WO2023273652A1

WO2023273652A1 - Diaphragm, lithium-ion battery, battery module, battery pack and power device

Info

Publication number: WO2023273652A1
Application number: PCT/CN2022/093203
Authority: WO
Inventors: 张倩倩; 李星; 金海族
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2021-07-02
Filing date: 2022-05-17
Publication date: 2023-01-05
Also published as: CN115566361A

Abstract

The present application relates to a diaphragm, a lithium-ion battery, a battery module, a battery pack and a power device. The diaphragm comprises a porous substrate; a first coating provided on at least one surface of the porous substrate, the first coating comprising inorganic particles and a binder; a second coating provided on at least part of the surface of the first coating, the second coating comprising ceramic fibers; and a third coating provided on at least part of the surface of the second coating, the third coating comprising polymer gel. The diaphragm provided by the present application can effectively improve the condition of poor infiltration caused by insufficient electrolyte or uneven distribution of a local area of a battery cell, thereby reducing the risk of local lithium precipitation of the battery cell, improving the capacity attenuation speed of the battery cell, and improving the cycle life of the battery cell.

Description

Isolation film, lithium-ion battery, battery module, battery pack and electrical device

Cross References to Related Applications

This application claims the priority of the Chinese patent application 202110751942.3 entitled "Separator, Lithium-ion Battery, Battery Module, Battery Pack, and Electrical Device" filed on July 2, 2021, the entire content of which is incorporated by reference incorporated into this article.

technical field

The present application relates to the battery field, in particular, to a separator, a lithium ion battery, a battery module, a battery pack and an electrical device.

Background technique

The battery separator is an insulating film with a porous structure and is an important part of the battery. It can block the positive and negative poles and prevent the positive and negative poles from short-circuiting inside the battery. There are nanoscale pores inside the battery separator, allowing lithium ions and other ions to pass through freely during charging and discharging, providing a channel for the rapid transmission of lithium ions between the positive and negative electrodes.

During the cycle of charging and discharging, the volume of lithium-ion batteries continues to expand, and the external manifestations are changes in thickness and stress. The expansion of the battery will cause the pole pieces to squeeze each other, and the electrolyte will be squeezed out, especially in the corner area of the battery. Because the Gap and stress in the corner area of the battery cell are different from those in the non-corner area, it is difficult for the separator to retain liquid, which makes the electrolyte distribution of the entire battery cell uneven, resulting in the lack of liquid and insufficient infiltration of some pole pieces, thereby releasing lithium. In addition, lack of electrolyte and insufficient wetting will lead to high internal resistance of the battery cell, capacity fading and reduced cycle performance, and may even cause safety problems.

Contents of the invention

In view of the problems existing in the background technology, the present application provides a separator, a lithium ion battery, a battery module, a battery pack, and an electrical device.

In a first aspect, the present application provides a separator, comprising: a porous substrate; a first coating, the first coating is disposed on at least one surface of the porous substrate, and the first coating includes inorganic particles and a binder; a second coating, the second coating is disposed on at least a part of the surface of the first coating, the second coating includes ceramic fibers; a third coating, the third coating Disposed on at least a portion of the surface of the second coating, the third coating includes a polymer gel.

Compared with the prior art, the isolation membrane provided by the present application sequentially includes a first coating layer and a second coating layer disposed on at least a part of the surface of the first coating layer on at least one surface of the porous substrate, and a second coating layer disposed on at least one surface of the porous substrate. A third coating on at least a portion of the surface of the second coating. Wherein, the first coating includes inorganic particles and binder, the second coating includes ceramic fibers, and the third coating includes polymer gel.

The isolation membrane provided by the present application adds a second coating and a third coating on the basis of the porous substrate and the first coating of inorganic particles. Among them, the ceramic fibers in the second coating have a certain flexibility and elasticity due to their "fluff"-like structure, which can enhance the liquid absorption capacity of the isolation membrane; the polymer gel in the third coating has a microporous structure, absorbing After the electrolyte swells, a lateral force is generated to press against the pole piece, which can improve the situation that the isolation membrane is difficult to maintain liquid and cause insufficient electrolyte. Therefore, the separator provided by the present application can improve the poor wetting of the battery cell caused by insufficient or uneven distribution of the local electrolyte.

In some optional embodiments, the second coating is provided with one or more areas, and the plurality of second coatings are distributed on at least a part of the surface of the first coating at intervals; and/or, the There are one or more third coating areas, and the multiple third coatings are distributed on at least a part of the surface of the second coating at intervals. A plurality of second and third coatings distributed at intervals can more effectively solve the problem of insufficient electrolyte or uneven distribution, while controlling the weight and cost of the battery cell and increasing the energy density of the battery.

In some optional embodiments, the ceramic fiber is selected from at least one of alumina ceramic fiber, silicon oxide ceramic fiber, silicon nitride ceramic fiber, barium titanate ceramic fiber, titanium oxide ceramic fiber, and magnesium oxide ceramic fiber . Among them, alumina ceramic fiber or silica ceramic fiber is cheap and light in weight, which can increase the energy density of the battery as much as possible while ensuring that the ceramic fiber can absorb liquid.

In some optional embodiments, the thickness of the second coating is 4 μm˜6 μm; further optionally, the thickness of the second coating is 5 μm˜5.5 μm. If the second coating is too thick, the energy density of the battery will be low, and the battery impedance will increase; if the second coating is too thin, the "fluff" structure will be less elastic and will not have a certain liquid absorption effect.

In some optional embodiments, the polymer gel is selected from at least one of the following types of polymer gels: polyimide, polyethylene terephthalate, polystyrene, polypropylene Nitrile, polymethylacrylate, polyether and fluoropolymer. The above-mentioned polymer gel layer not only has the function of retaining liquid, but also has the characteristics of good heat insulation, good corrosion resistance and good thermal stability.

