Isolating membrane, battery monomer, battery and electric device

Abstract

The invention provides an isolating membrane, a battery monomer, a battery and an electric device, and belongs to the technical field of batteries. In the first direction of the isolating membrane, the liquid absorption rate of the middle area of the isolating membrane is larger than that of the edge area of the isolating membrane, and the first direction is perpendicular to the thickness direction of the isolating membrane. According to the technical scheme, the battery performance can be improved.

Description

Separator, battery cell, battery and electrical device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an isolation membrane, a battery cell, a battery, and an electrical device. Background Art

[0002] With the increasing severity of environmental pollution, the new energy industry has attracted more and more attention. In the new energy industry, battery technology is an important factor in its development.

[0003] Separators, a crucial component of batteries, primarily separate the positive and negative electrodes. Their performance is crucial to the battery's electrochemical performance and safety. Therefore, developing a separator to improve battery performance is a pressing technical challenge.

[0004] Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a separator to improve battery performance.

[0006] In order to achieve the above-mentioned objectives, the present application provides an isolation membrane, a battery cell, a battery and an electrical device.

[0007] In a first aspect, the present application provides an isolation membrane, wherein along a first direction of the isolation membrane, the liquid absorption rate of the middle region of the isolation membrane is greater than the liquid absorption rate of the edge region of the isolation membrane, and the first direction is perpendicular to the thickness direction of the isolation membrane.

[0008] The present application provides a separator, wherein the liquid absorption rate of the central region of the separator is greater than the liquid absorption rate of the edge regions of the separator along a first direction of the separator, the first direction being perpendicular to the thickness direction of the separator. The ability of the central region of the separator to absorb electrolyte is greater than that of the edge regions. When the separator is used in a battery cell to separate the positive and negative electrode plates, the electrolyte can better pass through the central region of the separator and reach the electrode plates due to the stronger electrolyte absorption capacity of the central region of the separator. This can reduce the risk of black spots and lithium deposition caused by poor wettability in the center of the electrode plates, thereby improving battery performance.

[0009] In one possible implementation, the porosity of the central region is greater than that of the edge regions. This greater porosity in the central region than in the edge regions provides the central region of the separator with more abundant electrolyte transport pathways, facilitating high liquid absorption in the central region.

[0010] In one possible implementation, the porosity of the central region is 30% to 90%, and the porosity of the edge regions is 10% to 50%. Alternatively, the porosity of the central region is 50% to 90%, and the porosity of the edge regions is 10% to 40%. This ensures both the liquid absorption rate and the adhesiveness of the separator are well balanced.

[0011] In a possible implementation, the adhesiveness of the middle region is lower than that of the edge region, so that the adhesiveness of the isolation film can be improved by the edge region.

[0012] In one possible implementation, the isolation film includes a base film layer, a first coating layer, and a second coating layer. The first coating layer and the second coating layer are applied to the same side surface of the base film layer, with the first coating layer located in the central region and the second coating layer located in the edge region. By disposing the first coating layer and the second coating layer in different regions of the same side surface of the base film layer, different properties can be achieved in different regions of the isolation film.

[0013] In one possible implementation, the porosity of the first coating layer is greater than the porosity of the second coating layer, so that the porosity of the central region of the isolation membrane is greater than that of the edge regions, thereby providing the central region of the isolation membrane with a stronger liquid absorption capacity.

[0014] In one possible implementation, the material of the first coating layer includes a porous material and a first adhesive. Thus, the porous material achieves the porosity requirement of the first coating layer, and the first adhesive achieves bonding between the first coating layer and the base film layer.

[0015] In one possible implementation, the porous material includes at least one of aluminum oxide, carbon aerogel, and zeolite. This allows for flexible selection of the porous material based on actual needs. For example, aluminum oxide can be selected as the porous material to improve the heat resistance of the separator.

[0016] In a possible implementation, the aluminum oxide includes aluminum oxide, which is beneficial to improving the reliability of the first coating layer.

[0017] In one possible implementation, the first adhesive includes at least one of acrylic acid, water-based acrylic emulsion, and styrene-butadiene rubber emulsion. This can avoid a decrease in the liquid absorption rate of the first coating layer due to excessive adhesion of the first adhesive.

[0018] In a possible implementation, the mass ratio of the porous material to the first binder in the first coating layer is 4:1 to 10:1. In this way, both the liquid absorption rate and the adhesiveness of the first coating layer can be taken into consideration.

[0019] In one possible implementation, the second coating layer includes a second binder having greater adhesion than the first binder of the first coating layer. This improves the adhesion between the separator and the positive and negative electrode sheets when the separator is disposed between the positive and negative electrode sheets.

[0020] In a possible implementation, the second binder includes polyvinylidene fluoride, so that the adhesion requirement of the second coating layer can be met by polyvinylidene fluoride.

[0021] In a possible implementation, along the first direction, the size D2 of the first coating layer and the size D1 of the base film layer satisfy: 1 / 5D1≤D2≤1 / 2D1. In this way, both the adhesion and liquid absorption rate of the isolation film can be taken into account.

[0022] In one possible implementation, along the thickness direction of the isolation film, the size H2 of the first coating layer and the size H1 of the base film layer satisfy the following relationship: 1 / 8H1≤H2≤1 / 3H1. In this way, both the adhesion and liquid absorption rate of the isolation film can be taken into consideration.

[0023] In one possible implementation, along the thickness direction of the isolation film, the size H3 of the second coating layer and the size H1 of the base film layer satisfy the following relationship: 1 / 8H1≤H3≤1 / 3H1. In this way, both the adhesion and liquid absorption rate of the isolation film can be taken into consideration.

[0024] In one possible implementation, along the thickness direction of the isolation film, the dimension H2 of the first coating layer is equal to the dimension H3 of the second coating layer. This facilitates the preparation of the first coating layer and the second coating layer and reduces the preparation complexity.

[0025] In a possible implementation, along the thickness direction of the isolation membrane, the size H2 of the first coating layer is larger than the size H3 of the second coating layer, which is conducive to further improving the liquid absorption capacity of the isolation membrane.

