Battery, battery pack, and electric device

Abstract

The application relates to the technical field of batteries, and discloses a battery, a battery pack and a power utilization device, which comprise a roll core formed by winding positive electrode sheets, diaphragms and negative electrode sheets in a laminated mode, and the roll core comprises a flat area and first and second circular arc areas; along the winding direction of the roll core, the positive electrode sheets have positive electrode starting ends close to the starting position of winding; the roll core further comprises a support layer, the negative electrode sheets comprise negative electrode sheet bodies and negative electrode support layers, the support layer comprises the negative electrode support layers, the negative electrode support layers extend beyond the positive electrode starting ends and are located at least in the first circular arc area; at the first circular arc area, the total thickness of the support layer is d; along a second direction, the thickness of the roll core is D, the second direction is perpendicular to the first direction and the height direction of the roll core; the sag of the positive electrode sheets is L; and 10.8 <= d / (D*L) <= 10209.7 is met. According to the application, the risk of lithium precipitation of the negative electrode sheets is reduced to ensure the safety performance of the battery, and the problem of material falling of the positive electrode sheets is avoided to ensure the cycle life of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to batteries, battery packs, and electrical devices. Background Technology

[0002] Wound cells (cores) are typically formed by winding stacked positive electrode strips, separator strips, and negative electrode strips. During battery cycling, lithium plating can easily occur at the corners of the core, leading to insulation failure, internal short circuits, and increased risk of thermal runaway. Summary of the Invention

[0003] This invention provides a battery, a battery pack, and an electrical device to solve the problem in the prior art where lithium plating easily occurs at the corners of the battery core, leading to insulation failure, internal short circuits, and increased risk of thermal runaway.

[0004] In a first aspect, the present invention provides a battery comprising: A core is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet stacked together. The negative electrode sheet is positioned closer to the winding start position than the positive electrode sheet. The core includes a flat region and a first arc region and a second arc region located at opposite ends of the flat region along a first direction. Along the winding direction of the core, the positive electrode sheet has a positive electrode start end close to the winding start position. The core also includes a support layer. The negative electrode sheet includes a negative electrode sheet body and a negative electrode support layer. The support layer includes the negative electrode support layer, which extends beyond the positive electrode start end and is located at least in the first arc region. In the first arc region, the total thickness of the support layer is d (μm); along the second direction, the thickness of the core is D (mm), and the second direction is perpendicular to both the first direction and the height direction of the core; the lateral length of the end of the positive electrode sheet on the suspended side when it droops by 4cm is L2 (cm), the lateral length of the end of the positive electrode sheet on the suspended side when it droops by 2cm is L1 (cm), and the drooping degree of the positive electrode sheet is L, which satisfies L=(L2 / L1)-1; d, D and L satisfy 10.8≤d / (D×L)≤10209.7.

[0005] Beneficial effects: By limiting the value of d / (D×L), the risk of lithium plating on the negative electrode is reduced to ensure the safety performance of the battery, while the problem of material shedding on the positive electrode is avoided to ensure the cycle life of the battery. Specifically, if the value of d / (D×L) is too small, meaning the proportion of d is too small and / or the proportion of D is too large and / or the proportion of L is too large, an excessively large proportion of L will result in poor flexibility of the positive electrode sheet, making it difficult to bend in the arc area. This will lead to a larger gap between the innermost positive electrode sheet and the negative electrode sheet, affecting lithium-ion transport, increasing the risk of lithium plating, making the battery prone to self-discharge, and even causing insulation failure and short circuits. An excessively large proportion of D will result in an excessively thick cell, poor electrolyte wetting effect, and high ionic impedance between the positive and negative electrode sheets, increasing the risk of lithium plating on the negative electrode sheet. An excessively small proportion of d will easily cause insufficient support of the support layer for the negative electrode sheet adjacent to the innermost positive electrode sheet, resulting in an excessively large gap between the negative and positive electrode sheets, hindering lithium-ion transport, increasing the risk of lithium plating on the negative electrode sheet, and reducing the capacity of the wound core. Short circuits are prone to occur, which can lead to thermal runaway and affect battery safety. If the value of d / (D×L) is too large, that is, if the proportion of d is too large and / or the proportion of D is too small and / or the proportion of L is too small, the cell's ability to limit the expansion of the negative electrode in the arc area is small, resulting in increased expansion of the negative electrode and excessive compression of the positive electrode, causing material loss and affecting battery life. If the proportion of L is too small, the positive electrode is easy to bend and wrinkle during the expansion and compression of the negative electrode, causing material loss of the active material layer and affecting battery life. If the proportion of d is too large, the negative electrode on the innermost positive electrode in the arc area is too thick, resulting in excessive expansion of the negative electrode during battery charging, causing excessive compression of the innermost positive electrode in the arc area, causing material loss and affecting battery life.

[0006] Secondly, the present invention also provides a battery pack including the battery described above.

[0007] Thirdly, the present invention also provides an electrical device including the aforementioned battery pack. 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 cross-sectional schematic diagram of the first type of winding core according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the first type of support layer according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the second type of support layer according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the third type of support layer according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the fourth type of support layer according to an embodiment of the present invention; Figure 6 This is a cross-sectional schematic diagram of the second type of winding core according to an embodiment of the present invention; Figure 7 for Figure 6 The diagram shows a partial structural schematic of the core when it is in the unfolded state. Figure 8 This is a cross-sectional schematic diagram of the third type of winding core according to an embodiment of the present invention; Figure 9 for Figure 8 The diagram shows a partial structural schematic of the core when it is in the unfolded state. Figure 10 This is a cross-sectional schematic diagram of the fourth type of winding core according to an embodiment of the present invention; Figure 11 This is a cross-sectional schematic diagram of the fifth type of winding core according to an embodiment of the present invention; Figure 12 This is a schematic diagram of the composite current collector according to an embodiment of the present invention; Figure 13 This is a schematic diagram of the structure when the winding core of this invention has two parts; Figure 14 This is a front view of a winding core according to an embodiment of the present invention; Figure 15 This is a cross-sectional schematic diagram of the positive electrode active material layer facing the support layer according to an embodiment of the present invention; Figure 16 This is a cross-sectional schematic diagram of the positive electrode active material layer being disposed away from the support layer in an embodiment of the present invention; Figure 17 This is a schematic diagram of the positive electrode sheet drooping 4cm according to an embodiment of the present invention; Figure 18 This is a schematic diagram of the positive electrode sheet drooping 2cm in an embodiment of the present invention.

[0010] Explanation of reference numerals in the attached figures: 1. Positive electrode sheet; 11. Positive electrode starting end; 12. Positive electrode current collector layer; 13. Positive electrode active material layer; 14. Straight segment; 2. Separator; 21. Separator body; 22. Separator support layer; 3. Negative electrode sheet; 31. Negative electrode sheet body; 32. Negative electrode support layer; 321. Empty foil area; 3211. First end point; 3212. Second end point; 33. Negative electrode current collector layer; 331. Non-metallic layer; 332. Metallic layer; 34. Negative electrode active material layer; 35. Negative electrode starting end; 4. Support layer; 10. Core; 101. Straight area; 102. First arc area; 103. Second arc area; 104. Body part; 105. Electrode part; 1051. Single electrode. 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 with 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 is provided, comprising: The core 10 is formed by winding a positive electrode sheet 1, a separator 2, and a negative electrode sheet 3 stacked together. The negative electrode sheet 3 is positioned closer to the winding start position than the positive electrode sheet 1. The core 10 includes a flat region 101 and a first arc region 102 and a second arc region 103 disposed at opposite ends of the flat region 101 along a first direction. Along the winding direction of the core 10, the positive electrode sheet 1 has a positive electrode start end 11 close to the winding start position. The core 10 also includes a support layer 4. The negative electrode sheet 3 includes a negative electrode sheet body 31 and a negative electrode support layer 32. The support layer 4 includes the aforementioned negative electrode support layer 32. The negative electrode support layer 32 extends beyond the positive electrode start end 11 and is located at least in the first arc region 102. At the first arc region 102, the total thickness of the support layer 4 is d (μm); along the second direction, the thickness of the core 10 is D (mm), and the second direction is perpendicular to both the first direction and the height direction of the core 10; when the positive electrode 1 droops by 4cm, the lateral length of the end of the suspended side is L2 (cm), and when the positive electrode 1 droops by 2cm, the lateral length of the end of the suspended side is L1 (cm), and the drooping degree of the positive electrode 1 is L, which satisfies L=(L2 / L1)-1; d, D and L satisfy 10.8≤d / (D×L)≤10209.7.

[0014] By limiting the value of d / (D×L) in the battery of this embodiment, the risk of lithium plating on the negative electrode 3 is reduced to ensure the safety performance of the battery, while the problem of material shedding on the positive electrode 1 is avoided to ensure the cycle life of the battery.

[0015] Specifically, if the value of d / (D×L) is too small, that is, if the proportion of d is too small and / or the proportion of D is too large and / or the proportion of L is too large, the positive electrode 1 will have poor flexibility and will not be easy to bend in the arc area. This will result in a large gap between the innermost positive electrode 1 and the negative electrode 3, affecting lithium-ion transport, increasing the risk of lithium plating, making the battery prone to self-discharge, and even causing insulation failure and short circuit. If the proportion of D is too large, the cell will be too thick, the electrolyte wetting effect will be poor, the ion resistance between the positive electrode 1 and the negative electrode 3 will be large, and the risk of lithium plating in the negative electrode 3 will be increased. If the proportion of d is too small, the support layer 4 will not provide sufficient support for the negative electrode 3 adjacent to the innermost positive electrode 1, resulting in a large gap between the negative electrode 3 and the positive electrode 1, hindering the transport of lithium ions, increasing the risk of lithium plating in the negative electrode 3, and causing the core 10 to... Short circuits can easily occur, leading to thermal runaway risks and affecting battery safety performance. If the value of d / (D×L) is too large, that is, if the proportion of d is too large and / or the proportion of D is too small and / or the proportion of L is too small, the cell's ability to limit the expansion of the negative electrode 3 in the arc region is small, resulting in increased expansion of the negative electrode 3 and excessive compression of the positive electrode 1, causing material loss and affecting battery life. If the proportion of L is too small, the positive electrode 1 is easy to bend and wrinkle during the expansion and compression of the negative electrode 3, causing material loss of the active material layer and affecting battery life. If the proportion of d is too large, the negative electrode 3 on the inner side of the innermost positive electrode 1 in the arc region is too thick, resulting in excessive expansion of the negative electrode 3 during battery charging, causing excessive compression of the innermost positive electrode 1 in the arc region, causing material loss and affecting battery cycle life.