Optionally, the polymer gel is selected from at least one of the following types of polymer gels: polyimide, polyethylene terephthalate and polystyrene. Among them, polyimide not only has good mechanical properties and heat resistance, but also has good electrolyte wetting performance, which can make the separator maintain a strong structural stability and have a high electrolyte retention capacity. Polyethylene terephthalate has excellent electrical insulation, good electrical properties, good fatigue resistance, friction resistance and dimensional stability. Polystyrene is easy to process and form, cheap, and has good heat insulation, insulation and corrosion resistance.

In some optional embodiments, the thickness of the third coating is 3 μm˜5 μm, and optionally, the thickness of the third coating is 4 μm˜4.5 μm. If the third coating is too thick, it will not only reduce the energy density of the battery, but also increase the resistance of the electrolyte to pass through the coating, and the electrolyte will not be able to wet the entire separator well. If the third coating is too thin, it will affect the liquid retention ability of the gel, and the better liquid retention effect cannot be achieved.

In some optional embodiments, the particle diameter of the polymer gel particles in the third coating is 100 nm to 1000 nm; optionally, the particle diameter of the polymer gel particles in the third coating is 300nm ~ 500nm. If the particle size of the polymer gel particles is too small, the impedance of the isolation membrane will increase, it will be difficult for lithium ions to pass through the isolation membrane, and the transmission speed will decrease. However, if the particle size of the polymer gel particles is too large, the adsorption capacity of the separator to the electrolyte will be reduced, and the liquid retention effect will be affected.

In some optional embodiments, the polymer gel particles in the third coating are solid particles or hollow particles. When the polymer gel particles are hollow particles, the swelling effect of the polymer gel layer after absorbing the electrolyte is more significant, which can more effectively improve the electrolyte shortage caused by the difficulty of keeping the separator in liquid.

In some optional embodiments, the inorganic particles in the first coating include at least one of the following inorganic particles: silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, Magnesia, Zirconia and Tin Oxide.

Optionally, the binder in the first coating includes at least one of the following binders: styrene, acrylate, vinyl acetate, fatty acid vinyl ester, epoxy resin, linear polyester, polylidene fluoride Vinyl, polystyrene, polysulfide, polyacrylic acid, polyacrylate, polyurethane, polyisobutylene, polyvinyl alcohol, polyimide, polyacrylonitrile, polyethylene oxide, polyvinylpyrrolidone, styrene-butadiene rubber, and gelatin.

In a second aspect, the present application provides a lithium-ion battery, including a positive pole piece, a negative pole piece, a separator spaced between the positive pole piece and the negative pole piece, and an electrolyte, wherein the separator is according to the present application The isolation film of the first aspect.

In some optional embodiments, the lithium ion battery provided in the present application includes a wound electrode assembly, and the second coating is at least disposed on at least a part of the surface of the first coating in the corner region of the separator. The corner area is prone to poor wetting caused by insufficient electrolyte or uneven distribution. The second coating and at least part of the first coating surface on the corner area of the isolation film can effectively improve the cell due to the electrolyte in the corner area. Poor infiltration caused by insufficient or uneven distribution reduces the risk of local lithium deposition in the battery cell and improves the cycle life of the battery cell.

In some optional embodiments, a plurality of the second coatings are arranged at intervals on part of the surface of the first coating, and the total area of the arrangement area of the plurality of second coatings occupies the corner area of the isolation film. 88% to 95% of the area, and optionally, the total area of the multiple second coating areas accounts for 90% to 92% of the corner area of the isolation film. When the total area of the second coating is too large in the area of the separator in the corner area of the cell, the resistance of lithium ions passing through the separator will increase, the transmission rate will decrease, and the effect of the electrolyte infiltrating the separator will not reach the optimum level. better, the impedance of the entire lithium battery will also increase; when the total area of the second coating accounts for too small a proportion of the area of the isolation film in the corner area of the cell, the ceramic fiber "fluff" structure is less, and the isolation film in the corner area The liquid absorption capacity cannot be significantly improved, and at the same time, the lateral force generated by the swelling of the polymer gel after absorbing the electrolyte is small, and the liquid retention capacity of the isolation membrane in the corner area becomes poor.

In a third aspect, the present application provides a battery module, including the lithium ion battery in the second aspect of the present application.

In a fourth aspect, the present application provides a battery pack, including the lithium-ion battery of the second aspect of the present application or the battery module of the third aspect of the present application.

In the fifth aspect, the present application provides an electrical device, which includes the lithium-ion battery of the second aspect of the application or the battery module of the third aspect of the application or the battery pack of the fourth aspect of the application; wherein, the lithium-ion battery or A battery module or battery pack is used as a power source or an energy storage unit for an electrical device.

The lithium-ion battery, battery module, battery pack and electrical device of the present application include the separator of the first aspect of the present application, and thus at least have the same or similar technical effects as the above-mentioned lithium-ion battery.

