Pole piece assembly, battery and electric equipment

Abstract

The utility model discloses a pole piece assembly, a battery and electric equipment. The pole piece assembly is of a winding structure. A positive plate of the pole piece assembly comprises a positive current collector and a positive active layer, a first corner area of the positive active layer is provided with a plurality of first groove bodies, and the first groove bodies are arranged at intervals in the length direction of the positive plate. The negative plate comprises a negative current collector and a negative active layer, a second corner area of the negative active layer is provided with a plurality of second groove bodies, and the second groove bodies are arranged at intervals in the length direction of the negative plate. The width of each first groove body is W1, the depth of each first groove body is D1, the distance between every two adjacent first groove bodies is L1, the width of each second groove body is W2, the depth of each second groove body is D2, and the distance between every two adjacent second groove bodies is L2. The first groove body and the second groove body meet the condition that (W2 * D2 * L1) / (W1 * D1 * L2) is larger than or equal to 0.25 and smaller than or equal to 1.02. According to the scheme, the lithium ion de-intercalation speed, the liquid retention effect, the N / P ratio, the active substance loss, the rate capability, the material structure stability and the like of the battery can be balanced, and the battery performance is improved.

Description

Technical Field

[0001] This utility model relates to the field of wound battery technology, and in particular to an electrode assembly, a battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries have outstanding advantages such as high energy density, no memory effect, long cycle life, fast charging and discharging, and low self-discharge, and are widely used in consumer electronics, electric vehicles, and energy storage.

[0003] In existing technologies, during long-term charge-discharge cycles, lithium-ion batteries often experience lithium deposition at the negative electrode corners due to poor electrolyte wetting and drying. Simultaneously, the active material layer at these corners is subjected to bending and compression from the winding structure, leading to delamination and detachment between the active material layer and the current collector copper foil after cyclic expansion. This results in severe lithium deposition at the negative electrode corners in the later stages of cycling, significant cycle degradation, and impacts the long-term stability of the lithium battery. Furthermore, wound pouch batteries also suffer from excessive stress at the corners and a mismatch in CB values ​​caused by the cathode electrode covering the anode electrode, which also easily leads to lithium deposition at the corners. The resulting lithium dendrites not only increase the battery thickness but also pose a safety risk of internal short circuits by puncturing the separator. Utility Model Content

[0004] The main purpose of this invention is to propose an electrode assembly, a battery, and an electrical device, which aims to solve the technical problem of lithium plating at battery corners.

[0005] To achieve the above objectives, a first aspect of this utility model provides an electrode assembly, wherein the electrode assembly has a wound structure and comprises:

[0006] A positive electrode sheet includes a positive current collector and a positive active layer coated on the positive current collector. The positive active layer includes a first corner region, and the first corner region has a plurality of first grooves, each of which is arranged at intervals along the length direction of the positive electrode sheet.

[0007] A negative electrode sheet includes a negative electrode current collector and a negative electrode active layer coated on the negative electrode current collector. The negative electrode active layer includes a second corner region, and the second corner region has a plurality of second grooves, each of which is arranged at intervals along the length direction of the negative electrode sheet.

[0008] Wherein, the first groove has a groove width of W1 and a groove depth of D1, and the groove spacing between two adjacent first grooves is L1. The second groove has a groove width of W2 and a groove depth of D2, and the groove spacing between two adjacent second grooves is L2. The first groove and the second groove satisfy the condition: 0.25≤(W2×D2×L1) / (W1×D1×L2)≤1.02.

[0009] In some embodiments, the thickness of the positive electrode active layer is T1, wherein 30 μm ≤ T1 ≤ 70 μm, and the thickness of the negative electrode active layer is T2, wherein 25 μm ≤ T2 ≤ 60 μm.

[0010] In some embodiments, the groove depth D1 of the first groove body satisfies: 1 / 5T1≤D1≤1 / 2T1, the groove depth D2 of the second groove body satisfies: 1 / 3T2≤D2≤2 / 3T2, and the first groove body and the second groove body satisfy: 0.5≤D1 / D2≤2.

[0011] In some embodiments, the groove width W1 of the first groove body satisfies: 70μm≤W1≤180μm, the groove width W2 of the second groove body satisfies: 50μm≤W2≤110μm, and the first groove body and the second groove body satisfy: 1≤W1 / W2≤2.

[0012] In some embodiments, the spacing L1 between two adjacent first tanks satisfies: 70μm≤L1≤180μm, the spacing L2 between two adjacent second tanks satisfies: 50μm≤L2≤110μm, and the first tank and the second tank satisfy: 1≤L1 / L2≤2.

[0013] In some embodiments, the positive electrode active layer includes a first straight region connected to the first corner region, and the negative electrode active layer includes a second straight region connected to the second corner region; and

[0014] The first straight area and the second straight area satisfy the condition: 1.03≤N / P≤1.12; and / or, the first corner area and the second corner area satisfy the condition: 1.03≤N / P≤1.12.

