Battery

Abstract

The utility model provides a battery which comprises a positive plate and a negative plate, and the positive plate comprises a positive current collector and a positive active material layer arranged on at least one side of the positive current collector; the negative plate comprises a negative current collector and a negative active material layer arranged on at least one side of the negative current collector; at least one side of the positive plate is provided with at least one convex part, and at least one surface, far away from the negative current collector, of the negative active material layer is provided with at least one concave part, so that the problems of deformation and wrinkling of a battery cell after charging caused by volume expansion of an electrode material are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and particularly relates to a battery. Background Art

[0002] At present, lithium-ion batteries are widely used not only in portable electronic devices such as mobile phones and laptop computers, but also in electric devices such as electric vehicles and electric bicycles. Among them, the battery cell is the core component of the lithium-ion battery, and the battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0003] After the battery cell is lithiated, it will produce a certain degree of volume expansion. However, for the battery cells in the related art, the gap between the positive electrode sheet and the negative electrode sheet cannot accommodate the volume expansion of the electrode material, so that the battery cell is prone to deformation problems after charging, affecting the normal use of the battery cell. Summary of the Utility Model

[0004] In view of this, the embodiments of the present utility model are committed to providing a battery to improve the problem that the battery cell is deformed after charging due to the volume expansion of the electrode material.

[0005] The present utility model provides a battery, which includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector; the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector;

[0006] At least one side of the positive electrode sheet has at least one protrusion, and at least one surface of the negative active material layer far from the negative current collector has at least one recess.

[0007] Optionally, the positive electrode sheet has opposite first and second sides in the thickness direction. The first side has a plurality of recesses, and in the first direction, the recess directions of two adjacent recesses are the same;

[0008] The protrusion protruding in the direction away from the first side is formed at a position corresponding to the recess on the second side.

[0009] Optionally, the positive electrode sheet and the negative electrode sheet are stacked and wound to form a core. In the direction from the winding start end to the winding end of the positive electrode sheet, the positive electrode sheet sequentially includes a double-sided area and a single-sided area; the single-sided area is an area where the positive active material layer is disposed on one side of the positive current collector, and the double-sided area is an area where the positive active material layers are disposed on both sides of the positive current collector;

[0010] The recessed portion is provided on at least part of the double-sided area, and / or the side of the single-sided area coated with the positive electrode active material layer corresponds to the first side, and the recessed portion is provided on at least part of the single-sided area.

[0011] Optionally, the positive electrode sheet includes a flat area and a bent area;

[0012] The recessed portion is provided in the flat area and / or the bent area.

[0013] Optionally, the positive electrode sheet includes a positive electrode tab, a tab groove is provided on the second side, the positive electrode tab is located in the tab groove, and the positive electrode active material layer is provided at a position corresponding to the tab groove on the first side;

[0014] The recessed portion is provided at least at a position corresponding to the tab groove on the first side.

[0015] Optionally, both the edge area and the middle area of the first side have the recessed portion, and the recessed depth of the recessed portion in the edge area in the second direction is less than the recessed depth of the recessed portion in the middle area in the second direction.

[0016] Optionally, in the second direction, the recessed depth range of the recessed portion is 0.5 μm to 500 μm;

[0017] and / or, in the second direction, the protruding height range of the protruding portion is 0.5 μm to 500 μm;

[0018] and / or, in the second direction, the relationship between the recessed depth of the recessed portion and the protruding height of the protruding portion satisfies:

[0019] h≥H, and 0 μm≤h - H≤10 μm;

[0020] wherein, h is the recessed depth of the recessed portion, and H is the protruding height of the protruding portion;

[0021] and / or, in the first direction, the distance between two adjacent recessed portions is 500 μm to 5000 μm;

[0022] and / or, in the second direction, the relationship between the recessed depth of the recessed portion and the total thickness of the electrode sheet satisfies:

[0023] h = 0.1Z to 2Z; wherein, h is the recessed depth of the recessed portion, and Z is the total thickness of the electrode sheet.

[0024] Optionally, h = 0.2Z to 1.5Z.

[0025] Optionally, the size of the recess in the thickness direction of the negative electrode active material layer is smaller than the thickness of the negative electrode active material layer.

[0026] Optionally, there are a plurality of the recesses, and the plurality of recesses are arranged in sequence and are parallel to each other along a first direction;

[0027] And / or, in the second direction, the depth of the recess is 1 μm to 100 μm;

[0028] And / or, in the first direction, the width of the recess is 10 μm to 500 μm;

[0029] And / or, there are a plurality of the recesses, and in the first direction, the distance between two adjacent recesses is 1 μm to 5000 μm.

[0030] Optionally, in the second direction, the depth of the recess is 10 μm to 50 μm;

[0031] And / or, in the first direction, the width of the recess is 10 μm to 300 μm;

[0032] And / or, there are a plurality of the recesses, and in the first direction, the distance between two adjacent recesses is 100 μm to 2000 μm.

[0033] Optionally, in the first direction, the size of the end of the recess far from the negative electrode current collector is not less than the size of the end of the recess close to the negative electrode current collector;

[0034] And / or, in the first direction, the size of the end of the recess far from the negative electrode current collector is 2 μm to 5000 μm;

[0035] And / or, in the first direction, the size of the end of the recess close to the negative electrode current collector is 1 μm to 5000 μm;

[0036] And / or, there are a plurality of the recesses, and in the first direction, the distance between two adjacent recesses is 10 μm to 1000 μm.

[0037] Optionally, there are a plurality of the recesses, and in the first direction, the distance between two adjacent recesses is 50 μm to 400 μm.

[0038] The battery provided by the present utility model has at least one convex portion on at least one side of the positive electrode sheet, and at least one concave portion on at least one side of the negative electrode active material layer of the negative electrode sheet away from the negative electrode current collector, thereby increasing the gap between the positive electrode sheet and the negative electrode sheet. When the electrode material expands in volume, the increased gap can effectively accommodate the volume expansion of the electrode material, thereby improving to a certain extent the problems of deformation and wrinkling of the battery cell after charging.

[0039] Moreover, by setting the convex portion and the concave portion, the liquid storage capacity of the positive electrode sheet and the negative electrode sheet and the wettability of the electrolyte are improved, enabling lithium ions to quickly diffuse in the electrolyte, and improving the kinetic performance and cycle performance of the battery. In addition, the presence of the concave portion on the negative electrode sheet can effectively suppress the phenomenon of lithium deposition on the negative electrode. Especially in the negative electrode silicon-doped system, it can effectively suppress the huge volume expansion of the silicon system. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a structural cross-section of the positive electrode sheet according to an embodiment of the present utility model Figure 1 ;

[0041] Figure 2 is a structural cross-section of the positive electrode sheet according to an embodiment of the present utility model Figure 2 ;

[0042] Figure 3 is a schematic structural diagram of a battery cell according to an embodiment of the present utility model, in which a bending area is provided with a concave portion and a convex portion;

[0043] Figure 4 is a schematic structural diagram of a battery cell according to an embodiment of the present utility model, in which a flat area is provided with a concave portion and a convex portion;

[0044] Figure 5 is a schematic structure of the first side and the second side of the positive electrode sheet according to an embodiment of the present utility model Figure 1 ;

[0045] Figure 6 is a schematic structure of the first side and the second side of the positive electrode sheet according to an embodiment of the present utility model Figure 2 ;

[0046] Figure 7 is a schematic structure of the positive electrode sheet and the negative electrode sheet according to an embodiment of the present utility model Figure 1 ;

[0047] Figure 8 is Figure 7 an enlarged view of the structure at I in

[0048] Figure 9 is a schematic structure of the positive electrode sheet and the negative electrode sheet according to an embodiment of the present utility model Figure 2 ;

[0049] Figure 10 This is a schematic structural diagram of the negative electrode sheet according to an embodiment of the present invention.