[0026] In one possible implementation, along the thickness direction of the isolation film, the dimension H3 of the second coating layer and the dimension H1 of the base film layer satisfy the following relationship: 1 / 8H1≤H3<1 / 6H1; and the dimension H2 of the first coating layer and the dimension H1 of the base film layer satisfy the following relationship: 1 / 6H1≤H2≤1 / 4H1. This ensures both the adhesion and liquid absorption of the isolation film.

[0027] In a second aspect, the present application provides a battery cell, comprising: the isolation membrane in the first aspect and any possible implementation thereof, wherein the isolation membrane is used to isolate the positive electrode plate and the negative electrode plate of the battery cell.

[0028] In one possible implementation, the battery cell further includes an electrolyte having a viscosity in the range of 2 mPa·s to 7 mPa·s. Thus, the battery cell provided with the separator has high liquid absorption and wettability, which can reduce the risk of black spots or lithium deposition in the center of the electrode in the battery cell when the electrolyte viscosity is high.

[0029] In one possible implementation, the battery cell has a dimension of 160 mm to 250 mm along the first direction and a dimension of 160 mm to 300 mm along the second direction, with the second direction being perpendicular to the first direction and the thickness of the separator. Thus, a battery cell equipped with this separator has high liquid absorption and wettability, which reduces the risk of black spots or lithium deposition in the center of the electrode plate of the battery cell when the battery cell dimension in the first direction is large.

[0030] In one possible implementation, the battery cell further includes an electrode assembly having a dimension along the first direction of 150 mm to 200 mm and a dimension along the second direction of 130 mm to 250 mm, with the second direction being perpendicular to the first direction and the thickness of the separator. Thus, the battery cell provided with this separator has high liquid absorption capacity and wettability, which can reduce the risk of black spots or lithium deposition in the center of the negative electrode when the dimensions of the positive and negative electrode sheets are large in the first direction.

[0031] In one possible implementation, the specific surface area of ​​the graphite in the negative electrode sheet of the battery cell is 0.3 m 2 / g~5.0m 2 In this way, the battery cell provided with the separator has high liquid absorption capacity and wettability, and when the specific surface area of ​​the graphite in the negative electrode plate is large, the risk of black spots or lithium deposition in the center of the negative electrode plate can be reduced.

[0032] In a third aspect, the present application provides a battery, comprising the battery cell in the second aspect and any possible implementation thereof.

[0033] In a fourth aspect, the present application provides an electrical device comprising the battery described in the third aspect.

[0034] The present application provides a separator, wherein the liquid absorption rate of the central region of the separator is greater than the liquid absorption rate of the edge regions of the separator along a first direction of the separator, the first direction being perpendicular to the thickness direction of the separator. The ability of the central region of the separator to absorb electrolyte is greater than that of the edge regions. When the separator is used in a battery cell to separate the positive and negative electrode plates, the electrolyte can better pass through the central region of the separator and reach the electrode plates due to the stronger electrolyte absorption capacity of the central region of the separator. This can reduce the risk of black spots and lithium deposition caused by poor wettability in the center of the electrode plates, thereby improving battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a schematic diagram of an isolation membrane according to an embodiment of the present application;

[0036] FIG2 is a schematic diagram of an isolation membrane according to an embodiment of the present application;

[0037] FIG3 is a schematic diagram of an isolation membrane according to an embodiment of the present application;

[0038] FIG4 is a schematic diagram of an isolation membrane according to an embodiment of the present application;

[0039] FIG5 is a schematic diagram of an isolation membrane according to an embodiment of the present application;

[0040] FIG6 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0041] FIG7 is a schematic diagram of a battery module according to an embodiment of the present application;

[0042] FIG8 is a schematic diagram of a battery according to an embodiment of the present application;

[0043] FIG9 is a schematic diagram of an electrical device according to an embodiment of the present application. DETAILED DESCRIPTION

[0044] Below, the embodiments of the separator, battery cell, battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0045] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] 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.

[0048] Unless otherwise specified, all steps of the present application may 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.

[0049] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0050] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0051] A separator is an electrically insulating film. As a crucial component of a battery, it primarily separates the positive and negative electrodes. Separators typically consist of a base film layer and a coating applied to the base film. The coating improves the separator's performance.

[0052] Research has found that when the isolation membrane is applied to battery cells with pole pieces with larger width and height, due to the weak liquid absorption or wetting ability of the center position of the pole piece, black spots or lithium deposition caused by insufficient lithium insertion are likely to appear on the negative pole piece, thereby affecting the performance of the battery cell.

[0053] In view of this, the present application provides a separator having a higher liquid absorption rate in the central region than in the edge regions. This can improve the liquid absorption or wetting ability of the electrode center by increasing the liquid absorption capacity of the central region, thereby reducing the risk of black spots or lithium deposition.

[0054] [Isolation film]

[0055] FIG1 is a schematic diagram of an isolation film according to an embodiment of the present application. As shown in FIG1 , along a first direction of the isolation film 1 , the liquid absorption rate of the middle region 11 of the isolation film 1 is greater than the liquid absorption rate of the edge region 12 of the isolation film 1 .

[0056] The first direction is perpendicular to the thickness direction of the isolation film 1. For example, as shown in FIG1 , the first direction is the y direction in the figure, and the thickness direction of the isolation film 1 is perpendicular to the plane where the y direction is located, that is, the thickness direction of the isolation film 1 is perpendicular to the x direction and the y direction in FIG1 .

[0057] Optionally, the first direction is the width direction of the separator 1 , and before the separator 1 is wound or laminated to prepare a battery cell, the length of the separator 1 is greater than the width of the separator 1 .

[0058] The edge region 12 of the isolation film 1 is a region where both ends of the isolation film 1 are located along the first direction.

[0059] The middle region 11 of the isolation film 1 is a region along the first direction close to the center of the isolation film 1. Optionally, the middle region 11 of the isolation film 1 is a non-edge region.

[0060] The liquid absorption rate of the isolation membrane 1 is the ability of the isolation membrane 1 to absorb liquid, such as electrolyte, and can also be considered as the wettability of the isolation membrane 1 to the electrolyte. The definition and detection method of the liquid absorption rate are as follows.