[0015] In some embodiments, the second flat region is provided with a plurality of second grooves, each of which extends along the width direction of the negative electrode sheet and is spaced apart along the length direction of the negative electrode sheet.

[0016] In some embodiments, the first groove penetrates the positive electrode active layer along the width direction of the positive electrode sheet, and the first grooves are spaced apart and uniformly arranged along the length direction of the positive electrode sheet.

[0017] And / or,

[0018] The second groove extends through the negative electrode active layer along the width direction of the negative electrode sheet, and the second grooves are spaced apart and evenly arranged along the length direction of the negative electrode sheet.

[0019] A second aspect of this utility model provides a battery comprising the electrode assembly described in the above embodiments.

[0020] A third aspect of this utility model provides an electrical device including the battery described in the above embodiments, wherein the battery is used to supply power to the electrical device.

[0021] Compared with the prior art, the beneficial effects of this utility model include:

[0022] In the technical solution of this utility model, the electrode assembly has a wound structure. The electrode assembly includes a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive active layer coated on the positive current collector, the positive active layer including a first corner region. The negative electrode includes a negative current collector and a negative active layer coated on the negative current collector, the negative active layer including a second corner region.

[0023] In existing technologies, poor electrolyte wetting and easy drying at the corners of the negative electrode, coupled with the long-term bending and compression of the active material layer due to the winding structure, can lead to lithium plating at the corners. This solution addresses this issue by having multiple first grooves in the first corner region of the positive electrode active layer and multiple second grooves in the second corner region of the negative electrode active layer. This increases the surface area of ​​the active layer, improving electrolyte wetting; it also increases the lithium-ion insertion / extraction rate under high-rate charge / discharge; and it reduces the tortuosity of the electrode pores, increasing the lithium-ion diffusion coefficient. Therefore, this solution effectively alleviates the corner lithium plating problem.

[0024] In existing technologies, during the charging and discharging process of wound batteries, uneven stress occurs in the corner areas. The circular arc compression affects the electrolyte retention of the electrodes, and the rounded corners also cause differences in the N / P ratio of the active materials. This solution incorporates a groove in the corner area, which effectively reduces mechanical tension and resistance during cycling, minimizes deformation caused by uneven stress in the corner area, and improves the electrolyte retention. Furthermore, it balances the N / P ratio in the corner area, increasing the lithium-ion insertion / extraction rate and mitigating lithium desorption issues.

[0025] Furthermore, the first tank has a width of W1 and a depth of D1, with a spacing of L1 between adjacent first tanks; the second tank has a width of W2 and a depth of D2, with a spacing of L2 between adjacent second tanks. When W1 and D1 are too large and L1 is too small in the first tank, it can easily lead to excessive loss of active material in the positive electrode, reducing energy density. Conversely, when W1 and D1 are too small and L1 is too large in the first tank, the loss of active material in the positive electrode active layer is less, but it can lead to an imbalance in the N / P ratio in the first corner region and a limitation of the lithium-ion transport channel. When W2 and D2 are too large and L2 is too small in the second tank, excessive loss of active material in the negative electrode is likely, reducing the number of lithium storage sites in the second corner region and making lithium plating more likely. Conversely, when W2 and D2 are too small and L2 is too large in the second tank, on the one hand, the lithium intercalation channel is blocked, and lithium ion accumulation may occur on the surface of the negative electrode, increasing the risk of lithium plating; on the other hand, the excessive number of lithium storage sites in the second corner region of the negative electrode increases the N / P ratio, leading to more lithium delithiation of the active material in the positive electrode, affecting the structural stability of the material and damaging the battery's lifespan. This is especially true at high temperatures, where the increased material activity has a more significant impact on the structural stability of the material. In this design, the first and second tanks satisfy the condition: 0.25 ≤ (W2 × D2 × L1) / (W1 × D1 × L2) ≤ 1.02. This means that the lithium ion intercalation / deintercalation rate, liquid retention effect, N / P ratio, active material loss, rate performance, and structural stability of the material in the corner region are all balanced, thus improving battery performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a battery according to an embodiment of the present invention; wherein, a first straight area, a first corner area, a second straight area, a second corner area and a separator are shown, but the first tank and the second tank are not shown;

[0028] Figure 2 This is a side view of the positive electrode sheet in one embodiment of the present invention; wherein the positive electrode sheet is not wound, and the first corner area is connected to the first straight area;

[0029] Figure 3 This is a top view of the positive electrode sheet in one embodiment of the present invention; wherein, the positive electrode current collector, the positive electrode active layer, and the first tank are shown;

[0030] Figure 4This is a side view of the negative electrode sheet in one embodiment of the present invention; wherein the negative electrode sheet is not wound, and the second corner area is connected to the second straight area;

[0031] Figure 5 This is a top view of the negative electrode sheet in one embodiment of the present invention; wherein, the negative electrode current collector, the negative electrode active layer, and the second tank are shown;

[0032] Figure 6 This is a partial schematic diagram of the positive electrode sheet in one embodiment of the present invention; wherein, the first groove is shown;

[0033] Figure 7 This is a partial schematic diagram of the negative electrode sheet in one embodiment of the present invention; wherein, the second groove is shown.

