Battery cell and battery

Abstract

The utility model relates to the field of batteries, in particular to a battery cell and a battery. The battery cell comprises a positive plate and a negative plate, the positive plate comprises a positive current collector, a positive active material layer located on at least one side of the surface of the positive current collector and a positive lug, the positive lug is electrically connected with the positive current collector, the thickness of the positive current collector is 4-18 microns, and a plurality of first concave parts are formed in the edge of the width direction of the positive plate and the positive active material layer; the negative plate comprises a negative current collector, a negative active material layer located on at least one side of the surface of the negative current collector and a negative lug, the negative lug is electrically connected with the negative current collector, the thickness of the negative current collector is 2-30 microns, and the negative active material layer comprises a plurality of second concave parts; and the cathode current collector is a copper foil with the elongation percentage being greater than or equal to 3% and the tensile strength being greater than or equal to 400Mpa. The first concave part is arranged on the edge of the positive plate, and the second concave part is arranged on the negative plate, so that the wettability of the electrolyte on the electrode plates is improved, and the problem of local lithium precipitation can be improved under the condition of improving the overall surface density.

Description

Technical Field

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

[0002] With the rapid development of battery technology, people have put forward higher requirements on battery energy density, fast charging capability and charge and discharge rate. High energy density fast charging lithium battery is also the development trend of consumer batteries.

[0003] At present, when manufacturing some battery cells, the positive electrode sheet, separator and negative electrode sheet are stacked together, and then the head of the negative electrode sheet is used as the center, and the winding is carried out from the head to the tail to form a roll core, while when manufacturing other battery cells, the positive electrode sheet, separator and negative electrode sheet are first assembled to form a sandwich structure, and then multiple sandwich structures are stacked in parallel to form a stack. In order to improve the energy density of the battery, the electrode sheet is gradually developing in the direction of high compaction and thick electrode.

[0004] However, thick electrode and fast-charging batteries currently have problems with poor electrolyte wettability and lithium plating, which seriously affect the battery's cycle performance and safety. Utility Model Content

[0005] Based on this, the present application provides a battery cell and a battery to solve the problem in the related art that it is difficult for the electrolyte to completely infiltrate the active material layer of the electrode, resulting in lithium deposition and affecting battery performance.

[0006] The present application provides a battery cell, comprising a positive electrode sheet and a negative electrode sheet.

[0007] The positive electrode sheet includes a positive electrode current collector, a positive electrode active material layer located on at least one side of the surface of the positive electrode current collector, and a positive electrode ear, the positive electrode ear is electrically connected to the positive electrode current collector, the thickness of the positive electrode current collector is 4 μm-18 μm, and the edge of the positive electrode sheet in the width direction and the positive electrode active material layer contain a plurality of first recesses;

[0008] The negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer located on at least one side of the surface of the negative electrode current collector, and a negative electrode ear, the negative electrode ear is electrically connected to the negative electrode current collector, the thickness of the negative electrode current collector is 2 μm-30 μm, and the negative electrode active material layer contains a plurality of second recesses;

[0009] The negative electrode current collector is a copper foil with an elongation of ≥3% and a tensile strength of ≥400Mpa.

[0010] In a possible implementation, the first recess includes a plurality of first holes, the second recess includes a plurality of first grooves, the plurality of first holes are arranged along the length direction of the positive electrode sheet, and the first grooves extend along the width direction of the negative electrode sheet;

[0011] And / or, the battery cell comprises a straight region and a bent region, and the positive electrode active material layer comprises a plurality of second holes in the bent region.

[0012] In one possible implementation, the battery cell includes a straight area and a bending area, the positive electrode active material layer contains a plurality of second holes in the bending area, the thickness of the battery cell is a, and the overall width of the second holes in the bending area along the length direction of the positive electrode sheet is b. Along the length direction of the positive electrode sheet, b in the bending area gradually increases, and b satisfies: 0.1a≤b<2a.

[0013] In a possible implementation, at one side edge of the positive electrode sheet in the width direction, a plurality of first recesses are arranged continuously or at intervals along the length direction of the positive electrode sheet; and / or

[0014] At the other side edge of the positive electrode sheet in the width direction, a plurality of first recesses are arranged continuously or at intervals along the length direction of the positive electrode sheet.

[0015] In a possible implementation, a plurality of third holes are provided on the positive electrode active material layer in the middle of the width direction of the positive electrode sheet, the width of the positive electrode sheet is W along the width direction of the positive electrode sheet, the width of the first recessed area provided on one side of the width direction of the positive electrode sheet is W1, the width of the first recessed area provided on the other side of the width direction of the positive electrode sheet is W2, and the width of the third hole area provided in the middle is W3;

[0016] Among them, W1 and W2 satisfy: the range of W1 is 3mm-25mm; the range of W2 is 3mm-25mm.

[0017] In a possible implementation, the hole depth of the first recess is greater than or equal to the hole depth of the third hole, and the spacing between the first recesses is less than or equal to the spacing between the third holes;

[0018] And / or, in a partial area along one side of the length direction of the negative electrode sheet, only one side of the surface of the negative electrode collector contains the negative electrode active material layer, and in the positive electrode sheet area corresponding to the partial area, the first recess and the third hole are adjacent.

[0019] In a possible implementation, the battery cell also includes protective tape, which includes a positive electrode ear protection tape provided on the positive electrode sheet and covering the positive electrode ear position; and / or a negative electrode protection tape provided on the positive electrode sheet and corresponding to the negative electrode ear position; and / or a finishing tape provided on the positive electrode collector and connected to the edge of the positive electrode active material layer, and a plurality of fourth holes are opened on the positive electrode active material layer, and the plurality of fourth holes are arranged along the edge of the protective tape.

[0020] In a possible implementation, the width of the negative electrode sheet is X, and along the width direction of the negative electrode sheet, the width of the second recessed portion at the top of the negative electrode sheet is X1, and the width of the second recessed portion at the bottom of the negative electrode sheet is X2, wherein X1 and X2 satisfy: X1+X2≤X, and along the width direction of the negative electrode sheet, the second recessed portion at the top and the second recessed portion at the bottom are offset from each other or partially parallel;

[0021] And / or, the second recess is provided in the middle of the width direction of the negative electrode sheet, along the width direction of the negative electrode sheet, the width of the negative electrode sheet is X, the width of the bottom area without the second recess is X3, the width of the top area without the second recess is X4, the width of the middle second recess area is X5, X5 = X-X3-X4;

[0022] Among them, X3 and X4 satisfy: the range of X3 is 5mm-30mm; the range of X4 is 5mm-30mm.

[0023] In a possible implementation, both sides of the negative electrode current collector surface contain a layer of negative electrode active material.

[0024] The second recess is provided on the thicker negative electrode active material layer, or

[0025] The pore depth of the second recess on the thicker negative electrode active material layer is greater than or equal to the pore depth of the second recess on the thinner negative electrode active material layer, and the spacing between the second recesses on the thicker negative electrode active material layer is less than or equal to the spacing between the second recesses on the thinner negative electrode active material layer.