[0061] The electrolyte is absorbed by the capillary tube. When the capillary tube contacts the separator 1, the separator 1 absorbs the electrolyte in the capillary tube under capillary action. Different areas of the separator 1 absorb the electrolyte at different rates, which can reflect the wettability of different areas of the separator 1 for the electrolyte. The formula for liquid absorption rate is as follows: Wherein, v is the liquid absorption rate, d is the radius of the capillary (μm), h is the liquid absorption height of the electrolyte, which can be selected as 5 mm, ρ is the density of the electrolyte, and t is the liquid absorption time of the electrolyte.

[0062] The isolation membrane 1 is generally arranged between the positive electrode and the negative electrode of the battery cell to separate the positive electrode and the negative electrode. The liquid absorption capacity and wettability of the isolation membrane 1 are crucial to the performance of the electrode. If the liquid absorption capacity and wettability of the isolation membrane 1 are poor, the surface of the electrode is prone to black spots or lithium deposition due to insufficient lithium insertion. Along the first direction, the liquid absorption capacity of the middle area 11 of the isolation membrane 1 is greater than the liquid absorption rate of the edge area 12. In this way, the middle area 11 of the isolation membrane 1 has better liquid absorption capacity and wettability. When the isolation membrane 1 is arranged between the larger positive and negative electrode sheets, the risk of black spots or lithium deposition in the center of the electrode can be reduced.

[0063] The present application provides an isolation membrane 1, wherein the liquid absorption rate of the central region 11 of the isolation membrane 1 is greater than the liquid absorption rate of the edge region 12 of the isolation membrane 1 along a first direction of the isolation membrane 1, and the first direction is perpendicular to the thickness direction of the isolation membrane 1. The ability of the central region 11 of the isolation membrane 1 to absorb electrolyte is greater than that of the edge region 12. When the isolation membrane 1 is used in a battery cell to separate the positive electrode and the negative electrode, since the central region of the isolation membrane 1 has a stronger ability to absorb electrolyte, the electrolyte can better pass through the central region of the isolation membrane to reach and infiltrate the electrode, which can reduce the risk of black spots and lithium plating caused by poor wetting ability at the center of the electrode, thereby improving the safety, reliability and other performance of the battery.

[0064] In some embodiments, the porosity of the middle region 11 is greater than the porosity of the side regions 12 .

[0065] The porosity of the central region 11 may depend on the porosity of the material forming the central region 11, and the porosity of the edge region 12 may depend on the porosity of the material forming the edge region 12. Porosity can be defined as the ratio of the total volume of voids within a granular material to the apparent volume of the material.

[0066] Optionally, the porosity of the central region 11 and the edge region 12 can also be measured and calculated using corresponding testing methods. For example, the separator 1 in the central region or the edge region can be cut and its apparent volume V0 calculated. The actual volume V1 of the separator in the corresponding region can be measured using a true density tester. The porosity can then be expressed as: (V0-V1) / V0.

[0067] The greater the porosity, the greater the liquid absorption rate, and the higher the liquid absorption capacity and wetting ability. By setting the porosity of the central region 11 to be greater than the porosity of the edge region 12, the central region of the separator 1 has more abundant electrolyte transmission paths, which is conducive to achieving a high liquid absorption rate in the central region 11.

[0068] Optionally, the liquid absorption rate of the central region 11 can be increased by properly setting the tension when winding the separator 1. When the winding tension is low, the gap between the separator 1 and the positive or negative electrode sheet is larger, and the liquid absorption rate of the central region 11 of the separator 1 is low. When the winding tension is high, the capillary effect is weaker, and the liquid absorption rate of the central region 11 of the separator 1 is also low. When the separator 1, positive electrode sheet, and negative electrode sheet are wound using a winding device, properly setting the winding parameters (such as the winding tension) can increase the liquid absorption rate of the central region 11 of the separator 1.

[0069] In some embodiments, the porosity of the middle region 11 is 30% to 90%, for example 30%, 50%, 70%, 80%, 90%, and the porosity of the edge region 12 is 10% to 50%, for example 10%, 20%, 30%, 40%, 50%.

[0070] When the porosity of the middle region 11 is less than 30%, the liquid absorption rate of the middle region 11 is low, and the liquid absorption capacity and wettability of the middle region 11 are relatively low; when the porosity of the middle region 11 is greater than 90%, the adhesion of the middle region 11 of the isolation membrane 1 is low, and the adhesion between the isolation membrane 1 and the electrode is relatively low, which increases the risk of wrinkling and dislocation of the electrode.

[0071] When the porosity of the edge region 12 is less than 10%, the liquid absorption rate of the edge region 12 is low, and the liquid absorption capacity and wettability of the edge region 12 are relatively low; when the porosity of the edge region 12 is greater than 90%, the adhesion of the edge region 12 of the isolation membrane 1 is low, which increases the risk of wrinkling and dislocation of the electrode.

[0072] In the above embodiment, by setting the porosity of the middle region 11 and the edge region 12, the requirements of the isolation membrane 1 on liquid absorption rate and adhesion can be taken into account, and the liquid absorption capacity and wettability of the isolation membrane 1 can be improved under high adhesion.

[0073] Optionally, the porosity of the middle region 11 is 50% to 90%, and the porosity of the edge region 12 is 10% to 40%. This is beneficial to further improve the liquid absorption rate of the isolation membrane 1.

[0074] In some embodiments, the adhesiveness of the middle region 11 is lower than that of the side region 12. In this way, the adhesiveness of the side region 12 is higher, so that the adhesiveness requirement of the separator 1 can be achieved through the side region 12.

[0075] The adhesion of the middle region 11 or the edge region 12 can be characterized by the adhesion force. The test method of adhesion or adhesion force is as follows:

[0076] (1) Cut the isolation film of the area to be tested into a rectangular shape and prepare a piece of double-sided tape according to the size of the cut isolation film. For example, to test the adhesion of the middle area 11, cut the middle area 11 of the isolation film 1 and prepare a piece of double-sided tape according to the cut middle area 11 of the isolation film 1.

