Negative electrode sheet, cylindrical secondary battery and electronic device

Abstract

A negative electrode sheet, a cylindrical secondary battery and an electronic device. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer has a thickness of T0 µm; the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises silicon, and the mass percentage of silicon in the negative electrode active material layer is P0%; the negative electrode active material layer is provided with a plurality of grooves, and the grooving amount of the negative electrode active material layer is V0%, where V0%=(M1-M2) / M1×100%, M1 being the mass of the negative electrode active material layer before the grooves are provided, and M2 being the mass of the negative electrode active material layer after the grooves are provided; and V0, T0 and P0 satisfy: when 20<T0≤120 and 0≤P0≤90, 0.02≤V0≤30. The negative electrode sheet is applied to a cylindrical secondary battery, enabling the cylindrical secondary battery to have good cycling performance.

Description

Negative electrode plate, cylindrical secondary battery and electronic device Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a negative electrode, a cylindrical secondary battery, and an electronic device. Background Technology

[0002] In cylindrical secondary batteries, it is difficult for the electrolyte to penetrate or wet the electrode assembly along the axial direction. This is especially true for full-tab cylindrical secondary batteries, where the two ends along the axial direction are flattened areas of the tabs (empty foil areas), reducing wetting channels and hindering electrolyte flow. Poor electrolyte replenishment or flow during use can easily lead to interface failure in cylindrical secondary batteries, causing premature battery degradation. Therefore, improving the cycle performance of cylindrical secondary batteries has become a pressing technical problem to be solved in this field.

[0003] Summary of the Invention

[0004] The purpose of this application is to provide a negative electrode sheet, a cylindrical secondary battery, and an electronic device to improve the cycle performance of the cylindrical secondary battery.

[0005] It should be noted that, in the description of the invention in this application, a cylindrical lithium-ion battery is used as an example of a cylindrical secondary battery to explain the invention; however, the cylindrical secondary battery in this application is not limited to cylindrical lithium-ion batteries. The specific technical solution is as follows:

[0006] The first aspect of this application provides a negative electrode sheet, which includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The thickness of the negative active material layer is T0 μm. The negative active material layer includes a negative active material, which includes silicon element, and the mass percentage of silicon element in the negative active material layer is P0%. The negative active material layer is provided with a plurality of grooves, and the groove amount in the negative active material layer is V0%, where V0% = (M1-M2) / M1×100%, M1 is the mass of the negative active material layer before the grooves are provided, and M2 is the mass of the negative active material layer after the grooves are provided. V0 satisfies the following conditions with respect to T0 and P0: when 20 < T0 ≤ 120 and 0 ≤ P0 ≤ 90, 0.02 ≤ V0 ≤ 30. When the thickness of the negative electrode active material layer and the mass percentage of silicon in the negative electrode active material layer are within the aforementioned range, by setting multiple grooves on the negative electrode active material layer and controlling the number of grooves within the range of this application, it is beneficial to increase the electrolyte wetting channels on the negative electrode active material layer, improve the electrolyte flow rate, increase the electrolyte storage capacity in the negative electrode sheet, and provide sufficient lithium intercalation space in the negative electrode active material layer. This improves the electrolyte wetting performance of the negative electrode sheet, enhances its liquid storage and conductivity, and also improves the solid electrolyte interphase (SEI) impedance and lithium insertion / extraction impedance of the negative electrode sheet. When the negative electrode sheet is applied to a cylindrical secondary battery, the probability of insufficient electrolyte replenishment or poor flow is reduced, the charge / discharge kinetics of the cylindrical secondary battery are improved, and thus the cycle performance of the cylindrical secondary battery is enhanced.

[0007] In one or more embodiments of this application, when 20 < T0 ≤ 50, V0 and P0 satisfy the following conditions: 0 ≤ P0 < 20, 0.02 ≤ V0 ≤ 20; 20 ≤ P0 ≤ 90, 0.15 ≤ V0 ≤ 25. When the thickness T0 of the negative electrode active material layer satisfies 20 < T0 ≤ 50, the mass percentage of silicon in the negative electrode active material layer P0 and the groove amount V0 in the negative electrode active material layer are controlled within the above ranges, so that T0, P0, and V0 cooperate with each other, which is beneficial to improving the cycle performance of the cylindrical secondary battery.

[0008] In one or more embodiments of this application, when 50 < T0 ≤ 80, V0 and P0 satisfy the following relationships: 0 ≤ P0 < 20, 0.05 ≤ V0 ≤ 25; 20 ≤ P0 ≤ 90, 0.3 ≤ V0 ≤ 30. When the thickness T0 of the negative electrode active material layer satisfies 50 < T0 ≤ 80, controlling the mass percentage of silicon in the negative electrode active material layer P0 and the groove amount V0 in the negative electrode active material layer within the above ranges, so that T0, P0, and V0 cooperate with each other, it is beneficial to improve the cycle performance of the cylindrical secondary battery.

[0009] In one or more embodiments of this application, when 80 < T0 ≤ 120, V0 and P0 satisfy the following conditions: 0 ≤ P0 < 20, 0.15 ≤ V0 ≤ 30; 20 ≤ P0 ≤ 90, 0.5 ≤ V0 ≤ 30. When the thickness T0 of the negative electrode active material layer satisfies 80 < T0 ≤ 120, controlling the mass percentage of silicon in the negative electrode active material layer P0 and the groove amount V0 in the negative electrode active material layer within the above ranges, so that T0, P0, and V0 cooperate with each other, it is beneficial to improve the cycle performance of the cylindrical secondary battery.

[0010] In one or more embodiments of this application, 20 < T0 ≤ 50, 0.5 ≤ P0 ≤ 15, and 0.5 ≤ V0 ≤ 5. By controlling the thickness T0 of the negative electrode active material layer, the mass percentage of silicon in the negative electrode active material layer P0, and the number of grooves V0 in the negative electrode active material layer within the above ranges, the cycle performance of the cylindrical secondary battery is further improved.

[0011] In one or more embodiments of this application, 50 < T0 ≤ 80, 0.5 ≤ P0 ≤ 15, and 0.5 ≤ V0 ≤ 6. By controlling the thickness T0 of the negative electrode active material layer, the mass percentage of silicon in the negative electrode active material layer P0, and the number of grooves V0 in the negative electrode active material layer within the above ranges, the cycle performance of the cylindrical secondary battery is further improved.

[0012] In one or more embodiments of this application, 80 < T0 ≤ 120, 0.5 ≤ P0 ≤ 15, and 0.5 ≤ V0 ≤ 10. By controlling the thickness T0 of the negative electrode active material layer, the mass percentage of silicon in the negative electrode active material layer P0, and the number of grooves V0 in the negative electrode active material layer within the above ranges, the cycle performance of the cylindrical secondary battery is further improved.

[0013] In one or more embodiments of this application, the depth of each groove along the thickness direction of the negative electrode active material layer is h μm, where 5% × T0 ≤ h < 100% × T0. Controlling the groove depth within the above range is beneficial for improving the cycle performance of the cylindrical secondary battery.

[0014] In one or more embodiments of this application, 25% × T0 ≤ h ≤ 75% × T0. Adjusting the depth of the groove within the above range is beneficial for further improving the cycle performance of the cylindrical secondary battery.

[0015] In one or more embodiments of this application, the width of each groove along the length of the negative electrode active material layer is b μm, where 30 ≤ b ≤ 1000. Adjusting the groove width within the above range is beneficial for improving the cycle performance of the cylindrical secondary battery.

[0016] In one or more embodiments of this application, 70 ≤ b ≤ 500. Adjusting the width of the groove within the above range is beneficial for further improving the cycle performance of the cylindrical secondary battery.

[0017] In one or more embodiments of this application, the projection of each groove on the plane of the negative electrode active material layer has a length of L mm in the width direction of the negative electrode active material layer, and the width of the negative electrode active material layer is W mm, where 0.1W ≤ L ≤ W. Adjusting the length L of the groove within the above range is beneficial for improving the phenomenon of insufficient electrolyte wetting or poor flow, thereby improving the cycle performance of the cylindrical secondary battery.

[0018] In one or more embodiments of this application, 0.8W ≤ L ≤ W. Adjusting the length L of the groove within the above range helps to further improve the phenomenon of insufficient electrolyte wetting and replenishment or poor flow, thereby improving the cycle performance of the cylindrical secondary battery.

[0019] In one or more embodiments of this application, N grooves are provided per 10cm length of negative electrode active material layer, where 5 ≤ N ≤ 500. By controlling the number N of grooves provided in each 10cm length of negative electrode active material layer within the above range, the cylindrical secondary battery exhibits good cycle performance.

[0020] In one or more embodiments of this application, 20 ≤ N ≤ 200. By adjusting N within the above range, the cylindrical secondary battery exhibits good cycle performance.

[0021] In one or more embodiments of this application, the cross-sectional shape of the groove along the thickness direction of the negative electrode active material layer is rectangular, semi-circular, trapezoidal, triangular or curved.