[0026] In a possible implementation, in a direction perpendicular to the positive electrode current collector, projections of the first recesses on the two positive electrode active material layers are offset from each other or partially correspond to each other; and / or

[0027] In a direction perpendicular to the negative electrode current collector, the projections of the second concave portions on the two negative electrode active material layers are mutually offset or partially correspond to each other; and / or

[0028] The depth of the first recess is h3, the thickness of the positive electrode current collector is M, and the spacing between the first recesses on the positive electrode active material layer is L1, wherein L1 satisfies L1≥h3+M; and / or

[0029] The depth of the second recess is h4, the thickness of the negative electrode current collector is N, and the distance between the second recesses on the negative electrode active material layer is L2, wherein L2 satisfies L2≥h4+N.

[0030] In a possible implementation, the second recess includes a plurality of fifth holes and / or a plurality of first grooves, the fifth holes are opened along the thickness direction of the negative electrode sheet, the first grooves extend along the width direction of the negative electrode sheet, the thickness of the negative electrode current collector is N, and the thickness of the negative electrode active material layer is P;

[0031] The depth of the fifth hole is h5, which satisfies: 5 μm ≤ h5 ≤ 2P + N;

[0032] The depth of the first groove is h6, which satisfies: 5μm≤h6≤P.

[0033] In a possible implementation, the second recess includes a plurality of fifth holes and / or a plurality of first grooves, the fifth holes are opened along the thickness direction of the negative electrode sheet, and the first grooves extend along the width direction of the negative electrode sheet;

[0034] The negative electrode active material layer is provided with fifth holes, the hole spacing of the first concave portion is equal to 0.5-2 times the hole spacing of the fifth hole, the hole depth of the first concave portion is equal to 0.5-2 times the hole depth of the fifth hole, and the hole diameter of the first concave portion is equal to 0.5-2 times the hole diameter of the fifth hole;

[0035] And / or, a first groove is opened on the negative electrode active material layer, the hole spacing of the first groove is less than or equal to half of the spacing between the first grooves, the hole depth of the first groove is equal to 0.5-2 times the depth of the first groove, and the pore diameter of the first groove is equal to 0.5-1 times the groove width of the first groove.

[0036] In a possible implementation, the positive electrode current collector is an aluminum foil with an elongation ≥ 2% and a tensile strength ≥ 250 MPa.

[0037] On the other hand, the present application provides a battery, including a battery housing and the above-mentioned battery cell, wherein the battery cell is located in the battery housing.

[0038] The cell and battery provided in the present application have a first recess on the edge of the positive electrode sheet in the width direction, and a second recess on the negative electrode sheet, so that the thickness of the positive electrode collector is 4μm-18μm, and the thickness of the negative electrode collector is 2μm-30μm. The first recess provided on the positive electrode can knock out part of the active material, which can improve the CB value of the corresponding position. The pore structure can also store electrolyte, improve the wetting performance of the electrolyte on the electrode sheet, and further improve the edge lithium precipitation; the second recess provided on the negative sheet can increase the lithium insertion speed at the corresponding position, improve the negative electrode dynamics, and then increase the negative electrode surface density, improve the overall energy density of the cell, and alleviate the lithium precipitation problem. In addition, the liquid storage capacity can also be increased. By providing a first recess on the edge of the positive electrode sheet and providing a second recess on the negative electrode sheet, the problem of local lithium precipitation can be alleviated and improved while improving the overall surface density and battery energy density. Furthermore, since the positive electrode current collector and the negative electrode current collector are relatively thick, their strength is relatively high, and the positive electrode sheet or the negative electrode sheet will not break during processing due to the opening of the recess. In addition, the battery cell can be prevented from having corner cracks due to the cyclic expansion stress generated in the later stages of the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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.

[0040] Figure 1 This is one of the structural schematic diagrams of the positive electrode sheet of the battery cell provided in the embodiment of the present application;

[0041] Figure 2 This is a second structural schematic diagram of the positive electrode sheet of the battery cell provided in an embodiment of the present application;

[0042] Figure 3 The third structural schematic diagram of the positive electrode sheet of the battery cell provided in the embodiment of the present application;

[0043] Figure 4 This is a fourth structural schematic diagram of the positive electrode sheet of the battery cell provided in an embodiment of the present application;

[0044] Figure 5 This is a fifth structural schematic diagram of the positive electrode sheet of the battery cell provided in the embodiment of the present application;

[0045] Figure 6 This is the sixth structural schematic diagram of the positive electrode sheet of the battery cell provided in the embodiment of the present application;

[0046] Figure 7 The seventh structural schematic diagram of the positive electrode sheet of the battery cell provided in the embodiment of the present application;

[0047] Figure 8 The eighth structural schematic diagram of the positive electrode sheet of the battery cell provided in the embodiment of the present application;

[0048] Fig. 9 This is one of the structural schematic diagrams of the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0049] Fig.10 This is a second structural schematic diagram of the negative electrode sheet of the battery cell provided in an embodiment of the present application;

[0050] Fig.11 The third structural schematic diagram of the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0051] Fig.12 This is a fourth structural schematic diagram of the negative electrode sheet of the battery cell provided in an embodiment of the present application;

[0052] Fig.13 This is a fifth structural schematic diagram of the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0053] Fig.14 This is the sixth structural schematic diagram of the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0054] Fig.15 The seventh structural schematic diagram of the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0055] Fig.16 The eighth structural schematic diagram of the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0056] Fig.17 This is a ninth structural schematic diagram of the negative electrode sheet of the battery cell provided in an embodiment of the present application;

[0057] Fig.18 This is a tenth structural schematic diagram of the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0058] Fig.19 A schematic diagram of the structure of the negative electrode sheet of the battery cell provided in the embodiment of the present application in the bending area;

[0059] Fig. 20 This is one of the structural schematic diagrams of the holes on the positive electrode sheet and the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0060] Fig.21 This is a second structural schematic diagram of the holes on the positive electrode sheet and the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0061] Fig. 22 A schematic diagram of the structure of the hole on the positive electrode sheet of the battery cell provided in the embodiment of the present application;

[0062] Fig.23 This is one of the structural schematic diagrams of the holes on the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0063] Fig.24 The second structural schematic diagram of the hole on the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0064] Fig.25 This is one of the structural schematic diagrams of the positive electrode sheet and the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0065] Fig.26 This is a second structural schematic diagram of the positive electrode sheet and the negative electrode sheet of the battery cell provided in the embodiment of the present application;

[0066] Fig. 27 Schematic diagram of the structure of the battery cell provided in the embodiment of the present application.

[0067] Description of reference numerals:

[0068] 10-positive electrode sheet; 11-positive electrode current collector; 12-positive electrode active material layer; 121-first recess; 122-first side; 123-second side; 124-positive electrode ear groove; 125-second hole; 126-third hole; 127-fourth hole; 13-positive electrode ear; 20-negative electrode sheet; 21-negative electrode current collector; 22-negative electrode active material layer; 221-second recess; 222-third side; 223-fourth side; 224-fifth hole; 225-first recess; 226-negative electrode ear groove; 23-negative electrode ear; 30-protective tape. DETAILED DESCRIPTION

[0069] 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.

[0070] 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.

[0071] 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.

[0072] The terms "first", "second" and "third" (if any) in the specification and claims of this application and the above drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0073] 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.

