Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell, an electrode assembly and a current collecting component, the shell comprises an end wall, and a first liquid injection hole is formed in the end wall; the electrode assembly is accommodated in the shell, the electrode assembly comprises a winding structure formed by laminating and winding a first pole piece, a second pole piece and a diaphragm, the end part of the first pole piece comprises an empty foil area extending out of the diaphragm along the axial direction of the electrode assembly, the empty foil area comprises a first cutting section and an uncut section, the uncut section is bent to form a tab, and the first cutting section and the uncut section are connected with each other. The first cutting section is wound to form a first annular area, the area covered by the tab is a second annular area, and the first annular area comprises a third annular area which is not covered by the second annular area; the current collecting component is in welded connection with the tab and comprises a second liquid injection hole; projection is made in the axial direction of the electrode assembly, and the projection of the second liquid injection hole covers the third annular area. The technical problem that the infiltration efficiency of the electrolyte is low can be solved.

Description

Technical Field

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

[0002] Cylindrical batteries have been widely used in many aspects of modern society due to their advantages such as high energy efficiency and long cycle life. The electrode assembly is usually a wound structure, and there are tabs at both ends of the electrode assembly. A current collector member is electrically connected to the outside of the tab. Due to the obstruction of the current collector member and the tab, it brings great challenges to the electrolyte injection and the infiltration of the electrode assembly during the manufacturing process of the cylindrical battery, which not only limits the production efficiency of the cylindrical battery but also affects the performance of the battery. Therefore, improving the infiltration efficiency of the electrolyte is a technical problem that needs to be overcome in this field. Summary of the Utility Model

[0003] The utility model provides a secondary battery, a battery pack and an electronic device to improve the technical problem of low infiltration efficiency of the electrolyte.

[0004] To achieve the above object and other related objects, the utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery includes a housing, an electrode assembly and a current collector member; the housing includes an end wall, and a first liquid injection hole is provided on the end wall; the electrode assembly is accommodated in the housing, and the electrode assembly includes a first pole piece, a second pole piece and a diaphragm layer stacked and wound to form a wound structure. The end of the first pole piece includes an empty foil area extending out of the diaphragm along the axial direction of the electrode assembly. The empty foil area includes a first cut section close to the winding axis of the wound structure and an uncut section located radially outside the first cut section. The uncut section of the empty foil area is bent to form a tab. Along the radial direction of the electrode assembly, the first cut section is wound to form a first annular area, the area covered by the tab is a second annular area, and the first annular area includes a third annular area not covered by the second annular area; the current collector member is arranged between the electrode assembly and the end wall and is welded to the tab. The current collector member includes a second liquid injection hole; wherein, when projected along the axial direction of the electrode assembly towards the end face of the wound structure, the projection of the second liquid injection hole covers the third annular area.

[0005] In the above technical solution, the first cutting section of the empty foil area is wound to form a first annular area, the uncut section of the empty foil area is bent to form a tab, and the area covered by the tab is the second annular area. The first annular area includes a third annular area not covered by the second annular area, that is, the third annular area is exposed outside the second annular area without the shielding of the tab. Further, the projection of the second liquid injection hole of the current collector member covers the third annular area. The projection of the second liquid injection hole covering the third annular area means that the third annular area is exposed within the second liquid injection hole, which can achieve that the third annular area is neither shielded by the tab nor shielded by the current collector member. Therefore, when the electrolyte is injected from the first liquid injection hole, the electrolyte will directly flow into the third annular area exposed within the second liquid injection hole, and the electrolyte can be directly absorbed by the separator in the third annular area and radially penetrate to infiltrate the electrode assembly during the inflow process. This setting can improve the infiltration efficiency of the electrode assembly. At the same time, the third annular area is arranged around the winding axis of the winding structure, which can improve the uniformity of the electrolyte infiltration along the radial direction of the electrode assembly, thereby improving the performance and life of the battery.

[0006] In addition, the current collector member and the tab are welded and connected. Since there is no tab on the third annular area and the third annular area is exposed within the second liquid injection hole, it can effectively prevent the miswelding of the current collector member and the tab into the third annular area during welding, reducing the risk of scalding the separator.

[0007] In an example of the secondary battery of the present invention, the projection of the second liquid injection hole covers the first annular area.

[0008] In the above technical solution, the first annular area is formed by winding the first cutting section. Although part of the cut first annular area will be covered by the tab, compared with the uncut section, the area covered by the tab is still convenient for the inflow of the electrolyte. The electrolyte can flow in from the gap between the tab and the first annular area, and the electrolyte can be directly absorbed by the separator in the first annular area and radially penetrate to infiltrate the electrode assembly during the inflow process. This setting realizes that the first annular area is completely exposed within the second liquid injection hole, which can further improve the infiltration efficiency of the electrode assembly.

[0009] At the same time, the number of stacked layers of the tab in the part of the first annular area covered by the tab is small and it is not suitable for welding with the current collector member. Therefore, the first annular area is completely exposed within the second liquid injection hole, which can effectively prevent the miswelding of the current collector member and the tab into the area with fewer stacked layers of the tab, reducing the risk of welding through the tab and scalding the separator.

[0010] In an example of the secondary battery of the present invention, the inner radius of the second annular area is R1, the winding structure includes a winding hole at the center, and the radius of the winding hole is R2, where R1 - R2 ≥ 1 mm.

[0011] In the above technical solution, the inner circle of the second annular region is the inner circle of the tab covering region. The limitation of R1 - R2 ≥ 1 mm can achieve that there is an annular region with a width of at least 1 mm on the outer periphery of the winding hole that is not blocked by the tabs. The above annular region is the third annular region. This setting can ensure that the width of the third annular region is not less than 1 mm, further improving the infiltration efficiency of the electrode assembly, thereby enhancing the performance and lifespan of the battery.

[0012] In an example of the secondary battery of the present utility model, when projecting axially along the electrode assembly towards the end face of the winding structure, the projected area of the current collector member is S1, and the end face area of the winding structure is S2, where 0.9S2 ≥ S1 ≥ 0.4S2.

