Secondary battery, battery pack, electronic device, and method for assembling secondary battery

Abstract

The invention provides a secondary battery, a battery pack, an electronic device and an assembly method of the secondary battery. The secondary battery comprises a shell and an electrode assembly, the shell comprises a surrounding side wall, and an opening is formed in one end of the side wall; the electrode assembly is accommodated in the shell, and the electrode assembly comprises a tab facing the opening; the tab comprises a plurality of sub-tabs which are arranged at intervals along the circumferential direction of the electrode assembly, and each sub-tab is connected with the side wall in a welding manner, so that the technical problem that electric connection failure is easy to occur between the electrode assembly and the shell in the production process of the secondary battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a secondary battery, a battery pack, an electronic device, and an assembly method of the secondary battery. Background Art

[0002] Conventional cylindrical batteries typically incorporate a current collecting member near the opening of the casing. One end of the current collecting member is welded to the sidewall of the casing, while the other end is electrically connected to the tab of the electrode assembly, thereby achieving electrical connection between the casing and the electrode assembly. This complex structure and the accompanying assembly process are also complex, with numerous welding steps and a high probability of electrical connection failure during assembly. Summary of the Invention

[0003] The present invention provides a secondary battery, a battery pack, an electronic device and a secondary battery assembly method, so as to improve the technical problem of electrical connection failure between an electrode assembly and a housing during the production process of the secondary battery.

[0004] To achieve the above-mentioned objectives and other related objectives, the present invention provides a secondary battery, which includes: a shell and an electrode assembly; the shell includes a surrounding side wall, one end of which has an opening; the electrode assembly is accommodated in the shell, and the electrode assembly includes a pole ear facing the opening; the pole ear includes a plurality of sub-pole ears arranged at intervals along the circumference of the electrode assembly, and each sub-pole ear is welded to the side wall.

[0005] In this technical solution, by welding the electrode assembly's tabs directly to the housing, rather than requiring a transfer connection through a current collecting member, the structure is simplified, the number of welding steps is reduced, and the probability of electrical connection failure during assembly is lowered. This also significantly reduces the generation of metal shavings and slag inside the housing, lowering the risk of foreign matter buildup inside the housing. Furthermore, by eliminating an internal structural component, not only can production costs be reduced, but internal weight can also be reduced, contributing to an increase in the mass energy density of the secondary battery.

[0006] Furthermore, the tabs are configured to include multiple sub-tabs spaced apart along the circumference of the electrode assembly. Each sub-tab bears stress independently, reducing the risk of overall weld failure. The individual sub-tabs are welded independently, reducing the difficulty of the weld connection and further improving the reliability of the weld connection, thereby addressing the problem of electrical connection failure between the electrode assembly and the housing during secondary battery production.

[0007] In an example of the secondary battery of the present invention, the length of each sub-electrode tab along the axial direction of the electrode assembly is a, and the length of each sub-electrode tab along the circumferential direction of the electrode assembly is b, where a≥5mm and b≥10mm.

[0008] In the above technical solution, the sub-electrode tabs within this range can ensure both welding reliability and relatively stable current transmission to ensure lower internal resistance.

[0009] In an example of a secondary battery of the present invention, an electrode assembly includes a first electrode sheet, a second electrode sheet, and a winding structure formed by stacking and winding a diaphragm. The end of the first electrode sheet facing the opening includes multiple empty foil sheets extending from the diaphragm along the winding axis direction of the electrode assembly. Along the radial direction of the electrode assembly, multiple empty foil sheets are stacked and rolled up to form sub-pole ears. Multiple sub-pole ears are arranged at intervals along the circumference of the electrode assembly.

[0010] In this technical solution, multiple hollow foil sheets are radially gathered to form a sub-tab. Multiple sub-tabs are then spaced apart along the circumference of the electrode assembly. Each sub-tab bears its own stress independently, reducing the risk of overall weld failure. The individual welding of each sub-tab reduces the difficulty of the weld connection and further improves the reliability of the weld connection, thereby alleviating the problem of electrical connection failure between the electrode assembly and the housing during secondary battery production.

[0011] In an example of the secondary battery of the present invention, one end of the shell near the opening includes a rolling groove recessed into the interior of the shell, and the sub-electrode tabs are respectively welded to the rolling groove.

[0012] In the above technical solution, during the grooving process, the tab can use its inherent flexibility to absorb part of the bending deformation stress, thereby weakening the pulling effect on the welding area when the tab is bent and deformed during the grooving process. This can reduce the probability of failure of the electrical connection between the tab and the shell, and improve the yield and performance of the secondary battery.

[0013] Furthermore, the tab is configured to include multiple sub-tabs spaced apart along the circumference of the electrode assembly. This facilitates bending during grooving, thereby reducing the pulling force on the weld mark. This also alleviates the problem of tab wrinkles that can easily form on a full ring of tabs during grooving.

[0014] In an example of the secondary battery of the present invention, the rolling groove includes a first side surface facing the electrode assembly, and the sub-tab is welded to the first side surface.

[0015] In the above technical solution, the sub-tab is welded to the first side surface by first welding the tab to the sidewall and then forming a groove. This ensures that the weld mark between the tab and the sidewall is located on the first side surface of the groove. Welding the tab to the flat sidewall improves weld consistency. Furthermore, the groove creates a mechanical interlock between the tab and the housing, improving vibration and impact resistance.

[0016] In an example of the secondary battery of the present invention, along the radial direction of the electrode assembly, the end of the electrode assembly facing the opening includes, from outside to inside, a first tab area with a hollow foil and a first tab-free area without a hollow foil.

[0017] In the above technical solution, the first tab area with the empty foil is located closer to the side wall, which facilitates welding of the sub-tab and the side wall, reduces welding difficulty, and improves welding quality.

[0018] In an example of the secondary battery of the present invention, the length of the hollow foil extending from the separator gradually decreases from the radial inner side to the radial outer side of the electrode assembly.

[0019] In the above technical solution, to bring the tab closer to the sidewall, the radially inwardly located bare foil is folded toward the sidewall. This arrangement allows the bare foil to be folded sequentially from the radially inwardly located toward the sidewall, resulting in a uniformly shaped tab with a uniform thickness, preventing weld penetration in thinner areas of the tab. This arrangement further reduces welding difficulty and improves weld quality.

[0020] In an example of the secondary battery of the present invention, the rolling groove further includes a second side surface facing the opening and a third side surface connecting the first side surface and the second side surface, and the sub-tab is welded to the third side surface.

[0021] In the above technical solution, the sub-tab is welded to the third side surface by first machining a groove and then welding the sub-tab to the side of the groove facing the interior of the housing. This ensures that the weld mark between the sub-tab and the sidewall is located on the third side surface of the groove. This arrangement avoids pulling on the weld mark during the groove machining process, reducing the probability of weld failure. It also prevents the generation of metal debris in the weld area during the groove rolling process, thereby reducing the probability of short circuits caused by metal debris falling into the electrode assembly, thereby improving the safety performance of the secondary battery.

[0022] In an example of the secondary battery of the present invention, each sub-tab is at least partially located within the area surrounded by the third side surface.

[0023] In the above technical solution, the sub-electrode tab is brought closer to the third side surface, which facilitates welding of the sub-electrode tab and the third side surface, reduces welding difficulty, and improves welding quality.

