A battery, a battery module, a battery pack, and an electrical device

Abstract

The present application provides a battery, a battery module, a battery pack and an electrical device. The battery includes a positive electrode, a separator and a negative electrode. The separator includes a base film, a first coating provided on a first surface of the base film, and a second coating provided on a second surface of the base film. Wherein, the first coating includes a first polar substance, and there is a hydrogen bond between the first polar substance and the binder for the positive electrode; there is a hydrogen bond between the second polar substance and the binder for the negative electrode and / or the negative electrode active component. The present application can enhance the adhesion between the separator and the positive and negative electrodes through hydrogen bonds, reduce the cyclic expansion rate of the bare battery cell, and improve the high-rate discharge performance and cyclic performance of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and particularly to a battery, a battery module, a battery pack, and an electric device. Background Art

[0002] In recent years, with the increasingly wide application range of lithium-ion batteries, lithium-ion batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, as well as in multiple fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the great development of lithium-ion batteries, higher requirements are also put forward for their energy density, group margin, cycle / rate performance, and safety performance.

[0003] In addition, the separator is one of the components of the battery. The separator can effectively prevent the positive and negative electrodes from contacting each other and causing an internal short circuit. However, there is no hydrogen bond connection between the traditional separator and the positive or negative electrode. The separator and the positive or negative electrode are only in physical contact, which is likely to cause the bare battery cell to expand and is not conducive to the shaping of the battery cell. Therefore, the existing batteries still need to be improved. Summary of the Invention

[0004] The present application is made in view of the above problems, and its purpose is to provide a battery to further improve the comprehensive performance of the battery (high-rate discharge performance, cycle performance).

[0005] To achieve the above object, the present application provides a battery, a battery module, a battery pack, and an electric device.

[0006] In a first aspect of the present application, a battery is provided. The battery includes a positive electrode, a separator, and a negative electrode. The separator includes a base film, a first coating provided on a first surface of the base film, and a second coating provided on a second surface of the base film. Wherein, the first coating includes a first polar substance, and the first polar substance includes one or more of polyolefin amide, polyolefin imine, polyoxyalkylene, polyurethane, and polyurea substances. The first polar substance has a hydrogen bond with the positive electrode binder of the positive electrode; the second coating includes a second polar substance, and the second polar substance includes one or more of polyolefin amide, polyolefin imine, polyoxyalkylene, polyurethane, and polyurea substances. The second polar substance has a hydrogen bond with the negative electrode binder and / or the negative electrode active component of the negative electrode.

[0007] In this application, a hydrogen bond can be represented by X-H-Y, where X and Y can be independently selected from one of N, O, and F. It is easy to form a hydrogen bond between the positive electrode and the first polar substance (containing -YH) using a binder (containing -X); similarly, it is also easy to form a hydrogen bond between the negative electrode and the second polar substance (containing -YH) using a binder and / or a negative electrode active component (containing -HX). Therefore, in this application, the adhesion force between the separator and the positive and negative electrodes is enhanced through hydrogen bonds, thereby reducing the expansion of the bare battery cell during processing and the cyclic expansion rate after several cycles, improving the high-rate discharge capacity of the battery, shortening the lithium-ion transmission path, and enhancing the cycle performance of the battery.

[0008] In any embodiment, the peeling force between the first coating and the positive electrode is not less than 0.075 N, and can be optionally 0.075 N to 0.125 N; the peeling force between the second coating and the negative electrode is not less than 0.075 N, and can be optionally 0.075 N to 0.15 N. Thus, the magnitude of the adhesion force between the separator and the positive and negative electrodes can be characterized by the peeling force. When the peeling force is within a reasonable range, the bare battery cell is not easily expanded during processing and cycling, the separator is in close contact with the positive and negative electrodes, and the battery has strong high-rate discharge ability.

[0009] In any embodiment, the ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is (80 - 100)∶1; the ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is (32 - 50)∶1. Thus, by limiting and the values within a reasonable range, the optimal ratio of battery performance and cost can be balanced, and the high-rate discharge capacity and cycle performance of the battery can be improved.

[0010] In any embodiment, the ratio of the mass content w1 of the first polar substance in the first coating to the mass content w2 of the second polar substance in the second coating is 1∶(1 - 1.3). Thus, by limiting within a reasonable range, the tensions on both sides of the separator can be made consistent to prevent the risk of internal short circuit of the battery caused by inconsistent tensions, and the cycle performance of the battery can be improved.

[0011] In any embodiment, the mass content w1 of the first polar substance in the first coating is 80% to 90%, and the mass content m1 of the positive electrode binder in the film layer of the positive electrode is 0.9% to 1.2%. The mass content w2 of the second polar substance in the second coating is 80% to 90%, and the mass content m2 of the negative electrode binder in the film layer of the negative electrode is 2% to 3%. Thus, by limiting the above parameters within a reasonable range, the battery can have both good high-rate discharge performance and cycling performance.

[0012] In any embodiment, the first polar substance includes polyethylene oxide and polyacrylamide; wherein, the mass ratio C1 of polyethylene oxide to polyacrylamide is (2 to 6):1. The second polar substance includes polyethyleneimine and polyethylene oxide; wherein, the mass ratio C2 of polyethyleneimine to polyethylene oxide is (2 to 6):1. Thus, in the first polar substance, mixing a small amount of polyacrylamide long-chain molecules in polyethylene oxide can improve the cycling stability of the battery. In the second polar substance, adding a small amount of low-cost polyethylene oxide to the strongly polar polyethyleneimine will also form hydrogen bonds between them, further enhancing the adhesion force between the second polar substances, thereby further improving the high-rate discharge performance and cycling performance of the battery.

[0013] In any embodiment, the first coating includes a first reinforcing agent, and the mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating is (5 to 9):1; the second coating includes a second reinforcing agent, and the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating is (5 to 9):1. Thus, by respectively limiting the ratios of the first polar substance to the first reinforcing agent and the second polar substance to the second reinforcing agent on the separator within a reasonable range, hydrogen bonds can be formed between the first reinforcing agent and the first polar substance and between the second reinforcing agent and the second polar substance respectively, making the bare cell more tightly compacted during the processing, having a low cycling expansion rate after multiple cycles of charge and discharge, and improving the high-rate discharge performance and cycling performance of the battery.

[0014] In any embodiment, the mass content k1 of the first reinforcing agent in the first coating is not higher than the mass content k2 of the second reinforcing agent in the second coating. Thus, by limiting within a reasonable range, the tension on both sides of the separator can be kept consistent to prevent internal short circuit of the battery caused by inconsistent tension, and the cycling performance of the battery can be improved.

[0015] In any embodiment, the ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating is (0.8 - 1):1. Thus, by limiting the ratio of the mass contents of the reinforcing agents in the first coating and the second coating within a reasonable range, while improving the stability of the separator membrane, the influence on the lithium-ion transport kinetics during the charge and discharge process is relatively small, and the cycle performance and high-rate discharge performance of the battery can be improved.

[0016] In any embodiment, the first reinforcing agent or the second reinforcing agent includes one or more of polyvinylidene fluoride and sodium alginate. The binder for the positive electrode includes polyvinylidene fluoride, and the binder for the negative electrode includes one or more of styrene-butadiene rubber and sodium alginate.

[0017] In any embodiment, the negative active component includes a silicon-carbon mixture. In the silicon-carbon mixture, the particle size of silicon is 0.1 - 0.5 microns, the carbon is a mixed carbon of artificial graphite and natural graphite, and the content of the silicon-carbon mixture in the negative electrode film layer is 95% - 97%. Thus, by limiting the particle size of silicon within a reasonable range, the cycle performance of the battery can be better, and by limiting the content of the silicon-carbon mixture in the negative electrode film layer within a reasonable range, the high-rate charge and discharge performance of the battery can be achieved.

[0018] In any embodiment, the mass ratio of the first coating to the second coating is 1:(1 - 1.5). Thus, by limiting the coating amounts of the first coating and the second coating within a reasonable range, the tension of the separator membrane can be made consistent to prevent the risk of short circuit due to inconsistent tension, and the cycle performance of the battery can be improved.

[0019] In any embodiment, the first coating is prepared from a first coating slurry, and the first coating slurry includes the first polar substance, the first reinforcing agent, and a first solvent; wherein, the viscosity of the first coating slurry is 8000 mPa·s - 12000 mPa·s. The second coating is prepared from a second coating slurry, and the second coating slurry includes the second polar substance, the second reinforcing agent, and a second solvent; wherein, the viscosity of the second coating slurry is 5000 mPa·s - 20000 mPa·s. Thus, by limiting the first coating slurry and the second coating slurry within appropriate viscosity ranges respectively, the coating process of the first coating slurry or the second coating slurry on the base film can be optimized, the coating effect can be improved, and the consistency of the battery cells can be ensured, and the cycle performance and high-rate discharge performance of the battery can be improved.

[0020] In any embodiment, the positive electrode includes a positive electrode material LiNi x Co y Mn zO2, where x + y + z = 1, and x = 0.5 to 0.9; preferably, x = 0.5 to 0.7, or x = 0.8 to 0.9. The separator of the present application particularly has a significant effect on improving the cycle expansion rate of a bare battery cell containing a high-nickel cathode material. In particular, the separator of the present application has a more significant effect on improving the cycle expansion rate of a bare battery cell with a nickel content x = 0.5 to 0.7 in the cathode material. Therefore, it has a more significant effect on improving the high-rate discharge performance and cycle performance of high-nickel batteries.

[0021] The second aspect of the present application provides a battery module, including the battery of the first aspect of the present application.

[0022] The third aspect of the present application provides a battery pack, including the battery module of the second aspect of the present application.

[0023] The fourth aspect of the present application provides an electrical device, including at least one selected from the battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] There is a hydrogen bond between the first polar substance and the binder for the positive electrode in the present application, which can enhance the adhesion between the separator and the positive electrode. There is a hydrogen bond between the second polar substance and the binder for the negative electrode and / or the negative electrode active material, which can increase the adhesion between the separator and the negative electrode. There is a hydrogen bond between the first polar substance and the first reinforcing agent, which can enhance the adhesion between the first coating layer of the separator and the base film. There is a hydrogen bond between the second polar substance and the second reinforcing agent, which can enhance the adhesion between the second coating layer of the separator and the base film. Thus, the present application can improve the expansion of the bare battery cell during the processing and reduce the cycle expansion rate of the bare battery cell during the cycle, which is beneficial to the shaping of the bare battery cell, making the bare battery cell more compact and improving the high-rate discharge performance and cycle performance of the battery. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the reaction principle of the formation of hydrogen bonds between the polar substances on the separator and the positive and negative electrodes.

[0027] Figure 2 It is a schematic diagram of infrared characterization of Examples 1-4 and Comparative Examples 1-3 of the present application.

[0028] Figure 3 It is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0029] Figure 4 is Figure 3 The exploded view of the secondary battery according to an embodiment of the present application shown.

[0030] Figure 5It is a schematic diagram of a battery module according to an embodiment of the present application.

[0031] Figure 6 It is a schematic diagram of a battery pack according to an embodiment of the present application.

[0032] Figure 7 It is Figure 6 An exploded view of the battery pack according to an embodiment of the present application shown.

[0033] Figure 8 It is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0034] Explanation of reference numerals:

[0035] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed embodiments

[0036] Hereinafter, embodiments of the battery, battery module, battery pack, and electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0037] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are already listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0040] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0041] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0042] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0043] After long-term experience in preparing lithium-ion batteries, the inventors of this application found that: on the one hand, during the processing, the positive electrode, the separator, and the negative electrode are wound and compacted into a bare cell. Although the bare cell has been compacted during the processing, after a period of time, the bare cell itself will have a rebound tendency, which will cause the bare cell to expand. On the other hand, during the cycle process, the negative electrode active material itself, such as the graphite lattice, becomes larger, and the interlayer spacing between graphite sheets becomes larger, which will cause the thickness of the bare cell to become thicker, thereby causing the bare cell to expand.

[0044] Based on the above two reasons for the expansion of bare cells, bubbles will be generated after the expansion of bare cells, which will destroy the interface stability of the internal structure of the cell, causing the electrolyte to squeeze to the edge of the electrode, causing lithium precipitation problems. In addition, after the bare cell expands, the group margin of the cell becomes smaller, which will squeeze the aluminum shell and deform, resulting in a decrease in the cycle capacity of the battery, faster cycle decay, and reduced high-rate discharge performance.

[0045] Through a large number of experiments and studies, the inventor found that in order to suppress the influence of the swelling of the bare battery cell on the battery performance, the following ideas can be adopted: On the one hand, a polar substance can be coated on the surface of the base film of the separator. By forming hydrogen bonds between the polar substance and the binder for the positive electrode, the binder for the negative electrode or the negative active material, the adhesion between the separator and the positive electrode and the negative electrode can be increased. On the other hand, some reinforcing agents can be mixed into the polar substance to improve the adhesion of the separator. Therefore, starting from the synergistic effect of the two aspects, through the comprehensive modification of the separator and fully synergistically utilizing the above two aspects, a battery capable of significantly improving the adhesion between the separator and the positive electrode and the negative electrode is designed, and the swelling during the processing of the bare battery cell and the cycle swelling rate during the cycle use are reduced, and the high-rate discharge performance and cycle performance of the battery are greatly improved.

