collector as a working electrode and a lithium sheet as a counter electrode;

the amount of the electrodeposited metal lithium is 2-12 mAh/cm 2; further preferably 5 to 8mAh/cm 2.

10. Use of the lithium metal negative electrode according to claim 8 or the lithium metal negative electrode obtained by the method according to claim 9, wherein: the lithium ion battery is used as a negative electrode and assembled with a positive electrode, a diaphragm and electrolyte to obtain a lithium metal battery;

preferably, the lithium metal battery is a lithium sulfur battery, a lithium iodine battery, a lithium selenium battery, a lithium tellurium battery, a lithium oxygen battery or a lithium carbon dioxide battery.

Technical Field

The invention belongs to the field of energy storage materials, and particularly relates to a metal lithium cathode for a high-energy secondary lithium battery.

Background

Metallic lithium is an ideal material for secondary batteries due to its high specific capacity (3860mAh/g) and low electrode potential (-3.04V). Therefore, it is a dream for many material experts and researchers to use metallic lithium directly as a negative electrode material of a secondary battery.

The mechanism of action of the metallic lithium negative electrode in the battery is the deposition and dissolution of metallic lithium, which is essentially reflected by the formula: charging: li⁺+ e ═ Li; discharging: li-e ═ Li⁺. What occurs with the negative electrode unlike conventional lithium ion batteries is the intercalation and deintercalation of lithium ions in the graphite negative electrode.

The growth of lithium dendrites and the cracking, generation and continuous accumulation of SEI films on the surface of lithium metal always restrict the practical application of the lithium metal. To address the lithium dendrite problem, the prior art generally employs a 3D current collector with a high specific surface area to support the metallic lithium, thereby substantially reducing the apparent current density of the electrode. For example, the Chao Shen project group of the northwest university of industry [ K.Xie, W.Wei, K.Yuan, W.Lu, M.o, Z.Li, Q.Song, X. -R.Liu, J. -G.Wang, C.Shen, Toardrite-free lithium deposition site structures and interface synthesis effects of 3D graphene @ Ni scaffold, Acs applied Mater Inter 8 (2016)26091 and 26097 ] adopts foamed nickel modified by graphene as a working electrode, and realizes 100 stable cycles at a current density of 1mA/cm 2. Similarly, the Quan-Hong Yang project group of Shenzhen Qinghua institute [ Q.Yun, Y. -. B.He, W.Lv, Y.ZHao, B.Li, F.kang, Q. -H.Yang, Chemical dealloying derivative 3D porous current collector for Li metal alloys, Advanced Materials 28(32 (2016)6932-6939.] adopts the dealloyed porous copper as the current collector, and realizes 150-turn stable cycle at a current density of 1mA/cm 2. However, the 3D current collector with a high specific surface area causes a large amount of interfacial reactions, and a large amount of SEI film is generated on the 3D current collector, resulting in a large amount of consumption of active lithium metal and electrolyte. More seriously, the SEI film continues to expand during the continuous lithium deposition process, and continues to shrink during the lithium dissolution process. As the cycle progresses, the SEI film of this layer is broken and continuously generated and accumulated, resulting in an increase in polarization and a decrease in capacity of the battery, even causing a safety accident.

Therefore, constructing a stable SEI film is an important step in realizing industrial application of lithium metal. For example, the Yunhui Huang topic group of the university of science and technology [ J.Xiang, Y.ZHao, L.Yuan, C.Chen, Y.Shen, F.Hu, Z.Hao, J.Liu, B.Xu, Y.Huang, A.Strategy of selective and dense lithium ion deposition for lithium batteries, Nano Energy 42(2017)262 and 268 ] adopts a hollow carbon material coated by a Nafion layer as a current collector, and realizes stable circulation of 80 circles under the current density of 2mA/cm 2. However, during continuous cycling, the SEI film is continuously squeezed and shrunk due to deposition and dissolution of lithium, which eventually makes the cycling performance of the lithium metal battery difficult to meet the requirements of practical applications.

