Battery cell and lithium battery
By setting up hole groups in the corner area of the battery cell and adjusting the hole depth near the tab, the problems of electrolyte breakage and lithium plating at the corner are solved, thus improving the safety and service life of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHEJIANG LIWINON ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2025-06-16
- Publication Date
- 2026-07-14
AI Technical Summary
In existing MTS cells, lithium plating at the corners and electrolyte bridging are serious problems, leading to a decline in cell performance, especially in the current-concentrated area at the tabs.
Hole groups are set in the corner areas of the positive and negative electrodes of the battery cell, with the hole depth gradually decreasing from the center to the edge. Holes with increasing depth are also set near the tabs to adjust the current path and preserve the electrolyte.
It improves electrolyte bridging and lithium plating in the corner area, enhances the safety performance and lifespan of lithium-ion batteries, and maintains charging window performance and energy density.
Smart Images
Figure CN224501974U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of lithium battery technology, and in particular to a battery cell and a lithium battery. Background Technology
[0002] Currently, in existing MTS (Mid-Tapered Switch) cells, the areal density and compaction density of the cells are becoming increasingly higher. This leads to greater pressure on the corners of the cells. Due to compression at the corners during cycling, the electrolyte is squeezed out. As the electrolyte is gradually squeezed out, its quantity decreases, leading to a break in the electrolyte at the corner. Especially at the negative electrode convex side, due to the influence of the winding structure, the negative electrode convex side corresponds to the positive electrode concave side, resulting in a small CB value (the ratio of negative electrode capacity to positive electrode capacity), and the positive electrode concave side is thicker, making it prone to lithium plating and weakening its charging capacity. Conversely, the negative electrode concave side corresponds to the positive electrode convex side, resulting in a large CB value and less lithium plating, but the negative electrode concave side is thicker, making it difficult for inner-layer lithium ion transport and deteriorating discharge performance. Furthermore, in MTS structure cells, the current increases closer to the tabs, making lithium plating more likely. Utility Model Content
[0003] The purpose of this invention is to provide a battery cell and a lithium battery to solve the technical problem that lithium is easily deposited in the corner area of the battery cell in the prior art.
[0004] To achieve the above objectives, the first aspect of this utility model provides a battery cell, which includes: a positive electrode sheet, a negative electrode sheet, and a separator; the positive electrode sheet, the negative electrode sheet, and the separator are wound together to form a wound battery cell.
[0005] The positive electrode sheet has a positive corner region; the positive corner region includes a positive concave material region; the positive concave material region has a first hole group; the first hole group includes a plurality of first holes arranged sequentially along the width direction of the positive electrode sheet; the negative electrode sheet has a negative corner region; the negative corner region includes a negative concave material region; the negative concave material region has a second hole group; the second hole group includes a plurality of second holes arranged sequentially along the width direction of the negative electrode sheet;
[0006] In the same first hole group, the depth of the first hole is smaller the closer it is to the edge in the width direction of the positive electrode sheet; in the same second hole group, the depth of the second hole is smaller the closer it is to the edge in the width direction of the negative electrode sheet.
[0007] Preferably, one of the first holes in the first hole group is located at the center of the positive electrode concave fabric area in the width direction;
[0008] One of the second holes in the second hole group is located at the center of the negative electrode concave fabric area in the width direction.
[0009] Preferably, the first hole located at the center of the positive electrode concave fabric area in the width direction is the first central hole; in the same group of first holes, the number of first holes located on both sides of the first central hole in the width direction are equal and symmetrical about the first central hole;
[0010] The second hole located at the center of the negative electrode concave fabric area in the width direction is the second central hole; in the same group of second holes, the number of second holes located on both sides of the second central hole in the width direction are equal and symmetrical about the second central hole.
[0011] Preferably, the depth of the first central hole is D, and the depth of the other first holes in the same first hole group is Dn; n is the number of first holes between the first hole and the first central hole plus one; where Dn = D*(1-10%*n);
[0012] The depth of the second central hole is F, and the depth of the other second holes in the same second hole group is Fm; m is the number of second holes between the second hole and the second central hole plus one; where Fm = F * (1 - 10% * m).