[0046] Battery

[0047] In one embodiment of the present application, the present application provides a battery.

[0048] The battery includes a positive electrode, a separator, a negative electrode and an electrolyte. The separator includes a base film, a first coating provided on the first surface of the base film, and a second coating provided on the second surface of the base film. Among them,

[0049] The first coating includes a first polar substance, and the first polar substance includes one or more of polyolefin amide, polyolefin imine, polyoxyolefin, polyurethane, polyurea substances. There is a hydrogen bond between the first polar substance and the binder for the positive electrode of the positive electrode;

[0050] The second coating includes a second polar substance, and the second polar substance includes one or more of polyolefin amide, polyolefin imine, polyoxyolefin, polyurethane, polyurea substances. There is a hydrogen bond between the second polar substance and the binder for the negative electrode and / or the negative active component of the negative electrode.

[0051] The first coating on the separator of the present application is a structure with a predetermined thickness composed of the first polar substance. The first coating can be firmly bonded to the binder for the positive electrode through the first polar substance, thereby preventing the swelling during the processing of the bare battery cell and the cycle swelling rate during the cycle use.

[0052] Furthermore, the first polar substances such as polyolefin amides, polyolefin imines, polyalkylene oxides, polyurethanes, polyureas, etc. all include polar functional groups. On the one hand, hydrogen bonds can be formed between the polar functional groups and the binder for the positive electrode, improving the adhesion between the first coating and the positive electrode; on the other hand, the first polar substance itself is a binder, which can also improve the adhesion between the first coating and the positive electrode. Therefore, through the two aspects of the polar functional groups in the aforementioned first polar substance and the fact that the first polar substance itself is a binder, the first coating is more firmly bonded to the positive electrode.

[0053] Specifically, the first polar substance of the present application has a YH group, and Y is selected from one of N, O, and F. The binder for the positive electrode has an X group, and X is selected from one of N, O, and F. The binder for the positive electrode with the X group can form a hydrogen bond X-H-Y with the YH group in the first polar substance of the present application, thereby making the first coating of the present application more firmly bonded to the positive electrode of the present application. More specifically, as Figure 1 taking the binder for the positive electrode containing F as an example, since the binder for the positive electrode contains F, the binder for the positive electrode and the first polar substance (-OH) are likely to form a hydrogen bond.

[0054] The second coating of the separator membrane of the present application is a structure including a second polar substance with a predetermined thickness. The second coating can be firmly bonded to the binder for the negative electrode and / or the negative electrode active material through the second polar substance, thereby preventing expansion during the processing of the bare battery cell and the cycle expansion rate during the cycle use.

[0055] Furthermore, the second polar substances such as polyolefin amides, polyolefin imines, polyalkylene oxides, polyurethanes, polyureas, etc. all include polar functional groups. On the one hand, hydrogen bonds can be formed between the polar functional groups and the binder for the negative electrode and / or the negative electrode active material, improving the adhesion between the first coating and the negative electrode; on the other hand, the second polar substance itself is a binder, which can also improve the adhesion between the second coating and the negative electrode. Therefore, through the two aspects of the polar functional groups in the aforementioned second polar substance and the fact that the second polar substance itself is a binder, the second coating is more firmly bonded to the negative electrode.

[0056] Specifically, the second polar substance of the present application has a YH group, and Y is selected from one of N, O, and F. The binder for the negative electrode and / or the negative electrode active component has a -HX group, and X is selected from one of N, O, and F; the binder for the negative electrode and / or the negative electrode active component with the X group can form a hydrogen bond X-H-Y with the YH group in the second polar substance of the present application, thereby making the second coating of the present application more firmly bonded to the negative electrode of the present application. More specifically, as Figure 1, the negative electrode contains -OH / -COOH, and more specifically, the negative electrode active material contains -OH and the negative electrode binder contains -COOH. Therefore, it is also easy for the negative electrode active material or the negative electrode binder to form hydrogen bonds with the second polar substance (containing -NH2).

[0057] In this application, in the first coating and the second coating of the separator, the adhesion between the separator and the positive electrode and the negative electrode can be enhanced through hydrogen bonds respectively. Furthermore, the swelling of the bare battery cell during processing and the cyclic swelling rate during cyclic use can be reduced, which is beneficial to the shaping of the bare battery cell, making the bare battery cell tighter. As a result, the transmission path of lithium ions is shortened, enabling lithium ions to be transmitted faster, thereby improving the high-rate discharge performance and cyclic performance of the battery.

[0058] In some embodiments, the peel strength between the first coating and the positive electrode is not less than 0.075 N, and can be optionally 0.075 N to 0.125 N. The peel strength between the second coating and the negative electrode is not less than 0.075 N, and can be optionally 0.075 N to 0.15 N.

[0059] The peel strength generally refers to the maximum force required to peel a unit width of the materials adhered together from the contact surface. The peel strength can reflect the bonding strength of the materials. For the detailed test method of the peel strength, refer to the test method part of the examples. Specifically in this application, from a macroscopic perspective, the magnitude of the peel strength can be used to reflect the existence and strength of the hydrogen bonds between the separator and the positive electrode and the negative electrode, and further to reflect the magnitude of the adhesion between the separator and the positive and negative electrodes.

[0060] After a large number of experimental verifications, it is known to those skilled in the art that for a separator (if the first coating does not contain the first polar substance), the magnitude of the peel strength between it and the positive electrode is usually less than 0.035 N. At this time, the adhesion between the separator and the positive electrode is small, and there are no or very few hydrogen bonds. In this application, through the peel strength test between the surface of the positive electrode and the separator coating, it is unexpectedly found that by adding the first polar substance to the first coating, the peel strength between the first coating and the positive electrode is not less than 0.075 N. Therefore, it can be further proved that there are hydrogen bonds between the first polar substance and the binder of the positive electrode. In addition, it is known to those skilled in the art that for a separator (if the second coating does not contain the second polar substance), the magnitude of the peel strength between it and the negative electrode is usually also less than 0.035 N. At this time, the adhesion between the separator and the negative electrode is small, and there are no or very few hydrogen bonds. In this application, through the peel strength test between the surface of the negative electrode and the separator coating, it is unexpectedly found that by adding the second polar substance to the second coating, the peel strength between the second coating and the negative electrode is not less than 0.075 N, which can further prove that there are hydrogen bonds between the second polar substance and the binder of the negative electrode or the negative electrode active component.

[0061] In this application, when the peel strength between the first coating and the positive electrode or the peel strength between the second coating and the negative electrode is not less than 0.075 N, during the processing of the bare battery cell and during the recycling process, the bare battery cell is not likely to expand, the separator is in closer contact with the positive and negative electrodes, the transmission path of lithium ions is shortened, enabling lithium ions to be transmitted faster, thereby improving the high-rate discharge performance and cycling performance of the battery.

[0062] In some embodiments, the ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode can be (80 - 100)∶1.

[0063] In this application, it can be reflected by the relative content relationship between the first polar substance in the separator and the binder for the positive electrode.

[0064] Furthermore, when is less than 80∶1, on the one hand, it may be because the content of the first polar substance in the first coating is too small, resulting in fewer hydrogen bonds formed between the first polar substance and the binder for the positive electrode. Coupled with the insufficient cohesive force of the first polar substance itself, the adhesion between the first coating and the binder for the positive electrode is not firm, thus not being able to well solve the expansion problem during the processing and cycling of the bare battery cell. On the other hand, it may be because the content of the binder for the positive electrode is too much, which will block the electron transmission channel. In addition, usually the binder for the positive electrode is an inert insulator with poor conductivity and large polarization, affecting the cycling performance and high-rate discharge performance of the battery.

[0065] Furthermore, when is greater than 100∶1, on the one hand, it may be because the content of the first polar substance is too much. Firstly, it is easy to block the base film, thereby reducing the air permeability and affecting the kinetic performance of the separator. Secondly, in the later stage of cycling, the first polar substance is likely to fall off from the base film, resulting in poor cycling performance and poor high-rate discharge performance. On the other hand, it may be because the content of the binder for the positive electrode is too little, resulting in insufficient viscosity and small adhesion between the positive electrode and the first coating.

[0066] Therefore, when the value is within a reasonable range, it can reduce the expansion of the bare battery cell during the processing and recycling process, and improve the high-rate discharge performance and cycling performance of the battery.

[0067] Optionally, the ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 80∶1, 87∶1, 93∶1, 97∶1, or 100∶1, etc. It can be any of the above point values or a range value formed between any point values.

[0068] The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode can be (32 - 50):1.

[0069] In this application, it can be achieved through reflecting the relative content relationship between the second polar substance in the separator and the binder in the negative electrode.

[0070] Furthermore, when is less than 32:1, on the one hand, it may be due to too little content of the second polar substance in the second coating, resulting in fewer hydrogen bonds formed between the second polar substance and the binder for the negative electrode. Coupled with the insufficient binding force of the second polar substance itself, the binding force between the second coating and the binder for the negative electrode cannot be firm, thus not being able to well solve the expansion problem during the processing of the bare battery cell and the cycling process. On the other hand, it may be due to too much content of the binder for the negative electrode, which will block the electron transport channels. In addition, usually the binder for the negative electrode is an inert insulator with poor conductivity, large polarization, affecting the cycling performance and high-rate discharge performance of the battery.

[0071] Furthermore, when is greater than 50:1, on the one hand, it may be due to too much content of the second polar substance, which is likely to fall off easily in the middle and late stages of cycling, resulting in poor cycling performance and poor high-rate discharge performance. On the other hand, it may be due to too little content of the binder for the negative electrode, resulting in insufficient viscosity and small binding force between the negative electrode and the second coating.

[0072] Therefore, When the value is within a reasonable range, it can reduce the expansion of the bare battery cell during the processing of the bare battery cell and the cycling process, and improve the high-rate discharge performance and cycling performance of the battery.

[0073] Optionally, the ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode can be optionally 32:1, 36:1, 40:1, 45:1, or 50:1, etc. It can be any of the above point values or a range value formed between any point values.

[0074] In some embodiments, the ratio of the mass content w1 of the first polar substance in the first coating to the mass content w2 of the second polar substance in the second coating can be 1:(1 - 1.3).

[0075] In this application, it can be achieved through Reflects the content of the polar substances coated on the two surfaces of the separator membrane.

[0076] In this application, by limiting within a reasonable range, the tension of the separator membrane can be made consistent and more stable. On the one hand, it can prevent the risk of short circuit due to inconsistent tension. On the other hand, it can improve the cycle performance and high-rate discharge performance of the battery. If less than 1:1 or greater than 1:1.3, it will cause the surface tensions of the two surfaces of the separator membrane to be inconsistent, the separator membrane will wrinkle, bubbles will appear on the surface, the electrolyte infiltration will be poor, lithium deposition is likely to occur, the cycle performance will deteriorate, the cycle attenuation will become faster, and the high-rate discharge performance will deteriorate.

[0077] Optionally, the ratio of the mass content w1 of the first polar substance in the first coating to the mass content w2 of the second polar substance in the second coating is 1:1, or 1:1.3, etc. It can be any of the above point values or a range value composed of any point values therebetween.

[0078] Generally, the coating amounts of the first polar substance and the second polar substance should not differ too much. Optionally, the coating amounts of both can be basically equal, that is this can ensure that the bearing capacities of the two surfaces of the separator membrane are basically the same, and the cycle performance and high-rate discharge performance of the battery are better.

[0079] In some embodiments, the mass content w1 of the first polar substance in the first coating can be 80% - 90%.

[0080] In this application, the content of the first polar substance in the first coating can be reflected by w1.

[0081] In this application, the first polar substance is the main component in the first coating, which can increase the hydrogen bonds between the first polar substance and the binder used for the positive electrode, and thus make the adhesion between the first coating and the positive electrode better. If the content of the first polar substance in the first coating is less than 80%, fewer hydrogen bonds are generated with the binder used for the positive electrode, so the improvement of the adhesion between the separator membrane and the positive electrode is limited, and the improvement effect on the expansion during the processing of the bare battery cell and the cyclic use process is not obvious; if the content of the first polar substance in the first coating is greater than 90%, it is easy to block the base film, thereby reducing the air permeability and affecting the kinetic performance of the separator membrane.

[0082] Optionally, the mass content w1 of the first polar substance in the first coating can be selected as 80%, 85%, 90%, etc. w1 can be any of the above point values or a range value composed of any point values therebetween.

[0083] In some embodiments, the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode may be 0.9% to 1.2%.

[0084] In the present application, the content of the binder for the positive electrode in the positive electrode film layer can be reflected by m1.