[0074] At present, when the electrolyte in the battery core infiltrates into the interior of the active material layer, the electrolyte infiltrates from the side of the active material layer away from the current collector to the side of the active material layer close to the current collector through the gaps between the particles in the active material layer. However, the pole piece is gradually developing in the direction of high compaction and thick electrodes, that is, the thickness of the active material layer on the pole piece is thicker and the compaction degree of the active material layer is higher. At present, thick pole pieces and fast-charging batteries have the problem that the electrolyte is difficult to completely infiltrate the active material layer of the pole piece and lithium precipitation, which affects the cycle performance and safety of the battery.

[0075] Although there is a way in the prior art to set up a special rolling equipment and laser cleaning technology to set up a channel area on the negative electrode sheet, which can improve the dynamics of the negative electrode, thereby improving the negative electrode surface density, improving the overall energy density of the battery cell, and solving the problem of surface lithium deposition. However, before or after the negative electrode surface density is improved, the lithium deposition problem on the negative electrode sheet is not always a problem of lithium deposition on the entire surface. Most of them are local lithium deposition problems, such as edge lithium deposition, arc lithium deposition, and ear lithium deposition, etc. The most serious problem is the lithium deposition problem on the edge of the negative electrode.

[0076] After repeated thinking and verification, the inventor found that if several first recesses are opened at the edge of the positive electrode sheet, and several second recesses are set in the existing negative electrode sheet, so that the thickness of the positive electrode collector is 4μm-18μm, the thickness of the negative electrode collector is 2μm-30μm, and the negative electrode collector is a copper foil with an elongation rate of ≥3% and a tensile strength of ≥400Mpa, the recess set at the edge of the positive electrode sheet can knock out part of the active material, improve the CB (Cell Balance) value of the corresponding position, and store electrolyte, improve the wetting performance of the electrolyte on the electrode sheet, and further improve the edge lithium precipitation; the second recess opened on the negative electrode sheet can increase the lithium insertion speed at the corresponding position, improve the negative electrode dynamics, and then increase the negative electrode surface density, improve the overall energy density of the battery cell, and alleviate the lithium precipitation problem, and also increase the liquid storage capacity. By opening the first recess on the edge of the positive electrode sheet and opening the second recess on the negative electrode sheet, the local lithium precipitation problem can be alleviated and improved while improving the overall surface density and battery energy density. Furthermore, since the positive electrode collector and the negative electrode collector are thicker, their strength is higher, and the positive electrode sheet or the negative electrode sheet will not break during processing due to the opening of the recess. The battery cell can also be prevented from cracking at the corners due to the cyclic expansion stress generated in the later stages of the cycle.

[0077] The content of the utility model will be described in detail below with reference to the accompanying drawings so that those skilled in the art can understand the content of the utility model more clearly and in detail.

[0078] Reference Figure 1-Figure 27 As shown, the battery cell provided in the embodiment of the present application includes a positive electrode sheet 10 and a negative electrode sheet 20. The positive electrode sheet 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 located on at least one side of the surface of the positive electrode current collector 11. The edge of the positive electrode sheet 10 in the width direction, the positive electrode active material layer 12 contains a plurality of first recesses 121. The negative electrode sheet 20 includes a negative electrode current collector 21 and a negative electrode active material layer 22 located on at least one side of the surface of the negative electrode current collector 21. The negative electrode active material layer 22 contains a plurality of second recesses 221.

[0079] Several means that there may be one, two, three or more. Therefore, several first recesses 121 means that there may be one, two, three or more first recesses 121; several second recesses 221 means that there may be one, two, three or more second recesses 221.

[0080] The battery cell provided in this embodiment is a winding core, wherein the positive electrode sheet 10, the separator, and the negative electrode sheet 20 are stacked together and then wound along the length direction of the electrode sheet with a partial area on one side of the length direction of the negative electrode sheet 20 as the center.

[0081] In a possible implementation, the battery cell may also be a laminate, where the positive electrode sheet 10 , the separator, and the negative electrode sheet 20 are cut to a certain width and then stacked in sequence.

[0082] The separator is used to prevent a contact short circuit between the positive electrode sheet 10 and the negative electrode sheet 20 .

[0083] In order to improve the strength of the positive electrode sheet 10 and the negative electrode sheet 20, and avoid the problem of the positive electrode sheet 10 or the negative electrode sheet 20 being broken due to the opening of the first recess 121 or the second recess 221, and the problem of the corner of the battery cell being cracked during the cycle, the thickness of the positive electrode collector 11 is set to 4μm-18μm, and the thickness of the negative electrode collector 21 is set to 2μm-30μm.

[0084] The paste is directly applied on the current collector, that is, an active material layer is formed on the current collector, and the obtained pole piece is not prone to the problem of pole piece breakage during normal production and use. However, since recesses are formed on the positive electrode sheet 10 and the negative electrode sheet 20, a punching process is required, and the recesses opened will be formed on the active material layer or even on the current collector. The deeper the recesses opened, the smaller the spacing between the recesses, causing greater damage to the active material layer and even the current collector. In the subsequent processing, due to the force of the processing tools, cracks are likely to appear at the opening of the recesses, causing the problem of pole piece breakage. In addition, in the later stage of the cycle, due to the expansion phenomenon, the battery cell will generate corresponding cyclic expansion stress, which will cause tensile stress on the negative current collector 21 and the positive current collector 11, and the corners of the battery cell will crack and break, that is, the problem of corner cracks.

[0085] By using thicker positive electrode current collector 11 and negative electrode current collector 21, the structural strength is higher, which can increase the maximum bearing capacity of the electrode during processing, prevent the positive electrode 10 or the negative electrode 20 from breaking during processing, and resist the expansion stress during the cycle process to prevent the problem of battery cell corner cracking.

[0086] For example, aluminum foil may be used as the positive electrode current collector 11 , and copper foil may be used as the negative electrode current collector 21 .

[0087] Preferably, the positive electrode current collector 11 in the embodiment of the present application can be an aluminum foil with an elongation ≥2% and a tensile strength ≥250Mpa, which can reduce the probability of the positive electrode sheet 10 breaking during the manufacturing process and the charge and discharge cycle of the battery, and can prevent the positive electrode sheet 10 from cracking at the corners during the cycle.

[0088] Preferably, the negative electrode current collector 21 in the embodiment of the present application can be a copper foil with an elongation ≥3% and a tensile strength ≥400Mpa, which can reduce the probability of the negative electrode sheet 20 breaking during the manufacturing process and the charge and discharge cycle of the battery, and can prevent the negative electrode sheet 20 from cracking at the corners during the cycle.

[0089] During the use of the battery cell, the lithium insertion and removal on the negative electrode sheet 20 are repeated, so the active material layer will expand repeatedly during the cycle. In the late cycle of the battery cell, due to the expansion phenomenon, corresponding cyclic expansion stress will be generated, and tensile stress will be applied to the negative electrode collector 21 and the positive electrode collector 11, resulting in cracks and damage at the corners of the battery cell, i.e., corner cracks.

[0090] By using the positive electrode current collector 11 and the negative electrode current collector 21 with large elongation and tensile strength, the tensile strength is high, which can resist the expansion stress during the cycle, prevent the corner cracks of the battery cell, and prevent the positive electrode sheet 10 or the negative electrode sheet 20 from breaking during the processing; the current collector with strong ductility can prevent cracks from appearing at the opening of the recess, and also prevent the positive electrode sheet 10 or the negative electrode sheet 20 from breaking during the processing.

