Electrode plate, winding battery cell and electric equipment
By setting a thicker transition section on the electrode sheet, the problems of poor electrolyte wetting and insufficient strength in the battery bending area are solved, thereby improving the battery's safety and cycle performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-28
- Publication Date
- 2026-04-07
AI Technical Summary
During battery cycling, the small distance between the electrode plates and the separator in the bending area and the low electrolyte content result in poor electrolyte wetting and lithium plating problems.
A thicker transition section is provided on the electrode sheet. The transition section is located at the junction of the straight area and the bending area. This increases the electrolyte storage capacity in the bending area, improves the wetting effect, and enhances the strength of the transition area to prevent breakage.
It improves the electrolyte wetting effect in the bending area, reduces the risk of lithium plating, enhances battery safety and cycle performance, and prevents coating cracking or peeling.
Smart Images
Figure CN224096688U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to a battery technical field, concretely relates to an electrode sheet, winding electric core and electric equipment. BACKGROUND
[0002] The battery will exist the problem of lithium precipitation in the circulation process, especially the battery with the bending structure (such as winding structure). After forming, the spacing between the electrode sheet and the diaphragm in the bending area (or called arc) is often small, the electrolyte content is less, and the electrolyte infiltration effect is poor, which leads to the problem of lithium precipitation in the bending area. SUMMARY
[0003] Therefore, the utility model provides an electrode sheet, winding electric core and electric equipment to solve the problem of lithium precipitation in the bending area of the electrode sheet.
[0004] In a first aspect, the utility model provides an electrode sheet applied to a winding electric core, the electrode sheet is wound along the length direction to form a bending area and a straight area connected with each other, the electrode sheet comprises: a current collector, along the thickness direction of the electrode sheet, the current collector has two surfaces arranged oppositely; a functional layer arranged on at least one surface of the current collector; the functional layer comprises at least two first coating layers and at least one second coating layer, the first coating layer and the second coating layer are arranged alternately along the length direction of the electrode sheet; a transition part is arranged between the adjacent first coating layer and the second coating layer; the first coating layer is located in the straight area, and the second coating layer is located in the bending area; along the length direction of the electrode sheet, the transition part connects the adjacent first coating layer and the second coating layer; along the length direction of the electrode sheet, the thickness of at least one transition part connected to the two end sides of the second coating layer along the thickness direction of the electrode sheet is greater than the thickness of the second coating layer along the thickness direction of the electrode sheet.
[0005] In an alternative embodiment, along the length direction of the electrode sheet, the electrode sheet comprises a plurality of folding areas arranged in sequence, each folding area comprises a group of first coating layers, second coating layers and two transition parts located at the two end sides of the second coating layer; the two transition parts at the two end sides of the second coating layer are respectively a first transition part and a second transition part; one end of the electrode sheet along the length direction is a winding starting end, the folding area comprises a first folding area and a plurality of second folding areas arranged in sequence along the length direction of the electrode sheet, and the first folding area is close to the winding starting end; in the first folding area, at least one transition part located at the two end sides of the second coating layer is located in the straight area; and / or, in the second folding area, the second coating layer and the two transition parts are all located in the bending area; and / or, along the thickness direction of the electrode sheet, the thickness of the first transition part is greater than or equal to the thickness of the second transition part.
[0006] In an alternative embodiment, along the thickness direction of the electrode sheet, the thickness of at least one transition part located at the two end sides of the second coating layer is greater than the thickness of the first coating layer.
[0007] In one alternative embodiment, a functional layer is disposed on two surfaces of the current collector along the thickness direction of the electrode sheet; wherein the first transition portions of the functional layers on the two surfaces are staggered in the thickness direction of the electrode sheet.
[0008] In one optional embodiment, the electrode sheet is a positive electrode sheet, which includes a current collector and a functional layer; wherein, the delithiation capabilities of the first coating and the second coating of the positive electrode sheet are different; the delithiation capability of the second coating of the positive electrode sheet is less than that of the first coating; or, the specific capacity of the second coating of the positive electrode sheet is less than that of the first coating; or, the delithiation capabilities of the first coating and the second coating of the positive electrode sheet are the same; the areal density of the second coating of the positive electrode sheet is less than that of the first coating; or, the electrode sheet is a negative electrode sheet, which includes a current collector and a functional layer; wherein, the lithium intercalation capabilities of the first coating and the second coating of the negative electrode sheet are different; the lithium intercalation capability of the second coating of the negative electrode sheet is greater than that of the first coating; or, the specific capacity of the second coating of the negative electrode sheet is greater than that of the first coating; or, the lithium intercalation capabilities of the first coating and the second coating of the negative electrode sheet are the same; the areal density of the second coating of the negative electrode sheet is greater than that of the first coating.
[0009] In one optional embodiment, the first coating and the second coating have different delithiation or lithium insertion capabilities; the first transition portion includes a first sub-portion and a second sub-portion, the first sub-portion having the same delithiation or lithium insertion capability as the first coating, and the second sub-portion having the same delithiation or lithium insertion capability as the second coating; along the thickness direction of the electrode sheet, the second sub-portion covers the side of the first sub-portion away from the current collector; and / or, the second transition portion includes a third sub-portion and a fourth sub-portion, the third sub-portion having the same delithiation or lithium insertion capability as the first coating, and the fourth sub-portion having the same delithiation or lithium insertion capability as the second coating; along the thickness direction of the electrode sheet, the fourth sub-portion covers the side of the third sub-portion away from the current collector; or, the third sub-portion and the fourth sub-portion are fused together.
[0010] In one optional embodiment, along the thickness direction of the electrode sheet, the thickness of the first coating is H1, the thickness of the second coating is H2, and the thickness of the transition portion is H3; wherein, the thickness H3 of the transition portion satisfies: 0.005mm≤H3≤1mm; and / or, the thickness H1 of the first coating and the thickness H3 of the transition portion satisfy: H1≤H3≤1.8H1; and / or, the thickness H2 of the second coating and the thickness H3 of the transition portion satisfy: H2≤H3≤3H2; and / or, along the length direction of the electrode sheet, the length of the second coating is S2, and the length of the transition portion is S3; wherein, the length S2 of the second coating and the length S3 of the transition portion satisfy: 0.0025S2≤S3≤0.5S2.
[0011] Secondly, this utility model also provides a wound battery cell, comprising: a positive electrode sheet, a negative electrode sheet, and a separator, wherein the positive electrode sheet, the negative electrode sheet, and the separator are stacked and wound around a winding center to form a wound structure; the positive electrode sheet and / or the negative electrode sheet are the aforementioned electrode sheets.