[0013] Preferably, it further includes: a positive electrode tab; the positive electrode tab is connected to the positive electrode sheet; the positive electrode sheet extends along a first direction, the positive electrode sheet is provided with a third hole group, the third hole group includes a plurality of third holes arranged sequentially along the first direction, and the plurality of third holes are distributed on both sides of the positive electrode tab, wherein, in the same third hole group, the depth of the third hole closer to the positive electrode tab is greater.
[0014] Preferably, in the same group of third holes, the number of third holes located on both sides of the positive electrode tab in the first direction are equal and symmetrical about the positive electrode tab.
[0015] Preferably, the third hole adjacent to the positive electrode tab is a first standard hole; the depth of the first standard hole is H, and the depth of the other third holes in the same group of third holes is Hc, where c is the number of third holes between the third hole and the first standard hole plus one; wherein, Hc = H*(1-10%*c).
[0016] Preferably, it further includes: a negative electrode tab; the negative electrode tab is connected to the negative electrode sheet; the negative electrode sheet extends along a second direction, the negative electrode sheet is provided with a fourth hole group, the fourth hole group includes a plurality of fourth holes arranged sequentially along the second direction, and the plurality of fourth holes are distributed on both sides of the negative electrode tab, wherein, in the same fourth hole group, the depth of the fourth hole closer to the negative electrode tab is greater.
[0017] Preferably, within the same group of fourth holes, the number of fourth holes located on both sides of the negative electrode tab in the second direction is equal and symmetrical about the negative electrode tab. The fourth hole adjacent to the negative electrode tab is a second standard hole; the depth of the second standard hole is J, and the depth of the other fourth holes in the same group of fourth holes is Jw, where w is the number of fourth holes between the fourth hole and the second standard hole plus one; wherein, Jw = J*(1-10%*w).
[0018] The second aspect of this utility model provides a lithium battery, which includes: the cell as described above.
[0019] The beneficial effects of the battery cell and lithium battery provided by this utility model are as follows: The depth of the first hole closer to the center in the width direction in the first hole group is greater, so that the deeper first hole corresponds to the positive electrode corner area where electrolyte bridging and lithium plating are most severe, thereby improving the electrolyte bridging and lithium plating situation in the positive electrode corner area. Similarly, the depth of the second hole closer to the center in the width direction in the second hole group is greater, so that the deeper second hole corresponds to the negative electrode corner area where electrolyte bridging and lithium plating are most severe, thereby improving the electrolyte bridging and lithium plating situation in the negative electrode corner area. Furthermore, the depth of the second hole closer to the edge in the width direction of the negative electrode sheet is smaller, and the depth of the first hole closer to the edge in the width direction of the positive electrode sheet is smaller, enabling precise dynamic control. This solves the problem of varying degrees of electrolyte bridging and lithium plating severity caused by different corner locations in the battery cell, while ensuring the charging window performance of the battery cell and minimizing the reduction in battery cell energy density. This improves the safety performance of the lithium-ion battery and extends its service life.
[0020] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the positive electrode corner region of the battery cell according to an embodiment of the present invention;
[0022] Figure 2 This is a schematic diagram of the negative electrode corner region of the battery cell according to an embodiment of the present invention;
[0023] Figure 3 This is a schematic diagram of the structure of the positive electrode sheet in an embodiment of this utility model.
[0024] Figure 4 This is a schematic diagram of the negative electrode sheet of an embodiment of the present invention;
[0025] Figure 5 This is a schematic diagram of the connection structure between the positive electrode plate and the positive electrode tab in an embodiment of this utility model;
[0026] Figure 6 This is a schematic diagram of the connection structure between the negative electrode sheet and the negative electrode tab in an embodiment of this utility model.
[0027] 100, Positive electrode sheet; 110, Positive corner area; 111, Positive concave fabric area; 112, First hole group; 113, First hole; 113a, First central hole; 114, Positive convex fabric area; 115, Positive current collector; 120, Third hole group; 121, Third hole; 121a, First standard hole; 200, Negative electrode sheet; 210, Negative corner area; 211, Negative concave fabric area; 212, Second hole group; 213, Second hole; 213a, Second central hole; 214, Negative convex fabric area; 215, Negative current collector; 220, Fourth hole group; 221, Fourth hole; 221a, Second standard hole; 300, Separator; 400, Positive electrode tab; 500, Negative electrode tab. Detailed Implementation
[0028] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.
[0029] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.
[0030] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.
[0031] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.
