Battery monomer and preparation method thereof, battery device and power utilization device

Abstract

The invention belongs to the technical field of batteries, and particularly discloses a battery monomer, a preparation method thereof, a battery device and a power utilization device. The battery monomer comprises a positive pole piece, the positive pole piece comprises a positive pole film layer, the positive pole film layer comprises a first main body region and an edge region, the first main body region comprises a positive active material, the edge region comprises a positive active material and a porous material, and the surface density of the first main body region is greater than that of the edge region. The design mode provided by the invention is beneficial to improving the cycle service life of the battery.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a battery cell and a preparation method thereof, a battery device and an electrical device. Background Art

[0002] With the development of new energy technology, batteries are used more and more widely, such as in mobile phones, laptops, battery cars, electric cars, energy storage devices, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools, etc. This places higher and higher requirements on battery performance. Summary of the invention

[0003] The present application provides a battery cell and a preparation method thereof, a battery device and an electrical device. The battery cell is beneficial to improving the cycle life of the battery.

[0004] In a first aspect, the present application provides a battery cell, comprising a positive electrode sheet, a separator and a negative electrode sheet stacked in layers;

[0005] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer located on at least one side surface of the positive electrode current collector;

[0006] The positive electrode film layer comprises a first main body region and an edge region;

[0007] The first main body region includes a positive electrode active material;

[0008] The above-mentioned edge region includes positive electrode active material and porous material;

[0009] The surface density of the first main region is greater than the surface density of the edge region.

[0010] The positive electrode film layer of the present application includes a main area and an edge area. The difference between the main area and the edge area includes: the edge area includes a porous material, and the surface density of the edge area is smaller than that of the main area. Among them, the porous material in the edge area is convenient for absorbing electrolyte so that the edge position of the positive electrode film layer can store sufficient electrolyte, which alleviates the problem of battery cycle life attenuation caused by the obstruction of the transmission path of metal ions at the edge position of the positive electrode film layer. At the same time, the surface density of the edge area is smaller than that of the main area, that is, the mass of positive electrode active materials contained in the edge area per unit area is less than the mass of positive electrode active materials contained in the main area per unit area. This design method is conducive to reducing the probability of bulging edges at the edge position of the positive electrode film layer, and improving the uniformity of current distribution of the battery during charging and discharging to improve the cycle life of the battery.

[0011] In some embodiments, the separator includes a coating disposed toward the positive electrode film layer;

[0012] The coating comprises a second main region and an edge region,

[0013] The orthographic projection of the edge area of ​​the positive electrode film layer on the coating at least partially overlaps with the edge area of ​​the coating;

[0014] The edge region of the coating comprises a porous material.

[0015] The present application chooses to set porous materials on the edge area of ​​the positive electrode film layer and the edge area of ​​the coating of the isolation member at the same time, so as to facilitate the storage of sufficient electrolyte at the edge position of the positive electrode film layer, thereby further improving the cycle life of the battery.

[0016] In some embodiments, the average pore size of the porous material is 50 nm to 10 μm;

[0017] and / or;

[0018] The specific surface area of ​​the porous material is 20m 2 / g~110m 2 / g.

[0019] The average pore size or specific surface area of ​​the porous material of the present application satisfies the above numerical range, which facilitates the porous material to absorb the electrolyte and be fully infiltrated with the electrolyte.

[0020] In some embodiments, the porous material includes any one or more of montmorillonite, diatomaceous earth, and vermiculite.

[0021] The porous materials of the types listed in the present application contain interconnected or closed pores, which, on the one hand, facilitate the storage of electrolyte. On the other hand, the porous materials expand in volume after absorbing the electrolyte, thereby reducing the distance between the edge area of ​​the positive electrode film layer and the edge area of ​​the coating of the isolation member, thereby increasing the electrolyte infiltration path, facilitating the diffusion and infiltration of the electrolyte at different positions in the electrode piece, and improving the cycle life of the battery.

[0022] In some embodiments, in the edge region of the positive electrode film layer, the mass percentage content of the porous material is 0.1% to 1.0%.

[0023] The present application selects a porous material with a mass percentage content of 0.1% to 1.0%, which is convenient for absorbing and storing electrolyte to a certain extent, and has little effect on the positive electrode active material and other components in the positive electrode film layer.

[0024] In some embodiments, the edge region of the positive electrode film layer and the first main region extend along the first direction and are arranged in the second direction;

[0025] The first direction intersects with the second direction;

[0026] Along the second direction, the edge region of the positive electrode film layer includes an A surface and a B surface that are arranged opposite to each other, and the distance between the A surface and the B surface is T1;

[0027] Along the second direction, the first main body region includes a C surface and a D surface that are oppositely disposed, and a distance between the C surface and the D surface is T2;

[0028] Satisfies: T1:T2=(1~3):20.

[0029] In some embodiments, the edge region of the positive electrode film layer and the first main region extend along the first direction and are arranged in the second direction;

[0030] The first direction intersects with the second direction;

[0031] Along the second direction, the edge region of the positive electrode film layer includes an A surface and a B surface that are arranged opposite to each other, the B surface is close to the first main body region, and the distance between the A surface and the B surface is T1;

[0032] The area extending from the B surface to the position of 0.1×T1 is recorded as the first sub-edge area, and the area extending from the A surface to the position of 0.1×T1 is recorded as the second sub-edge area;

[0033] In the first sub-edge region of the positive electrode film layer, the mass percentage content of the porous material is w1;

[0034] In the second sub-edge region of the positive electrode film layer, the mass percentage content of the porous material is w2;

[0035] Satisfies w1 greater than w2.

[0036] The present application designs a first sub-edge region of the positive electrode film layer that is disposed close to the first main region, and a second sub-edge region of the positive electrode film layer that is disposed away from the first main region, and the first sub-edge region contains a higher mass percentage of porous material than the second sub-edge region. This design method not only facilitates the storage of sufficient electrolyte at the edge position of the positive electrode film layer, but also facilitates the electrolyte at the edge position to flow to the main region of the positive electrode film layer, and further evenly disperses the electrolyte at different positions of the positive electrode plate, so that the entire plate is fully and effectively infiltrated, thereby further improving the cycle life of the battery.

[0037] In some embodiments, the edge region of the positive electrode film layer and the first main region extend along the first direction and are arranged in the second direction;

[0038] The first direction intersects with the second direction;

[0039] Along the second direction, the edge region of the positive electrode film layer includes a first sub-edge positive electrode film layer and a second sub-edge positive electrode film layer; the first sub-edge positive electrode film layer and the second sub-edge positive electrode film layer are located on the same side of the first main region;

[0040] Along the second direction, the first sub-edge positive electrode film layer includes a B surface and an M surface, the B surface is close to the first main body region, and the distance between the B surface and the M surface is t11;

[0041] Along the second direction, the second sub-edge positive electrode film layer includes an A surface and an N surface, and the distance between the A surface and the N surface is t12; satisfying t11:t12=(0.5-1):(0.5-1);

[0042] In the first sub-edge positive electrode film layer, the mass percentage content w1 of the porous material is 0.5% to 1%;

[0043] In the second sub-edge positive electrode film layer, the mass percentage content w2 of the porous material is 0.1% to 0.3%.

[0044] In some embodiments, the surface density A1 of the first main region of the positive electrode film layer is 200 mg / 1540.25 mm 2 ~400mg / 1540.25mm 2 ;

[0045] and / or;

[0046] The surface density A2 of the edge area of ​​the positive electrode film layer is 170 mg / 1540.25 mm 2 ~380mg / 1540.25mm 2 .

[0047] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector;

[0048] The negative electrode film layer comprises a third main body region and an edge thinning region;

[0049] The orthographic projection of the edge thinning area of ​​the negative electrode film layer on the positive electrode film layer at least partially overlaps with the edge area of ​​the positive electrode film layer.

[0050] The present application describes a negative electrode film layer including a third main area and an edge thinning area. This design method conveniently and effectively reduces the probability of bulging edges appearing at the edge of the negative electrode film layer, and improves the cycle life of the battery by improving the uniformity of current distribution during the charge and discharge process of the battery.

[0051] The second aspect of the present application is to provide a method for preparing the battery monomer according to the first aspect, including preparing a positive electrode sheet, the process is as follows:

[0052] Providing a first positive electrode slurry comprising a positive electrode active material;

[0053] Providing a second positive electrode slurry comprising a positive electrode active material and a porous material;

[0054] Applying a first positive electrode slurry on at least one side of the positive electrode current collector moving along the first direction to form a first main positive electrode film layer, and applying a second positive electrode slurry to form an edge positive electrode film layer, wherein the edge positive electrode film layer and the first main positive electrode film layer are arranged in the second direction;

[0055] The first direction intersects with the second direction;

[0056] The coating thickness of the first main positive electrode film layer is greater than the coating thickness of the edge positive electrode film layer.

[0057] In some embodiments, the coating thickness of the first main positive electrode film layer is h1, and the coating thickness of the edge positive electrode film layer is h2;

[0058] Satisfies: h1 / h2=1.01~1.15.

[0059] In some embodiments, the edge positive electrode film layer includes an E surface disposed in contact with the positive electrode current collector, and an F surface disposed opposite to the E surface;

[0060] Along the second direction, the F surface is an inclined surface gradually approaching the E surface;

[0061] The average value of the distance between the E surface and the F surface is the coating thickness h2 of the edge positive electrode film layer.

[0062] A third aspect of the present application is to provide a battery device, which includes the battery cell described in the first aspect or the battery cell manufactured by the preparation method described in the second aspect.

[0063] A fourth aspect of the present application is to provide an electrical device, which includes the battery device described in the third aspect.

[0064] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0066] Figure 1 A schematic diagram of the battery structure of some embodiments of the present application;

[0067] Figure 2 This is a schematic diagram of the exploded structure of batteries in some embodiments of the present application;

[0068] Figure 3 A schematic diagram of a vehicle structure of some embodiments of the present application;

[0069] Figure 4 A schematic diagram of the structure of a battery pack according to some embodiments of the present application;

[0070] Figure 5 A schematic diagram of the structure of a secondary battery in some embodiments of the present application;

[0071] Figure 6 This is a schematic diagram of the structure of the positive electrode sheet of some embodiments of the present application;

[0072] FIG7 is a schematic diagram of the structure of the positive electrode film layer in some embodiments of the present application; wherein, Fig. 7A , Figure 7B and Figure 7C The different positional relationships between the main area and the edge area in the positive electrode film layer are illustrated;

[0073] Figure 8 A schematic structural diagram of the positional relationship between the positive electrode sheet and the separator in some embodiments of the present application;

[0074] FIG9 is another schematic diagram of the structure of the positive electrode sheet of some embodiments of the present application, wherein: Fig. 9A The schematic diagram of the structure of the positive electrode sheet during the coating process and after the battery is formed is shown; Fig. 9B , Fig. 9C and Fig.9D The different positional relationships between the main area and the edge area in the positive electrode film layer are illustrated;

[0075] Fig.10 This is a schematic diagram of the structure of the negative electrode sheet of some embodiments of the present application;

[0076] Fig.11 A schematic structural diagram of the positional relationship between the positive electrode sheet and the negative electrode sheet in some embodiments of the present application;

[0077] Fig.12This is a schematic diagram of the structure during the coating process of the positive electrode plate of some embodiments of the present application.

