Battery cell

Abstract

The invention 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 stacked 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] The present invention relates to the technical field of batteries, and in particular to a battery cell. Background Art

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

[0003] The battery cell is the core component of the lithium-ion battery. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer arranged on the surface of the positive electrode collector, and the negative electrode sheet includes a negative electrode collector and a negative electrode active material layer arranged on the surface of the negative electrode collector. The battery cell is immersed in an electrolyte, and lithium ions move between the positive and negative electrodes through the electrolyte, thereby realizing the charging and discharging of the battery. However, the volume energy density of the battery cell of the related art is low and cannot meet the performance requirements of the battery. Summary of the invention

[0004] In view of this, an embodiment of the present invention is directed to providing a battery cell to improve the volume energy density of the battery cell to a certain extent.

[0005] The present invention provides a battery core, comprising a first pole piece and a second pole piece, wherein the first pole piece and the second pole piece have different polarities, and the first pole piece and the second pole piece are stacked and wound to form a winding core;

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

[0007] The second pole sheet comprises a second pole lug, a second current collector and a second active material layer arranged on at least one side of the second current collector; a second pole lug groove is arranged on the second pole sheet, and the second pole lug is located in the second pole lug groove;

[0008] In the direction from the winding head end to the winding tail end of the winding core, the first pole piece includes a first main body region and a first thinning region, and 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 thinned area in the second direction at least partially overlaps with the projection of the first pole tab and / or the second pole tab in the second direction;

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

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

[0012] Optionally, along the direction from the inner winding circle to the outer winding circle of the winding core, the first pole lug and / or the second pole lug is arranged on the Nth circle of the winding core, where N is a positive integer;

[0013] At least part of the first thinned area is located at the N+1th circle and / or the N-1th circle of the winding core.

[0014] Optionally, along the direction from the inner winding circle to the outer winding circle of the winding core, at least two circles of the first pole sheet have the first thinned area.

[0015] Optionally, at least two circles of the first thinned area on the first pole sheet are arranged on both sides of a center line of the battery cell in the first direction.

[0016] Optionally, a tab protective tape is provided at a position of the battery cell 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 area and the thickness of the first thinning area, the total thickness d2 of the tab protection tape, and the thickness d3 of the tab corresponding to the tab protection tape satisfies: 10μm≤d1-(d2+d3)≤80μm.

[0018] Optionally, along the direction from the winding head end to the winding tail end of the winding core, the first pole sheet includes a double-sided area and a single-sided area, the single-sided area is an area where the first active material layer is provided on one side of the first current collector, and the double-sided area is an area where the first active material layer is provided on both sides of the first current collector;

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

[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 area in the second direction at least partially overlaps with the projection of the first pole tab in the second direction; the projection of the second sub-thinning area in the second direction at least partially overlaps with the projection of the second pole tab 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 winding head end to the winding tail end of the winding core, the first sub-thinning area and the second sub-thinning area extend toward each other and are connected.

[0024] Optionally, along the direction from the winding head end to the winding tail end of the winding core, the first main region includes a first area and a second area located on a side of the first area close to the first thinning area;

[0025] A thickness of the second region in the first direction is smaller than a thickness of the first region in the first direction.

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

[0027] Optionally, along the direction from the winding head end to the winding tail end of the winding core, the second pole piece includes a second main body region and a second thinned region, and the thickness of the second thinned region in the first direction is less than the thickness of the second main body region in the first direction;

[0028] A projection of the second thinned region in the second direction at least partially overlaps with a projection of the first pole tab and / or the second pole tab in the second direction.

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

[0030] The battery cell provided by the present invention is configured such that a first pole lug groove is arranged on the first pole sheet, the first pole lug is arranged in the first pole lug groove, a second pole lug groove is arranged on the second pole sheet, the second pole lug is arranged in the second pole lug groove, so that the first pole sheet includes a first main area and a first thinning area in the direction from the winding head end to the winding tail 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 area in the first direction, and the projection of the first thinning area in the second direction is at least partially overlapped with the projection of the first pole lug and / or the second pole lug in the second direction, so that at least the total thickness of the battery cell corresponding to the first pole lug and / or the second pole lug is thinned, and the thickness difference of the battery cell at different positions is balanced to a certain extent, and the uniformity of the thickness of the battery cell is improved, so that the thickness utilization space of the battery cell is improved while the total usage space remains unchanged, thereby realizing an improvement in the volume energy density of the battery cell.

