Battery monomer, isolating membrane, battery and power utilization device

Abstract

The invention relates to a battery monomer, an isolating membrane, a battery and a power utilization device. Each battery monomer comprises an isolating membrane, a negative pole piece and a positive pole piece; the isolating membrane is arranged between the negative pole piece and the positive pole piece; the isolating membrane comprises a base membrane; the base film comprises a first surface and a second surface; the first surface comprises a first coating, and the first coating comprises first particles; the second surface comprises a second coating, and the second coating comprises second particles; the DV50 of the first particulate matter is greater than the DV50 of the second particulate matter; the first coating faces the negative pole piece; and the second coating faces the positive pole piece. The first surface and the second surface of the isolating membrane are different in particle size, so that a proper gap can be formed between the positive pole piece and the negative pole piece at the corner of the battery, and meanwhile, the capacity of the battery is effectively maintained. And finally, on the premise that the battery capacity is basically unchanged, the problem of lithium precipitation of the positive and negative pole pieces at the corners of the battery can be solved by keeping a reasonable gap between the positive and negative pole pieces.

Description

Technical Field

[0001] The present application relates to a battery cell, a separator, a battery, and an electrical device. Background Art

[0002] As an emerging sustainable energy storage technology, lithium-ion batteries have the characteristics of low cost and environmental friendliness, so their application has been increasingly developed in recent years.

[0003] Therefore, higher requirements are put forward for improving the lithium plating problem at the corners of lithium-ion batteries. Summary of the invention

[0004] The purpose of the present application is to provide a battery cell, a separator, a battery, and an electrical device.

[0005] The embodiment of the present application is implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides a battery cell, including:

[0007] A separator, a negative electrode sheet and a positive electrode sheet; the separator is disposed between the negative electrode sheet and the positive electrode sheet; and is used to separate the negative electrode sheet from the positive electrode sheet;

[0008] The isolation film includes a base film; the base film includes a first surface and a second surface;

[0009] The first surface includes a first coating, the first coating includes first particulate matter;

[0010] The second surface includes a second coating, the second coating includes second particulate matter;

[0011] D of the first particle V 50 greater than the D of the second particle V 50;

[0012] The first coating faces the negative electrode; the second coating faces the positive electrode.

[0013] In the above technical solution, the first coating layer facing the negative electrode sheet includes the first particles, the second coating layer facing the positive electrode sheet includes the second particles, and the D of the first particles is V 50 greater than the D of the second particle V 50; On the one hand, larger particle size (D V 50) resists the large expansion of the negative electrode sheet, thereby maintaining the gap between the negative electrode sheet and the positive electrode sheet at the corner. V 50) have larger gaps between the particles, which further facilitates the infiltration of the electrolyte. On the other hand, the second surface of the separator faces the positive electrode sheet, and the smaller particle size (D V50) ensures that the gap between the positive and negative electrode sheets is not too large, so that the positive and negative electrode sheets are kept at an appropriate distance. In general, the particle size (D V 50) Different separators can both resist the expansion of the negative electrode and ensure a more appropriate gap between the positive and negative electrode sheets at the corners of the battery.

[0014] In some embodiments, the D of the first particle V 50 is greater than or equal to 15μm.

[0015] In some embodiments, the D of the second particle V 50 is less than or equal to 10μm.

[0016] In some embodiments, the D of the first particle V 50 is 15μm~30μm.

[0017] In some embodiments, the D of the second particle V 50 is 5μm~10μm.

[0018] In some embodiments, the thickness of the isolation film is 20 μm to 50 μm; the thickness of the first coating layer is 15 μm to 35 μm.

[0019] By setting the thickness of the isolation membrane and the thickness of the first coating within the above range, the thickness of the isolation membrane can be increased, and the increase in the thickness of the isolation membrane can increase the length of the pole piece wound around one circle, so that when the battery is under pressure, the increased length will be pressed to the corner, thereby achieving the purpose of creating a larger gap at the corner.

[0020] In some embodiments, the thickness of the isolation film is 20 μm to 50 μm; the thickness of the second coating layer is 5 μm to 15 μm.

[0021] In the above technical scheme, by setting the thickness of the isolation film to 20μm~50μm and the thickness of the second coating to 5μm~15μm, it is beneficial to control the gap between the positive electrode plate and the negative electrode plate at the corner of the battery within an appropriate range, which is beneficial to improving lithium deposition at the corner of the battery and is beneficial to the battery capacity.

[0022] In some embodiments, the first particulate matter includes at least one of organic particulate matter or inorganic particulate matter.

[0023] In some embodiments, the second particulate matter includes at least one of organic particulate matter or inorganic particulate matter.

[0024] In some embodiments, the organic particles include at least one of polyvinylidene fluoride particles, polyimide particles, or polyethylene oxide particles.

[0025] In some embodiments, the inorganic particulate matter includes at least one of alumina particles or boehmite particles.

[0026] In some embodiments, the surface density of the first coating layer and the second coating layer is 1 g / m 2 ~10g / m 2 ; Optionally, the surface density of the first coating and the second coating is equal.

