Cylindrical battery, battery pack, and electric device

Abstract

This application discloses a cylindrical battery, a battery pack, and an electrical device. The cylindrical battery includes an electrode assembly, a housing, and a current collector. The electrode assembly is housed within the housing, which includes a bottom wall. The bottom wall and the electrode assembly are disposed along the axial direction of the cylindrical battery, and the bottom wall includes a thinned portion. The current collector is disposed between the electrode assembly and the bottom wall, and is connected to the electrode assembly. The current collector is welded to a portion of the thinned portion to form a first welded portion. The relatively small thickness of the thinned portion helps to reduce welding power, reduce welding heat generation, enhance the welding strength between the bottom wall and the current collector, and improve the welding yield. The portion of the thinned portion not welded to the current collector is relatively weak and is more prone to breakage than other parts of the bottom wall. This can form a pressure relief structure for the cylindrical battery, which helps to reduce the risk of explosion due to excessive internal pressure, and improves the safety and reliability of the cylindrical battery.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a cylindrical battery, a battery pack, and an electrical device. Background Technology

[0002] Rechargeable batteries are batteries that can be recharged after being discharged to reactivate the active materials and continue to be used. Rechargeable batteries are widely used in electronic devices such as mobile phones, laptops, and drones.

[0003] The development of battery technology takes into account many design factors, such as energy density, cycle life, assembly efficiency, and processing technology, as well as battery safety performance. Summary of the Invention

[0004] This application provides a cylindrical battery, a battery pack, and an electrical device, which are beneficial for improving the welding efficiency and safety performance of cylindrical batteries.

[0005] In a first aspect, this application provides a cylindrical battery, comprising an electrode assembly, a housing, and a current collector. The electrode assembly is housed within the housing, which includes a bottom wall disposed along the axial direction of the cylindrical battery. The bottom wall includes a thinned portion. A current collector is disposed between the electrode assembly and the bottom wall, connected to the electrode assembly, and welded to a portion of the thinned portion to form a first welded portion. The relatively small thickness of the thinned portion helps to reduce welding power, reduce welding heat generation, enhance the welding strength between the bottom wall and the current collector, and improve the welding yield. The portion of the thinned portion not welded to the current collector is relatively weak and more prone to cracking than other parts of the bottom wall, forming a pressure relief structure for the cylindrical battery. This helps to reduce the risk of explosion due to excessive internal pressure, improving the safety and reliability of the cylindrical battery.

[0006] In one or more of the above optional embodiments, a recess is provided on the side of the bottom wall away from the current collector, and the recess corresponds to the thinning portion. The recess can provide a receiving space for the first welding portion, reducing the possibility that the first welding portion will protrude from the outer surface of the bottom wall in the direction away from the electrode assembly. This helps to improve the flatness of the bottom wall of the cylindrical battery and enhance its stability when installed with the battery holder or busbar. Furthermore, the first welding portion and the bottom wall can share a portion of the axial space, which helps to save space and increase the energy density of the cylindrical battery.

[0007] In one or more of the above optional embodiments, along the direction from the current collector to the bottom wall, the first weld portion does not extend beyond the surface of the bottom wall facing away from the current collector. The cylindrical battery can be supported on the support surface by the surface of the bottom wall, and the relatively flat surface of the bottom wall is beneficial to improving the stability of the cylindrical battery when installed with the battery bracket or busbar; the first weld portion can avoid the support surface, reducing the force on the first weld portion and lowering the risk of damage or failure of the first weld portion. Furthermore, the first weld portion does not occupy additional axial space, which is beneficial to improving structural compactness and increasing the energy density of the cylindrical battery.

[0008] In one or more of the above optional embodiments, the thinning portion is annular. Given a fixed area of ​​the thinning region on the bottom wall, the annular thinning portion has a wider distribution range, which helps to disperse the weak parts of the bottom wall and reduce the impact of the thinning portion on the overall structural strength of the bottom wall. Furthermore, the distribution of the thinning portion is relatively uniform along the circumference of the cylindrical battery, which helps to balance the structural strength of the bottom wall.

[0009] In one or more of the above optional embodiments, the first welded portion is arc-shaped, and the central angle corresponding to the first welded portion is 90°-270°. A central angle α greater than or equal to 90° increases the welding area between the bottom wall and the current collector, which is beneficial for improving current carrying capacity and enhancing the connection strength between the bottom wall and the current collector. An α less than or equal to 270° prevents the length of the first welded portion in the circumferential direction of its corresponding circle from being excessively long, allowing a relatively large exhaust channel to be formed between the bottom wall and the current collector. This facilitates rapid gas action on the area of ​​the bottom wall surrounded by the thinned portion, causing the portion of the thinned portion not welded to the current collector to rupture under internal pressure, thus facilitating smoother pressure release from the cylindrical battery.

[0010] In one or more of the above optional embodiments, there are multiple first welded portions, which are spaced apart circumferentially along the cylindrical battery. This allows multiple venting channels to be formed between the bottom wall and the current collector, spaced apart circumferentially along the cylindrical battery. Gas from different locations within the casing can flow through different venting channels and act on the area of ​​the bottom wall surrounded by the multiple first welded portions, thereby breaking through the portion of the thinned section not welded to the current collector. This helps shorten the airflow path and improve the pressure relief efficiency of the cylindrical battery. Furthermore, it also helps shorten the conductive path, improve current carrying capacity, reduce heat generation, and lower the risk of electrode assembly and bottom wall connection failure.

[0011] In one or more of the above optional embodiments, the first weld portion is arc-shaped, and the sum of the central angles corresponding to multiple first weld portions is 90°-270°. When the sum of the central angles corresponding to multiple first weld portions is greater than or equal to 90°, the welding area between the bottom wall and the current collector plate can be increased, which is beneficial for improving current carrying capacity and enhancing the connection strength between the bottom wall and the current collector plate. When the sum of the central angles corresponding to multiple first weld portions is less than or equal to 270°, the sum of the circumferential lengths of the multiple first weld portions in their corresponding circles is not excessively long, and the total area of ​​the exhaust channel formed between the bottom wall and the current collector plate is relatively large. This facilitates the rapid action of gas on the area of ​​the bottom wall surrounded by multiple first weld portions, thereby breaking through the portion of the thinned part not welded to the current collector plate, which is beneficial for smoother pressure release of the cylindrical battery.

