Electrode assembly and battery cell

Abstract

The utility model provides an electrode assembly and a battery cell, the electrode assembly comprises a winding structure, and the winding structure comprises a straight area, a first bending area and a second bending area; the winding structure comprises a first side face and a second side face which are located in the straight area and oppositely arranged in the first direction, a first end face located in the first bending area and a second end face located in the second bending area. The ending end of the negative plate is located in the first bending area, and the diaphragm covers the ending end of the negative plate; the electrode assembly further comprises a positioning layer, the positioning layer is connected to the outer side of the winding structure, the ending end of the diaphragm is fixed to the first side face, and the positioning layer at least extends to the second side face from the first end face in the winding direction. According to the electrode assembly and the battery cell provided by the invention, a reliable connecting structure can be formed between the ending end of the diaphragm and the first side surface, and after the ending end of the diaphragm is fixed, the diaphragm covers the ending end of the negative plate, so that a restraining force can be generated on the negative plate, and the negative plate is prevented from loosening.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, and in particular to an electrode assembly and a battery cell. BACKGROUND

[0002] As one of the typical packaging forms of power batteries, the square case battery cell has the advantages of relatively simple group structure and good heat dissipation. The square case battery cell includes a shell, a bare battery cell and a cover plate. The shell and the cover plate can jointly enclose a containing space, and the bare battery cell is arranged in the containing space. At present, the bare battery cell includes a laminated structure and a wound structure. The bare battery cell with the wound structure has the advantages of low cost, high production efficiency and few foreign matters or particles generated in the production process, and is widely used by various manufacturers.

[0003] The wound structure includes a flat area and two bending areas respectively connected to opposite ends of the flat area. The applicant has found that the end of the negative electrode sheet forming the wound structure is located in the bending area, which may cause a large gap between the positive electrode sheet and the negative electrode sheet in the bending area, and has a risk of loosening. UTILITY MODEL CONTENT

[0004] Therefore, the purpose of the present application is to provide an electrode assembly and a battery cell to at least partially solve the risk of loosening of the wound structure due to the end of the negative electrode sheet being located in the bending area.

[0005] To achieve the above purpose, the first aspect of the present application provides an electrode assembly, including a positive electrode sheet, a separator and a negative electrode sheet forming a wound structure; the wound structure includes a flat area and a first bending area and a second bending area respectively connected to opposite ends of the flat area; the wound structure includes a first side surface and a second side surface located in the flat area and oppositely arranged in a first direction, a first end surface located in the first bending area, and a second end surface located in the second bending area; in the winding direction, the first side surface, the second end surface, the second side surface and the first end surface are sequentially arranged; the end of the negative electrode sheet is located in the first bending area, and the separator covers the end of the negative electrode sheet; the electrode assembly further includes a positioning layer connected to the outer side of the wound structure, and fixing the end of the separator to the first side surface, and the positioning layer extends from the first end surface to the second side surface in the winding direction.

[0006] Optionally, the positioning layer extends from the first end surface to the second side surface in the winding direction.

[0007] Optionally, in the winding direction, the extension length of the positioning layer at the second side surface is a, and the length of the second side surface in the winding direction is b, a < b / 2.

[0008] Optionally,

[0009] Optionally, the electrode assembly comprises two winding structures stacked along the first direction, wherein the second side of one winding structure is adjacent to the first side of another winding structure, and the starting end of the positioning layer of each winding structure is located at the same side; and the starting end of the positioning layer is located at the first end face.

[0010] Optionally, along the winding direction, the ending end of the separator extends from the first bending area to the center position of the first side face.

[0011] Optionally, the electrode assembly comprises two winding structures stacked along the first direction, wherein the second side of one winding structure is adjacent to the first side of another winding structure, and the starting end of the positioning layer of each winding structure is located at the same side; and the starting end of the positioning layer is located at the first end face.

[0012] Optionally, the positioning layer comprises a base layer and an adhesive layer arranged on the surface of the base layer, and the base layer is connected with the separator through the adhesive layer; and the adhesive layer is uniformly provided with a hollow area.

