Battery

Abstract

The utility model provides a battery, and relates to the technical field of battery energy, the battery comprises a battery cell, the battery cell comprises a first pole piece, a second pole piece and a diaphragm located between the first pole piece and the second pole piece, the first pole piece, the diaphragm and the second pole piece are wound to form the battery cell, the first pole piece comprises a first current collector and a first active material layer, the first active material layer is arranged on at least one surface of the first current collector, the first active material layer comprises a first coating and a second coating, and the first coating is located between the first current collector and the second coating; the first active material layer comprises a first coating section, a second coating section and a third coating section which are adjacent in sequence along the winding direction, and the thickness of at least one of the first coating section and the third coating section is greater than that of the second coating section. The battery disclosed by the utility model is relatively high in energy density and charge-discharge efficiency.

Description

Technical Field

[0001] The present application relates to the field of battery energy technology, and in particular to a battery. Background Art

[0002] With the rapid development of 5G, people have higher and higher requirements for the battery life and charging speed of electronic products. Therefore, high energy density performance and fast charging performance are one of the main development directions of lithium-ion batteries at present.

[0003] In the related art, a lithium-ion battery mainly includes a battery case and a battery cell. The battery cell and the electrolyte are arranged in the battery case, and the current of the battery cell is conducted out through the pole ear. The battery cell may include a pole piece, and the pole piece may include a metal foil and a coating layer. The mixed slurry is formed on the metal foil through a coating drying process and a roller compaction process. However, when the slurry is coated on the metal foil, it is easy to cause the coating layer at the end of the pole piece to be thinner than the coating layer in the middle of the pole piece, which in turn causes lithium deposition problems at the end of the pole piece, thereby reducing the energy density and charge and discharge efficiency of the battery. Utility Model Content

[0004] Based on this, the present application provides a battery with high energy density and charge and discharge efficiency.

[0005] The embodiment of the present application provides a battery, the battery includes a battery cell, the battery cell includes a first pole piece, a second pole piece and a separator located between the first pole piece and the second pole piece, the first pole piece, the separator and the second pole piece are wound to form the battery cell, the first pole piece includes a first current collector and a first active material layer, the first active material layer is arranged on at least one side of the first current collector, the first active material layer includes a first coating layer and a second coating layer, and the first coating layer is located between the first current collector and the second coating layer;

[0006] The first active material layer includes a first coating segment, a second coating segment and a third coating segment which are adjacent to each other in sequence along the winding direction, and the thickness of at least one of the first coating segment and the third coating segment is greater than the thickness of the second coating segment.

[0007] In a possible implementation, in the battery provided by the present application, the first coating layer includes a first active material, and the first active material includes at least one of pure silicon particles, silicon alloys, silicon-carbon composite materials, and silicon-oxygen composite materials;

[0008] and / or, the second coating layer comprises a second active material, wherein the second active material comprises at least one of pure silicon particles, silicon alloys, silicon-carbon composite materials, and silicon-oxygen composite materials;

[0009] and / or, the first coating layer comprises a first conductive agent, the first conductive agent comprising at least one of superconducting carbon, acetylene black, Ketjen black, conductive carbon black, graphene, carbon dots, carbon nanotubes, carbon nanofibers, and graphite;

[0010] And / or, the second coating layer includes a second conductive agent, and the second conductive agent includes at least one of superconducting carbon, acetylene black, Ketjen black, conductive carbon black, graphene, carbon dots, carbon nanotubes, carbon nanofibers, and graphite.

[0011] In a possible implementation, in the battery provided by the present application, the ratio of the thickness of the first coating layer to the thickness of the second coating layer is greater than or equal to 0.1 and less than or equal to 1.

[0012] In a possible implementation, in the battery provided in the present application, the first current collector includes a first surface and a second surface that are arranged opposite to each other, and both the first surface and the second surface are provided with a first active material layer;

[0013] The thickness of the first coating segment on the first surface is greater than the thickness of the third coating segment on the first surface, and / or the thickness of the first coating segment on the second surface is less than the thickness of the third coating segment on the second surface.

[0014] In a possible implementation, in the battery provided in the present application, the difference in thickness between the first coating section and the second coating section is less than or equal to 7 μm, and the difference in thickness between the third coating section and the second coating section is less than or equal to 4 μm.

[0015] In a possible implementation, in the battery provided in the present application, the first coating section includes a first region and a second region adjacent to each other, the second region is located between the first region and the second coating section, and the thickness of the first region is greater than the thickness of the second region.