[0077] (2) Select a flat plate-like material as the first substrate. Attach one side of double-sided tape to the surface of the first substrate, and the other side of the tape to the isolation film to be tested. In other words, attach one surface of the isolation film to the first substrate using double-sided tape.

[0078] (3) Select a plate with an adhesive coating area as the second substrate and stick the second substrate to the other surface of the isolation film. At this time, the isolation film is located between the first substrate and the second substrate.

[0079] (4) Fix the same side of the first substrate and the second substrate at the lower end and the upper end of a universal tensile testing machine respectively for tensile testing. After the force relative displacement curve displayed on the universal tensile testing machine runs smoothly, record the tensile value, which reflects the bonding strength of the isolation film.

[0080] Figure 2 is a schematic diagram of an isolation film according to an embodiment of the present application, and Figure 3 is a schematic diagram of an isolation film according to an embodiment of the present application. In some embodiments, as shown in Figures 1 to 3 , the isolation film 1 includes a base film layer 20 , a first coating layer 21 , and a second coating layer 22 .

[0081] The first coating layer 21 and the second coating layer 22 are coated on the same side surface of the base film layer 20 , the first coating layer 21 is located in the middle area 11 , and the second coating layer 22 is located in the edge area 12 .

[0082] Along the thickness direction of the isolation film 1, the base film layer 20 has two opposite surfaces, namely a first surface 201 and a second surface 202. The first coating layer 21 and the second coating layer 22 are applied to the same side surface of the base film layer 20, that is, the first coating layer 21 and the second coating layer 22 are both applied to at least one of the first surface 201 and the second surface 202. It can also be said that the first coating layer 21 and the second coating layer 11 are in contact with the base film layer 20.

[0083] Figures 2 and 3 show that the first coating layer 21 and the second coating layer 11 are disposed on the second surface 202 of the base film layer 20. Figures 3 and 4 are schematic diagrams of an isolation film according to an embodiment of the present application. As shown in Figures 3 and 4, the first coating layer 21 and the second coating layer 11 are disposed on the first surface 201 and the second surface 202 of the base film layer 20.

[0084] In the above embodiment, the first coating layer 21 and the second coating layer 22 are arranged in different areas of the same side surface of the base film layer 20. In this way, the materials, structures, etc. of the first coating layer 21 and the second coating layer 22 can be set according to actual needs, so that different performances of different areas of the isolation membrane 1 can be achieved.

[0085] In some embodiments, the porosity of the first coating layer 21 is greater than the porosity of the second coating layer 22. This facilitates achieving a greater porosity in the central region 11 of the separator 1 than in the edge regions 12, thereby enabling the central region 11 of the separator 1 to have a stronger liquid absorption capacity.

[0086] In some embodiments, the material of the first coating layer 21 includes a porous material and a first binder.

[0087] A porous material is a material with a network structure composed of interconnected or closed pores. The porosity of a porous material is generally between 15% and 90%.

[0088] The first coating layer 21 includes a porous material. This allows the electrolyte to quickly penetrate the portion of the electrode corresponding to the first coating layer 21 through the porous material of the first coating layer 21, thereby improving injection efficiency. Furthermore, during high-temperature infiltration, the electrolyte can quickly penetrate the portion of the electrode corresponding to the first coating layer 21 through the porous material of the first coating layer 21, thereby reducing the likelihood of black spots, lithium deposition, and other issues arising from poor infiltration at this portion of the electrode.

[0089] In the above embodiment, the porosity requirement of the first coating layer 21 is achieved by the porous material, and the bonding between the first coating layer 21 and the base film layer 20 and the bonding between the isolation film 1 and the pole piece are achieved by the first adhesive.

[0090] In some embodiments, the porous material includes at least one of aluminum oxide, carbon aerogel, and zeolite. This allows for flexible selection of the porous material based on actual needs. For example, aluminum oxide can be selected as the porous material to improve the heat resistance of the separator.

[0091] The porosity of aluminum oxide, carbon aerogel, and zeolite is related to their processing and preparation technology, and the required porosity can be obtained through different process settings.

[0092] In some embodiments, the aluminum oxide includes aluminum oxide, which is beneficial to improving the reliability of the first coating layer 21 .

[0093] In some embodiments, the first adhesive comprises at least one of acrylic acid, water-based acrylic emulsion, and styrene-butadiene rubber emulsion. This can avoid a decrease in the liquid absorption rate of the first coating layer 21 due to excessive adhesion of the first adhesive.

[0094] In some embodiments, the mass ratio of the porous material to the first binder in the first coating layer 21 is 4:1 to 10:1, for example, 4:1, 6:1, 8:1, or 10:1.

[0095] When the mass ratio of the porous material to the first binder in the first coating layer 21 is less than 4:1, the porosity of the first coating layer 21 is low, and the liquid absorption capacity and wettability of the first coating layer 21 are low.

[0096] When the mass ratio of the porous material to the first adhesive in the first coating layer 21 is greater than 10:1, the bonding force between the first coating layer 21 and the electrode is relatively low, increasing the risk of wrinkling and dislocation of the electrode.

[0097] In the above embodiment, by setting the mass ratio of the porous material to the first adhesive in the first coating layer 21 to be 4:1 to 10:1, both the liquid absorption rate and the adhesiveness of the first coating layer 21 can be taken into consideration.

[0098] In some embodiments, the material of the second coating layer 22 includes a second binder, and the bonding strength of the second binder is greater than the bonding strength of the first binder of the first coating layer 21. In this way, when the separator 1 is disposed between the positive electrode sheet and the negative electrode sheet, the bonding strength between the separator 1 and the positive electrode sheet and the negative electrode sheet can be improved.

[0099] In some embodiments, the second adhesive includes polyvinylidene fluoride (PVDF), so that the second coating layer 22 can be bonded to the pole piece through PVDF, thereby reducing the risk of wrinkling and dislocation of the pole piece.

[0100] In some embodiments, along the first direction, a size D2 of the first coating layer 21 and a size D1 of the base film layer 20 satisfy: 1 / 5D1≤D2≤1 / 2D1.

