Battery cells, batteries, electrical devices

Abstract

This application relates to a battery cell, a battery, and an electrical device. An embodiment of this application provides a battery cell comprising: a negative electrode, a first separator, a second separator, and a positive electrode; the negative electrode, the first separator, the second separator, and the positive electrode are wound along a winding direction to form an electrode assembly, the electrode assembly including an arc-shaped corner region; in the arc-shaped corner region, the gap between the convex surface of the negative electrode and the concave surface of the positive electrode is a first gap; the gap between the concave surface of the negative electrode and the convex surface of the positive electrode is a second gap; the first separator is disposed in the first gap; the second separator is disposed in the second gap; the thickness of the first separator is greater than the thickness of the second separator.

Description

Technical Field

[0001] This application relates to a battery cell, a battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries, as an emerging sustainable energy storage technology, are characterized by low cost and environmental friendliness, and therefore their application has been increasingly developed in recent years.

[0003] Therefore, higher requirements are placed on improving the lithium plating problem in the corner area of ​​lithium-ion batteries. Summary of the Invention

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

[0005] The embodiments of this application are implemented as follows:

[0006] In a first aspect, embodiments of this application provide a single battery cell, comprising:

[0007] Negative electrode, first separator, second separator, and positive electrode;

[0008] A negative electrode sheet, a first separator, a second separator, and a positive electrode sheet are wound together in a winding direction to form an electrode assembly. The electrode assembly includes an arc-shaped corner region. In the arc-shaped corner region, the gap between the convex surface of the negative electrode sheet and the concave surface of the positive electrode sheet is a first gap; the gap between the concave surface of the negative electrode sheet and the convex surface of the positive electrode sheet is a second gap; the first separator is disposed in the first gap; and the second separator is disposed in the second gap.

[0009] The thickness of the first separator is greater than the thickness of the second separator.

[0010] After cycling, the first gap between the convex surface of the negative electrode and the concave surface of the positive electrode in the corner region always decreases more than the second gap between the concave surface of the negative electrode and the convex surface of the positive electrode. This causes lithium plating to occur first on the convex surface of the negative electrode in the corner region. Therefore, the above technical solution, by setting a thicker first separator film between the convex surface of the negative electrode and the concave surface of the positive electrode in the corner region, can increase the first gap; while setting a thinner second separator film between the concave surface of the negative electrode and the convex surface of the positive electrode in the corner region can prevent the second gap from becoming too large. Ultimately, by controlling the first and second gaps, the lithium plating problem in the battery corner region can be improved, and the battery cycle performance can be enhanced.

[0011] In some embodiments, at least one surface of the first isolation membrane is provided with a first coating; the first coating includes first particles;

[0012] At least one surface of the second isolation membrane is provided with a second coating; the second coating includes second particles;

[0013] The first particulate matter D V 50 is greater than the D of the second particulate matter V 50.

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

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

[0016] In some embodiments, the D of the first particulate matter V 50 represents 15μm~30μm.

[0017] In some embodiments, the D of the second particulate matter V 50 represents 5μm to 10μm.

[0018] In some embodiments, the thickness of the first separator is 35 μm to 65 μm.

[0019] In some embodiments, the thickness of the second separator is 15 μm to 25 μm.

[0020] In some embodiments, the areal density of both the first and second separators is 5 g / m³. 2 ~10g / m 2 Optionally, the difference in areal density between the first and second separator membranes is -1 g / m³. 2 ~1g / m 2 .

[0021] In some embodiments, the first particulate matter includes at least one of organic or inorganic particulate matter.

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

[0023] In some embodiments, the organic particulate matter includes at least one of polyvinylidene fluoride particles, polyimide particles, or polyethylene oxide particles.

[0024] In some embodiments, the inorganic particulate matter includes at least one of alumina particles or boehmite particles.

[0025] In some embodiments, the first separator membrane satisfies at least one of the following characteristics:

[0026] (1) The air permeability of the first separator is 425 seconds / 100 cc to 430 seconds / 100 cc;

[0027] (2) The porosity of the first separating membrane is 48%~50%;

[0028] (3) The liquid absorption rate of the first separating membrane is 130%~135%.

[0029] In some embodiments, the second separator membrane satisfies at least one of the following characteristics:

[0030] (1) The air permeability of the second separator is 316 seconds / 100 cc to 400 seconds / 100 cc;

[0031] (2) The porosity of the second separator is 30%~45%;

[0032] (3) The liquid absorption rate of the second separator is 110%~126%.

[0033] Secondly, embodiments of this application provide a battery, including the battery cell provided in the first aspect above.

[0034] Thirdly, embodiments of this application provide an electrical device, which includes a battery provided by any of the aforementioned implementation methods. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0037] Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0038] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0039] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0040] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0041] Figure 6 This is a schematic diagram of an electrical device that uses a battery as a power source according to one embodiment of this application;

[0042] Figure 7 This is a schematic diagram of an electrode assembly according to one embodiment of this application.

