Battery cell and battery

Abstract

This invention relates to the field of battery technology and discloses a battery cell and a battery, comprising: at least one of the positive and negative electrode sheets includes a current output layer, a first active layer, and a second active layer, the first and second active layers being respectively disposed on opposite sides of the current output layer along its thickness direction; the electrode sheet is bent to form a stacked transition region; the battery cell further includes a first protective layer disposed on the first active layer and a second protective layer disposed on the second active layer, at least a portion of the first protective layer and at least a portion of the second protective layer being disposed in the same stacked transition region; along the unfolding direction of the electrode sheet, the first protective layer and the second protective layer are staggered and partially overlap. This invention reduces the risk of material shedding from the first and second active layers while also reducing the lithium plating problem in the battery.

Description

[0001] This application is a divisional application of the invention patent application with publication number CN121546182A. The original application was filed on January 20, 2026; the application number was 2026100714697; and the invention was entitled "Battery Cell and Battery". Technical Field

[0002] This invention relates to the field of battery technology, specifically to battery cells and batteries. Background Technology

[0003] As the demand for battery energy density increases, the size of battery cells is also increasing. For wound battery cells, to reduce the risk of material loss in the bending areas of the electrodes, an adhesive layer is usually placed in the bending areas of the electrodes. However, the presence of the adhesive layer increases the risk of lithium plating in the battery, which can lead to safety issues such as battery short circuits. Summary of the Invention

[0004] This invention provides a battery cell and battery to solve the problem in the prior art that the presence of an adhesive layer increases the risk of lithium plating in the battery, thereby causing a short circuit.

[0005] In a first aspect, the present invention provides a battery cell manufactured by winding a stacked positive electrode sheet, an insulating film, and a negative electrode sheet, comprising: At least one of the positive and negative electrode plates includes a current output layer, a first active layer, and a second active layer, wherein the first active layer and the second active layer are respectively disposed on opposite sides of the current output layer along the thickness direction; the electrode plate is bent to form a stacked transition region; the battery cell further includes a first protective layer disposed on the first active layer and a second protective layer disposed on the second active layer, wherein at least a portion of the first protective layer and at least a portion of the second protective layer are disposed in the same stacked transition region; Along the unfolding direction of the electrode sheet, the first protective layer and the second protective layer are staggered and partially overlap. In the unfolding direction of the electrode sheet, the first protective layer includes a first side and a second side that are spaced apart from each other, and the second protective layer includes a third side and a fourth side that are spaced apart from each other. The first side is closer to the winding start end of the electrode sheet than the second side, the third side is closer to the winding start end of the electrode sheet than the fourth side, and the first side is closer to the winding start end of the electrode sheet than the third side. Along the unfolding direction of the electrode sheet, the distance from the first side to the starting end of the winding of the electrode sheet is d1mm, which satisfies 80mm≤d1mm≤700mm; Along the unfolding direction of the electrode sheet, the distance from the third side to the starting end of the winding of the electrode sheet is d2mm, which satisfies 80.5mm≤d2≤704mm.

[0006] Beneficial effects: By staggering the first and second protective layers located on opposite sides of the electrode, the problem of excessive stress concentration in the lamination transition zone can be reduced. Furthermore, by limiting the range of values ​​for d1 and d2, the transmission efficiency of the electrode in the winding start area is ensured while reducing the risk of active material shedding.

[0007] Secondly, the present invention also provides a battery comprising: shell; The aforementioned battery cell is disposed within the outer casing. Attached Figure Description

[0008] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0009] Figure 1 This is a schematic diagram of the structure of a current output layer, a first active layer, and a second active layer according to an embodiment of the present invention; Figure 2 A schematic diagram of the structure of the layered transition region of the present invention, showing the provision of a first protective layer and a second protective layer; Figure 3 for Figure 2 The front view of the electrode sheet in its unfolded state; Figure 4 for Figure 3 A schematic diagram showing partial dimensions of the electrode, the first protective layer, and the second protective layer; Figure 5 for Figure 3 A schematic diagram showing the additional dimensions of the electrode, the first protective layer, and the second protective layer; Figure 6 A schematic diagram of the structure in which protective layers are respectively provided for the two stacked transition regions of this invention; Figure 7 for Figure 6 The front view of the electrode sheet in its unfolded state; Figure 8 This is a front view of the first and second protective layers and the tab portion in a first positional relationship according to an embodiment of the present invention; Figure 9 This is a front view of the first and second protective layers and the tab portion in a second positional relationship according to an embodiment of the present invention; Figure 10This is a schematic diagram of the structure of a base layer and an adhesive layer according to an embodiment of the present invention; Figure 11 This is a schematic diagram of another base layer and adhesive layer according to an embodiment of the present invention; Figure 12 for Figure 11 A cross-sectional view along the AA direction; Figure 13 This is a schematic diagram of the structure of the central region and the edge region in an embodiment of the present invention; Figure 14 This is a front view of the protective layer extending beyond the edge of the active layer in an embodiment of the present invention. Figure 15 This is a front view of an embodiment of the invention where the end of the protective layer does not extend beyond the edge of the active layer. Figure 16 This is a schematic cross-sectional view of the battery cell in an embodiment of the present invention, in the direction perpendicular to the width of the electrode sheet; Figure 17 This is a schematic diagram of the battery explosion according to an embodiment of the present invention; Figure 18 This is a schematic diagram of the crease and protective layer in the layered transition area according to an embodiment of the present invention.

[0010] Explanation of reference numerals in the attached figures: 1. Electrode; 11. Current output layer; 111. Body; 112. Tab; 12. First active layer; 13. Second active layer; 14. Lamination transition area; 141. Crease; 15. Winding start end; 16. Horizontal connection area; 2. First protective layer; 21. First side; 22. Second side; 3. Second protective layer; 31. Third side; 32. Fourth side; 4. Third protective layer; 5. Fourth protective layer; 6. Base layer; 61. Through hole; 7. Adhesive layer; 71. Blank area; 72. Colloid area; 8. Central area; 9. Edge area; 10. Insulating film; 100, battery cell; 200, casing. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] The following is combined Figures 1 to 18 The following describes embodiments of the present invention.

[0013] According to an embodiment of the present invention, in one aspect, a battery cell is provided, which is manufactured by winding a positive electrode sheet, an insulating film, and a negative electrode sheet stacked together, comprising: At least one of the positive and negative electrode plates 1 includes a current output layer 11, a first active layer 12, and a second active layer 13. The first active layer 12 and the second active layer 13 are respectively disposed on opposite sides of the current output layer 11 along the thickness direction. The electrode plate 1 is bent to form a stacked transition region 14. The cell also includes a first protective layer 2 disposed on the first active layer 12 and a second protective layer 3 disposed on the second active layer 13. At least a portion of the first protective layer 2 and at least a portion of the second protective layer 3 are disposed in the same stacked transition region 14. The first protective layer 2 and the second protective layer 3 are staggered and partially overlapped along the unfolding direction of the electrode plate 1.

[0014] Furthermore, in one embodiment, the total width of the misaligned area between the first protective layer 2 and the second protective layer 3 is bmm, the width of the first protective layer 2 is B1mm, the width of the second protective layer 3 is B2mm, the outer perimeter of the battery cell is Lmm, and the elongation at break of the current output layer 11 is X%, satisfying 0.8×10 -2 ≤(b×L) / [X×(B1+B2) 2 ≤600×10 -2 .

[0015] By using the battery cell of this embodiment, the first protective layer 2 and the second protective layer 3 located on opposite sides of the electrode 1 are staggered, which can reduce the problem of excessive stress concentration at the lamination transition region 14. Furthermore, by adjusting (b×L) / [X×(B1+B2)]... 2 The range of values ​​for ] is limited to reduce the risk of material loss from the first active layer 12 and the second active layer 13, while also reducing the lithium plating problem in the battery.