[0101] When D2 is less than 1 / 5 of D1, the proportion of the first coating layer 21 is small, and the liquid absorption capacity and wettability of the isolation film 1 are low.

[0102] When D2 is greater than 1 / 2D1, the first coating layer 21 occupies a larger proportion. Although the isolation film 1 can have a higher liquid absorption rate, the adhesion of the isolation film 1 is weak, which increases the risk of wrinkling and dislocation of the electrode.

[0103] In the above embodiment, by setting 1 / 5D1≤D2≤1 / 2D1, both the adhesiveness and the liquid absorption rate of the isolation film 1 can be taken into consideration.

[0104] Optionally, along the first direction, the center of the first coating layer 21 coincides with the center of the isolation film 1 , and the first coating layer 21 is a coating layer with a certain width and symmetrically distributed along its center.

[0105] Optionally, the first coating layer 21 is a plurality of coating layers spaced apart in the first direction. In this case, D2 is the sum of the dimensions of the plurality of coating layers in the first direction.

[0106] In some embodiments, along the thickness direction of the isolation film 1 , the size H2 of the first coating layer 21 and the size H1 of the base film layer 20 satisfy: 1 / 8H1≤H2≤1 / 3H1.

[0107] As shown in FIG. 2 and FIG. 3 , the thickness direction of the isolation film 1 is the z direction in the figures.

[0108] When H2 is less than 1 / 8 H1, the thickness of the first coating layer 21 is small, the content of the porous material is low, the porosity of the central region 11 of the isolation membrane 1 is low, and the liquid absorption capacity and wettability are low.

[0109] When H2 is greater than 1 / 3H1, on the one hand, it is difficult to ensure the adhesion of the middle area of ​​the isolation membrane 1, which increases the risk of wrinkling and dislocation of the electrode; on the other hand, the isolation membrane 1 has a large thickness, resulting in the isolation membrane 1 occupying a larger space, which is not conducive to improving the energy density of the battery.

[0110] In the above embodiment, by setting 1 / 8H1≤H2≤1 / 3H1, both the adhesiveness and the liquid absorption rate of the isolation film 1 can be taken into consideration.

[0111] In some embodiments, along the thickness direction of the isolation film 1 , the size H3 of the second coating layer 22 and the size H1 of the base film layer 20 satisfy: 1 / 8H1≤H3≤1 / 3H1.

[0112] When H3 is less than 1 / 8H1, the thickness of the second coating layer 22 is small, the content of the second adhesive is low, and the bonding force between the edge area 12 of the isolation membrane 1 and the pole piece is weak, which increases the risk of dislocation and wrinkling of the pole piece.

[0113] When H3 is greater than 1 / 3H1, on the one hand, it is difficult to ensure the liquid absorption rate of the edge area 12 of the isolation membrane 1, which may cause black spots or lithium deposition at the position corresponding to the edge area 12 of the electrode; on the other hand, the isolation membrane 1 has a large thickness, resulting in the isolation membrane 1 occupying a large space, which is not conducive to improving the energy density of the battery.

[0114] In the above embodiment, by setting 1 / 8H1≤H3≤1 / 3H1, both the adhesiveness and the liquid absorption rate of the isolation film 1 can be taken into consideration.

[0115] In some embodiments, along the thickness direction of the isolation film 1, the dimension H2 of the first coating layer 21 is equal to the dimension H3 of the second coating layer. This facilitates the preparation of the first coating layer 21 and the second coating layer 22 and reduces the preparation complexity.

[0116] In some embodiments, along the thickness direction of the isolation film 1 , the dimension H2 of the first coating layer 21 is greater than the dimension H3 of the second coating layer 21 , which is beneficial for further improving the liquid absorption capacity of the isolation film 1 .

[0117] Optionally, the first coating layer 21 and the second coating layer 22 may be made of the same material. For example, the first coating layer 21 and the second coating layer 22 may include a porous material and a binder with weaker adhesion than PVDF. By setting the dimension H2 of the first coating layer to be larger than the dimension H3 of the second coating layer, the requirements for adhesion and liquid absorption rate of the separator 1 in the central region 11 and the edge region 12 can be met.

[0118] Optionally, the size H2 of the first coating layer 21 satisfies: 1 / 6H1≤H2≤1 / 3H1, and the size H3 of the second coating layer 22 and the size H1 of the base film layer satisfy: 1 / 8H1≤H3<1 / 6H1.

[0119] In some embodiments, along the thickness direction of the isolation film 1, the dimension H3 of the second coating layer 22 and the dimension H1 of the base film layer satisfy the following relationship: 1 / 8H1≤H3<1 / 6H1; and the dimension H2 of the first coating layer 21 and the dimension H1 of the base film layer 20 satisfy the following relationship: 1 / 6H1≤H2≤1 / 4H1. This ensures that both the adhesion and liquid absorption rate of the isolation film 1 are maintained.

[0120] [Battery Cell]

[0121] The present application provides a battery cell, comprising the separator 1 according to any one of the above embodiments, wherein the separator 1 is used to separate the positive electrode sheet and the negative electrode sheet in the battery cell.

[0122] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape.

[0123] FIG6 is a schematic diagram of a battery cell according to an embodiment of the present application. As shown in FIG6 , the battery cell 3 includes a housing 31 , a cover plate 32 , and an electrode assembly 33 disposed in the housing 31 .

[0124] The electrode assembly 33 can be made of a positive electrode sheet, a negative electrode sheet and a separator 1 through a winding process or a lamination process.

[0125] In some embodiments, the battery cell 3 further includes an electrolyte, and the viscosity of the electrolyte ranges from 2 mPa·s to 7 mPa·s.

[0126] Optionally, the present application does not impose any specific restrictions on the specific type of electrolyte, as long as it can meet the above viscosity range.

[0127] The greater the viscosity of the electrolyte, the less wettable the separator 1 and the electrode. When the viscosity of the electrolyte is greater than 4 mPa·s, the existing separator's ability to absorb and wet the electrolyte decreases. The separator 1 in the battery cell 3 of this embodiment has high absorption and wettability, which reduces the risk of black spots or lithium deposition in the center of the electrode in the battery cell 3 when the electrolyte viscosity is high.

