Battery cell and battery pack

Abstract

Disclosed in the present application are a battery cell and a battery pack. The battery cell comprises a jelly roll, wherein the jelly roll comprises a wound body and a tab bundle, the tab bundle comprising a converging portion and a dispersing portion arranged between the converging portion and the wound body; and the minimum distance between the end of the converging portion that is close to the dispersing portion and a side of the jelly roll in a first direction is d mm, and the average dimension of the wound body in the first direction is D, meeting 0<d≤D / 2. In the present application, the tab bundle can be directly welded to a terminal post, such that the battery cell has a more compact structure; in addition, tabs can be inserted into a casing with low tensile stress generated, ensuring the yield rate of jelly roll insertion into the casing, improving the reliability of the battery cell.

Description

Battery cells and battery packs

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese Patent Application No. 202410023684.0 filed on January 5, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of lithium batteries, and in particular to a battery cell and a battery pack. Background Art

[0004] The rapid development of new energy vehicles at this stage has placed great demands on power batteries and has also put forward higher requirements on the manufacturing process of power batteries in order to reduce the manufacturing cost of power batteries and improve their safety.

[0005] At present, in the existing electrode sheet structure, the heights of each tab are basically equal. After the tabs are gathered and pre-welded, the tabs are uneven in height and the top of the inner tab is too long. The gathered position of the tab deviates too much from the welding position, resulting in tab interference during subsequent processes and welding with the matching top cover and pole post, as well as large stress on each tab, which can easily lead to desoldering of the tabs and pole post or tearing of the tabs, thereby affecting the yield and service life of the battery cell.

[0006] Application Contents

[0007] The purpose of this application is to provide a battery cell and a battery pack to solve the problem that when the tabs are folded together, each tab generates large stress, resulting in poor reliability of the battery cell structure.

[0008] In order to achieve the above objectives, this application adopts the following technical solutions:

[0009] One aspect of the present application is to provide a battery cell having a first direction, including:

[0010] a housing having a receiving cavity with an opening;

[0011] a winding core, the winding core being received in the accommodating cavity;

[0012] The winding core includes a winding body and a tab bundle, the tab bundle includes a gathering portion and a dispersion portion, the dispersion portion is arranged between the gathering portion and the winding body; the gathering portion forms a gathering end close to one end of the dispersion portion, the minimum distance between the gathering end and one side of the winding core along the first direction is dmm, the average size of the winding body along the first direction is D, satisfying: 0<d≤D / 2.

[0013] Preferably, the tab bundle includes a plurality of tabs, a portion where the plurality of tabs are gathered, stacked, and welded forms the gathered portion, and a portion where the plurality of tabs are not welded forms the dispersed portion.

[0014] Preferably, the distance between the center of the tab bundle extension trajectory and the retracted end is between 0 and 300 mm.

[0015] Preferably, the distance between the center of the extension trajectory of the tab bundle and the retracted end is between 0 and 50 mm.

[0016] Preferably, the center of the extension trajectory of the tab bundle falls on the retracted end.

[0017] Preferably, the gathered portion includes a plurality of tab welding portions stacked and connected to the dispersed portion, wherein the plurality of tab welding portions have a minimum extension length L1 mm and a maximum extension length L2 mm, and satisfy the following relationship: 0.9≤L1 / L2≤1.2.

[0018] Preferably, the battery cell also includes a top cover assembly, which includes a cover body and a pole penetrating the cover body, the cover body covers the opening and is connected to the shell, one end of the pole extends into the accommodating cavity, and the other end is exposed on the side of the cover body away from the shell, and the pole ear bundle is welded and fixed to the pole.

[0019] Preferably, the winding body includes a diaphragm and a pole piece, the pole tab bundle includes a plurality of first pole tabs, and the plurality of first pole tabs are welded and fixed to form the gathered portion and the dispersed portion; the pole piece has a long side, and the plurality of first pole tabs are connected to the long side; the pole piece has a winding starting end and a winding ending end, and from the winding starting end to the winding ending end, the distance between one end of the plurality of first pole tabs away from the long side and the long side increases.

[0020] Preferably, the winding body includes a diaphragm and a pole piece, the pole tab bundle includes a plurality of first pole tabs, and the plurality of first pole tabs are welded and fixed to form the gathered portion and the dispersed portion; the pole piece has a long side, and the plurality of first pole tabs are connected to the long side; the pole piece has a winding starting end and a winding ending end, and from the winding starting end to the winding ending end, the distance between one end of the plurality of first pole tabs away from the long side and the long side first decreases and then increases.

[0021] Preferably, the winding body includes a diaphragm and a pole piece, the pole piece bundle includes a plurality of second pole pieces and a third pole piece, and the plurality of second pole pieces and the third pole pieces are welded and fixed to form the gathered portion and the dispersed portion; the pole piece has a long side, and the plurality of second pole pieces and the third pole pieces are alternately arranged and connected to the long side along the extension direction of the long side; the pole piece has a winding starting end and a winding ending end, and from the winding starting end to the winding ending end, the distance between the end of the plurality of second pole pieces away from the long side and the long side first decreases and then increases, and the distance between the end of the plurality of third pole pieces away from the long side and the long side increases.

[0022] Preferably, the distance between the end of the second tab away from the long side and the long side is L3 mm, and the distance between the end of the third tab away from the long side and the long side is L4 mm, satisfying: L3<L4.

[0023] Preferably, the extension length of the tab bundle is L mm, and the width of the cover is W mm, satisfying: 0.125≤L / W≤0.5.

[0024] Preferably, the number of the tab bundles is at least 2 and they are spaced apart along the second direction on the same side of the winding body, the number of the poles is at least 2 and they are spaced apart along the second direction to the cover body; the center distance between two adjacent tab bundles is M1mm, and the center distance between two adjacent poles respectively connected to the two adjacent tab bundles is M2mm, satisfying: M2≥M1, and the first direction intersects with the second direction.

