Cylindrical battery and battery pack

Abstract

A cylindrical battery (10) and a battery pack (1). The cylindrical battery (10) comprises a case (101), an electrode assembly (102) and a first insulating layer (103), wherein the case (101) has an accommodating cavity (1014); and the electrode assembly (102) is arranged in the accommodating cavity (1014). The electrode assembly (102) comprises a positive electrode sheet, a separator, and a negative electrode sheet (1021), wherein the positive electrode sheet has a positive electrode tab; the negative electrode sheet (1021) has a negative electrode tab (1022); and the positive electrode tab and the negative electrode tab (1022) are located at two ends of the electrode assembly (102). The first insulating layer (103) is provided on the surface of the negative electrode sheet (1021) facing the separator, and is arranged away from the negative electrode tab (1022).

Description

Cylindrical battery and battery pack

[0001] This application claims priority to Chinese patent application No. 202311201240.3 filed with the Patent Office of China on September 15, 2023. The entire contents of the above application are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a cylindrical battery and a battery pack. Background Art

[0003] During long-term cycling of cylindrical batteries, the negative electrode inside will expand and stretch, causing the diaphragm to be punctured by the negative electrode. SUMMARY OF THE INVENTION

[0004] When the separator is punctured, the negative electrode sheet's material area away from the negative electrode tab directly contacts the positive electrode tab, causing a short circuit. Currently, preventing this short circuit caused by contact between the negative electrode sheet's material area away from the negative electrode tab and the positive electrode tab after the separator is punctured remains a pressing technical challenge.

[0005] The present application provides a cylindrical battery and a battery pack to solve the problem in the related art of short circuit caused by the material area of ​​the negative electrode sheet away from the negative electrode tab contacting the positive electrode tab after puncturing the diaphragm.

[0006] In a first aspect, the present application provides a cylindrical battery. The cylindrical battery comprises a housing, an electrode assembly, and a first insulating layer. The housing has a receiving cavity; the electrode assembly is disposed within the receiving cavity; the electrode assembly comprises a positive electrode sheet, a separator, and a negative electrode sheet stacked and wound together; the positive electrode tab of the positive electrode sheet and the negative electrode tab of the negative electrode sheet are located at opposite ends of the electrode assembly; and the first insulating layer is disposed on the surface of the negative electrode sheet facing the separator, and is located at the end of the surface away from the negative electrode tab.

[0007] In a second aspect, the present application provides a battery pack comprising a plurality of the aforementioned cylindrical batteries, wherein the plurality of cylindrical batteries are connected in series or in parallel. Beneficial effects

[0008] In the present application, by providing a first insulating layer in the material area of ​​the negative electrode sheet away from the negative electrode tab side, when the material area of ​​the negative electrode sheet away from the negative electrode tab side pierces the diaphragm and extends toward the positive electrode tab, the material area of ​​the negative electrode sheet away from the negative electrode tab side can be blocked from the positive electrode tab with the help of the first insulating layer, thereby solving the short circuit problem in the related art caused by the material area of ​​the negative electrode sheet away from the negative electrode tab side contacting the positive electrode tab after piercing the diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG1 is an exploded view of a cylindrical battery provided in an embodiment of the present application;

[0010] FIG2 is a front view of a negative electrode sheet provided with a first insulating layer in an unfolded state according to an embodiment of the present application;

[0011] FIG3 is a top view of a first negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0012] FIG4 is a top view of a second negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0013] FIG5 is a front view of another negative electrode sheet provided with a first insulating layer in an unfolded state provided by an embodiment of the present application;

[0014] FIG6 is a top view of a third negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0015] 7 is a top view of a fourth negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0016] FIG8 is a top view of a fifth negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0017] FIG9 is a top view of a sixth negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0018] FIG10 is a top view of a seventh negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0019] FIG11 is a top view of an eighth negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0020] FIG12 is a top view of a ninth negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0021] 13 is a top view of a tenth negative electrode sheet provided with a first insulating layer according to an embodiment of the present application;

[0022] FIG14 is a top view of a negative electrode sheet provided with a first insulating layer and a second insulating layer according to an embodiment of the present application;

[0023] FIG15 is a schematic structural diagram of a battery pack provided in an embodiment of the present application.