[0013] In the above technical solution, the setting of S1 ≥ 0.4S2 can achieve that the current collector member has a large enough area to be welded to the tabs, so as to improve the welding firmness and reliability between the current collector member and the electrode assembly, and reduce the internal resistance of the battery. The setting of S1 ≤ 0.9S2 can ensure that the electrode assembly has an area greater than or equal to 0.1S2 that is not blocked by the current collector member and is exposed. This setting, on the one hand, facilitates the electrolyte to smoothly penetrate into the electrode assembly through the unblocked part, and on the other hand, facilitates the gas inside the electrode assembly to be discharged from the unblocked area, thereby improving the safety performance and comprehensive performance of the battery.

[0014] In an example of the secondary battery of the present utility model, the current collector member includes a plurality of tab connection parts distributed circumferentially. There is a transition connection part between every two adjacent tab connection parts. At least one through hole is provided on each transition connection part. Along the radial direction of the current collector member, the maximum width of the through hole is L, and the radius of the winding structure is R3, where L ≥ 0.5×(R3 - R2).

[0015] In the above technical solution, the through holes provided on the transition connection parts can be one or multiple. The above through holes are the parts of the current collector member that do not block the electrode assembly. R3 - R2 corresponds to the ring width of the end face of the winding structure. Further, it is limited that L ≥ 0.5×(R3 - R2), that is, the maximum value of the width of one through hole or the sum of the widths of multiple through holes on the same transition connection part is not less than 0.5 times the ring width of the end face of the winding structure. This setting can enable the electrolyte to infiltrate into the interior of the electrode assembly from the through holes, so as to improve the infiltration efficiency of the electrolyte. At the same time, a plurality of transition connection parts are distributed circumferentially along the current collector member, and each adjacent transition connection part is separated by a tab connection part, so that the through holes can be distributed more evenly circumferentially along the current collector member. This setting can further improve the uniformity of electrolyte infiltration, thereby enhancing the performance and lifespan of the battery.

[0016] In an example of the secondary battery of the present utility model, the current collector member includes a plurality of tab connection portions distributed circumferentially. A transition connection portion is provided between every two adjacent tab connection portions. The maximum distance from the outer peripheral edge of the transition connection portion to the center of the current collector member is R4, and the radius of the winding structure is R3, where R3 > R4.

[0017] In the above technical solution, the distance from the outermost part of the outer peripheral edge of the transition connection portion to the center of the first current collector member is less than the outer peripheral radius of the winding structure. This setting can further reduce the shielding of the current collector member on the electrode assembly, further improve the infiltration efficiency of the electrolyte, and thus improve the performance and lifespan of the battery. Additionally, it can prevent the situation where the current collector member interferes with the installation of the electrode assembly into the housing, improving the assembly efficiency and quality.

[0018] In an example of the secondary battery of the present utility model, the empty foil area further includes a second cut section located on the outer periphery of the winding structure and adjacent to the uncut section. Along the radial direction of the electrode assembly, the second cut section is wound to form a fourth annular region. The radius of the inner peripheral edge of the fourth annular region is R5, where R4 ≤ R5.

[0019] In the above technical solution, it can be achieved that the fourth annular region formed by winding the second cut section is not blocked by the tabs, and the fourth annular region is located on the outer periphery of the winding structure. At the same time, defining R4 ≤ R5, that is, the distance from the outermost part of the outer peripheral edge of the transition connection portion to the center of the first current collector member is less than or equal to the radius of the inner peripheral edge of the fourth annular region, then it can be achieved that the part of the fourth annular region located radially outside the transition connection portion is also not blocked by the current collector member. Therefore, when injecting electrolyte from the first injection hole, the electrolyte will directly flow into the exposed part of the fourth annular region. During the inflow process, the electrolyte can be directly absorbed by the separator of the fourth annular region and penetrate both circumferentially and radially, and infiltrate the electrode assembly. This setting can improve the infiltration efficiency of the electrode assembly. At the same time, the part of the fourth annular region not covered by the current collector member is distributed along the circumference of the current collector member, which can improve the uniformity of the electrolyte infiltration along the radial direction of the electrode assembly, thereby enhancing the performance and lifespan of the battery.

[0020] In an example of the secondary battery of the present utility model, along the axial direction of the current collector member, the current collector member at least covers part of the tabs located in the outermost circle of the winding structure.

[0021] In the above technical solution, at least part of the tabs located in the outermost circle of the winding structure can be covered and pressed by the current collector member, which can effectively prevent the tabs from warping, so as to reduce the risk of the tabs breaking and falling into the interior of the housing under external force, causing a short circuit.

[0022] In an example of the secondary battery of the present utility model, R3 - R4 ≥ 1 mm.

[0023] In the above technical solution, it is further defined that R3 - R4 ≥ 1 mm, which can achieve that while the transition connection part can cover and press as many outer - most tabs as possible, it can also ensure a large area of the electrode assembly that is not blocked, so as to reduce the risk of the tab breaking and falling into the interior of the housing under external force and improve the infiltration efficiency of the electrolyte.

[0024] In an example of the secondary battery of the present utility model, when projected along the axial direction of the electrode assembly towards the end face of the winding structure, the projection of the first liquid injection hole covers at least part of the third annular region covered by the projection of the second liquid injection hole.

[0025] In the above technical solution, the projection of the first liquid injection hole covers at least part of the third annular region covered by the projection of the second liquid injection hole, which can enable the electrolyte to directly flow into the part of the third annular region not blocked by the tabs and the current collector member when entering from the first liquid injection hole, so that the electrolyte can be directly absorbed by the separator in the third annular region and penetrate radially to infiltrate the electrode assembly. This setting can further improve the infiltration efficiency of the electrode assembly.

[0026] The present utility model also provides a battery pack, which includes the secondary battery of any one of the above.

[0027] The present utility model also provides an electronic device, which includes the above - mentioned battery pack.

[0028] In the secondary battery of the present utility model, the first cutting section of the empty foil area is wound to form the first annular region, the un - first - cut section of the empty foil area is bent to form tabs, the area covered by the tabs is the second annular region, the first annular region includes the third annular region not covered by the second annular region, that is, the third annular region is exposed outside the second annular region without the block of the tabs. Further, the projection of the second liquid injection hole of the current collector member covers the third annular region. The projection of the second liquid injection hole covering the third annular region is the part of the third annular region exposed within the second liquid injection hole, which can achieve that the third annular region is neither blocked by the tabs nor blocked by the current collector member. Therefore, when the electrolyte is injected from the first liquid injection hole, the electrolyte will directly flow into the third annular region exposed within the second liquid injection hole, and the electrolyte can be directly absorbed by the separator in the third annular region and penetrate radially to infiltrate the electrode assembly during the flowing process. This setting can improve the infiltration efficiency of the electrode assembly. At the same time, the third annular region is arranged around the winding axis of the winding structure, which can improve the uniformity of the electrolyte infiltrating along the radial direction of the electrode assembly, thereby enhancing the performance and life of the battery.