[0025] Preferably, the pole has a welding end, which is welded and fixed to the tab bundle; on a plane perpendicular to the third direction, the projected area of ​​the welding end along the third direction is larger than the projected area of ​​the folded portion along the third direction, and the third direction intersects with the first direction.

[0026] Another aspect of the present application is to provide a battery pack, which includes the above-mentioned battery cell.

[0027] Compared with the prior art, the battery cell and battery pack of the embodiment of the present application have the following advantages:

[0028] In the battery cell of the embodiment of the present application, the tab bundle in the winding core includes a gathered portion and a dispersed portion, the dispersed portion is connected to the winding body, and the gathered portion is close to one end of the dispersed portion to form a gathered end, and the minimum distance between the gathered end and one side of the winding core along the first direction is d, d is greater than zero and less than or equal to half of the average size D of the winding body along the first direction. Such a battery cell structure, on the one hand, can avoid the problem of poor welding caused by the interference between the tab bundle and other components due to the excessive length of the tab bundle, thereby improving the welding yield of the battery cell; on the other hand, since the distance between the gathered end and one side of the winding body is within a specific range, the tensile stress of multiple tabs is small when forming the tab bundle, and when welding with the pole post, the tab bundle will not cause large stress between the winding body and the pole post, which is beneficial to improving the yield rate of the tab welding; on the other hand, after the winding core and the shell are assembled into a battery cell, the tab bundle will not have a large tension stress, thereby avoiding damage such as tearing of the tab, thereby improving the reliability and service life of the battery cell structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a schematic structural diagram of a battery cell according to a first embodiment of the present application;

[0030] FIG2 is a schematic diagram of the structure of the battery cell in FIG1 without the top cover assembly assembled;

[0031] FIG3 is a bottom view of the battery cell in FIG1 after it is disassembled;

[0032] FIG4 is a side view schematic diagram of the battery cell in FIG1 after being disassembled;

[0033] FIG5 is a schematic structural diagram of the pole piece in the first embodiment of the present application;

[0034] FIG6 is a schematic diagram of the tabs of the winding core before folding in the first embodiment of the present application;

[0035] FIG7 is a schematic diagram of the winding body along the winding center axis in the first embodiment of the present application;

[0036] FIG8 is a schematic diagram of the winding core after the tabs are folded in the first embodiment of the present application;

[0037] FIG9 is a schematic structural diagram of a pole piece in a second embodiment of the present application;

[0038] FIG10 is a schematic diagram of the tabs of the winding core before folding in the second embodiment of the present application;

[0039] FIG11 is a schematic diagram of the tabs of the winding core after being folded in according to the second embodiment of the present application;

[0040] FIG12 is a schematic structural diagram of the pole piece according to the third embodiment of the present application;

[0041] FIG13 is a schematic diagram of the tabs of the winding core before folding in the third embodiment of the present application;

[0042] FIG14 is a schematic diagram of the winding core after the tabs are folded in according to the third embodiment of the present application;

[0043] FIG15 is an enlarged schematic diagram of portion A in FIG14 .

[0044] In the figure,

[0045] 10. Battery cells;

[0046] 11. Housing; 110. Accommodating chamber; 111. First side wall; 112. Second side wall;

[0047] 12. Winding core; 120. Pole piece; 1201. Winding start end; 1202. Winding end end; 1203. Long side; 1204. First pole tab; 1205. Second pole tab; 1206. Third pole tab; 121. Winding body; 122. Tab bundle; 1220. Welding area; 1221. Non-welding area; 1222. Gathering portion; 12221. Gathering end; 12222. Tab welding portion; 1223. Dispersion portion;

[0048] 13. Top cover assembly; 131. Cover body; 132. Pole; 1321. Welding end;

[0049] X, first direction; Y, second direction; Z, third direction;

[0050] MN: winding center axis;

[0051] α. Converge the center plane. DETAILED DESCRIPTION

[0052] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "top," "bottom," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections, indirect connections through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0054] In this application, the term "parallel" includes not only absolute parallelism but also the generally recognized parallelism in engineering practice, such as "parallel" refers to the state where the angle formed by a straight line, a straight line and a plane, or a plane and a plane is -1° to 1°. At the same time, "perpendicular" also includes not only absolute perpendicularity but also the generally recognized perpendicularity in engineering practice, such as "perpendicular" refers to the state where the angle formed by a straight line, a straight line and a plane, or a plane and a plane is 89° to 91°. Equal distances or equal angles include not only absolute equality but also the generally recognized equality in engineering practice, which may include a certain error, such as a tolerance range of -1% to 1%.

[0055] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0056] 1 to 4 , an embodiment of the present application provides a battery cell 10, the battery cell 10 having a first direction X, and the battery cell 10 including a shell 11 and a winding core 12; wherein the shell 11 has a receiving cavity 110 with an opening, and the shell 11 has a first side wall 111 and a second side wall 112, and the first side wall 111 and the second side wall 112 are arranged opposite to each other along the first direction X; the winding core 12 is accommodated in the receiving cavity 11; the winding core 12 includes a winding body 121 and a tab bundle 122, and the tab bundle 122 includes a gathering portion 1222 and a dispersion portion 1223, and the dispersion portion 1223 is arranged between the gathering portion 1222 and the winding body 121, and the dispersion portion 1223 is connected to the gathering portion 1222 and the winding body 121; the gathering portion 1222 is connected to one end of the dispersion portion 1223 to form a gathering end 12221, and the minimum distance d between the gathering end 12221 and one side of the winding core 12 along the first direction X is mm, the average size of the winding body 121 along the first direction X is D, 0<d≤D / 2; the tab bundle 122 includes a plurality of tabs (not shown in the figure), the parts where the plurality of tabs are gathered, stacked and welded form a gathered portion 1222, and the parts where the plurality of tabs are not welded form a dispersed portion 1223, and one end of the tab (not shown in the figure) is connected to the end of the winding body 121.

