Battery pole piece and battery cell
By designing continuous transverse curved tabs on the battery pole pieces, the problem of insufficient energy density and power density in traditional pole piece design is solved, achieving both high energy density and high power density, and improving the safety and manufacturing qualification rate of the battery cells.
Patent Information
- Application Number
- CN202422661481.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-01
- Publication Date
- 2025-09-12
- Estimated Expiration
- 2034-11-01
AI Technical Summary
The traditional cylindrical battery cell electrode design makes it difficult to achieve both high energy density and high power density. The tab design takes up space and poses a safety hazard. The mechanical flattening method produces metal chips, and the stacked tab solution has a high production defect rate.
The pole ear is designed with continuous transverse curved shape. The pole ear includes continuous peaks and troughs. The pole ear is foldable. Reserved areas are provided at both ends of the pole piece body. The pole ear-free area is located at the starting and ending ends of the winding. The cumulative height of the pole ear after folding is less than 1mm. The pole ear and the pole piece body are integrated into one structure.
The volume energy density and power density of the battery cell are improved, while the production defect rate is reduced, ensuring the safety and manufacturing qualification rate of the battery cell.
Smart Images
Figure CN223333803U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of new energy batteries, in particular to a battery pole piece and a battery core. Background Art
[0002] The development of secondary batteries is rapidly moving towards the direction of high energy density and high power density. For cylindrical cells, traditional manufacturing methods are difficult to achieve both energy density and power density. Figure 1 , the tab is inside the pole piece and extends across the width of the pole piece. Taking safety factors into consideration, high-temperature resistant tape is used to protect the area around the tab. This makes it impossible to coat the active material in the area covered by the high-temperature tape and cannot contribute to the capacity. At the same time, the thickness of the tab itself and the high-temperature tape will be around 0.15mm. This thickness will occupy a certain space in the winding core, further reducing the energy density of the battery cell. At the same time, for capacity and energy density considerations, the number of tabs needs to be strictly controlled in traditional designs, which limits the current path of the battery cell and the power density of the battery cell. In order to solve the problem of power density, a method of retaining part of the foil on the pole piece to form a continuous tab has been developed.
[0003] As shown in the reference diagram, a large portion of the foil is retained at one end of the electrode sheet to serve as the tabs for the positive and negative electrodes. The tab heights for the positive and negative electrodes, H1 and H2, are generally ≥ 5mm, depending on the design. After the core is formed, the foil area serves directly as the tab, welded directly to a separate metal collector plate or the package cover. The disadvantage of this tab design is that H1 and H2 must be ≥ 5mm. H0 represents the total cell height, and H3 represents the height of the main electrode area (H0 = H1 + H2 + H3). Therefore, this tab design occupies internal cell space, significantly reducing the cell's volumetric energy density. Alternatively, to increase volumetric energy density, the H1 portion is mechanically flattened, keeping the height within 2mm. However, this mechanical flattening method inevitably generates metal shavings, compromising the safety of the subsequent cell. To increase power density without sacrificing volumetric energy density, a stacked tab design has been proposed. Summary of the Invention
[0004] In order to solve the above-mentioned disadvantages of burning, the present invention provides a battery electrode. In order to solve the above-mentioned technical problems, the present invention solves them through the following technical solutions:
[0005] A battery electrode comprises a electrode body and a tab. A continuous, laterally extending, curved tab is provided at one end of the electrode body along its length. The tab extends from a foil at one end of the electrode body. The tab comprises continuous crests and troughs and is foldable. Reserved areas are provided at both ends of the electrode body in the length direction, and the reserved areas are not covered by the tab.
[0006] Preferably, the beginning of the curved tab is curved, and the ending of the curved tab is curved.
[0007] Preferably, the electrode body includes a negative electrode and a positive electrode, and the four corners of the positive electrode are rounded corners.
[0008] Preferably, the angle α between the top angle bisector of the peak of the pole tab and the vertical line in the length direction of the pole piece is in the range of 0 to ±12°.
[0009] Preferably, the height of the tab is in the range of 4.7 mm to 6.5 mm.
[0010] Preferably, the continuous wave crests and wave troughs form a plurality of small tabs, and the bottom width of each small tab ranges from 3 mm to 5 mm.
[0011] The present invention also proposes a battery cell, which includes a wound electrode as described above and a diaphragm, and the electrode tabs are folded toward the center hole of the battery cell. The battery cell includes an electrode tab area and a non-electrode tab area, and the non-electrode tab area is located at the starting end and the ending end of the electrode sheet winding. The non-electrode tab area after winding is located at the center and periphery of the battery cell.