[0016] It is worth noting that if (b×L) / [X×(B1+B2)] 2 If the value of ] is too small, the first protective layer 2 and the second protective layer 3 may cover the electrode 1 too much, affecting the lithium-ion transport efficiency. Lithium ions may easily precipitate and form lithium dendrites, which may then puncture the insulating film and cause a short circuit between the positive and negative electrodes, affecting the battery's safety performance. If (b×L) / [X×(B1+B2)] 2 If the value of ] is too large, it will easily increase the risk of breakage of the current output layer 11. In addition, the coverage of the first protective layer 2 and the second protective layer 3 on the first active layer 12 and the second active layer 13 is too small, which increases the risk of material falling off the first active layer 12 and the second active layer 13.

[0017] Preferably, in one embodiment, the total width bmm of the misalignment area of ​​the first protective layer 2 and the second protective layer 3, the width B1mm of the first protective layer 2, the width B2mm of the second protective layer 3, the outer perimeter Lmm of the battery cell, and the elongation at break X% of the current output layer 11 satisfy 17×10 -2 ≤(b×L) / [X×(B1+B2) 2 ≤450×10 -2 .

[0018] Optional, (b×L) / [X×(B1+B2)] 2 The value of ] is 0.8 × 10 -2 1×10 -2 10×10 -2 17×10 -2 50×10 -2 100×10 -2 200×10 -2 300×10 -2 400×10 -2 450×10 -2 500×10 -2 600×10 -2 It can be any value in the range or the value between any two values.

[0019] Research has found that the main reason for cell material loss is the stress concentration of the electrode 1 in the lamination transition zone 14 at the corner of the cell. Currently, electrical devices are increasingly demanding greater driving range and energy density, leading to continuously increasing requirements for battery capacity. Therefore, based on the original battery structure, cell size is constantly increasing, and double-sided coated electrodes 1, which coat both sides of the electrode 1 with active material, are introduced. For wound cells, the thickness of the double-sided coated electrode 1 is significantly increased compared to the original single-sided coated electrode 1. After winding, the lamination transition zone 14 at the corner of the cell becomes more prone to active material loss due to stress concentration. Furthermore, the active material on the inner side of the electrode 1 is subjected to compression, and the active material on the outer side of the electrode tab is subjected to stretching, both of which easily lead to material loss.

[0020] Therefore, in this embodiment, protective layers are provided on both active layers to improve the problem of material shedding from the active layers. However, after the protective layers are provided, lithium-ion transport between the positive and negative electrodes is hindered, resulting in severe lithium plating in the battery. This poses a risk of short circuits caused by lithium dendrites piercing the insulating film, affecting battery safety. Furthermore, in this embodiment, by limiting the relationship between the total width bmm of the misaligned area of ​​the first protective layer 2 and the second protective layer 3, the width B1mm of the first protective layer 2, the width B2mm of the second protective layer 3, the outer perimeter Lmm of the cell, and the elongation at break X% of the current output layer 11, both the risk of active material shedding and the lithium plating problem of the battery can be reduced.

[0021] It is understandable that (b×L) / [X×(B1+B2)] 2 = (1 / X) × (b / (B1+B2)) / ((B1+B2) / L). If the value of b / (B1+B2) is too large, it is easy to cause the area not covered by the first active layer 12 and the second active layer 13 to be too large, increasing the risk of material loss of the first active layer 12 and the second active layer 13; if the value of b / (B1+B2) is too small, the area completely covered by the first protective layer 2 and the second protective layer 3 of the first active layer 12 and the second active layer 13 will be too large, affecting the lithium ion transport efficiency and increasing the risk of lithium plating. If the value of (B1+B2) / L is too large, it is easy to cause the setting range of the first protective layer 2 and the second protective layer 3 to be too large, which can easily lead to the risk of lithium plating; if the value of (B1+B2) / L is too small, it is easy to cause the setting range of the first protective layer 2 and the second protective layer 3 to be too small, resulting in insufficient protection of the active layer and leading to the risk of material loss. If the value of X% is too small, it may cause the current output layer 11 to break, increasing the risk of material loss from the active layer; if the value of X% is too large, it may not meet the overall design requirements of the battery structure.

[0022] It should be noted that you should refer to [link / reference]. Figure 2 and Figure 3 The first protective layer 2 and the second protective layer 3 are offset and partially overlapped along the unfolding direction of the electrode 1. This means that the first protective layer 2 and the second protective layer 3 overlap, but are not completely overlapped. The first protective layer 2 has a portion extending beyond the second protective layer 3 along the unfolding direction of the electrode 1, and the second protective layer 3 also has a portion extending beyond the first protective layer 2 along the unfolding direction of the electrode 1. The overlapping portion of the first protective layer 2 and the second protective layer 3 can provide protection on opposite sides of the same lamination transition zone 14.

[0023] It is worth noting that the unfolding direction of electrode 1 refers to the length direction of electrode 1.

[0024] Specifically, in one embodiment, such as Figure 3As shown, in the unfolding direction of the electrode 1, the first protective layer 2 includes a first side 21 and a second side 22 that are arranged at a relatively distance from each other, and the second protective layer 3 includes a third side 31 and a fourth side 32 that are arranged at a relatively distance from each other. The first side 21 is closer to the winding start end 15 of the electrode 1 than the second side 22, the third side 31 is closer to the winding start end 15 of the electrode 1 than the fourth side 32, and the first side 21 is closer to the winding start end 15 of the electrode 1 than the third side 31.

[0025] That is, the first protective layer 2 is closer to the starting end 15 of the winding of the electrode 1 than the second protective layer 3.

[0026] Furthermore, in one embodiment, such as Figure 5 As shown, along the unfolding direction of electrode 1, the distance between the first side 21 and the third side 31 is b1mm, satisfying 0.5mm≤b1mm≤4mm. This setting reduces the risk of active material shedding while also mitigating lithium plating issues in the battery.

[0027] It is worth noting that if the value of b1mm is too large, it may result in an excessively large area of ​​the second active layer 13 not being covered, increasing the risk of material loss. If the value of b1mm is too small, it may result in the first protective layer 2 and the second protective layer 3 covering too large an area of ​​the first active layer 12 and the second active layer 13, affecting the lithium-ion transport efficiency and increasing the risk of lithium plating.

[0028] Optionally, b1mm can be any value from 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, or a value between any two of these values.

[0029] In one embodiment, such as Figure 4 As shown, along the unfolding direction of electrode 1, the distance from the first side 21 to the winding start end 15 of electrode 1 is d1mm, satisfying 80mm≤d1mm≤700mm. This setting ensures the transmission efficiency of electrode 1 in the winding start end 15 region while reducing the risk of active material loss.

[0030] It is worth noting that if the value of d1mm is too large, there is a risk that the lamination transition zone 14 located in the inner ring after the electrode 1 is wound may not be completely covered, increasing the risk of active material shedding. If the value of d1mm is too small, the lithium-ion transport space in the region at the starting end 15 of the electrode 1 winding is limited, the lithium-ion transport efficiency is low, and there is a risk of lithium plating.

[0031] Optionally, d1mm can be any value from 80mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, or a value between any two of these values.

[0032] In one embodiment, such as Figure 4 As shown, along the unfolding direction of electrode 1, the distance from the third side 31 to the winding start end 15 of electrode 1 is d2mm, satisfying 80.5mm≤d2mm≤704mm. This setting ensures the transmission efficiency of electrode 1 in the winding start end 15 area while reducing the risk of active material loss.

[0033] It is worth noting that if the value of d2mm is too large, there is a risk that the lamination transition zone 14 located in the inner ring after the electrode 1 is wound may not be completely covered, increasing the risk of active material shedding. If the value of d2mm is too small, the lithium-ion transport space in the region at the starting end 15 of the electrode 1 winding is limited, the lithium-ion transport efficiency is low, and there is a risk of lithium plating.

[0034] Optionally, d2mm can be any value from 80.5mm, 101mm, 151mm, 201mm, 251mm, 302mm, 352mm, 402mm, 452mm, 503mm, 553mm, 603mm, 653mm, 704mm, or a value between any two of these values.

[0035] In one embodiment, such as Figure 5 As shown, along the unfolding direction of electrode 1, the width of the overlapping area of ​​the first protective layer 2 and the second protective layer 3 is d3mm, satisfying 12mm≤d3mm≤59mm. This setting reduces the risk of active material shedding while also mitigating lithium plating issues in the battery.

