Battery cell

Abstract

The utility model provides a battery cell which comprises a first pole piece and a second pole piece, the polarity of the first pole piece is different from that of the second pole piece, and the first pole piece and the second pole piece are laminated and wound to form a roll core; the first pole piece comprises a first tab, and the second pole piece comprises a second tab; in the direction from the winding head end to the winding tail end of the winding core, the first pole piece comprises a first main body area and a first thinning area, and the thickness of the first thinning area in the first direction is smaller than that of the first main body area in the first direction; the projection of the first thinning area in the second direction is at least partially overlapped with the projection of the first tab and / or the second tab in the second direction, and the relationship between the total thickness H of the battery cell at the first tab or the second tab and the total thickness h of the battery cell at the center line in the second direction meets the condition that H-h is less than 1mm, therefore, the uniformity of the thickness of the battery cell is improved to a certain extent, and the volume energy density of the battery cell is further improved.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a battery cell. Background Technology

[0002] Currently, lithium-ion batteries are widely used not only in portable electronic devices such as mobile phones and laptops, but also in electric vehicles, electric bicycles and other electric equipment.

[0003] The battery cell is the core component of a lithium-ion battery. A battery cell includes a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. The positive electrode includes a positive current collector and a layer of positive active material on the surface of the current collector; the negative electrode includes a negative current collector and a layer of negative active material on the surface of the current collector. The battery cell is immersed in an electrolyte, and lithium ions move between the positive and negative electrodes through the electrolyte, thus enabling the battery to charge and discharge. However, the volumetric energy density of the battery cells in this technology is relatively low, failing to meet the performance requirements of the battery. Utility Model Content

[0004] In view of this, the present invention aims to provide a battery cell that can improve the volumetric energy density of the battery cell to a certain extent.

[0005] This utility model provides a battery cell, including a first electrode and a second electrode, wherein the first electrode and the second electrode have opposite polarities, and the first electrode and the second electrode are stacked and wound to form a core.

[0006] The first electrode includes a first tab, a first current collector, and a first active material layer disposed on at least one side of the first current collector; the first electrode has a first tab groove, and the first tab is located in the first tab groove;

[0007] The second electrode includes a second tab, a second current collector, and a second active material layer disposed on at least one side of the second current collector; the second electrode has a second tab groove, and the second tab is located in the second tab groove;

[0008] Along the direction from the first end to the last end of the winding of the core, the first electrode includes a first main body region and a first thinning region, wherein the thickness of the first thinning region in the first direction is less than the thickness of the first main body region in the first direction.

[0009] The projection of the first thinning region in the second direction at least partially overlaps with the projection of the first tab and / or the second tab in the second direction;

[0010] The relationship between the total thickness H of the battery cell at the first tab or the second tab and the total thickness h of the battery cell at the centerline in the second direction satisfies: Hh < 1 mm.

[0011] Optionally, the relationship between the total thickness H of the battery cell at the first tab or the second tab and the total thickness h of the battery cell at the centerline in the second direction satisfies: Hh < 0.3 mm.

[0012] Optionally, along the direction from the inner winding ring to the outer winding ring of the winding core, the first electrode tab and / or the second electrode tab are disposed on the Nth winding ring of the winding core, where N is a positive integer;

[0013] At least a portion of the first thinning zone is located on the N+1th and / or N-1th turns of the winding core.

[0014] Optionally, at least two turns of the first electrode sheet have the first thinning region along the direction from the inner winding to the outer winding of the core.

[0015] Optionally, at least two thinning zones on the first electrode are located on both sides of the centerline of the cell in the first direction.

[0016] Optionally, a protective adhesive film is provided on the battery cell at the position corresponding to the first tab and / or the second tab;

[0017] Along the first direction, the relationship between the difference d1 between the thickness of the first main body region and the thickness of the first thinning region, the total thickness d2 of the tab protective paper, and the thickness d3 of the tab corresponding to the tab protective paper satisfies: 10μm≤d1-(d2+d3)≤80μm.

[0018] Optionally, along the direction from the first end to the last end of the winding of the core, the first electrode includes a double-sided area and a single-sided area. The single-sided area is the area on one side of the first current collector where the first active material layer is disposed, and the double-sided area is the area on both sides of the first current collector where the first active material layer is disposed.

[0019] The first thinning region is located in the single-sided region; and / or, the first thinning region is located in the double-sided region.

[0020] Optionally, the first thinning region includes a first sub-thinning region and a second sub-thinning region;

[0021] The projection of the first sub-thinning region in the second direction at least partially overlaps with the projection of the first electrode in the second direction; the projection of the second sub-thinning region in the second direction at least partially overlaps with the projection of the second electrode in the second direction.

[0022] Along the first direction, the thickness of the first sub-thinning region is less than the thickness of the second sub-thinning region;

[0023] And / or, along the direction from the beginning to the end of the winding of the core, the first sub-thinning region and the second sub-thinning region extend toward each other and are connected.

[0024] Optionally, along the direction from the first end to the last end of the winding of the core, the first main body region includes a first region and a second region located on the side of the first region closer to the first thinning region.

[0025] The thickness of the second region in the first direction is less than the thickness of the first region in the first direction.

[0026] Optionally, the thickness of the second region gradually decreases in the direction away from the first region in the first direction.