[0012] Preferably, the tab includes a first portion for welding, a second portion for folding, and a third portion covered by the diaphragm.
[0013] Preferably, the height range of the first part is 4mm-5mm, the height range of the second part is 0.2mm-0.5mm, and the height range of the third part is 0.5mm-1.0mm.
[0014] Preferably, the range of the radius R0 of the center hole of the battery core is 1.5 mm ≤ R0 ≤ 3 mm.
[0015] Beneficial Effects: The present invention provides a battery pole piece, which has a structure that enhances the power density of the battery cell while ensuring high energy density. It also improves the electrical performance of the battery cell while ensuring a high manufacturing yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.
[0017] Figure 1 It is a schematic diagram of the electrode and battery cell in the prior art;
[0018] Figure 2 This is another schematic diagram of the structure of pole pieces and battery cells in the prior art;
[0019] Figure 3 This is another schematic diagram of the installation of pole pieces and battery core structures in the prior art;
[0020] Figure 4 It is a schematic diagram of a pole piece and a battery cell disclosed in Scheme 1;
[0021] Figure 5 It is a schematic diagram of a pole piece and a battery cell disclosed in Scheme 1;
[0022] Figure 6 This is a schematic diagram of a pole piece tearing disclosed in Scheme 1;
[0023] Figure 7 It is a schematic diagram of the positive and negative electrodes of a pole piece disclosed in Scheme 2;
[0024] Figure 8 This is a schematic diagram of the parameters of the positive and negative electrodes of a type of electrode disclosed in Scheme 2;
[0025] Figure 9 This is a schematic diagram of the stacking of the positive and negative electrodes of a type of electrode disclosed in Scheme 2;
[0026] Figure 10 This is the schematic diagram of the battery cell production disclosed in Scheme 2;
[0027] Figure 11 This is a schematic diagram of the collector plate for the battery cell installation in Option 2;
[0028] Figure 12 Schematic diagrams of two different structures of the pole tabs of the pole piece disclosed in Scheme 2;
[0029] Figure 13 This is a schematic diagram of one end of the pole piece after winding disclosed in Scheme 2. DETAILED DESCRIPTION
[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.
[0031] Solution 1: A battery electrode, comprising a electrode body and a tab, wherein the tab extends from a foil at one end of the electrode body (integrated structure), wherein the tab is cut into a plurality of small tabs, or sub-tabs, along the length direction of the electrode body.
[0032] like Figure 4-Figure 6, one end of the continuous (or integrated) current collector foil is cut along the length direction to form a nearly rectangular, discrete small tab. The small tab can be folded 90 degrees, folded to the end face of the core and welded to the collector plate or the outer cover of the packaging shell.
[0033] The cumulative height of the folded tabs is less than 1mm. Compared to the full-tab structure disclosed in the background art, which generally has a height of ≥5mm, this significantly improves space utilization. In the figure, H4 and H5 are the tab heights, H0 is the height of the main electrode area, and H0' is the total height of the cell after the tabs are folded. If the process allows, H0 is approximately equal to H0'.
[0034] However, this structure also has certain defects. This rectangular small tab has four straight corners, which are easily affected by external forces, such as deformation or tearing under large tension. In this way of cutting the tab, the tear of the small tab gradually develops into a scissor-like cutting effect under the action of tension, breaking the entire tab and causing process defects. Figure 6 The tearing area ① in the figure, the arrows pointing to both sides simulate the forces pointing to both sides, Figure 5 The cutting line in the above figure is 90° to the length direction of the electrode. Figure 5 The cutting line in the figure below is an inclined straight line, forming an acute angle with the length of the electrode. A 90° straight-line cut is prone to tearing. Experiments have shown that beveled straight-line cuts are even more prone to tearing, so a more advantageous electrode and lug structure is needed.
[0035] Solution 2: A battery electrode, comprising an electrode body and an ear, wherein one end of the electrode body is provided with a continuous transverse curved ear along the length direction, the ear extending from the foil at one end of the electrode body, and the ear comprises continuous crests and troughs. The transverse curved ear can also be understood as a wavy ear, for details, please refer to the attached Figure 7-10 In the figure, H6 and H7 are the tab heights.
[0036] Each small tab in the curved tab or the wavy tab gradually narrows from the root to the top, has a stable shape, and is not easily deformed or torn by external forces.
