Negative plate and electrode assembly
By setting an insulating and thermally conductive layer on the inner side of the negative electrode winding, the problem of heat dissipation near the tab of the lithium-ion battery is solved, thereby improving the heat dissipation efficiency and cycle life of the electrode assembly.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-01
- Publication Date
- 2026-03-31
AI Technical Summary
The temperature near the tabs of wound lithium-ion batteries is high and heat dissipation is difficult, resulting in a high temperature inside the cell, rapid electrolyte consumption, side reactions, and reduced battery cycle life.
An insulating and heat-conducting layer is placed on the inner side of the negative electrode sheet near the tab, so that it is located between the tab and the active material layer, thereby increasing the distance between the tab and the active material layer and improving heat dissipation efficiency.
By setting an insulating and thermally conductive layer, the heat dissipation efficiency of the inner layer of the electrode assembly is improved, side reactions are reduced, and the cycle life of the electrode assembly is increased.
Smart Images
Figure CN224067659U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of battery technology, specifically to a negative electrode sheet and electrode assembly. Background Technology
[0002] With the widespread application of lithium-ion batteries, in order to enhance product competitiveness and achieve the performance requirements of end products, lithium-ion batteries are exhibiting diversified size characteristics, while increasingly higher demands are being placed on the long cycle life of lithium-ion batteries. Currently, wound "long, narrow, and thick" lithium-ion batteries are prone to interface deterioration after long cycles, especially near the tabs, where high temperatures and poor heat dissipation lead to higher temperatures in the inner layers of the cell, faster electrolyte consumption, insufficient protection of the negative electrode by the electrolyte in the later stages, resulting in more side reactions, deterioration of capacity and thickness performance, and thus affecting the battery's cycle life. Therefore, overcoming the above-mentioned technical problems and defects has become a key issue that needs to be addressed. Utility Model Content
[0003] To address the problem of high temperature and difficulty in heat dissipation near the electrode tabs in existing batteries, this invention provides a negative electrode sheet and electrode assembly.
[0004] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows:
[0005] This utility model provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode tab;
[0006] Along the length of the negative electrode sheet, a first empty foil area, a first insulating and thermally conductive layer, and a first active material layer are provided on the first side of the negative electrode sheet; the negative electrode tab is disposed in the first empty foil area;
[0007] Along the length of the negative electrode sheet, a second empty foil area, a second insulating and thermally conductive layer, and a second active material layer are provided on the second side of the negative electrode sheet;
[0008] The first empty foil area and the second empty foil area are located on opposite sides of the starting end of the winding of the negative electrode sheet;
[0009] When winding the battery cell, the first side is located inside the winding of the negative electrode sheet, and the second side is located outside the winding of the negative electrode sheet.
[0010] Optionally, the first side of the negative electrode sheet is further provided with a third empty foil region, the third empty foil region being spaced between the first insulating and thermally conductive layer and the first active material layer; and / or,
[0011] The second side of the negative electrode sheet is also provided with a fourth empty foil area, which is spaced between the second insulating and thermally conductive layer and the second active material layer.
[0012] Optionally, the current collector includes multiple straight regions and multiple arc regions, which are alternately arranged, and sequentially include a first straight region, a first arc region, a second straight region, a second arc region, a third straight region, ... an nth straight region from the starting end to the ending end of the winding of the negative electrode sheet; the first empty foil region and the second empty foil region are located in the first straight region.
[0013] Optionally, the first insulating and thermally conductive layer is located in the first flat area and the first arc area.
[0014] Optionally, the second insulating and thermally conductive layer is located in the first flat area, the first arc area, the second flat area, and the second arc area.
[0015] Optionally, the thickness of the first insulating and thermally conductive layer is h1, in μm; the thickness of the first active material layer is h2, in μm; and h1 and h2 satisfy the relationship: 0.5≤h1 / h2≤1.
[0016] Optionally, the thickness of the second insulating and thermally conductive layer is h3, in μm; the thickness of the second active material layer is h4, in μm; and h3 and h4 satisfy the relationship: 0.5≤h3 / h4≤1.
[0017] Optionally, the distance between the negative electrode tab and the first insulating and thermally conductive layer is L1, in mm; the value of L1 is in the range of 2mm≤L1≤10mm.