[0027] Optionally, along the direction from the first end to the last end of the winding of the core, the second electrode includes a second main body region and a second thinning region, wherein the thickness of the second thinning region in the first direction is less than the thickness of the second main body region in the first direction.

[0028] The projection of the second thinning region in the second direction at least partially overlaps with the projection of the first tab and / or the second tab in the second direction.

[0029] Optionally, the thickness of the second thinning region in the first direction is greater than the thickness of the first thinning region in the first direction.

[0030] The battery cell provided by this utility model has a first tab groove on the first electrode sheet, with the first tab placed in the first tab groove, and a second tab groove on the second electrode sheet, with the second tab placed in the second tab groove. The first electrode sheet includes a first main body area and a first thinning area in the direction from the beginning to the end of the winding core. The thickness of the first thinning area in the first direction is less than the thickness of the first main body area in the first direction, and the projection of the first thinning area in the second direction at least partially overlaps with the projection of the first tab and / or the second tab in the second direction. This reduces the total thickness of the battery cell at least at the corresponding first tab and / or second tab, which to some extent balances the thickness difference of the battery cell at different positions and improves the uniformity of the battery cell thickness. Thus, without changing the total usable space, the battery cell thickness utilization space is improved, thereby achieving an increase in the volumetric energy density of the battery cell.

[0031] Meanwhile, by ensuring that the difference between the total thickness H of the battery cell at the first or second tab and the total thickness h of the battery cell at the centerline in the second direction is less than 1 mm, the thickness difference between the total thickness of the battery cell at the first or second tab and the middle part of the battery cell is not too large, thereby further improving the uniformity of the battery cell thickness and increasing the volumetric energy density of the battery cell.

[0032] Moreover, since the first electrode sheet is thinned at least at the position corresponding to the first tab and / or the second tab, if the electrode material expands in volume during the charging and discharging process, the position corresponding to the first thinning area can provide a certain buffer space for the expansion of the electrode material, so that the expansion stress of the electrode sheet can be effectively released, reducing the squeezing force between the first electrode sheet and the second electrode sheet, thereby reducing the risk of deformation and breakage of the first electrode sheet, the second electrode sheet, etc.

[0033] In addition, by thinning at least the position corresponding to the first tab and / or the second tab of the first electrode, the wetting effect of the electrolyte can be improved to a certain extent, so that lithium ions can diffuse rapidly in the electrolyte, thereby improving the kinetic performance and cycle performance of the battery. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the first electrode sheet in its unfolded state according to an embodiment of the present invention. Figure 1 ;

[0035] Figure 2 This is a schematic diagram of the structure of the core according to an embodiment of the present invention;

[0036] Figure 3 for Figure 2 Magnified local structure at the position corresponding to the first electrode tab in the middle Figure 1 ;

[0037] Figure 4 for Figure 2 Magnified local structures at corresponding positions of the first and second electrodes. Figure 1 ;

[0038] Figure 5 for Figure 2 Magnified local structures at corresponding positions of the first and second electrodes. Figure 2 ;

[0039] Figure 6 for Figure 2 Magnified local structure at the position corresponding to the first electrode tab in the middle Figure 2 ;

[0040] Figure 7 for Figure 2 Magnified local structure at the position corresponding to the first electrode tab in the middle Figure 3 ;

[0041] Figure 8 This is a schematic diagram of the structure of the first electrode sheet in its unfolded state according to an embodiment of the present invention. Figure 2 ;

[0042] Figure 9 This is a schematic diagram of the structure of the first electrode sheet in its unfolded state according to an embodiment of the present invention. Figure 3 ;

[0043] Figure 10 This is a schematic diagram of the structure of the second electrode sheet in the unfolded state according to an embodiment of the present invention;

[0044] Figure 11 This is a schematic diagram of the cross-sectional structure of the first electrode and the remaining parts of the battery cell in the thickness direction, excluding the first electrode, according to an embodiment of the present invention.

[0045] Among them, 1. First electrode; 11. First current collector; 12. First active material layer; 13. First main body region; 131. First region; 132. Second region; 133. Arc-shaped surface; 14. First thinning region; 141. First sub-thinning region; 142. Second sub-thinning region; 15. First tab; 16. First tab groove; 17. Double-sided region; 18. Single-sided region; 2. Second electrode; 21. Second current collector; 22. Second active material layer; 23. Second main body region; 24. Second thinning region; 25. Second tab; 26. Second tab groove; 3. Separator; 4. Tab protective adhesive paper. Detailed Implementation

[0046] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model are within the protection scope of the present utility model.

[0047] A lithium-ion battery cell typically consists of a positive electrode, a negative electrode, and a separator. The cell can be, for example, a wound core. Specifically, the positive electrode, separator, and negative electrode are stacked and wound from the inside out to form a wound core. The positive electrode has a positive tab, and the negative electrode has a negative tab; current is drawn out through these tabs to achieve charging and discharging of the battery.