[0027] In some embodiments, the isolation film satisfies at least one of the following characteristics:

[0028] (1) The air permeability of the isolation film is 390 seconds / 100cc to 450 seconds / 100cc;

[0029] (2) The porosity of the isolation membrane is 40% to 50%;

[0030] (3) The liquid absorption rate of the isolation film is 120% to 130%;

[0031] (4) The thickness of the base film is 3 μm to 10 μm.

[0032] In a second aspect, an embodiment of the present application provides an isolation film, including: a base film; the base film includes a first surface and a second surface;

[0033] The first surface includes a first coating, the first coating includes first particulate matter;

[0034] The second surface includes a second coating, the second coating includes second particulate matter;

[0035] D of the first particle V 50 greater than the D of the second particle V 50;

[0036] The first coating is used towards the negative electrode plate; the second coating is used towards the positive electrode plate.

[0037] In some embodiments, the isolation film satisfies at least one of the following characteristics:

[0038] (1) D of the first particle V 50: 15μm~35μm;

[0039] (2) D of the second particle V 50 is 5μm~10μm;

[0040] (3) The first particles and the second particles both include at least one of polyvinylidene fluoride particles, polyimide particles, polyethylene oxide particles, alumina particles, or boehmite particles;

[0041] (4) The surface density of the first coating and the second coating is 1g / m 2~10g / m 2 ;

[0042] (5) The surface density of the first coating layer and the second coating layer is the same.

[0043] In a third aspect, an embodiment of the present application provides a battery, comprising the battery cell provided in the first aspect.

[0044] In a fourth aspect, an embodiment of the present application provides an electrical device, the electrical device comprising a battery provided by any of the aforementioned implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0047] Figure 2 yes Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0048] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0049] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0050] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0051] Figure 6 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application;

[0052] Figure 7 is a schematic diagram of an electrode assembly according to an embodiment of the present application;

[0053] Figure 8 yes Figure 7 Enlarged view of point D in the middle.

[0054] icon:

[0055] 101 negative electrode plate; 102 separator; 103 positive electrode plate; 104 base film; 1021 first coating layer; 1022 second coating layer; 1023 first particles; 1024 second particles;

[0056] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0057] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0059] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0060] In the description of the embodiments of the present application, the orientations or positional relationships indicated by the technical terms "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0061] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0062] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0063] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the heights, lengths, widths, and other dimensions of the various components in the embodiments of the present application shown in the drawings, as well as the overall heights, lengths, widths, and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0064] During the battery cycle, the rebound rates of the positive and negative pole pieces are different. Especially during the charging process, the larger expansion of the negative pole piece often causes the gap between the negative pole piece and the positive pole piece at the corner of the wound battery to decrease sharply or even disappear. This will cause lithium deposition at the corner of the battery due to poor electrolyte infiltration, which ultimately manifests as a sharp decrease in battery capacity. Further research found that the gap between the negative pole piece and the positive pole piece at the corner of the wound battery cannot be too large, because a large gap will cause the electrolyte to "break the bridge", that is, the electrolyte cannot be fully infiltrated, which will also cause lithium deposition at the corner, and blindly increasing the gap will lead to a decrease in the length of the positive and negative pole pieces at the same volume, which will inevitably reduce the battery capacity.

[0065] Based on this, refer to Figure 7 In a first aspect, the present application provides a battery cell, including:

[0066] Separator 102, negative electrode sheet 101 and positive electrode sheet 103; Separator 102 is disposed between negative electrode sheet 101 and positive electrode sheet 103; and is used to separate negative electrode sheet 101 from positive electrode sheet 103;

[0067] The isolation film 102 includes a base film 104; the base film 104 includes a first surface and a second surface;

[0068] The first surface includes a first coating 1021, and the first coating 1021 includes first particles 1023;

[0069] The second surface includes a second coating 1022, and the second coating 1022 includes second particles 1024;

[0070] D of the first particle 1023 V 50 is greater than the D of the second particle 1024 V 50;

[0071] The first coating 1021 faces the negative electrode sheet 101 , and the second coating 1022 faces the positive electrode sheet 103 .

[0072] In the above technical solution, the first coating layer facing the negative electrode sheet includes the first particles, the second coating layer facing the positive electrode sheet includes the second particles, and the D of the first particles is V 50 greater than the D of the second particle V50; On the one hand, larger particle size (D V 50) resists the large expansion of the negative electrode sheet, thereby maintaining the gap between the negative electrode sheet and the positive electrode sheet at the corner. V 50) have larger gaps between the particles, which further facilitates the infiltration of the electrolyte. On the other hand, the second surface of the separator faces the positive electrode sheet, and the smaller particle size (D V 50) ensures that the gap between the positive and negative electrode sheets is not too large, so that the positive and negative electrode sheets are kept at an appropriate distance. In general, the particle size (D V 50) Different separators can both resist the large expansion of the negative electrode and ensure a more appropriate gap between the positive and negative electrode sheets at the corners of the battery.

[0073] In some embodiments of the present application, the battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. The positive electrode sheet includes a positive current collector and a positive electrode film layer; the negative electrode sheet includes a negative current collector and a negative electrode film layer; during the battery charging and discharging process, active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0074] In some embodiments of the present application, the positive electrode sheet 103 , the negative electrode sheet 101 and the separator 102 may be wound to form an electrode assembly.