[0024] In an example of the secondary battery of the present invention, along the radial direction of the electrode assembly, the end of the electrode assembly facing the opening includes, from outside to inside, a second tab-free area without hollow foil and a second tab-within area with hollow foil.

[0025] In the above technical solution, the second tab area with the empty foil is located closer to the third side surface, which facilitates welding of the sub-tab and the third side surface, reduces welding difficulty, and improves welding quality.

[0026] In an example of the secondary battery of the present invention, the expanded length of the second tab-free region is L1, the expanded total length of the first electrode sheet is L, and L1>0.3L.

[0027] In the above technical solution, the length of the second tab-free area is set to be greater than 0.3L, so that the second tab-containing area can be located within the area surrounded by the third side surface, thereby ensuring the stability of the welding area between the sub-tab and the third side surface.

[0028] In an example of the secondary battery of the present invention, the unfolded length of the second tab region is L2, the unfolded total length of the first electrode sheet is L, and L2>0.5L.

[0029] In the above technical solution, the length of the second tab area is set to be greater than 0.5L, which can not only fully meet the requirements of multi-tab welding, but also provide sufficient flow area to achieve lower internal resistance.

[0030] In an example of a secondary battery of the present invention, the sub-electrode tab includes a shell connecting portion, a transition portion and a gathering portion. The shell connecting portion is welded to the rolling groove. The gathering portion is formed by gradually gathering a plurality of stacked empty foils from their roots. The transition portion connects the shell connecting portion and the gathering portion. The transition portion and the shell connecting portion form a curved structure opening toward the interior of the shell.

[0031] In the above technical solution, the shell connection portion has a relatively flat welding surface, which helps reduce the risk of cold welds. The curved structure formed by the transition portion and the shell connection, which opens toward the shell interior, is flexible and can move slightly during the grooving process. This absorbs the bending stress of the sub-tab and relieves the pulling of the bending stress on the weld mark, thus preventing weld failure between the sub-tab and the shell.

[0032] In an example of the secondary battery of the present invention, the gathered portion is formed by gathering a plurality of stacked hollow foils simultaneously from the radially outer side and the radially inner side.

[0033] In this technical solution, the radially outer hollow foil is gathered centrally, creating a gap between the formed sub-electrode tab and the sidewalls, providing space for the curved structure formed in the transition section. The radially inner and outer hollow foils are also gathered centrally, which facilitates a symmetrical sub-electrode tab structure with a uniform thickness, thus reducing welding difficulty and improving welding quality.

[0034] In an example of the secondary battery of the present invention, the gathered portion is formed by a plurality of stacked hollow foils gathered from the radially outer side to the radially inner side.

[0035] In the above technical solution, the empty foil located on the radial outside is gathered toward the radial inside, so that the formed sub-electrode ear can be spaced apart from the side wall, thereby providing an accommodation space for the curved structure formed in the transition portion.

[0036] In an example of the secondary battery of the present invention, the length of the hollow foil extending from the separator gradually decreases from the radial outer side to the radial inner side of the electrode assembly.

[0037] In the above technical solution, the hollow foil is sequentially gathered from the radial outside to the radial inside, which can obtain a uniform and uniform sub-electrode tab, thus preventing the problem of welding through in the thinner area of ​​the sub-electrode tab. This arrangement can further reduce the difficulty of welding and improve the welding quality.

[0038] In an example of the secondary battery of the present invention, the first side surface gradually approaches the electrode assembly from the radial outer side to the radial inner side of the electrode assembly.

[0039] In the above technical solution, after the sub-tab is welded and sealed, it is hidden in the angle space formed by the first side surface and the end face of the electrode assembly, and does not occupy the remaining available space inside the shell, which can improve the space utilization rate. After the sealing is completed, the connection part of the first side surface and the third side surface of the rolling groove is close to the end face of the electrode assembly, which can limit the electrode assembly and improve the vibration resistance of the secondary battery.

[0040] The present invention also provides a battery pack, which includes any one of the above secondary batteries.

[0041] The present invention also provides an electronic device, which includes the battery pack.

[0042] The present invention also provides a method for assembling a secondary battery, wherein the secondary battery comprises a housing, an electrode assembly, and a cover plate, wherein the housing comprises a side wall, one end of the side wall having an opening, and the electrode assembly comprises a plurality of sub-electrode tabs spaced apart along its circumference. The method is characterized in that the method comprises the following steps:

[0043] Install the electrode assembly into the housing through the opening;

[0044] The plurality of sub-electrode tabs and the side wall form a welding area near the opening;

[0045] Welding the area to be welded to fixedly connect the plurality of sub-electrode tabs to the side wall and form weld marks;

[0046] Install the cover seal over the opening.

[0047] In this technical solution, by welding the electrode assembly's tabs directly to the housing, rather than requiring a transfer connection through a current collecting member, the structure is simplified, the number of welding steps is reduced, and the probability of electrical connection failure during assembly is lowered. This also significantly reduces the generation of metal shavings and slag inside the housing, lowering the risk of foreign matter buildup inside the housing. Furthermore, by eliminating an internal structural component, not only can production costs be reduced, but internal weight can also be reduced, contributing to an increase in the mass energy density of the secondary battery.

[0048] Furthermore, the tabs are configured to include multiple sub-tabs spaced apart along the circumference of the electrode assembly. Each sub-tab bears stress independently, reducing the risk of overall weld failure. The individual sub-tabs are welded independently, reducing the difficulty of the weld connection and further improving the reliability of the weld connection, thereby addressing the problem of electrical connection failure between the electrode assembly and the housing during secondary battery production.

[0049] In an example of the assembly method of the present invention, the processing steps of the electrode assembly include:

[0050] Stacking the first pole piece, the second pole piece and the diaphragm and winding them to form a winding structure;

[0051] The end of the first electrode sheet facing the opening includes a hollow foil area extending out of the diaphragm along the winding axis of the electrode assembly, and the hollow foil area is fixed by ultrasonic flat welding to form an annular electrode ear;

[0052] Part of the empty foil area is cut and removed to form a plurality of sub-electrode ears arranged at intervals along the circumference of the electrode assembly.

[0053] In the above technical solution, the empty foil area is first welded as a whole to form an integral annular pole ear, and then cut into multiple sub-pole ears arranged at intervals. This method has higher welding strength, better structural stability, better controllability of the spacing and size between multiple sub-pole ears, and higher dimensional accuracy.

[0054] In an example of the assembly method of the present invention, the processing steps of the electrode assembly include:

[0055] Die-cutting a plurality of spaced-apart empty foils at preset positions of the first pole piece;

[0056] The first electrode sheet, the second electrode sheet, and the diaphragm are stacked and wound to form a wound structure, wherein a plurality of hollow foils are arranged at intervals along the circumference of the electrode assembly to form a plurality of hollow foil groups, and each hollow foil group includes a plurality of hollow foils arranged sequentially along the radial direction of the electrode assembly;

[0057] The empty foils in each empty foil group are ultrasonically flat welded to form a plurality of sub-electrode tabs.