[0024] Description of Figure Numbers:

[0025] 1-battery pack; 10-cylindrical battery; 101-shell; 1011-upper cover; 1012-cylinder; 1013-lower cover; 1014-accommodation chamber; 102-electrode assembly; 1021-negative electrode sheet; 1022-negative electrode tab; 1023-material area; 1024-positive electrode tab; 103-first insulating layer; 1031-first sub-insulating layer; 104-second insulating layer; 20-box; 201-box cover; 202-box body. Modes for Carrying Out the Invention

[0026] Please refer to Figure 1, which is an exploded view of a cylindrical battery 10 provided in an embodiment of the present application. An embodiment of the present application provides a cylindrical battery 10, which includes a shell 101, an electrode assembly 102 and a first insulating layer 103. The shell 101 has a accommodating cavity 1014. The electrode assembly 102 is arranged in the accommodating cavity 1014. The electrode assembly 102 includes a positive electrode sheet, a separator and a negative electrode sheet 1021 that are stacked and wound. The positive electrode tab 1024 of the positive electrode sheet and the negative electrode tab 1022 of the negative electrode sheet 1021 are located at both ends of the electrode assembly 102. A first insulating layer 103 is provided on the surface of the negative electrode sheet 1021 facing the separator, and the first insulating layer 103 is located at one end of the surface away from the negative electrode tab 1022.

[0027] The negative electrode sheet 1021 includes a current collector and an active material layer disposed on the current collector. The area where the active material layer is located is the material area 1023. The surface of the active material layer facing away from the current collector is the surface of the negative electrode sheet 1021 facing the separator. One end of the current collector surface along the width direction is a blank area without an active material layer. The current collector located in this blank area is the negative electrode tab 1022. The first insulating layer 103 is disposed on the surface of the active material layer facing away from the current collector, and is located at the end of this surface away from the negative electrode tab 1022.

[0028] The first insulating layer 103 is a layer of material with insulating properties. It can be applied to the negative electrode sheet 1021 by coating or gluing. By weight, the first insulating layer 103 may comprise 20% to 40% ceramic, 15% to 60% binder, and 5% to 20% organic solvent. Ceramics include, but are not limited to, aluminum oxide, boehmite, and zirconium oxide. Binders include, but are not limited to, polyvinylidene fluoride, polytetrafluoroethylene, and sodium carboxymethyl cellulose. Organic solvents include, but are not limited to, i-methylpyrrolidone, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and highly insulating adhesive resins. The highly insulating adhesive resin may be a polyvinylidene fluoride binder. Polyvinylidene fluoride binders are formed by preparing a copolymer from organic monomers such as butyl acrylate, acrylonitrile, and vinyl acetate, which is then dispersed in an organic solvent with an inorganic filler. Inorganic fillers include, but are not limited to, potassium persulfate, sodium persulfate, and ammonium persulfate.

[0029] Specifically, the first insulating layer 103 may be made of any one or more insulating adhesives listed in the following table.

[0030] Table 1. Information description of some insulating adhesives

[0031] No. Insulating glue name Related information 1 Insulating glue A Mix aluminum oxide, polyvinylidene fluoride and n-methyl pyrrolidone in a mass ratio of 30:55:15, and stir evenly to obtain an insulating layer slurry with insulating properties 2 Insulating glue B Mix boehmite, polyvinylidene fluoride and n-methyl pyrrolidone in a mass ratio of 30:55:15, and stir evenly to obtain an insulating layer slurry with insulating properties 3 Insulating glue C Mix aluminum oxide, boehmite, polyvinylidene fluoride and n-methyl pyrrolidone in a mass ratio of 10:20:55:15, and stir evenly to obtain an insulating layer slurry with insulating properties

[0032] In this embodiment, a material area 1023 is provided on the surface of the negative electrode sheet 1021 facing the diaphragm, and a first insulating layer 103 is provided on the surface of one end of the material area 1023 away from the negative electrode tab 1022. Therefore, during the use of the cylindrical battery 10, when the negative electrode sheet 1021 expands and extends, causing the negative electrode sheet 1021 to pierce the diaphragm and extend toward the positive electrode tab 1022, the material area 1023 of the negative electrode sheet 1021 away from the negative electrode tab 1022 is blocked from the positive electrode tab 1024 by the first insulating layer 103, so as to avoid direct contact between the material area 1023 of the negative electrode sheet 1021 away from the negative electrode tab 1022 and the positive electrode tab 1024. This can solve the short circuit problem caused by the contact between the material area 1023 of the negative electrode sheet 1021 away from the negative electrode tab 1022 and the positive electrode tab 1024 in the related art, thereby improving the safety and stability of the battery.

