Winding battery cell
By setting localized depressions at the bending points of the positive and negative electrode sheets in the wound cell, the lithium plating problem caused by poor electrolyte wettability is solved, thereby improving battery performance and lifespan.
Patent Information
- Application Number
- CN202520263029.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-19
- Publication Date
- 2025-11-28
- Estimated Expiration
- 2035-02-19
AI Technical Summary
The reduced gap between the positive and negative electrode plates in the arc region of the wound battery cell leads to poor electrolyte wettability, resulting in lithium plating and affecting battery performance and lifespan.
Local depressions are created at the bends of the positive and negative electrodes to increase electrolyte storage space and improve fluidity. These depressions are formed by molding or etching.
It improves the storage and flow of electrolyte in the arc region, reduces lithium plating, and enhances battery performance and lifespan.
Smart Images
Figure CN223612462U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the technical field of lithium ion battery, especially relates to a winding electric core. BACKGROUND
[0002] Lithium ion battery is a new type of chemical power supply with high energy density, high power density and long life, and is widely used in electric vehicles, mobile communication, portable electronic equipment and other fields. Winding electric core is a common form of lithium ion battery electrode assembly, which is made by winding the positive plate, negative plate and isolation film together by winding machine, and the adjacent positive and negative plates are separated by the isolation film. Winding electric core has the advantages of compact structure, low cost and high production efficiency, but also has the problem of lithium precipitation at the corner.
[0003] Lithium precipitation refers to the phenomenon that part of lithium ions cannot be embedded in the negative electrode material during charging of lithium ion battery, and metal lithium is formed on the surface of the negative electrode. The positive and negative plates in the arc area of the winding electric core are extruded, which causes the gap between the positive and negative plates to become smaller, resulting in poor wettability or flowability of the electrolyte in the arc area, affecting the embedding of lithium ions, and thus lithium precipitation occurs. Lithium precipitation phenomenon will cause the performance of the battery to decline, the cycle life to be shortened, etc. Therefore, how to effectively avoid lithium precipitation in the arc area of the winding electric core has become a technical problem to be solved by the technical personnel in the field. UTILITY MODEL CONTENTS
[0004] In order to solve the problems and deficiencies in the prior art, the utility model provides a winding electric core, which comprises a positive plate, a negative plate and a separator, the positive plate comprises a positive current collector and a positive active material layer located on both sides of the positive current collector in the thickness direction, and the negative plate comprises a negative current collector and a negative active material layer located on both sides of the negative current collector in the thickness direction.
[0005] The positive plate and the negative plate are wound to form an arc area and a straight area, the positive plate comprises a plurality of first bending parts located in the arc area, and the negative plate comprises a plurality of second bending parts located in the arc area.
[0006] The positive active material layer of the first bending part has a plurality of first local recesses on the side away from the positive current collector;
[0007] The negative active material layer of the second bending part has a plurality of second local recesses on the side away from the negative current collector.
[0008] Optionally, the first local recess is a die pressing recess; and / or,
[0009] The second local recess is a die pressing recess.
[0010] Optionally, the first local recess is a thinning recess, and the surface density of the positive active material layer on each region of the first bending part is uniform; and / or,
[0011] The second local recess is a thinning recess, and the surface density of the negative active material layer on each region of the second bending part is uniform.
[0012] Optionally, the sum of the volumes of the plurality of first local recesses on the first bending part is greater than the sum of the volumes of the plurality of second local recesses on the adjacent second bending part.
[0013] Optionally, the width-thickness ratio of the wound battery cell is not greater than 10:1.
[0014] Optionally, the first local recess is a first spherical cap-shaped recess; and / or,
[0015] The second local recess is a second spherical cap-shaped recess.
[0016] Optionally, along the length direction of the positive electrode sheet, the spacing between two adjacent first spherical cap-shaped recesses is 3mm-5mm; and along the width direction of the positive electrode sheet, the spacing between two adjacent first spherical cap-shaped recesses is 2mm-4mm.
[0017] Optionally, the bottom surface radius of the first spherical cap-shaped recess is 0.5mm-1.5mm, and the height of the first spherical cap-shaped recess is 10%-30% of the thickness of the electrode sheet.
[0018] Optionally, the first local recess is a first groove, the depth of the first groove is a first depth, and the distance between two adjacent first grooves is a first pitch; and / or,
[0019] The first local recess is a second groove, the depth of the second groove is a second depth, and the distance between two adjacent second grooves is a second pitch.