[0091] Exemplarily, one of the positive electrode active material layers 12 has a first surface 122 facing away from the positive electrode current collector 11 , and the other positive electrode active material layer 12 has a second surface 123 facing away from the positive electrode current collector 11 .

[0092] A plurality of first recesses 121 are disposed on the first surface 122 and / or the second surface 123 .

[0093] The first recess 121 includes a first hole and / or a groove. The first hole is opened along the thickness direction of the positive electrode sheet 10 , and the groove can be opened along the length direction or the width direction of the positive electrode sheet 10 .

[0094] Preferably, the first recess 121 is a first hole, which enables the electrolyte to pass through the positive electrode sheet 10, thereby improving the flow of the electrolyte and enhancing the wetting ability of the electrolyte on the electrode sheet.

[0095] The present embodiment does not limit the number and number of rows of the first recesses 121, and those skilled in the art can set them as needed. Schematically, the first recesses 121 can be arranged in one row, two rows, etc. extending along the length direction of the positive electrode sheet 10. The first recesses 121 can be cylindrical holes, conical holes, prismatic holes, etc., and the first recesses 121 can be formed on the positive electrode sheet 10 by laser drilling.

[0096] like Figure 1 and Fig. 9 As shown, direction A is the length direction of the positive electrode sheet 10, and direction B is the width direction of the positive electrode sheet 10. Direction C is the length direction of the negative electrode sheet 20, and direction D is the width direction of the negative electrode sheet 20. The top and bottom of the positive electrode sheet 10 and the negative electrode sheet 20 are the two sides in direction B and direction D. In this application, the side of the positive electrode sheet 10 where the positive electrode ear 13 is provided is the top of the positive electrode sheet 10, and the other side is the bottom of the positive electrode sheet 10, and the side of the negative electrode sheet 20 where the negative electrode ear 23 is provided is the top of the negative electrode sheet 20, and the other side is the bottom of the negative electrode sheet 20.

[0097] It can be understood that after the positive electrode sheet 10 and the negative electrode sheet 20 are wound to form a battery cell, the battery cell includes a straight area and a bending area connected thereto. Among them, the length direction A of the positive electrode sheet 10 is the direction in which the positive electrode sheet 10 is wound. The length direction C of the negative electrode sheet 20 is the direction in which the negative electrode sheet 20 is wound. After the battery cell is formed, in the straight area, the number of layers corresponding to the positive electrode sheet 10 and the negative electrode sheet 20 is the number of folds.

[0098] In the present application, one side of the negative electrode sheet 20 in the length direction is recorded as the head of the negative electrode sheet 20, and the other side of the negative electrode sheet 20 in the length direction is recorded as the tail of the negative electrode sheet 20. The negative electrode sheet 20 is wound from the head to the tail along the length direction. In the battery cell, the head of the negative electrode sheet 20 is located at the center of the winding core, and the straight area of ​​the head is the first fold of the negative electrode sheet 20.

[0099] The positive electrode sheet 10 and the negative electrode sheet 20 are stacked, and the area of ​​the positive electrode sheet 10 corresponding to the first fold of the negative electrode sheet 20 is the first fold of the positive electrode sheet 10, and along the length direction of the positive electrode sheet 10, the first fold of the positive electrode sheet 10 is located at the head of the positive electrode sheet 10, which is the first straight area of ​​the positive electrode sheet 10.

[0100] like Figure 1 , Figure 2 and Figure 3 As shown, illustratively, a plurality of first recesses 121 are continuously arranged along the top edge and / or the bottom edge of the positive electrode active material layer 12 , that is, continuously arranged on one side edge or both side edges in the width direction B of the positive electrode sheet 10 .

[0101] Illustratively, a plurality of first recesses 121 may also be arranged at intervals along the top edge and / or the bottom edge of the positive electrode active material layer 12 , that is, at intervals along one side edge or both side edges in the width direction B of the positive electrode sheet 10 .

[0102] Among them, for battery cells with severe edge lithium deposition, the first recess 121 can be continuously set on the top edge and / or the bottom edge; if the edge lithium deposition only occurs on a part of the fold of the battery cell, the first recess 121 can be set for a part of the fold of the positive electrode sheet 10, that is, it can be set at intervals.

[0103] In one possible implementation, along the width direction of the positive electrode sheet 10, the width of the positive electrode sheet 10 is W, the overall width of the first recess 121 at the ear end is W1, and the overall width of the first recess 121 at the bottom end is W2, wherein W1 and W2 satisfy: W1≤0.5W, W2≤0.5W.

[0104] Preferably, W1 is in the range of 1 mm-30 mm, and W2 is in the range of 1 mm-30 mm. The overall width of the first recess 121 in the width direction of the positive electrode sheet 10 ensures the wetting performance of the electrolyte and the structural strength of the positive electrode current collector 11 .

[0105] The first recesses 121 provided at both side edges of the positive electrode sheet 10 can knock out part of the positive electrode active material at the corresponding position, thereby improving the CB value at the corresponding position. The pore structure can also store electrolyte, improve the wetting performance of the electrolyte on the electrode sheet, and further improve the lithium precipitation problem at the edges of both sides. Limiting the range of the first recesses 121 provided at both side edges of the positive electrode sheet 10 can prevent excessive damage to the positive electrode sheet 10 due to too many first recesses 121, thereby preventing the electrode sheet from breaking. It can also prevent the problem of capacity loss and battery energy density being affected due to too much knocking out of the positive electrode active material.

[0106] The overall width of the first recess 121 in the width direction of the positive electrode sheet 10 may be 1 mm, 5 mm, 10 mm, 20 mm or 30 mm, etc., which is not limited here.

[0107] When the overall width of the first recess 121 is less than 1 mm, the number and size of the first recess 121 are small, and the first recess 121 has a small effect on improving the wetting of the electrolyte into the positive electrode active material layer 12; when the overall width of the first recess 121 is greater than 30 mm, the positive electrode active material layer 12 loses more active material at the position of the first recess 121, affecting the energy density of the battery.

[0108] The overall width of the first recess 121 on the positive electrode sheet 10 needs to ensure the energy density of the battery while ensuring the improvement effect of the first recess 121 on the infiltration of the electrolyte into the positive electrode active material layer 12 .

[0109] like Figure 1 As shown, the positive electrode sheet 10 further includes a positive electrode ear 13. A positive electrode ear groove 124 is provided on the positive electrode active material layer 12, the bottom wall of the positive electrode ear groove 124 is the positive electrode collector 11, and the surrounding side is the positive electrode active material layer 12. The positive electrode ear 13 is provided in the positive electrode ear groove 124 and is electrically connected to the positive electrode collector 11.

[0110] like Figure 4 As shown, in a possible implementation, along the length direction of the positive electrode sheet 10 , the positive electrode ear groove 124 is located at the Nth fold of the positive electrode sheet 10 , and the first recess 121 is disposed between the N−4 fold and the N+4 fold of the positive electrode sheet 10 .

[0111] Since the current density at the positive electrode ear 13 is high, it is easy to cause lithium deposition at the edge of the adjacent area. Therefore, a first recess 121 is provided at the edge of several straight areas adjacent to the straight area welded to the positive electrode ear 13 to alleviate the lithium deposition at the edge caused by the high current density at the ear.

[0112] like Figure 5 and Figure 6As shown, the positive electrode active material layer 12 includes a plurality of second holes 125 on the bending area.