Description of drawings

Fig. 1 is a front view of an electric core according to a specific embodiment of the present application;

Fig. 2 is a side view of a battery cell according to a specific embodiment of the present application;

3 is a schematic diagram of the layered structure of the non-corner region of the isolation film according to a specific embodiment of the present application;

4 is a schematic diagram of the layered structure of the corner region of the isolation film according to a specific embodiment of the present application;

5 is a schematic diagram of a corner area of an isolation film according to a specific embodiment of the present application;

6 is a schematic diagram of a corner area of an isolation film according to a specific embodiment of the present application;

7 is a schematic diagram of a corner area of an isolation film according to a specific embodiment of the present application;

8 is a schematic diagram of a corner area of an isolation film according to a specific embodiment of the present application;

9 is a perspective view of a lithium-ion battery according to a specific embodiment of the present application;

Fig. 10 is an exploded view of the lithium ion battery shown in Fig. 9;

Fig. 11 is a perspective view of a battery module according to a specific embodiment of the present application;

Fig. 12 is a perspective view of a battery pack according to a specific embodiment of the present application;

Fig. 13 is an exploded view of the battery pack shown in Fig. 12;

Fig. 14 is a schematic diagram of an electrical device according to a specific embodiment of the present application.

Wherein, the reference signs are explained as follows:

1 battery pack;

2 upper box;

3 lower box;

4 battery modules;

5 secondary batteries;

51 shell;

52 electrode assemblies;

53 top cover assembly;

54S1 isolation film non-corner area;

54S2 isolation film corner area;

541 Porous substrates;

542 first coat;

543 second coat;

544 third coat.

detailed description

The present application will be further elaborated below in conjunction with specific embodiments. It should be understood that these specific examples are only used to illustrate the present application and are not intended to limit the scope of the present application.

battery separator

The first aspect of the present application provides a battery separator, including: a porous substrate; a first coating, the first coating is provided on at least one surface of the porous substrate, and the first coating includes an inorganic particles and a binder; a second coating, the second coating is disposed on at least a portion of the surface of the first coating, the second coating includes ceramic fibers; a third coating, the third coating A layer is disposed on at least a portion of the surface of the second coating, and the third coating includes a polymer gel.

In an embodiment of the present application, the isolation film includes a non-corner region and a corner region. Figure 1 is a front view of a cell in some embodiments of the present application, and Figure 1 shows the non-corner region 54S1 of the isolation film; Figure 2 is a side view of the cell in some embodiments of the present application, Figure 2 shows the corner of the isolation film Area 54S2.

Further, FIG. 3 shows a schematic diagram of the layered structure of the non-corner region of the isolation film. As shown in FIG. 3 , the non-corner region S1 of the isolation membrane includes a porous substrate 541 and a first coating 542 disposed on at least one surface of the porous substrate 541. The first coating 542 can be an isolation membrane in the prior art. Various conventional coatings on the surface, for example, the first coating 542 may include inorganic particles and binders, and the first coating 542 may further include other functional components.

FIG. 4 shows a schematic diagram of the layered structure of the corner region of the isolation film. As shown in FIG. 4 , the corner region S2 of the isolation membrane is based on the porous substrate 541 and the first coating 542 disposed on at least one surface of the porous substrate 541, and also includes at least a part of the surface disposed on the first coating 542. A second coating 543, and a third coating 544 disposed on at least a part of the surface of the second coating 543, wherein the second coating 543 includes ceramic fibers, and the third coating 544 includes polymer gel.

It can be seen that the embodiment of the present application provides a partitioned coating, in which a second coating and a third coating are added on the basis of the first coating in the corner area of the isolation film. In the second coating, the ceramic fiber has a certain flexibility and elasticity due to its "fluff"-like structure, which can enhance the liquid absorption capacity of the isolation membrane. In the third coating, the polymer gel has a microporous structure, and after absorbing the electrolyte, it swells and generates a lateral force to press against the pole piece, which can improve the situation of insufficient electrolyte caused by the difficulty of keeping the separator in liquid. Therefore, the separator of the embodiment of the present application can effectively improve the poor wetting of the battery cell caused by insufficient or uneven distribution of electrolyte in the corner area, reduce the risk of local lithium deposition in the battery cell, and improve the cycle life of the battery cell.

In some embodiments of the present application, the second coating and the third coating can also be added on the surface of the first coating in the non-corner area of the separator, so as to improve the problem caused by insufficient or uneven distribution of electrolyte in any local area of the battery cell. In case of poor infiltration.

In some embodiments of the present application, the second coating may cover the entire surface of the first coating, or may cover a part of the surface of the first coating.

In some embodiments of the present application, there may be one or more areas where the second coating is disposed. When there are multiple second coating areas, the multiple second coating areas are distributed on at least a part of the surface of the first coating at intervals. Optionally, the disposition areas of the plurality of second coatings are evenly spaced and distributed on at least a part of the surface of the first coating.

In some embodiments of the present application, the third coating is provided in one or more regions. When there are multiple third coating areas, the multiple third coatings are distributed on at least a part of the surface of the second coating at intervals. Optionally, the multiple third coatings are evenly spaced and distributed on at least a part of the surface of the second coating.

A plurality of second and third coatings distributed at intervals can more effectively solve the problem of insufficient or uneven distribution of electrolyte in the local area of the separator, and can also control the weight and cost of the battery cell and increase the energy density of the battery.

5 to 8 are schematic diagrams of the corner area of the isolation film according to some embodiments of the present application.

In Fig. 5, the second coating 543 covers the whole surface of the first coating (not shown in the figure), the third coating 544 covers the partial surface of the second coating 543, the second coating 543 and the third coating The setting area of 544 is one.

In Fig. 6, the second coating 543 covers the partial surface of the first coating 542, the third coating 544 covers the partial surface of the second coating 543, and the setting areas of the second coating 543 and the third coating 544 are both one.

In Fig. 7, the second coating 543 covers the whole surface of the first coating (not shown in the figure), the setting area of the third coating 544 is multiple, and the plurality of third coatings 544 are evenly spaced and distributed, covering the first coating 544. Part of the surface of the second coating 543 .

In FIG. 8 , a plurality of second coating layers 543 are distributed at intervals on part of the surface of the first coating layer 542 , and the third coating layer 544 covers part of the surface of the second coating layer 543 .

