Battery cell and electric equipment

Abstract

The invention provides a battery cell and electric equipment, the battery cell comprises a shell and an electrode assembly, and the shell comprises an end wall, a side wall and a transition wall; the transition wall is provided with a first end and a second end, the first end is connected with the side wall, the second end is connected with the end wall, and an opening is formed in the end, away from the transition wall, of the side wall in the first direction and opposite to the end wall. The electrode assembly is at least partially accommodated in the shell, the electrode assembly comprises a positive pole piece and a negative pole piece, and in the first direction, the negative pole piece exceeds one end, close to the end wall, of the positive pole piece in the direction pointing to the end wall from the opening; wherein the transition wall is of a non-equal-thickness structure, the minimum thickness of the transition wall is located at the first end, the positive pole piece is farther away from the end wall than the first end in the first direction, the minimum distance between the positive pole piece and the first end is L1, and L1 is larger than or equal to 0.5 mm and smaller than or equal to 3 mm, so that the battery cell has high safety performance and energy density.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell and an electrical device. Background Technology

[0002] Currently, with the rapid development of new energy technologies, battery cells have been widely used in electronic devices, electric vehicles, electric two-wheelers, power tools, and other fields. As the application of battery cells becomes more widespread, higher requirements are being placed on their safety performance. Summary of the Invention

[0003] This application provides a battery cell and an electrical device to improve the safety performance of the battery cell.

[0004] In a first aspect, embodiments of this application provide a battery cell, which includes a housing and an electrode assembly. The housing includes an end wall, a side wall, and a transition wall. The transition wall has a first end and a second end, the first end being connected to the side wall and the second end being connected to the end wall. Along a first direction, an opening is formed at the end of the side wall facing away from the transition wall, and the opening and the end wall are disposed opposite to each other. The electrode assembly is at least partially housed within the housing. The electrode assembly includes a positive electrode and a negative electrode. Along the first direction, the negative electrode extends beyond the end of the positive electrode near the end wall from the opening towards the end wall. The transition wall has a non-uniform thickness structure, with the minimum thickness of the transition wall located at the first end. Along the first direction, the positive electrode is further away from the end wall than the first end, and the minimum distance between the positive electrode and the first end is L1, where 0.5mm ≤ L1 ≤ 3mm. In one or more of the above optional embodiments, the end wall and side wall are connected by a transition wall, which can alleviate the stress concentration problem at the junction of the end wall and side wall, improve the strength of the shell, and thus alleviate the deformation problem of the shell during drop and roller tests. The minimum thickness of the transition wall is located at the first end, so the strength of the transition wall at the corresponding position at the first end is relatively weak. That is, the strength of the shell at the connection position of the transition wall and side wall is relatively weak. Therefore, the deformation position of the shell during drop and roller tests is located at the connection position of the transition wall and side wall and the surrounding area. Moreover, along the first direction, the positive electrode is farther away from the end wall than the first end. Therefore, the deformation position of the shell can avoid the overlapping area of ​​the positive electrode and negative electrode, reduce the risk of shell deformation and squeezing of the electrode assembly after the cell undergoes drop and roller tests, reduce the risk of thermal runaway of the cell, improve the safety performance of the cell, and improve the pass rate of the cell drop and roller tests. By setting L1 to be greater than or equal to 0.5mm, the distance between the positive electrode and the first end is made larger, ensuring that the deformation of the casing during drop and tumbling tests avoids the overlapping area of ​​the positive and negative electrodes, reducing the risk of thermal runaway and improving the safety performance and pass rate of drop and tumbling tests. By setting L1 to be less than or equal to 3mm, the distance between the positive electrode and the first end is not too large, which is beneficial to improving the energy density of the cell. Therefore, 0.5mm≤L1≤3mm gives the cell high safety performance and energy density.

[0005] In some embodiments of the first aspect of this application, 0.7mm ≤ L1 ≤ 2mm.

[0006] In one or more of the above optional embodiments, by making L1 greater than or equal to 0.7mm, the distance between the positive electrode and the first end is made larger, so that the deformation of the casing during drop and tumbling tests avoids the overlapping area of ​​the positive and negative electrodes, further reducing the risk of thermal runaway of the battery cell, further improving the safety performance of the battery cell and increasing the pass rate of drop and tumbling tests; by making L1 less than or equal to 2mm, the distance between the positive electrode and the first end is not too large, which is conducive to further improving the energy density of the battery cell. Therefore, 0.7mm≤L1≤2mm gives the battery cell higher safety performance and energy density.

[0007] In some embodiments of the first aspect of this application, along the first direction, the distance between the first end and the surface of the end wall facing the electrode assembly is L2, 0.5mm≤L2≤5mm.

[0008] In one or more of the above optional embodiments, by making L2 greater than or equal to 0.5mm, the distance between the first end and the end wall facing the electrode assembly is larger, reducing the risk of the transition wall squeezing the electrode assembly, thereby reducing the risk of thermal runaway caused by internal short circuits in the battery cell, improving the safety performance of the battery cell and increasing the pass rate of drop tests and roller tests; by making L2 less than or equal to 5mm, the distance between the first end and the end wall is not too large, which is beneficial to improving the energy density of the battery cell. Therefore, 0.5mm≤L2≤5mm gives the battery cell good safety performance and energy density.

[0009] In some embodiments of the first aspect of this application, 1mm ≤ L2 ≤ 3mm.

[0010] In one or more of the above optional embodiments, by making L2 greater than or equal to 1 mm, the distance between the first end and the end wall facing the electrode assembly is larger, further reducing the risk of the transition wall squeezing the electrode assembly, thereby further reducing the risk of thermal runaway caused by internal short circuits in the cell, further improving the safety performance of the cell and increasing the pass rate of the cell drop test and tumble test; by making L2 less than or equal to 3 mm, the distance between the first end and the end wall is not too large, which is conducive to further improving the energy density of the cell. Therefore, 0.5 mm ≤ L2 ≤ 5 mm, so that the cell has better safety performance and energy density.

[0011] In some embodiments of the first aspect of this application, the wall thickness of the end wall is greater than the wall thickness of the side wall.

[0012] In one or more of the above optional embodiments, by making the end wall thickness greater than the side wall thickness, the end wall and the connection position between the end wall and the transition wall have better strength, reducing the risk of the housing deforming at the end wall and the connection position between the end wall and the transition wall after the cell drop test and the drum test, or avoiding the deformation of the housing at the end wall and the connection position between the end wall and the transition wall after the cell drop test and the drum test, thereby improving the safety performance of the cell and increasing the pass rate of the cell drop test and the drum test.

[0013] In some embodiments of the first aspect of this application, the base metal of the shell is iron, the wall thickness of the end wall is H1, the wall thickness of the side wall is H2, and 0.05mm≤H1-H2≤0.4mm.

[0014] In one or more of the above optional embodiments, the base metal of the casing is iron, which is beneficial for the casing to have high strength, thereby improving the safety performance of the battery cell. By ensuring that H1-H2 is greater than or equal to 0.05 mm, a large thickness difference between the end wall and the side wall is achieved, resulting in a large strength difference between the end wall and the side wall. This increases the probability that the casing deformation location after the battery cell drop test and roller test is located at or near the connection point of the transition wall and the side wall, thereby reducing the risk of the battery cell squeezing the electrode assembly after casing deformation during drop and roller tests, reducing the risk of thermal runaway, improving the safety performance of the battery cell, and increasing the pass rate of drop and roller tests. H1-H2 is less than or equal to 0.4 mm, ensuring that the thickness difference between the end wall and the side wall is not too large, resulting in good strength for both the side wall and the end wall, improving the safety performance of the battery cell and increasing the pass rate of drop and roller tests. Therefore, 0.05 mm ≤ H1-H2 ≤ 0.4 mm results in good safety performance and a high pass rate for drop and roller tests.

[0015] In some embodiments of the first aspect of this application, 0.07mm ≤ H1 - H2 ≤ 0.2mm.

[0016] In one or more of the above optional embodiments, by ensuring that H1-H2 is greater than or equal to 0.07 mm, a greater thickness difference between the end wall and the side wall is achieved, resulting in a greater strength difference between the end wall and the side wall. This further increases the probability that the deformation location of the casing after the cell drop test and roller test is located at the connection point of the transition wall and the side wall and its vicinity. This further reduces the risk of the cell squeezing the electrode assembly after the casing deforms during the drop and roller tests, reduces the risk of thermal runaway, and further improves the safety performance of the cell and the pass rate of the drop and roller tests. H1-H2 is less than or equal to 0.2 mm, ensuring that the thickness difference between the end wall and the side wall is not too large, resulting in better strength for both the side wall and the end wall, improving the safety performance of the cell and the pass rate of the drop and roller tests. Therefore, 0.07 mm ≤ H1-H2 ≤ 0.2 mm results in better safety performance and a higher pass rate for the drop and roller tests.

[0017] In some embodiments of the first aspect of this application, the base metal of the shell is aluminum, the wall thickness of the end wall is H1, the wall thickness of the side wall is H2, and 0.1mm≤H1-H2≤0.8mm.