[0032] Please refer to the following: Figures 1 to 6 The battery cell provided in the embodiments of this utility model will now be described.
[0033] Reference Figure 1 and Figure 2 This embodiment provides a battery cell, comprising: a positive electrode 100, a negative electrode 200, and a separator 300; the positive electrode 100, the negative electrode 200, and the separator 300 are wound to form a wound-core battery cell; the separator 300 is located between the positive electrode 100 and the negative electrode 200; the positive electrode 100 is provided with a positive electrode corner region 110; the positive electrode corner region 110 includes a positive electrode concave surface region 111, a positive electrode convex surface region 114, and a positive electrode current collector 115; the positive electrode concave surface region 111 is provided with a first hole group 112; the first hole group 112 includes holes along the width direction of the positive electrode 100 (refer to...). Figure 3 Multiple first holes 113 are sequentially arranged in the Q direction; the negative electrode sheet 200 is provided with a negative electrode corner region 210; the negative electrode corner region 210 includes a negative electrode concave fabric region 211, a negative electrode convex fabric region 214, and a negative electrode current collector 215; the negative electrode concave fabric region 211 is provided with a second hole group 212; the second hole group 212 includes holes arranged along the width direction of the negative electrode sheet 200 (refer to...). Figure 3 Multiple second holes 213 are sequentially arranged in the P direction;
[0034] Reference Figure 3 and Figure 4 In the same first hole group 112, the depth of the first hole 113 is smaller as it is closer to the edge of the positive electrode 100 in the width direction; in the same second hole group 212, the depth of the second hole 213 is smaller as it is closer to the edge of the negative electrode 200 in the width direction.
[0035] The first hole 113 of the positive electrode concave surface area 111 of the positive electrode corner area 110 is used to store electrolyte. By setting the first hole group 112, the positive electrode corner area 110 can have enough space to store electrolyte, so as to reduce the risk of electrolyte being squeezed out during the cycle of the cell. In addition, in the same first hole group 112, the depth of the first hole 113 closer to the edge of the positive electrode sheet 100 in the width direction is smaller, that is, the depth of the first hole 113 closer to the center in the width direction is larger. The deeper the first hole 113, the better the effect of storing electrolyte. Similarly, the second hole 213 of the negative electrode concave fabric area 211 of the negative electrode corner area 210 is also used to store electrolyte. By setting the second hole group 212, the negative electrode corner area 210 can have enough space to store electrolyte, so as to reduce the risk of electrolyte being squeezed out during the cycle of the cell. In addition, in the same second hole group 212, the depth of the second hole 213 closer to the edge of the negative electrode sheet 200 in the width direction is smaller, that is, the depth of the second hole 213 closer to the center in the width direction is larger. The deeper the second hole 213, the better the effect of storing electrolyte.
[0036] In the actual charging and discharging process of the battery cell, the electrolyte bridging and lithium plating are most severe at the position closer to the center of the electrode in the width direction. The electrolyte bridging and lithium plating will gradually slow down along the edges of the electrodes on both sides.
[0037] In this embodiment, the depth of the first hole 113 closer to the center in the width direction in the first hole group 112 is greater. This means that the deeper first hole 113 corresponds to the positive electrode corner region where electrolyte bridging and lithium plating are most severe, thereby improving the electrolyte bridging and lithium plating situation in the positive electrode corner region 110. Similarly, the depth of the second hole 213 closer to the center in the width direction in the second hole group 212 is greater. This means that the deeper second hole 213 corresponds to the negative electrode corner region 210 where electrolyte bridging and lithium plating are most severe, thereby improving the electrolyte bridging situation in the negative electrode corner region 210. Furthermore, the depth of the second hole 213 is smaller closer to the edge of the negative electrode 200 in the width direction, and the depth of the first hole 113 is smaller closer to the edge of the positive electrode 100 in the width direction. This allows for precise control of the dynamics, which can solve the problem of varying degrees of electrolyte bridging and lithium plating caused by different corner positions of the battery cell, while ensuring the charging window performance of the battery cell and minimizing the reduction of the battery cell's energy density. This improves the safety performance of the lithium-ion battery and extends its service life.