[0043] icon:

[0044] 101 Negative electrode; 102 Second separator; 103 Positive electrode; 104 First separator;

[0045] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0046] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0048] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0049] In the description of the embodiments of this application, the technical terms "inner" and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0050] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0051] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0052] In the embodiments of this application, the same reference numerals denote 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 height, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall height, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0053] Research revealed that lithium plating at the corners of the negative electrode in wound batteries primarily occurs on the convex surface of the corner. Further measurement using high-resolution CT (computed tomography) revealed that the first gap between the convex surface of the negative electrode and the concave surface of the positive electrode at the corner is smaller than the second gap between the concave surface of the negative electrode and the convex surface of the positive electrode. This indicates that the first gap decreases more significantly after cycling, leading to poor electrolyte wetting on the convex surface of the negative electrode and causing lithium plating. Further research also found that when the second gap between the concave surface of the negative electrode and the convex surface of the positive electrode is too large, lithium plating penetrating the corner can occur on the concave surface of the negative electrode.

[0054] Based on this, refer to Figures 1-7 The first aspect of this application provides a battery cell, comprising:

[0055] The battery cell includes a negative electrode 101, a first separator 104, a second separator 102, and a positive electrode 103. The negative electrode 101, the first separator 104, the second separator 102, and the positive electrode 103 are wound together in a winding direction to form an electrode assembly. The electrode assembly includes an arc-shaped corner region. In the arc-shaped corner region, the gap between the convex surface of the negative electrode 101 and the concave surface of the positive electrode 103 is a first gap; the gap between the concave surface of the negative electrode 101 and the convex surface of the positive electrode 103 is a second gap; the first separator 104 is disposed in the first gap; and the second separator 102 is disposed in the second gap.

[0056] The thickness of the first separator 104 is greater than the thickness of the second separator 102.

[0057] After cycling, the first gap between the convex surface of the negative electrode and the concave surface of the positive electrode in the corner region always decreases more than the second gap between the concave surface of the negative electrode and the convex surface of the positive electrode. This leads to lithium plating occurring first on the convex surface of the negative electrode in the corner region. Therefore, the above technical solution, by setting a thicker first separator film between the convex surface of the negative electrode and the concave surface of the positive electrode in the corner region, can increase the first gap. Simultaneously, due to the larger particle size, the first separator film has a certain resistance to negative electrode expansion. Furthermore, the larger gaps between larger particles promote electrolyte flow and wetting. Conversely, by setting a thinner second separator film between the concave surface of the negative electrode and the convex surface of the positive electrode in the corner region, the second gap can be prevented from becoming excessively large. Ultimately, by controlling the first and second gaps, the lithium plating problem in the battery corner region can be improved, and the battery's cycle performance can be enhanced.

[0058] In some embodiments of this application, the aforementioned battery cell includes an electrode assembly and an electrolyte. The positive electrode includes a positive current collector and a positive electrode film; the negative electrode includes a negative current collector and a negative electrode film. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. A first separator is disposed in a first gap between the positive and negative electrode plates; a second separator is disposed in a second gap between the positive and negative electrode plates, serving to prevent short circuits between the positive and negative electrodes while allowing ions to pass through.

[0059] In some embodiments of this application, the positive electrode 103, the negative electrode 101, the first separator 104, and the second separator 102 can be formed into the above-mentioned electrode assembly by a winding process.

[0060] Figure 7 A wound electrode assembly is shown. Exemplarily, refer to... Figure 7 In some embodiments of this application, the positive electrode 103, negative electrode 101, first separator 104, and second separator 102 are formed into an electrode assembly by a winding process, and can be prepared according to the following method:

[0061] The die-cut first separator 104, second separator 102, negative electrode 101, and positive electrode 103 are stacked in the order of second separator 102, negative electrode 101, first separator 104, positive electrode 103, second separator 102, negative electrode 101, ... and then wound into an electrode assembly in the direction shown by arrow C in the figure.

[0062] from Figure 7It can be seen that the first separator 104 is disposed between the convex surface of the negative electrode and the concave surface of the positive electrode; the second separator 102 is disposed between the concave surface of the negative electrode and the convex surface of the positive electrode.

[0063] In the above technical solution, "convex surface" refers to the outer surface of the arc-shaped corner area of ​​the wound electrode assembly formed by the winding process (e.g., Figure 7 The convex surface is the surface indicated by arrow A); the concave surface refers to the inner arc surface of the arc-shaped corner area of ​​the wound electrode assembly formed by the winding process (e.g., Figure 7 The convex surface is the surface indicated by arrow B.

[0064] In some embodiments of this application, the wound electrode assembly described above, excluding the arc-shaped corner area, has a flat area remaining. The placement of the separator in the flat area is not limited. Optionally, in some embodiments, the same separator as the one used for the arc-shaped corner area can be selected.

[0065] Furthermore, in some embodiments of this application, at least one surface of the first isolation membrane is provided with a first coating; the first coating includes first particles;

[0066] At least one surface of the second isolation membrane is provided with a second coating; the second coating includes second particles;

[0067] The first particulate matter D V 50 is greater than the D of the second particulate matter V 50.