[0050] Among them, 1 is the positive electrode sheet; 11 is the positive current collector; 12 is the positive active material layer; 101 is the double-sided area; 102 is the single-sided area; 103 is the empty foil area; 104 is the straight area; 105 is the bent area; 13 is the first side; 131 is the recessed part; 14 is the second side; 141 is the protruding part; 15 is the positive electrode tab; 151 is the tab groove; 16 is the positive electrode tab protective glue; 17 is the negative electrode tab protective glue; 2 is the negative electrode sheet; 21 is the negative current collector; 22 is the negative active material layer; 23 is the negative electrode tab; 24 is the concave part; 3 is the end termination glue; 100 is the battery cell. Specific embodiments

[0051] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0052] The battery cell is the core component of a lithium-ion battery. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The battery cell can be formed into a wound battery cell, for example.

[0053] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector. The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the surface of the negative current collector. The capacity of the battery is provided by the electrochemical reaction between the active materials of the positive active material layer and the negative active material layer. The separator is located between the positive electrode sheet and the negative electrode sheet and is used to isolate the positive electrode sheet and the negative electrode sheet from contacting. The battery cell is immersed in the electrolyte and is packaged to obtain a wound battery.

[0054] After the battery cell is lithiated, it will undergo a certain degree of volume expansion. If the gap between the positive electrode sheet and the negative electrode sheet cannot accommodate the volume expansion of the electrode material, this will cause the battery cell to deform and wrinkle after charging, affecting the normal use of the battery cell.

[0055] Based on this, the present invention provides a battery. By making at least one side of the positive electrode sheet have at least one protruding part and making the negative electrode sheet have at least one concave part, through the setting of the concave part and the protruding part, the gap between the positive electrode sheet and the negative electrode sheet is increased, so as to accommodate the volume expansion of the electrode material through this gap, thereby improving the problem of deformation and wrinkling of the battery cell after charging to a certain extent.

[0056] The present invention will be described in detail below with reference to the accompanying drawings through specific embodiments:

[0057] This embodiment provides a battery, which can be used as a power source or an energy storage unit of an electronic device. The electronic device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, a tablet computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, an electric bicycle, etc.).

[0058] Referring to Figures 1 to 10 As shown, the battery provided in this embodiment includes a battery cell 100. The battery can be, for example, a lithium-ion battery. The battery cell 100 can be, for example, a wound battery cell.

[0059] Specifically, the battery cell 100 may include a positive electrode sheet 1, a negative electrode sheet 2, and a separator. The positive electrode sheet 1, the separator, and the negative electrode sheet 2 are stacked in sequence.

[0060] Among them, the positive electrode sheet 1 includes a positive electrode current collector 11 and a positive electrode active material layer 12, and the positive electrode active material layer 12 is disposed on at least one side of the positive electrode current collector 11. The negative electrode sheet 2 includes a negative electrode current collector 21 and a negative electrode active material layer 22, and the negative electrode active material layer 22 is disposed on at least one side of the negative electrode current collector 21.

[0061] Specifically, the positive electrode current collector 11 has opposite sides for coating the positive electrode active material layer 12. In specific implementation, the positive electrode active material layer 12 can be disposed on both sides of the positive electrode current collector 11, or only on one side of the positive electrode current collector 11, which can be specifically set according to actual needs.

[0062] The positive electrode current collector 11 is, for example, aluminum foil, specifically, it can be high-ductility aluminum foil. The material of the positive electrode active material layer 12 can be, for example, a positive electrode active material such as a ternary material or lithium iron phosphate.

[0063] The negative electrode current collector 21 has opposite sides for coating the negative electrode active material layer 22. In specific implementation, the negative electrode active material layer 22 can be disposed on both sides of the negative electrode current collector 21, or only on one side of the negative electrode current collector 21, which can be specifically set according to actual needs.

[0064] The negative electrode current collector 21 can be, for example, copper foil, and the material of the negative electrode active material layer 22 can be, for example, a negative electrode active material such as graphite or silicon-based.

[0065] Among them, at least one side of the positive electrode sheet 1 has at least one protruding portion 141. Exemplarily, referring to Figure 1As shown, at least one protruding portion 141 may be provided on one side of the positive electrode sheet 1. Specifically, the number of protruding portions 141 located on this side of the positive electrode sheet 1 may be one or more. For example, multiple protruding portions 141 are arranged at intervals along the length direction of the positive electrode sheet 1 on one side of the positive electrode sheet 1. Of course, it is also possible that at least one protruding portion 141 is provided on both sides of the positive electrode sheet 1.

[0066] Exemplarily, in specific implementation, the positive electrode sheet 1 can be roll-pressed from one side of the positive electrode sheet 1 by a roller with convex points designed on its surface, so as to form the protruding portion 141 on the opposite side of the positive electrode sheet 1. Of course, the above protruding portion 141 can also be formed by other means.

[0067] In specific implementation, the cross-sectional shape of the protruding portion 141 can be, for example, circular, oval, square and other shapes.

[0068] Due to the existence of the protruding portion 141, the buffer space formed between the protruding portion 141 and the area adjacent to the protruding portion 141 on the positive electrode sheet 1 can accommodate the volume expansion of the electrode material to a certain extent, thereby improving the problems of deformation and wrinkling of the battery cell after charging to a certain extent. Moreover, this buffer space can increase the liquid storage capacity, thereby improving the kinetic performance and cycle performance of the battery. For example, referring to Figure 1 As shown, when there are multiple protruding portions 141, the above buffer space is specifically the space defined between two adjacent protruding portions 141. For another example, when there is one protruding portion 141, the buffer space is specifically the space defined between the protruding portion 141 and the surface of the area adjacent to the protruding portion 141 on the positive electrode sheet 1.

[0069] Wherein, at least one concave portion 24 is provided on at least one surface of the negative electrode active material layer 22 away from the negative electrode current collector 21.