[0058] In this technical solution, multiple blank foil sheets are die-cut at predetermined locations, then coiled and flat-welded to form the sub-tabs. This method achieves high material utilization and reduces waste. Furthermore, each blank foil group is welded independently, creating a locally flexible connection that helps absorb radial stress during battery expansion.

[0059] In an example of the assembly method of the present invention, after the sub-electrode tab is fixedly connected to the side wall, the method further includes: rolling the side wall area corresponding to the weld mark to form a rolling groove, and allowing the rolling groove to limit the axial displacement of the electrode assembly.

[0060] In this technical solution, the tab is first welded to the sidewall, followed by the grooves. Welding the tab to the flat sidewall improves weld consistency. Furthermore, the grooves mechanically interlock the tab with the housing, improving vibration and impact resistance.

[0061] In one example of the assembly method of the present invention, after the electrode assembly is installed into the shell from the opening, it also includes: rolling the side wall area close to the opening to form a rolling groove, and allowing the rolling groove to limit the axial displacement of the electrode assembly, and the area to be welded formed by multiple sub-ears and the side wall is located in the rolling groove.

[0062] In the above technical solution, the groove is first processed, and then the sub-tab is welded to the side of the groove facing the inside of the housing. This assembly method avoids the strain on the weld mark during the groove process, reducing the probability of weld failure. It also prevents the generation of metal debris in the weld area during the groove process, thereby reducing the probability of short circuits caused by metal debris falling into the electrode assembly, thereby improving the safety performance of the secondary battery.

[0063] The secondary battery of the present invention directly welds the electrode assembly's tabs to the housing, replacing the need for a transfer connection via a current collecting member. This simplifies the structure, reduces the number of welding steps, and lowers the probability of electrical connection failure during assembly. It also significantly reduces the generation of metal shavings and slag inside the housing, minimizing the risk of foreign matter buildup inside the housing. Furthermore, by eliminating an internal structural component, production costs are reduced and internal weight is also reduced, contributing to an increase in the mass energy density of the secondary battery.

[0064] Furthermore, the tabs are configured to include multiple sub-tabs spaced apart along the circumference of the electrode assembly. Each sub-tab bears stress independently, reducing the risk of overall weld failure. The individual sub-tabs are welded independently, reducing the difficulty of the weld connection and further improving the reliability of the weld connection, thereby addressing the problem of electrical connection failure between the electrode assembly and the housing during secondary battery production. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0066] Figure 1 This is a schematic diagram of the overall structure of an example of a secondary battery of the present invention;

[0067] Figure 2 A cross-sectional view of the electrode assembly structure of an example of a secondary battery of the present invention;

[0068] Figure 3 An example of a secondary battery of the present invention Figure 1 A partial enlarged view of point A in the middle;

[0069] Figure 4 for Figure 3 A schematic diagram of the structure of the secondary battery of the present invention after completing each step in the assembly process;

[0070] Figure 5 for Figure 4 A schematic structural diagram of each step in an example of a processing step 1 of an electrode assembly of a secondary battery of the present invention after completion;

[0071] Figure 6 for Figure 4 A schematic structural diagram of each step in an example of a processing step 1 of an electrode assembly of a secondary battery of the present invention after completion;

[0072] Figure 7 An example of a secondary battery of the present invention Figure 1 A partial enlarged view of point A in the middle;

[0073] Figure 8 for Figure 7 A schematic diagram of the structure of the secondary battery of the present invention after completing each step in the assembly process;

[0074] Figure 9 An example of a secondary battery of the present invention Figure 1 A partial enlarged view of point A in the middle;

[0075] Figure 10 for Figure 9 A schematic diagram of the structure of the secondary battery of the present invention after completing each step in the assembly process;

[0076] Figure 11 for Figure 10 A schematic structural diagram of each step in an example of a processing step 1 of an electrode assembly of a secondary battery of the present invention after completion;

[0077] Figure 12 for Figure 10 A schematic structural diagram of each step in an example of a processing step 1 of an electrode assembly of a secondary battery of the present invention after completion;

[0078] Figure 13 An example of a secondary battery of the present invention Figure 1 A partial enlarged view of point A in the middle;

[0079] Figure 14 for Figure 13 A schematic diagram of the structure of the secondary battery of the present invention after completing each step in the assembly process;

[0080] Figure 15 An example of a secondary battery of the present invention Figure 1 A partial enlarged view of point A in the middle;

[0081] Figure 16 for Figure 15 A schematic diagram of the structure of the secondary battery of the present invention after completing each step in the assembly process;

[0082] Figure 17 for Figure 16 A schematic structural diagram of each step in an example of a processing step 1 of an electrode assembly of a secondary battery of the present invention after completion;

[0083] Figure 18 An example of a secondary battery of the present invention Figure 1 A partial enlarged view of point A in the middle;

[0084] Figure 19 This is a schematic structural diagram of an example of a battery pack of the present invention;

[0085] Figure 20 is a schematic structural diagram of an example of an electronic device of the present invention;

[0086] Figure 21 FIG. 1 is a flow chart illustrating an exemplary method for assembling a secondary battery according to the present invention.

[0087] Component number description:

[0088] 1. Electronic device; 10. Battery pack; 11. Working unit; 101. Housing; 102. Housing cover; 100. Secondary battery; 110. Housing; 111. End wall; 112. Side wall; 113. Opening; 114. Groove; 1141. First side surface; 1142. Second side surface; 1143. Third side surface; 120. Electrode assembly; 121. First electrode sheet; 1211. Negative electrode current collector; 1212. First coated area; 1213. First uncoated area; 122. Separator; 123. Second electrode sheet; 1231. Positive electrode current collector; 1232. Second coated area; 1233. Second uncoated area; 124. First pole tab; 1241. Sub-pole tab; 1242. First area with pole tabs; 1243. First area without pole tabs; 1244. Second area with pole tabs; 1245. Second area without pole tabs; 1246. Shell connection portion; 1247. Transition portion; 1248. Gathering portion; 1249. Weld mark; 125. Second pole tab; 126. Empty foil group; 1261. Empty foil; 130. Cover plate; 140. Pole. DETAILED DESCRIPTION

[0089] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the 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 the following examples and the features in the examples can be combined with each other unless they conflict. It should also be understood that the terms used in the examples of the present invention are for the purpose of describing specific embodiments, not for the purpose of limiting the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0090] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be used. Unless otherwise defined, all technical and scientific terms used herein are consistent with the prior art as understood by those skilled in the art and the description of the present invention. Any prior art methods, devices, and materials similar or equivalent to those in the examples of the present invention may also be used to implement the present invention.

[0091] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0092] See also Figures 1 to 21 The present invention provides a secondary battery 100, a battery pack 10, an electronic device 1, and an assembly method of the secondary battery 100. The secondary battery 100 directly welds the sub-electrode tab 1241 of the electrode assembly 120 to the shell 110, replacing the method of connecting through a current collecting component, thereby simplifying the structure, reducing the number of welding steps, and reducing the probability of electrical connection failure during the assembly process.

[0093] In the present invention, the secondary battery 100 may include a lithium-ion battery, a lithium-sulfur battery, a sodium-lithium-ion battery, a sodium-ion battery, or a magnesium-ion battery, etc., and the embodiments of the present invention are not limited thereto. Referring to FIG and FIG, the structure of the secondary battery 100 is further described. The secondary battery 100 includes a housing 110, an electrode assembly 120, a cap 130, and an electrode 140.