[0012] In one optional embodiment, the positive electrode sheet is the electrode sheet described above. The positive electrode sheet includes a first surface near the winding center and a second surface away from the winding center. The second coating of the positive electrode sheet includes a first sub-coating disposed on the first surface and a second sub-coating disposed on the second surface. The first sub-coating and the second sub-coating have different delithiation capabilities, with the first sub-coating having a lower delithiation capability than the second sub-coating. Alternatively, the specific capacity of the first sub-coating is lower than that of the second sub-coating. Or, the delithiation capabilities of the first sub-coating and the second sub-coating are the same, with the areal density of the first sub-coating being lower than that of the second sub-coating.
[0013] In one optional embodiment, the negative electrode sheet is the electrode sheet described above. The negative electrode sheet includes a third surface near the winding center and a fourth surface away from the winding center. The second coating of the negative electrode sheet includes a third sub-coating disposed on the third surface and a fourth sub-coating disposed on the fourth surface. The lithium intercalation capabilities of the third sub-coating and the fourth sub-coating are different, and the lithium intercalation capability of the fourth sub-coating is greater than that of the third sub-coating. Alternatively, the specific capacity of the fourth sub-coating is greater than that of the third sub-coating. Alternatively, the lithium intercalation capabilities of the third sub-coating and the fourth sub-coating are the same, and the areal density of the fourth sub-coating is less than that of the third sub-coating.
[0014] Thirdly, this utility model also provides an electrical device, including: an electrode sheet as described above; or a wound battery cell as described above.
[0015] Using the technical solution of this utility model, a transition section is provided between the first coating and the second coating. After the electrode sheet is wound, the first coating is located in the flat area, and the second coating is located in the bent area, that is, the transition section is located at the junction of the flat area and the bent area. Moreover, the thickness of at least one of the transition sections on both ends of the second coating is greater than that of the second coating. In this way, the two transition sections on both ends of the second coating can form a liquid storage tank in the bent area, increasing the amount of electrolyte stored in the bent area. Furthermore, the thicker transition section can increase the spacing between adjacent bent areas formed after the electrode sheet is wound, which is equivalent to increasing the channel for electrolyte to enter the bent area, improving the electrolyte wetting rate in the bent area, thereby improving the electrolyte wetting effect in the bent area, reducing the risk of lithium plating in the bent area, and improving the safety of the battery.
[0016] Furthermore, due to the structural characteristics of wound batteries, the stresses experienced by their straight and bent areas differ, with the electrode sheets closer to the bent area experiencing greater stress. During battery manufacturing and use, the transition area between the straight and bent areas of the wound cell experiences uneven stress, and stress concentration easily occurs in the bent area. Therefore, during cycling, fractures are prone to occur in the transition and bent areas. Additionally, the coating in the bent area may be subjected to significant physical stress, leading to cracks or peeling of the coating. The technical solution of this application has the following advantages: First, the thicker transition portion enhances the strength of the transition area between the straight and bent regions, enabling it to withstand greater stress changes and preventing tearing or breakage due to different stresses. Second, the thicker transition portion increases the spacing between adjacent bent regions formed after the electrode sheets are wound, preventing breakage caused by excessive expansion stress after battery cycling. Third, the thickness of the transition portion is greater than the thickness of the second coating, causing stress to preferentially act on or be compressed in the thicker transition portion after battery expansion, reducing or improving the problem of cracking or peeling of the coating in the bent region due to excessive stress. Attached Figure Description
[0017] To more clearly illustrate the specific embodiments of this utility model 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 this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0018] Figure 1 This is a planar schematic diagram of an electrode sheet according to an embodiment of the present utility model;
[0019] Figure 2 This is a side view of an electrode sheet according to an embodiment of the present invention;
[0020] Figure 3 This is a side view of an electrode sheet according to another embodiment of the present invention;
[0021] Figure 4 A schematic diagram of the structure of a battery cell using the electrode sheet of this utility model;
[0022] Figure 5 for Figure 4 A magnified view of part A in the diagram;
[0023] Figure 6 for Figure 4 A magnified view of part B in the diagram;
[0024] Figure 7 for Figure 4 A magnified view of part of C;
[0025] Figure 8 A partial structural schematic diagram of a battery cell using the electrode sheet of this utility model;
[0026] Figure 9 This is a cross-sectional view of the microstructure when the first and second coatings overlap each other;
[0027] Figure 10 This is a cross-sectional view of the microstructure of the first and second coatings in the fused state.
[0028] Explanation of reference numerals in the attached figures:
[0029] 1. Electrode sheet; 1a. Bending region; 1b. Straight region; 11. Current collector; 12. Functional layer; 121. First coating layer; 122. Second coating layer; 1221. First sub-coating layer; 1222. Second sub-coating layer; 1223. Third sub-coating layer; 1224. Fourth sub-coating layer; 123. Transition section; 1231. First transition section; 12311. First sub-section; 12312. Second sub-section; 1232. Second transition section; 1232 1. Third sub-section; 12322. Fourth sub-section; 13. Folded area; 131. First folded area; 132. Second folded area; 14. Winding start end; 10. Positive electrode sheet; 101. First surface; 102. Second surface; 20. Negative electrode sheet; 201. Third surface; 202. Fourth surface; 30. Separator; L. Length direction of electrode sheet; W. Width direction of electrode sheet; D. Thickness direction of electrode sheet; X. First direction. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0031] During battery cycling, electrolyte is consumed. Batteries with bent structures (such as wound structures) often have smaller gaps between the electrode plates and the separator in the bent areas (or arcs), resulting in lower electrolyte content. Insufficient electrolyte can obstruct the migration path of lithium ions, preventing them from fully embedding into the negative electrode material. This leads to lithium ions depositing as metal on the negative electrode surface, forming lithium dendrites and causing lithium plating.
[0032] Based on this, the present invention provides an electrode sheet, a wound battery cell, and an electrical device to improve the electrolyte wetting effect in the bending area and reduce the risk of lithium plating.
[0033] The following is combined Figures 1 to 10 The following describes embodiments of the present invention.
[0034] According to an embodiment of the present invention, in one aspect, an electrode sheet 1 for use with a wound battery cell is provided, such as... Figures 1-3 As shown, electrode 1 has a length direction L, a width direction W, and a thickness direction D. The length direction L, width direction W, and thickness direction D of the electrode 1 all intersect. In some cases, electrode 1 is rectangular, and the length direction L, width direction W, and thickness direction D of the electrode 1 are all perpendicular.