[0016] Optionally, d / (D×L) can take any value from 10.8, 16.7, 19, 20, 29, 34.7, 41.6, 42.8, 47.6, 50, 100, 159.4, 500, 778.6, 1000, 1500, 1558, 2000, 2500, 2516.9, 2608.3, 2701.8, 3000, 3500, 3547.1, 4000, 4500, 4785.8, 5000, 5500, 6000, 6500, 7000, 7496.1, 7500, 8000, 8500, 9000, 9500, 10000, 10209.7 or a value between any two values.

[0017] Preferably, the value of d / (D×L) satisfies 41.6≤d / (D×L)≤2608.3, and can be any value or a value between any two of 41.6, 42.8, 47.6, 50, 100, 159.4, 500, 778.6, 1000, 1500, 1558, 2000, 2500, 2516.9, and 2608.3. This setting further reduces the risk of lithium plating on the negative electrode 3 to ensure battery safety performance, and further prevents material shedding from the positive electrode 1 to ensure battery cycle life.

[0018] It is worth noting that the core 10 is formed by stacking the material strip in the order of "negative electrode-diaphragm-positive electrode-diaphragm", winding it at high speed around the winding needle to form a cylindrical structure, and then hot-pressing the cylindrical structure to form a columnar structure with a racetrack-shaped cross-section. The core 10 has advantages such as high production efficiency, low cost, good consistency, and high reliability. However, during the cycling process, the lithium plating problem at the corners (arc areas) of the core 10 becomes more serious, increasing the risk of insulation failure inside the core 10.

[0019] The study found that the main reason why lithium plating easily occurs at the corner of the core 10 is that when the cylindrical structure formed by winding is hot-pressed, the radius of curvature of the innermost negative electrode sheet of the core 10 is small at the corner (arc area). This results in a larger gap between the innermost positive electrode sheet and the innermost negative electrode sheet at the corner (the positive electrode sheet is harder than the negative electrode sheet, so after hot pressing, the curvature of the innermost positive electrode sheet at the corner will be greater than that of the negative electrode sheet, thus increasing the gap between them). The bonding effect between the innermost positive electrode sheet and the innermost negative electrode sheet is poor, which hinders lithium-ion transport and leads to lithium plating. The growth of lithium dendrites can easily pierce the separator and overlap with the positive electrode sheet, causing a short circuit in the core and leading to safety risks such as thermal runaway.

[0020] To ensure the full utilization of the battery cell's energy, the area of ​​the active material layer of the negative electrode needs to be increased to provide sufficient space for lithium intercalation. Therefore, the innermost electrode is usually a negative electrode (if the innermost electrode is a positive electrode, the lithium ions released from the innermost positive electrode cannot be quickly intercalated, leading to the formation of lithium dendrites and potentially causing internal insulation failure in the battery cell). Therefore, in this embodiment, the starting end of the negative electrode 3 extends beyond the starting end of the positive electrode 1 (i.e., along the winding direction of the core 10, the starting end of the negative electrode 3 is closer to the winding start position than the starting end of the positive electrode 1) to form a negative electrode support layer 32. This provides support for the innermost negative electrode body 31 at the first arc region 102, ensuring that the innermost negative electrode body 31 has a certain radius of curvature at the first arc region 102, so that the innermost negative electrode body 31... The curvature at the first arc region 102 is equal to or approximately equal to the curvature of the innermost positive electrode 1 at the first arc region 102, reducing the gap between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102, improving the bonding effect between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102, thereby improving the lithium ion transport effect, reducing the occurrence of lithium plating problems, and thus avoiding the short circuit problem of the core 10 and improving the safety performance of the battery.

[0021] However, researchers further discovered that when the thickness d (μm) of the support layer 4 is too large, the overall expansion size of the negative electrode 3 after charging is too large, which will exert greater compressive force on the innermost positive electrode 1 at the first arc region 102, increasing the risk of the innermost positive electrode 1 falling off, and thus affecting the cycle life of the battery. In addition, researchers also found that if the sag L of the positive electrode 1 is too small, the positive electrode 1 is easy to bend and wrinkle during the expansion and compression of the negative electrode 1, which will also increase the risk of the positive electrode 1 falling off. Furthermore, when the thickness D (mm) of the core 10 is small, the cell's effect on limiting the expansion of the negative electrode in the arc region is small, resulting in increased expansion of the negative electrode 1, excessive compression of the positive electrode 1, and thus material falling off. Therefore, when the thickness d (μm) of the support layer 4 is large, the risk of the positive electrode sheet falling off will increase. At this time, the values ​​of the sag L of the positive electrode sheet 1 and the thickness D (mm) of the core 10 can be increased to reduce the risk of the positive electrode sheet falling off and ensure the cycle life of the battery.

[0022] In summary, in this embodiment, by comprehensively controlling the values ​​of d (μm), D (mm) and L, the risk of lithium plating in the negative electrode 3 and the risk of material shedding in the positive electrode 1 can be reduced, thereby balancing the safety performance and cycle life of the battery.

[0023] It should be noted that the above-mentioned negative electrode 3 being positioned closer to the winding start position than the positive electrode 1 means that when the stacked positive electrode 1, separator 2, and negative electrode 3 are wound, the negative electrode 3 is located in the inner layer, and the positive electrode 1 is located in the outer layer.

[0024] It is worth noting that in this embodiment, the "winding start position" refers to the position where the beginning of the negative electrode exceeds the beginning of the positive electrode. The position where the beginning of the negative electrode is located is the winding start position, which is also the winding center position of the winding needle.

[0025] In one embodiment, such as Figures 2 to 4 As shown, the negative electrode 3 includes a negative electrode current collector layer 33 and a negative electrode active material layer 34 disposed on at least one side of the negative electrode current collector layer 33. At least a portion of the negative electrode support layer 32 is not provided with the negative electrode active material layer 34 to form an empty foil area 321. This arrangement avoids the negative electrode support layer 32 from expanding during charging due to the large amount of negative electrode active material layer, thereby avoiding compression of adjacent positive electrode sheets and thus preventing the positive electrode sheets from shedding material and affecting the lifespan of the battery cell.

[0026] It is understandable that, such as Figure 4 As shown, the negative electrode support layer 32 may only include the negative electrode current collector layer 33, in which case the entire negative electrode support layer 32 is an empty foil region 321; of course, as Figure 2 and Figure 3 As shown, the negative electrode support layer 32 may include both the negative electrode current collector layer 33 and the negative electrode active material layer 34. In this case, a portion of the negative electrode current collector layer 33 of the negative electrode support layer 32 needs to be without the negative electrode active material layer 34 to form an empty foil region 321.

[0027] Furthermore, in one embodiment, such as Figures 2 to 4 As shown, the thickness of the negative electrode current collector layer 33 is a (μm), satisfying 6≤a≤12. This configuration ensures the supporting effect of the negative electrode support layer 32 on the innermost negative electrode sheet body 31 while maintaining the energy density of the battery.

[0028] It is worth noting that if the value of a (μm) is too small, the structural strength of the negative electrode current collector layer 33 may be insufficient, resulting in the negative electrode current collector layer 33 being unable to provide effective support to the innermost negative electrode body 31. This would increase the gap between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102, thereby increasing the risk of lithium plating on the negative electrode 3. If the value of a (μm) is too large, the arrangement of the negative electrode current collector layer 33 may easily encroach on the space for the active material, affecting the energy density of the battery.

[0029] Optionally, the value of 'a' can be any one of 6, 7, 8, 9, 10, 11, or 12, or a value between any two of them.

[0030] It is worth noting that in practical applications, when negative electrode active material layers are provided on both opposite sides of the negative electrode current collector layer along its thickness direction, the minimum value of the thickness a (μm) of the negative electrode current collector layer can be 4 μm. That is, the value of the thickness a (μm) of the negative electrode current collector layer 33 satisfies 4 ≤ a ≤ 12. In this embodiment, the preferred value range of the thickness a (μm) of the negative electrode current collector layer 33 is 6 ≤ a ≤ 12.

[0031] Furthermore, in one embodiment, such as Figure 2 and Figure 3 As shown, along the winding direction of the core 10, the length of the empty foil area 321 is b (mm), satisfying 5≤b≤300. This setting ensures the support effect of the negative electrode support layer 32 on the innermost negative electrode body 31 while reducing the risk of material loss from the positive electrode 1.

[0032] It is worth noting that if the value of b (mm) is too large, the structural strength of the negative electrode support layer 32 may be insufficient, resulting in the negative electrode support layer 32 being unable to provide effective support to the innermost negative electrode body 31. This would increase the gap between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102, thereby increasing the risk of lithium plating on the negative electrode 3. If the value of b (mm) is too small, there may be too much negative electrode active material on the negative electrode support layer 32. When the battery is charging, the negative electrode support layer 32 will expand and increase, exerting greater compressive force on the innermost positive electrode 1, increasing the risk of material shedding from the innermost positive electrode 1.

[0033] Optionally, the value of b can be any one of the following: 5, 10, 20, 30, 40, 50, 80, 100, 120, 150, 180, 200, 220, 250, 280, 290, 300, or a value between any two of these.