[0034] Explanation of icon numbers:

[0035] Battery 1;

[0036] Electrode assembly 10;

[0037] Positive electrode 100; Positive current collector 110; Positive active layer 120; First corner region 121;

[0038] One tank body 1211; First straight section 122;

[0039] Negative electrode sheet 200; negative electrode current collector 210; negative electrode active layer 220; second corner region 221; second groove 2211; second straight region 222;

[0040] Diaphragm 300.

[0041] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0042] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0043] The first aspect of this utility model provides an electrode assembly 10 for use in a battery, which effectively mitigates lithium degradation issues. (See also...) Figure 1 The electrode assembly 10 has a wound structure. See below for reference. Figures 1 to 7 The electrode assembly 10 of this application will now be described. Specifically, the electrode assembly 10 includes a positive electrode 100 and a negative electrode 200.

[0044] Reference Figures 1 to 3 and Figure 6 The positive electrode 100 includes a positive current collector 110 and a positive active layer 120, the positive active layer 120 being coated on the positive current collector 110. It is understood that the positive active layer 120 can be coated on one or both sides of the positive current collector 110 along its thickness direction. The positive active layer 120 includes a first corner region 121, which refers to a region in the positive active layer 120 with a bent structure, where the surface of the positive active layer 120 is curved. It should be noted that the positive active layer 120 can have multiple first corner regions 121. Each first corner region 121 is provided with multiple first grooves 1211, and each first groove 1211 is spaced apart along the length direction of the positive electrode 100. (Refer to...) Figure 2 Orientation: The length direction of the positive electrode 100 is left-right.

[0045] Reference Figure 1 , Figure 4 , Figure 5 and Figure 7 The negative electrode 200 includes a negative electrode current collector 210 and a negative electrode active layer 220, the negative electrode active layer 220 being coated on the negative electrode current collector 210. The negative electrode active layer 220 can be coated on one or both sides of the negative electrode current collector 210 along its thickness direction. The negative electrode active layer 220 includes a second corner region 221, which refers to a region in the negative electrode active layer 220 with a bent structure, where the surface of the negative electrode active layer 220 is curved. It is understood that the negative electrode active layer 220 can have multiple second corner regions 221. The second corner region 221 is provided with multiple second grooves 2211, each second groove 2211 being spaced apart along the length direction of the negative electrode 200. (Refer to...) Figure 4 Orientation: The length direction of the negative electrode 200 can be left or right.

[0046] It is understood that the electrode assembly 10 may include a separator 300, which may be disposed between the positive electrode 100 and the negative electrode 200. The material of the separator 300 may include one or more of polyethylene, polypropylene, polyvinylidene fluoride and their multilayer composite membranes, etc. The specific arrangement of the separator 300 may be determined according to the actual situation.

[0047] Reference Figure 6 and Figure 7 The relative dimensions of the first groove 1211 and the second groove 2211 are described below. It should be noted that in this embodiment, both the first groove 1211 and the second groove 2211 can be isosceles trapezoidal grooves (the sides of the grooves have an incline). (Refer to...) Figure 6The width of the first groove 1211 is W1. Specifically, W1 can be the width at the opening of the first groove 1211. The depth of the first groove 1211 is D1. The spacing between two adjacent first grooves 1211 is L1. (Refer to...) Figure 7 The width of the second groove 2211 is W2. Specifically, W2 can be the width at the opening of the second groove 2211, and the depth of the second groove 2211 is D2. The distance between two adjacent second grooves 2211 is L2.

[0048] It should be noted that the first tank 1211 and the second tank 2211 satisfy the condition: 0.25 ≤ (W2×D2×L1) / (W1×D1×L2) ≤ 1.02. For example, (W2×D2×L1) / (W1×D1×L2) can be 0.25, 0.4, 0.55, 0.6, 0.72, 0.8, 0.95 or 1.02, and the specific ratio can be determined according to the actual situation.

[0049] In the technical solution of this utility model, the electrode assembly 10 has a wound structure. The electrode assembly 10 includes a positive electrode 100 and a negative electrode 200. The positive electrode 100 includes a positive current collector 110 and a positive active layer 120 coated on the positive current collector 110, the positive active layer 120 including a first corner region 121. The negative electrode 200 includes a negative current collector 210 and a negative active layer 220 coated on the negative current collector 210, the negative active layer 220 including a second corner region 221.