[0016] In a possible implementation, in the battery provided by the present application, the difference between the thickness of the first region and the thickness of the second coating section is greater than 0 and less than or equal to 7 μm;

[0017] and / or, a ratio of a thickness of the first region to a thickness of the second coating section is greater than 1 and less than or equal to 1.28;

[0018] and / or, a difference between a thickness of the second region and a thickness of the second coating section is greater than 0 and less than or equal to 6 μm;

[0019] And / or, a ratio of a thickness of the second region to a thickness of the second coating section is greater than 1 and less than or equal to 1.24.

[0020] In a possible implementation, in the battery provided by the present application, at least one end of the second coating along its own length direction covers at least one end of the first coating along its length direction;

[0021] Alternatively, two ends of the second coating along its length direction are flush with two ends of the first coating along its length direction.

[0022] In a possible implementation, in the battery provided in the present application, at least one end of the first coating along the length direction exceeds the end of the second coating along the length direction, and the difference in distance between the end of the first coating and the end of the second coating is less than or equal to 5 mm.

[0023] In a possible implementation, the battery provided by the present application further includes a separator and a second pole piece, the first pole piece, the separator and the second pole piece are sequentially stacked and wound, the second pole piece includes a second current collector and a second active material layer, and the second active material layer is disposed on at least one side of the second current collector;

[0024] The end of the third coating section away from one end of the second coating section exceeds the end of the second active material layer along its own length direction, and the difference in distance between the end of the third coating section and the end of the second active material layer is greater than or equal to 2 mm.

[0025] In a possible implementation, the battery provided in the present application further includes an insulating layer, which is disposed at at least one end of the second active material layer along the length direction, and the projection of the insulating layer on the first electrode sheet covers at least a portion of the third coating segment.

[0026] In a possible implementation, the battery provided by the present application, the first pole piece includes a first single-sided coating section having a first active material layer disposed on a single side, and a first double-sided coating section having a first active material layer disposed on both sides, and the first single-sided coating section and the first double-sided coating section are sequentially connected along the winding direction of the battery cell;

[0027] The battery core has a straight area and an arc area, the arc area is located at two opposite sides of the straight area, and the end of the first double-sided coating section close to the first single-sided coating section is located in the straight area.

[0028] In one possible implementation, in the battery provided in the present application, the end of the first single-sided coated section facing away from the first double-sided coated section is located in a straight area, and the difference in distance between the end of the first single-sided coated section facing away from the first double-sided coated section and the end of the second pole piece is less than or equal to 2 mm.

[0029] In a possible implementation, the battery provided by the present application, the second pole piece includes a second double-sided coating section with a second active material layer on both sides, a second single-sided coating section with a second active material layer on one side, and an empty foil section without a second active material layer, and the second double-sided coating section, the second single-sided coating section and the empty foil section are sequentially connected along the winding direction of the battery cell;

[0030] The second single-sided coated section and the hollow foil section are jointly arranged outside the battery core, and the end of the hollow foil section facing away from the second single-sided coated section is located in the middle of the straight area.

[0031] The battery provided by the present application includes a battery cell, the battery cell includes a first pole piece, the first pole piece includes a first current collector and a first active material layer, the first active material layer includes a first coating and a second coating, and the first active material layer includes a first coating section, a second coating section and a third coating section along the winding direction. By setting the first active material layer as a double-layer coating with different materials, the capacity of the battery cell is increased by the first coating, and the charge and discharge speed of the battery cell is increased by the second coating, and the thickness of the first coating section and / or the thickness of the third coating section is made greater than the thickness of the second coating section to ensure that the first coating section and / or the third coating section have sufficient lithium ion attachment sites, thereby avoiding lithium precipitation at both ends of the first active material layer along its own length direction, thereby improving the energy density of the battery cell. As a result, the energy density and charge and discharge speed of the battery provided by the present application are relatively high.

[0032] In addition to the technical problems solved by the embodiments of the present application described above, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions, other technical problems that can be solved by the battery provided by the present application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 A schematic diagram of the structure of a battery provided in an embodiment of the present application;

[0035] Figure 2 Schematic diagram of the structure of the first pole piece in the battery provided in the embodiment of the present application Figure 1 ;

[0036] Figure 3 for Figure 2 A top view of

[0037] Figure 4 Schematic diagram of the structure of the first pole piece in the battery provided in the embodiment of the present application Figure 2 ;

[0038] Figure 5 Schematic diagram of the structure of the first pole piece in the battery provided in the embodiment of the present application Figure 3 ;

[0039] Figure 6 Schematic diagram of the structure of the first pole piece in the battery provided in the embodiment of the present application Figure 4 ;

[0040] Figure 7 Schematic diagram of the structure of the first pole piece in the battery provided in the embodiment of the present application Figure 5 ;

[0041] Figure 8 Schematic diagram of the structure of the first pole piece in the battery provided in the embodiment of the present application Figure 6 ;

[0042] Fig. 9 A schematic diagram of the structure of the first pole piece and the second pole piece in the battery provided in an embodiment of the present application.