[0048] Among them, the volumetric energy density of a battery cell is one of the important indicators characterizing battery performance. Currently, the requirements for the volumetric energy density of battery cells are becoming increasingly stringent. To improve the volumetric energy density of a battery cell, this utility model provides a battery cell by setting a first tab groove on a first electrode sheet, with the first tab located within the first tab groove, and setting a second tab groove on a second electrode sheet, with the second tab located within the second tab groove. The first electrode sheet is thinned at least at the positions corresponding to the first tab and / or the second tab. Furthermore, by setting the difference between the total thickness of the battery cell at the first tab or the second tab and the total thickness at the centerline of the battery cell to be less than 1 mm, the total thickness at the corresponding tab positions of the battery cell is reduced to at least a certain extent. This balances the thickness difference of the battery cell at different positions, improves the uniformity of the battery cell thickness, and thus improves the utilization of the battery cell's thickness space, thereby achieving an increase in the volumetric energy density of the battery cell.

[0049] The battery cell provided by this utility model will be described in detail below with reference to the accompanying drawings and specific embodiments:

[0050] Reference Figures 1 to 11 As shown, this embodiment provides a battery cell, which is used in a battery, such as a lithium-ion battery. The battery can be used as a power source or energy storage unit for electronic devices, which may be, but are not limited to, mobile devices (mobile phones, laptops, tablets, etc.) and electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, electric bicycles, etc.).

[0051] The battery cell provided in this embodiment includes: a first electrode 1, a second electrode 2 and a separator 3. The first electrode 1 and the second electrode 2 have different polarities. The separator 3 is located between the first electrode 1 and the second electrode 2. The first electrode 1, the separator 3 and the second electrode 2 are stacked and wound to form a wound core.

[0052] Specifically, the first electrode 1 includes a first tab 15, a first current collector 11, and a first active material layer 12 disposed on at least one side of the first current collector 11. The first current collector 11 has two opposing sides, which are used to coat the first active material layer 12. In specific implementation, the first active material layer 12 can be disposed on both sides of the first current collector 11, or the first active material layer 12 can be disposed on only one side of the first current collector 11, depending on actual needs.

[0053] The second electrode 2 specifically includes: a second electrode tab 25, a second current collector 21, and a second active material layer 22 disposed on at least one side of the second current collector 21. The second current collector 21 has two opposing sides, which are used to coat the second active material layer 22. In specific implementation, the second active material layer 22 can be disposed on both sides of the second current collector 21, or the second active material layer 22 can be disposed on only one side of the second current collector 21, depending on actual needs.

[0054] For example, the first electrode 1 can be a positive electrode, and the second electrode 2 can be a negative electrode.

[0055] Specifically, the first current collector 11 is, for example, an aluminum foil, and the material of the first active material layer 12 can be, for example, a positive electrode active material such as lithium cobalt oxide, ternary materials, or lithium iron phosphate. The second current collector 21 can be, for example, a copper foil, and the material of the second active material layer 22 can be, for example, a negative electrode active material such as silicon-based or graphite.

[0056] Due to the arrangement of the first tab 15, the second tab 25, etc., the thickness of the battery cell is relatively thick at the positions of the first tab 15 and the second tab 25. This results in poor thickness uniformity of the battery cell at different positions. Since the battery cell performance indicators such as volumetric energy density are constrained by the maximum thickness of the battery cell, this will directly affect the volumetric energy density of the battery cell.

[0057] To improve the uniformity of cell thickness and increase the volumetric energy density of the cells, refer to Figures 1 to 5 As shown, in this embodiment of the battery cell, the first electrode plate 1 is provided with a first electrode slot 16, and the first electrode tab 15 is located in the first electrode slot 16. The second electrode plate 2 is provided with a second electrode slot 26, and the second electrode tab 25 is located in the second electrode slot 26.

[0058] The first tab 15 is accommodated by the first tab groove 16, which reduces the total thickness of the battery cell at the corresponding first tab 15, thereby increasing the volumetric energy density of the battery cell. In addition, the first tab groove 16 can limit the first tab 15 to a certain extent, thereby improving the convenience of installation of the first tab 15 and the stability of the first tab 15.

[0059] For example, the first electrode 15 can be welded to the first current collector 11. In a specific implementation, protective adhesive paper 4 can also be provided at the welding point of the first electrode 15 and on both sides of the first electrode 15 to protect the first electrode 15 and prevent short circuits from occurring.

[0060] The second tab 25 is accommodated by the second tab groove 26, which reduces the total thickness of the battery cell at the corresponding second tab 25, thereby increasing the volumetric energy density of the battery cell. In addition, the setting of the second tab groove 26 can limit the second tab 25 to a certain extent, thereby improving the ease of installation of the second tab 25 and the stability of the second tab 25.

[0061] For example, the second electrode 25 can be welded to the second current collector 21. In a specific implementation, electrode protective tape 4 can also be provided at the welding point of the second electrode 25 and on both sides of the second electrode 25 to protect the second electrode 25 and prevent short circuits from occurring.

[0062] Meanwhile, in the direction from the beginning to the end of the winding of the core, the first electrode 1 includes a first main body region 13 and a first thinning region 14, wherein the thickness d of the first thinning region 14 in the first direction is less than the thickness D of the first main body region 13 in the first direction.

[0063] It should be noted that the beginning of the winding can be understood as the area where the electrode winding begins during the battery cell winding process, i.e., the head area, which is located inside the battery cell. Correspondingly, the end of the winding can be understood as the area where the electrode winding ends.

[0064] Combination Figure 1 and Figure 2 As shown, the direction from the beginning to the end of the winding can be specifically as follows: Figure 1 The direction from left to right. Specifically, the first direction here can be... Figure 2 The vertical direction can be, for example, the thickness direction of the battery cell.