[0075] In some embodiments of the present application, the positive electrode sheet 103, the negative electrode sheet 101 and the separator 102 are wound to form an electrode assembly, which can be prepared in the following manner:

[0076] The die-cut isolation film 102, negative electrode sheet 101, and positive electrode sheet 103 are wound into an electrode assembly in the order of isolation film 102, negative electrode sheet 101, isolation film 102, positive electrode sheet 103, isolation film 102, negative electrode sheet 101, ... The winding process ensures that the first surface (first coating 1021) of the isolation film 102 faces the negative electrode sheet 101, and the second surface (second coating 1022) faces the positive electrode sheet 103.

[0077] For example, refer to Figure 7 , Figure 7 A wound electrode assembly is shown. Figure 7As shown, during winding, ensure that the first coating 1021 of the isolation film 102 is always facing the negative electrode sheet 101; and the second coating 1022 of the isolation film 102 is always facing the positive electrode sheet 103, thereby forming an isolation film 102, a negative electrode sheet 101, an isolation film 102, a positive electrode sheet 103, an isolation film 102, a negative electrode sheet 101... and so on, which are wound in sequence.

[0078] Figure 8 Shows Figure 7 A partial enlarged view of the isolation film 102, from Figure 8 It can be seen that the first coating layer 1021 of the isolation film 102 has a larger particle size (D V 50) of the first particle 1023, the second coating 1021 is set to a smaller particle size (D V 50) of the second particle 1024.

[0079] Further, in some embodiments of the present application, D of the first particle V 50 is greater than or equal to 15μm.

[0080] In the above technical solution, D of the first particle V 50 is greater than or equal to 15μm, which can better resist the larger expansion of the negative electrode sheet and thus maintain the gap between the positive electrode sheet and the negative electrode sheet, which is beneficial to improving lithium plating in the battery corners.

[0081] For example, in some embodiments of the present application, the D of the first particle V 50 is 15 μm, 20 μm, 25 μm, 30 μm or a range between any two of the foregoing values.

[0082] Further optionally, in some embodiments of the present application, D of the first particle V 50 is 15μm~30μm.

[0083] Further, in some embodiments of the present application, the D V 50 is less than 10μm.

[0084] In the above technical solution, D of the second particle V 50 is less than 10μm, and the smaller particles are oriented toward the positive electrode sheet with a smaller rebound rate so that the gap between the positive electrode sheet and the negative electrode sheet is not too large, which is beneficial to improving lithium deposition in the battery corners and is beneficial to the battery capacity.

[0085] For example, in some embodiments of the present application, the D of the second particle V 50 is 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm or a range between any two of the foregoing values.

[0086] Further optionally, in some embodiments of the present application, the D V 50 is 5 μm to 10 μm. For example, D V 50 is 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm or a range between any two of the foregoing values.

[0087] The above “D V "50" is a well-known meaning in the art, which indicates the particle size corresponding to when the cumulative volume distribution percentage of the particles reaches 50%, and can be measured by instruments and methods known in the art. For example, it can be measured by a laser particle size analyzer with reference to GB / T 19077-2016. The test instrument can be the Mastersizer 3000 laser particle size analyzer of Malvern Instruments Ltd., UK.

[0088] Furthermore, in some embodiments of the present application, the thickness of the isolation film is 20 μm to 50 μm; the thickness of the first coating layer is 15 μm to 35 μm.

[0089] In the above technical solution, by setting the thickness of the first coating to 10μm~20μm, the thickness of the isolation membrane can be increased. The increase in the thickness of the isolation membrane can increase the length of the pole piece wound around one circle. When the battery is under pressure, the increased length will be pressed to the corner, thereby achieving the purpose of creating a gap at the corner.

[0090] For example, in some embodiments of the present application, the thickness of the first coating is 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, or a range between any two of the foregoing values. For example, in some embodiments of the present application, the thickness of the isolation film is 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, or a range between any two of the foregoing values.

[0091] Furthermore, in some embodiments of the present application, the thickness of the isolation film is 20 μm to 50 μm; the thickness of the second coating layer is 5 μm to 15 μm.

[0092] In the above technical solution, by setting the thickness of the second coating to 5μm to 15μm, it is beneficial to control the gap between the positive electrode sheet and the negative electrode sheet at the corner of the battery within an appropriate range, which is beneficial to improving lithium deposition at the corner of the battery and is beneficial to the battery capacity.

[0093] For example, in some embodiments of the present application, the thickness of the second coating is 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, or a range between any two of the foregoing values. For example, in some embodiments of the present application, the thickness of the isolation film is 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, or a range between any two of the foregoing values.

[0094] Furthermore, in some embodiments of the present application, the first particulate matter includes at least one of organic particulate matter or inorganic particulate matter.

[0095] Furthermore, in some embodiments of the present application, the second particulate matter includes at least one of organic particulate matter or inorganic particulate matter.

[0096] Exemplarily, in some embodiments of the present application, the first particles and the second particles are both selected from any one of organic particles or inorganic particles; or in some embodiments of the present application, the first particles and the second particles are both selected from a mixture of organic particles and inorganic particles; or in some embodiments of the present application, the first particles are selected from any one of organic particles or inorganic particles; and the second particles are selected from a mixture of organic particles and inorganic particles; or in some embodiments of the present application, the first particles are selected from a mixture of organic particles and inorganic particles; and the second particles are selected from any one of organic particles or inorganic particles.