[0018] Optionally, the width of the third empty foil area is 2-6 mm; and / or, the width of the fourth empty foil area is 2-6 mm.
[0019] Optionally, the first insulating thermal conductive layer and the second insulating thermal conductive layer are each independently selected from one of the following: boron nitride insulating thermal conductive layer, alumina insulating thermal conductive layer, silicon carbide insulating thermal conductive layer, and polyimide insulating thermal conductive layer.
[0020] In another aspect, this utility model provides an electrode assembly, including the negative electrode sheet as described above.
[0021] Optionally, the length of the electrode assembly is L2 in mm; the width of the electrode assembly is L3 in mm; and the thickness of the electrode assembly is L4 in mm. The L2, L3, and L4 satisfy the following relationships: 1 ≤ L2 / L3 ≤ 5; 5 mm ≤ L4.
[0022] According to the negative electrode sheet provided by this utility model, an insulating and thermally conductive layer is provided on the inner side of the negative electrode sheet near the tab, and the insulating and thermally conductive layer is disposed between the tab and the active material layer; the insulating and thermally conductive layer has the advantage of good thermal conductivity, and can also increase the distance between the tab and the active material layer, thereby improving the heat dissipation efficiency of the inner layer of the electrode assembly; the negative electrode sheet structure of this application can solve the problem of slow heat dissipation of the inner layer of the electrode assembly, reduce the side reactions generated by the negative electrode sheet, and improve the cycle life of the electrode assembly. Attached Figure Description
[0023] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 This is a top view schematic diagram of the negative electrode sheet provided in an embodiment of this utility model;
[0025] Figure 2 This is a schematic diagram of the structure of the first side of the negative electrode sheet provided in an embodiment of the present invention;
[0026] Figure 3 This is a schematic diagram of the structure of the second side of the negative electrode sheet provided in an embodiment of the present invention;
[0027] Figure 4 This is a schematic diagram of the structure of an electrode assembly provided in an embodiment of the present invention;
[0028] The reference numerals in the accompanying drawings are as follows:
[0029] 10-Negative electrode sheet; 1-Negative current collector; 11-Straight region; 12-Circular arc region; 2-Negative electrode tab; 3-First side; 31-First empty foil region; 32-First insulating and thermally conductive layer; 33-First active material layer; 34-Third empty foil region; 4-Second side; 41-Second empty foil region; 42-Second insulating and thermally conductive layer; 43-Second active material layer; 44-Fourth empty foil region; 100-Electrode assembly; 20-Positive electrode sheet; 30-Separator. Detailed Implementation
[0030] To make the technical problems solved, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.
[0031] In the description of this utility model, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.
[0032] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0033] like Figures 1-3 As shown, in one embodiment, the present invention provides a negative electrode 10, which includes a negative current collector 1 and a negative electrode tab 2;
[0034] Along the length of the negative electrode sheet 10, the first side 3 of the negative electrode sheet 10 is provided with a first empty foil area 31, a first insulating and thermally conductive layer 32 and a first active material layer 33; the negative electrode tab 2 is provided in the first empty foil area 31;
[0035] Along the length of the negative electrode 10, the second side 4 of the negative electrode 10 is provided with a second empty foil area 41, a second insulating and heat-conducting layer 42, and a second active material layer 43;
[0036] The first empty foil region 31 and the second empty foil region 41 are located on opposite sides of the starting end of the winding of the negative electrode sheet 10;
[0037] When the electrode assembly 100 is wound, the first side 3 is located inside the winding of the negative electrode 10, and the second side 4 is located outside the winding of the negative electrode 10.
[0038] Specifically, because heat tends to accumulate in the inner layer of the electrode assembly 100, the heat transfer efficiency of the inner layer is low and the heat dissipation is slow. Especially near the tab, the temperature is high and heat dissipation is difficult, resulting in a higher temperature in the inner layer of the electrode assembly 100. The electrolyte is consumed faster, which leads to insufficient protection of the negative electrode 10 by the electrolyte in the later stage. The negative electrode 10 is prone to more side reactions, and the capacity and thickness performance of the electrode assembly 100 deteriorates, thereby affecting the cycle life of the electrode assembly 100.