[0029] In addition, the current collector member and the tabs are welded and connected. Since there are no tabs on the third annular region and the third annular region is exposed within the second liquid injection hole, it can effectively prevent the mis - welding of the current collector member and the tabs into the third annular region during welding, reducing the risk of scalding the separator. Brief Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other embodiments can be obtained based on these drawings.

[0031] Figure 1 Structural schematic diagram of an embodiment of a secondary battery of the present invention;

[0032] Figure 2 Cross-sectional view of the electrode assembly in an embodiment of a secondary battery of the present invention;

[0033] Figure 3 Exploded structural schematic diagram of the electrode assembly and the first current collector member in an embodiment of a secondary battery of the present invention;

[0034] Figure 4 For Figure 3 Partial enlarged view of part A in

[0035] Figure 5 Top view of the electrode assembly and the first current collector member in an embodiment of a secondary battery of the present invention;

[0036] Figure 6 Structural schematic diagram of the first empty foil area of the electrode assembly in an embodiment of a secondary battery of the present invention;

[0037] Figure 7 Schematic diagram of an embodiment of a battery pack of the present invention;

[0038] Figure 8 Schematic diagram of an embodiment of an electronic device of the present invention.

[0039] Description of Element Numbers

[0040] 1. Electronic device; 10. Battery pack; 11. Working part; 101. Box body; 102. Box cover; 100. Secondary battery; 110. Housing; 111. Second end wall; 112. Side wall; 113. Opening; 114. First end wall; 115. First liquid injection hole; 120. Electrode assembly; 121. Second pole piece; 1211. Positive current collector; 1212. Second coating area; 1213. Second empty foil area; 122. Separator; 123. First pole piece; 1231. Negative current collector; 1232. First coating area; 1233. First empty foil area; 12331. First cutting section; 12332. Uncut section; 12333. Second cutting section; 124. First tab; 1241. First annular area; 1242. Second annular area; 1243. Third annular area; 1244. Fourth annular area; 125. Second tab; 126. Winding structure; 127. Winding hole; 130. Terminal; 140. First current collecting member; 141. Tab connection part; 142. Transition connection part; 143. Second liquid injection hole; 144. Through hole; 145. Housing connection part; 150. Second current collecting member. Detailed implementation manners

[0041] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. It should also be understood that the terms used in the embodiments of the present invention are for the purpose of describing specific specific implementation manners, rather than for limiting the protection scope of the present invention. The test methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by each manufacturer.

[0042] When the embodiments give a numerical range, it should be understood that unless otherwise stated in the present invention, any value between the two endpoints of each numerical range and any one value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention are the same as those understood by those skilled in the art of the present technology field and the description of the present invention. Any method, device, and material similar or equivalent to the existing technology in the methods, devices, and materials in the embodiments of the present invention can also be used to implement the present invention.

[0043] It should be noted that terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of clear description, rather than used to limit the scope of implementation of the present utility model. The change or adjustment of their relative relationship, without substantial change in technical content, should also be regarded as the scope of implementation of the present utility model.

[0044] The secondary battery includes a housing and an electrode assembly. The electrode assembly is accommodated in the housing, and the electrode assembly is a component in the secondary battery where an electrochemical reaction occurs. The housing may contain one or more electrode assemblies.

[0045] The electrode assembly is mainly formed by winding or laminating a positive electrode tab and a negative electrode tab, and usually a separator is provided between the positive electrode tab and the negative electrode tab. The positive electrode tab includes a positive electrode current collector and a positive electrode active material, and the positive electrode active material is coated on the surface of the positive electrode current collector; the positive electrode current collector includes a coated area coated with the active material and a blank foil area not coated with the active material, and the blank foil area forms the positive electrode tab of the electrode assembly after winding. The negative electrode tab includes a negative electrode current collector and a negative electrode active material, and the negative electrode active material is coated on the surface of the negative electrode current collector; the negative electrode current collector includes a coated area coated with the active material and a blank foil area not coated with the active material, and the blank foil area forms the negative electrode tab of the electrode assembly after winding. Taking a lithium-ion secondary battery as an example, the material of the positive electrode current collector can be aluminum, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can be lithium cobaltate, lithium iron phosphate, ternary lithium or lithium manganate, etc. The material of the negative electrode current collector can be copper, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be carbon or silicon, etc. The material of the separator can be PP (polypropylene) or PE (polyethylene), etc. To protect and insulate the battery cell, an insulating film can also be coated outside the battery cell, and the insulating film can be synthesized from PP, PE, PET, PVC or other polymer materials.

[0046] The housing includes a first end wall and a second end wall arranged opposite to each other, and a side wall surrounding the first end wall and the second end wall. One end of the side wall has an opening, and the electrode assembly can be assembled into the housing through the opening of the housing. A first liquid injection hole is provided on the first end wall or the second end wall to inject electrolyte into the housing.

[0047] The tabs at both ends of the electrode assembly are respectively welded and connected with a current collecting member, and the current collecting member can optimize the collection and distribution of the current of the electrode assembly to improve the performance of the battery.

[0048] However, the inventor found that when injecting the electrolyte, the current collector member will cause a certain degree of blockage to the electrolyte from entering the electrode assembly. In addition, the structure of the ear bend also causes a certain degree of blockage to the entry of the electrolyte, reducing the efficiency of electrolyte infiltration, limiting the production efficiency of the battery and affecting the performance of the battery. Therefore, it is extremely necessary and urgent to improve the infiltration efficiency of the electrolyte.