[0018] In one or more of the above optional embodiments, the base metal of the casing is aluminum, which helps to reduce the weight of the casing and increase the energy density of the cell. By ensuring that H1-H2 is greater than or equal to 0.1 mm, a larger thickness difference between the end wall and the side wall is achieved, resulting in a larger strength difference between the end wall and the side wall. This increases the probability that the casing deformation location after drop and tumble tests will be located at or near the connection point of the transition wall and the side wall, thereby reducing the risk of the cell squeezing the electrode assembly after casing deformation during drop and tumble tests, reducing the risk of thermal runaway, improving the cell's safety performance, and increasing the pass rate of drop and tumble tests. H1-H2 is less than or equal to 0.8 mm, ensuring that the thickness difference between the end wall and the side wall is not too large, resulting in good strength for both the side wall and the end wall, improving the cell's safety performance and increasing the pass rate of drop and tumble tests. Therefore, 0.1 mm ≤ H1-H2 ≤ 0.8 mm indicates good cell safety performance and a high pass rate of drop and tumble tests.

[0019] In some embodiments of the first aspect of this application, 0.15mm ≤ H1-H2 ≤ 0.4mm.

[0020] In one or more of the above optional embodiments, by ensuring that H1-H2 is greater than or equal to 0.15mm, a greater thickness difference between the end wall and the side wall is achieved, resulting in a greater strength difference between the end wall and the side wall. This further increases the probability that the deformation location of the casing after the cell drop test and roller test is located at the connection point of the transition wall and the side wall and its vicinity. This further reduces the risk of the cell squeezing the electrode assembly after the casing deforms during the drop and roller tests, reduces the risk of thermal runaway, and further improves the safety performance of the cell and the pass rate of the drop and roller tests. H1-H2 is less than or equal to 0.4mm, ensuring that the thickness difference between the end wall and the side wall is not too large, resulting in better strength for both the side wall and the end wall, improving the safety performance of the cell and the pass rate of the drop and roller tests. Therefore, 0.15mm≤H1-H2≤0.4mm results in better safety performance and a higher pass rate for the drop and roller tests.

[0021] In some embodiments of the first aspect of this application, the thickness of the end wall is H1, where 0.1 mm ≤ H1 ≤ 1.0 mm.

[0022] In one or more of the above optional embodiments, by having H1 greater than or equal to 0.1 mm, the end wall has high strength, thereby giving the casing better strength and improving the safety performance of the battery cell; by having H1 less than or equal to 1 mm, the wall thickness of the end wall is not too large, which helps to reduce the weight of the casing and the space occupied, and improve the energy density of the battery cell. Therefore, 0.1 mm ≤ H1 ≤ 1.0 mm gives the battery cell high safety performance and energy density.

[0023] In some embodiments of the first aspect of this application, the wall thickness of the sidewall is H2, where 0.05mm ≤ H2 ≤ 0.8mm.

[0024] In one or more of the above optional embodiments, by having H2 greater than or equal to 0.05 mm, the sidewall has high strength, thereby giving the casing good strength and improving the safety performance of the battery cell; by having H2 less than or equal to 0.8 mm, the wall thickness of the sidewall is not too large, which helps to reduce the weight of the casing and the space occupied, and improve the energy density of the battery cell. Therefore, 0.05 mm ≤ H2 ≤ 0.8 mm gives the battery cell high safety performance and energy density.

[0025] In some embodiments of the first aspect of this application, the inner surface of the transition wall connects the inner surface of the side wall and the inner surface of the end wall.

[0026] In one or more of the above optional embodiments, the inner surface of the side wall and the inner surface of the end wall are connected by the inner surface of the transition wall, so that the end wall can transition to the side wall as smoothly as possible, reducing the risk of stress concentration at the junction of the end wall and the side wall of the shell.

[0027] In some embodiments of the first aspect of this application, the inner surface of the transition wall intersects with a cross section parallel to the first direction to form an arc.

[0028] In one or more of the above optional embodiments, an arc is formed by the inner surface of the transition wall intersecting with a section parallel to the first direction, so that the end wall can smoothly transition to the side wall, further reducing the risk of stress concentration at the junction of the end wall and the side wall of the shell.

[0029] In some embodiments of the first aspect of this application, the outer surface of the transition wall connects the outer surface of the side wall and the outer surface of the end wall.

[0030] In one or more of the above optional embodiments, the outer surface of the sidewall and the outer surface of the endwall are connected by the outer surface of the transition wall, so that the endwall can transition to the sidewall as smoothly as possible, reducing the risk of stress concentration at the junction of the endwall and the sidewall.

[0031] In some embodiments of the first aspect of this application, the outer surface of the transition wall intersects with a cross section parallel to the first direction to form an arc.

[0032] In one or more of the above optional embodiments, an arc is formed by the outer surface of the transition wall intersecting with a section parallel to the first direction, so that the end wall can smoothly transition to the side wall, reducing the risk of stress concentration at the junction of the end wall and the side wall of the shell.

[0033] In some embodiments of the first aspect of this application, the battery cell is a cylindrical battery cell.

[0034] In one or more of the above optional embodiments, the battery cell is a cylindrical battery cell. After drop and roller tests, the deformation position of the cylindrical battery cell casing avoids the overlapping area of ​​the positive and negative electrode plates, reducing the risk of the cylindrical battery cell casing deformation squeezing the electrode assembly after drop and roller tests, reducing the risk of thermal runaway of the cylindrical battery cell, improving the safety performance of the cylindrical battery cell and increasing the pass rate of drop and roller tests of the cylindrical battery cell.

[0035] In some embodiments of the first aspect of this application, the outer diameter of the sidewall is D, where 10mm ≤ D ≤ 100mm.

[0036] In one or more of the above optional embodiments, cylindrical cells with 10mm≤D≤100mm are classified as small cylindrical cells. Compared to other types of cylindrical cells, the casing of small cylindrical cells is more prone to deformation during drop and drum tests. By setting the transition wall of the small cylindrical cell to a non-uniform thickness structure, with the minimum wall thickness of the transition wall located at the first end, and the positive electrode plate being further away from the end wall along the first direction, the minimum distance between the positive electrode plate and the first end is L1, where 0.5mm≤L1≤3mm. This ensures that after drop and drum tests, the deformation location of the small cylindrical cell casing avoids the overlapping area of ​​the positive and negative electrode plates, reducing the risk of the casing deforming and squeezing the electrode assembly after drop and drum tests, reducing the risk of thermal runaway, improving the safety performance of the small cylindrical cell, and increasing the pass rate of drop and drum tests.

[0037] Secondly, embodiments of this application provide an electrical device, which includes the battery cell provided in any embodiment of the first aspect.

[0038] In one or more of the above optional embodiments, the battery cell provided in the first aspect embodiment has high safety performance, so that the electrical equipment powered by the battery cell has good electrical safety and reliability. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope.

[0040] Figure 1 Cross-sectional views of the battery cell provided in some embodiments of this application; Figure 2 Cross-sectional views of the battery cell provided for other embodiments of this application; Figure 3 A cross-sectional view of a battery cell provided in some embodiments of this application; Figure 4 A cross-sectional view of a battery cell provided for some embodiments of this application; Figure 5 Cross-sectional views of the housing provided for some embodiments of this application; Figure 6 Cross-sectional views of the housing provided for other embodiments of this application; Figure 7 For the electrode assembly to be housed in Figure 6 Sectional view of the middle shell; Figure 8 A cross-sectional view of the housing provided in some embodiments of this application; Figure 9 For the electrode assembly to be housed in Figure 8 Sectional view of the middle shell; Figure 10 A cross-sectional view of the housing provided for some embodiments of this application; Figure 11 A cross-sectional view of the housing provided in some further embodiments of this application; Figure 12 Cross-sectional views of a common housing are provided for further embodiments of this application; Figure 13 Cross-sectional views of the housing provided for other embodiments of this application; Figure 14 Cross-sectional views of a common housing are provided for other embodiments of this application; Figure 15 for Figure 1 Enlarged view of point C1.

[0041] Icons: 100-cell; 10-casing; 11-shell; 11a-opening; 111-end wall; 1111-inner surface of end wall; 1112-outer surface of end wall; 1113-first outer peripheral surface; 112-side wall; 1121-inner surface of side wall; 1122-outer surface of side wall; 1123-third end; 113-transition wall; 1131-first end; 1132-second end; 1133-inner surface of transition wall; 1134-outer surface of transition wall; 12-end cap; 20-electrode assembly; 21-positive electrode; 22-negative electrode; 23-separator; 24-positive electrode tab; 25-negative electrode tab; 30-terminal post; 40-current collector. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0044] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0045] In the description of the embodiments of this application, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing this application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0046] Currently, the application of rechargeable batteries is becoming increasingly widespread in the market. They are widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in power tools, drones, energy storage devices, and many other fields. As the application areas of rechargeable batteries continue to expand, the market demand is also constantly increasing.