[0038] In some embodiments of this utility model, one of the first holes 113 of the first hole group 112 is located at the center of the positive electrode concave fabric area 111 in the width direction; one of the second holes 213 of the second hole group 212 is located at the center of the negative electrode concave fabric area 211 in the width direction. This ensures that a first hole 113 is provided at the center of the positive electrode concave fabric area 111 in the width direction and a second hole 213 is provided at the center of the negative electrode concave fabric area 211 in the width direction, so as to better improve the electrolyte bridging and lithium plating in the corner area of the electrode.
[0039] Reference Figure 3 and Figure 4 In some embodiments of this utility model, the first hole 113 located at the center of the positive electrode concave fabric area 111 in the width direction is a first central hole 113a; in the same first hole group 112, the number of first holes 113 located on both sides of the first central hole 113a in the width direction is equal and symmetrical about the first central hole 113a; the symmetrically distributed first holes 113 can make the force in the corner area more even and make the drilling depth from the center of the electrode to the edge of the electrode orderly decrease, so as to better improve the electrolyte bridging and lithium plating in the corner area of the electrode; similarly, the second hole 213 located at the center of the negative electrode concave fabric area 211 in the width direction is a second central hole 213a; in the same second hole group 212, the number of second holes 213 located on both sides of the second central hole 213a in the width direction is equal and symmetrical about the second central hole 213a. The symmetrically distributed second holes 213 can make the stress in the corner area more even and make the drilling depth from the center of the electrode to the edge of the electrode decrease in an orderly manner, so as to better improve the electrolyte bridging and lithium plating in the corner area of the electrode.
[0040] In some embodiments of this utility model, reference is made to Figure 3 The depth of the first central hole 113a is D, and the depth of the other first holes 113 within the same first hole group 112 is Dn; n is the number of first holes 113 between the first hole 113 and the first central hole 113a plus one; wherein, the depth of the first central hole 113a is greater than the depth of the other first holes 113, that is, D≥Dn, and satisfies Dn=D*(1-10%*n), so as to ensure that the depth of the first hole 113 gradually decreases from the inside to the outside; in this embodiment, the first central hole 113a is symmetrically divided into 7 regions from the inside to the outside in the width direction, that is, Dn is D1 to D7; and the depth D of the first central hole 113a satisfies 0.1A≤D≤0.9A, where A is the thickness of the positive electrode concave fabric region 111, to avoid the first central hole 113a penetrating the front concave fabric region.
[0041] Reference Figure 4 The depth of the second central hole 213a is F, and the depth of the other second holes 213 within the same second hole group 212 is Fm; Fm is the number of second holes 213 between the second hole 213 and the second central hole 213a plus one; wherein, the depth of the second central hole 213a is greater than the depth of the other second holes 213, that is, F≥Fm, and satisfies Fm=F*(1-10%*m), so as to ensure that the depth of the second hole 213 gradually decreases from the inside to the outside; in this embodiment, the second central hole 213a is symmetrically divided into 7 regions from the inside to the outside in the width direction, that is, Fm is F1 to F7; and the depth F of the second central hole 213a satisfies 0.1B≤F≤0.9B, where B is the thickness of the positive electrode concave fabric region 111, to avoid the second central hole 213a penetrating the front concave fabric region.
[0042] It is understandable that the aperture size of the first hole 113 and the second hole 213 is 20 to 90 micrometers, the distance between two adjacent first holes 113 or second holes 213 is 1 millimeter to 3 millimeters, and the shape of the first hole 113 and the second hole 213 can be a variety of shapes such as round hole, strip, polygon.
[0043] In some embodiments of this utility model, reference is made to Figure 5 The battery cell also includes: a positive electrode tab 400; the positive electrode tab 400 is connected to the positive electrode plate 100; the positive electrode plate 100 is along a first direction (refer to...) Figure 5 Extending in the L direction, the positive electrode 100 is provided with a third hole group 120. The third hole group 120 includes a plurality of third holes 121 arranged sequentially along the first direction, and the plurality of third holes 121 are distributed on both sides of the positive electrode tab 400. In the same third hole group 120, the depth of the third hole 121 closer to the positive electrode tab 400 is greater. The third hole 121 adjacent to the positive electrode 100 must be at least 1 mm away from the positive electrode 100. The setting area of the third hole 121 is within 100 mm on both sides of the positive electrode tab 400 in the first direction, that is, the total length of the area where the third hole 121 can be set in the first direction is 200 mm.
