Battery cell, assembly method for battery cell, and battery pack

Abstract

A battery cell (1), an assembly method for the battery cell (1), and a battery pack. In the battery cell (1), tabs (22) in an electrode assembly (20) extend in a first direction (X) but are not bent; connecting pieces (31) are provided on end surfaces (2221) of second ends (222) of the tabs (22) exposed out of a body (21); the connecting pieces (31) are welded to the end surfaces (2221) of the second ends (222) to form welding marks (32); and the welding marks (32) extend in a second direction (Y). The tabs (22) can be connected to the connecting pieces (31) simply by exposing the tabs out of the body (21) by a short distance, thereby improving the capacity of the battery cell (1), and improving the energy density of the battery cell (1).

Description

Battery cell, battery cell assembly method, and battery pack

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 11, 2023, with application number 202311010207.2 and application name “Battery Cell, Assembly Method of Battery Cell and Battery Pack”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a battery cell, a method for assembling a battery cell, and a battery pack. Background Art

[0003] In existing battery cells, the tabs on the battery cells are mostly protruding along the third direction of the battery cells and are arranged on the main body of the battery cells. In order to connect with the adapter, the tabs extending along the third direction need to be bent and the bent tabs need to be connected to the adapter. This increases the bending process and affects the assembly efficiency of the battery cells. Technical Solutions

[0004] According to a first aspect of the present application, a battery cell is provided, comprising: a housing having a housing cavity; the battery cell further comprising: an electrode assembly disposed in the housing cavity, the electrode assembly comprising a main body and a tab connected to the main body, the main body having a first direction, the tab extending only along the first direction, the tab having a second end, the second end being located on a side of the tab away from the main body; a connecting assembly disposed on a side of the second end away from the main body and welded to an end surface of the second end; a weld mark formed at a location where the connecting assembly is welded to the end surface of the second end, the weld mark at least partially penetrating the connecting assembly along the first direction and partially embedded in the second end of the tab, the tab comprising a plurality of tab sheets stacked along a second direction, the weld mark being disposed along the second direction, the first direction intersecting the second direction; the housing having an opening, the main body having a mounting surface perpendicular to the first direction on a side facing the opening, and a distance L between the end surface of the second end of the tab and the mounting surface in the first direction, with 0.1 mm ≤ L ≤ 10 mm.

[0005] Optional, 0.5mm≤L≤5mm.

[0006] Optionally, the shell is provided with an opening, and the side of the main body facing the opening has a mounting surface perpendicular to the first direction, the orthographic projection of the weld mark on the mounting surface has two maximum contour points opposite to each other in the second direction, and there is a line segment extending along the second direction between the two maximum contour points, and the length L1 mm of the line segment is the maximum dimension of the orthographic projection of the weld mark on the mounting surface in the second direction; the shell includes two side walls arranged opposite to each other along the second direction, and the spacing between the two side walls in the second direction is L2 mm, satisfying: 0.5≤L1 / L2<1.

[0007] Optional, 0.6≤L1 / L2≤0.95.

[0008] Optionally, the connecting assembly includes a connecting piece and a terminal; the connecting piece includes a first section and a second section connected along a third direction, the first section is welded and fixed to the end face of the second end, the terminal is arranged on a side of the second section away from the main body in the first direction, and the terminal is electrically connected to the tab through the connecting piece; the first direction, the second direction and the third direction are perpendicular to each other.

[0009] Optionally, a weld mark is formed at the welding position between the connecting piece and the end face of the second end, and the weld mark at least partially penetrates the connecting piece along the first direction and is partially embedded in the second end of the tab. In the first direction, the thickness of the connecting piece is H1 mm, and the depth of the weld mark is H2 mm, satisfying the following: 0.5 mm + H1 ≤ H2 ≤ 1.5 mm + H1.

[0010] Optionally, the shell has an opening connecting the accommodating cavity with the outside world, and the battery cell also includes a top cover plate and a baffle, the top cover plate covers the opening of the shell, a first through hole and a second through hole are provided on the top cover plate, the first through hole and the second through hole are arranged at intervals along the third direction, and the terminal is inserted into the first through hole; the second through hole and the second end of the pole ear are arranged opposite to each other along the first direction, and the baffle is arranged in the second through hole, and the first direction, the second direction, and the third direction are perpendicular to each other.

[0011] Optionally, the battery cell further includes an insulating sheet, which is disposed between the baffle and the first section to insulate the connecting sheet from the baffle.

[0012] Optionally, the shape of the weld mark includes at least one of a circle, an arc, a slant line and a broken line.

[0013] Optionally, the shape of the weld mark is a slant line, and multiple weld mark units are provided on each connecting piece, and the multiple weld mark units form the weld mark. There is an angle between the length direction of each weld mark unit and the second direction, and the degree of the angle is 10° to 80°.