[0035] The electrode sheet 1 is adapted to be wound along its length L to form connected bending regions 1a and straight regions 1b. It can be understood that the electrode sheet 1 of this invention can be wound to form a wound battery cell, and the aforementioned bending regions 1a and straight regions 1b are also the bending regions 1a and straight regions 1b of the formed wound battery cell. Figure 4 As shown in the example, after the electrode sheet 1 is wound and formed, it forms a straight area 1b and two bent areas 1a. The two bent areas 1a are located at opposite ends of the straight area 1b along the first direction X.
[0036] Understandably, the electrode 1 can be either a positive electrode 10 or a negative electrode 20.
[0037] Specifically, such as Figure 1 As shown, the electrode sheet 1 includes a current collector 11 and a functional layer 12. Along the thickness direction D of the electrode sheet, the current collector 11 has two opposing surfaces, and the functional layer 12 is disposed on at least one of the surfaces of the current collector 11. The functional layer 12 includes at least two first coatings 121 and at least one second coating 122. Along the length direction L of the electrode sheet, the first coatings 121 and second coatings 122 are alternately disposed, and a transition portion 123 is provided between adjacent first coatings 121 and second coatings 122. The first coating 121 is located in the flat region 1b, and the second coating 122 is located in the bending region 1a. Along the length direction L of the electrode sheet, the transition portion 123 connects adjacent first coatings 121 and second coatings 122. Along the length direction L of the electrode sheet, the thickness of at least one transition portion 123 connecting both ends of the second coating 122 along the thickness direction D of the electrode sheet is greater than the thickness of the second coating 122 along the thickness direction D of the electrode sheet.
[0038] In some embodiments, along the length direction L of the electrode sheet, at least one of the transition portions 123 at both ends of the second coating 122 is located in the bending region 1a. Of course, in some embodiments, along the length direction L of the electrode sheet, at least one of the transition portions 123 at both ends of the second coating 122 may also be partially located in the bending region 1a and partially located in the straight region 1b.
[0039] In the technical solution of this application, a transition portion 123 is provided between the first coating 121 and the second coating 122. The first coating 121 is located in the straight region 1b, and the second coating 122 is located in the bending region 1a. That is, the transition portion 123 is located at the junction of the straight region 1b and the bending region 1a. Moreover, the thickness of at least one of the transition portions 123 on both ends of the second coating 122 is greater than that of the second coating 122. In this way, the two transition portions 123 on both ends of the second coating 122 can form a liquid storage tank in the bending region 1a, increasing the amount of electrolyte stored in the bending region 1a. Furthermore, the thicker transition portion 123 can increase the spacing between adjacent bending regions 1a formed after the electrode sheet 1 is wound, which is equivalent to increasing the channel for electrolyte to enter the bending region 1a, improving the electrolyte wetting rate in the bending region 1a, thereby improving the electrolyte wetting effect in the bending region 1a, reducing the risk of lithium plating in the bending region 1a, and improving the safety of the battery.
[0040] Furthermore, due to the structural characteristics of wound batteries, the stresses experienced by the flat region 1b and the bent region 1a are different, with the electrode sheet 1 closer to the bent region 1a experiencing greater stress. During the manufacturing and use of the battery, the transition area between the flat region 1b and the bent region 1a of the wound cell experiences uneven stress, and stress concentration easily occurs in the bent region 1a. Therefore, during cycling, the transition area and the bent region 1a are prone to breakage. At the same time, the coating of the bent region 1a may be subjected to significant physical stress, leading to problems such as coating cracking or peeling. The technical solution of this application has the following advantages: First, the thicker transition portion 123 enhances the strength of the transition area between the straight area 1b and the bent area 1a, enabling the transition area to withstand greater stress changes and preventing tearing or breakage due to different stresses. Second, the thicker transition portion 123 increases the spacing between adjacent bent areas 1a formed after the electrode sheet 1 is wound, preventing breakage caused by excessive expansion stress in the bent areas 1a after battery cycling. Third, the thickness of the transition portion 123 is greater than the thickness of the second coating 122, causing the stress to preferentially act on or be compressed in the thicker transition portion 123 after battery expansion, reducing or improving the problem of cracking or peeling of the coating in the bent area due to excessive stress.
[0041] Specifically, in some embodiments, such as Figure 1As shown, along the length direction L of the electrode sheet, the electrode sheet 1 includes a plurality of folded regions 13 arranged sequentially. Each folded region 13 includes a set of first coating 121, second coating 122 and two transition portions 123 located on both sides of the second coating 122.
[0042] In each folded region 13, the two transition portions 123 on both sides of the second coating 122 can both be located within the bending region 1a; or, one of the two transition portions 123 on both sides of the second coating 122 can be located within the bending region 1a and the other within the straight region 1b. Understandably, the two transition portions 123 on both sides of the second coating 122 are located at the junction of the bending region 1a and the straight region 1b, that is, the two transition portions 123 are located at opposite ends of the bending region 1a. As long as one transition portion 123 is located within the bending region 1a, the liquid storage tank formed between the two transition portions 123 is located within the bending region 1a, thereby reducing the risk of lithium plating in the bending region 1a.
[0043] Furthermore, in some embodiments, the folded region 13 includes a first folded region 131 and a plurality of second folded regions 132 sequentially arranged along the length direction L of the electrode sheet. One end of the electrode sheet 1 along the length direction is a winding start end 14, wherein the first folded region 131 is close to the winding start end 14, and the second folded regions 132 are located on the side of the first folded region 131 away from the winding start end 14. Figure 4 and Figure 7 As shown, in the second folded region 132, the second coating 122 and the two transition portions 123 are all located in the bending region 1a. In this embodiment, since the thickness of the transition portion 123 is greater than that of the second coating 122, that is, the transition portion 123 is raised in the bending region 1a, the fact that both transition portions 123 are located in the bending region 1a can increase the distance between the electrode sheet 1 and the separator 30, as well as the contact area with the electrolyte, so that the electrolyte can quickly wet the bending region 1a, improve the wetting effect of the electrolyte in the bending region 1a, and further reduce the risk of lithium plating.
[0044] In actual production, electrode sheet 1 needs to be welded with tabs before winding. After welding, solder joints will be generated on the tabs, which can easily puncture the separator 30 and cause a short circuit. Therefore, insulating adhesive is usually applied to the welding position between the tab and electrode sheet 1. As a result, after the electrode sheet 1 is wound into shape, it will increase the thickness of the local wound cell. The thickness at the tab welding position is 0.008-1mm thicker than other positions, which will cause uneven pressure during the compaction process and affect the quality of the battery.