Disclosure of Invention

In order to solve the problem that the conventional lithium metal battery is poor in battery performance due to the fact that lithium dendrites and an SEI film are prone to generating and the like, the first purpose of the invention is to provide a current collector for a metal lithium battery, and the current collector is used for solving the problems that the lithium dendrites and the SEI film are poor in stability and the like, so that the purpose of improving the electrical performance of the current collector is achieved.

The second purpose of the invention is to provide a preparation method of the current collector for the metal lithium battery.

The third purpose of the invention is to provide the application of the current collector in the lithium metal battery.

The fourth purpose of the invention is to provide aThe metallic lithium cathode of a secondary lithium battery aims at overcoming lithium dendrite, improving stability of SEI film, and improving electrical performance of the lithium metallic battery, especially high current density (2-5 mA/cm)²) The cycle performance of the following.

The fifth purpose of the invention is to provide a preparation method of the metal lithium negative electrode of the secondary lithium battery.

A sixth object of the present invention is to provide an application of the metallic lithium negative electrode of the secondary lithium battery.

A current collector for a metal lithium battery comprises a planar metal current collector, wherein the planar metal current collector is provided with a first surface and a second surface;

the planar metal current collector is provided with a plurality of independent pore passages which penetrate through the first surface and the second surface, and the cross sections of the pore passages are rectangular;

an insulating layer A is compounded on the metal of the first surface and/or the second surface of the planar metal current collector,

and insulating layers B are compounded on the metal of any two opposite surfaces in the pore channel.

The planar metal current collector is of a flat layered structure and is provided with an upper plane and a lower bottom surface (namely, the first surface and the second surface, which can also be understood as surfaces perpendicular to the thickness direction), the invention innovatively arranges a plurality of through holes along the thickness direction of the planar metal current collector, and innovatively arranges the shapes of the holes and the insulating layer A, B; the setting can fully reduce the apparent current density and regulate and control the growth interface of the metallic lithium. The current collector is beneficial to ensuring that the SEI film floats up and down in the pore canal in the deposition and dissolution processes of the metal lithium, and effectively avoids the extrusion and even the rupture of the SEI film in the deposition/dissolution processes of the traditional 3D lithium metal cathode; the electrical performance of the lithium metal battery can be remarkably improved, and particularly the cycle performance under high current density can be remarkably improved.

The planar metal current collector is a metal foil, and the material of the planar metal current collector is preferably at least one of copper, titanium, nickel, iron and chromium.

More preferably, the metal current collector is any one of a single metal current collector such as copper foil, titanium foil, nickel foil, iron foil, chromium foil and the like and binary or ternary alloy foils thereof, and the component ratio of the single metal current collector and the binary or ternary alloy foils is arbitrary; preferably a copper foil.

The thickness of the metal current collector is 5-500 mu m.

Preferably, the thickness of the metal current collector is 15-100 μm.

Preferably, the porosity is 10-90%; preferably 30 to 80%. At a preferred porosity, the current collector can have good mechanical strength and good toughness. While achieving uniform lithium deposition and dissolution at high current density and high area capacity.

More preferably, the porosity is 40-60%.

The first surface or the second surface refers to a surface perpendicular to the thickness direction. The first surface or the second surface and the separator are disposed opposite to each other when the battery is assembled.

Preferably, the method comprises the following steps: the pore canal is vertical to the surface of the plane metal current collector. That is, the pore passage penetrates the planar metal current collector in the thickness direction.

The cross section of the pore canal (a plane parallel to the first surface or the second surface of the planar current collector) is rectangular; the four sides of the rectangle can be the same or different; preferably different.

Preferably, the width of the pore channel (the width of the cross section) is 1-30 μm; more preferably 5 to 20 μm.

Preferably, the length of the pore channel (the length of the cross section) is 3-50 μm; more preferably 8 to 40 μm.

Preferably, the length-width ratio of the pore channel is 1-5: 1; preferably 1.5-3: 1.

The pore passages are arranged independently. By the arrangement, the interface reaction can be further reduced, and the electrical performance can be further improved.

