A pole piece and a lithium-ion battery

Abstract

The present invention provides a pole piece and a lithium-ion battery. In a first aspect of the present invention, there is provided a pole piece, which includes a current collector, a first active layer, and a second active layer. The first active layer is disposed on the surface of the current collector and is provided with a first groove. The second active layer is divided into a first part disposed in the first groove and a second part disposed on the surface of the first active layer away from the current collector. Wherein, a second groove is provided on the first part, a tab is disposed at the second groove and is electrically connected to the current collector, and the thickness of the first part of the second active layer is less than the total thickness of the first active layer and the second part of the second active layer. The pole piece provided by the present invention improves the charging risk at the tab connection position to a certain extent by reducing the thickness of the active layer near the tab, and improves the cycle performance of the lithium-ion battery.

Description

Technical Field

[0001] The present invention relates to a pole piece and a lithium-ion battery, and belongs to the technical field of lithium-ion batteries. Background Art

[0002] With the advent of the 5G era, the status of lithium-ion batteries has become increasingly important. At present, lithium-ion batteries are continuously developing towards high energy density and high fast charging rate. Currently, the connection position of the tab is adjusted from the edge of the pole piece to the middle position on the side of the pole piece to reduce the impedance of the lithium-ion battery.

[0003] However, when the position of the tab changes, the current density around the tab will increase, and with the cycling of the lithium-ion battery, lithium ions will precipitate, resulting in poor cycling performance of the lithium-ion battery. Therefore, how to solve the problem of poor cycling performance of lithium-ion batteries caused by this tab connection method has received more and more attention. Summary of the Invention

[0004] The present invention provides a pole piece to solve the problem of poor cycling performance of lithium-ion batteries caused by this tab connection method.

[0005] In a first aspect of the present invention, a pole piece is provided. The pole piece includes a current collector, a first active layer, and a second active layer. The first active layer is disposed on the surface of the current collector and is provided with a first groove. The second active layer is divided into a first part disposed in the first groove and a second part disposed on the surface of the first active layer away from the current collector.

[0006] Wherein, a second groove is provided on the first part, and the tab is disposed at the second groove and is electrically connected to the current collector. The thickness of the first part of the second active layer is less than the total thickness of the first active layer and the second part of the second active layer.

[0007] Currently, the pole pieces used in the prior art generally include a current collector and an active layer disposed on the surface of the current collector, and a groove is provided at the middle position on the side of the active layer. The tab is connected to the corresponding area on the current collector in this groove. To solve the problem of poor cycling performance of lithium-ion batteries caused by this tab connection method, the present invention reduces the thickness of the active layer around the position where the tab is located. Specifically, Figure 1a is the front view of the pole piece provided by an embodiment of the present invention, Figure 1b is the top view of the pole piece provided by an embodiment of the present invention, Figure 1c is the left view of the pole piece provided by an embodiment of the present invention, as Figure 1a - 1cAs shown in the figure, the electrode plate includes a current collector 1, a first active layer 2, a second active layer 3, and an electrode tab 4. Among them, the first active layer 2 is disposed on the surface of the current collector 1, and a first groove is provided on the first active layer 2. A first part of the second active layer is disposed in the first groove and in contact with the surface of the current collector 1, and a second part of the second active layer is disposed on the upper surface of the first active layer away from the current collector 1. A second groove is provided in the middle of the side surface of the first part of the second active layer for connecting the electrode tab 4. The thickness of the first part of the second active layer is less than the total thickness of the first active layer and the second part of the second active layer, so that the thickness of the active layer near the electrode tab is lower than that of the active layer in the area away from the electrode tab; wherein, the definition of the thickness of the electrode plate in this application is the same as that of the prior art, that is, the longest side in the electrode plate is the length of the electrode plate, the shortest side is the height of the electrode plate, and the side between the longest side and the shortest side is the width of the electrode plate, that is Figure 1a the longer side in it is the length of the electrode plate, and the shorter side is the height of the electrode plate, Figure 1b the shorter side in it is the width of the electrode plate, the value of the long side is the length of the electrode plate, the value of the high side is the thickness of the electrode plate, and the value of the wide side is the width of the electrode plate. Moreover, the first groove and the second groove are in the same directions as the length, width, and thickness of the electrode plate. The electrode plate provided by the present invention improves the charging risk at the connection position of the electrode tab to a certain extent by reducing the total thickness of the active layer around the electrode tab, and improves the cycle performance of the lithium-ion battery.