[0049] In view of this, the present utility model provides a technical solution. A first cutting section is provided on one side of the empty foil area close to the winding shaft and wound to form a first annular area. The first annular area includes a third annular area not covered by the ear. Further, the projection of the second liquid injection hole of the current collector member covers the third annular area. The third annular area covered by the projection of the second liquid injection hole is the third annular area exposed within the second liquid injection hole. This third annular area is neither blocked by the ear nor by the current collector member. Therefore, when injecting the electrolyte from the first liquid injection hole, the electrolyte can be directly absorbed by the separator in the third annular area during the inflow process and penetrate radially to infiltrate the electrode assembly, so as to improve the infiltration efficiency of the electrode assembly.

[0050] Please refer to Figures 1 to 8 , the present utility model provides a secondary battery 100, which includes: a housing 110, an electrode assembly 120, a pole column 130, and a current collector member.

[0051] Please refer to Figure 1 , the housing 110 includes an end wall, and a first liquid injection hole 115 is provided on the end wall. Specifically, in this embodiment, the housing 110 includes a first end wall 114 and a second end wall 111 arranged oppositely, and a side wall 112 surrounding the first end wall 114 and the second end wall 111; the first liquid injection hole 115 can be located on the first end wall 114 or the second end wall 111. The shape of the first liquid injection hole 115 can be circular, annular, petal-shaped, rectangular, oval, polygonal or other irregular shapes. Usually, a sealing cover adapted to it is also provided on the first liquid injection hole 115 to block the first liquid injection hole 115 after the liquid injection is completed. There is no limitation on this, as long as the first liquid injection hole 115 can be sealed.

[0052] Please refer to Figure 1, as long as a stable sealing and electrical connection relationship can be formed, the connection between the first end wall 114 and the side wall 112, and between the second end wall 111 and the side wall 112 can be achieved in various ways. For example, it can be integrally stamped, integrally cast, or separately welded. The surrounding of the side wall 112 is not limited. It can be cylindrically or prismatically surrounded, or can be surrounded along any other closed-loop contour that can match the first end wall 114 and the second end wall 111. As an embodiment, in this embodiment, the outer edges of the first end wall 114 and the second end wall 111 are circular, the side wall 112 is cylindrically surrounded around the outer edges of the first end wall 114 and the second end wall 111, the second end wall 111 and the side wall 112 are integrally formed, and a circular opening 113 is formed at one end of the side wall 112 close to the first end wall 114. In some embodiments, the electrolyte can be filled through the above-mentioned opening 113. A receiving cavity is formed within the housing 110 surrounded by the second end wall 111 and the side wall 112 for receiving the electrode assembly 120, the electrolyte, and other necessary battery components. Specifically, the diameter of the housing 110 can be determined according to the specific size of the electrode assembly 120, such as 18 mm, 21 mm, 46 mm, etc. The material of the housing 110 can be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent the housing 110 from rusting during long-term use, an anti-rust material such as metallic nickel can also be plated on the surface of the housing 110.

[0053] Please refer to Figures 1 to 2 , the electrode assembly 120 is received within the housing 110, and the electrode assembly 120 is the component in the secondary battery 100 where the electrochemical reaction occurs. The housing 110 can contain one or more electrode assemblies 120. The electrode assembly 120 includes a winding structure 126 formed by laminating and winding a first electrode plate 123, a second electrode plate 121, and a separator 122. The polarities of the first electrode plate 123 and the second electrode plate 121 are opposite. In some embodiments, the first electrode plate 123 is the positive electrode plate and the second electrode plate 121 is the negative electrode plate. In other embodiments, the first electrode plate 123 is the negative electrode plate and the second electrode plate 121 is the positive electrode plate.

[0054] Please refer to Figure 2 and Figure 6, in this embodiment, the first electrode tab 123 is a negative electrode tab. The first electrode tab 123 includes a negative current collector 1231 and a negative active material, and the negative active material is coated on the surface of the negative current collector 1231; the negative current collector 1231 includes a first coating area 1232 coated with the active material and an empty foil area not coated with the active material. For the convenience of distinction, the empty foil area on the first electrode tab 123 is defined as the first empty foil area 1233. The first empty foil area 1233 extends out of the separator 122 along the axial direction of the electrode assembly 120. The first empty foil area 1233 is located at the end of the first electrode tab 123. The first empty foil area 1233 includes a first cutting segment 12331 close to the winding axis of the winding structure 126 and an uncut segment 12332 located radially outside the first cutting segment 12331. The uncut segment 12332 of the first empty foil area 1233 is bent to form an electrode tab. For the convenience of distinction, the electrode tab on the first electrode tab 123 is defined as the first electrode tab 124, and the first electrode tab 124 is the corresponding negative electrode tab. Along the radial direction of the electrode assembly 120, the first cutting segment 12331 is wound to form a first annular area 1241, and the area covered by the electrode tab is a second annular area 1242. The first annular area 1241 includes a third annular area 1243 not covered by the second annular area 1242.

[0055] The above setting of the first cutting segment 12331 can, on the one hand, relieve the interference of the first empty foil area 1233 near the winding axis during bending. On the other hand, the first annular area 1241 includes a third annular area 1243 not covered by the second annular area 1242, that is, the third annular area 1243 is exposed outside the second annular area 1242 without the shielding of the electrode tab. During the inflow process, the electrolyte can be directly absorbed by the separator 122 in the third annular area 1243 and penetrate radially to infiltrate the electrode assembly 120. This setting can improve the infiltration efficiency of the electrode assembly 120.

[0056] Please refer to Figure 2 and Figure 6 , the second electrode tab 121 is a positive electrode tab. Specifically, the second electrode tab 121 includes a positive current collector 1211 and a positive active material, and the positive active material is coated on the surface of the positive current collector 1211; the positive current collector 1211 includes a second coating area 1212 coated with the active material and a second empty foil area 1213 not coated with the active material. The second empty foil area 1213 is located at the end of the second electrode tab 121. The second empty foil area 1213 extends out of the separator 122 at the other end along the axial direction of the electrode assembly 120 and is bent towards the winding axis to form a second electrode tab 125. The second electrode tab 125 is the corresponding positive electrode tab. It should be noted that both the second empty foil area 1213 and the first empty foil area 1233 can be provided with the first cutting segment 12331, or the first cutting segment 12331 can be provided only on one of the first empty foil area 1233 and the second empty foil area 1213 close to the electrolyte inflow end. There is no limitation on this.