[0034] Furthermore, in one embodiment, such as Figure 2 and Figure 3 As shown, along the winding direction of the core 10, the empty foil area 321 has a first end point 3211 near the winding start position. The first end point 3211 extends beyond the positive electrode start end 11 and is located between the positive electrode start end 11 and the winding start position. That is, along the winding direction of the core 10, the first end point 3211 is the beginning of the empty foil area 321, and the first end point 3211 is set closer to the winding start position than the positive electrode start end 11.

[0035] Optionally, in one embodiment, such as Figure 2As shown, along the winding direction of the core 10, the empty foil area 321 also has a second end point 3212 away from the winding start position. The second end point 3212 extends beyond the positive electrode start end 11 and is located between the positive electrode start end 11 and the winding start position. The dimension of the second end point 3212 extending beyond the positive electrode start end 11 is c (mm), satisfying 1≤c≤500. That is, along the winding direction of the core 10, the second end point 3212 is the tail end of the empty foil area 321, and the second end point 3212 is set closer to the winding start position than the positive electrode start end 11. At this time, by limiting the value of c (mm), while ensuring the support effect of the negative electrode support layer 32 on the innermost negative electrode sheet body 31, the risk of the positive electrode sheet 1 falling off is reduced.

[0036] It is worth noting that if the value of c (mm) is too small, the structural strength of the negative electrode support layer 32 may be insufficient, resulting in the negative electrode support layer 32 being unable to provide effective support to the innermost negative electrode body 31. This would increase the gap between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102, thereby increasing the risk of lithium plating on the negative electrode 3. If the value of c (mm) is too large, there may be too much negative electrode active material on the negative electrode support layer 32. When the battery is charging, the negative electrode support layer 32 will expand and increase, exerting greater compressive force on the innermost positive electrode 1, increasing the risk of material shedding from the innermost positive electrode 1.

[0037] Optionally, c can take any value from 1, 50, 150, 200, 250, 300, 350, 400, 450, 500, or a value between any two values.

[0038] Alternatively, in another embodiment, such as Figure 3 As shown, along the winding direction of the core 10, the empty foil area 321 also has a second end point 3212 far from the winding start position. The second end point 3212 does not exceed the positive electrode start end 11, which is located between the first end point 3211 and the second end point 3212. The thickness of the negative electrode active material layer 34 of the negative electrode body is e (μm), satisfying e≥100. That is, along the winding direction of the core 10, the second end point 3212 is the tail end of the empty foil area 321, and the second end point 3212 is set further away from the winding start position than the positive electrode start end 11. At this time, the negative electrode active material layer 34 needs to have a large thickness to increase the lithium ion capacity and avoid lithium plating problems. Furthermore, the thickness e (μm) of the negative electrode active material layer 34 of the negative electrode body satisfies e≤200.

[0039] As an alternative implementation, in one embodiment, such as Figure 2 , Figure 3 and Figure 5As shown, the negative electrode sheet 3 includes a negative electrode current collector layer 33 and a negative electrode active material layer 34 disposed on at least one side of the negative electrode current collector layer 33. The negative electrode support layer 32 has the negative electrode active material layer 34, and the thickness of the negative electrode active material layer 34 is e (μm), satisfying e≤180. That is, the negative electrode support layer 32 includes both the negative electrode current collector layer 33 and the negative electrode active material layer 34, and the negative electrode active material layer 34 can be completely disposed on the negative electrode current collector layer 33 of the negative electrode support layer 32 (e.g., ...). Figure 5 (As shown), or only a portion of the negative electrode active material layer 34 can be provided (e.g. Figure 2 and Figure 3 (As shown). At this time, the negative electrode active material layer 34 needs to have a small thickness to avoid the negative electrode support layer 32 expanding too much during battery charging, which would cause excessive extrusion pressure on the innermost positive electrode sheet 1 and reduce the risk of the positive electrode sheet 1 falling off.

[0040] In one embodiment, such as Figure 5 As shown, along the winding direction of the core 10, the negative electrode sheet 3 extends beyond the positive electrode starting end 11 by a dimension of g (mm), satisfying 10≤g≤600. This configuration ensures the support effect of the negative electrode support layer 32 on the innermost negative electrode sheet body 31 while reducing the risk of material loss from the positive electrode sheet 1.

[0041] It is worth noting that if the value of g (mm) is too small, the length of the negative electrode support layer 32 may be too short, resulting in the negative electrode support layer 32 being unable to provide effective support to the innermost negative electrode body 31. This would increase the gap between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102, thereby increasing the risk of lithium plating on the negative electrode 3. If the value of g (mm) is too large, the length of the negative electrode support layer 32 will be too long. Due to the limited space inside the core hole, the negative electrode sheets will be stacked, resulting in an excessively large total thickness of the negative electrode 3 inside the innermost positive electrode 1 at the first arc region 102. This would lead to excessive expansion of the negative electrode 3 during battery charging, resulting in excessive extrusion pressure on the innermost positive electrode 1 at the arc region, increasing the risk of material loss from the innermost positive electrode 1.

[0042] Optionally, g can take any value from 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, or a value between any two values.

[0043] In one embodiment, such as Figures 6 to 9As shown, the separator 2 includes a separator body 21 and a separator support layer 22. The support layer 4 also includes the aforementioned separator support layer 22. The separator support layer 22 is disposed on at least one side of the negative electrode support layer 32 along its thickness direction. The separator support layer 22 provides further support to the innermost negative electrode body 31 at the first arc region 102, further ensuring the adhesion between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102, and reducing the risk of lithium plating.

[0044] Furthermore, in one embodiment, such as Figure 8 and Figure 9 As shown, a diaphragm support layer 22 is provided on both opposite sides of the negative electrode support layer 32 along its thickness direction. Please refer to [the relevant documentation / reference here]. Figure 8 The innermost layer of the core is a diaphragm.

[0045] It is understandable that, such as Figures 1 to 5 As shown, the support layer 4 may consist only of the negative electrode support layer 32, in which case the total thickness d (μm) of the support layer 4 is the total thickness of the negative electrode support layer 32 at the first arc region 102. Figure 6 and Figure 7 As shown, the support layer 4 may also include a negative electrode support layer 32 and a membrane support layer 22 disposed on one side of the negative electrode support layer 32. In this case, the total thickness d (μm) of the support layer 4 is the total thickness of the negative electrode support layer 32 and the membrane support layer 22 at the first arc region 102. Of course, as Figure 8 and Figure 9 As shown, the support layer 4 may also include a negative electrode support layer 32 and a diaphragm support layer 22 disposed on opposite sides of the negative electrode support layer 32. In this case, the total thickness d (μm) of the support layer 4 is also the total thickness of the negative electrode support layer 32 and the diaphragm support layer 22 at the first arc region 102.

[0046] Furthermore, in one embodiment, such as Figure 7 As shown, within the support layer 4, the total thickness of the separator support layer 22 is i (μm), and the total thickness of the negative electrode support layer 32 is j (μm), satisfying 0.08≤i / j≤0.4. This configuration ensures the support effect of the support layer 4 on the innermost negative electrode body 31 while reducing the risk of material loss from the positive electrode 1.

[0047] It is worth noting that if the value of i / j is too large, it can easily lead to poor overall structural strength of the support layer 4 (because the separator 2 itself is relatively soft, its supporting effect is limited), resulting in the support layer 4 being unable to provide effective support to the innermost negative electrode body 31. This causes the gap between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102 to increase, which in turn increases the risk of lithium plating on the negative electrode 3. If the value of i / j is too small, it can easily lead to the negative electrode 3 on the inner side of the innermost positive electrode 1 at the first arc region 102 being too thick. This results in the negative electrode 3 expanding too much during battery charging, causing excessive extrusion pressure on the innermost positive electrode 1 at the arc region, increasing the risk of material loss from the innermost positive electrode 1.

[0048] Optionally, i / j can take any value from 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.25, 0.3, 0.32, 0.35, 0.38, 0.4, or a value between any two values.

[0049] In one embodiment, such as Figure 10 As shown, the negative electrode support layer 32 is located in the first arc region 102 and the second arc region 103, and at least one negative electrode support layer 32 is provided in the first arc region 102 and the second arc region 103. That is, the negative electrode support layer 32 can not only provide support for the innermost negative electrode body 31 in the first arc region 102, but also provide support for the innermost negative electrode body 31 in the second arc region 103, ensuring that the innermost negative electrode body 31 and the innermost positive electrode 1 can be effectively attached in both arc regions, further reducing the risk of lithium plating.

[0050] Of course, as alternative implementation methods, such as Figure 1 As shown, the negative electrode support layer 32 can bypass only the first arc region 102 to provide support for the innermost negative electrode body 31 in the first arc region 102.

[0051] In addition, when the negative electrode support layer 32 bypasses the first arc region 102 and the second arc region 103, the first arc region 102 and the second arc region 103 may have only one negative electrode support layer 32. Of course, the first arc region 102 and / or the second arc region 103 may also have multiple negative electrode support layers 32, that is, the negative electrode support layer 32 bypasses the first arc region 102 and / or the second arc region 103 multiple times.

[0052] In one embodiment, such as Figure 1 and Figure 11As shown, along the winding direction of the core 10, the negative electrode sheet 3 has a negative electrode starting end 35 near the winding start position, and the positive electrode starting end 11 and / or the negative electrode starting end 35 are located in the flat region 101. Preferably, both the positive electrode starting end 11 and the negative electrode starting end 35 are located in the flat region 101. This arrangement avoids deformation caused by the positive electrode starting end 11 and / or the negative electrode starting end 35 being located in the arc region, thereby reducing the risk of material loss from the positive electrode starting end 11 and / or the negative electrode starting end 35.