[0014] Optionally, a preset angle α is formed between the line segment and the third direction, and the preset angle α satisfies: 0°<α≤90°.

[0015] Optionally, the preset angle α satisfies: 85°≤α≤90°.

[0016] A second aspect of an embodiment of the present application provides a method for assembling a battery cell, comprising the following steps: installing an electrode assembly into a shell, with the second end of the electrode assembly's tab in a first direction facing the opening of the shell; welding at least a portion of the end surface of the second end of the tab to a connecting piece to form a weld mark, and the formed weld mark extends along the second direction.

[0017] A third aspect of the present application provides a battery pack, comprising the battery cells described in the first aspect, or comprising battery cells assembled by the battery cell assembly method described in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a schematic structural diagram of a battery cell provided in an embodiment of the present application;

[0019] FIG2 is an exploded view of FIG1 ;

[0020] FIG3 is a cross-sectional view taken along the line AA of FIG1 ;

[0021] FIG4 is an enlarged structural diagram of point B in FIG3 ;

[0022] FIG5 is a schematic diagram of a first structure of an electrode assembly in a battery cell provided in an embodiment of the present application;

[0023] FIG6 is an enlarged structural diagram of point C in FIG5 ;

[0024] FIG7 is a schematic diagram of the combined structure of the positive electrode tab, the negative electrode tab, the positive electrode sheet, the negative electrode sheet, and the separator in the electrode assembly of the battery cell provided in an embodiment of the present application;

[0025] FIG8 is a schematic diagram of the combined structure of the connecting sheet and the electrode assembly in one implementation of the battery cell provided in an embodiment of the present application;

[0026] FIG9 is a top view of FIG8;

[0027] FIG10 is a sectional view taken along the line DD in FIG8 ;

[0028] FIG11 is an enlarged structural diagram of point E in FIG10 ;

[0029] 12A to 12E are schematic structural diagrams of weld marks in battery cells provided in other implementations of the present application;

[0030] FIG13 is a schematic diagram of a second structure of an electrode assembly in a battery cell provided in an embodiment of the present application.

[0031] Description of reference numerals:

[0032] 1. Battery cell, 10. Housing, 101. Accommodation cavity, 11. Opening, 20. Electrode assembly, 21. Main body, 210. Mounting surface, 21a. Negative electrode sheet, 21b. Positive electrode sheet, 21c. Separator, 22. Tab, 22a. Negative tab, 22b. Positive tab, 221. First end, 222. Second end, 2221. End surface, 220. Tab, 30. Connector assembly, 31. Connecting piece, 311, first section, 312, second section, 32, weld mark, 320, line segment, 3201, maximum contour line, 321, weld mark unit, 33, terminal, 40, top cover plate, 401, first through hole, 402, second through hole, 41, baffle, 411, insulating sheet, 42, explosion-proof valve, 43, injection hole, 44, lower plastic; X, first direction, Y, second direction, Z, third direction.

[0033] Implementation Methods of the Application

[0034] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0035] In some embodiments of the present application, referring to FIG. 1 to FIG. 13 , a battery cell 1 is provided. The battery cell 1 includes a housing 10 , an electrode assembly 20 , and a connection assembly 30 .

[0036] 1 and 2 , the shell 10 is provided with an opening 11 , and referring to FIG3 to FIG4 , the shell 10 has a accommodating cavity 101 , the opening 11 is communicated with the accommodating cavity 101 , and the opening 11 connects the accommodating cavity 101 with the outside world. The shell 10 is a hexahedral structure. In the embodiment shown in FIG1 and FIG2 , the opening 11 is opened on the top surface of the shell 10 in its height direction.

[0037] 2 to 8 and 13 , the electrode assembly 20 is disposed in the accommodating cavity 101 . Referring to FIG. 2 to 8 and FIG. 13 , the electrode assembly 20 includes a main body 21 and a tab 22 connected to the main body 21 . The main body 21 has a first direction X, and the tab 22 extends only along the first direction X. In the embodiment shown in FIG. 2 to 8 and FIG. 13 , the first direction X is the height direction of the shell 10 . In other embodiments of the present application, the first direction X may also be the width direction or the height direction of the shell 10 , and may be selected based on the position of the tab 22 , such as tabs on the same side or tabs on opposite sides. The tab 22 has a first end 221 and a second end 222 oppositely arranged along the first direction X. The first end 221 of the tab 22 is connected to the main body 21 , and the second end 222 of the tab 22 is located on a side away from the main body 21 . A side of the main body 21 facing the opening 11 is a mounting surface 210 perpendicular to the first direction X, that is, the second end 222 is exposed from the mounting surface 210 of the main body 21 and faces the opening 11 of the shell 10 .