[0057] In this embodiment, by limiting the relationship between the minimum distance d between the retracted end 12221 and the side of the winding core 12 and the size D of the winding body 121, on the one hand, it can avoid the tab bundle 122 being too long, causing interference between the tab bundle 122 and other components in the battery cell 10 and causing poor welding, thereby improving the welding yield of the battery cell; on the other hand, it can reduce the stress of the tab bundle 122, avoid the occurrence of tab tearing, and further improve the yield of the battery cell.

[0058] In this embodiment, the technical effect is illustrated by the following test data:

[0059] From the above data, it can be seen that when d / D is 0, the number of torn layers of the tab is large, indicating that the tab bundle 122 is subjected to greater stress; and when d / D>0.5, the penetration depth is small, indicating that the welding effect is poor (generally, a penetration depth less than 300μm can be considered a cold weld); therefore, 0<d≤D / 2 is controlled. At this time, the number of torn layers of the tab is small and the penetration depth is also large, which can take into account both the stress condition of the tab bundle 122 and the welding yield.

[0060] In other embodiments, the battery cell satisfies the following relationship: D / 10≤d≤D / 2, so as to better balance the stress of the tab bundle 122 and the welding yield.

[0061] The number of tab tear layers can be obtained by observing the tab bundle 122 after welding through CT detection; the penetration depth can be measured by cutting the tab bundle 122 at the weld mark position after welding (metallographic cutting).

[0062] In some embodiments, the winding core 12 includes a positive electrode sheet, a negative electrode sheet and a separator, which are stacked in sequence and wound around the winding center axis MN to form the winding core 12, wherein the positive electrode sheet is partially coated with a positive electrode material and a portion is not coated with the positive electrode material to form a positive electrode tab, and the negative electrode sheet is partially coated with a negative electrode material and a portion is not coated with the negative electrode material to form a negative electrode tab; generally, the positive electrode sheet has multiple positive electrode tabs on the long side, and the negative electrode sheet also has multiple negative electrode tabs on the long side. After winding to form the winding core 12, the multiple positive electrode tabs are positioned correspondingly and fixed by welding to form a positive electrode tab bundle, and the multiple negative electrode tabs are positioned correspondingly and fixed by welding. A negative electrode tab bundle is formed. The tab bundle 122 in this embodiment can be a positive electrode tab bundle or a negative electrode tab bundle; wherein, the tab bundle 122 is straightened in a direction away from the winding body 121 so that the plane where the tab bundle 122 is located is parallel to the plane where the winding body 121 is located. It can be understood that the plane where the tab bundle 122 is located is the gathering center plane α, and all the tabs are gathered close to and welded to this plane. At this time, the tabs away from the gathering center plane α will bend in the extension direction when they are gathered towards the gathering center plane α. Therefore, the outer tabs will be subjected to greater stress. Therefore, the winding core 12 needs to be designed to reduce the tab stress and avoid tab tearing. The gathered end 12221 can be understood as the side of the positive electrode tab or the negative electrode tab welding position (weld mark) close to the winding body 121. FIG3 schematically shows the welding area 1220 and the non-welding area 1221. The side of the welding area 1220 close to the winding body 121 can be understood as the gathered end 12221. The electrode sheet 120 (positive electrode sheet or negative electrode sheet) has a winding start end 1201 and a winding end 1202. Specifically, the winding start end 1201 is located on the inner side of the winding core 12, and the winding end 1202 is located on the outer side of the winding core 12.

[0063] Referring to Figure 1 , the battery cell 10 further includes a top cover assembly 13, which includes a cover 131 and a terminal 132. The cover 131 covers the opening and is connected to the housing 11. The terminal 132 is disposed through the cover 131, with one end of the terminal 132 extending into the accommodating cavity 110 and the other end of the terminal 132 exposed on the side of the cover 131 facing away from the housing 11. The tab bundle 122 is welded to the end of the terminal 132 extending into the accommodating cavity 110. In some embodiments, the tab bundle 122 includes a gathered portion 1222 and a dispersed portion 1223. Specifically, the gathered portion 1222 is welded to the terminal 132. In some embodiments, the cover 131 is provided with at least two through-holes (not shown in the figure), the pole 132 includes a positive pole (not labeled in the figure) and a negative pole (not labeled in the figure), and the tab bundle 122 includes a positive tab bundle (not labeled in the figure) and a negative tab bundle (not labeled in the figure). The positive pole is passed through one of the through-holes and fixed to the cover 131. The positive tab bundle is welded to the end of the positive pole extending into the accommodating cavity 110. The negative pole is passed through the other through-hole and fixed to the cover 131. The negative tab bundle is welded to the end of the negative pole extending into the accommodating cavity 110. By directly welding the tab bundle 122 to the pole 132, the use of connecting pieces can be reduced, thereby reducing the number of parts, thereby improving the space utilization inside the battery cell, and reducing manufacturing costs.

[0064] Referring to Figures 4, 5, and 6, in some embodiments, there are two winding cores 12, which are arranged opposite each other along a first direction X. The tab bundles of the same polarity in the two winding cores 12 are welded to the same electrode 132. The extension length of the tab bundle 122 is L mm, and the width of the cover 131 is W mm, satisfying the following: 0.125 ≤ L / W ≤ 0.5. This ensures that when two or more winding cores 12 are arranged on opposite sides of the cover 131 and welded to the electrode simultaneously, the two opposing tab bundles 122 will not interfere with each other, thereby preventing poor welding caused by excessively long tab bundles 122. Furthermore, the length or area of ​​the tab bundles 122 available for welding is sufficient, thereby improving the welding reliability of the tab bundles 122. Furthermore, the winding cores 12 can be directly welded to the cover 131 without the need for additional connecting pieces between the tab bundles 122 and the cover 131, simplifying the structure of the top cover assembly 13 and facilitating improved space utilization of the battery cell 10.