[0013] Optionally, along the winding direction, the ending end of the separator extends from the first bending area to the center position of the first side face.

[0014] Optionally, the ending end of the positive electrode sheet is located in the first bending area, and the negative electrode sheet covers the ending end of the positive electrode sheet along the winding direction; along the first direction, the ending end of the positive electrode sheet and the ending end of the negative electrode sheet are respectively located at opposite sides of the center position of the first end face; and along the winding direction, the interval distance between the ending end of the negative electrode sheet and the ending end of the positive electrode sheet is 5mm to 15mm.

[0015] Based on the same inventive concept, the second aspect of the present application further provides an electrode assembly, comprising the electrode assembly as described in the first aspect.

[0016] As can be seen from the above, the electrode assembly and the electrode assembly provided by the present application fix the ending end of the separator on the first side face of the winding structure through the positioning layer, and the positioning layer extends from the first end face located at one end of the first side face to the second end face located at the opposite end of the first side face, and then to the second side face opposite to the first side face. In the embodiment, not only does the positioning layer have a large connection area with the outer surface of the winding structure, but also the ending end of the separator can be stably fixed on the first side face, and when the ending end of the separator is fixed, the negative electrode sheet can be restrained due to the covering of the ending end of the negative electrode sheet by the separator, thereby avoiding the loosening of the negative electrode sheet.

[0017] Meanwhile, the positioning layer is connected with the first end face, the first side face, the second end face and at least part of the second side face respectively, which can provide greater restraint force to the first bending area and the second bending area of the winding structure, reduce the gap between the positive electrode sheet and the negative electrode sheet in the first bending area and the second bending area, not only can reduce the risk of the winding structure from being scattered, but also can avoid lithium precipitation due to the large gap distance between the positive electrode sheet and the negative electrode sheet in the first bending area or the second bending area. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present application or the related art, the drawings needed to be used in the embodiments or the related art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 The schematic diagram of the electrode assembly of the first structure of the embodiment of the present application is shown in FIG. 1.

[0020] Figure 2 The schematic diagram of the stacking of two winding structures of the first structure of the embodiment of the present application is shown in FIG. 2.

[0021] Figure 3 The schematic diagram of the electrode assembly of the second structure of the embodiment of the present application is shown in FIG. 3.

[0022] Figure 4 The schematic diagram of the stacking of two winding structures of the second structure of the embodiment of the present application is shown in FIG. 4.

[0023] Figure 5a The schematic diagram of the positioning layer of the first structure of the embodiment of the present application is shown in FIG. 5.

[0024] Figure 5b The schematic diagram of the positioning layer of the second structure of the embodiment of the present application is shown in FIG. 6.

[0025] Figure 5c The schematic diagram of the positioning layer of the third structure of the embodiment of the present application is shown in FIG. 7.

[0026] Explanation of reference signs:

[0027] 100, negative electrode sheet; 110, tail end of the negative electrode sheet;

[0028] 200, positive electrode sheet; 210, tail end of the positive electrode sheet;

[0029] 300, separator; 310, tail end of the separator;

[0030] 400, first bending area; 500, flat area; 600, second bending area;

[0031] 700, first side surface; 700a, first side surface of the first winding structure; 700b, first side surface of the second winding structure;

[0032] 800, second side surface; 800a, second side surface of the first winding structure; 800b, second side surface of the second winding structure;

[0033] 900, first end surface; 900a, first end surface of the first winding structure; 900b, first end surface of the second winding structure;

[0034] 1000, second end surface; 1000a, second end surface of the first winding structure; 1000b, second end surface of the second winding structure;

[0035] 1100, positioning layer; 1100a, first positioning layer; 1100b, second positioning layer;

[0036] 1110, end of the positioning layer; 1110a, end of the first positioning layer; 1110b, end of the second positioning layer;

[0037] 1120, base layer; 1130, adhesive layer;

[0038] 1140, start of the positioning layer; 1140a, start of the first positioning layer; 1140b, start of the second positioning layer. DETAILED DESCRIPTION

[0039] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments and the accompanying drawings.