[0068] The thickness of the separator can be controlled by the particle size of the particles in the coating. Coating the separator with larger particles increases its thickness. This increased thickness allows for two main benefits: firstly, it increases the length of one revolution of the electrode, ensuring that the increased length is compressed at the corners when the battery is under pressure, thus creating a gap at the corners; secondly, the larger particles more effectively resist the expansion of the negative electrode, increasing the first gap between the convex surface of the negative electrode and the concave surface of the positive electrode in the arc-shaped corner area. Furthermore, the larger gaps between the larger particles promote electrolyte wetting. The above technical solution involves providing a first coating on at least one surface of the first separator; the first coating comprising first particles; and a second coating on at least one surface of the second separator; the second coating comprising second particles; and the first particles having a D... V 50 is greater than the D of the second particulate matter V 50; This can increase the first gap between the convex surface of the negative electrode and the concave surface of the positive electrode at the corner; thus helping to improve the problem of lithium deposition occurring first on the convex surface of the negative electrode at the corner.

[0069] Furthermore, in some embodiments of this application, the D of the first particulate matter V 50 is greater than or equal to 15μm.

[0070] In the above technical solution, the D of the first particulate matter V A value of 50 or greater than 15 μm can increase the first gap between the convex surface of the negative electrode and the concave surface of the positive electrode, which is beneficial to improving lithium deposition at the battery corner.

[0071] Exemplary, in some embodiments of this application, the D of the first particulate matter described above... V 50 is a range of 15μm, 20μm, 25μm, 28μm, 30μm, or any two of the aforementioned values.

[0072] Further, optionally, in some embodiments of this application, the D of the first particulate matter V 50 represents 15μm to 30μm. Exemplarily, in some embodiments of this application, the D of the first particle... V 50 represents 15μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, or any two of the aforementioned values.

[0073] Furthermore, in some embodiments of this application, the D of the second particulate matter V 50 is less than 10μm.

[0074] In the above technical solution, the D of the second particulate matter V The presence of smaller particles (less than 10 μm) in the second gap between the concave surface of the negative electrode and the convex surface of the positive electrode can improve lithium deposition on the concave surface of the negative electrode and improve battery cycle performance.

[0075] Exemplary, in some embodiments of this application, the D of the second particulate matter described above... V 50 is a range of 10μm, 9μm, 8μm, 7μm, 6μm, 5μm, 4μm, 3μm, 2μm, 1μm or any two of the aforementioned values.

[0076] Further, optionally, in some embodiments of this application, the D of the second particulate matter V 50 is 5μm~10μm. For example, the D of the second particulate matter... V 50 is 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm or any two of the aforementioned values.

[0077] The above "D" V"50" has a well-known meaning in the art, representing the particle size corresponding to a cumulative volume distribution percentage of 50% for either the first or second particulate matter, which can be determined using instruments and methods known in the art. For example, it can be determined using a laser particle size analyzer, referring to GB / T 19077-2016. The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0078] Furthermore, in some embodiments of this application, the thickness of the first separating membrane is 35 μm to 65 μm.

[0079] In the above technical solution, by setting the thickness of the first separator to 35μm to 65μm, it is beneficial to ensure the mechanical strength and structural stability of the first separator, and to ensure that the first gap between the convex surface of the negative electrode and the concave surface of the positive electrode is within an appropriate range, which is beneficial to improving the lithium plating problem at the battery corner.

[0080] For example, in some embodiments of this application, the thickness of the first isolation membrane is 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 42μm, 45μm, 48μm, 50μm, 52μm, 55μm, 58μm, 60μm, 61μm, 62μm, 63μm, 64μm, 65μm or a range between any two of the aforementioned values.

[0081] Furthermore, in some embodiments of this application, the thickness of the second separator is 15 μm to 25 μm.

[0082] In the above technical solution, by setting the thickness of the second separator to 15μm to 25μm, it is beneficial to ensure the mechanical strength and structural stability of the second separator, and to ensure that the second gap between the concave surface of the negative electrode and the convex surface of the positive electrode is within an appropriate range, which can improve lithium deposition on the concave surface of the negative electrode and is beneficial to the battery cycle performance.

[0083] For example, in some embodiments of this application, the thickness of the second isolation membrane is 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm or any two of the aforementioned values.

[0084] Furthermore, in some embodiments of this application, the areal density of both the first and second separators is 5 g / m³. 2 ~10g / m 2 .

[0085] In the above technical solution, the areal density of both the first and second isolation membranes is set to 5 g / m³. 2 ~10g / m2 It is beneficial to the battery's cycle performance.

[0086] For example, in some embodiments of this application, the areal density of the first and second separators can be selected from the following values: 5 g / m³ 2 5.5g / m 2 6g / m 2 6.5g / m 2 7g / m 2 7.5g / m 2 8g / m 2 8.5g / m 2 9g / m 2 9.5g / m 2 10g / m 2 Or the range between any two of the aforementioned values.

[0087] In some optional embodiments of this application, the areal density difference between the first coating and the second coating is -1 g / m³. 2 ~1g / m 2 For example, the areal density difference between the first coating and the second coating is -1 g / m³. 2 -0.8 g / m 2 -0.5g / m 2 -0.2g / m 2 0g / m 2 0.1 g / m 2 0.2g / m 2 0.3g / m 2 0.5g / m 2 0.8g / m 2 1g / m 2 Or the range between any two of the aforementioned values.