[0043] Description of reference numerals:

[0044] 100-first pole piece; 110-first current collector; 120-first active material layer; 121-first coating layer; 122-second coating layer; 123-first coating section; 1231-first region; 1232-second region; 124-second coating section; 125-third coating section; 130-first single-sided coating section; 140-first double-sided coating section;

[0045] 200 - second pole piece; 210 - second current collector; 220 - second active material layer; 230 - second double-sided coating section; 240 - second single-sided coating section; 250 - empty foil section;

[0046] 300-diaphragm;

[0047] 400-Insulation layer. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiment of the present application will be described in more detail below in conjunction with the drawings in the preferred embodiments of the present application. In the drawings, the same or similar reference numerals throughout represent the same or similar parts or parts with the same or similar functions. The described embodiments are part of the embodiments of the present application, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application. The embodiments of the present application are described in detail below in conjunction with the drawings.

[0049] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0050] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are orientations or positional relationships based on the drawings, and are only for the convenience of describing 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 a limitation on the present application.

[0051] The terms "first", "second", "third" (if any) in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the application described herein can be implemented in an order other than those illustrated or described herein, for example.

[0052] In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or display comprising a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or display.

[0053] In the related art, a lithium-ion battery mainly includes a battery case and a battery cell. The battery cell and the electrolyte are arranged in the battery case, and the current of the battery cell is conducted out through the pole ear. The battery cell may include a pole piece, and the pole piece may include a metal foil and a coating layer. The mixed slurry forms a coating layer on the metal foil through a coating drying process and a roller compaction process. However, when the slurry is coated on the metal foil, it is easy to cause the coating layer at the end of the pole piece to be thinner than the coating layer in the middle of the pole piece, which in turn causes the problem of lithium precipitation at the end of the pole piece. The growth of lithium dendrites will cause the internal resistance of the battery to increase, thereby reducing the energy density and charging and discharging efficiency of the battery.

[0054] In view of the above problems, an embodiment of the present application provides a battery, which forms a first coating layer and a second coating layer of different materials through two coatings, so as to increase the capacity of the battery cell through the first coating layer, and increase the charge and discharge speed of the battery cell through the second coating layer, and make the thickness of the first coating section and / or the third coating section greater than the thickness of the second coating section, so that the thickness of the first active material layer at the end along its own length direction will be greater than the thickness in the middle part, so that the end of the first electrode along its own length direction is not prone to lithium plating problems. Therefore, the battery provided by the embodiment of the present application has high energy density and charge and discharge efficiency.

[0055] The specific implementation of the battery provided in the embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0056] Reference Figures 1 to 5 As shown, the battery provided in the embodiment of the present application includes a battery cell, the battery cell includes a first electrode sheet 100, the first electrode sheet 100 includes a first current collector 110 and a first active material layer 120, the first active material layer 120 is coated on at least one side of the first current collector 110, the first active material layer 120 includes a first coating 121 and a second coating 122 along its thickness, and the first coating 121 and the second coating 122 are made of different materials, and the first coating 121 is located between the first current collector 110 and the second coating 122.

[0057] The first active material layer 120 includes a first coating segment 123 , a second coating segment 124 and a third coating segment 125 which are adjacent to each other in sequence along its length direction. The thickness of at least one of the first coating segment 123 and the third coating segment 125 is greater than the thickness of the second coating segment 124 .

[0058] It can be understood that before the first pole sheet 100 is wound to form a battery cell, its unfolded state is a rectangular sheet structure, the polarity of the first pole sheet 100 is negative, the first current collector 110 can be a copper foil, and the surface of the first current collector 110 can be coated with negative electrode active materials, such as graphite, silicon-doped graphite, silicon and hard carbon.