[0040] It should be noted that the relative arrangement of the components, numerical expressions and values set forth in these embodiments are not intended to limit the scope of the present application unless otherwise specifically stated.

[0041] It should be understood that the sizes of the various parts shown in the drawings are not necessarily drawn to scale for the sake of convenience.

[0042] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the scope of the application or its application or uses.

[0043] It should be noted that, unless otherwise defined, technical terms or scientific terms used in the embodiments of the present application shall have the common meaning understood by one of ordinary skill in the art to which the embodiments of the present application belong. The terms "first", "second", and similar terms used in the embodiments of the present application do not denote any order, quantity, or importance, but are merely used to distinguish different components. The terms "include", "contain", and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like are merely used to represent relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships can also be changed accordingly.

[0044] Figure 1 A schematic diagram of an electrode assembly of a first structure is shown in FIG. 1, which includes a positive electrode sheet 200, a separator 300, and a negative electrode sheet 100. Figure 1 The separator 300 can be provided with two separators, which are stacked in the order of the separator 300, the negative electrode sheet 100, the separator 300, and the positive electrode sheet 200 before winding to form a stacked structure, and then the stacked structure is wound around a winding needle to form a winding structure. The winding structure includes a flat area 500, and a first bending area 400 and a second bending area 600 connected to opposite ends of the flat area 500, respectively, and the end 110 of the negative electrode sheet is located in the first bending area 400. For the battery cell formed by the electrode assembly, on the one hand, the end 110 of the negative electrode sheet does not occupy the space in the thickness direction of the battery cell, which helps to improve the space utilization rate in the thickness direction of the battery cell and can improve the energy density of the battery cell in a limited space. On the other hand, if the end 110 of the negative electrode sheet is located in the flat area 500, then during the heat pressing and subsequent expansion process, a pressure mark will be generated at the location of the end 110 of the negative electrode sheet, stress concentration will occur, and even the positive electrode sheet 200 or the negative electrode sheet 100 will be broken.

[0045] In combination with the foregoing, when the end 110 of the negative electrode sheet is located in the first bending area 400, if the end 110 of the negative electrode sheet cannot be reliably fixed, the repeated expansion of the bare battery cell (JR) during charging and discharging can cause the first bending area 400 of the winding structure to loosen.

[0046] To avoid the above problems, as shown in FIG. 2, Figure 1 In some embodiments, the electrode assembly further includes a positioning layer 1100 for fixing the end 310 of the separator.

[0047] Specifically, as shown in FIG. 3, Figure 1The shown structure and direction are used as an example. The winding structure includes a first side surface 700 and a second side surface 800 oppositely arranged in the X direction (i.e., the thickness direction of the winding structure) of the flat area 500 and along the first direction, a first end surface 900 located in the first bending area 400, and a second end surface 1000 located in the second bending area 600. Along the winding direction, the first side surface 700, the second end surface 1000, the second side surface 800, and the first end surface 900 are sequentially arranged. Figure 1 In the shown direction, the first side surface 700 is an upper flat surface, the second side surface 800 is a lower flat surface, the first end surface 900 is a left arc-shaped surface, and the second end surface 1000 is a right arc-shaped surface. Figure 1

[0048] The exposed surface of the diaphragm 300 is configured as the first side surface 700, the second side surface 800, the first end surface 900, and the second end surface 1000. Except for the two ends along the winding axis direction, the remaining exposed surface is formed by the diaphragm 300, and the positive electrode sheet 200 and the negative electrode sheet 100 are covered by the surface.

[0049] It should be noted that the first side surface 700 and the second side surface 800 in the embodiment of the present application are located in the flat area 500 and are continuous flat surfaces formed by the diaphragm 300; the first end surface 900 is located in the first bending area 400 and is a continuous arc-shaped curved surface formed by the diaphragm 300; and the second end surface 1000 is located in the second bending area 600 and is a continuous arc-shaped curved surface formed by the diaphragm 300.