[0088] In the above technical solution, the areal density difference between the first and second separator membranes is -1 g / m³. 2 ~1g / m 2Given that the two are not significantly different, the thickness of the separator can be directly controlled by adjusting the particle size. The coating of the first separator contains larger-diameter first particles, while the coating of the second separator contains smaller-diameter second particles. During the winding process, the first separator is placed between the convex surface of the negative electrode and the concave surface of the positive electrode. On the one hand, the larger particles can more effectively resist the expansion of the negative electrode, preventing the gap between the convex and concave surfaces from decreasing too quickly. On the other hand, the larger particles in the first separator have more gaps, which can promote the full wetting of the electrolyte and improve the overall gap between the convex and concave surfaces of the negative and positive electrodes. The second separator, placed between the concave surface of the negative electrode and the convex surface of the positive electrode, can prevent the gap between the positive and negative electrodes from becoming too large.

[0089] Furthermore, in some embodiments of this application, the first particulate matter includes at least one of organic particulate matter or inorganic particulate matter.

[0090] In some embodiments, the second particulate matter includes at least one of organic or inorganic particulate matter.

[0091] In the above technical solution, by controlling that both the first particulate matter and the second particulate matter include at least one of organic or inorganic particulate matter, the thickness of the first separator and the second separator can be adjusted, which is beneficial to improving lithium plating at the battery corner.

[0092] For example, in some embodiments of this application, the first particulate matter and the second particulate matter are both selected from organic particulate matter or inorganic particulate matter; or in some embodiments of this application, the first particulate matter and the second particulate matter are both selected from a mixture of organic particulate matter and inorganic particulate matter; or in some embodiments of this application, the first particulate matter is selected from either organic particulate matter or inorganic particulate matter, while the second particulate matter is selected from a mixture of organic particulate matter and inorganic particulate matter; or in some embodiments of this application, the first particulate matter is selected from a mixture of organic particulate matter and inorganic particulate matter, while the second particulate matter is selected from either organic particulate matter or inorganic particulate matter.

[0093] Furthermore, in some embodiments of this application, the aforementioned organic particulate matter includes at least one of polyvinylidene fluoride particles, polyimide particles, or polyethylene oxide particles.

[0094] For example, in some embodiments of this application, the organic particulate matter includes any one of polyvinylidene fluoride (PVDF) particles, polyimide particles, or polyethylene oxide (PEO) particles; or in some embodiments of this application, the organic particulate matter includes a mixture of PVDF particles, polyimide particles, and PEO particles; or in some embodiments of this application, the organic particulate matter includes a mixture of PVDF particles and polyimide particles; or in some embodiments of this application, the organic particulate matter includes a mixture of polyimide particles and PEO particles.

[0095] Furthermore, in some embodiments of this application, the inorganic particulate matter includes at least one of alumina particles or boehmite particles.

[0096] For example, in some embodiments of this application, the inorganic particulate matter includes either alumina particles or boehmite particles; or in some embodiments of this application, the inorganic particulate matter includes a mixture of alumina particles and boehmite particles.

[0097] In other alternative embodiments, for example, the first particulate matter comprises a mixture of polyvinylidene fluoride particles, polyimide particles, polyethylene oxide particles, alumina particles, and boehmite particles; or in some of these exemplary embodiments, the second particulate matter comprises a mixture of polyvinylidene fluoride particles, polyimide particles, polyethylene oxide particles, alumina particles, and boehmite particles.

[0098] In some embodiments of this application, the air permeability of the first separator is 425 sec / 100 cc to 430 sec / 100 cc. Exemplarily, the air permeability of the separator is 425 sec / 100 cc, 426 sec / 100 cc, 427 sec / 100 cc, 428 sec / 100 cc, 429 sec / 100 cc, 430 sec / 100 cc, or a range between any two of the aforementioned values.

[0099] In some embodiments of this application, the porosity of the first separator is 48% to 50%; exemplarily, the porosity of the separator is 48%, 48.1%, 48.2%, 48.3%, 48.5%, 48.8%, 48.9%, 49%, 49.2%, 49.5%, 50%, or any two of the aforementioned values.

[0100] In some embodiments of this application, the liquid absorption rate of the first separator is 130% to 135%; for example, the liquid absorption rate of the separator is 130%, 131%, 132%, 133%, 134%, 135% or any two of the aforementioned values.

[0101] In some embodiments of this application, the air permeability of the second separator is 316 sec / 100 cc to 400 sec / 100 cc. Exemplarily, the air permeability of the separator is 316 sec / 100 cc, 317 sec / 100 cc, 320 sec / 100 cc, 330 sec / 100 cc, 350 sec / 100 cc, 380 sec / 100 cc, 390 sec / 100 cc, 400 sec / 100 cc, or a range between any two of the aforementioned values.

[0102] In some embodiments of this application, the porosity of the second separator is 30% to 45%; for example, the porosity of the separator is 30%, 31%, 32%, 33%, 34%, 35%, 36%, 38%, 40%, 41%, 42%, 43%, 44%, 45% or any two of the aforementioned values.

[0103] In some embodiments of this application, the liquid absorption rate of the second separator is 110% to 126%; for example, the liquid absorption rate of the separator is 110%, 112%, 115%, 118%, 120%, 122%, 125%, 126% or any two of the aforementioned values.