[0020] The second depth is less than the first depth; and / or,
[0021] The second pitch is greater than the first pitch.
[0022] Optionally, the first depth is (2-3) times the second depth; and / or,
[0023] The first pitch is (1 / 3-1 / 2) times the second pitch.
[0024] Optionally, the first depth is 10μm-25μm;
[0025] The first pitch is 0.5mm-1.5mm;
[0026] The width of the first groove is 50μm-150μm.
[0027] Compared with the prior art, the utility model has the beneficial effects that:
[0028] The first local recess and the second local recess are arranged, the gap between the first bending part and the adjacent second bending part is increased, the storage space of the electrolyte in the arc area is improved, the flowability of the electrolyte in the arc area is improved, and the problem of lithium precipitation of the battery in the arc area is improved.
[0029] The above and other objects, advantages and features of the present utility model will become more apparent from the following detailed description of the preferred embodiments thereof, when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0030] Some specific embodiments of the present utility model will be described in detail hereinafter with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference signs in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that the drawings are not necessarily drawn to scale. In the drawings:
[0031] Figure 1 is the structure diagram of the winding cell of one embodiment of the present utility model;
[0032] Figure 2 is the front view of the positive plate and the negative plate of one embodiment of the present utility model;
[0033] Figure 3 is the top view of the positive plate and the negative plate of one embodiment of the present utility model;
[0034] Figure 4 is the front view of the positive plate and the negative plate of another embodiment of the present utility model;
[0035] Figure 5 is the top view of the positive plate and the negative plate of another embodiment of the present utility model.
[0036] In the drawings: 1-winding cell, 10-arc area, 20-straight area; 30-positive plate, 31-first bending part, 32-positive active material layer, 33-first local recess, 34-positive current collector; 40-negative plate, 41-second bending part, 42-negative active material layer, 43-second local recess, 44-negative current collector. DETAILED DESCRIPTION
[0037] Reference will be made to Figures 1 to 4A winding electrode body according to an embodiment of the present application is described. In the description of the present embodiment, it should be understood that the terms "first", "second", etc. are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an indicated number of technical features. Therefore, the features with "first" and "second" can explicitly or implicitly include at least one of the features, that is, one or more of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited. When a certain feature "includes or contains" a certain feature or certain features, unless otherwise specifically described, it indicates that other features and can further include other features.
[0038] In the description of the present embodiment, the description of the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.
[0039] Figure 1 is a structural schematic diagram of a winding electrode body according to an embodiment of the present application. As Figure 1 indicated, and in combination with Figures 2 to 5 , the present application provides a winding electrode body. The winding electrode body 1 includes a positive electrode sheet 30, a negative electrode sheet 40 and a separator, the positive electrode sheet 30 includes a positive electrode current collector 34 and a positive electrode active material layer 32 located on both sides of the positive electrode current collector 34 in the thickness direction, the negative electrode sheet includes a negative electrode current collector 44 and a negative electrode active material layer 42 located on both sides of the negative electrode current collector 44 in the thickness direction, and the positive electrode sheet 30 and the negative electrode sheet 40 are wound to form an arc region 10 and a flat region 20. The positive electrode sheet 30 includes a plurality of first bending parts 31 located in the arc region 10, and the negative electrode sheet 40 includes a plurality of second bending parts 41 located in the arc region 10. The positive electrode active material layer 32 of the first bending part 31 has a plurality of first local recesses 33 on the side away from the positive electrode current collector; the negative electrode active material layer 42 of the second bending part 41 has a plurality of second local recesses 43 on the side away from the negative electrode current collector. Specifically, the positive electrode active material layer 32 of the first bending part 31 has a plurality of first local recesses 33 on the surface, and the negative electrode active material layer 42 of the second bending part 41 has a plurality of second local recesses 43 on the surface. The first local recess 33 and the second local recess 43 are both towards the inside of the winding electrode body 1.
[0040] In some embodiments of the utility model, the first local recess 33 is a thinning recess, and the density of the positive active material layer 32 in each region of the first bending part 31 is consistent. Specifically, the first local recess 33 is obtained by etching, local thin coating, grinding and the like.