[0094] See also Figure 1 The housing 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. The connection between the end wall 111 and the side wall 112 can be achieved in a variety of ways, as long as a stable seal and electrical connection can be established, such as integral stamping, integral casting, or separate welding. The shape of the side wall 112 is not limited and can be cylindrical or prismatic, or can be formed along any other closed-loop contour that matches the end wall 111. In this embodiment, the outer edge of the end wall 111 is circular, and the side wall 112 is cylindrical and surrounds the outer edge of the end wall 111. A circular opening 113 is formed at the end of the side wall 112 facing away from the end wall 111. A cavity is formed within the housing 110, enclosed by the end wall 111 and the side wall 112, for accommodating the electrode assembly 120, electrolyte, and other essential battery components. Specifically, the diameter of the housing 110 can be determined based on the specific dimensions of the electrode assembly 120, such as 18 mm, 21 mm, 46 mm, etc. The shell 110 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent the shell 110 from rusting during long-term use, a layer of rust-proof material such as metal nickel can be plated on the surface of the shell 110.

[0095] See also Figures 1 to 2 The electrode assembly 120 is housed in the housing 110. The electrode assembly 120 is a component where electrochemical reactions occur in the secondary battery 100. The housing 110 may contain one or more electrode assemblies 120. The electrode assembly 120 includes a first electrode sheet 121, a second electrode sheet 123, and a separator 122 stacked and wound to form a wound structure. The first electrode sheet 121 and the second electrode sheet 123 have opposite polarities. In some embodiments, the first electrode sheet 121 is a positive electrode sheet and the second electrode sheet 123 is a negative electrode sheet. In other embodiments, the first electrode sheet 121 is a negative electrode sheet and the second electrode sheet 123 is a positive electrode sheet.

[0096] See also Figure 1 、 Figure 2 and Figure 6 In this embodiment, the first electrode sheet 121 is a negative electrode sheet, and the first electrode sheet 121 includes a negative electrode current collector 1211 and a negative electrode active material. The negative electrode active material is coated on the surface of the negative electrode current collector 1211; the negative electrode current collector 1211 includes a first coated area 1212 coated with an active material and a first uncoated area 1213 not coated with an active material. The first uncoated area 1213 is located at the end of the first electrode sheet 121, and the first uncoated area 1213 extends out of the separator 122 along the winding axis direction of the electrode assembly 120 to form a pole ear. In order to distinguish it from the pole ear formed by the second electrode sheet 123, the pole ear located on the first electrode sheet 121 is called the first pole ear 124, and the first pole ear 124 is the corresponding negative electrode pole ear.

[0097] See also Figures 1 to 2 The second electrode sheet 123 is a positive electrode sheet. Specifically, the second electrode sheet 123 includes a positive electrode current collector 1231 and a positive electrode active material. The positive electrode active material is coated on the surface of the positive electrode current collector 1231; the positive electrode current collector 1231 includes a second coated area 1232 coated with an active material and a second uncoated area 1233 not coated with an active material. The second uncoated area 1233 is located at the end of the second electrode sheet 123. The other end of the second uncoated area 1233 extends out of the diaphragm 122 along the winding axis direction of the electrode assembly 120 and is bent toward the winding axis to form a second electrode tab 125. The second electrode tab 125 is the corresponding positive electrode tab.

[0098] See also Figures 1 to 2 The separator 122 is disposed between the first electrode sheet 121 and the second electrode sheet 123 to separate the positive electrode active material layer from the negative electrode active material layer. Taking the lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1231 can be aluminum, and the positive electrode active material layer includes a positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The material of the negative electrode current collector 1211 can be copper, and the negative electrode active material layer includes a negative electrode active material, which can be carbon or silicon. The base material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. To provide protection and insulation for the electrode assembly 120, an insulating film can also be coated on the outside of the electrode assembly 120. The insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other polymer materials.

[0099] See also Figure 1 and Figure 2Furthermore, the first tab 124 faces the end wall 111 or the opening 113, while the second tab 125 faces the other end of the housing 110. In this embodiment, the second tab 125 faces the end wall 111 and is electrically connected to the pole 140, causing the pole 140 to be positively charged. The first tab 124 faces the opening 113, and the housing 110 is electrically connected to the first tab 124, causing the housing 110 to be negatively charged. However, in other embodiments, the first tab 124 may be connected to the pole 140, while the second tab 125 may be connected to the housing 110.

[0100] See also Figure 1 The pole 140 is fixed to the end wall 111 and electrically connected to the electrode assembly 120. Specifically, the end wall 111 is provided with a pole hole, and the pole 140 is installed through the pole hole and is insulated from the end wall 111. The end of the pole 140 facing the electrode assembly 120 passes through the end wall 111 to be directly electrically connected to the second pole tab 125 or indirectly electrically connected through a transfer. The structure of the pole 140 can be any suitable form that can pass through the end wall 111 and electrically connect to the second pole tab 125 of the electrode assembly 120. For example, the cross-section can be circular, square, prismatic, or a special-shaped profile that can achieve stable electrical conduction. The pole hole corresponds to the shape of the pole 140. In this embodiment, the cross-section of the pole 140 is circular.

[0101] See also Figures 1 to 3 The cover plate 130 is sealed against the opening 113; the outer edge of the cover plate 130 corresponds to the shape of the opening 113 and is connected to the side wall 112 to seal the opening 113. In some embodiments, the cover plate 130 and the side wall 112 are pressed tightly together using a pier seal to form a reliable sealing connection. In other embodiments, the cover plate 130 and the side wall 112 are sealed and fixed together by welding, which is not limited to this.

[0102] See also Figures 3 to 18The tabs include multiple sub-tabs 1241 spaced apart along the circumference of the electrode assembly 120. The number of sub-tabs 1241 is not limited and can be two, four, six, eight, or more. The spacing between each sub-tab 1241 is not limited; preferably, the multiple sub-tabs 1241 are evenly distributed along the circumference of the electrode assembly 120. In this embodiment, four sub-tabs 1241 are provided, evenly distributed along the circumference of the electrode assembly 120. Each sub-tab 1241 is welded to the sidewall 112. Directly welding the sub-tabs 1241 to the housing 110 replaces the method of connecting via a current collecting member. This simplifies the structure, reduces the number of welding steps, and reduces the probability of electrical connection failure during assembly. It also significantly reduces the generation of metal shavings and slag inside the housing 110, reducing the risk of foreign matter inside the housing 110. Furthermore, by eliminating an internal structural component, not only can production costs be reduced, but internal weight can also be reduced, which helps improve the mass energy density of the secondary battery 100. Furthermore, the tabs are configured to include multiple sub-tabs 1241 spaced apart along the circumference of the electrode assembly 120. Each sub-tab 1241 independently withstands stress, reducing the risk of overall weld failure. Each sub-tab 1241 is welded independently, reducing the difficulty of the weld connection and further improving the reliability of the weld connection, thereby alleviating the problem of electrical connection failure between the electrode assembly 120 and the housing 110 during the production of the secondary battery 100.