[0012] In one or more of the above optional embodiments, a plurality of first welded portions are arranged at equal angular intervals around the center of the bottom wall. The distribution of the connection positions between the bottom wall and the collector plate is relatively uniform, which is beneficial to improving the connection effect between the bottom wall and the collector plate. Furthermore, the area of ​​the exhaust channel formed between any two adjacent first welded portions is approximately the same, which is beneficial to more uniform pressure relief.

[0013] In one or more of the above optional embodiments, the bottom wall includes a bottom wall body, and the thinned portion is connected to the bottom wall body; the thickness of the bottom wall body is H, and the thickness of the thinned portion is h; 0.15 ≤ h / H ≤ 0.6. h / H is greater than or equal to 0.15 to ensure that the thinned portion is not too thin relative to the bottom wall body, thereby reducing the risk of cracking failure of the thinned portion under conditions such as axial vibration or axial compression of the cylindrical battery, improving the structural stability of the cylindrical battery, and extending its service life. h / H is less than or equal to 0.6, making the thinned portion easier to weld through, which facilitates welding the bottom wall and current collector from the outside of the casing, improving welding effectiveness and welding effect.

[0014] In one or more of the above optional embodiments, the thickness of the thinned portion is h, and the thickness of the current collector is h1; 0.5 ≤ h1 / h ≤ 2. If h1 / h is greater than or equal to 0.5, the thickness of the current collector relative to the thinned portion will not be too thin, and the thickness of the thinned portion relative to the current collector will not be too thick. This reduces the risk of the current collector being melted through and facilitates welding through the thinned portion to achieve the connection between the bottom wall and the current collector. If h1 / h is less than or equal to 2, the thickness of the current collector relative to the thinned portion will not be too thick, and the thickness of the thinned portion relative to the current collector will not be too thin. This saves space occupied by the current collector in the axial direction and reduces the risk of cracking failure of the thinned portion under axial vibration or axial compression of the cylindrical battery, thereby improving the structural stability of the cylindrical battery and extending its service life.

[0015] In one or more of the above optional embodiments, the diameter of the cylindrical battery is D; the thinned portion is annular, and the inner diameter of the thinned portion is d; 1 / 2 ≤ d / D ≤ 2 / 3. When d / D is greater than or equal to 1 / 2, the thinned portion can enclose a relatively large area. After the thinned portion ruptures under the pressure inside the cylindrical battery, it can form a relatively large pressure relief port on the bottom wall, which is beneficial for increasing the pressure relief area and improving the pressure relief efficiency. Furthermore, the circumferential length of the thinned portion along the cylindrical battery can be appropriately increased, thereby providing a larger welding area for the thinned portion and the current collector, and allowing the thinned portion to retain a larger length not welded to the current collector, which is beneficial for the smooth rupture and pressure relief of the thinned portion. When d / D is less than or equal to 2 / 3, the thinned portion will not be too close to the connection point between the bottom wall and the side wall, which can reduce the stress influence on the thinned portion from the connection point between the bottom wall and the side wall, and is beneficial for the thinned portion to rupture promptly under the pressure inside the cylindrical battery.

[0016] In one or more of the above optional embodiments, the minimum width of the thinned portion in the radial direction of the cylindrical battery is w; the thickness of the thinned portion is h; 0.1 ≤ h / w ≤ 0.3. A h / w greater than or equal to 0.1 can improve the strength of the thinned portion, reduce the risk of cracking failure under axial vibration or axial compression of the cylindrical battery, improve the structural stability of the cylindrical battery, and extend its service life. A h / w less than or equal to 0.3 allows the thinned portion to have a relatively large width without being excessively thick, facilitating welding of the thinned portion and the current collector, and improving the welding yield.

[0017] In one or more of the above optional embodiments, the first weld portion is spaced apart from the surface of the manifold facing the electrode assembly in the axial direction. The first weld portion does not melt through the manifold, which helps to reduce the impact of the weld between the bottom wall and the manifold on the electrode assembly.

[0018] In one or more of the above optional embodiments, in the axial direction, the thickness of the current collector is h1, and the dimension of the portion of the first weld formed on the current collector is h2, where 1 / 3 ≤ h2 / h1 ≤ 2 / 3. If h2 / h1 is greater than or equal to 1 / 3, the penetration depth of the first weld within the current collector is not too small, which is beneficial for enhancing the welding strength between the current collector and the bottom wall. If h2 / h1 is less than or equal to 2 / 3, the penetration depth of the first weld within the current collector is not too large, which is beneficial for reducing the impact of the welding between the current collector and the bottom wall on the electrode assembly, reducing the risk of the current collector being melted through, and improving the reliability of the cylindrical battery.

[0019] In one or more of the above optional embodiments, the cylindrical battery further includes an end cap and an explosion-proof plate disposed on the end cap; the bottom wall and the end cap are arranged axially, and the end cap is connected to the housing; the burst pressure of the explosion-proof plate is less than the burst pressure of the thinned portion. When the pressure inside the cylindrical battery is relatively high but has not reached a certain level, the explosion-proof plate can burst before the thinned portion, and the pressure of the cylindrical battery can be relieved first by the flipping and bursting of the explosion-proof plate, which can reduce the possibility of the thinned portion breaking and reduce the possibility of electrolyte leakage, short circuits, etc., that may be caused by housing breakage. If the venting passage of the explosion-proof plate is blocked by the electrode assembly, or by electrolyte, electrode and separator residue, etc., when the pressure inside the cylindrical battery continues to increase, the thinned portion can burst to release gas, which is beneficial to improving the pressure relief efficiency.

[0020] In one or more of the above optional embodiments, the current collector is welded to the electrode assembly to form a second weld portion; in the axial direction of the cylindrical battery, the projection of the second weld portion is separate from the projection of the thinned portion. The second weld portion does not contact the thinned portion, which helps to reduce the impact on the strength of the portion of the thinned portion welded to the current collector and reduce the impact on the pressure relief of the portion of the thinned portion not welded to the current collector.

[0021] Secondly, this application provides a battery pack that includes the cylindrical battery provided in any embodiment of the first aspect.

[0022] Thirdly, this application provides an electrical device that includes a battery pack according to any embodiment of the second aspect. Attached Figure Description

[0023] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0024] Figure 1 This is a schematic diagram of the structure of a cylindrical battery provided in some embodiments of this application;

[0025] Figure 2 for Figure 1 A cross-sectional view of the cylindrical battery shown.