[0057] Please refer to Figures 1 to 2 , the separator 122 is disposed between the first electrode tab 121 and the second electrode tab 123 to isolate the positive electrode active material layer and the negative electrode active material layer. Taking the lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1211 can be aluminum, and the positive electrode active material layer includes a positive electrode active material, which can be lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate, etc. The material of the negative electrode current collector 1231 can be copper, and the negative electrode active material layer includes a negative electrode active material, which can be carbon or silicon, etc. The base material of the separator 122 can be polypropylene (PP for short) or polyethylene (PE for short), etc. To protect and insulate the battery cell, an insulating film can also be coated outside the battery cell, and the insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET for short), polyvinyl chloride (PVC for short) or other polymer materials.

[0058] Please refer to Figure 1 and Figure 2 , further, the first electrode tab 124 faces the first end wall 114 or the second end wall 111, then the second electrode tab 125 faces the other end of the housing 110. In this embodiment, the second electrode tab 125 faces the second end wall 111 and is electrically connected to the terminal 130 to make the terminal 130 positively charged, and the first electrode tab 124 faces the first end wall 114, and the housing 110 is electrically connected to the first electrode tab 124, thus being negatively charged. However, in other embodiments, the first electrode tab 124 can also be connected to the terminal 130, and the second electrode tab 125 can be connected to the housing 110.

[0059] Please refer to Figure 1 and Figure 2, Further, the current collecting member is disposed between the electrode assembly 120 and the end wall and is connected to the tab by welding. For the convenience of distinction and understanding, the current collecting member electrically connected to the first tab 124 is named the first current collecting member 140, and the current collecting member electrically connected to the second tab 125 is named the second current collecting member 150. The welding method can be ultrasonic welding, resistance welding, laser welding, etc., which is not limited herein. In this embodiment, the first current collecting member 140 is located between the first end wall 114 and the first tab 124. The first tab 124 is a negative tab, and it is preferable to select copper metal as the material of the first current collecting member 140. The second current collecting member 150 is located between the second end wall 111 and the second tab 125. The second tab 125 is a positive tab, and it is preferable to select aluminum metal as the material of the second current collecting member 150. It should be noted that the shapes of the first current collecting member 140 and the second current collecting member 150 can be any rotationally symmetric shapes, such as circular, square, regular polygon, petal-shaped or other shapes with a center of symmetry and can coincide with the original figure after rotating a certain angle around the center of symmetry. This is not limited herein, and it is suitable to be able to achieve a stable and reliable electrical connection relationship. The centers of the first current collecting member 140 and the second current collecting member 150 are their own centers of symmetry. To improve the positioning, processing convenience, interchangeability and unity of the current collecting member during installation, the first current collecting member 140 and the second current collecting member 150 in this embodiment both adopt a circular structure.

[0060] Please refer to Figure 1 and Figure 2, the terminal post 130 passes through the second end wall 111 and is insulated from the second end wall 111. The structural form of the terminal post 130 can be any suitable form that can pass through the second end wall 111 and be electrically connected to the first electrode tab 124 or the second electrode tab 125. For example, the cross-section can be circular, square, prismatic, or a special-shaped profile that can achieve stable electrical conduction. One end of the terminal post 130 facing the electrode assembly 120 passes through the second end wall 111 and is directly electrically connected to the first electrode tab 124 or the second electrode tab 125 or is electrically connected through an indirect transfer connection. For example, the terminal post 130 can be electrically connected to the second electrode tab 121 through a current collector member. One end of the terminal post 130 facing away from the electrode assembly 120 is exposed to the outside of the housing 110 to form a corresponding electrode. The electrical property of the terminal post 130 can be positive or negative. For example, in one embodiment, the terminal post 130 is electrically connected to the second electrode tab 121, and the second electrode tab 121 is of positive polarity, then the terminal post 130 is the positive electrode, and the housing 110 forms the corresponding negative electrode. In another embodiment, the second electrode tab 121 is of negative polarity, then the terminal post 130 is the negative electrode, and the housing 110 forms the corresponding positive electrode. In this embodiment, a terminal post mounting hole is provided on the second end wall 111. The terminal post 130 is sealed and insulated and is installed in the terminal post mounting hole. The terminal post 130 is electrically connected to the second electrode tab 125 through the second current collector member 150. One end of the terminal post 130 facing away from the electrode assembly 120 is exposed to the outside of the housing 110 and is positively charged.

[0061] The terminal post 130 is made of a conductive metal material. The material of the terminal post 130 can be aluminum. If the material of the terminal post 130 is aluminum, the riveting process can be easily performed. In this embodiment, the material of the terminal post 130 is aluminum and the polarity is positive. Correspondingly, the material of the housing 110 is low-carbon steel and forms the corresponding negative electrode. The terminal post 130 is electrically insulated from the second end wall 111 of the housing 110. The electrical insulation between the terminal post 130 and the second end wall 111 of the housing 110 can be achieved in various ways. For example, insulation can be achieved by placing an insulating washer between the terminal post 130 and the second end wall 111. Alternatively, insulation can be achieved by forming an insulating coating layer on a part of the terminal post 130. Alternatively, some of the above methods can be combined and applied.

[0062] In this embodiment, the electrode assembly 120 is electrically connected to the housing 110 through the first current collector member 140. Further, in some embodiments, the first current collector member 140 includes a housing connection portion 145 located on the outer peripheral edge of the first current collector member 140, and the housing connection portion 145 is welded to the side wall 112. The specific assembly process of this structure is that the housing connection portion 145 is first welded to the side wall 112, and then a rolling groove is formed on the side wall 112 by rolling. At the same time, the housing connection portion 145 welded to the side wall 112 continues to bend towards the axis of the housing 110. Then, the first end wall 114 is placed on the side of the rolling groove away from the first current collector member 140 and connected to the side wall 112 to seal the opening 113. The first end wall 114 is installed in a mechanical seal manner to seal the opening 113. In some other embodiments, the first end wall 114 seals the opening 113. The shape of the outer edge of the first end wall 114 corresponds to the shape of the opening 113. The outer edge of the first end wall 114 is welded to the side wall 112 to seal the opening 113, and the first current collector member 140 is welded to the first end wall 114. In this embodiment, the first tab 124 is a negative tab, and the welding connection between the first current collector member 140 and the side wall 112 makes the housing 110 negatively charged.