[0022] A second aspect of this application provides a cylindrical secondary battery, wherein the cylindrical secondary battery includes the negative electrode sheet described in any of the foregoing embodiments. Therefore, the cylindrical secondary battery has good cycle performance.

[0023] A third aspect of this application provides an electronic device comprising the cylindrical secondary battery described in any of the foregoing embodiments.

[0024] The beneficial effects of the embodiments of this application are as follows:

[0025] This application provides a negative electrode sheet, a cylindrical secondary battery, and an electronic device. The negative electrode sheet has grooves with a depth of V0 formed in a negative electrode active material layer with a thickness of T0 and a silicon mass percentage of P0. T0, P0, and V0 are controlled within the range specified in this application. This increases the electrolyte wetting channels on the negative electrode active material layer, improves the electrolyte flow rate, increases the electrolyte storage capacity in the negative electrode sheet, and provides sufficient lithium intercalation space within the negative electrode active material layer. This improves the electrolyte wetting performance of the negative electrode sheet, enhances its electrolyte storage and conductivity, and also improves the solid electrolyte interface film impedance and lithium intercalation / deintercalation impedance. When the negative electrode sheet is applied to a cylindrical secondary battery, the probability of insufficient electrolyte replenishment or poor flow is reduced, improving the charge-discharge kinetics of the cylindrical secondary battery and thus enhancing its cycle performance. Attached Figure Description

[0026] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0027] Figure 1 is a schematic cross-sectional view of the negative electrode sheet along its thickness and length directions in some embodiments of this application.

[0028] Figure 2 is a schematic cross-sectional view of the negative electrode sheet along its thickness and length directions in some other embodiments of this application.

[0029] Figure 3 is a schematic diagram of the structure in which the negative electrode active material layer itself forms a plane in the length and width directions in some embodiments of this application;

[0030] Figure 4 is a schematic diagram of the structure in which the negative electrode active material layer itself forms a plane in the length and width directions in some other embodiments of this application;

[0031] Figure 5 is a schematic diagram showing the positional relationship of the negative electrode tabs on the negative electrode sheet in some embodiments of this application;

[0032] Figure 6 is a schematic diagram showing the positional relationship of the positive electrode tabs on the positive electrode sheet in some embodiments of this application;

[0033] Figure 7 shows the impedance test diagrams for Example 1-1 and Comparative Example 1-1.

[0034] Reference numerals: 10-Negative electrode sheet; 11-Negative electrode current collector; 12-Negative electrode active material layer; 13-Groove; 14-Negative electrode tab; 21-Positive electrode current collector; 22-Positive electrode active material layer; 24-Positive electrode tab. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0036] In cylindrical secondary batteries, it is difficult for the electrolyte to penetrate or wet the electrode assembly along the axial direction. This is especially true for full-tab cylindrical secondary batteries, where the two ends along the axial direction are flattened areas of the tabs (empty foil areas), reducing wetting channels and making electrolyte flow difficult. Thus, cylindrical secondary batteries are prone to insufficient electrolyte replenishment or poor flow during use, easily leading to interface failure and premature battery degradation. The "replenishment" in "insufficient electrolyte replenishment" refers to the replenishment of free electrolyte into the electrodes after the tabs consume electrolyte during charge-discharge cycles. The electrodes refer to the positive and / or negative electrodes. The tabs refer to the positive and / or negative tabs. Based on the above problems, this application provides a negative electrode, a cylindrical secondary battery, and an electronic device.

[0037] It should be noted that, in the specific embodiments of this application, a cylindrical lithium-ion battery is used as an example of a cylindrical secondary battery to explain this application, but the cylindrical secondary battery of this application is not limited to a cylindrical lithium-ion battery.

[0038] The first aspect of this application provides a negative electrode sheet, which includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The thickness of the negative active material layer is T0 μm. The negative active material layer includes a negative active material, which includes silicon. The mass percentage of silicon in the negative active material layer is P0%. The negative active material layer has multiple grooves, and the amount of grooves in the negative active material layer is V0%, where V0% = (M1-M2) / M1 × 100%, and M1 is the mass of the negative active material layer before the grooves are formed, and M2 is the mass of the negative active material layer after the grooves are formed. V0 satisfies the following relationships with T0 and P0: 20 < T0 ≤ 120, 0 ≤ P0 ≤ 90, and 0.02 ≤ V0 ≤ 30. It is understood that when P0 = 0, the mass percentage of silicon in the negative active material layer is 0%, and the negative active material does not include silicon.

[0039] For ease of understanding, in this application, the length direction of the negative electrode sheet is defined as X, the width direction as Y, and the thickness direction as Z. It should be understood that the above definitions of directions are for the purpose of conveniently describing this application, and the directions defined in this application can be understood based on the relative positions of the elements in the accompanying drawings and actual products. Furthermore, the width, length, and thickness directions of the negative electrode active material layer and the negative electrode current collector are the same as those of the negative electrode sheet. The aforementioned "negative electrode active material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode active material layer is disposed on one or both surfaces of the negative electrode current collector. The aforementioned "surface" can be a portion of the surface of the negative electrode current collector or all of its surfaces. As shown in Figure 1, the negative electrode sheet 10 includes a negative electrode current collector 11 and a negative electrode active material layer 12. The negative electrode active material layer 12 is disposed on one surface of the negative electrode current collector 11, and the thickness of the negative electrode active material layer 12 is indicated by T0. The negative electrode active material layer 12 has multiple grooves 13. Of course, the negative electrode active material layer 12 can also be disposed on the other surface of the negative electrode current collector 11. In this application, the thickness T0 of the negative electrode active material layer 12 refers to the thickness of a single layer of negative electrode active material layer 12 without the grooves 13. As shown in FIG2, the negative electrode sheet 10 includes a negative electrode current collector 11 and a negative electrode active material layer 12. The negative electrode active material layer 12 is disposed on two surfaces of the negative electrode current collector 11. The thickness of the negative electrode active material layer 12 is shown as T0. The negative electrode active material layer 12 is provided with a plurality of grooves 13. It should be noted that the shape, number, depth, width, length, etc. of the grooves in the accompanying drawings of this application are only illustrative examples and are not intended to limit the scope of this application.

[0040] For example, T0 is 21, 34, 50, 59, 67, 80, 82, 94, 108, 120, or any value within any two of the above ranges. For example, P0 is 0, 1, 2, 3, 5, 7, 10, 13, 16, 20, 30, 40, 52, 60, 70, 76, 82, 90, or any value within any two of the above ranges. For example, V0 is 0.02, 3, 5, 7, 10, 15, 18, 20, 25, 27, 30, or any value within any two of the above ranges. When the thickness T0 of the negative electrode active material layer and the mass percentage P0 of silicon in the negative electrode active material layer are within the above ranges, if V0 is less than 0.02, the groove amount in the negative electrode active material layer is too small, the groove function is difficult to exert, the increase in wetting channels in the negative electrode sheet is not significant, and the improvement in electrolyte flow is not significant; if V0 is greater than 30, the loss of the negative electrode active material layer is too large, the energy density provided by the negative electrode sheet is too small, which will affect the energy density of the cylindrical secondary battery. Furthermore, the number of lithium ions extracted from the positive electrode sheet and their insertion sites in the negative electrode sheet is reduced, which will cause lithium plating on the surface of the negative electrode sheet, resulting in interface failure between the negative electrode sheet and the electrolyte, affecting the performance of the cylindrical secondary battery, such as cycle performance, kinetic performance, safety performance, and rate performance.

[0041] When the thickness of the negative electrode active material layer and the mass percentage of silicon in the negative electrode active material layer are within the aforementioned range, and multiple grooves are formed on the negative electrode active material layer, and the number of grooves in the negative electrode active material layer is controlled within the range of this application, it is beneficial to increase the electrolyte wetting channels on the negative electrode active material layer, improve the electrolyte flow rate, increase the electrolyte storage capacity in the negative electrode sheet, and provide sufficient lithium intercalation space in the negative electrode active material layer. This improves the electrolyte wetting performance of the negative electrode sheet, enhances the electrolyte storage and conductivity of the negative electrode sheet, and also improves the solid electrolyte interphase (SEI) impedance and lithium intercalation / deintercalation impedance of the negative electrode sheet. When the negative electrode sheet is applied to a cylindrical secondary battery, the probability of insufficient electrolyte replenishment or poor flow in the cylindrical secondary battery is reduced, improving the charge-discharge kinetics of the cylindrical secondary battery and thus enhancing its cycle performance.