[0038] 7 and 13 , the main body 21 includes a pole piece and a diaphragm. Specifically, the main body 21 includes a negative pole piece 21a, a positive pole piece 21b and a diaphragm 21c. The diaphragm 21c is arranged between the negative pole piece 21a and the positive pole piece 21b to form insulation between the negative pole piece 21a and the positive pole piece 21b. The pole tab 22 includes a negative pole tab 22a and a positive pole tab 22b. The negative pole tab 22a is connected to the negative pole piece 21a, and the positive pole tab 22b is connected to the positive pole piece 21b. The pole tab 22 includes a first end 221 and a second end 222 arranged opposite to each other along the first direction X. The first end 221 is located on the inner side of the main body 21 and is connected to the pole piece. The second end 222 is exposed on the side of the main body 21 facing the opening 11. The pole tab 22 extends along the first direction X.

[0039] 2 to 4 and 8 to 11 and 12A to 12E, the connecting assembly 30 is provided on a side of the second end 222 of the tab 22 away from the main body 21, and the connecting assembly 30 is welded and fixed to the end face 2221 of the second end 222. Specifically, in the embodiment shown in FIG2 to 4 and 8 to 11 and 12A to 12E, the connecting assembly 30 includes a connecting piece 31, which is provided on the end face 2221 of the second end 222 of the tab 22, and at least a portion of the end face 2221 of the second end 222 is welded to the connecting piece 31. The welding position between the connecting piece 31 and the end face 2221 of the second end 222 forms a welding mark 32, which extends along the second direction Y, and the second direction Y intersects with the first direction X. Specifically, in the embodiment shown in FIG2 to 4 and 8 to 11 and 12A to 12E, the first direction X is orthogonal to the second direction Y. The tab 22 extends along the first direction X. The end surface 2221 of the second end 222 of the tab 22 is a surface of the second end 222 away from the first end 221 in the first direction X.

[0040] Among them, the welding mark 32 extends along the second direction Y. The welding mark 32 may extend along the second direction Y in the form of a straight line, the welding mark 32 may extend along the second direction Y in the form of a curve, or the welding mark 32 may extend along the second direction Y in the form of a broken line. The specific selection can be made according to actual usage.

[0041] In addition, the pole piece and the pole ear 22 are integrally formed. Specifically, the portion of the pole piece surface on which the active material layer is provided constitutes the pole piece, and the portion on which the active material layer is not provided is cut to form the pole ear 22. The second end 222 of the pole ear 22 is used to be electrically connected through the connecting assembly 30 to provide electrical energy to the external electrical equipment. In the existing battery cell, the length of the portion of the pole ear exposed from the main body is relatively large, resulting in the portion of the pole ear exposed from the main body occupying too much space inside the shell in the first direction X, thereby affecting the volume occupied by the main body inside the accommodating cavity 101 of the shell. Even if the pole ear is bent and connected to the connecting piece to reduce the occupancy rate of the space occupied, the bent pole ear will still occupy a certain space, and the bending process of the pole ear will be increased, thereby increasing the manufacturing cost.

[0042] The battery cell provided in the embodiment of the present application welds the connecting piece 31 to the end face 2221 of the second end 222 of the pole tab 22, forming a weld mark 32 at the welding position. The portion of the pole tab 22 exposed from the mounting surface 210 of the main body 21 can be connected to the connecting piece 31 without bending, and the pole tab 22 only needs to be exposed from the mounting surface 210 of the main body 21 for a short distance to be connected to the connecting piece 31, thereby reducing the height of the pole tab 22 in the third direction Z, thereby reducing the space of the accommodating cavity 101 occupied by the pole tab 22 in the first direction X, and the saved space can be used to increase the volume of the main body 21 in the electrode assembly 20, thereby increasing the capacity of the battery cell 1.

[0043] In some embodiments of the present application, referring to Figures 5-6 and 8-13 , the tab 22 includes a plurality of tab sheets 220 , which are stacked along a second direction Y. The weld mark 32 extends along the second direction Y, i.e., the extension direction of the weld mark 32 coincides with the stacking direction of the plurality of tab sheets 220 . As a result, when the connecting tab 31 is welded to the tab 22 , as shown in Figure 11 , the melted connecting tab 31 and the tab sheet 220 are perpendicular to each other, forming a T-shaped structure. This ensures the stability of the connection between the connecting tab 31 and the tab sheet 220 . Furthermore, since there is a gap between two adjacent tab sheets 220 in the second direction Y, and this gap extends along a third direction Z, if the weld mark 32 is provided along the third direction Z, the melted connecting tab 31 formed by welding may fall into the gap between the two adjacent tab sheets 220 , resulting in a risk of a cold weld between the connecting tab 31 and the tab 22 , thereby affecting the stability of the connection between the connecting tab 31 and the tab 22 .