[0039] Specifically, for the sake of simplicity in the following description, the first insulating and thermally conductive layer 32 and the second insulating and thermally conductive layer 42 are collectively referred to as the insulating and thermally conductive layer; the first active material layer 33 and the second active material layer 43 are collectively referred to as the active material layer.
[0040] In this application, an insulating and thermally conductive layer is provided on the inner side of the negative electrode 10 near the electrode tab. The insulating and thermally conductive layer is disposed between the electrode tab and the active material layer. The insulating and thermally conductive layer has the advantage of good thermal conductivity and can increase the distance between the electrode tab and the active material layer, thereby improving the heat dissipation efficiency of the inner layer of the electrode assembly 100.
[0041] The negative electrode 10 structure of this application can solve the problem of slow heat dissipation in the inner layer of the electrode assembly 100, reduce the side reactions generated by the negative electrode 10, and improve the cycle life of the electrode assembly 100.
[0042] like Figure 2 As shown, in one embodiment, the first side 3 of the negative electrode 10 is further provided with a third empty foil region 34, which is spaced between the first insulating and thermally conductive layer 32 and the first active material layer 33; and / or,
[0043] The second side 4 of the negative electrode 10 is also provided with a fourth empty foil region 44, which is spaced between the second insulating and thermally conductive layer 42 and the second active material layer 43.
[0044] The third empty foil area 34 provided between the first insulating and thermally conductive layer 32 and the first active material layer 33 serves to reserve space for the coating tail of the active material, and the coating tail can fall at this place.
[0045] The fourth empty foil area 44 is provided between the second insulating and thermally conductive layer 42 and the second active material layer 43 to reserve space for the coating tail of the active material, and the coating end can fall in this area.
[0046] like Figure 4 As shown, in one embodiment, the current collector includes multiple straight regions 11 and multiple arc regions 12, which are alternately arranged. Along the starting end of the winding of the negative electrode sheet 10, it includes a first straight region, a first arc region, a second straight region, a second arc region, ... an nth straight region. The first empty foil region 31 and the second empty foil region 41 are located in the first straight region.
[0047] The first empty foil region 31 and the second empty foil region 41 are located in the first flat region. The negative electrode tab 2 is located in the first empty foil region 31. The electrode tab is closer to the active material layer, which has the effect of improving welding strength and reducing contact resistance.
[0048] Furthermore, the length direction of the negative electrode sheet 10 is the length direction of the first empty foil area 31 and the second empty foil area 41. The lengths of the first empty foil area 31 and the second empty foil area 41 are the same, thereby preventing the negative electrode sheet 10 from breaking due to misalignment of the two fabric areas during rolling.
[0049] like Figures 1-2 As shown, in one embodiment, the first insulating and thermally conductive layer 32 is located in the first arc region and the second flat region.
[0050] A first insulating and thermally conductive layer 32 is provided on the inner side of the winding of the negative electrode sheet 10. The first insulating and thermally conductive layer 32 is located in the first flat area and the first arc area. The first insulating and thermally conductive layer 32 is disposed between the electrode tab and the first active material layer 33. The first insulating and thermally conductive layer 32 has the advantage of good thermal conductivity and can increase the distance between the electrode tab and the first active material layer 33, thereby improving the heat dissipation efficiency of the inner layer of the electrode assembly 100.
[0051] like Figures 1-2 As shown, in one embodiment, the second insulating and thermally conductive layer 42 is located in the first flat region, the first arc region, the second flat region, and the second arc region.
[0052] A second insulating and thermally conductive layer 42 is provided on the outer side of the negative electrode sheet 10. The second insulating and thermally conductive layer 42 is located in the first arc region, the second flat region, the second arc region, and the third flat region. The second insulating and thermally conductive layer 42 is disposed between the second empty foil region 41 and the second active material layer 43. The second insulating and thermally conductive layer 42 has the advantage of good thermal conductivity and can increase the distance between the electrode tab and the second active material layer 43, thereby improving the heat dissipation efficiency of the inner layer of the electrode assembly 100.
[0053] Furthermore, the length of the second insulating and thermally conductive layer 42 is greater than that of the first insulating and thermally conductive layer 32, thereby achieving the function of filling the first insulating and thermally conductive layer 32 in the first empty foil area 31 and the second insulating and thermally conductive layer 42 in the second empty foil area 41 without changing the original design of the electrode assembly 100, and also making the thickness distribution of the first active material layer 33 and the second active material layer 43 on both sides of the negative electrode sheet 10 uniform.