[0103] See also Figure 6 In one example of the secondary battery 100 of the present invention, the length of each sub-tab 1241 along the axial direction of the electrode assembly 120 is a, and the length of each sub-tab 1241 along the circumferential direction of the electrode assembly 120 is b, where a ≥ 5 mm and b ≥ 10 mm. Sub-tabs 1241 within this range ensure both reliable welding and relatively stable current transmission, thus ensuring low internal resistance.

[0104] See also Figures 3 to 18In one example of the secondary battery 100 of the present invention, the end of the first electrode sheet 121 facing the opening 113 includes multiple hollow foils 1261 extending from the separator 122 along the winding axis of the electrode assembly 120. It should be noted that multiple hollow foil groups 126 are arranged along the circumference of the electrode assembly 120. In the radial direction of the electrode assembly 120, each hollow foil group 126 includes multiple hollow foils 1261. Multiple hollow foils 1261 in each hollow foil group 126 are stacked and gathered to form a sub-electrode tab 1241. The number of hollow foils 1261 is not limited, and a suitable number is sufficient to achieve a secure weld with the housing 110 and stable current transmission. The multiple hollow foils 1261 are fixed by ultrasonic welding to form a fixed connection. Multiple hollow foil groups 126 arranged at intervals along the circumference of the electrode assembly 120 form corresponding sub-electrode tabs 1241. Each sub-electrode tab 1241 independently withstands stress, which can reduce the risk of overall welding failure. Each sub-electrode tab 1241 is welded independently, which reduces the difficulty of welding connection and further improves the reliability of welding connection, thereby improving the problem of electrical connection failure between the electrode assembly 120 and the shell 110 during the production process of the secondary battery 100.

[0105] See also Figure 3 、 Figure 7 、 Figure 9 、 Figure 13 、 Figure 15 and Figure 18 In one example of a secondary battery 100 according to the present invention, one end of the housing 110 near the opening 113 includes a groove 114 recessed into the interior of the housing 110. The groove 114 can restrict the movement of the electrode assembly 120 toward the opening 113. The groove 114 includes a first side 1141 facing the electrode assembly 120, a second side 1142 facing the opening 113, and a third side 1143 connecting the first side 1141 and the second side 1142. The cover plate 130 is placed on the second side 1142. A sealing ring is provided between the cover plate 130 and the housing 110. The edge of the opening 113 is sealed so that the cover plate 130 presses against the sealing ring, forming a secure connection. The sub-pole tabs 1241 are respectively welded to the grooves 114. The sub-pole tabs 1241 can be welded to the first side 1141 or the third side 1143. There is no limitation on the position where the sub-tab 1241 is welded to the rolling groove 114 , as long as a stable electrical connection between the sub-tab 1241 and the housing 110 can be achieved.

[0106] In this embodiment, when processing the groove 114, the tab can utilize its inherent flexibility to absorb some of the bending and deformation stress, thereby weakening the pulling effect on the weld area caused by the bending and deformation of the tab during the groove 114 process. This can reduce the probability of electrical connection failure between the tab and the housing 110, thereby improving the yield rate and performance of the secondary battery 100. The tab is configured to include multiple sub-tabs 1241 spaced apart along the circumference of the electrode assembly 120. In this technical solution, the tab is configured to bend with the groove 114 during the groove 114 process, thereby weakening the pulling force of the tab on the weld mark 1249. It can also improve the problem of tab wrinkles easily generated when the entire ring of tabs is grooved 114.

[0107] See also Figure 3 、 Figure 13 、 Figure 15 and Figure 18 In an example of the secondary battery 100 of the present invention, the sub-pole tab 1241 is welded to the first side surface 1141. Specifically, in this embodiment, the sub-pole tab 1241 is first welded to the side wall 112, and then the rolling groove 114 is processed. The weld mark 1249 for welding the sub-pole tab 1241 to the side wall 112 is located on the first side surface 1141 of the rolling groove 114. In this embodiment, the sub-pole tab 1241 is welded to the flat side wall 112, which helps to improve the consistency of the weld point. In addition, the rolling groove 114 allows the sub-pole tab 1241 to form a mechanical interlock with the housing 110, which has better anti-vibration and impact resistance.

[0108] See also Figure 5 、 Figure 6 and Figure 17 , Figure 5 、 Figure 6 and Figure 17 The first figure in the figure is an expanded view of the first electrode sheet 121, with the jagged side located at the center after winding, and the second figure is the electrode assembly 120 after winding. In an example of the secondary battery 100 of the present invention, along the radial direction of the electrode assembly 120, the end of the electrode assembly 120 facing the opening 113 includes, from the outside to the inside, a first tab area 1242 with a hollow foil 1261 and a first tab-free area 1243 without a hollow foil 1261. This arrangement can make the first tab area 1242 with a hollow foil 1261 located closer to the side wall 112, making it easier to weld the sub-tab 1241 and the side wall 112, reducing the difficulty of welding and improving the welding quality. The lengths of the first tab area 1242 and the first tab-free area 1243 are not limited, and are adaptively designed according to the different diameters of the battery, so as to achieve firm welding with the shell 110 and stable current transmission.

[0109] See also Figure 6In an example of the secondary battery 100 of the present invention, the length of the hollow foil 1261 extending from the radial inner side to the radial outer side of the electrode assembly 120 gradually decreases. The change of the hollow foil 1261 is not shown in the figure, but it can be understood that Figure 6 The height a of the empty foil 1261 shown in the figure gradually decreases from left to right. In this embodiment, in order to make the sub-pole lug 1241 closer to the side wall 112, the empty foil 1261 located on the radial inner side needs to be retracted in the direction close to the side wall 112. The setting of this technical solution can achieve: after the empty foil 1261 is successively retracted from the radial inner side toward the direction close to the side wall 112, a sub-pole lug 1241 with a uniform thickness and a tendency to be neat can be obtained, thereby preventing the problem of welding through in the thinner area of ​​the sub-pole lug 1241. This setting can further reduce the difficulty of welding and improve the welding quality.

[0110] See also Figure 7 and Figure 9 In one example of the secondary battery 100 of the present invention, the tab 1241 is welded to the third side surface 1143. In this embodiment, the groove 114 is first machined, and then the tab 1241 is welded to the side of the groove 114 facing the interior of the housing 110. This results in the weld mark 1249 between the tab 1241 and the sidewall 112 being located on the third side surface 1143 of the groove 114. Figure 7 Secondary battery 100 and Figure 9 In the secondary batteries 100 , the sub-electrode tabs 1241 are welded to the third side surface 1143 . Figure 7 For details on the processing of the secondary battery 100, please refer to Figure 8 . Figure 9 For details on the processing of the secondary battery 100, please refer to Figure 10 Both of the above methods can avoid pulling on the weld mark 1249 during the groove rolling process 114, reducing the probability of weld failure. At the same time, they can also prevent the generation of metal debris in the weld area during the groove rolling process 114, thereby reducing the probability of short circuits caused by metal debris falling into the electrode assembly 120, thereby improving the safety performance of the secondary battery 100.