[0036] It is worth noting that if the value of d3mm is too large, the first protective layer 2 and the second protective layer 3 may cover too large an area of ​​the first active layer 12 and the second active layer 13, affecting the lithium-ion transport efficiency and increasing the risk of lithium plating. If the value of d3mm is too small, the first active layer 12 and the second active layer 13 may not be covered by too large an area, increasing the risk of material loss from the first active layer 12 and the second active layer 13.

[0037] Optionally, d3mm can be any value from 12mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 59mm, or a value between any two of these values.

[0038] In one embodiment, such as Figure 5 As shown, in the unfolding direction of electrode 1, the second side 22 is closer to the winding start end 15 of electrode 1 than the fourth side 32. The distance between the second side 22 and the fourth side 32 is b2mm, satisfying 0.5mm≤b2mm≤4mm. This setting reduces the risk of active material shedding while also reducing the lithium plating problem in the battery.

[0039] It is worth noting that if the value of b2mm is too large, the area not covered by the first active layer 12 may be too large, increasing the risk of material loss. If the value of b2mm is too small, the area completely covered by the first protective layer 2 and the second protective layer 3 by the first active layer 12 and the second active layer 13 may be too large, affecting the lithium-ion transport efficiency and increasing the risk of lithium plating.

[0040] Optionally, b2mm can be any value from 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, or a value between any two of these values.

[0041] In one embodiment, such as Figure 4 As shown, along the unfolding direction of electrode 1, the distance from the second side 22 to the winding start end 15 of electrode 1 is d4mm, satisfying 90mm≤d4mm≤730mm. This setting ensures the transmission efficiency of electrode 1 in the winding start end 15 region while reducing the risk of active material loss.

[0042] It is worth noting that if the value of d4mm is too large, there is a risk that the lamination transition zone 14 located in the inner ring after the electrode 1 is wound may not be completely covered, increasing the risk of active material shedding. If the value of d4mm is too small, the lithium-ion transport space in the region at the starting end 15 of the electrode 1 winding is limited, the lithium-ion transport efficiency is low, and there is a risk of lithium plating.

[0043] Optionally, d4mm can be any value from 90mm, 110mm, 160mm, 210mm, 260mm, 310mm, 360mm, 420mm, 470mm, 520mm, 570mm, 620mm, 670mm, 730mm, or a value between any two of these values.

[0044] In one embodiment, such as Figure 4 As shown, along the unfolding direction of electrode 1, the distance from the fourth side 32 to the winding start end 15 of electrode 1 is d5mm, satisfying 90.5mm≤d5mm≤734mm. This setting ensures the transmission efficiency of electrode 1 in the winding start end 15 area while reducing the risk of active material loss.

[0045] It is worth noting that if the value of d5mm is too large, there is a risk that the lamination transition area 14 in the inner ring after the electrode 1 is wound may not be completely covered, increasing the risk of active material shedding. If the value of d5mm is too small, the lithium-ion transport space in the region at the starting end 15 of the electrode 1 winding is limited, the lithium-ion transport efficiency is low, and there is a risk of lithium plating.

[0046] Optionally, d5mm can be any value from 90.5mm, 111mm, 161mm, 211mm, 261mm, 312mm, 362mm, 422mm, 472mm, 523mm, 573mm, 623mm, 673mm, 734mm, or a value between any two of these values.

[0047] In one embodiment, such as Figure 6 and Figure 7 As shown, the battery cell also includes a third protective layer 4 disposed on the first active layer 12 and a fourth protective layer 5 disposed on the second active layer 13. At least a portion of the third protective layer 4 and at least a portion of the fourth protective layer 5 are disposed in the same stacking transition region 14. Along the unfolding direction of the electrode sheet 1, the third protective layer 4 and the fourth protective layer 5 are staggered and partially overlap. That is, the third protective layer 4 and the fourth protective layer 5 provide protection for another stacking transition region 14.

[0048] Specifically, in one embodiment, such as Figure 6 As shown, the electrode 1 also has a horizontal connecting region 16 connected to the lamination transition region 14. The horizontal connecting region 16 has lamination transition regions 14 connected to opposite sides of each other along the unfolding direction of the electrode 1. The first protective layer 2 and the third protective layer 4 are respectively disposed in two lamination transition regions 14 connected to the same horizontal connecting region 16. That is, the lamination transition regions 14 corresponding to the first protective layer 2 and the second protective layer 3, and the lamination transition regions 14 corresponding to the third protective layer 4 and the fourth protective layer 5, are two adjacent lamination transition regions 14.

[0049] Furthermore, in one embodiment, such as Figure 7 As shown, along the unfolding direction of electrode 1, the distance between the first protective layer 2 and the third protective layer 4 is d6mm, satisfying 110mm≤d6mm≤310mm. This setting avoids the shedding of active material while reducing the risk of lithium plating in the battery.

[0050] It is worth noting that if the value of d6mm is too large, the protective layer may cover too little of the lamination transition region 14, posing a risk of material loss in the uncovered areas of the lamination transition region 14. If the value of d6mm is too small, the protective layer may cover too much of the lamination transition region 14, affecting the lithium-ion transport efficiency and exacerbating the lithium plating problem in the battery.

[0051] Optionally, d6mm can be any value from 110mm, 150mm, 180mm, 200mm, 210mm, 250mm, 280mm, 300mm, 310mm, or a value between any two of these values.

[0052] Furthermore, in one embodiment, such as Figure 7 As shown, along the unfolding direction of electrode 1, the distance between the second protective layer 3 and the fourth protective layer 5 is d7mm, satisfying 110mm≤d7mm≤310mm. This setting avoids the shedding of active material while reducing the risk of lithium plating in the battery.

[0053] It is worth noting that if the value of d7mm is too large, the protective layer may cover too little of the lamination transition region 14, posing a risk of material loss in the uncovered areas of the lamination transition region 14. If the value of d7mm is too small, the protective layer may cover too much of the lamination transition region 14, affecting the lithium-ion transport efficiency and exacerbating the lithium plating problem in the battery.

[0054] Optionally, d7mm can be any value from 110mm, 150mm, 180mm, 200mm, 210mm, 250mm, 280mm, 300mm, 310mm, or a value between any two of these values.

[0055] In one embodiment, such as Figure 8 As shown, the current output layer 11 includes a body portion 111 and an electrode tab portion 112 extending from the body portion 111 along at least one edge of the electrode 1 in the width direction; along the unfolding direction of the electrode 1, the electrode tab portion 112 adjacent to the winding start end 15 of the electrode 1 is located between the winding start end 15 of the electrode 1 and the first protective layer 2.

[0056] It is understood that in this embodiment, no layer transition region 14 is provided between the winding start end 15 and the adjacent tab portion 112. This arrangement can improve the current transmission rate of the electrode 1 near the winding start end 15 and avoid the safety risk of lithium plating at the bending point of the electrode 1 near the winding start end 15 due to the protective layer blocking ion transport during battery charging and discharging.

[0057] Furthermore, in one embodiment, such as Figure 8 As shown, along the unfolding direction of the electrode 1, the distance between the tab 112 adjacent to the winding start end 15 of the electrode 1 and the first side 21 is d8mm, satisfying 20mm≤d8mm≤200mm. This setting reduces the risk of active material shedding while facilitating the winding process of the electrode 1.

[0058] It is worth noting that if the value of d8mm is too large, the distance between the winding start end 15 and the tab 112 may be too close, resulting in the length of the electrode 1 in the area near the winding start end 15 being too small, which is not conducive to the winding process of the electrode 1. If the value of d8mm is too small, the distance between the first protective layer 2 and the tab 112 may be too close. The first protective layer 2 will be greatly affected by the heat generated by the tab 112, which may reduce the adhesion of the first protective layer 2, making it easy to fall off or even peel off the first active layer 12.

[0059] Optionally, d8mm can be any value from 20mm, 50mm, 80mm, 100mm, 120mm, 150mm, 180mm, 200mm, or a value between any two of these values.