[0104] In some embodiments of this application, the first and second separator membranes described above can be prepared in the following ways:

[0105] A first slurry is made from first particles containing a larger Dv50, and the first slurry is coated on at least one surface of a base film to form a first coating; the coating is dried; and a first release film is obtained.

[0106] A second slurry containing a second particulate with a smaller Dv50 is prepared, and the second slurry is coated on at least one surface of a base film to form a second coating; dried; a second separator is obtained.

[0107] In some embodiments of this application, both the first coating and the second coating described above further include an adhesive; optionally, in some embodiments of this application, for example, the adhesive may be selected from at least one of polyacrylate, polyethersulfone, polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, vinyl alcohol, or polyurethane.

[0108] In some embodiments of this application, the base film is made of at least one of polypropylene or polyethylene. Exemplarily, the base film is made of either polypropylene or polyethylene; or in some embodiments of this application, the base film is made of a mixture of polypropylene and polyethylene.

[0109] In other optional embodiments of this application, the material of the 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 particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0110] [Positive electrode plate]

[0111] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0112] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0113] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0114] In some embodiments, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials 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 include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2), and at least one of its modified compounds. Examples of olivine-structured lithium phosphate may include but are not limited to lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon.

[0115] 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 one or more of lithium transition metal oxides represented by the general formula Li a Ni b Co c M d O e A f and their 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.

[0116] In some embodiments, by way of example, the positive electrode active material for a lithium-ion battery may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0117] In this application, the modified compounds of the above-mentioned positive electrode active materials may be those that have undergone doping modification and / or surface coating modification of the positive electrode active materials.

[0118] As an optional technical approach in this application, the polyanionic compound can be Li 1+x Mn 1-y A y P 1-z R z O4; where 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 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 B, S, Si and N.

[0119] As an optional technical approach in this 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 Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements selected from B, S, Si, and N; D includes one or more elements selected from 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.

[0120] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0121] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0122] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0123] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0124] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0125] [Negative electrode plate]

[0126] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector.

[0127] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0128] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0129] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. 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, and 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, this application is not limited to these materials, and other conventional 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.

[0130] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive 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).

[0131] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0132] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0133] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0134] In other embodiments, the current collector of the negative electrode may typically include a current collector body and an undercoating layer, wherein the undercoating layer may be disposed on at least one side of the current collector body.

[0135] It should be noted that, in selecting the positive and negative active materials in this application, it is necessary to ensure that the rebound rate of the negative electrode is greater than that of the positive electrode when the battery cell is fully charged.

[0136] For example, in some embodiments of this application, the method for testing the rebound rate is as follows: First, the thickness of the unfilled negative and positive electrode sheets after winding is measured using a micrometer and recorded as t1; then, the normally manufactured battery is fully charged and disassembled to separate the positive and negative electrode sheets, and the thickness of the positive and negative electrode sheets is measured and recorded as t2. Rebound rate = (t2-t1) / t1.

[0137] [Electrolytes]

[0138] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0139] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0140] In some embodiments, the electrolyte salt may 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0141] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0142] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0143] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0144] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0145] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0146] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. An electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0147] Some embodiments of this application provide a battery, including the battery cell provided in any of the foregoing embodiments.

[0148] In the above technical solutions, the term "battery" can be at least one of a battery cell, a battery module, or a battery pack.

[0149] For example, in some embodiments, battery cells can be assembled into battery modules, and the number of battery cells contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0150] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0151] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0152] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0153] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0154] Some embodiments of this application provide an electrical device, which includes a battery cell provided in any of the foregoing embodiments, or the electrical device includes a battery provided in any of the foregoing embodiments.

[0155] 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, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0156] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0157] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0158] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0159] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0160] Example 1

[0161] A battery cell is provided, prepared according to the following steps:

[0162] [Preparation of the separating membrane]:

[0163] First particles (polyvinylidene fluoride PVDF particles) with a Dv50 of 15 μm and binder (polyacrylate) were added to deionized water at a mass ratio of 9:1. The mixture was stirred in a high-speed mixer to obtain a uniformly dispersed first coating slurry, referred to as the "first slurry". Similarly, second particles (polyvinylidene fluoride PVDF particles) with a Dv50 of 10 μm and binder (polyacrylate) were added to deionized water at a mass ratio of 9:1. The mixture was stirred in a high-speed mixer to obtain a uniformly dispersed second coating slurry, referred to as the "second slurry". The solid content of both the first and second slurries was 50 wt.%.

[0164] The first slurry was coated onto both surfaces of a 5 μm thick polypropylene (PP) base film using an extrusion coating method; then, it was placed in a vacuum dryer at 50°C for 12 h, followed by hot pressing using a calender to prepare the first release film; the areal density of the first release film was 5 g / m³. 2 The thickness of the first separating membrane is 36.7 μm. The air permeability of the first separating membrane is 425 seconds / 100 cc; the porosity of the first separating membrane is 50%; and the liquid absorption rate of the first separating membrane is 135%.