[0037] At the same time, there is no straight line intersection between the tab and the pole piece, especially the pole piece main body at the trough position is an arc-shaped transition relationship, as shown in the area marked ② in the figure, which is not easy to tear under the action of tension and develop into damage that cuts off the entire pole piece.
[0038] More specifically, the starting point S of the curved tab is curved, and the ending point E of the curved tab is curved. Figure 8 exhibit.
[0039] Preferably, the electrode body includes a negative electrode and a positive electrode, and the four corners of the positive electrode are rounded corners, such as R1, R2, R3, and R4 in the figure. The four rounded corners can be the same, that is, R1 = R2 = R3 = R4, or they can be different, that is, R1 ≠ R2 ≠ R3 ≠ R4.
[0040] Preferably, the angle α between the top angle bisector of the peak of the pole tab and the vertical line in the length direction of the pole piece is in the range of 0 to ±12°.
[0041] Preferably, the height of the tab is in the range of 4.7 mm to 6.5 mm.
[0042] Preferably, the continuous wave crests and wave troughs form a plurality of small tabs, and the bottom width of each small tab ranges from 3 mm to 5 mm.
[0043] Further disclosed is a battery cell comprising a wound electrode sheet, as disclosed above, and a separator, with the electrode tabs folded toward the center hole of the battery cell. Specifically, the battery cell comprises a positive electrode sheet, a negative electrode sheet, and a separator. The positive and negative electrode sheets are separated by the separator.
[0044] A more complete installation structure also includes a collecting plate, such as Figure 10 and Figure 11 As shown, the wound pole pieces form a winding core, the pole tabs are folded and flattened, and then the current collecting plates are welded to the surfaces of the pole tabs at both ends of the winding core through welding wires.
[0045] Among them, the battery cell includes a tab area and a tab-free area. The tab-free area is located at the starting end and the ending end of the electrode winding, and the tab-free area after winding is located at the center and periphery of the battery cell.
[0046] Preferably, the cumulative height of all tabs after folding is less than 1 mm.
[0047] Figure 10 It can be seen that the pole piece is wound, and the total height H0' after the pole tab is folded is approximately equal to the height H0 of the pole piece body, which effectively improves the volume energy density.
[0048] Preferably, the range of the radius R0 of the center hole of the battery core is 1.5 mm ≤ R0 ≤ 3 mm.
[0049] Further references Figure 7-13 , analyze the various parameter designs of the pole piece, as follows:
[0050] Tab shape parameter S = f(t, h, b, α), where:
[0051] t (t1 to tn) is the peak-to-valley transition zone of the curved tab curve, which is a non-straight line zone. This embodiment discloses that there is no straight line parallel to the length side of the pole piece, so t=0 can be defined.
[0052] h (h1 to hn) is the height of the transverse curved tab, that is, the height difference between the crest and the trough.
[0053] Optionally, the height difference between each crest and trough of the transverse curved tab is the same, or the height difference between each crest and trough is different. For n tabs on a pole piece, the heights of each tab can be the same, i.e., h1=h2=···=hn, or the heights of each tab can be different, i.e., h1≠h2≠h3≠···≠hn.
[0054] Specifically, preferably, the tab includes a first portion for welding, a second portion for folding, and a third portion covered by the diaphragm. The tab height range includes the height of the first portion for welding, the height of the second portion for folding, and the height of the third portion covered by the diaphragm.
[0055] Correspondingly, the height range of the first portion is 4mm-5mm, the height range of the second portion is 0.2mm-0.5mm, and the height range of the third portion is 0.5mm-1.0mm. Therefore, as disclosed above, the height range of the tab is 4.7mm-6.5mm. Figure 9 The diagram shows the size and structure of the positive and negative electrodes, as well as the structure of the tabs in use, with some parts covered and some exposed. Since the separator is generally larger than the negative and positive electrodes, the second part is interpreted as the third part covered by the separator. A is the positive electrode, B is the negative electrode, and C is the tab.
[0056] b is the bottom width of the small tab, or the distance between two adjacent valleys. For the n small tabs on the pole piece body, the root widths of each small tab can be the same, i.e., b1 = b2 = ... = bn. Alternatively, the root widths of each tab can be different, i.e., b1 ≠ b2 ≠ b3 ≠ ... ≠ bn. Alternatively, the root widths of each tab can be partially the same and partially different. Preferably, they are the same, and parameters such as t, h, b, and α remain consistent.