[0026] Figure 3 for Figure 2 A magnified structural diagram of region A in the middle;

[0027] Figure 4 for Figure 1 An enlarged schematic diagram of a portion of the structure of another cross-sectional view of the cylindrical battery shown.

[0028] Figure 5 A schematic diagram of the bottom wall structure of a cylindrical battery provided in some embodiments of this application;

[0029] Figure 6 A schematic diagram of the bottom wall structure of a cylindrical battery provided in other embodiments of this application;

[0030] Figure 7 This is a schematic diagram of the battery pack structure provided in some embodiments of this application;

[0031] Figure 8 The diagram shows the structure of electrical equipment provided in some embodiments of this application.

[0032] The reference numerals in the accompanying drawings for the specific embodiments are as follows:

[0033] Cylindrical battery 1, electrode assembly 10, housing 20, bottom wall 21, thinning part 211, recess 212, bottom wall body 213, surface 21a, center 21b, side wall 22, end cap 30, current collector 40, first welding part 51, second welding part 52, explosion-proof sheet 60, axis a, axial direction X;

[0034] Battery pack 100, electrical equipment 1000. Detailed Implementation

[0035] 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 described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0036] The terms "first," "second," "third," etc., used in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0037] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0038] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0039] In the embodiments of this application, "parallel" includes not only the case of absolute parallelism, but also the case of approximate parallelism as commonly understood in engineering; similarly, "perpendicular" also includes not only the case of absolute perpendicularity, but also the case of approximate perpendicularity as commonly understood in engineering. For example, if the angle between two directions is 85°-95°, the two directions can be considered perpendicular; if the angle between two directions is 0°-10°, the two directions can be considered parallel.

[0040] The cylindrical battery, battery pack, and electrical device of this application are described below with reference to the accompanying drawings.

[0041] Reference Figures 1 to 8 This application provides a cylindrical battery 1, which can be a lithium-ion battery, a sodium-lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, or other types of batteries.

[0042] For example, the cylindrical battery 1 can be a 21700 battery, an 18650 battery, a 46800 battery, a 49480 battery, or other types of cylindrical batteries.

[0043] In some embodiments, the cylindrical battery 1 is a secondary battery. After discharge, the secondary battery can be recharged to activate the active materials and continue to be used.

[0044] In some embodiments, the cylindrical battery 1 includes an electrode assembly 10. The electrode assembly 10 includes a first electrode and a second electrode with opposite polarities. During the charging and discharging process of the cylindrical battery 1, active ions (e.g., lithium ions) are inserted and extracted back and forth between the first electrode and the second electrode. One of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode.

[0045] In some embodiments, the electrode assembly 10 further includes a separator disposed between the first electrode and the second electrode, the separator insulating the first electrode and the second electrode. The separator helps reduce the risk of short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0046] In some embodiments, the first electrode includes a first electrode body and a first tab, and the second electrode includes a second electrode body and a second tab. The first electrode body includes a first current collector and a first active material layer coated on the surface of the first current collector, and the first tab is connected to the first current collector. The second electrode body includes a second current collector and a second active material layer coated on the surface of the second current collector, and the second tab is connected to the second current collector. One of the first tab and the second tab is a positive tab, and the other is a negative tab. Optionally, the first tab is integrally formed with the first current collector, and the second tab is integrally formed with the second current collector.

[0047] In some embodiments, the cylindrical battery 1 includes a housing 20, and an electrode assembly 10 is housed within the housing 20. The interior of the housing 20 defines a cylindrical space, and the shape of the electrode assembly 10 can be matched to the shape of the space defined inside the housing 20.

[0048] In some embodiments, the housing 20 includes a bottom wall 21 disposed along the axial direction X of the cylindrical battery 1 with respect to the electrode assembly 10. The bottom wall 21 can be used to support the electrode assembly 10 and other components housed within the housing 20.

[0049] In some embodiments, the bottom wall 21 may be electrically connected to the electrode assembly 10, and the bottom wall 21 forms an electrode terminal of the cylindrical battery 1, which can eliminate a traditional electrode terminal and simplify the structure of the cylindrical battery 1.

[0050] In some embodiments, the housing 20 includes a sidewall 22 surrounding the electrode assembly 10. The sidewall 22 is generally cylindrical. A bottom wall 21 is connected to the sidewall 22, and the bottom wall 21 and the sidewall 22 together enclose a cylindrical space within the housing 20.

[0051] The bottom wall 21 and the side wall 22 can be integrally formed or connected by welding, bonding, riveting or other suitable methods.

[0052] In some embodiments, the housing 20 may be an open-end structure. The housing 20 may have an opening at one end along the axial direction X of the cylindrical battery 1, allowing the cylindrical space within the housing 20 to be exposed to the outside. The bottom wall 21 and the housing opening are arranged opposite each other along the axial direction X of the cylindrical battery 1.

[0053] In some embodiments, the cylindrical battery 1 includes an end cap 30, a bottom wall 21, and the end cap 30 is disposed along the axial direction X of the cylindrical battery 1, and the end cap 30 is connected to the housing 20.

[0054] End cap 30 can be attached to side wall 22. End cap 30 can close the housing opening, thereby sealing the cylindrical space inside housing 20.

[0055] The end cap 30 can be directly connected to the side wall 22, or it can be indirectly connected to the side wall 22 through other structures.

[0056] The housing 20 and end cap 30 can be made of steel, aluminum, composite metal, or other conductive materials. The housing 20 and end cap 30 can be made of the same or different materials.

[0057] In some embodiments, the end cap 30 is insulated from the sidewall 22 and electrically connected to the electrode assembly 10. The end cap 30 can form an electrode terminal of the cylindrical battery 1, which can eliminate a traditional electrode terminal and simplify the structure of the cylindrical battery 1.

[0058] In some embodiments, the cylindrical battery 1 includes a current collector 40 disposed between the electrode assembly 10 and the bottom wall 21, and the current collector 40 is connected to the electrode assembly 10.

[0059] The collector plate 40 can be connected to the tab of the electrode assembly 10 by welding or other suitable means.

[0060] In some embodiments, the current collector 40 is connected to the bottom wall 21. The current collector 40 enables electrical connection between the electrode assembly 10 and the bottom wall 21, which simplifies the assembly process of the cylindrical battery 1 and improves assembly efficiency.

