Single cell and battery pack

Abstract

The application discloses a single battery and a battery pack, which have an axial direction and a radial direction. The single battery comprises a shell and a roll core. The roll core comprises a positive electrode sheet layer, a diaphragm layer and a negative electrode sheet layer which are stacked and wound. The negative electrode sheet layer comprises a negative electrode current collector and a negative electrode active layer. The negative electrode current collector comprises a negative electrode tab area and a negative electrode coating area. The negative electrode active layer is arranged on at least one side of the negative electrode coating area in the radial direction. The positive electrode sheet layer comprises a positive electrode current collector and a positive electrode active layer. The positive electrode current collector comprises a positive electrode tab area and a positive electrode coating area. The positive electrode active layer is arranged on at least one side of the positive electrode coating area in the radial direction. The negative electrode active layer comprises an adjacent main body part and a thinned part. The CB value of the main body part is greater than or equal to 1, and the CB value of the thinned part is less than 1. The end of the positive electrode active layer close to the negative electrode tab area is arranged opposite to the main body part. By arranging the end of the positive electrode active layer close to the negative electrode tab area opposite to the main body part, the gap between the two is reduced, and the risk of lithium precipitation is reduced.

Description

Technical Field

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

[0002] The technology behind large cylindrical batteries with full tabs and high energy density, high power density, and high volumetric density is improving, and market demand is increasing. Due to the high energy density requirements of cylindrical cells, the internal design of the cells is extremely limited. Existing coating and thinning technologies make it difficult to control the width of the thinned area within the specified range. As a result, after winding the negative electrode sheet, there is often an area with a CB value less than 1, which poses a significant risk of lithium plating and is detrimental to the battery's long-cycle performance. Furthermore, the presence of the thinned area often creates a gap between the positive and negative electrodes, increasing polarization. The presence of this gap also reduces the battery's energy density and the overall flatness of the cell.

[0003] Therefore, there is a need to improve the existing technology. Summary of the Invention

[0004] The present invention aims to at least solve the problem in the prior art of excessively large gap between the end of the positive electrode active layer near the negative electrode tab region and the main body, and provides a single cell and a battery pack.

[0005] According to one aspect of the present application, the present application provides a single battery having mutually perpendicular axial and radial directions, the single battery comprising: a shell and a winding core, the winding core being accommodated in the shell, the winding core comprising a positive electrode layer, a separator layer and a negative electrode layer stacked and wound, the separator layer being arranged between the positive electrode layer and the negative electrode layer; wherein the negative electrode layer comprises a negative electrode current collector and a negative electrode active layer, in the axial direction, the negative electrode current collector comprises a negative electrode tab region and a negative electrode coating region, the negative electrode tab region being arranged on one side or both sides of the negative electrode coating region in the axial direction, the negative electrode tab region having a plurality of tabs, the negative electrode active layer being arranged on at least one side of the negative electrode coating region in the radial direction, in the axial direction, The negative electrode active layer includes adjacent main parts and thinned parts, and the thinned parts are arranged on one side or both sides of the negative electrode coating area in the axial direction, and the main part is connected to the side of the thinned part away from the negative electrode tab area; the CB value corresponding to the main part is greater than or equal to 1, and the CB value corresponding to the thinned part is less than 1; the positive electrode layer includes a positive electrode collector and a positive electrode active layer, in the axial direction, the positive electrode collector includes a positive electrode tab area and a positive electrode coating area, the positive electrode tab area is arranged on one side or both sides of the positive electrode coating area in the axial direction, the positive electrode tab area has multiple tabs, and the positive electrode active layer is arranged on at least one side of the positive electrode coating area in the radial direction; the end of the positive electrode active layer close to the negative electrode tab area is arranged opposite to the main part.

[0006] Furthermore, the dimension of the thinned portion in the axial direction is L1 mm, the end of the positive electrode active layer close to the negative electrode tab area is the target end, and the dimension of the portion of the negative electrode active layer exceeding the target end in the axial direction is O mm, satisfying: 1.5≤L1≤O.

[0007] Optionally, 1.5<O≤5.

