Pole piece, battery cell, battery pack and pole piece design method

Abstract

The invention relates to the technical field of batteries, and provides a pole piece, a battery cell, a battery pack and a pole piece design method. The pole piece comprises a main body part and a pole lug, the main body portion is configured to be wound to form a winding core. The main body portion has a winding start end and a winding stop end. The direction from the winding starting end to the winding ending end is the winding direction. And the at least two tabs are arranged on one side of the main body part at intervals along the winding direction. And in the winding direction, the heights of the tabs at the odd number positions and the heights of the tabs at the even number positions have opposite gradual change tendencies. Therefore, the integrity of the welding marks can be ensured, and the phenomena of tab tearing and the like caused by interference can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a pole piece, a battery cell, a battery pack and a pole piece design method. Background Art

[0002] In the related art, the wound battery is usually designed with a single lug, that is, after winding, the core pack leads out the lug on the lower side of the winding center plane, and the lug is bent and welded to the connecting piece. However, the current lugs are usually designed with equal height. If the lug height is small, it will cause incomplete welding marks after bending some lugs, resulting in the actual flow area of ​​the lug being lower than the designed flow area; if the lug height is large, it will cause interference when welding some lugs after bending, and in severe cases, it will cause the lug to tear. Summary of the invention

[0003] The embodiments of the present invention provide a pole piece, a battery cell, a battery pack and a pole piece design method, which can ensure that the welding mark of the pole ear is complete and avoid interference during welding after the pole ear is bent.

[0004] In a first aspect, an embodiment of the present invention provides a pole piece, comprising:

[0005] A main body portion is configured to be wound to form a winding core, the main body portion having a winding start end and a winding end end, and a direction from the winding start end to the winding end end is a winding direction;

[0006] There are at least two pole tabs, which are spaced apart at one side of the main body along the winding direction. Along the winding direction, the heights of the pole tabs at odd positions and the heights of the pole tabs at even positions have opposite gradient trends.

[0007] In one embodiment, the heights of the tabs at odd positions decrease, and the heights of the tabs at even positions increase, wherein the height of the tab at position 1 is less than the height of the tab at position 2.

[0008] In one embodiment, the pole piece has a winding state, and the winding state corresponds to a winding center plane, wherein, in the winding state, the pole ears of odd-numbered positions and the pole ears of even-numbered positions are respectively located on opposite sides of the winding center plane, and the projections of all the pole ears in the first direction at least partially overlap, wherein the first direction is set at an angle to the winding center plane.

[0009] In one embodiment, in the winding state, all the pole ears are bent toward a connecting piece and welded to the connecting piece, wherein when the pole ears are in the bent state, the distance between the shortest free end of the pole ear and the longest free end of the pole ear is Y, satisfying: 0 mm ≤ Y ≤ 1 mm.

[0010] In some embodiments, when the tabs are in a bent state, free ends of all tabs are flush.

[0011] In one embodiment, along the first direction, the main body has a proximal end close to the connecting piece, and a distance X between the proximal end and the connecting piece satisfies: 1 mm ≤ X ≤ 3 mm.

[0012] In a second aspect, an embodiment of the present invention provides a battery cell, comprising:

[0013] case;

[0014] A connecting piece, comprising a positive connecting piece and a negative connecting piece, wherein the positive connecting piece has a positive electrode ear connecting portion, and the negative connecting piece has a negative electrode ear connecting portion;

[0015] A core package is arranged in the shell, the core package includes a winding core, the winding core includes a positive electrode sheet, a negative electrode sheet and a separator, at least one of the positive electrode sheet and the negative electrode sheet is the electrode sheet as described above, wherein the positive electrode ears of the positive electrode sheet are all bent and welded to the positive electrode ear connecting part, and the negative electrode ears of the negative electrode sheet are all bent and welded to the negative electrode ear connecting part.

[0016] In one embodiment, the number of the positive electrode lugs is set to 2n, the height of the positive electrode lug at position (2n-1) is the smallest, the height of the positive electrode lug at position 2n is the largest, and the height of the positive electrode lug at position one is less than the height of the positive electrode lug at position two, wherein n≥1, and n is an integer.

[0017] In one embodiment, the height of the 2n-position positive electrode ear is positively correlated with the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the length of the positive electrode ear welding area, and the length of the positive electrode ear bending area.

[0018] In one embodiment, the height of the 2n-position positive electrode ear is a, the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear is O, the length of the positive electrode ear welding area is L1, and the length of the positive electrode ear bending area is L2, satisfying: a=L1+L2+O.

[0019] In one embodiment, the positive electrode ear connection portion includes two spaced connection ears, and the positive electrode ears of the positive electrode sheet are bent and welded to the connection ears, wherein the length of the positive electrode ear welding area is positively correlated with the width of the weld mark and the width of the connection ear.

[0020] In one embodiment, the positive electrode ear is configured to be welded to the connecting ear through at least two rounds of welding processes, and the width of the weld mark formed on the positive electrode ear by the last round of welding process is W2, and the width of the connecting ear is W3, satisfying: L1=0.5(W2+W3)+k1, where k1 is the first preset margin.

[0021] In one embodiment, the core packs are provided in at least two numbers, and the two core packs form a core pack pair, and the positive electrode ear is welded to the corresponding connecting ear after being raised by the welding seat, wherein the length of the bending area of ​​the positive electrode ear is positively correlated with the distance between the two core packs in the core pack pair before being combined and the thickness of a single core pack, and is negatively correlated with the width of the positive electrode connecting sheet, the height of the raised welding seat, and the total thickness of all positive electrode ears welded on the same connecting ear.

[0022] In one embodiment, the distance between the two core packages before assembling is H3, the thickness of the single core package is T0, the width of the positive electrode connecting piece is W1, the height of the welding seat is H0, and the total thickness of all positive electrode ears welded on the same connecting ear is H4, satisfying:

[0023]

[0024] In one embodiment, the positive electrode ear connection portion includes two spaced connection ears, the positive electrode ears of the positive electrode sheet are bent and welded to the connection ears, the core packs are provided in at least two, and the two core packs form a core pack pair, wherein the height of the positive electrode ear at position (2n-1) is positively correlated with the sum of the lengths of the roots of the negative electrode ear of the diaphragm and the roots of the positive electrode ear of the diaphragm, the spacing between the two core packs in the core pack pair before the cores are closed, the width of the weld mark and the width of the connection ear, and is negatively correlated with the width of the positive electrode connecting sheet.

[0025] In one embodiment, the height of the (2n-1)-position positive ear is b, the spacing between the two cores before being wrapped is H3, the width of the positive electrode connecting piece is W1, the width of the weld mark is W2, the width of the connecting ear is W3, and the sum of the lengths of the roots of the negative ear of the diaphragm and the positive ear of the diaphragm is O, satisfying: b=0.5(H3-W1)+0.5(W2+W3)+O+k2, wherein k2 is the second preset margin.

[0026] In one embodiment, the distance between the two cores before being wrapped is positively correlated with the distance between the positive electrode connecting piece and the main body and the distance between the edge of the positive electrode connecting piece and the inner wall of the shell.

[0027] In one embodiment, the distance between the two cores before being wrapped is H3, the distance between the positive electrode connecting piece and the main body is D1, and the distance between the edge of the positive electrode connecting piece and the inner wall of the shell is D2, satisfying:

[0028]

[0029] In one embodiment, the shell is connected to a shell cover, wherein the distance between the positive electrode connecting piece and the main body is positively correlated with the height of the shell and the compression amount of the diaphragm, and is negatively correlated with the distance between the positive electrode connecting piece and the shell cover, the thickness of the positive electrode connecting piece, the total thickness of all positive electrode ears welded on the same connecting ear, and the distance between the diaphragm and the lower surface of the shell.

[0030] In one embodiment, the height of the shell is H10, the compression amount of the diaphragm is k3, the distance from the positive electrode connecting piece to the shell cover is H6, the thickness of the positive electrode connecting piece is H7, the total thickness of all positive electrode ears welded on the same connecting ear is H4, and the distance between the diaphragm and the lower surface of the shell is H9, satisfying: D1 = H10-H6-H7-H4-(H9-k3).

[0031] In one embodiment, the diaphragm compression amount satisfies the following range: 1.5≤k3≤2.5.

[0032] In one embodiment, the total thickness of the two core packages is W6, and the width of the shell is W5, satisfying: 0.5(W6-W1)≤D2≤0.5(W5-W1).

[0033] In one embodiment, the distance between the positive electrode connecting piece and the main body has a maximum value and a minimum value, which are D1max and D1min, respectively, and the distance between the edge of the positive electrode connecting piece and the inner side wall of the shell has a maximum value and a minimum value, which are D2max and D2min, respectively, wherein D1max=H10-H6-H7-H4-(H9-2.5), D1min=H10-H6-H7-H4-(H9-1.5), D2max=0.5(W5-W1), D2min=0.5(W6-W1), satisfying:

[0034]

[0035] In some embodiments, the number of the negative electrode ears is set to (2n+2), the height of the negative electrode ear at position (2n+1) is the smallest, the height of the negative electrode ear at position (2n+2) is the largest, the height of the negative electrode ear at position one is less than the height of the negative electrode ear at position two, wherein the height of the negative electrode ear at position (2n+2) is the same as the height of the positive electrode ear at position 2n.

[0036] In a third aspect, an embodiment of the present invention provides a battery pack, comprising the battery cell as described above.

[0037] In a fourth aspect, an embodiment of the present invention provides a pole piece design method, which is applied to the aforementioned battery cell, and the method comprises:

[0038] Based on the design parameters of the battery cell, obtaining the maximum height and the minimum height of the tab;

[0039] Along the winding direction, the heights of the pole lugs at odd positions and the heights of the pole lugs at even positions have opposite gradient trends, and the projections of all pole lugs welded to the pole lug connecting portions of the same connecting sheet in the same winding core in the first direction at least partially overlap.

[0040] In one embodiment, the design parameters of the battery cell include a first design parameter and a second design parameter, the core package is provided in at least two, and the two core packages form a core package pair, and the maximum height of the tab and the minimum height of the tab are obtained based on the design parameters of the battery cell, including:

[0041] Based on the first design parameter, obtaining a distance between the two core packages in the core package pair before being combined;

[0042] Based on the second design parameter and the distance between the two cores before being wrapped together, the maximum height of the tab and the minimum height of the tab are obtained.