[0044] In some embodiments of the present application, referring to Figures 5, 6, 11 and 13, the end surface 2221 of the second end 222 of the pole tab 22 has a length S in the second direction Y, and the multiple pole tab sheets 220 forming the pole tab 22 have different heights in the first direction X. Specifically, the heights of the pole tab sheets 220 corresponding to the two ends of the length S of the pole tab 22 are lower than the heights of the pole tab sheets 220 corresponding to the middle section of the length S of the pole tab 22, and the heights of the pole tab sheets 220 corresponding to the middle section of the length S of the pole tab 22 are the same, forming an isosceles trapezoidal structure of the second end 222 of the pole tab 22, and the connecting sheet 31 is welded to the pole tab 22 in the middle section of the length S to form a weld mark 32.

[0045] In some embodiments of the present application, referring to Figures 8-9 and 12A-12E, the main body 21 has a mounting surface 210 perpendicular to the first direction X. The orthographic projection of the weld mark 32 on the mounting surface 210 has two maximum contour points (not shown) that are opposite in the second direction Y. A line segment 320 extending along the second direction Y is defined between the two maximum contour points. The length L1 mm of the line segment 320 is the maximum dimension of the orthographic projection of the weld mark 32 on the mounting surface 210 in the second direction Y. Furthermore, referring to Figure 1, the housing 10 includes two side walls disposed opposite each other in the second direction Y. The spacing between the two side walls in the second direction Y is L2 mm, satisfying the following condition: 0.5 ≤ L1 / L2 < 1. Specifically, the ratio of L1 to L2 can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.96, 0.97, 0.98, 0.99, or a range between any two of these values. Where L2 is the distance between the inner surfaces of the two opposing walls of the housing 10 in the second direction Y. A larger ratio of L1 to L2 indicates a larger maximum dimension L1 of the weld mark 32 in the second direction Y. Since the body 21 of the electrode assembly 20 has a width S (not shown) between the opposing walls in the second direction Y, the maximum dimension L1 of the weld mark 32 in the second direction Y is smaller than S. When 0.5 ≤ L1 / L2 < 1 is satisfied, the actual capacity / rated capacity ratio of the battery cell is high. In other words, the energy corresponding to the tab can be fully utilized. Furthermore, when 0.5 ≤ L1 / L2 < 1 is satisfied, the welding yield of the battery cell is high. On the other hand, if the ratio of L1 to L2 is less than 0.5, the actual capacity / rated capacity of the battery cell is too small, resulting in a low actual capacity that fails to meet the capacity requirements. If the ratio of L1 to L2 is greater than or equal to 1, laser welding becomes more difficult and easily welds to the aluminum shell on both sides, resulting in a low welding yield of the battery cell. Furthermore, the larger L1, the larger S, that is, the more space inside the accommodating cavity 101 occupied by the main body 21 in the second direction Y, the greater the capacity of the electrode assembly. Therefore, when the ratio of L1 to L2 is within the above range, the capacity of the electrode assembly 20 can be guaranteed while preventing the width S of the main body 21 from being too large, causing the main body 21 to abut against the opposite side walls of the housing 10 in the second direction Y. This leaves room for the main body 21 to expand in the second direction Y, thus preventing the expansion of the electrode assembly 20 from being restricted during the cycling of the battery cell 1, which could affect the service life and usable capacity of the battery cell 1. If the ratio of L1 to L2 is less than 0.5, the volume of the electrode assembly 20 is too small and the capacity of the battery cell 1 is too low. If the ratio of L1 to L2 is ≥1, the expansion space of the main body 21 is affected, thus shortening the service life of the battery cell 1.

[0046] Among them, the method of determining the line segment 320 is: using the contour line of the positive projection of the weld mark 32 on the plane where the mounting surface 210 is located as a reference, draw a circumscribed rectangle, and the contour line of the positive projection is inscribed in the rectangle. In the second direction Y, the circumscribed rectangle has two sides opposite to each other along the second direction Y, and the two sides extend along the third direction Z respectively to form a maximum contour line 3201. A line segment extending along the second direction Y and connecting the two maximum contour lines 3201 is made between the two maximum contour lines 3201, which is the line segment 320.

[0047] In some embodiments of the present application, 0.6≤L1 / L2≤0.95.

[0048] In some embodiments of the present application, the values ​​of L1 and L2 can be measured multiple times using a measuring instrument such as a laser rangefinder or a vernier caliper, and then the average value is calculated.

[0049] In some embodiments of the present application, line segment 320 forms a preset angle with the third direction Z, wherein the preset angle α satisfies the following conditions: 0° < α ≤ 90°. When the angle α satisfies the following conditions: 0° < α ≤ 90°, the connection strength between the tab and the connecting piece 31 is maintained, while also ensuring that energy from the core electrode can be transferred through the tab, thus ensuring that the actual capacity / rated capacity of the battery cell meets the requirements.