[0044] In the actual charging and discharging process of the battery cell, the current is greater closer to the positive electrode tab 400 on the positive electrode 100, and the lithium plating is more severe. The current is smaller further away from the positive electrode tab 400, and the lithium plating is less severe. In this embodiment, a third hole 121 is opened near the positive electrode tab 400, which can effectively adjust the current path. By increasing the anisotropy of the electrode microstructure, the local current density is dispersed, and the thermodynamic driving force for lithium metal deposition is reduced. Moreover, depending on the different lithium plating conditions, the depth of the third hole 121 is greater closer to the positive electrode tab 400 and the depth of the third hole 121 is smaller further away from the positive electrode tab 400. This can effectively improve the lithium plating situation and enhance the liquid retention performance. Therefore, by arranging a third hole 121 in the material area near the positive electrode 100 in this embodiment, precise control of the dynamics can be achieved. While ensuring the charging window performance of the cell and minimizing the reduction of the cell's energy density, the problem of varying degrees of lithium plating due to different currents at the electrode tabs can be solved. At the same time, the liquid retention performance is improved, thereby enhancing the safety performance of the lithium-ion battery and extending its service life.
[0045] Within the same group 120 of third holes, the number of third holes 121 located on both sides of the positive electrode tab 400 in the first direction are equal and symmetrical about the positive electrode tab 400. The symmetrical distribution of the third holes 121 allows for more uniform stress distribution on the positive electrode tab 400 and enables an orderly decrease in the drilling depth of the positive electrode tab 400 towards both sides in the first direction, thereby better improving lithium deposition at the connection point between the tab and the electrode sheet.
[0046] In some embodiments of this utility model, reference is made to Figure 5 The third hole 121 adjacent to the positive electrode tab 400 is a first standard hole 121a; the depth of the first standard hole 121a is H, and the depth of the other third holes 121 within the same third hole group 120 is Hc, where c is the number of third holes 121 between the first standard hole 121 and the third hole 121a plus one; wherein, the depth of the first standard hole 121a is greater than the depth of the other third holes 121, i.e., H≥Hc, and satisfies Hc = H*(1-10%*c) to ensure that the depth of the third hole 121 gradually decreases from the tab outwards; in this embodiment, the positive electrode tab 400 is symmetrically divided into 7 regions from the inside to the outside in the first direction, i.e., Hc is H1 to H7; and the depth H of the first standard hole 121a satisfies 0.1Z≤H≤0.9Z, where Z is the thickness of the single material area of the positive electrode sheet 100, to avoid the first standard hole 121a penetrating the material area of the positive electrode sheet 100.
[0047] In some embodiments of this utility model, reference is made to Figure 6The battery cell also includes: a negative electrode tab 500; the negative electrode tab 500 is connected to the negative electrode plate 200; the negative electrode plate 200 is along a second direction (refer to...) Figure 6 Extending in the K direction, the negative electrode 200 is provided with a fourth hole group 220, which includes a plurality of fourth holes 221 arranged sequentially along the second direction, and the plurality of fourth holes 221 are distributed on both sides of the negative electrode tab 500. In the same fourth hole group 220, the depth of the fourth hole 221 closer to the negative electrode tab 500 is greater.
[0048] The fourth hole 221 adjacent to the negative electrode plate 200 needs to be at least 1 mm away from the negative electrode plate 200. The area where the fourth hole 221 is set is within 100 mm on both sides of the negative electrode tab 500 in the second direction. That is, the total length of the area where the fourth hole 221 can be set in the second direction is 200 mm.
[0049] In the actual charging and discharging process of the battery cell, the current is greater closer to the negative electrode tab 500 on the negative electrode plate 200, and the lithium plating is more severe. The current is smaller further away from the negative electrode tab 500, and the lithium plating is less severe. In this embodiment, a fourth hole 221 is opened near the negative electrode tab 500, which can effectively adjust the current path. By increasing the anisotropy of the electrode microstructure, the local current density is dispersed, and the thermodynamic driving force for lithium metal deposition is reduced. Moreover, depending on the different lithium plating conditions, the depth of the fourth hole 221 is greater closer to the negative electrode tab 500, and the depth of the fourth hole 221 is smaller further away from the negative electrode tab 500. This can effectively improve the lithium plating situation and enhance the liquid retention performance. Therefore, in this embodiment, a fourth hole 221 is arranged in the material area near the negative electrode 200, which can achieve precise control of the dynamics. It can still solve the problem of different lithium plating severity caused by different currents at the electrode tabs while ensuring the charging window performance of the cell and minimizing the reduction of the cell's energy density. At the same time, it can improve the liquid retention performance, thereby improving the safety performance of the lithium-ion battery and extending its service life.