[0078] The reference numerals in the specific implementation manner are as follows:

[0079] 10000, vehicles;

[0080] 1000, battery; 2000, controller; 3000, motor;

[0081] 100. Battery cell;

[0082] 200, box body; 210, first part; 220, second part;

[0083] 10. Secondary battery;

[0084] 101, housing; 102, electrode assembly; 103, cover plate;

[0085] 1. Negative electrode sheet; 11. Negative electrode current collector; 12. Negative electrode film layer; 12a. Third main body area; 12b. Edge thinning area;

[0086] 2. positive electrode sheet; 21. positive electrode current collector; 22. positive electrode film layer; 22a. first main body region; 22b. edge region of the positive electrode film layer; 22b1. first sub-edge region; 22b2. second sub-edge region;

[0087] 22bb, first sub-edge positive electrode film layer; 22ba, second sub-edge positive electrode film layer;

[0088] 22a', first main positive electrode film layer; 22b', edge positive electrode film layer;

[0089] 3. Isolation member; 31. Coating; 31a. Second main body region; 31b. Edge region of coating;

[0090] First direction: the extension direction or length direction of the pole piece, also referred to as the y direction of the coordinate axis;

[0091] Second direction: the width direction of the pole piece, also referred to as the x-direction of the coordinate axis;

[0092] The third direction: the coordinate axis z direction, which can also be the thickness direction or stacking direction of the pole piece. DETAILED DESCRIPTION

[0093] Hereinafter, the battery cell and its preparation method, battery device and electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0094] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0095] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0096] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0097] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0098] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0099] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0100] If not otherwise specified, in this application, the terms "first", "second", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary and secondary relationship of the indicated technical features.

[0101] Unless otherwise specified, in this application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple sheets" refers to more than two sheets (including two sheets).

[0102] Unless otherwise specified, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" 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, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present application.

[0103] Batteries have been widely used in various products due to their high energy density, long cycle life, safety and reliability. In recent years, as the demand for batteries as energy has increased significantly, higher requirements have been placed on battery performance, such as cycle life.

[0104] In the coating process of battery preparation, the active material forms an active material layer on the surface of the current collector. Since the coating at the edge of the current collector is difficult to control, after the battery is formed, the edge of the active material layer will produce a bulging phenomenon, that is, the thickness of the edge of the active material layer is greater than the thickness of the middle area. This phenomenon easily leads to uneven current distribution and polarization during the charge and discharge process of the battery. In order to alleviate this phenomenon, the prior art discloses that in the preparation process of the battery, the edge of the active material layer is thinned so that the thickness of the edge is less than the thickness of the middle area. However, this design method brings new technical problems: the distance between the edge positions of adjacent active material layers is greater than the distance between the middle areas of adjacent active material layers, and the edge positions of the active material layer are easily not fully infiltrated by the electrolyte, which leads to many problems. For example, for lithium-ion batteries, the transmission path of lithium ions at the edge of the active material layer is blocked, the polarization of this position is serious, the impedance becomes larger, and then purple spots and lithium precipitation appear, which further accelerates the consumption of the electrolyte, accelerates the local aging rate in the battery, and the cycle performance of the battery is attenuated and ultimately affects the life of the battery.

[0105] Based on the above considerations, in order to improve the cycle life of the battery, the present application conducted relevant experimental research and obtained a battery cell and its preparation method, a battery device and an electrical device.

[0106] First, the present application discloses a battery cell, which includes a positive electrode sheet, a separator and a negative electrode sheet which are stacked;

[0107] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer located on at least one side surface of the positive electrode current collector;

[0108] The positive electrode film layer comprises a first main body region and an edge region;

[0109] The first main body region includes a positive electrode active material;

[0110] The above-mentioned edge region includes positive electrode active material and porous material;

[0111] The surface density of the first main region is greater than the surface density of the edge region.

[0112] The positive electrode film layer of the present application includes a main area and an edge area. The difference between the main area and the edge area includes: the edge area includes a porous material, and the surface density of the edge area is smaller than that of the main area. Among them, the porous material in the edge area is convenient for absorbing electrolyte so that the edge position of the positive electrode film layer can store sufficient electrolyte, which alleviates the problem of battery cycle life attenuation caused by the obstruction of the transmission path of metal ions at the edge position of the positive electrode film layer. At the same time, the surface density of the edge area is smaller than that of the main area, that is, the mass of positive electrode active materials contained in the edge area per unit area is less than the mass of positive electrode active materials contained in the main area per unit area. This design method is conducive to reducing the probability of bulging edges at the edge position of the positive electrode film layer, and improving the uniformity of current distribution of the battery during charging and discharging to improve the cycle life of the battery.

[0113] Therefore, the battery cell provided in the present application is conducive to improving the cycle life of the battery, thereby enhancing the user experience.

[0114] Electrode assembly

[0115] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator, which is arranged between the negative electrode sheet and the positive electrode sheet. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, which can prevent the positive and negative electrodes from short-circuiting, and at the same time allow active ions to pass through.

[0116] Battery device

[0117] The battery apparatus mentioned in the embodiments of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple battery cells, which are connected in series, in parallel or in mixed connection through a busbar component.

[0118] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0119] As an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing a plurality of battery cells to form an independent module. As an example, the battery module may be formed by bundling a plurality of battery cells by a cable tie.

[0120] In some embodiments, the battery device may be a battery pack, which includes a case and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the case.

[0121] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box by fixing the battery module in the box.

[0122] As an example, the battery cell assembly may also be housed in the case by directly fixing a plurality of battery cells to the case.

[0123] As an example, the box may include a first box and a second box. The first box and the second box are buckled together to form a closed space inside the box to accommodate the battery cell assembly. The closed here means covered or closed, which can be sealed or unsealed. The first box can be a top cover or a bottom plate.

[0124] As an example, the box body may include a top cover, a frame and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0125] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0126] The battery cell of the present application may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte composed of the above-mentioned battery cell. The outer package of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package 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 the plastic includes but is not limited to polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0127] The present application has no particular limitation on the shape of the battery, which may be cylindrical, square or any other shape. For example, Figure 1 The secondary battery 10 is a square structure as an example.

[0128] According to some embodiments of the present application, Figure 2, the outer packaging may include a shell 101 and a cover plate 103. Among them, the shell 101 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 101 has an opening connected to the receiving cavity, and the cover plate 103 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 102 through a winding process or a lamination process. The electrode assembly 102 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 102. The number of electrode assemblies 102 contained in the secondary battery 10 can be one or more, and those skilled in the art can select according to specific actual needs.

[0129] The electrode assembly 102 provided in the present application is applied to a battery cell, which is beneficial to improving the performance of the battery cell. The battery cell can be used as a power source for an electrical device or as an energy storage unit for an electrical device. The electrical device is applied to the power field, such as mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited to the above-mentioned fields.

[0130] For the convenience of explanation, some embodiments of the present application are described by taking a vehicle as an example of an electrical device.

[0131] Please refer to Figure 3 , Figure 3 A schematic diagram of the structure of a vehicle 10000 provided for some embodiments of the present application. The vehicle 10000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 1000 is provided inside the vehicle 10000, and the battery 1000 may be provided at the bottom, head or tail of the vehicle 10000. The battery 1000 may be used to power the vehicle 10000, for example, the battery 1000 may be used as an operating power source for the vehicle 10000. The vehicle 10000 may also include a controller 2000 and a motor 3000, and the controller 2000 is used to control the battery 1000 to power the motor 3000, for example, for the starting, navigation and working power requirements of the vehicle 10000 during driving.

[0132] In some embodiments of the present application, the battery 1000 can not only serve as the operating power source of the vehicle 10000, but also serve as the driving power source of the vehicle 10000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 10000.

[0133] Please refer to Figure 4 , Figure 4An exploded view of a battery 1000 provided in some embodiments of the present application. The battery 1000 includes a housing 200 and a battery cell 100. Conventional battery cells include primary batteries or secondary batteries. The present application specifically protects secondary batteries 10. The battery cell 100 is accommodated in the housing 200. The housing 200 is used to provide a storage space for the battery cell 100. The housing 200 can adopt a variety of structures.

[0134] In some embodiments, the box 200 may include a first portion 210 and a second portion 220, the first portion 210 and the second portion 220 cover each other, and the first portion 210 and the second portion 220 jointly define a storage space for accommodating the battery cell 100. The second portion 220 may be a hollow structure with one end open, and the first portion 210 may be a plate-like structure, and the first portion 210 covers the open side of the second portion 220, so that the first portion 210 and the second portion 220 jointly define a storage space; the first portion 210 and the second portion 220 may also be hollow structures with one side open, and the open side of the first portion 210 covers the open side of the second portion 220. Of course, the box 200 formed by the first portion 210 and the second portion 220 may be in various shapes, such as a cylinder, a cuboid, etc.

[0135] In the battery 1000, there may be multiple battery cells 100, and the multiple battery cells 100 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 100 are both connected in series and in parallel. The multiple battery cells 100 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 100 is accommodated in the box 200; of course, the battery 1000 may also be a battery 1000 module formed by connecting multiple battery cells 100 in series, in parallel, or in a mixed connection, and then the multiple battery 1000 modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 200. The battery 1000 may also include other structures, for example, the battery 1000 may also include a busbar component for realizing electrical connection between the multiple battery cells 100.

[0136] Battery Cell

[0137] In some embodiments, the present application discloses a battery cell, which includes a stacked positive electrode plate, an isolation member and a negative electrode plate; the positive electrode film layer includes a first main region and an edge region; the first main region includes a positive electrode active material; the edge region includes a positive electrode active material and a porous material; the surface density of the first main region is greater than the surface density of the above-mentioned edge region.

[0138] The battery cell of the present application may be a secondary battery, which refers to a battery cell that can be used continuously by activating the active material by charging after the battery cell is discharged. The battery cell may be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, a lithium metal battery, a sodium metal battery, a lithium-sulfur battery, a magnesium-ion battery, a nickel-hydrogen battery, a nickel-cadmium battery, a lead-acid battery, etc., and the embodiments of the present application are not limited thereto. In the specific embodiments of the present application, the technical solution of the present application is mainly described by taking a lithium-ion battery as an example.

[0139] The positive electrode sheet 2, the separator 3 and the negative electrode sheet 1 of the present application can be wound or laminated to form a secondary battery. Figure 5 The secondary battery 10 is formed by a winding method, and the Figure 5 It can be seen that a negative electrode sheet 1 or a positive electrode sheet 2 is placed between two adjacent separators 3, and the negative electrode sheets 1 and the positive electrode sheets 2 are alternately arranged in sequence along the stacking direction (coordinate axis z direction). The number and size of the negative electrode sheets 1 and / or the positive electrode sheets 2 can be selected according to actual conditions, and this application will not be repeated. Figure 5 Only one winding method is illustrated in the figure, and other laminations or winding methods are within the protection scope of this application.

[0140] like Figure 6 As shown in the figure, the positive electrode sheet 2 includes a positive electrode current collector 21 and a positive electrode film layer 22 located on at least one side of the positive electrode current collector 21, wherein: Figure 6 It is shown that a positive electrode film layer 22 is arranged on the surface of any side of the positive electrode current collector 21, and the positive electrode film layer 22 can also be located on the surface of both sides of the positive electrode current collector 21. The formation method of the positive electrode film layer 22 on the surface of the positive electrode current collector 21 includes any conventional method in the art, such as coating, deposition, etc. The structure of the negative electrode plate of the present application remains the same as that of the positive electrode plate, and the present application will not be repeated here. Coating includes any one or more of roller coating, extrusion coating, blade coating and gravure coating. Deposition includes any one or more of physical deposition and chemical deposition.

[0141] The positive electrode film layer 22 of the present application includes a first main region 22a and an edge region 22b of the positive electrode film layer, wherein the first main region 22a refers to the positive electrode film layer region corresponding to the large surface of the battery cell, and the edge region 22b of the positive electrode film layer refers to the region corresponding to the side of the first main region 22a, as shown in FIG. Fig. 7A , 7B 7C illustrate several different positional relationships between the first main region 22a and the edge region 22b of the positive electrode film layer, and FIG. 7 is only a simple illustration. In fact, other positional relationships are also within the protection scope of this application.