[0097] Furthermore, in some embodiments of the present application, the above-mentioned organic particles include: at least one of polyvinylidene fluoride particles, polyimide particles or polyethylene oxide particles.

[0098] Exemplarily, in some embodiments of the present application, the above-mentioned organic particles include: any one of polyvinylidene fluoride particles, polyimide particles or polyethylene oxide particles; or in some embodiments of the present application, the above-mentioned organic particles include: a mixture of polyvinylidene fluoride particles, polyimide particles and polyethylene oxide particles; or in some embodiments of the present application, the above-mentioned organic particles include: a mixture of polyvinylidene fluoride particles and polyimide particles; or in some embodiments of the present application, the above-mentioned organic particles include: a mixture of polyimide particles and polyethylene oxide particles.

[0099] Furthermore, in some embodiments of the present application, the inorganic particulate matter includes at least one of aluminum oxide particles or boehmite particles.

[0100] For example, in some embodiments of the present application, the inorganic particulate matter includes: any one of aluminum oxide particles or boehmite particles; or in some embodiments of the present application, the above-mentioned inorganic particulate matter includes: a mixture of aluminum oxide particles and boehmite particles.

[0101] In other optional embodiments, exemplarily, the first particulate matter includes a mixture of polyvinylidene fluoride particles, polyimide particles, polyethylene oxide particles, aluminum oxide particles and boehmite particles; or in some exemplary embodiments of the present invention, the second particulate matter includes a mixture of polyvinylidene fluoride particles, polyimide particles, polyethylene oxide particles, aluminum oxide particles and boehmite particles.

[0102] Furthermore, in some embodiments of the present application, the surface density of the first coating and the second coating are both 1 g / m 2 ~10g / m 2 .

[0103] In some embodiments of the present application, for example, the surface density of the first coating and the second coating are both 1 g / m 2 , 2g / m 2 , 3g / m 2 , 4g / m 2 , 5g / m 2 , 6g / m 2 , 7g / m 2 , 8g / m 2 , 9g / m 2 , 10g / m 2 Or the range between any two of the above values.

[0104] In some optional embodiments of the present application, the difference in surface density between the first coating and the second coating is within ±1 g / m 2 For example, the difference in surface density between the first coating and the second coating is -1 g / m 2 、-0.5g / m 2 、-0.2g / m 2 , 0 / m 2 , 0.2g / m 2 , 0.5g / m 2 , 1g / m 2 Or the range between any two of the above values.

[0105] In some optional embodiments of the present application, the surface density of the first coating layer and the second coating layer is equal. For example, the surface density of the first coating layer and the second coating layer is 1 g / m 2 , 2g / m 2 , 3g / m 2 , 4g / m 2 , 5g / m2 , 6g / m 2 , 7g / m 2 , 8g / m 2 , 9g / m 2 , 10g / m 2 Or the range between any two of the above values.

[0106] In the above technical solution, the surface density of the first coating and the second coating is equal, and the first coating contains first particles with a larger particle size, while the second coating contains second particles with a smaller particle size. The first particles with a larger particle size will inevitably make the thickness of the first coating greater than the thickness of the second coating. Therefore, during the winding process, the first coating is directed toward the negative electrode sheet with a larger rebound rate, which, on the one hand, can resist the larger expansion of the negative electrode and thus maintain the gap between the positive and negative electrode sheets. On the other hand, the larger gaps between the particles in the first coating can promote the full infiltration of the electrolyte and improve the gap between the positive and negative electrode sheets as a whole. The second coating is directed toward the positive and negative electrode sheets with a smaller rebound rate, which can achieve the purpose of preventing the gap between the positive and negative electrode sheets from being too large.

[0107] In some embodiments of the present application, the air permeability of the isolation film is 390 seconds / 100cc to 450 seconds / 100cc. Exemplarily, the air permeability of the isolation film is 390 seconds / 100cc, 392 seconds / 100cc, 395 seconds / 100cc, 398 seconds / 100cc, 400 seconds / 100cc, 410 seconds / 100cc, 420 seconds / 100cc, 430 seconds / 100cc, 440 seconds / 100cc, 450 seconds / 100cc, or a range between any two of the foregoing values.

[0108] In some embodiments of the present application, the porosity of the isolation membrane is 40% to 50%; illustratively, the porosity of the isolation membrane is 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or a range after any two of the foregoing values.

[0109] In some embodiments of the present application, the liquid absorption rate of the isolation membrane is 120% to 130%; illustratively, the liquid absorption rate of the isolation membrane is 120%, 121%, 122%, 123%, 124%, 125%, 126%, 127%, 128%, 129%, 130% or a range between any two of the foregoing values.

[0110] In some embodiments of the present application, the thickness of the base film is 3μm to 10μm; exemplarily, the thickness of the base film is 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm or a range between any two of the foregoing values.

[0111] In some embodiments of the present application, the material of the base film includes at least one of polypropylene or polyethylene. Exemplarily, the material of the base film is selected from any one of polypropylene or polyethylene; or in some embodiments of the present application, the material of the base film is selected from a mixture of polypropylene and polyethylene.