[0065] The projection of the first thinning region 14 in the second direction at least partially overlaps with the projection of the first tab 15 and / or the second tab 25 in the second direction.

[0066] The second direction here can specifically be... Figure 2 The left and right directions in the text can be, for example, the width direction of the battery cell.

[0067] Specifically, the projection of the first thinning region 14 in the second direction can at least partially overlap with the projection of the first tab 15 in the second direction. That is, along the thickness direction of the battery cell, the position of the first thinning region 14 corresponds to the position of the first tab 15, thereby reducing the total thickness of the battery cell at the first tab 15 to a certain extent. Alternatively, the projection of the first thinning region 14 in the second direction can at least partially overlap with the projection of the second tab 25 in the second direction. That is, along the thickness direction of the battery cell, the position of the first thinning region 14 corresponds to the position of the second tab 25, thereby reducing the total thickness of the battery cell at the second tab 25 to a certain extent. Alternatively, a portion of the projection of the first thinning region 14 in the second direction can at least partially overlap with the projection of the first tab 15, and another portion of the projection of the first thinning region 14 can at least partially overlap with the projection of the second tab 25, thereby reducing the total thickness of the battery cell at the first tab 15 and the second tab 25 to a certain extent. The above settings balance the thickness difference of the battery cell at different locations to a certain extent, improve the uniformity of the battery cell thickness, and increase the utilization of the battery cell thickness space while keeping the total usable space unchanged, thereby achieving an increase in the volumetric energy density of the battery cell.

[0068] For example, in a specific implementation, the active material layer at least corresponding to the first tab 15 and / or the second tab 25 of the first electrode 1 can be thinned. For example, at least part of the active material layer on the first electrode 1 located on the outer or inner winding of the first tab 15 can be removed by laser burning, thereby forming a thinning area at the corresponding position of the first electrode 1, such as forming a thinning groove, thereby reducing the total thickness of the battery cell at the position of the first tab 15 and / or the second tab 25.

[0069] Of course, in other implementation methods, the thinning of the corresponding position of the first electrode 1 can also be achieved through other mechanical means.

[0070] Reference Figure 1 As shown, specifically, a portion of the active material layer at the location corresponding to the first tab 15 and / or the second tab 25 on one side of the first current collector 11 can be thinned. Alternatively, the entire active material layer at the corresponding location on one side of the first current collector 11 can be thinned. Furthermore, part or all of the active material layer at the corresponding locations on both sides of the first current collector 11 can be thinned, depending on the required thickness.

[0071] Reference Figure 2 As shown, the total thickness H of the cell at the first tab 15 or the second tab 25 is... Figure 2 The dimension of the cell along the vertical direction at the first tab 15 or the second tab 25 and the total thickness h of the cell at the centerline oo in the second direction. Figure 2 The relationship between the dimensions of the battery cell along the vertical direction at the center line oo satisfies: Hh < 1 mm.

[0072] The second direction here can be Figure 2 The left and right directions in the text can specifically refer to the width direction of the core.

[0073] For example, the difference can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 0.99mm.

[0074] This design ensures that the thickness difference between the battery cell at the tab and the battery cell centerline is not too large, thereby further improving the uniformity of the battery cell thickness at the tab and the centerline oo, thus making better use of the thickness space and further improving the volumetric energy density of the battery cell.

[0075] In other implementations, the first electrode 1 can also be a negative electrode and the second electrode 2 can be a positive electrode.

[0076] The battery cell provided in this embodiment has a first tab groove 16 on the first electrode plate 1, and a first tab 15 is disposed in the first tab groove 16. A second tab groove 26 is provided on the second electrode plate 2, and a second tab 25 is disposed in the second tab groove 26. The first electrode plate 1 includes a first main body region 13 and a first thinning region 14 in the direction from the beginning to the end of the winding of the core. The thickness of the first thinning region 14 in the first direction is less than the thickness of the first main body region 13 in the first direction. The projection of the first thinning region 14 in the second direction at least partially overlaps with the projection of the first tab 15 and / or the second tab 25 in the second direction. This reduces the total thickness of the battery cell at least at the corresponding first tab 15 and / or second tab 25, which balances the thickness difference of the battery cell at different positions to a certain extent and improves the uniformity of the battery cell thickness. Thus, the thickness utilization space of the battery cell is improved without changing the total usable space, thereby improving the volumetric energy density of the battery cell.

[0077] Meanwhile, by ensuring that the difference between the total thickness H of the battery cell at the first tab 15 or the second tab 25 and the total thickness h of the battery cell at the centerline in the second direction is less than 1 mm, the difference between the total thickness of the battery cell at the first tab 15 or the second tab 25 and the thickness at the center of the battery cell is not too large, thereby improving the uniformity of the battery cell thickness and further improving the volumetric energy density of the battery cell.

[0078] In other words, with the same cell volumetric energy density, the cell in this embodiment occupies less thickness space, which is beneficial for the development of thinner and lighter electronic devices.

[0079] Moreover, since the first electrode 1 is thinned at least at the position corresponding to the first tab 15 and / or the second tab 25, if the electrode material expands in volume during the charging and discharging process, the position corresponding to the first thinning area 14 can provide a certain buffer space for the expansion of the electrode material, so that the expansion stress of the electrode can be effectively released, reducing the compressive force between the first electrode 1 and the second electrode 2, thereby reducing the risk of deformation and breakage of the first electrode 1 and the second electrode 2.