[0042] In some embodiments of this application, when 20 < T0 ≤ 50, V0 and P0 satisfy the following conditions: 0 ≤ P0 < 20, 0.02 ≤ V0 ≤ 20; 20 ≤ P0 ≤ 90, 0.15 ≤ V0 ≤ 25. For example, when 20 < T0 ≤ 50 and 0 ≤ P0 < 20, V0 is 0.02, 1, 2, 3, 4, 5, 7, 8, 9, 10, 13, 15, 17, 20, or any value between any two of the above ranges. For example, when 20 < T0 ≤ 50 and 20 ≤ P0 ≤ 90, V0 is 0.15, 3, 5, 7, 9, 11, 13, 15, 17, 20, 22, 25, or any value between any two of the above ranges. When the thickness T0 of the negative electrode active material layer satisfies 20 < T0 ≤ 50, the mass percentage of silicon in the negative electrode active material layer P0 and the groove amount V0 in the negative electrode active material layer are controlled within the above range. This allows T0, P0, and V0 to work together, which is beneficial for improving the wettability of the negative electrode sheet to the electrolyte, as well as improving the SEI impedance and lithium insertion / extraction impedance of the negative electrode sheet. When the negative electrode sheet is applied to cylindrical secondary batteries, the probability of insufficient electrolyte replenishment or poor flow in the cylindrical secondary battery is reduced, improving the charge / discharge kinetics of the cylindrical secondary battery, and thus enhancing its cycle performance.

[0043] In some embodiments of this application, when 50 < T0 ≤ 80, V0 and P0 satisfy the following conditions: 0 ≤ P0 < 20, 0.05 ≤ V0 ≤ 25; 20 ≤ P0 ≤ 90, 0.3 ≤ V0 ≤ 30. For example, when 50 < T0 ≤ 80 and 0 ≤ P0 < 20, V0 is 0.05, 1, 3, 4, 6, 7, 8, 9, 10, 13, 15, 17, 20, 22, 25, or any value between any two of the above ranges. For example, when 50 < T0 ≤ 80 and 20 ≤ P0 ≤ 90, V0 is 0.3, 3, 5, 7, 9, 11, 13, 15, 17, 20, 22, 25, 30, or any value between any two of the above ranges. When the thickness T0 of the negative electrode active material layer satisfies 50 < T0 ≤ 80, the mass percentage of silicon in the negative electrode active material layer P0 and the groove amount V0 in the negative electrode active material layer are controlled within the above range. This allows T0, P0, and V0 to work together, which is beneficial for improving the wettability of the negative electrode sheet to the electrolyte, and also for improving the SEI impedance and lithium insertion / extraction impedance of the negative electrode sheet. When the negative electrode sheet is applied to cylindrical secondary batteries, the probability of insufficient electrolyte replenishment or poor flow in the cylindrical secondary battery is reduced, improving the charge / discharge kinetics of the cylindrical secondary battery, and thus enhancing the cycle performance of the cylindrical secondary battery.

[0044] In some embodiments of this application, when 80 < T0 ≤ 120, V0 and P0 satisfy the following conditions: 0 ≤ P0 < 20, 0.15 ≤ V0 ≤ 30; 20 ≤ P0 ≤ 90, 0.5 ≤ V0 ≤ 30. For example, when 80 < T0 ≤ 120 and 0 ≤ P0 < 20, V0 is 0.15, 3, 5, 7, 9, 11, 13, 15, 17, 20, 22, 25, 30, or any value between any two of the above ranges. For example, when 80 < T0 ≤ 120 and 20 ≤ P0 ≤ 90, V0 is 0.5, 5, 9, 11, 15, 20, 25, 30, or any value between any two of the above ranges. When the thickness T0 of the negative electrode active material layer satisfies 80 < T0 ≤ 120, the mass percentage of silicon in the negative electrode active material layer P0 and the groove amount V0 in the negative electrode active material layer are controlled within the above range. This allows T0, P0, and V0 to work together, which is beneficial for improving the wettability of the negative electrode sheet to the electrolyte, and also for improving the SEI impedance and lithium insertion / extraction impedance of the negative electrode sheet. When the negative electrode sheet is applied to cylindrical secondary batteries, the probability of insufficient electrolyte replenishment or poor flow in the cylindrical secondary battery is reduced, improving the charge / discharge kinetics of the cylindrical secondary battery, and thus enhancing the cycle performance of the cylindrical secondary battery.

[0045] In some embodiments of this application, 20 < T0 ≤ 50, 0.5 ≤ P0 ≤ 15, and 0.5 ≤ V0 ≤ 5. For example, T0 is 21, 30, 35, 40, 42, 50, or any value between any two of the above ranges. P0 is 0.5, 2, 3, 5, 7, 8, 10, 11, 12, 15, or any value between any two of the above ranges. V0 is 0.5, 1, 2, 3, 4, 5, or any value between any two of the above ranges. The thickness T0 of the negative electrode active material layer, the mass percentage of silicon in the negative electrode active material layer P0, and the number of grooves V0 in the negative electrode active material layer are controlled within the above ranges. T0, P0, and V0 work together to provide a higher capacity and lower volume expansion of the negative electrode, which is beneficial to further improve the wettability of the negative electrode to the electrolyte, and also beneficial to further improve the SEI impedance and lithium insertion / extraction impedance of the negative electrode. When negative electrode sheets are applied to cylindrical secondary batteries, the probability of insufficient electrolyte replenishment or poor flow in cylindrical secondary batteries is further reduced, thereby further improving the charge-discharge kinetics of cylindrical secondary batteries and further enhancing their cycle performance.

[0046] In some embodiments of this application, 50 < T0 ≤ 80, 0.5 ≤ P0 ≤ 15, and 0.5 ≤ V0 ≤ 6. For example, T0 is 51, 60, 65, 71, 76, 80, or any value between any two of the above ranges. P0 is 0.5, 2, 3, 5, 7, 8, 10, 11, 12, 15, or any value between any two of the above ranges. V0 is 0.5, 1, 2, 3, 4, 5, 6, or any value between any two of the above ranges. The thickness T0 of the negative electrode active material layer, the mass percentage of silicon in the negative electrode active material layer P0, and the number of grooves V0 in the negative electrode active material layer are controlled within the above ranges. T0, P0, and V0 work together to provide a higher capacity and lower volume expansion of the negative electrode, which is beneficial to further improve the wettability of the negative electrode to the electrolyte, and also beneficial to further improve the SEI impedance and lithium insertion / extraction impedance of the negative electrode. When negative electrode sheets are applied to cylindrical secondary batteries, the probability of insufficient electrolyte replenishment or poor flow in cylindrical secondary batteries is further reduced, thereby further improving the charge-discharge dynamics of cylindrical secondary batteries and further enhancing their cycle performance.

[0047] In some embodiments of this application, 80 < T0 ≤ 120, 0.5 ≤ P0 ≤ 15, and 0.5 ≤ V0 ≤ 10. For example, T0 is 81, 90, 95, 100, 112, 120, or any value between any two of the above ranges. P0 is 0.5, 2, 3, 5, 7, 8, 10, 11, 12, 15, or any value between any two of the above ranges. V0 is 0.5, 1, 2, 3, 4, 5, 6, 8, 10, or any value between any two of the above ranges. The thickness T0 of the negative electrode active material layer, the mass percentage of silicon in the negative electrode active material layer P0, and the number of grooves V0 in the negative electrode active material layer are all controlled within the above ranges. The interaction of T0, P0, and V0, while ensuring the negative electrode provides high capacity and low volume expansion, further improves the wettability of the negative electrode to the electrolyte, and also helps to further improve the SEI impedance and lithium insertion / extraction impedance of the negative electrode. When the negative electrode is applied to cylindrical secondary batteries, the probability of insufficient electrolyte replenishment or poor flow is further reduced, thus further improving the charge-discharge kinetics of the cylindrical secondary battery and consequently enhancing its cycle performance.

[0048] This application does not impose any particular restrictions on the method of controlling the amount of grooves V0% in the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, it can be achieved by controlling at least one of the depth, width, length, or number of grooves, or it can be achieved by controlling the mass of the negative electrode active material layer before the grooves are set.

[0049] This application does not impose any particular restrictions on the method of controlling the mass percentage P0% of silicon in the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, it can be achieved by controlling the type of negative electrode active material.

[0050] In some embodiments of this application, the depth of each groove is h μm along the thickness direction of the negative electrode active material layer, where 5% × T0 ≤ h < 100% × T0. As shown in Figures 1 and 2, the depth of the groove 13 along the thickness direction Z of the negative electrode active material layer 12 is indicated by h. For example, h is 5% × T0, 13% × T0, 25% × T0, 35% × T0, 46% × T0, 55% × T0, 60% × T0, 75% × T0, 86% × T0, 90% × T0, 99% × T0, or any value between any two of the above ranges. Controlling the groove depth within the above range is beneficial for improving the wetting of the negative electrode sheet with the electrolyte and increasing the penetration efficiency of the negative electrode sheet into the electrolyte. Applying the negative electrode sheet to a cylindrical secondary battery is beneficial for improving the cycle performance of the cylindrical secondary battery. In this application, "groove depth h" refers to the vertical distance from the surface of the negative electrode sheet to the deepest point of the groove.