[0047] Thermal runaway often occurs in battery cells after drop and tumble drying tests. One cause of this thermal runaway is casing deformation compressing the electrode assembly, leading to internal short circuits and ultimately thermal runaway. This phenomenon is particularly severe for small cylindrical cells where casing indentation causes thermal runaway, thus affecting the cell's safety performance. Related technologies address this by increasing casing thickness and rigidity to mitigate indentation deformation and reduce the risk of thermal runaway. However, this method significantly increases cell weight, and stress concentration at casing corners can still cause severe deformation leading to thermal runaway.

[0048] Based on the above considerations, in order to improve the safety performance of the battery cell, this application provides a battery cell including a housing and an electrode assembly. The housing includes an end wall, a side wall, and a transition wall. The transition wall has a first end and a second end, the first end being connected to the side wall and the second end being connected to the end wall. Along a first direction, an opening is formed at the end of the side wall opposite to the transition wall, and the opening and the end wall are disposed opposite to each other. The electrode assembly is at least partially housed within the housing. The electrode assembly includes a positive electrode and a negative electrode. Along the first direction, the negative electrode extends beyond the end of the positive electrode near the end wall from the opening towards the end wall. The transition wall has a non-uniform thickness structure, with the minimum wall thickness of the transition wall located at the first end. Along the first direction, the positive electrode is further away from the end wall than the first end, and the minimum distance between the positive electrode and the first end is L1, where 0.5mm ≤ L1 ≤ 3mm.

[0049] The connection between the end walls and side walls via a transition wall alleviates stress concentration at the junction of the end walls and side walls, improving the strength of the shell and thus mitigating deformation during drop and roller tests. Since the minimum wall thickness of the transition wall is located at the first end, its strength at that corresponding position is weaker. This means the shell's strength is weaker at the connection point between the transition wall and side wall. Consequently, deformation during drop and roller tests occurs at the connection point of the transition wall and side wall and its vicinity. Furthermore, along the first direction, the positive electrode is further away from the end wall than at the first end, allowing the shell deformation to avoid the overlapping area of ​​the positive and negative electrodes. This reduces the risk of shell deformation compressing the electrode assembly after drop and roller tests, lowers the risk of thermal runaway, improves the safety performance of the battery cell, and increases the pass rate of drop and roller tests. By setting L1 to be greater than or equal to 0.5mm, the distance between the positive electrode and the first end is made larger, ensuring that the deformation of the casing during drop and tumbling tests avoids the overlapping area of ​​the positive and negative electrodes, reducing the risk of thermal runaway and improving the safety performance and pass rate of drop and tumbling tests. By setting L1 to be less than or equal to 3mm, the distance between the positive electrode and the first end is not too large, which is beneficial to improving the energy density of the cell. Therefore, 0.5mm≤L1≤3mm gives the cell high safety performance and energy density.

[0050] The secondary batteries disclosed in the embodiments of this application can be used, but are not limited to, in electrical equipment such as electric two-wheelers, power tools, drones, and energy storage devices. Battery cells conforming to the operating conditions of this application can also be used as the power system for electrical equipment.

[0051] This application provides an electrical device that uses battery cells as a power source. The electrical device can be, but is not limited to, electronic devices, power tools, electric vehicles, drones, and energy storage devices. Electronic devices can include mobile phones, tablets, laptops, etc.; power tools can include electric drills, chainsaws, etc.; and electric vehicles can include electric cars, electric motorcycles, electric bicycles, etc.

[0052] like Figure 1 As shown, this application provides a battery cell 100, which includes a housing 10 and an electrode assembly 20, with the electrode assembly 20 housed within the housing 10.

[0053] The electrode assembly 20 includes a negative electrode plate 22, a positive electrode plate 21, a separator 23, a positive electrode tab 24, and a negative electrode tab 25. The positive electrode tab 24 is connected to the positive electrode plate 21, and the negative electrode tab 25 is connected to the negative electrode plate 22. The positive electrode tab 24 and the negative electrode tab 25 can be a full-tab structure or a split-tab structure.

[0054] The separator 23 provides insulation between the positive electrode 21 and the negative electrode 22 to reduce the risk of short circuit in the cell 100. The material of the separator 23 may include PP (polypropylene) or PE (polyethylene), etc.

[0055] The electrode assembly 20 has a wound structure. The negative electrode 22, the separator 23, the positive electrode 21, and another separator 23 are stacked in a specific order and then wound to form the wound electrode assembly 20; alternatively, the separator 23, the positive electrode 21, another separator 23, and the negative electrode 22 are stacked in a specific order and then wound to form the wound electrode assembly 20. Figure 2 As shown), flat structure ( Figure 3 (as shown in the image) etc.

[0056] like Figure 4 As shown, the electrode assembly 20 can also be a stacked structure. Positive electrode 21 and negative electrode 22 are stacked, with a separator 23 placed between adjacent positive electrode 21 and negative electrode 22 to insulate and isolate them, reducing the risk of short circuits between them. The stacking direction of the positive electrode 21 and negative electrode 22 can be perpendicular to the first direction.

[0057] The outer casing 10 can be a rigid casing 11, such as a stainless steel casing or an aluminum casing, to form a steel-cased battery or an aluminum-cased battery, respectively.

[0058] like Figure 1 As shown, the outer casing 10 includes a housing 11 and an end cap 12. The housing 11 is a component for housing the electrode assembly 20, with at least a portion of the electrode assembly 20 housed within the housing 11. The housing 11 can have various shapes, such as cylindrical, cuboid, etc. The housing 11 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The electrode assembly 20 can be partially or completely located within the housing 11. Figure 1 , Figure 2 As shown, the casing 11 has a cylindrical structure, and the battery cell 100 is a cylindrical battery cell 100. For example... Figure 3 , Figure 4 As shown, the shell 11 has a rectangular structure.

[0059] The housing 11 includes an end wall 111, a side wall 112, and a transition wall 113. The transition wall 113 has a first end 1131 and a second end 1132. The side wall 112 extends circumferentially along the end wall 111 to form a columnar structure. The first end 1131 is connected to the side wall 112, and the second end 1132 is connected to the end wall 111. The end wall 111 and the side wall 112 are connected by the transition wall 113, which can alleviate the stress concentration problem at the junction of the end wall 111 and the side wall 112, improve the strength of the housing 11, and thus alleviate the problem of deformation of the housing 11 during drop tests and roller tests.

[0060] The first end 1131 and the second end 1132 are the two end faces of the transition wall 113, respectively. Along the first direction, the side wall 112 has a third end 1123, and the first end 1131 and the third end 1123 are connected. The end wall 111 has a first outer peripheral surface 1113 extending circumferentially along the end wall 111, and the first outer peripheral surface 1113 is connected to the second end 1132.

[0061] The end wall 111, side wall 112, and transition wall 113 can be integrally formed, meaning that the shell 11 is an integrally formed structure. For example, the shell 11 can be manufactured by integral forming methods such as stamping, stretching, and casting.

[0062] Of course, the end wall 111, side wall 112 and transition wall 113 can also be set separately and connected, such as the transition wall 113 and side wall 112 being welded together, or the transition wall 113 and end wall 111 being welded together.

[0063] The transition wall 113 has an inner surface 1133 facing the electrode assembly 20 and an outer surface 1134 facing away from the electrode assembly 20. In a first direction, the end wall 111 has an inner surface 1111 facing the electrode assembly 20 and an outer surface 1112 facing away from the electrode assembly 20.

[0064] In some embodiments, the inner surface 1133 of the transition wall and the inner surface 1111 of the end wall can be directly connected, such as... Figure 5 As shown, the inner surface 1133 of the transition wall is connected to the edge of the end wall 111 and the outer edge of the inner surface 1111 of the end wall, so that the transition between the end wall 111 and the transition wall 113 can be as smooth as possible, and the stress concentration at the connection position of the end wall 111 and the transition wall 113 can be alleviated.

[0065] The sidewall 112 has an inner surface 1121 facing the electrode assembly 20 and an outer surface 1122 facing away from the electrode assembly 20.

[0066] In some embodiments, the inner surface 1133 of the transition wall and the inner surface 1121 of the side wall can be directly connected, such as... Figure 5 As shown, the outer surface 1134 of the transition wall is connected to the edge of the side wall 112 and the outer edge of the inner surface 1121 of the side wall, so that the transition between the side wall 112 and the transition wall 113 can be as smooth as possible, and the stress concentration at the connection position of the end wall 111 and the transition wall 113 can be alleviated.

[0067] like Figure 5 As shown, the inner surface 1133 of the transition wall connects the inner surface 1121 of the side wall and the inner surface 1111 of the end wall. That is, the inner surface 1133 of the transition wall directly connects to the inner surface 1111 of the end wall, and the inner surface 1133 of the transition wall directly connects to the inner surface 1121 of the side wall. By connecting the inner surface 1121 of the side wall and the inner surface 1111 of the end wall through the inner surface 1133 of the transition wall, the end wall 111 can transition to the side wall 112 as smoothly as possible, reducing the risk of stress concentration at the junction of the end wall 111 and the side wall 112 of the shell 11.