[0053] Furthermore, in one embodiment, such as Figure 1 and Figure 11 As shown, on a projection plane perpendicular to the second direction, the orthographic projections of the positive electrode starting end 11 and the negative electrode starting end 35 are spaced apart. That is, along the first direction, the positive electrode starting end 11 and the negative electrode starting end 35 are spaced apart. This arrangement avoids the positive electrode starting end 11 and the negative electrode starting end 35 overlapping and applying shear force to the negative electrode sheet 3, and avoids the negative electrode sheet 3 being subjected to concentrated force and tearing.

[0054] It should be noted that if the positive electrode starting end 11 and the negative electrode starting end 35 coincide, during the hot pressing process after the cell is manufactured, the positive electrode starting end 11 and the negative electrode starting end 35 will coincide and apply shear force to the negative electrode sheet 3, causing stress concentration.

[0055] It is worth noting that the positive electrode 1 has a straight segment 14 connected to the positive electrode starting end 11 and located in the flat region 101. On the projection plane perpendicular to the second direction, the orthographic projection of the negative electrode starting end 35 does not fall on the orthographic projection of the straight segment 14 (e.g., Figure 1 (as shown), or, the orthographic projection of the negative pole starting end 35 falls on the orthographic projection of the straight line segment 14 (as shown). Figure 11 (As shown).

[0056] Furthermore, in one embodiment, such as Figure 1 and Figure 11 As shown, along the first direction, the distance between the positive electrode starting end 11 and the negative electrode starting end 35 is p (mm), and the size of the core 10 is q (mm), satisfying 0.018≤p / q≤0.86. This setting reduces the risk of material loss from the positive electrode starting end 11 and / or the negative electrode starting end 35, while also reducing the risk of tearing of the negative electrode sheet 3.

[0057] It is worth noting that if the value of p / q is too small, the distance between the positive electrode starting end 11 and the negative electrode starting end 35 may be too close, increasing the risk of stress concentration in the negative electrode sheet 3, and thus increasing the risk of tearing of the negative electrode sheet 3. If the value of p / q is too large, the distance between the positive electrode starting end 11 and / or the negative electrode starting end 35 and the arc area may be too close, causing the positive electrode starting end 11 and / or the negative electrode starting end 35 to be prone to deformation, increasing the risk of material loss from the positive electrode starting end 11 and / or the negative electrode starting end 35.

[0058] Optionally, p / q can take any value from 0.018, 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.86, or a value between any two values.

[0059] Specifically, in one embodiment, along the first direction, the distance p (mm) between the positive electrode starting end 11 and the negative electrode starting end 35 satisfies 5 ≤ ​​p ≤ 240.

[0060] Optionally, p can take any value from 5, 10, 20, 30, 40, 50, 80, 100, 120, 150, 180, 200, 210, 220, 230, 240, or a value between any two values.

[0061] Preferably, the value of p satisfies 10≤p≤200, and can be any value among 10, 20, 30, 40, 50, 80, 100, 120, 150, 180, and 200, or a value between any two values.

[0062] Specifically, in one embodiment, along the first direction, the dimension q (mm) of the core 10 satisfies 100≤q≤280.

[0063] Optionally, q can take any value from 100, 110, 120, 130, 140, 150, 180, 200, 220, 250, 260, 270, 280, or a value between any two values.

[0064] Preferably, the value of q satisfies 120≤q≤250, and can be any value among 120, 130, 140, 150, 180, 200, 220, and 250, or a value between any two values.

[0065] In one embodiment, such as Figure 10 As shown, in the first arc region 102, the support layer 4 includes at least two negative electrode support layers 32. That is, the negative electrode support layer 32 passes around the first arc region 102 at least twice to enhance the support effect on the innermost negative electrode sheet body 31 in the first arc region 102.

[0066] Furthermore, in one embodiment, the negative electrode 3 includes a negative electrode current collector layer 33 and a negative electrode active material layer 34 disposed on at least one side of the negative electrode current collector layer 33. The thickness of the negative electrode active material layer 34 of the negative electrode support layer is e (μm), satisfying 30≤e≤180. That is, the thickness of the negative electrode active material layer 34 is further limited to avoid the negative electrode active material layer 34 being too thick, thereby avoiding excessive expansion of the negative electrode 3 on the inner side of the innermost positive electrode 1 during battery charging, avoiding excessive extrusion pressure on the innermost positive electrode 1, and reducing the risk of material loss from the positive electrode 1.

[0067] It is worth noting that the negative electrode active material layer 34 can be provided only on one side of the negative electrode current collector layer 33 along its thickness direction. Of course, the negative electrode active material layer 34 can also be provided on both opposite sides of the negative electrode current collector layer 33 along its thickness direction.

[0068] It should be noted that the thickness e (μm) of the negative electrode active material layer 34 satisfies 30 ≤ e ≤ 200. Furthermore, when the material of the negative electrode active material layer includes silicon-carbon, the value of e satisfies 30 ≤ e ≤ 160; when the material of the negative electrode active material layer includes graphite, the value of e satisfies 40 ≤ e ≤ 200.

[0069] Optionally, the value of e can be any one of the following: 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, or a value between any two of these.

[0070] In one embodiment, such as Figure 12 As shown, the negative electrode sheet 3 includes a negative electrode current collector layer 33 and a negative electrode active material layer 34 disposed on at least one side of the negative electrode current collector layer 33. The negative electrode current collector layer 33 includes a non-metallic layer 331 and a metallic layer 332 disposed on at least one side of the non-metallic layer 331 along its thickness direction. That is, the negative electrode current collector layer 33 is a composite current collector, which has better elastic deformation properties, enabling the negative electrode support layer 32 to have a better support effect.

[0071] Furthermore, in one embodiment, such as Figure 12 As shown, along the thickness direction of the negative electrode current collector layer 33, the thickness of the non-metallic layer 331 is t1 (μm), and the thickness of the metallic layer 332 is t2 (μm), satisfying 0.3≤t1 / t2≤10. This configuration effectively improves the support effect of the negative electrode support layer 32 while ensuring the current-carrying capacity of the negative electrode current collector layer 33.

[0072] It is worth noting that if the value of t1 / t2 is too small, the thickness of the non-metallic layer 331 may be too small, resulting in insufficient improvement in the elastic deformation performance of the negative electrode support layer 32, and thus failing to effectively enhance the support effect of the negative electrode support layer 32. If the value of t1 / t2 is too large, the thickness of the metallic layer 332 may be too small, thereby affecting the current-carrying capacity of the negative electrode current collector layer 33.

[0073] Optionally, t1 / t2 can take any value from 0.3, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a value between any two values.

[0074] Specifically, in one embodiment, the thickness t1 (μm) of the non-metallic layer 331 satisfies 2≤t1≤10.

[0075] Optionally, t1 can take any value from 2, 3, 4, 5, 6, 7, 8, 9, 10 or a value between any two values.

[0076] Specifically, in one embodiment, the thickness t2 (μm) of the metal layer 332 satisfies 1≤t2≤6.

[0077] Optionally, t2 can take any value from 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, or a value between any two values.

[0078] It should be noted that, as Figure 12 As shown, when metal layers 332 are provided on both opposite sides of the non-metallic layer 331 along its thickness direction, the thickness t2 (μm) of the metal layer 332 is the sum of the thicknesses of the two metal layers 332. That is, the thickness of one metal layer 332 is t21 (μm), and the thickness of the other metal layer 332 is t22 (μm), thus satisfying t2 = t21 + t22. When a metal layer 332 is provided on one side of the non-metallic layer 331 along its thickness direction, the thickness t2 (μm) of the metal layer 332 is the thickness of that metal layer.

[0079] It should be noted that the non-metallic layer 331 is typically a polymer material. Materials for the non-metallic layer 331 include polyamide (PA), polyterephthalate, polyimide (PI), polyethylene (PE), polypropylene (PP), polyethylene terephthalate, polybutylene terephthalate, polystyrene (PPE), polyvinyl chloride (PVC), aramid, acrylonitrile-butadiene-styrene copolymer (ABS), polybutylene terephthalate (PET), poly(p-phenylene terephthalamide) (PPTA), polypropylene (PPE), polyoxymethylene (POM), epoxy resin, phenolic resin, polytetrafluoroethylene (PTEE), polyvinylidene fluoride (PVDF), silicone rubber, polycarbonate (PC), polyvinyl alcohol (PVA), and polyethylene glycol (PEG). The metal layer 332 is made of at least one of the following: cellulose, starch, protein, derivatives of the above materials, cross-linked products of the above materials, and copolymers of the above materials; the metal layer 332 is made of aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.

[0080] In one embodiment, such as Figure 14 As shown, along the first direction, the dimension of the straight region 101 is x1 (mm), and the total dimension of the first arc region 102 and the second arc region 103 is x2 (mm), satisfying 0.1≤x2 / x1≤0.45. This configuration ensures the bonding effect between the innermost negative electrode body 31 and the innermost positive electrode 1 to reduce the risk of lithium plating on the negative electrode 3, while also reducing the internal resistance of the core 10.

[0081] It is worth noting that if the value of x2 / x1 is too large, the size of the flat region 101 may be too large, resulting in a decrease in the overall curvature of the arc region. This, in turn, leads to a smaller curvature of the innermost negative electrode body 31, increasing the gap between the innermost negative electrode body 31 and the innermost positive electrode 1, thus increasing the risk of lithium plating on the negative electrode 3. If the value of x2 / x1 is too small, the size of the arc region may be too large, resulting in poor lithium ion transport in the arc region. This affects the overall current carrying capacity of the core 10, leading to an increase in the internal resistance of the core 10.

[0082] Optionally, x2 / x1 can be any value from 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or a value between any two values.

[0083] Specifically, in one embodiment, along the first direction, the dimension x1 (mm) of the straight region 101 satisfies 60≤x1≤264.

[0084] Optionally, x1 can be any value from 60, 80, 100, 120, 150, 180, 200, 220, 240, 250, 260, 264 or a value between any two values.