[0050] The tail end 110 of the negative electrode sheet is located in the first bending area 400, and the diaphragm 300 covers the tail end 110 of the negative electrode sheet. The positioning layer 1100 is connected to the outer side of the winding structure and fixes the tail end 310 of the diaphragm to the first side surface 700. The positioning layer 1100 extends at least from the first end surface 900 to the second side surface 800 along the winding direction.

[0051] For example, the positioning layer 1100 can be an insulating tape.

[0052] For example, the starting end 1140 of the positioning layer can be located at the center position of the first end surface 900 along the winding direction.

[0053] ​After the positive electrode sheet 200, the separator 300 and the negative electrode sheet 100 are wound to form the winding structure, the tail end 110 of the negative electrode sheet is located at the first bending area 400, and the outermost coil of the separator 300 covers the tail end 110 of the negative electrode sheet and extends to the first side surface 700 in the winding direction. When the tail end 310 of the separator is fixed by the positioning layer 1100, one end of the positioning layer 1100 (the end as the starting end 1140 of the positioning layer, and the opposite end of the positioning layer 1100 in the extension direction as the tail end 1110 of the positioning layer) is aligned with and connected to the preset position on the first end surface 900, and then the positioning layer 1100 is extended from the first end surface 900 to the second side surface 800 in the winding direction, and during the extension, the positioning layer 1100 is connected to the first end surface 900, the tail end 310 of the separator, the first side surface 700, the second end surface 1000 and at least part of the second side surface 800, respectively.

[0054] The electrode assembly provided by the embodiment fixes the tail end 310 of the separator to the first side surface 700 of the winding structure through the positioning layer 1100, and the positioning layer 1100 extends from the first end surface 900 at one end of the first side surface 700 to the second end surface 1000 at the opposite end of the first side surface 700 and to the second side surface 800 opposite to the first side surface 700. In this embodiment, not only does the positioning layer 1100 have a large connection area with the outer surface of the winding structure, but also the tail end 310 of the separator can be stably fixed to the first side surface 700. Moreover, after the tail end 310 of the separator is fixed, the tail end 110 of the negative electrode sheet is covered by the separator 300, so that a restraining force can be generated on the negative electrode sheet 100 to prevent the negative electrode sheet 100 from loosening.

[0055] Meanwhile, the positioning layer 1100 is connected to the first end surface 900, the first side surface 700, the second end surface 1000 and at least part of the second side surface 800, respectively, so that a large restraining force can be provided on the first bending area 400 and the second bending area 600 of the winding structure, and the gap between the positive electrode sheet 200 and the negative electrode sheet 100 in the first bending area 400 and the second bending area 600 is reduced. This not only reduces the risk of the winding structure being scattered, but also avoids lithium precipitation due to a large gap distance between the positive electrode sheet 200 and the negative electrode sheet 100 in the first bending area 400 or the second bending area 600.

[0056] As shown in FIG. 1, the tail end 110 of the negative electrode sheet is located at the first bending area 400, and the tail end 310 of the separator is located at the second bending area 600. Figure 1 In some embodiments, in the winding direction, the extension length of the positioning layer 1100 on the second side surface 800 is a, and the length of the second side surface 800 in the winding direction is b, a < b / 2.

[0057] When the end 1110 of the positioning layer is located at the second side 800, the end 1110 of the positioning layer should not exceed the center of the second side 800 in the winding direction. If the end 1110 of the positioning layer exceeds the center of the second side 800 in the winding direction, when the two winding structures are stacked and the ends 1110 of the two positioning layers are adjacent in the stacking direction, the parts of the positioning layers 1100 near the ends of the two winding structures will have an overlapping area (the part of the end 1110 of the positioning layer exceeding the center of the second side 800), and there will be a large height difference between the overlapping area and other positions of the winding structure. When the battery cell formed by the winding structure is subjected to long-term charging and discharging, the winding structure will swell, and stress concentration will easily occur in the overlapping area, thereby adversely affecting the positive plate 200 and the negative plate 100 and reducing the cycle life of the battery cell.