[0057] The preferred solution is to use a value of b ranging from 3 mm to 1 / 10 * PI() * (Rmax - W1). Rmax is the outer diameter of the winding core, and PI() is a function call used to obtain the value of pi. W1 prevents direct contact between the tab and the side wall of the package shell. It is a safe distance between the tab and the outer diameter edge of the winding core after winding. The range of W1 is (1≤W1≤1.5).
[0058] Therefore, the width b of the bottom of the small tab is selected between 3 mm and 5 mm, preferably 4 mm.
[0059] It should be noted that the selection of the pole tab height h at the starting end of the pole piece winding affects the selection of b and the value of x.
[0060] Optionally, a reserved area is provided at each end of the pole piece's length, where no tabs are present. As needed, a tab-free area of a certain length, x and z, is reserved at the start and end of the pole piece winding, respectively, where x > 0 and z > 0. The tab-covered area has a length y, which is the same as the total tab length.
[0061] x corresponds to the winding starting point and must ensure that the center hole of the tab is unobstructed after winding. That is, x corresponds to the length of the tab within the radius range [R0 to (R0 + W0)]. R0 is the radius of the center hole in the winding core, and its value range is generally 1.5mm ≤ R0 ≤ 3mm.
[0062] W0=hc, W0 is the width of the tab after folding, h is the height of the tab, and c is the portion of the tab blocked by the diaphragm.
[0063] z corresponds to the winding end. The tabs must maintain a safe distance from the outer diameter of the package core to prevent direct contact between the tabs and the sidewalls of the package shell. This distance is defined as W1 (1≤W1≤1.5), and z corresponds to the length of the pole piece within the radius of [(Rmax-W1) to Rmax]. Rmax is the outer diameter of the core, marked as R1 in the figure.
[0064] α is the angle between the bisector of the top angle of the tab and the vertical line along the length of the pole piece. Preferably, the angle α between the bisector of the top angle of the tab and the vertical line along the length of the pole piece is in the range of 0 to ±10°. More preferably, it is in the range of 0 to ±5°, and the most preferred is 0°. In the figure, the angle corresponding to the peak is β (i.e., the top angle of the tab), and the bisector of the top angle of the tab divides β into β / 2.
[0065] refer to Figure 8 The two figures in the figure show that Figure 12 In the above figure, the small tab has a relatively inclined shape. At this time, the α angle is relatively large, but the maximum cannot exceed 10°. Experiments show that the internal resistance is relatively high when it exceeds 10°. Figure 12 The small tab in the figure below is more positive in shape than that in the figure above, or is more inclined to an isosceles structure. At this time, the angle α is relatively small. If it is an isosceles structure, the angle bisector of the top of the tab is perpendicular to the length direction of the pole piece, or the angle between it and the vertical line of the length direction of the pole piece is 0°. Experiments show that the resistance value with an α angle of 0° is relatively small.
[0066] Further disclosed is a process for manufacturing a tab, comprising: taking a metal current collector foil, coating an active material on the main body of the pole piece, and reserving an uncoated area on the surface of the metal current collector foil while coating the active material. The reserved uncoated area is parallel to the length of the pole piece, and the width of the reserved uncoated area is set as needed, generally ranging from 5 mm to 2*h (where h is the height of the tab). The reserved uncoated foil area is cut to form the tab of the pole piece.
[0067] Another proposed tab manufacturing process involves taking a metal current collector foil, reserving an area for the pole piece body, i.e., the area for coating the active material, and reserving an area for the tab. The data is the same or similar to the above scheme. The metal current collector foil is then cut in the reserved tab area to form the pole piece tab. The pole piece body is then coated with the active material. Therefore, in this application, the tab and the pole piece body are an integrated structure, i.e., the structure mentioned above where the tab extends from the foil at one end of the pole piece body.
[0068] The tabs of the present invention were implemented on cylindrical 4680 battery cells, and the following experimental parameters were obtained as shown in Tables 1 and 2. For example, the specific parameters include a core center hole diameter of 6 mm, 20 tab welding layers, 10 protective layers, a positive electrode sheet thickness of 0.110 mm, a negative electrode sheet thickness of 0.120 mm, and a separator thickness of 0.012 mm.
[0069] Table 1 Cylindrical 4680 battery cell capacity, internal resistance and defect rate test table-1
[0070]
[0071] Table 2 Cylindrical 4680 battery cell capacity, internal resistance and defect rate test table-2
[0072]
[0073] In Examples 1 to 6, h = 5 mm. Since the height of the tabs in this group is the smallest, the width of the tabs on one end of the cell after being bent 90° is also the smallest, thus not blocking the center hole. Figure 9 In Examples 1 to 6, the x value on the electrode is the smallest, x = 338 mm. For electrode pieces of the same length, the longest electrode tab area corresponds to the lowest internal resistance value of the corresponding battery cell.