[0070] Exemplarily, for example, when the negative electrode active material layer 22 is provided only on one side of the negative electrode current collector 21, at least one concave portion 24 that is recessed in the direction towards the negative electrode current collector 21 is provided on the surface of the negative electrode active material layer 22 away from the negative electrode current collector 21. For another example, when the negative electrode active material layer 22 is provided on both sides of the negative electrode current collector 21, it is possible to make at least one concave portion 24 that is recessed in the direction towards the negative electrode current collector 21 only on the surface of the negative electrode active material layer 22 located on one side of the negative electrode current collector 21 away from the negative electrode current collector 21, or it is also possible to make at least one concave portion 24 that is recessed in the direction towards the negative electrode current collector 21 on the negative electrode active material layers 22 located on both sides of the negative electrode current collector 21.

[0071] Exemplarily, for example, the recess 24 can be formed on the negative electrode active material layer 22 by means of laser wire bonding or punching. The recess 24 can be formed into a microporous channel structure, for example. By providing the recess 24 on the negative electrode active material layer 22, the presence of the recess 24 can release the expansion space of the electrode sheet, and at the same time increase the liquid storage amount and the wettability of the electrolyte, enabling lithium ions to diffuse rapidly in the electrolyte, thereby improving the kinetic performance and cycling performance of the battery. In addition, such a setting effectively suppresses the lithium deposition phenomenon on the negative electrode. Especially in the negative electrode silicon-doped system, it can effectively suppress the huge volume expansion of the silicon system.

[0072] For the battery provided in this embodiment, by making at least one side of the positive electrode sheet 1 have at least one protrusion 141, and making at least one side of the negative electrode active material layer 22 of the negative electrode sheet 2 away from the negative electrode current collector 21 have at least one recess 24, the gap between the positive electrode sheet 1 and the negative electrode sheet 2 is increased. When the electrode material expands in volume, the increased gap can effectively accommodate the volume expansion of the electrode material, thereby improving to a certain extent the problems of deformation and wrinkling of the battery cell after charging. Moreover, by providing the protrusion 141 and the recess 24, the liquid storage amount of the positive electrode sheet 1 and the negative electrode sheet 2 and the wettability of the electrolyte are improved, enabling lithium ions to diffuse rapidly in the electrolyte, thereby improving the kinetic performance and cycling performance of the battery. In addition, the presence of the recess 24 on the negative electrode sheet 2 can also effectively suppress the lithium deposition phenomenon on the negative electrode. Especially in the negative electrode silicon-doped system, it can effectively suppress the huge volume expansion of the silicon system.

[0073] Continue to refer to Figure 1 and Figure 2 As shown, in some embodiments, the positive electrode sheet 1 has opposite first side 13 and second side 14 in the thickness direction. The first side 13 has a plurality of recessed portions 131, and in the first direction, the recessed directions of two adjacent recessed portions 131 are the same. Refer to Figure 1 As shown, the thickness direction here can specifically be Figure 1 the up and down direction in Figure 1 and the first direction here is

[0074] the left and right direction in

[0075] Exemplarily, the recess 131 can be formed, for example, by the positive current collector 11 and the positive active material layer 12 being recessed in the direction towards the second side 14, and the protrusion 141 is formed at the position corresponding to the recess 131 on the second side 14. In specific implementation, the recess 131 can be formed, for example, by rolling the first side 13 of the electrode sheet with a roller having bumps on its surface. That is, the roller presses a part of the positive active material layer 12 and the positive current collector 11 in the direction towards the second side 14, so that this part of the positive active material layer 12 and the positive current collector 11 protrude in the direction towards the second side 14, thereby forming a recess 131 on the first side 13 and simultaneously forming a protrusion 141 on the second side 14.

[0076] Compared with the solution where only a recess 131 is formed on the first side 13 and the second side 14 remains unchanged (that is, by punching holes on the first side 13 to remove part of the positive active material layer to form the recess), since the material at the protrusion 141 in this embodiment is formed by the protrusion of the material at the original recess 131, such a setting can avoid waste of the material of the positive active material layer 12 and avoid the occurrence of capacity loss.

[0077] Of course, the recess 131 and the protrusion 141 can also be formed by other means.

[0078] Exemplarily, when the positive current collector 11 is coated with the positive active material layer 12 on both sides, at this time, the recess 131 is specifically formed by the positive current collector 11 and the positive active material layers 12 on both sides of the positive current collector 11 being recessed in the direction towards the second side 14. When the positive current collector 11 is coated with the positive active material layer 12 on only one side, at this time, the side coated with the positive active material layer 12 corresponds to the above-mentioned first side 13, and the recess 131 is specifically formed by the positive current collector 11 and the positive active material layer 12 coated on one side of the positive current collector 11 being recessed in the direction towards the second side 14, and the side of the positive current collector 11 not coated with the positive active material layer 12 correspondingly forms a protrusion 141.

[0079] In specific implementation, the recess 131 can be, for example, a pit, a groove, etc., and the protrusion 141 can be, for example, a convex bump. The cross-sectional shape of the recess 131 can be a circular shape, an elliptical shape, a square shape, etc., and the cross-sectional shape of the protrusion 141 can also be a circular shape, an elliptical shape, a square shape, etc.

[0080] In addition, multiple recesses 131 on the electrode sheet can be arranged along the length direction of the positive electrode sheet, or along the width direction of the positive electrode sheet, or arranged in an array manner, an arc manner, etc. Correspondingly, the arrangement manner of the protrusions 141 on the positive electrode sheet changes according to the arrangement manner of the recesses 131. This embodiment does not make a special limitation on this.

[0081] The battery provided by the above embodiments has multiple recesses 131 on the first side 13 of the positive electrode sheet. In the first direction, the recess directions of two adjacent recesses 131 are the same. At the position corresponding to the recess 131 on the second side 14, a protrusion 141 protruding away from the first side 13 is formed. That is to say, the first side 13 of the positive electrode sheet 1 forms the recess 131, and the second side 14 of the positive electrode sheet 1 correspondingly forms the protrusion 141. That is, an uneven texture is formed on the positive electrode sheet 1, thereby increasing the gap between the positive electrode sheet 1 and the negative electrode sheet 2. When the electrode material expands in volume, the increased gap can effectively accommodate the volume expansion of the electrode material, thereby improving the problem of deformation and wrinkling of the battery cell after charging to a certain extent. Moreover, by providing the recess 131 and the protrusion 141, the liquid retention ability of the electrode sheet for the electrolyte is improved, the wetting effect of the electrolyte is improved, and thus the cycle performance of the battery is effectively improved.

[0082] In some embodiments, since the recess 131 can be formed by the positive electrode current collector 11 and the positive electrode active material layer 12 recessing in the direction of the second side 14, and at the same time, a protrusion 141 protruding away from the first side 13 is formed at the position corresponding to the recess 131 on the second side 14 of the electrode sheet. Compared with the solution of only forming a recess on the first side of the positive electrode sheet and not providing a protrusion, since the material at the protrusion 141 in some embodiments can be formed by the material at the original recess 131 protruding towards the second side, such a setting can avoid the situation of battery capacity loss caused by waste of the material of the positive electrode active material layer 12, thereby ensuring the battery capacity to a certain extent.