[0061] In some embodiments, the bottom wall 21 includes a thinning portion 211, and the manifold 40 is welded to a portion of the thinning portion 211 to form a first weld portion 51.

[0062] The thickness of the thinned portion 211 can be less than the thickness of other parts of the bottom wall 21.

[0063] In some embodiments, the bottom wall 21 includes a bottom wall body 213, and a thinning portion 211 is connected to the bottom wall body 213. The thickness of the thinning portion 211 may be less than the thickness of the bottom wall body 213.

[0064] In some examples, the thinning portion 211 may be formed by recessing the outer surface of the bottom wall 21 toward the electrode assembly 10. In other examples, the thinning portion 211 may also be formed by recessing the inner surface of the bottom wall 21 toward the direction away from the electrode assembly 10. In still other examples, the thinning portion 211 may also be formed by recessing the inner surface of the bottom wall 21 toward the direction away from the electrode assembly 10, and the outer surface of the bottom wall 21 being recessed toward the direction closer to the electrode assembly 10.

[0065] The embodiments of this application do not impose any particular limitation on the shape of the thinning portion 211. For example, the thinning portion 211 can be circular, square, annular, arc-shaped, strip-shaped or other suitable shapes.

[0066] The thinned portion 211 is separated from the side wall 22 and is not directly connected to the side wall 22, which is beneficial to improving the connection strength between the bottom wall 21 and the side wall 22, and also beneficial to the welding between the thinned portion 211 and the collector plate 40.

[0067] The manifold 40 can be welded to a portion of the thinned section 211 by laser welding, ultrasonic welding or other suitable welding methods.

[0068] The first weld portion 51 may be exposed on the side of the bottom wall 21 facing away from the electrode assembly 10. The first weld portion 51 may be formed by through welding a portion of the thinned portion 211 and the manifold 40 from the outside of the housing 20.

[0069] The collector plate 40 is welded to a part of the thinning section 211. The thickness of the thinning section 211 is relatively small, and the bottom wall 21 and the collector plate 40 can be welded through the thinning section 211 from the outside of the shell 20. This helps to reduce welding power, reduce welding heat generation, enhance the welding strength between the bottom wall 21 and the collector plate 40, and improve the welding yield.

[0070] Only a portion of the thinned section 211 is welded to the current collector 40, while another portion is not welded to the current collector 40. This unwelded portion of the thinned section 211 is relatively thin and more prone to rupture than other parts of the bottom wall 21, thus forming a pressure relief structure for the cylindrical battery 1. When the internal pressure of the cylindrical battery 1 becomes excessive due to overcharging, thermal runaway, or other reasons, the unwelded portion of the thinned section 211 can rupture promptly under the internal gas pressure of the cylindrical battery 1, thereby releasing the internal pressure. This helps reduce the risk of explosion due to excessive internal gas pressure in the cylindrical battery 1, improving its safety and reliability.

[0071] In some embodiments, a recess 212 is provided on the side of the bottom wall 21 away from the collector plate 40, and the recess 212 is correspondingly provided with the thinned portion 211. The recess 212 and the thinned portion 211 may be correspondingly provided along the axial direction of the cylindrical battery 1.

[0072] The recess 212 can be formed by the bottom wall 21 being recessed from the outer surface of the electrode assembly 10 away from the electrode assembly 10 in the direction close to the electrode assembly 10.

[0073] The recess 212 can be formed by stamping, cutting or other suitable methods. The forming process is simple and helps to improve the production efficiency of the cylindrical battery 1.

[0074] In this embodiment, a recess 212 is provided on the side of the bottom wall 21 away from the current collector 40 to form a thinned portion 211. The recess 212 can provide a accommodating space for the first welding portion 51, reducing the possibility that the first welding portion 51 will protrude from the outer surface of the bottom wall 21 in the direction away from the electrode assembly 10. This helps to reduce the shaking of the cylindrical battery 1 and improve its installation stability. Furthermore, the first welding portion 51 and the bottom wall 21 can share part of the space in the axial direction X, which helps to save space and increase the energy density of the cylindrical battery 1.

[0075] In some embodiments, the cross section of the recess 212 that is coplanar with the axis a of the cylindrical battery 1 is triangular or trapezoidal. The cross section of the recess 212 being triangular or trapezoidal means that the overall cross section of the recess 212 is approximately triangular or trapezoidal, but is not required to be strictly triangular or trapezoidal.

[0076] In this embodiment, by providing a recess 212 with a triangular or trapezoidal cross-sectional shape, the thickness of the thinned portion 211 along the axial direction of the cylindrical battery 1 is gradually varied. This makes it more advantageous for the thinned portion 211 to break at its thinnest point, thereby releasing the pressure inside the cylindrical battery 1.

[0077] In some embodiments, refer to Figure 3 Along the direction from the collector plate 40 to the bottom wall 21, the first welded part 51 does not extend beyond the surface 21a of the bottom wall 21 facing away from the collector plate 40.

[0078] The first weld portion 51 does not protrude from the surface 21a of the bottom wall 21. The cylindrical battery 1 can be supported on the support surface through the surface 21a of the bottom wall 21. The surface 21a of the bottom wall 21 is relatively flat, which helps to improve the stability of the cylindrical battery 1 when installed with the battery bracket or busbar. The first weld portion 51 can avoid the support surface, reducing the force on the first weld portion 51 and reducing the risk of damage or failure of the first weld portion 51. In addition, the first weld portion 51 does not occupy additional space in the axial direction X, which helps to improve the structural compactness and increase the energy density of the cylindrical battery 1.

[0079] In some embodiments, the thinning portion 211 is annular.

[0080] Optionally, the center of the circle corresponding to the thinned portion 211 may be located on the axis a of the cylindrical battery 1. The thinned portion 211 extends around the axis a of the cylindrical battery 1.

[0081] Alternatively, the center of the circle corresponding to the thinned portion 211 can be slightly offset from the axis a of the cylindrical battery 1.

[0082] With a fixed area of ​​the thinned region of the bottom wall 21, the distribution range of the annular thinned portion 211 is wider, which helps to disperse the weak parts of the bottom wall 21 and reduce the impact of the thinned portion 211 on the overall structural strength of the bottom wall 21. Furthermore, the distribution of the thinned portion 211 is relatively uniform along the circumference of the cylindrical battery 1, which helps to balance the structural strength of the bottom wall 21.