[0059] In order to alleviate the problem of lithium deposition at the end of the first pole piece 100, the thickness of the first active material layer 120 at both ends along its own length direction should be greater than the thickness of the first active material layer 120 in the middle along its own length direction, that is, the thickness of the first coating section 123 may be greater than the thickness of the second coating section 124, or the thickness of the third coating section 125 may be greater than the thickness of the second coating section 124, or the thickness of the first coating section 123 and the thickness of the third coating section 125 may be greater than the thickness of the second coating section 124. In this way, the two ends of the first active material layer 120 along its own length direction will not be thinner than the middle part of the first active material layer 120 along its own length direction, so that the two ends of the first active material layer 120 along its own length direction can have enough space for lithium ions to be embedded, thereby alleviating the problem of lithium deposition at the end of the first pole piece 100, thereby improving the energy density of the battery.

[0060] Among them, refer to Figure 2 As shown, during coating, the first current collector 110 moves relative to the die along its own length direction, and then the slurry is uniformly coated on the first current collector 110 along the length direction of the first current collector 110 through the die. The first coating section 123 is the front end of the coating direction, and the third coating section 125 is the rear end of the coating direction. Exemplarily, when both sides of the first current collector 110 have the first active material layer 120, the coating directions of the two sides of the first current collector 110 can be opposite, that is, in the first active material layer 120 on the opposite sides of the first current collector 110, the positions of the first coating section 123 and the third coating section 125 relative to the second coating section 124 are opposite.

[0061] When applying the slurry, along the coating direction, a double-layer die head can be used to simultaneously apply the two slurries to the same surface of the first current collector 110, so that a first active material layer 120 composed of a first coating layer 121 and a second coating layer 122 is formed on the surface of the first current collector 110, and the first coating layer 121 and the second coating layer 122 are made of different materials, the first coating layer 121 has a higher energy density, thereby ensuring that the battery has a higher capacity, and the second coating layer 122 can accelerate the embedding of lithium ions, thereby reducing the possibility of lithium deposition in the battery and improving the charge and discharge efficiency of the battery. Such a setting can make the battery have both a higher energy density and a faster charge and discharge speed.

[0062] The battery provided in the embodiment of the present application includes a battery cell, the battery cell includes a first pole piece 100, the first pole piece 100 includes a first current collector 110 and a first active material layer 120, the first active material layer 120 includes a first coating 121 and a second coating 122 along its thickness direction, and the first active material layer 120 includes a first coating section 123, a second coating section 124 and a third coating section 125 along its length direction. By setting the first active material layer 120 as a double-layer coating with different materials, the capacity of the battery cell is increased by the first coating 121, and the charge and discharge speed of the battery cell is increased by the second coating 122, and by making the thickness of the first coating section 123 and / or the thickness of the third coating section 125 greater than the thickness of the second coating section 124, it is ensured that the first coating section 123 and / or the third coating section 125 have sufficient lithium ion attachment sites, thereby avoiding lithium deposition at both ends of the first active material layer 120 along its length direction, thereby improving the energy density of the battery cell. Therefore, the energy density and charge and discharge speed of the battery provided in the embodiment of the present application are relatively high.

[0063] In order to improve the energy density and charge and discharge speed of the battery, in one possible implementation, the first active material of the first coating 121 includes at least one of pure silicon particles, silicon alloys, silicon-carbon composite materials, and silicon-oxygen composite materials, and / or the second active material of the second coating 122 includes at least one of pure silicon, silicon alloys, silicon-carbon composite materials, and silicon-oxygen composite materials.

[0064] Since the material of the first coating 121 and the second coating 122 are made of different types of graphite materials, and the first active material of the first coating 121 and the second active material of the second coating 122 are selected from pure silicon particles, silicon alloys, silicon-carbon composite materials and silicon-oxygen composite materials, or a combination of multiple materials, the first coating 121 can be made of a material with a higher energy density to increase the energy density of the battery, and the second coating 122 can be made of a material with fast charging performance to increase the charging and discharging speed of the battery.

[0065] Since the active material of the first coating 121 can be made of a single material or a composite of multiple materials, in order to improve the energy density of the first coating 121, in one possible implementation, the average gram capacity of the first coating 121 is greater than the average gram capacity of the second coating 122. In this way, the average gram capacity of the first coating 121 is larger and its energy density is relatively high.

[0066] In some embodiments, the ratio of the thickness of the first coating 121 to the thickness of the second coating 122 is greater than or less than 0.1, and less than or equal to 1. In other words, the first coating 121 is thinner and the second coating 122 is thicker, or the first coating 121 and the second coating 122 are of equal thickness.