[0051] In some embodiments of this application, 25% × T0 ≤ h ≤ 75% × T0. For example, h is 25% × T0, 35% × T0, 46% × T0, 55% × T0, 60% × T0, 75% × T0, or any value between any two of the above ranges. Controlling the depth of the groove within the above range is beneficial for further improving the wetting of the negative electrode sheet with the electrolyte and increasing the penetration efficiency of the negative electrode sheet into the electrolyte. Therefore, applying the negative electrode sheet to a cylindrical secondary battery is beneficial for further improving the cycle performance of the cylindrical secondary battery.

[0052] In some embodiments of this application, the width of each groove is b μm along the length direction of the negative electrode active material layer, where 30 ≤ b ≤ 1000. As shown in Figures 1 and 2, the width of the groove 13 along the length direction X of the negative electrode active material layer 12 is indicated by b. For example, b is 30, 50, 100, 200, 300, 500, 800, 1000, or any value between any two of the above ranges. Adjusting the groove width within the above range is beneficial for improving the wetting of the negative electrode sheet with the electrolyte. Applying the negative electrode sheet to a cylindrical secondary battery is beneficial for further improving the cycle performance of the cylindrical secondary battery. In this application, "groove width b" refers to the maximum horizontal distance of the groove measured along the length direction of the negative electrode active material layer.

[0053] In some embodiments of this application, 70 ≤ b ≤ 500. For example, b is 70, 100, 120, 150, 200, 300, 350, 420, 500, or any value between any two of the above ranges. Adjusting the depth of the groove within the above range is beneficial for further improving the wetting of the negative electrode sheet with the electrolyte. Therefore, applying the negative electrode sheet to a cylindrical secondary battery is beneficial for further improving the cycle performance of the cylindrical secondary battery.

[0054] In some embodiments of this application, on the plane of the negative electrode active material layer, the length of the projection of each groove in the width direction of the negative electrode active material layer is L mm, and the width of the negative electrode active material layer is W mm, where 0.1W ≤ L ≤ W. As shown in Figures 3 and 4, on the plane XOY of the negative electrode active material layer 12, the length of the projection of the groove 13 in the width direction Y of the negative electrode active material layer 12 is shown as L, and the width of the negative electrode active material layer 12 in the width direction Y is shown as W. It is understood that the above-mentioned "projection of the groove" refers to the orthographic projection of the groove. For example, L is 0.1W, 0.2W, 0.3W, 0.4W, 0.5W, 0.6W, 0.7W, 0.8W, 0.9W, W, or any value between any two of the above ranges. Adjusting the groove length L within the aforementioned range facilitates electrolyte flow within the negative electrode, improves the electrolyte wetting performance of the negative electrode, and enhances its SEI impedance and lithium insertion / extraction impedance. Applying the negative electrode to cylindrical secondary batteries helps address insufficient electrolyte replenishment or poor flow, thereby improving the cycle performance of the cylindrical secondary batteries.

[0055] In some embodiments of this application, 0.8W ≤ L ≤ W. For example, L is 0.8W, 0.86W, 0.9W, W, or any value between any two of the above ranges. Adjusting the groove length L within the above range can further improve the wettability of the negative electrode to the electrolyte, and further improve the SEI impedance and lithium insertion / extraction impedance of the negative electrode. Applying the negative electrode to a cylindrical secondary battery is beneficial for further improving the phenomenon of insufficient electrolyte replenishment or poor flow, thereby improving the cycle performance of the cylindrical secondary battery.

[0056] In some embodiments of this application, the groove extends through both end faces of the negative electrode active material layer along the width direction of the negative electrode active material layer. For example, as shown in FIG3, the groove 13 extends through both end faces of the negative electrode active material layer 12 along the width direction Y. The length L of the projection of the groove 13 onto the width direction Y of the negative electrode active material layer 12 is equal to the width W of the negative electrode active material layer 12, i.e., L = W. In other embodiments of this application, the groove extends through one end face of the negative electrode active material layer along the width direction of the negative electrode active material layer. For example, as shown in FIG4, the groove 13 extends through one end face of the negative electrode active material layer 12 along the width direction Y. The length L of the projection of the groove 13 onto the width direction Y of the negative electrode active material layer 12 is less than the width W of the negative electrode active material layer 12, 0.1W ≤ L < W.

[0057] This application does not impose any particular limitation on the width of the negative electrode active material layer. Those skilled in the art can choose according to the actual situation, as long as the purpose of this application can be achieved.

[0058] In some embodiments of this application, N grooves are provided per 10cm length of the negative electrode active material layer, where 5 ≤ N ≤ 500. For example, N can be 5, 10, 20, 50, 70, 100, 160, 200, 240, 300, 400, 420, 500, or any value within any two of the above ranges. Controlling the number of grooves N per 10cm length of the negative electrode active material layer within the above range facilitates the uniform distribution of grooves on the negative electrode active material layer. This allows for uniform flow of the electrolyte on the negative electrode active material layer and reduces the probability of uneven distribution due to the grooves. This ensures a uniform distribution of the negative electrode active material layer on the negative electrode current collector, reducing the risk of lithium plating caused by uneven lithium ion insertion. This improves the wettability of the negative electrode sheet to the electrolyte and enhances its SEI impedance and lithium insertion / extraction impedance. When applied to cylindrical secondary batteries, these batteries exhibit excellent cycle performance.

[0059] In some embodiments of this application, 20 ≤ N ≤ 200. For example, N is 20, 50, 70, 100, 160, 200, or any value between any two of the above ranges. Adjusting N within the above range is beneficial for further improving the wettability of the negative electrode to the electrolyte, and improving the SEI impedance and lithium insertion / extraction impedance of the negative electrode. When the negative electrode is applied to a cylindrical secondary battery, the cylindrical secondary battery exhibits good cycle performance.

[0060] In some embodiments of this application, the cross-sectional shape of the groove along the thickness direction of the negative electrode active material layer is rectangular, semi-circular, trapezoidal, triangular, or curved. For example, as shown in Figures 1 and 2, the cross-sectional shape of the groove 13 along the thickness direction Z of the negative electrode active material layer 12 is rectangular. The groove shape described above facilitates the flow of electrolyte.

[0061] This application does not impose any particular limitation on the type of negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material may include, but is not limited to, at least one of artificial graphite, natural graphite, silicon-oxygen materials, silicon-carbon materials, hard carbon materials, soft carbon materials, or lithium metal.

[0062] This application does not impose any particular limitation on the negative electrode current collector, as long as it achieves the purpose of this application. For example, the negative electrode current collector may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collectors (such as lithium copper composite current collectors, carbon copper composite current collectors, nickel copper composite current collectors, titanium copper composite current collectors, etc.). In this application, there is no particular limitation on the thickness of the negative electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode current collector can be from 4 μm to 20 μm.

[0063] In one embodiment of this application, the negative electrode active material layer may further include at least one of a negative electrode conductive agent, a dispersant, or a negative electrode binder. This application does not impose any particular limitation on the types of negative electrode conductive agents, dispersants, and negative electrode binders in the negative electrode active material layer, as long as the purpose of this application is achieved. This application also does not impose any particular limitation on the mass ratio of the negative electrode active material, negative electrode conductive agent, dispersant, and negative electrode binder in the negative electrode active material layer, as long as the purpose of this application is achieved.

[0064] This application does not impose any particular restrictions on the preparation method of the negative electrode sheet, as long as it can achieve the purpose of this application. For example, the preparation method of the negative electrode sheet includes, but is not limited to, the following steps: (1) coating a negative electrode slurry on one surface of the negative electrode current collector, drying and cold pressing to form a semi-finished negative electrode sheet with a single-sided coating of negative electrode active material layer; or, uniformly coating a negative electrode slurry on one surface of the negative electrode current collector, drying, uniformly coating a negative electrode slurry on the other surface of the negative electrode current collector, drying and cold pressing to form a semi-finished negative electrode sheet with a double-sided coating of negative electrode active material layer; (2) setting grooves on the negative electrode active material layer, and cutting to obtain the negative electrode sheet. This application does not impose any particular restrictions on the solid content of the above-mentioned negative electrode slurry, and those skilled in the art can choose according to actual needs, as long as it can achieve the purpose of this application. This application does not impose any particular restrictions on the above-mentioned drying, cold pressing, and cutting process parameters, and those skilled in the art can choose according to actual needs, as long as it can achieve the purpose of this application. This application does not impose any particular restrictions on the preparation method of the grooves, and those skilled in the art can choose according to actual needs, as long as it can achieve the purpose of this application. For example, this can be achieved through laser etching.

[0065] A second aspect of this application provides a cylindrical secondary battery, wherein the cylindrical secondary battery includes the negative electrode sheet described in any of the foregoing embodiments. Therefore, the cylindrical secondary battery exhibits good cycle performance and low impedance.