[0050] In existing technologies, poor electrolyte wetting and easy drying at the corners of the negative electrode, coupled with the long-term bending and compression of the active material layer at the corners by the winding structure, can lead to lithium plating at the corners. In this solution, the first corner region 121 of the positive electrode active layer 120 has multiple first grooves 1211, and the second corner region 221 of the negative electrode active layer 220 has multiple second grooves 2211. This increases the surface area of ​​the active layer, improving electrolyte wetting; it also increases the lithium-ion insertion / extraction rate under high-rate charge / discharge; and it reduces the tortuosity of the electrode pores, increasing the lithium-ion diffusion coefficient. Therefore, this solution effectively alleviates the corner lithium plating problem.

[0051] In existing technologies, during the charging and discharging process of wound batteries, uneven stress occurs in the corner areas. The circular arc compression affects the electrolyte retention of the electrodes, and the rounded corners also cause differences in the N / P ratio of the active materials. This solution incorporates a groove in the corner area, which effectively reduces mechanical tension and resistance during cycling, minimizes deformation caused by uneven stress in the corner area, and improves the electrolyte retention. Furthermore, it balances the N / P ratio in the corner area, increasing the lithium-ion insertion / extraction rate and mitigating lithium desorption issues.

[0052] Furthermore, the first tank 1211 has a width of W1 and a depth of D1, with a spacing of L1 between adjacent first tanks 1211; the second tank 2211 has a width of W2 and a depth of D2, with a spacing of L2 between adjacent second tanks 2211. When W1 and D1 of the first tank 1211 are too large and L1 is too small, it is easy to cause excessive loss of active material in the positive electrode 100, which will reduce the energy density; conversely, when W1 and D1 of the first tank 1211 are too small and L1 is too large, the loss of active material in the positive electrode active layer 120 is less, but it will cause an imbalance in the N / P ratio of the first corner region 121 and restrict the lithium-ion transport channel. When W2 and D2 of the second tank 2211 are too large and L2 is too small, it can easily lead to excessive loss of active material in the negative electrode 200 and a reduction in lithium storage sites in the second corner region 221, making lithium plating more likely. Conversely, when W2 and D2 of the second tank 2211 are too small and L2 is too large, on the one hand, the lithium intercalation channel is blocked, and lithium ions may accumulate on the surface of the negative electrode 200, increasing the risk of lithium plating; on the other hand, the excessive number of lithium storage sites in the second corner region 221 of the negative electrode 200 increases the N / P ratio, resulting in more delithiation of the active material in the positive electrode 100, affecting the structural stability of the material and damaging the battery's lifespan. This is especially true at high temperatures, where the increased material activity has a more significant impact on the material's structural stability. The first tank 1211 and the second tank 2211 of this scheme satisfy the condition: 0.25≤(W2×D2×L1) / (W1×D1×L2)≤1.02. That is, the lithium-ion insertion / extraction rate, liquid retention effect, N / P ratio, active material loss, rate performance and structural stability of the material in the corner region of this scheme are all balanced, which can improve battery performance.

[0053] Reference Figure 2 and Figure 3 The thickness setting of the positive electrode active layer 120 is described below. In some embodiments, the thickness of the positive electrode active layer 120 is T1, wherein 30μm ≤ T1 ≤ 70μm. Exemplarily, T1 can be 30μm, 35μm, 42μm, 50μm, 58μm, 63μm, or 70μm, etc. When the positive electrode active layer 120 is too thick, the lithium-ion diffusion path becomes longer, reducing the lithium-ion transfer rate; decreasing electron conduction efficiency, increasing internal resistance, and leading to defects such as poor heat dissipation and stress concentration. When the positive electrode active layer 120 is too thin, i.e., insufficient active material, the battery cannot generate sufficient current, reducing the battery capacity and energy density. The positive electrode active layer 120 of this solution adopts the above-mentioned thickness setting to balance lithium-ion transfer rate, battery capacity, and energy density, thereby improving battery performance.

[0054] Reference Figure 4 and Figure 5The thickness setting of the negative electrode active layer 220 is described below. In some embodiments, the thickness of the negative electrode active layer 220 is T2, wherein 25μm≤T2≤60μm. Exemplarily, T2 can be 25μm, 28μm, 33μm, 45μm, 50μm, 57μm, or 60μm, etc. When the negative electrode active material layer is too thick, the lithium-ion diffusion path becomes longer, reducing the reaction rate; it also increases internal resistance, reducing charge and discharge efficiency; and it can also form lithium deposition and dendrites, affecting battery safety. When the negative electrode active material layer is too thin, the negative electrode cannot effectively store lithium, affecting battery capacity and energy density. The negative electrode active layer 220 of this solution adopts the above-mentioned thickness setting, which can balance lithium-ion transfer rate, battery capacity, and energy density, thereby improving battery performance.