[0111] See also Figures 7 to 10 In an example of the secondary battery 100 of the present invention, each sub-electrode tab 1241 is at least partially located in the area surrounded by the third side surface 1143. In one embodiment, refer to Figure 9 , the sub-electrode tabs 1241 are all located in the area surrounded by the third side surface 1143. In another embodiment, see Figure 7, only part of the sub-electrode tab 1241 is located within the area surrounded by the third side surface 1143. This arrangement allows the sub-electrode tab 1241 to be at least partially close to the third side surface 1143, facilitating welding of the sub-electrode tab 1241 and the third side surface 1143, reducing welding difficulty and improving welding quality.

[0112] See also Figure 11 and Figure 12 In one example of the secondary battery 100 of the present invention, along the radial direction of the electrode assembly 120, the end of the electrode assembly 120 facing the opening 113 includes, from the outside to the inside, a second tab-free region 1245 without a hollow foil sheet 1261 and a second tab-filled region 1244 with a hollow foil sheet 1261. Specifically, the second tab-free region 1245 surrounds the second tab-filled region 1244. This arrangement allows the second tab-filled region 1244 with a hollow foil sheet 1261 to be located closer to the third side surface 1143, facilitating welding between the sub-tab 1241 and the third side surface 1143, reducing welding difficulty and improving welding quality.

[0113] See also Figure 11 and Figure 12 In one example of the secondary battery 100 of the present invention, the expanded length of the second tab-free region 1245 is L1, the expanded total length of the first electrode sheet 121 is L, and L1 is greater than 0.3L. The length of the second tab-free region 1245 being greater than 0.3L allows the second tab-containing region 1244 to be located within the area enclosed by the third side surface 1143, thereby ensuring the stability of the weld area between the sub-tab 1241 and the third side surface 1143.

[0114] See also Figure 11 and Figure 12 In one example of the secondary battery 100 of the present invention, the expanded length of the second tab region 1244 is L2, the total expanded length of the first electrode sheet 121 is L, and L2 is greater than 0.5L. The length of the second tab region 1244 being greater than 0.5L fully meets the requirements for welding multiple tabs while providing ample flow area for lower internal resistance.

[0115] See also Figure 13 and Figure 15 In one example of the secondary battery 100 of the present invention, the sub-electrode tab 1241 includes a housing connection portion 1246, a transition portion 1247, and a gathered portion 1248. The housing connection portion 1246 is welded to the rolling groove 114. The gathered portion 1248 is formed by a plurality of stacked hollow foils 1261 that gradually converge from their bases. The gathered portion 1248 gradually converges from the bases of the hollow foils 1261 until it is compacted. The compacted portion is then secured by ultrasonic flat welding. Figure 13 For details on the processing of the secondary battery 100, please refer to Figure 14 . Figure 15For details on the processing of the secondary battery 100, please refer to Figure 16 . The shell connection portion 1246 formed in this way has a relatively flat welding surface, which is conducive to reducing the risk of cold welding. The transition portion 1247 connects the shell connection portion 1246 and the gathering portion 1248. The transition portion 1247 and the shell connection portion 1246 form a curved structure toward the internal opening 113 of the shell 110. Since the curved structure is flexible, the specific shape of the curved structure is not limited. As long as it can move slightly between the shell connection portion 1246 and the gathering portion 1248. Since the curved structure is a flexible structure, it can move slightly during the processing of the rolling groove 114, absorb the bending stress of the sub-pole ear 1241, relieve the pulling of the bending stress on the weld mark 1249, and prevent the welding failure of the sub-pole ear 1241 and the shell 110.

[0116] See also Figure 13 and Figure 14 In an example of the secondary battery 100 of the present invention, the gathered portion 1248 is formed by a plurality of stacked empty foils 1261 that are simultaneously gathered from the radially outer side and the radially inner side. The formed gathered portion 1248 is similar to an isosceles triangle. In this embodiment, the empty foils 1261 located on the radially outer side are gathered in the center, which can create a distance between the formed sub-pole tab 1241 and the side wall 112, providing space for the curved structure formed by the transition portion 1247. The empty foils 1261 located on the radially inner and outer sides are also gathered in the center, which is conducive to forming a symmetrical structure of the sub-pole tab 1241 with a uniform thickness, which helps to reduce the difficulty of welding and improve the welding quality.

[0117] See also Figure 15 and Figure 16 In one example of the secondary battery 100 of the present invention, the converged portion 1248 is formed by stacking multiple hollow foil sheets 1261 radially outward and inward. This converged portion 1248 resembles a right triangle. The hollow foil sheets 1261 located radially outward converge radially inward, creating a distance between the formed sub-electrode tab 1241 and the sidewall 112, providing space for the curved structure formed by the transition portion 1247.

[0118] See also Figure 17 In one example of the secondary battery 100 of the present invention, the length of the hollow foil 1261 extending beyond the separator 122 gradually decreases from the radially outer side to the radially inner side of the electrode assembly 120. By gradually converging the hollow foil 1261 from the radially outer side to the radially inner side, a uniform sub-electrode tab 1241 is formed, preventing weld penetration in thinner areas of the sub-electrode tab 1241. This arrangement further reduces welding difficulty and improves welding quality.

[0119] See also Figure 18In one example of the secondary battery 100 of the present invention, the first side surface 1141 gradually approaches the electrode assembly 120 from the radially outer side to the radially inner side of the electrode assembly 120. This arrangement allows the sub-tab 1241 to be hidden within the angle formed by the first side surface 1141 and the end face of the electrode assembly 120 after welding and encapsulation, without occupying the remaining available space within the housing 110, thereby improving space utilization. After encapsulation, the connection between the first side surface 1141 and the third side surface 1143 of the rolling groove 114 approaches the end face of the electrode assembly 120, which can limit the electrode assembly 120 and improve the vibration resistance of the secondary battery 100.

[0120] See also Figure 19 The present invention further provides a battery pack 10, comprising any of the aforementioned secondary batteries 100. In one embodiment of the battery pack 10 of the present invention, the battery pack 10 comprises a housing 101, a housing cover 102, and a plurality of secondary batteries 100. The plurality of secondary batteries 100 are placed within the housing 101 and connected in series or in parallel, or in a combination of these. The housing cover 102 seals the housing 101 to protect the plurality of secondary batteries 100. It should be noted that, in addition to the secondary batteries 100 of the present invention, the battery pack 10 may also include a thermal management system, a circuit board, and other components. The battery pack 10 may be a battery module, a battery pack, an energy storage cabinet, or the like; these will not be described in detail here.

[0121] See also Figure 20 The present invention also provides an electronic device 1, which includes the above-mentioned battery pack 10. The working part 11 is electrically connected to the battery pack 10 to obtain power support. As an example, the electronic device 1 is a vehicle, and the vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc., but is not limited to this. The working part 11 is the vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides power support for the driving of the vehicle or the operation of the electrical components in the vehicle. However, in some other embodiments, the electronic device 1 can also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. Spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.; the working part 11 can be a unit component that can obtain power from the battery pack 10 and perform corresponding work, such as a fan blade rotation unit, a vacuum cleaner's dust collection unit, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys; electric tools include metal cutting tools, grinding tools, assembly tools, and railway tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The present embodiment does not impose any particular restrictions on the electronic device 1.