[0080] In addition, by thinning at least the position corresponding to the first tab 15 and / or the second tab 25 of the first electrode 1, the wetting effect of the electrolyte can be improved to a certain extent, so that lithium ions can diffuse rapidly in the electrolyte, thereby improving the kinetic performance and cycle performance of the battery.

[0081] Furthermore, when the first electrode 1 is a positive electrode and the second electrode 2 is a negative electrode, the first electrode 1 is thinned at least at the position corresponding to the first tab 15 and / or the second tab 25. This reduces the mass of the active material of the first electrode 1 to a certain extent, thereby reducing the amount of lithium ions received by the second electrode 2, thus reducing the risk of lithium plating and improving the battery's electrical performance, safety, and lifespan.

[0082] Furthermore, in some embodiments, the relationship between the total thickness H of the battery cell at the first tab 15 or the second tab 25 and the total thickness h of the battery cell at the centerline in the second direction satisfies: Hh < 0.3 mm.

[0083] This design further ensures that the thickness of the cell at the tab is not too large, thereby improving the uniformity of the cell thickness at the tab and at the center line oo, thus making better use of the thickness space and further improving the volumetric energy density of the cell.

[0084] Reference Figure 3 As shown, in some embodiments, the projection of the first thinning region 14 in the second direction at least partially overlaps with the projection of the first tab 15 in the second direction, and the projection width W2 of the first thinning region 14 in the second direction is greater than the projection width W1 of the first tab groove in the second direction.

[0085] The second direction here is Figure 3 The left and right directions in the middle can be the width direction of the battery cell, and the projected width is the projected size of the first thinning area 14 along the left and right directions.

[0086] This design can absorb the thickness of the first tab groove 16, the first tab 15, and the tab protective paper 4 to a certain extent, thereby further reducing the total thickness of the battery cell at the corresponding position of the first tab 15, and further improving the volumetric energy density of the battery cell.

[0087] Reference Figure 4 As shown, in some embodiments, the projection of the first thinning region 14 in the second direction at least partially overlaps with the projection of the second tab 25 in the second direction, and the projection width W2 of the first thinning region 14 in the second direction is greater than the projection width W3 of the second tab groove 26 in the second direction.

[0088] The second direction here is Figure 4 The left and right directions in the middle can specifically refer to the width direction of the battery cell. Here, the projected width is specifically along the first thinning region 14. Figure 4 The projection size in the left and right directions.

[0089] This design can absorb the thickness of the second tab groove 26, the second tab 25, and the tab protective paper 4 to a certain extent, thereby further reducing the total thickness of the battery cell at the corresponding position of the second tab 25, and further improving the volumetric energy density of the battery cell.

[0090] Combination Figures 2 to 5 As shown, in some embodiments, a first tab 15 and / or a second tab 25 are disposed on the Nth turn of the winding core along the direction from the inner turn to the outer turn, where N is a positive integer. At least a portion of the first thinning region 14 is located on the N+1th and / or N-1th turns of the winding core.

[0091] This ensures that at least part of the first thinning region 14 is positioned near the first tab 15 and / or the second tab 25, thereby better balancing the total thickness of the cell at the corresponding tab positions and improving the uniformity of the cell thickness.

[0092] Taking the first tab 15 as an example, if the first tab 15 is located in the third turn of the winding core, at least part of the first thinning area 14 on the first electrode 1 can be located in the fourth turn of the winding core and correspond to the first tab 15, that is, located in the outer ring of the first tab 15. In other words, at least part of the first thinning area 14 is located near the first tab 15, so as to better balance the total thickness of the cell at the corresponding position of the first tab 15 and improve the uniformity of the cell thickness.

[0093] Of course, at least part of the first thinning zone 14 can also be located in the second ring of the core and correspond to the first tab 15, that is, located in the inner ring of the first tab 15.

[0094] In specific implementation, the first thinning region 14 on the first electrode 1 can be one or at least two. When there are at least two first thinning regions 14, after the first electrode 1 is wound, one or more turns of the first electrode 1 can have the first thinning region 14.

[0095] Combination Figure 2 and Figure 6 As shown, in some embodiments, at least two turns of the first electrode 1 have a first thinning region 14 along the direction from the inner winding to the outer winding of the core, and the projection of the first thinning region 14 in the second direction at least partially overlaps with the projection of the first electrode tab 15 and / or the second electrode tab 25.

[0096] In specific implementation, the first thinning regions 14 located on different rings of the first electrode 1 can all correspond to the first tab 15, so as to further reduce the total thickness of the battery cell at the first tab 15 and improve the uniformity of the overall thickness of the battery cell; refer to Figure 6 As shown, for example, there are two rings with a first thinning area 14, and both of the first thinning areas 14 are set with a first tab 15.

[0097] Alternatively, the first thinning region 14 located on different rings of the first electrode 1 can all correspond to the second tab 25, so as to further reduce the total thickness of the cell at the second tab 25 and improve the uniformity of the overall thickness of the cell.