[0085] When m1 is within this range, it can make the positive electrode and the first coating have a strong bonding force, thereby reducing the swelling during the processing or recycling of the bare battery cell, improving the high-rate discharge performance and cycle performance of the battery. Generally, the content of the binder for the positive electrode in the positive electrode sheet cannot be too large. When m1 is greater than 1.2%, the content of the binder for the positive electrode is too much, which will block the electron transport channels. In addition, generally, the binder for the positive electrode is an inert insulator with poor electrical conductivity and large polarization, which affects the cycle performance and high-rate discharge performance of the battery. Generally, the content of the binder for the positive electrode in the positive electrode sheet cannot be too small either. When m1 is less than 0.9%, due to the too small content of the binder for the positive electrode, the viscosity may be insufficient and the bonding force between the positive electrode and the first coating is small.

[0086] Optionally, the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode can be selected as 0.9%, 1%, or 1.2%, etc. m1 can be any of the above point values or the range values composed of any point values.

[0087] Thus, by limiting the above parameters w1 and m1 within a reasonable range, the kinetic performance and the bonding force between the first coating and the positive electrode can be taken into account, obtaining the optimal ratio of the two, and improving the high-rate discharge performance and cycle performance of the battery.

[0088] In some embodiments, the mass content w2 of the second polar substance in the second coating may be 80% to 90%.

[0089] In the present application, the content of the second polar substance in the second coating can be reflected by w2.

[0090] In the present application, the second polar substance is the main component in the second coating, which can increase the hydrogen bond between the second polar substance and the binder for the negative electrode, and further make the bonding force between the second coating and the negative electrode better. If the content of the second polar substance in the second coating is lower than 80%, fewer hydrogen bonds are generated with the binder for the negative electrode, and the improvement of the adhesion between the separator and the negative electrode is limited, and the improvement effect of the swelling of the bare battery cell during the processing and recycling is not obvious; if the content of the second polar substance in the second coating is greater than 90%, it is easy to block the base film, thereby reducing the air permeability and affecting the kinetic performance of the separator.

[0091] Optionally, the mass content w2 of the second polar substance in the second coating may be selected as 80%, 85%, 90%, etc. w2 may be any of the above point values or a range value composed of any point values between them.

[0092] In some embodiments, the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode may be 2% - 3%.

[0093] In the present application, the content of the binder for the positive electrode in the negative electrode film layer can be reflected by m2.

[0094] In the present application, within this range, m2 can enable a strong bonding force between the negative electrode and the second coating, thereby reducing the swelling during the processing of the bare electric core or during the recycling process, and improving the high-rate discharge performance and cycling performance of the battery. Generally, the content of the binder for the negative electrode in the negative electrode sheet cannot be too large. When m1 is greater than 3%, the content of the binder for the negative electrode is too much, which will block the electron transport channel. In addition, generally, the binder for the negative electrode is an inert insulator with poor conductivity and large polarization, which affects the cycling performance and high-rate discharge performance of the battery. Generally, the content of the binder for the negative electrode in the negative electrode sheet cannot be too small either. When m1 is less than 2%, due to too little content of the binder for the negative electrode, the viscosity may not be enough, and the bonding force between the negative electrode and the second coating is small.

[0095] Optionally, the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode may be selected as 2%, 2.6%, 3%, etc. m2 may be any of the above point values or a range value composed of any point values between them.

[0096] Thus, by limiting the above parameters w2 and m2 within a reasonable range, the kinetic performance and the bonding force between the second coating and the negative electrode can be taken into account, achieving the optimal ratio of the two, and improving the high-rate discharge performance and cycling performance of the battery.

[0097] In some embodiments, the first polar substance includes polyethylene oxide and polyacrylamide. Among them, the mass ratio C1 of polyethylene oxide to polyacrylamide may be (2 - 6) : 1.

[0098] Generally, different polar substances can play different functions, so the advantages of each substance can be combined. Specifically in the present application, in the first active substance, polyethylene oxide is a lithium ion conductor, with characteristics such as high conductivity, low activation energy, and the most negative electrode potential, which can accelerate the conduction of lithium ions and needs to be the main component in the first polar substance. Compared with polyethylene oxide (PEO), polyacrylamide has a longer chain length, a larger molecular weight, and good thermal stability. And usually, the side connected to the positive electrode has been oxidized under high voltage. Therefore, if a small amount of long-chain molecules such as polyacrylamide is mixed in polyethylene oxide, especially within the range defined in the present application, the cycling stability and high-rate discharge performance of the battery can be improved.

[0099] Furthermore, if the mass ratio C1 of polyethylene oxide to polyacrylamide is less than 2:1, since polyacrylamide is not a lithium ion conductor, the lithium ion conduction rate will be slow, affecting the cycle performance and high-rate discharge performance of the battery. If the mass ratio C1 of polyethylene oxide to polyacrylamide is greater than 6:1, the content of polyacrylamide is too small, resulting in poor thermal stability.

[0100] Optionally, the mass ratio C1 of polyethylene oxide to polyacrylamide can be selected as 2:1, 3:1, 4.5:1, 5:1, or 6:1, etc. C1 can be any of the above point values or a range value composed of any point values therebetween.

[0101] The second polar substance includes polyethyleneimine and polyethylene oxide. Among them, the mass ratio C2 of polyethyleneimine to polyethylene oxide can be (2-6):1.

[0102] Generally, different polar substances can play different functions, so the advantages of each substance can be combined. Specifically in this application, in the second active substance, both polyethyleneimine and polyethylene oxide are lithium ion conductors, with characteristics such as high conductivity, low activation energy, and the most negative electrode potential, which can accelerate the conduction of lithium ions. In addition, the second active substance is located on the side connected to the negative electrode. Since the negative electrode active substance such as graphite is prone to swelling, a more polar binder such as polyethyleneimine (PEI) needs to be selected. In addition, since polyethylene oxide is cheaper than polyethyleneimine, considering cost factors, a small amount of polyethylene oxide can be added to polyethyleneimine. Especially within the scope defined in this application, while reducing costs, hydrogen bonds will also be formed between the two, further enhancing the adhesive force, reducing the swelling during the processing of the bare battery cell and during the cyclic use, and improving the cycle performance and high-rate discharge performance of the battery.

[0103] If the mass ratio C2 of polyethyleneimine to polyethylene oxide is less than 2:1, since polyethyleneimine has strong polarity, if the content is too small, fewer hydrogen bonds will be formed between the second polar substance and the binder for the negative electrode or the negative electrode active substance, the adhesion of the second coating to the negative electrode will decrease, the swelling of the bare battery cell during the processing of the bare battery cell and during the cyclic use will be reduced, affecting the cycle performance and high-rate discharge performance of the battery. If the mass ratio C2 of polyethyleneimine to polyethylene oxide is greater than 6:1, the cost will increase.

[0104] Optionally, the mass ratio C2 of polyethyleneimine to polyethylene oxide can be selected as 2:1, 3:1, 4.5:1, 5:1, or 6:1, etc. C2 can be any of the above point values or a range value composed of any point values therebetween.

[0105] In some embodiments, among the first polar substance or the second polar substance, the polyamides may be, for example, one or a combination of more than one of polyacrylamide (PAM), nylon-66, nylon-6, etc. The weight-average molecular weight of the polyamides may be 20,000 to 80,000; it may be optionally 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, or 80,000, etc. The weight-average molecular weight of the polyamides may be any of the above point values or a range value composed of any point values therebetween.

[0106] In some embodiments, among the first polar substance or the second polar substance, the polyalkyleneimines may be, for example, one or more of polyethyleneimine (PEI), polyethylenepolyamine, etc. The weight-average molecular weight of the polyimines may be 70,000 to 100,000; it may be optionally 70,000, 80,000, 90,000, or 100,000, etc. The weight-average molecular weight of the polyalkyleneimines may be any of the above point values or a range value composed of any point values therebetween.

[0107] In some embodiments, among the first polar substance or the second polar substance, the polyalkylene oxides may be, for example, polyethylene oxide (PEO), etc. The weight-average molecular weight of the polyalkylene oxides may be 100,000 to 200,000; it may be optionally 100,000, 120,000, 140,000, 160,000, 180,000, or 200,000, etc. The weight-average molecular weight of the polyalkylene oxides may be any of the above point values or a range value composed of any point values therebetween.

[0108] In some embodiments, among the first polar substance or the second polar substance, the polyurethanes may be, for example, a class of polymers containing -NHCOO- in the general formula. More specifically, the polyurethanes may be formed by polymerization of at least one monomer selected from polyisocyanates, toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), polyphenyl polymethylene polyisocyanate (PAPI), or copolymerization of two or more monomers. The polymerization methods include random copolymerization, block copolymerization, etc. The weight-average molecular weight of the polyurethanes may be 1,000 to 10,000; it may be optionally 1,000, 5,000, or 10,000, etc. The weight-average molecular weight of the polyurethanes may be any of the above point values or a range value composed of any point values therebetween.

[0109] In some embodiments, among the first polar substance or the second polar substance, the polyureas may be, for example, a class of polymers containing -NHCONH- in the general formula. More specifically, the polyureas may be one or more of polyureas, urea-formaldehyde resins, etc. The weight-average molecular weight of the polyurea substances may be 5,000 to 50,000; it may be optionally 5,000, 10,000, 20,000, 30,000, 40,000, or 50,000, etc. The weight-average molecular weight of the polyureas may be any of the above point values or a range value composed of any point values therebetween.

[0110] In some embodiments, the first coating includes a first reinforcing agent, and the mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating may be (5-9):1.

[0111] In this application, by to reflect the content relationship between the first reinforcing agent and the first polar substance.

[0112] In this application, since there is a risk that the first polar substance will detach from the base film in the middle or late stage of the battery cycle, therefore, the first reinforcing agent can be used to enhance the adhesion of the first polar substance to the base film. Only when the ratio of the first polar substance to the first reinforcing agent on the separator film is within a reasonable range can the swelling of the bare battery cell during processing and the cycle swelling rate during cyclic use be reduced, and the cycle performance and high-rate discharge performance of the battery be improved. When is greater than 9:1, the content of the first polar substance is too high. On the one hand, it is easy to block the base film, thereby reducing the air permeability and affecting the kinetic performance of the separator film. On the other hand, in the middle and late stages of the cycle, the first polar substance is easy to fall off from the base film, resulting in poor cycle performance and poor high-rate discharge performance. When is less than 5:1, the content of the first polar substance in the first coating is too low, resulting in fewer hydrogen bonds formed between the first polar substance and the binder for the positive electrode. Coupled with the insufficient adhesion of the first polar substance itself, the adhesion between the first coating and the binder for the positive electrode cannot be firm, thus the swelling problem during the processing and cyclic use of the bare battery cell cannot be well solved.

[0113] Furthermore, analyzing the hydrogen bond formation mechanism between the first reinforcing agent and the first polar substance, since the first reinforcing agent (containing F) can easily form a hydrogen bond Y-H-F with the first polar substance (-YH), the first reinforcing agent can make the first polar substance stably exist on the separator film. Thereby, the swelling of the bare battery cell during processing and the cycle swelling rate during cyclic use can be reduced, and the cycle performance and high-rate discharge performance of the battery can be improved.

[0114] Optionally, the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating may be 5:1, 5.3:1, 6:1, 8:1, 9:1, etc. It can be any of the above point values or a range value composed of any point values between them.

[0115] In some embodiments, the second coating includes a second reinforcing agent, and the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating It can be (5 - 9)∶1.

[0116] In the present application, by to reflect the content relationship between the second reinforcing agent and the second polar substance.

[0117] In the present application, since there is a risk that the second polar substance detaches from the base film in the middle or late stage of the battery cycle, therefore, the second reinforcing agent can be used to enhance the adhesion of the second polar substance to the base film. Only when the ratio of the second polar substance to the second reinforcing agent on the separator film is within a reasonable range can the expansion of the bare battery cell during processing and the cycle expansion rate during cyclic use be reduced, and the cycle performance and high-rate discharge performance of the battery be improved. When the content ratio is greater than 9∶1, the content of the second polar substance is relatively excessive, and it is likely to fall off in the middle and late stages of the cycle, resulting in poor cycle performance and poor high-rate discharge performance. When the content ratio is less than 5∶1, the content of the second polar substance in the second coating is too small, resulting in fewer hydrogen bonds formed between the second polar substance and the binder for the negative electrode. Coupled with the insufficient adhesion of the second polar substance itself, the adhesion between the second coating and the binder for the negative electrode cannot be firm, and thus the expansion problem during the processing and cyclic use of the bare battery cell cannot be well solved.

[0118] Furthermore, analyzing the hydrogen bond formation mechanism between the second reinforcing agent and the second polar substance, the second reinforcing agent (containing F) and the second polar substance (-YH) are prone to form hydrogen bonds Y-H-F. The second reinforcing agent can make the second polar substance stably exist on the separator film, thereby reducing the expansion of the bare battery cell during processing and the cycle expansion rate during cyclic use, and improving the cycle performance and high-rate discharge performance of the battery.

[0119] Optionally, the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating can be 5∶1, 5.3∶1, 6∶1, 8∶1, 9∶1, etc. It can be any of the above point values or a range value composed of any point values between them.