[0050] Within the same group 220 of fourth holes, the number of fourth holes 221 located on both sides of the negative electrode tab 500 in the second direction are equal and symmetrical about the negative electrode tab 500. The symmetrical distribution of the fourth holes 221 allows for more uniform stress distribution on the negative electrode tab 500 and enables an orderly reduction in the drilling depth of the negative electrode tab 500 towards both sides in the second direction, thereby better improving lithium deposition at the connection point between the tab and the electrode sheet.
[0051] Reference Figure 6In some embodiments of this utility model, the fourth hole 221 adjacent to the negative electrode tab 500 is a second standard hole 221a; the depth of the second standard hole 221a is J, and the depth of the other fourth holes 221 within the same fourth hole group 220 is Jw, where w is the number of fourth holes 221 between the fourth hole 221 and the second standard hole 221a plus one; wherein, the depth of the second standard hole 221a is greater than the depth of the other fourth holes 221, i.e., Jw. ≥Jw, and satisfy Jw=J*(1-10%*w), to ensure that the depth of the fourth hole 221 gradually decreases from the tab outwards; in this embodiment, the negative electrode tab 500 is symmetrically divided into 7 regions from the inside to the outside in the second direction, that is, Jw is J1 to J7; and the depth J of the second standard hole 221a satisfies 0.1V≤J≤0.9V, where V is the thickness of the single material area of the negative electrode sheet 200, to avoid the second standard hole 221a penetrating the material area of the negative electrode sheet 200.
[0052] It is understandable that the aperture size of the third hole 121 and the fourth hole 221 is 20 to 90 micrometers, the spacing between two adjacent third holes 121 or fourth holes 221 is 1 millimeter to 3 millimeters, and the shape of the third hole 121 and the fourth hole 221 can be a variety of shapes such as round hole, strip, polygon.
[0053] This embodiment also provides a lithium battery, comprising: a battery cell as described above. In the first hole group 112 of the battery cell, the depth of the first hole 113 closer to the center in the width direction is greater, so that the deeper first hole 113 corresponds to the positive electrode corner region where electrolyte bridging and lithium plating are most severe, thereby improving the electrolyte bridging and lithium plating situation in the positive electrode corner region 110. Similarly, in the second hole group 212, the depth of the second hole 213 closer to the center in the width direction is greater, so that the deeper second hole 213 corresponds to the negative electrode corner region 210 where electrolyte bridging and lithium plating are most severe, thereby improving the electrolyte bridging and lithium plating situation in the negative electrode corner region 210. The depth of the second hole 213, which is closer to the edge of the negative electrode 200 in the width direction, is smaller, and the depth of the first hole 113, which is closer to the edge of the positive electrode 100 in the width direction, is smaller. This allows for precise control of the dynamics, which can solve the problem of different degrees of electrolyte breakage and lithium plating caused by different corner positions of the battery cell, while ensuring the charging window performance of the battery cell and minimizing the reduction of the battery cell's energy density. This improves the safety performance of the lithium-ion battery and extends its service life.
[0054] Example 1:
[0055] Positive electrode 100: Active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and uniformly coated onto an aluminum current collector in an N-methylpyrrolidone solvent system at a weight ratio of 97.9:0.6:0.5:1.0, and then cold-pressed into strips to obtain positive electrode 100.
[0056] Negative electrode 200: The active material, dispersant and binder are mixed in a weight ratio of 97.7:1:1.3 to prepare a slurry; the slurry is coated onto a copper current collector to obtain a negative electrode material, and then cold-pressed and slit to obtain negative electrode 200.
[0057] The positive electrode 100 and negative electrode 200 are etched using laser etching technology in the concave corner areas. Specifically, laser etching is performed on the concave corner surfaces of the electrodes (i.e., machining the first hole 113 and the second hole 213). The drilling depths D and F are 1 / 5 of the thickness of the concave fabric area, and the hole depth gradually decreases from the center of the electrode to its edge. Simultaneously, the third hole 121 and the fourth hole 221 are machined at the positions of the positive electrode tab 400 and the negative electrode tab 500 (corresponding to a position 1 mm away from the tab). The drilling depths H and J are 1 / 5 of the thickness of the single fabric area, and the hole depth gradually decreases from the tab to the position away from the tab.