[0058] Therefore, when the end 1110 of the positioning layer is located at the second side 800, the embodiment limits the relationship between a and b as a < b / 2, that is, limits the end 1110 of the positioning layer to the part of the second side 800 near the second end surface 1000, which helps to avoid stress concentration of the battery cell formed by the winding structure in the cycle of charging and discharging, and helps to improve the cycle life of the battery cell.

[0059] As Figure 1 In some embodiments,

[0060] When the two winding structures are stacked and the ends 1110 of the two positioning layers are adjacent in the stacking direction, the area between the ends 1110 of the two positioning layers will have a height difference with the area where the positioning layer 1100 is provided due to the absence of the positioning layer 1100. If If the spacing distance between the ends 1110 of the positioning layers of the two winding structures is large, the adverse effects of the above-mentioned height difference on the winding structure will be more obvious, which will further affect the cycle life of the battery cell. At the same time, when the positioning layer 1100 is needed to insulate and separate the two winding structures, if the area between the ends 1110 of the two positioning layers where the positioning layer 1100 is not provided is too large, the insulation effect between the two winding structures will also be invalid. If < 5 mm, the two winding structures may still have the aforementioned overlapping area of the positioning layer 1100 when they are stacked.

[0061] The embodiment limits the relationship between a and b as which helps to improve the cycle life of the battery cell formed by the winding structure.

[0062] Figure 2 The stacking schematic diagram of two winding structures of the second structure is shown as follows: Figure 2The electrode assembly includes two wound structures stacked along a first direction, wherein the second side 800 of one wound structure is adjacent to the second side 800 of the other wound structure, and the end 1110 of the positioning layer of each of the two wound structures is disposed opposite to each other; the end 1110 of the positioning layer is located on the second side 800.

[0063] by Figure 2 Taking the structure and orientation shown as an example, the upper winding structure is defined as the first winding structure, and the lower winding structure is defined as the second winding structure. The first side surface 700a of the first winding structure and the first side surface 700b of the second winding structure are far apart from each other, while the second side surface 800a of the first winding structure and the second side surface 800b of the second winding structure are adjacent to each other. The first end face 900a of the first winding structure and the second end face 1000b of the second winding structure are both located on the left side, and the second end face 1000a of the first winding structure and the first end face 900b of the second winding structure are both located on the right side.

[0064] The first winding structure includes a first positioning layer 1100a, with its starting end 1140a located on the first end face 900a of the first winding structure and its ending end 1110a located on the second side face 800a of the first winding structure. Correspondingly, the second winding structure includes a second positioning layer 1100b, with its starting end 1140b located on the first end face 90b of the second winding structure and its ending end 1110b located on the second side face 800b of the second winding structure.

[0065] In this embodiment, the end 1110a of the first positioning layer and the end 1110b of the second positioning layer are located in the same space along the first direction, which can make full use of the space in the first direction and help to improve the energy density of the battery cell formed by the first winding structure and the second winding structure.

[0066] Meanwhile, the distance between the end 1110a of the first positioning layer and the end 1110b of the second positioning layer is moderate (i.e., it conforms to the limitation on the relationship between a and b in the above embodiment), which can make the internal stress distribution of the battery cell formed by the first winding structure and the second winding structure more uniform.

[0067] In addition, the first side 700a of the first winding structure is covered by the first positioning layer 1100a, the first side 700b of the second winding structure is covered by the second positioning layer 1100b, and the larger area between the second side 800a of the first winding structure and the second side 800b of the second winding structure is also provided with the first positioning layer 1100a and the second positioning layer 1100b. When the first positioning layer 1100a and the second positioning layer 1100b have an insulating function, the first winding structure and the second winding structure can have good insulation effects between each other and between each of them and the shell, and the cell assembly process (such as the cell assembly process) can be omitted. The cell assembly process (such as the cell assembly process) can be omitted, which helps to save the internal space of the cell and improve the production efficiency.