It should be noted that what are shown in Fig. 5 to Fig. 8 are only several examples of the corner area of the isolation film according to the embodiment of the present application, but the shapes of the first coating, the second coating and the third coating can be Optionally, the positions of the first coating, the second coating, and the third coating are not limited thereto.

In addition, the materials of the first coating, the second coating and the third coating can be synthesized according to existing literature methods or can be purchased through commercial channels, and the first coating, the second coating and the third coating can be sprayed , photolithography, printing and other methods well known to those skilled in the art.

In some embodiments of the present application, the ceramic fibers may be selected from at least one of alumina ceramic fibers, silica ceramic fibers, silicon nitride ceramic fibers, barium titanate ceramic fibers, titanium oxide ceramic fibers, and magnesium oxide ceramic fibers. A sort of. Among them, alumina ceramic fiber or silica ceramic fiber is cheap and light in weight, which can increase the energy density of the battery as much as possible while ensuring that the ceramic fiber can absorb liquid.

In some embodiments of the present application, the thickness of the second coating layer may be 4 μm˜6 μm. In another part of the embodiments of the present application, the thickness of the second coating may be 5 μm˜5.5 μm. If the second coating is too thick, the energy density of the battery will be low, and the battery impedance will increase; if the second coating is too thin, the "fluff" structure will be less elastic and will not have a certain liquid absorption effect.

In some embodiments of the present application, the polymer gel can be selected from at least one of the following types of polymer gels: polyimide, polyethylene terephthalate, polystyrene, Polyacrylonitrile, polymethylacrylate, polyether and fluoropolymer. The above-mentioned polymer gel layer not only has the function of retaining liquid, but also has the characteristics of good heat insulation, good corrosion resistance and good thermal stability.

In another part of the implementation of the present application, the polymer gel can be selected from at least one of the following types of polymer gels: polyimide, polyethylene terephthalate and polystyrene . Among them, polyimide not only has good mechanical properties and heat resistance, but also has good electrolyte wetting performance, which can make the separator maintain a strong structural stability and have a high electrolyte retention capacity. Polyethylene terephthalate has excellent electrical insulation, good electrical properties, good fatigue resistance, friction resistance and dimensional stability. Polystyrene is easy to process and form, cheap, and has good heat insulation, insulation and corrosion resistance.

In some embodiments of the present application, the thickness of the third coating layer may be 3 μm˜5 μm. In another part of the embodiments of the present application, the thickness of the third coating layer may be 4 μm˜4.5 μm. If the third coating layer is too thick, it will not only reduce the energy density of the battery, but also increase the resistance of the electrolyte to pass through the coating, and the electrolyte will not be able to wet the entire separator well. And when the third coating is too thin, it will affect the liquid retention capacity of the gel, and the better liquid retention effect cannot be achieved.

In some embodiments of the present application, the particle diameter of the polymer gel particles in the third coating layer may be 100 nm˜1000 nm. In another part of the embodiments of the present application, the particle diameter of the polymer gel particles in the third coating layer may be 300nm-500nm. If the particle size of the polymer gel particles is too small, the impedance of the isolation membrane will increase, it will be difficult for lithium ions to pass through the isolation membrane, and the transmission speed will decrease. However, if the particle size of the polymer gel particles is too large, the adsorption capacity of the separator to the electrolyte will be reduced, and the liquid retention effect will be affected.

In some embodiments of the present application, the polymer gel particles in the third coating may be solid particles or hollow particles. When the polymer gel particles are hollow particles, the third coating can have a more sufficient swelling effect after absorbing the electrolyte, which can more effectively improve the situation that the isolation membrane is difficult to maintain and cause insufficient electrolyte.

In some embodiments of the present application, the inorganic particles in the first coating may include at least one of the following inorganic particles: silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, Magnesia, Zirconia and Tin Oxide.

In some embodiments of the present application, the binder in the first coating may include at least one of the following binders: styrene, acrylate, vinyl acetate, fatty acid vinyl ester, epoxy resin, linear polyester , polyvinylidene fluoride, polystyrene, polysulfide rubber, polyacrylic acid, polyacrylate, polyurethane, polyisobutylene, polyvinyl alcohol, polyimide, polyacrylonitrile, polyethylene oxide, polyvinylpyrrolidone, styrene-butadiene rubber and gelatin.

Button ion battery

In some embodiments of the present application, the lithium-ion battery may include a wound electrode assembly, and the second coating is disposed on at least a part of the surface of the first coating in the corner area of the separator, thereby effectively improving the thickness of the corner area. The poor infiltration of the battery cell due to insufficient electrolyte or uneven distribution reduces the risk of local lithium deposition in the battery cell, slows down the capacity attenuation, and improves the cycle life and safety performance of the battery cell.

In some embodiments of the present application, a plurality of the second coatings may be arranged at intervals on part of the surface of the first coating, and the total area of the arrangement area of the plurality of second coatings may account for the spaced area. 88% to 95% of the corner area of the membrane. In another part of the embodiments of the present application, the total area of the plurality of second coating layers may account for 90%-92% of the corner area of the isolation film. In these embodiments, the second coating and the third coating may have the same shape and size, and are sequentially stacked on the surface of the first coating. When the total area of the setting area of the second coating accounts for an excessively large proportion of the corner area of the isolation film, the resistance of lithium ions passing through the isolation film will increase. As a result, the transmission rate of lithium ions decreases, the effect of the electrolyte infiltrating the separator is not optimal, and the impedance of the entire lithium battery will also increase. When the total area of the setting area of the second coating is too small in the area of the corner area of the isolation film, the ceramic fiber "fluff" structure is less, and the liquid absorption capacity of the isolation film in the corner area cannot be significantly improved, and at the same time, the polymer coagulates After the glue absorbs the electrolyte, it swells and produces a small lateral force. As a result, the liquid retaining ability of the isolation film in the corner region deteriorates.