[0066] The cylindrical secondary battery of this application includes a positive electrode sheet. This application does not impose any particular limitation on the positive electrode sheet, as long as it achieves the purpose of this application. In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is disposed on one or both surfaces of the positive current collector. The aforementioned "surface" can be a portion of the surface of the positive current collector or the entire surface of the positive current collector. This application does not impose any particular limitation on the positive current collector, as long as it achieves the purpose of this application. For example, the positive current collector can contain aluminum foil or aluminum alloy foil, etc. The positive active material layer of this application contains a positive active material. This application does not impose any particular limitation on the type of positive active material, as long as it achieves the purpose of this application. For example, the positive active material can contain at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate, etc. In this application, the positive electrode active material may further include non-metallic elements, which may include at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur. These elements can further improve the stability of the positive electrode active material. In this application, there are no particular limitations on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the purpose of this application is achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm. The thickness of a single-layer positive electrode active material layer is 30 μm to 120 μm. Optionally, the positive electrode active material layer may further include at least one of a positive electrode conductive agent or a positive electrode binder. This application does not particularly limit the types of positive electrode conductive agents and positive electrode binders in the positive electrode active material layer, as long as the purpose of this application is achieved. This application does not particularly limit the mass ratio of the positive electrode active material, positive electrode conductive agent, and positive electrode binder in the positive electrode active material layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved.

[0067] The cylindrical secondary battery of this application also includes a separator for separating the positive electrode and the negative electrode. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the separator material may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The separator type may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane. This application does not impose any particular limitation on the separator thickness, as long as it achieves the purpose of this application.

[0068] The cylindrical secondary battery of this application also includes an electrolyte. This application does not impose any particular limitation on the electrolyte, as long as it achieves the purpose of this application. For example, in some embodiments, the electrolyte includes a lithium salt and a non-aqueous solvent. The lithium salt may include at least one of LiPF6, LiNO3, LiBF4, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), or lithium difluoroborate. This application does not limit the content of lithium salt in the electrolyte, as long as it achieves the purpose of this application. This application does not impose any particular limitation on the non-aqueous solvent, as long as it achieves the purpose of this application. For example, the non-aqueous solvent may include, but is not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorocarbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, or methyl ethyl carbonate. The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate, propylene carbonate (PC), butylene carbonate, or vinylene carbonate. Fluorinated carbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1,2-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The aforementioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0069] The cylindrical secondary battery of this application also includes a casing for housing the positive electrode, negative electrode, separator, and electrolyte, as well as other components known in cylindrical secondary batteries in this application. This application does not limit the aforementioned other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application.

[0070] The cylindrical secondary battery described in this application is not particularly limited and may include any device in which an electrochemical reaction occurs. For example, a cylindrical secondary battery may include, but is not limited to, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0071] This application does not impose any particular limitation on the preparation method of the cylindrical secondary battery. Any preparation method known in the art can be used, as long as it can achieve the purpose of this application. For example, the preparation method of the cylindrical secondary battery includes, but is not limited to, the following steps: stacking the separator, positive electrode, separator and negative electrode in sequence, and winding and folding them as needed to obtain a wound electrode assembly; placing the electrode assembly into the housing; injecting electrolyte into the housing and sealing it to obtain a cylindrical secondary battery.

[0072] A third aspect of this application provides an electronic device comprising the cylindrical secondary battery described in any of the foregoing embodiments. Therefore, the electronic device exhibits good performance in use.

[0073] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. For example, the electronic device may include, but is not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors.

[0074] Example

[0075] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below.

[0076] Test methods and equipment:

[0077] Testing the thickness T0 of the negative electrode active material layer:

[0078] The lithium-ion battery was discharged to 2.0V at 0.1C at room temperature (25±3℃). After standing for 60 minutes, the negative electrode sheet was disassembled. The negative electrode sheet was soaked in dimethyl carbonate (DMC) for 20 minutes and then dried in an oven at 60℃ for 12 hours to obtain a negative electrode sheet sample. Using a micrometer, after calibration, the negative electrode sheet width was measured at 20% of the width of the negative electrode sheet from the head (the end where the negative electrode tab is located). At the same time, points were taken every 10% of the length of the negative electrode sheet along the length direction. If a groove was set at the sampling point, the measurement point was moved along the length direction to the position immediately adjacent to the sampling point but without a groove. The thickness of the negative electrode sheet at 10 points was measured and the average value was calculated and recorded as the average thickness T0' of the negative electrode sheet. At the same time, the thickness of the negative current collector at 10 points was measured and the average value was calculated and recorded as the average thickness T of the negative current collector. foil Then the thickness of the negative electrode active material layer T0 = T0' - T foil .

[0079] Test for silicon content (P0%):

[0080] The measurements were taken using an inductively coupled plasma optical emission spectrometer (ICP, manufacturer: PE, USA, model: OPTIMA 7000DV), following the reference test standard: EPA 6010D-2014; the specific steps are as follows:

[0081] (1) Sample preparation: The lithium-ion battery was discharged to 2.0V at 0.1C at room temperature (25±3℃). After standing for 60 minutes, the negative electrode sheet was disassembled. The negative electrode sheet was soaked in DMC for 20 minutes and then placed in an oven to dry at 60℃ for 12 hours. Then, along the length of the negative electrode sheet, a sample was cut from the head, middle and tail of the negative electrode sheet (the size of each sample should meet the requirement that the mass of the negative electrode active material layer powder obtained later is 180±10mg). A total of three samples were obtained. The following steps (2) to (5) were performed on the three samples respectively:

[0082] (2) The negative electrode active material layer powder was scraped off and weighed in a dry atmosphere with argon protection. Then the negative electrode active material layer powder was placed in a nickel crucible, 1.4±0.1g of KOH was added to the nickel crucible, and the mixture was kept at 400℃ for 45min. Then 80±5ml of boiling water was added, and the crucible was covered and soaked for 60min to obtain the sample solution.

[0083] (3) Calibration of instruments: ICP is calibrated using a known standard solution (1 g / L dissolved in standard concentration nitric acid, the standard solution is a commercially available standard product, item number 08729, Sigma-Aldrich);

[0084] (4) Set the working conditions of ICP: Argon secondary pressure 0.6MPa, cooling water temperature 20℃, radio frequency power 1300W, vertical observation height 15mm, RF frequency 40.68MHz, auxiliary gas flow rate 0.2L / min, atomizing gas pressure 0.2MPa, cooling gas flow rate 15L / min, pump speed 1.5mL / min.

[0085] (5) After diluting the sample solution 10 times, inject it into the ICP through the injection system, and obtain the silicon content in the sample solution using the winLAB32 software that comes with the ICP.

[0086] (6) The average value of the silicon content measured in each of the three samples is the mass percentage of silicon in the negative electrode active material layer, P0.

[0087] Test for groove depth V0%:

[0088] The lithium-ion battery was discharged to 2.0V at 0.1C at room temperature (25±3℃). After standing for 60 minutes, the negative electrode sheet was disassembled. Both the double-sided and single-sided empty foil areas of the negative electrode sheet were completely removed, leaving only the area where the negative current collector has a negative electrode active material layer on both sides. The negative electrode sheet after removing the empty foil area was soaked in DMC for 20 minutes and then dried in an oven at 60℃ for 12 hours to obtain the negative electrode sheet sample (denoted as sample a). The total mass m of sample a was weighed using an electronic balance. a The area of ​​the region in sample a where the double-sided negative electrode active material layer is set is measured to be L0; the double-sided negative electrode active material layer in a part of sample a is completely scraped off and the thickness T of the negative electrode current collector is measured. Cu Then, the total mass of the negative electrode active material layer after setting the groove is M2 = m a -L0×T Cu ×ρ Cu Cut a section of the electrode sheet without grooves from sample a (denoted as sample 1), and denote its area as L1. Weigh sample 1 and take its mass m1. Then, the total mass of the negative electrode active material layer before the grooves are set can be calculated as M1 = m1 × L0 / L1 - L0 × T Cu ×ρ Cu . ρ Cu The density of the negative electrode current collector used in the tested examples and comparative examples.

[0089] Groove depth V0% = (M1-M2) / M1×100%.

[0090] Diffusion distance test:

[0091] 0.1 mL of the electrolyte from Example 1-1 was dropped onto the center point of the negative electrode active material layer region along its width. The diffusion distance of the electrolyte along the width of the negative electrode was measured every 1 minute, for a total standing time of 12 minutes. The recorded diffusion distance was plotted on the y-axis against the measurement time points on the x-axis to obtain a diffusion distance-time curve. The y-value corresponding to x = 2 minutes was taken as the measured diffusion distance value.

[0092] Impedance testing:

[0093] Two identical negative electrode sheets from each embodiment and comparative example are placed in a standard fixture with a certain opening area and then connected to electrode tabs to serve as working electrodes. The negative electrode sheet body is then immersed in the electrolyte prepared in Example 1-1 to form a symmetrical battery.