[0068] In other embodiments, the inner surface 1133 of the transition wall and the inner surface 1111 of the end wall can be indirectly connected, such as... Figure 6 , Figure 7As shown, the end wall 111 has a first outer peripheral surface 1113. A portion of the first outer peripheral surface 1113 is connected to the second end 1132, and another portion of the first outer peripheral surface 1113 is connected to the inner surface 1111 of the end wall and the inner surface 1133 of the transition wall, so as to achieve indirect connection between the inner surface 1133 of the transition wall and the inner surface 1111 of the end wall. In this scheme, the electrode assembly 20 is located on the side of the inner surface 1111 of the end wall, so that there is a large gap between the electrode assembly 20 and the inner surface 1133 of the transition wall. This can not only store the electrolyte, but also increase the distance between the electrode assembly 20 and the inner surface 1133 of the transition wall, reduce the risk of short circuit caused by the transition wall 113 squeezing the electrode assembly 20, and improve the safety performance of the cell 100.

[0069] In other embodiments, the inner surface 1133 of the transition wall and the inner surface 1121 of the side wall can be indirectly connected, such as... Figure 8 , Figure 9 As shown, the sidewall 112 has a third end 1123. A portion of the third end 1123 is connected to the first end 1131, and the other portion of the third end 1123 is connected to the inner surface 1121 of the sidewall and the inner surface 1133 of the transition wall, so as to achieve indirect connection between the inner surface 1133 of the transition wall and the inner surface 1121 of the sidewall. In this scheme, the sidewall 112 can protrude the transition wall 113 towards the electrode assembly 20, so that there is a large gap between the electrode assembly 20 and the inner surface 1133 of the transition wall. This can not only store the electrolyte, but also increase the distance between the electrode assembly 20 and the inner surface 1133 of the transition wall, reduce the risk of short circuit caused by the transition wall 113 squeezing the electrode assembly 20, and improve the safety performance of the cell 100.

[0070] like Figures 5-9 As shown, in some embodiments, the inner surface 1133 of the transition wall intersects with a cross section parallel to the first direction to form an arc. It can be understood that the transition wall 113 is an arc-shaped wall. By forming an arc by the inner surface 1133 of the transition wall intersecting with a cross section parallel to the first direction, the end wall 111 can smoothly transition to the side wall 112, further reducing the risk of stress concentration at the junction of the end wall 111 and the side wall 112 of the housing 11.

[0071] Of course, in other embodiments, the inner surface 1133 of the transition wall may intersect with the cross section parallel to the first direction to form other forms of linearity, such as... Figure 10 As shown, the inner surface 1133 of the transition wall can also form an inclined straight line when it intersects with the section parallel to the first direction.

[0072] In some embodiments, the outer surface 1134 of the transition wall and the outer surface 1112 of the end wall can be directly connected, such as... Figures 5-10As shown, the outer surface 1134 of the transition wall is connected to the outer edge of the end wall 111 and the outer edge of the outer surface 1112 of the end wall, so that the transition between the end wall 111 and the transition wall 113 can be as smooth as possible, and the stress concentration at the connection position of the end wall 111 and the transition wall 113 can be alleviated.

[0073] In some embodiments, the outer surface 1134 of the transition wall and the outer surface 1122 of the sidewall can be directly connected, such as... Figures 5-10 As shown, the outer surface 1134 of the transition wall is connected to the outer edge of the side wall 112 and the outer surface 1122 of the side wall, so that the transition between the side wall 112 and the transition wall 113 can be as smooth as possible, and the stress concentration at the connection position of the side wall 112 and the transition wall 113 can be alleviated.

[0074] like Figures 5-10 As shown, the outer surface 1134 of the transition wall connects the outer surface 1122 of the side wall and the outer surface 1112 of the end wall. That is, the outer surface 1134 of the transition wall directly connects to the outer surface 1112 of the end wall, and the outer surfaces 1134 of the transition walls are connected to the outer surfaces 1122 of the side walls. By connecting the outer surfaces 1122 of the side wall and the outer surfaces 1112 of the end wall through the outer surface 1134 of the transition wall, the end wall 111 can transition to the side wall 112 as smoothly as possible, reducing the risk of stress concentration at the junction of the end wall 111 and the side wall 112 of the shell 11.

[0075] In the embodiment where the inner surface 1133 of the transition wall connects the inner surface 1121 of the side wall and the inner surface 1111 of the end wall, and the outer surface 1134 of the transition wall connects the outer surface 1122 of the side wall and the outer surface 1112 of the end wall, the wall thickness of the end wall 111 can be the same as the wall thickness of the transition wall 113 at the second end 1132, and the wall thickness of the transition wall 113 at the first end 1131 can be the same as the wall thickness of the side wall 112.

[0076] In other embodiments, the outer surface 1134 of the transition wall and the outer surface 1112 of the end wall can be indirectly connected, such as... Figure 11 , Figure 12 As shown, a portion of the first outer peripheral surface 1113 of the end wall 111 is connected to the second end 1132, and another portion of the first outer peripheral surface 1113 is connected to the outer surface 1112 of the end wall and the outer surface 1134 of the transition wall, so as to achieve indirect connection between the outer surface 1112 of the end wall and the outer surface 1134 of the transition wall. In this scheme, the end wall 111 protrudes outward. After the battery cell 100 is installed in the electrical equipment or placed in other spaces, there is a large gap between the area of ​​the transition wall 113 near the end wall 111 and the external structure of the battery cell 100. This can reduce the risk of the battery cell 100 being deformed by external pressure at the transition wall 113, thereby reducing the risk of short circuit of the battery cell 100.

[0077] In other embodiments, the outer surface 1134 of the transition wall and the outer surface 1122 of the sidewall can be indirectly connected, such as... Figure 13 , Figure 14 As shown, a portion of the third end 1123 is connected to the first end 1131, and another portion of the third end 1123 is connected to the outer surface 1122 of the sidewall and the outer surface 1134 of the transition wall. In this design, the sidewall 112 protrudes outward, and after the battery cell 100 is installed in an electrical appliance or placed in another space, there is a large gap between the area along the transition wall 113 near the end wall 111 and the external structure of the battery cell 100. This reduces the risk of the battery cell 100 being deformed by external pressure at the transition wall 113, thereby reducing the risk of short circuit of the battery cell 100.

[0078] In some embodiments, the outer surface 1134 of the transition wall intersects with a cross section parallel to the first direction to form an arc. It can be understood that the transition wall 113 is an arc-shaped wall. By forming an arc by the outer surface 1134 of the transition wall intersecting with a cross section parallel to the first direction, the end wall 111 can smoothly transition to the side wall 112, further reducing the risk of stress concentration at the junction of the end wall 111 and the side wall 112 in the housing 11.

[0079] Of course, in other embodiments, the outer surface 1134 of the transition wall may intersect with the cross section parallel to the first direction to form other forms of linearity, such as... Figure 10 As shown, the outer surface 1134 of the transition wall can also form an inclined straight line when it intersects with the section parallel to the first direction.

[0080] It should be noted that the dashed line marked P1 in the accompanying drawings of this application represents the connecting plane between the transition wall 113 and the side wall 112. The connecting plane between the side wall 112 and the transition wall 113 is a plane passing through the intersection of the inner surface 1111 of the end wall and the inner surface 1121 of the side wall, and parallel to the first end 1131. P1 shows not only the connecting plane between the transition wall 113 and the side wall 112, but also the first end 1131 of the transition wall 113 and the third end 1123 of the side wall 112.

[0081] The dashed line marked on P2 represents the connecting plane between the transition wall 113 and the end wall 111. The connecting plane between the end wall 111 and the transition wall 113 is a plane passing through the intersection of the inner surface 1111 of the end wall and the inner surface 1133 of the transition wall and parallel to the first direction X. P2 shows not only the connecting plane between the transition wall 113 and the side wall 112, but also the second end 1132 of the transition wall 113 and the first outer peripheral surface 1113 of the end wall 111.

[0082] Along the first direction, an opening 11a is formed at the end of the side wall 112 opposite to the transition wall 113. The opening 11a and the end wall 111 are disposed opposite to each other, and the end cap 12 closes the opening 11a. Here, "closed" means to cover or shut, which can be either sealed or unsealed.

[0083] In an embodiment where the electrode assembly 20 is a wound structure, the extension direction of the winding axis of the electrode assembly 20 is parallel to the first direction. The positive electrode tab 24 and the negative electrode tab 25 can be located on the same side of the electrode assembly 20 along the first direction, or the positive electrode tab 24 and the negative electrode tab 25 can be located on opposite sides of the electrode assembly 20 along the first direction.

[0084] The end cap 12 and the housing 11 together define a receiving space for accommodating the electrode assembly 20 and other components. The end cap 12 can be connected to the housing 11 by welding or other means to close the opening 11a of the housing 11. The shape of the end cap 12 can be adapted to the shape of the housing 11. For example, if the housing 11 is a cuboid structure, the end cap 12 can be a rectangular plate structure adapted to the housing 11; or if the housing 11 is a cylindrical structure, the end cap 12 can be a circular plate structure adapted to the housing 11. The end cap 12 can also be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The end cap 12 and the housing 11 can be made of the same or different materials.