[0128] In some embodiments, a dimension d1 of the battery cell 3 along a first direction is 160 mm to 250 mm, and a dimension d2 along a second direction is 160 mm to 300 mm. The second direction is perpendicular to the first direction and the thickness direction of the separator 1 .

[0129] The dimension d1 along the first direction and the dimension d2 along the second direction of the battery cell 3 are respectively the maximum dimensions along the first direction and the second direction, and the dimensions can be measured by a caliper.

[0130] As shown in FIG6 , the first direction is the y direction in the figure, and the second direction is the x direction in the figure.

[0131] The size of the pole piece in the battery cell 3 is adapted to the size of the battery cell 3. The larger the battery cell 3, the larger the pole piece. During the electrolyte infiltration of the pole piece, the electrolyte diffuses from the edge of the pole piece toward the center of the pole piece, resulting in poor wettability in the center of the pole piece. The separator 1 of the battery cell 3 of this embodiment has high liquid absorption and wettability. When the size of the battery cell 3 in the first direction is large, the risk of black spots or lithium deposition in the center of the pole piece in the battery cell 3 can be reduced.

[0132] In some embodiments, a dimension d3 of the electrode assembly 33 along a first direction is 150 mm to 200 mm, and a dimension d4 along a second direction is 130 mm to 250 mm. The second direction is perpendicular to the first direction and the thickness direction of the separator 1 .

[0133] Since the electrode assembly 33 is formed by winding or stacking the positive electrode sheet, the separator 1 and the negative electrode sheet, the dimensions of the positive electrode sheet or the negative electrode sheet in the first direction and the second direction in the battery cell 3 are roughly the same as the dimensions of the electrode assembly 33 in the first direction and the second direction.

[0134] For example, the separator 1, the positive electrode sheet, and the negative electrode sheet in Figure 1 are wound to form an electrode assembly 33. Optionally, in combination with Figures 1 and 6, the first direction is the y direction in Figures 1 and 6, that is, the y direction in Figure 1 and the y direction in Figure 6 are both the first direction.

[0135] The dimension d3 along the first direction and the dimension d4 along the second direction of the electrode assembly 33 are respectively the maximum dimensions along the first direction and the second direction, and the dimensions can be measured by a caliper.

[0136] The separator 1 of the battery cell 3 of this embodiment has high liquid absorption capacity and wettability, which can reduce the risk of black spots or lithium deposition at the center of the negative electrode when the size of the electrode assembly 33 in the first direction is large.

[0137] In some embodiments, the specific surface area of ​​the graphite in the negative electrode sheet 32 ​​is 0.3 m 2 / g~5.0m 2 / g. Thus, the battery cell 3 provided with the separator 1 has a high liquid absorption capacity and wettability. When the specific surface area of ​​the graphite in the negative electrode sheet 32 ​​is large, for example, greater than 1.2m 2 / g, the risk of black spots or lithium deposition at the center of the negative electrode sheet 32 ​​can be reduced.

[0138] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in a battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0139] Figure 7 is a schematic diagram of a battery module according to one embodiment of the present application. Referring to Figure 7 , within a battery module 4, multiple battery cells 3 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 3 may be secured together using fasteners.

[0140] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 3 are accommodated in the accommodation space.

[0141] Figure 8 is a schematic diagram of a battery according to an embodiment of the present application. As shown in Figure 8 , the present application provides a battery 5 comprising a battery cell 3 according to any of the above embodiments.

[0142] The battery cells 3 can be directly assembled into the battery 5 , or they can be assembled into battery modules first, and then multiple battery modules can be assembled into the battery 5 .

[0143] Figure 9 is a schematic diagram of an electric device according to an embodiment of the present application. As shown in Figure 9 , the present application provides an electric device 6 including the battery 5 according to the above embodiment.

[0144] Example

[0145] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0146] [Method for preparing isolation film]

[0147] A polyethylene porous film is provided as the base film layer; the dual extrusion ports of the extrusion device are modulated, and two different slurries are extruded and coated onto the base film layer from the extrusion port of the extrusion device by controlling the slit width of the extrusion port and the metering pump. The coating thickness and width are precisely controlled by the slit width of the dual extrusion port and the metering pump to finally obtain an isolation film.

[0148] [Test method for porosity in different areas of the separator]

[0149] Take the isolation film from different areas and use tweezers to select >20 good-looking, smooth discs and place them into the sample cup. Record the number of discs and calculate the apparent volume V0.

[0150] Place the sample cup in the true density tester. A sealed test system is used, and helium is introduced according to a specific procedure. The pressure of the gas in the sample chamber and expansion chamber is measured, and the true volume V1 is calculated according to Bohr's law (PV = nRT). This provides the porosity of the isolation membrane in the test area. The porosity of the isolation membrane in the test area is calculated as: (V0 - V1) / V0.

[0151] The specific configurations of the isolation membranes of Examples 1-27 and Comparative Examples 1-2 are shown in Table 1. The structures of Examples 1-27 can be seen in conjunction with Figures 1-3. In Comparative Examples 1-2, the isolation membranes did not utilize a zoned coating method. In Comparative Example 1, the base membrane layer was coated solely with a porous material, while in Comparative Example 2, the base membrane layer was coated solely with PVDF.

[0152] Table 1 Specific parameters of Examples 1-27 and Comparative Examples 1-2

[0153] In Table 1, A1 is the porosity of the middle region 11 of the isolation membrane 1, A2 is the porosity of the edge region 12 of the isolation membrane 1, the porous material is the porous material in the first coating layer 21, the first adhesive is the adhesive in the first coating layer 21, A3 is the mass ratio of the porous material in the first coating layer 21 to the first adhesive, the second adhesive is the adhesive in the second coating layer 22, D1 is the size of the isolation membrane along the first direction, D2 is the size of the first coating layer along the first direction, H1 is the thickness of the base film layer 20, H2 is the thickness of the first coating layer 21, and H3 is the thickness of the second coating layer 22.