[0008] In a specific embodiment, in order to further improve the cycle performance of the lithium-ion battery, the thickness of the first active layer should be appropriately reduced, that is, the thickness of the second active layer is greater than the thickness of the first active layer. In addition, since the first part of the second active layer is disposed in the first groove, the force received during the subsequent rolling process of the electrode plate is small, resulting in a difference in the thickness of the first part and the second part of the second active layer. Specifically, the thickness of the first part of the second active layer is greater than the thickness of the second part.

[0009] According to Figure 1a - 1c the structure of the electrode plate shown in the figure, it is necessary to improve the existing coating equipment to ensure the position and area of the first groove, which will not only increase the preparation cost, but also be unfavorable for the preparation of other electrode plate structures. Therefore, the width of the first groove can be increased to be the same as the width of the current collector, that is, the first groove divides the first active layer into two independent parts, and the middle blank part is the first groove. For example:

[0010] Figure 2a is the front view of the electrode plate provided by another embodiment of the present invention, Figure 2b is the top view of the electrode plate provided by another embodiment of the present invention, as Figure 2a - 2bAs shown, the electrode includes a current collector 1, a first active layer 2, a second active layer 3, and an electrode tab 4. The first active layer 2 is provided with a first groove, and the width of the first groove is the same as the width of the current collector 1, that is, the first groove divides the first active layer 2 into two left and right parts. The first part of the second active layer 3 is disposed in the first groove, and the second part of the second active layer 3 is disposed on the upper surface of the first active layer 2 away from the current collector 1. Since the width of the first groove is the same as the width of the current collector, the second part of the second active layer 3 is also divided into two independent parts on the left and right.

[0011] It can be understood that with the intersection of the diagonals of the vertical projection area of the second groove on the current collector as the center, the center of the vertical projection of the second groove on the current collector is located within the first groove.

[0012] Continue to refer to Figure 1b Or Fig. 2b, it can be seen that the center of the vertical projection of the second groove on the current collector is located within the first groove. In order to further improve the cycling performance of the lithium-ion battery, the second groove can be arranged as close as possible to the center of the first groove so that the thicknesses of the active layers on both sides of the electrode tab are the same.

[0013] The applicant's research found that the area ratio of the cross-sections of the first groove and the second groove in the length direction has a greater impact on the performance of the lithium-ion battery. Specifically, the vertical projection area of the second groove on the current collector is 1% - 50% of the vertical projection area of the first groove on the current collector. In the specific preparation process, those skilled in the art can determine the widths of the first groove and the second groove, and adjust the area ratio by adjusting the length ranges of the two.

[0014] Refer to the appendix Figure 2a , a slope is formed on one side of the second part close to the first part.

[0015] In order to improve the fast charging performance of the lithium-ion battery, when the electrode is a negative electrode, the average particle size of the active material in the second active layer is 5 - 20 μm, and the graphitization degree is 90% - 98%.

[0016] The electrode provided by the present invention is also applicable to the positive electrode, and when the electrode is a positive electrode, the material of the first active layer usually uses a highly viscous substance to improve the safety performance of the lithium-ion battery. However, due to the large viscosity of this substance, when cleaning the area where the first groove is located in the first active layer, the highly viscous substance cannot be thoroughly cleaned, resulting in residues of the highly viscous substance in the area corresponding to the first groove, which affects the connection between the tab and the current collector, and causes the tab to be unable to be connected to the middle position on the side of the current collector. Therefore, the use of the electrode structure provided by the present invention can effectively avoid this problem, that is, the first active layer uses a highly viscous substance, and subsequently only the second active layer needs to be cleaned, without cleaning the first active layer. Specifically, the highly viscous substance refers to an adhesive with a molecular weight of 800,000-2,000,000 included in the active layer material, and the mass of the adhesive is 3%-40% of the total mass of the first active layer.