[0113] The second hole 125 is provided in the bending area of ​​the positive electrode sheet 10 to knock out part of the active material and improve the CB value at the bending area. The hole structure can also store electrolyte, improve the wetting performance of the electrolyte on the electrode sheet, and further improve the arc lithium deposition problem.

[0114] The second hole 125 is disposed in a bending area of ​​a part of the folds or in a bending area of ​​the entire folds.

[0115] The second hole 125 is disposed on the first surface 122 and / or the second surface 123 .

[0116] In one possible implementation, the thickness of the battery cell is a, and along the length direction of the positive electrode sheet 10, the overall width of the second hole 125 in any bending zone is b. Starting from the head of the positive electrode sheet 10, that is, the starting direction of winding, b in the bending zone gradually increases, and b satisfies: 0.1a≤b<2a.

[0117] Since starting from the starting position, as the battery cell is wound, the width of the bending zone gradually increases, and therefore the corresponding b also gradually increases, thereby improving the wetting performance of the electrolyte on the electrode in the corresponding bending zone and improving the arc lithium deposition problem.

[0118] like Figure 7 As shown, a plurality of third holes 126 are also provided on the positive active material layer 12 along the middle of the width direction of the positive electrode sheet 10. Along the length direction of the positive electrode sheet 10, the third holes 126 are provided simultaneously with the first recesses 121, so that the positive electrode sheet 10 is provided with holes on the entire surface or on a part of the surface in the winding direction. Wherein, along the width direction of the positive electrode sheet 10, the width of the positive electrode sheet is W, the width of the first recess area at the bottom is W1, the width of the first recess area at the top is W2, and the width of the third hole area in the middle is W3, W3 = W-W1-W2;

[0119] Among them, W1 and W2 satisfy: the range of W1 is 3mm-25mm; the range of W2 is 3mm-25mm.

[0120] For thick electrode, high energy density battery cells, since the electrode sheet is thick (the thickness of the single-sided positive electrode active material layer 12 is ≥ 40μm), the wettability of the electrolyte is poor. By setting channels on the entire surface of the positive electrode sheet 10 while increasing the surface density, the wetting effect of the electrolyte can be increased to prevent lithium deposition on the entire surface.

[0121] Preferably, the hole depth of the first recessed portion 121 is greater than or equal to the hole depth of the third hole 126 , and the spacing between the first recessed portions 121 is less than or equal to the spacing between the third holes 126 .

[0122] For the edge region, the first recesses 121 are deep and the spacing between the first recesses 121 is small, which means that more active materials are removed from the edge region than from the middle region. Therefore, the CB value of the edge region is higher than that of the middle region, which can effectively improve edge lithium deposition.

[0123] The hole depth of the first recess 121 is deeper than that of the third hole 126. Therefore, under the condition of the same hole diameter, the positive electrode active material knocked out at the first recess 121 (edge ​​area) is more than the positive electrode active material knocked out at the third hole 126 (middle area); the spacing between the first recesses 121 is smaller than the spacing between the third holes 126, which is equivalent to that the holes in the edge area are denser. Under the condition of the same hole diameter and hole depth, more positive electrode active materials are knocked out in the edge area; thus, more active materials are knocked out in the edge area than in the middle area. Therefore, compared with the middle area, the negative electrode corresponding to the edge area has a high lithium insertion ability and a higher CB value. At the same time, the edge area can store more electrolyte, which improves the wetting performance of the electrolyte to the edge area of ​​the electrode piece, and can effectively improve the problem of lithium precipitation at the edge.

[0124] Exemplarily, one negative electrode active material layer 22 has a third surface 222 facing away from the negative electrode current collector 21, and the other negative electrode active material layer 22 has a fourth surface 223 facing away from the negative electrode current collector 21. The area on the negative electrode sheet 20 where both the third surface 222 and the fourth surface 223 exist is recorded as the double-sided area of ​​the negative electrode sheet 20.

[0125] In a possible implementation, along the length direction of the negative electrode sheet 20, that is, along the direction C, the negative electrode sheet 20 has only the third surface 222 in the straight area of ​​the winding head, and does not have the fourth surface 223, that is, at the head of the negative electrode sheet 20, the negative electrode sheet 20 only includes one negative electrode active material layer 22, which is recorded as the single-sided area of ​​the negative electrode sheet 20. In the area of ​​the positive electrode sheet 10 corresponding to the single-sided area of ​​the negative electrode sheet 20 (the first fold of the negative electrode sheet 20 corresponds to the first fold, the second fold and the bending area between the first and second folds of the positive electrode sheet 10), the positive electrode sheet 10 is provided with channels on the entire surface, that is, the first recess 121 and the third hole 126 are adjacent to the straight area and the bending area of ​​the first fold and the second fold of the positive electrode sheet 10.

[0126] Preferably, along the winding direction, the straight area and the bent area of ​​the first and second folds of the positive electrode sheet 10 are provided with channels on the entire surface of the positive electrode sheet 10, and the channels extend to the straight area of ​​the third fold. The length extending to the third fold is 0.1-0.5 times the length of the straight area of ​​the third fold.

[0127] In a possible implementation, the surface densities of the positive electrode active material layer 12 on the first surface 122 and the second surface 123 are different, and the thicknesses of the coating paste are different.

[0128] The first concave portion 121, the second hole 125 or the third hole 126 is arranged at the edge, the bending area or the middle of the side with thicker paste thickness; and / or at the edge, the bending area or the middle of the side with thinner paste thickness. Figures 1 to 7 .

[0129] Setting the positive and negative sides with different paste thicknesses is used to alleviate the arc lithium deposition phenomenon. Opening the positive electrode on the basis of the positive and negative sides can further alleviate the arc lithium deposition and avoid the problem of surface lithium deposition on the side with thicker paste thickness.

[0130] like Figure 8 As shown, the battery cell further includes a protective adhesive tape 30 disposed on the positive electrode sheet 10 . A plurality of fourth holes 127 are formed on the positive electrode active material layer 12 , and the plurality of fourth holes 127 are arranged along the edge of the protective adhesive tape 30 .

[0131] The protective tape 30 includes a positive electrode ear protective tape provided on the positive electrode sheet 10 and covering the position of the positive electrode ear 13, a negative electrode protective tape provided on the positive electrode sheet 10 and corresponding to the position of the negative electrode ear, and a finishing tape provided on the positive electrode collector 11 and connected to the edge of the positive electrode active material layer 12, that is, along the length direction of the positive electrode sheet 10, the tail of the positive electrode sheet 10, the edge of the positive electrode active material layer 12 and the exposed position of the positive electrode collector 11 are provided with the finishing tape.

[0132] The fourth hole 127 is disposed at the edge of the corresponding adhesive tape to alleviate the lithium deposition problem at the corresponding tab position, the end, and the edge of the adhesive tape.

[0133] like Figures 9 to 19 As shown, the second recess 221 includes a plurality of fifth holes 224 and / or a plurality of first grooves 225. The second recess 221 is provided on the third surface 222 and / or the fourth surface 223. The fifth hole 224 is opened along the thickness direction of the negative electrode sheet 20. The first groove 225 extends along the width direction of the negative electrode sheet 20, that is, extends along the direction D.

[0134] like Fig. 9 As shown, in a possible implementation, the fifth hole 224 is arranged on the entire surface or on a part of the folded surface of the negative electrode active material layer 22 along the winding direction.