[0031] At the same time, by making the difference between the total thickness H of the battery cell at the first pole ear or the second pole ear and the total thickness h of the battery cell at the midline in the second direction less than 1 mm, it is ensured that the thickness difference between the total thickness of the battery cell at the first pole ear or the second pole ear and the middle of the battery cell will not be too large, thereby further improving the uniformity of the battery cell thickness and improving the volume energy density of the battery cell.

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

[0033] In addition, by thinning the first pole piece at least at the position corresponding to the first pole ear and / or the second pole ear, 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 battery's kinetic performance and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The structure of the first pole piece in an expanded state according to an embodiment of the present invention is shown in FIG. Figure 1 ;

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

[0036] Figure 3 for Figure 2 The local structure of the first pole ear corresponding to the position of the enlarged Figure 1 ;

[0037] Figure 4 for Figure 2 The local structure of the first and second pole tabs in the image is enlarged. Figure 1 ;

[0038] Figure 5 for Figure 2 The local structure of the first and second pole tabs in the image is enlarged. Figure 2 ;

[0039] Figure 6 for Figure 2 The local structure of the first pole ear corresponding to the position of the enlarged Figure 2 ;

[0040] Figure 7 for Figure 2 The local structure of the first pole ear corresponding to the position of the enlarged Figure 3 ;

[0041] Figure 8 The structure of the first pole piece in an expanded state according to an embodiment of the present invention is shown in FIG. Figure 2 ;

[0042] Fig. 9 The structure of the first pole piece in an expanded state according to an embodiment of the present invention is shown in FIG. Figure 3 ;

[0043] Fig.10 It is a schematic structural diagram of the second pole piece in an unfolded state according to an embodiment of the present invention;

[0044] Fig.11 It is a schematic diagram of the cross-sectional structure of the first pole piece and the remaining parts of the battery cell except the first pole piece in the thickness direction according to an embodiment of the present invention.

[0045] Among them, 1. first pole piece; 11. first current collector; 12. first active material layer; 13. first main area; 131. first region; 132. second region; 133. arc surface; 14. first thinning area; 141. first sub-thinning area; 142. second sub-thinning area; 15. first pole ear; 16. first pole ear groove; 17. double-sided area; 18. single-sided area; 2. second pole piece; 21. second current collector; 22. second active material layer; 23. second main area; 24. second thinning area; 25. second pole ear; 26. second pole ear groove; 3. diaphragm; 4. pole ear protective tape. DETAILED DESCRIPTION

[0046] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0047] The battery cell of a lithium-ion battery generally includes a positive electrode sheet, a negative electrode sheet and a separator. The battery cell can be a winding core, for example. Specifically, the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound from the inside to the outside to form a winding core. The positive electrode sheet is provided with a positive electrode ear, and the negative electrode sheet is provided with a negative electrode ear. The current is drawn out through the electrode ears to realize the charging and discharging of the battery.

[0048] Among them, the volume energy density of the battery cell is one of the important indicators to characterize the performance of the battery. At present, the volume energy density of the battery cell is required to be higher and higher. In order to improve the volume energy density of the battery cell, an embodiment of the present invention provides a battery cell, by setting a first pole lug groove on the first pole sheet, so that the first pole lug is located in the first pole lug groove, setting a second pole lug groove on the second pole sheet, so that the second pole lug is located in the second pole lug groove, thinning the position of at least the first pole lug and / or the second pole lug of the first pole sheet, and by setting the difference between the total thickness of the battery cell at the first pole lug or the second pole lug and the total thickness at the center line of the battery cell to less than 1mm, so as to at least reduce the total thickness of the corresponding pole lug position of the battery cell, thereby balancing the thickness difference of the battery cell at different positions, improving the uniformity of the thickness of the battery cell, and then improving the thickness utilization space of the battery cell, and realizing the improvement of the volume energy density of the battery cell.

[0049] The battery cell provided by the present invention is described in detail below with reference to the accompanying drawings through specific embodiments:

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

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

[0052] Specifically, the first pole piece 1 includes a first pole ear 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 opposite sides, and the two opposite sides 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 only on one side of the first current collector 11, which can be set according to actual needs.