[0083] Moreover, in some embodiments, by making the recess directions of two adjacent recesses 131 the same, compared with the solution where the recess directions of two adjacent recesses are opposite, such a setting of the present invention can, on the one hand, avoid the situation where the positive electrode sheet 1 extends too much and causes the positive electrode sheet 1 to break during the manufacturing process to a certain extent, and on the other hand, can avoid the situation where the positive electrode sheet 1 is too thick and causes the volume energy density of the battery cell to decrease to a certain extent. That is, while avoiding the breakage of the positive electrode sheet 1, the volume energy density of the battery cell is ensured.

[0084] In addition, since the protrusion 141 can be formed by providing the recess 131 on the positive electrode sheet 1, that is, the compaction of a partial area of the positive electrode sheet 1 is relatively increased, thereby improving the adhesion and structural strength of the active material layer of the positive electrode sheet 1, increasing the peeling force between the positive electrode active material layer 12 and the positive electrode current collector 11 to a certain extent, and thus improving the problems of active material shedding and large expansion of the positive electrode sheet 1 during the cycle process, and improving the stability of the battery cell during cycling and storage.

[0085] Combined with Figures 1 to 4As shown, in some embodiments, the battery cell 100 may specifically be a wound battery cell, that is, the positive electrode sheet 1, the separator, and the negative electrode sheet are stacked and wound from the inside out to form the battery cell 100. In the direction from the winding start end of the positive electrode sheet 1 to the winding end of the electrode sheet (for example Figure 2 in the direction indicated by the dashed arrow in

[0086] It should be noted that the winding start end can be understood as the region where the winding of the positive electrode sheet 1 starts during the winding process of the battery cell 100, that is, the head region, which is located inside the battery cell 100. Correspondingly, the winding end can be understood as the region where the winding of the positive electrode sheet 1 ends. Referring to Figure 3 as shown, the end of the positive electrode sheet 1 is generally connected by the end termination adhesive 3.

[0087] Among them, the double-sided region 101 specifically refers to the region where the positive electrode active material layers 12 are coated on both sides of the positive electrode current collector 11 corresponding to this section of the positive electrode sheet 1. The single-sided region 102 specifically refers to the region where the positive electrode active material layer 12 is coated on only one side of the positive electrode current collector 11 corresponding to this section of the positive electrode sheet 1, and the side of the single-sided region 102 coated with the positive electrode active material layer 12 corresponds to the first side 13 of the positive electrode sheet. The empty foil region 103 specifically refers to the region where the positive electrode active material layer 12 is not coated on the positive electrode current collector 11 corresponding to this section of the positive electrode sheet 1.

[0088] Since in the process of manufacturing the battery cell 100, the single-sided region of the positive electrode sheet is thinner than the double-sided region of the positive electrode sheet, the single-sided region is prone to overvoltage, and overvoltage is likely to cause lithium deposition, resulting in a decrease in battery charge and discharge performance, cycle performance, etc. Based on this, referring to Figure 2 as shown, in some embodiments, at least part of the single-sided region 102 is provided with a recess 131. That is to say, the first active layer of the single-sided region 102 and the positive electrode current collector 11 are recessed in the direction towards the second side 14 of the electrode sheet, a recess 131 is formed on the first side 13 of the single-sided region 102, and a corresponding protrusion 141 is formed on the side where the first active layer is not coated.

[0089] By forming the recess 131 and the protrusion 141 on the positive electrode sheet 1, the specific surface area of the positive electrode sheet 1 is increased, and the lithium ion transmission channel is extended, so that lithium ions will not be transmitted to the negative electrode sheet 2 too quickly, thereby avoiding the situation of excessive lithium ion aggregation on the negative electrode sheet 2 and causing lithium deposition, thus ensuring the charge and discharge and cycle performance of the battery to a certain extent.

[0090] That is to say, by providing the recess 131 on the single-sided region 102 at the winding end of the positive electrode sheet 1, while achieving the alleviation of the volume expansion of the battery cell and improving the problem of deformation of the battery cell 100 after charging, the lithium deposition phenomenon is also improved to a certain extent.

[0091] In some embodiments, with reference to Figure 1 and Figure 6 as shown, at least part of the double-sided area 101 is provided with a recess 131.

[0092] By providing the recess 131 on the first side of the double-sided area 101, a protrusion 141 is formed on the second side of the double-sided area 101, thereby increasing the gap between the positive and negative electrode plates. Through this gap, the volume expansion of the electrode material can be better accommodated, and to a certain extent, the problem of deformation of the battery cell 100 after charging is improved.

[0093] In some embodiments, in combination with Figure 1 and Figure 6 as shown, the recess 131 can also be provided on both the single-sided area 102 and the double-sided area 101, thereby increasing the setting range of the recess 131, further increasing the gap volume, so that the gap can better relieve the volume expansion of the electrode material, and further improving the problems of deformation and wrinkling of the battery cell 100.

[0094] With reference to Figure 3 and Figure 4 as shown, when the battery cell 100 is a wound battery cell, the positive electrode plate 1 specifically includes: a flat area 104 and a bent area 105.

[0095] In specific implementation, the positioning of the specific position of the bent area 105 can be calculated through the design of the number of turns of the core, and the precise positioning of the bent area 105 can be achieved in combination with the existing positioning device.

[0096] In the actual manufacturing process, the bent area is generally subjected to relatively large extrusion during winding, resulting in difficulty in storing the electrolyte. Based on this, continuing to refer to Figure 3, in some embodiments, the recess 131 is provided in the bent area 105 of the positive electrode plate 1. It can be understood that the recess 131 is provided on the first side 13 of the bent area 105 of the positive electrode plate 1 (such as Figure 3 the side of the positive electrode plate 1 facing the winding center in ), correspondingly, a protrusion 141 corresponding to the recess 131 is formed on the second side 14 of the bent area 105.

[0097] By providing the recess 131 and the protrusion 141 in the bent area 105, the width of the core is widened, and the space between the positive electrode plate 1 and the separator is increased, which is beneficial to the storage of the electrolyte, and thus the liquid retention amount in the bent area 105 is increased. While alleviating the problem of volume expansion, the cycle performance of the battery is improved. Moreover, the design of the recess 131 extends the lithium ion transmission channel in the bent area 105, thereby avoiding to a certain extent the situation where lithium ions rapidly aggregate on the negative electrode plate 2 and cause lithium precipitation on the negative electrode plate 2, thereby improving the cycle performance. In addition, such a setting can also release the stress in the bent area 105, further improving the strength and stability of the bent area 105.

[0098] Referring to Figure 4 as shown, in some embodiments, the recess 131 is provided in the flat region 104 of the positive electrode sheet 1. It can be understood that the recess 131 is specifically formed on the first side 13 of the flat region 104 (such as Figure 4 the side of the middle electrode sheet facing the winding center), and correspondingly, a protrusion 141 is formed on the second side 14 of the flat region 104.