[0058] Diaphragm 300: The base membrane is made of one of the following: polyethylene base membrane, polypropylene base membrane, polypropylene / polyethylene / polypropylene composite base membrane, polyimide base membrane, polyvinylidene fluoride membrane, polyethylene nonwoven base membrane, polypropylene nonwoven base membrane, and polyimide nonwoven base membrane. A first coating of vinylidene fluoride and ceramic particles and a second coating of styrene-butadiene rubber and ceramic particles are respectively coated on both sides of the base membrane to make diaphragm 300.
[0059] Electrolyte: Ethyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) are mixed in a volume ratio of 1:1:4:4. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare the electrolyte.
[0060] Full cell preparation: The above-mentioned positive electrode 100, separator 300 and negative electrode 200 are wound or stacked to make a bare cell, and then packaged and injected with electrolyte to make a finished lithium battery.
[0061] Example 2:
[0062] The composition of the positive electrode 100, negative electrode 200, separator 300, and electrolyte is the same as in Example 1. The difference is that in Example 2, the perforation depths D and F are half the thickness of the concave fabric area, and the perforation depths H and J are half the thickness of the single fabric area.
[0063] Example 3:
[0064] The positive electrode 100, negative electrode 200, separator 300, and electrolyte have the same composition as in Example 1. The difference is that in Example 2, the perforation depths D and F are 4 / 5 of the thickness of the concave fabric area, and the perforation depths H and J are 4 / 5 of the thickness of the single fabric area.
[0065] Comparison Case 1:
[0066] The composition of the positive electrode 100, negative electrode 200, separator 300, and electrolyte is the same as in Example 1. The difference is that in Comparative Case 1, laser etching technology is not used to drill holes in the concave area at the corner of the positive electrode 100 and the negative electrode 200 and at the electrode tab.
[0067] Comparative Case 2: The composition of positive electrode 100, negative electrode 200, separator 300, and electrolyte is the same as that of Example 1. The difference is that in Comparative Case 2, the perforation depths D and F are 1 / 5 of the thickness of the concave fabric area, the hole depth from the center of the electrode to the edge of the electrode is consistent, the perforation depths H and J are 1 / 5 of the thickness of the single fabric area, and the hole depth from the tab to the position away from the tab is consistent.
[0068] The summary table of examples and comparative cases is shown in Table 1 below.
[0069] The lithium batteries obtained from Examples 1, 2, and 3, Comparative Case 1, and Comparative Case 2 were tested. The test items were as follows:
[0070] The battery was cycled at 2C DC to 4.5V, CV 0.05C; 1C DC to 3.0V to obtain the first discharge capacity.
[0071] In addition, with
[0072] Cycling at 2C / 2.1C / 2.2C / 2.3C / 2.4C / 2.5C / 2.6C / 2.7C / 2.8C / 2.9C / 3C / 3.1C / 3.2C / 3.3C / 3.4C / 3.5C / 3.6C / 3.7C / 3.8C / 3.9C / 4C CC to 4.5V, CV 0.05C; 1C DC to 3.0V for 20 cycles yields battery lithium plating window data.
[0073] Wherein, liquid retention coefficient = liquid retention volume / first discharge capacity * 1000;
[0074] Cycle life test: Cycle steps 2C CC 4.5V, CV 0.05C; 1C DC 3.0V, the test ends when the capacity retention rate is 80%.
[0075] The resulting data comparison table between the embodiments and the comparative cases is shown in Table 2.
[0076] Table 1: Summary Table of Examples and Comparative Cases
[0077]
[0078] Table 2: Data Comparison Table between Examples and Comparative Cases
[0079]
[0080]
[0081] Comparative test data shows that machining the first hole 113 and the second hole 213 on the concave surface of the electrode at the corner of the cell can achieve precise dynamic control; machining the third hole 121 and the fourth hole 221 on the material area of the electrode near the tab can also achieve precise dynamic control. This can solve the problems of different electrolyte bridging and lithium plating severity caused by different corner positions, and different lithium plating severity caused by different currents at the tab positions, while ensuring the charging window performance of the cell and minimizing the reduction of the cell's energy density. At the same time, it improves the liquid retention performance, thereby improving the safety performance and extending the service life of lithium-ion batteries.