[0033] The dimension of the first insulating layer 103 along the length of the negative electrode sheet 1021 is S1, and the length dimension of the negative electrode sheet 1021 is S, satisfying: S1 ≤ S. When S1 < S, the first insulating layer 103 can be provided at any position along the length of the negative electrode sheet 1021. In this case, the first insulating layer 103 covers the edge portion of the negative electrode sheet 1021 away from the negative electrode tab 1022, thereby blocking the positive electrode tab 1024 from the partial material area 1023 of the negative electrode sheet 1021 away from the negative electrode tab 1022. As shown in Figures 2 to 4, Figure 2 is a front view of the unfolded negative electrode sheet 1021 provided with the first insulating layer 103 according to an embodiment of the present application, Figure 3 is a top view of the first negative electrode sheet 1021 provided with the first insulating layer 103 according to an embodiment of the present application, and Figure 4 is a top view of the second negative electrode sheet 1021 provided with the first insulating layer 103 according to an embodiment of the present application. In Figures 2 and 3, the first insulating layer 103 is provided at one end of the negative electrode sheet 1021 in the longitudinal direction; in Figure 4, the first insulating layer 103 is provided at a position in the middle of the length of the negative electrode sheet 1021. When S1=S, as shown in Figure 5, Figure 5 is a front view of another embodiment of the present application provided with a negative electrode sheet 1021 provided with a first insulating layer 103 in an unfolded state. At this time, the first insulating layer 103 completely covers the edge of the negative electrode sheet 1021 away from the negative electrode tab 1022, thereby blocking the positive electrode tab 1024 from the entire material area 1023 of the negative electrode sheet 1021 away from the negative electrode tab 1022.

[0034] The dimension L1 of the first insulating layer 103 along the width of the negative electrode sheet 1021 satisfies the following conditions: 0.1 mm ≤ L1 ≤ 50 mm. If L1 is less than 0.1 mm, the coverage area of ​​the first insulating layer 103 is too small, potentially preventing short circuits during the expansion and elongation of the negative electrode sheet 1021. If L1 is greater than 50 mm, the coverage area of ​​the first insulating layer 103 will significantly exceed the overhang area, hindering lithium insertion and extraction.

[0035] In one embodiment, the dimension of the first insulating layer 103 in the thickness direction of the negative electrode sheet 1021 is d, which satisfies:

[0036] ; (1)

[0037] in,

[0038] S is the length of the negative electrode sheet 1021 (mm);

[0039] r is the radius of the winding needle used to form the electrode assembly (mm);

[0040] a is the thickness of the positive electrode sheet (mm);

[0041] b is the thickness of the diaphragm (mm);

[0042] D is the thickness of the negative electrode sheet 1021 (mm);

[0043] n is the number of turns of the negative electrode sheet.

[0044] The formula for calculating the length S2 of the negative electrode sheet 1021 without the first insulating layer 103 is: S2 = [(a + 2b) (n + 1) n + (2n - 1) nD + 2r] π. Based on this formula, the formula for calculating the length S of the negative electrode sheet 1021 with the first insulating layer 103 is: S = [(d + a + 2b) (n + 1) n + (2n - 1) nD + 2r] π. Transforming this formula yields: , which is the maximum value of d that meets the requirements of the electrode assembly assembly dimensions and other requirements. This yields formula (1). Then, based on the set length of the negative electrode sheet 1021, the maximum value of the dimension d of the first insulating layer 103 in the thickness direction of the negative electrode sheet 1021 can be calculated. A dimension d within this range allows the electrode assembly to be automatically inserted into the shell, and after insertion, a gap exists between the electrode assembly 102 and the shell 101 that meets the design requirements for electrode sheet expansion and electrolyte injection.

[0045] In one embodiment, the dimension d of the first insulating layer 103 in the thickness direction of the negative electrode sheet 1021 further satisfies:

[0046] ; (2)

[0047] Wherein, R is the radius of the housing 101 (mm).

[0048] Based on formula (1), a more optimal range of values ​​for size d can be obtained according to the group margin calculation formula, namely formula (2). Values ​​of size d within this range can achieve higher energy density while maintaining the technical effects corresponding to formula (1).