[0142] The porous material of the present application refers to a material that contains interconnected or closed pores to form a network structure. The porous material can easily absorb electrolyte so that sufficient electrolyte is stored at the edge of the positive electrode film layer, thereby alleviating the problem of battery cycle life degradation caused by the obstruction of the metal ion transmission path at the edge of the positive electrode film layer.

[0143] The surface density of this application refers to the material mass per unit area, and the calculation formula of the surface density is: surface density = single-sided film weight / single-sided film area, where the single-sided film weight can be obtained by direct weighing, and the single-sided film area can be obtained by the area calculation formula based on the shape of the film. The surface density of the edge area of ​​this application is smaller than that of the main area, that is, the mass of the positive electrode active material contained in the edge area per unit area is smaller than the mass of the positive electrode active material contained in the main area per unit area. This design method is conducive to reducing the probability of bulging edges at the edge of the positive electrode film layer, and improving the uniformity of the current distribution of the battery during the charging and discharging process to improve the cycle life of the battery.

[0144] At the same time, this application Figure 5 The specific positional relationship between the negative electrode plate 1, the positive electrode plate 2 and the separator 3 is described in the specification. According to the CB value (the ratio of the negative electrode capacity on the opposite side to the positive electrode capacity) and the calculation formula when the battery is designed: CB value = negative electrode active material gram capacity × negative electrode surface density × negative electrode active material content / positive electrode active material gram capacity × positive electrode surface density × positive electrode active material content. Since the surface density of the edge area of ​​the positive electrode film layer is less than the surface density of the first main area, that is, the surface density of the edge area of ​​the positive electrode film layer becomes smaller, it is applied to the above-mentioned CB value calculation formula. Under the premise that other variables remain unchanged, the CB value becomes larger. Therefore, the design method provided in the present application is also conducive to improving the CB value of the battery at the edge position, so that in the harsh environment where the electrolyte dries up at the edge position of the battery, the probability of lithium plating at the edge position of the battery is also effectively reduced, thereby further improving the cycle life of the battery.

[0145] In some embodiments, Figure 8 In the embodiment, the separator 3 includes a coating 31 disposed toward the positive electrode film layer 22; the coating 31 includes a second main region 31a and an edge region 31b of the coating, and the orthographic projection of the edge region 22b of the positive electrode film layer on the coating 31 at least partially overlaps with the edge region 31b of the coating; the edge region 31b of the coating includes a porous material, and the present application is Figure 8 FIG. 3 shows only one edge region of the coating 31 of the spacer 3 , but in fact, an edge region 31 b of the coating on the other side also exists.

[0146] This application is Figure 8The positive electrode film layer 22 described in 7C is illustrated, and the edge area 31b of the coating corresponds to the edge area 22b of the positive electrode film layer, that is, the orthographic projection of the edge area 22b of the positive electrode film layer on the above-mentioned coating 31 overlaps at least partially with the edge area 31b of the coating, and the at least partial overlap here includes complete overlap, and the present application is mainly described in the subsequent specific embodiments in the design mode of complete overlap. The present application further selects that a porous material is provided on the edge area 31b of the coating, and the porous material is the same as the porous material contained in the edge area 22b of the above-mentioned positive electrode film layer, for example, the function to be achieved is the same, but the specific type can be the same or different.

[0147] The present application chooses to set porous materials on both the edge area 22b of the positive electrode film layer and the edge area 31b of the coating of the separator 3, so as to facilitate the storage of sufficient electrolyte at the edge position of the positive electrode film layer, thereby further improving the cycle life of the battery.

[0148] In some embodiments, the average pore size of the porous material is 50 nm to 10 μm;

[0149] In some embodiments, the specific surface area of ​​the porous material is 20 m 2 / g~110m 2 / g;

[0150] In some embodiments, the median particle size Dv50 of the porous material is 10 μm to 50 μm.

[0151] The average pore size of the present application refers to the average value of the pore sizes contained in various pore structures in the porous material. The average pore size of the porous material of the present application is 50nm~10μm, that is, most of the pores in the porous material are large pores, which are convenient for storing electrolyte.

[0152] In these embodiments, the present application discloses that the average pore size of the porous material is any one of 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any one of the values ​​satisfying the above ranges.

[0153] The method for determining the average pore size of the porous material of the present application includes any conventional determination method in the art, such as nitrogen adsorption desorption instrument and mercury intrusion instrument. Specifically, the test instrument used is ASAP2460-physical adsorption analyzer, the material sample after drying and degassing is placed in liquid nitrogen, different test pressures are adjusted, the adsorption amount of nitrogen is measured respectively, and the adsorption and desorption isotherms are drawn. The shape of the pores is determined according to the shape of the hysteresis loop, the pore distribution is calculated according to different pore models, and the pore size distribution curve of the pores is fitted using the BJH model to obtain the average pore size.

[0154] The specific surface area of ​​this application refers to the total area per unit mass of the material. The specific surface area of ​​the porous material in this application is 20m 2 / g~110m 2 / g, which is convenient for absorbing the electrolyte and being fully infiltrated with the electrolyte.

[0155] The present application discloses in these examples that the specific surface area of ​​the porous material is 20 m 2 / g, 30m 2 / g, 40m 2 / g, 50m 2 / g, 60m 2 / g, 70m 2 / g, 80m 2 / g, 90m 2 / g、100m 2 / g, 110m 2 / g or any of the values ​​satisfying the above ranges.

[0156] The specific surface area of ​​the porous material of the present application can be determined by any conventional method in the art, such as referring to GB / T19587-2004, using nitrogen adsorption specific surface area analysis and testing method, and calculating the specific surface area of ​​the porous material by BET (Brunauer Emmett Teller) method. The testing instrument can be TRISTAR II 3020 specific surface area and porosity analyzer from Micromeritics, USA.

[0157] The median particle size Dv50 of this application refers to the particle size larger than it accounts for 50% of the volume of particles, and the particle size smaller than it also accounts for 50% of the volume of particles, which is also called the median diameter, and is usually used to indicate the average particle size of particles. The median particle size of the porous material of this application needs to match the median particle size of the positive electrode active material, and the two cannot be significantly different, so that the porous material has little effect on the positive electrode active material and other components in the positive electrode film layer while playing the role of adsorbing and storing electrolyte.

[0158] The present application discloses in these embodiments that the median particle size Dv50 of the porous material is any one of 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or any one of the values ​​within the above ranges.

[0159] In these embodiments, the present application selects to refer to the laser diffraction particle size analysis method for determination, specifically refers to the standard GB / T19077-2016 to obtain the particle size distribution diagram, and then obtains it by calculation.

[0160] In some embodiments, the porous material includes any one or more of montmorillonite, diatomaceous earth, and vermiculite.

[0161] The montmorillonite in the present application refers to a layered mineral composed of extremely fine aluminum silicate particles. The interior of the layered mineral contains interconnected or closed pores, which is convenient for storing electrolyte on the one hand. On the other hand, the montmorillonite expands in volume after absorbing the electrolyte, thereby reducing the distance between the edge area 22b of the positive electrode film layer and the edge area 31b of the coating of the isolation member 3, thereby increasing the electrolyte infiltration path, facilitating the diffusion and infiltration of the electrolyte at different positions in the electrode piece, and improving the cycle life of the battery.

[0162] The diatomaceous earth of the present application is a siliceous rock, and the vermiculite of the present application is a magnesium-containing aluminum silicate with a layered structure. The diatomaceous earth and vermiculite of the present application have similar properties to the above-mentioned montmorillonite, that is, they are convenient for storing electrolytes and can expand in volume after absorbing electrolytes. Therefore, any one or more of the diatomaceous earth and vermiculite provided in the present application are also beneficial to the diffusion and infiltration of electrolytes at different positions in the electrode, thereby improving the cycle life of the battery.

[0163] In some embodiments, in the edge region of the positive electrode film layer, the mass percentage content of the porous material is 0.1% to 1.0%.

[0164] The mass percentage content of the porous material in the edge area of ​​the positive electrode film layer of this application refers to the amount added during the preparation process. Since the porous material has stable properties, the mass change rate is negligible. This application selects the porous material to have a mass percentage content of 0.1% to 1.0%, which is convenient for absorbing and storing electrolyte to a certain extent, and has little effect on the positive electrode active material and other components in the positive electrode film layer.

[0165] In these embodiments, the present application discloses that in the edge area of ​​the above-mentioned positive electrode film layer, the mass percentage content of the above-mentioned porous material is any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or any one of the values ​​in any two of the above ranges.

[0166] In some embodiments, the present application selects the above Figure 7CThe schematic positive electrode film layer 22 is specifically described, and further combined with Fig. 9A , Fig. 9B It can be seen that the edge area 22b and the first main area 22a of the positive electrode film layer extend along the first direction and are arranged in the second direction; the first direction in these embodiments of the present application refers to the coordinate axis y direction, which also refers to the length direction or extension direction of the positive electrode plate 2, and the second direction refers to the coordinate axis x direction, which also refers to the width direction of the positive electrode plate 2. The present application further discloses that the coordinate axis x direction intersects and is perpendicular to the coordinate axis y direction. Fig. 9A The figure shows that there are two edge regions 22b of the positive electrode film layer, which are located on both sides of the first main region 22a along the second direction. The shape, size, etc. of the edge regions 22b of the two positive electrode film layers are consistent. This design is adopted in the present application to facilitate the preparation of the film layer and the infiltration of the electrolyte into the film layer. Fig. 9B , along the second direction (coordinate axis x direction), the edge region 22b of the positive electrode film layer includes an A surface and a B surface that are arranged oppositely, the B surface is close to the first main region 22a, and the distance between the A surface and the B surface is T1, which also refers to the width value of the edge region 22b of the positive electrode film layer in the second direction. Along the second direction (coordinate axis x direction), the first main region 22a includes a C surface and a D surface that are arranged oppositely, and the distance between the C surface and the D surface is T2, and in Fig. 9B In the embodiment, the B surface can refer to both the C surface and the D surface. The letter symbols in the present application are only for reference in the drawings. Further, the width of the edge region 22b of the positive electrode film layer and the width of the first main region 22a of the positive electrode film layer satisfy: T1:T2=(1-3):20. Fig. 9B For the positive electrode film layer of the schematic structure, along the second direction, the ratio between the width value T1 of the edge region 22b of the positive electrode film layer on one side of the first main region 22a, the width value T2 of the first main region 22a, and the width value T1 of the edge region 22b of the positive electrode film layer on the other side of the first main region 22a is: T1: T2: T1 = (1-3): 20: (1-3). That is, after the width value of the positive electrode film layer along the second direction is disclosed in this application, the positional relationship between the edge region 22b of the positive electrode film layer and the first main region 22a can be determined according to the above proportional relationship.