[0043] In one embodiment, the pole ear connecting portion includes two spaced-apart connecting ears, and the pole ear is welded to the connecting ears after being bent, and the first design parameter includes: the height of the shell, the compression amount of the diaphragm, the distance from the connecting piece to the shell cover, the thickness of the connecting piece, the total thickness of all pole ears welded on the same connecting ear, the distance between the diaphragm and the lower surface of the shell, the total thickness of the two core packages and the width of the shell.

[0044] In one embodiment, obtaining the spacing between the two core packages in the core package pair before being combined based on the first design parameter includes:

[0045] Based on the height H10 of the shell, the compression amount k3 of the diaphragm, the distance H6 from the connecting piece to the shell cover, the thickness H7 of the connecting piece, the total thickness H4 of all the tabs welded on the same connecting tab, and the distance H9 between the diaphragm and the lower surface of the shell, the distance D1 between the connecting piece and the main body is obtained, wherein the following relationship is satisfied:

[0046] D1=H10-H6-H7-H4-(H9-k3);

[0047] Based on the total thickness W6 of the two core packages, the width W5 of the shell, and the width W1 of the connecting piece, a distance D2 between the edge of the connecting piece and the inner side wall of the shell is obtained, wherein the following relationship is satisfied:

[0048] 0.5(W6-W1)≤D2≤0.5(W5-W1);

[0049] Based on the distance D1 between the connecting piece and the main body and the distance D2 between the edge of the connecting piece and the inner wall of the shell, the distance H3 between the two cores before being wrapped together is obtained, wherein the following relationship is satisfied:

[0050]

[0051] In one embodiment, the distance between the connecting piece and the main body has a maximum value and a minimum value, which are D1max and D1min, respectively, and the distance between the edge of the connecting piece and the inner side wall of the shell has a maximum value and a minimum value, which are D2max and D2min, respectively, wherein D1max=H10-H6-H7-H4-(H9-2.5), D1min=H10-H6-H7-H4-(H9-1.5), D2max=0.5(W5-W1), D2min=0.5(W6-W1), satisfying the following relationship:

[0052]

[0053] In one embodiment, the pole ear connection portion includes two spaced-apart connecting ears, and the pole ear is welded to the connecting ears after being bent, and the second design parameters include: the sum of the lengths of the roots of the negative pole ear and the positive pole ear of the diaphragm, the width of the weld mark, the width of the connecting ear, the first preset margin, the second preset margin, the width of the connecting sheet, the thickness of a single core package, and the height of the weld seat.

[0054] In one embodiment, the obtaining of the maximum height and the minimum height of the tab based on the second design parameter and the distance between the two cores before the cores are wrapped together includes:

[0055] Based on the width W2 of the weld mark, the width W3 of the connection ear and the first preset margin k1, the length L1 of the positive electrode ear welding area is obtained, wherein the following relationship is satisfied:

[0056] L1=0.5(W2+W3)+k1;

[0057] Based on the distance H3 between the two core packages before assembling, the width W1 of the connecting sheet, the thickness T0 of a single core package, and the height H4 of the weld seat, the length L2 of the bending area of ​​the positive electrode ear is obtained, where the following relationship is satisfied:

[0058]

[0059] Based on the lengths O of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the length L1 of the positive electrode ear welding area, and the length L2 of the positive electrode ear bending area, the maximum height a of the electrode ear is obtained, wherein the following relationship is satisfied:

[0060] a=L1+L2+O.

[0061] In one embodiment, the obtaining of the maximum height and the minimum height of the tab based on the second design parameter and the distance between the two cores before the core is wrapped together further includes:

[0062] Based on the length and O of the base of the negative electrode ear of the diaphragm and the base of the positive electrode ear of the diaphragm, the spacing H3 before the two cores are wrapped together, the width W1 of the connecting piece, the width W2 of the weld mark, the width W3 of the connecting ear, and the second preset margin k2, the minimum height b of the electrode ear is obtained, wherein the following relationship is satisfied:

[0063] b=0.5(H3-W1)+0.5(W2+W3)+O+k2.

[0064] In one embodiment, along the winding direction, the height of the pole lugs at odd positions and the height of the pole lugs at even positions have an opposite gradual change trend, and the projections of all the pole lugs welded to the pole lug connecting portions of the same connecting sheet in the same winding core in the first direction at least partially overlap, including:

[0065] Along the winding direction, the heights of the tabs at odd positions are arranged to decrease, and the heights of the tabs at even positions are arranged to increase, and the projections of all tabs welded to the same connecting tab in the same winding core in the first direction at least partially overlap.

[0066] In one embodiment, along the winding direction, the heights of the tabs at odd positions are arranged to decrease, and the heights of the tabs at even positions are arranged to increase, and the projections of all tabs welded to the tab connection portions of the same connecting sheet in the same winding core in the first direction are at least partially overlapped, including:

[0067] Based on the number of the tabs, the maximum height of the tabs, and the minimum height of the tabs, obtaining a tolerance of a height variation of the tabs;

[0068] Along the winding direction, the heights of the pole ears at odd positions are set in descending order according to the value of the tolerance, and the heights of the pole ears at even positions are set in increasing order according to the value of the tolerance, so that the height of the pole ear at position one is smaller than the height of the pole ear at position two, and the projections of all the pole ears welded to the same connecting ear in the same winding core in the first direction at least partially overlap.

[0069] Beneficial effects of the embodiments of the present invention:

[0070] In an embodiment of the present invention, the winding of the main body to form a winding core allows at least two tabs to satisfy the opposite gradient trend of the height of the tabs at odd positions and the height of the tabs at even positions along the winding direction, so that the height of each tab is slightly different. When all tabs are bent and welded to the connecting sheet, the integrity of the weld mark can be ensured, and interference that causes tab tearing can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0072] Figure 1 is a schematic diagram of the structure of a pole piece provided by an embodiment of the present invention;

[0073] Figure 2 is a schematic structural diagram of a pole piece provided by an embodiment of the present invention when it is wound to form a winding core;

[0074] Figure 3 It is a schematic diagram of the structure of the electrode sheet provided by an embodiment of the present invention when it is wound to form a winding core and the electrode ear is bent and welded to the connecting sheet;

[0075] Figure 4 is a top view of a winding core provided by an embodiment of the present invention;

[0076] Figure 5 is a cross-sectional view of a battery cell provided by an embodiment of the present invention;

[0077] Figure 6 It is a schematic diagram of a partial structure before the core is wrapped together according to an embodiment of the present invention;

[0078] Figure 7 is a schematic structural diagram of a connecting piece provided by an embodiment of the present invention;

[0079] Figure 8 is a schematic flow chart of a pole piece design method provided by an embodiment of the present invention;

[0080] Fig. 9 is a flow chart of a method for obtaining the maximum height and the minimum height of a tab provided by an embodiment of the present invention;

[0081] Fig.10 It is a flow chart of a method for obtaining the distance between two cores before they are wrapped together, provided by an embodiment of the present invention;

[0082] Fig.11It is a schematic flow chart of a method for obtaining the maximum height of a tab provided in an embodiment of the present invention.

[0083] Reference numerals:

[0084] 10-pole piece, 110-main body, 120-pole ear, 130-winding starting end, 140-winding ending end, 160-close end, 20-winding core, 210-winding center plane, 30-shell, 310-shell cover, 40-connecting piece, 410-connecting ear, 50-core package. DETAILED DESCRIPTION

[0085] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the drawings; while "inside" and "outside" refer to the outline of the device.

[0086] like Figures 1 to 4 As shown, an embodiment of the present application provides a pole piece, including a main body 110 and a pole ear 120. The main body 110 is configured to be wound to form a winding core 20. The main body 110 has a winding starting end 130 and a winding ending end 140. The direction from the winding starting end 130 to the winding ending end 140 is the winding direction. The pole ears 120 are provided in at least two, and are arranged at intervals on one side of the main body 110 along the winding direction. Along the winding direction, the height of the pole ears 120 located at odd positions has an opposite gradient trend to the height of the pole ears 120 located at even positions.

[0087] In the embodiment of the present application, the winding core 20 is formed by winding the main body 110, so that at least two tabs 120 satisfy the height of the tabs 120 located at odd positions and the height of the tabs 120 located at even positions along the winding direction have an opposite gradient trend, so that the height of each tab 120 is slightly different. When all the tabs 120 are bent and welded to the connecting sheet 40, the integrity of the weld mark can be guaranteed, and interference and tearing of the tabs 120 can be avoided.

[0088] Among them, along the winding direction, the height of the tabs 120 at odd positions and the height of the tabs 120 at even positions have an opposite gradual change trend, including: the height of the tabs 120 at odd positions decreases, and the height of the tabs 120 at even positions increases. Or, the height of the tabs 120 at odd positions increases, and the height of the tabs 120 at even positions decreases.

[0089] The height of the tabs 120 located at odd positions decreases, and the height of the tabs 120 located at even positions increases, which means: for different tabs 120 at odd positions, the height of each tab 120 decreases; for different tabs 120 at even positions, the height of each tab 120 increases. Alternatively, the height of the tabs 120 located at odd positions increases, and the height of the tabs 120 located at even positions decreases, which means: for different tabs 120 at odd positions, the height of each tab 120 increases; for different tabs 120 at even positions, the height of each tab 120 decreases. In this way, it can be ensured that all tabs 120 do not interfere with each other after bending, and the integrity of the weld mark is ensured.

[0090] The height of the tab 120 refers to the distance between an end of the tab 120 away from the main body 110 and an end of the tab 120 close to the main body 110 .

[0091] In some embodiments, the number of tabs 120 can be 2n, where n≥1 and n is an integer. The 2n tabs 120 are respectively defined as the No. 1 tab, the No. 2 tab, the No. 3 tab, ..., the No. 2n tab. Among them, the No. 1 tab is arranged near the winding start end 130, and the No. 2n tab is arranged near the winding end 140. Based on the winding direction being the direction from the winding start end 130 to the winding end 140, the No. 1 tab is in the central area of ​​the winding core 20, and the No. 2n tab is in the edge area of ​​the winding core 20.