[0112] In other optional embodiments of the present application, the material of the above-mentioned base film can be selected from at least one of glass fiber, non-woven fabric or polyvinylidene fluoride. The base film can be a single-layer film or a multi-layer composite film, without special restrictions. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without special restrictions.

[0113] Some embodiments of the present application provide an isolation film, including: a base film; the base film includes a first surface and a second surface;

[0114] The first surface includes a first coating, the first coating includes first particulate matter;

[0115] The second surface includes a second coating, the second coating includes second particulate matter;

[0116] The Dv50 of the first particle is greater than the Dv50 of the second particle;

[0117] The first coating is used towards the negative electrode plate; the second coating is used towards the positive electrode plate.

[0118] Further, in some embodiments of the present application, the Dv50 of the first particles is 15 μm to 30 μm; illustratively, the Dv50 of the first particles is 15 μm to 30 μm; 15 μm, 20 μm, 25 μm, 30 μm or a range between any two of the foregoing values.

[0119] Further, in some embodiments of the present application, the Dv50 of the second particles is 5 μm to 10 μm; illustratively, the Dv50 of the second particles is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or a range between any two of the foregoing values.

[0120] Furthermore, in some embodiments of the present application, the first particles and the second particles both include at least one of polyvinylidene fluoride particles, polyimide particles, polyethylene oxide particles, alumina particles or boehmite particles.

[0121] Furthermore, in some embodiments of the present application, the surface density of the first coating and the second coating are both 1 g / m 2 ~10g / m 2 For example, the surface density of the first coating and the second coating can be selected to be 1g / m 2 , 2g / m 2 , 3g / m 2 , 4g / m 2 , 5g / m 2 , 6g / m 2 , 7g / m 2 , 8g / m 2 , 9g / m 2 , 10g / m 2 Or the range between any two of the above values.

[0122] Further, in some embodiments of the present application, the surface density of the first coating layer and the second coating layer is the same.

[0123] In some embodiments of the present application, the above-mentioned isolation film can be prepared by the following method:

[0124] The first particles with a larger Dv50 are made into a first slurry, and the second particles with a smaller Dv50 are made into a second slurry. The first slurry is applied on the first surface of the base film; the second slurry is applied on the second surface of the base film; and the steps of drying are performed to form a first coating and a second coating.

[0125] In some embodiments of the present application, the first coating and the second coating mentioned above also contain a binder; optionally, in some embodiments of the present application, illustratively, the binder mentioned above can be selected from at least one of polyacrylate, polyethersulfone, polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, vinyl alcohol or polyurethane.

[0126] [Positive electrode]

[0127] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0128] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0129] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (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.).

[0130] In some embodiments, the positive electrode active material may include at least one of the following materials: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 、LiMn 2 O 4 ), 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 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al0.05 O 2 ) and at least one of its modified compounds, etc. Examples of the lithium phosphate with olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (which may also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0131] In some embodiments, in order to further improve the energy density of the battery, the positive electrode active material for a lithium-ion battery may include a lithium transition metal oxide having the general formula Li a Ni b Co c M d O e A f and one or more of its modified compounds. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0132] In some embodiments, by way of example, the positive electrode active material for a lithium-ion battery may include LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O 2 , LiFePO 4 and LiMnPO 4 and one or more of them.

[0133] In the present application, the modified compound of each positive electrode active material mentioned above may be a compound obtained by doping and / or surface coating the positive electrode active material.

[0134] As an optional technical method of the present application, the polyanionic compound can be Li 1+x Mn 1-y A y P 1-z R z O 4 ; wherein x is any value in the range of -0.100 to 0.100, y is any value in the range of 0.001 to 0.500, z is any value in the range of 0.001 to 0.100, A includes one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and R includes one or more elements selected from the group consisting of B, S, Si and N.

[0135] As an optional technical method of the present application, the polyanionic compound can be Li a A e Mn 1-f B f P 1-g C g O 4-n D n , wherein A includes one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from the group consisting of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements selected from the group consisting of B, S, Si, and N; D includes one or more elements selected from the group consisting of S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the positive electrode active material is electrically neutral.

[0136] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0137] In the list of positive electrode materials in this application, the molar content of O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0138] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder 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 fluorine-containing acrylate resin.

[0139] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0141] [Negative electrode]

[0142] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.

[0143] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0144] 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 base 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 (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.).

[0145] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0146] In some embodiments, the negative electrode film layer may further include a binder. The 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).

[0147] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0148] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0149] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0150] In other embodiments, the current collector of the negative electrode plate may generally include a current collector body and an undercoat layer, the undercoat layer may be disposed on at least one side of the current collector body, the undercoat layer substantially does not contain negative electrode active materials, and may include a small amount of carbon material, but the thickness of the coating formed by the carbon material is thin and cannot function as a negative electrode active material. In this embodiment, the negative electrode plate may be a plate without a negative electrode active material layer. For a negative electrode plate without a negative electrode active material layer, when the current collector of the negative electrode plate does not contain an undercoat layer, the film layer may be disposed on the surface of at least one side of the current collector; when the current collector of the negative electrode plate includes an undercoat layer, the film layer may be disposed on the surface of the undercoat layer on the side away from the current collector.

[0151] [Electrolytes]

[0152] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0153] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0154] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0155] In some embodiments, the solvent can 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, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0156] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0157] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0158] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0159] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0160] In some embodiments, reference Figure 2, the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0161] Some embodiments of the present application provide a battery, comprising a battery cell provided by any of the aforementioned embodiments.