[0055] The following describes the relative dimensions of the depth of the first trench 1211 and the thickness of the positive electrode active layer 120 in some embodiments. The trench depth D1 of the first trench 1211 satisfies: 1 / 5T1 ≤ D1 ≤ 1 / 2T1. Exemplarily, D1 can be 1 / 5T1, 1 / 4T1, 1 / 3T1, or 1 / 2T1, etc. The following describes the relative dimensions of the depth of the second trench 2211 and the thickness of the negative electrode active layer 220 in some embodiments. The trench depth D2 of the second trench 2211 satisfies: 1 / 3T2 ≤ D2 ≤ 2 / 3T2. Exemplarily, D2 can be 1 / 3T2, 1 / 2T2, or 2 / 3T2, etc.

[0056] If the depth of the first tank 1211 and the second tank 2211 is too deep, it will lead to excessive loss of active material, affecting energy density, etc.; if the depth of the first tank 1211 and the second tank 2211 is too shallow, the improvement on the lithium-ion insertion / extraction rate is not significant. The first tank 1211 and the second tank 2211 of this solution adopt the above-mentioned tank depth, which can balance the loss of battery active material, energy density and lithium-ion insertion / extraction rate, thereby improving battery performance.

[0057] The relative depths of the first groove 1211 and the second groove 2211 are described below. The first groove 1211 and the second groove 2211 satisfy the condition: 0.5 ≤ D1 / D2 ≤ 2. For example, D1 / D2 can be 0.5, 0.8, 1, 1.2, 1.5, 1.8, or 2. The specific groove depth settings of the first groove 1211 and the second groove 2211 can be determined according to actual circumstances.

[0058] The specific settings for the groove width of the first groove 1211 are described below. In some embodiments, the groove width W1 of the first groove 1211 satisfies: 70μm ≤ W1 ≤ 180μm. For example, W1 can be 70μm, 85μm, 90μm, 100μm, 115μm, 140μm, 150μm, or 180μm, etc. The specific settings for the groove width of the second groove 2211 are described below. In some embodiments, the groove width W2 of the second groove 2211 satisfies: 50μm ≤ W2 ≤ 110μm. For example, W2 can be 50μm, 60μm, 75μm, 80μm, 90μm, 104μm, or 110μm, etc.

[0059] When the widths of the first tank 1211 and the second tank 2211 are too wide, excessive loss of active material will occur, affecting energy density, etc.; when the widths of the first tank 1211 and the second tank 2211 are too narrow, the improvement on lithium-ion insertion / extraction speed is not significant. The first tank 1211 and the second tank 2211 in this solution adopt the aforementioned tank widths, which can balance the loss of battery active material, energy density, and lithium-ion insertion / extraction speed, thereby improving battery performance.

[0060] The relative sizes of the groove widths of the first groove 1211 and the second groove 2211 in some embodiments are described below. The first groove 1211 and the second groove 2211 satisfy the condition: 1 ≤ W1 / W2 ≤ 2. For example, W1 / W2 can be 1, 1.2, 1.4, 1.7, 1.8 or 2. The specific groove width settings of the first groove 1211 and the second groove 2211 can be determined according to the actual situation.

[0061] The following describes the spacing of the plurality of first grooves 1211 in the positive electrode 100 in some embodiments. In some embodiments, the spacing between two adjacent first grooves 1211 can be uniform. In other embodiments, the spacing between two adjacent first grooves 1211 can also be non-uniform. Some embodiments of this application are illustrated using the example of a uniform spacing between two adjacent first grooves 1211. This solution can reduce the difficulty of grooving and reduce processing costs. The spacing L1 between two adjacent first grooves 1211 satisfies: 70μm ≤ L1 ≤ 180μm. For example, L1 can be 70μm, 75μm, 83μm, 90μm, 120μm, 148μm, 165μm, or 180μm, etc.

[0062] The following describes the spacing of the multiple second grooves 2211 of the negative electrode 200 in some embodiments. In some embodiments, the spacing between two adjacent second grooves 2211 can be uniform. In other embodiments, the spacing between two adjacent second grooves 2211 can also be non-uniform. Some embodiments of this application are illustrated using the example of a uniform spacing between two adjacent second grooves 2211. This solution can reduce the difficulty of grooving and reduce processing costs. The spacing L2 between two adjacent second grooves 2211 satisfies: 50μm≤L2≤110μm. For example, L2 can be 50μm, 54μm, 60μm, 66μm, 75μm, 82μm, 98μm, 105μm, or 110μm, etc. It should be noted that the first groove 1211 and the second groove 2211 satisfy: 1≤L1 / L2≤2. For example, L1 / L2 can be 1, 1.2, 1.5, 1.7, 1.9 or 2, etc.