[0122] See also Figure 21 The present invention also provides an assembly method of a secondary battery 100, wherein the secondary battery 100 includes a housing 110, an electrode assembly 120, and a cover plate 130. The housing 110 includes a side wall 112, one end of the side wall 112 having an opening 113. The electrode assembly 120 includes a plurality of sub-electrode tabs 1241 spaced apart along its circumference. Figure 4 (A) Figure 8 (A) Figure 10 (A) Figure 14 (A) and Figure 16 (A) is shown. It is characterized in that the assembly method includes the following steps:

[0123] S1. Install the electrode assembly 120 into the housing 110 through the opening 113 .

[0124] The structural diagram after completing this step is as follows: Figure 4 (B) Figure 8 (B) Figure 10 (B) Figure 14 (B) and Figure 16 As shown in Figure (B), the specific installation method of the electrode assembly 120 is not limited, provided that the electrode assembly 120 can be installed into the housing 110 through the opening 113. For example, it can be installed manually or by a robot. Multiple sub-electrode tabs 1241 are located on the side of the electrode assembly 120 facing the opening 113.

[0125] S2, forming a welding area between the plurality of sub-electrode tabs 1241 and the side wall 112 near the opening 113;

[0126] After completing this step, the structural diagram is still the same Figure 4 (B) Figure 8 (B) Figure 10 (B) Figure 14 (B) and Figure 16 Specifically, the plurality of sub-electrode tabs 1241 and the side wall 112 may be overlapped at an angle to form a region to be welded. The plurality of sub-electrode tabs 1241 and the side wall 112 may also be overlapped vertically to form a region to be welded.

[0127] S3 . Welding the area to be welded to fix the plurality of sub-electrode tabs 1241 to the side wall 112 and form weld marks 1249 .

[0128] The structural diagram after completing this step is as follows: Figure 4 (C) Figure 8 (D) Figure 10 (C) Figure 14 (C) and Figure 16When welding the area to be welded, the welding can be performed on the inside of the shell 110 or on the outside of the shell 110, as long as a weld mark 1249 that meets the strength requirements can be formed between the plurality of sub-electrode tabs 1241 and the side wall 112.

[0129] S4. Install the cover plate 130 at the opening 113 in a sealed manner.

[0130] The structural diagram after completing this step is as follows: Figure 4 (D) Figure 8 (E) Figure 10 (D) Figure 14 (D) and Figure 16 The outer edge of the cover plate 130 is overlapped on the surface of the rolling groove 114 facing the opening 113 through a sealing ring, and then the opening 113 area of ​​the side wall 112 is sealed, so that the cover plate 130 is sealed and installed at the opening 113 position of the housing 110.

[0131] See also Figures 3 to 18 In the above assembly method, the tabs of the electrode assembly 120 are directly welded to the housing 110, replacing the conventional method of connecting via a current collecting member. This simplifies the structure, reduces the number of welding steps, and reduces the probability of electrical connection failure during assembly. It also significantly reduces the generation of metal shavings and slag inside the housing 110, lowering the risk of foreign matter inside the housing 110. Furthermore, by eliminating an internal structural component, not only can production costs be reduced, but internal weight can also be reduced, which helps to improve the mass energy density of the secondary battery 100.

[0132] Furthermore, the tabs are configured to include multiple sub-tabs 1241 spaced apart along the circumference of the electrode assembly 120. Each sub-tab 1241 independently withstands stress, reducing the risk of overall weld failure. Each sub-tab 1241 is welded independently, reducing the difficulty of the weld connection and further improving the reliability of the weld connection, thereby alleviating the problem of electrical connection failure between the electrode assembly 120 and the housing 110 during the production of the secondary battery 100.

[0133] See also Figure 5 and Figure 11 In an example of the assembly method of the present invention, the processing steps of the electrode assembly 120 include:

[0134] The first electrode piece 121 , the second electrode piece 123 and the diaphragm 122 are stacked and wound to form a wound structure.

[0135] The end of the first electrode sheet 121 facing the opening 113 includes a hollow foil region extending from the separator 122 along the winding axis of the electrode assembly 120. The hollow foil region is ultrasonically welded to form an annular electrode tab. It should be noted that the hollow foil region is the portion of the first uncoated region 1213 extending from the separator 122.

[0136] Part of the empty foil area is cut and removed to form a plurality of sub-electrode tabs 1241 arranged at intervals along the circumference of the electrode assembly 120 .

[0137] In the above processing steps, the empty foil area is first welded as a whole to form an integral annular pole ear, and then cut into multiple sub-pole ears 1241 arranged at intervals. This method has higher welding strength, better structural stability, better controllability of the spacing and size between the multiple sub-pole ears 1241, and higher dimensional accuracy.

[0138] See also Figure 6 、 Figure 12 and Figure 17 In an example of the assembly method of the present invention, the processing steps of the electrode assembly 120 include:

[0139] Die-cut a plurality of spaced-apart empty foils 1261 at predetermined positions of the first pole piece 121 ;

[0140] The first electrode sheet 121, the second electrode sheet 123, and the separator 122 are stacked and wound to form a wound structure. A plurality of hollow foils 1261 are arranged at intervals along the circumference of the electrode assembly 120 to form a plurality of hollow foil groups 126. In the radial direction of the electrode assembly 120, each hollow foil group 126 includes a plurality of hollow foils 1261 arranged sequentially.

[0141] The empty foils 1261 in each empty foil group 126 are ultrasonically flat-welded to form a plurality of sub-electrode tabs 1241 .

[0142] In the above processing steps, multiple blank foils 1261 are first die-cut at predetermined locations, then wound, and then flat-welded to form sub-tabs 1241. This method has a high material utilization rate and reduces material waste. Moreover, each blank foil group 126 is independently welded, which easily forms a localized flexible connection, helping to absorb radial stress when the battery expands.

[0143] See also Figure 4 (D) Figure 14 (D) and Figure 16 (D) In ​​an example of the assembly method of the present invention, after the sub-electrode ear 1241 is fixedly connected to the side wall 112, it also includes: rolling the side wall 112 area corresponding to the weld mark 1249 to form a rolling groove 114, and allowing the rolling groove 114 to limit the axial displacement of the electrode assembly 120.

[0144] See also Figure 4 、 Figure 14 and Figure 16 In this embodiment, the tab 1241 is first welded to the sidewall 112, and then the groove 114 is machined. Welding the tab 1241 to the flat sidewall 112 improves weld consistency. Furthermore, the groove 114 mechanically interlocks the tab 1241 with the housing 110, improving vibration and impact resistance.

[0145] See also Figure 8 (D) and Figure 10 (C) In an example of the assembly method of the present invention, after the electrode assembly 120 is installed into the housing 110 through the opening 113, the method further includes: rolling the sidewall 112 area near the opening 113 to form a rolling groove 114, and making the rolling groove 114 limit the axial displacement of the electrode assembly 120, and the area to be welded formed by the multiple sub-electrode tabs 1241 and the sidewall 112 is located in the rolling groove 114. It should be noted that Figure 8 (C) shows the state where the tab 1241 is bent along with the forming process of the groove 114. On this basis, the groove 114 is continuously rolled until the following is formed: Figure 8 The sub-tab 1241 shown in (D) and the rolling groove 114 form a welding area.