[0135] like Fig.10 As shown, in a possible implementation, the first groove 225 is arranged on the entire surface or on a part of the folded surface of the negative electrode active material layer 22 along the winding direction.

[0136] By providing the fifth hole 224 or the first groove 225 on the entire surface or a part of the folded surface of the negative electrode sheet 20, the surface density and the negative electrode dynamics of the negative electrode can be improved, the lithium plating of the negative electrode can be alleviated, and the liquid storage capacity can be increased.

[0137] Preferably, the second recess 221 is the first groove 225, which can be opened by a laser, and the first groove 225 can be opened continuously, thereby improving the flow of the electrolyte, enhancing the wetting ability of the electrolyte to the electrode, alleviating the lithium plating of the negative electrode, and increasing the liquid storage capacity.

[0138] like Fig.11 As shown, in a possible implementation, the width of the negative electrode sheet 20 is X, and along the width direction of the negative electrode sheet 20, the width of the fifth hole 224 and / or the first groove 225 at the top of the negative electrode sheet 20 is X1, and the width of the fifth hole 224 and / or the first groove 225 at the bottom of the negative electrode sheet 20 is X2, wherein X1 and X2 satisfy: X1+X2≤X, and along the width direction of the negative electrode sheet 20, the center direction of the fifth hole 224 or the first groove 225 at the top is equal to the width of the fifth hole 224 or the first groove 225 at the bottom. The center directions are offset or partially parallel. The offset means that along the width direction of the negative electrode sheet 20, after the fifth hole 224 or the first groove 225 at the top is extended, there is no overlapping part between the two. The partially parallel means that along the width direction of the negative electrode sheet 20, after the fifth hole 224 or the first groove 225 at the top is extended, there is a certain overlapping part between the fifth hole 224 or the first groove 225 at the bottom after the extension, but it is not a complete overlap.

[0139] When the area of ​​the laser action is smaller than the area of ​​the pole piece, only one laser head can be set at the top and bottom of the pole piece respectively to work, so that the sum of the width of the top second recess 221 and the width of the bottom second recess 221 is less than or equal to the width of the pole piece, and the top and bottom second recesses 221 are misaligned or partially parallel to each other.

[0140] like Fig.12 and Fig.13 As shown, the negative electrode sheet 20 also includes an area where only the negative electrode current collector 21 exists in the straight area of ​​the winding head, which is located on one side of the length direction of the negative electrode sheet 20, and is recorded as an empty foil area, that is, the negative electrode sheet 20 includes an empty foil area, a single-sided area, and a double-sided area along the length direction. In order to avoid the negative electrode sheet 20 from breaking, if the negative electrode active material layer 22 is provided with a first groove 225, the negative electrode active material layer 22 is not provided with the first groove 225 in the range of 1mm-5mm at the junction with the exposed negative electrode current collector 21 on one side of the single-sided area and the double-sided area along the length direction.

[0141] If the fifth hole 224 is provided on the negative electrode active material layer 22 , all positions of the negative electrode sheet 20 can be opened.

[0142] The negative electrode sheet 20 further includes a negative electrode tab 23. A negative electrode tab groove 226 is provided on the negative electrode active material layer 22, the bottom wall of the negative electrode tab groove 226 is the negative electrode current collector 21, and the surrounding side is the negative electrode active material layer 22. The negative electrode tab 23 is provided in the negative electrode tab groove 226 and is electrically connected to the negative electrode current collector 21.

[0143] In a possible implementation, along the length direction of the negative electrode sheet 20 , the negative electrode ear groove 226 is located at the Nth fold of the negative electrode sheet 20 , and the second recess 221 is disposed between the N−4 fold and the N+4 fold of the negative electrode sheet 20 .

[0144] Along the width direction of the negative electrode sheet 20 , the width of the negative electrode ear groove 226 is Y1 , and the overall width of the second recess 221 at the electrode ear end is Z1 , wherein Z1 satisfies: W1 ≤ Y1 + 10 mm.

[0145] The second recess 221 is formed at the tab of the negative electrode sheet 20 , and the first recess 121 is formed at the upper edge of the positive electrode 10 , which can effectively alleviate the problem of lithium deposition at the negative tab 23 and the edge of the negative tab 23 .

[0146] like Fig.14 and Fig.15 As shown, in a possible implementation, the second recess 221 is disposed in the middle of the negative electrode sheet 20 in the width direction.

[0147] Along the width direction of the negative electrode sheet 20, the width of the negative electrode sheet 20 is X, the width of the bottom area without the second recess 221 is X3, the width of the top area without the second recess 221 is X4, and the width of the center second recess 221 area is X5, X5=X-X3-X4.

[0148] Among them, X3 and X4 satisfy: the range of X3 is 5mm-30mm; the range of X4 is 5mm-30mm.

[0149] For thick electrode cells, since the electrode sheets are thick and the electrolyte wetting performance is poor, a second recess 221 is provided in the middle of the negative electrode sheet 20 to improve the wetting effect of the electrolyte in the middle of the negative electrode sheet 20. In addition, by providing a first recess 121 at the edge of the positive electrode sheet 10, the problems of edge lithium deposition and surface lithium deposition can be appropriately reduced.

[0150] like Fig.16 and Fig.17 As shown, in a possible implementation, the second recess 221 may also be provided at an edge of the negative electrode sheet 20 in the width direction.

[0151] like Fig.18 As shown, in a possible implementation, the second recess 221 is disposed on the negative electrode active material layer 22 in the bending area.

[0152] The second recess 221 is provided in the bending area of ​​the negative electrode sheet 20, and the second hole 125 is provided on the positive electrode sheet 10, so that the local CB value at the bending area can be improved. The hole structure can also store electrolyte, improve the wetting performance of the electrolyte on the electrode sheet, and alleviate arc lithium deposition.

[0153] In a possible implementation, the thickness of the battery cell is a, and along the length direction of the negative electrode sheet 20, the overall width of the second recess 221 in any bending area is c, where c satisfies: 0.1a≤c<2a.

[0154] like Fig.19 As shown, in a possible implementation, the second recess 221 of the bending zone is arranged on the convex part of the bending zone, that is, on the third surface 222, the thickness of the battery cell is a, and the overall width c of the second recess 221 satisfies: 0.1a≤c<2a; the thickness of the negative electrode active material layer 22 is h1, the thickness of the negative electrode current collector 21 is h2, and the pore depth h of the second recess 221 satisfies: h1+h2≤h≤2h1+h2.

[0155] The arc lithium deposition problem can be solved by providing a semi-through hole or a through hole with a hole depth exceeding half of the depth on the convex part of the arc region of the negative electrode sheet 20 .

[0156] In a possible implementation, the surface density of the negative electrode active material layer 22 on the third surface 222 and the fourth surface 223 are different, and the thickness of the coating paste is different.

[0157] Exemplarily, the negative electrode active material layer 22 located on one side of the negative electrode current collector 21 is the first layer, that is, the negative electrode active material layer 22 where the third surface 222 is located, and the negative electrode active material layer 22 located on the other side of the negative electrode current collector 21 is the second layer, that is, the negative electrode active material layer 22 where the fourth surface 223 is located, and the thickness of the first layer is greater than the thickness of the second layer. The first layer is provided with a second recess 221, or the first layer and the second layer are provided with a second recess 221.