[0167] In some embodiments, the present application selects the above Figure 7C The schematic positive electrode film layer 22 is specifically described, and further combined with Fig. 9A , 9CIt can be seen that the edge area 22b and the first main area 22a of the positive electrode film layer extend along the first direction and are arranged in the second direction; the first direction in these embodiments of the present application refers to the coordinate axis y direction, which also refers to the length direction or extension direction of the positive electrode plate 2, and the second direction refers to the coordinate axis x direction, which also refers to the width direction of the positive electrode plate 2. The present application further discloses that the coordinate axis x direction intersects and is perpendicular to the coordinate axis y direction. Fig. 9A FIG. 2 shows that there are two edge regions 22 b of the positive electrode film layer, which are located on both sides of the first main region 22 a along the second direction. The shape, size, etc. of the edge regions 22 b of the two positive electrode film layers are consistent. Fig. 9C , along the second direction (x direction of the coordinate axis), the edge area 22b of the positive electrode film layer includes an A surface and a B surface that are relatively arranged, and the B surface is close to the above-mentioned first main area 22a, and the distance between the A surface and the B surface is T1, and the area formed by extending from the above-mentioned B surface to the position of 0.1×T1 is recorded as the first sub-edge area 22b1, and the area formed by extending from the above-mentioned A surface to the position of 0.1×T1 is recorded as the second sub-edge area 22b2; as mentioned above, the edge area 22b of the positive electrode film layer contains a porous material, and in the first sub-edge area 22b1 of the positive electrode film layer, the mass percentage content of the porous material is w1; in the second sub-edge area 22b2 of the positive electrode film layer, the mass percentage content of the porous material is w2; satisfying that w1 is greater than w2. This application is in Fig. 9C It is shown that the first sub-edge area 22b1 of the positive electrode film layer is arranged close to the first main area 22a, and the second sub-edge area 22b2 of the positive electrode film layer is arranged away from the first main area 22a, and the first sub-edge area 22b1 contains a higher mass percentage of porous material than the second sub-edge area 22b2. This design method not only facilitates the storage of sufficient electrolyte at the edge position of the positive electrode film layer, but also facilitates the electrolyte at the edge position to flow to the main area of ​​the positive electrode film layer, and further evenly disperses the electrolyte at different positions of the positive electrode plate, so that the entire plate is fully and effectively infiltrated, thereby further improving the cycle life of the battery.

[0168] In some embodiments, the present application selects the above Figure 7C The schematic positive electrode film layer 22 is specifically described, and further combined with Fig. 9A , Fig.9D It can be seen that the edge area 22b and the first main area 22a of the positive electrode film layer extend along the first direction and are arranged in the second direction; the first direction in these embodiments of the present application refers to the coordinate axis y direction, which also refers to the length direction or extension direction of the positive electrode plate 2, and the second direction refers to the coordinate axis x direction, which also refers to the width direction of the positive electrode plate 2. The present application further discloses that the coordinate axis x direction intersects and is perpendicular to the coordinate axis y direction. Fig. 9AFIG. 2 shows that there are two edge regions 22 b of the positive electrode film layer, which are located on both sides of the first main region 22 a along the second direction. The shape, size, etc. of the edge regions 22 b of the two positive electrode film layers are consistent. Fig.9D , along the second direction, the edge region 22b of the positive electrode film layer includes a first sub-edge positive electrode film layer 22bb and a second sub-edge positive electrode film layer 22ba; along the second direction, the first sub-edge positive electrode film layer 22bb includes a B surface and an M surface, and the distance between the B surface and the M surface is t11; along the second direction, the second sub-edge positive electrode film layer 22ba includes an A surface and an N surface, and the distance between the A surface and the N surface is t12; as mentioned above, t11 and t12 refer to the width values ​​of each sub-edge positive electrode film layer in the second direction. Wherein, Fig.9D It is illustrated that the above-mentioned N surface and M surface are the same plane, but are represented by different symbols. At the same time, the above-mentioned N surface and M surface can also be different planes. Correspondingly, the edge area 22b of the positive electrode film layer includes three or more sub-edge positive electrode film layers, and this application is only for illustration in the accompanying drawings and does not represent actual significance.

[0169] The present application focuses on explaining that the edge region 22b of the positive electrode film layer includes two sub-edge positive electrode film layers, namely the first sub-edge positive electrode film layer 22bb and the second sub-edge positive electrode film layer 22ba, and the ratio between the width t11 of the first sub-edge positive electrode film layer 22bb in the second direction and the width t12 of the second sub-edge positive electrode film layer 22ba in the second direction satisfies t11:t12=(0.5~1):(0.5~1); as mentioned above, the edge region 22b of the positive electrode film layer contains a porous material, and in the first sub-edge positive electrode film layer 22bb, the mass percentage content w1 of the porous material is 0.5%~1%; in the second sub-edge positive electrode film layer 22ba, the mass percentage content w2 of the porous material is 0.1%~0.3%. The present application gives the specific structure of the edge region of the positive electrode film layer here, and the present application will focus on it in subsequent specific embodiments.

[0170] In some embodiments, the surface density A1 of the first main region is 200 mg / 1540.25 mm 2 ~400mg / 1540.25mm 2 .

[0171] In some embodiments, the surface density A2 of the edge area of ​​the positive electrode film layer is 170 mg / 1540.25 mm 2 ~380mg / 1540.25mm 2 .

[0172] The present application describes the specific values ​​of the surface density of the main area and the edge area of ​​the positive electrode film layer in the above embodiments. The present application elaborates in detail the influence of the design methods of different surface densities on the battery performance of the present application in subsequent specific embodiments.

[0173] In some embodiments, in combination Fig.10 It can be seen that the above-mentioned negative electrode sheet 1 includes a negative electrode current collector 11 and a negative electrode film layer 12 located on at least one side of the surface of the above-mentioned negative electrode current collector 11; the negative electrode film layer 12 includes a third main area 12a and an edge thinning area 12b; the third main area 12a of the present application has the same meaning as the first main area 22a of the above-mentioned positive electrode film layer 22, and the second main area 31a of the separator 3, and the position is also corresponding. Specifically, the orthographic projection of the edge thinning area 12b of the above-mentioned negative electrode film layer 12 on the above-mentioned positive electrode film layer 22 at least partially overlaps with the edge area 22b of the above-mentioned positive electrode film layer, which can be as shown Fig.11 For example, at least partial overlap here includes complete overlap, and the present application is mainly described in the subsequent specific embodiments in the design manner of complete overlap.

[0174] This application is Fig.10 It is described that the negative electrode film layer 12 includes a third main area 12a and an edge thinning area 12b. This design method is convenient and effective in reducing the probability of bulging edges appearing at the edge of the negative electrode film layer, and improves the uniformity of current distribution during the charge and discharge process of the battery to increase the cycle life of the battery.

[0175] This application is Fig.11 The specific positional relationship between the negative electrode plate 1, the positive electrode plate 2 and the separator 3 is described in the specification. According to the CB value (the ratio of the negative electrode capacity on the opposite side to the positive electrode capacity) and the calculation formula when the battery is designed: CB value = negative electrode active material gram capacity × negative electrode surface density × negative electrode active material content / positive electrode active material gram capacity × positive electrode surface density × positive electrode active material content. Since the surface density of the edge area of ​​the positive electrode film layer is less than the surface density of the first main area, that is, the surface density of the edge area of ​​the positive electrode film layer becomes smaller, it is applied to the above CB value calculation formula. Under the premise that other variables remain unchanged, the CB value becomes larger. Therefore, the design method provided in the present application is also beneficial to improving the CB value of the battery at the edge position. Therefore, even in the harsh environment where the electrolyte dries up at the edge position of the battery, the probability of lithium plating at the edge position of the battery is effectively reduced, thereby further improving the cycle life of the battery.

[0176] Method for preparing positive electrode sheet

[0177] Some embodiments of the present application disclose a method for preparing a positive electrode sheet, comprising the following process:

[0178] Providing a first positive electrode slurry comprising a positive electrode active material;

[0179] Providing a second positive electrode slurry comprising a positive electrode active material and a porous material;

[0180] The first positive electrode slurry is coated on at least one side of the positive electrode current collector moving along the first direction to form a first main positive electrode film layer, and the second positive electrode slurry is coated to form an edge positive electrode film layer, and the edge positive electrode film layer and the first main positive electrode film layer are arranged in the second direction; the first direction intersects the second direction. The coating thickness of the first main positive electrode film layer is greater than the coating thickness of the edge positive electrode film layer.

[0181] like Fig.12 As shown in FIG. 1 , the first positive electrode slurry is coated on both sides of the positive electrode current collector 21 moving along the first direction (the y direction of the coordinate axis) to form a first main positive electrode film layer 22a′. The first main positive electrode film layer 22a′ here is the same as the above Fig. 9A At the same time, the second positive electrode slurry is applied to the surfaces of both sides of the positive electrode current collector 11 moving along the first direction (the y direction of the coordinate axis) to form an edge positive electrode film layer 22b', where the edge positive electrode film layer 22b' is the same as the above Fig. 9A The edge area 22b of the positive electrode film layer corresponds to the edge area 22b of the positive electrode film layer, and when coating, the coating thickness of the first main positive electrode film layer 22a' is greater than the coating thickness of the above-mentioned edge positive electrode film layer 22b'. The coating thickness here refers to the distance between the upper and lower end surfaces of the positive electrode film layer that are relatively arranged along the coordinate axis z. As mentioned above, since the coating at the edge position of the current collector is not easy to control, after the battery is formed, the edge position of the film layer will produce a bulging edge phenomenon. For example, the thickness of the edge area of ​​the positive electrode film layer is greater than the thickness of the middle main area. This phenomenon easily leads to uneven current distribution during the charging and discharging process of the battery and then forms polarization. In order to alleviate this phenomenon, the present application selects the coating thickness of the first main positive electrode film layer 22a' to be greater than the coating thickness of the above-mentioned edge positive electrode film layer 22b', which is equivalent to thinning the edge area 22b of the positive electrode film layer. At the same time, the edge positive electrode film layer 22b' of the present application comprises a porous material compared to the first main positive electrode film layer 22a'. As mentioned above, the porous material of the present application expands in volume after absorbing the electrolyte, that is, the edge positive electrode film layer 22b' expands in volume. Fig. 9A The area enclosed by the dotted line corresponds to Fig.12 The edge positive electrode film layer 22b' expands in volume after absorbing the electrolyte to form Fig. 9A The schematic diagram of the edge region 22b of the positive electrode film layer, Fig. 9AThe schematic diagram shows one of the structures in which the volume of the edge positive electrode film layer 22b' expands. In the battery cell, after the volume of the edge positive electrode film layer 22b' expands, the distance between the edge areas 22b of the adjacent positive electrode film layers is reduced, and the edge positive electrode film layer 22b' absorbs and stores sufficient electrolyte, which increases the infiltration path of the electrolyte and alleviates the problem of battery cycle life degradation caused by the obstruction of the transmission path of metal ions at the edge of the positive electrode film layer.

[0182] In some embodiments, the coating thickness of the first main positive electrode film layer 22a' is h1, and the coating thickness of the edge positive electrode film layer 22b' is h2; and the following relation is satisfied: h1 / h2=1.01-1.15.

[0183] The coating thickness of the present application refers to the distance between the upper and lower end surfaces of the positive electrode film layer relatively arranged along the coordinate axis z direction, and specifically refers to the average value of the distance between the upper and lower end surfaces of the positive electrode film layer relatively arranged. Fig.12 The coating thickness h1 of the first main positive electrode film layer 22a' and the coating thickness h2 of the edge positive electrode film layer 22b' are shown in the figure; the coating thickness can be obtained by conventional measurement methods in the art when preparing positive electrode sheets, such as micrometer, scanning electron microscope, etc.

[0184] In these embodiments, the present application discloses that the ratio between the coating thickness h1 of the first main positive electrode film layer 22a' and the coating thickness h2 of the above-mentioned edge positive electrode film layer 22b' is any one of 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15 or any one of the values ​​satisfying the above-mentioned range.

[0185] In some embodiments, in combination Fig.12 It can be seen that the edge positive electrode film layer 22b' includes an E surface arranged in contact with the positive electrode current collector 21, and an F surface arranged opposite to the E surface; along the second direction, the F surface is an inclined surface gradually approaching the E surface; the coating thickness h2 of the edge positive electrode film layer 22b' of the present application refers to the average value, that is, the distance between the E surface and the F surface at different positions is summed up by a mathematical function and then averaged. Fig.12 The h2 shown in the figure only represents the coating thickness at this position. The actual average coating thickness needs to be obtained by adding and averaging the above mathematical function. The mathematical function here can refer to any conventional function in the art. The mathematical function can be calculated to meet the requirements. Fig.12 Average coating thickness for schematic structures.