[0162] In the above technical solution, the term "battery" may refer to at least one of a battery cell, a battery module or a battery pack.

[0163] For example, in some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0164] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0165] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0166] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0167] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0168] Some embodiments of the present application provide an electrical device, which includes the battery cell provided by any of the aforementioned embodiments, or the electrical device includes the battery provided by any of the aforementioned embodiments.

[0169] The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may 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 and satellites, energy storage systems, etc., but are not limited thereto.

[0170] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0171] Figure 6 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the battery, a battery pack or a battery module can be used.

[0172] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery may be used as a power source.

[0173] Hereinafter, the 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 limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0174] Example 1

[0175] A battery cell is provided, which is prepared according to the following steps:

[0176]

Isolation film preparation

[0177] A first particle (polyvinylidene fluoride PVDF particle) with a Dv50 of 15 μm and a binder (polyacrylate) were added to deionized water at a mass ratio of 9:1, and stirred in a high-speed mixer to obtain a uniformly dispersed first coating slurry, referred to as the "first slurry"; similarly, a second particle (polyvinylidene fluoride PVDF particle) with a Dv50 of 10 μm and a binder (polyacrylate) were added to deionized water at a mass ratio of 9:1, and stirred in a high-speed mixer to obtain a uniformly dispersed second coating slurry, referred to as the "second slurry", and the solid matter content in the first slurry and the second slurry was 50 wt.%. The first slurry and the second slurry were respectively coated on the first surface and the second surface of a polypropylene base film (PP) with a thickness of 5 μm by extrusion coating, ensuring that the coating surface density of the first surface and the second surface was the same, and then placed in a vacuum dryer at 50°C for 12 hours, and then hot-pressed by a calender to prepare an isolation film with different particle sizes on the first surface and the second surface. The thickness of the first coating layer is 16.8 μm; the thickness of the second coating layer is 12.4 μm. The surface density of the first coating layer and the second coating layer is 5 g / m 2 The air permeability of the isolation membrane is 390 seconds / 100cc; the porosity of the isolation membrane is 46%; the liquid absorption rate of the isolation membrane is 121%; and the thickness of the isolation membrane is 34.2 μm. See Table 2 for details.

[0178]

Negative electrode sheet preparation

[0179] The negative electrode material (graphite), conductive agent (acetylene black), binder styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 97.3:1.2:0.8:0.7, and deionized water was added as a solvent, and the mixture was stirred and mixed to obtain a negative electrode slurry. The negative electrode slurry was then coated on both surfaces of the negative electrode current collector copper foil, dried, and cold pressed to a compaction density of 1.65 g / cc to obtain a negative electrode sheet.

[0180]

Positive electrode sheet preparation

[0181] The positive electrode material 0.4Li 2 MnO 3 0.6LiNi 0.5 Mn 0.5 O 2 , conductive agent (acetylene black), and binder PVDF (polyvinylidene fluoride) are mixed in a weight ratio of 94:4:2, and solvent N-methylpyrrolidone is added. The mixture is fully stirred and mixed to obtain a positive electrode slurry, which is then coated on both surfaces of the positive electrode current collector aluminum foil. The positive electrode sheet is obtained after drying and cold pressing to a compaction density of 1.65 g / cc.

[0182]

Electrolyte preparation

[0183] In an argon atmosphere glove box with a water content of <10 ppm, EC (ethylene carbonate), PC (polycarbonate), and DMC (dimethyl carbonate) were mixed at a weight ratio of EC:PC:DMC=3:3:3, and then LiPF 6 , and additives such as vinyl carbonate (VC), dithiothreitol (DTD), and propylene sulfite (PS), after being stirred evenly, an electrolyte is obtained; wherein LiPF 6 The concentration is 1 mol / L, and the mass percentages of VC, DTD, and PS are 3%, 1%, and 1%, respectively.

[0184]

Battery assembly

[0185] The die-cut separator, negative electrode sheet, and positive electrode sheet are wound into an electrode assembly in the order of separator, negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet, etc. During the winding process, ensure that the first surface (first coating) of the separator faces the negative electrode sheet and the second surface (second coating) faces the positive electrode sheet. The electrode assembly is placed in an outer package and injected with the aforementioned electrolyte, and then a battery cell is obtained through formation, aging and other processes.

[0186] Embodiment 2-6

[0187] The differences from Example 1 are shown in Table 2.

[0188] Comparative Example 1

[0189] The difference from Example 1 is the Dv50 of the first particle and the second particle; and the battery assembly, wherein the Dv50 of the first particle and the second particle of this comparative example is shown in Table 2; the battery assembly steps of this comparative example are as follows:

[0190] The die-cut separator, negative electrode sheet, and positive electrode sheet are wound into an electrode assembly in the order of separator, negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet, etc. During the winding process, ensure that the first surface (first coating) of the separator faces the positive electrode sheet and the second surface (second coating) faces the negative electrode sheet. The electrode assembly is placed in an outer package and injected with the aforementioned electrolyte, and then a battery cell is obtained through formation, aging and other processes.