[0054] like Figures 1-2 As shown, in one embodiment, the thickness of the first insulating and thermally conductive layer 32 is h1, in μm; the thickness of the first active material layer 33 is h2, in μm; h1 and h2 satisfy the relationship: 0.5≤h1 / h2≤1.
[0055] Specifically, the ratio of the thickness of the first insulating and thermally conductive layer 32 to the thickness of the first active material layer 33 is any one value or a range of any two values from 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or 1; in a preferred embodiment, the ratio of the thickness of the first insulating and thermally conductive layer 32 to the thickness of the first active material layer 33 is 0.6-0.9.
[0056] When the ratio of the thickness of the first insulating thermally conductive layer 32 to the thickness of the first active material layer 33 is 0.5-1, it significantly improves the internal heat dissipation of the electrode assembly 100 without affecting the internal thickness expansion of the electrode assembly 100. When the ratio of the thickness of the first insulating thermally conductive layer 32 to the thickness of the first active material layer 33 is less than 0.5, the thickness of the first insulating thermally conductive layer 32 is too thin and cannot achieve the purpose of heat dissipation; when the ratio of the thickness of the first insulating thermally conductive layer 32 to the thickness of the first active material layer 33 is greater than 1, it will cause bulging inside the electrode assembly 100 and uneven thickness distribution.
[0057] like Figures 1-2 As shown, in one embodiment, the thickness of the second insulating and thermally conductive layer 42 is h3, in μm; the thickness of the second active material layer 43 is h4, in μm; h3 and h4 satisfy the relationship: 0.5≤h3 / h4≤1.
[0058] Specifically, the ratio of the thickness of the second insulating and thermally conductive layer 42 to the thickness of the second active material layer 43 is any one value or a range of any two values from 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1; in a preferred embodiment, the ratio of the thickness of the second insulating and thermally conductive layer 42 to the thickness of the second active material layer 43 is 0.6-0.9.
[0059] When the ratio of the thickness of the second insulating and thermally conductive layer 42 to the thickness of the second active material layer 43 is 0.5-1, it significantly improves the internal heat dissipation of the electrode assembly 100 without affecting the internal thickness expansion of the electrode assembly 100. When the ratio of the thickness of the second insulating and thermally conductive layer 42 to the thickness of the second active material layer 43 is less than 0.5, the thickness of the second insulating and thermally conductive layer 42 will be too thin, failing to achieve the purpose of heat dissipation; when the ratio of the thickness of the second insulating and thermally conductive layer 42 to the thickness of the second active material layer 43 is greater than 1, it will cause bulging inside the electrode assembly 100 and uneven thickness distribution.
[0060] like Figures 1-2 As shown, in one embodiment, the distance between the negative electrode tab 2 and the first insulating and heat-conducting layer 32 is L1, in mm; the value of L1 ranges from 2 mm ≤ L1 ≤ 10 mm.
[0061] Specifically, the distance between the negative electrode tab 2 and the first insulating and heat-conducting layer 32 is any one value or any two values from 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm; in a preferred embodiment, the distance between the negative electrode tab 2 and the first insulating and heat-conducting layer 32 is 2mm≤L1≤5mm.
[0062] When the distance between the negative electrode tab 2 and the first insulating and thermally conductive layer 32 is 2mm ≤ L1 ≤ 10mm, it reduces the adhesive application distance. Only a 12-15mm wide strip of conventional adhesive tape is needed to cover the burrs at the end of the material area and the welding burrs of the negative electrode tab 2, without wasting the empty foil area. When the distance between the negative electrode tab 2 and the first insulating and thermally conductive layer 32 is less than 2mm, dust generated by the welding vibration of the negative electrode sheet 10 falls on the welding position, resulting in poor welding. When the distance between the negative electrode tab 2 and the first insulating and thermally conductive layer 32 is greater than 5mm, it will cause the adhesive application size to become wider and waste the area of the first empty foil area 31. When the distance between the negative electrode tab 2 and the first insulating and thermally conductive layer 32 is greater than 10mm, a wider strip of adhesive tape is required, increasing the process difficulty.