[0186] In the above description of the positive electrode film layer, the present application discloses Fig. 9A and9C Schematically, the edge area 22b of the positive electrode film layer includes a first sub-edge area 22b1 arranged close to the first main body 22a and a second sub-edge area 22b2 arranged away from the first main body 22a, and the mass percentage content of the porous material in the first sub-edge area 22b1 is greater than the mass percentage content of the porous material in the second sub-edge area 22b2.

[0187] At the same time, this application further Fig. 9A and Fig.9D It is shown that the edge area 22b of the positive electrode film layer includes a first sub-edge positive electrode film layer 22bb and a second sub-edge positive electrode film layer 22ba, and the mass percentage content of the porous material in the first sub-edge positive electrode film layer 22bb arranged close to the first main area 22a is greater than the mass percentage content of the porous material in the second sub-edge positive electrode film layer 22ba arranged away from the first main area 22a.

[0188] When preparing the edge positive electrode film layer 22b' of the above-mentioned positive electrode film layer, the present application can divide the edge positive electrode film layer 22b' into different sub-edge positive electrode film layers, and then coat each different sub-edge positive electrode film layer with an electrode slurry containing porous materials with different contents. The advantage of this design method is that it is convenient for storing sufficient electrolyte at the edge position of the positive electrode film layer, and allows the electrolyte at the edge position to flow to the main area of ​​the positive electrode film layer, further making the electrolyte at different positions of the positive electrode plate evenly dispersed, so that the entire plate is fully and effectively infiltrated, thereby further improving the cycle life of the battery.

[0189] [Positive electrode]

[0190] According to some embodiments of the present application, as described above, the positive electrode sheet includes a current collector and a positive electrode film layer located on at least one side of the current collector. The positive electrode film layer includes a positive electrode active material. The structure of the main area and the edge area of ​​the positive electrode film layer of the present application is as described above, and the biggest difference between the components included in the main area and the edge area is the porous material, and the types of other components can be the same or different.

[0191] According to some embodiments of the present application, when the positive electrode plate is applied to a lithium-ion battery, the positive electrode active material includes but is not limited to one or a combination of two or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium phosphate containing an olivine structure; wherein the structural formula of the lithium phosphate containing an olivine structure is: LiFe 1-x-y Mn x M yPO4, 0≤x≤1, 0≤y<1, 0≤x+y≤1, M includes one or a combination of two or more transition metal elements or non-transition metal elements other than Fe and Mn, and M further includes any one or more of Cr, Mg, Ti, Al, Zn, W, Nb, and Zr.

[0192] The present application specifically includes but is not limited to LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM111), 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 Any one or more of O2, LiFePO4 (LFP) and LiMnPO4.

[0193] According to some embodiments of the present application, when the positive electrode plate is used in a sodium ion battery, the positive electrode active material includes but is not limited to at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. Among them, in the sodium transition metal oxide, the transition metal can be any one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. The sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1. Polyanionic compounds include sodium vanadium trifluorophosphate (Na3V2(PO4)2F3), sodium vanadium fluorophosphate (NaVPO4F), sodium vanadium phosphate (Na3V2(PO4)3), Na4Fe3(PO4)2P2O7, NaFePO4, and any one or more thereof. Prussian blue compounds are Na x M1M2(CN)6, wherein M1 and M2 are one or more of Fe, Mn, Co, Ni, Cu, Zn, Cr, Ti, V, Zr, and Ce, and 0<x≤2.

[0194] According to some embodiments of the present application, the positive electrode film layer also includes a conductive agent, a binder, etc. The conductive agent includes but is not limited to any one or more of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene and carbon nanofibers. The binder includes but is not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc. The positive electrode current collector in the present application is as described above, and the present application is not repeated here.

[0195] The positive electrode current collector of the present application may be a metal foil or a composite current collector, wherein the metal foil may be an aluminum foil, and 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 such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0196] The method for forming the positive electrode film layer of the present application includes mixing the above-mentioned raw materials with a solvent (such as nitrogen methyl pyrrolidone) in a certain mass ratio to form a positive electrode slurry, and evenly coating the positive electrode slurry on both sides of the current collector; controlling a certain single-sided coating weight; after drying, using a cold press to compact to a certain compaction density, thereby obtaining a positive electrode sheet containing a positive electrode film layer.

[0197] [Negative electrode]

[0198] The negative electrode sheet of the present application includes a current collector and a negative electrode film layer located on one side surface or both sides surface of the current collector. Generally speaking, the negative electrode film layer is located on both sides surface of the current collector, and the formation method includes coating or deposition. The present application will take both sides as an example in the following.

[0199] The present application discloses in some embodiments that the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes one or more of a carbonaceous material, a silicon-based material, a silicon-carbon composite material, a tin-based material and its alloy material. The carbonaceous material in the present application includes one or more combinations of artificial graphite, natural graphite, soft carbon and hard carbon. Among them, artificial graphite, natural graphite, soft carbon, hard carbon, etc. include materials of any form conventional in the art, and include any conventional manufacturers and models in the art. The silicon-based material in the present application includes one or two of silicon-oxygen materials or silicon-carbon materials, or silicon-carbon composites. The tin-based and alloy materials in the present application include but are not limited to Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, etc. And the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for lithium-ion batteries or sodium-ion batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0200] The present application discloses in some embodiments that the conductive agent comprises one or more of a point-shaped conductive agent, a linear conductive agent, and a planar conductive agent, wherein the point-shaped conductive agent comprises one or more of conductive carbon black (Super P or Super S), acetylene black, conductive graphite (KS-6 or KS-15 or SFG-6 or SFG-15), and Ketjen black, the linear conductive agent comprises one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers, and the planar conductive agent comprises but is not limited to graphene.

[0201] The present application discloses in some embodiments that the negative electrode film layer includes a binder and a dispersant, etc. The binder includes but is not limited to polyvinyl alcohol, polyethylene glycol, sodium carboxymethyl cellulose, polyethylene oxide, polyacrylic acid, polyacrylamide, sodium alginate, styrene-butadiene rubber (SBR), etc. The dispersant also includes any conventional type in the art, such as cellulose and its salts, specifically including but not limited to methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, etc.

[0202] The negative electrode current collector of the present application may be a metal foil or a composite current collector, wherein the metal foil may be a copper foil, and 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 such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and the like.

[0203] The method for forming the negative electrode film layer of the present application includes mixing the above-mentioned raw materials with a solvent (such as deionized water) in a certain mass ratio to form a negative electrode slurry, defoaming the negative electrode slurry, and then evenly coating the negative electrode slurry on both sides of the negative electrode collector; controlling the single-sided coating weight; drying, and compacting to a certain compaction density using a cold press to obtain a negative electrode sheet containing a negative electrode film layer.

[0204] [Isolator]

[0205] Some embodiments of the present application disclose an isolating element. The present application has no particular limitation on the type of isolating element, and any known porous isolating element with good chemical stability and mechanical stability can be selected.

[0206] In some embodiments, the isolating element includes a base material layer and a coating disposed on the surface of the base material layer; the base material of the base material layer includes one or more of polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide and polyamide; the coating includes an inorganic coating and / or an organic coating. The base material layer has a good permeability to metal ions, which is conducive to the migration of metal ions; the surface of the base material layer is provided with a coating, and the coating can further improve the mechanical properties of the isolating membrane. Further, the inorganic coating includes a ceramic coating, and the ceramic particles in the ceramic coating include one or more of SiO2, Al2O3, AlOOH, CaO, TiO2, MgO, ZnO, ZrO2, Mg(OH)2 and BaSO4. The ceramic coating of the present application plays an insulating role, reducing the probability of short circuit caused by piercing the isolating element. That is, the present application uses an isolating element containing a ceramic coating, which first reduces the probability of short circuit. Even if a short circuit occurs, the current collector designed by the present application can improve safety by cutting off the short circuit in a short time.

[0207] In some embodiments, the organic coating includes an organic polymer coating, and the polymer material of the organic polymer coating includes one or more of polyethylene (PE), polypropylene (PP), polyphenylene terephthalamide (PPTA), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyimide (PI) and polyamide (PA). The polymer coating can be made of the same or different materials as the base material layer, and the thickness of the polymer coating and the base material layer can be different. Further, the thickness of the polymer coating is less than the thickness of the base material layer.

[0208] In other embodiments, the material of the spacer can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The spacer can be a single-layer film or a multi-layer composite film, without particular limitation. When the spacer is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0209] At the same time, as described above for battery cells, Figure 8 Schematically, the above-mentioned separator 3 includes a coating 31 arranged toward the above-mentioned positive electrode film layer 22; the coating 31 includes a second main area 31a and an edge area 31b of the coating, and the orthographic projection of the edge area 22b of the positive electrode film layer on the above-mentioned coating 31 at least partially overlaps with the edge area 31b of the coating; the edge area 31b of the coating includes a porous material. The present application describes in subsequent specific embodiments that the orthographic projection of the edge area 22b of the positive electrode film layer on the above-mentioned coating 31 completely overlaps with the edge area 31b of the coating, and in order for the separator to play a good role in isolating the positive and negative electrodes, the orthographic projection area of ​​the edge area 31b of the coating on the coating 31 is larger than the orthographic projection area of ​​the edge area 22b of the positive electrode film layer on the above-mentioned coating 31. The specific size of the orthographic projection area of ​​the edge area 31b of the coating on the coating 31 needs to be described according to the actual battery design, and the present application does not limit it.

[0210] [Electrolytes]

[0211] In some embodiments of the present application, an electrolyte is disclosed. The electrolyte of the present application may be in a liquid state, a solid state, or a gel state. Among them, the solid state is a solid electrolyte, the liquid state is a liquid electrolyte, and the gel state is a gel electrolyte. The lithium-ion battery of the present application uses a liquid electrolyte, that is, an electrolyte. The electrolyte contains an electrolyte salt and an organic solvent. Among them, the types of electrolyte salts include any conventional types in the art, for example, including but not limited to inorganic metal salts, such as RClO4, RAsF6, RPF6, RBF4, RSbF6, RSO3F, RN(FSO2)2, etc.; fluorine-containing organic metal salts, such as RCF3SO3, RN(FSO2)(CF3SO2), RN(CF3SO2)2, RN(C2F5SO2)2, cyclic 1,3-hexafluoropropane disulfonyl imide lithium, cyclic 1,2-tetrafluoroethane disulfonyl imide lithium, RN(CF3SO2)(C4F9S O2), RC(CF3SO2)3, RPF4(CF3)2, RPF4(C2F5)2, RPF4(CF3SO2)2, RPF4(C2F5SO2)2, RBF2(CF3)2, RBF2(C2F5)2, RBF2(CF3SO2)2, RBF2(C2F5SO2)2, etc.; and metal salts containing dicarboxylic acid complexes, such as lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium tris(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, etc. The metal and R here contain lithium ions or sodium ions.

[0212] According to some embodiments of the present application, the concentration of the electrolyte salt in the electrolyte is 0.1mol / L to 4mol / L. The present application discloses in these embodiments that the concentration of the electrolyte salt is 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1mol / L, 1.2mol / L, 1.5mol / L, 1.8mol / L, 2mol / L, 2.2mol / L, 2.5mol / L, 2.8mol / L, 3mol / L, 3.2mol / L, 3.5mol / L, 3.8mol / L, 4mol / L, or any one of the values ​​satisfying the above range.