[0017] In addition, the thicknesses of the first active layer and the second active layer in the electrode have a great influence on the performance of the lithium-ion battery. Through research by the inventors of the present application, it is found that when the thickness ratio of the first active layer increases, the cycle performance of the lithium-ion battery will moderately decline. Therefore, the thickness of the first active layer is 5%-80% of the total thickness of the first active layer and the second part of the second active layer.

[0018] When the electrode is a positive electrode, the thickness of the first active layer should be appropriately reduced. For example, Figure 3 is the front view of the positive electrode provided by an embodiment of the present invention. As Figure 3 shown, when the electrode is a positive electrode, the thickness of the first part of the second active layer is higher than the thickness of the first active layer.

[0019] Based on the electrode structure provided by the present invention, those skilled in the art can combine with the existing electrode preparation method. Specifically, first, prepare the first active layer slurry and the second active layer slurry; secondly, coat the prepared first active layer slurry on the surface of the current collector, and perform blank coating in the area corresponding to the first groove to obtain the first active layer provided with the first groove. Then, coat the second active layer slurry according to the conventional electrode coating process. Among them, part of the second active layer slurry fills the first groove under the action of gravity to obtain the first part of the second active layer, and the remaining part of the second active layer slurry obtains the second part of the second active layer. Finally, clean the active layer in a part of the area in the first part located in the first groove to obtain the second groove, and set the tab in the second groove and electrically connect it to the current collector to obtain the electrode.

[0020] Those skilled in the art can select the materials for the positive electrode sheet and the negative electrode sheet in combination with the existing technology. For example, when the electrode sheet is a positive electrode sheet, the current collector can be aluminum foil, and the positive electrode active material includes at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based materials, and lithium nickel cobalt aluminate;

[0021] When the electrode sheet is a negative electrode sheet, the current collector can be copper foil, and the negative electrode active material includes at least one of artificial graphite, natural graphite, and modified graphite;

[0022] The adhesives and conductive agents used for the positive electrode sheet and the negative electrode sheet are the same. Specifically, the adhesive can include at least one of polyvinylidene fluoride (PVDF), copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber (SBR); the conductive agent can include at least one of conductive carbon black, carbon nanotubes, conductive graphite, and graphene; a thickening agent can also be included in the negative electrode sheet, and the thickening agent can be sodium carboxymethyl cellulose.

[0023] It can be understood that the second groove is used to connect the tab. Therefore, along the width direction of the current collector, the width of the second groove is smaller than the width of the first groove.

[0024] In the actual preparation process, in order to facilitate the connection between the tab and the current collector, the vertical projection area of the second groove on the current collector can be increased so that the vertical projection area of the second groove on the current collector is larger than the area of the tab connection area on the current collector.

[0025] Figure 4 This is a top view of the tab provided by another embodiment of the present invention, as Figure 4 shown, the length and width of the first groove are both larger than the area of the tab connection area on the current collector, so as to facilitate the connection between the tab 4 and the current collector 1.

[0026] Furthermore, the width of the second groove is 1-2 times the width of the tab connection area, and the length of the second groove is 1-2 times the length of the tab connection area.

[0027] In summary, the present invention provides an electrode sheet, which improves the charging risk at the tab connection position to a certain extent by reducing the thickness of the active layer near the tab, and improves the cycle performance of the lithium-ion battery.

[0028] The second aspect of the present invention provides a lithium-ion battery, including any one of the above electrode sheets.

[0029] The present invention provides a pole piece. Based on the pole piece provided by the present invention, those skilled in the art can prepare a lithium-ion battery in combination with the existing technology. The lithium-ion battery provided by the present invention has good cycle performance.

[0030] The implementation of the present invention has at least the following advantages:

[0031] 1. For the pole piece provided by the present invention, by reducing the thickness of the active layer near the tab, the charging risk at the tab connection position is improved to a certain extent, and the cycle performance of the lithium-ion battery is enhanced.

[0032] 2. The pole piece provided by the present invention is applicable to both the positive pole piece and the negative pole piece.