[0050] In some embodiments of the present application, referring to FIG. 9 and FIG. 12A to FIG. 12E , a preset angle is formed between the line segment 320 and the third direction Z, and the preset angle α satisfies: 85°≤α≤90°. When the angle α satisfies this range, the connection strength between the tab and the connecting piece 31 can be ensured to be better, and at the same time, the ratio of the actual capacity / rated capacity of the battery cell is larger, and the battery cell capacity is higher.

[0051] In some embodiments of the present application, referring to Figures 8 and 9, the shape of the weld mark 32 is rectangular, and there are three weld marks 32 on each connecting piece 31, which are arranged at intervals along the third direction Z, and the two maximum contour points are located at the opposite ends of the weld mark 32 in the second direction Y.

[0052] In some embodiments of the present application, referring to FIG. 12A , the shape of the weld mark 32 is a wavy broken line, the number of the weld mark 32 on each connecting piece 31 is one, and the two maximum contour points are respectively located at opposite ends of the weld mark 32 in the second direction Y.

[0053] In some embodiments of the present application, referring to Figure 12B, the shape of the weld mark 32 is a slant line, and multiple weld marks 321 are provided on each connecting piece 31. The multiple weld marks 321 form the weld mark 32. There is an angle between the length direction of each weld mark unit 321 and the second direction Y, and the degree of the angle is 10° to 80°. The two maximum contour points of each weld mark unit 321 are respectively located at the opposite ends of the weld mark unit 321 in the second direction Y. The multiple weld marks 321 are arranged at intervals along the second direction Y. Each weld mark unit 321 has a maximum dimension in the second direction Y. The sum of the maximum dimensions of the multiple weld marks 321 on the same connecting piece 31 is the maximum dimension L1 of the weld mark 32 on the connecting piece 31.

[0054] In some embodiments of the present application, referring to Figure 12C, the shape of the weld mark 32 is circular, and multiple weld marks 321 are provided on each connecting piece 31. The multiple weld marks 321 form the weld mark 32, and the two maximum contour points of each weld mark unit 321 are respectively located at two opposite tangent points of the weld mark unit 321 in the second direction Y. The multiple weld marks 321 are arranged at intervals along the second direction Y, and each weld mark unit 321 has a maximum dimension in the second direction Y. The sum of the maximum dimensions of the multiple weld marks 321 on the same connecting piece 31 is the maximum dimension L1 of the weld mark 32 on the connecting piece 31.

[0055] In some embodiments of the present application, referring to Figure 12D, the shape of the weld mark 32 is a three-segment fold line, the number of weld marks 32 on each connecting piece 31 is one, and the two maximum contour points are respectively located at the opposite ends of the three-segment fold line weld mark 32 in the second direction Y.

[0056] In some embodiments of the present application, referring to FIG. 12E , the shape of the weld mark 32 is arc-shaped, the number of the weld mark 32 on each connecting piece 31 is one, and the two maximum contour points are respectively located at opposite ends of the arc-shaped weld mark 32 in the second direction Y.

[0057] In some embodiments of the present application, the weld mark 32 at least partially penetrates the connecting piece 31 along the first direction X and extends to the second end 222 of the tab 22. During the welding process, a portion of the connecting piece 31 is melted to penetrate the connecting piece 31 and melt a portion of the tab 22, so that the tab 22 is fixedly connected to the connecting piece 31, thereby ensuring the stability of the connection between the tab 22 and the connecting piece 31.

[0058] In some embodiments of the present application, in the first direction X, the thickness of the connecting piece 31 is H1 mm, and the depth of the weld mark 32 is H2 mm, satisfying: 0.5 mm + H1 ≤ H2 ≤ 1.5 mm + H1. Specifically, the value of H2 can be 0.5 mm + H1, 0.6 mm + H1, 0.7 mm + H1, 0.8 mm + H1, 0.9 mm + H1, 1.0 mm + H1, 1.1 mm + H1, 1.2 mm + H1, 1.3 mm + H1, 1.4 mm + H1, 1.5 mm + H1, or a range value consisting of any two values ​​therein. The depth H2 of the weld mark 32 is the sum of the thickness H1 of the connecting tab 31 and the depth of the weld mark 32 extending within the tab 22. Since the thickness H1 of the connecting tab 31 in each battery cell 1 is fixed, the depth of the weld mark 32 is determined by the melting depth of the weld mark 32 at the second end 222 of the tab 22. When the depth of the weld mark 32 is within the above range, the connection stability between the connecting tab 31 and the tab 22 is ensured while preventing the weld mark 32 from being too deep and causing damage to the main body 21 of the electrode assembly 20. If the value of H2 is less than 0.5 mm + H1, the depth of the weld mark 32 is too shallow, the stability of the tab 22 and the connecting tab 31 is insufficient, and the tab 22 and the connecting tab 31 are prone to loosening during the recycling of the battery cell 1, affecting the normal use of the battery cell 1. If the value of H2 is higher than 1.5mm+H1, the depth of the weld mark 32 is too deep, and too much of the electrode tab 22 melts during welding, resulting in the unmelted electrode tab 22 being exposed from the mounting surface 210 of the main body 21 for a short length in the first direction X, affecting the connection stability between the electrode tab 22 and the connecting piece 31, and there is a possibility of affecting the stability of the output power of the electrode assembly 20.