[0146] See also Figure 8 and Figure 10 In this embodiment, the groove 114 is first machined, and then the sub-electrode tab 1241 is welded to the side of the groove 114 facing the interior of the housing 110. This assembly method avoids pulling on the weld mark 1249 during the groove 114 machining process, reducing the probability of weld failure. It also prevents the generation of metal debris in the welding area during the groove 114 machining process, thereby reducing the probability of short circuits caused by metal debris falling into the electrode assembly 120, thereby improving the safety performance of the secondary battery 100.

[0147] The secondary battery of the present invention replaces the method of connecting the electrode assembly's tabs directly to the housing by welding them together, simplifying the structure, reducing the number of welding steps, and lowering the probability of electrical connection failure during assembly. The tabs are configured to include multiple sub-tabs spaced apart along the circumference of the electrode assembly, with each sub-tab independently bearing stress, which can reduce the risk of overall welding failure. The independent welding of each sub-tab reduces the difficulty of the weld connection, further improving the reliability of the weld connection, and thereby alleviating the problem of electrical connection failure between the electrode assembly and the housing during secondary battery production.

[0148] Therefore, the present invention effectively overcomes some practical problems in the prior art and thus has high utilization value and practical significance. The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A secondary battery, characterized in that: include: The housing comprises a surrounding side wall, wherein one end of the side wall has an opening; an electrode assembly housed in the housing, the electrode assembly comprising a tab facing the opening; The electrode tab includes a plurality of sub-tabs spaced apart along the circumference of the electrode assembly, and each of the sub-tabs is welded to the side wall.

2. The secondary battery according to claim 1, wherein Along the axial direction of the electrode assembly, the length of each sub-electrode lug is a, and along the circumferential direction of the electrode assembly, the length of each sub-electrode lug is b, wherein a≥5mm, b≥10mm.

3. The secondary battery according to claim 1, wherein The electrode assembly includes a first electrode plate, a second electrode plate, and a winding structure formed by stacking and winding a diaphragm. The end of the first electrode plate facing the opening includes a plurality of empty foils extending from the diaphragm along the winding axis direction of the electrode assembly. Along the radial direction of the electrode assembly, the plurality of empty foils are stacked and gathered to form the sub-pole ears. Along the circumference of the electrode assembly, a plurality of the sub-pole ears are arranged at intervals.

4. The secondary battery according to claim 3, wherein One end of the shell close to the opening includes a rolling groove recessed into the interior of the shell, and the sub-tabs are respectively connected to the rolling groove by welding.

5. The secondary battery according to claim 4, wherein The rolling groove includes a first side surface facing the electrode assembly, and the sub-tab is welded to the first side surface.

6. The secondary battery according to claim 5, characterized in that Along the radial direction of the electrode assembly, one end of the electrode assembly facing the opening includes, from outside to inside, a first tab-containing area provided with the empty foil and a first tab-free area without the empty foil.

7. The secondary battery according to claim 6, characterized in that The length of the hollow foil extending from the diaphragm gradually decreases from the radial inner side to the radial outer side of the electrode assembly.

8. The secondary battery according to claim 4, wherein The rolling groove further includes a second side surface facing the opening and a third side surface connecting the first side surface and the second side surface, and the sub-tab is welded to the third side surface.

9. The secondary battery according to claim 8, wherein Each of the sub-tabs is at least partially located within the area surrounded by the third side surface.

10. The secondary battery according to claim 9, wherein Along the radial direction of the electrode assembly, one end of the electrode assembly facing the opening includes, from outside to inside, a second tab-free area without the empty foil and a second tab-provided area with the empty foil.

11. The secondary battery according to claim 10, wherein The unfolded length of the second tab-free region is L1, and the unfolded total length of the first pole piece is L, wherein L1>0.3L.

12. The secondary battery according to claim 10, characterized in that The unfolded length of the second electrode tab region is L2, and the unfolded total length of the first electrode piece is L, wherein L2>0.5L.

13. The secondary battery according to claim 5, characterized in that The sub-pole ear includes a shell connecting portion, a transition portion and a gathering portion. The shell connecting portion is welded to the rolling groove. The gathering portion is formed by gradually gathering a plurality of stacked empty foils from their roots. The transition portion connects the shell connecting portion and the gathering portion. The transition portion and the shell connecting portion form a curved structure opening toward the interior of the shell.

14. The secondary battery according to claim 13, wherein: The gathered portion is formed by gathering a plurality of stacked hollow foil sheets simultaneously from the radially outer side and the radially inner side in a central direction.

15. The secondary battery according to claim 13, wherein The gathered portion is formed by gathering a plurality of stacked hollow foil sheets from a radially outer side toward a radially inner side.

16. The secondary battery according to claim 15, characterized in that The length of the hollow foil extending from the diaphragm gradually decreases from the radial outer side to the radial inner side of the electrode assembly.

17. The secondary battery according to any one of claims 5 to 16, characterized in that: From the radial outer side to the radial inner side of the electrode assembly, the first side surface gradually approaches the electrode assembly.

18. A battery pack, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 17.

19. An electronic device, characterized in that: A battery pack comprising the battery pack of claim 18.

20. A method for assembling a secondary battery, wherein the secondary battery comprises a housing, an electrode assembly, and a cover plate, wherein the housing comprises a side wall, one end of the side wall having an opening, and the electrode assembly comprises a plurality of sub-electrode tabs spaced apart along its circumference; The assembly method comprises the following steps: Installing the electrode assembly into the housing through the opening; The plurality of sub-electrode tabs and the side wall form a to-be-welded area at a position close to the opening; Welding the area to be welded to fixedly connect the plurality of sub-electrode tabs to the side wall and form weld marks; The cover plate is sealed and installed at the opening.

21. The assembly method according to claim 20, characterized in that: The processing steps of the electrode assembly include: Stacking the first pole piece, the second pole piece and the diaphragm and winding them to form a winding structure; The end of the first electrode sheet facing the opening includes a hollow foil area extending out of the diaphragm along the winding axis of the electrode assembly, and the hollow foil area is fixed by ultrasonic flat welding to form an annular electrode ear; Part of the empty foil area is cut and removed to form a plurality of sub-electrode ears arranged at intervals along the circumference of the electrode assembly.

22. The assembly method according to claim 20, characterized in that: The processing steps of the electrode assembly include: Die-cutting a plurality of spaced-apart empty foils at preset positions of the first pole piece; The first electrode sheet, the second electrode sheet, and the diaphragm are stacked and wound to form a wound structure, wherein the plurality of hollow foils are arranged at intervals along the circumference of the electrode assembly to form a plurality of hollow foil groups, and each hollow foil group includes a plurality of hollow foils arranged sequentially along the radial direction of the electrode assembly; The empty foils in each group of the empty foils are ultrasonically flat-welded to form a plurality of the sub-electrode tabs.

23. The assembly method according to claim 20, characterized in that: After the sub-electrode tab is fixedly connected to the side wall, the method further includes: rolling the side wall area corresponding to the weld mark to form a rolling groove, and allowing the rolling groove to limit the axial displacement of the electrode assembly.

24. The assembly method according to claim 20, characterized in that: After the electrode assembly is installed into the shell from the opening, it also includes: rolling the side wall area close to the opening to form a rolling groove, and allowing the rolling groove to limit the axial displacement of the electrode assembly, and the area to be welded formed by the multiple sub-tabs and the side wall is located in the rolling groove.

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