In some embodiments of the present application, the positive electrode sheet of the lithium ion battery includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. In the positive electrode sheet, the positive active material layer may be disposed on one surface of the positive current collector or on both surfaces of the positive current collector.

Those skilled in the art can choose an appropriate method to prepare the positive electrode sheet, for example, may include the following steps: After mixing the positive electrode active material, binder, and conductive agent to form a slurry, coating it on the positive electrode current collector.

Wherein, the specific type of positive electrode active material is not particularly limited, as long as it can meet the requirements of inserting and extracting lithium ions. The positive electrode active material can be either a layered structure material, allowing lithium ions to diffuse in a two-dimensional space, or a spinel structure, allowing lithium ions to diffuse in a three-dimensional space. Optionally, the positive electrode active material may be selected from one or more of lithium transition metal oxides, compounds obtained by adding other transition metals or non-transition metals or non-metals to lithium transition metal oxides. Specifically, the positive electrode active material can be selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, olivine structure containing One or more of lithium phosphates.

Among them, the general formula of lithium-containing phosphate with olivine structure can be LiFe _1-xy Mn _x M' _y PO ₄ , 0≤x≤1, 0≤y<1, 0≤x+y≤1, M' can be One or more selected from other transition metal elements or non-transition metal elements except Fe and Mn, M' can be selected from one or more of Cr, Mg, Ti, Al, Zn, W, Nb, Zr kind. More optionally, the lithium-containing phosphate of olivine structure can be selected from one or more of lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate.

The lithium transition metal oxide may be selected from LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _x Co _y Mn _1-xy O ₂ , LiNi _x Co _y Al _1-xy O ₂ , LiNi _x Mn _2-x One or more of O ₄ , where 0<x<1, 0<y<1, 0<x+y<1. Alternatively, the lithium transition metal oxide may be selected from LiCoO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.8 One or more of Co _0.1 Mn _0.1 O ₂ , LiNi _0.8 Co _0.15 Mn _0.05 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiNi _0.5 Mn _1.5 O ₄ , LiMn ₂ O ₄ .

In the positive electrode sheet, the positive active material layer may further include a conductive agent and a binder, wherein the type and content of the conductive agent and the binder are not specifically limited, and may be selected according to actual needs. The binder usually includes a fluorine-containing polyolefin binder, and water is usually a good solvent relative to the fluorine-containing polyolefin binder, that is, the fluorine-containing polyolefin binder is usually in Good solubility in water, for example, the fluorine-containing polyolefin binder can include but not limited to polyvinylidene fluoride (PVDF), vinylidene fluoride copolymer or their modification (for example, carboxylic acid, acrylic acid , modified acrylonitrile) derivatives, etc. In the positive electrode material layer, the mass percentage of the binder may be due to the poor conductivity of the binder itself, so the amount of the binder cannot be too high. Optionally, the mass percentage of the binder in the positive electrode active material layer is less than or equal to 2wt%, so as to obtain lower resistance of the electrode sheet. The conductive agent of the positive electrode sheet can be various conductive agents suitable for secondary batteries in the art, for example, it can include but not limited to acetylene black, conductive carbon black, carbon fiber (VGCF), carbon nanotube (CNT), Ketjen One or more combinations of black. The weight of the conductive agent may account for 1wt%-10wt% of the total mass of the positive electrode material layer. More optionally, the weight ratio of the conductive agent to the positive active material in the positive electrode sheet is greater than or equal to 1.5:95.5.

In the positive pole piece, the type of the positive current collector is not specifically limited, and can be selected according to actual needs. The positive current collector can usually be a layered body, and the positive current collector is usually a structure or part that can collect current. The positive current collector can be various materials suitable for use as the positive current collector of the electrochemical energy storage device in the art. For example, the positive electrode current collector may include but not limited to metal foil, more specifically may include but not limited to nickel foil and aluminum foil.

In some embodiments of the present application, the negative electrode sheet of the lithium ion battery generally includes a negative electrode current collector and a negative electrode active material layer located on the surface of the negative electrode current collector, and the negative electrode active material layer generally includes a negative electrode active material. The negative electrode active material can be various materials suitable for the negative electrode active material of lithium-ion batteries in the art, for example, can include but not limited to graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microspheres, silicon-based materials , tin-based materials, lithium titanate or other metals capable of forming alloys with lithium. Wherein, the graphite can be selected from one or more combinations of artificial graphite, natural graphite and modified graphite; the silicon-based material can be selected from elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon alloys A combination of one or more; the tin-based material can be selected from one or more of simple tin, tin oxide, and tin alloys.

The negative electrode current collector is usually a structure or part that collects current. The negative electrode current collector can be a variety of materials suitable for use as a lithium ion battery negative electrode collector in the art. For example, the negative electrode current collector can include but is not limited to Metal foil, more specifically, may include but not limited to copper foil. In addition, the negative electrode sheet can also be a lithium sheet.