[0120] In some embodiments, the mass content k1 of the first reinforcing agent in the first coating is not higher than the mass content k2 of the second reinforcing agent in the second coating.

[0121] In the present application, the content of the reinforcing agent coated on both surfaces of the separator film can be reflected by k1 and k2, and the difference between k1 and k2 should not be too large.

[0122] Generally, when k1 is not higher than k2, the tension of the separator can be kept consistent and more stable. On the one hand, it can prevent the risk of short circuit caused by inconsistent tension. On the other hand, it can improve the cycle performance and high-rate discharge performance of the battery. If the difference in the content of k1 and k2 is too large, the surface tensions of the two surfaces of the separator will be inconsistent, the separator will wrinkle, bubbles will appear on the surface, the electrolyte infiltration will be poor, lithium deposition is likely to occur, the cycle performance will deteriorate, the cycle attenuation will become faster, and the high-rate discharge performance will deteriorate.

[0123] In some embodiments, the ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating can be (0.8 - 1)∶1.

[0124] In the present application, it can reflect the relative content of the reinforcing agents on the two surfaces of the separator. Thus, by limiting the appropriate ratio of the reinforcing agents, the stability of the separator can be improved. At the same time, the influence on the lithium-ion transport kinetics is small, and the cycle performance and high-rate discharge performance of the battery can be improved. However, if is less than 0.8∶1 or is greater than 1∶1, the surface tensions of the two surfaces of the separator will be inconsistent, the separator will wrinkle, bubbles will appear on the surface, the electrolyte infiltration will be poor, lithium deposition is likely to occur, the cycle performance will deteriorate, the cycle attenuation will become faster, and the high-rate discharge performance will deteriorate.

[0125] Among them, preferably, the contents on the two surfaces of the separator are basically the same, which can reduce the difference between the two surfaces of the separator.

[0126] Optionally, the ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating can be 0.80∶1, 0.9∶1, 0.95∶1, or 1∶1, etc. It can be any of the above point values or a range value composed of any point values between them.

[0127] In some embodiments, the mass content k1 of the first reinforcing agent in the first coating can be 10% - 20%. The mass percentage content k2 of the second reinforcing agent in the second coating can be 10% - 20%.

[0128] In the present application, the content of the first reinforcing agent in the first coating can be reflected by k1. The content of the second reinforcing agent in the second coating can be reflected by k2.

[0129] In this application, the content of the first reinforcing agent in the first coating and the content of the second reinforcing agent in the second coating should not differ too much. If the contents of k1 and k2 differ too much, the surface tensions of the two sides of the separator will be inconsistent, the separator will wrinkle, air bubbles will appear on the surface, the electrolyte infiltration will be poor, lithium plating is likely to occur, the cycle performance will deteriorate, the cycle attenuation will become faster, and the high-rate discharge performance will deteriorate. Thus, by limiting the above parameters within a reasonable range, while improving the stability of the separator, the impact on the lithium-ion transport kinetics is small, the kinetics and viscosity can be balanced, the optimal ratio can be achieved, and the cycle performance and high-rate discharge performance of the battery can be improved.

[0130] Optionally, the contents on both sides of the separator are basically the same, which can reduce the differences between the two sides of the separator, keep the separator tension consistent, and prevent wrinkling.

[0131] Optionally, the mass content k1 of the first reinforcing agent in the first coating can be 14%, 16.6%, 18%, 19%, or 20%, etc. k1 can be any of the above point values or a range value composed of any point values between them.

[0132] Optionally, the mass percentage content k2 of the second reinforcing agent in the second coating can be 10%, 11%, 14%, 15.8%, 16.6%, 17%, or 20%, etc. k2 can be any of the above point values or a range value composed of any point values between them.

[0133] In some embodiments, the first reinforcing agent or the second reinforcing agent includes one or more of polyvinylidene fluoride and sodium alginate. Among them, due to the low cost of polyvinylidene fluoride, polyvinylidene fluoride can be preferentially used. The binder for the positive electrode includes polyvinylidene fluoride. The binder for the negative electrode includes one or more of styrene-butadiene rubber and sodium alginate.

[0134] In some embodiments, the weight-average molecular weight of the first reinforcing agent or the second reinforcing agent is 0.05×10⁴ - 60×10⁴; it can be optionally 0.05×10⁴, 1×10⁴, 10×10⁴, 20×10⁴, 30×10⁴, 40×10⁴, 50×10⁴, or 60×10⁴, etc. The weight-average molecular weight of the first reinforcing agent or the second reinforcing agent can be any of the above point values or a range value composed of any point values between them.

[0135] Furthermore, the weight-average molecular weight of the polyvinylidene fluoride can be 10×10⁴ - 60×10⁴; it can be optionally 10×10⁴, 20×10⁴, 30×10⁴, 40×10⁴, 50×10⁴, or 60×10⁴, etc. The weight-average molecular weight of the polyvinylidene fluoride can be any of the above point values or a range value composed of any point values between them.

[0136] Furthermore, the weight-average molecular weight of sodium alginate can be 0.05 to 50,000; it can be optionally 0.05×10⁴, 1×10⁴, 2×10⁴, 3×10⁴, 4×10⁴, or 5×10⁴, etc. The weight-average molecular weight of sodium alginate can be any of the above point values or the range values formed between any point values. Among them, the aforementioned polyvinylidene fluoride and sodium alginate can be applicable to the first reinforcing agent, the second reinforcing agent, the binder for the positive electrode, or the binder for the negative electrode.

[0137] In some embodiments, the mass ratio of the first coating layer to the second coating layer can be 1:(1 to 1.5).

[0138] In the present application, the content of the coating materials on both sides of the separator membrane can be reflected by the first coating layer and the second coating layer, and the difference between the two should not be too large; thus, by limiting the coating amounts of the first coating layer and the second coating layer within a reasonable range, the tension of the separator membrane can be made consistent and more stable. On the one hand, it can prevent the risk of short circuit due to inconsistent tension. On the other hand, it can improve the cycle performance and high-rate discharge performance of the battery. If the contents of the first coating layer and the second coating layer differ too much, it will cause the surface tensions of the two surfaces of the separator membrane to be inconsistent, the separator membrane will wrinkle, bubbles will appear on the surface, the electrolyte infiltration will be poor, lithium deposition is likely to occur, the cycle performance will deteriorate, the cycle attenuation will become faster, and the high-rate discharge performance will deteriorate.

[0139] Optionally, the mass ratio of the first coating layer to the second coating layer can be 1:1, 1:2, 1:3, 1:4, 1:5, etc. The mass ratio of the first coating layer to the second coating layer can be any of the above point values or the range values formed between any point values.

[0140] In some embodiments, the first coating layer or the second coating layer may further include a filler. The filler can be, for example, alumina, which can improve the heat resistance and stability of the coating layer. When used in combination with the first polar substance, it can reduce the swelling of the bare battery cell during the processing and cyclic use processes, and improve the cycle performance and high-rate discharge performance of the battery. The content of the filler is not particularly limited. For example, the mass ratio of the filler in the first coating layer or the second coating layer can be greater than 0 and less than or equal to 25%. If the content of the filler in the first coating layer or the second coating layer is greater than 25%, it will cause the pores of the base film to be blocked, resulting in a slow ion transport rate and affecting the cycle performance and high-rate discharge performance of the battery.

[0141] Optionally, the mass percentage of the filler in the first coating layer or the second coating layer can be 3.2%, 8%, 10%, 15%, 18.9%, 20%, or 25%, etc. The mass ratio of the filler in the first coating layer or the second coating layer can be any of the above point values or the range values formed between any point values.

[0142] In some embodiments, the first coating is obtained by preparing from a first coating slurry. The first coating slurry includes the first polar substance, the first reinforcing agent, and a first solvent; wherein, the viscosity of the first coating slurry can be 8,000 mPa·s to 12,000 mPa·s.

[0143] In this application, the preparation method of the first coating slurry can adopt the well-known methods in the art. For example, it can be mixing the first polar substance and the first reinforcing agent in the first solvent to form a uniform slurry, which is the first coating slurry. Optionally, during the preparation of the first coating slurry, the first polar substance, the first reinforcing agent, and a filler can also be mixed and then dissolved in the first solvent during the preparation process. The dosage between each substance can be set with reference to the mass ratio of each component in the first coating described above in this application.

[0144] In this application, the viscosity of the first coating slurry has a great influence on coating and the electrochemical performance of the battery cell. If the viscosity of the first coating slurry is too high, it is easy to form a gel, and the coating is uneven, resulting in poor consistency of the battery cell, and the cycle performance and high-rate discharge performance of the battery will be reduced. If the viscosity of the first coating slurry is too low, the first coating slurry cannot be well coated on the base film. Therefore, by limiting the viscosity of the first coating slurry within a suitable range, the first coating slurry can be better coated on the base film, and the consistency of the battery cell can be ensured, and the cycle performance and high-rate discharge performance of the battery can be improved.

[0145] Optionally, the viscosity of the first coating slurry can be 8,000 mPa·s, 9,000 mPa·s, 10,000 mPa·s, 11,000 mPa·s, or 12,000 mPa·s, etc. The weight-average molecular weight of the first coating slurry can be any of the above point values or a range value composed of any point values.

[0146] Further, there is generally no limitation on the first solvent. More specifically, when the first reinforcing agent is selected from sodium alginate, there is no limitation on the selection of the first solvent. When the first reinforcing agent is selected from polyvinylidene fluoride, the first solvent is selected from organic solvents, and the organic solvents can be, for example, N,N-dimethylpyrrolidone, acetone, etc.

[0147] In some embodiments, the second coating is obtained by preparing from a second coating slurry, and the preparation method of the second coating can adopt the well-known methods in the art. The second coating slurry includes the second polar substance, the second reinforcing agent, and a second solvent; wherein, the viscosity of the second coating slurry is 5,000 mPa·s to 20,000 mPa·s.

[0148] In this application, the preparation method of the second coating slurry can adopt the well-known methods in the art. For example, the second polar substance and the second reinforcing agent can be mixed in the second solvent to form a uniform slurry, which is the second coating slurry. Optionally, during the preparation of the second coating slurry, the second polar substance, the second reinforcing agent, and the filler can also be mixed and then dissolved in the second solvent. The dosage between each substance can be set with reference to the mass ratio of each component in the second coating described above in this application.

[0149] In this application, the viscosity of the second coating slurry has a great influence on coating and the electrochemical performance of the battery cell. If the viscosity of the second coating slurry is too high, it is easy to form a gel, resulting in uneven coating and poor consistency of the battery cell, and the cycle performance and high-rate discharge performance of the battery will be reduced. If the viscosity of the second coating slurry is too low, the second coating slurry cannot be well coated on the base film. Therefore, by limiting the viscosity of the second coating slurry within a suitable range, the second coating slurry can be better coated on the base film, and the consistency of the battery cell can be ensured, and the cycle performance and high-rate discharge performance of the battery can be improved.

[0150] Optionally, the viscosity of the second coating slurry can be 5000 mPa·s, 8000 mPa·s, 10000 mPa·s, 13000 mPa·s, 15000 mPa·s, 18000 mPa·s, or 20000 mPa·s, etc. The weight-average molecular weight of the second coating slurry can be any of the above point values or a range value composed of any point values between them.

[0151] Furthermore, the second solvent is usually not limited. More specifically, when the second reinforcing agent is selected from sodium alginate, the choice of the second solvent is not limited. When the second reinforcing agent is selected from polyvinylidene fluoride, the second solvent is selected from organic solvents, and the organic solvents can be, for example, N,N-dimethylpyrrolidone, acetone, etc.

[0152] [Base film]

[0153] In some embodiments, this application does not particularly limit the type of the base film, and any well-known porous structure base film with good chemical stability and mechanical stability can be selected.

[0154] In some embodiments, the material of the base film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0155] [Negative electrode]

[0156] The negative electrode includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes negative electrode active components.

[0157] In some embodiments, the negative electrode active components include a silicon-carbon mixture. For the silicon-carbon mixture, the particle size of silicon can be 0.1 - 0.5 microns. The carbon is a mixed carbon of artificial graphite and natural graphite.

[0158] In this application, the particle size of silicon has a relatively large impact on the electrochemical performance. Micron-sized silicon has a smaller specific surface area compared to nano-sized silicon, fewer side reactions, better cycle performance of the battery, and better high-rate discharge performance. Therefore, micron-sized silicon is selected.

[0159] Optionally, the particle size of the silicon is 0.1 micron, 0.3 micron, 0.5 micron, etc. The particle size of silicon can be any of the above point values or a range value composed of any point values between them.

[0160] Optionally, C:Si in the silicon-carbon mixture can be 95 - 97∶3 - 5, etc. More specifically, C:Si can be 95∶5.

[0161] Furthermore, the content of the silicon-carbon mixture in the negative electrode film layer can be 95% - 97%. Since the content of the silicon-carbon mixture affects the energy density of the battery cell, generally, the content of the silicon-carbon mixture in the negative electrode film layer needs to be greater than 95% to achieve a high capacity of the battery and improve the cycle performance and high-rate discharge performance of the battery.