[0067] It is understandable that the conductive agent can improve the conductivity of electrons, thereby making the battery have good charge and discharge performance. In a possible implementation, the first coating includes a first conductive agent, and the first conductive agent includes one, two or more of superconducting carbon, acetylene black, Ketjen black, conductive carbon black, graphene, carbon dots, carbon nanotubes, carbon nanofibers, and graphite. And / or, the second coating includes a second conductive agent, and the second conductive agent includes one, two or more of superconducting carbon, acetylene black, Ketjen black, conductive carbon black, graphene, carbon dots, carbon nanotubes, carbon nanofibers, and graphite.

[0068] In this way, the energy density of the first coating layer can be improved by adjusting the ratio of various components in the first conductive agent, and the charge and discharge performance of the second coating layer can be improved by adjusting the ratio of various components in the second conductive agent, thereby improving the energy density and charge and discharge efficiency of the first electrode at the same time.

[0069] In some embodiments, the first coating section 123 and the third coating section 125 are both thicker than the second coating section 124, that is, the thickness of the first coating section 123 and the thickness of the third coating section 125 are both thicker than the thickness of the second coating section 124, so as to ensure that the first active material layer 120 is not thin at both ends along its own length direction, so that both ends of the first active material layer 120 along its own length direction have sufficient space for lithium ions to be embedded, thereby avoiding lithium plating at both ends of the first active material layer 120 along its own length direction, thereby improving the energy density of the battery.

[0070] In some embodiments, the first current collector 110 includes a first surface and a second surface disposed opposite to each other, the first surface and the second surface are both provided with a first active material layer 120, the thickness of the first coating section 123 located on the first surface is greater than the thickness of the third coating section 125 located on the first surface, and / or, the thickness of the first coating section 123 located on the second surface is less than the thickness of the third coating section 125 located on the second surface. It should be noted that when the slurry containing the active material is coated on the first surface and the second surface respectively, so that the first surface and the second surface are both provided with the first active material layer, if the coating directions of the first surface and the second surface are just opposite, along the coating direction of the first active material layer, the thickness of the front end of the first active material layer 120 is greater than the thickness of the rear end of the first active material layer 120, so that the thickness of the rear end of the first active material layer 120 is smaller, thereby effectively reducing the volume of the battery cell, thereby improving the energy density of the battery.

[0071] In order to make the thickness of the first coating section 123 greater than the thickness of the third coating section 125, in specific implementation, the thickness difference between the first coating section 123 and the second coating section 124 is less than or equal to 7 μm, and the thickness difference between the third coating section 125 and the second coating section 124 is less than or equal to 4 μm.

[0072] With such a configuration, the thickness of the first coating segment 123 can be greater than that of the third coating segment 125, and the thickness of the first coating segment 123 can be greater than that of the second coating segment 124, and the thickness of the third coating segment 125 can be greater than that of the second coating segment 124, so that the first coating segment 123 and the third coating segment 125 have sufficient attachment sites for lithium ion embedding, thereby reducing the possibility of lithium precipitation in the first coating segment 123 and the third coating segment 125. At the same time, the first coating segment 123 and the third coating segment 125 will not be too thick relative to the second coating segment 124, so as to avoid excessive increase in the volume of the battery cell.

[0073] Reference Figure 4 and Figure 5 As shown, in some embodiments, the first coating segment 123 includes an adjacent first region 1231 and a second region 1232, the second region 1232 is located between the first region 1231 and the second coating segment 124, the thickness of the first region 1231 is greater than the thickness of the second region 1232, wherein the thickness difference between the first region 1231 and the second coating segment 124 is less than or equal to 7 μm, and the thickness difference between the second region 1232 and the second coating segment 124 is less than or equal to 6 μm.

[0074] That is to say, the thickness of the first region 1231 is greater than that of the second region 1232. In this way, the thickness of the end of the first coating section 123 away from the second coating section 124 can be ensured to be larger, so as to ensure the thickness of the front end of the first active material layer 120 along the winding direction, thereby avoiding lithium deposition at the front end of the first active material layer 120 along the winding direction, thereby improving the energy density of the battery.