[0094] The fabricated symmetrical cell was connected to a VMP3 electrochemical workstation, and the electrochemical impedance spectroscopy (EIS) function was selected for testing. The frequency range was 30 mHz to 500 kHz, and the amplitude was 5 mV. After the test, the raw data was obtained, including the frequency (f / hz), the real part of the impedance (Z'), and the imaginary part of the impedance (-Z”). The low-frequency region with diagonal lines related to diffusion was removed.

[0095] The raw data was imported into the EIS-BR refinement software developed by ATL to obtain the EBR plot. The EBR plot was then processed using Origin software to separate the peaks, yielding impedance response peaks F1 to F4, with frequency responses located at 10°C and 10°C respectively. -4 s, 10 -3 s, 10 -2 s, 10 -1 The magnitude is on the order of s. The electrochemical process corresponding to the F1 peak area is a conductive network, and the electrochemical process corresponding to the F2 peak area is Li. + Based on the impedance of the SEI, the electrochemical process corresponding to the F3 peak area is desolvation and lithium intercalation impedance of the negative electrode active material, while the electrochemical process corresponding to the F4 peak area is Si alloying. The smaller the peak areas of F2 and F3, the smaller the impedance.

[0096] Cyclic performance testing:

[0097] The lithium-ion batteries of each embodiment and comparative example were connected to the "Newway" cyclic test channel with a 5V / 60A range and a temperature auxiliary module, and cyclic tests were conducted at 25±2℃.

[0098] When the thickness T0 of the negative electrode active material layer in the negative electrode sheet satisfies 20 < T0 ≤ 80, the cyclic process is as follows:

[0099] (1) Perform two small-rate recovery operations: charge at a constant current of 1.5C to 4.2V, then charge at a constant voltage of 4.2V to 200mA and let stand for 10 minutes; discharge at a constant current of 0.2C to 2.5V and let stand for 10 minutes.

[0100] (2) Charge the battery at a constant current of 1.5C to 4.2V, then charge it at a constant voltage of 4.2V to 0.05C, and let it stand for 10 minutes; discharge it at a constant current of 6C to 2.5V, and let it stand for 30 minutes; the upper limit of temperature protection during the discharge process is 75℃. After reaching the upper limit of temperature protection, the lithium-ion battery is cooled to 50℃ and then discharged again at a constant current of 6C until it reaches 2.5V. After every 50 cycles, perform two small-rate recovery steps (1). Record the discharge capacity C1 of each cycle, take the discharge capacity of the first cycle as the base capacity C0, and use the value of C1 / C0×100% as the y-axis (i.e., capacity retention rate) and the number of cycles as the x-axis.

[0101] When the thickness T0 of the negative electrode active material layer in the negative electrode sheet satisfies 80 < T0 ≤ 120, the cycle process is as follows:

[0102] (1) Perform two small-rate recovery operations: charge to 4.2V with a constant current of 0.5C, then charge to 200mA with a constant voltage of 4.2V and let stand for 10 minutes; discharge to 2.5V with a constant current of 0.2C and let stand for 10 minutes.

[0103] (2) Charge the battery at a constant current of 0.5C to 4.2V, then charge it at a constant voltage of 4.2V to 0.05C, and let it stand for 10 minutes; discharge it at a constant current of 1C to 2.5V, and let it stand for 30 minutes; the upper limit of temperature protection during the discharge process is 75℃. After reaching the upper limit of temperature protection, the lithium-ion battery is cooled to 50℃ and then discharged again at a constant current of 6C until it reaches 2.5V. After every 50 cycles, perform two small-rate recovery steps (1). Record the discharge capacity C1 of each cycle, take the discharge capacity of the first cycle as the base capacity C0, and use the value of C1 / C0×100% as the y-axis (i.e., capacity retention rate) and the number of cycles as the x-axis.

[0104] Cycling performance is characterized by the number of cycles when the capacity retention rate is 90%; the more cycles, the better the cycling performance.

[0105] Example 1-1

[0106] <Preparation of Negative Electrode Sheets>

[0107] The negative electrode active material, the negative electrode conductive agent conductive carbon black (SWCNT), and the negative electrode binder styrene-butadiene rubber (SBR, with a weight average molecular weight of 5×10⁻⁶) are combined. 6The surfactant sodium carboxymethyl cellulose (CMC-Na) was mixed in a mass ratio of 96.7:0.3:1.8:1.2, and then deionized water was added as a solvent. The mixture was stirred under vacuum until a homogeneous negative electrode slurry with a solid content of 50 wt% was obtained. The negative electrode active materials were artificial graphite and silicon oxide materials, with a mass ratio of artificial graphite to silicon oxide materials of 87:13. The silicon oxide material contained 48% silicon by mass, and P0 = 6%.

[0108] The negative electrode slurry is uniformly coated onto one surface of the copper foil used as the negative electrode current collector, and then dried at 90°C to obtain a negative electrode sheet with a single-sided coating of the negative electrode active material layer. The above steps are then repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of the negative electrode active material layer. After cold pressing, the negative electrode sheet is obtained, wherein the copper foil thickness is 8 μm, the single-layer thickness of the negative electrode active material layer T0 = 46 μm, and the coating areal density of the negative electrode active material layer is 115 mg / 1540 mm². 2 The width W of the negative electrode active material layer is 59 mm. After setting grooves with the parameters described below on the two negative electrode active material layers using laser grooving, they are slit to obtain a negative electrode sheet with a length × width of 1400 mm × 61 mm. The negative electrode tab is shown in Figure 5. When the negative electrode active material layer 12 is set on the surface of the negative electrode current collector 11, the area shown in the dashed box A along the width direction Y of the negative electrode current collector 11 is reserved as the negative electrode tab 14.

[0109] The groove setting parameters are as follows:

[0110] Along the thickness direction of the negative electrode active material layer, the groove depth h = 47.8% × T0 = 22 μm. Along the length direction of the negative electrode active material layer, the groove width b = 70 μm. On the plane of the negative electrode active material layer, the projection of the groove onto the width direction of the negative electrode active material layer has a length L = W = 59 mm. N = 56 grooves are provided for every 10 cm of negative electrode active material layer, and the grooves are evenly spaced. Along the thickness direction of the negative electrode active material layer, the cross-sectional shape of the groove is rectangular (see Figure 2).

[0111] <Preparation of the positive electrode>

[0112] Lithium nickel cobalt manganese oxide (LiNi) is used as the positive electrode active material. 0.91 Co 0.06 Mn 0.03 O2, positive electrode conductive agent: multi-walled carbon nanotubes (CNTs), positive electrode conductive agent: conductive carbon black (Super P), positive electrode binder: polyvinylidene fluoride (PVDF, weight average molecular weight 5×10⁻⁶). 5The materials were mixed at a mass ratio of 97:0.6:1:1.4, with N-methylpyrrolidone (NMP) added as a solvent. The mixture was stirred under vacuum until a homogeneous positive electrode slurry with a solid content of 75 wt% was obtained. The positive electrode slurry was uniformly coated onto one surface of a 13 μm thick aluminum foil used as a positive electrode current collector, and dried at 100°C to obtain a positive electrode sheet with a single-sided coating of the positive active material layer. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of the positive active material layer. After cold pressing and slitting, positive electrode sheets with dimensions of 1450 mm × 63 mm were obtained for later use. The single-layer thickness of the positive active material layer was 42 μm, and the coating areal density was 250 mg / 1540 mm². 2 The setting of the positive electrode tab is shown in Figure 6. When the positive active material layer 22 is set on the surface of the positive current collector 21, the area shown by the dashed box B along the width direction Y of the positive current collector 21 is reserved as the positive electrode tab 24.

[0113] <Preparation of the diaphragm>

[0114] Alumina and PVDF were mixed at a mass ratio of 90:10 and dissolved in deionized water to form a ceramic slurry with a solid content of 50 wt%. The ceramic slurry was then uniformly coated onto a surface of a porous substrate (polyethylene, 9 μm thick, average pore size 0.073 μm, porosity 26%) using a microgravure coating method. After drying, a bilayer structure, i.e., a membrane, was obtained, consisting of a ceramic coating and the porous substrate. The thickness of a single layer of the ceramic coating was 2 μm.

[0115] <Preparation of Electrolyte>

[0116] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 2:1:1 to obtain a non-aqueous solution. Then, lithium hexafluorophosphate and fluoroethylene carbonate (FEC) were added to the non-aqueous solvent and mixed thoroughly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L. The mass ratio of the non-aqueous solvent to FEC was 95:5.

[0117] <Preparation of Lithium-ion Batteries>

[0118] The prepared separator, positive electrode, separator, and negative electrode are stacked sequentially, and then wound, flattened, welded to the current collector, installed in the casing, inkjet-printed, vacuum dried, injected with electrolyte (injection coefficient 1.45 g / Ah), sealed, and subjected to high-temperature standing before formation capacity testing to obtain a cylindrical lithium-ion battery. The upper limit of formation voltage is 3.6V, the formation temperature is 45℃, and the formation standing time is 2 hours.