[0085] Specifically, in one embodiment, along the first direction, the total dimension x2 (mm) of the first arc region 102 and the second arc region 103 satisfies 8≤x2≤20.

[0086] Optionally, x2 can be any value from 8, 9, 10, 11, 12, 14, 15, 16, 18, 19, 20, or a value between any two values.

[0087] It is understandable that, such as Figure 14 As shown, along the first direction, the size of the first arc region 102 is x21 (mm), and the size of the second arc region 103 is x22 (mm), thus satisfying x2 = x21 + x22.

[0088] Specifically, in one embodiment, at the first arc region 102, the total thickness d (μm) of the support layer 4 satisfies 280≤d≤1920. This setting reduces the risk of lithium plating on the negative electrode 3 to ensure the safety performance of the battery, while preventing material shedding from the positive electrode 1 to ensure the cycle life of the battery.

[0089] It is worth noting that if the value of d (μm) is too small, the support layer 4 may not provide sufficient support for the negative electrode 3 adjacent to the innermost positive electrode 1, resulting in an excessively large gap between the negative electrode 3 and the positive electrode 1. This hinders the transport of lithium ions, increases the risk of lithium plating on the negative electrode 3, and makes the core 10 prone to short circuits, which in turn leads to the risk of thermal runaway and affects the safety performance of the battery. If the value of d (μm) is too large, the negative electrode 3 on the innermost positive electrode 1 in the arc area may be too thick, resulting in excessive expansion of the negative electrode 3 during battery charging. This causes excessive pressure on the innermost positive electrode 1 in the arc area, increasing the risk of material loss from the positive electrode 1 and thus affecting the cycle life of the battery.

[0090] Optionally, d can take any value from 280, 300, 302.1, 320, 343.5, 350, 354.5, 355.3, 400, 450, 500, 569.9, 600, 799.4, 800, 985.1, 1000, 1200, 1285.2, 1305.5, 1439.8, 1439.9, 1440, 1479.5, 1500, 1598.2, 1600, 1779.7, 1800, 1850.3, 1919, 1920, or a value between any two values.

[0091] Preferably, the value of d satisfies 350≤d≤1440, and can be any value or a value between any two of the following: 350, 354.5, 355.3, 400, 450, 500, 569.9, 600, 799.4, 800, 985.1, 1000, 1200, 1285.2, 1305.5, 1439.8, 1439.9, 1440. This setting can further reduce the risk of lithium plating on the negative electrode 3 to ensure the safety performance of the battery, and further prevent the positive electrode 1 from shedding material to ensure the cycle life of the battery.

[0092] It is worth noting that when the negative electrode support layer has a negative electrode active material layer, the value range of d is further preferably 450≤d≤1440, and can be any value among 450, 500, 569.9, 600, 799.4, 800, 985.1, 1000, 1200, 1285.2, 1305.5, 1439.8, 1439.9, and 1440, or a value between any two of these values.

[0093] Specifically, in one embodiment, the thickness D (mm) of the core 10 along the second direction satisfies 8 ≤ D ≤ 35. This configuration ensures the battery's cycle life while reducing the risk of lithium plating on the negative electrode 3, thereby guaranteeing the battery's safety performance.

[0094] It is worth noting that if D (mm) is too large, the cell may become too thick, resulting in poor electrolyte wetting and high ionic resistance between the positive and negative electrodes. This hinders lithium-ion transport, increases the risk of lithium plating on the negative electrode 3, and makes the core 10 prone to short circuits, potentially leading to thermal runaway and affecting battery safety. Conversely, if D (mm) is too small, the cell's ability to limit the expansion of the arc-shaped negative electrode is insufficient, causing excessive expansion of the negative electrode. This can lead to excessive compression of the positive electrode, resulting in material loss and impacting battery life.

[0095] Optionally, the value of D can be any one of the following: 8, 8.13, 8.63, 9, 9.07, 10, 10.06, 10.45, 11, 11.04, 12, 12.05, 12.35, 14, 15, 16, 18, 19.74, 20, 22, 24, 24.41, 25, 25.69, 26, 26.6, 28, 29.65, 29.98, 30, 31, 32, 33, 33.05, 33.85, 34, 34.67, 35, or a value between any two of these values.

[0096] Preferably, the value of D satisfies 10 ≤ D ≤ 30, and can be any value from 10, 10.06, 10.45, 11, 11.04, 12, 12.05, 12.35, 14, 15, 16, 18, 19.74, 20, 22, 24, 24.41, 25, 25.69, 26, 26.6, 28, 29.65, 29.98, 30, or a value between any two of these. This setting further ensures the battery's cycle life and further reduces the risk of lithium plating on the negative electrode, thus guaranteeing the battery's safety performance.

[0097] Specifically, in one embodiment, the sag L of the positive electrode 1 satisfies 0.02≤L≤0.8. This setting avoids material loss from the positive electrode 1 to ensure the cycle life of the battery, while also preventing wrinkles from forming on the positive electrode 1 after winding, which would affect the lithium-ion transport effect.

[0098] It is worth noting that if the value of L is too small, the positive electrode sheet is prone to bending and wrinkling during the expansion and compression of the negative electrode sheet, increasing the risk of material loss from the positive electrode sheet 1 and thus affecting the cycle life of the battery. If the value of L is too large, the positive electrode sheet is prone to poor flexibility and is not easy to bend in the arc area, resulting in a larger gap between the innermost positive and negative electrode sheets, which affects lithium-ion transport, increases the risk of lithium plating, makes the battery prone to self-discharge, and may even lead to insulation failure and short circuit.

[0099] Optionally, L can take any value from 0.02, 0.021, 0.032, 0.041, 0.042, 0.05, 0.051, 0.064, 0.082, 0.1, 0.105, 0.15, 0.2, 0.25, 0.254, 0.265, 0.3, 0.302, 0.345, 0.35, 0.399, 0.4, 0.446, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.799, 0.8, or a value between any two values.

[0100] Preferably, the value of L satisfies 0.05 ≤ L ≤ 0.4, and can be any value or a value between any two of the following: 0.05, 0.051, 0.064, 0.082, 0.1, 0.105, 0.15, 0.2, 0.25, 0.254, 0.265, 0.3, 0.302, 0.345, 0.35, 0.399, 0.4. This setting can further prevent the positive electrode sheet 1 from shedding material, thus ensuring the cycle life of the battery, and further prevent the positive electrode sheet 1 from wrinkling after winding, which would affect the lithium ion transport effect.

[0101] Specifically, in one embodiment, such as Figure 18As shown, when the positive electrode plate hangs down by 2cm, the lateral length L1 (cm) of the end of the suspended side satisfies 4≤L1≤9.

[0102] Optionally, L1 can take any value from 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, or a value between any two values.

[0103] Specifically, in one embodiment, such as Figure 17 As shown, when the positive electrode plate hangs down by 4cm, the lateral length L2 (cm) of the end of the suspended side satisfies 5≤L2≤11.

[0104] Optionally, L2 can take any value from 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, or a value between any two values.

[0105] In one embodiment, such as Figure 13 As shown, the battery includes at least two cores 10 arranged along a second direction, and the thickness D (mm) of each core 10 satisfies D≤32. The battery contains multiple cores 10, each with a smaller thickness, which increases the curvature of the innermost negative electrode body 31 at the first arc region 102, reduces the gap between the innermost negative electrode body 31 and the innermost positive electrode 1 at the first arc region 102, and lowers the risk of lithium plating.

[0106] In one embodiment, such as Figure 14 As shown, the core 10 includes a body portion 104 and an electrode tab portion 105 extending from at least one end of the body portion 104 along the height direction of the core 10. Along a first direction, the minimum distance between the electrode tab portion 105 and the first arcuate region 102 or the second arcuate region 103 is k (mm), satisfying 10 ≤ k ≤ 100. This configuration ensures the flow capacity of the core 10 while avoiding the risk of tearing of the electrode tab portion 105.

[0107] It is worth noting that if the value of k (mm) is too large, the flow path from the first arc region 102 or the second arc region 103 to the tab 105 may be too long, affecting the overall flow capacity of the core 10. If the value of k (mm) is too small, the distance between the tab 105 and the first arc region 102 or the second arc region 103 may be too close, which may cause the tab 105 to deform and thus increase the risk of tearing.

[0108] Optionally, k can be any value from 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or a value between any two values.

[0109] In one embodiment, such as Figure 14As shown, the core 10 includes a body portion 104 and an electrode tab portion 105 extending from at least one end of the body portion 104 along the height direction of the core 10. The electrode tab portion 105 includes several layers of single electrode tabs 1051 stacked together. Along the first direction, the width of a single electrode tab 1051 is f (mm), satisfying 30≤f≤60. This arrangement ensures the current carrying capacity of the electrode tab portion 105 while avoiding the risk of short circuits caused by overlapping with other parts.

[0110] It is worth noting that if the value of f (mm) is too small, the current-carrying capacity of the tab 105 may be insufficient, resulting in severe overheating and increasing the risk of thermal runaway. If the value of f (mm) is too large, it may cause overlap between adjacent tabs 105, leading to short circuit problems.

[0111] Optionally, f can take any value from 30, 35, 40, 45, 50, 55, 60, or a value between any two values.

[0112] In one embodiment, the positive electrode 1 includes a positive current collector layer 12 and a positive active material layer 13 disposed on at least one side of the positive current collector layer 12.

[0113] It is worth noting that the positive electrode active material layer 13 can be provided on only one side of the positive electrode current collector layer 12 along its thickness direction. Of course, the positive electrode active material layer 13 can also be provided on both opposite sides of the positive electrode current collector layer 12 along its thickness direction.

[0114] Optionally, in one embodiment, such as Figure 15 As shown, the positive electrode active material layer 13 is positioned towards the support layer 4, and the sag L of the positive electrode sheet 1 satisfies 0.02≤L≤0.6. With this configuration, the positive electrode active material layer 13 is directly subjected to the compressive force of the negative electrode sheet 3 inside the innermost positive electrode sheet 1, increasing the risk of material loss of the positive electrode sheet 1. Therefore, by further limiting the value of L, the flexibility of the positive electrode sheet 1 is increased, giving it better elastic deformation performance and reducing the risk of material loss.