[0158] When the second recesses 221 are provided on both the first layer and the second layer, the hole depth of the second recesses 221 on the first layer is greater than or equal to the hole depth of the second recesses 221 on the second layer, and the spacing between the second recesses 221 on the first layer is less than or equal to the spacing between the second recesses 221 on the second layer.

[0159] Exemplarily, the first recess 121, the second hole 125, the third hole 126 and the fourth hole 127 on the positive electrode sheet 10 and the fifth hole 224 and the first groove 225 on the negative electrode sheet 20 are all composed of multiple matrices, and the number of matrices = (corresponding electrode segment length-normal area length) / single matrix width, wherein the normal area length is the length of the non-pore-making area on the electrode sheet.

[0160] Since both the second surface 123 and the fourth surface 223 have relatively large single-surface areas, preferably, the number of matrices on the first surface 122 is ≥ the number of matrices on the second surface 123 , and the number of matrices on the third surface 222 is ≥ the number of matrices on the fourth surface 223 .

[0161] A single matrix contains at least one hole or groove, and the distance between two adjacent matrices is 0-2 mm.

[0162] Since the active area of ​​the laser is smaller than the length of the pole piece, multiple lasers can be set up for drilling and grooving operations. The size of the laser is the size of the corresponding matrix. By setting the spacing between the lasers, the drilling speed is increased and the operation efficiency is improved.

[0163] The present embodiment does not limit the shapes of the first concave portion 121, the second hole 125, the third hole 126, the fourth hole 127, the fifth hole 224 and the first groove 225, and those skilled in the art can set them as needed. Schematically, the first concave portion 121, the second hole 125, the third hole 126, the fourth hole 127, and the fifth hole 224 can be the same and can be formed by drilling with the same laser.

[0164] like Fig. 20 and Fig.21 As shown, the opening forms of the first recess 121, the second hole 125, the third hole 126, the fourth hole 127, the fifth hole 224 and the first groove 225 are exemplarily cited, and the first recess 121 is shown in the figure.

[0165] In the direction perpendicular to the positive electrode current collector 11 , the projections of the first recess 121 , the second hole 125 , the third hole 126 , and the fourth hole 127 on the first surface 122 are offset from or partially correspond to the projections of the first recess 121 , the second hole 125 , the third hole 126 , and the fourth hole 127 on the second surface 123 .

[0166] In a direction perpendicular to the negative electrode current collector 21 , the projection of the fifth hole 224 and the first groove 225 on the third surface 222 and the projection of the fifth hole 224 and the first groove 225 on the fourth surface 223 are offset from or partially correspond to each other.

[0167] The staggered holes can improve the toughness of the corresponding pole pieces and avoid the problem of belt breakage.

[0168] like Fig. 22As shown, in a possible implementation, the depth of the first recess 121, the second hole 125, the third hole 126, the fourth hole 127, and the fifth hole 224 is h3, the thickness of the positive electrode collector 11 is M, and the spacing between the first recess 121, the second hole 125, the third hole 126, the fourth hole 127, and the fifth hole 224 on the positive electrode active material layer 12 is L1, wherein L1 satisfies L1≥h3+M.

[0169] like Fig.23 As shown, the depth of the fifth hole 224 and / or the first groove 225 is h4, the thickness of the negative electrode current collector 21 is N, and the spacing between the fifth holes 224 and / or the first grooves 225 on the negative electrode active material layer 22 is L2, wherein L2 satisfies L2≥h4+N.

[0170] When the spacing and depth between the holes on the positive electrode sheet 10 and the negative electrode sheet and the thickness of the corresponding current collector meet the above relationship, the electrode sheet breakage and the corner cracking problem during the cycle process can be effectively avoided.

[0171] like Fig.24 As shown, in a possible implementation, the thickness of the negative electrode current collector 21 is N, the thickness of the negative electrode active material layer 22 is P, the depth of the fifth hole 224 is h5, satisfying: 5μm≤h5≤2P+N; the depth of the first groove 225 is h6, satisfying: 5μm≤h6≤P.

[0172] Since the opening area of ​​the first groove 225 is larger than that of the fifth hole 224 , the depth of the first groove 225 is sufficient to expose the negative electrode current collector 21 , thereby preventing the electrode sheet from being broken.

[0173] In a possible implementation, the first recess 121 is formed at the edge of the positive active material layer 12 of the positive electrode sheet 10, and the fifth hole 224 is formed on the entire surface of the negative active material layer 22 of the negative electrode sheet 20. The hole spacing of the first recess 121 is equal to 0.5-2 times the hole spacing of the fifth hole 224, the hole depth of the first recess 121 is equal to 0.5-2 times the hole depth of the fifth hole 224, and the hole diameter of the first recess 121 is equal to 0.5-2 times the hole diameter of the fifth hole 224.

[0174] like Fig.25 As shown, in a possible implementation, a first recess 121 is provided at the edge of the positive active material layer 12 of the positive electrode sheet 10, and a first groove 225 is provided on the entire surface of the negative active material layer 22 of the negative electrode sheet 20. The hole spacing of the first recess 121 is less than or equal to half of the groove spacing of the first groove 225, the hole depth of the first recess 121 is equal to 0.5-2 times the depth of the first groove 225, and the hole diameter of the first recess 121 is equal to 0.5-1 times the groove width of the first groove 225.

[0175] like Fig.26 As shown, in a possible implementation, the positive active material layer 12 of the positive electrode sheet 10 has a first recess 121 at its edge, and the positive active material layer 12 has a second hole 125 at its bending area. The negative active material layer 22 of the negative electrode sheet 20 has a first groove 225 on its entire surface.

[0176] like Fig. 27 , which is a schematic diagram of the structure of the battery cell provided in the embodiment of the present application. Direction E is the thickness direction of the battery cell.

[0177] After the positive electrode sheet 10, the separator, and the negative electrode sheet 20 are stacked together, the positive electrode sheet 10, the separator, and the negative electrode sheet 20 are wound along the length direction of the electrode sheet with a portion of the area on one side of the length direction of the negative electrode sheet 20 as the center to form a battery cell. The battery cell includes a straight area ( Fig. 27 The middle position of the battery cell) and the bending area connected to it ( Fig. 27 The left and right ends of the battery cell).

[0178] Preferably, the first groove 225 is not provided on the convex portion of the arc region of the negative electrode sheet 20 , that is, on the third surface 222 of the bending region.

[0179] The first groove 225 is not provided in the arc region of the negative electrode sheet 20, so that the negative electrode sheet 20 can be prevented from losing powder when being wound, thereby avoiding lithium deposition in the arc region and improving the cycle performance of the battery.

[0180] The present application also provides a battery, comprising a battery housing and the above-mentioned battery cell, wherein the battery cell is located in the battery housing.

[0181] The battery provided in the present application adopts the above-mentioned battery cell. By opening a first recess on the edge of the positive electrode sheet and opening a second recess on the negative electrode sheet, it is possible to alleviate and improve the problem of local lithium plating while improving the overall surface density and battery energy density. The electrolyte can more easily infiltrate the active material layer of the electrode sheet, and the battery's rate, storage, and cycle performance can be guaranteed.