[0083] In some embodiments, refer to Figure 5 The first welded part 51 is arc-shaped, and the central angle α corresponding to the first welded part 51 is 90°-270°.

[0084] Optionally, the center of the circle corresponding to the first welded portion 51 may be located on the axis a of the cylindrical battery 1. The first welded portion 51 may extend continuously around the axis a of the cylindrical battery 1.

[0085] In the extending direction of the first weld portion 51, the two ends of the first weld portion 51 are spaced apart, and a portion of the thinning portion 211 can be connected between the two ends of the first weld portion 51.

[0086] Optionally, the central angle α corresponding to the first welded part 51 can be 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, 180°, 190°, 200°, 210°, 220°, 230°, 240°, 250°, 260°, 270°, or any value between any two of them.

[0087] In this embodiment, the central angle α corresponding to the first welded part 51 is set to be greater than or equal to 90°, which can increase the welding area between the bottom wall 21 and the collector plate 40, which is beneficial to improve the flow capacity and enhance the connection strength between the bottom wall 21 and the collector plate 40.

[0088] The first welded portion 51 blocks the airflow along the radial direction of the cylindrical battery 1. In this embodiment, the central angle α corresponding to the first welded portion 51 is set to be less than or equal to 270°. The length of the first welded portion 51 in the circumferential direction of its corresponding circle is not too long. A relatively large exhaust channel can be formed between the bottom wall 21 and the collector plate 40 so that the gas can act quickly on the area of ​​the bottom wall 21 surrounded by the thinned portion 211, so that the part of the thinned portion 211 that is not welded to the collector plate 40 will break under the action of internal pressure, which is conducive to the smoother depressurization of the cylindrical battery 1.

[0089] In this embodiment, the central angle α corresponding to the first welded part 51 is set to 90°-270°, which is beneficial to balancing the connection strength between the bottom wall 21 and the current collector 40, as well as the pressure relief effect of the cylindrical battery 1.

[0090] In other embodiments, reference is made to Figure 6 There are multiple first welding parts 51, and the multiple first welding parts 51 are arranged at intervals along the circumference of the cylindrical battery 1.

[0091] The first welded portion 51 can be dot-shaped, strip-shaped, or arc-shaped. Multiple first welded portions 51 can have the same shape or different shapes.

[0092] Multiple first welding parts 51 can be arranged at equal angles along the circumference of the cylindrical battery 1, or they can be arranged at unequal angles.

[0093] In some examples, two adjacent first weld portions 51 may be connected by a portion of the thinning portion 211. In other examples, a portion of the thinning portion 211 and a portion of the bottom wall body 213 may be provided between two adjacent first weld portions 51.

[0094] The first weld portion 51 blocks the airflow along the radial direction of the cylindrical battery 1. The portion of the bottom wall 21 located between two adjacent first weld portions 51 can form a gap with the collector plate 40 to allow airflow. In this embodiment, the bottom wall 21 and the collector plate 40 are connected by a plurality of first weld portions 51 spaced apart along the circumference of the cylindrical battery 1. A plurality of exhaust channels spaced apart along the circumference of the cylindrical battery 1 can be formed between the bottom wall 21 and the collector plate 40. Gas at different locations inside the housing 20 can flow through different exhaust channels and act on the area of ​​the bottom wall 21 surrounded by the plurality of first weld portions 51, thereby breaking through the portion of the thinned portion 211 that is not welded to the collector plate 40, which helps to shorten the airflow path and improve the pressure relief efficiency of the cylindrical battery 1.

[0095] Furthermore, current can be transmitted between the electrode assembly 10 and the bottom wall 21 through multiple spaced first welded portions 51, which helps to shorten the conductive path, improve the current carrying capacity, and reduce heat generation. Even if some of the first welded portions 51 fail to weld due to reasons such as poor soldering, the current can still be transmitted between the electrode assembly 10 and the bottom wall 21 through other first welded portions 51, which helps to reduce the risk of connection failure between the electrode assembly 10 and the bottom wall 21.

[0096] In some embodiments, refer to Figure 6 The first welding part 51 is arc-shaped, and the sum of the central angles of the multiple first welding parts 51 is 90°-270°.

[0097] Optionally, a plurality of first welded portions 51 may be distributed on the same ring. The center of the circle corresponding to the plurality of first welded portions 51 may be located on the axis a of the cylindrical battery 1.

[0098] The central angle corresponding to each first welded part 51 is β. The central angle β corresponding to multiple first welded parts 51 can be the same or different.

[0099] Optionally, the sum of the central angles corresponding to the plurality of first welded portions 51 can be 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, 180°, 190°, 200°, 210°, 220°, 230°, 240°, 250°, 260°, 270° or any value between any two of them.

[0100] In this embodiment, the sum of the central angles corresponding to the plurality of first welding parts 51 is set to be greater than or equal to 90°, which can increase the welding area between the bottom wall 21 and the collector plate 40, which is beneficial to improve the flow capacity and enhance the connection strength between the bottom wall 21 and the collector plate 40.

[0101] In this embodiment, the sum of the central angles corresponding to the plurality of first welded portions 51 is set to be less than or equal to 270°, and the sum of the lengths of the plurality of first welded portions 51 in the circumferential direction of their corresponding circles is not too long. The total area of ​​the exhaust channel formed between the bottom wall 21 and the collector plate 40 is relatively large, which facilitates the rapid action of gas on the area of ​​the bottom wall 21 surrounded by the plurality of first welded portions 51, thereby breaking through the part of the thinned portion 211 that is not welded to the collector plate 40, which is conducive to the smoother depressurization of the cylindrical battery 1.

[0102] In this embodiment, the sum of the central angles corresponding to the multiple first welding parts 51 is set to 90°-270°, which is beneficial to balancing the connection strength between the bottom wall 21 and the current collector 40, as well as the pressure relief effect of the cylindrical battery 1.

[0103] In some embodiments, a plurality of first welded portions 51 are arranged at equal angular intervals around the center 21b of the bottom wall 21.

[0104] In the circumferential direction of the cylindrical battery 1, the included angle formed by the lines connecting the adjacent ends of any two adjacent first welded portions 51 to the center 21b of the bottom wall 21 is the same. For example, the first welded portion 51 is arc-shaped, and the included angle formed by the lines connecting the adjacent ends of two adjacent first welded portions 51 to the center of the bottom wall 21 refers to the central angle corresponding to the portion between the two adjacent first welded portions 51.