[0098] Alternatively, the first thinning region 14 on one or more turns corresponds to the first tab 15, and the first thinning region 14 on another or more turns corresponds to the second tab 25. While reducing the thickness of the first tab 15 and the second tab 25 corresponding to the cell, the force balance of the first electrode 1 can be improved to a certain extent by distributing multiple first thinning regions 14 in different turns, thereby improving the structural stability of the first electrode 1.

[0099] Furthermore, continue to refer to Figure 6 As shown, at least two thinning regions 14 on the first electrode 1 are respectively located on both sides of the center line ss of the cell in the first direction. The first direction here specifically refers to... Figure 6 The up and down directions in the middle.

[0100] This design improves the balance of forces on both sides of the cell. For example, during the charging and discharging process, when the electrode material expands, this design can prevent uneven forces on both sides of the cell from causing deformation, thereby improving the overall stability of the cell structure and ensuring the performance and lifespan of the battery.

[0101] Reference Figure 7 As shown, in some embodiments, along the first direction (specifically, it can be...) Figure 7 The relationship between the thickness D of the first main body region 13 and the thickness d of the first thinning region 14 (i.e., the thickness that is thinned at this position of the first electrode 1), the total thickness d2 of the electrode tab protective paper 4, and the thickness d3 of the electrode tab corresponding to the electrode tab protective paper 4 satisfies: 10μm≤d1-(d2+d3)≤80μm.

[0102] For example, the difference can be 10μm, 20μm, 30μm, 40μm, 45μm, 50μm, 60μm, 70μm, or 80μm.

[0103] Continue to refer to Figure 7As shown, taking the position corresponding to the first electrode tab 15 as an example, the thickness d3 of the electrode tab here is, for example, the thickness d3 of the first electrode tab 15, and the total thickness d2 of the electrode tab protective paper 4 here is, for example, the sum of the thicknesses of all electrode tab protective paper 4 corresponding to the first electrode tab 15. For example, electrode tab protective paper 4 is provided on both the upper and lower sides of the first electrode tab 15, and electrode tab protective paper 4 is also provided on the side of the second electrode plate 2 adjacent to the first electrode tab 15 facing the first electrode tab 15. The thickness of each electrode tab protective paper 4 is d0, and the total thickness d2 of the electrode tab protective paper 4 here can be, for example, the sum of the thicknesses d0 of the four electrode tab protective paper 4.

[0104] Of course, the specific number of protective adhesive strips corresponding to the first tab 15 or the second tab 25 can be set according to the actual situation.

[0105] This configuration further ensures the total thickness of the battery cell at the first tab 15, thereby further improving the uniformity of the battery cell thickness.

[0106] Combination Figure 2 and Figure 8 As shown, along the direction from the beginning to the end of the winding of the core, the first electrode 1 includes a double-sided region 17 and a single-sided region 18. The single-sided region 18 is the area on one side of the first current collector 11 where the first active material layer 12 is provided, and the double-sided region 17 is the area on both sides of the first current collector 11 where the first active material layer 12 is provided.

[0107] In some embodiments, at least a portion of the first thinning region 14 is located in the single-sided region 18.

[0108] During the cell manufacturing process, the single-sided region 18 of the first electrode 1 is thinner than the double-sided region 17. The single-sided region 18 is easily over-voltaged, which can lead to poor electrolyte wetting in this area, resulting in reduced battery charge-discharge performance and cycle performance. By setting at least part of the first thinning region 14 in the single-sided region 18, the total thickness at the corresponding positions of the first tab 15 and / or the second tab 25 of the cell is reduced, while the electrolyte wetting effect is improved to a certain extent, thereby improving the battery's charge-discharge and cycle performance.

[0109] In some embodiments, at least a portion of the first thinning region 14 is located in the double-sided region 17.

[0110] Since the double-sided region 17 is relatively thicker, by setting the first thinning region 14 in the double-sided region 17, the total thickness at the position of the first tab 15 and / or the second tab 25 of the battery cell is reduced, and the volumetric energy density of the battery cell is increased. At the same time, it can also effectively accommodate the volume expansion of the electrode material, reduce the extrusion pressure between the first electrode 1 and the second electrode 2, and further reduce the risk of deformation and breakage of the first electrode 1 and the second electrode 2.

[0111] In some embodiments, a first thinning region 14 may be provided on both the double-sided region 17 and the single-sided region 18, thereby further reducing the total thickness of the battery cell at the positions of the first tab 15 and / or the second tab 25, improving the uniformity of the battery cell thickness, and further improving the volumetric energy density of the battery cell.

[0112] Continue to refer to Figure 4 As shown, the first thinning region 14 includes a first sub-thinning region 141 and a second sub-thinning region 142;

[0113] The first sub-thinning region 141 is in the second direction (specifically, it can be...). Figure 4 The projection of the second sub-thinning region 142 in the left-right direction overlaps at least partially with the projection of the first electrode 15 in the second direction; the projection of the second sub-thinning region 142 in the second direction overlaps at least partially with the projection of the second electrode 25 in the second direction.

[0114] In other words, the thickness of the battery cell at the corresponding positions of the first tab 15 and the second tab 25 is reduced, thereby further improving the uniformity of the battery cell thickness.