[0092] like Figure 1 As shown, in some embodiments, the heights of the tabs 120 located at odd positions decrease, and the heights of the tabs 120 located at even positions increase, wherein the height of the tab 120 at position 1 is less than the height of the tab 120 at position 2.

[0093] It is understandable that based on the above-mentioned height variation law, Figure 2 As shown, after the pole piece 10 is wound into the winding core 20, the height of the pole tabs 120 can be increased or decreased successively. When all the pole tabs 120 are bent and welded to the connecting sheet 40, the integrity of the weld mark can be ensured, and the phenomenon of the pole tabs 120 being torn due to interference can be avoided.

[0094] In some embodiments, the pole piece 10 has a winding state. The winding state corresponds to a winding center plane 210. In the winding state, the pole lugs 120 of odd positions and the pole lugs 120 of even positions are respectively located on opposite sides of the winding center plane 210, and the projections of all the pole lugs 120 in the first direction at least partially overlap. The first direction is set at an angle to the winding center plane 210.

[0095] It is understandable that the pole piece 10 can form a winding core 20 in a wound state. The formed winding core 20 is an axisymmetric structure. The winding center plane 210 passes through the symmetry axis of the winding core 20 and is the symmetry plane of the winding core 20. Figure 4 As shown in FIG. 1 , when the winding core 20 is set as a racetrack-shaped winding core, the winding center plane 210 is parallel to the length direction of the winding core 20, and the winding center plane 210 is located in the middle of the width direction of the winding core 20. Thus, the winding center plane 210 can be used to divide the winding core 20 into an upper area and a lower area. Figure 2 As shown, the tabs 120 of odd-numbered positions can be located in the lower region, and the tabs 120 of even-numbered positions can be located in the upper region. In this case, the height of the tabs 120 of odd-numbered positions decreases, and the height of the tabs 120 of even-numbered positions increases. Alternatively, the tabs 120 of odd-numbered positions can be located in the upper region, and the tabs 120 of even-numbered positions can be located in the lower region. In this case, the height of the tabs 120 of odd-numbered positions increases, and the height of the tabs 120 of even-numbered positions decreases.

[0096] The projections of all the pole tabs 120 in the first direction at least partially overlap, so that all the pole tabs 120 can be welded to the same connecting sheet 40 after being bent along the first direction. As the pole sheet 10 is gradually wound, the size of the formed winding core 20 is gradually increased. To ensure that the projections of all the pole tabs 120 in the first direction at least partially overlap, the distance between two adjacent pole tabs 120 can be gradually increased.

[0097] In some embodiments, projections of all the tabs 120 in the first direction completely overlap.

[0098] Based on the fact that the pole ears 120 are arranged on both sides of the opposite sides of the winding center plane 210, the winding core 20 can form a "double pole ear" structure. In the related art, the winding core 20 only leads out the pole ears 120 on one side of the winding center plane 210, forming a "single pole ear" structure. The "double pole ear" structure in the embodiment of the present application is completely folded and welded to a connecting piece 40. Compared with the "single pole ear" structure, the number of pole ears 120 can be doubled, the current flow area of ​​the pole ears 120 is increased, and the internal resistance and temperature rise of the battery are reduced. At the same time, combined with the height variation rules of the pole ears 120 in odd positions and the pole ears 120 in even positions, the integrity of the battery core weld mark of the "double pole ear" structure can be ensured, and interference of the pole ears 120 during ultrasonic welding can be avoided.

[0099] Take the case where the odd-numbered tabs 120 are located in the lower area, the even-numbered tabs 120 are located in the upper area, and the height of the odd-numbered tabs 120 decreases, while the height of the even-numbered tabs 120 increases. At this time, the height of the topmost tab 120 is the longest, and the height of the bottommost tab 120 is the shortest. When all the tabs 120 are bent, on the one hand, it can ensure that the topmost tab 120 has enough area for ultrasonic welding to ensure that the weld mark is complete. On the other hand, it can prevent the bottommost tab 120 from being too long and causing interference in bending and / or welding.

[0100] like Figure 2 and Figure 4 As shown, the first direction is perpendicular to the winding center plane 210. Alternatively, the first direction may also be arranged at an acute angle or an obtuse angle with the winding center plane 210. The first direction may be the thickness direction of the winding core 20.

[0101] The pole piece 10 can be wound into a cylindrical winding core, a square winding core, or a racetrack-shaped winding core. In the embodiment of the present application, the pole piece 10 is preferably wound into a racetrack-shaped winding core.

[0102] In some embodiments, in the wound state, all the tabs 120 are bent toward a connecting sheet 40 and welded to the connecting sheet 40. When the tabs 120 are in the bent state, the distance between the free end of the shortest tab 120 and the free end of the longest tab 120 is Y, satisfying: 0 mm ≤ Y ≤ 1 mm.

[0103] It is understandable that when the tab 120 is in a bent state, the free end of the shortest tab 120 and the free end of the longest tab 120 are within a range of less than or equal to 1 mm, which can ensure the integrity of the weld mark and avoid interference and tearing of the tab 120.

[0104] It should be noted that after all the tabs 120 are bent, the free end of the shortest tab 120 can be made to extend beyond the free end of the longest tab 120, and at this time, the free end of the shortest tab 120 is further away from the main body 110. Alternatively, the free end of the longest tab 120 can be made to extend beyond the free end of the longest tab 120, and at this time, the free end of the longest tab 120 is further away from the main body 110.

[0105] For example, the distance Y between the free end of the shortest tab 120 and the free end of the longest tab 120 is set to 0.2 mm, 0.5 mm, 0.8 mm, 1 mm, or any value therebetween.

[0106] In some embodiments, when the tabs 120 are in a bent state, the free ends of all the tabs 120 are flush.

[0107] It can be understood that making the free ends of all the tabs 120 flush when in the bent state so that all the tabs 120 can be aligned with the connecting sheet 40 can improve the aesthetics on the one hand and improve the welding quality on the other.

[0108] The connecting piece 40 is usually close to one side of the shorter tab 120 .

[0109] like Figure 3 As shown, in some embodiments, along the first direction, the main body 110 has a proximal end 160 proximal to the connecting piece 40. The distance between the proximal end 160 and the connecting piece 40 is X, which satisfies: 1 mm ≤ X ≤ 3 mm.

[0110] It is understandable that, based on the selection of the position of the connecting piece 40, it can be ensured that after the tabs 120 are bent, the free ends of all tabs 120 are flush. If the distance X between the proximal end 160 and the connecting piece 40 is less than 1 mm, the length of the uppermost tab 120 may be insufficient, resulting in an incomplete weld mark. If the distance X between the proximal end 160 and the connecting piece 40 is greater than 3 mm, the lowermost tab 120 may not be welded to the connecting piece 40.

[0111] For example, the distance X between the proximal end 160 and the connecting piece 40 can be set to 1 mm, 2 mm, or 3 mm, or any value therebetween.

[0112] like Figures 5 to 7 As shown, in the second aspect, an embodiment of the present invention provides a battery cell, including a shell 30, a connecting sheet 40 and a core package 50. The connecting sheet 40 includes a positive connecting sheet and a negative connecting sheet. The positive connecting sheet has a positive ear connecting portion. The negative connecting sheet has a negative ear connecting portion. The core package 50 is disposed in the shell 30. The core package 50 includes a winding core 20. The winding core 20 includes a positive electrode sheet, a negative electrode sheet and a separator. At least one of the positive electrode sheet and the negative electrode sheet is a electrode sheet 10 as in the aforementioned embodiment. Among them, the positive electrode ears of the positive electrode sheet are all bent and welded to the positive electrode connecting sheet. The negative electrode ears of the negative electrode sheet are all bent and welded to the negative electrode ear connecting portion.

[0113] In the embodiment of the present application, the winding core 20 is formed by winding the main body 110, so that at least two tabs 120 satisfy the height of the tabs 120 located at odd positions and the height of the tabs 120 located at even positions along the winding direction have an opposite gradient trend, so that the height of each tab 120 is slightly different. When all the tabs 120 are bent and welded to the connecting sheet 40, the integrity of the weld mark can be guaranteed, and interference and tearing of the tabs 120 can be avoided.

[0114] Among them, two core packages 50 can be arranged in each shell 30, and the two core packages 50 can form a core package pair. Then the two core packages 50 are directly arranged in the shell 30 after the cores are combined. Alternatively, at least two core package pairs can be arranged in each shell 30, and then every two corresponding core packages 50 are combined into a core package pair and then respectively arranged in the shell 30. In the embodiment of the present application, it is preferred to arrange a core package pair in a shell 30. For the same core package pair, the two core packages 50 are folded in the direction close to each other to complete the core combination. That is: the tabs 120 of the two winding cores 20 are bent in the direction close to each other.

[0115] The connecting piece 40 is used as a current collector and is welded to all corresponding pole tabs 120. Specifically, the connecting piece 40 includes a positive pole connecting piece and a negative pole connecting piece. The positive pole tab connecting portion of the positive pole connecting piece is used to weld the positive pole tab, and the negative pole tab connecting portion of the negative pole connecting piece is used to weld the negative pole tab. The positive pole connecting piece and the negative pole connecting piece can be welded to the same shell cover 310 to achieve electrical connection between the two. Among them, the pole tab 120 is usually welded to the connecting piece 40 by ultrasonic welding.

[0116] In some embodiments, the positive electrode tab connection portion of the positive electrode tab includes two spaced connection tabs 410. The positive electrode tabs of the positive electrode tab are all bent and welded to the connection tabs 410.

[0117] In some embodiments, the positive electrode connecting tab and the negative electrode connecting tab have the same structure.

[0118] like Figures 1 to 3 As shown, in some embodiments, the number of positive electrode ears is set to 2n. The height of the positive electrode ear at position (2n-1) is the smallest. The height of the positive electrode ear at position 2n is the largest. And the height of the positive electrode ear at position 1 is less than the height of the positive electrode ear at position 2. Wherein, n≥1, and n is an integer.

[0119] It can be understood that, based on setting the tabs 120 to an even number, and making the height of the positive tab at position (2n-1) the smallest, the height of the positive tab at position 2n the largest, and the height of the positive tab at position 1 less than the height of the positive tab at position 2, when the positive electrode sheet is wound into a winding core 20, the height of the positive tabs can be increased or decreased in sequence. When all the positive tabs are bent and welded to the positive electrode connecting sheet, the integrity of the weld mark can be ensured, and interference and tearing of the positive tabs can be avoided.