[0008] Furthermore, the negative electrode current collector further includes an empty foil area, which is connected between the negative electrode tab area and the negative electrode coating area in the axial direction, wherein the size of the empty foil area in the axial direction is L2 mm, satisfying: 0.5≤L2≤5.

[0009] Furthermore, the main body portion includes a main body sub-portion and a transition sub-portion, the transition sub-portion is connected between the main body sub-portion and the thinning portion, the radial size of the main body sub-portion is larger than the radial size of the transition sub-portion, and the radial size of the transition sub-portion gradually increases in the direction approaching the main body sub-portion, and the end of the positive electrode active layer close to the negative electrode tab area is arranged opposite to the main body sub-portion.

[0010] Furthermore, the main body portion includes a main body sub-portion and a transition sub-portion, the transition sub-portion is connected between the main body sub-portion and the thinning portion, the radial size of the main body sub-portion is larger than the radial size of the transition sub-portion, and the radial size of the transition sub-portion gradually increases in the direction approaching the main body sub-portion, and the end of the positive electrode active layer close to the negative electrode tab area is arranged opposite to the transition sub-portion.

[0011] Furthermore, the dimension of the main body sub-section in the axial direction is L3 mm, satisfying: 75≤L3≤80.5.

[0012] Furthermore, the dimension of the transition sub-portion in the axial direction is L4 mm, satisfying: 5≤L4≤20.

[0013] Furthermore, a dimension of the thinned portion in the radial direction gradually decreases in a direction away from the main body portion.

[0014] According to another aspect of the present application, a battery pack is provided, comprising any of the aforementioned single cells.

[0015] The beneficial effects of the present application are: different from the existing technology, the present application reduces the gap between the end of the positive electrode active layer close to the negative electrode tab area and the main body by arranging the end of the positive electrode active layer close to the negative electrode tab area relative to the main body, thereby improving the energy density and being beneficial to improving the overall flatness of the battery cell, and the CB value corresponding to the main body is greater than or equal to 1, reducing the risk of lithium plating during the cycle process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings will make the technical solutions and other beneficial effects of the present application apparent.

[0017] Figure 1 This is a cross-sectional view of a winding core provided in an embodiment of the present application.

[0018] Figure 2 This is a schematic diagram of a negative electrode layer coating provided in an embodiment of the present application.

[0019] Figure 3 This is a cross-sectional view of a winding core provided in another embodiment of the present application.

[0020] Figure 4 This is a schematic diagram of a positive electrode layer, a separator layer, and a negative electrode layer provided in an embodiment of the present application.

[0021] In the picture:

[0022] 10. Winding core; 11. Positive electrode sheet; 111. Target end; 112. Positive current collector; 1121. Positive electrode tab area; 1122. Positive electrode coating area; 113. Positive electrode active layer; 12. Separator layer; 13. Negative electrode sheet; 131. Negative electrode current collector; 1311. Negative electrode tab area; 1312. Negative electrode coating area; 1313. Empty foil area; 132. Negative electrode active layer; 1321. Main body; 13211. Main body sub-section; 13212. Transition sub-section; 1322. Thinning section. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the terms in this application based on the specific circumstances.

[0025] In order to solve the technical problem in the prior art that the gap between the end of the positive electrode active layer near the negative electrode tab area and the main body is too large, one embodiment of the present application provides a single cell. The single cell has mutually perpendicular axial and radial directions, and the single cell includes: a shell and a winding core, the winding core is accommodated in the shell, the winding core includes stacked and wound positive electrode sheets, diaphragm layers and negative electrode sheets, the diaphragm layer is arranged between the positive electrode sheets and the negative electrode sheets; wherein, the negative electrode sheets include a negative electrode current collector and a negative electrode active layer, in the axial direction, the negative electrode current collector includes a negative electrode tab area and a negative electrode coating area, the negative electrode tab area is arranged on one side or both sides of the negative electrode coating area in the axial direction, the negative electrode tab area has a plurality of tabs, the negative electrode active layer is arranged on at least one side of the negative electrode coating area in the radial direction, and in the axial direction, the negative electrode active layer includes adjacent The main body and the thinned portion are provided on one or both sides of the negative electrode coating area in the axial direction, and the main body is connected to the side of the thinned portion away from the negative electrode tab area; the CB value corresponding to the main body is greater than or equal to 1, and the CB value corresponding to the thinned portion is less than 1; the positive electrode sheet layer includes a positive electrode current collector and a positive electrode active layer, in the axial direction, the positive electrode current collector includes a positive electrode tab area and a positive electrode coating area, the positive electrode tab area is provided on one or both sides of the positive electrode coating area in the axial direction, the positive electrode tab area has multiple tabs, and the positive electrode active layer is provided on at least one side of the positive electrode coating area in the radial direction; the end of the positive electrode active layer close to the negative electrode tab area is arranged opposite to the main body. The following is a detailed explanation.