[0063] When the spacing between two adjacent first cells 1211 and the spacing between two adjacent second cells 2211 are too small, excessive loss of active material will occur, affecting energy density, etc.; when the spacing between two adjacent first cells 1211 and the spacing between two adjacent second cells 2211 are too large, the improvement on lithium-ion insertion / extraction rate is not significant. The above-mentioned spacing between the first cells 1211 and the second cells 2211 in this design balances the loss of active material, energy density, and lithium-ion insertion / extraction rate, thereby improving battery performance.

[0064] Reference Figures 1 to 3 In some embodiments, the positive electrode active layer 120 includes a first flat region 122, which is connected to a first corner region 121. The first flat region 122 refers to a region in the positive electrode active layer 120 that has a flat structure, i.e., the surface of the positive electrode active layer 120 in this region is a straight plane. It should be noted that the positive electrode active layer 120 may have multiple first flat regions 122. The negative electrode active layer 220 includes a second flat region 222, which is connected to a second corner region 221. The second flat region 222 refers to a region in the negative electrode active layer 220 that has a flat structure, i.e., the surface of the negative electrode active layer 220 in this region is a straight plane. The negative electrode active layer 220 may include multiple second flat regions 222.

[0065] The following describes the N / P value settings for batteries in some embodiments. The formula for calculating the battery N / P ratio is: N / P = (Specific capacity of negative electrode active material × Negative electrode density × Negative electrode active material content) / (Specific capacity of positive electrode active material × Positive electrode density × Positive electrode active material content). The first flat region 122 and the second flat region 222 satisfy: 1.03 ≤ N1 / P1 ≤ 1.12. For example, N1 / P1 can be 1.03, 1.05, 1.07, 1.09, or 1.12, etc. In other embodiments, the first corner region 121 and the second corner region 221 satisfy: 1.03 ≤ N2 / P2 ≤ 1.12. For example, N2 / P2 can be 1.03, 1.05, 1.07, 1.09, or 1.12, etc.

[0066] An excessively high N / P ratio leads to overcapacity, reduced lithium-ion utilization, decreased charge / discharge efficiency, and poor cycle stability. Conversely, an excessively low N / P ratio results in decreased battery energy density, rapid capacity decay, or lithium deposition, potentially causing internal short circuits and safety hazards. This solution, by employing the aforementioned settings, maximizes battery energy density, improves efficiency, and extends lifespan.

[0067] The following describes the specific configuration of the second flat region 222 in some embodiments. In some embodiments, the second flat region 222 is provided with a plurality of second grooves 2211, and the structure of each second groove 2211 may be identical. Each second groove 2211 may extend along the width direction of the negative electrode 200 and be arranged at intervals along the length direction of the negative electrode 200. Refer to Figure 5 In terms of orientation, the second grooves 2211 can be arranged at uniform intervals along the left-right direction. Lithium plating occurs in the negative electrode 200. Because the lithium intercalation capacity of the negative electrode is insufficient to consume the lithium ions transferred from the positive electrode, the second flat region 222 of this design has multiple second grooves 2211, which can improve the kinetic performance of the negative electrode and enhance the diffusion capacity of lithium ions. It should be noted that the first flat region 122 of the positive electrode 100 can be without grooves, thus avoiding the loss of active material affecting the battery capacity. Furthermore, if grooves are formed in the positive electrode 100, it will increase the lithium ion extraction rate, adding a burden to the lithium intercalation operation of the negative electrode 200.

[0068] Reference Figure 2 and Figure 3 The specific arrangement of the multiple first trenches 1211 is described below. In some embodiments, each first trench 1211 is arranged uniformly and at intervals along the length direction of the positive electrode sheet 100. It should be noted that the interval between two adjacent first trenches 1211 can be uniform. The first trenches 1211 can penetrate the positive electrode active layer 120 along the width direction of the positive electrode sheet 100. (Refer to...) Figure 2Orientation: The width direction of the positive electrode sheet 100 can point in the vertical direction, and the first groove 1211 can penetrate the positive electrode active layer 120 in the vertical direction. The first groove 1211 of this solution adopts the above-mentioned configuration, which facilitates processing and can effectively reduce the risk of cracking, powder shedding, or breakage of the positive electrode active layer 120 in the first corner area 121 or the positive electrode current collector 110.

[0069] Reference Figure 4 and Figure 5 The specific arrangement of the multiple second trenches 2211 is described below. In some embodiments, each second trench 2211 is arranged uniformly and at intervals along the length direction of the negative electrode sheet 200. It should be noted that the interval between two adjacent second trenches 2211 can be uniform. The second trenches 2211 can penetrate the negative electrode active layer 220 along the width direction of the negative electrode sheet 200. (Refer to...) Figure 4 The width direction of the negative electrode sheet 200 can point vertically, and the second groove 2211 can penetrate the negative electrode active layer 220 along the width direction of the negative electrode sheet 200. The second groove 2211 of this solution adopts the above-mentioned configuration, which facilitates processing and can effectively reduce the risk of cracking, powder shedding, or breakage of the negative electrode active layer 220 in the second corner area 221 or the negative electrode current collector 210.