[0120] The height of the positive electrode lug may vary in an isotropic manner, that is, the heights of all positive electrode lugs are distributed in an equidistant manner. Based on the height difference between the positive electrode lug at position (2n-1) and the positive electrode lug at position 2n, and combined with the number of all positive electrode lugs, the height tolerance of the positive electrode lug may be calculated to calculate the height of all positive electrode lugs.

[0121] In some embodiments, the height of the 2n-position positive electrode ear is positively correlated with the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the length of the positive electrode ear welding area, and the length of the positive electrode ear bending area.

[0122] It can be understood that the height of the positive electrode ear at position 2n increases with the increase of the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the length of the positive electrode ear welding area, and the length of the positive electrode ear bending area, and decreases with the decrease of the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the length of the positive electrode ear welding area, and the length of the positive electrode ear bending area. The positive correlation may be a linear relationship, an exponential relationship, or the like.

[0123] Based on the design of the above three parameters, the maximum height of the positive electrode ear can be directly calculated, which is convenient for the processing and forming of the positive electrode ear.

[0124] In some embodiments, the height of the positive electrode ear at position 2n is a. The sum of the lengths of the base of the negative electrode ear of the separator and the base of the positive electrode ear of the separator is O. The length of the positive electrode ear welding area is L1. The length of the positive electrode ear bending area is L2. Satisfies: a=L1+L2+O.

[0125] It can be understood that the height of the positive electrode ear at position 2n is linearly related to the sum of the lengths of the roots of the negative electrode ear and the positive electrode ear of the diaphragm, the length of the positive electrode ear welding area, and the length of the positive electrode ear bending area. Based on the above relationship, the height of the positive electrode ear at position 2n can be quickly calculated.

[0126] Among them, the length of the base of the negative ear of the diaphragm is O1, and the length of the base of the positive ear of the diaphragm is O2. Satisfies: O=O1+O2. The length of the base of the negative ear of the diaphragm and the length of the base of the positive ear of the diaphragm are the design parameters of the battery cell. Based on the model of the battery cell, the length of the base of the negative ear of the diaphragm and the length of the base of the positive ear of the diaphragm can be directly obtained, thereby obtaining the sum of the length of the base of the negative ear of the diaphragm and the base of the positive ear of the diaphragm.

[0127] In some embodiments, the length of the positive tab welding area is positively correlated with the width of the weld mark and the width of the connecting tab 410 .

[0128] It is understandable that the length of the positive electrode ear welding area increases with the increase of the width of the weld mark and the width of the connecting ear 410, and decreases with the decrease of the width of the weld mark and the width of the connecting ear 410. The positive correlation may be a linear relationship, an exponential relationship, or the like.

[0129] In some embodiments, the positive electrode tab is configured to be welded to the connecting tab 410 by at least two welding processes. The width of the weld mark formed on the positive electrode tab by the last welding process is W2. The width of the connecting tab 410 is W3. It satisfies: L1 = 0.5 (W2 + W3) + k1. Where k1 is the first preset margin.

[0130] It is understandable that if there are a large number of positive tabs, at least two rounds of welding processes are required to weld all the tabs 120 to the corresponding connecting tabs 410. The last round of welding process can form a weld mark with a width of W2 on the topmost positive tab. The length of the positive tab welding area is calculated by combining the width of the weld mark with the width of the connecting tab 410.

[0131] The width of the weld mark and the width of the connecting ear 410 are design parameters of the battery cell. Based on the model of the battery cell, the width of the weld mark and the width of the connecting ear 410 can be directly obtained, thereby obtaining the length of the positive electrode ear welding area.

[0132] In some embodiments, the following is satisfied: 1≤k1≤2. For example, the first preset margin k1 is set to 1, 1.5, 2, or any value therebetween.

[0133] In some embodiments, the positive electrode tab is welded to the corresponding connecting tab 410 after being raised by the welding seat. The length of the bending area of ​​the positive electrode tab is positively correlated with the distance between the two core packages 50 before being combined and the thickness of a single core package 50, and negatively correlated with the width of the positive electrode connecting sheet, the height of the welding seat, and the total thickness of all positive electrode tabs welded on the same connecting tab 410.

[0134] It can be understood that, in order to facilitate the welding of the positive electrode ear, after the height of the positive electrode ear is raised by the welding seat, the positive electrode ear is bent toward the connecting ear 410 and ultrasonically welded. Based on the above relationship, the length of the bending area of ​​the positive electrode ear increases with the increase of the distance between the two core packages 50 before the core is closed and the thickness of a single core package 50, decreases with the decrease of the distance between the two core packages 50 before the core is closed and the thickness of a single core package 50, decreases with the increase of the width of the positive electrode connecting piece, the height of the welding seat, and the total thickness of all positive electrode ears welded on the same connecting ear 410, and increases with the decrease of the width of the positive electrode connecting piece, the height of the welding seat, and the total thickness of all positive electrode ears welded on the same connecting ear 410. Among them, the positive correlation and negative correlation can be a linear relationship, an exponential relationship, etc.

[0135] In some embodiments, the distance between two core packs 50 before being joined is H3. The thickness of a single core pack 50 is T0. The width of the positive electrode connecting sheet is W1. The height of the welding seat is H0. The total thickness of all positive electrode ears welded on the same connecting ear 410 is H4. Satisfy:

[0136]

[0137] It is understandable that after all the positive electrode ears are bent so that the free ends are aligned and welded to the positive electrode connecting sheet, the bent area of ​​the positive electrode ears is usually an inclined surface. Figure 5As shown, before the core package 50 is assembled on the shell 30, one end of the positive electrode ear bending area is connected to the core package 50, and the other end is connected to the positive electrode connecting piece, so that the inclined surface and the surface of the core package 50 and the line from the positive electrode connecting piece to the core package 50 enclose a right triangle. The length of one of the right-angled sides can be obtained by using the difference between the spacing before the core package 50 is closed and the width of the positive electrode connecting piece, and the length of the other right-angled side can be obtained by using the difference between the thickness of a single core package 50 and the height of the welding seat, and the total thickness of all positive electrodes welded on the same connecting ear 410. Thus, the length of the inclined surface is obtained, thereby reflecting the length of the positive electrode ear bending area.

[0138] Among them, the thickness of a single core pack 50, the width of the positive electrode connecting piece, and the height of the welding seat are all design parameters. Based on the model of the battery cell, the thickness of a single core pack 50, the width of the positive electrode connecting piece, and the height of the welding seat can be directly obtained, and combined with the distance between the two core packs 50 before the core is closed, the length of the positive ear bending area can be obtained.

[0139] In some embodiments, the height of the positive electrode ear at position (2n-1) is positively correlated with the sum of the lengths of the roots of the negative electrode ear and the positive electrode ear of the diaphragm, the spacing before the two core packages 50 are combined, the width of the weld mark and the width of the connecting ear 410, and is negatively correlated with the width of the positive electrode connecting piece.

[0140] It can be understood that the height of the positive electrode ear at position (2n-1) increases with the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the spacing before the two core packs 50 are closed, the width of the weld mark, and the width of the connecting ear 410, decreases with the decrease of the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the spacing before the two core packs 50 are closed, the width of the weld mark, and the width of the connecting ear 410, decreases with the increase of the width of the positive electrode connecting sheet, and increases with the decrease of the width of the positive electrode connecting sheet. The positive correlation and negative correlation may be a linear relationship, an exponential relationship, etc.

[0141] Based on the design of the above four parameters, the minimum height of the positive electrode ear can be directly calculated, which is convenient for the processing and forming of the positive electrode ear.

[0142] like Figure 5 and Figure 6 As shown, in some embodiments, the height of the positive ear at position (2n-1) is b. The distance between the two core packages 50 before closing the core is H3. The width of the positive electrode connecting piece is W1. The width of the weld mark is W2. The width of the connecting ear 410 is W3. The sum of the lengths of the base of the negative electrode ear of the diaphragm and the base of the positive electrode ear of the diaphragm is O. Satisfies: b = 0.5 (H3-W1) + 0.5 (W2 + W3) + O + k2. Wherein, k2 is the second preset margin.

[0143] It can be understood that the height of the positive electrode ear at position (2n-1) is linearly related to the sum of the lengths of the roots of the negative electrode ear and the positive electrode ear of the diaphragm, the spacing between the two core packages 50 before they are combined, the width of the weld mark, the width of the connecting ear 410, and the width of the positive electrode connecting piece. Based on the above relationship, the height of the positive electrode ear at position (2n-1) can be quickly calculated.

[0144] The length and the root of the negative electrode ear of the diaphragm and the root of the positive electrode ear of the diaphragm, the width of the weld mark, the width of the connecting ear 410, and the width of the positive electrode connecting piece are all design parameters of the battery cell. Based on the model of the battery cell, the length and the root of the negative electrode ear of the diaphragm and the root of the positive electrode ear of the diaphragm, the width of the weld mark, the width of the connecting ear 410, and the width of the positive electrode connecting piece can be directly obtained, thereby obtaining the height of the positive electrode ear at position (2n-1).

[0145] In some embodiments, the following is satisfied: 1≤k2≤2. For example, the second preset margin k2 is set to 1, 1.5, 2, or any value therebetween.

[0146] In some embodiments, the distance between the two core packages 50 before being combined is positively correlated with the distance between the positive electrode connecting piece and the main body 110 and the distance between the edge of the positive electrode connecting piece and the inner wall of the shell 30 .

[0147] It can be understood that the distance between the two core packages 50 before being closed increases with the increase of the distance between the positive electrode connecting piece and the main body 110 and the distance between the edge of the positive electrode connecting piece and the inner side wall of the shell 30, and decreases with the decrease of the distance between the positive electrode connecting piece and the main body 110 and the distance between the edge of the positive electrode connecting piece and the inner side wall of the shell 30. The positive correlation may be a linear relationship or an exponential relationship.