[0026] See Figure 1 and Figure 2 , Figure 1 is a cross-sectional view of a winding core provided in an embodiment of the present application. Figure 2 This is a schematic diagram of a negative electrode layer coating provided in an embodiment of the present application.

[0027] In one embodiment, a single battery comprises a shell and a winding core 10, wherein the single battery has mutually perpendicular axial directions ( Figure 1 direction Y, the same below) and radial direction ( Figure 1As shown in the direction of X, the same below, the winding core 10 is accommodated in the shell, the winding core 10 is stacked and wound by the positive sheet layer 11, the diaphragm layer 12 and the negative sheet layer 13, the diaphragm layer 12 is arranged between the positive sheet layer 11 and the negative sheet layer 13; The negative sheet layer 13 includes a negative current collector 131 and a negative active layer 132, and the negative current collector 131 includes a negative tab area 1311 and a negative coating area 1312 distributed along the axial direction of the single battery, the negative tab area 1311 is arranged on one side of the negative coating area 1312 in the axial direction, and the negative tab area 1311 has a plurality of tabs, and the negative coating area 1312 is provided with a negative active layer 132 on both sides in the radial direction, in some embodiments, the negative active layer 132 can also be arranged on one side of the negative coating area 1312, which will not be described here; At the same time, the positive sheet layer 11 includes a positive current collector 112 and a positive active layer 113, in the axial direction, the positive current collector 112 includes a positive tab area 1121 and a positive coating area 1122, the positive tab area 1121 is arranged on one side of the positive coating area 1122 in the axial direction, the positive tab area 1121 has a plurality of tabs, and the positive active layer 113 is arranged on both sides of the positive coating area 1122 in the radial direction, in some embodiments, the positive active layer 113 can also be arranged on one side of the positive coating area 1122, which will not be described here.

[0028] It should be noted that the single battery includes but is not limited to lithium ion secondary battery, sodium lithium ion battery, sodium ion battery or magnesium ion battery, etc., the tabs in the negative tab area 1311 can be formed by cutting, at this time the negative tab area 1311 is integrally arranged with the negative coating area 1312, in some embodiments, the negative tab area 1311 can also be formed by welding the tabs on the negative coating area 1312, which will not be described here; And in this embodiment, one side of the negative coating area 1312 is provided with the negative tab area 1311, in some embodiments, both sides of the negative coating area 1312 in the axial direction can be provided with the negative tab area 1311, and the positive tab area 1121 is arranged in the same way, which will not be described here.

[0029] Please continue to refer to Figure 1The negative electrode active layer 132 includes an adjacent main body 1321 and a thinned portion 1322, the main body 1321 and the thinned portion 1322 are distributed along the axial direction, and the thinned portion 1322 is arranged on one side of the negative electrode coating area 1312 in the axial direction. In some embodiments, the thinned portion 1322 can also be arranged on both sides of the negative electrode coating area 1312 in the axial direction, but is not limited to this. At the same time, the main body 1321 is connected to the side of the thinned portion 1322 away from the negative electrode tab area 1311; the CB value corresponding to the main body 1321 is greater than or equal to 1, and the CB value corresponding to the thinned portion 1322 is less than 1. The end of the positive electrode active layer 113 close to the negative electrode tab area 1311 is arranged opposite to the main body 1321. By setting the CB value corresponding to the main body 1321 to be greater than or equal to 1, the gap between the end of the positive electrode active layer 113 close to the negative electrode tab area 1311 and the main body 1321 is smaller, which reduces the risk of lithium plating of the battery cell, improves the cycle performance, and improves the flatness of the battery cell.