[0063] like Figures 1-2 As shown, in one embodiment, the width of the third empty foil area 34 is 2-6 mm; and / or, the width of the fourth empty foil area 44 is 2-6 mm.
[0064] Specifically, the width of the third empty foil area 34 is any one value or any two values from 0mm, 1mm, 2mm, 3mm, 4mm, 5mm or 6mm; in a preferred embodiment, the width of the third empty foil area 34 is 2-4mm.
[0065] When the width of the third empty foil area 34 is 2-6mm, it provides space for coating tailing, resulting in a tailing area at the end of the coating process. This tailing space allows for independent adjustment of the coating direction, ensuring that the starting end of the coating of the first active material layer 33 and the ending end of the coating of the first insulating and thermally conductive layer 32 can both be located in the third empty foil area 34. When the width of the third empty foil area 34 is less than 2mm, the coating direction becomes fixed, and the ending end of the coating of the first insulating and thermally conductive layer 32 cannot fall into the third empty foil area 34. When the width of the third empty foil area 34 is greater than 6mm, the utilization rate of the third empty foil area 34 becomes insufficient, and the adhesive tape covering the first active material layer 33 and the first insulating and thermally conductive layer 32 becomes wider.
[0066] Specifically, the width of the fourth empty foil area 44 is any one value or a range of any two values among 2mm, 3mm, 4mm, 5mm or 6mm; in a preferred embodiment, the width of the fourth empty foil area 44 is 2-4mm.
[0067] When the width of the fourth empty foil area 44 is 2-6mm, it provides space for coating tailing, resulting in a tailing area at the end of the coating process. This tailing space allows for independent adjustment of the coating direction, ensuring that the starting end of the second active material layer 43 and the ending end of the second insulating and thermally conductive layer 42 can both be located in the fourth empty foil area 44. When the width of the fourth empty foil area 44 is less than 2mm, the coating direction becomes fixed, and the ending end of the second insulating and thermally conductive layer 42 coating cannot fall into the fourth empty foil area 44. When the width of the fourth empty foil area 44 is greater than 6mm, the utilization rate of the fourth empty foil area 44 becomes insufficient, and the adhesive tape covering the second active material layer 43 and the second insulating and thermally conductive layer 42 becomes wider.
[0068] like Figures 1-2 As shown, in one embodiment, the first insulating thermally conductive layer 32 and the second insulating thermally conductive layer 42 are each independently selected from one of the following: boron nitride insulating thermally conductive layer, alumina insulating thermally conductive layer, silicon carbide insulating thermally conductive layer, and polyimide insulating thermally conductive layer.
[0069] Choosing one of the following as the first insulating thermally conductive layer 32, the second insulating thermally conductive layer 42—boron nitride insulating thermally conductive layer, alumina insulating thermally conductive layer, silicon carbide insulating thermally conductive layer, or polyimide insulating thermally conductive layer—not only has the advantage of good thermal conductivity, but also increases the spacing between the tab and the active material layer. This solves the problem of slow heat dissipation in the inner layer of the electrode assembly 100, improves the heat dissipation efficiency of the inner layer of the electrode assembly 100, reduces the side reactions generated by the negative electrode 10, and improves the cycle life of the electrode assembly 100.
[0070] In another aspect, this utility model provides an electrode assembly 100, including the negative electrode 10 as described above.
[0071] The electrode assembly 100 of this application includes a positive electrode 20, a negative electrode 10 and a separator 30. The separator 30 is placed between the positive electrode 20 and the negative electrode 10 and is formed by winding. The electrode assembly 100 of this application has the advantages of high heat dissipation efficiency, few side reactions of the negative electrode 10 and high cycle life.
[0072] like Figures 1-2 As shown, in one embodiment, the length of the electrode assembly 100 is L2, in mm; the width of the electrode assembly 100 is L3, in mm; and the thickness of the electrode assembly 100 is L4, in mm. L2, L3, and L4 satisfy the following relationships: 1 ≤ L2 / L3 ≤ 5; 5 mm ≤ L4.