[0075] Exemplarily, along the winding direction, the first region 1231 may be a region ranging from 1 to 9 mm from the end of the front end of the first active material layer 120, and the second region 1232 may be a region ranging from 9 to 25 mm from the end of the front end of the first active material layer 120. Alternatively, the first region 1231 may be a region ranging from 2 to 8 mm from the end of the front end of the first active material layer 120, and the second region 1232 may be a region ranging from 8 to 30 mm from the end of the front end of the first active material layer 120. Alternatively, the first region 1231 may be a region ranging from 2 to 12 mm from the end of the front end of the first active material layer 120, and the second region 1232 may be a region ranging from 12 to 40 mm from the end of the front end of the first active material layer 120. Specifically, the length of the first region 1231 may refer to Figure 4 and Figure 5 The length of the second region 1232 can refer to L1 in Figure 4 and Figure 5 L2 in.

[0076] In some embodiments, the difference between the thickness of the first region 1231 and the thickness of the second coating segment 124 is greater than 0 and less than or equal to 7 μm. And / or, the ratio of the thickness of the first region 1231 to the thickness of the second coating segment 124 is greater than 1 and less than or equal to 1.28. And / or, the difference between the thickness of the second region 1232 and the thickness of the second coating segment 124 is greater than 0 and less than or equal to 6 μm. And / or, the ratio of the thickness of the second region 1232 to the thickness of the second coating segment 124 is greater than 1 and less than or equal to 1.24. This arrangement ensures the thickness of the first coating segment 123, thereby ensuring that lithium ions have sufficient attachment sites, thereby reducing the probability of lithium precipitation in the first coating segment 123.

[0077] Exemplarily, the difference between the thickness of the first region 1231 and the thickness of the second coating section 124 may be any one of 0.1 μm, 1 μm, 2 μm, 4 μm, 5 μm, 7 μm or any two numerical ranges. And / or, the ratio of the thickness of the first region 1231 to the thickness of the second coating section 124 may be any one of 1.1, 1.2, 1.25, 1.28 or any two numerical ranges. And / or, the difference between the thickness of the second region 1232 and the thickness of the second coating section 124 may be any one of 0.2 μm, 1 μm, 3 μm, 4 μm, 5 μm, 6 μm or any two numerical ranges. And / or, the ratio of the thickness of the second region 1232 to the thickness of the second coating section 124 may be any one of 1.05, 1.1, 1.22, 1.24 or any two numerical ranges.

[0078] Reference Figure 6 and Figure 7 As shown, in some embodiments, at least one end of the second coating 122 along its length direction covers at least one end of the first coating 121 along its length direction. Alternatively, both ends of the second coating 122 along its length direction are flush with both ends of the first coating 121 along its length direction.

[0079] In the above configuration, the first coating layer 121 will not extend beyond the second coating layer 122 , thereby facilitating the stability of the first electrode sheet 100 and controlling the thickness of the first active material layer 120 at both ends along its length direction.

[0080] Reference Figure 8 As shown, in some embodiments, due to limitations of the coating process, at least one end of the first coating 121 along its own length direction exceeds the end of the second coating 122 along its own length direction, and the difference in distance between the end of the first coating 121 and the end of the second coating 122 is less than or equal to 5 mm.

[0081] That is to say, in the above-mentioned setting, the first coating 121 exceeds the second coating 122, and the end of the first coating 121 and the end of the second coating 122 are partially misaligned. In order to ensure the stability of the first electrode 100 and the thickness of the first active material layer 120 at both ends, the misalignment distance between the end of the first coating 121 and the end of the second coating 122 should be set between 0-5㎜. For example, the difference in distance between the end of the first coating 121 and the end of the second coating 122 can be any one of 0.5㎜, 1㎜, 1.2㎜, 2㎜, 5㎜ or within any two numerical ranges.

[0082] Reference Figure 1 and Fig. 9 As shown, in a possible implementation, the battery cell may further include a diaphragm 300 and a second pole piece 200. The first pole piece 100, the diaphragm 300 and the second pole piece 200 are stacked and wound in sequence. The second pole piece 200 includes a second current collector 210 and a second active material layer 220. The second active material layer 220 is arranged on at least one side of the second current collector 210.

[0083] It should be understood that after the first electrode sheet 100, the diaphragm 300 and the second electrode sheet 200 are stacked and wound in sequence to form a battery cell, at the innermost side and the outermost side of the battery cell, the end of the first active material layer 120 should exceed the end of the second active material layer 220 by a certain range. This is because the end of the rear end of the first active material layer 120 along the winding direction is thin, that is, the end edge of the third coating section 125 away from the second coating section 124 is jagged, and the edge of one end of the third coating section 125 away from the second coating section 124 is jagged. The range is relatively thin, and the end of the third coating section 125 exposes part of the first current collector 110. In order to avoid the end of the third coating section 125 that is away from the second coating section 124 from corresponding to the end of the second active material layer 220, in a specific implementation, the end of the third coating section 125 that is away from the second coating section 124 exceeds the end of the second active material layer 220 along its own length direction, and the difference in distance between the end of the third coating section 125 and the end of the second active material layer 220 is greater than or equal to 2mm, thereby improving the safety performance of the battery. Specifically, the difference in distance between the end of the third coating section 125 and the end of the second active material layer 220 can refer to Fig. 9 L3 and L4 in.