[0045] Based on this, in some embodiments, the thickness of the transition portion 123 is greater than the thickness of the first coating 121 along the thickness direction D of the electrode sheet. In the first folded region 131, at least one transition portion 123 located at both ends of the second coating 122 is located in the flat region 1b. It should be noted that, as... Figure 1 As shown, the first folded area 131 is close to the winding start end 14. After winding, as... Figure 4 As shown, the first folding region 131 is the region near the winding center of the wound cell. The region where the first coating 121 is located in the first folding region 131 is located in the flat region 1b, forming the winding start section of the electrode sheet 1. The region where the second coating 122 is located in the first folding region 131 is located in the bending region 1a, forming the first bending region of the electrode sheet 1.
[0046] For example, such as Figures 4-6 As shown, in the first folded region 131, one of the two transition sections 123 is located in the straight region 1b, and the other is located in the bending region 1a.
[0047] In the above embodiment, since the thickness of the transition portion 123 is greater than the thickness of the first coating 121, after winding, the transition portion 123 located in the flat region 1b can compensate for the uneven thickness of the wound cell caused by the thickening of the tab position. As a result, during the formation process, the degree of formation of different parts of the electrode tends to be uniform, so that the internal stress between the active material particles inside the electrode is released, so as to better exert the capacity.
[0048] In some embodiments, such as Figure 2 As shown, the thickness of the transition portion 123 is H3. The thickness H3 of the transition portion 123 satisfies: 0.005mm≤H3≤1mm. Within this thickness range, the transition portion 123 can be close to the increase in thickness of the wound cell caused by the electrode welding, so as to further ensure that the transition portion 123 can produce a thickness compensation effect in the flat region 1b.
[0049] The transition portion 123 includes a first transition portion 1231 and a second transition portion 1232, which are located on opposite sides of the second coating 122 along the length direction L of the electrode sheet. In the above embodiment, either the first transition portion 1231 or the second transition portion 1232 can be located in the flat region 1b.
[0050] Understandably, the thickness H3 of the transition portion 123 can refer to either the thickness of the first transition portion 1231 or the thickness of the second transition portion 1232.
[0051] In some embodiments, such as Figure 2As shown, along the thickness direction D of the electrode sheet, the thickness of the first coating 121 is H1, and the thickness of the second coating 122 is H2. The thickness H1 of the first coating 121 and the thickness H3 of the transition portion 123 satisfy: H1 ≤ H3 ≤ 1.8H1. And / or, the thickness H2 of the second coating 122 and the thickness H3 of the transition portion 123 satisfy: H2 ≤ H3 ≤ 3H2. In this embodiment, by limiting the relationship between H3 and H1 and H2, it is possible to avoid excessive local thickness of the wound cell after winding due to excessive thickness of the transition portion 123, ensuring the tightness of the fit between adjacent electrode sheets 1 (e.g., positive electrode sheet 10 and negative electrode sheet 20) in the wound cell, thereby improving the cycle performance of the wound cell.
[0052] Understandably, in the above embodiments, the thickness H3 of the transition portion 123 can refer to either the thickness of the first transition portion 1231 or the thickness of the second transition portion 1232.
[0053] Furthermore, in some embodiments, such as Figure 1 As shown, along the length L of the electrode sheet, the length of the first coating 121 is S1, the length of the second coating 122 is S2, and the length of the transition portion 123 is S3. The lengths S2 and S3 of the second coating 122 and the transition portion 123 satisfy: 0.0025S2≤S3≤0.5S2. This ensures that only a small portion of the electrode sheet 1 protrudes in the bending region 1a, preventing excessively large lengths in the thicker areas of the bending region 1a, which would result in poor overall thickness consistency and deteriorated cycle performance.
[0054] Understandably, the second coating 122 is located within the bending region 1a. As the number of winding bends increases, the length S2 of the second coating 122 can increase with the increase in the number of winding bends, thereby ensuring that the transition portion 123 can fall into the predetermined position. That is, in the direction away from the winding start end 14, the length S2 of the second coating 122 gradually increases in the first fold region 131 and the subsequent second fold region 132.
[0055] Understandably, the present invention does not specifically limit the length S1 of the first coating 121, as long as it matches the length of the straight region 1b in the first direction X.
[0056] In some embodiments, the transition portion 123 includes a first transition portion 1231 and a second transition portion 1232, which are located on opposite sides of the second coating 122 along the length direction L of the electrode sheet. The thickness of the first transition portion 1231 is greater than or equal to the thickness of the second transition portion 1232 along the thickness direction D of the electrode sheet, to facilitate rapid wetting of the gaps in the electrode sheet 1 by the electrolyte and reduce the risk of lithium plating in the bending region 1a.
[0057] Furthermore, in some embodiments, such as Figure 3 As shown, two functional layers 12 are provided, each disposed on one of the two surfaces of the current collector 11 along the thickness direction D of the electrode sheet. The first transition portions 1231 of the two functional layers 12 are staggered along the thickness direction D of the electrode sheet. In this embodiment, since the thickness of the first transition portion 1231 is greater than or equal to the thickness of the second transition portion 1232, by staggering the first transition portions 1231 of the two functional layers 12, the overall thickness of the electrode sheet 1 can be reduced, avoiding thickness anomalies after winding and forming, which would result in poor overall thickness consistency and deteriorated cycle performance.
[0058] For example, in the thickness direction D of the electrode sheet, the first transition portion 1231 on one surface of the current collector 11 can be disposed opposite to the second transition portion 1232 on the other surface. Alternatively, the first transition portion 1231 on one surface of the current collector 11 can be disposed alternately with the second transition portion 1232 on the other surface, and the staggered distance between the two in the length direction L of the electrode sheet is controlled between 0-0.5SB, so as to ensure that the first transition portions 1231 on the two surfaces of the current collector 11 in the bending area 1a do not overlap, thereby reducing the overall thickness of the electrode sheet 1, avoiding thickness abnormalities after winding and forming, resulting in poor overall thickness consistency and deteriorated cycle performance.
[0059] In some embodiments, the electrode sheet 1 includes a positive electrode sheet 10 and a negative electrode sheet 20, both of which include the aforementioned current collector 11 and functional layer 12. It is understood that the current collector 11 of the positive electrode sheet 10 and the current collector 11 of the negative electrode sheet 20 are made of different materials, and the functional layer 12 of the positive electrode sheet 10 and the functional layer 12 of the negative electrode sheet 20 are also made of different materials.