[0099] By providing the recess 131 in the flat region 104, the space between the flat region 104 and the opposite negative electrode sheet 2 is increased, which can effectively alleviate the problem of volume expansion of the battery cell 100. Moreover, the concave-convex pattern on the surface of the positive electrode sheet 1 can increase the contact area between the positive electrode sheet 1 and the electrolyte, thereby improving the wettability of the electrolyte and the ion transport rate, improving the rate performance of the battery, and at the same time increasing the liquid retention capacity of the battery cell 100, and further improving the cycle performance of the battery.

[0100] In other embodiments, the recess 131 and the protrusion 141 can also be provided in the flat region 104 and the bent region 105 at the same time to further increase the setting range of the recess 131, so as to better alleviate the problem of volume expansion and further avoid the deformation and wrinkling of the battery cell 100.

[0101] Referring to Figure 5 and Figure 6 as shown, in specific implementation, the positive electrode sheet includes a positive electrode tab 15. In some embodiments, a tab groove 151 for mounting the positive electrode tab 15 is provided on the second side 14 of the positive electrode sheet. In specific implementation, the positive electrode tab 15 can be welded in the tab groove 151 by laser welding. It can be understood that the corresponding positive electrode current collector 11 in the tab groove 151 is exposed, and the positive electrode tab 15 is welded to the positive electrode current collector 11 exposed in the tab groove 151. Of course, the positive electrode tab 15 can also be connected in the tab groove 151 by other means.

[0102] Among them, a positive electrode active material layer 12 is coated at the position of the tab groove 151 corresponding to the first side 13. In specific implementation, during the process of welding the positive electrode tab 15 to the tab groove 151, if the positive electrode active material layer 12 at the position of the tab groove 151 corresponding to the first side 13 is partially damaged due to welding, it will affect the normal migration of lithium ions. Based on this, in some embodiments, a recess 131 is provided at least at the position corresponding to the tab groove 151 on the first side 13 (such as Figure 5 area A in). It can be understood that a protrusion 141 is formed correspondingly on the second side 14.

[0103] By providing a recess 131 at a position corresponding to the tab groove 151 on the first side 13, the gap between the first side 13 and the corresponding negative electrode sheet 2 is increased. The existence of this gap can not only increase the liquid retention capacity of the electrode sheet, thus ensuring the normal transmission of lithium ions and guaranteeing the performance of the battery, but also effectively relieve the volume expansion of the battery cell 100.

[0104] Generally, a tab protection adhesive is provided in the area where the tab is provided on the electrode sheet. For example, referring to Figure 6 As shown, a positive tab protection adhesive 16 is provided at the position corresponding to the positive tab 15 on the first side 13 of the positive electrode sheet and at the position corresponding to the positive tab 15 on the second side 14 of the electrode sheet to protect the positive tab 15, and the provision of the positive tab protection adhesive 16 can prevent short-circuiting between the positive and negative electrodes. In addition, a negative tab protection adhesive 17 is provided at the position on the first side 13 of the positive electrode sheet corresponding to the tab of the opposing negative electrode sheet and at the position on the second side 14 of the positive electrode sheet corresponding to the tab of the opposing negative electrode sheet to protect the tab of the negative electrode sheet, and the negative tab protection adhesive 17 can prevent short-circuiting between the positive and negative electrodes.

[0105] Since the first side 13 of the positive electrode sheet has a recess 131 and the second side 14 of the positive electrode sheet has a protrusion 141, the friction force of the adhesive application area of the positive electrode sheet 1 (such as the positions corresponding to the positive tab protection adhesive 16 and the negative tab protection adhesive 17 in Figure 6 ) becomes larger. That is, compared with a normal electrode sheet, the surface of the positive electrode sheet 1 with a recess 131 and a protrusion 141 is relatively rough, with concave pits on one side and convex points on the other side, and the friction force with the adhesive layer is significantly increased, thus preventing the adhesive layer from peeling off.

[0106] In some embodiments, both the edge region and the middle region of the first side 13 have a recess 131, and the recess depth of the recess 131 in the edge region in the second direction is less than the recess depth of the recess 131 in the middle region in the second direction. The second direction here is, for example, Figure 1 the up-down direction shown, specifically, for example, the thickness direction of the positive electrode sheet 1.

[0107] This setting can ensure the interfacial adhesion between the positive and negative electrodes and the separator, thereby improving the stability of the entire electrode sheet.

[0108] If the recess depth is too large, the protrusion height on the back surface of the positive electrode sheet 1 will also increase, which will cause the active particles at the protruding position to collapse and break during winding, resulting in a low porosity of the electrode sheet, a decrease in the amount of electrolyte absorbed by the electrode sheet, and difficulty for the electrolyte to penetrate into the interior of the electrode sheet. The direct consequence is that the specific capacity of the material is poorly utilized, resulting in a low capacity of the battery, and the liquid retention capacity is poor, leading to poor cycle performance of the battery.

[0109] Based on this, referring to Figure 1 As shown, exemplarily, in the second direction (such asFigure 1 In the up and down direction (in the figure), the depression depth h of the depression portion 131 can be between 0.5 μm and 500 μm. Specifically, for example, it can be 0.5 μm, 1 μm, 10 μm, 50 μm, 100 μm, 200 μm, 250 μm, 300 m, 400 μm, 500 μm. The depression depth h of the depression portion 131 can specifically be Figure 1 the distance between the highest plane of the first side 13 of the electrode tab and the lowest point in the inner cavity of the depression portion 131.

[0110] In some embodiments, exemplarily, in the second direction, the protrusion height H of the protrusion portion 141 can be between 0.5 μm and 500 μm. Specifically, for example, it can be 0.5 μm, 1 μm, 10 μm, 50 μm, 100 μm, 200 μm, 250 μm, 300 m, 400 μm, 500 μm. The protrusion height H of the protrusion portion 141 can specifically be Figure 1 the distance between the highest plane of the second side 14 of the positive electrode tab and the lowest point of the protrusion portion 141.

[0111] Such a setting can, to a certain extent, avoid the situation where the active particles at the protruding position collapse and break, and while achieving the mitigation of volume expansion, it ensures the capacity and cycle performance of the battery.

[0112] Specifically, the depression depth h of the depression portion 131 and the protrusion height H of the protrusion portion 141 can satisfy the following relationship:

[0113] h ≥ H, and 0 μm ≤ h - H ≤ 10 μm;

[0114] Such a setting can further avoid the situation where the protrusion height is too large, resulting in the collapse and breakage of the active particles at the protruding position, leading to low capacity and poor cycle ability of the battery, and also, to a certain extent, avoid the situation where the electrode tab is too thick and affects the volume energy density of the battery cell 100.

[0115] Referring to Figure 1 As shown, the distance P between two adjacent depression portions 131 can be between 500 μm and 5000 μm. For example, it can be 500 μm, 1000 μm, 2000 μm, 2500 μm, 2750 μm, 3000 μm, 4000 μm, 5000 μm. The distance P between two adjacent depression portions 131 here is specifically the distance between the centers of two adjacent depression portions 131.