[0070] A second aspect of this utility model provides a battery, which includes the electrode assembly 10 described in the above embodiment. This application uses a lithium battery as an example for illustration. It is understood that the positive electrode current collector 110 can be made of aluminum, and the positive electrode active layer 120 can be made of lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode current collector 210 can be made of copper, and the negative electrode active layer 220 can be made of carbon or silicon, etc. This solution achieves a balance in lithium-ion insertion / extraction rate, liquid retention effect, N / P ratio, active material loss, rate performance, and material structure stability, thus improving battery performance.

[0071] A third aspect of this utility model provides an electrical device, which includes the battery described in the above embodiment. The battery is used to supply power to the electrical device. It is understood that the electrical device can be a mobile phone, tablet computer, laptop computer, battery-powered toy, power tool, or electric vehicle, etc., and the specific application depends on the actual situation. The battery in this solution can ensure the stability and reliability of the electrical device's operation.

[0072] The following describes the specific fabrication process of batteries in some embodiments:

[0073] Preparation of positive electrode 100: The cathode active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and uniformly coated onto both sides of the positive electrode current collector 110 in an N-methylpyrrolidone solvent system at a weight ratio of 97.6:0.5:0.6:1.3. Then, the mixture is dried, cold-pressed, and slit to obtain the positive electrode 100. Subsequently, multiple first grooves 1211 are formed in the positive electrode 100.

[0074] Preparation of negative electrode 200: Anode active material graphite, conductive agent (SP and CNT mixed in a mass ratio of 0.45:0.05), and binder (SBR and PAALi mixed in a mass ratio of 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2. The resulting anode active material slurry is uniformly coated onto both sides of the negative electrode current collector 210, and then dried, cold-pressed, and slit to obtain negative electrode 200. Subsequently, multiple second grooves 2211 are formed in the negative electrode 200.

[0075] Preparation of diaphragm 300: A ceramic mixture is coated on the surface of polyethylene (PE) to serve as a diaphragm.

[0076] Electrolyte preparation: Ethyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) were mixed in a volume ratio of 1.2:1:4:4. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare the electrolyte.

[0077] Battery fabrication: The above-mentioned positive electrode 100 with the first groove 1211, separator 300, and negative electrode 200 with the second groove 2211 are wound to form a bare cell, and then packaged and injected with electrolyte to form a finished lithium battery 1.

[0078] Table 1 shows the electrode assembly 10 setting parameters for some embodiments and comparative examples of this application.

[0079]

[0080] Table 1

[0081] The following describes the relevant test settings for the battery in some embodiments:

[0082] (1) Short-term lithium plating test: The lithium plating test was carried out at 25°C as follows: charged to 4.5V with constant current and constant voltage at 3C, cut-off current at 0.02C; rested for 5 minutes; discharged to 3.0V with constant current at 0.7C; a total of 50 cycles were performed. Then the battery was disassembled and the lithium plating on the surface of the negative electrode 200 was observed.

[0083] (2) Cyclic test: Under 25℃ environment, perform cyclic test according to the following method: a. Charging mode: 2.8C CC to 4.27V, 2C CC to 4.35V, CV to 1.8C, 1.8C CC to 4.45V, CV to 1.5C, 1.5C CC to 4.5V, CV to 1.2C, 1.2C CC to 4.55V, CV to 0.25C; b. Discharging mode: 0.7C DC to 3.0V.

[0084] 500-week Fading = Discharge capacity in week 500 / Discharge capacity in week 1 * 100%;

[0085] Under 45℃ conditions, perform cyclic testing according to the following methods: a) Charging mode: 2.8C CC to 4.27V, 2CCC to 4.35V, CV to 1.8C, 1.8C CC to 4.45V, CV to 1.5C, 1.5C CC to 4.5V, CV to 1.2C, 1.2C CC to 4.55V, CV to 0.25C; b) Discharging mode: 0.7C DC to 3.0V.

[0086] 400-week Fading = Discharge capacity in week 400 / Discharge capacity in week 1 * 100%;

[0087] (3) Liquid retention test: Liquid retention = Injection volume - Liquid loss. It should be noted that the initial injection volume in some embodiments of this application is 8.25g.

[0088] The above tests were performed on some embodiments of this application and the batteries of the comparative examples, and the results are shown in Table 2.