[0041] In the above embodiments, the first local recess 33 and the second local recess 43 are arranged, the gap between the first bending part 31 and the second bending part 41 is increased, and the storage space of the electrolyte in the arc area 10 is improved. The increase of the electrolyte storage space can store more electrolyte, thereby improving the flowability of the electrolyte in the arc area 10, and further realizing the improvement of the lithium precipitation problem existing in the arc area 10 of the battery.
[0042] In some embodiments of the utility model, the width-thickness ratio of the winding cell 1 is not greater than 10:1. That is, the width-thickness ratio of the winding cell 1 is less than 10:1.
[0043] The greater the width-thickness ratio of the cell, the greater the bending radius of the arc area tab, and the more the inside of the first bending part 31 corresponding to the outside of the second bending part 41 in a unit angle, which is more likely to cause lithium precipitation in the arc area 10. Controlling the width-thickness ratio of the winding cell 1 within a certain range can reduce the first bending part 31 corresponding to the outside of the second bending part 41 in a unit angle, increase the CB value of the material, and thus improve the lithium precipitation of the winding cell 1 in the arc area 10.
[0044] In some embodiments of the utility model, the first local recess 33 is a die pressing recess. Specifically, a tool such as an embossing roller, an embossing plate and the like is used to obtain the first local recess 33 by die pressing forming through the application of external pressure.
[0045] In some embodiments of the utility model, the second local recess 43 is a die pressing recess. Specifically, a tool such as an embossing roller, an embossing plate and the like is used to obtain the second local recess 43 by die pressing forming through the application of external pressure. The obtaining method of the second local recess 43 can be the same as or different from that of the first local recess 33.
[0046] In some embodiments of the utility model, the first local recess 33 is a thinning recess, and the density of the positive active material layer 32 in each region of the first bending part 31 is consistent. Specifically, the first local recess 33 is obtained by etching, local thin coating, grinding and the like.
[0047] In some embodiments of the utility model, the second local recess 43 is a thinning recess, and the density of the negative active material layer 42 in each region of the second bending part 41 is consistent. Specifically, the second local recess 43 is obtained by etching, local thin coating, grinding and the like. The obtaining method of the second local recess 43 can be the same as or different from that of the first local recess 33.
[0048] In some embodiments of the utility model, the sum of the volumes of the plurality of first partial recesses 33 on the first bending part 31 is greater than the sum of the volumes of the plurality of second partial recesses 43 on the adjacent second bending part 41.
[0049] Specifically, the sum of the volumes of the plurality of first partial recesses 33 on each first bending part 31 is greater than the sum of the volumes of the plurality of second partial recesses 43 on the adjacent second bending part 41. That is, the reduced positive active material on each first bending part 31 is more than the reduced negative active material on the adjacent second bending part 41. This processing mode improves the CB value of the positive and negative electrodes and further improves the lithium precipitation in the arc region 10.
[0050] In some embodiments of the utility model, the first partial recess 33 is a first spherical cap-shaped pit. Specifically, a mold pressing tool is used to obtain the first partial recess 33 on the first bending part 31. In this embodiment, the first partial recess 33 is arranged in a spherical cap shape so that the stress inside the first partial recess 33 is uniform, and the active material on the surface of the first partial recess 33 will not be damaged, such as scratches, when the mold pressing tool is demolded.
[0051] In some embodiments of the utility model, the second partial recess 43 is a second spherical cap-shaped pit. Specifically, a mold pressing tool is used to obtain the second partial recess 43 on the second bending part 41. In this embodiment, the second partial recess 43 is arranged in a spherical cap shape so that the stress inside the second partial recess 43 is uniform, and the active material on the surface of the second partial recess 43 will not be damaged, such as scratches, when the mold pressing tool is demolded.
[0052] In some embodiments of the utility model, along the length direction of the positive electrode sheet 30, the distance between two adjacent first spherical cap-shaped pits is 3mm~5mm. Specifically, along the length direction of the positive electrode sheet 30, the distance between two adjacent first spherical cap-shaped pits can be any value between 3mm and 5mm, such as 3.0mm, 3.7mm, 4.0mm, 4.3mm, or 5.0mm, and so on. Along the width direction of the positive electrode sheet 30, the distance between two adjacent first spherical cap-shaped pits is 2~4mm. Specifically, along the width direction of the positive electrode sheet 30, the distance between two first spherical cap-shaped pits can be any value between 2mm and 4mm, such as 2.0mm, 2.7mm, 3.0mm, 3.3mm, or 4.0mm, and so on. It should be noted that the distance between any two adjacent first spherical cap-shaped pits can be equal or not equal.