[0116] In specific implementation, the depression depth and width of each depression portion 131 can be equal or unequal. The distance between two adjacent depression portions 131 can be equal or unequal.

[0117] Taking the formation of the recessed portion 131 and the protruding portion 141 by rolling as an example, if the positive electrode material is commercial lithium cobaltate and the tap density of lithium cobaltate is 4.1 - 4.3 g / cm 3 , after the recessed portion 131 and the protruding portion 141 are formed on the positive electrode sheet 1 of this embodiment, the local maximum compaction of the positive electrode sheet 1 needs to be less than the maximum compaction of lithium cobaltate, which is 4.3 g / cm 3 , to avoid over-pressing the electrode sheet. If the positive electrode material is commercial ternary material and the tap density of the ternary material is 3.4 - 3.7 g / cm 3 , after the recessed portion 131 and the protruding portion 141 are formed on the positive electrode sheet 1 of this embodiment, the local maximum compaction of the positive electrode sheet 1 needs to be less than the maximum compaction of the positive electrode material, which is 3.7 g / cm 3 , to avoid over-pressing the electrode sheet.

[0118] The greater the recess depth h, the greater the compaction of the active material in the recessed area, and Z1 ≤ Z, referring to Figure 1 , where Z1 is the thickness of the electrode sheet at the area with the maximum compaction, that is, the distance between the lowest point of the recessed portion 131 and the lowest point of the protruding portion 141, and Z is the total thickness of the electrode sheet. If over-pressing occurs, the degree of extrusion between the material particles in the over-pressed positive electrode sheet is too large, which will cause the porosity of the positive electrode sheet to be low and the amount of electrolyte absorbed by the electrode sheet to decrease, thereby leading to low capacity of the battery. For a battery with poor liquid retention ability, the polarization is very large during the cycling process, the attenuation is very fast and the internal resistance is relatively large, resulting in a decrease in battery performance.

[0119] Based on this, continuing to refer to Figure 1 shown, in some embodiments, along the second direction ( Figure 1 the up-down direction in

[0120] ), the relationship between the recess depth h of the recessed portion 131 and the total thickness Z of the positive electrode sheet satisfies:

[0121] h = 0.1Z ~ 2Z

[0122] Such a setting can ensure that the recess depth h is not too large, that is, to avoid situations such as low battery capacity and poor cycling performance caused by over-pressing.

[0123] Specifically, the negative electrode sheet 2 further includes a negative electrode tab 23. Specifically, a tab groove can be provided on the negative electrode active material layer 22, and the negative electrode tab 23 can be installed in the tab groove, for example, by welding.

[0124] In some embodiments, the size of the concave portion 24 in the thickness direction of the negative electrode active material layer 22 is smaller than the thickness of the negative electrode active material layer 22. For example, referring to Figure 10 shown, the thickness direction is, for example, Figure 10In the up-down direction, the concave portion 24 is specifically a blind hole, that is, the concave portion 24 does not penetrate through the negative electrode active material layer 22. Such a setting not only increases the liquid storage capacity and the wettability of the electrolyte and releases the expansion space of the battery cell, but also, compared with the solution where the concave portion 24 penetrates through the negative electrode active material layer 22, can avoid the problem of battery capacity attenuation caused by excessive loss of the negative electrode active material layer 22.

[0125] Of course, in other embodiments, the concave portion 24 can also be a through hole, that is, the concave portion 24 penetrates through the negative electrode active material layer 22.

[0126] Among them, the concave portion 24 can be arranged perpendicular to the negative electrode active material layer 22, that is, the axial direction of the concave portion 24 can be consistent with the thickness direction of the negative electrode active material layer 22. Or, the concave portion 24 can also be inclined with respect to the thickness direction of the negative electrode active material layer 22, that is, there is an included angle between the axial direction of the concave portion 24 and the thickness direction of the negative electrode active material layer 22.

[0127] Refer to Figure 7 and Figure 8 As shown, in some embodiments, the above-mentioned concave portion 24 can be specifically formed on the negative electrode sheet 2 by means of laser scribing.

[0128] Specifically, the concave portion 24 can be, for example, a strip-shaped hole. Exemplarily, refer to Figure 7 As shown, the cross-sectional shape of the concave portion 24 in the first direction is strip-shaped. The first direction here is, for example, Figure 7 the left-right direction in

[0129] In some embodiments, refer to Figure 7 As shown, there are multiple concave portions 24, and the multiple concave portions 24 can be arranged in sequence and parallel to each other in the first direction. Exemplarily, each concave portion 24 extends along the Figure 7 up-down direction of

[0130] Of course, in other implementation manners, each of the concave portions 24 can also extend along the Figure 7 left-right direction in

[0131] Exemplarily, in the second direction, the depth of the concave portion 24 can specifically be between 1 μm and 100 μm, and can be, for example, 1 μm, 10 μm, 30 μm, 50 μm, 60 μm, 70 μm, 90 μm, 100 μm. The second direction here can specifically be the thickness direction of the negative electrode sheet 2. The depth of the concave portion 24 can specifically be the dimension of the concave portion 24 in the thickness direction of the negative electrode sheet 2.

[0132] Further, the depth of the recess 24 can be set between 10 μm and 50 μm, so as to avoid, to a certain extent, the situation that the negative electrode active material layer 22 loses too much and causes the reduction of the battery capacity while ensuring the liquid storage capacity and the release of the expansion space.

[0133] Referring to Figure 8 As shown, in some embodiments, in the first direction, the width a of the recess 24 can specifically be between 10 μm and 500 μm, for example, it can specifically be 10 μm, 20 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm. The first direction here can be, for example, Figure 8 the left - right direction in

[0134] Further, the width a of the recess 24 can be set between 10 μm and 300 μm, so as to avoid, to a certain extent, the situation that the negative electrode active material layer 22 loses too much and causes the reduction of the battery capacity while ensuring the liquid storage capacity and the release of the expansion space.

[0135] Among them, continuing to refer to Figure 8 As shown, the distance b between two adjacent recesses 24 can be between 1 μm and 5000 μm, for example, it can be 1 μm, 100 μm, 1000 μm, 2000 μm, 3000 μm, 4000 μm, 5000 μm. The distance b between the two recesses 24 specifically refers to the distance between the centers of the two recesses 24.

[0136] Further, the distance b between two adjacent recesses 24 can be set between 100 μm and 2000 μm.

[0137] Referring to Figure 9 and Figure 10 As shown, in some embodiments, the recess 24 can specifically be formed on the negative electrode active material layer 22 by laser drilling. The cross - section of the recess 24 can be, for example, circular, elliptical and other shapes.

[0138] Referring to Figure 10 As shown, in some embodiments, in the first direction, the dimension E of the end of the recess 24 far from the negative electrode current collector 21 can be not less than the dimension F of the end of the recess 24 close to the negative electrode current collector 21.