[0162] Optionally, the content of the silicon-carbon mixture in the negative electrode film layer can be 95.9%, 96%, 96.7%, 96.8%, or 97%, etc. The content of the silicon-carbon mixture in the negative electrode film layer can be any of the above point values or a range value composed of any point values between them.

[0163] Optionally, the negative electrode active components can adopt negative electrode active materials known in the art for batteries. As an example, the negative electrode active components can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can be selected from at least one of elemental silicon, silicon oxides, silicon nitrides, and silicon alloys. The tin-based materials can be selected from at least one of elemental tin, tin oxides, and tin alloys. However, this application is not limited to these materials, and other traditional materials that can be used as negative electrode active components of the battery can also be used. These negative electrode active components can be used alone or in combination of two or more.

[0164] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0165] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0166] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The negative electrode binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). Optionally, the negative electrode binder is selected from styrene-butadiene rubber (SBR) and sodium alginate (SA).

[0167] In some embodiments, the negative electrode film layer may further optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0168] In some embodiments, the negative electrode film layer may further optionally include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0169] In some embodiments, the negative electrode may be prepared by the following method: dispersing the above components for preparing the negative electrode, such as the negative electrode active component, the conductive agent, the binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode can be obtained.

[0170] [Positive Electrode]

[0171] The positive electrode includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode material of the first aspect of the present application.

[0172] In some embodiments, the positive electrode includes the positive electrode material LiNi x Co y Mn z O2, where x + y + z = 1, x = 0.5 to 0.9, optionally, x = 0.5 to 0.7, x = 0.8 to 0.9.

[0173] In this application, generally speaking, the nickel content in the positive electrode material can be greater than 0.5. However, due to the different expansion changes of the bare cells in different positive electrode system cells, the separator film of this application has a particularly significant improvement effect on the cyclic expansion rate of the bare cells containing high-nickel positive electrode materials.

[0174] More specifically, when the nickel content x = 0.5 - 0.7, the unit cell parameters of the positive electrode material change greatly, and the volume change of the positive electrode material is also large. Eventually, the expansion of the bare cell changes greatly compared to the initial expansion of the bare cell, and the obtained cyclic expansion rate of the bare cell is small. Within the aforementioned range in this application, the cyclic expansion rate of the bare cell is improved more significantly, and the cycle retention rate is better. When the nickel content is, for example, 0.8 - 0.9, although the change in the unit cell parameters of the positive electrode material is small, since the cyclic expansion rate of the final bare cell is also very small, it is still within the range required by this application.

[0175] Optionally, x = 0.4, x = 0.5, x = 0.6, x = 0.7, x = 0.8 or x = 0.9, etc. The nickel content can be any of the above point values or the range values composed of any point values.

[0176] Optionally, the positive electrode material can be LiNi 0.4 Co 0.4 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, etc.

[0177] Further optionally, the positive electrode active material may be a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which may also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which may also be abbreviated as NCM 211 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and their modified compounds, etc. Examples of the lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (which may also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0178] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0179] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0180] In some embodiments, the positive electrode film layer may further optionally include a binder for the negative electrode. As an example, the binder for the negative electrode may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. Optionally, the binder for the negative electrode is selected from polyvinylidene fluoride (PVDF).

[0181] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0182] In some embodiments, the positive electrode can be prepared by the following method: dispersing the above-mentioned components for preparing the positive electrode, such as the positive electrode material, conductive agent, binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode can be obtained.

[0183] [Electrolyte]

[0184] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. There is no specific limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0185] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0186] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluorooxalate phosphate.

[0187] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0188] In some embodiments, the electrolyte may further optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, and the like.

[0189] The battery of the present application will be described below with appropriate reference to the accompanying drawings.

[0190] In one embodiment of the present application, a secondary battery is provided. Generally, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode and the negative electrode. The electrolyte functions to conduct ions between the positive electrode and the negative electrode. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly functioning to prevent short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0191] In some embodiments, the positive electrode, the negative electrode, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0192] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0193] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and as plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0194] The present application does not particularly limit the shape of the secondary battery, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 is a secondary battery 5 with a square structure as an example.

[0195] In some embodiments, referring to Figure 4 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be disposed on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte infiltrates the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0196] In addition, the battery module, battery pack, and electrical device of the present application will be described below with appropriate reference to the accompanying drawings.

[0197] Battery module

[0198] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries included in the battery module can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery module.

[0199] Figure 5 As an example, it is the battery module 4. Refer to Figure 5 , in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0200] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0201] Battery pack

[0202] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0203] Figure 6 and Figure 7 As an example, it is the battery pack 1. Refer to Figure 6 and Figure 7 , in the battery pack 1, it can include a battery box and a plurality of battery modules 4 arranged 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 modules 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0204] Power-consuming device

[0205] In addition, the present application further provides a power-consuming device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack can be used as the power supply of the power-consuming device or as the energy storage unit of the power-consuming device. The power-consuming device can include mobile devices (such as mobile phones, laptops, 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, satellites, energy storage systems, etc., but not limited thereto.

[0206] As the power-consuming device, the secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0207] Figure 8 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or a battery module can be adopted.

[0208] The device as another example can be a mobile phone, a tablet computer, a laptop computer, etc. The device usually requires being thin and light, and a secondary battery can be adopted as the power source.

[0209] Embodiment

[0210] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those without specific technologies or conditions noted in the embodiments, the technologies or conditions described in the literature in the art or according to the product specifications are followed. For the reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchase.

[0211] Embodiment 1-1:

[0212] 1. Preparation of the separator

[0213] 1) Dissolve the first polar substance PEO and alumina in NMP at a mass ratio of 80:20, stir evenly to obtain the first coating slurry, and coat the first coating slurry on the A side of the PE base film (the side of the PE base film close to the positive electrode) by gravure coating.

[0214] 2) Dissolve the second polar substance PEI and alumina in deionized water at a mass ratio of 80:20, stir evenly to obtain the second coating slurry, and coat the second coating slurry on the B side of the PE base film (the side of the PE base film close to the negative electrode) by gravure coating.

[0215] 3) Dry the PE base film coated with the first coating slurry in step 1) and the second coating slurry in step 2) at 60°C for 1 h to form the first coating and the second coating on both surfaces of the PE base film, and prepare the separator.

[0216] 2. Preparation of the positive electrode

[0217] Mix the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the positive electrode binder PVDF, and conductive carbon in a mass ratio of 97:1.07:1.93, dissolve them in NMP, stir for 6 h to obtain the positive electrode slurry, coat the positive electrode slurry on the aluminum foil, dry it, and prepare the positive electrode after cold pressing.

[0218] The ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 75:1.

[0219] 3. Preparation of the negative electrode

[0220] SA and SBR are mixed in a mass ratio of 80:20 to obtain the binder for the negative electrode. Then, the negative electrode active material carbon-silicon mixture (C:Si = 95:5), the binder for the negative electrode, and carbon nanotubes are mixed in a mass ratio of 97:2.66:0.34 and dissolved in water, and stirred for 6 h to obtain the negative electrode slurry. The negative electrode slurry is coated on a copper foil, dried, and cold-pressed to prepare the negative electrode.

[0221] The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is 30:1.

[0222] 4. Preparation of the battery

[0223] The positive electrode, the separator, and the negative electrode are stacked in sequence. Among them, the first coating of the separator contacts the positive electrode, and the second coating of the separator contacts the negative electrode, and then wound to obtain a bare battery cell. The bare battery cell is placed in an aluminum shell, the top cover is welded, and after processes such as liquid injection, high-temperature standing, formation, and aging, a lithium-ion battery is obtained.

[0224] Examples 1-2:

[0225] The preparation process of the lithium-ion battery generally refers to Example 1-1, the difference is that the mass ratio of the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and conductive carbon is 97:1:2; the mass ratio of the negative electrode active material carbon-silicon mixture, the binder for the negative electrode, and carbon nanotubes is 97:2.5:0.5.

[0226] The ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 80:1. The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is 32:1.

[0227] Examples 1-3:

[0228] The preparation process of the lithium-ion battery generally refers to Example 1-1, the difference is that the positive electrode active material LiNi 0.6 Co 0.2 Mn0.2 The mass ratio of O2, the binder PVDF for the positive electrode, and conductive carbon is 97∶0.91∶2.09; the mass ratio of the carbon-silicon mixture as the negative electrode active material, the binder for the negative electrode, and carbon nanotubes is 97∶2.2∶0.8.

[0229] The ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 87∶1. The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is 36∶1.

[0230] Examples 1-4:

[0231] The preparation process of the lithium-ion battery generally refers to Examples 1-1, and the positive electrode active material is LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and conductive carbon have a mass ratio of 97∶0.86∶2.14; the mass ratio of the carbon-silicon mixture as the negative electrode active material, the binder for the negative electrode, and carbon nanotubes is 97∶2∶1.

[0232] The ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 93∶1. The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is 40∶1.

[0233] Examples 1-5:

[0234] The preparation process of the lithium-ion battery generally refers to Examples 1-1, except that the positive electrode active material is LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and conductive carbon have a mass ratio of 97∶0.82∶2.18; the mass ratio of the carbon-silicon mixture as the negative electrode active material, the binder for the negative electrode, and carbon nanotubes is 97∶1.77∶1.23.

[0235] The ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 97∶1. The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is 45∶1.

[0236] Examples 1-6:

[0237] The preparation process of the lithium-ion battery generally refers to Example 1-1, with the difference that the mass ratio of the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and the conductive carbon is 97∶0.8∶2.2; the mass ratio of the negative electrode active material carbon-silicon mixture, the binder for the negative electrode, and the carbon nanotubes is 97∶1.6∶1.4.

[0238] The ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 100∶1. The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is 50∶1.

[0239] Example 1-7:

[0240] The preparation process of the lithium-ion battery generally refers to Example 1-1, with the difference that the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and the conductive carbon are mixed in a mass ratio of 97∶0.76∶2.24; the mass ratio of the negative electrode active material carbon-silicon mixture, the binder for the negative electrode, and the carbon nanotubes is 97∶1.5∶1.5.

[0241] The ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 105∶1. The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is 53∶1.

[0242] Example 2-1:

[0243] 1. Preparation of the separator

[0244] 1) Dissolve the first polar substance PAM and alumina in NMP in a mass ratio of 96.8∶3.2, stir evenly to obtain the first coating slurry, and coat the first coating slurry on the A side of the PE base film (the side of the PE base film close to the positive electrode) by gravure coating.

[0245] 2) Dissolve the second polar substance PEO and alumina in deionized water in a mass ratio of 77.5∶22.5, stir evenly to obtain the second coating slurry, and coat the second coating slurry on the B side of the PE base film (the side of the PE base film close to the negative electrode) by gravure coating.

[0246] 3) After coating the first coating slurry in step 1) and the second coating slurry in step 2), the PE-based film is dried at 60 °C for 1 h to form the first coating and the second coating on both surfaces of the PE-based film, and the separator film is prepared.

[0247] Among them, the ratio of the mass content w1 of the first polar substance in the first coating to the mass content w2 of the second polar substance in the second coating is 1:0.8.

[0248] 2. Preparation of the positive electrode

[0249] The positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and conductive carbon are mixed at a mass ratio of 97:1:2, dissolved in NMP, and stirred for 6 h to obtain the positive electrode slurry. The positive electrode slurry is coated on the aluminum foil, dried, and cold-pressed to prepare the positive electrode.

[0250] 3. Preparation of the negative electrode

[0251] SA and SBR are mixed at a mass ratio of 80:20 to obtain the binder for the negative electrode. Then, the negative electrode active material carbon-silicon mixture (C:Si = 95:5), the binder for the negative electrode, and carbon nanotubes are mixed at a mass ratio of 97:2.5:0.5, dissolved in water, and stirred for 6 h to obtain the negative electrode slurry. The negative electrode slurry is coated on the copper foil, dried, and cold-pressed to prepare the negative electrode.

[0252] 4. Preparation of the battery

[0253] The positive electrode, the separator film, and the negative electrode are stacked in sequence. Among them, the first coating of the separator film is in contact with the positive electrode, and the second coating of the separator film is in contact with the negative electrode, and then wound to obtain a bare battery cell. The bare battery cell is placed in an aluminum shell, the top cover is welded, and after processes such as liquid injection, high-temperature standing, formation, and aging, the lithium-ion battery is obtained.

[0254] Example 2-2:

[0255] It is basically the same as Example 2-1, except that the mass ratio of the first polar substance PAM and alumina is 85:15; the mass ratio of the second polar substance PEO and alumina is 85:15. The ratio of the mass content w1 of the first polar substance in the first coating to the mass content w2 of the second polar substance in the second coating is 1:1.

[0256] Example 2-3:

[0257] The preparation process of the lithium-ion battery generally refers to Example 2-1, with the difference that the mass ratio of the first polar substance PAM to alumina is 71.1:28.9; the mass ratio of the second polar substance PEO to alumina is 92.5:7.5. The ratio of the mass content w1 of the first polar substance in the first coating to the mass content w2 of the second polar substance in the second coating is 1:1.3.