[0148] In some embodiments, the distance between the two core packs 50 before being closed is H3. The distance between the positive electrode connecting piece and the main body 110 is D1. The distance between the edge of the positive electrode connecting piece and the inner wall of the shell 30 is D2. Satisfy:

[0149]

[0150] It is understandable that the distance between the two core packages 50 before being closed can be directly obtained based on the design parameters of the battery cell based on the above formula. After obtaining the distance between the two core packages 50 before being closed, the maximum height and minimum height of the positive electrode ear can be obtained based on the above formula.

[0151] The distance between the positive electrode connecting piece and the main body 110 refers to the distance between the positive electrode connecting piece and the main body 110 when the two core packs 50 are in the core-closed state. The distance between the edge of the positive electrode connecting piece and the inner side wall of the shell 30 refers to the distance between the end of the positive electrode connecting piece close to the inner side wall of the shell 30 and the inner side wall of the shell 30 after the two core packs 50 are in the core-closed state and installed in the shell 30.

[0152] In some embodiments, the housing 30 is connected to a housing cover 310. The spacing between the positive electrode connecting piece and the main body 110 is positively correlated with the height of the housing 30 and the compression amount of the diaphragm, and negatively correlated with the spacing between the positive electrode connecting piece and the housing cover 310, the thickness of the positive electrode connecting piece, the total thickness of all positive electrode ears welded on the same connecting ear 410, and the spacing between the diaphragm and the lower surface of the housing 30.

[0153] It can be understood that the distance between the positive electrode connecting piece and the main body 110 increases with the increase of the height of the shell 30 and the compression of the diaphragm, decreases with the decrease of the height of the shell 30 and the compression of the diaphragm, decreases with the increase of the distance between the positive electrode connecting piece and the shell cover 310, the thickness of the positive electrode connecting piece, the total thickness of all positive ears welded on the same connecting ear 410, and the distance between the diaphragm and the lower surface of the shell 30, and increases with the decrease of the distance between the positive electrode connecting piece and the shell cover 310, the thickness of the positive electrode connecting piece, the total thickness of all positive ears welded on the same connecting ear 410, and the distance between the diaphragm and the lower surface of the shell 30.

[0154] In some embodiments, the height of the housing 30 is H10. The compression amount of the diaphragm is k3. The distance between the positive electrode connecting piece and the housing cover 310 is H6. The thickness of the positive electrode connecting piece is H7. The total thickness of all positive electrode ears welded to the same connecting ear 410 is H4. The distance between the diaphragm and the lower surface of the housing 30 is H9. Satisfies: D1 = H10-H6-H7-H4-(H9-k3).

[0155] Among them, the height of the shell 30, the compression of the diaphragm, the distance from the positive electrode connecting piece to the shell cover 310, the thickness of the positive electrode connecting piece, the total thickness of all positive electrodes welded on the same connecting ear 410, and the distance between the diaphragm and the lower surface of the shell 30 are all design parameters. Based on the model of the battery cell, the height of the shell 30, the compression of the diaphragm, the distance from the positive electrode connecting piece to the shell cover 310, the thickness of the positive electrode connecting piece, the total thickness of all positive electrodes welded on the same connecting ear 410, and the distance between the diaphragm and the lower surface of the shell 30 can be directly obtained, so as to calculate the distance between the positive electrode connecting piece and the main body 110 based on the above formula.

[0156] In some embodiments, the diaphragm compression amount satisfies the following range: 1.5≤k3≤2.5.

[0157] For example, the diaphragm compression amount k3 can be set to 1.5, 2, 2.5, or any value therebetween. The value of the diaphragm compression amount k3 can be selected based on production experience and in combination with the model of the battery cell.

[0158] In some embodiments, the total thickness of the two core packs 50 is W6. The width of the housing 30 is W5. The following conditions are satisfied: 0.5(W6-W1)≤D2≤0.5(W5-W1).

[0159] It can be understood that when the two core packs 50 are combined and assembled in the shell 30, if the edge of the core pack 50 is in contact with the inner surface of the shell 30, the distance between the edge of the positive electrode connecting sheet and the inner wall of the shell 30 is exactly equal to half of the difference between the total thickness of the two core packs 50 and the width of the positive electrode connecting sheet; if the edge of the core pack 50 is spaced from the inner surface of the shell 30, the distance between the edge of the positive electrode connecting sheet and the inner wall of the shell 30 can be equal to half of the difference between the width of the shell 30 and the width of the positive electrode connecting sheet. Therefore, based on this relationship, the distance range between the edge of the positive electrode connecting sheet and the inner wall of the shell 30 can be defined, and any value can be taken within the distance range.

[0160] In some embodiments, the distance between the positive electrode connecting piece and the main body 110 has a maximum value and a minimum value, which are D1max and D1min, respectively. The distance between the edge of the positive electrode connecting piece and the inner wall of the shell 30 has a maximum value and a minimum value, which are D2max and D2min, respectively. Wherein, D1max=H10-H6-H7-H4-(H9-2.5), D1min=H10-H6-H7-H4-(H9-1.5), D2max=0.5(W5-W1), D2min=0.5(W6-W1). Satisfy:

[0161]

[0162] It is understandable that the value of the diaphragm compression amount k3 and the distance range between the edge of the positive electrode connecting piece and the inner wall of the shell 30 will affect the distance between the two core packages 50 before they are joined. Therefore, the distance range between the two core packages 50 before they are joined can be calculated first, and a reasonable value can be selected within the distance range to ensure that the two core packages 50 meet the requirements for joining, and the core packages 50 after joining can be assembled in the shell 30 and taken out from the shell 30.

[0163] Here, H3 cannot be equal to the minimum value calculated using D1min and D2min, so as to prevent the core package 50 from being completely attached to the inner surface of the shell 30 and thus making it impossible to remove the core package 50 .

[0164] In some embodiments, the number of negative electrode ears is set to (2n+2). The height of the negative electrode ear at position (2n+1) is the smallest. The height of the negative electrode ear at position (2n+2) is the largest. The height of the negative electrode ear at position 1 is less than the height of the negative electrode ear at position 2. Among them, the height of the negative electrode ear at position (2n+2) is the same as the height of the positive electrode ear at position 2n.

[0165] It is understandable that, in order to make each negative electrode ear satisfy the above relationship, after the negative electrode sheet is wound into the winding core 20, the height of the negative electrode ear can be increased or decreased in sequence. When all the negative electrode ears are bent and welded to the negative electrode connecting sheet, the integrity of the weld mark can be guaranteed, and interference and tearing of the negative electrode ear can be avoided. The number of negative electrode ears is two more than the number of positive electrode ears, so that the height of the negative electrode ear at position (2n+2) is the same as the height of the positive electrode ear at position 2n, then there is no need to repeatedly calculate the maximum height of the negative electrode ear, which is convenient for the rapid manufacture of the negative electrode ear.

[0166] In some embodiments, the height of the negative electrode lug at position (2n+1) can be made equal to the height of the positive electrode lug at position (2n-1). In this case, the minimum height calculated in the positive electrode lug can be directly used as the minimum height of the negative electrode lug. Based on the minimum height and maximum height of the negative electrode lug and the number of negative electrode lugs, the height tolerance can be calculated, and then the length of all negative electrode lugs can be calculated based on the tolerance.

[0167] In some embodiments, the height of the negative electrode lug at position (2n-1) can be made equal to the height of the positive electrode lug at position (2n-1). In this case, the minimum height calculated in the positive electrode lug can be directly used as the height of the negative electrode lug at position (2n-1). Based on the negative electrode lug at position (2n-1), the maximum height of the negative electrode lug, and the number of negative electrode lugs, the height tolerance can be calculated, and then the length of all negative electrode lugs can be inferred based on the tolerance.

[0168] In a third aspect, an embodiment of the present invention provides a battery pack, comprising the battery cell as described above.

[0169] In the embodiment of the present application, the winding core 20 is formed by winding the main body 110, so that at least two tabs 120 satisfy the height of the tabs 120 located at odd positions and the height of the tabs 120 located at even positions along the winding direction have an opposite gradient trend, so that the height of each tab 120 is slightly different. When all the tabs 120 are bent and welded to the connecting sheet 40, the integrity of the weld mark can be guaranteed, and interference and tearing of the tabs 120 can be avoided.

[0170] like Figure 8 As shown, in a fourth aspect, an embodiment of the present invention provides a pole piece 10 design method, which is applied to the aforementioned battery cell, and the method includes:

[0171] S810 . Obtain a maximum height of the tab 120 and a minimum height of the tab 120 based on design parameters of the battery cell.

[0172] S820, along the winding direction, the heights of the pole tabs 120 at odd positions and the heights of the pole tabs 120 at even positions have opposite gradient trends, and the projections of all the pole tabs 120 on the pole tab connecting portions welded to the same connecting sheet 40 in the same winding core 20 in the first direction at least partially overlap.

[0173] Based on the above height variation rule, when the pole piece 10 is wound into the winding core 20, the height of the pole tab 120 can be increased or decreased successively. When all the pole tabs 120 are bent and welded to the connecting sheet 40, the integrity of the weld mark can be ensured, and the phenomenon of the pole tab 120 tearing due to interference can be avoided.

[0174] The pole piece 10 can form a winding core 20 in a wound state. The formed winding core 20 is an axisymmetric structure. The winding center plane 210 passes through the symmetry axis of the winding core 20. Therefore, the winding core 20 can be divided into an upper area and a lower area by using the winding center plane 210. Figure 2 As shown, the tabs 120 of odd-numbered positions can be located in the lower region, and the tabs 120 of even-numbered positions can be located in the upper region. In this case, the height of the tabs 120 of odd-numbered positions decreases, and the height of the tabs 120 of even-numbered positions increases. Alternatively, the tabs 120 of odd-numbered positions can be located in the upper region, and the tabs 120 of even-numbered positions can be located in the lower region. In this case, the height of the tabs 120 of odd-numbered positions increases, and the height of the tabs 120 of even-numbered positions decreases.

[0175] Among them, the projections of all the pole tabs 120 welded to the pole tab connection portion of the same connecting sheet 40 in the same winding core 20 in the first direction at least partially overlap, so that all the pole tabs 120 can be welded to the same connecting sheet 40 after being bent along the first direction. As the pole sheet 10 is gradually wound, the size of the formed winding core 20 is gradually increased. In order to ensure that the projections of all the pole tabs 120 welded to the pole tab connection portion of the same connecting sheet 40 in the first direction at least partially overlap, the distance between two adjacent pole tabs 120 can be gradually increased.