[0049] Please refer to Figure 6, which is a top view of a third embodiment of the present application, including a negative electrode sheet 1021 provided with a first insulating layer 103. In one embodiment, the first insulating layer 103 includes multiple first sub-insulating layers 1031, which are disposed on the same side of the negative electrode sheet 1021 and are stacked sequentially along the thickness direction of the negative electrode sheet 1021.

[0050] Along the direction close to the negative electrode sheet 1021, the dimensions of each first sub-insulating layer 1031 in the thickness direction of the negative electrode sheet 1021 are d1, d2, ..., d i , where i is a natural number, i≥2, and Σ di=d. It can be understood that according to the thickness d of the first insulating layer 103, the number of layers of the first sub-insulating layer 1031 can be selectively designed, for example, i=2, or i=3, or i=4, or i=5, so that Σ di The value of can be in the above formula (1) or formula (2).

[0051] In the embodiment shown in FIG6 , multiple layers of the first sub-insulating layer 1031 can be disposed on the same side of the negative electrode sheet 1021 by coating. This facilitates controlling the thickness of the first insulating layer 103 and improves the insulation properties of the first insulating layer 103 , thereby increasing the internal resistance between the material region 1023 of the negative electrode sheet 1021 away from the negative electrode tab 1022 and the positive electrode tab 1024 , thereby improving the insulation properties between the material region 1023 of the negative electrode sheet 1021 away from the negative electrode tab 1022 and the positive electrode tab 1024 .

[0052] Please refer to Figures 7 to 9. Figure 7 is a top view of a fourth negative electrode sheet 1021 provided with a first insulating layer 103 according to an embodiment of the present application, Figure 8 is a top view of a fifth negative electrode sheet 1021 provided with a first insulating layer 103 according to an embodiment of the present application, and Figure 9 is a top view of a sixth negative electrode sheet 1021 provided with a first insulating layer 103 according to an embodiment of the present application. In one embodiment, the first insulating layer 103 includes multiple first sub-insulating layers 1031. The negative electrode sheet 1021 has a first side and a second side opposite to each other. Some of the first sub-insulating layers 1031 are provided on the first side, and the remaining first sub-insulating layers 1031 are provided on the second side. The first sub-insulating layers 1031 located on the same side of the negative electrode sheet 1021 are stacked sequentially along the thickness direction of the negative electrode sheet 1021.

[0053] A portion of the first sub-insulating layer 1031 is disposed on the first side of the negative electrode sheet 1021, and another portion of the first sub-insulating layer 1031 is disposed on the second side of the negative electrode sheet 1021, as shown in Figures 7, 8, and 9. In Figure 7, a first sub-insulating layer 1031 is disposed on both sides of the negative electrode sheet 1021. The dimensions of these two first sub-insulating layers 1031 in the thickness direction of the negative electrode sheet 1021 are d1 and d2, respectively, with d1 + d2 = d. In Figure 8, two first sub-insulating layers 1031 are disposed on both sides of the negative electrode sheet 1021. From the first side to the second side of the negative electrode sheet 1021, the dimensions of the multiple first sub-insulating layers 1031 in the thickness direction of the negative electrode sheet 1021 are d1, d2, d3, and d4, respectively, with d1 + d2 + d3 + d4 = d. In Figure 9, three first sub-insulating layers 1031 are provided on one side of the negative electrode sheet 1021, and two first sub-insulating layers 1031 are provided on the other side of the negative electrode sheet 1021. From the first side to the second side of the negative electrode sheet 1021, the dimensions of the multiple first sub-insulating layers 1031 in the thickness direction of the negative electrode sheet 1021 are d1, d2, d3, d4, and d5, respectively, where d1+d2+d3+d4+d5=d.

[0054] A first sub-insulating layer 1031 is provided on both sides of the negative electrode sheet 1021, so that the first insulating layer 103 blocks the two surfaces of the negative electrode sheet 1021 in the thickness direction away from the negative electrode tab 1022 from the positive electrode tab 1024, so that after the diaphragm is punctured, the material area 1023 on the two surfaces of the negative electrode sheet 1021 in the thickness direction away from the negative electrode tab 1022 can be prevented from directly contacting the positive electrode tab.