[0053] If the distance between two adjacent first spherical cap-shaped recesses is too small, the single slot cannot store electrolyte. If the distance between two adjacent first spherical cap-shaped recesses is too large, the storage of electrolyte is limited. In the above two cases, the lithium precipitation phenomenon in the arc region 10 is not obviously improved. The distance between two adjacent first spherical cap-shaped recesses along the length direction of the positive plate 30 is 3mm-5mm, and the distance between two adjacent first spherical cap-shaped recesses along the width direction of the positive plate 30 is 2mm-4mm. The distance between any two adjacent first spherical cap-shaped recesses is controlled in a reasonable range, which can form single slot to store electrolyte, and can also avoid that the distance is too large to limit the storage amount of electrolyte between the first bending part 31 and the second bending part 41, thereby effectively improving the lithium precipitation of the battery in the arc region 10.
[0054] In some embodiments of the present application, the bottom surface radius of the first spherical cap-shaped recess is 0.5mm-1.5mm, and the height of the first spherical cap-shaped recess is 10%-30% of the thickness of the plate.
[0055] That is, the bottom surface radius of the first spherical cap-shaped recess can be any value between 0.5mm and 1.5mm, such as 0.5mm, 0.7mm, 1.0mm, 1.3mm, 1.5mm, etc. The height of the first spherical cap-shaped recess can be 10%, 15%, 20% or 30% of the thickness of the positive plate 30, etc. It should be noted that the bottom surface radius of the plurality of first spherical cap-shaped recesses can be the same or different, and the height of the plurality of first spherical cap-shaped recesses can be the same or different.
[0056] The bottom surface radius of the first spherical cap-shaped recess is too small or too large, which cannot improve the lithium precipitation in the arc region 10. If the height of the first spherical cap-shaped recess is too small, the storage amount of electrolyte is limited, and the lithium precipitation in the arc region 10 is not obviously improved. If the height of the first spherical cap-shaped recess is too large, the material is subjected to too large extrusion force, and the plate is at risk of breaking. If the bottom surface radius and the height of the first spherical cap-shaped recess are too small, the recess is approximately not set on the positive plate 30, the gap between the positive plate 30 and the negative plate 40 is not obviously changed. Of course, the storage amount of electrolyte in the arc region 10 is not obviously increased, and thus the lithium precipitation in the arc region 10 is not obviously improved.
[0057] In the present embodiment, the bottom surface radius of the first spherical cap-shaped recess is 0.5mm-1.5mm, and the height is 10%-30% of the thickness of the plate, which can increase the storage amount of electrolyte, improve the lithium precipitation in the arc region 10, and avoid the breaking of the plate.
[0058] In some embodiments of the present application, the first local recess 33 is a first groove, and the second local recess 43 is a second groove. The first groove and the second groove are both die grooves.
[0059] Specifically, a plurality of first grooves are obtained by die pressing on the side of the first bent portion 31 away from the positive current collector 34, and the first grooves extend along the width direction of the positive plate 30. A plurality of second grooves are obtained by die pressing on the side of the second bent portion 41 away from the negative current collector 44, and the second grooves extend along the width direction of the negative plate 40.
[0060] In the embodiment, the arrangement of the first grooves and the second grooves increases the volume between the first bent portion 31 and the second bent portion 41, and improves the storage space of the electrolyte in the arc region 10. The increase of the electrolyte storage space can store more electrolyte, thereby improving the flowability of the electrolyte in the arc region 10, and further improving the problem of lithium precipitation existing in the arc region 10 of the battery.
[0061] It should be noted that the first grooves can be arranged on one side of the first bent portion 31, or arranged on both sides of the first bent portion 31. Of course, the second grooves can be arranged on one side of the second bent portion 41, or arranged on both sides of the second bent portion 41.
[0062] In some embodiments of the utility model, the first local recess 33 is a first groove, and the second local recess 43 is a second groove. This arrangement increases the volume between the first bent portion 31 and the second bent portion 41, and improves the storage space of the electrolyte in the arc region 10. The increase of the electrolyte storage space can store more electrolyte, thereby improving the flowability of the electrolyte in the arc region 10, and further improving the problem of lithium precipitation existing in the arc region 10 of the battery.