[0105] The multiple first welded parts 51 are arranged at equal angles, and the distribution of the connection positions between the bottom wall 21 and the collector plate 40 is relatively uniform, which is beneficial to improving the connection effect between the bottom wall 21 and the collector plate 40. In addition, the area of ​​the exhaust channel formed between any two adjacent first welded parts 51 is approximately the same, which is beneficial to more uniform pressure relief.

[0106] In some embodiments, the thickness of the bottom wall body 213 is H, and the thickness of the thinned portion 211 is h, where 0.15 ≤ h / H ≤ 0.6.

[0107] The base wall 213 can be of uniform thickness or unequal thickness. In some examples, the base wall 213 is of uniform thickness, with a thickness of H at any location. In other examples, the base wall 213 can be of unequal thickness, where the thickness H can be the average thickness of the base wall 213. For example, the thickness can be measured at any 50 locations and then averaged.

[0108] The thinning portion 211 can be of uniform thickness or of unequal thickness. The thickness h of the thinning portion 211 means that the minimum thickness of the thinning portion 211 is h.

[0109] In some examples, the thinning portion 211 has a uniform thickness, and the thickness at any position of the thinning portion 211 is h. In other examples, the thinning portion 211 has a non-uniform thickness, for example, the thickness of the thinning portion 211 can be gradually set along the axial direction of the cylindrical battery 1, and h is the thickness at the thinnest position of the thinning portion 211.

[0110] Optionally, h / H can be 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, or any value between two of these.

[0111] In some embodiments, the thickness H of the bottom wall body 213 can be 0.5mm-1.0mm.

[0112] In some embodiments, the thickness h of the thinned portion 211 can be 0.15mm-0.3mm.

[0113] The thickness of the thinned part 211 will affect the welding effect between the thinned part 211 and the collector plate 40, and will also affect the overall structural strength of the bottom wall 21.

[0114] In this embodiment, h / H is set to be greater than or equal to 0.15 so that the thinned portion 211 is not too thin relative to the bottom wall body 213. This reduces the risk of cracking and failure of the thinned portion 211 under conditions such as axial vibration or axial compression of the cylindrical battery 1, improves the structural stability of the cylindrical battery 1, and extends its service life.

[0115] In this embodiment, h / H is set to less than or equal to 0.6, making the thinned portion 211 easier to weld through. This facilitates welding the bottom wall 21 and the manifold 40 from the outside of the housing 20, improving welding effectiveness and welding results.

[0116] In this embodiment, h / H is set to 0.15-0.6, which is beneficial for balancing the structural stability of the cylindrical battery 1, as well as the welding effectiveness and welding effect between the bottom wall 21 and the current collector 40.

[0117] In some embodiments, the thickness of the thinning portion 211 is h, and the thickness of the collector plate 40 is h1, where 0.5 ≤ h1 / h ≤ 2.

[0118] The collector plate 40 can be of uniform or unequal thickness. In some examples, the collector plate 40 is of uniform thickness, with a thickness of h1 at any location. In other examples, the collector plate 40 can be of unequal thickness, where the thickness h1 can be the average thickness of the collector plate 40. For example, the thickness can be measured at any 50 locations on the collector plate 40, and then the average value can be taken.

[0119] The thickness h of the thinning section 211 can be the same as or different from the thickness h1 of the collector plate 40.

[0120] Optionally, h1 / h can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or any value between any two of them.

[0121] In some embodiments, the thickness h1 of the manifold 40 can be 0.15mm-0.3mm.

[0122] In this embodiment, h1 / h is set to be greater than or equal to 0.5, so that the thickness of the collector plate 40 relative to the thinning part 211 is not too thin, and the thickness of the thinning part 211 relative to the collector plate 40 is not too thick. This reduces the risk of the collector plate 40 being melted through, and also facilitates the connection between the bottom wall 21 and the collector plate 40 by welding through the thinning part 211.

[0123] In this embodiment, h1 / h is set to be less than or equal to 2, so that the thickness of the current collector 40 relative to the thinning portion 211 is not too thick and the thickness of the thinning portion 211 relative to the current collector 40 is not too thin. This not only helps to save the space occupied by the current collector 40 in the axial direction X, but also reduces the risk of cracking and failure of the thinning portion 211 under the condition that the cylindrical battery 1 is subjected to axial vibration or axial compression, thereby improving the structural stability of the cylindrical battery 1 and extending its service life.

[0124] In some embodiments, refer to Figure 6 The diameter of the cylindrical battery 1 is D, the thinned part 211 is annular, and the inner diameter of the thinned part 211 is d, 1 / 2≤d / D≤2 / 3.

[0125] Alternatively, d / D can be 1 / 2, 2 / 3, or any value between 1 / 2 and 2 / 3.

[0126] In this embodiment, d / D is set to be greater than or equal to 1 / 2. The thinned portion 211 can form a relatively large area. After the thinned portion 211 ruptures under the pressure inside the cylindrical battery 1, it can form a relatively large pressure relief port on the bottom wall 21, which is beneficial to increasing the pressure relief area and improving the pressure relief efficiency. Furthermore, the length of the thinned portion 211 along the circumference of the cylindrical battery 1 can be appropriately increased, thereby providing a larger welding area for the thinned portion 211 and the current collector 40, and allowing the thinned portion 211 to retain a large length that is not welded to the current collector 40, which is beneficial to the smooth rupture and pressure relief of the thinned portion 211.

[0127] In this embodiment, d / D is set to less than or equal to 2 / 3, so that the thinned portion 211 will not be too close to the connection position between the bottom wall 21 and the side wall 22. This can reduce the stress on the thinned portion 211 from the connection position between the bottom wall 21 and the side wall 22, which is beneficial for the thinned portion 211 to break in time under the pressure inside the cylindrical battery 1.

[0128] In some embodiments, the diameter D of the cylindrical battery 1 can be 30mm-65mm.

[0129] In some embodiments, the minimum width of the thinned portion 211 in the radial direction of the cylindrical battery 1 is w, and the thickness of the thinned portion 211 is h, where 0.1 ≤ h / w ≤ 0.3.

[0130] The minimum width w of the thinned portion 211 refers to the minimum radial width of the part of the thinned portion 211 with the smallest thickness.