[0055] When the first sub-insulating layer 1031 has multiple layers, the multiple layers of the first sub-insulating layer 1031 can be made of the same insulating material or different insulating materials, as shown in Figures 10 to 13. Figure 10 is a top view of the seventh negative electrode sheet 1021 provided with the first insulating layer 103 according to an embodiment of the present application, Figure 11 is a top view of the eighth negative electrode sheet 1021 provided with the first insulating layer 103 according to an embodiment of the present application, Figure 12 is a top view of the ninth negative electrode sheet 1021 provided with the first insulating layer 103 according to an embodiment of the present application, and Figure 13 is a top view of the tenth negative electrode sheet 1021 provided with the first insulating layer 103 according to an embodiment of the present application. In Figure 10, two layers of the first sub-insulating layer 1031 are provided on one side of the negative electrode sheet 1021, and the two layers of the first sub-insulating layer 1031 are made of different insulating materials. In Figure 11 , a first sub-insulating layer 1031 is provided on both sides of the negative electrode sheet 1021, and the insulating materials of the first sub-insulating layers 1031 on each side of the negative electrode sheet 1021 are different. In Figure 12 , two first sub-insulating layers 1031 are provided on both sides of the negative electrode sheet 1021. Of the first sub-insulating layers 1031 on both sides, the first sub-insulating layer 1031 directly applied on the negative electrode sheet 1021 is made of one insulating material, and the other first sub-insulating layer 1031 applied on the first sub-insulating layer 1031 is made of another insulating material. In Figure 13, the first sub-insulating layers 1031 on both sides of the negative electrode sheet 1021 can be arranged in mirror symmetry with respect to the negative electrode sheet 1021. For example, two layers of first sub-insulating layers 1031 are arranged on both sides of the negative electrode sheet 1021, and one first sub-insulating layer 1031 directly coated on one side of the negative electrode sheet 1021 uses the first insulating material, and the other first sub-insulating layer 1031 coated on the first sub-insulating layer 1031 uses the second insulating material; one first sub-insulating layer 1031 directly coated on the other side of the negative electrode sheet 1021 uses the second insulating material, and the other sub-insulating layer coated on the first sub-insulating layer 1031 uses the first insulating material.

[0056] The multi-layer first sub-insulating layer 1031 uses different insulating materials, so that the first insulating layer 103 can obtain the comprehensive performance of multiple different insulating materials, which is beneficial to improving the insulation between the material area 1023 of the negative electrode sheet 1021 away from the negative electrode tab 1022 and the positive electrode tab 1024.

[0057] According to the aforementioned partial insulation glue information description table, the following four groups of control experiments were conducted on the setting of the first insulation layer 103.

[0058] The first group: the negative electrode sheet 1021 is not provided with the first insulating layer 103 .

[0059] The second group: the insulating glue A is evenly coated on one side of the negative electrode sheet 1021 and on the material area away from the negative electrode tab 1022 to form the first insulating layer 103. The first insulating layer 103 includes a plurality of first sub-insulating layers 1031, and the thickness d of the first sub-insulating layer 1031 is 1000 nm. i The average value is 5.7 μm, and its length S1 is consistent with the length S of the negative electrode sheet.

[0060] Group 3: Insulation glue A was evenly applied to both sides of the negative electrode sheet 1021, away from the negative electrode tab 1022, to form the first insulating layer 103. The thickness of the first sub-insulating layer 1031 applied on both sides of the negative electrode sheet 1021 was 5.5 μm and 5.7 μm, respectively, and its length S1 was consistent with the length S of the negative electrode sheet.

[0061] Group 4: Insulation glues A and B were evenly applied to both sides of the negative electrode sheet 1021, away from the negative electrode tab 1022, to form the first insulating layer 103. The thickness of the first sub-insulating layer 1031 applied on both sides of the negative electrode sheet 1021 was 5.7 μm and 9.5 μm, respectively, and its length S1 was consistent with the length S of the negative electrode sheet.

[0062] The internal resistance of the four groups of negative electrode sheets 1021 on the side away from the negative electrode tab 1022 was measured by a four-probe method to obtain the following internal resistance data table.

[0063] Table 2. Internal resistance measurement table of four groups of negative electrode sheets 1021

[0064] Experimental group internal resistance / mΩ Group 1 11.3 Group 2 12.4 Group 3 13.7 Group 4 16.4

[0065] It can be seen from Table 2 that the thicker the first insulating layer 103 is and the more insulating glue is coated on both sides of the negative electrode sheet 1021 , the higher the internal resistance of the corresponding negative electrode sheet 1021 .