[0033] 3. When the pole piece is a positive pole piece, the pole piece structure provided by the present invention can avoid the problem that the tab cannot be connected to the center of the side of the current collector due to the presence of high-viscosity substances in the first active layer.

[0034] 4. The lithium-ion battery provided by the present invention has good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1a is the front view of the pole piece provided by an embodiment of the present invention;

[0036] Figure 1b is the top view of the pole piece provided by an embodiment of the present invention;

[0037] Figure 1c is the left view of the pole piece provided by an embodiment of the present invention;

[0038] Figure 2a is the front view of the pole piece provided by another embodiment of the present invention;

[0039] Figure 2b is the top view of the pole piece provided by another embodiment of the present invention;

[0040] Figure 3 is the front view of the pole piece provided by still another embodiment of the present invention;

[0041] Figure 4 is the top view of the pole piece provided by still another embodiment of the present invention.

[0042] DESCRIPTION OF THE REFERENCE NUMERALS:

[0043] 1: Current collector;

[0044] 2: First active layer;

[0045] 3: Second active layer;

[0046] 4: Tab. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will, in conjunction with the embodiments of the present invention, clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are some, rather than all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0048] Embodiment 1

[0049] The electrode provided in this embodiment is a positive electrode, and the front view of its structure is as Figure 3 shown, the top view is as Figure 4 shown, and the left view is as Figure 1c shown, where:

[0050] The current collector is aluminum foil with a width of 79 mm;

[0051] The width of the first groove is 79 mm and the length is 15 mm;

[0052] The width of the second groove is 25 mm and the length is 10 mm;

[0053] The thickness of the first active layer is 10 μm, and the thickness of the second active layer is 80 μm;

[0054] The material used for the first active layer is a highly viscous substance, including lithium cobaltate, conductive carbon, and polyvinylidene fluoride. Among them, the molecular weight of polyvinylidene fluoride is 800,000, and the mass of polyvinylidene fluoride is 20% of the total mass of the first active layer.

[0055] Embodiment 2

[0056] The electrode provided in this embodiment is a negative electrode, and the front view of its structure is as Figure 2a shown, the top view is as Figure 4 shown, and the left view is as Figure 1c shown, where:

[0057] The current collector is copper foil with a width of 81 mm;

[0058] The width of the first groove is 81 mm and the length is 50 mm;

[0059] The width of the second groove is 25 mm and the length is 10 mm;

[0060] The thickness of the first active layer is 50 μm, and the thickness of the second active layer is 50 μm;

[0061] The active material used for the second active layer is graphite, the average particle size of graphite is 15 μm, and the graphitization degree is 94%.

[0062] Example 3

[0063] The electrode provided in this example is a negative electrode, and its front view of the structure is as shown in Figure 3 shown, and the top view is as shown in Figure 4 shown, and the left view is as shown in Figure 1c shown, where:

[0064] The current collector is a copper foil with a width of 81 mm;

[0065] The width of the first groove is 81 mm and the length is 50 mm;

[0066] The width of the second groove is 25 mm and the length is 10 mm;

[0067] The thickness of the first active layer is 30 μm, and the thickness of the second active layer is 70 μm;

[0068] The active material used in the second active layer is graphite, the average particle size of the graphite is 15 μm, and the graphitization degree is 94%.

[0069] Example 4

[0070] The electrode provided in this example is a negative electrode, and its front view of the structure is as shown in Figure 3 shown, and the top view is as shown in Figure 4 shown, and the left view is as shown in Figure 1c shown, where:

[0071] The current collector is a copper foil with a width of 81 mm;

[0072] The width of the first groove is 81 mm and the length is 50 mm;

[0073] The width of the second groove is 25 mm and the length is 10 mm;

[0074] The thickness of the first active layer is 40 μm, and the thickness of the second active layer is 60 μm;

[0075] The active material used in the second active layer is graphite, the average particle size of the graphite is 15 μm, and the graphitization degree is 94%.