[0085] In embodiments where the battery cell 100 is a rigid-cased battery cell 100, one or two terminals 30 are insulatedly disposed on the outer casing 10 of the rigid-cased battery cell 100. If one terminal 30 is insulatedly disposed on the outer casing 10, the terminal 30 and the outer casing 10 are electrically connected to two tabs of opposite polarity of the electrode assembly 20, respectively. The terminal 30 and the outer casing 10 serve as two electrode terminals of opposite polarity of the battery cell 100, used to connect the battery cell 100 to an external device for charging and discharging. If two terminals 30 are insulatedly disposed on the outer casing 10, the two terminals 30 are connected to two tabs of opposite polarity of the electrode assembly 20, respectively, so that the two terminals 30 serve as two electrode terminals of opposite polarity of the battery cell 100, used to connect the battery cell 100 to an external device for charging and discharging. The electrode terminals can be disposed on the end cap 12, on the housing 11, or both the end cap 12 and the housing 11 can be provided with electrode terminals. Figure 1 The diagram shows that the end cap 12 is provided with a pole post 30. The pole post 30 is connected to the positive electrode tab 24 through a current collector 40, and the end wall 111 is connected to the negative electrode tab 25 through another current collector 40. Thus, the pole post 30 and the end wall 111 respectively form two electrode terminals with opposite polarities of the cell 100.

[0086] In this embodiment, along the first direction, the negative electrode 22 extends beyond the end of the positive electrode 21 near the end wall 111 from the opening 11a, and the negative electrode 22 extends beyond the end of the positive electrode 21 near the opening 11a from the end wall 111, so as to reduce the risk of lithium plating in the cell 100 and improve the safety performance of the cell 100.

[0087] In this embodiment, the transition wall 113 is a non-uniform thickness structure, and the minimum wall thickness of the transition wall 113 is located at the first end 1131. Specifically, along the extension direction of the transition wall 113 from the second end 1132 to the first end 1131, the wall thickness of the transition wall 113 gradually decreases, so that the minimum wall thickness of the transition wall 113 is located at the first end 1131. Since the minimum wall thickness of the transition wall 113 is located at the first end 1131, the strength of the transition wall 113 at the corresponding position of the first end 1131 is relatively weak. That is, the strength of the shell 11 at the connection between the transition wall 113 and the side wall 112 is relatively weak. Therefore, the deformation of the shell 11 during the drop and roller tests is located at the connection between the transition wall 113 and the side wall 112 and the area nearby. In addition, along the first direction, the positive electrode 21 is farther away from the end wall 111 than the first end 1131. Therefore, the deformation of the shell 11 can avoid the overlapping area of ​​the positive electrode 21 and the negative electrode 22, reducing the risk of the shell 11 deforming and squeezing the electrode assembly 20 after the cell 100 undergoes drop and roller tests, reducing the risk of thermal runaway of the cell 100, improving the safety performance of the cell 100, and improving the pass rate of the drop and roller tests of the cell 100.

[0088] The transition wall 113 has an inner surface 1133 facing the electrode assembly 20 and an outer surface 1134 facing away from the electrode assembly 20. The wall thickness at any location of the transition wall 113 can be the minimum distance between any location on the inner surface 1133 of the transition wall and the outer surface 1134 of the transition wall. For example, as... Figure 1 , Figure 5 As shown, the inner surface 1133 of the transition wall has a position A1, and the wall thickness of the transition wall 113 at position A1 is the distance between the outer surface 1134 of the transition wall and position B1, which is the closest to position A1.

[0089] Along the extension direction of the transition wall 113 extending from the second end 1132 to the first end 1131, the wall thickness of the transition wall 113 can also vary in a gradient. For example, along the extension direction of the transition wall 113 extending from the second end 1132 to the first end 1131, the transition wall 113 includes a plurality of wall segments connected in sequence. The wall segments have a uniform thickness structure, and in two adjacent wall segments, the wall segment closer to the first end 1131 has a smaller thickness than the wall segment farther from the first end 1131.

[0090] Along the extension direction of the transition wall 113 from the second end 1132 to the first end 1131, the wall thickness of the transition wall 113 may also exhibit other varying trends. For example, along the extension direction of the transition wall 113 from the second end 1132 to the first end 1131, the transition wall 113 includes a plurality of wall segments connected in sequence, some of which are of uniform thickness, and the thickness of some of which gradually decreases.

[0091] like Figure 15 As shown, in this embodiment, along the first direction, the positive electrode 21 is further away from the end wall 111 than the first end 1131, and the minimum distance between the positive electrode 21 and the first end 1131 is L1, 0.5mm≤L1≤3mm.

[0092] For example, L1 can be 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3mm, etc., and a range of values ​​between any two of these values.

[0093] By ensuring L1 is greater than or equal to 0.5 mm, the distance between the positive electrode 21 and the first end 1131 is relatively large. This ensures that the deformation of the casing 11 during drop tests and drum tests avoids the overlapping area of ​​the positive electrode 21 and the negative electrode 22, reducing the risk of thermal runaway in the cell 100 and improving its safety performance and pass rate in drop and drum tests. By ensuring L1 is less than or equal to 3 mm, the distance between the positive electrode 21 and the first end 1131 is not too large, which is beneficial for improving the energy density of the cell 100. Therefore, 0.5 mm ≤ L1 ≤ 3 mm ensures that the cell 100 has high safety performance and energy density.

[0094] In some embodiments, 0.7mm ≤ L1 ≤ 2mm.

[0095] For example, L1 can be 0.7mm, 0.9mm, 1.1mm, 1.3mm, 1.4mm, 1.6mm, 1.7mm, 1.9mm, 2mm, etc., and a range of values ​​between any two of these values.

[0096] By ensuring L1 is greater than or equal to 0.7 mm, the distance between the positive electrode 21 and the first end 1131 is increased, ensuring that the deformation of the casing 11 during drop and tumble tests avoids the overlapping area of ​​the positive electrode 21 and the negative electrode 22, further reducing the risk of thermal runaway in the cell 100, and further improving the safety performance and pass rate of the cell 100 in drop and tumble tests. By ensuring L1 is less than or equal to 2 mm, the distance between the positive electrode 21 and the first end 1131 is not too large, which is beneficial to further improving the energy density of the cell 100. Therefore, 0.7 mm ≤ L1 ≤ 2 mm gives the cell 100 higher safety performance and energy density.

[0097] like Figure 15 As shown, in some embodiments, along the first direction, the distance between the first end 1131 and the surface of the end wall 111 facing the electrode assembly 20 is L2, 0.5mm≤L2≤5mm.

[0098] L2 is a symbol representing the distance between the surfaces of the first end 1131 and the end wall 111 facing the electrode assembly 20 along the first direction. It does not mean that the distance between any position of the first end 1131 and the surface of the end wall 111 facing the electrode assembly 20 in the first direction is the same. Understandably, the distance between any position of the first end 1131 and the surface of the end wall 111 facing the electrode assembly 20 in the first direction satisfies 0.5mm-5mm.

[0099] For example, L2 can be 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, etc., and a range of values ​​between any two of these values.

[0100] By ensuring that L2 is greater than or equal to 0.5 mm, the distance between the first end 1131 and the surface of the end wall 111 facing the electrode assembly 20 is relatively large, reducing the risk of the transition wall 113 squeezing the electrode assembly 20. This reduces the risk of thermal runaway caused by internal short circuits in the cell 100, improving the safety performance of the cell 100 and increasing the pass rate of drop tests and roller tests. By ensuring that L2 is less than or equal to 5 mm, the distance between the first end 1131 and the end wall 111 is not too large, which is beneficial to improving the energy density of the cell 100. Therefore, 0.5 mm ≤ L2 ≤ 5 mm gives the cell 100 good safety performance and energy density.

[0101] In some embodiments, 1mm ≤ L2 ≤ 3mm.

[0102] For example, L2 can be 1mm, 1.1mm, 1.3mm, 1.4mm, 1.6mm, 1.7mm, 1.9mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, etc., as well as a range of values ​​between any two of these values.

[0103] By ensuring that L2 is greater than or equal to 1 mm, the distance between the first end 1131 and the surface of the end wall 111 facing the electrode assembly 20 is increased, further reducing the risk of the transition wall 113 squeezing the electrode assembly 20. This further reduces the risk of thermal runaway caused by a short circuit inside the cell 100, further improving the safety performance of the cell 100 and increasing the pass rate of the drop test and roller test. By ensuring that L2 is less than or equal to 3 mm, the distance between the first end 1131 and the end wall 111 is not too large, which is conducive to further improving the energy density of the cell 100. Therefore, 0.5 mm ≤ L2 ≤ 5 mm gives the cell 100 better safety performance and energy density.

[0104] The wall thickness of end wall 111 is the distance between two opposite surfaces of end wall 111 in the first direction. End wall 111 can be of uniform thickness, meaning the wall thickness is the same at any position, which facilitates the manufacturing and shaping of housing 11. Of course, the wall thickness of end wall 111 can also be of non-uniform thickness, which allows for flexible design of the cell 100 structure, matching the installation space of electrical equipment, and enabling housing 10 to have better strength performance.