[0059] In some embodiments of the present application, the depth H2 of the weld mark 32 is measured by randomly selecting 5 measurement points on a cross section containing the weld mark 32 track, selecting a microscope with a suitable magnification, observing each measurement point, and taking the average value to obtain the depth H2 at the weld mark 32 track.

[0060] In some embodiments of the present application, a welding penetration microscope system (GRM-600) and a two-dimensional image measurement system (GM-2000M) produced by Shanghai Guangmi Instrument Co., Ltd. are used to measure the depth H2 of the weld mark 32.

[0061] In some embodiments of the present application, referring to FIG. 7 , in the first direction X, the distance between the end surface 2221 of the second end 222 of the tab 22 and the mounting surface 210 is L, that is, the length of the tab 22 exposed from the side of the main body 21 facing the opening 11 is L. In other words, the length of the tab 22 exposed from the mounting surface 210 of the main body 21 is L, and 0.1 mm ≤ L ≤ 10 mm. Specifically, the value of L can be 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or a range consisting of any two of these values. When the value of L is within the above range, the connection stability and strength between the tab 22 and the connecting piece 31 can be ensured while not occupying excessive space within the accommodating cavity 101 in the first direction X, thereby improving the space utilization within the accommodating cavity 101. When the L value is less than 0.1 mm, the length of the tab 22 exposed from the mounting surface 210 of the main body 21 is too short, and the weld mark 32 formed by welding is too shallow, affecting the connection stability between the connecting piece 31 and the tab 22. When the L value is greater than 10 mm, the tab 22 occupies too much space in the first direction X, and the space occupancy rate of the main body 21 within the accommodating cavity 101 is low, affecting the capacity of the battery cell 1.

[0062] In some embodiments of the present application, 0.5 mm ≤ L ≤ 5 mm.

[0063] In some embodiments of the present application, the method for measuring L is: select multiple points at the intersection of the tab 22 and the mounting surface 210, measure the vertical distance between each point and the end face 2221 in the first direction X using a laser rangefinder or a micrometer, and take the average value as the L value.

[0064] In some embodiments of the present application, referring to Figures 1 to 4, the connection assembly 30 further includes a terminal 33. Referring to Figures 2 to 4 and Figures 8 to 11 and Figures 12A to 12E, the connecting piece 31 includes a first section 311 and a second section 312 connected in sequence along the third direction Z, the first section 311 is arranged on the end surface 2221 of the second end 222, and the first section 311 and the end surface 2221 of the second end 222 are welded to form a weld mark 32, that is, the weld mark 32 is formed on a side of the first section 311 facing away from the main body 21 in the first direction X, the terminal 33 is arranged on a side of the second section 312 facing away from the main body 21 in the first direction X, the terminal 33 is electrically connected to the tab 22 through the connecting piece 31, and the second section 312 of the connecting piece 31 is arranged on the mounting surface 210 of the main body 21 to increase the contact area between the connecting piece 31 and the mounting surface 210, thereby ensuring the stability of the connecting piece 31.

[0065] In some embodiments of the present application, the terminal 33 is integrally formed with the connecting piece 31. The structural design of the terminal 33 and the connecting piece 31 being integrally formed allows the integrated terminal 33 and the connecting piece 31 to be integrally mounted on the mounting surface 210 of the main body 21 along the first direction X during assembly of the battery cell 1, thereby improving the assembly efficiency and convenience of the battery cell 1.

[0066] In some embodiments of the present application, referring to Figures 1 to 4, the battery cell 1 further includes a top cover plate 40 and a baffle plate 41. The top cover plate 40 covers the opening 11 of the housing 10. The top cover plate 40 defines a first through hole 401 and a second through hole 402. The first through hole 401 and the second through hole 402 are spaced apart along the third direction Z. The terminal 33 is inserted into the first through hole 401. The second through hole 402 is positioned opposite the second end 222 of the tab 22 along the first direction X. The baffle plate 41 is disposed within the second through hole 402. The provision of the second through hole 402 allows the connecting piece 31 to be first mounted on the mounting surface 210 of the main body 21 during assembly of the battery cell 1. After the top cover plate 40 is assembled, the connecting piece 31 can be welded to the tab 22 through the second through hole 402, thereby improving the assembly efficiency of the battery cell 1. After welding is completed, the baffle plate 41 can be used to seal the second through hole 402 to ensure the sealing of the housing 10. The baffle 41 and the first section 311 of the connecting piece 31 are disposed opposite to each other along the first direction X.