[0060] Furthermore, in one embodiment, when d8mm≤150mm, the total width bmm of the misalignment area of ​​the first protective layer 2 and the second protective layer 3 satisfies 1mm≤bmm≤6mm.

[0061] It is worth noting that when the value of d8mm is small, the risk of material falling off the first active layer 12 increases. Therefore, by further reducing the value of bmm, the risk of material falling off the first active layer 12 can be reduced.

[0062] As an alternative implementation method, such as Figure 9 As shown, the current output layer 11 includes a body portion 111 and an electrode tab portion 112 extending from the body portion 111 along at least one edge of the electrode 1 in the width direction; along the unfolding direction of the electrode 1, a first protective layer 2 and a second protective layer 3 are provided between the winding start end 15 of the electrode 1 and the adjacent electrode tab portion 112.

[0063] It is understood that, in alternative embodiments, at least one layered transition region 14 is provided between the winding start end 15 of the electrode 1 and the adjacent electrode tab 112.

[0064] Furthermore, in alternative implementations, such as Figure 9 As shown, along the unfolding direction of the electrode 1, the distance between the tab 112 adjacent to the winding start end 15 of the electrode 1 and the fourth side 32 is d9mm, satisfying 20mm≤d9mm≤160mm. This setting reduces the risk of active material shedding while also reducing the risk of lithium plating in the battery.

[0065] It is worth noting that if the value of d9mm is too large, the second protective layer 3 may be too close to the winding start end 15. The lithium-ion transport space in the region of the winding start end 15 of the electrode 1 is limited, resulting in low lithium-ion transport efficiency and a risk of lithium plating. If the value of d9mm is too small, the second protective layer 3 may be too close to the tab 112. The second protective layer 3 will be greatly affected by the heat generated by the tab 112, which may reduce the adhesion of the second protective layer 3 and cause it to fall off or even peel off the second active layer 13.

[0066] Optionally, d9mm can be any value among 20mm, 50mm, 80mm, 100mm, 120mm, 150mm, and 160mm, or a value between any two of these values.

[0067] In one embodiment, such as Figure 3 As shown, the width B1mm of the first protective layer 2 and the width B2mm of the second protective layer 3 satisfy 0mm≤|B1mm-B2mm|≤4mm. This setting ensures the protective effect of the first protective layer 2 and the second protective layer 3 on the first active layer 12 and the second active layer 13.

[0068] It is worth noting that if the value of |B1mm-B2mm| is too large, that is, if the width difference between the first protective layer 2 and the second protective layer 3 is too large, it is easy to cause insufficient protection on the side with smaller width, which may lead to the risk of material falling off.

[0069] Optionally, |B1mm-B2mm| can be any value from 0mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, or a value between any two of these values.

[0070] In one embodiment, such as Figure 2 As shown, along the thickness direction of electrode 1, the thickness of the first protective layer 2 and / or the second protective layer 3 is t μm, satisfying 20 μm ≤ t μm ≤ 100 μm. This configuration ensures protection of the active material while reducing the risk of lithium plating in the battery.

[0071] It is worth noting that if the value of tμm is too small, the protective layer will have a poor protective effect on the active layer, which can easily lead to material shedding. If the value of tμm is too large, it will affect the lithium-ion transport effect, which can easily lead to lithium plating, and then cause lithium dendrites to pierce the insulating film, resulting in short circuits between the positive and negative electrodes, thus affecting the safety performance of the battery.

[0072] Optionally, tμm can be any value from 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, or a value between any two of these values.

[0073] It is understandable that the thicknesses of the first protective layer 2 and the second protective layer 3 can be the same or different. In addition, since the protective layer located inside the electrode 1 is usually compressed and the protective layer located outside the electrode 1 is usually stretched, the thickness of the protective layer located inside the electrode 1 is usually greater than the thickness of the protective layer located outside the electrode 1.

[0074] In one embodiment, such as Figures 10 to 12 As shown, the first protective layer 2 includes a base layer 6 and an adhesive layer 7. The adhesive layer 7 is bonded to the first active layer 12, and the base layer 6 is located on the side of the adhesive layer 7 facing away from the first active layer 12. The second protective layer 3 includes a base layer 6 and an adhesive layer 7. The adhesive layer 7 is bonded to the second active layer 13, and the base layer 6 is located on the side of the adhesive layer 7 facing away from the second active layer 13. That is, the base layer 6 is bonded to the first active layer 12 and the second active layer 13 using the adhesive layer 7.

[0075] Specifically, the material of base layer 6 can be: polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, or hexafluoropropylene. Vinylidene fluoride copolymer, tetrafluoropropylene Vinylidene fluoride copolymer, trifluorochloropropylene At least one of the following: vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, nonwoven fabric, etc.

[0076] Specifically, the adhesive layer 7 can be made of at least one of the following: acrylic-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic-grafted polyethylene, maleic anhydride-grafted polyethylene, acrylic-grafted polypropylene, polyvinylidene fluoride, maleic anhydride-grafted polypropylene, carboxymethyl cellulose, polyimide, polyetherimide, styrene-isoprene-styrene copolymer rubber, polyethylene phthalate, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone type resin, polyurethane, styrene-isoprene-styrene copolymer, etc.

[0077] As an alternative implementation, the first protective layer 2 and the second protective layer 3 may also be coatings.

[0078] Specifically, the coating consists of adhesives and fillers.

[0079] The adhesives include styrene-butadiene copolymers, acrylate-styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylonitrile-butadiene-styrene copolymers, acrylic rubber, butyl rubber, styrene-butadiene rubber, fluororubber, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM) rubber, ethylene propylene diene monomer (EPDM) rubber, polyethylene oxide, polyepoxychloropropane, polyvinylpyrrolidone, polyphosphazene, polyacrylonitrile, polystyrene, polyvinylpyridine, chlorosulfonated polyethylene, polyester resin, acrylic resin, phenolic resin, epoxy resin, fluorocarbon resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropyl cellulose, diacetylcellulose, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyacrylic acid, polyimide, polyamide-imide, polyimide-polyamide-imide copolymer, and one or more polymers in which the aforementioned polymers are partially or completely substituted by alkali metals.

[0080] The filler includes one or more of ceramics, silicates, minerals, and glass, and optionally includes one or more of alumina, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, boehmite, mica, bentonite, hydropyrite, kaolin, and talc.

[0081] Furthermore, in one embodiment, such as Figure 12 As shown, the thickness of the base layer 6 is t1μm, satisfying 10μm≤t1μm≤70μm. This design ensures protection of the active materials while avoiding any impact on the battery's volumetric energy density.

[0082] It is worth noting that if the value of t1μm is too small, the base layer 6 may be pierced by lithium dendrites, leading to a short circuit risk between the positive and negative electrodes. If the value of t1μm is too large, the base layer 6 will occupy too much space within the battery, affecting the volumetric energy density of the battery.

[0083] Optionally, t1μm can be any value among 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, and 70μm, or a value between any two of these values.

[0084] Furthermore, in one embodiment, such as Figure 12 As shown, the thickness of the adhesive layer 7 is t2μm, satisfying 10μm≤t2μm≤50μm. This setting ensures the reliable adhesion of the protective layer on the lamination transition region 14 while avoiding any impact on the volumetric energy density of the battery.

[0085] It is worth noting that if the value of t2μm is too small, the adhesion between the adhesive layer 7 and the lamination transition region 14 may be weak, causing the protective layer to easily detach from the lamination transition region 14, and even peeling off the active layer. If the value of t2μm is too large, the adhesive layer 7 will occupy too much space in the battery, affecting the volumetric energy density of the battery.

[0086] Optionally, t2μm can be any value from 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm or a value between any two of these values.

[0087] In one embodiment, such as Figure 10 and Figure 11 As shown, the base layer 6 is provided with through holes 61 that extend along the thickness direction, and the pore density of the through holes 61 ranges from 1% to 30%. This arrangement ensures the adhesion between the protective layer and the lamination transition zone 14, while also ensuring the wetting effect of the electrolyte and the lithium ion transport efficiency.