[0105] The sidewall 112 has an inner surface 1121 facing the electrode assembly 20 and an outer surface 1122 facing away from the electrode assembly 20. The wall thickness at any location of the sidewall 112 can be the minimum distance between any location on the inner surface 1121 and the outer surface 1122 of the sidewall. For example, as... Figure 1 , Figure 5 As shown, the inner surface 1121 of the sidewall has a position A2, and the wall thickness of the sidewall 112 at position A2 is the distance between the outer surface 1122 of the sidewall and position B2, which is the closest to position A2.

[0106] The sidewall 112 can be of uniform thickness, meaning that the wall thickness is the same at any position on the sidewall 112, which facilitates the manufacturing and shaping of the housing 11. Of course, the wall thickness of the sidewall 112 can also be of non-uniform thickness, which is beneficial for the flexible design of the structure of the battery cell 100, can match the installation space of the electrical equipment, and can enable the housing 10 to have better strength performance.

[0107] The wall thickness of the end wall 111 can be the same as that of the side wall 112, which facilitates the manufacturing and forming of the shell 11. It can also reduce the occurrence of weak areas in the shell 10 due to the large difference in strength between the end wall 111 and the side wall 112, thus contributing to the overall strength of the shell 11.

[0108] The wall thickness of the end wall 111 can also be different from the wall thickness of the side wall 112, that is, the wall thickness of the end wall 111 is greater than or less than the wall thickness of the side wall 112.

[0109] For example, in some embodiments, the wall thickness of end wall 111 is greater than the wall thickness of side wall 112. That is, the wall thickness of end wall 111 at any position is greater than the wall thickness of side wall 112 at any position, or the minimum wall thickness of end wall 111 is greater than the maximum wall thickness of side wall 112.

[0110] Since the sidewall 112 has a larger area than the endwall 111, while ensuring that the strength of the sidewall 112 meets the design requirements of the cell 100, the wall thickness of the sidewall 112 is smaller than that of the endwall 111, which can support the weight of the cell 100 and improve the energy density of the cell 100.

[0111] Furthermore, since the minimum wall thickness of the transition wall 113 is located at the first end 1131, the wall thickness of the transition wall 113 is larger at the second end 1132. Since the wall thickness of the end wall 111 is greater than the wall thickness of the side wall 112, the end wall 111 and the transition wall 113 can have a larger connection area. This results in the end wall 111 and the connection position between the end wall 111 and the transition wall 113 having better strength. This reduces the risk of deformation of the housing 11 at the connection position between the end wall 111 and the transition wall 113 after the drop test and the roller test of the battery cell 100, or avoids deformation of the housing 11 at the connection position between the end wall 111 and the transition wall 113 after the drop test and the roller test of the battery cell 100. This improves the safety performance of the battery cell 100 and increases the pass rate of the drop test and the roller test of the battery cell 100.

[0112] In some embodiments, the base metal of the housing 11 is iron. It should be noted that iron as the base metal of the housing 11 means that the weight percentage of iron in the housing 11 is greater than or equal to 90%. Using iron as the base metal of the housing 11 is beneficial for the housing 11 to have higher strength, thereby improving the safety performance of the battery cell 100.

[0113] In an embodiment where the base metal of the housing 11 is iron, the wall thickness of the end wall 111 is H1, the wall thickness of the side wall 112 is H2, and 0.05mm≤H1-H2≤0.4mm.

[0114] That is, the wall thickness of end wall 111 is greater than the wall thickness of side wall 112, and the difference in wall thickness between end wall 111 and side wall 112 is not less than 0.05mm and not greater than 0.4mm.

[0115] It should be noted that H1 represents the wall thickness of end wall 111, but does not mean that the wall thickness of end wall 111 is the same at any position. Similarly, H2 represents the wall thickness of side wall 112, but does not mean that the wall thickness of side wall 112 is the same at any position. In some embodiments, the wall thickness of end wall 111 at any position is greater than the wall thickness of side wall 112 at any position, and the difference between the wall thickness of end wall 111 at any position and the wall thickness of side wall 112 at any position is not less than 0.05 mm and not greater than 0.4 mm.

[0116] For example, H1-H2 can be 0.05mm, 0.08mm, 0.1mm, 0.12mm, 0.15mm, 0.18mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, etc., and the range between any two of these values.

[0117] By ensuring that H1-H2 is greater than or equal to 0.05 mm, a significant thickness difference is created between the end wall 111 and the side wall 112, resulting in a significant strength difference between them. This increases the probability that the deformation location of the housing 11 after drop and drum tests is located at or near the connection point of the transition wall 113 and the side wall 112. This reduces the risk of the housing 11 deforming and crushing the electrode assembly 20 after drop and drum tests, thus lowering the risk of thermal runaway in the battery cell 100 and improving its overall performance. The safety performance of the battery cell 100 is improved, and the pass rate of drop and roller tests is increased. H1-H2 is less than or equal to 0.4mm, so that the thickness difference between the end wall 111 and the side wall 112 is not too large, so that both the side wall 112 and the end wall 111 have good strength, thus improving the safety performance of the battery cell 100 and increasing the pass rate of drop and roller tests. Therefore, 0.05mm≤H1-H2≤0.4mm, the battery cell 100 has good safety performance and a high pass rate of drop and roller tests.

[0118] In some embodiments, 0.07mm ≤ H1 - H2 ≤ 0.2mm.

[0119] For example, H1-H2 can be 0.07mm, 0.09mm, 0.1mm, 0.11mm, 0.13mm, 0.14mm, 0.16mm, 0.17mm, 0.19mm, 0.2mm, etc., and the range between any two of these values.

[0120] By ensuring that H1-H2 is greater than or equal to 0.07 mm, a greater thickness difference is achieved between the end wall 111 and the side wall 112, resulting in a greater strength difference between them. This further increases the probability that the deformation location of the housing 11 after the drop and drum tests of the battery cell 100 is located at or near the connection point of the transition wall 113 and the side wall 112. This further reduces the risk of the battery cell 100 compressing the electrode assembly 20 after the housing 11 deforms following the drop and drum tests, thus reducing the risk of thermal runaway in the battery cell 100 and further improving its performance. The safety performance of cell 100 and the pass rate of cell 100 drop test and tumble test are improved; H1-H2 is less than or equal to 0.2mm, so that the thickness difference between end wall 111 and side wall 112 is not too large, so that both side wall 112 and end wall 111 have better strength, thus improving the safety performance of cell 100 and the pass rate of cell 100 drop test and tumble test; therefore, 0.07mm≤H1-H2≤0.2mm, cell 100 has better safety performance and a higher pass rate of cell 100 drop test and tumble test.

[0121] In some other embodiments, the base metal of the housing 11 is aluminum. It should be noted that aluminum as the base metal of the housing 11 means that the weight percentage of aluminum in the housing 11 is greater than or equal to 90%. Using aluminum as the base metal of the housing 11 helps to reduce the weight of the housing 11 and increase the energy density of the battery cell 100.

[0122] In embodiments where the base metal of the housing 11 is aluminum, 0.1mm ≤ H1 - H2 ≤ 0.8mm.

[0123] That is, the wall thickness of end wall 111 is greater than the wall thickness of side wall 112, and the difference in wall thickness between end wall 111 and side wall 112 is not less than 0.1 mm and not greater than 0.8 mm. In some embodiments, the wall thickness of end wall 111 at any position is greater than the wall thickness of side wall 112 at any position, and the difference in wall thickness between end wall 111 at any position and side wall 112 at any position is not less than 0.1 mm and not greater than 0.8 mm.

[0124] For example, H1-H2 can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, etc., and the range between any two of these values.

[0125] By ensuring that H1-H2 is greater than or equal to 0.1 mm, a significant thickness difference is created between the end wall 111 and the side wall 112, resulting in a significant strength difference between them. This increases the probability that the deformation location of the housing 11 after drop and drum tests is located at or near the connection point of the transition wall 113 and the side wall 112. This reduces the risk of the housing 11 deforming and crushing the electrode assembly 20 after drop and drum tests, thus lowering the risk of thermal runaway in the battery cell 100 and improving its overall performance. The safety performance of the battery cell 100 is improved, and the pass rate of drop and roller tests is increased. H1-H2 is less than or equal to 0.8mm, so that the thickness difference between the end wall 111 and the side wall 112 is not too large, so that both the side wall 112 and the end wall 111 have good strength, thus improving the safety performance of the battery cell 100 and increasing the pass rate of drop and roller tests. Therefore, 0.1mm≤H1-H2≤0.8mm, the battery cell 100 has good safety performance and a high pass rate of drop and roller tests.

[0126] In some embodiments, 0.15mm ≤ H1 - H2 ≤ 0.4mm.

[0127] Examples include 0.15mm, 0.18mm, 0.19mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, 0.25mm, 0.26mm, 0.28mm, 0.32mm, 0.35mm, 0.38mm, 0.4mm, etc., and the range between any two of these values.