[0165] The second slurry was coated onto both surfaces of a 5 μm thick polypropylene (PP) base film using an extrusion coating method; then, it was placed in a vacuum dryer at 50°C for 12 h, followed by hot pressing using a calender to prepare the second release film; the areal density of the second release film was 5 g / m³. 2 The thickness of the second separator is 26 μm. The air permeability of the second separator is 400 seconds / 100 cc; the porosity of the second separator is 45%; and the liquid absorption rate of the second separator is 126%.

[0166] [Preparation of negative electrode sheet]:

[0167] 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. Deionized water was added as a solvent, and the mixture was stirred thoroughly to obtain a uniform negative electrode slurry. The negative electrode slurry was then coated onto 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 the negative electrode sheet.

[0168] [Preparation of positive electrode sheet]:

[0169] The cathode material is 0.4Li₂MnO₃·0.6LiNi 0.5 Mn 0.5O2, conductive agent (acetylene black), and binder PVDF (polyvinylidene fluoride) are mixed in a weight ratio of 94:4:2. N-methylpyrrolidone solvent is added and the mixture is stirred thoroughly to obtain a positive electrode slurry. The slurry is then coated on both surfaces of the positive electrode current collector aluminum foil, dried, and cold-pressed to a compaction density of 1.65 g / cc to obtain the positive electrode sheet.

[0170] [Electrolyte preparation]:

[0171] In an argon-atmosphere glove box with a water content of <10 ppm, EC (ethylene carbonate), PC (polycarbonate), and DMC (dimethyl carbonate) were mixed in a weight ratio of EC:PC:DMC=3:3:3. Then, LiPF6, along with additives vinylene carbonate (VC), vinyl sulfate (DTD), and propylene sulfite (PS), were added and stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L, and the mass percentages of VC, DTD, and PS were 3%, 1%, and 1%, respectively.

[0172] [Battery Assembly]:

[0173] The die-cut first separator, second separator, negative electrode, and positive electrode are wound into an electrode assembly in the order of second separator, negative electrode, first separator, positive electrode, second separator, negative electrode, etc. The electrode assembly is then placed in an outer packaging and injected with the electrolyte. After formation and aging processes, a battery cell is obtained. This battery cell is as follows: Figure 7 As shown, in the arc-shaped corner area, the gap between the convex surface of the negative electrode and the concave surface of the positive electrode is the first gap; the gap between the concave surface of the negative electrode and the convex surface of the positive electrode is the second gap; a first separator is disposed in the first gap; and a second separator is disposed in the second gap.

[0174] Examples 2-6

[0175] The differences from Example 1 are detailed in Table 2.

[0176] Comparative Example 1

[0177] The difference from Example 1 lies in the preparation of the separator membrane. The first and second separator membranes in this comparative example are the same; specifically as follows:

[0178] Polyvinylidene fluoride (PVDF) particles with a Dv50 of 10 μm and 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 slurry; the solid content of the slurry was 50 wt.%.

[0179] The slurry was coated onto both surfaces of a 5 μm thick polypropylene (PP) base film using an extrusion coating method; then it was placed in a vacuum dryer at 50 °C for 12 h, and then hot-pressed through a calender to prepare the first and second release films.

[0180] The areal density of both the first and second separators is 5 g / m³. 2 The thickness of both the first and second separating membranes is 25.3 μm. The air permeability of both the first and second separating membranes is 370 seconds / 100 cc; the porosity of both the first and second separating membranes is 40%; and the liquid absorption rate of both the first and second separating membranes is 120%. See Table 2 for details.

[0181] [Performance Testing]:

[0182] Performance tests of each embodiment and comparative sample:

[0183] 1. Performance testing of the separator membrane

[0184] (1) Air permeability test of the separator membrane:

[0185] The air permeability of the separator membrane was tested using a standard separator membrane permeability meter. A 100mm × 100mm sample of the separator membrane was taken, ensuring the sample was intact and undamaged. A pressure of 1.21 kPa was applied using the separator membrane permeability meter under normal pressure, and the area through which 100 mL of air passed was measured to be 6.45 cm². 2 The time required for the isolation membrane sample. Three samples were tested for each example or comparative example isolation membrane, and the average of the three measurements was taken as the air permeability of the isolation membrane.

[0186] (2) Porosity test of the isolation membrane:

[0187] The porosity of the separator was determined using a gravimetric method. First, a volume V portion of the separator was weighed and recorded as m0. The weighed separator was then completely immersed in n-hexadecane reagent for 2 hours. Afterward, the separator was removed, and any remaining reagent was wiped off the surface with lint-free paper. The separator was then weighed and recorded as m1. The porosity of the separator was calculated using the following formula:

[0188]

[0189] In the above formula, ε represents porosity (%), and "ρ" represents the density of n-hexadecane (g / cm³). 3 .

[0190] (3) Liquid absorption rate test of the separating membrane:

[0191] First, weigh the separator and record the mass as m0. Immerse the weighed separator completely in the aforementioned electrolyte solution for 2 hours. Then, remove it and wipe off any remaining electrolyte on the surface with lint-free paper. Weigh it again and record the mass as m1. Calculate the liquid absorption rate of the separator using the following formula:

[0192]

[0193] In the above formula, θ represents the liquid absorption rate, in units of %.