[0191] Comparative Example 2

[0192] The difference from Example 1 is the preparation of the isolation film. The isolation film of this comparative example is prepared as follows:

[0193] Polyvinylidene fluoride PVDF particles with a Dv50 of 10 μm and a binder (polyacrylate) are added to deionized water in a mass ratio of 9:1, and stirred in a high-speed mixer to obtain a uniformly dispersed slurry; the content of solid matter in the slurry is 50wt.%. The slurry is applied to the first and second surfaces of a polypropylene base film (PP) with a thickness of 5 μm by extrusion coating, ensuring that the coating surface density of the first and second surfaces is the same, and then placed in a vacuum dryer at 50°C for 12 hours, and then hot-pressed by a calender to prepare an isolation film with the same particle size on the first and second surfaces. The thickness of the first coating is 12.5 μm; the thickness of the second coating is 12.4 μm. The surface density of the first coating and the second coating is 5g / m 2 The air permeability of the isolation membrane is 370 seconds / 100cc; the porosity of the isolation membrane is 40%; the liquid absorption rate of the isolation membrane is 120%; and the thickness of the isolation membrane is 20.3 μm. See Table 2 for details.

[0194]

Performance test

[0195] Performance tests of various examples and comparative examples:

[0196] 1. Isolation film performance test

[0197] (1) Air permeability test of isolation film:

[0198] The air permeability of the isolation membrane is tested using a conventional isolation membrane air permeability tester. A isolation membrane sample with a cut-off area of ​​100mm×100mm is taken to ensure that the sample is intact and undamaged. A pressure of 1.21kPa is applied through the isolation membrane air permeability tester in a normal pressure environment. The area through which 100mL of air passes is 6.45cm 2 The time required for the isolation film sample. Three samples of each isolation film of the embodiment or comparative example were tested, and the average value of the three measurement results was taken as the air permeability of the isolation film.

[0199] (2) Porosity test of isolation membrane:

[0200] The porosity of the isolation membrane is tested by weighing method. First, weigh the isolation membrane with volume V and record it as m. 0 , completely immerse the weighed isolation membrane in the n-hexadecane reagent for 2 hours, then take out the isolation membrane and wipe off the residual reagent on the surface of the isolation membrane with dust-free paper, weigh the isolation membrane and record it as m1, and calculate the porosity of the isolation membrane using the following formula:

[0201]

[0202] In the above formula, ε is the porosity, unit: %; "ρ" is the density of n-hexadecane, unit: g / cm 3 .

[0203] (3) Liquid absorption test of isolation film:

[0204] First, weigh the mass of the isolation membrane and record it as m 0 , completely immerse the weighed separator in the aforementioned electrolyte for 2 hours, then take it out and wipe off the residual electrolyte on the surface of the separator with dust-free paper, and then weigh it again and record it as m 1 , use the following formula to calculate the liquid absorption rate of the isolation membrane:

[0205]

[0206] In the above formula, θ is the liquid absorption rate, unit: %.

[0207] (4) Test of isolation film thickness:

[0208] The thickness of the isolation film is tested using a micrometer, and the micrometer is calibrated using a standard gauge block before each test. During the test, 7 or more random positions are selected for each embodiment or comparative example each time, and after obtaining ≥ 7 readings, the maximum and minimum values ​​are removed and the average value is calculated as the thickness of the isolation film.

[0209] 2. Battery performance test

[0210] (1) Gap test between positive electrode and negative electrode:

[0211] The gap between the positive and negative pole pieces of the battery cells that have been off the production line through normal processes is measured by computed tomography (CT). CT images are scanned from top to bottom from the top corners of the positive and negative poles of the battery cells. The CT images at the position of 15 mm from top to bottom are taken, and the spacing is measured every 5 layers of negative pole pieces from the inside to the outside of the battery corner, which are recorded as L. 0 , L 1 , L 2 ,……,L n The average gap between the negative electrode sheet and the positive electrode sheet of every 5 layers is recorded as l 0 , l 1 , l 2 ,……,l n The average gap between the negative electrode and the positive electrode of the battery cell is recorded as Calculated by the following formula

[0212]

[0213] (2) Battery cell cycle performance test:

[0214] At 25℃, the battery was charged to 4.4V at a constant current of 1C, then charged at a constant voltage of 4.4V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 1C. The first cycle discharge capacity (C d1 ); Repeat the charge and discharge until the 500th cycle, and the discharge capacity after 500 cycles is recorded as C dn .

[0215] Capacity retention rate (%) = discharge specific capacity after 500 cycles (C dn ) / First week discharge capacity (C d1 ).

[0216] (3) The level of lithium deposition at the interface of the negative electrode corner after 500 cycles of the battery cell. The criteria are shown in Table 1:

[0217] Table 1

[0218]

[0219] After the battery cells of each embodiment or comparative example are cycled for 500 cycles, the determination of lithium deposition on the interface at the negative electrode corner is as follows:

[0220] After 500 cycles, the battery cell was charged to 4.4V at a constant current of 1C, and then charged at a constant voltage of 4.4V until the current dropped to 0.05C. The battery cell was then disassembled to determine the lithium deposition at the corner of the negative electrode interface. The lithium deposition at the corner of the negative electrode of each embodiment or comparison example was graded according to the judgment level in Table 1 above.