[0154] The isolation membranes obtained in the above Examples 1-27 and Comparative Examples 1-2 were tested for liquid absorption performance and prepared into lithium-ion batteries for performance testing. The test parameters and results are shown in Tables 2 and 3.

[0155] [Liquid absorption performance test]

[0156] The isolation membrane to be verified and the positive and negative electrode sheets are wound into an electrode assembly (where the positive and negative electrode sheets of different embodiments are exactly the same, only the isolation membranes are different), the electrode assembly is placed in a square aluminum shell, the electrolyte is injected into the aluminum shell so that the electrolyte liquid level just exceeds the height of the electrode assembly, and the liquid level at this time is marked as X. The overall mass at this time is measured with a high-precision balance and marked as mass M0. The top is sealed with aluminum-plastic film to prevent outside air from entering. The aluminum-plastic film is opened every 5 minutes, and the aluminum shell is injected with liquid so that the electrolyte liquid level after each injection is maintained at the initial liquid level. The overall mass at this time is measured with a balance, and the above steps are repeated. The time interval of each 5-minute interval is T0, T1, T2...Tn, and the overall mass of the battery cell every 5 minutes is M1, M2...Mn, with T0 as the maximum value. 0.5 、T1 0.5 、T2 0.5 、T3 0.5 ...Tn 0.5 As the horizontal axis, (M1-M0), (M2-M0), (M3-M0) ... (Mn-M0) as the vertical axis, the fitting diagram is obtained to obtain the slope K, the slope K is used as the liquid absorption capacity (unit is g / min 0.5 )size.

[0157] [Preparation of lithium-ion battery cells]

[0158] Preparation of the positive electrode sheet: 1) Mix polyvinylidene fluoride (PVDF), lithium-ion positive electrode material NCM523, and conductive agent (carbon black Super P) in a mass ratio of 90:5:5. Use N-methyl-pyrrolidone (NMP) as the solvent. Adjust the solvent addition amount to control the slurry viscosity to 100-20,000 mPa.s. Apply the slurry to the positive electrode current collector using a coater or sprayer. After drying at 85°C, cold press the slurry. Then trim, cut, and slit the slurry. Dry the slurry at 85°C under vacuum for 4 hours. Weld the tabs to produce a lithium-ion battery cell positive electrode sheet that meets the requirements.

[0159] Preparation of negative electrode sheets: Active material graphite, conductive agent Super-P, thickener CMC, and adhesive SBR are added to solvent deionized water in a mass ratio of 96.5:1.0:1.0:1.5 and mixed evenly to form a negative electrode slurry; the negative electrode slurry is coated on the current collector copper foil and dried at 85°C, and then trimmed, cut into pieces, and striped, and then dried under vacuum conditions at 110°C for 4 hours, and the tabs are welded to form a lithium-ion battery cell negative electrode sheet that meets the requirements.

[0160] Preparation of the electrolyte: A mixture of ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) was used as a non-aqueous organic solvent, wherein the mass ratio of each component was EC:PC:DEC = 30:30:40, and lithium hexafluorophosphate (LiPF6) was used as the lithium salt to prepare an electrolyte with a concentration of 1M.

[0161] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to act as an insulator. The sheets are then wound into a square bare cell with a thickness of 8 mm, a width of 60 mm, and a length of 130 mm. The bare cell is placed in an aluminum foil packaging bag, vacuum-baked at 75°C for 10 hours, injected with electrolyte, vacuum-sealed, and left to stand for 24 hours. The cell is then charged to 4.5V at a constant current of 0.1C (160mA), then charged at a constant voltage of 4.5V until the current drops to 0.05C (80mA), and then discharged to 2.8V at a constant current of 0.1C (160mA). This cycle is repeated twice, and finally charged to 3.8V at a constant current of 0.1C (160mA). This completes the preparation of the lithium-ion battery cell.

[0162] To further test the performance of the separator, the separator of Example 1 was applied to several different lithium-ion batteries. Specific parameters are shown in Table 2. In Table 2, b1 is the viscosity of the electrolyte, d1 is the size of the battery cell along the first direction, d2 is the size of the battery cell along the second direction, d3 is the size of the electrode assembly along the first direction, d4 is the size of the electrode assembly along the second direction, and b2 is the specific surface area of ​​the graphite in the negative electrode sheet.

[0163] [Test method for specific surface area]

[0164] Take an appropriate amount of sample in a dedicated sample tube, heat and vacuum degas for 2 hours, cool to room temperature, weigh, and subtract the mass of the sample tube to obtain the sample mass. Place the sample in a nitrogen adsorption-desorption instrument. At a constant low temperature, measure the amount of gas adsorbed on the solid surface at different pressures. Based on the multilayer adsorption theory (BET theory) and formula, calculate the monolayer adsorption amount in the sample, and thus calculate the specific surface area per unit mass of the solid sample.

[0165] [Electrolyte viscosity test method]

[0166] The viscosity of the electrolyte can be measured using a Brookfield DV-2T viscometer. The specific test method includes: rinsing the sample cup and rotor with the electrolyte sample, maintaining a constant temperature of 25°C, selecting a fixed #18 rotor at 70 rpm, selecting the Multi-Point Average data acquisition mode, and starting automatic testing.

[0167] Table 2 Specific parameters of different lithium-ion batteries in Examples 28-31

[0168] [Battery cell performance test]

[0169] The battery was charged to full capacity with a current of 1 / 3C, and the state of charge (SOC) of the battery cell was adjusted to 100% SOC. The battery cell was tested using X-ray tomography to observe whether the internal structure of the electrode assembly was wrinkled or deformed.

[0170] After the test is completed, the battery cells are disassembled in a drying room, the electrode assembly is taken out, and the negative electrode sheets are unfolded from the outer circle in sequence according to the number of folds. The interface of the negative electrode is observed to see if there are black spots, lithium precipitation, and wrinkles on the interface.