[0131] Optionally, the cross-section of the recess 212 corresponding to the thinning portion 211 can be trapezoidal, and the minimum width w of the thinning portion 211 refers to the width of the portion of the thinning portion 211 corresponding to the top surface of the trapezoid.

[0132] Optionally, h / w can be 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, or any value between the two.

[0133] In some embodiments, the minimum width w of the thinned portion 211 can be 1mm-1.5mm.

[0134] In this embodiment, h / w is set to be greater than or equal to 0.1, which can improve the strength of the thinned part 211, reduce the risk of cracking failure of the thinned part 211 under conditions such as axial vibration or axial compression of the cylindrical battery 1, improve the structural stability of the cylindrical battery 1, and extend its service life.

[0135] In this embodiment, h / w is set to less than or equal to 0.3, the thinning part 211 has a relatively large width, and the thickness of the thinning part 211 is not too thick, which facilitates the welding of the thinning part 211 and the manifold 40 and improves the welding efficiency.

[0136] In some embodiments, the first weld portion 51 is spaced apart from the surface of the current collector 40 facing the electrode assembly 10 along the axial direction X of the cylindrical battery.

[0137] The surface of the manifold 40 facing the electrode assembly 10 is closer to the electrode assembly 10 than the first weld portion 51. The first weld portion 51 is entirely located on the side of this surface facing away from the electrode assembly 10. In other words, the first weld portion 51 does not melt through the manifold 40, which helps to reduce the impact of the weld between the bottom wall 21 and the manifold 40 on the electrode assembly 10.

[0138] In some embodiments, the thickness of the current collector 40 in the axial direction X of the cylindrical battery 1 is h1, and the size of the portion of the first welded portion 51 formed on the current collector 40 is h2, where 1 / 3 ≤ h2 / h1 ≤ 2 / 3.

[0139] The portion of the first weld 51 formed on the collector plate 40 is the portion where the first weld 51 is directly connected to the collector plate 40. The dimension of the portion of the first weld 51 formed on the collector plate 40 in the axial direction X is the penetration depth of the first weld 51 within the collector plate 40.

[0140] Optionally, h2 / h1 can be 1 / 3, 4 / 9, 5 / 9, 2 / 3, or any value between any two of them.

[0141] In this embodiment, h2 / h1 is set to be greater than or equal to 1 / 3, so that the penetration depth of the first welded part 51 in the manifold 40 is not too small, which is beneficial to enhance the welding strength between the manifold 40 and the bottom wall 21.

[0142] In this embodiment, h2 / h1 is set to be less than or equal to 2 / 3, so that the penetration depth of the first weld 51 in the current collector 40 is not too large. This helps to reduce the impact of the welding between the current collector 40 and the bottom wall 21 on the electrode assembly 10, reduce the risk of the current collector 40 being melted through, and improve the reliability of the cylindrical battery 1.

[0143] In this embodiment, h2 / h1 is set to 1 / 3-2 / 3, which is beneficial for balancing the welding strength between the current collector 40 and the bottom wall 21, as well as the reliability of the cylindrical battery 1.

[0144] In some embodiments, the cylindrical battery 1 further includes an explosion-proof sheet 60 disposed on the end cap 30.

[0145] The explosion-proof plate 60 can be connected to the end cap 30 by welding, riveting or other suitable means.

[0146] When the internal pressure of the cylindrical battery 1 exceeds the upper limit that the explosion-proof plate 60 can withstand, the gas inside the cylindrical battery 1 can cause the explosion-proof plate 60 to flip and explode away from the electrode assembly 10, thereby achieving the purpose of pressure relief. This helps to reduce the risk of the cylindrical battery 1 exploding due to excessive internal pressure and improves the safety performance of the cylindrical battery 1.

[0147] The explosion-proof plate 60 and the thinning section 211 can respectively form two pressure relief structures for the cylindrical battery 1. When the internal pressure of the cylindrical battery 1 is too high, the gas inside the cylindrical battery 1 can be discharged through the flipping and bursting of the explosion-proof plate 60; when the internal pressure of the cylindrical battery 1 continues to increase, the gas inside the cylindrical battery 1 can also be discharged through the rupture of the thinning section 211. The cylindrical battery 1 can be depressurized in different directions through two pressure relief structures under different internal pressures, which is beneficial to improving the pressure relief efficiency and further improving the safety performance and reliability of the cylindrical battery 1.

[0148] In some embodiments, the burst pressure of the explosion-proof disc 60 is less than the burst pressure of the thinning portion 211. In other words, the maximum pressure that the thinning portion 211 withstands when it bursts is greater than the maximum pressure that the explosion-proof disc 60 withstands when it bursts.

[0149] When the pressure inside the cylindrical battery 1 is relatively high but has not reached a certain level, the explosion-proof plate 60 can burst before the thinning part 211. The pressure of the cylindrical battery 1 can be relieved by the flipping and bursting of the explosion-proof plate 60, which can reduce the possibility of the thinning part 211 breaking and reduce the possibility of electrolyte leakage, short circuit and other phenomena that may be caused by the breakage of the casing 20.

[0150] In some embodiments, the venting passage of the explosion-proof sheet 60 is blocked by the electrode assembly 10, or by electrolyte, electrode and separator residue, etc. When the pressure inside the cylindrical battery 1 continues to increase, the thinning portion 211 can burst to release gas, which is beneficial to improve the pressure relief efficiency.

[0151] In some embodiments, the burst pressure of the thinned portion 211 can be 2.5 MPa-3 MPa.

[0152] In some embodiments, the burst pressure of the explosion-proof disc 60 can be 1.6MPa-1.8MPa.

[0153] In some embodiments, the burst pressure of the thinned portion 211 can be measured as follows: prepare a housing 20 with the thinned portion 211 on the bottom wall 21; prepare an end cap 30; drill a circular hole in the end cap 30, the diameter of which can be 4 mm; assemble the housing 20 and the end cap 30 to obtain a cylindrical battery; use a clamp to fix the obtained cylindrical battery about 10 mm away from the end cap 30; open the inflation valve of the air pressure burst testing machine (model SC-QYBP-10, Xiamen Sanchuang Scientific Instruments Testing Equipment Co., Ltd.), and inflate the inside of the housing 20 through the circular hole of the end cap 30 at a speed of 0.1 MPa / s until the thinned portion 211 of the bottom wall 21 bursts.