[0063] Further, please refer to Figure 1 and Figure 3 , in this embodiment, a first liquid injection hole 115 is provided on the first end wall 114, and the first current collector member 140 includes a second liquid injection hole 143. The shape of the second liquid injection hole 143 can be circular, annular, petal-shaped, rectangular, oval, polygonal or other irregular shapes. The position of the second liquid injection hole 143 on the first current collector member 140 is not limited. It can be a rotationally symmetric figure with the center of the first current collector member 140 as the center of symmetry, or it can be arranged irregularly. There is no limitation on this. The second liquid injection hole 143 in this embodiment is a circular central hole penetrating the thickness direction of the first current collector member 140. In some other embodiments, a first liquid injection hole 115 is provided on the second end wall 111, and the second current collector member 150 includes a second liquid injection hole 143. It should be noted that the following examples are all described with the first current collector member 140 as an example, but the following technical solutions are equally applicable to the second current collector member 150 and will achieve the same technical effects, which will not be elaborated here.

[0064] Please refer to Figure 1 and Figures 3 to 6, in order to enable the electrolyte to be better directly absorbed by the separator 122 of the third annular region 1243 during the inflow process, further project along the axial direction of the electrode assembly 120 towards the end face of the winding structure 126. The projection of the second liquid injection hole 143 covers the third annular region 1243, that is, the third annular region 1243 is exposed within the second liquid injection hole 143, which can achieve that the third annular region 1243 is neither blocked by the first tab 124 nor blocked by the first current collector member 140. Therefore, when the electrolyte is injected from the first liquid injection hole 115, the electrolyte will directly flow into the third annular region 1243 exposed within the second liquid injection hole 143, and the electrolyte can be directly absorbed by the separator 122 of the third annular region 1243 and penetrate radially to infiltrate the electrode assembly 120 during the inflow process. This setting can improve the infiltration efficiency of the electrode assembly 120. At the same time, the third annular region 1243 is arranged around the winding axis of the winding structure 126, which can improve the uniformity of the electrolyte infiltration along the radial direction of the electrode assembly 120, thereby enhancing the performance and lifespan of the battery.

[0065] In addition, the first current collector member 140 and the first tab 124 are welded and connected. Since there is no first tab 124 on the third annular region 1243 and the third annular region 1243 is exposed within the second liquid injection hole 143, it can effectively prevent the first current collector member 140 and the first tab 124 from being accidentally welded into the third annular region 1243 during welding, reducing the risk of scalding the separator 122.

[0066] Further, in an example of the secondary battery 100 of the present utility model, the projection of the second liquid injection hole 143 covers the first annular region 1241. The first annular region 1241 is formed by winding the first cutting segment 12331. Although part of the first annular region 1241 after cutting will be covered by the first tab 124, compared with the uncut segment 12332, the above-mentioned region covered by the first tab 124 is still convenient for the inflow of the electrolyte. The electrolyte can flow in from the gap between the first tab 124 and the first annular region 1241, and the electrolyte can be directly absorbed by the separator 122 of the first annular region 1241 and penetrate radially to infiltrate the electrode assembly 120 during the inflow process. This setting realizes that the first annular region 1241 is completely exposed within the second liquid injection hole 143, which can further improve the infiltration efficiency of the electrode assembly 120. At the same time, the number of stacked layers of the first tab 124 in the part of the first annular region 1241 covered by the first tab 124 is small and not suitable for welding with the first current collector member 140. Therefore, the first annular region 1241 being completely exposed within the second liquid injection hole 143 can effectively prevent the first current collector member 140 and the first tab 124 from being accidentally welded to the region where the number of stacked layers of the first tab 124 is small, reducing the risk of welding through the first tab 124 and scalding the separator 122.

[0067] Please refer toFigure 5 and Figure 6 , in an example of the secondary battery 100 of the present utility model, the inner radius of the second annular region 1242 is R1, the winding structure 126 includes a winding hole 127 at the center, and the radius of the winding hole 127 is R2, where R1 - R2 ≥ 1 mm. For example, it can be 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, etc. The inner circle of the second annular region 1242 is the inner circle of the covering region of the first tab 124. The limitation of R1 - R2 ≥ 1 mm can achieve that there is an annular region with a width of at least 1 mm on the outer periphery of the winding hole 127 that is not blocked by the first tab 124. The above annular region is the third annular region 1243. This setting can ensure that the width of the third annular region 1243 is not less than 1 mm, further improving the infiltration efficiency of the electrode assembly 120, thereby enhancing the performance and lifespan of the battery.

[0068] Please refer to Figure 3 , Figure 5 and Figure 6 , in an example of the secondary battery 100 of the present utility model, when projecting along the axial direction of the electrode assembly 120 onto the end face of the winding structure 126, the projected area of the first current collector member 140 is S1, and the end face area of the winding structure 126 is S2, where 0.9S2 ≥ S1 ≥ 0.4S2. For example, it can be 0.9S2, 0.8S2, 0.6S2, or 0.4S2, etc. The setting of S1 ≥ 0.4S2 can achieve that the first current collector member 140 has a large enough area to be welded to the first tab 124, so as to improve the firm reliability of the welding between the first current collector member 140 and the electrode assembly 120 and the effect of reducing the internal resistance of the battery. The setting of S1 ≤ 0.9S2 can ensure that the electrode assembly 120 has an area greater than or equal to 0.1S2 that is not blocked by the first current collector member 140 and is exposed. On the one hand, this setting is conducive to the electrolyte passing through the unblocked part and smoothly infiltrating into the electrode assembly 120. On the other hand, it is conducive to the gas inside the electrode assembly 120 discharging from the unblocked area, thereby improving the safety performance and comprehensive performance of the battery.

[0069] Please refer to Figure 3 and Figure 5 , in an example of the secondary battery 100 of the present utility model, the first current collector member 140 includes a plurality of tab connection parts 141 distributed circumferentially. The tab connection part 141 is the area where the first current collector member 140 is welded to the first tab 124. The number of tab connection parts 141 can be 2, 3, 4, or more, and there is no limitation on this. A transition connection part 142 is provided between every two adjacent tab connection parts 141. The transition connection part 142 connects the adjacent tab connection parts 141, making the first current collector member 140 have better integrity and being conducive to assembly and welding.