[0053] The second pole piece 2 specifically includes: a second pole ear 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 opposite sides, and the two opposite sides 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 only on one side of the second current collector 21, which can be set according to actual needs.

[0054] Exemplarily, the first electrode sheet 1 may be, for example, a positive electrode sheet, and the second electrode sheet 2 may be, for example, a negative electrode sheet.

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

[0056] Due to the arrangement of the first pole ear 15 and the second pole ear 25, the thickness of the battery cell at the first pole ear 15 and the second pole ear 25 is relatively thick, which leads to poor thickness uniformity of the battery cell at different positions. Battery cell performance indicators such as volume energy density are all constrained by the maximum thickness of the battery cell, which directly affects the volume energy density of the battery cell.

[0057] In order to improve the uniformity of the cell thickness and the volume energy density of the cell, refer to Figures 1 to 5 As shown, in the battery cell of this embodiment, the first pole piece 1 is provided with a first pole lug groove 16, and the first pole lug 15 is located in the first pole lug groove 16. The second pole piece 2 is provided with a second pole lug groove 26, and the second pole lug 25 is located in the second pole lug groove 26.

[0058] The first pole lug 15 is accommodated by the first pole lug groove 16, thereby reducing the total thickness of the battery cell at the location corresponding to the first pole lug 15, thereby improving the volume energy density of the battery cell; in addition, the setting of the first pole lug groove 16 can limit the first pole lug 15 to a certain extent, thereby improving the convenience of installation of the first pole lug 15 and the stability of the first pole lug 15.

[0059] For example, the first pole tab 15 can be welded to the first current collector 11. In specific implementation, pole tab protection tape 4 can be provided at the welding position of the first pole tab 15 and at both sides of the first pole tab 15 to protect the first pole tab 15 and avoid short circuit and the like.

[0060] The second pole lug 25 is accommodated by the second pole lug groove 26, which reduces the total thickness of the battery cell at the location corresponding to the second pole lug 25, thereby improving the volume energy density of the battery cell; in addition, the provision of the second pole lug groove 26 can limit the second pole lug 25 to a certain extent, thereby improving the convenience of installation of the second pole lug 25 and the stability of the second pole lug 25.

[0061] Exemplarily, the second pole ear 25 can be welded to the second current collector 21. In specific implementation, pole ear protection tape 4 can be provided at the welding point of the second pole ear 25 and on both sides of the second pole ear 25 to protect the second pole ear 25 and avoid short circuit and the like.

[0062] At the same time, in the direction from the winding head end to the winding tail end of the winding core, the first pole piece 1 includes a first main area 13 and a first thinning area 14, and the thickness d of the first thinning area 14 in the first direction is less than the thickness D of the first main area 13 in the first direction.

[0063] It should be noted that the winding head end can be understood as the area where the pole piece starts to be wound during the winding process of the battery cell, that is, the head area, which is located inside the battery cell. Correspondingly, the winding tail end can be understood as the area where the pole piece is wound to the end.

[0064] Combination Figure 1 and Figure 2 As shown, the direction from the winding head end to the winding tail end can be specifically Figure 1 The first direction here can be specifically Figure 2 The up-down direction in the figure may be, for example, the thickness direction of the battery cell.

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

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

[0067] Specifically, the projection of the first thinning area 14 in the second direction is at least partially overlapped with the projection of the first pole lug 15 in the second direction, that is, along the thickness direction of the battery cell, the position of the first thinning area 14 corresponds to the position of the first pole lug 15, thereby reducing the total thickness of the battery cell at the first pole lug 15 to a certain extent. Alternatively, the projection of the first thinning area 14 in the second direction is at least partially overlapped with the projection of the second pole lug 25 in the second direction, that is, along the thickness direction of the battery cell, the position of the first thinning area 14 corresponds to the position of the second pole lug 25, thereby reducing the total thickness of the battery cell at the second pole lug 25 to a certain extent. Alternatively, a part of the projection of the first thinning area 14 in the second direction is at least partially overlapped with the projection of the first pole lug 15, and another part of the projection of the first thinning area 14 is at least partially overlapped with the projection of the second pole lug 25, thereby reducing the total thickness of the battery cell at the first pole lug 15 and the second pole lug 25 to a certain extent. The above arrangement balances the thickness difference of the battery cells at different positions to a certain extent, improves the uniformity of the thickness of the battery cells, and increases the thickness utilization space of the battery cells while keeping the total usable space unchanged, thereby achieving an increase in the volume energy density of the battery cells.