In some embodiments of the present application, the electrolyte solution of the lithium-ion battery can be various electrolyte solutions suitable for lithium-ion batteries in the art, for example, the electrolyte solution usually includes an electrolyte and a solvent, and the electrolyte usually includes a lithium salt . More specifically, the lithium salt may be an inorganic lithium salt and/or an organic lithium salt, specifically including but not limited to LiPF ₆ , LiBF ₄ , LiN(SO ₂ F) ₂ (abbreviated as LiFSI), LiN(CF ₃ A combination of one or more of SO ₂ ) ₂ (abbreviated as LiTFSI), LiClO ₄ , LiAsF ₆ , LiB(C ₂ O ₄ ) ₂ (abbreviated as LiBOB), LiBF ₂ C ₂ O ₄ (abbreviated as LiDFOB) . For another example, the concentration of the electrolyte may be 0.8 mol/L˜1.5 mol/L. The solvent can be a variety of solvents suitable for the electrolyte of lithium-ion secondary batteries in the art. The solvent of the electrolyte is usually a non-aqueous solvent, which can be an organic solvent, specifically including but not limited to ethylene carbonate, A combination of one or more of propylene carbonate, butylene carbonate, pentene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate or their halogenated derivatives.

In some embodiments of the present application, the method for preparing the lithium-ion battery should be known to those skilled in the art, for example, each of the positive electrode sheet, the separator and the negative electrode sheet can be a layered body , so that it can be cut to the target size and then stacked in sequence, and can also be wound to the target size to form a battery cell, and can be further combined with the electrolyte to form a lithium-ion battery.

FIG. 9 shows a perspective view of a lithium-ion battery according to a specific embodiment of the present application, and FIG. 10 is an exploded view of the lithium-ion battery shown in FIG. 9 . Referring to FIG. 9 and FIG. 10 , a lithium-ion battery 5 according to the present application (hereinafter referred to as a battery cell 5 ) includes an outer package 51 , an electrode assembly 52 , a top cover assembly 53 and an electrolyte (not shown). Wherein the electrode assembly 52 is accommodated in the casing 51, and the number of the electrode assembly 52 is not limited, and may be one or more.

It should be noted that the battery cell 5 shown in FIG. 9 is a can-type battery, but the application is not limited thereto. The battery cell 5 may be a pouch-type battery, that is, the casing 51 is replaced by a metal plastic film and the top cover is omitted. Component 53.

battery module

A third aspect of the present application provides a battery module, which includes the lithium-ion battery described in the second aspect of the present application. In some embodiments, the lithium-ion batteries can be assembled into a battery module, and the number of lithium-ion batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. FIG. 11 is a perspective view of a battery module 4 as an example. Referring to FIG. 11 , in the battery module 4 , a plurality of lithium-ion batteries 5 may be arranged sequentially along the length direction of the battery module 4 . Of course, it can also be arranged in any other manner. Further, the plurality of lithium ion batteries 5 can be fixed by fasteners. Optionally, the battery module 4 may also include a casing with an accommodating space, and a plurality of lithium-ion batteries 5 are accommodated in the accommodating space.

battery pack

A fourth aspect of the present application provides a battery pack, which includes the battery module described in the third aspect of the present application. In some embodiments, the above-mentioned battery modules can be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack. FIG. 12 is a perspective view of the battery pack 1 as an example, and FIG. 13 is an exploded view of the battery pack shown in FIG. 12 . Referring to FIGS. 12 and 13 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 . Multiple battery modules 4 can be arranged in the battery box in any manner.

Electrical device

A fifth aspect of the present application provides an electric device, which includes the lithium-ion battery described in the second aspect of the present application, or the battery module described in the third aspect of the present application, or the battery pack described in the fourth aspect of the present application. The lithium ion battery, or the battery module, or the battery pack can be used as a power source of the electric device or an energy storage unit of the electric device. The electric device can be, but not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

The electric device can select a lithium-ion battery, a battery module or a battery pack according to its usage requirements.

Fig. 14 shows a schematic diagram of an electrical device according to a specific embodiment of the present application. The electric device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the electric device for the lithium-ion battery, a battery pack or battery module can be used.

As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like. The electrical device is usually required to be light and thin, and the lithium-ion battery of the present application can be used as a power source.

Those skilled in the art can understand that: in the above-mentioned different embodiments of the application, various limitations or optional ranges for the selection of components in the electrochemically active material, the content of the components and the physical and chemical performance parameters of the material can be combined arbitrarily. Various embodiments obtained by combination are still within the scope of this application, and are regarded as a part of the disclosure content of this specification.

Unless otherwise specified, various parameters involved in this specification have common meanings known in the art and can be measured by methods known in the art. For example, it can be tested according to the methods given in the examples of this application. In addition, the optional ranges and options of various parameters given in various optional embodiments can be combined arbitrarily, and all combinations thus obtained are considered to be within the scope of the disclosure of the present application.

The advantages of the present application are further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application.

Preparation of separator

1. Take a 7 μm base film commonly used in the field, and apply a first coating on its surface by a conventional method, and the thickness of the first coating is also conventionally selected, for example, 2 μm;

2. Mix ceramic fiber, polyvinylidene fluoride, styrene-butadiene rubber (SBR), and water in a mass ratio of 40:1:9:50 to obtain ceramic fiber slurry;

3. Mix and disperse the polymer gel, water and polyvinylidene fluoride according to the mass ratio of 35:60:5 to obtain the polymer gel slurry;

4. Apply the ceramic fiber on the surface of the first coating by gravure coating, and then dry it in an oven at 40°C to 50°C;

5. The polymer gel is coated on the surface of the ceramic fiber by means of spin spraying, and then dried in an oven at 50° C. to 60° C. to finally obtain the isolation film described in this application.

Preparation of lithium-ion batteries

1. Preparation of positive electrode sheet

The positive electrode active material LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523), the conductive agent carbon black (Super P) and the binder polyvinylidene fluoride (PVDF) were mixed in an appropriate amount of solvent N-formaldehyde at a mass ratio of 96.2:2.7:1.1. NMP was mixed uniformly to obtain a positive electrode slurry, which was coated on an aluminum foil of a positive electrode current collector, and the positive electrode sheet was obtained through drying, cold pressing, slitting, cutting and other processes.