[0070] Please refer toFigure 5 and Figure 6 , further, at least one through hole 144 is provided on each transition connection part 142. Along the radial direction of the first current collecting member 140, the maximum width of the through hole 144 is L. A plurality of rays are made through the center of the first current collecting member 140. Among the above rays, a ray that intersects with the through hole 144 to form the maximum width is taken, and the width of the corresponding through hole 144 is the maximum width of the through hole 144. The radius of the winding structure 126 is R3. Wherein, L≥0.5×(R3 - R2), for example, it can be 0.5×(R3 - R2), 0.55×(R3 - R2), 0.6×(R3 - R2) or 0.65×(R3 - R2), etc. The through holes 144 provided on the transition connection part 142 can be one or multiple. For example, in this embodiment, two through holes 144 are provided on each transition connection part 142. The above through holes 144 are the parts on the first current collecting member 140 that do not block the electrode assembly 120. The maximum width of the larger kidney-shaped hole is shown by L1, and the maximum width of the smaller oval hole is shown by L2. L is the sum of L1 and L2. R3 - R2 corresponds to the ring width of the end face of the winding structure 126. Further, it is defined that L≥0.5×(R3 - R2), that is, the maximum value of the width of one through hole 144 or the sum of the widths of multiple through holes 144 on the same transition connection part 142 is not less than 0.5 times the ring width of the end face of the winding structure 126. This setting can enable the electrolyte to infiltrate into the inside of the electrode assembly 120 from the through hole 144 to improve the infiltration efficiency of the electrolyte. At the same time, a plurality of transition connection parts 142 are distributed along the circumferential direction of the first current collecting member 140, and each adjacent transition connection part 142 is separated by the tab connection part 141, so that the through holes 144 can be more evenly distributed along the circumferential direction of the first current collecting member 140. This setting can further improve the uniformity of electrolyte infiltration, thereby improving the performance and life of the battery.

[0071] Please refer to Figure 5 and Figure 6, in an example of the secondary battery 100 of the present utility model, the maximum distance from the outer peripheral edge of the transition connection portion 142 to the center of the first current collector member 140 is R4. Since the shape of the outer peripheral edge of the transition connection portion 142 is not limited and can be circular, polygonal, petal-shaped, or have depressions provided on the outer peripheral edge of a circle, etc., R4 is the distance from the outer peripheral edge of the transition connection portion 142 to the farthest point from the center of the first current collector member 140. The radius of the winding structure 126 is R3. Preferably, R3 > R4, that is, the distance from the outer peripheral edge of the transition connection portion 142 to the farthest point from the center of the first current collector member 140 is less than the outer peripheral edge radius of the winding structure 126. This setting can further reduce the shielding of the electrode assembly 120 by the first current collector member 140, further improve the infiltration efficiency of the electrolyte, and thus improve the performance and lifespan of the battery. Additionally, it can also prevent the situation where the first current collector member 140 interferes with the installation of the electrode assembly 120 into the housing 110, improving the assembly efficiency and assembly quality.

[0072] Please refer to Figure 5 and Figure 6 , in an example of the secondary battery 100 of the present utility model, the first empty foil area 1233 further includes a second cut section 12333 located on the outer periphery of the winding structure 126 and adjacent to the uncut section 12332. Along the radial direction of the electrode assembly 120, the second cut section 12333 winds to form a fourth annular area 1244. The radius of the inner peripheral edge of the fourth annular area 1244 is R5. Preferably, R4 ≤ R5. In this technical solution, the fourth annular area 1244 formed by winding the second cut section 12333 is not shielded by the first tab 124, and the fourth annular area 1244 is located on the outer periphery of the winding structure 126. At the same time, by defining R4 ≤ R5, that is, the distance from the outer peripheral edge of the transition connection portion 142 to the farthest point from the center of the first current collector member 140 is less than or equal to the radius of the inner peripheral edge of the fourth annular area 1244, it can be achieved that the part of the fourth annular area 1244 located radially outside the transition connection portion 142 is also not shielded by the first current collector member 140. Therefore, when the electrolyte is injected from the first liquid injection hole 115, the electrolyte will directly flow into the exposed part of the fourth annular area 1244. During the inflow process, the electrolyte can be directly absorbed by the separator 122 of the fourth annular area 1244 and penetrate both circumferentially and radially, and infiltrate the electrode assembly 120. This setting can improve the infiltration efficiency of the electrode assembly 120. At the same time, the part of the fourth annular area 1244 not covered by the first current collector member 140 is distributed along the circumferential direction of the first current collector member 140, which can improve the uniformity of the electrolyte infiltration along the radial direction of the electrode assembly 120, thereby enhancing the performance and lifespan of the battery.

[0073] Please refer to Figure 3, considering that the first tab 124 located in the outermost circle is in a free state and has a risk of breaking off, in an example of the secondary battery 100 of the present utility model, along the axial direction of the first current collector member 140, the first current collector member 140 at least covers a part of the first tab 124 located in the outermost circle of the winding structure 126. At least a part of the first tab 124 located in the outermost circle of the winding structure 126 can be covered and pressed by the first current collector member 140, which can effectively prevent the first tab 124 from warping, so as to reduce the risk that the first tab 124 breaks under the action of external force and falls into the interior of the housing 110, causing a short circuit.

[0074] Please refer to Figure 5 and Figure 6 , in an example of the secondary battery 100 of the present utility model, it is further defined that R3 - R4 ≥ 1 mm, for example, it can be 1 mm, 2 mm, 3 mm, etc. That is, the difference between the radius of the winding structure 126 and the shortest distance from the outer peripheral edge of the transition connection part 142 to the center of the first current collector member 140 is defined to be greater than or equal to 1 mm. It can be realized that while the transition connection part 142 can cover and press as much of the first tab 124 in the outermost circle as possible, it can also ensure a relatively large area of the electrode assembly 120 that is not blocked, so as to achieve the effect of both reducing the risk that the first tab 124 breaks under the action of external force and falls into the interior of the housing 110 and improving the infiltration efficiency of the electrolyte.