[0060] In some embodiments, electrode 1 is a positive electrode 10, or there are two electrode 1s, one of which is a positive electrode 10 and the other is a negative electrode 20. The first coating 121 and the second coating 122 of the positive electrode 10 are made of different materials, which can also be understood as the first coating 121 and the second coating 122 of the positive electrode 10 having different delithiation capabilities. In this case, the delithiation capability of the second coating 122 of the positive electrode 10 is less than that of the first coating 121, or the specific capacity of the second coating 122 of the positive electrode 10 is less than that of the first coating 121, so that the rate at which lithium ions are removed from the positive electrode 10 in the bending region 1a is slowed down, alleviating the lithium plating problem in the bending region 1a.
[0061] Furthermore, the transition portion 123 of the positive electrode 10 includes a first transition portion 1231 and a second transition portion 1232. The first transition portion 1231 includes a first sub-portion 12311 and a second sub-portion 12312. The first sub-portion 12311 is made of the same material as the first coating 121, and the second sub-portion 12312 is made of the same material as the second coating 122. This can also be understood as the first sub-portion 12311 having the same delithiation capability as the first coating 121, and the second sub-portion 12312 having the same delithiation capability as the second coating 122. Along the thickness direction D of the electrode sheet, the second sub-portion 12312 covers the side of the first sub-portion 12311 that is away from the current collector 11. With this configuration, the lithium insertion capacity or specific capacity of the first transition portion 1231 should be between that of the first coating 121 and the second coating 122. Since the second sub-portion 12312 is located on the outermost side in the thickness direction of the electrode sheet 1, the lithium removal capacity or specific capacity of the first transition portion 1231 is closer to that of the second sub-portion 12312, that is, the lithium removal capacity or specific capacity of the second coating 122. Therefore, the lithium removal capacity or specific capacity of the first transition portion 1231 is less than that of the first coating 121, which reduces the removal of lithium ions and further alleviates the lithium plating problem in the bending region 1a.
[0062] In some embodiments, the second transition portion 1232 includes a third sub-portion 12321 and a fourth sub-portion 12322. The third sub-portion 12321 is made of the same material as the first coating 121, and the fourth sub-portion 12322 is made of the same material as the second coating 122. Alternatively, it can be understood that the third sub-portion 12321 has the same delithiation capability as the first coating 121, and the fourth sub-portion 12322 has the same delithiation capability as the second coating 122. Along the thickness direction D of the electrode sheet, the fourth sub-portion 12322 covers the side of the third sub-portion 12321 that is away from the current collector 11. With this configuration, the delithiation capacity or specific capacity of the second transition portion 1232 should be between that of the first coating 121 and the second coating 122. Since the fourth sub-portion 12322 is located on the outermost side in the thickness direction of the electrode sheet 1, the delithiation capacity or specific capacity of the second transition portion 1232 is closer to that of the fourth sub-portion 12322, that is, the delithiation capacity or specific capacity of the second coating 122. Therefore, the delithiation capacity or specific capacity of the second transition portion 1232 is less than that of the first coating 121, thereby reducing the release of lithium ions and further alleviating the lithium plating problem in the bending region 1a.
[0063] Alternatively, in some embodiments, the third sub-part 12321 and the fourth sub-part 12322 are fused together. Since there is a difference in the delithiation capability or specific capacity between the first coating 121 and the second coating 122, the delithiation capability or specific capacity of the third sub-part 12321 and the fourth sub-part 12322 after fusion should be between the first coating 121 and the second coating 122, which can also satisfy the requirement that the delithiation capability or specific capacity of the second transition part 1232 is less than that of the first coating 121.
[0064] Understandably, in the actual processing, both the first transition portion 1231 and the second transition portion 1232 are composed of the paste that forms the first coating 121 and the second coating 122. When the second sub-part 12312 covers the first sub-part 12311 or the fourth sub-part 12322 covers the third sub-part 12321, its microstructure is as follows: Figure 9 As shown, it is easier to form a thicker transition portion 123. When the third sub-part 12321 and the fourth sub-part 12322 merge, the paste forming the first coating 121 and the second coating 122 flows towards each other and merges, as shown in the microstructure diagram. Figure 10 As shown, it is easier to form a thinner transition portion 123 so that the thickness of the second transition portion 1232 is less than that of the first transition portion 1231.
[0065] Of course, in some embodiments, the first transition portion 1231 may also be a combination of the first sub-portion 12311 and the second sub-portion 12312, or along the thickness direction D of the electrode sheet, the first sub-portion 12311 may cover the side of the second sub-portion 12312 away from the current collector 11. Correspondingly, in some embodiments, in the second transition portion 1232, along the thickness direction D of the electrode sheet, the third sub-portion 12321 may also cover the side of the fourth sub-portion 12322 away from the current collector 11.
[0066] In other embodiments, the first coating 121 and the second coating 122 of the positive electrode 10 are made of the same material. This can also be understood as the first coating 121 and the second coating 122 of the positive electrode 10 having the same delithiation capability. In this case, the areal density of the second coating 122 of the positive electrode 10 is less than that of the first coating 121. Thus, the second coating 122 contains less positive electrode active material per unit area, that is, less lithium ions are delithiated, thereby alleviating the lithium plating problem in the bending region 1a.
[0067] In some embodiments, the electrode sheet is a negative electrode sheet 20, or there are two electrode sheets 1, one of which is a positive electrode sheet 10 and the other is a negative electrode sheet 20. The first coating 121 and the second coating 122 of the negative electrode sheet 20 are made of different materials, which can also be understood as the first coating 121 and the second coating 122 of the negative electrode sheet 20 having different lithium intercalation capabilities. In this case, the lithium intercalation capability of the second coating 122 of the negative electrode sheet 20 is greater than that of the first coating 121, or the specific capacity of the second coating 122 of the negative electrode sheet 20 is greater than that of the first coating 121. Thus, in the bending region 1a, the second coating 122 can provide sufficient intercalation sites for lithium ions extracted from the positive electrode sheet 10, thereby reducing the risk of lithium plating in the bending region 1a.