[0082] The above are merely preferred embodiments of this utility model. It should be noted that, for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this utility model, and these improvements and substitutions should also be considered within the protection scope of this utility model.
Claims
1. A battery cell, characterized in that, include: Positive electrode, negative electrode, and separator; the positive electrode, negative electrode, and separator are wound together to form a wound-core battery cell; The positive electrode sheet has a positive corner region; the positive corner region includes a positive concave material region; the positive concave material region has a first hole group; the first hole group includes a plurality of first holes arranged sequentially along the width direction of the positive electrode sheet; the negative electrode sheet has a negative corner region; the negative corner region includes a negative concave material region; the negative concave material region has a second hole group; the second hole group includes a plurality of second holes arranged sequentially along the width direction of the negative electrode sheet; In the same first hole group, the depth of the first hole is smaller the closer it is to the edge in the width direction of the positive electrode sheet; in the same second hole group, the depth of the second hole is smaller the closer it is to the edge in the width direction of the negative electrode sheet.
2. The battery cell according to claim 1, characterized in that, One of the first holes in the first hole group is located at the center of the positive electrode concave fabric region in the width direction; One of the second holes in the second hole group is located at the center of the negative electrode concave fabric area in the width direction.
3. The battery cell according to claim 2, characterized in that, The first hole located at the center of the positive electrode concave fabric area in the width direction is the first central hole; in the same group of first holes, the number of first holes located on both sides of the first central hole in the width direction are equal and symmetrical about the first central hole; The second hole located at the center of the negative electrode concave fabric area in the width direction is the second central hole; in the same group of second holes, the number of second holes located on both sides of the second central hole in the width direction are equal and symmetrical about the second central hole.
4. The battery cell according to claim 3, characterized in that, The depth of the first central hole is D, and the depth of the other first holes in the same first hole group is Dn; n is the number of first holes between the first hole and the first central hole plus one; where Dn = D*(1-10%*n); The depth of the second central hole is F, and the depth of the other second holes in the same second hole group is Fm; m is the number of second holes between the second hole and the second central hole plus one; where Fm = F * (1 - 10% * m).
5. The battery cell according to claim 1, characterized in that, Also includes: A positive electrode tab; the positive electrode tab is connected to the positive electrode sheet; the positive electrode sheet extends along a first direction, and the positive electrode sheet is provided with a third hole group, the third hole group including a plurality of third holes arranged sequentially along the first direction, and the plurality of third holes are distributed on both sides of the positive electrode tab, wherein, in the same third hole group, the depth of the third hole closer to the positive electrode tab is greater.
6. The battery cell according to claim 5, characterized in that, In the same group of third holes, the number of third holes located on both sides of the positive electrode tab in the first direction are equal and symmetrical about the positive electrode tab.
7. The battery cell according to claim 6, characterized in that, The third hole adjacent to the positive electrode tab is the first standard hole; the depth of the first standard hole is H, and the depth of the other third holes in the same group of third holes is Hc, where c is the number of third holes between the third hole and the first standard hole plus one; where Hc = H*(1-10%*c).
8. The battery cell according to claim 1, characterized in that, Also includes: A negative electrode tab; the negative electrode tab is connected to the negative electrode sheet; the negative electrode sheet extends along a second direction, and the negative electrode sheet is provided with a fourth hole group, the fourth hole group including a plurality of fourth holes arranged sequentially along the second direction, and the plurality of fourth holes are distributed on both sides of the negative electrode tab, wherein, in the same fourth hole group, the depth of the fourth hole closer to the negative electrode tab is greater.
9. The battery cell according to claim 8, characterized in that, In the same group of fourth holes, the number of fourth holes located on both sides of the negative electrode tab in the second direction is equal and symmetrical about the negative electrode tab. The fourth hole adjacent to the negative electrode tab is the second standard hole. The depth of the second standard hole is J, and the depth of the other fourth holes in the same group of fourth holes is Jw, where w is the number of fourth holes between the fourth hole and the second standard hole plus one. Wherein, Jw = J*(1-10%*w).
10. A lithium battery, characterized in that, include: The battery cell as described in any one of claims 1 to 9.