[0068] Figure 3 A schematic diagram of an electrode assembly of the second structure is shown as Figure 3 The positioning layer 1100 extends at least to the connection between the second side 800 and the first end surface 900, and the extension length of the positioning layer 1100 is c, and the circumference of the winding structure along the winding direction is d, and c≤0.9d.

[0069] In combination with the foregoing embodiments, if the end 1110 of the positioning layer is located on the part of the second side 800 close to the first end surface 900 and does not cover the second side 800, the height difference formed by the position of the end 1110 of the positioning layer will adversely affect the cycle life of the cell. If c>0.9d, or even the end 1110 of the positioning layer exceeds the start 1140 of the positioning layer along the winding direction, i.e., c>d, then during the charging and discharging cycle of the cell, the transverse expansion of the positive plate 200 or the negative plate 100 cannot be released, and during the cycle, the positive plate 200 or the negative plate 100 may wrinkle and lithium may be separated, or even a safety problem may occur.

[0070] Therefore, the relationship between c and d is limited to c≤0.9d in this embodiment, which can further increase the restraining force provided by the positioning layer 1100 to the winding structure, make the restraining force on the winding structure more uniform, and ensure that the cell formed by the winding structure has high safety. In addition, it can also reduce the assembly difficulty and process requirement of the cell, which is helpful to improve the production capacity and is suitable for mass production.

[0071] Figure 4 A schematic diagram of the stacking of two winding structures of the second structure is shown as Figure 4 In some embodiments, the electrode assembly includes two winding structures stacked along a first direction, and along the stacking direction of the two winding structures, the second side 800 of one winding structure is adjacent to the first side 700 of the other winding structure, and the start 1140 of the positioning layer of each of the two winding structures is located on the same side; the start 1140 of the positioning layer is located on the first end surface 900.

[0072] by Figure 4 Taking the structure and orientation shown as an example, the first side surface 700a of the first winding structure and the second side surface 800b of the second winding structure are far apart from each other, while the second side surface 800a of the first winding structure and the first side surface 700b of the second winding structure are adjacent to each other. The first end face 900a of the first winding structure and the first end face 900b of the second winding structure are both located on the left side, and the second end face 1000a of the first winding structure and the second end face 1000b of the second winding structure are both located on the right side.

[0073] The starting end 1140a of the first positioning layer is located at the first end face 900a of the first winding structure, and the ending end 1110a of the first positioning layer is located at the connection between the second side face 800a and the first end face 900a of the first winding structure. Correspondingly, the starting end 1140b of the second positioning layer is located at the first end face 900b of the second winding structure, and the ending end 1110b of the second positioning layer is located at the connection between the second side face 800b and the first end face 900b of the second winding structure.

[0074] In this embodiment, since the first positioning layer 1100a is disposed as a whole between the first winding structure and the second winding structure, the problem of stress concentration caused by the height difference between the end 1110 of the positioning layer and the adjacent area is avoided. This makes the internal stress of the battery cell formed by the first winding structure and the second winding structure more uniform, which helps to improve the cycle life of the battery cell.

[0075] Figure 5a The positioning layer 1100 of the first structure is shown. Figure 5b The second type of positioning layer 1100 is shown. Figure 5c The third type of positioning layer 1100 is shown, such as Figure 5a , Figure 5b and Figure 5c In some embodiments, the positioning layer 1100 includes a base layer 1120 and an adhesive layer 1130 disposed on the surface of the base layer 1120. The base layer 1120 is connected to the diaphragm 300 through the adhesive layer 1130. The adhesive layer 1130 is uniformly provided with hollow areas.

[0076] For example, the base layer 1120 can be an insulating material layer.

[0077] For example, the surface of the base layer 1120 away from the diaphragm 300 may also have an adhesive layer 1130 in at least a portion of the area, so that the two wound structures can be connected to each other as a whole when stacked by the adhesive layer 1130 disposed on the outside of the base layer 1120.