[0076] Example 5

[0077] The electrode provided in this example is a negative electrode, and its front view of the structure is as shown in Figure 2a shown, and the top view is as shown in Figure 4 shown, and the left view is as shown in Figure 1c shown, where:

[0078] The current collector is a copper foil with a width of 81 mm;

[0079] The width of the first groove is 81 mm and the length is 50 mm;

[0080] The width of the second groove is 25 mm and the length is 10 mm;

[0081] The thickness of the first active layer is 50 μm and the thickness of the second active layer is 50 μm;

[0082] The active material used in the second active layer is graphite. The average particle size of the graphite is 10 μm and the graphitization degree is 92%.

[0083] Example 6

[0084] The electrode provided in this example is a negative electrode. Its front view of the structure is as shown in Figure 2a shown, the top view is as shown in Figure 4 shown, and the left view is as shown in Figure 1c shown, where:

[0085] The current collector is a copper foil with a width of 81 mm;

[0086] The width of the first groove is 81 mm and the length is 50 mm;

[0087] The width of the second groove is 25 mm and the length is 10 mm;

[0088] The thickness of the first active layer is 50 μm and the thickness of the second active layer is 50 μm;

[0089] The active material used in the second active layer is graphite. The average particle size of the graphite is 10 μm and the graphitization degree is 95%.

[0090] Example 7

[0091] The electrode provided in this example is a negative electrode. Its front view of the structure is as shown in Figure 2a shown, the top view is as shown in Figure 4 shown, and the left view is as shown in Figure 1c shown, where:

[0092] The current collector is a copper foil with a width of 81 mm;

[0093] The width of the first groove is 81 mm and the length is 50 mm;

[0094] The width of the second groove is 25 mm and the length is 10 mm;

[0095] The thickness of the first active layer is 50 μm and the thickness of the second active layer is 50 μm;

[0096] The active material used in the second active layer is graphite. The average particle size of the graphite is 15 μm and the graphitization degree is 92%.

[0097] Example 8

[0098] The electrode provided in this embodiment is a negative electrode, and its front view of the structure is as shown in Figure 2a , the top view is as shown in Figure 4 , and the left view is as shown in Figure 1c . Among them:

[0099] The current collector is a copper foil with a width of 81 mm;

[0100] The width of the first groove is 81 mm and the length is 50 mm;

[0101] The width of the second groove is 25 mm and the length is 10 mm;

[0102] The thickness of the first active layer is 50 μm, and the thickness of the second active layer is 50 μm;

[0103] The active material used in the second active layer is graphite, the average particle size of the graphite is 15 μm, and the graphitization degree is 95%.

[0104] Comparative Example 1

[0105] The electrode provided in this comparative example is a positive electrode, including a current collector and an active layer provided on the surface of the current collector. The tab is connected to the outermost edge side of the current collector. Among them:

[0106] The current collector is an aluminum foil with a width of 79 mm;

[0107] The thickness of the active layer is 90 μm.

[0108] Comparative Example 2

[0109] The electrode provided in this comparative example is a negative electrode, including a current collector and a first active layer and a second active layer provided on the surface of the current collector. A groove is provided in the middle of the sides of the first active layer and the second active layer, and the tab is connected in this groove. Among them:

[0110] The current collector is a copper foil with a width of 81 mm;

[0111] The width of the groove is 25 mm and the length is 10 mm;

[0112] The total thickness of the first active layer and the second active layer is 100 μm.

[0113] Based on the electrodes provided in Embodiments 1-8 and Comparative Examples 1-2 of the present invention, lithium-ion batteries are prepared by matching negative electrodes / positive electrodes, separators, and electrolytes with the same structure. For example, if Embodiment 1 and Comparative Example 1 are positive electrodes, the structure of the corresponding negative electrode is the same as that of the positive electrode. If Embodiments 2-8 and Comparative Example 2 are negative electrodes, the structure of the corresponding positive electrode is the same as that of the negative electrode, and the cycle performance of the lithium-ion batteries is tested.

[0114] Among them, the positive electrode material was purchased from Xiamen Xiatung New Energy Materials Co., Ltd., the negative electrode material was purchased from Shanghai Shanshan Technology Co., Ltd., the diaphragm was purchased from Dongguan Zhuogao Electronic Technology Co., Ltd., and the electrolyte was purchased from Shenzhen Xinzhoubang Technology Co., Ltd.