[0030] Please continue reading Figure 1 In one embodiment, the axial dimension of the thinned portion 1322 is L1 mm, the end of the positive electrode active layer 113 close to the negative electrode tab region 1311 is the target end 111, and the axial dimension of the portion of the negative electrode active layer 132 that protrudes from the target end 111 is O mm, satisfying the following conditions: 1.5≤L1≤O. The CB value corresponding to the thinned portion 1322 is less than 1. When 1.5≤L1≤O, it can be ensured that the target end 111 is always facing the main portion 1321 (the CB value corresponding to the main portion 1321 is greater than or equal to 1). At this time, the thinned portion 1322 is located above the target end 111 ( Figure 1 The gap between the target end 111 and the negative electrode active layer 132 is reduced, the risk of lithium plating of the battery cell is reduced, the cycle performance is improved, and the flatness of the battery cell is improved.

[0031] Please continue reading Figure 1 and Figure 2 In one embodiment, the negative electrode current collector 131 further includes an empty foil area 1313, which is axially connected between the negative electrode tab area 1311 and the negative electrode coating area 1312. Figure 1 The axial dimension of the negative electrode active layer 132 can be increased ( Figure 1 The longitudinal direction of the negative electrode active layer 132 is increased, that is, the axial dimension of the negative electrode active layer 132 is increased, so that part of the negative electrode active layer 132 covers the empty foil area 1313. After winding, the target end portion 111 does not fall within the thinned portion 1322 (that is, in the radial direction, the target end portion 111 and the thinned portion 1322 are not opposite to each other), thereby reducing the gap between the target end portion 111 and the negative electrode active layer 132.

[0032] Please continue reading Figure 1In an embodiment, the main body part 1321 includes a main body subpart 13211 and a transition subpart 13212, the transition subpart 13212 is connected between the main body subpart 13211 and the thinning part 1322, the main body subpart 13211 has a larger radial dimension than the transition subpart 13212, and the radial dimension of the transition subpart 13212 gradually increases in a direction close to the main body subpart 13211. In this embodiment, the target end part 111 is arranged opposite to the main body subpart 13211. Since the main body subpart 13211 has a larger radial dimension than the transition subpart 13212, the distance between the target end part 111 and the main body subpart 13211 is smaller, which is more conducive to the flatness of the battery cell and reduces the risk of lithium precipitation.

[0033] It should be noted that since the CB value corresponding to the thinning part 1322 is less than 1, and the CB value corresponding to the main body part 1321 (including the main body subpart 13211 and the transition subpart 13212) is greater than or equal to 1, the radial dimension of the thinning part 1322 is smaller than the radial dimension of the transition subpart 13212. In some embodiments, the radial dimension of the thinning part 1322 can also gradually decrease from bottom to top (in the viewing angle) according to the specific coating process, which will not be described here. Figure 1

[0034] Referring to Figure 3 , Figure 3 is a cross-sectional view of a battery core provided in another embodiment of the present application.

[0035] In an embodiment, the target end part 111 is arranged opposite to the transition subpart 13212. This arrangement can ensure that the gap between the target end part 111 and the transition subpart 13212 meets the use requirements and reduces the risk of lithium precipitation.

[0036] It should be noted that without adjusting the coating equipment, the axial dimensions of the transition subpart 13212 and the thinning part 1322 remain unchanged, and the axial length of the main body subpart 13211 is increased to meet the use requirements of the battery cell, which will not be described here.

[0037] ​In some embodiments, the dimension of the overhanging portion of the negative active layer 132 relative to the target end portion 111 in the axial direction is O mm, which satisfies: 1.5 < O ≤ 5, for example, one of 1.7, 3, 4, 5 or a range value composed of any two of them; the dimension of the empty foil area 1313 in the axial direction is L2 mm, which satisfies: 0.5 ≤ L2 ≤ 5, for example, one of 0.5, 2, 3, 4, 5 or a range value composed of any two of them; the dimension of the main body sub-portion 13211 in the axial direction is L3 mm, which satisfies: 75 ≤ L3 ≤ 80.5, for example, one of 75, 77, 79, 80.5 or a range value composed of any two of them; the dimension of the transition sub-portion 13212 in the axial direction is L4, which satisfies: 5 ≤ L4 ≤ 20, for example, one of 5, 10, 15, 20 or a range value composed of any two of them; in this way, by reasonable setting, the gap between the end portion of the positive active layer 113 close to the negative tab area 1311 and the main body portion 1321 can be reduced, the energy density is improved, and the overall flatness of the battery is improved.