[0073] When L2, L3, and L4 satisfy the relationship: 1≤L2 / L3≤5; 5mm≤L4, it is a long, narrow, and thick electrode assembly 100 recognized in the art. In this application, an insulating and thermally conductive layer is provided on the inner side of the negative electrode sheet 10 near the negative electrode tab 2. The insulating and thermally conductive layer is disposed between the negative electrode tab 2 and the active material layer. The insulating and thermally conductive layer has the advantage of good thermal conductivity and can increase the distance between the negative electrode tab 2 and the active material layer, thereby improving the heat dissipation efficiency of the inner layer of the electrode assembly 100.
[0074] The negative electrode 10 structure of this application can solve the problem of slow heat dissipation in the inner layer of the electrode assembly 100, reduce the side reactions generated by the negative electrode 10, and improve the cycle life of the electrode assembly 100.
[0075] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.
Claims
1. A negative electrode sheet, characterized by: The negative electrode sheet comprises a negative electrode current collector and a negative electrode tab; The first side of the negative electrode sheet is provided with a first empty foil area, a first insulating and heat conducting layer and a first active material layer along the length direction of the negative electrode sheet; and the negative electrode tab is arranged in the first empty foil area; The second side of the negative electrode sheet is provided with a second empty foil area, a second insulating and heat conducting layer and a second active material layer along the length direction of the negative electrode sheet; The first empty foil area and the second empty foil area are located on opposite sides of the winding starting end of the negative electrode sheet; During winding of the battery cell, the first side is located on the winding inner side of the negative electrode sheet, and the second side is located on the winding outer side of the negative electrode sheet.
2. The negative electrode sheet according to claim 1, characterized by: The first side of the negative electrode sheet is further provided with a third empty foil area, and the third empty foil area is spaced between the first insulating and heat conducting layer and the first active material layer; and / or, The second side of the negative electrode sheet is further provided with a fourth empty foil area, and the fourth empty foil area is spaced between the second insulating and heat conducting layer and the second active material layer.
3. The negative electrode sheet according to claim 2, characterized by: The current collector comprises a plurality of flat areas and a plurality of circular arc areas, the plurality of flat areas and the plurality of circular arc areas are arranged alternately, and sequentially comprise a first flat area, a first circular arc area, a second flat area, a second circular arc area, a third flat area,..., and an n-th flat area from the winding starting end to the winding ending end of the negative electrode sheet; the first empty foil area and the second empty foil area are located in the first flat area.
4. The negative electrode sheet according to claim 3, characterized by: The first insulating and heat conducting layer is located in the first flat area and the first circular arc area.
5. The negative electrode sheet according to claim 3, characterized by: The second insulating and heat conducting layer is located in the first flat area, the first circular arc area, the second flat area and the second circular arc area.
6. The negative electrode sheet according to claim 1, characterized by: The thickness of the first insulating and heat conducting layer is h1, unit: μm; the thickness of the first active material layer is h2, unit: μm; the h1 and the h2 satisfy the relationship: 0.5≤h1 / h2≤1.
7. The negative electrode sheet according to claim 1, characterized by: The thickness of the second insulating and heat conducting layer is h3, unit: μm; the thickness of the second active material layer is h4, unit: μm; the h3 and the h4 satisfy the relationship: 0.5≤h3 / h4≤1.
8. The negative electrode sheet according to claim 7, characterized by: The distance between the negative electrode tab and the first insulating and heat conducting layer is L1, unit: mm; the value range of the L1 is 2mm≤L1≤10mm.
9. The negative electrode sheet according to claim 2, characterized by: The width of the third empty foil area is 2-6mm; and / or, the width of the fourth empty foil area is 2-6mm.
10. The negative electrode sheet according to claim 1, characterized by: The first insulating and heat conducting layer and the second insulating and heat conducting layer are each independently selected from one of a boron nitride insulating and heat conducting layer, an aluminum oxide insulating and heat conducting layer, a silicon carbide insulating and heat conducting layer, and a polyimide insulating and heat conducting layer.
11. An electrode assembly characterized by: The electrode assembly comprises the negative electrode sheet according to any one of claims 1-10.
12. The electrode assembly of claim 11, wherein: The length of the electrode assembly is L2, unit: mm; the width of the electrode assembly is L3, unit: mm; the thickness of the electrode assembly is L4, unit: mm; the L2, the L3 and the L4 satisfy the relationship: 1≤L2 / L3≤5; 5mm≤L4.