[0065] In this embodiment, the above technical effects can be illustrated by the following tests:

[0066] From the above data, it can be seen that when L / W is less than 0.125, the extension length of the tab bundle 122 is relatively small, and the length or area used for welding will also be correspondingly smaller, resulting in lower welding strength and smaller penetration depth, and thus the welding reliability of the tab bundle 122 is poor; when L / W is greater than 0.5, the length of the tab bundle 122 is larger, and the length of the tab bundle 122 used for welding will be larger, so that the welding area is larger. Although the welding strength is greater at this time, due to the excessive length of the tab bundle 122, interference of the tab bundle 122 will occur, and the minimum penetration depth will be smaller, that is, a cold weld will occur; when 0.125≤L / W≤0.5, the welding strength and penetration depth can be better taken into account, thereby improving the yield of the battery cell.

[0067] The welding strength is tested by fixing the pole 132 and applying a tensile force to the tab bundle 122 until the pole 132 and the tab bundle 122 are separated, and recording the tensile force, which is the welding strength.

[0068] In some embodiments, the distance between the center of the extension trajectory of the tab bundle 122 and the retracted end 12221 is between 0 and 300 mm. In other embodiments, the distance between the center of the extension trajectory of the tab bundle 122 and the retracted end 12221 is between 0 and 50 mm, which can effectively improve the yield rate of the winding core 12 into the shell 11. Among them, the tab bundle 122 is straightened in the direction away from the winding body 121 so that the plane of the tab bundle 122 is parallel to the plane of the winding body 121, and then a ruler is used to measure the maximum distance between the end of the tab bundle 122 away from the winding body and the end of the winding body 121 close to the tab bundle 122, and then the position of the tab bundle 122 corresponding to the middle value is taken to obtain the center of the extension trajectory of the tab bundle 122.

[0069] In some embodiments, the center of the extension trajectory of the tab bundle 122 falls on the gathered end 12221, that is, the extension lengths of the gathered portion 1222 and the dispersed portion 1223 are equal. In this way, the welding length of the tab bundle 122 is larger, thereby making the welding area larger and having a better welding effect.

[0070] Please refer to Figures 6, 8, 14, and 15. In some embodiments, there are two winding cores 12, and the two winding cores 12 are arranged opposite to each other along the first direction X. The tab bundles of the same polarity in the two winding cores 12 are welded and fixed to the same pole 132. The gathering portion 1222 includes a plurality of tab welding portions 12222 that are stacked and connected to the dispersion portion 1223. The plurality of tab welding portions 12222 have a minimum extension length L1mm and a maximum extension length L2mm, satisfying: 0.9≤L1 / L2≤1.2, so that the ends of the plurality of tab welding portions 12222 are basically flush, so that the tab bundle 122 has a good appearance structure, and the uneven ends can be avoided from affecting the adjacent tab bundles 122, so as to reduce the risk of cold welding and explosion points in the welding of the tab bundle 122 and the pole 132, thereby improving the yield rate.

[0071] In this embodiment, the above technical effects can be illustrated by the following tests:

[0072] The above data shows that when L1 / L2 is less than 0.9, the weld mark will extend beyond the tab bundle 122, resulting in poor weld appearance. When L1 / L2 is greater than 1.2, the penetration depth will be small, indicating a poor weld. A value of 0.9≤L1 / L2≤1.2 can effectively balance the width of the weld mark extension and the penetration depth, thereby achieving a good welding yield. The weld mark extension width refers to the maximum distance between the side of the weld mark facing away from the dispersed portion 1223 and the side of the tab bundle 122 facing away from the dispersed portion 1223, with the direction from the dispersed portion 1223 to the converged portion 1222 being the positive direction. This can be obtained by taking at least three measurements with a vernier caliper and taking the average value.

[0073] Referring to Figure 5, in some embodiments, the winding body 121 includes a diaphragm and a pole piece 120, and the pole piece bundle 122 includes a plurality of first pole pieces 1204, and the plurality of first pole pieces 1204 are welded and fixed to form a gathered portion 1222 and a dispersed portion 1223; wherein, as described above, the pole piece 120 can be a positive pole piece or a negative pole piece; the pole piece 120 has a long side 1203, and the plurality of first pole pieces 1204 are connected to the long side 1203; from the winding starting end 1201 to the winding end 1202, the distance between one end of the plurality of first pole pieces 1204 facing away from the long side 1203 and the long side 1203 is L5 mm, and L5 first decreases and then increases. In some embodiments, after the pole piece 120 and the separator are wound into the winding core 12, the number of the plurality of first pole tabs 1204 with the smallest L5 is one. Therefore, when the plurality of first pole tabs 1204 in the winding core 12 are gathered into the tab bundle 122, the other opposing tabs located on either side of the first pole tab 1204 with the smallest L5 converge toward the first pole tab 1204 with the smallest L5. In some embodiments, the other opposing tabs located on either side of the first pole tab 1204 with the smallest L5 converge symmetrically toward the first pole tab 1204 with the smallest L5, thereby forming a tab bundle 122 with a relatively neat appearance. In this embodiment, the minimum distance between the gathered end 12221 and one side of the winding core 12 along the first direction X is d, where 0 < d < D / 2.