[0038] The performance of the technical solutions provided by the embodiments of the present application is evaluated below in combination with specific embodiments.

[0039] In order to illustrate the influence of different values of L1 and O on the performance of the battery, the specific parameters and test results of embodiments 1-6 are provided below for illustration, which are shown in Table 1.

[0040] Table 1

[0041]

[0042] Taking a 46950 size cylindrical battery as an example, the volumetric energy density requirement is ≥265 Wh / L, 45℃

[0043] 3C / 3C cycle 500 times capacity retention rate > 90%, which means it meets the design requirements. As can be seen from Table 1, the volumetric energy density and 45℃ 3C / 3C cycle 500 times capacity retention rate of embodiments 1-6 all meet the requirements. The volumetric energy density is the 25℃ 1C discharge capacity of the battery divided by the battery volume; the cycle capacity retention rate is the ratio of the 3C discharge capacity after 500 times of 3C charge and 3C discharge cycles to the 3C discharge capacity of the 0th cycle at 45℃.

[0044] In order to illustrate the influence of different values of L2 and L3 on the performance of the battery, the specific parameters and test results of embodiments 7-13 are provided below for illustration, which are shown in Table 2.

[0045] Table 2

[0046]

[0047]

[0048] Taking a cylindrical battery with a 46950 size as an example, the volumetric energy density requirement is ≥265 Wh / L, the range of the height of the wound core after flattening is 84.3±1.0 mm, and the wound core cannot enter the shell if it is too large, and the wound core will shake in the shell or even be separated from the shell if it is too small, and IMP≤2.5 mΩ, which indicates that the design requirements are met. As can be seen from Table 2, the test results of Examples 7-13 all meet the requirements. The volumetric energy density is obtained by dividing the 25℃ 1C discharge capacity of the battery by the volume of the battery; the height of the wound core is tested by the CCD height measurement structure of the winding equipment; and IMP is obtained by using an insulation resistance tester to test the positive and negative poles of the battery in the delivery state.

[0049] In order to illustrate the influence of different L4 on the performance of the battery, the specific parameters and test results of Examples 16-21 are provided below for illustration, which are shown in Table 3.

[0050] Table 3

[0051]

[0052] Taking a cylindrical battery with a 46950 size as an example, the volumetric energy density requirement is ≥265 Wh / L, the coating & rolling process yield is greater than 90%, and IMP≤2.5 mΩ, which indicates that the design requirements are met. As can be seen from Table 3, the test results of Examples 16-21 all meet the requirements. The volumetric energy density is obtained by dividing the 25℃ 1C discharge capacity of the battery by the volume of the battery; and IMP is obtained by using an insulation resistance tester to test the positive and negative poles of the battery in the delivery state.

[0053] On the other hand, the single battery in any one of the embodiments can be used in a battery pack.

[0054] In various embodiments of the present application, the terms or descriptions of different embodiments are consistent and can be mutually referred to if there is no special description and logical conflict, and the technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationship.

[0055] It can be understood that the various numbers involved in the embodiments of the present application are only for differentiation for convenience of description, and do not limit the scope of the embodiments of the present application. The size of the serial number of each process does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic.

[0056] The single battery and the battery pack provided by the embodiments of the present application are described in detail above, and the principles and implementation manners of the present application are described by applying specific examples; the above description of the embodiments is only used to help understand the single battery and the core idea thereof; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application, and the above description should not be understood as a limitation on the present application.