[0068] Exemplarily, in a specific implementation, the active material layer of at least the position of the first pole sheet 1 corresponding to the first pole ear 15 and / or the second pole ear 25 can be thinned, for example, by removing at least a portion of the active material layer on the first pole sheet 1 located on the outer circle or the inner circle of the first pole ear 15 by laser burning, so that a thinning area is formed at the corresponding position of the first pole sheet 1, for example, a thinning groove is formed, thereby reducing the total thickness of the battery cell at the position of the first pole ear 15 and / or the second pole ear 25.

[0069] Of course, in other implementations, the thinning of the corresponding position of the first pole piece 1 may also be achieved by other mechanical means.

[0070] Reference Figure 1 As shown, a portion of the active material layer at the position corresponding to the first pole tab 15 and / or the second pole tab 25 on one side of the first current collector 11 may be thinned. Of course, the entire active material layer at the corresponding position on one side of the first current collector 11 may also be thinned. In addition, part or all of the active material layer at the corresponding positions on both sides of the first current collector 11 may also be thinned, and the thickness of the thinning may be designed according to the actual need.

[0071] Reference Figure 2 As shown, at the same time, the total thickness H ( Figure 2 The size of the battery cell along the vertical direction at the first pole ear 15 or the second pole ear 25) and the total thickness h ( Figure 2 The relationship between the dimensions of the battery cell at the center line oo along the up and down directions satisfies: Hh<1mm.

[0072] The second direction here can be Figure 2 The left and right direction in the drawing may specifically be the width direction of the winding core.

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

[0074] This arrangement can ensure that the difference between the thickness of the battery cell at the pole ear and the thickness at the center line of the battery cell will not be too large, thereby further improving the uniformity of the thickness of the battery cell at the pole ear and the thickness of the battery cell at the center line oo, thereby better utilizing the thickness space and further improving the volume energy density of the battery cell.

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

[0076] The battery cell provided in this embodiment is provided with a first pole lug groove 16 on the first pole sheet 1, and the first pole lug 15 is provided in the first pole lug groove 16; a second pole lug groove 26 is provided on the second pole sheet 2, and the second pole lug 25 is provided in the second pole lug groove 26, so that the first pole sheet 1 includes a first main area 13 and a first thinning area 14 in the direction from the winding head end to the winding tail end of the winding core, and the thickness of the first thinning area 14 in the first direction is less than the thickness of the first main area 13 in the first direction, and the projection of the first thinning area 14 in the second direction is at least partially overlapped with the projection of the first pole lug 15 and / or the second pole lug 25 in the second direction, so that at least the total thickness of the battery cell corresponding to the first pole lug 15 and / or the second pole lug 25 is thinned, and the thickness difference of the battery cell at different positions is balanced to a certain extent, and the uniformity of the thickness of the battery cell is improved, thereby improving the thickness utilization space of the battery cell while keeping the total usage space unchanged, thereby achieving an improvement in the volume energy density of the battery cell.

[0077] At the same time, by making the difference between the total thickness H of the battery cell at the first pole ear 15 or the second pole ear 25 and the total thickness h of the battery cell at the midline in the second direction less than 1 mm, it is ensured that the difference between the total thickness of the battery cell at the first pole ear 15 or the second pole ear 25 and the thickness in the middle of the battery cell will not be too large, thereby improving the uniformity of the battery cell thickness and further improving the volume energy density of the battery cell.

[0078] In other words, under the condition of the same cell volume energy density, the cell of this embodiment occupies a smaller thickness space, which is conducive to the development of electronic equipment towards lighter and thinner.

[0079] Moreover, since at least the position corresponding to the first pole piece 15 and / or the second pole piece 25 is thinned, if the electrode material expands in volume during the charging and discharging process of the battery cell, 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 pole piece can be effectively released, thereby reducing the squeezing force between the first pole piece 1 and the second pole piece 2, and thereby reducing the risk of deformation and fracture of the first pole piece 1, the second pole piece 2, etc.

[0080] In addition, by thinning the first pole piece 1 at least at the position corresponding to the first pole ear 15 and / or the second pole ear 25, 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 battery's dynamic performance and cycle performance.