[0063] In some embodiments of the utility model, the first local recess 33 is a first groove, and the second local recess 43 is a second groove. This arrangement increases the volume between the first bent portion 31 and the second bent portion 41, and improves the storage space of the electrolyte in the arc region 10. The increase of the electrolyte storage space can store more electrolyte, thereby improving the flowability of the electrolyte in the arc region 10, and further improving the problem of lithium precipitation existing in the arc region 10 of the battery.
[0064] In some embodiments of the utility model, the first local recess 33 is a first groove, and the distance between two adjacent first grooves is a first distance, and the depth of the first groove is a first depth. The second local recess 43 is a second groove, the distance between two adjacent second grooves is a second distance, and the depth of the second groove is a second depth. The second distance is greater than the first distance.
[0065] Specifically, a plurality of first grooves are arranged on the side of the first bending portion 31 away from the positive current collector 34, and the first grooves extend along the width direction of the positive plate 30. A plurality of second grooves are arranged on the side of the second bending portion 41 away from the negative current collector 44, and the second grooves extend along the width direction of the negative plate 40. The opening directions of the first grooves and the second grooves are opposite, and the pitch of the second grooves is greater than the pitch of the first grooves, that is, the first grooves are arranged more densely than the second grooves. The first grooves are obtained by etching, thin coating, grinding, etc.
[0066] In the embodiment, the amount of positive active material reduced on the positive plate 30 is greater than the amount of negative active material reduced on the negative plate 40, so that the lithium precipitation in the arc region 10 is better improved.
[0067] In some embodiments of the utility model, the first depth is (2-3) times of the second depth, and the first pitch is (1 / 3-1 / 2) times of the second pitch. That is, the depth of the first groove is greater than the depth of the second groove, and the pitch of the first groove is smaller than the pitch of the second groove, which means that the first groove is arranged more densely.
[0068] In some embodiments of the utility model, the first depth is 10-25 μm. Specifically, the depth of the first groove on the first bending portion 31 is any value between 10 μm and 25 μm, such as 10 μm, 11 μm, 13 μm, 15 μm, 17 μm, 20 μm, 22 μm or 25 μm. Preferably, the depth of the first groove is 15 μm.
[0069] The depth of the first groove is too small or too large, which cannot improve the lithium precipitation in the arc region 10. If the depth of the first groove is too large, the material will be subjected to too large a pressing force, and the plate will be at risk of breaking. If the depth of the first groove is too small, it is similar to not arranging the groove, and the gap between the positive plate 30 and the negative plate 40 does not change significantly. Of course, the storage capacity of the electrolyte in the arc region 10 will not be significantly increased, and thus the lithium precipitation in the arc region 10 will not be significantly improved. The depth of the first groove is 10-25 μm, which can increase the storage capacity of the electrolyte and improve the lithium precipitation in the arc region 10.
[0070] In some embodiments of the utility model, the first pitch is 0.5-1.5 mm. That is, the pitch between two adjacent first grooves along the length direction of the positive plate 30 can be any value between 0.5 mm and 1.5 mm, such as 0.5 mm, 0.8 mm, 1.2 mm or 1.5 mm, etc. Preferably, the first pitch is 1.0 mm.
[0071] In the embodiment, the interval of two adjacent first grooves along the length direction of the positive plate 30 is 0.5mm-1.5mm, which can form single slot storage of electrolyte, and avoid too large interval to cause too large storage of electrolyte between the first bending part 31 and the second bending part 41, thereby effectively improving lithium precipitation of the battery in the arc area 10.
[0072] In some embodiments of the utility model, the width of the first groove is 50-150μm. Specifically, the width of each first groove can be the same or different.
[0073] In the embodiment, the width of the first groove is 50-150μm, which can increase the storage of electrolyte and improve lithium precipitation in the arc area 10.
[0074] The utility model also provides a battery, and the battery contains the winding electric core as described in any one of the above embodiments. In the embodiment, the battery can improve lithium precipitation in the arc area and improve the use safety performance of the battery.
[0075] The utility model also provides a battery module, and the battery module includes a plurality of batteries in any one of the above embodiments, and the plurality of batteries are connected in series.
[0076] The battery module of the application contains a plurality of batteries, effectively expands the capacity of the battery module, and expands the application range of the battery module. The skilled person in the art can select a suitable number according to the application and capacity of the battery module.
[0077] The utility model also provides a battery module, and the battery module includes a plurality of batteries in any one of the above embodiments, and the plurality of batteries are connected in parallel.