[0068] Furthermore, the transition portion 123 of the negative electrode 20 includes a first transition portion 1231 and a second transition portion 1232. The first transition portion 1231 includes a first sub-portion 12311 and a second sub-portion 12312. The first sub-portion 12311 is made of the same material as the first coating 121, and the second sub-portion 12312 is made of the same material as the second coating 122. This can also be understood as the first sub-portion 12311 having the same lithium intercalation capability as the first coating 121, and the second sub-portion 12312 having the same lithium intercalation capability as the second coating 122. Along the thickness direction D of the electrode sheet, the second sub-portion 12312 covers the side of the first sub-portion 12311 that is away from the current collector 11. With this configuration, the lithium intercalation capacity or specific capacity of the first transition portion 1231 should be between that of the first coating 121 and the second coating 122. Since the second sub-portion 12312 is located on the outermost side in the thickness direction of the electrode sheet 1, the lithium intercalation capacity or specific capacity of the first transition portion 1231 is closer to that of the second sub-portion 12312, that is, the lithium intercalation capacity or specific capacity of the second coating 122. Therefore, the lithium intercalation capacity or specific capacity of the first transition portion 1231 is greater than that of the first coating 121. The first transition portion 1231 can provide sufficient intercalation sites for lithium ions extracted from the positive electrode sheet 10 to reduce the risk of lithium plating in the bending region 1a.
[0069] In some embodiments, the second transition portion 1232 includes a third sub-portion 12321 and a fourth sub-portion 12322. The third sub-portion 12321 is made of the same material as the first coating 121, and the fourth sub-portion 12322 is made of the same material as the second coating 122. Alternatively, it can be understood that the third sub-portion 12321 has the same lithium intercalation capability as the first coating 121, and the fourth sub-portion 12322 has the same lithium intercalation capability as the second coating 122. Along the thickness direction D of the electrode sheet, the fourth sub-portion 12322 covers the side of the third sub-portion 12321 that is away from the current collector 11. With this configuration, the lithium intercalation capacity or specific capacity of the second transition portion 1232 should be between that of the first coating 121 and the second coating 122. Since the fourth sub-portion 12322 is located on the outermost side in the thickness direction of the electrode sheet 1, the lithium intercalation capacity or specific capacity of the second transition portion 1232 is closer to that of the fourth sub-portion 12322, that is, the lithium intercalation capacity or specific capacity of the second coating 122. Therefore, the lithium intercalation capacity or specific capacity of the second transition portion 1232 is greater than that of the first coating 121. The second transition portion 1232 can provide sufficient intercalation sites for lithium ions extracted from the positive electrode sheet 10 to reduce the risk of lithium plating in the bending region 1a.
[0070] Alternatively, in some embodiments, the third sub-part 12321 and the fourth sub-part 12322 are fused together. Since there is a difference in the delithiation capability or specific capacity between the first coating 121 and the second coating 122, the lithium insertion capability or specific capacity after the third sub-part 12321 and the fourth sub-part 12322 are fused together should be between the first coating 121 and the second coating 122, which can also satisfy the requirement that the lithium insertion capability or specific capacity of the second transition part 1232 is greater than that of the first coating 121.
[0071] In other embodiments, the first coating 121 and the second coating 122 of the negative electrode 20 are made of the same material, which can also be understood as the first coating 121 and the second coating 122 of the negative electrode 20 having the same lithium intercalation capability. The areal density of the second coating 122 of the negative electrode 20 is greater than that of the first coating 121. Thus, the second coating 122 has more lithium intercalation sites per unit area, enabling more lithium ions to be intercalated, thereby reducing the risk of lithium plating in the bending region 1a.
[0072] It should be noted that the lithium delithiation capability or lithium insertion capability of the first coating 121 and the second coating 122 mentioned in the above embodiments are different. Specifically, it can refer to the difference between the lithium delithiation capability of the first coating 121 participating in the battery cycle process and the lithium delithiation capability of the second coating 122 participating in the battery cycle process.
[0073] Understandably, the materials of the first sub-part 12311, the second sub-part 12312, the third sub-part 12321, and the fourth sub-part 12322 of the positive electrode 10 are not the same as those of the first sub-part 12311, the second sub-part 12312, the third sub-part 12321, and the fourth sub-part 12322 of the negative electrode 20.
[0074] According to an embodiment of the present invention, another aspect provides a wound battery cell, including a positive electrode 10, a negative electrode 20 and a separator 30. The positive electrode 10, the negative electrode 20 and the separator 30 are stacked and wound around a winding center to form a wound structure; the positive electrode 10 and / or the negative electrode 20 are the electrode sheets 1 described in the above embodiments.
[0075] Specifically, the positive electrode 10, separator 30, and negative electrode 20 are stacked sequentially, with the separator 30 located between the positive electrode 10 and the negative electrode 20. It can be understood that in the wound cell of this invention, both the positive electrode 10 and the negative electrode 20 may use the electrode sheet 1 with the transition portion 123 of this invention, or only one of the positive electrode 10 and the negative electrode 20 may use the electrode sheet 1 with the transition portion 123 of this invention. The key is that the transition portion 123 can form a liquid storage tank within the bending area 1a, increasing the electrolyte storage capacity of the bending area 1a, and increasing the spacing between adjacent bending areas 1a formed after the electrode sheet 1 is wound, thereby improving the electrolyte wetting rate in the bending area 1a and enhancing the wetting effect of the electrolyte in the bending area 1a. This reduces the risk of lithium plating in the bending area 1a and improves the safety of the battery.
[0076] In some embodiments, the positive electrode 10 is the electrode 1 described in the above embodiments, such as... Figure 8 As shown, the positive electrode 10 includes a first surface 101 near the winding center and a second surface 102 away from the winding center. The second coating 122 of the positive electrode 10 includes a first sub-coating 1221 disposed on the first surface 101 and a second sub-coating 1222 disposed on the second surface 102. The first sub-coating 1221 and the second sub-coating 1222 are made of different materials, which can also be understood as the first sub-coating 1221 and the second sub-coating 1222 having different delithiation capabilities. In this case, the delithiation capability of the first sub-coating 1221 is less than that of the second sub-coating 1222, or the specific capacity of the first sub-coating 1221 is less than that of the second sub-coating 1222. Figure 8 As shown, since the first surface 101 of the positive electrode 10 faces the negative electrode 20 which is closer to the winding center, the area of the first surface 101 in the bending region 1a is larger than the surface area of the corresponding negative electrode 20 in the bending region 1a. This results in more active material of the positive electrode 10 in the bending region 1a and less active material of the corresponding negative electrode 20. Consequently, the lithium ions extracted from the positive electrode 10 cannot be fully embedded in the negative electrode 20, making the first surface 101 prone to lithium plating in the bending region 1a. In this embodiment, by making the lithium extraction capacity or specific capacity of the first sub-coating 1221 smaller than that of the second sub-coating 1222, the number of lithium ions extracted from the first surface 101 is reduced, eliminating the influence of the difference in active material between the positive electrode 10 and the negative electrode 20 in the bending region 1a. This allows the lithium ions extracted from the first surface 101 of the positive electrode 10 to be fully embedded in the negative electrode 20, thereby reducing the risk of lithium plating.