[0258] Example 2-4:

[0259] The preparation process of the lithium-ion battery generally refers to Example 2-1, with the difference that the mass ratio of the first polar substance PAM to alumina is 65:35; the mass ratio of the second polar substance PEO to alumina is 97.5:2.5. The ratio of the mass content w1 of the first polar substance in the first coating to the mass content w2 of the second polar substance in the second coating is 1:1.5.

[0260] Example 3-1:

[0261] 1. Preparation of the separator

[0262] 1) Dissolve the first polar substance polyurea and alumina in NMP at a mass ratio of 75:25, stir evenly to obtain the first coating slurry, and coat the first coating slurry on the A side of the PE base film (the side of the PE base film close to the positive electrode) by gravure coating.

[0263] 2) Dissolve the second polar substance PAM and alumina in deionized water at a mass ratio of 75:25, stir evenly to obtain the second coating slurry, and coat the second coating slurry on the B side of the PE base film (the side of the PE base film close to the negative electrode) by gravure coating.

[0264] 3) Dry the PE base film coated with the first coating slurry in step 1) and the second coating slurry in step 2) at 60 °C for 1 h to form the first coating and the second coating on both surfaces of the PE base film, and obtain the separator by preparation.

[0265] 2. Preparation of the positive electrode

[0266] Mix the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the positive electrode binder PVDF, and conductive carbon in a mass ratio of 97:0.8:2.2, dissolve them in NMP to obtain the positive electrode slurry, stir for 6 h, coat the positive electrode slurry on the aluminum foil, dry it, and prepare the positive electrode after cold pressing.

[0267] 3. Preparation of the negative electrode

[0268] Mix SA and SBR in a mass ratio of 80:20 to obtain a binder for the negative electrode. Then, mix the negative electrode active material carbon-silicon mixture (C:Si = 95:5), the binder for the negative electrode, and carbon nanotubes in a mass ratio of 97:1.8:1.2, dissolve them in water, and stir for 6 h to obtain a negative electrode slurry. Coat the negative electrode slurry on a copper foil, dry it, and prepare the negative electrode after cold pressing.

[0269] 4. Preparation of the battery

[0270] Stack the positive electrode, the separator, and the negative electrode in sequence. Among them, the first coating of the separator contacts the positive electrode, and the second coating of the separator contacts the negative electrode. Then, wind them to obtain a bare battery cell. Place the bare battery cell into an aluminum shell, weld the top cover, and obtain a lithium-ion battery through processes such as liquid injection, high-temperature standing, formation, and aging.

[0271] Example 3-2:

[0272] The preparation process of the lithium-ion battery generally refers to Example 3-1, except that the mass ratio of the first polar substance polyurea in the first coating is 80%; the mass ratio of the second polar substance PAM in the second coating is 80%. The mass ratio of the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and conductive carbon is 97:0.9:2.3. The mass ratio of the negative electrode active material carbon-silicon mixture, the binder for the negative electrode, and carbon nanotubes is 97:2:1.

[0273] Example 3-3:

[0274] The preparation process of the lithium-ion battery generally refers to Example 3-1, except that the mass ratio of the first polar substance polyurea in the first coating is 85%; the mass ratio of the second polar substance PAM in the second coating is 85%. The mass ratio of the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and conductive carbon is 97:1:2. The mass ratio of the negative electrode active material carbon-silicon mixture, the binder for the negative electrode, and carbon nanotubes is 97:2.6:0.4.

[0275] Example 3-4:

[0276] The preparation process of the lithium-ion battery generally refers to Example 3-1, except that the mass ratio of the first polar substance polyurea in the first coating is 90%; the mass ratio of the second polar substance PAM in the second coating is 90%. The mass ratio of the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2The mass ratio of O2, the binder PVDF for the positive electrode, and conductive carbon is 97∶1.2∶1.8. The mass ratio of the negative electrode active material carbon-silicon mixture, the binder for the negative electrode, and carbon nanotubes is 97∶3∶0.

[0277] Examples 3-5:

[0278] The preparation process of the lithium-ion battery generally refers to Example 3-1, except that the mass proportion of the first polar substance polyurea in the first coating is 92%; the mass proportion of the second polar substance PAM in the second coating is 92%. The positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the binder PVDF for the positive electrode, and conductive carbon have a mass ratio of 97∶1.5∶0.5. The mass ratio of the negative electrode active material carbon-silicon mixture, the binder for the negative electrode, and carbon nanotubes is 96.8∶3.2∶0.

[0279] Example 4-1:

[0280] 1. Preparation of the separator

[0281] 1) Dissolve the first polar substance PEO, the first reinforcing agent PVDF, and alumina in NMP according to the mass ratio of 80∶14∶6, stir evenly to obtain the first coating slurry, and coat the first coating slurry on the A side of the PE base film (the side of the PE base film close to the positive electrode) by gravure coating.

[0282] 2) Dissolve the second polar substance PEI and the first reinforcing agent PVDF in deionized water according to the mass ratio of 80∶20, stir evenly to obtain the second coating slurry, and coat the second coating slurry on the B side of the PE base film (the side of the PE base film close to the negative electrode) by gravure coating.

[0283] 3) Dry the PE base film after coating the first coating slurry in step 1) and the second coating slurry in step 2) at 60°C for 1 h to form the first coating and the second coating on both surfaces of the PE base film, and obtain the separator by preparation.

[0284] Among them, the ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating is 0.7∶1.

[0285] 2. Preparation of the positive electrode

[0286] Put the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2O2, the binder PVDF for the positive electrode, and conductive carbon are mixed in a mass ratio of 97:1:2, dissolved in NMP, and stirred for 6 h to obtain the positive electrode slurry. The positive electrode slurry is coated on aluminum foil, dried, and cold-pressed to prepare the positive electrode.

[0287] 3. Preparation of the negative electrode

[0288] SA and SBR are mixed in a mass ratio of 80:20 to obtain the binder for the negative electrode. Then, the negative electrode active material carbon-silicon mixture (C:Si = 95:5), the binder for the negative electrode, and carbon nanotubes are mixed in a mass ratio of 97:2.5:0.5, dissolved in water, and stirred for 6 h to obtain the negative electrode slurry. The negative electrode slurry is coated on copper foil, dried, and cold-pressed to prepare the negative electrode.

[0289] 4. Preparation of the battery

[0290] The positive electrode, separator, and negative electrode are stacked in sequence. Among them, the first coating of the separator is in contact with the positive electrode, and the second coating of the separator is in contact with the negative electrode, and then wound to obtain a bare battery cell. The bare battery cell is placed in an aluminum shell, the top cover is welded, and after processes such as liquid injection, high-temperature standing, formation, and aging, a lithium-ion battery is obtained.

[0291] Example 4-2:

[0292] The preparation process of the lithium-ion battery generally refers to Example 4-1, the difference is that the mass ratio of the first polar substance PEO, the first reinforcing agent PVDF, and alumina is 80:16.6:3.4. The ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating is 0.8:1.

[0293] Example 4-3:

[0294] The preparation process of the lithium-ion battery generally refers to Example 4-1, the difference is that the mass ratio of the first polar substance PEO, the first reinforcing agent PVDF, and alumina is 80:18:2. The ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating is 0.9:1.

[0295] Example 4-4:

[0296] The preparation process of the lithium-ion battery generally refers to Example 4-1, the difference is that the mass ratio of the first polar substance PEO, the first reinforcing agent PVDF, and alumina is 80:19:1. The ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating is 0.95:1.

[0297] Examples 4-5:

[0298] The preparation process of the lithium-ion battery generally refers to Example 4-1, except that the mass ratio of the first polar substance PEO to the first reinforcing agent PVDF is 80:20. The ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating is 1:1.

[0299] Example 5-1:

[0300] 1. Preparation of the separator

[0301] 1) Dissolve the first polar substance PAM, the first reinforcing agent PVDF, and alumina in NMP in a mass ratio of 80:17.4:2.6, stir evenly to obtain the first coating slurry, and coat the first coating slurry on the A side of the PE base film (the side of the PE base film close to the positive electrode) by gravure coating.

[0302] 2) Dissolve the second polar substance PEO and the first reinforcing agent PVDF in deionized water in a mass ratio of 83:17, stir evenly to obtain the second coating slurry, and coat the second coating slurry on the B side of the PE base film (the side of the PE base film close to the negative electrode) by gravure coating.

[0303] 3) Dry the PE base film coated with the first coating slurry in step 1) and the second coating slurry in step 2) at 60 °C for 1 h to form the first coating and the second coating on both surfaces of the PE base film, and obtain the separator by preparation.

[0304] Among them, the mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating is 4.6:1; the second coating includes the second reinforcing agent, and the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating is 4.9:1.

[0305] 2. Preparation of the positive electrode

[0306] Mix the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the positive electrode binder PVDF, and conductive carbon in a mass ratio of 97:1:2, dissolve them in NMP, stir for 6 h to obtain the positive electrode slurry, coat the positive electrode slurry on the aluminum foil, dry it, and prepare the positive electrode after cold pressing.

[0307] 3. Preparation of the negative electrode

[0308] Mix SA and SBR in a mass ratio of 80:20 to obtain a binder for the negative electrode. Then, mix the negative electrode active material carbon-silicon mixture (C:Si = 95:5), the binder for the negative electrode, and carbon nanotubes in a mass ratio of 97:2.5:0.5, dissolve them in water, and stir for 6 hours to obtain a negative electrode slurry. Coat the negative electrode slurry on a copper foil, dry it, and cold press it to prepare the negative electrode.

[0309] 4. Preparation of the battery

[0310] Stack the positive electrode, separator, and negative electrode in sequence. Among them, the first coating of the separator contacts the positive electrode, and the second coating of the separator contacts the negative electrode. Then, wind them to obtain a bare battery cell. Place the bare battery cell into an aluminum shell, weld the top cover, and obtain a lithium-ion battery through processes such as liquid injection, high-temperature standing, formation, and aging.

[0311] Example 5-2:

[0312] The preparation process of the lithium-ion battery generally refers to Example 5-1, except that the mass ratio of the first polar substance PAM, the first reinforcing agent PVDF, and alumina is 80:16:4. The mass ratio of the second polar substance PEO and the second reinforcing agent PVDF is 83.4:16.6.

[0313] The mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating is 5:1; the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating is 5:1.

[0314] Example 5-3:

[0315] The preparation process of the lithium-ion battery generally refers to Example 5-1, except that the mass ratio of the first polar substance PAM, the first reinforcing agent PVDF, and alumina is 80:15:5. The mass ratio of the second polar substance PEO, the second reinforcing agent PVDF, and alumina is 84.2:15.8.

[0316] The mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating is 5.3:1; the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating is 5.3:1.

[0317] Example 5-4:

[0318] The preparation process of the lithium-ion battery generally refers to Example 5-1, with the difference that the mass ratio of the first polar substance PAM, the first reinforcing agent PVDF, and alumina is 80∶13.3∶6.7. The mass ratio of the second polar substance PEO and the second reinforcing agent PVDF is 86∶14.

[0319] The mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating is 6∶1; the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating is 6∶1.

[0320] Example 5-5:

[0321] The preparation process of the lithium-ion battery generally refers to Example 5-1, with the difference that the mass ratio of the first polar substance PAM, the first reinforcing agent PVDF, and alumina is 80∶10∶10. The mass ratio of the second polar substance PEO and the second reinforcing agent PVDF is 89∶11.

[0322] The mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating is 8∶1; the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating is 8∶1.

[0323] Example 5-6:

[0324] The preparation process of the lithium-ion battery generally refers to Example 5-1, with the difference that the mass ratio of the first polar substance PAM, the first reinforcing agent PVDF, and alumina is 80∶8.9∶11.1. The mass ratio of the second polar substance PEO, the second reinforcing agent PVDF, and alumina is 90∶10.

[0325] The mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating is 9∶1; the second coating includes the second reinforcing agent, and the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating is 9∶1.

[0326] Example 5-7:

[0327] The preparation process of the lithium-ion battery generally refers to Example 5-1, with the difference that the mass ratio of the first polar substance PAM, the first enhancer PVDF, and alumina is 80:8.6:11.4. The mass ratio of the second polar substance PEO and the second enhancer PVDF is 90.3:9.7.

[0328] The mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first enhancer in the first coating is 9.3:1; the second coating includes the second enhancer, and the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second enhancer in the second coating is 9.3:1.

[0329] Example 6-1:

[0330] 1. Preparation of the separator

[0331] 1) Dissolve the first polar substance PEO and the first enhancer PVDF in NMP at a mass ratio of 80:20, stir evenly to obtain the first coating slurry, and coat the first coating slurry on the A side of the PE base film (the side of the PE base film close to the positive electrode) by gravure coating.