[0081] In addition, when the first pole piece 1 is a positive pole piece and the second pole piece 2 is a negative pole piece, since the first pole piece 1 is thinned at least at the position corresponding to the first pole ear 15 and / or the second pole ear 25, the amount of active material in the first pole piece 1 is reduced to a certain extent, thereby reducing the amount of lithium ions received by the second pole piece 2, thereby reducing the risk of lithium plating and improving the electrical performance, safety and life of the battery.

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

[0083] This arrangement can further ensure that the thickness of the battery cell at the pole ear will not be too large, thereby further improving the uniformity of the thickness of the battery cell at the pole ear and the thickness of the battery cell at the center line oo, thereby better utilizing the thickness space and further improving the volume energy density of the battery 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 pole 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 pole tab groove in the second direction.

[0085] The second direction here is Figure 3 The left-right direction in the figure may specifically be the width direction of the battery cell, and the projected width may specifically be the projected dimension of the first thinned area 14 along the left-right direction.

[0086] Such a configuration can absorb the thickness of the first pole tab groove 16 , the first pole tab 15 , and the pole tab protective tape 4 to a certain extent, thereby further reducing the total thickness of the battery cell at the position corresponding to the first pole tab 15 , and further improving the volume 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 pole 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 pole tab groove 26 in the second direction.

[0088] The second direction here is Figure 4 The left and right directions in the figure may be specifically the width direction of the battery cell, where the projection width is specifically the width of the first thinned area 14 along the Figure 4 The projection size in the left and right directions.

[0089] Such a configuration can absorb the thickness of the second pole tab groove 26, the second pole tab 25 and the pole tab protective tape 4 to a certain extent, thereby further reducing the total thickness of the battery cell at the position corresponding to the second pole tab 25, and further improving the volume energy density of the battery cell.

[0090] Combination Figures 2 to 5 As shown, in some embodiments, along the direction from the inner winding circle to the outer winding circle of the winding core, the first pole tab 15 and / or the second pole tab 25 are arranged at the Nth circle of the winding core, where N is a positive integer. At least part of the first thinned area 14 is located at the N+1th circle and / or the N-1th circle of the winding core.

[0091] In this way, at least part of the first thinned area 14 is disposed adjacent to the first pole tab 15 and / or the second pole tab 25 , thereby being able to better balance the total thickness of the battery cell at the corresponding pole tab position and improve the uniformity of the battery cell thickness.

[0092] Taking the first pole ear 15 as an example, for example, the first pole ear 15 is arranged on the third turn of the winding core, here at least part of the first thinning area 14 on the first pole sheet 1 can be located on the fourth turn of the winding core, and correspond to the first pole ear 15, that is, located on the outer circle of the first pole ear 15, that is, at least part of the first thinning area 14 is arranged adjacent to the first pole ear 15, so as to better balance the total thickness of the battery cell at the position corresponding to the first pole ear 15 and improve the uniformity of the battery cell thickness.

[0093] Of course, at least a portion of the first thinned area 14 may be located on the second circle of the winding core and correspond to the first pole tab 15 , that is, located on the inner circle of the first pole tab 15 .

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

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

[0096] In a specific implementation, the first thinned areas 14 located on different circles of the first pole piece 1 may all correspond to the first pole ear 15, so as to further reduce the total thickness of the battery cell at the first pole ear 15 and improve the uniformity of the overall thickness of the battery cell; Figure 6 As shown, for example, there are two circles each having a first thinning area 14 , and the two first thinning areas 14 are both arranged corresponding to the first pole lugs 15 .

[0097] Alternatively, the first thinned areas 14 located on different circles of the first pole piece 1 may all correspond to the second pole tab 25 to further reduce the total thickness of the battery cell at the second pole tab 25 and improve the uniformity of the overall thickness of the battery cell.

[0098] Alternatively, the first thinning area 14 on one or more circles corresponds to the first pole ear 15, and the first thinning area 14 on another circle or more circles corresponds to the second pole ear 25. While reducing the thickness of the first pole ear 15 and the second pole ear 25 corresponding to the battery cell, by arranging multiple first thinning areas 14 in different circles, the force balance of the first pole piece 1 can be improved to a certain extent, thereby improving the structural stability of the first pole piece 1.