[0171] Table 3 Test results

[0172] As shown in Examples 1-31 and Comparative Examples 1-2, if only a porous material layer is provided on the base film layer, the adhesion of the isolation film is poor, and deformation of the electrode assembly and wrinkling of the pole piece are likely to occur; if only PVDF is coated on the base film layer, the liquid absorption rate of the isolation film is poor, and black spots and lithium deposition are likely to appear on the pole piece.

[0173] In combination with Examples 1-4 and Examples 20-21, by reasonably setting the porosity of the middle area and the edge area, both liquid absorption rate and adhesion can be taken into account.

[0174] As shown in Examples 1-19 and 24-27, by reasonably setting the sizes of the middle area and the side areas, both liquid absorption rate and adhesion can be taken into account.

[0175] As shown in Example 1 and Examples 28-31, the isolation membrane of the present application can be applied to electrolytes with a wider viscosity range, larger electrode assemblies and battery cells, and graphite negative electrodes with a larger specific surface area.

[0176] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A separation film, wherein: Along a first direction of the isolation film (1), the liquid absorption rate of the middle region (11) of the isolation film (1) is greater than the liquid absorption rate of the edge region (12) of the isolation film (1), and the first direction is perpendicular to the thickness direction of the isolation film (1).

2. The isolation film according to claim 1, wherein: The porosity of the middle region (11) is greater than the porosity of the edge region (12).

3. The isolation film according to claim 2, wherein: The porosity of the middle region (11) is 30% to 90%, and the porosity of the edge region (12) is 10% to 50%; optionally, the porosity of the middle region (11) is 50% to 90%, and the porosity of the edge region (12) is 10% to 40%.

4. The isolation film according to any one of claims 1 to 3, wherein: The adhesiveness of the middle region (11) is lower than the adhesiveness of the edge region (12).

5. The isolation film according to any one of claims 1 to 4, wherein: The isolation film (1) comprises a base film layer (20), a first coating layer (21) and a second coating layer (22), wherein the first coating layer (21) and the second coating layer (22) are coated on the same side surface of the base film layer (20), the first coating layer (21) is located in the middle area (11), and the second coating layer (22) is located in the edge area (12).

6. The isolation film according to claim 5, wherein: The porosity of the first coating layer (21) is greater than the porosity of the second coating layer (22).

7. The isolation film according to claim 5 or 6, wherein: The material of the first coating layer (21) includes a porous material and a first binder.

8. The isolation film according to claim 7, wherein: The porous material includes at least one of aluminum oxide, carbon aerogel and zeolite.

9. The isolation film according to claim 8, wherein: The aluminum oxide includes aluminum oxide.

10. The isolation film according to any one of claims 7 to 9, wherein: The first adhesive includes at least one of acrylic acid, water-based acrylic emulsion, and styrene-butadiene rubber emulsion.

11. The isolation film according to any one of claims 7 to 10, wherein: The mass ratio of the porous material in the first coating layer (21) to the first binder is 4:1 to 10:

1.

12. The isolation film according to any one of claims 5 to 11, wherein: The material of the second coating layer (22) includes a second adhesive, and the adhesiveness of the second adhesive is greater than the adhesiveness of the first adhesive of the first coating layer (21).

13. The isolation film according to claim 12, wherein: The second binder includes polyvinylidene fluoride.

14. The isolation film according to any one of claims 5 to 13, wherein: Along the first direction, a size D2 of the first coating layer (21) and a size D1 of the base film layer (20) satisfy the following relationship: 1 / 5D1≤D2≤1 / 2D1.

15. The isolation film according to any one of claims 5 to 14, wherein: Along the thickness direction of the isolation film (1), the size H2 of the first coating layer (21) and the size H1 of the base film layer (20) satisfy the following relationship: 1 / 8H1≤H2≤1 / 3H1.

16. The isolation film according to any one of claims 5 to 15, wherein: Along the thickness direction of the isolation film (1), the size H3 of the second coating layer (22) and the size H1 of the base film layer (20) satisfy the following relationship: 1 / 8H1≤H3≤1 / 3H1.

17. The isolation film according to any one of claims 5 to 16, wherein: Along the thickness direction of the isolation film (1), the size H2 of the first coating layer (21) is equal to the size H3 of the second coating layer (22).

18. The isolation film according to any one of claims 5 to 16, wherein: Along the thickness direction of the isolation film (1), a size H2 of the first coating layer (21) is greater than a size H3 of the second coating layer (22).

19. The isolation film according to claim 18, wherein: Along the thickness direction of the isolation film (1), the size H3 of the second coating layer (22) and the size H1 of the base film layer (20) satisfy the following relationship: 1 / 8H1≤H3<1 / 6H1; the size H2 of the first coating layer (21) and the size H1 of the base film layer (20) satisfy the following relationship: 1 / 6H1≤H2≤1 / 4H1.

20. A battery cell, wherein: include: The separator (1) according to any one of claims 1 to 19, wherein the separator (1) is used to separate the positive electrode sheet and the negative electrode sheet in the battery cell (3).

21. The battery cell according to claim 20, wherein: The battery cell (3) further comprises an electrolyte, wherein the viscosity of the electrolyte ranges from 2 mPa·s to 7 mPa·s.

22. The battery cell according to claim 20 or 21, wherein: The dimension d1 of the battery cell (3) along the first direction is 160 mm to 250 mm, and the dimension d2 along the second direction is 160 mm to 300 mm, and the second direction is perpendicular to the first direction and the thickness direction of the isolation film (1).

23. The battery cell according to any one of claims 20 to 22, wherein: The battery cell (3) further comprises an electrode assembly (33), wherein the dimension d3 of the electrode assembly (33) along the first direction is 150 mm to 200 mm, and the dimension d4 along the second direction is 130 mm to 250 mm, wherein the second direction is perpendicular to the first direction and the thickness direction of the isolation film (1).

24. The battery cell according to any one of claims 20 to 23, wherein: The specific surface area of ​​the graphite in the negative electrode sheet of the battery cell (3) is 0.3 m 2 / g~5.0m 2 / g.

25. A battery, wherein: It comprises a battery cell (3) as claimed in any one of claims 20 to 24.

26. An electrical device, wherein: Comprising a battery as claimed in claim 25.

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