[0074] Please refer to Figures 5 and 6. In some embodiments, among the multiple first pole ears 1204, the number of the first pole ear 1204 with the smallest L5 is one and is located in the middle of the multiple first pole ears 1204. The number of first pole ears 1204 on both sides of the first pole ear 1204 with the smallest L5 is the same and both are odd numbers. When the pole piece 120 is in the expanded state and the multiple pole ears are in the separated state, the first pole ears 1204 on both sides are symmetrically arranged relative to the first pole ear 1204 in the middle. The first pole ears 1204 on both sides are converged toward the first pole ear 1204 in the middle, and along the direction perpendicular to the first pole ear 1204 in the middle, the relative first pole ears 1204 that are at the same distance from the first pole ear 1204 in the middle have the same height. Such a tab structure is beneficial to reducing the degree of deformation of each tab when multiple tabs are welded into a tab bundle 122. When the winding core 12 is flipped into the shell, each tab can be put into the shell with a small stress, without causing a large stress between the tab bundle 122 and the pole 132. This is beneficial to ensuring the yield rate of the winding core 12 into the shell. After being assembled into the battery cell 10, the tab bundle 122 will not have a large tension stress, thereby improving the reliability of the battery cell 10 structure.

[0075] Referring to FIG. 9 , in some embodiments, a plurality of second pole tabs 1205 and a plurality of third pole tabs 1206 are provided along the long side 1203 of the pole piece 120. The second pole tabs 1205 and the third pole tabs 1206 are alternately spaced along the extending direction of the long side 1203. The second pole tabs 1205 and the third pole tabs 1206 collectively form a pole tab bundle 122. From the winding starting end 1201 to the winding ending end 1202, the distance L3 between the ends of the plurality of second pole tabs 1205 facing away from the long side 1203 and the long side 1203 first decreases and then increases, while the distance L4 between the ends of the plurality of third pole tabs 1206 facing away from the long side 1203 and the long side 1203 increases. There is one second pole tab 1205 with the smallest L3. The number of second pole tabs 1205 is an even number, and the second pole tab 1205 with the smallest L3 is located in the middle of the plurality of second pole tabs 1205. The number of third pole tabs 1206 is an odd number. After the electrode sheet 120 is wound into a core and before the plurality of second electrode tabs 1205 and the plurality of third electrode tabs 1203 are gathered into the electrode tab bundle 122, the plurality of second electrode tabs 1205 and the plurality of third electrode tabs 1206 are disposed on opposite sides of the second electrode tab 1205 having the smallest L3. Along a direction perpendicular to the second electrode tab 1205 and away from the second electrode tab 1205 having the smallest L3, the height of the second electrode tab 1205 gradually increases, and the height of the third electrode tab 1206 gradually increases. The relationship between the distance L3 between the end of the second electrode tab 1205 facing away from the long side 1203 and the long side 1203 and the distance L4 between the end of the third electrode tab 1206 facing away from the long side 1203 and the long side 1203 satisfies the following: L3 < L4. Such a tab structure is beneficial to reducing the stress generated by each tab when it is welded into a tab bundle 122, and reducing the degree of tab deformation. When the winding core 12 is flipped into the shell, it will not cause large stress between the tab bundle 122 and the pole 132, which is beneficial to ensuring the yield rate of the winding core 12 into the shell and improving the reliability of the battery cell 10 structure.

[0076] Referring to Figures 12 and 13 , in some embodiments, the distance L6 between the ends of the plurality of first electrode tabs 1204 facing away from the long side 1203 and the long side 1203 increases from the winding starting end 1201 to the winding ending end 1202. Two adjacent first electrode tabs 1204 are grouped together, and the L6 of the two first electrode tabs 1204 within the same group is equal. The distance L6 between the ends of the first electrode tabs 1204 facing away from the long side 1203 and the long side 1203 in each group gradually increases from the winding starting end 1201 to the winding ending end 1202. With such a tab structure, when the tabs are folded into a tab bundle 122, the deformation of each tab is relatively small. In the process of welding to the pole post 132 and folding into the shell, the pulling degree on each tab is relatively small. Moreover, when two winding cores 12 are arranged side by side or multiple winding cores 12 are welded into the shell with the same top cover assembly 13, the winding bodies 121 that are close to each other are more compact and more convenient to put into the shell when the degree of deformation of the tabs is relatively small, which effectively avoids the outer layer of the winding body 121 from being scratched or wrinkled when being put into the shell, effectively improving the yield rate of the winding core 12 putting into the shell. After the battery cell 10 is put into the shell, the tab bundle 122 will not have a large tension stress, which is beneficial to improving the structural reliability of the battery cell 10.

[0077] In some embodiments, the number of tab bundles 122 is at least two and they are spaced apart along the second direction Y on the same side of the winding body 121, and the number of poles 132 is at least two and they are spaced apart along the second direction Y on the cover 131; the center distance between two adjacent tab bundles 122 is M1 mm, and the center distance between two adjacent poles 132 respectively connected to the two adjacent tab bundles 122 is M2 mm, satisfying: M2 ≥ M1, wherein the first direction X intersects with the second direction Y, and preferably, the first direction X is perpendicular to the second direction Y. Such an arrangement allows the tab bundles 122 to be as close to the middle position of the winding core 12 as possible to avoid the tab bundles 122 being too close to the inner wall of the shell 11 (such as the first side wall 111 or the second side wall 112) and causing leakage problems.

[0078] In some embodiments, the electrode 132 has a welding end 1321, which is welded to the tab bundle 122. On a plane perpendicular to a third direction Z, the projected area of ​​the welding end 1321 along the third direction Z is larger than the projected area of ​​the gathered portion 1222 along the third direction Z. The third direction Z intersects with the first direction X, and preferably, the third direction Z is perpendicular to the first direction X. In this embodiment, the first direction X, the second direction Y, and the third direction Z are perpendicular to each other. This configuration maximizes the welding area between the electrode 132 and the tab bundle 122, thereby improving the reliability of the direct welding between the electrode 132 and the tab bundle 122. Furthermore, the increased welding area helps improve the current flow capacity between the tab bundle 122 and the electrode 132.