[0128] By ensuring that H1-H2 is greater than or equal to 0.15 mm, a greater thickness difference is achieved between the end wall 111 and the side wall 112, resulting in a greater strength difference between them. This further increases the probability that the deformation location of the housing 11 after the drop and drum tests of the battery cell 100 is located at or near the connection point of the transition wall 113 and the side wall 112. This further reduces the risk of the battery cell 100 compressing the electrode assembly 20 after the housing 11 deforms following the drop and drum tests, thus reducing the risk of thermal runaway in the battery cell 100 and further improving its performance. The safety performance of cell 100 and the pass rate of cell 100 drop test and tumble test are improved; H1-H2 is less than or equal to 0.4mm, so that the thickness difference between end wall 111 and side wall 112 is not too large, so that both side wall 112 and end wall 111 have better strength, thus improving the safety performance of cell 100 and the pass rate of cell 100 drop test and tumble test; therefore, 0.15mm≤H1-H2≤0.4mm, cell 100 has better safety performance and a higher pass rate of cell 100 drop test and tumble test.

[0129] In some embodiments, 0.1mm ≤ H1 ≤ 1.0mm.

[0130] For example, H1 can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, etc., and a range of values ​​between any two of these values.

[0131] By ensuring that H1 is greater than or equal to 0.1 mm, the end wall 111 has high strength, which in turn gives the casing 11 good strength, thereby improving the safety performance of the cell 100. By ensuring that H1 is less than or equal to 1.0 mm, the wall thickness of the end wall 111 is not too large, which helps to reduce the weight and space occupied by the casing 11 and improve the energy density of the cell 100. Therefore, 0.1 mm ≤ H1 ≤ 1.0 mm gives the cell 100 high safety performance and energy density.

[0132] In some embodiments, the thickness of the end wall 111 can vary depending on the material of the housing 11. For example, if the base metal of the housing 11 is iron, then H1 ≤ 0.5 mm. By ensuring that H1 is greater than or equal to 0.1 mm, the end wall 111 has better strength, thereby improving the strength of the housing 11 and enhancing the safety performance of the battery cell 100. By ensuring that H1 is less than or equal to 0.5 mm, the thickness of the end wall 111 with the base metal being iron is not too large, which helps to reduce the weight of the battery cell 100 and increase its energy density.

[0133] For example, if the base metal of the casing 11 is aluminum, then 0.5mm < H1 ≤ 1.0mm. By having H1 greater than 0.5mm, the end wall 111 has better strength, thereby giving the casing 11 better strength and improving the safety performance of the cell 100. By having H1 less than or equal to 1.0mm, the thickness of the end wall 111 with the base metal being aluminum is not too large, which helps to reduce the weight of the cell 100 and increase its energy density.

[0134] In some embodiments, 0.05mm ≤ H2 ≤ 0.8mm.

[0135] For example, H2 can be 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, etc., as well as a range between any two of these values.

[0136] By ensuring that H2 is greater than or equal to 0.05 mm, the sidewall 112 has high strength, which in turn gives the casing 11 good strength, thereby improving the safety performance of the cell 100. By ensuring that H2 is less than or equal to 0.8 mm, the wall thickness of the sidewall 112 is not too large, which helps to reduce the weight and space occupied by the casing 11 and improve the energy density of the cell 100. Therefore, 0.05 mm ≤ H2 ≤ 0.8 mm ensures that the cell 100 has high safety performance and energy density.

[0137] In some embodiments, the wall thickness of the sidewall 112 can be different for housings 11 made of different materials. For example, if the base metal of the housing 11 is iron, then 0.05mm ≤ H2 ≤ 0.4mm. With H2 greater than or equal to 0.05mm, the endwall 111 has better strength, thereby giving the housing 11 better strength and improving the safety performance of the battery cell 100. With H2 less than or equal to 0.4mm, the thickness of the sidewall 112 with the base metal being iron is not too large, which helps to reduce the weight of the battery cell 100 and increase its energy density.

[0138] For example, if the base metal of the casing 11 is aluminum, then 0.4mm < H2 ≤ 0.8mm. With H2 greater than or equal to 0.4mm, the sidewall 112 has good strength, thereby giving the casing 11 good strength and improving the safety performance of the cell 100. With H2 less than or equal to 0.8mm, the thickness of the sidewall 112 with the aluminum base metal is not too large, which helps to reduce the weight of the cell 100 and increase its energy density.

[0139] In embodiments where the housing 11 has a cylindrical structure, the battery cell 100 is a cylindrical battery cell 100. The outer diameter of the sidewall 112 is D, where 10mm ≤ D ≤ 100mm.

[0140] Cylindrical cells 100 with a diameter of 10mm ≤ D ≤ 100mm are classified as small cylindrical cells. The casing 11 of these small cylindrical cells is more prone to deformation during drop and tumbling tests compared to other types of cylindrical cells 100. To mitigate this, the transition wall 113 of the small cylindrical cell 100 is designed with a non-uniform thickness structure. The minimum wall thickness of the transition wall 113 is located at the first end 1131. Along the first direction, the positive electrode 21 is further away from the end wall 111 than the first end 1131. The minimum distance between the positive electrode 21 and the first end 1131 is L. 1. With a thickness of 0.5mm ≤ L1 ≤ 3mm, the deformation position of the casing 11 of the small cylindrical cell 100 avoids the overlapping area of ​​the positive electrode 21 and the negative electrode 22 after drop and roller tests. This reduces the risk of the casing 11 deforming and squeezing the electrode assembly 20 after drop and roller tests, reduces the risk of thermal runaway of the small cylindrical cell 100, improves the safety performance of the small cylindrical cell 100, and increases the pass rate of drop and roller tests.

[0141] Of course, cell 100 can also be other forms of cell 100, such as prismatic cell 100, cylindrical cell 100, etc.

[0142] This application also provides an electrical device, which includes the battery cell 100 provided in any of the above embodiments.

[0143] Cell 100 provides electrical energy to electrical equipment.

[0144] The battery cell 100 provided in any of the above embodiments has high safety performance, which enables electrical equipment powered by the battery cell 100 to have good electrical safety and reliability.

[0145] The battery cell 100 was subjected to drop and tumble tests. The safety performance of the battery cell 100 was determined based on the pass rates of the drop and tumble tests. The higher the pass rates of the drop and tumble tests, the better the safety of the battery cell 100. The energy density of the battery cell 100 was also tested using the following methods: Drop test method: Fully charge cell 100 (e.g., charge at a constant current of 0.2C to 4.2V, then charge at a constant voltage of 4.2V to 0.05C), and then conduct a drop test. The drop conditions include: ① a drop height of 1.2m, ② a drop on a concrete surface, ③ one drop headfirst, one drop bottomfirst, and one drop sideways counts as one round; ④ the cell is continuously dropped for 15 rounds, and the voltage and internal resistance of cell 100 are measured and recorded after each round of testing until the cell fails; ⑤ the cell passes the standard: after 15 rounds of testing, the cell does not catch fire or explode, and the voltage drop does not exceed 30%.

[0146] Roller test method: Fully charge cell 100 (e.g., charge at a constant current of 0.2C to 4.2V, then charge at a constant voltage of 4.2V to 0.05C), and then perform a roller test. The roller conditions include: ① using an octagonal cage with a drop height of 1m, ② rotation speed of 66r / min, ③ test duration of 90min per round; ④ continuously test the cell for 10 rounds, and record the voltage and internal resistance of cell 100 after each round of testing, until the cell fails; ⑤ the cell passes the standard: after 10 rounds of testing, it does not catch fire or explode, and the internal resistance growth rate does not exceed 50%.

[0147] Energy density measurement methods: Charge cell 100 at a constant current of 0.2C to 4.2V, then charge it at a constant voltage of 4.2V to 0.05C, and finally discharge it at a constant current of 0.2C to 2.5V. Measure the discharge energy Ene (usually in Wh) of cell 100. Use vernier calipers to measure the diameter and height (if it is a cylindrical cell) or length, width, and height (if it is a prismatic cell). Calculate the volume V (usually in L) according to the corresponding volume calculation method. Then the energy density is Ene / V (usually in Wh / L).

[0148] Example 1: Preparation method of cell 100: (a) Preparation of negative electrode plate 22 Artificial graphite (anode active material), silicon carbide (SiC) (anode active material), sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 82.45:14.55:1.7:1.3. Deionized water was then added as a solvent, and the mixture was stirred until homogeneous, yielding a negative electrode slurry with a solid content of 45 wt%. This negative electrode slurry was uniformly coated onto one surface of a 4 μm thick copper foil current collector. After drying at 105 °C, a negative electrode sheet 22 with a first negative electrode material layer coated on one side was obtained. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet 22 with both a first and a second negative electrode material layer coated. After cold pressing, cutting, and slitting, negative electrode sheets 22 with dimensions of 67.45 mm × 1730 mm were obtained for later use. The coating weight of the first and second negative electrode material layers was 0.06 g / 1540.25 mm. 2 The compacted density is 1.60 g / mm². 3 The first negative electrode material layer has a size of 62mm × 1730mm, the second negative electrode material layer has the same size as the first negative electrode material layer, and the width of the empty foil area of ​​the negative electrode sheet 22 is 5.45mm.