[0084] Reference Fig. 9 As shown, in some embodiments, the battery cell may further include an insulating layer 400 , which is disposed at at least one end of the second active material layer 220 along its own length direction, and the projection of the insulating layer 400 on the first pole piece 100 covers at least a portion of the third coating section 125 .

[0085] It should be noted that, at the outermost side of the battery cell, the insulating layer 400 should cover the end of the second active material layer 220 in the range of 0-5 mm, for example, 0.5-3.5 mm. In addition, since the third coating section 125 is the rear end of the first active material layer 120 along the winding direction, the end edge of the third coating section 125 is serrated, and the end of the third coating section 125 exposes part of the first current collector 110. In order to ensure the safety performance of the battery, at least part of the insulating layer 400 should be isolated between the third coating section 125 and the end of the second active material layer 220 to avoid short circuit of the battery cell.

[0086] Reference Figure 1 As shown, in a possible implementation, the first pole piece 100 includes a first single-sided coated section 130 having a first active material layer 120 on a single side, and a first double-sided coated section 140 having a first active material layer 120 on both sides. The first single-sided coated section 130 and the first double-sided coated section 140 are connected in sequence along the winding direction of the battery cell. The battery cell has a straight area and an arc area. The arc area is located on opposite sides of the straight area. The end of the first double-sided coated section 140 close to the first single-sided coated section 130 is located in the straight area.

[0087] In the above-mentioned arrangement, the end of the first single-sided coated section 130 facing away from the first double-sided coated section 140 can be located in the straight area or in the arc area, but the end of the first double-sided coated section 140 close to the first single-sided coated section 130 is located in the straight area, and not in the arc area, thereby reducing the volume of the battery cell and improving the energy density of the battery.

[0088] In some embodiments, the end of the first single-sided coating section 130 away from the first double-sided coating section 140 is located in the straight area, and the projection of one end of the first single-sided coating section 130 away from the first double-sided coating section 140 on the second pole piece 200 covers the end of the second pole piece 200, and the difference in distance between the end of the first single-sided coating section 130 away from the first double-sided coating section 140 and the end of the second pole piece 200 is less than or equal to 2 mm. In this way, the width of the battery cell can be reduced, and then the volume of the battery cell can be reduced, thereby improving the energy density of the battery.

[0089] Reference Figure 1 As shown, in a possible implementation, the second pole piece 200 includes a second double-sided coated section 230 with a second active material layer 220 on both sides, a second single-sided coated section 240 with a second active material layer 220 on one side, and an empty foil section 250 without a second active material layer 220, and the second double-sided coated section 230, the second single-sided coated section 240 and the empty foil section 250 are connected in sequence along the winding direction of the battery cell.

[0090] The second single-sided coated section 240 and the hollow foil section 250 are jointly arranged outside the battery cell, and the end of the hollow foil section 250 facing away from the second single-sided coated section 240 is located in the middle of the straight area.

[0091] That is to say, the outermost layer of the battery cell is coated with the second current collector 210, so that the outermost second active material layer 220 will not be located in the arc area, thereby reducing the volume of the battery cell and ensuring the safety performance of the battery cell, thereby improving the volume energy density of the battery cell.

[0092] 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 it. 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 with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery, characterized in that: The battery cell comprises a first pole piece, a second pole piece, and a diaphragm located between the first pole piece and the second pole piece; the first pole piece, the diaphragm, and the second pole piece are wound to form the battery cell; The first pole piece includes a first current collector and a first active material layer, the first active material layer is disposed on at least one side of the first current collector, the first active material layer includes a first coating layer and a second coating layer, and the first coating layer is located between the first current collector and the second coating layer; The first active material layer includes a first coating segment, a second coating segment and a third coating segment which are adjacent to each other in sequence along a winding direction, and a thickness of at least one of the first coating segment and the third coating segment is greater than a thickness of the second coating segment.