[0075] Please refer to Figure 1 and Figure 5 , in an example of the secondary battery 100 of the present utility model, when projecting along the axial direction of the electrode assembly 120 towards the end face of the winding structure 126, the projection of the first liquid injection hole 115 covers at least a part of the third annular region 1243 covered by the projection of the second liquid injection hole 143. It can be realized that when the electrolyte enters from the first liquid injection hole 115, it can directly flow into the part of the third annular region 1243 that is not blocked by the first tab 124 and the first current collector member 140, so that the electrolyte can be directly absorbed by the separator 122 of the third annular region 1243 and penetrate radially to infiltrate the electrode assembly 120. This setting can further improve the infiltration efficiency of the electrode assembly 120.

[0076] Please refer to Figure 7, the present utility model further provides a battery pack 10, and the battery pack 10 includes the secondary battery 100 of any one of the above. In an embodiment of the battery pack 10 of the present utility model, the battery pack 10 includes a box body 101, a box cover 102, and a plurality of secondary batteries 100. The plurality of secondary batteries 100 are placed in the box body 101 and are connected in series or in parallel with each other, or in a mixed connection of series and parallel. The box cover 102 covers the box body 101 to protect the plurality of secondary batteries 100. It should be noted that in addition to the secondary battery 100 of the present utility model, the battery pack 10 may also include parts such as a battery pack thermal management system and a circuit board. The battery pack 10 may be a battery module or a battery pack, an energy storage electric cabinet, etc.; details will not be elaborated here one by one.

[0077] Please refer to Figure 8 , the present utility model further provides an electronic device 1, and the electronic device 1 includes the battery pack 10 described above. The working part 11 is electrically connected to the battery pack 10 to obtain electrical energy support. As an example, the electronic device 1 is a vehicle, and the vehicle may be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid electric vehicle, or an extended-range electric vehicle, etc., but is not limited thereto. The working part 11 is the vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides electrical energy support for the running of the vehicle or the operation of the electrical components in the vehicle. However, in some other embodiments, the electronic device 1 may also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, and an electric tool, etc. The spacecraft includes an airplane, a rocket, a space shuttle, and a spaceship, etc.; the working part 11 may be a unit component that can obtain the electrical energy of the battery pack 10 and perform corresponding work, such as the fan blade rotation unit of a fan, the dust suction working unit of a vacuum cleaner, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy, and an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact electric drill, a concrete vibrator, and a power planer, etc. The embodiments of the present application do not impose special restrictions on the above-mentioned electronic device 1.

[0078] The secondary battery of the present utility model is provided with a first cutting section on one side of the empty foil area close to the winding shaft and wound to form a first annular area. The first annular area includes a third annular area not covered by the tab. Further, the projection of the second liquid injection hole of the current collector member covers at least part of the third annular area. The part of the third annular area covered by the projection of the second liquid injection hole is the part exposed within the second liquid injection hole. This part of the third annular area is neither blocked by the tab nor blocked by the current collector member. Therefore, when the electrolyte is injected from the first liquid injection hole, the electrolyte can be directly absorbed by the separator in the third annular area during the inflow process and radially penetrate to infiltrate the electrode assembly, so as to improve the infiltration efficiency of the electrode assembly. Therefore, the present utility model effectively overcomes some practical problems in the prior art and thus has high utilization value and practical significance. The above embodiments are only illustrative of the principles and effects of the present utility model and are not used to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A secondary battery, characterized in that, Comprising: A housing including an end wall, on which a first liquid injection hole is provided; An electrode assembly accommodated in the housing, the electrode assembly including a winding structure formed by laminating and winding a first pole piece, a second pole piece, and a separator. The end of the first pole piece includes an empty foil area extending axially of the electrode assembly out of the separator. The empty foil area includes a first cut section close to the winding axis of the winding structure and an uncut section located radially outside the first cut section. The uncut section of the empty foil area is bent to form a tab. Along the radial direction of the electrode assembly, the first cut section is wound to form a first annular area, the area covered by the tab is a second annular area, and the first annular area includes a third annular area not covered by the second annular area; A current collector member disposed between the electrode assembly and the end wall and welded to the tab. The current collector member includes a second liquid injection hole; Wherein, when projected axially of the electrode assembly onto the end face of the winding structure, the projection of the second liquid injection hole covers the third annular area.

2. The secondary battery according to claim 1, wherein The projection of the second liquid injection hole covers the first annular area.

3. The secondary battery according to claim 1, wherein The inner radius of the second annular area is R1, the winding structure includes a winding hole at the center, and the radius of the winding hole is R2, wherein R1 - R2 ≥ 1 mm.

4. The secondary battery according to claim 3, wherein When projected axially of the electrode assembly onto the end face of the winding structure, the projected area of the current collector member is S1, and the end face area of the winding structure is S2, wherein 0.9S2 ≥ S1 ≥ 0.4S2.

5. The secondary battery according to claim 4, characterized in that, The current collector member includes a plurality of tab connection portions distributed circumferentially. A transition connection portion is provided between every two adjacent tab connection portions. At least one through hole is provided on each transition connection portion. Along the radial direction of the current collector member, the maximum width of the through hole is L, and the radius of the winding structure is R3, wherein L ≥ 0.5×(R3 - R2).

6. The secondary battery according to claim 1, characterized in that, The current collector member includes a plurality of tab connection portions distributed circumferentially. A transition connection portion is provided between every two adjacent tab connection portions. The maximum distance from the outer peripheral edge of the transition connection portion to the center of the current collector member is R4, and the radius of the winding structure is R3, wherein R3 > R4.

7. The secondary battery according to claim 6, characterized in that, The empty foil area further includes a second cut section located on the outer periphery of the winding structure and adjacent to the uncut section. Along the radial direction of the electrode assembly, the second cut section is wound to form a fourth annular area, and the inner peripheral radius of the fourth annular area is R5, wherein R4 ≤ R5.

8. The secondary battery according to claim 6, wherein, Axially along the current collector member, the current collector member at least covers a part of the tab located on the outermost circle of the winding structure.

9. The secondary battery according to claim 8, wherein R3 - R4 ≥ 1 mm.

10. The secondary battery according to claim 1, characterized in that, When projected axially of the electrode assembly onto the end face of the winding structure, the projection of the first liquid injection hole covers at least a part of the third annular area covered by the projection of the second liquid injection hole.

11. A battery pack, characterized in that, Including the secondary battery according to any one of claims 1 to 10.

12. An electronic device, characterized in that, Including the battery pack according to claim 11.

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