[0078] In the embodiment, the plurality of batteries are connected in parallel, which can make the battery module have higher battery capacity, and when the energy of one battery is exhausted or a fault occurs, it does not affect the continuous power supply of other batteries in the battery module, thereby ensuring the continuous operation of the electric equipment.
[0079] The utility model also provides a battery module, and the battery module includes a plurality of batteries produced by the battery production equipment in any one of the above embodiments, and the plurality of batteries are connected in series.
[0080] The battery module of the application contains a plurality of batteries, effectively expands the capacity of the battery module, and expands the application range of the battery module. The skilled person in the art can select a suitable number according to the application and capacity of the battery module.
[0081] In some other embodiments of the utility model, the battery module includes a plurality of batteries produced by the battery production equipment in any one of the above embodiments, and the plurality of batteries are connected in parallel.
[0082] In the embodiment, the plurality of batteries are connected in parallel, so that the battery module can have higher battery capacity, and when one battery is exhausted or fails, the other batteries in the battery module can continue to supply power, thereby ensuring continuous operation of the electrical equipment.
[0083] At this point, those skilled in the art should recognize that, although the present application has been shown and described in detail in the above embodiments, many other variations or modifications can be determined or deduced directly according to the disclosure of the present application without departing from the spirit and scope of the present application. Therefore, the scope of the present application should be understood and recognized as covering all these other variations or modifications.
Claims
1. A wound battery cell, comprising a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet comprising a positive electrode current collector and positive electrode active material layers on both sides of the positive electrode current collector in the thickness direction of the positive electrode current collector, the negative electrode sheet comprising a negative electrode current collector and negative electrode active material layers on both sides of the negative electrode current collector in the thickness direction of the negative electrode current collector, characterized in that, the positive electrode sheet and the negative electrode sheet are wound to form a circular arc region and a flat region, the positive electrode sheet comprises a plurality of first bending portions in the circular arc region, and the negative electrode sheet comprises a plurality of second bending portions in the circular arc region; the positive electrode active material layer on the side away from the positive electrode current collector of the first bending portion has a plurality of first local recesses; and the negative electrode active material layer on the side away from the negative electrode current collector of the second bending portion has a plurality of second local recesses. 2.The wound battery cell according to claim 1, characterized in that, the first local recess is a die-pressed recess; and / or the second local recess is a die-pressed recess. 3.The wound battery cell according to claim 1, characterized in that, the first local recess is a thinning recess, and the density of the positive electrode active material layer in each region on the first bending portion is uniform; and / or the second local recess is a thinning recess, and the density of the negative electrode active material layer in each region on the second bending portion is uniform. 4.The wound battery cell according to claim 3, characterized in that, the sum of the volumes of the plurality of first local recesses on the first bending portion is greater than the sum of the volumes of the plurality of second local recesses on the adjacent second bending portion. 5.The wound battery cell according to claim 1, characterized in that, the width-thickness ratio of the wound battery cell is not greater than 10:
1. 6.The wound battery cell according to claim 1, characterized in that, the first local recess is a first spherical cap-shaped recess; and / or the second local recess is a second spherical cap-shaped recess. 7.The wound battery cell according to claim 6, characterized in that, along the length direction of the positive electrode sheet, the distance between two adjacent first spherical cap-shaped recesses is 3mm to 5mm; and along the width direction of the positive electrode sheet, the distance between two adjacent first spherical cap-shaped recesses is 2mm to 4mm. 8.The wound battery cell according to claim 6, characterized in that, the bottom surface radius of the first spherical cap-shaped recess is 0.5mm to 1.5mm, and the height of the first spherical cap-shaped recess is 10% to 30% of the thickness of the electrode sheet. 9.The wound battery cell according to claim 4, characterized in that, the first local recess is a first groove, the depth of the first groove is a first depth, and the distance between two adjacent first grooves is a first pitch; and / or the first local recess is a second groove, the depth of the second groove is a second depth, and the distance between two adjacent second grooves is a second pitch; the second depth is less than the first depth; and / or the second pitch is greater than the first pitch. 10.The wound battery cell according to claim 9, characterized in that, the first depth is (2 to 3) times the second depth; and / or the first pitch is (1 / 3 to 1 / 2) times the second pitch. 11.The wound cell according to claim 9, wherein, the first depth is 10 μm to 25 μm; the first interval is 0.5 mm to 1.5 mm; a width of the first groove is 50 μm to 150 μm.