[0332] 2) Dissolve the second polar substance PEO and the first enhancer PVDF in deionized water at a mass ratio of 80:20, stir evenly to obtain the second coating slurry, and coat the second coating slurry on the B side of the PE base film (the side of the PE base film close to the negative electrode) by gravure coating.

[0333] 3) Dry the PE base film coated with the first coating slurry in step 1) and the second coating slurry in step 2) at 60°C for 1 h to form the first coating and the second coating on both surfaces of the PE base film, and obtain the separator by preparation.

[0334] 2. Preparation of the positive electrode

[0335] Mix the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the positive electrode binder PVDF, and conductive carbon in a mass ratio of 97:1:2, dissolve them in NMP, stir for 6 h to obtain the positive electrode slurry, coat the positive electrode slurry on the aluminum foil, dry it, and obtain the positive electrode after cold pressing.

[0336] 3. Preparation of the negative electrode

[0337] Mix SA and SBR in a mass ratio of 80:20 to obtain a binder for the negative electrode. Then, mix the negative electrode active material carbon-silicon mixture (C:Si = 95:5; the particle size of Si is 0.05 μm), the binder for the negative electrode, and carbon nanotubes in a mass ratio of 95.9:2.5:1.6, dissolve them in water, and stir for 6 h to obtain a negative electrode slurry. Coat the negative electrode slurry on a copper foil, dry it, and prepare the negative electrode after cold pressing.

[0338] 4. Preparation of the battery

[0339] Stack the positive electrode, separator, and negative electrode in sequence. Among them, make the first coating of the separator contact the positive electrode and the second coating of the separator contact the negative electrode, and then wind to obtain a bare battery cell. Place the bare battery cell into an aluminum shell, weld the top cover, and obtain a lithium-ion battery through processes such as liquid injection, high-temperature standing, formation, and aging.

[0340] Example 6-2:

[0341] The preparation process of the lithium-ion battery generally refers to Example 6-1, the difference is that the negative electrode active material carbon-silicon mixture (C:Si = 95:5; the particle size of Si is 0.1 μm), the binder for the negative electrode, and carbon nanotubes are in a mass ratio of 96.7:2.5:0.8.

[0342] Example 6-3:

[0343] It is basically the same as Example 6-1, the difference is that the negative electrode active material carbon-silicon mixture (the particle size of Si is 0.3 μm), the binder for the negative electrode, and carbon nanotubes are in a mass ratio of 97:2.5:0.5.

[0344] Example 6-4:

[0345] The preparation process of the lithium-ion battery generally refers to Example 6-1, the difference is that the negative electrode active material carbon-silicon mixture (C:Si = 95:5; the particle size of Si is 0.5 μm), the binder for the negative electrode, and carbon nanotubes are in a mass ratio of 96.8:2.5:0.7.

[0346] Example 6-5:

[0347] The preparation process of the lithium-ion battery generally refers to Example 6-1, the difference is that the negative electrode active material carbon-silicon mixture (the particle size of Si is 0.6 μm), the binder for the negative electrode, and carbon nanotubes are in a mass ratio of 96:2.5:1.5.

[0348] Example 7-1:

[0349] 1. Preparation of the separator

[0350] 1) Dissolve the first polar substance PEO and the first reinforcing agent PVDF in NMP at a mass ratio of 80:20, stir evenly to obtain the first coating slurry, and coat the first coating slurry on the A side of the PE base film (the side of the PE base film close to the positive electrode) by gravure coating.

[0351] 2) Dissolve the second polar substance PEO and the first reinforcing agent PVDF in deionized water at a mass ratio of 80:20, stir evenly to obtain the second coating slurry, and coat the second coating slurry on the B side of the PE base film (the side of the PE base film close to the negative electrode) by gravure coating.

[0352] 3) Dry the PE base film coated with the first coating slurry in step 1) and the second coating slurry in step 2) at 60 °C for 1 h to form a first coating and a second coating on both surfaces of the PE base film, and obtain a separator membrane by preparation.

[0353] 2. Preparation of the positive electrode

[0354] Mix the positive electrode active material LiNi 0.4 Co 0.4 Mn 0.2 O2, the positive electrode binder PVDF, and conductive carbon in a mass ratio of 97:1:2, dissolve them in NMP, stir for 6 h to obtain the positive electrode slurry, coat the positive electrode slurry on the aluminum foil, dry it, and prepare the positive electrode after cold pressing.

[0355] 3. Preparation of the negative electrode

[0356] Mix SA and SBR in a mass ratio of 80:20 to obtain the negative electrode binder, and then mix the negative electrode active material carbon-silicon mixture (C:Si = 95:5; the particle size of Si is 0.3 μm), the negative electrode binder, and carbon nanotubes in a mass ratio of 97:2.5:0.5, dissolve them in water, stir for 6 h to obtain the negative electrode slurry, coat the negative electrode slurry on the copper foil, dry it, and prepare the negative electrode after cold pressing.

[0357] 4. Preparation of the battery

[0358] Stack the positive electrode, the separator membrane, and the negative electrode in sequence. Among them, contact the first coating of the separator membrane with the positive electrode and contact the second coating of the separator membrane with the negative electrode, and then wind to obtain a bare battery core. Put the bare battery core into the aluminum shell, weld the top cover, and obtain a lithium-ion battery through processes such as liquid injection, high-temperature standing, formation, and aging.

[0359] Example 7-2:

[0360] The preparation process of the lithium-ion battery generally refers to Example 7-1, the difference is that the positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O2.

[0361] Example 7-3:

[0362] The preparation process of the lithium-ion battery generally refers to Example 7-1, except that the positive active material is LiNi 0.6 Co 0.2 Mn 0.2 O2.

[0363] Example 7-4:

[0364] The preparation process of the lithium-ion battery generally refers to Example 7-1, except that the positive active material is LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0365] Example 7-5:

[0366] The preparation process of the lithium-ion battery generally refers to Example 7-1, except that the positive active material is LiNi 0.9 Co 0.05 Mn 0.05 O2.

[0367] Example 8-1:

[0368] 1. Preparation of the separator

[0369] 1) Mix PEO and PAM in a mass ratio of 1.8:1 to obtain a first polar substance. The first polar substance and a first reinforcing agent PVDF are dissolved in NMP in a mass ratio of 80:20, and stirred evenly to obtain a first coating slurry. The first coating slurry is coated on the A side of the PE base film (the side of the PE base film close to the positive electrode) by gravure coating.

[0370] 2) Mix PEI and PEO in a mass ratio of 1.8:1 to obtain a second polar substance. The second polar substance and the first reinforcing agent PVDF are dissolved in deionized water in a mass ratio of 80:20, and stirred evenly to obtain a second coating slurry. The second coating slurry is coated on the B side of the PE base film (the side of the PE base film close to the negative electrode) by gravure coating.

[0371] 3) Dry the PE base film coated with the first coating slurry in step 1) and the second coating slurry in step 2) at 60 °C for 1 h to form a first coating and a second coating on both surfaces of the PE base film, and obtain the separator by preparation.

[0372] 2. Preparation of the positive electrode

[0373] The positive active material LiNi 0.4 Co 0.4 Mn 0.4O2, the binder PVDF for the positive electrode, and conductive carbon are mixed in a mass ratio of 97:1:2, dissolved in NMP, and stirred for 6 h to obtain the positive electrode slurry. The positive electrode slurry is coated on aluminum foil, dried, and cold-pressed to prepare the positive electrode.

[0374] 3. Preparation of the negative electrode

[0375] SA and SBR are mixed in a mass ratio of 80:20 to obtain the binder for the negative electrode. Then, the negative electrode active material carbon-silicon mixture (C:Si = 95:5; the particle size of Si is 0.3 μm), the binder for the negative electrode, and carbon nanotubes are mixed in a mass ratio of 97:2.5:0.5, dissolved in water, and stirred for 6 h to obtain the negative electrode slurry. The negative electrode slurry is coated on copper foil, dried, and cold-pressed to prepare the negative electrode.

[0376] 4. Preparation of the battery

[0377] The positive electrode, separator, and negative electrode are stacked in sequence. Among them, the first coating of the separator is in contact with the positive electrode, and the second coating of the separator is in contact with the negative electrode, and then wound to obtain a bare battery cell. The bare battery cell is placed in an aluminum shell, the top cover is welded, and after processes such as liquid injection, high-temperature standing, formation, and aging, a lithium-ion battery is obtained.

[0378] Example 8-2:

[0379] The preparation process of the lithium-ion battery generally refers to Example 8-1, the difference is that the mass ratio of PEO and PAM in the first polar substance is 2:1; the mass ratio of PEI and PEO in the first polar substance is 2:1.

[0380] Example 8-3:

[0381] The preparation process of the lithium-ion battery generally refers to Example 8-1, the difference is that the mass ratio of PEO and PAM in the first polar substance is 3:1; the mass ratio of PEI and PEO in the first polar substance is 3:1.

[0382] Example 8-4:

[0383] The preparation process of the lithium-ion battery generally refers to Example 8-1, the difference is that the mass ratio of PEO and PAM in the first polar substance is 4.5:1; the mass ratio of PEI and PEO in the first polar substance is 4.5:1.

[0384] Example 8-5:

[0385] The preparation process of the lithium-ion battery generally refers to Example 8-1, the difference is that the mass ratio of PEO and PAM in the first polar substance is 5:1; the mass ratio of PEI and PEO in the first polar substance is 5:1.

[0386] Example 8-6:

[0387] The preparation process of the lithium-ion battery generally refers to Example 8-1, with the difference that the mass ratio of PEO to PAM in the first polar substance is 6:1; the mass ratio of PEI to PEO in the first polar substance is 6:1.

[0388] Example 8-7:

[0389] The preparation process of the lithium-ion battery generally refers to Example 8-1, with the difference that the mass ratio of PEO to PAM in the first polar substance is 6.3:1; the mass ratio of PEI to PEO in the first polar substance is 6.3:1.

[0390] Comparative Example 1:

[0391] The preparation process of the lithium-ion battery generally refers to Example 1-2, with the difference that it does not contain the first polar substance PEO and the second polar substance PEI.

[0392] Comparative Example 2:

[0393] The preparation process of the lithium-ion battery generally refers to Example 1-2, with the difference that it does not contain PEO in the first polar substance, and the proportion of the second polar substance PEI in the second coating is 100%.

[0394] Comparative Example 3:

[0395] The preparation process of the lithium-ion battery generally refers to Example 1-2, with the difference that it does not contain PEI in the second polar substance, and the proportion of the first polar substance PEO in the first coating is 100%.

[0396] II. Performance Testing

[0397] 1. Test Method for the Peel Strength between the Surfaces of the Positive and Negative Electrodes and the Coating of the Separator

[0398] Cut the separators of the examples and comparative examples into test samples with a length of 100 mm and a width of 10 mm respectively. Take a stainless steel plate with a width of 25 mm, stick double-sided tape (width 11 mm), and paste the test sample on the double-sided tape on the stainless steel plate. Roll a 2000 g pressure roller back and forth on its surface three times (300 mm / min). Bend the test sample by 180 degrees, manually peel the organic-inorganic mixed layer of the test sample from the base film by 25 mm, fix the test sample on a testing machine (such as INSTRON 336), make the peeling surface consistent with the force line of the testing machine, and the testing machine continuously peels at 30 mm / min. For the obtained peel strength curve, take the average value of the stable section as the peel strength F0, then calculate the adhesion force F between the organic-inorganic mixed layer and the current collector in the test sample through the following formula. F = F0 / the width of the test sample (the measurement unit of F: N / m).

[0399] 2. Infrared Spectroscopy Test

[0400] According to the infrared spectroscopy analysis method of GB / T6040-2002 standard, an IS10 type Fourier transform infrared spectrometer of Nicolet Company in the United States was used. The positive electrode powder was obtained by suction filtration of the positive electrode slurry obtained in the examples and comparative examples; the first coating slurry obtained in the examples and comparative examples was coated on a PE base film. After suction filtration, the PE base film was removed to obtain the first coating powder. The positive electrode powder and the first coating powder were mixed, and after further drying, a mixed powder was obtained; the mixed powder was subjected to infrared testing. The infrared testing method between the second coating and the negative electrode is the same as above.

[0401] 3. Room Temperature Cycling Performance: In an environment of 25°C, the batteries of all examples and comparative examples were charged with constant current and constant voltage at a charging current of 1C until the upper limit voltage reached 4.35V. Then, a constant current discharge was carried out at a discharge current of 1C until the final voltage reached 2.8V, and the first discharge capacity value C0 at this time was recorded. Subsequently, the batteries of all examples and comparative examples were charged at 0.33C0 and discharged at 1C0 at a voltage of 3.3 - 4.3V, and continuously cycled, and the discharge capacity Cn after 1000 cycles was recorded. The capacity retention rate of the 1000th cycle = (discharge capacity of the 1000th cycle / discharge capacity of the first cycle) × 100%.

[0402] 4. High Rate Discharge Capacity: In an environment of 25°C, the batteries of all examples and comparative examples were charged with constant current and constant voltage at a charging current of 1 / 3C until the upper limit voltage reached 4.35V. Then, a constant current discharge was carried out at discharge currents of 1 / 3C, 3C, and 5C until the final voltage reached 2.8V, and the discharge capacity value at this time was recorded.