[0089]

[0090] Table 2

[0091] Referring to Tables 1 and 2, as shown in Examples 1-10 and Comparative Examples 1-2, setting grooves on the positive electrode 100 and negative electrode 200 of the electrode assembly 10 is beneficial for electrolyte wetting, increases battery electrolyte retention, and provides a guarantee for long-term cycling. Cyclic performance tests and short-term lithium plating tests show that this solution can improve lithium-ion kinetics, enhance cycle performance, and effectively alleviate the corner lithium plating problem. In Comparative Examples 1-2, the increased parameters of the first groove 1211 of the positive electrode 100 lead to excessive loss of active material. On the one hand, the short-term lithium plating phenomenon shows that the purple spots in the corner area are not fully intercalated with lithium ions, resulting in lower battery capacity. On the other hand, although it has little impact on battery performance at room temperature, it severely affects the battery's operation in high-temperature environments. By adjusting the parameters of the first tank 1211 and the second tank 2211 of the electrode assembly 10, after satisfying 0.25≤(W2×D2×L1) / (W1×D1×L2)≤1.02, the battery's dynamic performance, liquid retention, loss of active material, and material structure stability are all balanced, ensuring that the battery has the best performance.

[0092] It should be noted that if any directional indication (such as up, down, left, right, front, back, etc.) is involved in the embodiments of this utility model, such directional indication is only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. When a directional reference is introduced in a specific embodiment, unless the direction is specifically limited to unidirectional, the direction can be unidirectional or bidirectional (two parallel and opposite directions). Whether it is unidirectional or bidirectional depends on what those skilled in the art can achieve. When the directional reference is bidirectional, it should be considered that two parallel and different embodiments have been introduced simultaneously.

[0093] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or," "and / or," or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where A and B are simultaneously satisfied. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0094] The above are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural transformations made based on the inventive concept of this utility model and the contents of this utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this utility model.

Claims

1. An electrode assembly, characterized in that, The electrode assembly has a wound structure, and the electrode assembly includes: A positive electrode sheet includes a positive current collector and a positive active layer coated on the positive current collector. The positive active layer includes a first corner region, and the first corner region has a plurality of first grooves, each of which is arranged at intervals along the length direction of the positive electrode sheet. A negative electrode sheet includes a negative electrode current collector and a negative electrode active layer coated on the negative electrode current collector. The negative electrode active layer includes a second corner region, and the second corner region has a plurality of second grooves, each of which is arranged at intervals along the length direction of the negative electrode sheet. Wherein, the first groove has a groove width of W1 and a groove depth of D1, and the groove spacing between two adjacent first grooves is L1. The second groove has a groove width of W2 and a groove depth of D2, and the groove spacing between two adjacent second grooves is L2. The first groove and the second groove satisfy the condition: 0.25≤(W2×D2×L1) / (W1×D1×L2)≤1.

02.

2. The electrode assembly as described in claim 1, characterized in that, The thickness of the positive electrode active layer is T1, wherein 30μm≤T1≤70μm, and the thickness of the negative electrode active layer is T2, wherein 25μm≤T2≤60μm.

3. The electrode assembly as described in claim 2, characterized in that, The groove depth D1 of the first groove body satisfies: 1 / 5T1≤D1≤1 / 2T1, the groove depth D2 of the second groove body satisfies: 1 / 3T2≤D2≤2 / 3T2, and the first groove body and the second groove body satisfy: 0.5≤D1 / D2≤2.

4. The electrode assembly as described in claim 1, characterized in that, The width W1 of the first tank satisfies: 70μm≤W1≤180μm, the width W2 of the second tank satisfies: 50μm≤W2≤110μm, and the first tank and the second tank satisfy: 1≤W1 / W2≤2.

5. The electrode assembly as described in claim 1, characterized in that, The distance L1 between two adjacent first tanks satisfies: 70μm≤L1≤180μm, the distance L2 between two adjacent second tanks satisfies: 50μm≤L2≤110μm, and the distance between the first tank and the second tank satisfies: 1≤L1 / L2≤2.

6. The electrode assembly as described in claim 1, characterized in that, The positive electrode active layer includes a first straight region connected to the first corner region, and the negative electrode active layer includes a second straight region connected to the second corner region; and The first straight area and the second straight area satisfy the condition: 1.03≤N / P≤1.12; and / or, the first corner area and the second corner area satisfy the condition: 1.03≤N / P≤1.

12.

7. The electrode assembly as described in claim 6, characterized in that, The second flat region is provided with a plurality of second grooves, each of which extends along the width direction of the negative electrode sheet and is arranged at intervals along the length direction of the negative electrode sheet.

8. The electrode assembly as described in claim 1, characterized in that, The first groove penetrates the positive electrode active layer along the width direction of the positive electrode sheet, and each of the first grooves is spaced apart and evenly arranged along the length direction of the positive electrode sheet; And / or, The second groove extends through the negative electrode active layer along the width direction of the negative electrode sheet, and the second grooves are spaced apart and evenly arranged along the length direction of the negative electrode sheet.

9. A battery, characterized in that, Includes the electrode assembly as described in any one of claims 1-8.

10. Electrical equipment, characterized in that, Includes the battery as described in claim 9, the battery being used to power the electrical device.

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