[0099] Further, continue to refer to Figure 6 As shown, the first thinned areas 14 on at least two circles of the first pole piece 1 are arranged on both sides of the center line ss of the battery cell in the first direction. The first direction here is specifically Figure 6 The up and down directions in .

[0100] This arrangement can improve the balance of forces on both sides of the battery cell. For example, when the electrode material expands during the charging and discharging process of the battery cell, this arrangement can avoid the deformation of the battery cell due to uneven forces on both sides of the battery cell, thereby improving the stability of the overall structure of the battery cell and ensuring the performance and life of the battery.

[0101] Reference Figure 7 As shown, in some embodiments, along the first direction (specifically, Figure 7 In the up and down direction), the difference d1 between the thickness D of the first main area 13 and the thickness d of the first thinned area 14 (i.e., the thickness of the first pole piece 1 that is thinned at this position), the total thickness d2 of the pole ear protection tape 4, and the thickness d3 of the pole ear corresponding to the pole ear protection tape 4 satisfy the relationship: 10μm≤d1-(d2+d3)≤80μm.

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

[0103] Continue to refer to Figure 7As shown, the position corresponding to the first pole lug 15 is taken as an example for explanation, the thickness d3 of the pole lug here is, for example, the thickness d3 of the first pole lug 15, and the total thickness d2 of the pole lug protection tape 4 here is, for example, the sum of the thicknesses of all the pole lug protection tapes 4 corresponding to the first pole lug 15. Exemplarily, the pole lug protection tape 4 is provided on the upper side and the lower side of the first pole lug 15, and the pole lug protection tape 4 is also provided on the side of the second pole piece 2 adjacent to the first pole lug 15 facing the first pole lug 15, and the thickness of each pole lug protection tape 4 is d0, and the total thickness d2 of the pole lug protection tape 4 here can be, for example, the sum of the thicknesses d0 of the four pole lug protection tapes 4.

[0104] Of course, the specific number of tab protection tapes corresponding to the first tab 15 or the second tab 25 can be set according to actual conditions.

[0105] In this way, the above arrangement further ensures the total thickness of the battery cell at the first electrode tab 15, thereby further improving the uniformity of the thickness of the battery cell.

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

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

[0108] During the battery cell manufacturing process, the single-sided area 18 of the first pole piece 1 is thinner than the double-sided area 17, and the single-sided area 18 is easily over-pressurized. Over-pressurization can easily lead to poor electrolyte wetting effect in this area, thereby causing the battery's charge and discharge performance, cycle performance, etc. to be reduced. By setting at least a portion of the first thinned area 14 in the single-sided area 18, while reducing the total thickness of the battery cell at the position corresponding to the first pole ear 15 and / or the second pole ear 25, the electrolyte wetting effect is improved to a certain extent, thereby improving the battery's charge and discharge, cycle and other performances.

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

[0110] Since the thickness of the double-sided area 17 is relatively thick, by setting the first thinning area 14 in the double-sided area 17, the total thickness of the battery cell at the position corresponding to the first pole ear 15 and / or the second pole ear 25 can be reduced, thereby improving the volume energy density of the battery cell. At the same time, it can also further effectively accommodate the volume expansion of the electrode material, reduce the squeezing pressure between the first pole piece 1 and the second pole piece 2, and further reduce the risk of deformation and breakage of the first pole piece 1 and the second pole piece 2.

[0111] In some embodiments, the first thinning area 14 can also be set on both the double-sided area 17 and the single-sided area 18, so as to further reduce the total thickness of the battery cell at the position of the first pole ear 15 and / or the second pole ear 25, improve the uniformity of the battery cell thickness, and further improve the volume 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 area 141 is located in the second direction (specifically, Figure 4 The projection of the second sub-thinning area 142 in the second direction at least partially overlaps with the projection of the second pole ear 25 in the second direction.

[0114] That is to say, the thickness of the battery cell at the positions corresponding to the first electrode tab 15 and the second electrode tab 25 is reduced, thereby further improving the uniformity of the thickness of the battery cell.

[0115] Combination Figure 2 and Figure 4 As shown, there is a first folded portion B of the second pole sheet 2 at the position corresponding to the first pole ear 15 of the battery cell, which may cause the thickness of the battery cell at the position corresponding to the first pole ear 15 to be greater than the thickness of the battery cell at the position corresponding to the second pole ear 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 pole ear 15 and the total thickness of the battery cell at the position corresponding to the second pole ear 25, in some embodiments, along the first direction (specifically, Figure 4 In the up-down direction in the middle), the thickness d4 of the first sub-thinning region 141 is less than the thickness d5 of the second sub-thinning region 142.