[0115] Combination Figure 2 and Figure 4 As shown, the battery cell also has a first fold portion B of the second electrode 2 at the position corresponding to the first electrode 15. This may cause the thickness of the battery cell at the position corresponding to the first electrode 15 to be greater than the thickness of the battery cell at the position corresponding to the second electrode 25. Based on this, in order to improve the uniformity of the total thickness of the battery cell at the position corresponding to the first electrode 15 and the position corresponding to the second electrode 25, in some embodiments, along the first direction (specifically, it can be...) Figure 4 (in the vertical direction), the thickness d4 of the first sub-thinning region 141 is less than the thickness d5 of the second sub-thinning region 142.

[0116] In other words, the total thickness subtracted at the corresponding first tab 15 of the first electrode 1 is greater than the total thickness subtracted at the corresponding second sub-thinning region 142 of the first electrode 1, thereby absorbing the thickness of the first tab 15 and the first fold region of the second electrode 2 to a certain extent, so as to reduce the total thickness of the cell at the corresponding first tab 15, further improving the uniformity of the overall thickness of the cell, thereby effectively improving the volumetric energy density of the cell.

[0117] Combination Figure 4 and Figure 5 As shown, along the direction from the beginning to the end of the winding core, the first sub-thinning region 141 and the second sub-thinning region 142 extend toward each other and are connected.

[0118] In other words, the thinning areas at at least two locations can be integrated into a single unit, thereby effectively covering both the first tab 15 and the second tab 25 simultaneously, further improving the uniformity of the overall cell thickness. This configuration also makes thinning the first electrode 1 more convenient.

[0119] Reference Figure 9 As shown, in some embodiments, the direction along the winding start end to winding end of the core (e.g., ...) Figure 9 In the direction from left to right, the first main body region 13 includes a first region 131 and a second region 132 located on the side of the first region 131 near the first thinning region 14. The second region 132 is located in the first direction (e.g., in the direction from left to right). Figure 9 The thickness D2 in the vertical direction (specifically, the thickness direction of the core) is less than the thickness D1 in the first region 131 in the first direction.

[0120] This configuration reduces the total thickness at least at the positions of the first tab 15 and / or the second tab 25 of the battery cell, while allowing for a better transition between the first main body region 13 and the first thinning region 14, preventing stress concentration at the joint from causing the first electrode 1 to crack or the active material layer to shed powder.

[0121] In some embodiments, the thickness D2 of the second region 132 gradually decreases in the direction away from the first region 131. For example, along... Figure 9 In the direction from left to right, the thickness D2 of the second region 132 gradually decreases.

[0122] This further allows for a smoother transition between the first main body region 13 and the first thinning region 14, further preventing stress concentration that could lead to joint breakage or bulging. This design also helps to better release the active energy of this portion of the first main body region 13. Furthermore, by reducing the amount of active material at the ends of the first main body region 13, the risk of lithium plating in the corresponding area of ​​the second electrode 2 is further reduced.

[0123] Continue to refer to Figure 9 As shown, the surface of the second region 132 facing away from the first current collector 11 is an arc-shaped surface 133. This further enables a smoother transition between the first main body region 13 and the first thinning region 14, further avoiding stress concentration that could lead to joint breakage or bulging.

[0124] Reference Figure 11 As shown, Figure 11 The upper part is a schematic diagram of the cross-sectional structure of the first pole piece 1. Figure 11 The lower half, A, is a schematic diagram showing the thickness variation of the battery cell across its cross-section, excluding the first electrode 1. Figure 11 It can be seen that the first thinning area 14 on the first electrode 1 has been thinned at the corresponding position, which to a certain extent balances the thickness of the cell at least at the tab, thereby improving the thickness uniformity of the entire cell and helping to improve the volumetric energy density of the cell.

[0125] In some embodiments, refer to Figure 10 As shown, along the direction from the beginning to the end of the winding of the core, the second electrode 2 includes a second main body region 23 and a second thinning region 24. The thickness c of the second thinning region 24 in the first direction is less than the thickness e of the second main body region 23 in the first direction.

[0126] The projection of the second thinning region 24 in the second direction at least partially overlaps with the projection of the first tab 15 and / or the second tab 25 in the second direction.

[0127] The first direction here can specifically be... Figure 10 The vertical direction can be, for example, the thickness direction of the battery cell. The second direction can specifically be... Figure 10 The left and right directions in the text can be, for example, the width direction of the battery cell.

[0128] In other words, while thinning is performed at least at the position corresponding to the first tab 15 and / or the second tab 25 of the first electrode 1, thinning is also performed at least at the position corresponding to the first tab 15 and / or the second tab 25 of the second electrode 2. The uniformity of the cell thickness is further improved by the combination of thinning of the first electrode 1 and the second electrode 2, thereby improving the volumetric energy density of the cell.

[0129] The method and principle of thinning on the second electrode 2 are the same as those of the first electrode 1, and will not be repeated here. For details, please refer to the description of the above embodiments.

[0130] To reduce the risk of lithium plating, when the second thinning region 24 is formed on the second electrode 2, the second thinning region 24 can be formed at the position of the second electrode 2 corresponding to the first thinning region 14 of the first electrode 1, and at least part of the second thinning region 24 is set to correspond to the first tab 15 and / or the second tab 25.