[0213] As described above, the organic solvent includes any one or more of carboxylic acid ester compounds, carbonate compounds, and ether compounds. Among them, the carboxylic acid ester compounds include one or more of ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), propyl acetate (PA), methyl propionate (MP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL); the carbonate compounds include one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), and fluoroethylene carbonate (FEC). The ether compounds include at least one of tetrahydrofuran, dimethyltetrahydrofuran, tetrahydropyran, dimethyltetrahydropyran, 1,2-dimethoxyethane, dipropylene glycol dimethyl ether, or dimethyl phthalate. The organic solvent of the present application further comprises one or two of nitrile solvents and sulfone solvents, wherein the nitrile solvent comprises one or more of acetonitrile (AN), glutaronitrile (GLN) and adiponitrile (ADN). The sulfone solvent comprises at least one or a combination of two of sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0214] According to some embodiments of the present application, the electrolyte further comprises a film-forming stabilizer, which comprises a positive electrode film-forming stabilizer and a negative electrode film-forming stabilizer, wherein the positive electrode film-forming stabilizer comprises carbonate additives and / or sulfate additives, and the carbonate additives include one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinyl ethylene carbonate (VEC) and dioctyl carbonate (CC). Sulfate additives include cyclic sulfonate additives and / or alkyl sulfate additives; further, cyclic sulfonate additives include one or more of 1,3-propane sultone (PS), propylene sultone (PES), and 3-fluoro-1,3-propane sultone (FPS); alkyl sulfate additives include one or more of vinyl sulfate (DTD), diethyl sulfate (DES) and dimethyl sulfate (DMS). The negative electrode film-forming stabilizer includes one or more of boron lithium salt or sodium salt, phosphorus-containing lithium salt or sodium salt, and sulfur-containing lithium salt or sodium salt; boron-containing lithium salt or sodium salt includes one or more of lithium or sodium tetrafluoroborate (LiBF4, NaBF4), lithium or sodium bisoxalate borate (LiBOB, NaBOB) and lithium or sodium bisfluorooxalate borate (LiDFOB, NaDFOB); phosphorus-containing lithium salt or sodium salt includes one or more of lithium or sodium difluorophosphate (LiPO2F2, NaPO2F2), lithium or sodium fluorophosphate (Li2PO3F, Na2PO3F) and lithium or sodium phosphate (Li3PO4, Na3PO4). Sulfur-containing lithium salt or sodium salt includes one or more of lithium or sodium fluorosulfonate (LiFSO3, NaFSO3), lithium or sodium sulfate (Li2SO4, Na2SO4), and lithium or sodium aminosulfonate (LiSO3NH2, NaSO3NH2).

[0215] In some embodiments, the above-mentioned electrolyte also includes an ionic liquid additive, the cation of which includes any one or more of nitrogen-containing onium ions and phosphonium-containing onium ions, and the anion of which includes any one or more of halogen ions, phosphate ions, borate ions, and sulfonyl imide anions.

[0216] In this application, the electrolyte is the carrier of ion transmission in the battery, and plays the role of conducting ions between the positive and negative electrodes of the battery. The type of electrolyte affects the safety of the battery. Ionic liquid additives refer to salts that are added to the electrolyte in a relatively small amount, are completely composed of cations and anions, and are liquid at room temperature or near room temperature, where room temperature refers to 25°C ± 5°C. Ionic liquid additives themselves have high thermal stability and low volatility. At the same time, the ionic liquid additives can also improve the stability of the negative electrode active material by forming a solid electrolyte interface film (SEI) and improving the stability of the film, thereby improving the safety of the battery.

[0217] In some embodiments, the cation of the ionic liquid additive comprises 1-butyl-3-methylimidazolium ([Bmin] + )、1-benzyl-3-methylimidazolium ([Bzmin] + ), 3-methyl-1-ethoxycarbonylmethylimidazolium ([Etmim] + )、1-alkyl-3-methylimidazolium ([Cnmim] + ), 1-[(trimethylsilyl)methyl]benzotriazolium ([SiMBIM] + )、N-alkyl-N-methylpiperidinium ([CnC1pip] + ), 5-azoniaspiro[4.4]nonane ([AS[mn]] + ), trihexyl(tetradecyl)phosphine ion ([Tf2N] + ), tetrabutylphosphine ion ([Pnnnn] + ), n-butyl-N-methylpyrrolidinium ([Pyr 14 ] + ) can be one or more of tetrabutylphosphine ion or n-butyl-N-methylpyrrolidinium.

[0218] In some embodiments, the anion of the ionic liquid additive comprises a chloride ion ([Cl] - ), bromide ion ([Br] - ), iodide ion ([I] - ), hexafluorophosphate ([PF6] - ), tetrafluoroborate ([BF4] - ), dicyandiamide anion ([N(CN)2] - ), bis(fluorosulfonyl)imide anion ([FSI] - ), bis(trifluoromethylsulfonyl)imide ([TFSI] - ) can be one or more of hexafluorophosphate or bis(fluorosulfonyl)imide anions.

[0219] In some embodiments, the ionic liquid additive includes one or more of tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imide, n-butyl-N-methylpyrrolidine hexafluorophosphate, n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imide, 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-benzyl-3-methylimidazolium bis(fluorosulfonyl)imide, and can be selected from tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imide, n-butyl-N-methylpyrrolidine hexafluorophosphate, and n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imide.

[0220] The battery cell of the present application will be described in detail below in conjunction with specific embodiments.

[0221] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0222] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0223] Conventional techniques of inorganic chemistry within the art can be used in this application. In the following examples, efforts are made to ensure the accuracy of the numbers used (including amounts, temperatures, reaction times, etc.), but some experimental errors and deviations should be considered. The temperatures (in degrees Celsius) used in the following examples are expressed in ° C, and the pressure is atmospheric pressure or near atmospheric pressure. All pharmaceutical reagents are purchased at AR grade, and all reactions are carried out under argon protection. Unless otherwise noted, all reagents are obtained from commercial channels.

[0224] Experimental materials:

[0225] The positive electrode active material, negative electrode active material, porous filler, etc. are all commercially available.

[0226] Among them, the performance parameters of the porous filler are shown in Table 1:

[0227] Table 1 Performance parameters of porous fillers

[0228] Serial number Average pore size Specific surface area Dv50 1-1(montmorillonite) 75nm <![CDATA[50m 2 / g]]> 20μm 1-2(diatomaceous earth) 102nm <![CDATA[43m 2 / g]]> 45μm 1-3(Vermiculite) 54nm <![CDATA[78m 2 / g]]> 30μm

[0229] Preparation Example 1-1

[0230] A method for preparing a positive electrode sheet is provided, wherein the structure of the positive electrode sheet is as follows Fig. 9A Schematic diagram, and the content of porous material in the edge area is evenly distributed; the preparation process is as follows:

[0231] S1. Provide the first positive electrode slurry: add the lithium-rich positive electrode material 0.4Li2MnO3·0.6LiNi 0.5Mn 0.5 O2, conductive agent SP, and binder PVDF (polyvinylidene fluoride) are mixed in a weight ratio of 94:4:2, and a solvent nitrogen methyl pyrrolidone is added, and the mixture is stirred and mixed to obtain a first positive electrode slurry, which is used to prepare a first main positive electrode film layer;

[0232] S2. Provide the second positive electrode slurry: 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.5 O2, conductive agent SP, binder PVDF (polyvinylidene fluoride), montmorillonite (1-1 in Table 1) are mixed in a weight ratio of 93.5:4:2:0.5, and a solvent of nitrogen methyl pyrrolidone is added, and the mixture is stirred and mixed to obtain a second positive electrode slurry, which is used to prepare an edge positive electrode film layer;

[0233] S3, coating the first positive electrode slurry on both sides of the positive electrode current collector moving along the first direction to form a first main positive electrode film layer, and coating the second positive electrode slurry on the same side of the positive electrode current collector and on both sides of the first main positive electrode film layer to form edge positive electrode film layers; the average coating thickness of the first main positive electrode film layer is h1, and the average coating thickness of the edge positive electrode film layer is h2; h1 / h2=1.1;

[0234] The coating width of the first main positive electrode film layer in the second direction is T2, and the coating width of the edge positive electrode film layers on both sides of the first main positive electrode film layer in the second direction is T1, T1:T2=2:20, that is, the coating width T1 of the edge positive electrode film layer in the second direction is 10% of the coating width T2 of the first main positive electrode film layer in the second direction.

[0235] Preparation Example 1-2

[0236] A method for preparing a positive electrode sheet is provided, which differs from Preparation Example 1-1 in that:

[0237] S2. Provide the second positive electrode slurry: 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.5 O2, conductive agent SP, binder PVDF (polyvinylidene fluoride), and vermiculite (1-3 in Table 1) were mixed in a weight ratio of 93.9:4:2:0.1; other aspects remained the same as Preparation Example 1-1.

[0238] Preparation Example 1-3

[0239] A method for preparing a positive electrode sheet is provided, which differs from Preparation Example 1-1 in that:

[0240] S2. Provide the second positive electrode slurry: 0.4Li2MnO3·0.6LiNi 0.5 Mn0.5 O2, conductive agent SP, binder PVDF (polyvinylidene fluoride), and diatomaceous earth (1-2 in Table 1) were mixed in a weight ratio of 93:4:2:1; other aspects remained the same as Preparation Example 1-1.

[0241] Comparative Preparation Example 1

[0242] A method for preparing a positive electrode sheet is provided, and the difference between the method and Preparation Example 1-1 is that the second positive electrode slurry does not contain a porous material, and the composition of the second positive electrode slurry is the same as that of the first positive electrode slurry. Other aspects are the same as Preparation Example 1-1.

[0243] Comparative Preparation Example 2

[0244] A method for preparing a positive electrode sheet is provided, wherein the structure of the positive electrode sheet is as follows Figure 6 As shown in FIG. 1 , no difference in coating thickness is set at the edge of the positive electrode film layer, and no porous filler is added, and other aspects remain the same as those of Preparation Example 1-1.

[0245] Preparation Example 2-1

[0246] A method for preparing a positive electrode sheet is provided, which differs from Preparation Example 1-1 in that:

[0247] S3, the ratio between the average coating thickness h1 of the first main positive electrode film layer and the average coating thickness h2 of the edge positive electrode film layer: h1 / h2=1.01;

[0248] The ratio of the coating width T1 of the edge positive electrode film layer on both sides of the first main positive electrode film layer in the second direction to the coating width T2 of the first main positive electrode film layer in the second direction is: T1:T2=1:20, that is, the coating width T1 of the edge positive electrode film layer in the second direction is 5% of the coating width T2 of the first main positive electrode film layer in the second direction. Other aspects remain the same as Preparation Example 1-1.

[0249] Preparation Example 2-2

[0250] A method for preparing a positive electrode sheet is provided, which differs from Preparation Example 1-1 in that:

[0251] S3, the ratio between the average coating thickness h1 of the first main positive electrode film layer and the average coating thickness h2 of the edge positive electrode film layer: h1 / h2=1.15;

[0252] The ratio of the coating width T1 of the edge positive electrode film layer on both sides of the first main positive electrode film layer in the second direction to the coating width T2 of the first main positive electrode film layer in the second direction is: T1:T2=3:20, that is, the coating width T1 of the edge positive electrode film layer in the second direction is 15% of the coating width T2 of the first main positive electrode film layer in the second direction. Other aspects remain the same as Preparation Example 1-1.

[0253] Preparation Example 2-3

[0254] A method for preparing a positive electrode sheet is provided, which differs from Preparation Example 1-1 in that:

[0255] S3, the ratio between the average coating thickness h1 of the first main positive electrode film layer and the average coating thickness h2 of the edge positive electrode film layer: h1 / h2=1.1;

[0256] The ratio between the coating width T1 of the edge positive electrode film layer on both sides of the first main positive electrode film layer in the second direction and the coating width T2 of the first main positive electrode film layer in the second direction is: T1:T2=4:20, that is, the coating width T1 of the edge positive electrode film layer in the second direction is 20% of the coating width T2 of the first main positive electrode film layer in the second direction. Other aspects remain the same as Preparation Example 1-1.