[0088] It is worth noting that by opening through holes 61 on the base layer 6, wetting channels for electrolyte are provided, making the electrolyte wetting more thorough and serving as a lithium ion transport channel. This significantly reduces lithium plating inside the battery, reduces the formation of lithium dendrites, and lowers the risk of short circuits caused by puncturing the insulating film.

[0089] It should be further noted that if the pore density is too small, the channels for electrolyte and lithium ion transport will be too small, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of short circuits between the positive and negative electrodes due to puncture of the insulating film, thus affecting the safety performance of the battery. If the pore density is too large, it can easily affect the reliability of the bonding layer 7 to the lamination transition region 14, which can easily lead to the protective layer falling off, or even peeling off the active layer.

[0090] Optionally, the pore density of the through hole 61 can be any value among 1%, 5%, 10%, 15%, 20%, 25%, and 30%, or a value between any two of these values.

[0091] In this embodiment, the pore density measurement method is as follows: Remove the protective layer from the battery sample and dry it at 60°C for 60 minutes. After ensuring the sample is dry, measure the length and width of the protective layer sample with a micrometer and calculate the sample area.

[0092] The pore structure of the through-holes in the protective layer sample was observed using a scanning electron microscope (SEM), and the total area of ​​the through-holes on the protective layer sample was measured.

[0093] Pore ​​density calculation formula: Pore density = (Total area of ​​through holes / Sample area) × 100%.

[0094] In one embodiment, such as Figure 10 As shown, the pore size Dμm of the through-hole 61 satisfies 10μm≤Dμm≤500μm. This setting ensures the adhesion between the protective layer and the lamination transition region 14, while also guaranteeing the wetting effect of the electrolyte and the lithium ion transport efficiency.

[0095] It is worth noting that if the value of Dμm is too small, the channels for electrolyte and lithium ion transport will be too small, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of short circuits between the positive and negative electrodes due to puncture of the insulating film, thus affecting the safety performance of the battery. If the value of Dμm is too large, it can easily affect the reliability of the adhesion of the adhesive layer 7 to the lamination transition region 14, which can easily lead to the detachment of the protective layer, or even the peeling off of the active layer.

[0096] Optionally, Dμm can be any value from 10μm, 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, or a value between any two of these values.

[0097] It should be noted that the through hole 61 is provided through the base layer 6 along the thickness direction of the electrode 1. The diameter of the through hole 61 refers to the diameter of the orthographic projection of the through hole 61 onto a projection plane perpendicular to the thickness direction.

[0098] Furthermore, in one embodiment, both the first protective layer 2 and the second protective layer 3 are provided with through holes 61. This further ensures the wetting effect of the electrolyte and the lithium-ion transport efficiency.

[0099] In one embodiment, such as Figure 10 and Figure 11 As shown, the adhesive layer 7 includes a blank area 71. On the projection plane perpendicular to the thickness direction, the area ratio of the orthographic projection of the blank area 71 on the orthographic projection of the adhesive layer 7 is k, which satisfies 6%≤k≤50%.

[0100] It is worth noting that if the value of k is too large, the setting range of the colloidal region 72 may be too small, affecting the reliability of the bonding between the protective layer and the lamination transition region 14, which may easily lead to the protective layer falling off, or even peeling off the active layer. If the value of k is too small, the area available for setting the through hole 61 will be too small, and the base layer 6 will have too great a blocking effect on the electrolyte and lithium ions, affecting the wetting effect of the electrolyte and the transport efficiency of lithium ions, increasing the risk of lithium dendrite formation, and increasing the risk of short circuit between the positive and negative electrodes due to the puncture of the insulating film, thus affecting the safety performance of the battery.

[0101] Optionally, k can take any value from 6%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a value between any two values.

[0102] It should be noted that, in one embodiment, the projected area of ​​the adhesive layer 7 on the projection plane perpendicular to the thickness direction is 700 mm². 2 Up to 4600mm 2 The projected area of ​​blank area 71 is 300 mm². 2 Up to 2300mm 2 .

[0103] Specifically, in one alternative implementation, such as Figure 10 As shown, along the unfolding direction of the electrode 1, blank areas 71 are provided on opposite sides of the base layer 6. That is, along the unfolding direction of the electrode 1, the middle area of ​​the base layer 6 is the colloidal area 72, and the opposite sides of the colloidal area 72 are blank areas 71. Of course, blank areas 71 can also be provided between two colloidal areas 72 along the unfolding direction of the electrode 1. In another optional embodiment, as... Figure 11 and Figure 12 As shown, along the width direction of the electrode 1, the blank area 71 is set on the opposite sides of the base layer 6. That is, along the width direction of the electrode 1, the middle area of ​​the base layer 6 is the colloidal area 72, and the opposite sides of the colloidal area 72 are blank areas 71. Of course, a blank area 71 can also be set between the two colloidal areas 72 along the width direction of the electrode 1.

[0104] It is understandable that blank area 71 refers to the area where no colloid is set.

[0105] In one embodiment, such as Figure 13 As shown, along the unfolding direction of electrode 1, the first protective layer 2 and / or the second protective layer 3 include a central region 8 and edge regions 9 disposed on opposite sides of the central region 8. The thickness of the central region 8 is t3μm, and the thickness of the edge regions 9 is t4μm, satisfying t3μm>t4μm, 25μm≤t3μm≤100μm, and 20μm≤t4μm≤95μm. It is worth noting that the central region 8 of the protective layer is usually positioned corresponding to the location where stress is more concentrated and material shedding is more severe in the lamination transition zone 14. To improve the protective effect of the protective layer, the thickness of the central region 8 can be increased.

[0106] Optionally, t3μm can be any value from 25μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, or a value between any two of these values.

[0107] Optionally, t4μm can be any value among 20μm, 25μm, 35μm, 45μm, 55μm, 65μm, 75μm, 85μm, and 95μm, or a value between any two of these values.

[0108] In one embodiment, such as Figure 14 As shown, along the width direction of electrode 1, the end of the first protective layer 2 extends beyond the edge of the first active layer 12 on the same side and / or the end of the second protective layer 3 extends beyond the edge of the second active layer 13 on the same side, with an extension distance of c1mm, satisfying 0.1mm≤c1mm≤10mm. This configuration ensures that the protective layer can completely cover the edge of the active layer, further avoiding the problem of material shedding from the active layer, while also avoiding any impact on the energy density of the battery.

[0109] It is worth noting that if the value of c1mm is too small, it cannot guarantee effective coverage of the edge of the active layer, and there is still a risk of material falling off. Furthermore, when bonding the protective layer to electrode 1, the length available for gripping is too small, which is not convenient for the bonding process. If the value of c1mm is too large, it is easy to cause additional space occupation in the battery after the cell is installed in the casing, which will affect the energy density of the battery.

[0110] Optionally, c1mm can be any value from 0.1mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, or a value between any two of these values.

[0111] As an alternative implementation, in another embodiment, such as Figure 15 As shown, along the width direction of electrode 1, the end of the first protective layer 2 does not extend beyond the edge of the first active layer 12 on the same side, and the distance between the end of the first protective layer 2 and the edge of the first active layer 12 is c2mm; and / or, the end of the second protective layer 3 does not extend beyond the edge of the second active layer 13 on the same side, and the distance between the end of the second protective layer 3 and the edge of the second active layer 13 is c2mm, satisfying 1mm≤c2mm≤15mm. This configuration reduces the risk of material shedding from the active layer while also reducing the risk of lithium plating in the battery.

[0112] It is worth noting that if the value of c2mm is too large, the coverage area of ​​the protective layer over the lamination transition region 14 may be too small, posing a risk of material loss in the uncovered areas of the lamination transition region 14. If the value of c2mm is too large, the coverage area of ​​the lamination transition region 14 will be too large, affecting the lithium-ion transport efficiency and exacerbating the lithium plating problem in the battery.

[0113] Optionally, c2mm can be any value from 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, or a value between any two of these values.