2. Preparation of Negative Electrode Piece

Negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose sodium (CMC-Na) are mixed in appropriate amount according to mass ratio 96.4:0.7:1.8:1.1 The solvent is mixed evenly in deionized water to obtain negative electrode slurry, and the negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through drying, cold pressing, slitting, cutting and other processes.

3. Isolation film

As the isolation film, the isolation films prepared in the examples and comparative examples of the present application were used.

4. Preparation of Electrolyte

Mix ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a mass ratio of 30:70 to obtain an organic solvent, dissolve the fully dried electrolyte salt LiPF ₆ in the above mixed solvent, and the concentration of the electrolyte salt is 1.0 mol/L, the electrolyte solution was obtained after mixing evenly.

5. Preparation of lithium-ion batteries

Stack the positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is between the positive and negative electrode sheets to play the role of isolation, and then wind the electrode assembly; put the electrode assembly in the outer packaging, put The electrolyte solution prepared above is injected into the dried lithium-ion battery, and the secondary battery is obtained through processes such as vacuum packaging, standing still, formation, and shaping.

The separators and lithium ion batteries of Examples 1-22 and Comparative Examples 1-12 were prepared according to the above method.

Battery performance test

1. 1500 cycles capacity and capacity retention:

Cycle performance test: 25°C, 1C/1C, 1500 cycles.

2. Cell lithium analysis:

The battery that has completed the test is disassembled to observe the situation of lithium precipitation at the interface. According to the situation of lithium separation at the corner, the degree of lithium separation is divided, so as to evaluate the improvement effect of the separator described in this application on the lithium separation at the corner of the cell. The division is based on the percentage (A) of the corner area where lithium is deposited in the corner area.

According to the situation of lithium analysis, the degree of lithium analysis is divided into the following table (degree of lithium analysis: I < II < III < IV).

Table 1 Classification table of lithium analysis degree

析锂面积占比Lithium analysis area ratio	析锂程度划分Lithium analysis degree division
A＜0.3％A<0.3%	ⅠI
0.3％≤A＜1％0.3%≤A<1%	ⅡII
1％≤A≤3％1%≤A≤3%	ⅢIII
A≥3％A≥3%	ⅣIV

Parameters and detection results of embodiment and comparative example

The parameters and performance testing data of Examples 1-30 and Comparative Examples 1-4 are shown in Table 2.

Table 2 embodiment and the parameter of comparative example and performance detection data

Examples 1-6 show the effect of the thickness of the second coating on the technical effect. The thickness of the second coating can be 4 μm˜6 μm; optionally, the thickness of the second coating is 5 μm˜5.5 μm. When the thickness of the second coating exceeds 6 μm, the energy density of the battery will be low, and the battery impedance will increase; and when the thickness of the second coating layer is less than 4 μm, the "fluff" structure will be less elastic and will not work well. liquid absorption effect.

Examples 3, 7-10 show examples where the third coating comprises different kinds of polymer gels. Applying polyimide, polyethylene terephthalate, polystyrene, polyacrylonitrile, polymethyl acrylate and other polymer gels to the third coating can achieve better technical effects, The capacity and capacity retention rate of the battery after 1500 cycles are at a relatively high level, and lithium precipitation is not easy to occur. Among them, polyimide not only has good mechanical properties and heat resistance, but also has good electrolyte wettability, which can make the separator maintain a strong structural stability and have a high electrolyte retention capacity, which is a relatively good choice.

Examples 3, 11-15 show the influence of the thickness of the third coating on the technical effect. The thickness of the third coating may be 3 μm˜5 μm, optionally, the thickness of the third coating may be 4 μm˜4.5 μm. When the thickness of the third coating exceeds 5 μm, the energy density of the battery may decrease, and the resistance of the electrolyte to pass through the coating increases, and the electrolyte cannot wet the entire separator well. However, when the thickness of the third coating layer is less than 3 μm, the liquid retention capacity of the gel will be affected, and a better liquid retention effect cannot be achieved.

Example 3, 16-20, shows the effect of the particle size of the polymer gel particles in the third coating on the technical effect. The particle diameter of the polymer gel particles in the third coating can be 100nm-1000nm; optionally, the particle diameter of the polymer gel particles in the third coating is 300nm-500nm. The particle size of the polymer gel particles is less than 100nm, which will increase the resistance of the isolation membrane, and it will be difficult for lithium ions to pass through the isolation membrane, and the transmission speed will be reduced; while the particle size of the polymer gel particles is greater than 1000nm, then It will reduce the adsorption capacity of the separator to the electrolyte, which will have a certain adverse effect on the liquid retention effect.

Examples 3, 21 show the effect of hollow/solid gel particles on technical performance. When the polymer gel particles are hollow particles, the swelling effect of the polymer gel layer after absorbing the electrolyte is more significant, which can more effectively improve the electrolyte shortage caused by the difficulty of keeping the separator in liquid.

Examples 3, 22-26 show the influence of the ratio of the total area of the second coating to the corner area of the isolation film on the technical effect. The total area of the setting area of the second coating can account for 88% to 95% of the area of the corner area of the isolation film. Optionally, the total area of multiple second coatings can account for the area of the corner area of the isolation film. 90% to 92% of that. When the total area of the second coating is greater than 95% of the corner area of the separator, the resistance of lithium ions passing through the separator increases, the transmission rate decreases, and the effect of the electrolyte infiltrating the separator is not optimal. The impedance of the lithium battery will also increase; when the total area of the second coating accounts for less than 88% of the corner area of the separator, the ceramic fiber "fluff" structure is less, and the liquid absorption capacity of the separator in the corner area cannot be significantly At the same time, the lateral force generated by the swelling of the polymer gel after absorbing the electrolyte is small, and the liquid retention capacity of the isolation film in the corner area becomes poor.