[0194] (4) Testing of the thickness of the separator membrane:

[0195] The thickness of the separator was measured using a micrometer, with the micrometer calibrated using standard gauge blocks before each test. During testing, for each embodiment or comparative example, seven or more random locations were selected each time, and after obtaining ≥7 readings, the maximum and minimum values ​​were removed, and the average value was taken as the thickness of the separator.

[0196] 2. Battery performance test

[0197] (1) Gap test between positive and negative electrode plates:

[0198] The gap between the positive and negative electrode plates of a battery cell produced through normal processes is measured using computed tomography (CT) scanning technology. CT images are scanned from top to bottom from the apex of the positive and negative electrodes of the battery cell. A CT image taken at a position 15 mm from top to bottom is used. The distance between the tangent of the innermost negative electrode convex surface and the tangent of the outermost positive electrode convex surface in the horizontal corner area is measured as the gap between the convex surface of the negative electrode plate and the concave surface of the positive electrode plate. The average value of the gaps between the convex surfaces of all negative electrode plates and the concave surfaces of the positive electrode plates in a battery cell is then used as the gap between the convex surfaces of the negative electrode plates and the concave surfaces of the positive electrode plates in the battery cell. The distance between the tangent of the innermost positive electrode convex surface and the tangent of the outermost negative electrode convex surface in the corner area is taken as the gap between the positive electrode convex surface and the negative electrode concave surface. The average value of the gaps between the positive electrode convex surface and the negative electrode concave surface of all the positive electrode convex surfaces in a single cell is taken as the gap between the positive electrode convex surface and the negative electrode concave surface of the battery cell.

[0199] (2) Cycle performance test of individual battery cells:

[0200] Under a constant temperature environment of 25℃, the capacitor was charged to 4.4V with a constant current of 1C, then charged at a constant voltage of 4.4V until the current dropped to 0.05C, and finally discharged to 2.5V with a constant current of 1C. The discharge specific capacity (C) of the first cycle was obtained. d1 Repeat this charge-discharge cycle until the 500th cycle, and the discharge specific capacity after 500 cycles is denoted as C. dn .

[0201] Capacity retention (%) = Discharge specific capacity after 500 cycles (C) dn ) / First-week discharge specific capacity (C d1 ).

[0202] (3) The criteria for determining the degree of lithium deposition at the interface corner of the negative electrode after 500 cycles of a single battery cell are shown in Table 1:

[0203] Table 1

[0204]

[0205] The determination of lithium deposition at the negative electrode corner interface after cycling the individual cells of each embodiment or comparative example for 500 cycles:

[0206] After 500 cycles, the battery cells were 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. Subsequently, the cells were disassembled to determine the lithium deposition at the corner of the negative electrode interface. The lithium deposition at the concave and convex surfaces of the corner area of ​​the negative electrode in each embodiment or comparative example was determined according to the determination level in Table 1 above.

[0207] The performance test results of each embodiment and comparative example are shown in Tables 3 and 4.

[0208] Table 2 Separator preparation parameters

[0209]

[0210] Table 3 Performance of the separating membrane

[0211]

[0212] Table 4. Battery cell performance

[0213]

[0214] As can be seen from the data in Table 3 above:

[0215] Compared to Comparative Example 1, the first isolation membranes of Examples 1-4 showed improved air permeability, porosity, and liquid absorption rate, indicating that larger particles do not significantly affect the porosity of the base membrane.

[0216] As shown in Table 3 above, when the coating density is 5 g / m², 2When the PVDF particle size (Dv50) is ≤20μm, the air permeability, porosity, and liquid absorption rate of the separator increase with increasing Dv50. This is because very small particles, due to their dense distribution, will block the pores on the base film, leading to a decrease in the air permeability, porosity, and liquid absorption rate of the separator. As the particle size increases, the probability of blocking the pores on the base film decreases, thus increasing the air permeability, porosity, and liquid absorption rate of the separator. However, when Dv50 ≥20μm, the air permeability, porosity, and liquid absorption rate of the separator become essentially the same, because very large particles can no longer block the pores on the base film. Under the same coating areal density, the thickness of the separator increases with increasing particle size.

[0217] The coating surface density is 10 g / m 2 The thickness of the separator film coated with PVDF of 15μm Dv50 is different from that of PVDF of 30μm Dv50 but with a coating areal density of only 5g / m³. 2 The thickness of the coated separators is about the same, but the air permeability, porosity and liquid absorption rate of the former are reduced. This is because the coating density increases and more particles accumulate, so the thickness increases, but at the same time the pores of the base film are blocked, and the porosity, liquid absorption rate and other indicators decrease.

[0218] Under the same coating density, the thickness, porosity, and liquid absorption rate of the isolation films formed by coating PVDF and Al2O3 particles with the same Dv50 are not significantly different.

[0219] As can be seen from the data in Table 4 above:

[0220] Compared with Comparative Example 1, the gap between the convex surface of the negative electrode and the concave surface of the positive electrode in each embodiment is increased, which can effectively improve the lithium deposition on the convex surface of the negative electrode and improve the cycle performance of the corresponding lithium-ion secondary battery.