[0119] Examples 1-2

[0120] <Preparation of the positive electrode>

[0121] In addition to adjusting the single-layer thickness of the positive electrode active material layer to 22μm, the coating surface density of the positive electrode active material layer was also adjusted to 125mg / 1540mm. 2 Except for the above, the rest is the same as in Example 1-1.

[0122] <Preparation of Negative Electrode Sheets>

[0123] In addition to adjusting the relevant preparation parameters according to Table 1, the coating surface density of the negative electrode active material layer was adjusted to 58 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0124] The preparation of the separator, electrolyte, and lithium-ion battery are the same as in Examples 1-1.

[0125] Examples 1-3

[0126] <Preparation of the positive electrode>

[0127] In addition to adjusting the single-layer thickness of the positive electrode active material layer to 28μm, the coating surface density of the positive electrode active material layer was also adjusted to 163mg / 1540mm. 2 Except for the above, the rest is the same as in Example 1-1.

[0128] <Preparation of Negative Electrode Sheets>

[0129] In addition to adjusting the relevant preparation parameters according to Table 1, the coating surface density of the negative electrode active material layer was adjusted to 75 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0130] The preparation of the separator, electrolyte, and lithium-ion battery are the same as in Examples 1-1.

[0131] Examples 1-4

[0132] Except for the use of artificial graphite as the negative electrode active material in the <Preparation of Negative Electrode Sheet>, the rest is the same as in Example 1-1.

[0133] Examples 1-5 to Examples 1-24

[0134] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0135] The change in P0% is achieved by adjusting the mass ratio of artificial graphite and silicon oxide materials in the negative electrode active material.

[0136] Examples 1-25 to Examples 1-31

[0137] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0138] The groove extends along the width of the negative electrode active material layer to the side of the negative electrode active material layer away from the negative electrode tab.

[0139] Examples 1-32 to Examples 1-37

[0140] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0141] Example 2-1

[0142] <Preparation of the positive electrode>

[0143] In addition to adjusting the single-layer thickness of the positive electrode active material layer to 46μm, the coating surface density of the positive electrode active material layer was also adjusted to 275mg / 1540mm. 2 Except for the above, the rest is the same as in Example 1-1.

[0144] <Preparation of Negative Electrode Sheets>

[0145] In addition to adjusting the relevant preparation parameters according to Table 2, the coating surface density of the negative electrode active material layer was adjusted to 128 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0146] The preparation of the separator, electrolyte, and lithium-ion battery are the same as in Examples 1-1.

[0147] Example 2-2

[0148] <Preparation of the positive electrode>

[0149] In addition to adjusting the single-layer thickness of the positive electrode active material layer to 59 μm, the coating surface density of the positive electrode active material layer was also adjusted to 353 mg / 1540 mm. 2 Except for the above, the rest is the same as in Example 1-1.

[0150] <Preparation of Negative Electrode Sheets>

[0151] In addition to adjusting the relevant preparation parameters according to Table 2, the coating surface density of the negative electrode active material layer was adjusted to 163 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0152] The preparation of the separator, electrolyte, and lithium-ion battery are the same as in Examples 1-1.

[0153] Example 2-3

[0154] <Preparation of the positive electrode>

[0155] In addition to adjusting the single-layer thickness of the positive electrode active material layer to 73μm, the coating surface density of the positive electrode active material layer was also adjusted to 434mg / 1540mm. 2 Except for the above, the rest is the same as in Example 1-1.

[0156] <Preparation of Negative Electrode Sheets>

[0157] In addition to adjusting the relevant preparation parameters according to Table 2, the coating surface density of the negative electrode active material layer was adjusted to 200 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0158] The preparation of the separator, electrolyte, and lithium-ion battery are the same as in Examples 1-1.

[0159] Examples 2-4

[0160] Except for the use of artificial graphite as the negative electrode active material in the <Preparation of Negative Electrode Sheet>, the rest is the same as in Example 2-2.

[0161] Examples 2-5 to 2-16

[0162] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as in Examples 2-2.

[0163] The change in P0% is achieved by adjusting the mass ratio of artificial graphite and silicon oxide materials in the negative electrode active material.

[0164] Example 3-1

[0165] <Preparation of the positive electrode>

[0166] In addition to adjusting the single-layer thickness of the positive electrode active material layer to 74μm, the coating surface density of the positive electrode active material layer was also adjusted to 437mg / 1540mm. 2 Except for the above, the rest is the same as in Example 1-1.

[0167] <Preparation of Negative Electrode Sheets>

[0168] In addition to adjusting the relevant preparation parameters according to Table 3, the coating surface density of the negative electrode active material layer was adjusted to 202 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0169] The preparation of the separator, electrolyte, and lithium-ion battery are the same as in Examples 1-1.

[0170] Example 3-2

[0171] <Preparation of the positive electrode>

[0172] In addition to adjusting the single-layer thickness of the positive electrode active material layer to 91 μm, the coating surface density of the positive electrode active material layer was also adjusted to 540 mg / 1540 mm. 2 Except for the above, the rest is the same as in Example 1-1.

[0173] <Preparation of Negative Electrode Sheets>

[0174] In addition to adjusting the relevant preparation parameters according to Table 3, the coating surface density of the negative electrode active material layer was adjusted to 250 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0175] The preparation of the separator, electrolyte, and lithium-ion battery are the same as in Examples 1-1.

[0176] Example 3-3

[0177] <Preparation of the positive electrode>

[0178] In addition to adjusting the single-layer thickness of the positive electrode active material layer to 109 μm, the coating surface density of the positive electrode active material layer was also adjusted to 646 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0179] <Preparation of Negative Electrode Sheets>

[0180] In addition to adjusting the relevant preparation parameters according to Table 3, the coating surface density of the negative electrode active material layer was adjusted to 300 mg / 1540 mm². 2 Except for the above, the rest is the same as in Example 1-1.

[0181] The preparation of the separator, electrolyte, and lithium-ion battery are the same as in Examples 1-1.

[0182] Examples 3-4

[0183] Except for the use of artificial graphite as the negative electrode active material in the <Preparation of Negative Electrode Sheet>, the rest is the same as in Examples 3-2.

[0184] Examples 3-5 to 3-16

[0185] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as in Examples 3-2.

[0186] The change in P0% is achieved by adjusting the mass ratio of artificial graphite and silicon oxide materials in the negative electrode active material.

[0187] Comparative Example 1-1

[0188] Except for the absence of grooves, it is the same as Examples 1-9.

[0189] Comparative Examples 1-2

[0190] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Examples 1-9.

[0191] Comparative Examples 1-3

[0192] Except for the absence of grooves, it is the same as Examples 1-13.

[0193] Comparative Examples 1-4

[0194] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Examples 1-13.

[0195] Comparative Examples 1-5

[0196] Except for the absence of grooves, it is the same as Examples 1-14.

[0197] Comparative Examples 1-6

[0198] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Examples 1-14.

[0199] Comparative Example 2-1

[0200] Except for the absence of grooves, it is the same as in Examples 2-13.

[0201] Comparative Example 2-2

[0202] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as in Examples 2-13.

[0203] Comparative Examples 2-3

[0204] Except for the absence of grooves, it is the same as in Examples 2-14.

[0205] Comparative Examples 2-4

[0206] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as in Examples 2-14.

[0207] Comparative Example 3-1

[0208] Except for the absence of grooves, it is the same as in Examples 3-13.

[0209] Comparative Example 3-2

[0210] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as in Examples 3-13.

[0211] The preparation and performance parameters of each embodiment and comparative example are shown in Tables 1 to 3.

[0212] Table 1

[0213] Note: In Table 1, "\" indicates that there is no corresponding parameter.

[0214] As can be seen from Examples 1-1 to 1-37 and Comparative Examples 1-1 to 1-6, in the cylindrical secondary batteries of this application, when the thickness T0 of the negative electrode active material layer in the negative electrode sheet satisfies 20 < T0 ≤ 50 mm and the mass percentage of silicon in the negative electrode active material layer is within the range of this application, by setting grooves on the negative electrode active material layer and controlling the amount of grooves in the negative electrode active material layer within the range of this application, the negative electrode sheet can have a longer electrolyte diffusion distance and lower impedance, and the cylindrical secondary battery has more cycle cycles, indicating that the cycle performance of the cylindrical secondary battery in the examples has been improved. In contrast, the cylindrical secondary batteries of the comparative examples do not have grooves set on the negative electrode active material layer with a thickness T0 satisfying 20 < T0 ≤ 50 mm, or the amount of grooves in the negative electrode active material layer is not within the range of this application, resulting in fewer cycle cycles for the cylindrical secondary batteries of the comparative examples, indicating that the cycle performance of the cylindrical secondary batteries of the comparative examples is poor.

[0215] Figure 7 shows the impedance test curves of Example 1-1 and Comparative Example 1-1. The gray curve is the impedance test curve of Example 1-1, and the black curve is the impedance test curve of Comparative Example 1-1. As can be seen from Figure 7, compared with the test curve of Comparative Example 1-1, the F2 peak area and F3 peak area of ​​Example 1-1 are smaller, indicating that Example 1-1 has a smaller SEI impedance and lithium intercalation impedance.