Preferably, the method comprises the following steps: the pore canal has a smooth surface. The smooth surface facilitates uniform nucleation of metallic lithium, which in turn facilitates the formation of a uniform and stable SEI film for uniform deposition and dissolution of subsequent metallic lithium.

Preferably, the metal of the two surfaces with large area in the pore channel is compounded with an insulating layer B. That is, the insulating material is not compounded on the metal on the two surfaces with smaller area in the pore passage of the planar metal current collector, and the insulating material is compounded on the other metal surfaces. So set up, be favorable to guaranteeing that SEI film floats from top to bottom at the broadside (the less surface in area) in metal lithium deposit and dissolution process to avoid taking place the extrusion and the fracture of SEI film in lithium deposit dissolution process.

The long side (the surface with the larger area) is coated with the insulating layer B so that lithium can be deposited only on the wide side of the rectangular channel. Lithium metal is accompanied by the formation of a surface SEI during the initial deposition process, and then lithium metal continues to be deposited under the SEI film. The amount of SEI formed can be effectively reduced by depositing lithium on the wide surface, so that the loss of active lithium is effectively reduced, and the cycle performance of the battery is finally improved.

Preferably, the insulating layer A, B is made of at least one material selected from polyvinyl alcohol, polytetrafluoroethylene, polyethylene, polypropylene, polybutylene, polyisobutylene, polyvinylidene chloride, polyvinylidene fluoride, polyethylene terephthalate, and polystyrene.

Preferably, the insulating layer A, B is the same material.

Preferably, the thickness of the insulating layer A is 0.0001-0.006 times of that of the planar current collector; preferably 0.02-3 μm; preferably 0.05 to 2 μm; more preferably 0.1 to 0.5 μm.

Preferably, the thickness of the insulating layer B is less than 0.001 to 0.05 times the width of the pore. Preferably 0.02-1.5 μm; preferably 0.05 to 1.2 μm; more preferably 0.1 to 0.5 μm.

In the invention, the pore canal of the current collector is obtained by a focused ion beam etching technology.

The invention provides a preparation method of a current collector for a metal lithium battery, wherein the pore canal is formed on the planar metal current collector by etching through a focused ion beam etching method; subsequently coating the polymer of the insulating layer to form insulating layers A and B; and preparing the current collector for the metal lithium battery.

In the field of metallic lithium anodes of the present invention, lithium deposition is carried out in an organic based electrolyte having a greater viscosity than an aqueous electrolyte. The etching process must consider the wettability to organic electrolyte, the deposition uniformity of metal lithium, the apparent area and the mechanical strength in the subsequent electrodeposition process. In order to obtain a material which is innovatively suitable for a lithium metal anode, the invention innovatively utilizes a focused ion beam etching technology and innovatively finds that a material which meets the requirement of a lithium metal anode can be obtained under the control of etching voltage and etching time.

Preferably, the etching voltage is 3-40 kV; preferably 5-30 kV. The etching voltage is low, the etching is slow, and the improvement of the working efficiency is not facilitated. If the voltage is too high, the surface of the working electrode is easily burnt, which is not beneficial to preparing the working electrode with a smooth surface.

Further preferably, the etching voltage is 10-20 kV.

Preferably, the etching time is 0.2-10 h; preferably 0.5 to 7 hours. The pore channel is too shallow in the short etching time, so that the surface area of the working electrode is not favorably improved, and a small amount of metal lithium can be stored. However, if the etching time is too long, the pores are very large, which is also disadvantageous to increase the surface area of the working electrode, and the mechanical strength of the electrode is greatly reduced due to the too large pores.

Further preferably, the etching time is 1-4 h.

The insulating layer can be formed by a coating method, for example, by coating the insulating layer after slurrying the material.

The invention also provides application of the current collector for the metal lithium battery, and the current collector is used for preparing a lithium metal negative electrode. In the application, the pore channel is filled with the lithium metal by the existing method to prepare the lithium metal cathode.

The invention also provides a metal lithium negative electrode of a secondary lithium battery, which comprises the current collector and metal lithium filled in the current collector pore passage.