[0115] Alternatively, in one embodiment, such as Figure 16 As shown, the positive electrode active material layer 13 is disposed away from the support layer 4. At this time, the positive electrode sheet 1 facing the support layer 4 does not have the positive electrode active material layer 13. Therefore, when subjected to the extrusion force of the negative electrode sheet 3 inside the innermost positive electrode sheet 1, the risk of the positive electrode sheet 1 falling off can be reduced.

[0116] In one embodiment, the battery further includes a housing having a receiving space, and the core 10 is disposed within the housing.

[0117] According to an embodiment of the present invention, in another aspect, a battery pack is also provided, including the battery described above.

[0118] According to an embodiment of the present invention, in another aspect, an electrical device is also provided, including the battery pack described above.

[0119] 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.

[0120] The preparation of the example battery and the comparative battery includes the following steps: (1) Preparation of the positive electrode: The positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., 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, the positive electrode sheet is obtained by rolling and slitting.

[0121] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98): (1~4): (1~4).

[0122] (2) Preparation of negative electrode: The negative electrode active material, conductive agent (e.g., acetylene black), thickener (e.g., carboxymethyl cellulose (CMC)), and binder (e.g., styrene-butadiene rubber (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. Finally, the negative electrode sheet is obtained by rolling and slitting.

[0123] Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (2~4): (1~2): (1~4).

[0124] (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.

[0125] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0126] (5) Preparation of lithium-ion batteries: The positive electrode, separator, and negative electrode are fed into a winding machine in the order of "separator-negative electrode-separator-positive electrode" and fixed on a winding needle. A bare cell is formed by winding, with the negative electrode support layer extending beyond the beginning of the positive electrode and bypassing the first arc region. The bare cell is then hot-pressed to obtain the battery cell. The current output terminal (tab) of the cell is electrically connected to the current output terminal (terminal) of the battery, and the cell is placed inside the battery casing. The battery is dried, injected with electrolyte, and then encapsulated, allowed to stand, formed, and capacitated to obtain a lithium-ion battery. The hot-pressing conditions are: temperature: 60~120℃, hot-pressing pressure range: 100~25000kgf, and hot-pressing time range: 60~200s.

[0127] In addition to the above-mentioned battery material selection, this application may also select other materials, and is not limited to the materials limited by the above preparation method. 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 conductive agent in the positive electrode sheet can also be selected from one or more graphite, superconducting carbon, Ketjen black, Super P, carbon nanotubes, graphene, and carbon nanofibers; the binder in the positive electrode sheet can also be selected from one or more polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, and carboxymethyl chitosan; the positive electrode current collector can also be selected from one or more stainless steel, aluminum, nickel, carbon electrode, carbon, nickel, and titanium with silver plating; the positive electrode current collector can also include composite current collectors, which may include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming metallic materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on a polymer substrate (such as a substrate of polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.).

[0128] The negative electrode active material can be selected from one or more of the following negative electrode active main materials: artificial graphite, natural graphite, silicon carbide, silicon oxide, lithium titanate, etc.; the conductive agent in the negative electrode sheet can be selected from one or more of the following: conductive carbon black, conductive graphite, carbon nanotubes, graphene, carbon fiber, etc.; the binder in the negative electrode sheet can be selected from one or more of the following: styrene-butadiene rubber, polyacrylic acid and its salts, sodium alginate, etc.; the thickener in the negative electrode sheet can be selected from one or more of the following: sodium carboxymethyl cellulose, polyacrylonitrile multi-component copolymer, etc.; the negative electrode current collector can also be selected from one or more of the following: stainless steel with silver plating, stainless steel, copper, nickel, carbon electrode, carbon, nickel, titanium, etc.; the negative electrode current collector can also include composite current collectors, which can 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, copper, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.).

[0129] The membrane material can be selected from at least one of glass fiber, nonwoven fabric, polypropylene (PP) and polyvinylidene fluoride.

[0130] The differences between the embodiments and comparative examples are the values ​​of d, D, and L. Apart from these, all other characteristics of the battery are the same, as shown in Table 1.

[0131] Specifically, the measurement method for d is as follows: The battery is discharged to its lower limit voltage at a discharge rate of 0.33C under conditions of 25℃. The maximum spacing along the second direction in the straight region within the innermost positive electrode is measured. Five measurements are taken, and the average value is recorded as d1 (μm). The thickness of a single-layer negative electrode is recorded as d2 (μm), and the thickness of a single-layer separator is recorded as d3 (μm), satisfying d = d1 - 2 × (d2 + d3). It is worth noting that the innermost positive electrode refers to the region that starts from the positive electrode starting point and wraps around the electrode until it coincides with the positive electrode starting point.

[0132] When the positive electrode active material includes nickel-cobalt-manganese ternary materials, the upper limit voltage of the battery is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material includes lithium iron phosphate, the upper limit voltage of the battery is 3.65V and the lower limit voltage is 2.5V.

[0133] Specifically, the adjustment methods for d are as follows: d can be adjusted by increasing the thickness of the negative electrode active material layer (the thickness of the negative electrode active material layer ranges from 90 to 190 μm). The greater the thickness of the negative electrode active material layer, the greater d, and the smaller the thickness of the negative electrode active material layer, the smaller d. Alternatively, d can be adjusted by adjusting the number of negative electrode support layers (the number of negative electrode support layers ranges from 4 to 8 layers). The more layers, the greater d, and the fewer layers, the smaller d. Alternatively, d can be adjusted by adjusting the number of membrane layers (the number of membrane layers ranges from 6 to 20 layers). The more layers, the greater d, and the fewer layers, the smaller d.

[0134] Specifically, the test method for D is as follows: the battery is discharged to the lower limit voltage at a discharge rate of 0.33C under the condition of 25℃, and the thickness of a single cell is measured with a micrometer and recorded as D (mm).

[0135] When the positive electrode active material includes nickel-cobalt-manganese ternary materials, the upper limit voltage of the battery is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material includes lithium iron phosphate, the upper limit voltage of the battery is 3.65V and the lower limit voltage is 2.5V.

[0136] Specifically, the D value can be adjusted by regulating the thickness of the active material layer in the electrode (the active material layer thickness ranges from 30 to 210 μm, where the active material layer thickness ranges from 40 to 200 μm when the electrode is a negative electrode and from 30 to 210 μm when the electrode is a positive electrode). The thicker the active material layer, the larger the D value of the cell thickness; the thinner the active material layer, the smaller the D value of the cell thickness. Alternatively, the D value can be adjusted by regulating the thickness of the separator (the separator thickness ranges from 7 to 40 μm). The thicker the separator, the larger the D value of the cell thickness; the thinner the separator, the smaller the D value of the cell thickness.

[0137] Specifically, the L test method is as follows: The battery is discharged to the lower limit voltage at a discharge rate of 0.33C at 25℃. The battery is then disassembled, the positive electrode is removed, and cut into 4cm × 25cm test samples. These samples are immersed in dimethyl carbonate (DMC) for 4 hours, then left to stand for 30 minutes at 25℃ with a dew point ≤ -30℃. Under these conditions, the test samples are placed on a platform of a certain height. One side of the test sample is then fixed, while the other side hangs naturally. The lateral length (mainly the lateral length of the hanging end of the electrode) is measured when the sample hangs 4cm and 2cm respectively. (Details are as follows...) Figure 17 As shown, when the suspended portion of the sample hangs down naturally by 4cm, the horizontal length of the test sample end corresponding to the suspended portion in the horizontal direction is L2 (cm). When the sample hangs down by 2cm using the same test method (e.g.) Figure 18As shown in the figure, the horizontal length of the end of the suspended test sample in the horizontal direction is L1 (cm). The value of L can be calculated according to the formula L=(L2 / L1)-1.

[0138] Specifically, the method for controlling L is as follows: L can be adjusted by regulating the compaction density of the active material layer of the positive electrode (compaction density range 2.4~3.8 g / cm³). 3 The higher the compaction density, the larger L is, and the lower the compaction density, the smaller L is; or it can be adjusted by the mass content of the binder in the positive electrode active material layer (the mass content of the binder ranges from 0.2% to 4.0%). The higher the mass content of the binder in the positive electrode active material layer, the smaller L is, and the lower the mass content of the binder in the positive electrode active material layer, the larger L is.

[0139] 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: Cyclic Capacity Retention Test Following the battery preparation method described above, 50 batteries were prepared for each embodiment and comparative example. The values ​​of d, D, and L for each embodiment and comparative example are shown in Table 1 below. Except for these, the remaining structures are the same. The batteries were discharged at a rate of 0.33C to the lower limit voltage at a temperature of 25°C, allowed to stand for 10 minutes, and then charged at a rate of 0.33C to the upper limit voltage. The batteries were then charged at a constant voltage until the cutoff current equals 0.05C, allowed to stand for 10 minutes, and this cycle was repeated 3 times. The discharge amount in the 3rd cycle was recorded as the actual capacity of the battery, denoted as C1. At a temperature of 25°C, the batteries were charged at a rate of 1C1 (1 times the actual capacity) to the upper limit voltage, and then charged at a constant voltage until the cutoff current equals 0.05C. After standing for 20 minutes, the batteries were charged at a rate of 1C1 (1 times the actual capacity) to the upper limit voltage. Discharge at the discharge rate of the actual capacity until the lower limit voltage is reached. After standing for 20 minutes, charge at 1C1 (1 times the actual capacity) and discharge at 1C1 (1 times the actual capacity) until the discharge capacity is less than 0.8 times the actual capacity (i.e., the discharge capacity is less than 80% of the actual capacity). Record the number of cycles at this point. If the number of cycles is greater than or equal to 1200, it is considered qualified; if it is less than 1200, it is considered unqualified. Record the number of unqualified batteries as n. Calculate the percentage of unqualified batteries in the cycle using the formula: (n / 50) × 100%. If the percentage of unqualified batteries in the cycle is less than or equal to 2%, the test result is good. If the percentage of unqualified batteries in the cycle is greater than 2% and less than or equal to 6%, the test result is qualified. If the percentage of unqualified batteries in the cycle is greater than 6%, the test result is unqualified.