[0078] like Figure 5aThe adhesive layer 1130 can be a plurality of point structures uniformly distributed and separated from each other.

[0079] The adhesive layer 1130 can be a plurality of point structures uniformly distributed and separated from each other. Figure 5b The adhesive layer 1130 can be a plurality of strip structures uniformly distributed and separated from each other.

[0080] The adhesive layer 1130 can be a plurality of strip structures uniformly distributed and separated from each other. Figure 5c The adhesive layer 1130 can be a mesh structure.

[0081] In this embodiment, the adhesive layer 1130 is uniformly arranged in the hollow area, which can ensure that the adhesive force of the adhesive layer 1130 on the base layer 1120 is relatively uniform, and ensure that a reliable connection is formed between the base layer 1120 and the separator 300. At the same time, in the hollow area, since the adhesive layer 1130 is not arranged, a gap can exist between the base layer 1120 and the surface of the separator 300, and the electrolyte in the battery cell can flow in the gap to improve the wettability of the electrolyte.

[0082] The adhesive layer 1130 can be a mesh structure. Figure 1 In some embodiments, along the winding direction, the tail end 310 of the separator extends to the center position of the first side surface 700 from the first bending area 400.

[0083] The first side surface 700 is a large-area flat surface, and the tail end 310 of the separator is connected to the center position of the first side surface 700 through the positioning layer 1100, which can further improve the connection reliability of the tail end 310 of the separator and the first side surface 700, and reduce the risk of loosening of the tail end 310 of the separator during the charge and discharge cycle of the battery cell formed by the winding structure.

[0084] The adhesive layer 1130 can be a mesh structure. Figure 1 In some embodiments, the tail end 210 of the positive electrode sheet is located in the first bending area 400, and the tail end 110 of the negative electrode sheet covers the tail end 210 of the positive electrode sheet along the winding direction; along the first direction, the tail end 210 of the positive electrode sheet and the tail end 110 of the negative electrode sheet are located on opposite sides of the center position of the first end surface 900; and along the winding direction, the interval distance between the tail end 110 of the negative electrode sheet and the tail end 210 of the positive electrode sheet is 5mm to 15mm.

[0085] It should be noted that the center position of the first end surface 900 is the top of the arc-shaped curved surface configured as the first end surface 900.

[0086] If the tail end 210 of the positive electrode sheet and the tail end 110 of the negative electrode sheet are located on the same side of the center position of the first end surface 900, stress concentration may occur, which is not conducive to the restraint of the separator 300 on the positive electrode sheet 200 and the negative electrode sheet 100, and is not conducive to reducing the gap between the positive electrode sheet 200 and the negative electrode sheet 100 in the first bending area 400.

[0087] If the interval distance between the tail end 210 of the positive electrode sheet and the tail end 110 of the negative electrode sheet is too small, the two will additionally increase the length of the winding structure, which is not conducive to the rational use of the internal space of the battery cell. If the interval distance between the tail end 210 of the positive electrode sheet and the tail end 110 of the negative electrode sheet is too large, the negative electrode sheet 100 will extend beyond the area of the positive electrode sheet 200, and this area cannot be used for charging and discharging, which will result in a lower energy density of the battery cell formed by the winding structure.

[0088] Therefore, in the embodiment, the tail end 110 of the negative electrode sheet and the tail end 210 of the positive electrode sheet are arranged on the opposite sides of the center position of the first end face 900, and the interval distance between the tail end 110 of the negative electrode sheet and the tail end 210 of the positive electrode sheet is limited to 5mm to 15mm, which can not only ensure that the battery cell formed by the winding structure has a larger energy density, but also enable the separator 300 to better constrain the positive electrode sheet 200 and the negative electrode sheet 100, thereby helping to reduce the gap between the positive electrode sheet 200 and the negative electrode sheet 100 in the first bending area 400.

[0089] Based on the same inventive concept, in combination with the description of the electrode assembly of each of the above embodiments, the embodiment provides a battery cell having the corresponding technical effects of the electrode assembly of each of the above embodiments, which will not be described here.