The lithium metal negative electrode of the secondary lithium battery is composed of a planar metal current collector rich in vertical rectangular micron pore channels, an insulating layer uniformly covering the upper surface (a first surface or a second surface) of the planar metal current collector and the long surface (surface with large area) of the rectangular micron pore channels, and lithium metal filled in the rectangular micron pore channels.

According to the lithium metal cathode, the pore channel provides a high working area, and the circulation of a battery under high current density is facilitated. Meanwhile, the insulating layer A covering the upper surface of the metal current collector avoids preferential deposition of lithium on the surface close to the diaphragm. In addition, the insulating layer B covering the long surface (surface with a larger area) of the rectangular micron pore channel is beneficial to deposition of metal lithium on the wide surface (surface with a smaller area) of the micron pore channel, and is beneficial to ensuring that an SEI film floats up and down in the pore channel (preferably on the wide surface) in the processes of deposition and dissolution of the metal lithium, so that extrusion and cracking of the SEI film in the process of deposition and dissolution of the lithium are avoided. The lithium metal cathode designed in such a way can realize ultra-stable and ultra-long-time circulation.

Preferably, the content of the metal lithium is 12-88 vol.%; preferably 32 to 78 vol.%.

The invention also provides a preparation method of the metallic lithium cathode of the secondary lithium battery, and metallic lithium is filled in the current collector pore canal by an electrodeposition or melting method to prepare the metallic lithium cathode.

Preferably, the pore is filled with metallic lithium by electrodeposition.

Preferably, the electrodeposition step is: and performing electrodeposition in an organic solvent containing a lithium salt by using the current collector as a working electrode and a lithium sheet as a counter electrode.

The amount of the electrodeposited metal lithium is 2-12 mAh/cm 2; further preferably 5 to 8mAh/cm 2.

The invention also provides application of the metal lithium cathode, and the metal lithium cathode is used as a cathode and assembled with a positive electrode, a diaphragm and electrolyte to obtain a lithium metal battery.

The invention also provides a lithium metal battery loaded with the lithium metal negative electrode.

Preferably, the lithium metal battery is a lithium sulfur battery, a lithium iodine battery, a lithium selenium battery, a lithium tellurium battery, a lithium oxygen battery or a lithium carbon dioxide battery.

When assembling the battery, the button battery is coated with an insulating layer A on one side. During cell assembly, the insulating layer a side is adjacent to the separator.

And the soft package battery is coated with an insulating layer A in a double-sided mode.

Has the advantages that:

the provided metal lithium cathode for the high-energy secondary lithium battery has the advantages that the specific surface area is increased by the vertical rectangular micron pore channel, and the apparent current density is favorably and fully reduced. The existence of the insulating layer on the surface of the metal current collector and the insulating layer on the long surface (surface with large area) of the rectangular micron pore channel can effectively prevent the metal lithium from growing on the interfaces, so that the metal lithium can fully grow on the wide surface of the rectangular micron pore channel. The design is beneficial to ensuring that the SEI film floats up and down on the wide surface in the metal lithium deposition and dissolution processes, and effectively avoiding the extrusion and even the cracking of the SEI film in the traditional 3D lithium metal negative electrode deposition/dissolution process.

Drawings

Fig. 1 is a schematic diagram of a vertical rectangular microchannel modified titanium foil in example 1.

Fig. 2 is a schematic view of a polyethylene-modified titanium foil with vertical rectangular micro-cells as in example 1.

Fig. 3 is a graph of the cycle performance of the titanium foil, the vertical rectangular microchannel modified titanium foil, and the polyethylene modified vertical rectangular microchannel titanium foil of example 1.

Fig. 4 is a schematic view of the polyethylene-modified vertical rectangular micro-porous titanium foil after lithium deposition in example 3.

Wherein 1 is a metal substrate; 2 is a vertical rectangular micron pore channel; 3 is an insulating layer A; 4 is an insulating layer B; 5 is metallic lithium.

Detailed Description

The following is a detailed description of the preferred embodiments of the invention and is not intended to limit the invention in any way, i.e., the invention is not intended to be limited to the embodiments described above, and modifications and alternative compounds that are conventional in the art are intended to be included within the scope of the invention as defined in the claims.