Claims

1. A single battery, characterized in that: The single battery has an axial direction (Y) and a radial direction (X) perpendicular to each other, and includes: a housing; and A winding core (10) is accommodated in the shell, the winding core (10) comprising a positive electrode layer (11), a separator layer (12), and a negative electrode layer (13) stacked and wound, the separator layer (12) being arranged between the positive electrode layer (11) and the negative electrode layer (13); The negative electrode layer (13) includes a negative electrode current collector (131) and a negative electrode active layer (132). In the axial direction (Y), the negative electrode current collector (131) includes a negative electrode tab region (1311) and a negative electrode coating region (1312). The negative electrode tab region (1311) is arranged on one side or both sides of the negative electrode coating region (1312) in the axial direction (Y). The negative electrode tab region (1311) has a plurality of tabs. The negative electrode active layer (132) is arranged on the negative electrode coating region (1312) in the radial direction (X). ), in the axial direction (Y), the negative electrode active layer (132) includes adjacent main parts (1321) and thinned parts (1322), the thinned parts (1322) are arranged on one side or both sides of the negative electrode coating area (1312) in the axial direction (Y), and the main part (1321) is connected to the side of the thinned part (1322) away from the negative electrode tab area (1311); the CB value corresponding to the main part (1321) is greater than or equal to 1, and the CB value corresponding to the thinned part (1322) is less than 1; The positive electrode sheet (11) comprises a positive electrode current collector (112) and a positive electrode active layer (113); in the axial direction (Y), the positive electrode current collector (112) comprises a positive electrode tab region (1121) and a positive electrode coating region (1122); the positive electrode tab region (1121) is arranged on one side or both sides of the positive electrode coating region (1122) in the axial direction (Y); the positive electrode tab region (1121) has a plurality of tabs; the positive electrode active layer (113) is arranged on at least one side of the positive electrode coating region (1122) in the radial direction (X); the end of the positive electrode active layer (113) close to the negative electrode tab region (1311) is arranged opposite to the main body (1321); The dimension of the thinned portion (1322) in the axial direction (Y) is L1 mm, the end of the positive electrode active layer (113) close to the negative electrode tab region (1311) is the target end (111), and the dimension of the portion of the negative electrode active layer (132) that exceeds the target end (111) in the axial direction (Y) is O mm, satisfying: 1.5≤L1≤O, 1.5<O≤5.

2. The single cell according to claim 1, wherein: The negative electrode current collector (131) further includes an empty foil area (1313), and the empty foil area (1313) is connected between the negative electrode tab area (1311) and the negative electrode coating area (1312) in the axial direction (Y), wherein the size of the empty foil area (1313) in the axial direction (Y) is L2 mm, satisfying: 0.5≤L2≤5.

3. The single cell according to claim 1, wherein: The main body (1321) includes a main body sub-section (13211) and a transition sub-section (13212), wherein the transition sub-section (13212) is connected between the main body sub-section (13211) and the thinned portion (1322), the size of the main body sub-section (13211) in the radial direction (X) is larger than the size of the transition sub-section (13212) in the radial direction (X), and the size of the transition sub-section (13212) in the radial direction (X) gradually increases in the direction approaching the main body sub-section (13211), and the end of the positive electrode active layer (113) close to the negative electrode tab area (1311) is arranged opposite to the main body sub-section (13211).

4. The single cell according to claim 1, wherein: The main body (1321) includes a main body sub-section (13211) and a transition sub-section (13212), wherein the transition sub-section (13212) is connected between the main body sub-section (13211) and the thinned portion (1322), the size of the main body sub-section (13211) in the radial direction (X) is larger than the size of the transition sub-section (13212) in the radial direction (X), and the size of the transition sub-section (13212) in the radial direction (X) gradually increases in the direction approaching the main body sub-section (13211), and the end of the positive electrode active layer (113) close to the negative electrode tab area (1311) is arranged opposite to the transition sub-section (13212).

5. The single cell according to claim 3 or 4, characterized in that: The dimension of the main body sub-section (13211) in the axial direction (Y) is L3 mm, satisfying: 50≤L3≤100.

6. The single cell according to claim 3 or 4, characterized in that: The dimension of the transition sub-section (13212) in the axial direction (Y) is L4 mm, satisfying: 5≤L4≤20.

7. The single cell according to claim 1, wherein: The dimension of the thinned portion (1322) in the radial direction (X) gradually decreases in a direction away from the main body portion (1321).

8. A battery pack, characterized in that: The method comprises the single cell according to any one of claims 1 to 7.

Images