[0139] The first direction here can specifically be Figure 10The left - right direction in [description] can be, for example, the length direction of the negative electrode sheet 2. The dimension E of the end of the recess 24 away from the negative electrode current collector 21 can be, for example, the dimension of the end of the recess 24 away from the negative electrode current collector 21 in the left - right direction. The dimension F of the end of the recess 24 close to the negative electrode current collector 21 can be, for example, the dimension of the end of the recess 24 close to the negative electrode current collector 21 in the left - right direction.

[0140] In the direction from top to bottom along Figure 10 in [description], for example, the dimension E of the top end of the recess 24 can be made larger than the dimension F of the bottom end of the recess 24, so that the recess 24 is formed into a tapered hole with a larger top and a smaller bottom.

[0141] For example, when the cross - sectional shape of the recess 24 is circular, the dimension E of the end of the recess 24 away from the negative electrode current collector 21 is specifically the aperture of the end of the recess 24 away from the negative electrode current collector 21, and the dimension F of the end of the recess 24 close to the negative electrode current collector 21 is specifically the aperture of the end of the recess 24 close to the negative electrode current collector 21.

[0142] Such a setting improves the wettability and liquid retention capacity of the electrolyte, and at the same time, makes the negative electrode sheet 2 not easily collapse during the winding or hot - pressing process of the electrode sheet, thereby improving the structural stability of the negative electrode sheet 2 and the battery cell 100.

[0143] Exemplarily, specifically, the dimension E of the end of the recess 24 away from the negative electrode current collector 21 can be between 2μm and 5000μm, such as 2μm, 100μm, 1000μm, 2000μm, 3000μm, 4000μm, 5000μm. Specifically, the dimension F of the end of the recess 24 close to the negative electrode current collector 21 can be between 1μm and 5000μm, such as 1μm, 100μm, 1000μm, 2000μm, 3000μm, 4000μm, 5000μm.

[0144] Exemplarily, the recess 24 is specifically multiple. In the first direction, the distance C between two adjacent recesses 24 can be between 10μm and 1000μm, such as 10μm, 20μm, 100μm, 300μm, 500μm, 700μm, 800μm, 900μm, 1000μm. The first direction here is, for example, Figure 10 the left - right direction in [description], specifically, it can be the length direction of the negative electrode sheet 2. The distance C between the two recesses 24 here specifically refers to the center - to - center distance between the two recesses 24.

[0145] Further, the distance C between two adjacent recesses 24 can be set between 50μm and 400μm.

[0146] The embodiments of the present application will be further described below in conjunction with the experimental results.

[0147] Example 1

[0148] 1) Preparation of the positive electrode sheet

[0149] Lithium cobalt oxide, a conductive agent (a mixture of conductive carbon black and carbon nanotubes), and polyvinylidene fluoride PVDF are placed in N-methylpyrrolidone NMP according to a mass ratio of 98.20:1.00:0.80, and stirred evenly to obtain a positive electrode paste.

[0150] The positive electrode paste is evenly coated on both the front and back sides of the aluminum foil, and after drying, rolling, slitting, cleaning, and sheet making in sequence, a positive electrode sheet is obtained.

[0151] 2) Preparation of the negative electrode sheet

[0152] Graphite, Si, conductive carbon black, a binder, and carboxymethyl cellulose CMC are placed in deionized water according to a mass ratio of 93:7:0.05:2.4:0.35, and stirred evenly to obtain a negative electrode paste.

[0153] The negative electrode paste is evenly coated on the negative electrode current collector, and is subjected to drying, rolling, and slitting treatments in sequence.

[0154] Laser scribing is performed on the main body area of the slit negative electrode sheet to form recesses 24 on the negative electrode active material layer 22 of the negative electrode sheet. Here, the distance b between the recesses 24 is set to 1 mm as shown, for example. Figure 8 as shown is set to 1 mm.

[0155] Among them, the power of the laser scribing can be set to 30% of the normal power.

[0156] The negative electrode sheet after laser scribing is washed and made into a sheet to obtain a negative electrode sheet.

[0157] 3) Preparation of the battery

[0158] For example, the separator uses a 7-μm-thick base material + ceramic + coated separator.

[0159] The electrolyte includes a lithium salt LiPF6 and a solvent. The solvent includes ethylene carbonate EC, diethyl carbonate DEC, and ethyl methyl carbonate EMC, and the molar ratio of the three is DEC:EC:EMC = 1:1:1.

[0160] After the above-mentioned slit positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, an embossing roller is added on the running path of the positive electrode sheet of the winding machine to perform embossing treatment on the positive electrode sheet, so as to form a recess 131 on the first side 13 of the positive electrode sheet and a corresponding protrusion 141 on the second side 14 of the positive electrode sheet.

[0161] Specifically, the pressure can be adjusted by a cylinder to control the depression depth and protrusion height of the electrode sheet.

[0162] Then, it is wound into a wound-type structure of the battery cell 100. After the battery cell 100 is encapsulated, injected with electrolyte, formed, and secondarily sealed, a lithium-ion battery is obtained.

[0163] Example 2

[0164] The positive electrode sheet is provided with a recessed portion 131 and a protruding portion 141, and no laser scribing is performed on the negative electrode sheet.

[0165] The rest is the same as in Example 1.

[0166] Example 3

[0167] The positive electrode sheet is provided with a recessed portion 131 and a protruding portion 141, and the negative electrode sheet is laser drilled.

[0168] 2) Preparation of the negative electrode sheet

[0169] Graphite, Si, conductive carbon black, binder, and carboxymethyl cellulose CMC are placed in deionized water according to a mass ratio of 93:7:0.05:2.4:0.35, and stirred evenly to obtain a negative electrode slurry.

[0170] The negative electrode slurry is evenly coated on the negative electrode current collector, and is successively subjected to drying, rolling, and slitting treatments.

[0171] Laser drilling is performed in the main body area of the slit negative electrode sheet, and drilling is performed within 4 ± 0.5 mm from the edge of the negative electrode main body area. Here, the distance C between the concave portions 24 and the concave portions 24 is set to 200 μm as shown. Among them, the power of the laser drilling can be set to 30% of the normal power. Figure 10 As shown, it is set to 200 μm. Among them, the power of the laser drilling can be set to 30% of the normal power.

[0172] The laser-drilled negative electrode sheet is obtained after cleaning and sheet making.

[0173] The rest is the same as in Example 1.

[0174] Comparative example

[0175] The positive electrode sheet is not provided with a recessed portion 131 and a protruding portion 141, and the negative electrode sheet is not provided with a concave portion 24 (i.e., no laser scribing or laser drilling is performed).

[0176] The rest is the same as in Example 1.

[0177] Table 1

[0178]

[0179] Among them, the wrinkling ratio of the bare battery cell is obtained by disassembling the newly charged battery cell.

[0180] The interfacial lithium plating ratio is determined by disassembling the battery cells after the same number of cycles (such as 300 cycles) and counting the ratio of the battery cells with lithium plating.