[0140] When the positive electrode active material includes nickel-cobalt-manganese ternary materials, the upper limit voltage of the battery is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material includes lithium iron phosphate, the upper limit voltage of the battery is 3.65V and the lower limit voltage is 2.5V.

[0141] The positive electrode active material used in this test was selected from LiNi. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, all other positive electrode materials meet the above test requirements, and 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 all other negative electrode materials meet the above test requirements, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2; the hot pressing conditions are: hot pressing temperature: 80℃, hot pressing pressure: 8000kgf, and hot pressing time: 100s.

[0142] Performance 2: Battery Voltage Drop Test Following the battery preparation method described above, 50 batteries were prepared for each embodiment and comparative example. The values ​​of d, D, and L for each embodiment and comparative example are shown in Table 1 below. Except for these, the remaining structures are identical. The batteries were discharged at a rate of 0.33C to the lower limit voltage at a temperature of 25°C, allowed to stand for 10 minutes, and then charged at a rate of 0.33C to the upper limit voltage. The batteries were then charged at a constant voltage until the cutoff current equals 0.05C, allowed to stand for 10 minutes, and this cycle was repeated 3 times. The discharge amount in the 3rd cycle was recorded as the actual capacity of the battery, denoted as C1. At a temperature of 25°C, the batteries were charged at a rate of 2C1 (twice the actual capacity) to the upper limit voltage and then charged at a constant voltage until the cutoff current equals 0.05C. After resting for 20 minutes, discharge at a rate of 2C1 (twice the actual capacity) until the lower limit voltage is reached. After resting for 20 minutes, charge at 2C1 (one time the actual capacity). After 600 cycles of this 2C1 (one time the actual capacity) discharge cycle, charge the battery at a rate of 0.33C1 until the upper limit voltage is reached, and then charge at a constant voltage until the cutoff current equals 0.05C1. After resting for 5 minutes, measure the voltage and record it as V1. After resting for 24 hours at 25℃ and 40% humidity, measure the voltage at this time and record it as V2. Calculate the voltage difference after 24 hours using the formula: voltage difference = V1 - V2. If the voltage difference is greater than 30mV, the battery is considered unqualified, and the number is recorded as n. If the voltage difference is less than 30mV... If the battery has a voltage of mV, then it is qualified. According to the formula, the battery failure rate = (n / 50) × 100%. If the battery failure rate is less than or equal to 4%, the test result is good. If the battery failure rate is greater than 4% and less than or equal to 8%, the test result is qualified. If the battery failure rate is greater than 8%, the test result is unqualified.

[0143] The positive electrode active material used in this test was selected from LiNi. 0.6 Co 0.2 Mn 0.2Taking O2 as an example, all other positive electrode materials meet the above test requirements, and 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 all other negative electrode materials meet the above test requirements, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2; the hot pressing conditions are: hot pressing temperature: 80℃, hot pressing pressure: 8000kgf, and hot pressing time: 100s.

[0144] Table 1:

[0145] As can be seen from Table 1, in Examples 1 to 18, the value of d / (D×L) is in the range of 10.8 to 10209.7. Therefore, the test results of the cycle capacity retention rate test and the battery voltage drop test of the batteries in Examples 1 to 18 are all unqualified.

[0146] Furthermore, in Examples 11 to 18, the value of d / (D×L) is in the range of 41.6 to 2608.3. Therefore, the battery in Examples 11 to 18 has good test results for both cycle capacity retention rate and battery voltage drop.

[0147] Furthermore, in Examples 1, 2, 6, 8, and 9, the value of d / (D×L) is in the range of 10.8 to 10209.7, but not in the range of 41.6 to 2608.3 and less than 41.6. Therefore, the battery voltage drop test results of the batteries in Examples 1, 2, 6, 8, and 9 are qualified.

[0148] Furthermore, in Examples 3 to 5, 7 and 10, the value of d / (D×L) is in the range of 10.8 to 10209.7, but not in the range of 41.6 to 2608.3 and is greater than 2608.3. Therefore, the battery in Examples 3 to 5, 7 and 10 has qualified test results for cycle capacity retention rate.

[0149] As can be seen from Table 1, in Comparative Example 1 and Comparative Example 3, the value of d / (D×L) is not in the range of 10.8 to 10209.7 and is less than 10.8, which leads to the failure of the battery voltage drop test results of Comparative Example 1 and Comparative Example 3.

[0150] As can be seen from Table 1, in Comparative Example 2 and Comparative Example 4, the value of d / (D×L) is not in the range of 10.8 to 10209.7 and is greater than 10209.7, which leads to the failure of the battery cycle capacity retention rate test results of Comparative Example 2 and Comparative Example 4.

[0151] The following is an explanation of the terms used in this application.

[0152] Battery packs can serve as the operating power source for electrical devices, or as the driving power source for electrical devices, replacing or partially replacing fuel or natural gas to provide driving power for vehicles. Electrical devices include: energy storage devices, electric ships, aircraft, laptops, power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other technological fields.

[0153] A battery pack consists of multiple batteries, which can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple batteries are connected in both series and parallel.

[0154] The battery pack is a cluster-level battery structure formed by multiple batteries connected in series, where the number of batteries in each cluster is strictly configured according to voltage and capacity requirements. Specifically, the battery cells of the battery pack include multiple batteries with similar capacity and internal resistance. Some of the batteries are connected in series to form a cluster that meets the preset power supply voltage requirements, and at least one spare battery among the multiple batteries is bypassed.

[0155] The battery pack may include battery cells and a switching control unit.

[0156] A battery can store chemical energy and controllably convert it into electrical energy. In recyclable batteries, the active materials can be reactivated by charging after discharge, allowing for continued use. A battery consists of a casing and battery cells housed within the casing.

[0157] A housing is a component used to provide a space to house and isolate electrode assemblies (cells) and other parts from the external environment. A housing generally includes a body with an opening at at least one end and a receiving cavity. The opening of the housing can be closed by a cover plate, sealing and isolating the internal environment of the battery cell from the external environment. Housing materials include, but are not limited to, copper, iron, aluminum, stainless steel, and aluminum alloys.

[0158] A cover is a component that seals the opening of the battery cell to isolate the internal environment of the battery cell from the external environment. Cover materials include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, and aluminum-plastic film.

[0159] A battery cell is the component in a battery where electrochemical reactions occur; it is the smallest unit in a battery capable of carrying out electrochemical reactions such as charging and discharging. A battery cell is the basic unit of a battery and typically includes a positive electrode, a negative electrode, and a separator. Lithium-ion battery cells primarily function by the movement of lithium ions between the positive and negative electrodes.

[0160] The positive electrode sheet includes a positive current collector and a positive active material, with the positive active material layer coated on at least one surface of the positive current collector.

[0161] The positive electrode active material layer includes: a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes, but is not limited to, at least one of the following: lithium phosphates, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive electrode active materials in batteries. These positive electrode active materials can be used alone or in combination of two or more. Lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., 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, at least one of lithium cobalt oxides (e.g., LiCoO2), lithium nickel oxides (e.g., LiNiO2), lithium manganese oxides (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt aluminum oxides, lithium nickel cobalt manganese oxides, and their modified compounds. Lithium nickel cobalt manganese oxides satisfy the general chemical formula LiNi. x Co y Mn z M f O2, where 0.1 < x < 1, 0.1 < y < 1, 0.1 < z < 1, and x + y + z + f = 1, M is a dopant element, and M includes at least one of Al, Mg, Ti, Zr, B, P, Nb, Ta, W, Zr, and V.

[0162] The positive electrode current collector includes a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. The positive electrode current collector can also include a composite current collector, which may include a polymer material substrate and a metal layer. Composite current collectors are formed by forming a metal material (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.).

[0163] 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, Super P, etc.), carbon nanotubes, graphene and carbon nanofibers.

[0164] 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.

[0165] Similarly, the negative electrode sheet includes a negative current collector and a layer of negative active material disposed on at least one surface of the negative current collector.

[0166] The negative electrode 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. The negative electrode current collector can also include composite current collectors, which may include a polymer material base layer and a metal layer. Composite current collectors are formed by forming metal materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0167] The negative electrode active material layer includes the negative electrode active material, conductive components, and binders. 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-ammonia composites. The conductive agent can be conductive carbon black, carbon nanotubes, etc., and the binder can be styrene-butadiene rubber, polyacrylic acid, etc.

[0168] A separator is positioned between the positive and negative electrode plates to separate them and prevent short circuits caused by contact. The separator's dimensions extend beyond the positive and negative electrode plates. The separator can be at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF). A coating can also be applied to the separator surface. This coating can be inorganic or organic, wherein the inorganic coating material includes at least one of alumina, silicon dioxide, titanium dioxide, magnesium oxide, zirconium oxide, and boehmite; and the organic coating includes at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0169] The battery cell also includes tabs, which are located on one side of the positive / negative current collector and are either separate from or integrally formed with the current collector. The tabs are electrically connected to the current collector to conduct current through it. When the tabs and current collector are separate, they can be connected by welding. The tabs are made of a highly conductive metal material (such as copper, aluminum, or nickel).