[0066] In one embodiment, when there are multiple first sub-insulating layers 1031, the sizes of the multiple first sub-insulating layers 1031 in the thickness direction of the negative electrode sheet 1021 from one side to the other are d1, d2, ..., d i , where i is a natural number, i≥2, and satisfies: 0.15<d1:d i ≤1.

[0067] By d1:d i The limitation can ensure that the thickness of the first sub-insulating layers 1031 does not vary too much, making the thickness distribution of the first sub-insulating layers 1031 as uniform as possible, thereby improving the bonding stability between two adjacent first sub-insulating layers 1031. Optionally, 0.2<d1:di≤0.75.

[0068] Please refer to Figure 14, which is a top view of a negative electrode sheet 1021 provided with a first insulating layer 103 and a second insulating layer 104 according to an embodiment of the present application. In one embodiment, one end surface of the negative electrode sheet 1021 in the longitudinal direction is a first end surface, which is located at the periphery of the electrode assembly 102, and the second insulating layer 104 is provided on the first end surface.

[0069] The first end surface of the negative electrode sheet 1021 is located at the periphery of the electrode assembly 102. When the negative electrode sheet 1021 expands and stretches, it deforms significantly, potentially puncturing the separator and posing a short circuit risk. Therefore, a second insulating layer 104 is provided on the first end surface to isolate the first end surface from the positive electrode sheet as it punctures the separator and extends toward the positive electrode sheet, thereby improving the stability of the cylindrical battery 10.

[0070] The second insulating layer 104 is also a layer of insulating material, similar to the first insulating layer 103. There are many choices of insulating materials for the first insulating layer 103 and the second insulating layer 104. The specific raw materials are not limited and can be selected according to the actual application environment.

[0071] In one embodiment, the second insulating layer 104 covers the first end surface. The second insulating layer 104 completely covers the first end surface, thereby completely isolating the positive electrode sheet from the first end surface. Furthermore, when the negative electrode sheet 1021 is cut, the first end surface, serving as the cutting surface for the negative electrode sheet 1021, may have burrs. After the second insulating layer 104 is provided, the second insulating layer 104 covers the burrs, preventing the burrs on the cutting surface from puncturing the separator, thereby improving the stability of the cylindrical battery 10.

[0072] In one embodiment, the dimension of the second insulating layer 104 in the thickness direction of the negative electrode sheet 1021 is L2, the thickness of the negative electrode sheet 1021 is D, and the following conditions are met: D≤L2≤50 mm; the dimension of the second insulating layer 104 in the length direction of the negative electrode sheet 1021 is d0, and the following conditions are met: 0.001 mm≤d0≤10 mm.

[0073] When L2 is less than the thickness D of the negative electrode sheet 1021, the second insulating layer 104 cannot completely cover the first end face. When L2 is greater than 50mm, it is not conducive to the winding of the negative electrode sheet 1021, and it is also easy to cause the second insulating layer 104 to fall off from the first end face. When d0 is less than 0.001mm, the deformation of the first end face when the negative electrode sheet 1021 is wound will cause the second insulating layer 104 to be damaged, so that when the negative electrode sheet 1021 expands and stretches, the active material of the negative electrode sheet 1021 extends from the damaged part and punctures the diaphragm. When d0 is greater than 10mm, the protective layer is too thick and will protrude too much at the end of the negative electrode sheet, thereby affecting the void volume in the battery cavity after assembly, and then causing the void to be too small.

[0074] Illustratively, D≤L2≤30 mm, 0.01 mm≤d0≤1 mm.

[0075] In one embodiment, both the positive electrode tab 1024 and the negative electrode tab 1022 are flattened tabs. Flattening the tabs can effectively reduce the space occupied by the tabs, thereby increasing the energy density of the battery. However, after the tabs are flattened, the positive electrode tabs will move closer to the end of the negative electrode sheet away from the negative electrode tab. This results in that when the negative electrode sheet expands and stretches, the edge of the material area of ​​the negative electrode sheet 1021 away from the negative electrode tab side 1022 punctures the diaphragm and is more likely to contact the positive electrode tab 1024. In this embodiment, a first insulating layer is provided at the edge of the material area of ​​the negative electrode sheet 1021 away from the negative electrode tab side 1022, which can greatly improve the stability of the cylindrical battery with flattened tabs.