[0079] It should be noted that, after multiple pole tabs are gathered and welded into a pole tab bundle 122, at least part of the first pole tab 1204, the second pole tab 1205, and the third pole tab 1206 are tilted to varying degrees, and after the pole tab bundle 122 is welded to the pole column 132, the first pole tab 1204, the second pole tab 1205, and the third pole tab 1206 are tilted and deformed to varying degrees. Therefore, the "distance between the end of the first pole tab 1204, the second pole tab 1205, and the third pole tab 1206 facing away from the long side 1203 and the long side 1203" mentioned in the embodiment of this application refers to the length of each pole tab in its straight state after the pole piece 120 is wound into a winding core 12 and before the multiple pole tabs are welded.

[0080] Based on the above-mentioned battery cells 10, an embodiment of the present application further provides a battery module, which includes at least two battery cells 10 as described in any one of the above items, and the multiple battery cells 10 are electrically connected. In some embodiments, two adjacent battery cells 10 in the battery module are connected in series. In some embodiments, some of the battery cells 10 in the battery module are connected in series to form modules, and the battery cells 10 of each module are then connected in parallel with each other. The battery module provided in the embodiment of the present application has the above-mentioned structure in its battery cells 10, so that each battery cell 10 in the battery module has good structural reliability, so that the battery module as a whole also exhibits good structural reliability.

[0081] Based on the aforementioned battery cell 10 or battery module, embodiments of the present application further provide a battery pack comprising the aforementioned battery cell 10, which is referred to as a CTP (Cell to Pack); or, alternatively, a battery pack comprising at least one of the aforementioned battery modules, which is referred to as an MTP (Module to Pack). Because the battery pack provided in this embodiment includes the aforementioned battery cell 10, and the tab bundle 122 of the battery cell 10 has minimal tension stress, the battery pack has a high structural reliability.

[0082] In order to better illustrate the technical solution of the present application, a number of embodiments are provided below for further explanation.

[0083] Example 1

[0084] This embodiment provides a pole piece and a battery cell.

[0085] 1 to 8 , an odd number of first pole tabs 1204 are provided on the long side 1203 of the pole piece 120 of this embodiment (seven first pole tabs 1204 are shown in the figure), the pole piece 120 has a winding start end 1201 and a winding end 1202 opposite to the winding start end 1201, the pole piece 120 includes a current collector (not shown in the figure) and an active layer attached to the surface of the current collector (not shown in the figure), and the odd number of first pole tabs 1204 are provided from the winding start end 1201 to the winding end 1202. The starting end 1201 to the winding end 1202 are arranged at intervals on the long side 1203 of the pole piece 120 and are connected to the pole piece 120, and from the winding starting end 1201 to the winding end 1202, the odd-numbered first pole ears 1204 are distributed with a trend that the distance L5 between the end of the first pole ear 1204 facing away from the long side 1203 and the long side 1203 first decreases and then increases, and the first pole ear 1204 with the smallest L5 is located in the middle of the odd-numbered first pole ears 1204. After the pole piece 120 is wound into the winding core 12 from the winding starting end 1201 to the winding end 1202, the number of the first pole ear 1204 with the smallest L5 in the odd-numbered first pole ears 1204 is one, so that when the odd-numbered first pole ears 1204 in the winding core 12 are gathered into the pole ear bundle 122, the other relative pole ears arranged on both sides of the first pole ear 1204 with the smallest L5 are gathered toward the first pole ear 1204 with the smallest L5. In the obtained winding core 12, the L5 of the two first pole tabs 1204 with the same distance from the first pole tab 1204 with the smallest L5 differs by less than 10 mm. By directly using ultrasonic welding, all the first pole tabs 1204 can be respectively gathered from both sides toward the first pole tab 1204 with the smallest L5 to obtain a pole tab bundle 122. In the winding core 12 obtained in this embodiment, the minimum distance d between the gathered end 12221 of the pole tab bundle and the side of the winding core 12 along the first direction X is greater than zero and less than D / 2, and the distance between the end of all the pole tab welding parts 12222 in the pole tab bundle away from the winding main body 121 and the winding main body 121 is relatively small, and a relatively neat end portion can be obtained without cutting the pole tab bundle, effectively solving the problems of welding leaks, cold welding, and explosion points caused by the unevenness of the pole tabs in the pole tab bundle 122 when welding the pole tab bundle 122 to the pole column 132.

[0086] Please refer to Figure 1. The battery cell 10 provided in this embodiment includes a shell 11, two winding cores 12 and a top cover assembly 13. The shell 11 is provided with a accommodating cavity 110, and the accommodating cavity 110 has an opening (not marked in the figure); each winding core 12 includes a diaphragm and a pole piece 120 in this embodiment (including a positive pole piece and a negative pole piece), and the diaphragm and the pole piece 120 form a winding body 121. When wound into a winding core 12, the diaphragm is used to separate the positive electrode sheet and the negative electrode sheet. The electrode sheet 120 and the diaphragm are wound into a winding body 121. Except for the first electrode tab 1204 with the smallest L5, the other first electrode tabs 1204 are correspondingly gathered from both sides of the first electrode tab 1204 with the smallest L5 to the first electrode tab 1204 with the smallest L5. After ultrasonic welding, the electrode tab bundle 122 (including the positive electrode tab bundle and the negative electrode tab bundle) is obtained, and the ends of the electrode tab bundle 122 are relatively neat; the top cover assembly 13 includes a cover body 131 and a pole column 132 (including a positive pole column and a negative pole column). The pole 132 is passed through the cover body 131 and is correspondingly partially exposed on both sides of the cover body 131; each winding core 12 is welded to the pole 132 through the tab bundle 122 (that is, the positive pole tab bundle is welded to the positive pole, and the negative pole tab bundle is welded to the negative pole), and the two winding cores 12 are respectively arranged at both ends of the cover body 131 in the first direction X, and are flipped with the position where their respective tab bundles 122 are welded to the pole 132 as the flipping center, so that the winding bodies 121 of the two winding cores 12 are abutted against each other, and the two winding cores 12 abutting against each other are accommodated in the accommodating cavity 110, and the tab bundle 122 is located on one side of the opening, the cover body 131 covers the opening and is welded to the shell 11, and the end of the pole 132 facing away from the tab bundle 122 is exposed outside the shell 11 to facilitate connection with an external wire.