[0090] A battery cell comprising the electrode assembly of each of the above embodiments.

[0091] It should be noted that the above describes some embodiments of the present application. Other embodiments are within the scope of the appended claims.

[0092] Each of the embodiments in the present application is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be mutually referred to.

[0093] The description of the present application is given for the purpose of illustration and description, and is not exhaustive or limiting to the present application. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are chosen and described in order to better illustrate the principles and practical application of the present application, and to enable those of ordinary skill in the art to understand the present application in order to design various embodiments with various modifications for specific purposes.

[0094] Those skilled in the art should understand: the discussion of the above any embodiment is only exemplary, and is not intended to imply that the scope of the application is limited to these examples; in the idea of the present application, the above embodiments or the technical features in different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the embodiments of the present application as described above, which are not provided in details for the sake of brevity.

[0095] Although the present application has been described in conjunction with the specific embodiments thereof, it is to be understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description.

[0096] Embodiments of the present application are intended to cover all such alternatives, modifications, and variations which fall within the scope of the present application. Accordingly, any omission, modification, equivalent replacement, improvement, etc. made in the spirit and principle of the embodiments of the present application should be included in the protection scope of the present application.

Claims

1. An electrode assembly, characterized in that, The device includes a positive electrode sheet, a separator, and a negative electrode sheet forming a wound structure. The wound structure includes a straight region and a first bending region and a second bending region connected to opposite ends of the straight region. The wound structure includes a first side surface and a second side surface located in the straight region and arranged opposite to each other along a first direction, a first end face located in the first bending region, and a second end face located in the second bending region. The first side surface, the second end face, the second side surface, and the first end face are arranged sequentially along the winding direction. The tail end of the negative electrode sheet is located within the first bending region, and the separator covers the tail end of the negative electrode sheet. The electrode assembly further includes a positioning layer connected to the outside of the winding structure and fixing the end of the diaphragm to the first side surface; the positioning layer extends at least from the first end face to the second side surface along the winding direction.

2. The electrode assembly according to claim 1, characterized in that, Along the winding direction, the positioning layer extends a length on the second side, and the length of the second side along the winding direction is b, where a < b / 2.

3. The electrode assembly according to claim 2, characterized in that, 4. The electrode assembly according to claim 1, characterized in that, The electrode assembly includes two wound structures stacked along the first direction, wherein the second side of one of the wound structures is adjacent to the second side of the other wound structure, and the tail ends of the positioning layers of the two wound structures are disposed opposite to each other; the tail ends of the positioning layers are located on the second side.

5. The electrode assembly according to claim 1, characterized in that, Along the winding direction, the positioning layer extends at least to the connection between the second side surface and the first end surface, and the extension length of the positioning layer is c, and the circumference of the winding structure along the winding direction is d, where c≤0.9d.

6. The electrode assembly according to claim 5, characterized in that, The electrode assembly includes two wound structures stacked along the first direction, wherein the second side of one of the wound structures is adjacent to the first side of the other wound structure, and the starting ends of the positioning layers of the two wound structures are located on the same side; the starting ends of the positioning layers are located on the first end face.

7. The electrode assembly according to claim 1, characterized in that, The positioning layer includes a base layer and an adhesive layer disposed on the surface of the base layer. The base layer is connected to the diaphragm through the adhesive layer. The adhesive layer is uniformly provided with hollow areas.

8. The electrode assembly according to claim 1, characterized in that, Along the winding direction, the end of the diaphragm extends from the first bending area to the center of the first side surface.

9. The electrode assembly according to claim 1, characterized in that, The end of the positive electrode is located within the first bending area, and the negative electrode covers the end of the positive electrode along the winding direction; along the first direction, the end of the positive electrode and the end of the negative electrode are located on opposite sides of the center of the first end face; along the winding direction, the distance between the end of the negative electrode and the end of the positive electrode is 5mm to 15mm.

10. A battery cell, characterized in that, Includes the electrode assembly as described in any one of claims 1 to 9.

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