[0221] The performance test results of various embodiments and comparative examples are shown in Table 3 and Table 4.

[0222] Table 2 Preparation parameters of isolation film

[0223]

[0224] Table 3 Isolation film properties

[0225]

[0226] Table 4 Battery cell performance

[0227]

[0228]

[0229] From the data in Table 3 above, we can see that:

[0230] Compared with Comparative Examples 1 and 2, the air permeability, porosity, and liquid absorption of the separators of each embodiment are not reduced, which indicates that the particles with larger particle size will not have much impact on the pores of the base film. However, the air permeability, porosity, and liquid absorption of the separator of Comparative Example 2 are relatively low, which is not conducive to battery performance.

[0231] Compared with Comparative Example 2, the thickness of the isolation film in each embodiment is increased, which shows that the scheme of each embodiment is beneficial to improving the gap between the positive electrode sheet and the negative electrode sheet, and is beneficial to improving lithium deposition at the corners of the battery cell.

[0232] From the data in Table 4 above, we can see that:

[0233] Compared with Comparative Example 2, the thickness of the isolation film in each embodiment is increased, and the gap between the positive electrode plate and the negative electrode plate is increased, so that the lithium deposition condition at the interface of the positive and negative electrode plates is improved, and the corresponding cycle performance of the lithium ion secondary battery is improved.

[0234] From the comparison between Example 3 and Comparative Example 1, although the thickness of the separator is almost the same, and the gap between the positive electrode and the negative electrode of the lithium-ion battery is also similar, the lithium deposition condition of the corner of the negative electrode of Comparative Example 1 is very poor. This is because the particle size (D V 50) The larger first coating is toward the positive electrode, while the particle size (D V 50) The smaller second coating is toward the negative electrode plate, resulting in the expansion of the negative electrode plate not being effectively resisted, causing the negative electrode plate to cling to the separator, and poor electrolyte infiltration between the negative electrode plate and the separator, which ultimately leads to aggravated lithium plating of the negative electrode plate.

[0235] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. A battery cell, characterized in that: include: A separator, a negative electrode sheet and a positive electrode sheet; the separator is disposed between the negative electrode sheet and the positive electrode sheet; and is used to separate the negative electrode sheet from the positive electrode sheet; The isolation film includes a base film; the base film includes a first surface and a second surface; The first surface includes a first coating, the first coating includes first particulate matter; The second surface includes a second coating, the second coating includes second particulate matter; The D of the first particle V 50 is greater than the D of the second particle V 50; The first coating faces the negative electrode plate; the second coating faces the positive electrode plate.

2. The battery cell according to claim 1, characterized in that: The D of the first particle V 50 is greater than or equal to 15μm.

3. The battery cell according to claim 1 or 2, characterized in that: The D of the second particle V 50 is less than or equal to 10μm.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The D of the first particle V 50 is 15μm~30μm.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The D of the second particle V 50 is 5μm~10μm.

6. The battery cell according to any one of claims 1 to 5, characterized in that: The thickness of the isolation film is 20 μm to 50 μm; the thickness of the first coating layer is 15 μm to 35 μm.

7. The battery cell according to any one of claims 1 to 6, characterized in that: The thickness of the isolation film is 20 μm to 50 μm; the thickness of the second coating layer is 5 μm to 15 μm.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The first particulate matter includes at least one of organic particulate matter or inorganic particulate matter; and / or The second particulate matter includes at least one of organic particulate matter or inorganic particulate matter.

9. The battery cell according to claim 8, characterized in that: The organic particles include at least one of polyvinylidene fluoride particles, polyimide particles or polyethylene oxide particles.

10. The battery cell according to claim 8, characterized in that: The inorganic particles include at least one of aluminum oxide particles or boehmite particles.

11. The battery cell according to any one of claims 1 to 10, characterized in that: The surface density of the first coating and the second coating is 1g / m 2 ~10g / m 2 ; Optionally, the surface density of the first coating and the second coating is equal.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The isolation film satisfies at least one of the following characteristics: (1) The air permeability of the isolation film is 390 seconds / 100cc to 450 seconds / 100cc; (2) The porosity of the isolation membrane is 40% to 50%; (3) The liquid absorption rate of the isolation film is 120% to 130%; (4) The thickness of the base film is 3 μm to 10 μm.

13. A separation film, characterized in that: include: A base film; the base film comprises a first surface and a second surface; The first surface includes a first coating, the first coating includes first particulate matter; The second surface includes a second coating, the second coating includes second particulate matter; The D of the first particle V 50 is greater than the D of the second particle V 50; The first coating is used to face the negative electrode plate; the second coating is used to face the positive electrode plate.

14. The isolation membrane according to claim 13, characterized in that: The isolation film satisfies at least one of the following characteristics: (1) D of the first particle V 50: 15μm~30μm; (2) D of the second particle V 50 is 5μm~10μm; (3) The first particles and the second particles both include at least one of polyvinylidene fluoride particles, polyimide particles, polyethylene oxide particles, alumina particles, or boehmite particles; (4) The surface density of the first coating and the second coating is 1 g / m 2 ~10g / m 2 ; (5) The surface density of the first coating layer and the second coating layer is the same.

15. A battery, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 12.

16. An electrical device, characterized in that: The electrical device comprises the battery according to claim 15.

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