[0115] The performance test method of lithium-ion batteries is:

[0116] The lithium ion batteries prepared on the basis of Example 1 and Comparative Example 1 were subjected to a 2C / 0.7C charge and discharge cycle test at 25°C, and the cycle retention rate (%) was calculated. The surface temperature of the battery cell was monitored by a temperature sensor, and the difference between the maximum value and the initial temperature was recorded as the temperature rise (°C) of the lithium ion battery. The test results are shown in Table 1.

[0117] The lithium-ion batteries prepared based on Examples 2-8 and Comparative Example 2 were subjected to 2C / 0.7 C charge-discharge cycle tests at 25°C / 10°C, and the cycle retention rates (%) were calculated. The test results are shown in Table 2.

[0118] Table 1 Performance test results of lithium ion batteries provided in Example 1 and Comparative Example 1

[0119]

[0120] Table 2 Cyclic performance test results of lithium ion batteries provided in Examples 2-8 and Comparative Example 2

[0121]

[0122] It can be seen from Table 1-2 that the lithium ion batteries provided in Examples 1-8 all have good cycle performance; according to the data provided in Examples 2-4, as the proportion of the first active layer to the total thickness of the active layer increases, the performance of the lithium ion battery will decrease moderately, and therefore, the thickness of the first active layer should be controlled; according to the data provided in Examples 5-8, in the negative electrode sheet, as the average particle size and degree of graphitization of the negative electrode active material in the second active layer increase, the cycle retention rate of the lithium ion battery will decrease.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pole piece, characterized in that, The electrode includes a current collector, a first active layer, and a second active layer. The first active layer is disposed on the surface of the current collector and is provided with a first groove, and the first active layer is not provided in the first groove. The second active layer is divided into a first part disposed in the first groove and a second part disposed on the surface of the first active layer away from the current collector; Wherein, a second groove is provided on the first part, and the tab is disposed at the second groove and is electrically connected to the current collector. The thickness of the first part of the second active layer is less than the total thickness of the first active layer and the second part of the second active layer; The electrode is a positive electrode or a negative electrode; When the electrode is a positive electrode, the positive active material of the positive electrode includes at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based material, and lithium nickel cobalt aluminate; When the electrode is a negative electrode, the negative active material of the negative electrode includes at least one of artificial graphite, natural graphite, and modified graphite.

2. The pole piece according to claim 1, characterized in that, The thickness of the second active layer is greater than the thickness of the first active layer; and / or, the thickness of the first part of the second active layer is greater than the thickness of the second part.

3. The pole piece according to claim 1, wherein The width of the first groove is the same as the width of the current collector.

4. The pole piece according to claim 1, characterized in that, The vertical projection area of the second groove on the current collector is 1%-50% of the vertical projection area of the first groove on the current collector.

5. The pole piece according to any one of claims 1-4, characterized in that, The electrode is a negative electrode, and the average particle size of the negative active material in the second active layer is 5-20 μm, and the graphitization degree is 90%-98%.

6. The pole piece according to any one of claims 1-4, characterized in that, The electrode is a positive electrode. The molecular weight of the binder in the first active layer is 800,000-2,000,000, and the mass of the binder is 3%-40% of the total mass of the first active layer.

7. The pole piece according to claim 1, characterized in that, The thickness of the first active layer is 5%-80% of the total thickness of the first active layer and the second part of the second active layer.

8. The pole piece according to claim 1, wherein Along the width direction of the current collector, the width of the second groove is less than the width of the first groove.

9. The pole piece according to claim 1, characterized in that, The width of the second groove is 1-2 times the width of the tab connection area, and the length of the second groove is 1-2 times the length of the tab connection area.

10. The pole piece according to claim 1, wherein The center of the vertical projection of the second groove on the current collector is located in the first groove.

11. The pole piece according to claim 1, characterized in that, A slope is formed on the side of the second part close to the first part.

12. A lithium-ion battery, characterized in that, An electrode according to any one of claims 1-11 above is included.

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