[0077] Alternatively, in some embodiments, the first sub-coating 1221 and the second sub-coating 1222 are made of the same material, which can also be understood as the first sub-coating 1221 and the second sub-coating 1222 having the same delithiation capability. In this case, the areal density of the first sub-coating 1221 is less than that of the second sub-coating 1222, so as to reduce the lithium ions extracted from the first surface 101, eliminate the influence of the difference in active material between the positive electrode 10 and the negative electrode 20 in the bending region 1a, and enable the lithium ions extracted from the first surface 101 of the positive electrode 10 to be completely embedded in the negative electrode 20, thereby reducing the risk of lithium plating.
[0078] In some embodiments, the negative electrode 20 is the electrode 1 described in the above embodiments, such as... Figure 8 As shown, the negative electrode 20 includes a third surface 201 near the winding center and a fourth surface 202 away from the winding center. The second coating 122 of the negative electrode 20 includes a third sub-coating 1223 disposed on the third surface 201 and a fourth sub-coating 1224 disposed on the fourth surface 202. The third sub-coating 1223 and the fourth sub-coating 1224 are made of different materials, which can also be understood as the third sub-coating 1223 and the fourth sub-coating 1224 having different lithium intercalation capabilities. In this case, the lithium intercalation capability of the fourth sub-coating 1224 is greater than that of the third sub-coating 1223; or, the specific capacity of the fourth sub-coating 1224 is greater than that of the third sub-coating 1223.
[0079] Understandably, the wound cell is formed by winding together a positive electrode 10, a negative electrode 20, and a separator 30 disposed between the positive electrode 10 and the negative electrode 20, wherein the first surface 101 of the positive electrode 10 faces the fourth surface 202 of the negative electrode 20. In this embodiment, by making the lithium intercalation capability or specific capacity of the fourth sub-coating 1224 disposed on the fourth surface 202 greater than that of the third sub-coating 1223 disposed on the third surface 201, the fourth surface 202 provides more lithium intercalation sites for lithium ions extracted from the first surface 101 in the bending region 1a, eliminating the influence of the difference in active materials between the positive electrode 10 and the negative electrode 20 in the bending region 1a, so that the lithium ions extracted from the first surface 101 of the positive electrode 10 can be completely intercalated into the negative electrode 20, reducing the risk of lithium plating.
[0080] Alternatively, in other embodiments, the third sub-coating 1223 and the fourth sub-coating 1224 are made of the same material, and the areal density of the fourth sub-coating 1224 is less than that of the third sub-coating 1223, so as to provide more lithium intercalation sites for lithium ions extracted from the first surface 101, eliminate the influence of the difference in active materials between the positive electrode 10 and the negative electrode 20 in the bending region 1a, and enable the lithium ions extracted from the first surface 101 of the positive electrode 10 to be completely intercalated into the negative electrode 20, thereby reducing the risk of lithium plating.
[0081] It should be noted that the specific capacity of the first coating 121, the second coating 122, the first transition portion 1231, and the second transition portion 1232 can be measured using the half-cell method. The specific implementation method is as follows: the material to be tested is used as the working electrode and assembled into a half-cell with a reference electrode (such as a lithium sheet); the electrochemical workstation is used to set a certain charge-discharge rate for testing.
[0082] The delithiation or lithium insertion capabilities of the first coating 121, the second coating 122, the first transition portion 1231, and the second transition portion 1232 can be measured using chronoamperometry (GITT). GITT is based on chronopotential analysis, which calculates the lithium ion diffusion coefficient in the test material by applying a constant current for a short period. The lithium ion diffusion coefficient is used to measure the delithiation or lithium insertion capability of the corresponding test material. A larger lithium ion diffusion coefficient indicates a faster migration rate of lithium ions in the electrode material, meaning a greater delithiation or lithium insertion capability of the corresponding test material.
[0083] According to an embodiment of the present invention, in another aspect, an electrical device is also provided, comprising: an electrode sheet 1 as described in the above embodiments; or, a wound battery cell as described in the above embodiments, for providing electrical energy.
[0084] It is understood that the wound battery cell and electrical device of this utility model include the electrode sheet 1 of this utility model, and therefore have the same technical effects as the electrode sheet 1 of this utility model, which will not be described again here.
[0085] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.
[0086] Although embodiments of the present 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 present invention, and such modifications and variations all fall within the scope defined by the appended claims.
Claims
1. An electrode sheet used in a wound battery cell; the electrode sheet (1) is wound along its length direction (L) to form connected bending regions (1a) and straight regions (1b); characterized in that, The electrode sheet (1) includes: The current collector (11) has two opposing surfaces along the thickness direction (D) of the electrode sheet; A functional layer (12) is disposed on at least one surface of the current collector (11); the functional layer (12) includes at least two first coatings (121) and at least one second coating (122), and the first coatings (121) and the second coatings (122) are alternately disposed along the length direction (L) of the electrode sheet; a transition portion (123) is provided between adjacent first coatings (121) and second coatings (122); the first coating (121) is located in the straight area (1b), and the second coating (122) is located in the bent area (1a); along the length direction (L) of the electrode sheet, the transition portion (123) connects adjacent first coatings (121) and second coatings (122); along the length direction (L) of the electrode sheet, at least one of the transition portions (123) connected to both ends of the second coating (122) has a thickness in the thickness direction (D) of the electrode sheet greater than the thickness of the second coating (122) in the thickness direction (D) of the electrode sheet.
2. The electrode sheet according to claim 1, characterized in that, Along the length direction (L) of the electrode sheet, the electrode sheet (1) includes a plurality of folded regions (13) arranged sequentially. Each folded region (13) includes a set of first coating (121), second coating (122) connected together, and two transition portions (123) located at both ends of the second coating (122). The two transition portions (123) at both ends of the second coating (122) are respectively the first transition portion (1231) and the second transition portion (1232). One end of the electrode sheet (1) along the length direction is the winding start end (14). The folded area (13) includes a first folded area (131) and a plurality of second folded areas (132) arranged sequentially along the length direction (L) of the electrode sheet. The first folded area (131) is close to the winding start end (14). In the first folded region (131), at least one of the transition portions (123) located at both ends of the second coating (122) is located in the flat region (1b). And / or, In the second folded region (132), the second coating (122) and the two transition portions (123) are both located in the bending region (1a). And / or, Along the thickness direction (D) of the electrode sheet, the thickness of the first transition portion (1231) is greater than or equal to the thickness of the second transition portion (1232).