Embodiments 3 and 27 show the influence of the distribution of the added second coating and third coating on the technical effect. A plurality of second coatings and third coatings distributed at intervals can more effectively solve the problem of insufficient electrolyte or uneven distribution, while controlling the weight and cost of the battery cell and increasing the energy density of the battery.

Examples 28-30 show some other different types of ceramic fibers and polymer gels as the materials of the second coating and the third coating, which are applied to the examples of the implementation of the application, and can realize the separation film of the application technical effect.

The surface of the corner area of the isolation film of Comparative Example 1 is only provided with the first coating; the surface of the corner area of the isolation film of Comparative Example 2 is only provided with the first coating and the second coating; the surface of the corner area of the isolation film of Comparative Example 3 is only provided with There is a first coating and a third coating; the difference between Comparative Example 4 and Example 3 is that the positions of the second coating and the third coating are exchanged. The cycle performance and capacity retention rate of Comparative Examples 1-4 are obviously insufficient compared with the examples, and the situation of lithium precipitation is aggravated. From the comparison of the data of the comparative example and the embodiment, it can be seen that the separator provided by the application can effectively improve the poor infiltration of the battery cell caused by insufficient or uneven distribution of electrolyte in the corner area, reduce the risk of local lithium deposition in the battery cell, and improve the energy of the battery. Density, prolong the cycle life of the battery.

According to the disclosure and teaching of the above specification, those skilled in the art may also make changes and modifications to the above implementation manners. Therefore, the present application is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present application should also fall within the protection scope of the claims of the present application. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present application.

Claims

A barrier film comprising:

Porous substrate;

a first coating, the first coating is disposed on at least one surface of the porous substrate, the first coating includes inorganic particles and a binder;

a second coating, the second coating is disposed on at least a portion of the surface of the first coating, and the second coating includes ceramic fibers;

A third coating, the third coating is disposed on at least a part of the surface of the second coating, and the third coating includes polymer gel.
The separator according to claim 1, wherein,

The setting area of the second coating is one or more, and the plurality of second coatings are distributed on at least a part of the surface of the first coating at intervals; and/or,

There are one or more third coating areas, and the multiple third coatings are distributed on at least a part of the surface of the second coating at intervals.
The separator according to claim 1 or 2, wherein the ceramic fiber is selected from alumina ceramic fiber, silicon oxide ceramic fiber, silicon nitride ceramic fiber, barium titanate ceramic fiber, titanium oxide ceramic fiber, magnesium oxide ceramic fiber at least one of fibers.
The separator according to any one of claims 1-3, wherein the thickness of the second coating is 4 μm˜6 μm, optionally, the thickness of the second coating is 5 μm˜5.5 μm.
The separator according to any one of claims 1-4, wherein the polymer gel is selected from at least one of the following types of polymer gels: polyimide, polyethylene terephthalate Glycol ester, polystyrene, polyacrylonitrile, polymethylacrylate, polyether and fluoropolymer;

Optionally, the polymer gel is selected from at least one of the following types of polymer gels: polyimide, polyethylene terephthalate and polystyrene.
The separator according to any one of claims 1-5, wherein the thickness of the third coating is 3 μm˜5 μm, optionally, the thickness of the third coating is 4 μm˜4.5 μm.
The isolation film according to any one of claims 1-6, wherein the particle size of the polymer gel in the third coating is 100 nm to 1000 nm, and optionally, in the third coating The particle size of the polymer gel is 300nm-500nm.
The separator according to any one of claims 1-7, wherein the polymer gel particles in the third coating layer are solid particles or hollow particles.
The separator according to any one of claims 1-8, wherein the inorganic particles in the first coating include at least one of the following inorganic particles: silicon oxide, aluminum oxide, boehmite, barium sulfate , calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide;

Optionally, the binder in the first coating includes at least one of the following binders: styrene, acrylate, vinyl acetate, fatty acid vinyl ester, epoxy resin, linear polyester, polylidene fluoride Vinyl, polystyrene, polysulfide, polyacrylic acid, polyacrylate, polyurethane, polyisobutylene, polyvinyl alcohol, polyimide, polyacrylonitrile, polyethylene oxide, polyvinylpyrrolidone, styrene-butadiene rubber, and gelatin.
A lithium ion battery comprising:

Positive pole piece, negative pole piece, separator between positive pole piece and negative pole piece, electrolyte,

Wherein, the isolation film is the isolation film according to any one of claims 1-9.
The lithium ion battery according to claim 10, comprising a wound electrode assembly, the second coating is at least provided on at least a part of the surface of the first coating in the corner area of the separator.
The lithium-ion battery according to claim 11, wherein a plurality of the second coatings are arranged at intervals on part of the surface of the first coating,

The total area of the plurality of second coatings accounts for 88% to 95% of the area of the corner area of the isolation film; optionally, the total area of the plurality of second coatings accounts for 88% to 95% of the area of the corner area of the isolation film. 90% to 92%.
A battery module, comprising the lithium ion battery according to any one of claims 10-12.
A battery pack, comprising the lithium ion battery according to any one of claims 10-12 or the battery module according to claim 13.
An electrical device, comprising the lithium ion battery according to any one of claims 10-12, or the battery module according to claim 13, or the battery pack according to claim 14, the lithium The ion battery or the battery module or the battery pack is used as a power source of the electric device or an energy storage unit of the electric device.