[0116] That is to say, the total thickness subtracted at the first pole ear 15 of the first pole piece 1 is made greater than the total thickness subtracted at the second sub-thinning area 142 of the first pole piece 1, thereby absorbing the thickness of the first pole ear 15 and the first folding area of ​​the second pole piece 2 to a certain extent, so as to reduce the total thickness of the battery cell corresponding to the first pole ear 15, further improving the uniformity of the overall thickness of the battery cell, thereby effectively improving the volume energy density of the battery cell.

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

[0118] That is to say, the thinning areas at at least two positions can be formed into a whole, thereby achieving effective coverage of the first pole tab 15 and the second pole tab 25 at the same time, thereby further improving the uniformity of the overall thickness of the battery cell. Moreover, such an arrangement makes it more convenient to perform thinning on the first pole sheet 1.

[0119] Reference Fig. 9 As shown, in some embodiments, along the direction from the winding head end to the winding tail end of the winding core (for example, Fig. 9 In the direction from left to right in the figure, the first main region 13 includes a first region 131 and a second region 132 located on one side of the first region 131 close to the first thinning region 14. The second region 132 is Fig. 9 The thickness D2 in the up and down direction (specifically, the thickness direction of the winding core) is smaller than the thickness D1 of the first region 131 in the first direction.

[0120] This arrangement can reduce the total thickness of at least the battery cell corresponding to the first pole ear 15 and / or the second pole ear 25, while allowing a better transition between the first main area 13 and the first thinning area 14, preventing stress concentration at the junction of the two from causing the first pole piece 1 to rupture or the active material layer to fall off.

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

[0122] This further enables a smoother transition between the first main region 13 and the first thinned region 14, further avoiding stress concentration that may cause fracture or bulging at the joint, and such a configuration helps to better release the active energy of the first main region 13. In addition, by reducing the amount of active material at the end of the first main region 13, the risk of lithium deposition in the corresponding area of ​​the second pole piece 2 is further reduced.

[0123] Continue to refer to Fig. 9 As shown, the surface of the second region 132 facing away from the first current collector 11 is an arc surface 133. This further enables a smoother transition between the first main region 13 and the first thinned region 14, further avoiding stress concentration that causes fracture or bulging at the joint.

[0124] Reference Fig.11 As shown, Fig.11 The upper part in the figure is a schematic diagram of the cross-sectional structure of the first pole piece 1. Fig.11 The lower half A in FIG. 1 is a schematic diagram of the thickness variation of other parts of the battery cell except the first pole piece 1 in the cross-sectional direction. Fig.11 It can be seen that the corresponding position of the first thinning area 14 on the first pole piece 1 has been thinned, which to a certain extent balances the thickness of the battery cell at least at the pole ear, thereby improving the thickness uniformity of the entire battery cell, which is beneficial to improving the volume energy density of the battery cell.

[0125] In some embodiments, reference Fig.10 As shown, along the direction from the winding head end to the winding tail end of the winding core, the second pole piece 2 includes a second main area 23 and a second thinning area 24, and the thickness c of the second thinning area 24 in the first direction is less than the thickness e of the second main area 23 in the first direction.

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

[0127] The first direction here can be specifically Fig.10 The up and down direction in the diagram may be, for example, the thickness direction of the battery cell. The second direction may be Fig.10 The left and right direction in the figure may be, for example, the width direction of the battery cell.

[0128] That is to say, while thinning is provided at least at the position corresponding to the first pole ear 15 and / or the second pole ear 25 of the first pole sheet 1, thinning is also provided at least at the position corresponding to the first pole ear 15 and / or the second pole ear 25 of the second pole sheet 2. The uniformity of the thickness of the battery cell is further improved through the thinning combination of the first pole sheet 1 and the second pole sheet 2, thereby improving the volume energy density of the battery cell.

[0129] The manner and implementation principle of the thinning process on the second pole piece 2 are the same as those of the first pole piece 1 , which will not be described in detail here. For details, please refer to the description of the above embodiment.