[0076] As shown in FIG15 , FIG15 is a schematic diagram of the structure of a battery pack 1 provided in an embodiment of the present application. An embodiment of the present application also provides a battery pack 1. The battery pack 1 includes a plurality of cylindrical batteries 10, which are connected in series or in parallel. The battery pack 1 also includes a box body 20, which includes a box cover 201 and a box body 202. The box cover 201 covers the box body 202 to form a closed cylindrical battery mounting cavity. Multiple cylindrical batteries 10 are arranged in the cylindrical battery mounting cavity.

Claims

1. A cylindrical battery comprising: The housing (101) has a receiving cavity (1014); An electrode assembly (102) is arranged in the accommodating cavity (1014); the electrode assembly (102) comprises a positive electrode sheet, a separator and a negative electrode sheet (1021) which are stacked and wound; a positive electrode tab (1024) of the positive electrode sheet and a negative electrode tab (1022) of the negative electrode sheet (1021) are located at two ends of the electrode assembly (102); A first insulating layer (103) is provided on the surface of the negative electrode sheet (1021) facing the separator, and the first insulating layer (103) is located at an end of the surface away from the negative electrode tab (1022).

2. The cylindrical battery according to claim 1, wherein: The dimension of the first insulating layer (103) in the thickness direction of the negative electrode sheet (1021) is d, which satisfies: ； in, S is the length of the negative electrode sheet (1021) (mm); r is the radius (mm) of the winding needle used when winding to form the electrode assembly (102); a is the thickness of the positive electrode sheet (mm); b is the thickness of the diaphragm (mm); D is the thickness of the negative electrode sheet (1021) (mm); n is the number of turns of the negative electrode sheet (1021).

3. The cylindrical battery according to claim 2, wherein: The dimension d of the first insulating layer (103) in the thickness direction of the negative electrode sheet (1021) also satisfies: ； in, R is the radius (mm) of the shell (101).

4. The cylindrical battery according to claim 1, wherein: The first insulating layer (103) comprises a plurality of first sub-insulating layers (1031), wherein the plurality of first sub-insulating layers (1031) are arranged on the same side of the negative electrode sheet (1021), and the plurality of first sub-insulating layers (1031) are stacked in sequence along the thickness direction of the negative electrode sheet (1021).

5. The cylindrical battery according to any one of claims 1 to 4, wherein: The first insulating layer (103) includes a plurality of first sub-insulating layers (1031); the negative electrode sheet (1021) has a first side and a second side opposite to each other; part of the first sub-insulating layer (1031) is arranged on the first side, and the rest of the first sub-insulating layer (1031) is arranged on the second side; the first sub-insulating layers (1031) located on the same side of the negative electrode sheet (1021) are stacked in sequence along the thickness direction of the negative electrode sheet (1021).

6. The cylindrical battery according to claim 4 or 5, wherein: From one side of the negative electrode sheet (1021) to the other side of the negative electrode sheet (1021), the dimensions of the multi-layer first sub-insulating layer (1031) in the thickness direction of the negative electrode sheet (1021) are d1, d2, ..., d i , where i is a natural number, i≥2, and satisfies: 0.15<d1:d i ≤1.

7. The cylindrical battery according to any one of claims 1 to 6, wherein: One end face of the negative electrode sheet (1021) in the longitudinal direction is a first end face, the first end face is located at the periphery of the electrode assembly (102), and a second insulating layer (104) is provided on the first end face.

8. The cylindrical battery according to claim 7, wherein: The second insulating layer (104) covers the first end surface.

9. The cylindrical battery according to claim 7 or 8, wherein: The dimension of the second insulating layer (104) in the thickness direction of the negative electrode sheet (1021) is L2, the thickness of the negative electrode sheet (1021) is D, and the following conditions are satisfied: D≤L2≤50 mm; the dimension of the second insulating layer (104) in the length direction of the negative electrode sheet (1021) is d0, and the following conditions are satisfied: 0.001 mm≤d0≤10 mm.

10. The cylindrical battery according to any one of claims 1 to 9, wherein: The positive electrode tab (1024) and the negative electrode tab (1022) are both flattened tabs.

11. A battery pack, comprising a plurality of cylindrical batteries (10) according to any one of claims 1 to 10, wherein the plurality of cylindrical batteries (10) are connected in series or in parallel.

Images