[0149] (II) Preparation of positive electrode 21 The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi). 0.9 Co 0.5 Mn0.5 O2), polyvinylidene fluoride (PVDF) binder, and conductive carbon black were dispersed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 97.1:1.6:1.3 and thoroughly mixed to obtain a positive electrode slurry with a solid content of 72 wt%. The positive electrode slurry was uniformly coated on one surface of a 11 μm thick aluminum foil for the positive electrode current collector and dried at 105 °C to obtain a positive electrode sheet 21 with a first positive electrode material layer coated on one side. Then, the above steps were repeated on the other surface of the aluminum foil for the positive electrode current collector to obtain a positive electrode sheet 21 with a first positive electrode material layer and a second positive electrode material layer coated.

[0150] The coating weight of the first and second positive electrode material layers is 0.15g / 1540.25mm. 2 The compacted density is 3.5 g / mm². 3 The positive electrode 21 has a size of 65.75mm×1688mm, the first positive electrode material layer has a size of 60mm×1688mm, and the second positive electrode material layer has the same size as the first positive electrode material layer.

[0151] (iii) Thickness of the separator 23 A polyethylene (PE) film with a thickness of 12 μm was used as the separator 23.

[0152] (iv) Preparation of electrolyte In a dry argon-atmospheric glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1:1 to obtain a base solvent (lithium salt solvent). Then, lithium hexafluorophosphate (LiPF6), along with vinylene carbonate (VC) and fluoroethylene carbonate (FEC) as additives, were added to the base solvent, with VC and FEC each added at 1%. After thorough mixing, an electrolyte was obtained. Based on the mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, with the remainder being the base solvent.

[0153] (V) Preparation of Cell 100 The separator 23, negative electrode 22, separator 23, and positive electrode 21 prepared above are stacked sequentially and wound to form an electrode assembly 20. The electrode assembly 20 is then subjected to transfer welding, packaging into a casing, inkjet printing, vacuum drying, electrolyte injection, high-temperature settling, vacuum sealing, and formation to obtain a lithium-ion battery (cell 100). The upper limit of the formation voltage is 3.6V, and the formation temperature is 70℃. Specifically, in the extension direction of the transition wall 113 of the casing 11 of the cell 100, extending from the end wall 111 to the side wall 112, the wall thickness of the transition wall 113 gradually decreases. After being placed in the casing, the positive electrode 21 of the electrode assembly 20 is further away from the end wall 111 than the first end 1131 connecting the transition wall 113 and the side wall 112. Along the first direction, the distance between the positive electrode 21 and the first end 1131 is 0.5mm.

[0154] Examples 1-34 Except for adjusting the relevant dimensional parameters of the battery cell 100 according to Table 1, the rest is the same as in Example 1.

[0155] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is whether the transition wall 113 is a structure of uniform thickness; the other parameters are the same.

[0156] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the distance between the positive electrode 21 and the first end 1131 in the first direction X is different, while the other parameters are the same.

[0157] The relevant parameters and performance tests of Comparative Example 3, Examples 1 to 34 are shown in Table 1: Table 1

[0158] As shown in Table 1: (1) As can be seen from Comparative Examples 1, 2, 3 and Examples 1-6, when the transition wall 113 is a non-uniform thickness structure and the minimum wall thickness of the transition wall 113 is located at the first end 1131, the pass rate of the drum test and the pass rate of the drop test of the battery cell are significantly increased. Compared with the case where L1 < 0.5 mm, the pass rate of the drum test and the pass rate of the drop test of the battery cell 100 are higher when L1 ≥ 0.5 mm, especially when L1 ≥ 0.7 mm. As L1 increases, the space inside the housing 11 that is not utilized by the electrode assembly 20 decreases, which increases the energy density loss and makes the energy density of the battery cell 100 lower. When L1 ≤ 3 mm, the battery cell has a higher energy density, especially when L1 ≤ 2 mm, the energy density of the battery cell is higher. Therefore, with a diameter of 0.5mm≤L1≤3mm, the cell 100 exhibits high pass rates in both the roller test and drop test, as well as high energy density. Consequently, the cell 100 possesses good mechanical properties, safety performance, and energy density. In particular, with a diameter of 0.7mm≤L1≤2mm, the cell 100 exhibits even higher pass rates in both the roller test and drop test, as well as high energy density. Therefore, the cell 100 possesses even better mechanical properties, safety performance, and energy density.

[0159] (2) As can be seen from Examples 1 and 7-12, when L2≥0.5mm, the pass rate of the roller test and the drop test of the battery cell 100 are both high. Especially when L2≥1mm, the pass rate of the roller test and the drop test of the battery cell 100 are even higher. However, as L2 increases, the energy density of the battery cell 100 tends to decrease. When L2≤5mm, the battery cell 100 has a high energy density. Especially when L2≤3mm, the energy density of the battery cell 100 is even higher. Therefore, when 0.5mm≤L2≤5mm, the pass rate of the roller test, the drop test and the energy density of the battery cell 100 are all high. Therefore, the battery cell 100 has good mechanical performance, safety performance and energy density. Especially when 1mm≤L1≤3mm, the pass rate of the roller test, the drop test and the energy density of the battery cell 100 are better overall. Therefore, the battery cell 100 has better mechanical performance, safety performance and energy density.

[0160] (3) As can be seen from Examples 1 and 13-20, when the base metal of the shell 11 is iron, the pass rate of the roller test, the pass rate of the drop test and the energy density of the cell 100 are all high when 0.05mm≤H1-H2≤0.4mm. Therefore, the cell 100 has good mechanical properties, safety performance and energy density. Especially when 0.07mm≤H1-H2≤0.2mm, the overall mechanical properties, safety performance and energy density of the cell 100 are better.

[0161] (4) As can be seen from Examples 21-28, when the base metal of the shell 11 is aluminum, 0.1mm≤H1-H2≤0.8mm, the pass rate of the roller test, the pass rate of the drop test and the energy density of the cell 100 are all high. Therefore, the cell 100 has good mechanical properties, safety performance and energy density; especially when 0.15mm≤H1-H2≤0.4mm, the overall mechanical properties, safety performance and energy density of the cell 100 are better.

[0162] (5) As can be seen from Examples 29-34, when 10mm≤D≤100mm, the drop test pass rate and roller test pass rate of the battery cell 100 are higher when the solution provided in this application is adopted, and the battery cell 100 has higher mechanical performance and safety performance.

[0163] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art.

Claims

1. A battery cell, characterized in that, include: The housing includes an end wall, a side wall, and a transition wall. The transition wall has a first end and a second end. The first end is connected to the side wall, and the second end is connected to the end wall. Along a first direction, an opening is formed at the end of the side wall opposite to the transition wall. The opening and the end wall are disposed opposite to each other. An electrode assembly, at least partially housed within the housing, includes a positive electrode and a negative electrode, wherein, along the first direction, the negative electrode extends beyond the end of the positive electrode near the end wall from the opening toward the end wall. Wherein, along the extension direction of the transition wall from the second end to the first end, the wall thickness of the transition wall gradually decreases, the transition wall is a non-uniform thickness structure, the minimum wall thickness of the transition wall is located at the first end, along the first direction, the positive electrode is farther away from the end wall than the first end, and the minimum distance between the positive electrode and the first end is L1, 0.5mm≤L1≤3mm.

2. The battery cell according to claim 1, characterized in that, 0.7mm≤L1≤2mm.

3. The battery cell according to claim 1 or 2, characterized in that, Along the first direction, the distance between the first end and the surface of the end wall facing the electrode assembly is L2, 0.5mm≤L2≤5mm, preferably 1mm≤L2≤3mm.

4. The battery cell according to any one of claims 1-3, characterized in that, The thickness of the end wall is greater than the thickness of the side wall.

5. The battery cell according to claim 4, characterized in that, The base metal of the shell is iron, the wall thickness of the end wall is H1, and the wall thickness of the side wall is H2, with 0.05mm≤H1-H2≤0.4mm, preferably 0.07mm≤H1-H2≤0.2mm.

6. The battery cell according to claim 4, characterized in that, The base metal of the shell is aluminum, the wall thickness of the end wall is H1, and the wall thickness of the side wall is H2, with 0.1mm≤H1-H2≤0.8mm, preferably 0.15mm≤H1-H2≤0.4mm.

7. The battery cell according to any one of claims 1-6, characterized in that, The end wall thickness is H1, 0.1mm≤H1≤1.0mm; and / or, the side wall thickness is H2, 0.05mm≤H2≤0.8mm.

8. The battery cell according to any one of claims 1-7, characterized in that, The inner surface of the transition wall connects the inner surface of the side wall and the inner surface of the end wall.

9. The battery cell according to claim 8, characterized in that, The inner surface of the transition wall intersects with a cross section parallel to the first direction to form an arc.

10. The battery cell according to any one of claims 1-9, characterized in that, The outer surface of the transition wall connects the outer surface of the side wall and the outer surface of the end wall.

11. The battery cell according to claim 10, characterized in that, The outer surface of the transition wall intersects with a cross section parallel to the first direction to form an arc.

12. The battery cell according to any one of claims 1-11, characterized in that, The battery cell is a cylindrical battery cell.

13. The battery cell according to claim 12, characterized in that, The outer diameter of the sidewall is D, where 10mm ≤ D ≤ 100mm.

14. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1-13.

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