3. The electrode sheet according to claim 2, characterized in that, Along the thickness direction (D) of the electrode sheet, the thickness of at least one of the transition portions (123) located at both ends of the second coating (122) is greater than the thickness of the first coating (121).
4. The electrode sheet according to claim 2, characterized in that, Along the thickness direction (D) of the electrode sheet, the functional layer (12) is disposed on two surfaces of the current collector (11); wherein the first transition portions (1231) of the functional layer (12) on the two surfaces are staggered in the thickness direction (D) of the electrode sheet.
5. The electrode sheet according to claim 4, characterized in that, The electrode sheet (1) is a positive electrode sheet (10), and the positive electrode sheet (10) includes the current collector (11) and the functional layer (12). Wherein, the first coating (121) and the second coating (122) of the positive electrode (10) have different delithiation capabilities; the delithiation capability of the second coating (122) of the positive electrode (10) is less than that of the first coating (121); or, the specific capacity of the second coating (122) of the positive electrode (10) is less than that of the first coating (121); or, The first coating (121) and the second coating (122) of the positive electrode (10) have the same delithiation capability; the areal density of the second coating (122) of the positive electrode (10) is less than the areal density of the first coating (121); or, The electrode sheet (1) is a negative electrode sheet (20), and the negative electrode sheet (20) includes the current collector (11) and the functional layer (12). Wherein, the lithium intercalation capabilities of the first coating (121) and the second coating (122) of the negative electrode (20) are different, and the lithium intercalation capability of the second coating (122) of the negative electrode (20) is greater than that of the first coating (121); or, the specific capacity of the second coating (122) of the negative electrode (20) is greater than that of the first coating (121); or, The first coating (121) and the second coating (122) of the negative electrode (20) have the same lithium intercalation capability; the areal density of the second coating (122) of the negative electrode (20) is greater than the areal density of the first coating (121).
6. The electrode sheet according to claim 5, characterized in that, The first coating (121) and the second coating (122) have different delithiation or lithium insertion capabilities; the first transition portion (1231) includes a first sub-part (12311) and a second sub-part (12312), the first sub-part (12311) has the same delithiation or lithium insertion capability as the first coating (121), and the second sub-part (12312) has the same delithiation or lithium insertion capability as the second coating (122); Along the thickness direction (D) of the electrode sheet, the second sub-part (12312) covers the side of the first sub-part (12311) away from the current collector (11); And / or, The second transition section (1232) includes a third subsection (12321) and a fourth subsection (12322). The third subsection (12321) has the same delithiation or lithium insertion capability as the first coating (121), and the fourth subsection (12322) has the same delithiation or lithium insertion capability as the second coating (122). Along the thickness direction (D) of the electrode sheet, the fourth sub-part (12322) covers the side of the third sub-part (12321) away from the current collector (11); or, the third sub-part (12321) and the fourth sub-part (12322) are intertwined.
7. The electrode sheet according to any one of claims 1-6, characterized in that, Along the thickness direction (D) of the electrode sheet, the thickness of the first coating (121) is H1, the thickness of the second coating (122) is H2, and the thickness of at least one transition portion (123) located at both ends of the second coating (122) is H3. Wherein, the thickness H3 of at least one of the transition portions (123) located at both ends of the second coating (122) satisfies: 0.005 mm ≤ H3 ≤ 1 mm; And / or, The thickness H1 of the first coating (121) and the thickness H3 of the transition portion (123) satisfy: H1≤H3≤1.8H1; And / or, The thickness H2 of the second coating (122) and the thickness H3 of the transition portion (123) satisfy: H2≤H3≤3H2; And / or, Along the length direction (L) of the electrode sheet, the length of the second coating (122) is S2, and the length of the transition portion (123) is S3; Wherein, the length S2 of the second coating (122) and the length S3 of the transition portion (123) satisfy: 0.0025 S2≤S3≤0.5 S2.
8. A wound battery cell, characterized in that, include: A positive electrode (10), a negative electrode (20), and a separator (30) are stacked and wound around a winding center to form a wound structure. The positive electrode (10) and / or the negative electrode (20) are electrode plates (1) according to any one of claims 1-7.
9. The wound battery cell according to claim 8, characterized in that, The positive electrode (10) is the electrode sheet (1) according to any one of claims 1-7. The positive electrode (10) includes a first surface (101) near the winding center and a second surface (102) away from the winding center. The second coating (122) of the positive electrode (10) includes a first sub-coating (1221) disposed on the first surface (101) and a second sub-coating (1222) disposed on the second surface (102). The first sub-coating (1221) and the second sub-coating (1222) have different delithiation capabilities, with the first sub-coating (1221) having a lower delithiation capability than the second sub-coating (1222); or, the specific capacity of the first sub-coating (1221) is lower than that of the second sub-coating (1222). or, The first sub-coating (1221) and the second sub-coating (1222) have the same delithiation capability, and the areal density of the first sub-coating (1221) is less than that of the second sub-coating (1222).
10. The wound battery cell according to claim 8 or 9, characterized in that, The negative electrode (20) is the electrode sheet (1) according to any one of claims 1-7. The negative electrode (20) includes a third surface (201) near the winding center and a fourth surface (202) away from the winding center. The second coating (122) of the negative electrode (20) includes a third sub-coating (1223) disposed on the third surface (201) and a fourth sub-coating (1224) disposed on the fourth surface (202). The third sub-coating (1223) and the fourth sub-coating (1224) have different lithium intercalation capabilities, with the fourth sub-coating (1224) having a greater lithium intercalation capability than the third sub-coating (1223); or, the fourth sub-coating (1224) has a greater specific capacity than the third sub-coating (1223). or, The third sub-coating (1223) and the fourth sub-coating (1224) have the same lithium intercalation capability, and the areal density of the fourth sub-coating (1224) is less than that of the third sub-coating (1223).
11. An electrical appliance, characterized in that, include: Electrode sheet (1) as described in any one of claims 1-7; Alternatively, a wound cell as described in any one of claims 8-10.