[0114] In one embodiment, the electrode 1 is wound into several turns, and a first protective layer 2 and a second protective layer 3 are provided within the first five turns near the starting end 15 of the winding of the electrode 1. The electrode 1 experiences greater stress within the first five turns near the starting end 15 of the winding, making it more prone to material shedding. Therefore, providing protective layers within the first five turns near the starting end 15 of the winding of the electrode 1 reduces the risk of material shedding while ensuring the volumetric energy density of the battery.

[0115] Optionally, a protective layer may be provided within five turns of the starting end 15 of the winding near the electrode 1, or a protective layer may be provided only in the first turn, the first two turns, or at intervals.

[0116] In one embodiment, such as Figure 16 and Figure 18 As shown, the electrode 1 is wound in several turns, and a crease 141 is formed in the layer transition area 14 of the first turn near the starting end 15 of the winding of the electrode 1. The first protective layer 2 and the second protective layer 3 cover the crease 141.

[0117] Furthermore, in one embodiment, such as Figure 18 As shown, along the unfolding direction of electrode 1, the edge of the first protective layer 2 extends beyond the crease 141 by a distance of r1mm, and the edge of the second protective layer 3 extends beyond the crease 141 by a distance of r2mm, satisfying r1mm≥3mm and r2mm≥3mm.

[0118] In one embodiment, the total width bmm of the misaligned area between the first protective layer 2 and the second protective layer 3 satisfies 1mm ≤ bmm ≤ 8mm. This configuration reduces the risk of active material shedding while also reducing the risk of lithium plating in the battery.

[0119] It is worth noting that if the value of bmm is too large, it is easy to cause the first active layer 12 and the second active layer 13 to be covered by too large an area, which increases the risk of material loss of the first active layer 12 and the second active layer 13; if the value of bmm is too small, the first protective layer 2 and the second protective layer 3 will cover too large an area of ​​the first active layer 12 and the second active layer 13, which will affect the lithium ion transport efficiency and increase the risk of lithium plating.

[0120] Optionally, bmm can be any value from 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, or a value between any two of these values.

[0121] Understandably, please refer to Figure 5 The total width of the misaligned area between the first protective layer 2 and the second protective layer 3 is bmm = b1mm + b2mm.

[0122] In one embodiment, such as Figure 3 As shown, the width B1mm of the first protective layer 2 satisfies 10mm≤B1mm≤30mm. This setting reduces the risk of active material shedding while also reducing the risk of lithium plating in the battery.

[0123] It is worth noting that if the value of B1mm is too large, the first protective layer 2 may cover too much of the first active layer 12, affecting the lithium-ion transport efficiency and increasing the risk of lithium plating in the battery. If the value of B1mm is too small, the first protective layer 2 may not provide sufficient protection for the first active layer 12, leading to the risk of material loss from the first active layer 12.

[0124] Optionally, B1mm can be any value from 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 28mm, 30mm, or a value between any two of these values.

[0125] In one embodiment, such as Figure 3 As shown, the width B2mm of the second protective layer 3 satisfies 10mm≤B2mm≤30mm. This setting reduces the risk of active material shedding while also reducing the risk of lithium plating in the battery.

[0126] It is worth noting that if the value of B2mm is too large, the second protective layer 3 may cover too much of the second active layer 13, affecting the lithium-ion transport efficiency and increasing the risk of lithium plating in the battery. If the value of B2mm is too small, the second protective layer 3 may not provide sufficient protection for the second active layer 13, leading to the risk of material loss from the second active layer 13.

[0127] Optionally, B2mm can be any value from 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 28mm, 30mm, or a value between any two of these values.

[0128] In one embodiment, the outer circumference Lmm of the battery cell satisfies 240mm≤Lmm≤640mm. This setting reduces the risk of active material shedding while ensuring the battery's energy density.

[0129] It is worth noting that if the value of Lmm is too large, it can easily cause greater stress concentration in the lamination transition region 14, increasing the risk of active material shedding. If the value of Lmm is too small, it will reduce the energy density of the battery.

[0130] Optionally, Lmm can be any value from 240mm, 280mm, 300mm, 340mm, 380mm, 400mm, 440mm, 480mm, 500mm, 540mm, 580mm, 600mm, 640mm, or a value between any two of these values.

[0131] In one embodiment, the elongation at break X% of the current output layer 11 satisfies 2% ≤ X% ≤ 12%. This setting reduces the risk of material loss from the active layer while meeting design requirements.

[0132] It should be noted that elongation at break is used to measure a material's ability to undergo plastic deformation. The higher the elongation at break, the better the toughness and the stronger the plastic deformation; the lower the elongation at break, the more brittle the material, the less it is resistant to deformation, and the more easily it breaks.

[0133] It is worth noting that if the value of X% is too small, the current output layer 11 is prone to breakage under the large stress at the layer transition region 14, which in turn exacerbates the risk of material loss from the active layer. If the value of X% is too large, it may lead to problems that do not meet the overall battery design requirements.

[0134] Optionally, X% can be any value from 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or a value between any two values.

[0135] According to an embodiment of the present invention, another aspect provides a battery, comprising: a casing; and the aforementioned battery cell disposed within the casing.

[0136] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0137] The preparation of the example battery and the comparative battery includes the following steps: (1) Preparation of the positive electrode: The prepared positive electrode active material, conductive agent acetylene black, and binder PVDF are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, it is cold-pressed and slit to obtain the positive electrode sheet. Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98):(4~1):(4~1).

[0138] (2) Preparation of negative electrode: The negative electrode active material, conductive agent acetylene black, thickener CMC, and binder SBR are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained. The ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0139] (3) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0140] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0141] (5) Preparation of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a bare battery cell. Protective layers are adhered to both active layers at the transition zone between the electrode layers. The bare cell is placed in a prismatic battery casing. The battery is dried, injected with electrolyte, and then encapsulated, allowed to stand, formed, and volume-adjusted to obtain a lithium-ion battery.

[0142] The positive electrode active material can be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate; the negative electrode active material can be selected from one or more negative electrode active main materials, such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0143] The relevant performance of the batteries in the above embodiments and comparative examples was tested, and the test results are recorded in Table 1. The test methods are as follows: Performance 1: Battery capacity retention rate Following the battery preparation method described above, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. The parameters of the protective layer and cell in the lithium-ion batteries obtained in each embodiment and comparative example are shown in Table 1. All other structures are identical. The lithium-ion battery was charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, and then charged with a constant voltage of 0.33C until the current dropped to 0.05C. After standing for 5 minutes, the battery was discharged with a constant current of 0.33C to the lower limit voltage. This process was repeated three times to obtain the third discharge capacity Q1, which was taken as the fixed capacity.

[0144] The lithium-ion battery is charged at room temperature (25℃) with a constant current of 0.33C to the upper limit voltage, then charged with a constant voltage of 0.33C until the current drops to 0.05C. After resting for 5 minutes, the battery is discharged with a constant current of 0.33C to the lower limit voltage. This constitutes one cycle. After n cycles, the discharge capacity Qn of the battery on the nth cycle is recorded. The battery capacity retention rate is calculated using the formula "Battery capacity retention rate = Qn / Q1 × 100%". The number of cycles n when the capacity retention rate first falls below 80% is recorded as the number of cycles for that battery. If n is less than 1200, the battery is considered unqualified; if n is greater than or equal to 1200 and less than 1400, the battery is considered qualified; and if n is greater than or equal to 1400, the battery is considered good.

[0145] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0146] In this test, the active material for the positive electrode of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0147] Performance 2: Battery Lithium Plating Following the battery preparation method described above, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. The parameters of the protective layer and cell in the lithium-ion batteries obtained in each embodiment and comparative example are shown in Table 1. All other structures are identical. The lithium-ion battery was charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, then charged at a constant voltage until the current dropped to 0.05C. After standing for 5 minutes, the battery was discharged with a constant current of 0.33C to the lower limit voltage. This constituted one cycle, and 2000 cycles were performed. Then, the lithium-ion battery was charged at 0.33C to the upper limit voltage, with a cutoff current less than or equal to 0.05C, resulting in a fully charged battery.