[0216] When the thickness T0 of the negative electrode active material layer satisfies 20 < T0 ≤ 50, the mass percentage of silicon in the negative electrode active material layer P0% and the groove amount V0% in the negative electrode active material layer typically affect the cycle performance of the cylindrical secondary battery. As can be seen from Examples 1-1 to 1-16, cylindrical secondary batteries with T0, P0%, and V0% all within the scope of this application exhibit better cycle performance due to the longer electrolyte diffusion distance and lower impedance of the negative electrode sheet. However, when the negative electrode active material layer contains silicon, an increase in the mass percentage of silicon P0% in the negative electrode active material layer will affect the number of cycles of the electrochemical device. In Examples 1-1, 1-4 to 1-7, the thickness T0 of the negative electrode active material layer and the groove amount V0% in the negative electrode active material are the same. In Example 1-4, the mass percentage content of silicon element in the negative electrode active material layer is P0% = 0%, and its cycle count reaches a maximum of 390 cycles. In Example 1-7, the mass percentage content of silicon element in the negative electrode active material layer is P0% = 19%, and its cycle count is affected by the silicon element content, which is 142 cycles.

[0217] The depth h of the groove typically affects the cycle performance of cylindrical secondary batteries. As can be seen from Examples 1-1, 1-17 to 1-21, cylindrical secondary batteries with a groove depth h within the scope of this application exhibit good cycle performance due to the longer electrolyte diffusion distance and lower impedance of the negative electrode. Compared to Examples 1-1, 1-17 to 1-19, although Examples 1-20 have a longer electrolyte diffusion distance and lower impedance, the groove depth h in Examples 1-20 leads to a localized imbalance in the negative electrode composition, resulting in a lower cycle count for the cylindrical secondary battery.

[0218] The width b of the groove typically affects the cycle performance of a cylindrical secondary battery. As can be seen from Examples 1-1, 1-22 to 1-28, a cylindrical secondary battery with a groove width b within the scope of this application has a longer electrolyte diffusion distance and lower impedance in its negative electrode, resulting in good cycle performance.

[0219] The length L of the groove typically affects the cycle performance of a cylindrical secondary battery. As can be seen from Examples 1-1, 1-29 to 1-31, a cylindrical secondary battery with a groove length L within the scope of this application has a longer electrolyte diffusion distance and lower impedance in its negative electrode, resulting in good cycle performance.

[0220] The number N of grooves per 10cm of negative electrode active material layer typically affects the cycle performance of cylindrical secondary batteries. As can be seen from Examples 1-1, 1-32 to 1-37, cylindrical secondary batteries with N of grooves per 10cm of negative electrode active material layer within the scope of this application exhibit better cycle performance due to the longer electrolyte diffusion distance and lower impedance of the negative electrode sheet.

[0221] Table 2

[0222] Note: In Table 2, "\" indicates that there is no corresponding parameter.

[0223] As can be seen from Examples 2-1 to 2-16 and Comparative Examples 2-1 to 2-4, in the cylindrical secondary battery of this application, when the thickness T0 of the negative electrode active material layer in the negative electrode sheet satisfies 50 < T0 ≤ 80, and the mass percentage of silicon in the negative electrode active material layer P0% and the groove amount V0% in the negative electrode active material layer are within the range of this application, by setting grooves on the negative electrode active material layer and controlling the groove amount in the negative electrode active material layer within the range of this application, the negative electrode sheet can have a longer electrolyte diffusion distance and lower impedance, and the cylindrical secondary battery has more cycle cycles, indicating that the cycle performance of the cylindrical secondary battery in the examples has been improved. In contrast, the cylindrical secondary battery of the comparative examples, which does not have grooves set on the negative electrode active material layer with a thickness T0 satisfying 50 < T0 ≤ 80, or whose groove amount in the negative electrode active material layer is not within the range of this application, has a shorter electrolyte diffusion distance and lower impedance, and the cylindrical secondary battery has fewer cycle cycles. Among them, the number of cycles decreased significantly in Examples 2-13 compared to Examples 2-12, because the mass percentage of silicon element P0% in the negative electrode active material layer increased.

[0224] Table 3

[0225] Note: In Table 3, "\" indicates that there is no corresponding parameter.

[0226] As can be seen from Examples 3-1 to 3-16, Comparative Examples 3-1 and 3-2, in the cylindrical secondary battery of this application, when the thickness T0 of the negative electrode active material layer in the negative electrode sheet satisfies 80 < T0 ≤ 120, and the mass percentage of silicon in the negative electrode active material layer P0% and the groove amount V0% in the negative electrode active material layer are within the range of this application, by setting grooves on the negative electrode active material layer and controlling the groove amount in the negative electrode active material layer within the range of this application, the negative electrode sheet can have a longer electrolyte diffusion distance and lower impedance, and the cylindrical secondary battery has more cycle cycles, indicating that the cycle performance of the cylindrical secondary battery in the examples has been improved. In contrast, the cylindrical secondary battery of the comparative examples, which does not have grooves set on the negative electrode active material layer with a thickness T0 satisfying 80 < T0 ≤ 120, or whose groove amount in the negative electrode active material layer is not within the range of this application, has a shorter electrolyte diffusion distance and lower impedance, and the cylindrical secondary battery has fewer cycle cycles.

[0227] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0228] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0229] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer has a thickness of T0 μm; the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises silicon, and the mass percentage of the silicon in the negative electrode active material layer is P0%; the negative electrode active material layer is provided with a plurality of grooves, and the groove amount in the negative electrode active material layer is V0%, V0% = (M1-M2) / M1×100%, wherein M1 is the mass of the negative electrode active material layer before the plurality of grooves are provided, and M2 is the mass of the negative electrode active material layer after the plurality of grooves are provided; and V0, T0 and P0 satisfy the following conditions: 20 < T0≤ 120, 0≤ P0≤ 90, and 0.02≤ V0≤ 30. 20 < T0≤ 50, 0≤ P0< 20, 0.02≤ V0≤ 20; 20≤ P0≤ 90, and 0.15≤ V0≤ 25. wherein 50 < T0≤ 80, 0≤ P0< 20, 0.05≤ V0≤ 25; 20≤ P0≤ 90, and 0.3≤ V0≤ 30. 80 < T0≤ 120, 0≤ P0< 20, 0.15≤ V0≤ 30; 20≤ P0≤ 90, and 0.5≤ V0≤ 30.

2. The negative electrode sheet according to claim 1, wherein 20 < T0≤ 50, 0.5≤ P0≤ 15, and 0.5≤ V0≤ 5.

3. The negative electrode sheet according to claim 1 or 2, wherein 50 < T0≤ 80, 0.5≤ P0≤ 15, and 0.5≤ V0≤ 6.

4. The negative electrode sheet according to any one of claims 1 to 3, wherein 80 < T0≤ 120, 0.5≤ P0≤ 15, and 0.5≤ V0≤ 10.

5. The negative electrode sheet according to any one of claims 1 to 4, wherein In the thickness direction of the negative electrode active material layer, the depth of each groove is h μm, and 5%×T0≤ h < 100%×T0.

6. The negative electrode sheet according to any one of claims 1 to 5, wherein 25%×T0≤ h≤ 75%×T0.

7. The negative electrode sheet according to any one of claims 1 to 6, wherein In the length direction of the negative electrode active material layer, the width of each groove is b μm, and 30≤ b≤ 1000.

8. The negative electrode sheet according to any one of claims 1 to 7, wherein In the plane of the negative electrode active material layer, the length of the projection of each groove in the width direction of the negative electrode active material layer is L mm, the width of the negative electrode active material layer is W mm, and 0.1W≤ L≤ W.

9. The negative electrode sheet according to claim 8, wherein 0.8W≤ L≤ W.

10. The negative electrode sheet according to any one of claims 1 to 9, wherein The negative electrode active material layer is provided with N grooves per 10 cm in length, and 5≤ N≤ 500.

11. The negative electrode sheet according to claim 10, wherein 70≤b≤500。 12. The negative electrode sheet according to any one of claims 1 to 11, wherein In the thickness direction of the negative electrode active material layer, the cross-sectional shape of the groove is rectangular, semicircular, trapezoidal, triangular or curved.

13. The negative electrode sheet according to claim 12, wherein The cylindrical secondary battery comprises the negative electrode sheet according to any one of claims 1 to 16.

14. The negative electrode sheet according to any one of claims 1 to 13, wherein The electronic device comprises the cylindrical secondary battery according to claim 17.

15. The negative electrode sheet according to claim 14, wherein 20≤N≤200。 16. The negative electrode sheet according to any one of claims 1 to 15, wherein ​ 17. A cylindrical secondary battery, wherein ​ 18. An electronic device, wherein, ​

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