[0221] Based on the PVDF particle size, separator thickness, gap between the convex surface of the negative electrode and the concave surface of the positive electrode, and lithium plating level at the corner of the convex surface of the negative electrode in Examples 1-3 and Comparative Example 1, under the same separator coating areal density, as the PVDF particle size (Dv50) increases, the separator thickness gradually increases, causing an increase in the gap between the convex surface of the negative electrode and the concave surface of the positive electrode. However, the lithium plating condition at the corner of the convex surface of the negative electrode first changes from level four to level one as the gap between the convex surface of the negative electrode and the concave surface of the positive electrode increases from 16.8 μm to 32.7 μm. Then, when the gap further increases to 36.2 μm, the lithium plating condition deteriorates and drops to level two. Meanwhile, the lithium plating at the concave corner of the negative electrode also exhibits the same pattern: as the gap between the concave surface of the negative electrode and the convex surface of the positive electrode increases from approximately 12.4 μm to about 17 μm, the lithium plating level improves; however, as the gap further increases to 21.3 μm, the lithium plating level decreases. This indicates that:

[0222] (1) Under the same areal density conditions, the increase of particle size (Dv50) can increase the thickness of the separator, thereby increasing the gap between the positive and negative electrode plates at the corner. However, only a suitable gap can improve the lithium plating situation at the corner of the negative electrode plate.

[0223] (2) When the particle size (Dv50) of the first particulate matter is 15μm ~ 30μm and the thickness of the separator is about 35μm ~ 65μm, so that the gap between the convex surface of the negative electrode and the concave surface of the positive electrode is about 25μm ~ 50μm, the lithium plating at the corner of the convex surface of the negative electrode is improved.

[0224] (3) When the particle size (Dv50) of the second particulate matter is 5~10μm and the thickness of the separator is about 15~25μm, so that the gap between the concave surface of the negative electrode and the convex surface of the positive electrode is about 10~17μm, the lithium plating state at the corner of the concave surface of the negative electrode is improved.

[0225] (4) When the particle size of the separator between the convex surface of the negative electrode and the concave surface of the positive electrode is 25 μm, and the particle size of the separator between the concave surface of the negative electrode and the convex surface of the positive electrode is 10 μm, the lithium plating state at the corner of the battery can be improved, thereby improving the cycle performance of the lithium-ion secondary battery.

[0226] The comparison between Examples 3 and 4 shows that under the same particle size of Al2O3 and PVDF, there is no significant difference in the thickness of the separator and the gap between the positive and negative electrode plates, resulting in the same lithium plating condition at the corner of the negative electrode plate. This indicates that inorganic or organic particles can play a similar role.

[0227] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A battery cell, characterized in that, include: A negative electrode sheet, a first separator, a second separator, and a positive electrode sheet are wound together along a winding direction to form an electrode assembly. The electrode assembly includes an arc-shaped corner region. In the arc-shaped corner region, the gap between the convex surface of the negative electrode sheet and the concave surface of the positive electrode sheet is a first gap; the gap between the concave surface of the negative electrode sheet and the convex surface of the positive electrode sheet is a second gap; the first separator is disposed in the first gap; and the second separator is disposed in the second gap. The thickness of the first separator is greater than the thickness of the second separator; at least one surface of the first separator is provided with a first coating; the first coating includes first particles; at least one surface of the second separator is provided with a second coating; the second coating includes second particles; the D of the first particles V 50 is 15μm~30μm; the D of the second particulate matter V 50 is 5μm~10μm; the thickness of the first separator is 35μm~65μm; the thickness of the second separator is 15μm~25μm.

2. The battery cell according to claim 1, characterized in that, The areal density of both the first and second separator membranes is 5 g / m³. 2 ~10g / m 2 .

3. The battery cell according to any one of claims 1-2, characterized in that, The difference in areal density between the first and second separator membranes is -1 g / m³. 2 ~1g / m 2 .

4. The battery cell according to any one of claims 1-2, characterized in that, The first particulate matter includes at least one of organic or inorganic particulate matter; and / or The second particulate matter includes at least one of organic or inorganic particulate matter.

5. The battery cell according to claim 4, characterized in that, The organic particulate matter includes at least one of polyvinylidene fluoride particles, polyimide particles, or polyethylene oxide particles.

6. The battery cell according to claim 4, characterized in that, The inorganic particulate matter includes at least one of alumina particles or boehmite particles.

7. The battery cell according to any one of claims 1-2, characterized in that, The first separator membrane satisfies at least one of the following characteristics: (1) The air permeability of the first separator is 425 seconds / 100 cc to 430 seconds / 100 cc; (2) The porosity of the first separator is 48%~50%; (3) The liquid absorption rate of the first isolation membrane is 130%~135%.

8. The battery cell according to any one of claims 1-2, characterized in that, The second separator membrane satisfies at least one of the following characteristics: (1) The air permeability of the second separator is 316 seconds / 100 cc to 400 seconds / 100 cc; (2) The porosity of the second separator is 30%~45%; (3) The liquid absorption rate of the second isolation membrane is 110%~126%.

9. A battery, characterized in that, Includes the battery cell described in any one of claims 1-8.

10. An electrical device, characterized in that, The electrical device includes the battery as described in claim 9.

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