[0257] Preparation Example 3-1

[0258] A method for preparing a positive electrode sheet is provided, wherein the structure of the positive electrode sheet is as follows Fig.9D Schematic diagram, and the content gradient distribution of the porous material in the edge area; the preparation process is as follows:

[0259] S1. Provide the first positive electrode slurry: Li-rich positive electrode material 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.5 O2, conductive agent SP, and binder PVDF (polyvinylidene fluoride) are mixed in a weight ratio of 94:4:2, and a solvent nitrogen methyl pyrrolidone is added, and the mixture is stirred and mixed to obtain a first positive electrode slurry, which is used to prepare a first main positive electrode film layer;

[0260] S2, providing a second positive electrode slurry: the second positive electrode slurry includes a second A-sub positive electrode slurry and a second B-sub positive electrode slurry, the second A-sub positive electrode slurry includes 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.5 O2, conductive agent SP, binder PVDF (polyvinylidene fluoride), montmorillonite (1-1 in Table 1) are mixed in a weight ratio of 93.2:4:2:0.8. The second B-sub positive electrode slurry includes 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.5O2, conductive agent SP, binder PVDF (polyvinylidene fluoride), and montmorillonite (1-1 in Table 1) were mixed in a weight ratio of 93.8:4:2:0.2;

[0261] S3, coating the first positive electrode slurry on both sides of the positive electrode current collector moving along the first direction to form a first main positive electrode film layer, coating the second A sub-positive electrode slurry on the same side of the positive electrode current collector and on both sides of the first main positive electrode film layer to form a first sub-edge positive electrode film layer, and coating the second B sub-positive electrode slurry to form a second sub-edge positive electrode film layer, wherein the ratio between the coating width t11 of the first sub-edge positive electrode film layer in the second direction and the coating width t12 of the second sub-edge positive electrode film layer in the second direction is: t11:t12=1:1;

[0262] The coating width of the first main positive electrode film layer in the second direction is T2, and the coating width of the edge positive electrode film layers on both sides of the first main positive electrode film layer in the second direction is T1, T1:T2=2:20, that is, the coating width T1 of the edge positive electrode film layer in the second direction is 10% of the coating width T2 of the first main positive electrode film layer in the second direction;

[0263] At the same time, the average coating thickness of the first main positive electrode film layer is h1, and the average coating thickness of the edge positive electrode film layer is h2; h1 / h2=1.1. Other aspects are the same as those of Preparation Example 1-1.

[0264] Preparation Example 3-2

[0265] A method for preparing a positive electrode sheet is provided, wherein the structure of the positive electrode sheet is as follows Fig.9D Schematic diagram, and the content gradient distribution of the porous material in the edge area; the difference between this preparation example and preparation example 3-1 is that: the second positive electrode slurry includes a second A-sub positive electrode slurry and a second B-sub positive electrode slurry, and the second A-sub positive electrode slurry includes 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.5 O2, conductive agent SP, binder PVDF (polyvinylidene fluoride), montmorillonite (1-1 in Table 1) are mixed in a weight ratio of 93.8:4:2:0.2. The second B-sub positive electrode slurry includes 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.5 O2, conductive agent SP, binder PVDF (polyvinylidene fluoride), and montmorillonite (1-1 in Table 1) were mixed in a weight ratio of 93.2:4:2:0.8; other aspects remained the same as Preparation Example 3-1.

[0266] The parameters of each positive electrode are listed in Table 2.

[0267] Table 2-1 Parameter list of positive electrode

[0268]

[0269] Table 2-2 Parameter list of positive electrode

[0270]

[0271] Example 1-1

[0272] A method for preparing a battery cell is provided, wherein the structure diagram of the pole piece of the battery cell is as follows Fig.11 Hint.

[0273] The preparation method of the battery cell includes the following preparation process:

[0274] A positive electrode sheet prepared in Preparation Example 1-1 is provided.

[0275] Preparation of negative electrode sheet:

[0276] Artificial graphite, conductive agent SP, stabilizer carboxymethyl cellulose and binder SBR are dispersed in deionized water in a mass ratio of 95:1.0:1.5:2.5 to form a negative electrode slurry, and the negative electrode slurry is evenly coated on the surface of the copper foil. The coating edge of the negative electrode film layer is also provided with a thinning area, and the structure is as follows: Fig.10 As shown, a nine-section oven with temperature settings of 100°C / 100°C / 95°C / 85°C / 85°C / 80°C / 80°C / 80°C / 60°C is used for drying, and then a cold press is used for compacting.

[0277] Isolators available:

[0278] A porous polyethylene (PE) film with a thickness of 13 μm was used as the separator.

[0279] Provide electrolyte:

[0280] In an argon atmosphere glove box with a water content of <10ppm, EC (ethylene carbonate), PC (polycarbonate), and DMC (dimethyl carbonate) are mixed in a weight ratio of EC:PC:DMC=3:3:3, and then LiPF6, VC, DTD and PS are added and stirred evenly to obtain an electrolyte, wherein the concentration of LiPF6 in the lithium-ion battery electrolyte is 1 mol / L, and the mass percentages of VC, DTD, and PS are 3%, 1%, and 1%, respectively, to obtain an electrolyte.

[0281] Assembling battery cells:

[0282] The positive electrode sheet, separator, and negative electrode sheet are wound in sequence. Figure 5As shown in the figure, the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the corresponding assembly forms a wound bare cell; the wound bare cell is placed in an outer packaging shell, and the electrolyte is injected after drying, and the battery cell is obtained through vacuum packaging, standing, forming, shaping and other processes.

[0283] Example 1-2

[0284] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Preparation Example 1-2, and other aspects are the same as those in Example 1-1.

[0285] Examples 1-3

[0286] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Preparation Example 1-3, and other aspects are the same as those in Example 1-1.

[0287] Comparative Example 1

[0288] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Comparative Preparation Example 1, and other aspects are the same as those in Example 1-1.

[0289] Comparative Example 2

[0290] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Comparative Preparation Example 2, and other aspects are the same as those in Example 1-1.

[0291] Example 2-1

[0292] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Preparation Example 2-1, and other aspects are the same as those in Example 1-1.

[0293] Example 2-2

[0294] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Preparation Example 2-2, and other aspects are the same as those in Example 1-1.

[0295] Example 2-3

[0296] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Preparation Example 2-3, and other aspects are the same as those in Example 1-1.

[0297] Example 3-1

[0298] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Preparation Example 3-1, and other aspects are the same as those in Example 1-1.

[0299] Example 3-2

[0300] A method for preparing a battery cell is provided. The battery cell adopts the positive electrode plate prepared in Preparation Example 3-2, and other aspects are the same as those in Example 1-1.

[0301] Example 4

[0302] A method for preparing a battery cell is provided, wherein the separator of the battery cell comprises: a porous polyethylene (PE) film with a thickness of 13 μm is used as a base film, an organic polymer coating (PE) is formed on both side surfaces of the base film, and the edge area of ​​the organic polymer coating contains a porous material with a mass percentage of 0.5% (1-1 in Table 1); the orthographic projection of the edge area of ​​the positive electrode film layer on the above-mentioned coating completely overlaps with the edge area of ​​the coating, and other aspects remain the same as Example 1-1.

[0303] Example 5

[0304] A method for preparing a battery cell is provided, in which the edge area of ​​the negative electrode plate of the battery cell is not thinned, that is, the coating thickness of the main area and the edge area of ​​the negative electrode film layer is the same, and other aspects remain the same as Example 1-1.

[0305] The performance tests of the batteries prepared in the above embodiments and comparative examples of the present application are as follows:

[0306] (1) Surface density of positive electrode film:

[0307] In the process of preparing the positive electrode film layer, the surface density of the edge area and the main area of ​​the positive electrode film layer can be obtained according to the calculation formula of the surface density: surface density = single-sided film layer weight / single-sided film layer area.

[0308] For a battery cell, at 25°C, the battery is fully charged (charged to 4.4V at a constant current of 1 / 3C), the battery is disassembled to obtain the positive electrode plate, the positive electrode current collector and the positive electrode film layer are cut by a cryo-focused ion beam to obtain the positive electrode film layer, and the cryo-focused ion beam (FIB) is further used to perform fine slicing of the positive electrode film layer at different width positions (second direction) to obtain the surface density of the edge area and the main area of ​​the positive electrode film layer, the weight and area of ​​each different area are tested respectively, and then the surface density is calculated using the above-mentioned surface density calculation formula.

[0309] (2) CB value of the battery:

[0310] The CB value of the battery is the Cell Balance value, which is calculated as follows:

[0311]

[0312] Among them, the specific capacity of the positive / negative electrode active materials needs to be completed through the power-off test. The test process is as follows:

[0313] (2.1) Making button batteries:

[0314] a. Solution preparation and stirring: Take a clean container and add nitrogen methyl pyrrolidone, wherein 170g of nitrogen methyl pyrrolidone is prepared for the positive electrode slurry; 150g of nitrogen methyl pyrrolidone is prepared for the negative electrode slurry; the container containing the weighed nitrogen methyl pyrrolidone solvent is placed in a fast stirring fixed frame, and the speed is adjusted to 600rpm for stirring for 1h;

[0315] b. Adding additives and stirring: Weigh 6g of PVDF and 6g of SP as the positive electrode solvent; weigh 9g of PVDF and 2.7g of SP as the negative electrode solvent; adjust the speed to 600rpm; first slowly add PVDF to the container and adjust to 2200rpm. After PVDF is completely dissolved (15-20min), reduce the speed to 600rpm and add SP. Adjust the speed to 2200rpm and stir until the slurry is free of particles and silky and bright (40-50min); after the SP and PVDF solutions are stirred into a particle-free state, remove them, weigh them, and put them into the degassing machine (16min), cover the degassing machine, set the program, start the degassing machine until it ends, and the positive and negative solutions are prepared respectively. They are sealed and stored in a drying room for subsequent use;

[0316] c. Add the main powder and stir: weigh 6.0g of positive electrode solution, then add 3.20g of positive electrode active material (0.4Li2MnO3·0.6LiNi 0.5 Mn 0.5 O2), weigh 4.92g of negative electrode solution, add 4.58g of negative electrode active material (artificial graphite), cover the container lid, put it into the mixer together with the clamp, and set the stirring process to 900rpm for pre-stirring for 60s; 2200rpm for stirring for 8-13min;

[0317] d. Coating and drying: Spray ethanol evenly on a clean and flat glass plate, paste a wrinkle-free current collector Al / Cu foil on the surface, place the glass plate with the current collector on the automatic coating machine, clamp it, write the order number and name with a Mark pen on the blank space at the top, spread the slurry evenly on the front of the current collector, place the scraper on the front of the slurry, turn on the coating machine switch to let the scraper scrape at a uniform speed of 3cm / s, ensure that there are no bubbles, the surface is smooth, and it becomes a mirror surface; let the membrane air dry naturally for 1 to 2 minutes, then put the coated membrane together with the glass plate into a 100℃ blast drying oven, and control the drying time to 2 hours;

[0318] e. Pole cold pressing: compaction density controls the positive electrode film layer to 2.1g / cm 3 , the negative electrode film is 1.5g / cm 3 ;

[0319] f. Punching, weighing and baking: Punch the current collector upwards, apply force at a uniform speed, quickly press down the pressure rod, punch into small discs with a diameter of 14 mm, release the pressure rod, change the position of the membrane and continue punching. Punch at least 6 pole pieces for each sample, then put the pole piece into a dust-free paper bag with tweezers, and finally clean the punching machine with dust-free paper dipped in alcohol; put a piece of dust-free paper in the center of the weighing table, use tweezers to gently clamp the pole piece and put it on the weighing table for weighing, and put the weighed pole piece into a vacuum drying oven;

[0320] g. Button production: Take out the vacuum-baked electrode, put it in a PE bag and put it into the transition compartment of the glove box. Put the prepared positive and negative electrode shells, foam nickel, isolation film, dust-free paper, and tweezers into the transition compartment of the glove box. In the glove box, lay the negative electrode shell flat on a piece of dust-free paper, put a nickel mesh in the negative electrode shell with the convex side facing up, brush the surface oxide film of the prepared lithium sheet with a brush, and then place it on the nickel mesh with the brushed side facing up; inject electrolyte into the positive and negative electrodes respectively, and add 5 to 7 drops of electrolyte with a 2.5 ml medical syringe. Drop electrolyte and then place the separator on the lithium sheet, ensuring that it is placed concentrically with the negative electrode shell, nickel foam, and lithium sheet. Place the electrode in the middle of the separator, single-sided electrode, with the active material facing down, and finally cover the positive electrode shell steadily; button battery sealing: The negative electrode of the battery is on top, placed in the groove of the sealing machine, with a piece of dust-free paper on top, and the button battery is removed from the sealing machine with insulated tweezers, and the button battery is placed in the corresponding dust-free paper bag, removed from the glove box, and placed in a constant temperature room to rest, and the negative electrode is left to rest for 5 hours. The production method of the positive button battery is the same as above.