[0182] 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 cell, characterized in that: Including positive and negative electrodes. The positive electrode sheet comprises a positive electrode current collector, a positive electrode active material layer located on at least one side of the surface of the positive electrode current collector, and a positive electrode ear, wherein the positive electrode ear is electrically connected to the positive electrode current collector, the thickness of the positive electrode current collector is 4 μm-18 μm, and the edge of the positive electrode sheet in the width direction and the positive electrode active material layer contain a plurality of first recesses; The negative electrode sheet comprises a negative electrode current collector, a negative electrode active material layer located on at least one side of the surface of the negative electrode current collector, and a negative electrode ear, wherein the negative electrode ear is electrically connected to the negative electrode current collector, the thickness of the negative electrode current collector is 2 μm-30 μm, and the negative electrode active material layer comprises a plurality of second recesses; The negative electrode current collector is a copper foil with an elongation of ≥3% and a tensile strength of ≥400Mpa.

2. The battery cell according to claim 1, characterized in that: The first concave portion includes a plurality of first holes, and the second concave portion includes a plurality of first grooves, wherein the plurality of first holes are arranged along the length direction of the positive electrode sheet, and the first grooves extend along the width direction of the negative electrode sheet; And / or, the battery cell comprises a straight region and a bent region, and the positive electrode active material layer comprises a plurality of second holes in the bent region.

3. The battery cell according to claim 1, characterized in that: The battery cell includes a straight area and a bending area, the positive electrode active material layer contains a plurality of second holes in the bending area, the thickness of the battery cell is a, and along the length direction of the positive electrode sheet, the overall width of the second holes in the bending area is b, and along the length direction of the positive electrode sheet, b in the bending area gradually increases, and b satisfies: 0.1a≤b<2a.

4. The battery cell according to claim 1, characterized in that: At one side edge of the positive electrode sheet in the width direction, a plurality of the first recesses are arranged continuously or at intervals along the length direction of the positive electrode sheet; and / or At the other side edge of the positive electrode sheet in the width direction, a plurality of the first recesses are arranged continuously or at intervals along the length direction of the positive electrode sheet.

5. The battery cell according to claim 1, characterized in that: A plurality of third holes are provided on the positive electrode active material layer in the middle of the width direction of the positive electrode sheet. The width of the positive electrode sheet is W along the width direction of the positive electrode sheet. The width of the first recessed area provided on one side of the width direction of the positive electrode sheet is W1, the width of the first recessed area provided on the other side of the width direction of the positive electrode sheet is W2, and the width of the third hole area provided in the middle is W3; Among them, W1 and W2 satisfy: the range of W1 is 3mm-25mm; the range of W2 is 3mm-25mm.

6. The battery cell according to claim 5, characterized in that: The hole depth of the first recess is greater than or equal to the hole depth of the third hole, and the spacing between the first recesses is less than or equal to the spacing between the third holes; And / or, in a partial area along one side of the negative electrode sheet in the length direction, only one side of the surface of the negative electrode collector contains the negative electrode active material layer, and in the positive electrode sheet area corresponding to the partial area, the first recess and the third hole are adjacent.

7. The battery cell according to claim 1, characterized in that: The battery cell also includes protective tape, which includes a positive electrode ear protection glue arranged on the positive electrode sheet and covering the positive electrode ear position; and / or a negative electrode protection glue arranged on the positive electrode sheet and corresponding to the negative electrode ear position; and / or a finishing glue arranged on the positive electrode collector and connected to the edge of the positive electrode active material layer, and a plurality of fourth holes are opened on the positive electrode active material layer, and the plurality of fourth holes are arranged along the edge of the protective tape.

8. The battery cell according to claim 1, characterized in that: The width of the negative electrode sheet is X, and along the width direction of the negative electrode sheet, the width of the second recessed portion at the top of the negative electrode sheet is X1, and the width of the second recessed portion at the bottom of the negative electrode sheet is X2, wherein X1 and X2 satisfy: X1+X2≤X, and along the width direction of the negative electrode sheet, the second recessed portion at the top and the second recessed portion at the bottom are mutually offset or partially parallel; And / or, the second recess is provided in the middle of the negative electrode sheet in the width direction, along the width direction of the negative electrode sheet, the width of the negative electrode sheet is X, the width of the bottom area without the second recess is X3, the width of the top area without the second recess is X4, the width of the middle area of ​​the second recess is X5, X5 = X-X3-X4; Among them, X3 and X4 satisfy: the range of X3 is 5mm-30mm; the range of X4 is 5mm-30mm.

9. The battery cell according to claim 1, characterized in that: Both sides of the negative electrode current collector surface contain a layer of the negative electrode active material layer. The second recess is provided on the thicker negative electrode active material layer, or The pore depth of the second recess on the thicker negative electrode active material layer is greater than or equal to the pore depth of the second recess on the thinner negative electrode active material layer, and the spacing between the second recesses on the thicker negative electrode active material layer is less than or equal to the spacing between the second recesses on the thinner negative electrode active material layer.

10. The battery cell according to claim 1, characterized in that: In a direction perpendicular to the positive electrode current collector, projections of the first recesses on the two positive electrode active material layers are mutually offset or partially correspond to each other; and / or In a direction perpendicular to the negative electrode current collector, projections of the second recesses on the two negative electrode active material layers are mutually offset or partially correspond to each other; and / or The depth of the first recess is h3, the thickness of the positive electrode current collector is M, and the distance between the first recesses on the positive electrode active material layer is L1, wherein L1 satisfies L1≥h3+M; and / or The depth of the second recess is h4, the thickness of the negative electrode current collector is N, and the distance between the second recesses on the negative electrode active material layer is L2, wherein L2 satisfies L2≥h4+N.

11. The battery cell according to claim 1, characterized in that: The second recess includes a plurality of fifth holes and / or a plurality of first grooves, the fifth holes are opened along the thickness direction of the negative electrode sheet, the first grooves extend along the width direction of the negative electrode sheet, the thickness of the negative electrode current collector is N, and the thickness of the negative electrode active material layer is P; The depth of the fifth hole is h5, which satisfies: 5 μm ≤ h5 ≤ 2P + N; The depth of the first groove is h6, which satisfies: 5 μm≤h6≤P.

12. The battery cell according to claim 1, characterized in that: The second recess includes a plurality of fifth holes and / or a plurality of first grooves, the fifth holes are opened along the thickness direction of the negative electrode sheet, and the first grooves extend along the width direction of the negative electrode sheet; The negative electrode active material layer is provided with the fifth hole, the hole spacing of the first concave portion is equal to 0.5-2 times the hole spacing of the fifth hole, the hole depth of the first concave portion is equal to 0.5-2 times the hole depth of the fifth hole, and the pore diameter of the first concave portion is equal to 0.5-2 times the pore diameter of the fifth hole; And / or, the negative electrode active material layer is provided with the first groove, the hole spacing of the first groove is less than or equal to half of the spacing between the first grooves, the hole depth of the first groove is equal to 0.5-2 times the depth of the first groove, and the aperture of the first groove is equal to 0.5-1 times the groove width of the first groove.

13. The battery cell according to claim 1, characterized in that: The positive electrode current collector is an aluminum foil with an elongation of ≥2% and a tensile strength of ≥250Mpa.

14. A battery, characterized in that: The invention comprises a battery casing and a battery cell as claimed in any one of claims 1 to 13, wherein the battery cell is located in the battery casing.

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