[0067] In some embodiments of the present application, referring to FIG. 1 to FIG. 4 , the battery cell 1 further includes an insulating sheet 411 , which is disposed between the baffle 41 and the first section 311 to insulate the connecting sheet 31 from the baffle 41 to prevent short circuit.

[0068] 1 to 4 , the battery cell 1 further includes an explosion-proof valve 42 , a liquid injection hole 43 , and a lower plastic 44 . The explosion-proof valve 42 and the liquid injection hole 43 are spaced apart along the third direction Z on the top cover plate 40 . The lower plastic 44 is disposed on a surface of the top cover plate 40 facing the main body 21 in the first direction X.

[0069] In some embodiments of the present application, a method for assembling the battery cell 1 is provided, comprising the following steps:

[0070] S100, installing the electrode assembly 20 into the housing 10, with the second end 222 of the tab 22 of the electrode assembly 20 in the first direction X facing the opening 11 of the housing 10;

[0071] S110 , welding at least a portion of the end surface 2221 of the second end 222 of the tab 22 to the connecting piece 31 to form a weld mark 32 , wherein the weld mark 32 extends along the second direction Y.

[0072] In some embodiments of the present application, step S110 also includes: welding at least a portion of the end surface 2221 of the second end 222 of the tab 22 to the portion where the connecting piece 31 is in contact by laser penetration welding, wherein the laser penetrates the connecting piece 31 along the first direction X and extends to the second end 222, fusing the connecting piece 31 and the second end 222 to form a weld mark 32, and the laser moves along the second direction Y so that the formed weld mark 32 extends along the second direction Y.

[0073] In some embodiments of the present application, step S110 also includes: covering the top cover plate 40 on the opening 11 of the shell 10, and welding the connecting piece 31 and the end face 2221 of the second end 222 with a laser through the second through hole 402 on the top cover plate 40. After welding is completed, the baffle 41 is welded in the second through hole 402.

[0074] In some embodiments of the present application, a battery pack is provided, including a battery cell 1 .

[0075] In some embodiments of the present application, a battery pack is provided, which includes battery cells 1 assembled by the battery cell assembly method as described above.

[0076] In some embodiments, embodiments 1 to 6 are further provided. The battery cells of each embodiment are the same as FIG. 1 of the present application and all satisfy 0.5≤L1 / L2<1. Meanwhile, comparative examples 1 to 2 are provided. The comparative examples do not satisfy 0.5≤L1 / L2<1.

[0077] The battery cells of each embodiment and comparative example were subjected to performance tests, specifically actual capacity / rated capacity and welding yield.

[0078] The test process is as follows: Regarding the measurement of actual capacity / rated capacity, the actual capacity is discharged at a constant current of rated current to the termination voltage, and the discharge amount is the actual capacity. The rated current and termination voltage are tested with the current and voltage set when the battery is produced or shipped. The rated capacity is measured with the capacity set when the battery is produced or shipped.

[0079] Regarding the measurement of welding yield: randomly select some battery samples and observe the welding conditions of the tabs and the connecting pieces. If there are weld marks or burns on the aluminum shell, such batteries are welding failures. If the weld marks are only on the tabs and the connecting pieces when welding, such battery cells are welding qualified pieces. The welding yield is obtained by subtracting the number of welding failures from the total number of samples and dividing it by the total number of samples.

[0080] About the measurement of tensile force: Fix the snack with a clamp, pull the connecting piece with a tensile gauge, and measure the tensile force value displayed on the tensile gauge when the connecting piece and the tab are peeled off.

[0081] About the measurement of battery cell internal resistance: Use HI-POT equipment to measure the internal resistance of the battery cell.

[0082] The test results are shown in Table 1 and Table 2.

[0083] Table 1

[0084] Table 2

[0085] As can be seen from the example in Table 1 above, when the battery cell satisfies 0.5≤L1 / L2<1, the ratio of the battery cell's actual capacity to rated capacity is above 0.95, meaning the battery cell can effectively transfer the energy from the electrode through the tab. At the same time, the welding pass rate between the tab and the connecting tab can reach over 97%, indicating a high welding pass rate. However, when L1 / L2<0.5, the actual capacity / rated capacity of the battery cell is below 0.7, and a large portion of the electrode energy cannot be transferred through the tab, resulting in a significant reduction in the actual capacity of the battery cell. Furthermore, when L1 / L2≥1, the tab and connecting tab are easily welded to the casing, resulting in a significant drop in the welding pass rate, which is below 20%.

[0086] From the example in Table 2 above, it can be seen that when the battery cell meets the following requirements: 0.5mm+H1≤H2≤1.5mm+H1, the tensile force between the connecting piece and the tab after welding is large, above 39N, and the connection between the connecting piece and the tab is firm. At the same time, the internal resistance of the battery cell is low, all below 195MΩ.