[0170] The electrolyte is located between the positive and negative electrodes, serving to conduct ions between them. Electrolytes include liquid electrolytes, gel polymer electrolytes, and solid electrolytes; among them, liquid electrolytes refer to electrolytes that are in a liquid state, possessing the function of conducting ions while isolating electrons; liquid electrolytes are composed of chemical substances such as solvents, electrolyte salts, and additives; solvents can be carbonates, carboxylic acid esters, or ethers, etc.; electrolyte salts can be lithium salts, sodium salts, or zinc salts; additives can be ethylene carbonate, fluoroethylene carbonate, propylene sulfite, ethylene sulfite, etc.

[0171] A battery includes terminals, which are used to electrically connect the electrode assembly (cell) located inside the casing to external devices (adjacent batteries or other electrical equipment) located outside the casing. The battery can discharge to external devices through the cell output terminals (tabs) and terminals, and an external power source can charge the battery through the terminals and cell output terminals (tabs). The terminals can be directly electrically connected to the cell tabs, or they can be electrically connected to the tabs through adapters.

[0172] The electrode post is made of metal materials including but not limited to copper, aluminum, aluminum alloy, and copper-aluminum alloy.

[0173] 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. A battery, characterized in that, include: The core (10) is formed by winding a positive electrode sheet (1), a separator (2) and a negative electrode sheet (3) stacked together. The negative electrode sheet (3) is positioned closer to the winding start position than the positive electrode sheet (1). The core (10) includes a flat region (101) and a first arc region (102) and a second arc region (103) located at opposite ends of the flat region (101) along a first direction. Along the winding direction of the core (10), the positive electrode sheet (1) has a positive electrode start end (11) close to the winding start position. The core (10) also includes a support layer (4). The negative electrode sheet (3) includes a negative electrode sheet body (31) and a negative electrode support layer (32). The support layer (4) includes the negative electrode support layer (32). The negative electrode support layer (32) extends beyond the positive electrode start end (11) and is located at least in the first arc region (102). At the first arc region (102), the total thickness of the support layer (4) is d (μm); along the second direction, the thickness of the core (10) is D (mm), and the second direction is perpendicular to both the first direction and the height direction of the core (10); when the positive electrode (1) droops by 4cm, the lateral length of the end of the suspended side is L2 (cm), when the positive electrode (1) droops by 2cm, the lateral length of the end of the suspended side is L1 (cm), and the drooping degree of the positive electrode (1) is L, satisfying L=(L2 / L1)-1; d, D and L satisfy 10.8≤d / (D×L)≤10209.

7.

2. The battery according to claim 1, characterized in that, The negative electrode sheet (3) includes a negative electrode current collector layer (33) and a negative electrode active material layer (34) disposed on at least one side of the negative electrode current collector layer (33). At least a portion of the negative electrode support layer (32) is not provided with the negative electrode active material layer (34) to form an empty foil region (321). The thickness of the negative electrode current collector layer (33) is a (μm), which satisfies 6≤a≤12.

3. The battery according to claim 1, characterized in that, The negative electrode sheet (3) includes a negative electrode current collector layer (33) and a negative electrode active material layer (34) disposed on at least one side of the negative electrode current collector layer (33). At least a portion of the negative electrode support layer (32) is not provided with the negative electrode active material layer (34) to form an empty foil area (321). Along the winding direction of the core (10), the length of the empty foil area (321) is b (mm), which satisfies 5≤b≤300.

4. The battery according to claim 1, characterized in that, The negative electrode sheet (3) includes a negative electrode current collector layer (33) and a negative electrode active material layer (34) disposed on at least one side of the negative electrode current collector layer (33). At least a portion of the negative electrode support layer (32) is not provided with the negative electrode active material layer (34) to form an empty foil area (321). Along the winding direction of the core (10), the empty foil area (321) has a first end point (3211) near the winding start position. The first end point (3211) extends beyond the positive electrode start end (11) and is located between the positive electrode start end (11) and the winding start position.

5. The battery according to claim 4, characterized in that, Along the winding direction of the core (10), the empty foil area (321) also has a second end point (3212) away from the winding start position. The second end point (3212) extends beyond the positive electrode start end (11). The second end point (3212) is located between the positive electrode start end (11) and the winding start position. The dimension of the second end point (3212) extending beyond the positive electrode start end (11) is c (mm), which satisfies 1≤c≤500.

6. The battery according to claim 4, characterized in that, Along the winding direction of the core (10), the empty foil area (321) also has a second end point (3212) away from the winding start position. The second end point (3212) does not extend beyond the positive electrode start end (11). The positive electrode start end (11) is located between the first end point (3211) and the second end point (3212). The thickness of the negative electrode active material layer (34) of the negative electrode sheet body is e (μm), which satisfies e≥100.

7. The battery according to claim 1, characterized in that, The negative electrode sheet (3) includes a negative electrode current collector layer (33) and a negative electrode active material layer (34) disposed on at least one side of the negative electrode current collector layer (33). The negative electrode support layer (32) has the negative electrode active material layer (34). The thickness of the negative electrode active material layer (34) is e (μm), which satisfies e≤180.

8. The battery according to claim 1, characterized in that, Along the winding direction of the core (10), the negative electrode sheet (3) extends beyond the positive electrode starting end (11) by a dimension of g (mm), satisfying 10≤g≤600.

9. The battery according to claim 1, characterized in that, The diaphragm (2) includes a diaphragm body (21) and a diaphragm support layer (22). The support layer (4) further includes the diaphragm support layer (22). The diaphragm support layer (22) is disposed on at least one side of the negative electrode support layer (32) along its thickness direction.

10. The battery according to claim 9, characterized in that, The negative electrode support layer (32) has a diaphragm support layer (22) on both sides along its thickness direction.

11. The battery according to claim 9, characterized in that, Within the support layer (4), the total thickness of the diaphragm support layer (22) is i (μm), and the total thickness of the negative electrode support layer (32) is j (μm), satisfying 0.08≤i / j≤0.

4.

12. The battery according to any one of claims 1 to 11, characterized in that, The negative electrode support layer (32) is located in the first arc region (102) and the second arc region (103), and at least one layer of the negative electrode support layer (32) is provided in the first arc region (102) and the second arc region (103).

13. The battery according to any one of claims 1 to 11, characterized in that, Along the winding direction of the core (10), the negative electrode sheet (3) has a negative electrode starting end (35) near the winding start position, and the positive electrode starting end (11) and / or the negative electrode starting end (35) are located in the flat region (101).

14. The battery according to claim 13, characterized in that, On a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode starting end (11) and the orthographic projection of the negative electrode starting end (35) are spaced apart.

15. The battery according to claim 14, characterized in that, Along the first direction, the distance between the positive electrode starting end (11) and the negative electrode starting end (35) is p (mm), and the size of the core (10) is q (mm), satisfying 0.018≤p / q≤0.

86.

16. The battery according to any one of claims 1 to 11, characterized in that, At the first arc region (102), the support layer (4) includes at least two layers of the negative electrode support layer (32).

17. The battery according to claim 16, characterized in that, The negative electrode sheet (3) includes a negative electrode current collector layer (33) and a negative electrode active material layer (34) disposed on at least one side of the negative electrode current collector layer (33). The thickness of the negative electrode active material layer (34) of the negative electrode support layer is e (μm), which satisfies 30≤e≤180.

18. The battery according to any one of claims 1 to 11, characterized in that, The negative electrode sheet (3) includes a negative electrode current collector layer (33) and a negative electrode active material layer (34) disposed on at least one side of the negative electrode current collector layer (33). The negative electrode current collector layer (33) includes a non-metallic layer (331) and a metallic layer (332) disposed on at least one side of the non-metallic layer (331) along its thickness direction.

19. The battery according to claim 18, characterized in that, Along the thickness direction of the negative electrode current collector layer (33), the thickness of the non-metallic layer (331) is t1 (μm) and the thickness of the metallic layer (332) is t2 (μm), satisfying 0.3≤t1 / t2≤10.

20. The battery according to any one of claims 1 to 11, characterized in that, Along the first direction, the dimension of the straight area (101) is x1 (mm), and the total dimension of the first arc area (102) and the second arc area (103) is x2 (mm), satisfying 0.1≤x2 / x1≤0.

45.

21. The battery according to any one of claims 1 to 11, characterized in that, At the first arc region (102), the total thickness d (μm) of the support layer (4) satisfies 280 ≤ d ≤ 1920; and / or, Along the second direction, the thickness D (mm) of the core (10) satisfies 8 ≤ D ≤ 35; and / or, The sag L of the positive electrode (1) satisfies 0.02≤L≤0.

8.

22. The battery according to any one of claims 1 to 11, characterized in that, The battery includes at least two winding cores (10) arranged along a second direction, and the thickness D (mm) of each winding core (10) satisfies D≤32.

23. The battery according to any one of claims 1 to 11, characterized in that, The core (10) includes a body portion (104) and an electrode portion (105) extending from at least one end of the body portion (104) along the height direction of the core (10). Along a first direction, the minimum distance between the electrode portion (105) and the first arc region (102) or the second arc region (103) is k (mm), satisfying 10≤k≤100.

24. The battery according to any one of claims 1 to 11, characterized in that, The core (10) includes a body portion (104) and an electrode portion (105) extending from the body portion (104) along at least one end of the core (10) in the height direction. The electrode portion (105) includes a plurality of stacked single electrode portions (1051). Along the first direction, the width of the single electrode portion (1051) is f (mm), which satisfies 30≤f≤60.

25. The battery according to any one of claims 1 to 11, characterized in that, The positive electrode (1) includes a positive current collector layer (12) and a positive active material layer (13) disposed on at least one side of the positive current collector layer (12).

26. The battery according to claim 25, characterized in that, The positive electrode active material layer (13) is disposed facing the support layer (4), and the sag L of the positive electrode sheet (1) satisfies 0.02≤L≤0.

6.

27. The battery according to claim 25, characterized in that, The positive electrode active material layer (13) is disposed away from the support layer (4).

28. A battery pack, characterized in that, The battery includes any one of claims 1 to 27.

29. An electrical appliance, characterized in that, Includes the battery pack as described in claim 28.

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