2. The battery according to claim 1, characterized in that The first coating layer includes a first active material, the first active material includes one of pure silicon particles, silicon alloys, silicon-carbon composite materials, and silicon-oxygen composite materials; and / or, the second coating layer comprises a second active material, the second active material comprising one of graphite, pure silicon particles, silicon alloys, silicon-carbon composite materials, and silicon-oxygen composite materials; and / or, the first coating layer comprises a first conductive agent, wherein the first conductive agent comprises one of superconducting carbon, acetylene black, Ketjen black, conductive carbon black, graphene, carbon dots, carbon nanotubes, carbon nanofibers, and graphite; And / or, the second coating layer includes a second conductive agent, and the second conductive agent includes one of superconducting carbon, acetylene black, Ketjen black, conductive carbon black, graphene, carbon dots, carbon nanotubes, carbon nanofibers, and graphite.

3. The battery according to claim 1, characterized in that The ratio of the thickness of the first coating layer to the thickness of the second coating layer is greater than or equal to 0.1 and less than or equal to 1.

4. The battery according to any one of claims 1 to 3, characterized in that: The first current collector comprises a first surface and a second surface arranged opposite to each other, and the first surface and the second surface are both provided with the first active material layer; The thickness of the first coating section located on the first surface is greater than the thickness of the third coating section located on the first surface; And / or, the thickness of the first coating section located on the second surface is smaller than the thickness of the third coating section located on the second surface.

5. The battery according to claim 4, characterized in that The difference in thickness between the first coating section and the second coating section is less than or equal to 7 μm; And / or, a thickness difference between the third coating section and the second coating section is less than or equal to 4 μm.

6. The battery according to any one of claims 1 to 3, characterized in that: The first coating section includes a first region and a second region which are adjacent to each other. The second region is located between the first region and the second coating section. The thickness of the first region is greater than that of the second region.

7. The battery according to claim 6, characterized in that The difference between the thickness of the first region and the thickness of the second coating section is greater than 0 and less than or equal to 7 μm; and / or, a ratio of a thickness of the first region to a thickness of the second coating section is greater than 1 and less than or equal to 1.28; and / or, a difference between a thickness of the second region and a thickness of the second coating section is greater than 0 and less than or equal to 6 μm; And / or, a ratio of a thickness of the second region to a thickness of the second coating section is greater than 1 and less than or equal to 1.

24.

8. The battery according to any one of claims 1 to 3, characterized in that: At least one end of the second coating along its own length direction covers at least one end of the first coating along its length direction; Alternatively, two ends of the second coating along its own length direction are flush with two ends of the first coating along its length direction.

9. The battery according to any one of claims 1 to 3, characterized in that: At least one end of the first coating extends beyond the end of the second coating along the length direction, and the difference in distance between the end of the first coating and the end of the second coating is less than or equal to 5 mm.

10. The battery according to any one of claims 1 to 3, characterized in that: The second pole piece includes a second current collector and a second active material layer, and the second active material layer is disposed on at least one side of the second current collector; The end of the third coating section away from one end of the second coating section exceeds the end of the second active material layer along the length direction, and the difference in distance between the end of the third coating section and the end of the second active material layer is greater than or equal to 2 mm.

11. The battery according to claim 10, characterized in that It also includes an insulating layer, which is arranged on at least one end of the second active material layer, and the projection of the insulating layer on the first pole piece covers at least a portion of the third coating section.

12. The battery according to claim 11, characterized in that The first pole piece includes a first single-sided coating section having the first active material layer disposed on one side and a first double-sided coating section having the first active material layer disposed on both sides, wherein the first single-sided coating section and the first double-sided coating section are sequentially connected along the winding direction of the battery cell; The battery core has a straight area and an arc area, the arc areas are located at two opposite sides of the straight area, and the end of the first double-sided coating section close to the first single-sided coating section is located in the straight area.

13. The battery according to claim 12, characterized in that The end of the first single-sided coated section facing away from the first double-sided coated section is located in the straight area, and the difference in distance between the end of the first single-sided coated section facing away from the first double-sided coated section and the end of the second pole piece is less than or equal to 2 mm.

14. The battery according to claim 13, characterized in that The second pole piece includes a second double-sided coated section with the second active material layer on both sides, a second single-sided coated section with the second active material layer on one side, and a hollow foil section without the second active material layer, wherein the second double-sided coated section, the second single-sided coated section and the hollow foil section are sequentially connected along the winding direction of the battery cell; The second single-sided coated section and the hollow foil section are jointly arranged outside the battery core, and the end of the hollow foil section facing away from the second single-sided coated section is located in the middle of the straight area.

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