[0176] In some embodiments, projections of all the tabs 120 welded to the tab connecting portions of the same connecting sheet 40 in the first direction completely overlap.

[0177] Since the pole lugs 120 are arranged on both sides of the opposite sides of the winding center plane 210, the winding core 20 can form a "double pole lug" structure. In the related art, the pole lug 120 is only led out on one side of the winding center plane 210, which is a "single pole lug" structure. The "double pole lug" structure in the embodiment of the present application is completely folded and welded to a connecting piece 40, which can double the number of pole lugs 120, increase the flow area of ​​the pole lugs 120, and reduce the internal resistance and temperature rise of the battery. And combined with the height variation rules of the pole lugs 120 in odd positions and the pole lugs 120 in even positions, the integrity of the "double pole lug" battery core welding mark can be ensured, and interference during the welding of the pole lugs 120 can be avoided.

[0178] Among them, along the winding direction, the height of the tabs 120 at odd positions and the height of the tabs 120 at even positions have an opposite gradual change trend, including: the height of the tabs 120 at odd positions decreases, and the height of the tabs 120 at even positions increases. Or, the height of the tabs 120 at odd positions increases, and the height of the tabs 120 at even positions decreases.

[0179] The height of the tabs 120 located at odd positions decreases, while the height of the tabs 120 located at even positions increases, which means: for different tabs 120 at odd positions, the height of each tab 120 decreases; for different tabs 120 at even positions, the height of each tab 120 increases. Alternatively, the height of the tabs 120 located at odd positions increases, while the height of the tabs 120 located at even positions decreases, which means: for different tabs 120 at odd positions, the height of each tab 120 increases; for different tabs 120 at even positions, the height of each tab 120 decreases. In this way, it is ensured that all tabs 120 welded to the tab connection portion of the same connecting sheet 40 do not interfere with each other after bending, and the integrity of the weld mark is ensured.

[0180] The height of the tab 120 refers to the distance from one end of the tab 120 away from the main body 110 to the main body 110 .

[0181] Take the case where the odd-numbered tabs 120 are located in the lower area, the even-numbered tabs 120 are located in the upper area, and the height of the odd-numbered tabs 120 decreases, while the height of the even-numbered tabs 120 increases. At this time, the height of the topmost tab 120 is the longest, and the height of the bottommost tab 120 is the shortest. When all the tabs 120 welded to the same connecting tab 410 are bent, on the one hand, it can ensure that the topmost tab 120 has enough area for ultrasonic welding to ensure that the weld mark is complete. On the other hand, it can prevent the bottommost tab 120 from being too long and causing interference in bending and / or welding.

[0182] like Fig. 9As shown, in some embodiments, the design parameters of the battery cell include a first design parameter and a second design parameter. The core package 50 is provided in at least two numbers, and the two core packages 50 form a core package pair. Based on the design parameters of the battery cell, the maximum height of the tab 120 and the minimum height of the tab 120 are obtained, including:

[0183] S910. Based on the first design parameter, obtain the distance between the two core packages 50 before they are combined.

[0184] S920 , based on the second design parameter and the distance between the two core packages 50 before being combined, obtain the maximum height of the tab 120 and the minimum height of the tab 120 .

[0185] It can be understood that the first design parameter of the battery cell is used to calculate the distance between the two core packages 50 before the cores are assembled, and then the second design parameter of the battery cell and the distance between the two core packages 50 before the cores are assembled are used to calculate the maximum height and the minimum height of the tab 120. Thus, the maximum height and the minimum height of the tab 120 in the pole piece 10 are determined.

[0186] In some embodiments, the tab connection portion includes two spaced connection tabs 410, and the tab 120 is bent and welded to the connection tab 410. The first design parameters include: the height of the shell 30, the compression amount of the diaphragm, the distance between the connecting piece 40 and the shell cover 310, the thickness of the connecting piece 40, the total thickness of all tabs 120 welded on the same connection tab 410, the distance between the diaphragm and the lower surface of the shell 30, the total thickness of the two core packs 50, and the width of the shell 30.

[0187] It is understandable that the above parameters are all known fixed values ​​based on the model of the battery cell. Therefore, the distance between the two core packages 50 before closing the cores can be quickly calculated based on the above parameters.

[0188] like Fig.10 As shown, in some embodiments, based on the first design parameter, obtaining the distance between the two core packages 50 before the cores are closed includes:

[0189] S1010, based on the height H10 of the housing 30, the compression amount k3 of the diaphragm, the distance H6 from the connecting piece 40 to the housing cover 310, the thickness H7 of the connecting piece 40, the total thickness H4 of all the tabs 120 welded on the same connecting ear 410, and the distance H9 between the diaphragm and the lower surface of the housing 30, obtain the distance D1 between the connecting piece 40 and the main body 110, wherein the following relationship is satisfied:

[0190] D1=H10-H6-H7-H4-(H9-k3).

[0191] Based on the model of the battery cell, the height of the shell 30, the compression amount of the diaphragm, the distance from the connecting piece 40 to the shell cover 310, the thickness of the connecting piece 40, the total thickness of all the pole ears 120 welded on the same connecting ear 410, and the distance between the diaphragm and the lower surface of the shell 30 can be directly obtained, so as to calculate the distance between the connecting piece 40 and the main body 110 based on the above formula.

[0192] In some embodiments, the diaphragm compression amount satisfies the following range: 1.5≤k3≤2.5.

[0193] For example, the diaphragm compression amount k3 can be set to 1.5, 2, 2.5, or any value therebetween. The value of the diaphragm compression amount k3 can be selected based on production experience and in combination with the model of the battery cell.

[0194] S1020, based on the total thickness W6 of the two core packages 50, the width W5 of the shell 30, and the width W1 of the connecting sheet 40, obtain a distance D2 between the edge of the connecting sheet 40 and the inner side wall of the shell 30, wherein the following relationship is satisfied:

[0195] 0.5(W6-W1)≤D2≤0.5(W5-W1).

[0196] It can be understood that after the two core packages 50 are combined and assembled in the shell 30, if the edge of the core package 50 is in contact with the inner surface of the shell 30, the distance between the edge of the connecting sheet 40 and the inner side wall of the shell 30 is exactly equal to half of the difference between the total thickness of the two core packages 50 and the width of the connecting sheet 40; if the edge of the core package 50 is spaced from the inner surface of the shell 30, the distance between the edge of the connecting sheet 40 and the inner side wall of the shell 30 can be equal to half of the difference between the width of the shell 30 and the width of the connecting sheet 40. Therefore, the distance range between the edge of the connecting sheet 40 and the inner side wall of the shell 30 can be defined based on this relationship, and any value can be taken within the distance range.

[0197] S1030, based on the distance D1 between the connecting piece 40 and the main body 110 and the distance D2 between the edge of the connecting piece 40 and the inner wall of the shell 30, obtain the distance H3 between the two core packages 50 before they are combined, wherein the following relationship is satisfied:

[0198]

[0199] It is understandable that the distance between the two core packages 50 before being combined can be directly obtained based on the design parameters of the battery cell based on the above formula. After obtaining the distance between the two core packages 50 before being combined, the maximum height and minimum height of the tab 120 can be obtained based on the above formula.

[0200] The distance between the connecting piece 40 and the main body 110 refers to the distance between the connecting piece 40 and the main body 110 when the two core packages 50 are in the core-closed state. The distance between the edge of the connecting piece 40 and the inner wall of the shell 30 refers to the distance between the end of the connecting piece 40 close to the inner wall of the shell 30 and the inner wall of the shell 30 after the two core packages 50 are in the core-closed state and installed in the shell 30.

[0201] In some embodiments, the distance between the connecting piece 40 and the main body 110 has a maximum value and a minimum value, which are D1max and D1min, respectively. The distance between the edge of the connecting piece 40 and the inner wall of the shell 30 has a maximum value and a minimum value, which are D2max and D2min, respectively. Wherein, D1max=H10-H6-H7-H4-(H9-2.5), D1min=H10-H6-H7-H4-(H9-1.5), D2max=0.5(W5-W1), D2min=0.5(W6-W1), satisfying the following relationship:

[0202]

[0203] It is understandable that the value of the diaphragm compression amount k3 and the distance range between the edge of the connecting piece 40 and the inner wall of the shell 30 will affect the distance between the two core packages 50 before they are joined. Therefore, the distance range between the two core packages 50 before they are joined can be calculated first, and a reasonable value can be selected within the distance range to ensure that the two core packages 50 meet the requirements of joining the cores, and the core packages 50 after joining the cores can be assembled in the shell 30 and can be taken out of the shell 30.

[0204] Here, H3 cannot be equal to the minimum value calculated using D1min and D2min, so as to prevent the core package 50 from being completely attached to the inner surface of the shell 30 and thus making it impossible to remove the core package 50 .

[0205] In some embodiments, the second design parameters include: the sum of the lengths of the roots of the negative electrode ears and the positive electrode ears of the diaphragm, the width of the weld mark, the width of the connecting ear 410, the first preset margin, the second preset margin, the width of the connecting piece 40, the thickness of a single core package 50, and the height of the weld seat elevation.

[0206] It is understandable that the above parameters are all known fixed values ​​based on the model of the battery cell. Therefore, the maximum height of the tab 120 and the minimum height of the tab 120 can be quickly calculated based on the above parameters.

[0207] like Fig.11 As shown, in some embodiments, based on the second design parameter and the distance between the two core packages 50 before the core is closed, the maximum height of the tab 120 and the minimum height of the tab 120 are obtained, including:

[0208] S1110, based on the width W2 of the weld mark, the width W3 of the connecting ear 410 and the first preset margin k1, the length L1 of the positive electrode ear welding area is obtained, wherein the following relationship is satisfied:

[0209] L1 = 0.5 (W2 + W3) + k1.

[0210] The width W2 of the weld mark is the width of the weld mark formed on the pole tab 120 by the last round of welding process. It is understandable that if there are a large number of pole tabs 120, all the pole tabs 120 need to be welded to the corresponding connecting tabs 410 by at least two rounds of welding process. The last round of welding process can form a weld mark with a width of W2 on the topmost pole tab 120. The length of the positive pole tab welding area is calculated by combining the width of the weld mark with the width of the connecting tab 410.