[0403] 5. Test Method for Winding Component Cycle Expansion Rate

[0404] For the hot-pressed bare battery cell, use a vernier caliper to measure the thickness. After 1000 cycles, disassemble the battery cell and measure the thickness of the bare battery cell. The expansion rate = (diameter of the bare battery cell after cycling - diameter of the bare battery cell before cycling) / thickness of the bare battery cell before cycling.

[0405] The relevant parameters and performance test results of the batteries in the above Examples 1-1 to 1-7 are shown in Table 1 below.

[0406] Table 1: Parameters and Performance Test Results of Examples 1-1 to 1-7

[0407]

[0408]

[0409] The relevant parameters and performance test results of the batteries in the above Examples 2-1 to 2-4 are shown in Table 2 below.

[0410] Table 2: Parameters and Performance Test Results of Examples 2-1 to 2-4

[0411]

[0412]

[0413] The relevant parameters and performance test results of the batteries in the above Examples 3-1 to 3-5 are shown in Table 3 below.

[0414] Table 3: Parameters and Performance Test Results of Examples 3-1 to 3-5

[0415]

[0416]

[0417] The relevant parameters and performance test results of the batteries in the above Examples 4-1 to 4-5 are shown in Table 4 below.

[0418] Table 4: Parameters and Performance Test Results of Examples 4-1 to 4-5

[0419]

[0420]

[0421] The relevant parameters and performance test results of the batteries in the above Examples 5-1 to 5-7 are shown in Table 5 below.

[0422] Table 5: Parameters and Performance Test Results of Examples 5-1 to 5-7

[0423]

[0424]

[0425] The relevant parameters and performance test results of the batteries in the above Examples 6-1 to 6-5 are shown in Table 6 below.

[0426] Table 6: Parameters and Performance Test Results of Examples 6-1 to 6-5

[0427]

[0428]

[0429] The relevant parameters and performance test results of the batteries in the above Examples 7-1 to 7-5 are shown in Table 7 below.

[0430] Table 7: Parameter and performance test results of Examples 7-1 to 7-5

[0431]

[0432]

[0433] The relevant parameters and performance test results of the batteries of Examples 8-1 to 8-7 are shown in Table 8 below.

[0434] Table 8: Parameter and performance test results of Examples 8-1 to 8-7

[0435]

[0436]

[0437] The relevant parameters and performance test results of the batteries of Comparative Examples 1 to 3 are shown in Table 9 below.

[0438] Table 9: Parameter and performance test results of Comparative Examples 1 to 3

[0439]

[0440]

[0441] According to the above results, in Table 1, and reflect the influence of the relative content relationship between the first polar substance in the separator and the binder for the positive electrode, and the relative content relationship between the second polar substance and the binder in the negative electrode on the battery performance. Examples 1-1 to 1-7 achieved good effects on battery performance such as cycle expansion rate, capacity retention rate after 1000 cycles, and 5C discharge capacity by adjusting as well as Especially at (80-100):1, at (32-50):1, the battery performance is better.

[0442] In Table 2, reflects the influence of the ratio of the relative content of the first polar substance in the separator in the first coating to the relative content of the second polar substance in the second coating on the battery performance. Examples 2-1 to 2-4 achieved good effects on battery performance such as cycle expansion rate, capacity retention rate after 1000 cycles, and 5C discharge capacity by adjusting Especially in the range of 1:(1-1.3), the battery performance is better.

[0443] In Table 3, while maintaining When it is basically a fixed value, in Examples 3-1 to 3-5, by comprehensively adjusting the mass content w1 of the first polar substance in the first coating, the mass content m1 of the positive electrode binder in the film layer of the positive electrode, the mass content w2 of the second polar substance in the second coating, and the mass content m2 of the negative electrode binder in the film layer of the negative electrode, good effects are achieved in battery performance such as cyclic swelling rate, capacity retention rate after 1000 cycles, and 5C discharge capacity. Especially when m1 is in the range of 1% to 1.2% and m2 is in the range of 2% to 3%, the battery performance is better.

[0444] In Table 4, in Examples 4-1 to 4-5, by adjusting the mass ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating, good effects are achieved in battery performance such as cyclic swelling rate, capacity retention rate after 1000 cycles, and 5C discharge capacity. Especially in the range of (0.8 - 1):1, the battery performance is better.

[0445] In Table 5, in Examples 5-1 to 5-7, by adjusting the mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating Hydrogen bonds are easily formed between the reinforcing agent and the polar substance, which can reduce the swelling of the bare battery cell, thereby improving the battery performance. Good effects are achieved in battery performance such as cyclic swelling rate, capacity retention rate after 1000 cycles, and 5C discharge capacity. Especially both are in the range of (5 - 9):1, the battery performance is better.

[0446] In Table 6, Examples 6-1 to 6-5 reflect the influence of the particle size of silicon on the battery performance. Good effects are achieved in battery performance such as cyclic swelling rate, capacity retention rate after 1000 cycles, and 5C discharge capacity. Especially when the particle size of silicon is in the range of 0.1 to 0.5 microns, the battery performance is better.

[0447] In Table 7, in Examples 7-1 to 7-4, by adjusting the Ni content in the ternary positive electrode material, the swelling of the bare battery cell can be significantly improved, and good effects are achieved in battery performance such as cyclic swelling rate and capacity retention rate after 1000 cycles. Especially when the Ni content is in the range of 0.5 to 0.9, the battery performance is better.

[0448] In Table 8, in Examples 8-1 to 8-7, by adjusting the mass ratio C1 of polyethylene oxide to polyacrylamide and the mass ratio C2 of polyethyleneimine to polyethylene oxide, good effects were achieved in battery performance such as cyclic swelling rate, capacity retention rate after 1000 cycles, and 5C discharge capacity. Especially when the values of C1 and C2 are respectively in the range of (2-6):1, the battery performance is better.

[0449] In contrast, in Table 9, in Comparative Examples 1 to 3, no effective improvement was achieved in battery performance such as cyclic swelling rate, capacity retention rate after 1000 cycles, and 5C discharge capacity.

[0450] In addition, as Figure 1 shown, the first polar substance is PEO, the first reinforcing agent is PVDF, the binder for the positive electrode is PEO, the second polar substance is PEI, the second reinforcing agent is PVDF, the binders for the negative electrode are SA and SBR, and the negative electrode active material is a carbon-silicon mixture.

[0451] Between the positive electrode and the separator, F on the binder PVDF for the positive electrode forms a hydrogen bond with H of the first polar substance PEO.

[0452] In the first coating, F on the first reinforcing agent PVDF forms a hydrogen bond with H of the first polar substance PEO.

[0453] Between the negative electrode and the separator, since the electronegativity N < O < F, H on -OH in the carbon-silicon mixture is more electron-deficient than H of -NH2. Therefore, N of -NH2 in the second polar substance PEI easily forms a hydrogen bond with H of -OH in the carbon-silicon mixture. Similarly, N of -NH2 in the second polar substance PEI forms a hydrogen bond with H of -COOH in the binder SA for the negative electrode. Hydrogen bonds can be formed between H of -OH in the carbon-silicon mixture and H of -COOH in SA.

[0454] In the second coating, F of the second reinforcing agent PVDF forms a hydrogen bond with H of PEI.

[0455] As Figure 2 shown, between 3200 cm -1 ~3600 cm -1 is the peak of the hydrogen bond. When the first polar substance or the second polar substance is not added in Comparative Example 1, almost no hydrogen bond is generated. While in Example 1, since hydrogen bond connections are generated on both the A and B surfaces, the peak is wide and obvious. In addition, it should be noted that the bond energy size order of the four hydrogen bonds O-H-O, F-H-O, N-H-O, and F-H-N is F-H-O > F-H-N > O-H-O > N-H-O, and the difference in bond energy between 25 - 40 KJ / mol is relatively small. There are multiple hydrogen bonds in a wave number range. Normally, the more hydrogen bonds, the more and wider the peaks are shown.

[0456] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition in essence of the technical idea and achieving the same effects within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A battery, characterized in that, the battery includes a positive electrode, a separator, and a negative electrode. The separator includes a base film, a first coating provided on the first surface of the base film, and a second coating provided on the second surface of the base film. Among them, the first coating includes a first polar substance, and the first polar substance includes one or more of polyolefin amides, polyolefin imines, polyoxyolefins, polyurethanes, and polyureas. There is a hydrogen bond between the first polar substance and the binder for the positive electrode of the positive electrode; the second coating includes a second polar substance, and the second polar substance includes one or more of polyolefin amides, polyolefin imines, polyoxyolefins, polyurethanes, and polyureas. There is a hydrogen bond between the second polar substance and the binder for the negative electrode of the negative electrode and / or the negative electrode active component; the peeling force between the first coating and the positive electrode is not less than 0.075 N; the peeling force between the second coating and the negative electrode is not less than 0.075 N.

2. The battery according to claim 1, characterized in that, the peeling force between the first coating and the positive electrode is 0.075 N to 0.125 N; the peeling force between the second coating and the negative electrode is 0.075 N to 0.15 N.

3. The battery according to claim 1 or 2, characterized in that, The ratio of the mass content w1 of the first polar substance in the first coating to the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is (80 to 100):1; The ratio of the mass content w2 of the second polar substance in the second coating to the mass content m2 of the negative electrode binder in the film layer of the negative electrode is (32 to 50):

1.

4. The battery according to claim 1, characterized in that, The ratio of the mass content w1 of the first polar substance in the first coating to the mass content w2 of the second polar substance in the second coating is 1:(1 to 1.3).

5. The battery according to claim 1, characterized in that, the mass content w1 of the first polar substance in the first coating is 80% to 90%, and the mass content m1 of the binder for the positive electrode in the film layer of the positive electrode is 0.9% to 1.2%; the mass content w2 of the second polar substance in the second coating is 80% to 90%, and the mass content m2 of the binder for the negative electrode in the film layer of the negative electrode is 2% to 3%.

6. The battery according to claim 1, characterized in that, the first polar substance includes polyethylene oxide and polyacrylamide; among them, the mass ratio C1 of polyethylene oxide to polyacrylamide is (2 to 6):1; the second polar substance includes polyethyleneimine and polyethylene oxide; among them, the mass ratio C2 of polyethyleneimine to polyethylene oxide is (2 to 6):

1.

7. The battery according to claim 1, characterized in that, The first coating includes a first reinforcing agent, and the mass ratio of the mass content w1 of the first polar substance in the first coating to the mass content k1 of the first reinforcing agent in the first coating is (5-9):1; the second coating includes a second reinforcing agent, and the mass ratio of the mass content w2 of the second polar substance in the second coating to the mass content k2 of the second reinforcing agent in the second coating is (5-9):

1.

8. The battery according to claim 7, characterized in that, the mass content k1 of the first reinforcing agent in the first coating is not higher than the mass content k2 of the second reinforcing agent in the second coating.

9. The battery according to claim 7, characterized in that, The ratio of the mass content k1 of the first reinforcing agent in the first coating to the mass content k2 of the second reinforcing agent in the second coating is (0.8 - 1):

1.

10. The battery according to claim 7, characterized in that, the first reinforcing agent or the second reinforcing agent includes one or more of polyvinylidene fluoride and sodium alginate; the binder for the positive electrode includes polyvinylidene fluoride, and the binder for the negative electrode includes one or more of styrene-butadiene rubber and sodium alginate.

11. The battery according to claim 1, characterized in that, The negative electrode active component includes a silicon-carbon mixture. In the silicon-carbon mixture, the particle size of silicon is 0.1 to 0.5 microns, and the carbon is a mixed carbon of artificial graphite and natural graphite. The content of the silicon-carbon mixture in the film layer of the negative electrode is 95% - 97%.

12. The battery according to claim 1, wherein the mass ratio of the first coating layer to the second coating layer is 1:(1 - 1.5).

13. The battery according to claim 7, wherein the first coating layer is obtained by preparing with a first coating slurry, and the first coating slurry includes the first polar substance, the first reinforcing agent and a first solvent; wherein the viscosity of the first coating slurry is 8000 mPa·s to 12000 mPa·s; the second coating layer is obtained by preparing with a second coating slurry, and the second coating slurry includes the second polar substance, the second reinforcing agent and a second solvent; wherein the viscosity of the second coating slurry is 5000 mPa·s to 20000 mPa·s.

14. The battery according to claim 1, wherein the positive electrode includes a positive electrode material LiNixCoyMnzO2, x + y + z = 1, and x = 0.5 to 0.

9.

15. The battery according to claim 14, wherein x = 0.5 to 0.7, x = 0.8 to 0.

9.

16. A battery module, characterized in that, including the battery according to any one of claims 1 to 15.

17. A battery pack, characterized in that, including the battery module according to claim 16.

18. An electrical device, characterized in that, including one or more selected from the battery according to any one of claims 1 to 15, the battery module according to claim 16, or the battery pack according to claim 17.

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