[0087] Example 2

[0088] This embodiment provides a pole piece and a battery cell.

[0089] Referring to Figures 9 to 11 and Figures 1 to 4 , the pole piece of this embodiment differs from the pole piece of the first embodiment in the distribution of the multiple pole tabs. In this embodiment, the second pole tabs 1205 and the third pole tabs 1206 in the pole piece 120 are alternately spaced along the extension direction of the long side 1203. The second pole tabs 1205 and the third pole tabs 1206 together form a pole tab bundle 122. There are multiple second pole tabs 1205 (four in the figure), and there are multiple third pole tabs 1206 (three in the figure). From the winding starting end 1201 to the winding ending end 1202, the distance L3 between the ends of the multiple second pole tabs 1205 facing away from the long side 1203 and the long side 1203 first decreases and then increases, while the distance L4 between the ends of the multiple third pole tabs 1206 facing away from the long side 1203 and the long side 1203 increases, and L3 is less than L4.

[0090] After the pole piece 120 is wound into the winding core 12, a single winding turns out two pole ears. Except for the second pole ear 1205 with the smallest L3, the other second pole ears 1205 are located on the same side of the second pole ear 1205 with the smallest L3, and the height of the second pole ear 1205 gradually increases in the direction away from the second pole ear 1205 with the smallest L3; all the third pole ears 1206 are located on the same side of the second pole ear 1205 with the smallest L3, and the height of the third pole ears 1206 gradually increases in the direction away from the second pole ear 1205 with the smallest L3. When all the tabs are gathered and welded into a tab bundle 122, the other second tabs 1205 except the second tab 1205 with the smallest L3 and all the third tabs 1206 are respectively moved closer to the second tab 1205 with the smallest L3 from both sides of the second tab 1205 with the smallest L3, and ultrasonic welding is performed to obtain the tab bundle 122. In the winding core 12 obtained in this embodiment, the minimum distance d between the gathered end 12221 of the tab bundle and the side of the winding core 12 along the first direction X is greater than zero and less than D / 2, and the distance between the end of all the tab welding parts 12222 in the tab bundle 122 away from the winding main body 121 and the winding main body 121 is relatively small, so that a relatively neat end portion can be obtained without cutting the tab bundle, and the problems of welding leaks, cold welding, and explosion points caused by the unevenness of the tabs in the tab bundle 122 when the tab bundle 122 is welded to the pole column can be solved.

[0091] Aside from the above differences, the other structures of the electrode sheet 120 of this embodiment are the same as those of the electrode sheet 120 of Example 1. The battery cell 10 of this embodiment is formed by winding the electrode sheet 120 of this embodiment, and the remaining components are the same as those of Example 1, so the electrode sheet 120 and battery cell 10 will not be described in detail here.

[0092] Example 3

[0093] This embodiment provides a pole piece and a battery cell.

[0094] Please refer to Figures 12 to 14 and Figures 1 to 4. The difference between the pole piece of this embodiment and the pole piece of the first embodiment is that the distribution of the multiple pole ears is different. In the pole piece 120 of this embodiment, the number of first pole ears 1204 is an even number (8 in the figure). From the starting end 1201 of the winding to the end 1202 of the winding, each two adjacent first pole ears 1204 form a pole ear group. The distance L6 between the end of the two first pole ears 1204 facing away from the long side 1203 and the long side 1203 in the same group is equal. From the starting end 1201 of the winding to the end 1202 of the winding, L6 of the first pole ears 1204 of each group gradually increases. When the pole piece 120 is wound into a winding core 12, there are two pole ears in a single winding, and the two pole ears in the same winding are symmetrically arranged relative to the plane where the winding center line is located. The pole ear heights of the two pole ears in the same winding are the same. Specifically, the two first pole ears 1204 close to the winding starting end 1201 constitute the two pole ears of the innermost circle, and the pole ear group composed of the two first pole ears 1204 next close to the winding starting end 1201 constitutes the two pole ears of the next inner circle, and so on. As a result, in the obtained winding core 12, the two first pole ears 1204 in the same pole ear group are arranged symmetrically with each other. When all the tabs are gathered and welded into a tab bundle 122, the two first tabs 1204 of the innermost circle move closer to each other, while the other first tabs 1204 move closer to the first tab 1204 of the innermost circle. After ultrasonic welding, the tab bundle 122 is obtained. The winding center axis MN of the winding core 12 obtained in this embodiment falls within the gathering center plane α, and the distance between the end of the multiple tab welding parts 12222 in the tab bundle 122 away from the winding main body 121 is relatively small. There is no need to cut the tab bundle to obtain a relatively neat end, and it can solve the problems of welding leakage, cold welding, explosion point, etc. caused by the unevenness of the tabs in the tab bundle 122 when welding the tab bundle 122.

[0095] Aside from the above differences, the other structures of the electrode sheet 120 of this embodiment are the same as those of the electrode sheet 120 of Example 1. The battery cell 10 of this embodiment is formed by winding the electrode sheet 120 of this embodiment, and the remaining components are the same as those of Example 1, so the electrode sheet 120 and battery cell 10 will not be described in detail here.

[0096] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and replacements can be made without departing from the technical principles of the present application. These improvements and replacements should also be regarded as the scope of protection of the present application.