[0321] (2.2) Capacity test:

[0322] Place the button on the test capacity channel to confirm the positive and negative charge and discharge process:

[0323] Positive electrode charging and discharging process:

[0324] Let stand for 3 hours, then charge at a constant current of 0.1C to a cut-off voltage of 4.5V, charge at a constant voltage of 4.5V until the current drops from 0.1C to 0.05A, then discharge at a constant current of 0.1C to 2.5V. The amount of electricity discharged by constant current discharge divided by the weight of the positive electrode active material is the discharge gram capacity;

[0325] Negative electrode charging and discharging process:

[0326] Let it stand for 5 hours, then discharge at a constant current of 0.05C, with a cut-off voltage of 0.005V, let it stand for 30 minutes, then discharge at a constant current of 0.05A to 0V, let it stand for 30 minutes, discharge at a constant current of 0.01A to 0V, let it stand for 5 hours, charge at a current of 0.1C, with a cut-off voltage of 2.5V, the amount of electricity released during the discharge process divided by the weight of the negative electrode active material is the discharge gram capacity of the negative electrode material.

[0327] (3) Expansion rate of the positive electrode film edge area:

[0328] When the battery cell is in the initial state, the thickness of the edge area of ​​the positive electrode film layer is h2 (thickness after cold pressing);

[0329] At 25°C, the battery is fully charged (charged to 4.4V at 1 / 3C constant current), the battery is disassembled to take out the positive electrode plate, and the positive electrode plate sample is finely sliced ​​at different width positions (second direction) of the positive electrode film layer using a cryo-focused ion beam (FIB) (generally, the thickness of the positive electrode film layer edge area at 5 different positions in the width direction is obtained) to obtain the average thickness of the positive electrode film layer edge area, and h2' is obtained. The expansion rate of the positive electrode film layer edge area = (h2'-h2) / h2×100%.

[0330] Table 3-1 Battery performance list

[0331]

[0332]

[0333] Combining the preparation examples and the comparative examples, it can be seen that the present application adds a porous material to the edge area of ​​the positive electrode film layer, so that the edge area of ​​the positive electrode film layer expands in volume, thereby reducing the distance between the edge areas of the adjacent positive electrode film layers. At the same time, since the surface density of the edge area of ​​the positive electrode film layer is less than the surface density of the first main area, the CB value of the battery at the edge position is also increased.

[0334] (4) Test the capacity retention rate of the battery after 500 cycles at 25°C:

[0335] Under a constant temperature environment of 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 to obtain the first cycle discharge capacity (Cd1); this charging and discharging was repeated until the 500th cycle, and the discharge capacity after 500 cycles was recorded as Cdn.

[0336] Capacity retention rate (%) = discharge specific capacity after 500 cycles (Cdn) / first cycle discharge specific capacity (Cd1).

[0337] (5) Determination and analysis of lithium deposition on the surface of the negative electrode after the battery has been cycled 500 times at 25°C:

[0338] After the battery has been cycled 500 times according to the above-mentioned cycle method, the battery is disassembled, and the positive and negative electrode plates are further separated. A scanning electron microscope is used to observe the lithium deposition on the surface of the negative electrode plate, especially the lithium deposition on the surface at the edge area of ​​the negative electrode plate.

[0339] Among them, the judgment criteria are as shown in the following table;

[0340] Table 3-2 Determination level of lithium deposition on the surface of negative electrode

[0341]

[0342] Table 3-3 Battery performance list

[0343]

[0344]

[0345] In combination with the embodiments of the present application, it can be seen that the present application adds porous materials to the edge area of ​​the positive electrode film layer. Compared with the design method of the control example without adding porous materials, the design method provided by the present application is conducive to improving the cycle life of the battery. At the same time, it can also reduce the probability of lithium deposition on the electrode.

[0346] Further combined with Example 1-1, Example 2-1 to Example 2-3, it can be seen that the coating width and coating thickness of the edge area of ​​the positive electrode film layer affect the cycle life of the battery. Generally speaking, within a certain range, the coating width and coating thickness of the edge area of ​​the positive electrode film layer increase, which is beneficial to increase the cycle life of the battery, but also brings the risk of increased probability of lithium plating. The design method provided in the present application is conducive to controlling the above-mentioned probability of lithium plating.

[0347] Combining Example 1-1, Example 3-1 and Example 3-2, it can be seen that the positive electrode active material is coated in different areas on the edge area of ​​the positive electrode film layer so that different areas contain different contents of porous materials. This design method is beneficial to further increase the cycle life of the battery.

[0348] In combination with Example 1-1 and Example 4, it can be seen that the present application chooses to set porous materials on the edge area of ​​the positive electrode film layer and the edge area of ​​the coating of the isolation member at the same time, so as to facilitate the storage of sufficient electrolyte at the edge position of the positive electrode film layer and further improve the cycle life of the battery.

[0349] Combining Example 1-1 and Example 5, it can be seen that although the CB value of the battery can be increased to a certain extent without thinning the negative electrode film layer, the cycle life of the battery is reduced. This may be because the non-thinning method brings side effects to a certain extent.

[0350] In summary, the design method provided in this application is conducive to improving the cycle life of the battery.

[0351] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: It includes a positive electrode sheet, a separator and a negative electrode sheet which are stacked; The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer located on at least one side surface of the positive electrode current collector; The positive electrode film layer includes a first main region and an edge region; The first main body region includes a positive electrode active material; The edge region includes positive electrode active material and porous material; The surface density of the first main region is greater than the surface density of the edge region.

2. The battery cell according to claim 1, characterized in that: The separator includes a coating disposed toward the positive electrode film layer; The coating comprises a second main region and an edge region, The orthographic projection of the edge area of ​​the positive electrode film layer on the coating layer at least partially overlaps with the edge area of ​​the coating layer; The edge region of the coating comprises a porous material.

3. The battery cell according to any one of claims 1 to 2, characterized in that: The average pore size of the porous material is 50nm to 10μm; and / or; The specific surface area of ​​the porous material is 20 m 2 / g~110m 2 / g.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The porous material includes any one or more of montmorillonite, diatomaceous earth and vermiculite.

5. The battery cell according to any one of claims 1 to 4, characterized in that: In the edge area of ​​the positive electrode film layer, the mass percentage content of the porous material is 0.1% to 1.0%.

6. The battery cell according to any one of claims 1 to 5, characterized in that: The edge region of the positive electrode film layer and the first main region extend along the first direction and are arranged in the second direction; The first direction intersects the second direction; Along the second direction, the edge region of the positive electrode film layer includes an A surface and a B surface that are arranged opposite to each other, and the distance between the A surface and the B surface is T1; Along the second direction, the first main body region includes a C surface and a D surface that are oppositely arranged, and a distance between the C surface and the D surface is T2; Satisfies: T1:T2=(1~3):

20.

7. The battery cell according to any one of claims 1 to 6, characterized in that: The edge region of the positive electrode film layer and the first main region extend along the first direction and are arranged in the second direction; The first direction intersects the second direction; Along the second direction, the edge region of the positive electrode film layer includes an A surface and a B surface that are arranged opposite to each other, the B surface is close to the first main body region, and the distance between the A surface and the B surface is T1; The area extending from the B surface to the position of 0.1×T1 is recorded as the first sub-edge area, and the area extending from the A surface to the position of 0.1×T1 is recorded as the second sub-edge area; In the first sub-edge region of the positive electrode film layer, the mass percentage content of the porous material is w1; In the second sub-edge region of the positive electrode film layer, the mass percentage content of the porous material is w2; Satisfies w1 greater than w2.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The edge region of the positive electrode film layer and the first main region extend along the first direction and are arranged in the second direction; The first direction intersects the second direction; Along the second direction, the edge region of the positive electrode film layer includes a first sub-edge positive electrode film layer and a second sub-edge positive electrode film layer; the first sub-edge positive electrode film layer and the second sub-edge positive electrode film layer are located on the same side of the first main body region; Along the second direction, the first sub-edge positive electrode film layer includes a B surface and an M surface, the B surface is close to the first main body region, and the distance between the B surface and the M surface is t11; Along the second direction, the second sub-edge positive electrode film layer includes an A surface and an N surface, and the distance between the A surface and the N surface is t12; satisfying t11:t12=(0.5-1):(0.5-1); In the first sub-edge positive electrode film layer, the mass percentage content w1 of the porous material is 0.5% to 1%; In the second sub-edge positive electrode film layer, the mass percentage content w2 of the porous material is 0.1% to 0.3%.

9. The battery cell according to any one of claims 1 to 8, characterized in that: The surface density A1 of the first main region of the positive electrode film layer is 200 mg / 1540.25 mm 2 ~400mg / 1540.25mm 2 ; and / or; The surface density A2 of the edge area of ​​the positive electrode film layer is 170 mg / 1540.25 mm 2 ~380mg / 1540.25mm 2 .

10. The battery cell according to any one of claims 1 to 9, characterized in that: The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer located on at least one side surface of the negative electrode current collector; The negative electrode film layer includes a third main body region and an edge thinning region; The orthographic projection of the edge thinning area of ​​the negative electrode film layer on the positive electrode film layer at least partially overlaps with the edge area of ​​the positive electrode film layer.

11. A method for preparing a battery monomer according to claim 1, characterized in that: Including the preparation of positive electrode sheet, the process is as follows: Providing a first positive electrode slurry comprising a positive electrode active material; Providing a second positive electrode slurry comprising a positive electrode active material and a porous material; Applying a first positive electrode slurry on at least one side of the positive electrode current collector moving along the first direction to form a first main positive electrode film layer, and applying a second positive electrode slurry to form an edge positive electrode film layer, wherein the edge positive electrode film layer and the first main positive electrode film layer are arranged in the second direction; The first direction intersects the second direction; The coating thickness of the first main positive electrode film layer is greater than the coating thickness of the edge positive electrode film layer.

12. The preparation method according to claim 11, characterized in that: The coating thickness of the first main positive electrode film layer is h1, and the coating thickness of the edge positive electrode film layer is h2; Satisfies: h1 / h2=1.01~1.

15.

13. The preparation method according to any one of claims 11 to 12, characterized in that: The edge positive electrode film layer comprises an E surface arranged in contact with the positive electrode current collector, and an F surface arranged opposite to the E surface; Along the second direction, the F surface is an inclined surface gradually approaching the E surface; The average value of the distance between the E surface and the F surface is the coating thickness h2 of the edge positive electrode film layer.

14. A battery device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 10 or the battery cell prepared by the preparation method according to any one of claims 11 to 13.

15. An electrical device, characterized in that: A battery device comprising the battery device of claim 14.

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