[0087] Dangdang battery cells meet the following requirements: 0.5mm + H1 ≤ H2 ≤ 1.5mm + H1. If H2 is too large, the internal resistance of the battery cell will increase. If H2 is too small, the tension between the connector and the tab will be insufficient, and the connector will easily separate from the tab, causing the battery cell to fail.

[0088] The above is a detailed introduction to a battery cell, a battery cell assembly method and a battery pack provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, based on the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A battery cell, comprising: A housing having a receiving cavity; wherein The battery cell further comprises: An electrode assembly is disposed in the accommodating cavity, the electrode assembly comprises a main body and a pole ear connected to the main body, the main body has a first direction, the pole ear only extends along the first direction, the pole ear has a second end, and the second end is located on a side of the pole ear away from the main body; A connecting component, the connecting component is arranged at a side of the second end away from the main body and is welded and fixed to the end face of the second end; a weld mark is formed at the welding position between the connecting component and the end face of the second end, the weld mark at least partially penetrates the connecting component along the first direction and is partially embedded in the second end of the pole ear, the pole ear includes a plurality of pole ear sheets, the plurality of pole ear sheets are stacked along the second direction, the weld mark is arranged along the second direction, and the first direction intersects with the second direction; The shell is provided with an opening, and the main body has a mounting surface perpendicular to the first direction on one side facing the opening. In the first direction, the distance between the end surface of the second end of the tab and the mounting surface is L, 0.1mm≤L≤10mm.

2. The battery cell according to claim 1, wherein: 0.5mm≤L≤5mm.

3. The battery cell according to claim 1, wherein: The shell is provided with an opening, and the side of the main body facing the opening has a mounting surface perpendicular to the first direction, the orthographic projection of the weld mark on the mounting surface has two maximum contour points opposite to each other in the second direction, and a line segment extending along the second direction is provided between the two maximum contour points, and the length L1mm of the line segment is the maximum size of the orthographic projection of the weld mark on the mounting surface in the second direction; the shell includes two side walls arranged opposite to each other along the second direction, and the spacing between the two side walls in the second direction is L2mm, satisfying: 0.5≤L1 / L2<1.

4. The battery cell according to claim 3, wherein: 0.6≤L1 / L2≤0.

95.

5. The battery cell according to claim 1, wherein: The connection assembly includes a connection piece and a terminal; The connecting piece includes a first section and a second section connected along a third direction, and the first section is welded to an end surface of the second end. The terminal is arranged on a side of the second section away from the main body in the first direction, and the terminal is electrically connected to the tab through the connecting piece; The first direction, the second direction and the third direction are perpendicular to each other.

6. The battery cell according to claim 5, wherein: A weld mark is formed at the end surface welding position of the connecting piece and the second end, and the weld mark at least partially penetrates the connecting piece along the first direction and is partially embedded in the second end of the pole ear. In the first direction, the thickness of the connecting piece is H1mm, and the depth of the weld mark is H2mm, satisfying: 0.5mm+H1≤H2≤1.5mm+H1.

7. The battery cell according to claim 5, wherein: The shell has an opening connecting the accommodating cavity with the outside, and the battery cell further includes a top cover plate and a baffle plate, the top cover plate is covered on the opening of the shell, a first through hole and a second through hole are formed on the top cover plate, the first through hole and the second through hole are arranged at intervals along the third direction, and the terminal is inserted into the first through hole; The second through hole and the second end of the pole ear are arranged opposite to each other along the first direction, and the baffle is arranged in the second through hole, wherein the first direction, the second direction and the third direction are perpendicular to each other.

8. The battery cell according to claim 7, wherein: The battery cell further includes an insulating sheet disposed between the baffle and the first segment so as to insulate the connecting sheet from the baffle.

9. The battery cell according to claim 1, wherein: The shape of the weld mark includes at least one of a circle, an arc, a slant line and a broken line.

10. The battery cell according to claim 9, wherein: The shape of the weld mark is an oblique line. A plurality of weld mark units are arranged on each connecting piece. The plurality of weld mark units form the weld mark. There is an angle between the length direction of each weld mark unit and the second direction, and the degree of the angle is 10° to 80°.

11. The battery cell according to claim 3, wherein: A preset angle α is formed between the line segment and the third direction, and the preset angle α satisfies: 0°<α≤90°.

12. The battery cell according to claim 11, wherein: The preset angle α satisfies: 85°≤α≤90°.

13. A method for assembling a battery cell according to any one of claims 1 to 12, wherein: The steps include: Installing the electrode assembly into the housing, with the second end of the electrode lug of the electrode assembly in the first direction facing the opening of the housing; At least a portion of the end surface of the second end of the electrode tab is welded to the connecting piece to form a weld mark, and the formed weld mark extends along the second direction.

14. A battery pack, wherein: The battery pack includes the battery cell according to any one of claims 1 to 12.

15. A battery pack, characterized in that: The battery pack includes battery cells assembled by the battery cell assembling method according to claim 13 .

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