[0148] Disassemble the battery, then remove the electrodes and observe the lithium plating on the surface of the negative electrode in the stacked transition region. The portion where the projection of a single protective layer coincides with the electrode is the first region. The lithium plating area of ​​the first region is measured and recorded as S1, and the area of ​​the first region is recorded as S2. According to the formula, the percentage of the lithium plating area on the surface of the negative electrode stacked transition region = (S1 / S2) × 100%, the percentage of the lithium plating area on the surface of the negative electrode stacked transition region is calculated. If the lithium plating area on the surface of the negative electrode stacked transition region is less than 10%, it is considered as no / slight lithium plating; if the lithium plating area on the surface of the negative electrode stacked transition region is 10% to 50%, it is considered as moderate lithium plating; and if the lithium plating area on the surface of the negative electrode stacked transition region is greater than 50%, it is considered as severe lithium plating.

[0149] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0150] In this test, the positive electrode active material of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder satisfies 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder satisfies 95:2:1:2.

[0151] The following steps can be used to measure the elongation at break: Remove the electrode from the battery sample, scrape off the active layer on the surface of the electrode to expose the current output layer, and use it as a test sample. Use a shearing machine to cut the test sample into (152±0.5) mm × (13±0.25) mm, ensuring that the cut test sample is smooth and free of burrs, notches, wrinkles and obvious mechanical damage.

[0152] The testing tool is a tensile testing machine. Marking lines are drawn on the specimen, with a distance L0 between the two marking lines being 50 mm. The distance between the marked lines and the clamps of the tensile testing machine is not less than 3 mm.

[0153] The specimen is placed in the clamps of the tensile testing machine, centered, with the specimen axis aligned with the clamp axis. At room temperature (25℃), the distance between the machine clamps is 75mm, and the tensile speed is 50mm / min. The specimen is stretched until it breaks. The broken ends of the specimen are then joined together, and the distance L1 between the two marked lines is measured.

[0154] The formula for the elongation at break X% is X%=[(L1-L0) / L0]×100%.

[0155] The elongation at break can be controlled using the following methods: The elongation at break of the current output layer in the electrode can be adjusted by controlling the material, such as pure copper, pure aluminum, or the proportion of doping elements in the alloy. For example, appropriately doping an aluminum electrode with iron can improve its elongation at break. Alternatively, the elongation at break of the current output layer can be altered by changing its thickness or by using a composite current collector.

[0156] The following steps can be used to measure the circumference of a battery cell: Use a bendable measuring tape to wrap around the outer circumference of the battery cell, measure the dimensions around the circumference and record them. The measurement accuracy needs to be at least 0.1mm.

[0157] Table 1:

[0158] As can be seen from Table 1, in Examples 1 to 15, (b×L) / [X×(B1+B2)] 2 The values ​​of ] are all within 0.8 × 10 -2 Up to 600×10 -2 Within the specified range, therefore, the batteries of Examples 1 to 15 do not have any unqualified capacity retention rate, and the batteries do not have serious lithium plating problems.

[0159] As can be seen from Table 1, in Comparative Examples 1, 3 and 4, (b×L) / [X×(B1+B2)] 2 The value of ] is not greater than 0.8 × 10 -2 Up to 600×10 -2 Within the range and greater than 600×10 -2 This resulted in the batteries in Comparative Examples 1, 3, and 4 failing to meet the battery capacity retention rate standard.

[0160] As can be seen from Table 1, in Comparative Example 2, (b×L) / [X×(B1+B2)] 2 The value of ] is not greater than 0.8 × 10 -2 Up to 600×10 -2 Within the range and less than 0.8×10 -2 This resulted in a serious lithium plating problem in the battery of Comparative Example 2.

[0161] The following defines and explains some of the terms used in this application.

[0162] The positive electrode is one of the core components in a battery that carries the positive electrode active material. During charging, metal ions (such as lithium ions) are released from the crystal lattice of the positive electrode active material (oxidation reaction), migrate through the electrolyte, and intercalate into the negative electrode. During discharging, metal ions (such as lithium ions in a lithium battery) are released from the negative electrode and intercalate into the crystal lattice of the positive electrode active material (reduction reaction), thus realizing the storage and release of lithium ions.

[0163] A positive electrode generally includes a positive current collector (current output layer) and a positive active material layer. The positive active material layer is coated on at least one surface of the positive current collector and includes: positive active material, conductive agent and binder.

[0164] The positive electrode active material is the donor of metal ions, such as lithium ions and sodium ions, provided by the battery cell. For example, in the positive electrode of a lithium-ion battery, the positive electrode active material can reversibly intercalate and deintercalate lithium ions, serving as the core carrier for the battery's storage and release of chemical energy. Positive electrode active materials include, but are not limited to, at least one of the following: lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive electrode active materials for batteries. These positive electrode active materials can be used alone or in combination of two or more. Among them, lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15Al 0.05 At least one of O2 and its modified compounds.

[0165] The positive electrode conductive agent includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, SuperP, etc.), carbon nanotubes, graphene and carbon nanofibers.

[0166] The positive electrode binder includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0167] During battery charging, active ions (such as Li) from the positive electrode are embedded in the negative electrode, while electrons from the positive electrode are transferred to the negative electrode through an external circuit to maintain charge balance. During discharge, the active ions (such as Li) previously embedded in the negative electrode can be released, while electrons from the negative electrode are transferred to the positive electrode through an external circuit to maintain charge balance, thus achieving energy storage and release.

[0168] The negative electrode sheet includes a negative current collector (current output layer) and a negative active layer disposed on at least one surface of the negative current collector. The negative current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. Composite current collectors may include a polymer base material and a metal layer. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). The negative active layer includes a negative active material, a conductive agent, and a binder.

[0169] The negative electrode active material can be carbon-based materials such as graphite, porous carbon, hard carbon, soft carbon, and mesophase carbon microspheres, or silicon-based materials such as elemental silicon, silicon oxides, silicon-carbon composites, and silicon-nitrogen composites, or tin-based materials (elemental tin, tin oxides, and tin alloys, etc.), or lithium titanate materials, or metallic lithium materials, etc. The conductive agent can be conductive carbon black, carbon nanotubes, etc., and the binder can be styrene-butadiene rubber, polyacrylic acid, etc.

[0170] The positive current collector serves as a substrate and is mainly used to attach the positive active material, thereby collecting the current generated by the positive active material and outputting the current to the outside.

[0171] The positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, it can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0172] The negative electrode current collector serves to collect current and acts as a carrier for the negative electrode slurry. The negative electrode slurry (negative electrode active material, conductive agent, binder, etc.) is coated onto the negative electrode current collector. The negative electrode current collector collects electrons from the negative electrode active material and conducts them to the external circuit, realizing the process of converting chemical energy into electrical energy.

[0173] The negative electrode current collector can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium, and can be surface-plated with silver. Composite current collectors may include a polymer substrate and a metal layer. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0174] The tab is located on one side of the positive / negative current collector and is separately or integrally formed with the current collector. It is electrically connected to the current collector to conduct the current on the corresponding current collector. The tab is made of a composite material formed by a base layer of a highly conductive metal material (such as copper, aluminum, copper or nickel) and a metal layer.

[0175] A diaphragm (insulating membrane) is placed between the positive and negative electrode plates to separate them and prevent them from short-circuiting due to contact.

[0176] The diaphragm can be at least one of glass fiber, nonwoven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. A coating can also be applied to the diaphragm surface. The coating can be an inorganic coating and / or an organic coating, wherein the inorganic coating material includes at least one of alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, and boehmite; and the organic coating includes at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0177] A wound cell (wound core) generally refers to a cell made by winding continuous positive electrode plates, negative electrode plates, and separators. The separator is located between adjacent positive and negative electrode plates.