[0181] The cycle life at 25 °C is the number of cycles after the battery cell capacity decays to 85% of the initial capacity.

[0182] The thickness expansion rate of the battery = (the fully charged thickness of the battery after N cycles - the thickness of the battery sample) / the thickness of the battery sample * 100%. Here, N is 800 for example. The thickness expansion rate after 800 cycles is the thickness expansion rate of the battery cell at 25 °C after 800 cycles.

[0183] From the results in Table 1, it can be seen that for the battery provided by the embodiment of the present invention, by forming a concave portion 131 on the first side 13 of the positive electrode plate and forming a convex portion 141 on the second side 14 while forming the concave portion 131, and punching / wiring on the surface of the negative electrode plate 2 to form a concave portion 24, the deformation and wrinkling ratios of the battery cell 100 after charging are significantly reduced, and the thickness expansion rate is significantly reduced, thus effectively alleviating the problem of deformation and wrinkling of the battery cell after charging caused by the volume expansion of the electrode material. Moreover, the lithium plating phenomenon is significantly improved, and in Embodiment 1 and Embodiment 3, after punching / wiring on the negative electrode plate 2 to form a concave portion 24, the lithium plating ratio is further reduced. In addition, the peeling force of the active material layer corresponding to Embodiment 1 to Embodiment 3 is significantly increased, and the cycle life of the battery is significantly improved.

[0184] In this article, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, or an indirect connection through an intermediate medium, which can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances. In addition, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application.

[0185] In this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or apparatus comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or apparatus. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

[0186] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A battery, characterized in that, It includes a positive electrode sheet (1) and a negative electrode sheet (2). The positive electrode sheet (1) includes a positive electrode current collector (11) and a positive electrode active material layer (12) provided on at least one side of the positive electrode current collector (11); the negative electrode sheet (2) includes a negative electrode current collector (21) and a negative electrode active material layer (22) provided on at least one side of the negative electrode current collector (21). At least one side of the positive electrode sheet (1) has at least one protrusion (141), and at least one surface of the negative electrode active material layer (22) away from the negative electrode current collector (21) has at least one recess (24).

2. The battery according to claim 1, wherein The positive electrode sheet (1) has opposite first side (13) and second side (14) in the thickness direction. The first side (13) has a plurality of recesses (131), and in the first direction, the recess directions of two adjacent recesses (131) are the same; At a position corresponding to the recess (131) on the second side (14), the protrusion (141) protruding in a direction away from the first side (13) is formed.

3. The battery according to claim 2, characterized in that, The positive electrode sheet (1) and the negative electrode sheet (2) are stacked and wound to form a core. In the direction from the winding start end to the winding end of the positive electrode sheet (1), the positive electrode sheet (1) sequentially includes a double-sided area (101) and a single-sided area (102). The single-sided area (102) is an area where the positive electrode active material layer (12) is provided on one side of the positive electrode current collector (11), and the double-sided area (101) is an area where the positive electrode active material layer (12) is provided on both sides of the positive electrode current collector (11); At least part of the double-sided area (101) is provided with the recess (131), and / or the side of the single-sided area (102) coated with the positive electrode active material layer (12) corresponds to the first side (13), and at least part of the single-sided area (102) is provided with the recess (131).

4. The battery according to claim 2, wherein The positive electrode sheet (1) includes a flat area (104) and a bent area (105); The recess (131) is provided in the flat area (104) and / or the bent area (105).

5. The battery according to claim 2, characterized in that, The positive electrode sheet (1) includes a positive electrode tab (15). A tab groove (151) is provided on the second side (14). The positive electrode tab (15) is located in the tab groove (151), and the positive electrode active material layer (12) is provided at a position on the first side (13) corresponding to the tab groove (151); At least a position on the first side (13) corresponding to the tab groove (151) is provided with the recess (131).

6. The battery according to claim 2, wherein, Both the edge area and the middle area of the first side (13) have the recess (131), and the recess depth of the recess (131) in the edge area in the second direction is less than the recess depth of the recess (131) in the middle area in the second direction.

7. The battery according to any one of claims 2 to 6, characterized in that, In the second direction, the recess depth range of the recess (131) is 0.5 μm to 500 μm; And / or, in the second direction, the protruding height of the protruding portion (141) ranges from 0.5 μm to 500 μm; And / or, in the second direction, the depression depth of the recessed portion (131) and the protruding height of the protruding portion (141) satisfy: h≥H, and 0 μm≤h - H≤10 μm; wherein, h is the depression depth of the recessed portion (131), and H is the protruding height of the protruding portion (141); And / or, in the first direction, the distance between two adjacent recessed portions (131) is 500 μm to 5000 μm; And / or, in the second direction, the relationship between the depression depth of the recessed portion (131) and the total thickness of the positive electrode sheet (1) satisfies: h = 0.1Z to 2Z; wherein, h is the depression depth of the recessed portion (131), and Z is the total thickness of the positive electrode sheet (1).

8. The battery according to claim 7, wherein In the second direction, the relationship between the depression depth of the recessed portion (131) and the total thickness of the positive electrode sheet (1) satisfies: h = 0.2Z to 1.5Z; wherein, h is the depression depth of the recessed portion (131), and Z is the total thickness of the positive electrode sheet (1).

9. The battery according to any one of claims 1 to 6, characterized in that, The size of the concave portion (24) in the thickness direction of the negative electrode active material layer (22) is smaller than the thickness of the negative electrode active material layer (22).

10. The battery according to any one of claims 1 to 6, characterized in that, There are multiple concave portions (24), and the multiple concave portions (24) are arranged in sequence and are parallel to each other in the first direction; And / or, in the second direction, the depth of the concave portion (24) is 1 μm to 100 μm; And / or, in the first direction, the width of the concave portion (24) is 10 μm to 500 μm; And / or, there are multiple concave portions (24), and in the first direction, the distance between two adjacent concave portions (24) is 1 μm to 5000 μm.

11. The battery according to claim 10, wherein, In the second direction, the depth of the concave portion (24) is 10 μm to 50 μm; And / or, in the first direction, the width of the concave portion (24) is 10 μm to 300 μm; And / or, there are multiple concave portions (24), and in the first direction, the distance between two adjacent concave portions (24) is 100 μm to 2000 μm.

12. The battery according to any one of claims 1 to 6, characterized in that, In the first direction, the size of the end of the concave portion (24) far from the negative electrode current collector (21) is not less than the size of the end of the concave portion (24) close to the negative electrode current collector (21); And / or, in the first direction, the size of the end of the concave portion (24) far from the negative electrode current collector (21) is 2 μm to 5000 μm; And / or, in the first direction, the size of the end of the concave portion (24) close to the negative electrode current collector (21) is 1 μm to 5000 μm; And / or, there are multiple concave portions (24), and in the first direction, the distance between two adjacent concave portions (24) is 10 μm to 1000 μm.

13. The battery according to claim 12, characterized in that, There are multiple concave portions (24), and in the first direction, the distance between two adjacent concave portions (24) is 50 μm to 400 μm.

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