[0211] In some embodiments, the following is satisfied: 1≤k1≤2. For example, the first preset margin k1 is set to 1, 1.5, 2, or any value therebetween.

[0212] S1120, based on the distance H3 between the two core packages 50 before merging, the width W1 of the connecting sheet 40, the thickness T0 of a single core package 50, and the height H4 of the welding seat, the length L2 of the bending area of ​​the positive electrode ear is obtained, wherein the following relationship is satisfied:

[0213]

[0214] It is understandable that after all the tabs 120 welded to the same connecting tab 410 are bent so that the free ends are aligned and welded to the connecting sheet 40, the bent area of ​​the positive tab is usually an inclined surface. Figure 5 As shown, before the core package 50 is assembled on the shell 30, one end of the positive electrode ear bending area is connected to the core package 50, and the other end is connected to the connecting piece 40, so that the inclined surface and the surface of the core package 50 and the connecting piece 40 to the core package 50 enclose a right triangle. The length of one of the right-angled sides can be obtained by using the difference between the spacing before the core package 50 is closed and the width of the connecting piece 40, and the length of the other right-angled side can be obtained by using the difference between the thickness of a single core package 50 and the height of the welding seat, and the total thickness of all the pole ears 120 welded on the same connecting ear 410. In this way, the length of the inclined surface is obtained, thereby reflecting the length of the positive electrode ear bending area.

[0215] S1130, based on the lengths O of the base of the negative electrode ear of the diaphragm and the base of the positive electrode ear of the diaphragm, the length L1 of the positive electrode ear welding area, and the length L2 of the positive electrode ear bending area, obtain the maximum height a of the electrode ear 120, wherein the following relationship is satisfied:

[0216] a=L1+L2+O.

[0217] Among them, the length of the base of the negative ear of the diaphragm is O1, and the length of the base of the positive ear of the diaphragm is O2. Satisfies: O=O1+O2. The length of the base of the negative ear of the diaphragm and the length of the base of the positive ear of the diaphragm are the design parameters of the battery cell. Based on the model of the battery cell, the length of the base of the negative ear of the diaphragm and the length of the base of the positive ear of the diaphragm can be directly obtained, thereby obtaining the sum of the length of the base of the negative ear of the diaphragm and the base of the positive ear of the diaphragm.

[0218] In some embodiments, based on the second design parameter and the distance between the two core packages 50 before the core is closed, obtaining the maximum height of the tab 120 and the minimum height of the tab 120 further includes:

[0219] Based on the lengths O of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the spacing H3 before the two core packs 50 are combined, the width W1 of the connecting piece 40, the width W2 of the weld mark, the width W3 of the connecting ear 410, and the second preset margin k2, the minimum height b of the electrode ear 120 is obtained, wherein the following relationship is satisfied:

[0220] b=0.5(H3-W1)+0.5(W2+W3)+O+k2.

[0221] It can be understood that the height of the positive electrode ear at position (2n-1) is linearly related to the sum of the lengths of the roots of the negative electrode ear and the positive electrode ear of the diaphragm, the spacing between the two core packages 50 before they are combined, the width of the weld mark, the width of the connecting ear 410, and the width of the connecting sheet 40. Based on the above relationship, the height of the positive electrode ear at position (2n-1) can be quickly calculated.

[0222] The length and the root of the negative electrode ear of the diaphragm and the root of the positive electrode ear of the diaphragm, the width of the weld mark, the width of the connecting ear 410, and the width of the connecting piece 40 are all design parameters of the battery cell. Based on the model of the battery cell, the length and the root of the negative electrode ear of the diaphragm and the root of the positive electrode ear of the diaphragm, the width of the weld mark, the width of the connecting ear 410, and the width of the connecting piece 40 can be directly obtained, thereby obtaining the height of the positive electrode ear at position (2n-1).

[0223] In some embodiments, the following is satisfied: 1≤k2≤2. For example, the second preset margin k2 is set to 1, 1.5, 2, or any value therebetween.

[0224] In some embodiments, along the winding direction, the height of the tabs 120 at odd positions and the height of the tabs 120 at even positions have an opposite gradient trend, and the projections of all tabs 120 welded to the tab connection portions of the same connecting sheet in the same winding core 20 in the first direction at least partially overlap, including:

[0225] Along the winding direction, the heights of the tabs 120 at odd positions are arranged to decrease, while the heights of the tabs 120 at even positions are arranged to increase, and the projections of all tabs 120 welded to the same connecting tab 410 in the same winding core 20 in the first direction at least partially overlap.

[0226] It is understandable that, based on the above-mentioned height variation rule, after the pole piece 10 is wound into the winding core 20, the height of the pole lug 120 can be increased or decreased in sequence. When all the pole lugs 120 welded on the same connecting lug 410 are bent and welded to the connecting sheet 40, the integrity of the weld mark can be ensured, and the phenomenon of tearing of the pole lug 120 caused by interference can be avoided.

[0227] In some embodiments, along the winding direction, the heights of the tabs 120 at odd positions are arranged to decrease, and the heights of the tabs 120 at even positions are arranged to increase, and the projections of all the tabs 120 welded to the tab connection portions of the same connecting sheet in the same winding core 20 in the first direction are at least partially overlapped, including:

[0228] Based on the number of the tabs 120 , the maximum height of the tabs 120 , and the minimum height of the tabs 120 , a tolerance of the height variation of the tabs 120 is obtained.

[0229] Along the winding direction, the heights of the pole lugs 120 at odd positions are set to decrease with the value of the tolerance, and the heights of the pole lugs 120 at even positions are set to increase with the value of the tolerance, so that the height of the pole lug at position one is smaller than the height of the pole lug at position two, and the projections of all the pole lugs 120 welded to the same connecting lug 410 in the same winding core 20 in the first direction at least partially overlap.

[0230] It is understandable that the tolerance of the height variation of the tab 120 is calculated based on the maximum height and the minimum height of the tab 120 and the number of the tabs 120. Based on the tolerance, the heights of all the tabs 120 can be calculated to facilitate the processing of the tabs 120.

[0231] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, 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 invention.

Claims

1. A pole piece, characterized in that: include: A main body portion is configured to be wound to form a winding core, the main body portion having a winding start end and a winding end end, and a direction from the winding start end to the winding end end is a winding direction; There are at least two pole tabs, which are spaced apart at one side of the main body along the winding direction. Along the winding direction, the heights of the pole tabs at odd positions and the heights of the pole tabs at even positions have opposite gradient trends.

2. The pole piece according to claim 1, characterized in that: The heights of the tabs at odd positions decrease, and the heights of the tabs at even positions increase, wherein the height of the tab at position one is less than the height of the tab at position two.

3. The pole piece according to claim 1 or 2, characterized in that: The pole piece has a winding state, and the winding state corresponds to a winding center plane, wherein, in the winding state, the pole ears of odd-numbered positions and the pole ears of even-numbered positions are respectively located on opposite sides of the winding center plane, and the projections of all the pole ears in a first direction at least partially overlap, wherein the first direction is set at an angle to the winding center plane.

4. The pole piece according to claim 3, characterized in that: In the wound state, all the pole ears are bent toward a connecting piece and welded to the connecting piece, wherein when the pole ears are in the bent state, the distance between the shortest free end of the pole ear and the longest free end of the pole ear is Y, satisfying: 0 mm ≤ Y ≤ 1 mm.

5. The pole piece according to claim 4, characterized in that: When the pole lugs are in a bent state, the free ends of all the pole lugs are flush.

6. The pole piece according to claim 4, characterized in that: Along the first direction, the main body has a proximal end close to the connecting piece, and a distance X between the proximal end and the connecting piece satisfies: 1 mm ≤ X ≤ 3 mm.

7. A battery cell, characterized in that: include: case; A connecting piece, comprising a positive connecting piece and a negative connecting piece, wherein the positive connecting piece has a positive electrode ear connecting portion, and the negative connecting piece has a negative electrode ear connecting portion; A core package is arranged in the shell, the core package includes a winding core, the winding core includes a positive electrode sheet, a negative electrode sheet and a separator, at least one of the positive electrode sheet and the negative electrode sheet is a electrode sheet as described in any one of claims 1 to 6, wherein the positive electrode ears of the positive electrode sheet are all bent and welded to the positive electrode ear connecting portion, and the negative electrode ears of the negative electrode sheet are all bent and welded to the negative electrode ear connecting portion.

8. The battery cell according to claim 7, characterized in that: The number of the positive electrode ears is set to 2n, the height of the positive electrode ear at position (2n-1) is the smallest, the height of the positive electrode ear at position 2n is the largest, and the height of the positive electrode ear at position one is smaller than the height of the positive electrode ear at position two, wherein n≥1, and n is an integer.

9. The battery cell according to claim 8, characterized in that: The height of the 2n-position positive electrode ear is positively correlated with the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the length of the positive electrode ear welding area, and the length of the positive electrode ear bending area.

10. The battery cell according to claim 9, characterized in that: The height of the 2n-position positive electrode ear is a, the sum of the lengths of the base of the negative electrode ear and the base of the positive electrode ear is O, the length of the positive electrode ear welding area is L1, and the length of the positive electrode ear bending area is L2, satisfying: a=L1+L2+O.

11. The battery cell according to claim 10, characterized in that: The positive electrode ear connection portion includes two spaced connection ears, and the positive electrode ears of the positive electrode sheet are all bent and welded to the connection ears, wherein the length of the positive electrode ear welding area is positively correlated with the width of the weld mark and the width of the connection ear.

12. The battery cell according to claim 11, characterized in that: The positive electrode ear is configured to be welded to the connecting ear through at least two rounds of welding processes, and the width of the weld mark formed on the positive electrode ear by the last round of welding process is W2, and the width of the connecting ear is W3, satisfying: L1=0.5(W2+W3)+k1, where k1 is the first preset margin.

13. The battery cell according to claim 11, characterized in that: The core packages are provided with at least two, and the two core packages form a core package pair, and the positive electrode ear is welded to the corresponding connecting ear after being raised by the welding seat, wherein the length of the bending area of ​​the positive electrode ear is positively correlated with the distance between the two core packages in the core package pair before being combined and the thickness of a single core package, and is negatively correlated with the width of the positive electrode connecting sheet, the height of the raised welding seat, and the total thickness of all positive electrode ears welded on the same connecting ear.