Claims

1. A battery cell having a first direction (X), wherein, The battery cell comprises: A housing (11), wherein the housing (11) has a receiving cavity (110) provided with an opening; A winding core (12), the winding core (12) being accommodated in the accommodating cavity (110); The winding core (12) comprises a winding body (121) and a tab bundle (122); the tab bundle (122) comprises a gathering portion (1222) and a dispersion portion (1223); the dispersion portion (1223) is arranged between the gathering portion (1222) and the winding body (121); the gathering portion (1222) is connected to one end of the dispersion portion (1223) to form a gathering end (12221); the minimum distance between the gathering end (12221) and one side of the winding core (12) along the first direction (X) is d mm; the average size of the winding body (121) along the first direction (X) is D, satisfying: 0<d≤D / 2.

2. The battery cell according to claim 1, wherein the pole tab bundle (122) comprises a plurality of pole tabs (1204; 1205; 1206), the portion where the plurality of pole tabs (1204; 1205; 1206) are gathered, stacked and welded forms the gathered portion (1222), and the portion where the plurality of pole tabs (1204; 1205; 1206) are not welded forms the dispersed portion (1223).

3. The battery cell according to claim 1, wherein, The distance between the center of the extension trajectory of the pole lug bundle (122) and the retracted end (12221) is between 0 and 300 mm.

4. The battery cell according to claim 3, wherein, The distance between the center of the extension trajectory of the pole lug bundle (122) and the retracted end (12221) is between 0 and 50 mm.

5. The battery cell according to claim 1, wherein, The center of the extension trajectory of the pole lug bundle (122) falls on the retracted end (12221).

6. The battery cell according to claim 1, wherein, The gathering portion (1222) includes a plurality of tab welding portions (12222) stacked and connected to the dispersion portion (1223), wherein the plurality of tab welding portions (12222) have a minimum extension length L1 mm and a maximum extension length L2 mm, satisfying 0.9≤L1 / L2≤1.

2.

7. The battery cell according to claim 1, wherein, The battery cell further comprises a top cover assembly (13), the top cover assembly (13) comprising a cover body (131) and a pole (132) penetrating the cover body (131), the cover body (131) covering the opening and connected to the shell (11), one end of the pole (132) extending into the accommodating cavity (110), and the other end exposed on a side of the cover body (131) facing away from the shell (11), and the pole lug bundle (122) is welded and fixed to the pole (132).

8. The battery cell according to claim 1, wherein, The winding body (121) includes a separator and a pole piece (120). The tab bundle (122) includes a plurality of first tabs (1204), and the plurality of first tabs (1204) are welded and fixed to form the converging portion (1222) and the diverging portion (1223). The pole piece has a long side (1203), and the plurality of first tabs (1204) are connected to the long side (1203). The pole piece (120) has a winding start end (1201) and a winding end (1202). From the winding start end (1201) to the winding end (1202), the distance between the end of the plurality of first tabs (1204) facing away from the long side (1203) and the long side (1203) increases.

9. The battery cell according to claim 1, wherein, The winding body (121) includes a separator and a pole piece (120). The tab bundle (122) includes a plurality of first tabs (1204), and the plurality of first tabs (1204) are welded and fixed to form the converging portion (1222) and the diverging portion (1223). The pole piece (120) has a long side (1203), and the plurality of first tabs (1204) are connected to the long side (1203). The pole piece (120) has a winding start end (1201) and a winding end (1202). From the winding start end (1201) to the winding end (1202), the distance between the end of the plurality of first tabs (1204) facing away from the long side (1203) and the long side (1203) first decreases and then increases.

10. The battery cell according to claim 1, wherein, The winding body (121) includes a separator and a pole piece (120). The tab bundle (122) includes a plurality of second tabs (1205) and a plurality of third tabs (1206), and the plurality of second tabs (1205) and the plurality of third tabs (1206) are welded and fixed to form the converging portion (1222) and the diverging portion (1223). The pole piece (120) has a long side (1203), and the plurality of second tabs (1205) and the plurality of third tabs (1206) are alternately arranged at intervals along the extending direction of the long side (1203) and are connected to the long side (1203). The pole piece (120) has a winding start end (1201) and a winding end (1202). From the winding start end (1201) to the winding end (1202), the distance between the end of the plurality of second tabs (1205) facing away from the long side (1203) and the long side (1203) first decreases and then increases, and the distance between the end of the plurality of third tabs (1206) facing away from the long side (1203) and the long side (1203) increases.

11. The battery cell according to claim 10, wherein, The distance between the end of the second tab (1205) facing away from the long side (1203) and the long side (1203) is L3 mm, and the distance between the end of the third tab (1206) facing away from the long side (1203) and the long side (1203) is L4 mm, satisfying: L3 < L4.

12. The battery cell according to claim 7, wherein, The extension length of the tab bundle (122) is L mm, and the width of the cover body (131) is W mm, satisfying: 0.125≤L / W≤0.

5.

13. The battery cell according to claim 7, wherein, The number of the pole lug bundles (122) is at least 2 and they are arranged at intervals along the second direction (Y) on the same side of the winding body (121); the number of the poles (132) is at least 2 and they are arranged at intervals along the second direction (Y) on the cover body (131); the center distance between two adjacent pole lug bundles (122) is M1 mm, and the center distance between two adjacent poles (132) respectively connected to the two adjacent pole lug bundles (122) is M2 mm, satisfying: M2≥M1, and the first direction (X) intersects with the second direction (Y).

14. The battery cell according to claim 7, wherein, The pole (132) has a welding end (1321), and the welding end (1321) is welded and fixed to the pole lug bundle (122); on a plane perpendicular to a third direction (Z), a projection area of ​​the welding end (1321) along the third direction (Z) is larger than a projection area of ​​the folded portion (1222) along the third direction (Z), and the third direction (Z) intersects with the first direction (X).

15. The battery cell according to claim 1, wherein, The battery cell satisfies: D / 10<d≤D / 2.

16. A battery pack, wherein, The battery pack comprises the battery cell according to any one of claims 1 to 15.

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