[0178] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electric cell, characterized by, It is manufactured by winding a stacked positive electrode sheet, an insulating film, and a negative electrode sheet, including: At least one of the positive and negative electrode plates (1) includes a current output layer (11), a first active layer (12), and a second active layer (13). The first active layer (12) and the second active layer (13) are respectively disposed on opposite sides of the current output layer (11) along the thickness direction. The electrode plate (1) is bent to form a stacked transition region (14). The battery cell also includes a first protective layer (2) disposed on the first active layer (12) and a second protective layer (3) disposed on the second active layer (13). At least a portion of the first protective layer (2) and at least a portion of the second protective layer (3) are disposed in the same stacked transition region (14). Along the unfolding direction of the electrode (1), the first protective layer (2) and the second protective layer (3) are staggered and partially overlap. In the unfolding direction of the electrode (1), the first protective layer (2) includes a first side (21) and a second side (22) that are arranged at a distance from each other. The second protective layer (3) includes a third side (31) and a fourth side (32) that are arranged at a distance from each other. The first side (21) is closer to the winding start end (15) of the electrode (1) than the second side (22). The third side (31) is closer to the winding start end (15) of the electrode (1) than the fourth side (32). The first side (21) is closer to the winding start end (15) of the electrode (1) than the third side (31). Along the unfolding direction of the electrode (1), the distance from the first side (21) to the winding start end (15) of the electrode (1) is d1mm, which satisfies 80mm≤d1mm≤700mm; Along the unfolding direction of the electrode (1), the distance from the third side (31) to the winding start end (15) of the electrode (1) is d2mm, which satisfies 80.5mm≤d2≤704mm.

2. The electric cell of claim 1, wherein, Along the unfolding direction of the electrode (1), the distance between the first side (21) and the third side (31) is b1mm, which satisfies 0.5mm≤b1mm≤4mm.

3. The electric cell of claim 1, wherein, In the unfolding direction of the electrode (1), the second side (22) is closer to the winding start end (15) of the electrode (1) than the fourth side (32), and the distance between the second side (22) and the fourth side (32) is b2mm, satisfying 0.5mm≤b2mm≤4mm.

4. The electric cell of claim 3, wherein, Along the unfolding direction of the electrode (1), the distance from the second side (22) to the winding start end (15) of the electrode (1) is d4mm, satisfying 90mm≤d4mm≤730mm; and / or, Along the unfolding direction of the electrode (1), the distance from the fourth side (32) to the winding start end (15) of the electrode (1) is d5mm, satisfying 90.5mm≤d5mm≤734mm.

5. The electric cell of claim 1, wherein, The cell further includes a third protective layer (4) disposed on the first active layer (12) and a fourth protective layer (5) disposed on the second active layer (13). At least a portion of the third protective layer (4) and at least a portion of the fourth protective layer (5) are disposed in the same stacked transition region (14). Along the unfolding direction of the electrode (1), the third protective layer (4) and the fourth protective layer (5) are staggered and partially overlap.

6. The electric cell of any one of claims 1 to 5, wherein, The current output layer (11) includes a body portion (111) and an electrode tab portion (112) extending from the body portion (111) along at least one edge in the width direction of the electrode (1). Along the unfolding direction of the electrode (1), the tab (112) adjacent to the winding start end (15) of the electrode (1) is located between the winding start end (15) of the electrode (1) and the first protective layer (2).

7. The electric cell of any one of claims 1 to 5, wherein, The current output layer (11) includes a body portion (111) and an electrode tab portion (112) extending from the body portion (111) along at least one edge in the width direction of the electrode (1). Along the unfolding direction of the electrode (1), the first protective layer (2) and the second protective layer (3) are provided between the winding start end (15) of the electrode (1) and the adjacent electrode tab (112).

8. The electric cell of any one of claims 1 to 5, wherein, Along the thickness direction of the electrode (1), the thickness of the first protective layer (2) and / or the second protective layer (3) is tμm, satisfying 20μm≤tμm≤100μm.

9. The electric cell of claim 8, wherein, The thickness of the first protective layer (2) is the same as the thickness of the second protective layer (3); or, The thickness of the first protective layer (2) is different from the thickness of the second protective layer (3).

10. The electric cell of claim 8, wherein, The thickness of the protective layer located inside the electrode (1) in the first protective layer (2) and the second protective layer (3) is greater than the thickness of the protective layer located outside the electrode (1).

11. The electric cell of any one of claims 1 to 5, wherein, The first protective layer (2) includes a base layer (6) and an adhesive layer (7), the adhesive layer (7) being bonded to the first active layer (12), and the base layer (6) being located on the side of the adhesive layer (7) facing away from the first active layer (12); and / or, The second protective layer (3) includes a base layer (6) and an adhesive layer (7), the adhesive layer (7) being bonded to the second active layer (13), and the base layer (6) being located on the side of the adhesive layer (7) facing away from the second active layer (13).

12. The electric cell of claim 11, wherein, The thickness of the base layer (6) is t1μm, satisfying 10μm≤t1μm≤70μm; and / or, The thickness of the adhesive layer (7) is t2μm, which satisfies 10μm≤t2μm≤50μm.

13. The electric cell of claim 11, wherein, The base layer (6) is provided with through holes (61) that extend through the thickness direction. The pore density of the through holes (61) ranges from 1% to 30%, and / or the pore diameter Dμm of the through holes (61) satisfies 10μm≤Dμm≤500μm.

14. The electric cell of claim 13, wherein, Both the first protective layer (2) and the second protective layer (3) are provided with the through hole (61).

15. The electric cell of claim 11, wherein, The adhesive layer (7) includes a blank area (71). On the projection plane perpendicular to the thickness direction, the area ratio of the orthographic projection of the blank area (71) on the orthographic projection of the adhesive layer (7) is k, which satisfies 6%≤k≤50%.

16. The electric cell of claim 15, wherein, The orthogonal projection area of the adhesive layer (7) is 700mm 2 to 4600mm 2 on the projection plane perpendicular to the thickness direction. 2 The orthogonal projection area of the blank area (71) is 300mm 2 to 2300mm.

17. The electric cell of claim 15, wherein, Along the unfolding direction of the electrode (1), the blank area (71) is set on opposite sides of the base layer (6); or, A blank area (71) is provided between the two colloidal regions (72) along the unfolding direction of the electrode (1); or, Along the width direction of the electrode (1), the blank area (71) is set on opposite sides of the base layer (6); or, A blank area (71) is provided between the two colloidal regions (72) along the width direction of the electrode (1).

18. The electric cell of any one of claims 1 to 5, wherein, The first protective layer (2) and / or the second protective layer (3) are coatings.

19. The electric cell of claim 18, wherein, The coating consists of an adhesive and a filler.

20. The electric cell of any one of claims 1 to 5, wherein, Along the unfolding direction of the electrode (1), the first protective layer (2) and / or the second protective layer (3) include a central region (8) and edge regions (9) disposed on opposite sides of the central region (8). The thickness of the central region (8) is t3μm, and the thickness of the edge regions (9) is t4μm, satisfying t3μm>t4μm, 25μm≤t3μm≤100μm, and 20μm≤t4μm≤95μm.

21. The electric cell of any one of claims 1 to 5, wherein, Along the width direction of the electrode (1), the end of the first protective layer (2) extends beyond the edge of the first active layer (12) on the same side and / or the end of the second protective layer (3) extends beyond the edge of the second active layer (13) on the same side, and the extension distance is c1mm, satisfying 0.1mm≤c1mm≤10mm.

22. The electric cell of any one of claims 1 to 5, wherein, Along the width direction of the electrode (1), the end of the first protective layer (2) does not extend beyond the edge of the first active layer (12) on the same side and the distance between the end of the first protective layer (2) and the edge of the first active layer (12) is c2mm, and / or, the end of the second protective layer (3) does not extend beyond the edge of the second active layer (13) on the same side and the distance between the end of the second protective layer (3) and the edge of the second active layer (13) is c2mm, satisfying 1mm≤c2mm≤15mm.

23. The electric cell of any one of claims 1 to 5, wherein, The electrode (1) is wound in several turns, and the first protective layer (2) and the second protective layer (3) are provided within five turns near the starting end (15) of the winding of the electrode (1).

24. The electrically core of any one of claims 1-5, wherein, The electrode (1) is wound in several turns, and a crease (141) is formed in the first turn of the first turn near the starting end (15) of the winding of the electrode (1). The first protective layer (2) and the second protective layer (3) cover the crease (141).

25. A battery, characterized in that, include: shell; The battery cell according to any one of claims 1 to 24 is disposed within the housing.

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