[0154] In some embodiments, the burst pressure of the explosion-proof disc 60 can be measured as follows: Prepare a housing 20 with a circular hole on the bottom wall 21, the diameter of which can be 4 mm; prepare an end cap 30 with the explosion-proof disc 60; assemble the housing 20 and the end cap 30 to obtain a cylindrical battery; use a clamp to fix the obtained cylindrical battery about 10 mm away from the end cap 30; open the inflation valve of the air pressure burst testing machine (model SC-QYBP-10, Xiamen Sanchuang Scientific Instruments Testing Equipment Co., Ltd.), and inflate the inside of the housing 20 through the circular hole on the bottom wall 21 at a speed of 0.1 MPa / s until the explosion-proof disc 60 bursts.

[0155] In some embodiments, the current collector 40 is welded to the electrode assembly 10 to form a second weld portion 52. Along the axial direction X of the cylindrical battery 1, the projection of the second weld portion 52 is separate from the projection of the thinned portion 211. In other words, the projection of the second weld portion 52 does not overlap with the projection of the thinned portion 211.

[0156] The second welded part 52 can extend radially along the cylindrical battery 1.

[0157] Optionally, the thinning portion 211 can be annular. In some examples, the second welding portion 52 may be located inside the thinning portion 211 along the radial direction of the cylindrical battery 1, and the thinning portion 211 may surround the radially outer side of the second welding portion 52. In other examples, the second welding portion 52 may also be located outside the thinning portion 211 along the radial direction of the cylindrical battery 1.

[0158] The projection of the second welded portion 52 is separate from the projection of the thinned portion 211. The second welded portion 52 will not contact the thinned portion 211, which helps to reduce the impact on the strength of the portion of the thinned portion 211 that is welded to the collector plate 40, and to reduce the impact on the pressure relief of the portion of the thinned portion 211 that is not welded to the collector plate 40.

[0159] According to the second aspect of this application, referring to Figure 7 This application also provides a battery pack 100, which includes a plurality of cylindrical batteries 1 provided according to any embodiment of this application.

[0160] In some embodiments, the battery pack 100 further includes a plurality of busbars. The busbars connect to the cylindrical batteries 1. At least two cylindrical batteries 1 can be connected in series or in parallel via the busbars.

[0161] According to the third aspect of this application, referring to Figure 8 This application also provides an electrical device 1000, which includes a battery pack 100 provided in any embodiment of this application. The battery pack 100 can provide electrical energy for the operation of the electrical device 1000.

[0162] The electrical device 1000 in this application embodiment can be a portable device, an electric toy, a drone, a power tool, an energy storage system, etc. Power tools include metal cutting power tools, cleaning tools, etc., such as electric drills, electric wrenches, vacuum cleaners, robot vacuum cleaners, etc. This application embodiment does not impose any special limitations on the above-mentioned electrical device.

[0163] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A cylindrical battery, characterized in that, include: Electrode assembly; A housing, in which the electrode assembly is housed, the housing including a bottom wall, the bottom wall and the electrode assembly being disposed along the axial direction of the cylindrical battery, the bottom wall including a thinned portion; A current collector is disposed between the electrode assembly and the bottom wall. The current collector is connected to the electrode assembly and is welded to a portion of the thinned portion to form a first welded portion.

2. The cylindrical battery according to claim 1, characterized in that, A recess is provided on the side of the bottom wall away from the collector plate, and the recess is provided corresponding to the thinning part.

3. The cylindrical battery according to claim 2, characterized in that, Along the direction from the collector plate to the bottom wall, the first welded portion does not extend beyond the surface of the bottom wall facing away from the collector plate.

4. The cylindrical battery according to any one of claims 1-3, characterized in that, The thinned portion is annular.

5. The cylindrical battery according to any one of claims 1-4, characterized in that, The first welded part is arc-shaped, and the central angle corresponding to the first welded part is 90°-270°.

6. The cylindrical battery according to any one of claims 1-4, characterized in that, There are multiple first welded portions, and the multiple first welded portions are arranged at intervals along the circumference of the cylindrical battery.

7. The cylindrical battery according to claim 6, characterized in that, The first welded part is arc-shaped, and the sum of the central angles corresponding to the plurality of first welded parts is 90°-270°.

8. The cylindrical battery according to claim 6 or 7, characterized in that, The plurality of first welded portions are arranged at equal angular intervals around the center of the bottom wall.

9. The cylindrical battery according to any one of claims 1-8, characterized in that, The bottom wall includes a bottom wall body, and the thinned portion is connected to the bottom wall body; The thickness of the main bottom wall is H, and the thickness of the thinned portion is h; 0.15≤h / H≤0.

6.

10. The cylindrical battery according to any one of claims 1-9, characterized in that, The thickness of the thinned part is h, and the thickness of the collector plate is h1; 0.5≤h1 / h≤2.

11. The cylindrical battery according to any one of claims 1-10, characterized in that, The diameter of the cylindrical battery is D; The thinning section is annular, and the inner diameter of the thinning section is d; 1 / 2≤d / D≤2 / 3.

12. The cylindrical battery according to any one of claims 1-11, characterized in that, In the radial direction of the cylindrical battery, the minimum width of the thinned portion is w; the thickness of the thinned portion is h; 0.1≤h / w≤0.

3.

13. The cylindrical battery according to any one of claims 1-12, characterized in that, In the axial direction, the first weld portion is spaced apart from the surface of the manifold facing the electrode assembly.

14. The cylindrical battery according to any one of claims 1-13, characterized in that, In the axial direction, the thickness of the collector plate is h1, and the size of the portion of the first welded part formed on the collector plate is h2, where 1 / 3 ≤ h2 / h1 ≤ 2 / 3.

15. The cylindrical battery according to any one of claims 1-14, characterized in that, The cylindrical battery also includes an end cap and an explosion-proof sheet disposed on the end cap; The bottom wall and the end cap are arranged along the axial direction, and the end cap is connected to the housing; The burst pressure of the explosion-proof sheet is less than the burst pressure of the thinned portion.

16. The cylindrical battery according to any one of claims 1-15, characterized in that, The collector plate is welded to the electrode assembly to form a second welded portion; Along the axial direction of the cylindrical battery, the projection of the second welded portion is separate from the projection of the thinned portion.

17. A battery pack, characterized in that, Includes multiple cylindrical batteries according to any one of claims 1-16.

18. An electrical appliance, characterized in that, Includes the battery pack according to claim 17.

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