[0130] In order to reduce the risk of lithium plating, when forming the second thinning zone 24 on the second pole piece 2, the second thinning zone 24 can be formed at a position of the second pole piece 2 corresponding to the first thinning zone 14 of the first pole piece 1, and at least part of the second thinning zone 24 is arranged corresponding to the first pole ear 15 and / or the second pole ear 25.

[0131] That is to say, the first thinning area 14 can be set on one or more circles of the first pole piece 1, or the second thinning area 24 can be set at the position corresponding to the first thinning area 14 of the second pole piece 2 at the same time. By combining one or more groups of first thinning areas 14 and second thinning areas 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 volume energy density of the battery cell can be improved.

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

[0133] In other words, the thickness subtracted from the second pole piece 2 is less than or equal to the thickness subtracted from the first pole piece 1, thereby ensuring that the second pole piece 2 can effectively cover the first pole piece 1, further preventing the occurrence of lithium deposition to a certain extent. That is, such a setting can improve the uniformity of the thickness of the battery cell and increase the volume energy density of the battery cell while further preventing the occurrence of lithium deposition.

[0134] According to tests, when the maximum thickness of the battery cell is greater than 1 mm, the above thinning setting can reduce the maximum thickness of the battery cell by at least 0.05 mm to 0.15 mm, and increase the volume energy density by more than 10%.

[0135] In this article, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, or it can be indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0136] In this article, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery cell, characterized in that: The device comprises a first pole piece and a second pole piece, wherein the first pole piece and the second pole piece have different polarities, and the first pole piece and the second pole piece are stacked and wound to form a winding core; The first pole piece includes a first pole ear, a first current collector, and a first active material layer disposed on at least one side of the first current collector; A first pole lug groove is provided on the first pole sheet, and the first pole lug is located in the first pole lug groove; The second pole sheet comprises a second pole lug, a second current collector and a second active material layer arranged on at least one side of the second current collector; a second pole lug groove is arranged on the second pole sheet, and the second pole lug is located in the second pole lug groove; In the direction from the winding head end to the winding tail end of the winding core, the first pole piece includes a first main body region and a first thinning region, and 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 thinned area in the second direction at least partially overlaps with the projection of the first pole tab and / or the second pole tab in the second direction; The relationship between the total thickness H of the battery cell at the first pole tab or the second pole tab and the total thickness h of the battery cell at the midline 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 pole tab or the second pole tab and the total thickness h of the battery cell at the midline 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 circle to the outer winding circle of the winding core, the first pole lug and / or the second pole lug is arranged on the Nth circle of the winding core, where N is a positive integer; At least part of the first thinned area is located at the N+1th circle and / or the N-1th circle of the winding core.

4. The battery cell according to claim 1, characterized in that: Along the direction from the inner winding circle to the outer winding circle of the winding core, at least two circles of the first pole piece have the first thinned area.

5. The battery cell according to claim 4, characterized in that: At least two circles of the first thinned areas on the first pole sheet are arranged on both sides of the center line of the battery core in the first direction.

6. The battery cell according to claim 1, characterized in that: A tab protective adhesive tape is provided at a position of the battery cell 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 area and the thickness of the first thinning area, the total thickness d2 of the tab protection tape, and the thickness d3 of the tab corresponding to the tab protection tape satisfies: 10μm≤d1-(d2+d3)≤80μm.

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

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 area in the second direction at least partially overlaps with the projection of the first pole tab in the second direction; the projection of the second sub-thinning area in the second direction at least partially overlaps with the projection of the second pole tab 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 winding head end to the winding tail end of the winding core, the first sub-thinning area and the second sub-thinning area extend toward each other and are connected.

9. The battery cell according to claim 1, characterized in that: In the direction from the winding head end to the winding tail end of the winding core, the first main region includes a first area and a second area located on a side of the first area close to the first thinning area; A thickness of the second region in the first direction is smaller than a thickness of the first region in the first direction.

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

11. The battery cell according to any one of claims 1 to 10, characterized in that: In the direction from the winding head end to the winding tail end of the winding core, the second pole piece includes a second main body region and a second thinned region, and the thickness of the second thinned region in the first direction is less than the thickness of the second main body region in the first direction; A projection of the second thinned region in the second direction at least partially overlaps with a projection of the first pole tab and / or the second pole tab in the second direction.

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

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