[0131] In other words, a first thinning region 14 can be set on one or more turns of the first electrode 1, or a second thinning region 24 can be set on the second electrode 2 at the position corresponding to the first thinning region 14. By combining one or more sets of the first thinning region 14 and the second thinning region 24, the thickness of the battery cell can be adjusted, the uniformity of the overall thickness of the battery cell can be improved, and the volumetric energy density of the battery cell can be increased.

[0132] Furthermore, combined Figure 1 and Figure 10 As shown, in some embodiments, the thickness c of the second thinning region 24 in the first direction can be greater than the thickness d of the first thinning region 14 in the first direction.

[0133] In other words, the thickness subtracted from the second electrode 2 is less than or equal to the thickness subtracted from the first electrode 1, thereby ensuring that the second electrode 2 can effectively cover the first electrode 1 and further prevent lithium plating to a certain extent. That is, this setting can improve the uniformity of cell thickness and increase the volumetric energy density of the cell while further preventing lithium plating.

[0134] Tests have shown that when the maximum thickness of the battery cell is greater than 1 mm, the above thinning settings can reduce the maximum thickness of the battery cell by at least 0.05 mm to 0.15 mm, increasing the volumetric energy density by more than 10%.

[0135] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection or an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Furthermore, the terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0136] In this document, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0137] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications or equivalent substitutions made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A battery cell, characterized in that, It includes a first electrode and a second electrode, the first electrode and the second electrode have different polarities, and the first electrode and the second electrode are stacked and wound to form a core; The first electrode includes a first tab, a first current collector, and a first active material layer disposed on at least one side of the first current collector; The first electrode plate is provided with a first electrode tab groove, and the first electrode tab is located in the first electrode tab groove; The second electrode includes a second tab, a second current collector, and a second active material layer disposed on at least one side of the second current collector; the second electrode has a second tab groove, and the second tab is located in the second tab groove; Along the direction from the first end to the last end of the winding of the core, the first electrode includes a first main body region and a first thinning region, wherein the thickness of the first thinning region in the first direction is less than the thickness of the first main body region in the first direction. The projection of the first thinning region in the second direction at least partially overlaps with the projection of the first tab and / or the second tab in the second direction; The relationship between the total thickness H of the battery cell at the first tab or the second tab and the total thickness h of the battery cell at the centerline in the second direction satisfies: Hh < 1 mm.

2. The battery cell according to claim 1, characterized in that, The relationship between the total thickness H of the battery cell at the first tab or the second tab and the total thickness h of the battery cell at the centerline in the second direction satisfies: Hh < 0.3 mm.

3. The battery cell according to claim 1, characterized in that, Along the direction from the inner winding ring to the outer winding ring of the winding core, the first electrode tab and / or the second electrode tab are disposed on the Nth winding ring of the winding core, where N is a positive integer; At least a portion of the first thinning zone is located on the N+1th and / or N-1th turns of the winding core.

4. The battery cell according to claim 1, characterized in that, Along the direction from the inner winding to the outer winding of the core, at least two turns of the first electrode sheet have the first thinning region.

5. The battery cell according to claim 4, characterized in that, At least two thinning zones on the first electrode are located on both sides of the centerline of the cell in the first direction.

6. The battery cell according to claim 1, characterized in that, The battery cell is provided with tab protective paper at the position corresponding to the first tab and / or the second tab; Along the first direction, the relationship between the difference d1 between the thickness of the first main body region and the thickness of the first thinning region, the total thickness d2 of the tab protective paper, and the thickness d3 of the tab corresponding to the tab protective paper satisfies: 10μm≤d1-(d2+d3)≤80μm.

7. The battery cell according to claim 1, characterized in that, Along the direction from the first end to the last end of the winding of the core, the first electrode includes a double-sided area and a single-sided area. The single-sided area is the area on one side of the first current collector where the first active material layer is disposed, and the double-sided area is the area on both sides of the first current collector where the first active material layer is disposed. The first thinning region is located in the single-sided region; and / or, the first thinning region is located in the double-sided region.

8. The battery cell according to claim 1, characterized in that, The first thinning region includes a first sub-thinning region and a second sub-thinning region; The projection of the first sub-thinning region in the second direction at least partially overlaps with the projection of the first electrode in the second direction; the projection of the second sub-thinning region in the second direction at least partially overlaps with the projection of the second electrode in the second direction. Along the first direction, the thickness of the first sub-thinning region is less than the thickness of the second sub-thinning region; And / or, along the direction from the beginning to the end of the winding of the core, the first sub-thinning region and the second sub-thinning region extend toward each other and are connected.

9. The battery cell according to claim 1, characterized in that, Along the direction from the first end to the last end of the winding of the core, the first main body region includes a first region and a second region located on the side of the first region closer to the first thinning region; The thickness of the second region in the first direction is less than the thickness of the first region in the first direction.

10. The battery cell according to claim 9, characterized in that, The thickness of the second region gradually decreases in the direction away from the first region.

11. The battery cell according to any one of claims 1 to 10, characterized in that, Along the direction from the first end to the last end of the winding of the core, the second electrode includes a second main body region and a second thinning region, wherein the thickness of the second thinning region in the first direction is less than the thickness of the second main body region in the first direction. The projection of the second thinning region in the second direction at least partially overlaps with the projection of the first tab and / or the second tab in the second direction.

12. The battery cell according to claim 11, characterized in that, The thickness of the second thinning region in the first direction is greater than the thickness of the first thinning region in the first direction.

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