14. The battery cell according to claim 13, characterized in that: The distance between the two core packages before assembling is H3, the thickness of the single core package is T0, the width of the positive electrode connecting piece is W1, the height of the welding seat is H0, and the total thickness of all positive electrode ears welded on the same connecting ear is H4, satisfying:

15. The battery cell according to claim 8, characterized in that: The positive electrode ear connection portion includes two connection ears arranged at intervals, and the positive electrode ears of the positive electrode sheet are all bent and welded to the connection ears. The core packages are provided in at least two, and the two core packages form a core package pair, wherein the height of the positive electrode ear at position (2n-1) is positively correlated with the sum of the lengths of the roots of the negative electrode ear of the diaphragm and the roots of the positive electrode ear of the diaphragm, the spacing between the two core packages in the core package pair before the cores are closed, the width of the weld mark and the width of the connection ear, and is negatively correlated with the width of the positive electrode connecting sheet.

16. The battery cell according to claim 15, characterized in that: The height of the positive ear at position (2n-1) is b, the distance between the two cores before they are wrapped together is H3, the width of the positive connecting piece is W1, the width of the weld mark is W2, the width of the connecting ear is W3, and the sum of the lengths of the roots of the negative ear and the positive ear of the diaphragm is O, satisfying: b=0.5(H3-W1)+0.5(W2+W3)+O+k2, where k2 is the second preset margin.

17. The battery cell according to claim 14 or 16, characterized in that: The distance between the two cores before being wrapped together is positively correlated with the distance between the positive electrode connecting piece and the main body and the distance between the edge of the positive electrode connecting piece and the inner wall of the shell.

18. The battery cell according to claim 17, characterized in that: The distance between the two cores before being wrapped is H3, the distance between the positive electrode connecting piece and the main body is D1, and the distance between the edge of the positive electrode connecting piece and the inner wall of the shell is D2, which satisfies:

19. The battery cell according to claim 18, characterized in that: The shell is connected to a shell cover, wherein the distance between the positive electrode connecting piece and the main body is positively correlated with the height of the shell and the compression amount of the diaphragm, and is negatively correlated with the distance between the positive electrode connecting piece and the shell cover, the thickness of the positive electrode connecting piece, the total thickness of all positive electrode ears welded on the same connecting ear, and the distance between the diaphragm and the lower surface of the shell.

20. The battery cell according to claim 19, characterized in that: The height of the shell is H10, the compression amount of the diaphragm is k3, the distance from the positive electrode connecting piece to the shell cover is H6, the thickness of the positive electrode connecting piece is H7, the total thickness of all positive electrode ears welded on the same connecting ear is H4, and the distance between the diaphragm and the lower surface of the shell is H9, satisfying: D1 = H10-H6-H7-H4-(H9-k3).

21. The battery cell according to claim 20, characterized in that: The diaphragm compression amount satisfies the following range: 1.5≤k3≤2.

5.

22. The battery cell according to claim 21, characterized in that: The total thickness of the two core packages is W6, and the width of the shell is W5, satisfying: 0.5(W6-W1)≤D2≤0.5(W5-W1).

23. The battery cell according to claim 22, characterized in that: The distance between the positive electrode connecting piece and the main body has a maximum value and a minimum value, which are D1max and D1min, respectively. The distance between the edge of the positive electrode connecting piece and the inner side wall of the shell has a maximum value and a minimum value, which are D2max and D2min, respectively. Among them, D1max=H10-H6-H7-H4-(H9-2.5), D1min=H10-H6-H7-H4-(H9-1.5), D2max=0.5(W5-W1), D2min=0.5(W6-W1), satisfying:

24. The battery cell according to any one of claims 8 to 23, characterized in that: The number of the negative electrode ears is set to (2n+2), the height of the negative electrode ear at position (2n+1) is the smallest, the height of the negative electrode ear at position (2n+2) is the largest, the height of the negative electrode ear at position one is less than the height of the negative electrode ear at position two, wherein the height of the negative electrode ear at position (2n+2) is the same as the height of the positive electrode ear at position 2n.

25. A battery pack, characterized in that: Comprising a battery cell as described in any one of claims 7-24.

26. A pole piece design method, characterized in that: Applied to the battery cell according to any one of claims 7 to 24, the method comprises: Based on the design parameters of the battery cell, obtaining the maximum height and the minimum height of the tab; Along the winding direction, the heights of the pole lugs at odd positions and the heights of the pole lugs at even positions have opposite gradient trends, and the projections of all pole lugs welded to the pole lug connecting portions of the same connecting sheet in the same winding core in the first direction at least partially overlap.

27. The method according to claim 26, characterized in that The design parameters of the battery cell include a first design parameter and a second design parameter, the number of the core packs is at least two, and the two core packs form a core pack pair, and the maximum height of the tab and the minimum height of the tab are obtained based on the design parameters of the battery cell, including: Based on the first design parameter, obtaining a distance between the two core packages in the core package pair before being combined; Based on the second design parameter and the distance between the two cores before being wrapped together, the maximum height of the tab and the minimum height of the tab are obtained.

28. The method according to claim 27, characterized in that The pole ear connecting portion includes two connecting ears arranged at intervals, and the pole ear is welded to the connecting ears after being bent. The first design parameter includes: the height of the shell, the compression amount of the diaphragm, the distance from the connecting piece to the shell cover, the thickness of the connecting piece, the total thickness of all pole ears welded on the same connecting ear, the distance between the diaphragm and the lower surface of the shell, the total thickness of the two core packs and the width of the shell.

29. The method according to claim 28, characterized in that The obtaining, based on the first design parameter, a distance between the two core packages in the core package pair before being combined, comprises: Based on the height H10 of the shell, the compression amount k3 of the diaphragm, the distance H6 from the connecting piece to the shell cover, the thickness H7 of the connecting piece, the total thickness H4 of all the tabs welded on the same connecting tab, and the distance H9 between the diaphragm and the lower surface of the shell, the distance D1 between the connecting piece and the main body is obtained, wherein the following relationship is satisfied: D1=H10-H6-H7-H4-(H9-k3); Based on the total thickness W6 of the two core packages, the width W5 of the shell, and the width W1 of the connecting piece, a distance D2 between the edge of the connecting piece and the inner side wall of the shell is obtained, wherein the following relationship is satisfied: 0.5(W6-W1)≤D2≤0.5(W5-W1); Based on the distance D1 between the connecting piece and the main body and the distance D2 between the edge of the connecting piece and the inner wall of the shell, the distance H3 between the two cores before being wrapped together is obtained, wherein the following relationship is satisfied:

30. The method according to claim 29, characterized in that The distance between the connecting piece and the main body has a maximum value and a minimum value, which are D1max and D1min, respectively. The distance between the edge of the connecting piece and the inner side wall of the shell has a maximum value and a minimum value, which are D2max and D2min, respectively. Among them, D1max=H10-H6-H7-H4-(H9-2.5), D1min=H10-H6-H7-H4-(H9-1.5), D2max=0.5(W5-W1), D2min=0.5(W6-W1), satisfying the following relationship:

31. The method according to claim 27, characterized in that The pole ear connection portion includes two spaced connection ears, and the pole ear is welded to the connection ears after being bent. The second design parameters include: the sum of the lengths of the roots of the negative pole ear and the positive pole ear of the diaphragm, the width of the weld mark, the width of the connection ear, the first preset margin, the second preset margin, the width of the connecting sheet, the thickness of a single core package, and the height of the weld seat.

32. The method according to claim 31, characterized in that The obtaining of the maximum height and the minimum height of the tab based on the second design parameter and the distance between the two cores before the core is wrapped together comprises: Based on the width W2 of the weld mark, the width W3 of the connection ear and the first preset margin k1, the length L1 of the electrode ear welding area is obtained, wherein the following relationship is satisfied: L1=0.5(W2+W3)+k1; Based on the distance H3 between the two core packages before merging, the width W1 of the connecting sheet, the thickness T0 of a single core package, and the height H4 of the welding seat, the length L2 of the tab bending area is obtained, where the following relationship is satisfied: Based on the lengths O of the base of the negative electrode ear and the base of the positive electrode ear of the diaphragm, the length L1 of the electrode ear welding area, and the length L2 of the electrode ear bending area, the maximum height a of the electrode ear is obtained, wherein the following relationship is satisfied: a=L1+L2+O.

33. The method according to claim 31, characterized in that The step of obtaining the maximum height and the minimum height of the tab based on the second design parameter and the distance between the two cores before the cores are wrapped together further includes: Based on the length and O of the base of the negative electrode ear of the diaphragm and the base of the positive electrode ear of the diaphragm, the spacing H3 before the two cores are wrapped together, the width W1 of the connecting piece, the width W2 of the weld mark, the width W3 of the connecting ear, and the second preset margin k2, the minimum height b of the electrode ear is obtained, wherein the following relationship is satisfied: b=0.5(H3-W1)+0.5(W2+W3)+O+k2.

34. The method according to any one of claims 26 to 33, characterized in that: The step of making the height of the pole lugs at odd positions and the height of the pole lugs at even positions have an opposite gradual change trend along the winding direction, and making the projections of all the pole lugs welded to the pole lug connecting portions of the same connecting sheet in the same winding core at least partially overlap in the first direction, including: Along the winding direction, the heights of the tabs at odd positions are arranged to decrease, and the heights of the tabs at even positions are arranged to increase, and the projections of all tabs welded to the same connecting tab in the same winding core in the first direction at least partially overlap.

35. The method according to claim 34, characterized in that The method of decreasing the height of the tabs at odd positions and increasing the height of the tabs at even positions along the winding direction, and making the projections of all tabs welded to the tab connection portions of the same connecting sheet in the same winding core at least partially overlap in the first direction, includes: Based on the number of the tabs, the maximum height of the tabs, and the minimum height of the tabs, obtaining a tolerance of a height variation of the tabs; Along the winding direction, the heights of the pole ears at odd positions are set in descending order according to the value of the tolerance, and the heights of the pole ears at even positions are set in increasing order according to the value of the tolerance, so that the height of the pole ear at position one is smaller than the height of the pole ear at position two, and the projections of all the pole ears welded to the same connecting ear in the same winding core in the first direction at least partially overlap.

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