[0074] In Examples 1 to 6, different angles α between the pole tab and the pole piece are used, with α being 0°, 5° and 10° respectively. Figure 12 As the angle between the tab and the pole piece increases, the base of the tab gradually becomes sharper. This type of tab shows an increasing tendency to break during cutting and subsequent winding.
[0075] In Examples 7 to 12, the height of the tab is h = 5.5 mm, and the tab-free area of the electrode is x = 505 mm. As the tab area on the electrode decreases, the internal resistance of the battery cells of this group increases to a certain extent.
[0076] Examples 7 to 12, with different angles α between the tab and the pole piece, show the same trend as that of Examples 1 to 6, that is, the tab breakage increases with increasing angle.
[0077] In Examples 13 to 21, the height of the tab h=6 mm, and the corresponding x=700 mm, and the resistance of the corresponding battery cell is further increased.
[0078] As the x value increases, the width range of the tab on the pole piece is expanded from 3 mm to 4 mm allowed in the original embodiments 1 to 12 to 3 mm to 5 mm.
[0079] In Examples 13 to 21, the tab widths b = 3 mm, b = 4 mm, and b = 5 mm exhibited differences in process yield. Within the 3 mm to 5 mm range, the process yield improved with increasing tab width. This means that smaller tab curvatures facilitate manufacturing.
[0080] Among them, Comparative Example 1 is a traditional welding structure, Comparative Example 2 is a method of retaining part of the foil on the electrode sheet to form a continuous electrode ear as mentioned in the background technology, and Comparative Example 3 is the structure disclosed in Scheme 1 above.
[0081] Among these three structures, the internal resistance of Comparative Example 1 is high, the capacity of Comparative Example 2 is relatively low, and although the electrical performance parameters of Comparative Example 3 are good, its production defect rate is high.
[0082] Furthermore, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may vary. Any equivalent or simple variations based on the structure, features, and principles described in this utility model are included within the scope of protection of this utility model. Those skilled in the art of the present invention may make various modifications, additions, or substitutions to the described specific embodiments, and these modifications, as long as they do not deviate from the structure of this utility model or exceed the scope defined by these claims, shall fall within the scope of protection of this utility model.
Claims
1. A battery electrode, characterized in that: It includes a pole piece body and a pole ear. One end of the pole piece body is provided with a continuous laterally extending curved pole ear along the length direction. The pole ear extends from the foil at one end of the pole piece body. The pole ear includes continuous peaks and troughs and is foldable. Reserved areas are provided at both ends of the pole piece body in the length direction, and the reserved areas are not covered by the pole ear.
2. A battery electrode according to claim 1, characterized in that: The beginning of the curved tab is curved, and the ending of the curved tab is curved.
3. A battery electrode according to claim 1, characterized in that: The electrode body includes a negative electrode and a positive electrode, and the four top corners of the positive electrode are rounded corners.
4. A battery electrode according to claim 1, characterized in that: The angle α between the top angle bisector of the peak of the pole ear and the vertical line in the length direction of the pole piece is in the range of 0 to ±12°.
5. A battery electrode according to claim 1, characterized in that: The height range of the tabs is 4.7mm-6.5mm.
6. A battery electrode according to claim 1, characterized in that: Continuous wave crests and troughs form a number of small pole ears, and the bottom width of each small pole ear ranges from 3mm to 5mm.
7. A battery cell, characterized in that: The battery cell includes a wound electrode as described in any one of claims 1 to 6, and a diaphragm, and the electrode tabs are folded toward the center hole of the battery cell. The battery cell includes an electrode tab area and a non-electrode tab area, and the non-electrode tab area is located at the starting end and the ending end of the electrode winding. The non-electrode tab area after winding is located at the center and periphery of the battery cell.
8. The battery cell according to claim 7, characterized in that: The tab includes a first portion for welding, a second portion for folding, and a third portion covered by a diaphragm.
9. The battery cell according to claim 8, characterized in that: The height range of the first part is 4mm-5mm, the height range of the second part is 0.2mm-0.5mm, and the height range of the third part is 0.5mm-1.0mm.
10. The battery cell according to claim 7, characterized in that: The range of the center hole radius R0 of the battery cell is 1.5mm≤R0≤3mm.