Negative electrode sheet, positive electrode sheet, battery cell, and battery

Abstract

The utility model relates to battery technology field, concretely provides a negative pole piece, positive pole piece, electric core and battery, aims at solving the problem that the way of setting micropore in the edge area of pole piece and filling active substance in the micropore in prior art cannot more comprehensive restrain lithium precipitation phenomenon. For this purpose, the negative pole piece of the utility model has first edge area, negative pole main area and second edge area, the negative pole main area is located between first edge area and second edge area, first edge area and second edge area all are coated first negative pole active coating, the negative pole main area is coated second negative pole active coating, first negative pole active coating is used for making first edge area and second edge area compared with coating second negative pole active coating potential to improve. The above setting can average the potential distribution of negative pole piece whole, and the risk of local lithium precipitation is inhibited. And first negative pole active coating is coated, and the risk of lithium precipitation is more comprehensively reduced.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically providing a negative electrode sheet, a positive electrode sheet, a battery cell, and a battery. Background Technology

[0002] With the rapid development of the new energy industry, higher requirements have been placed on the energy density, safety performance, and cycle life of lithium-ion batteries. During the charging process, lithium ions are released from the positive electrode, pass through the electrolyte and the separator, and are eventually embedded in the negative electrode material. However, in practical applications, especially under harsh conditions such as high-current fast charging or low temperature, lithium metal deposition (lithium plating) is very likely to occur at the edge of the negative electrode.

[0003] Lithium plating not only irreversibly depletes the active lithium source, causing rapid capacity decay, but more seriously, the deposited lithium dendrites can puncture the separator, triggering internal short circuits and posing a serious safety hazard. Therefore, effectively suppressing lithium plating on electrodes is a challenge for improving the fast-charging performance, cycle life, and safety of lithium-ion batteries.

[0004] To mitigate lithium plating on electrodes, existing technologies involve creating micropores at the edges of the positive and negative electrodes using etching or stamping techniques. Then, negative electrode active material to increase the negative electrode potential is filled into these micropores, and positive electrode active material to decrease the positive electrode potential is filled into the micropores. However, this method may limit the contact area between the active material and the current collector, as well as the ion / electron transport pathways, due to the pore structure, thus failing to comprehensively suppress lithium plating.

[0005] Accordingly, there is a need in the art for a new negative electrode, positive electrode, cell, and battery to solve the above problems. Utility Model Content

[0006] The present invention aims to solve the above-mentioned technical problems, namely, the problem that the existing technology of setting micropores in the edge area of ​​the electrode and filling the micropores with active material cannot more comprehensively suppress lithium plating.

[0007] This utility model provides a negative electrode sheet, which has a first edge region, a negative electrode body region, and a second edge region. The first edge region and the second edge region are disposed opposite to each other. The negative electrode body region is located between the first edge region and the second edge region. Both the first edge region and the second edge region are coated with a first negative electrode active coating. The negative electrode body region is coated with a second negative electrode active coating. The first negative electrode active coating is a coating with a potential higher than that of the second negative electrode active coating.

[0008] In the above-mentioned optional technical solutions for the negative electrode sheet, the specific capacity of the active material and / or the content of the conductive agent in the first negative electrode active coating is higher than that in the second negative electrode active coating; and / or the kinetic performance of the active material in the first negative electrode active coating is better than that in the second negative electrode active coating.

[0009] In the above-mentioned optional technical solutions for the negative electrode sheet, the first edge region is located on one side of the negative electrode tab of the negative electrode sheet.

[0010] In the above-mentioned optional technical solutions for the negative electrode sheet, the width of the first negative electrode active coating in the first edge region is greater than the width of the first negative electrode active coating in the second edge region.

[0011] In the above-mentioned optional technical solutions for the negative electrode sheet, the first negative electrode active coating is continuously coated on the entire length direction of the first edge region and / or the second edge region; and / or the first edge region and the second edge region are located on both sides of the width direction of the negative electrode sheet.

[0012] In the above-mentioned optional technical solutions for the negative electrode sheet, the sum of the widths of the first negative electrode active coating in the first edge region and the second edge region is h. h and the lithium-ion diffusion coefficient Ds of the first negative electrode active coating material satisfy the following formula: f(h,Ds)=a×ln(h)+b+c×ln(Ds)+d, where h is in meters (m) and Ds is in meters (m). 2 / s, a, b, c, d are preset coefficients, and f(h, Ds) is a preset value greater than 0.

[0013] On the other hand, the present invention also provides a positive electrode sheet having a third edge region, a positive electrode body region and a fourth edge region, wherein the third edge region and the fourth edge region are disposed opposite to each other, the positive electrode body region is located between the third edge region and the fourth edge region, both the third edge region and the fourth edge region are coated with a first positive electrode active coating, and the positive electrode body region is coated with a second positive electrode active coating, wherein the first positive electrode active coating is a coating with a potential lower than that of the second positive electrode active coating.

[0014] In the above-mentioned optional technical solutions for the positive electrode sheet, the specific capacity of the active material and / or the content of the conductive agent in the first positive electrode active coating is lower than that in the second positive electrode active coating; and / or the kinetic performance of the active material in the second positive electrode active coating is better than that in the first positive electrode active coating.

[0015] In the above-mentioned optional technical solutions for the positive electrode sheet, the third edge region is located on one side of the positive electrode tab of the positive electrode sheet.

[0016] In the above-mentioned optional technical solutions for the positive electrode sheet, the width of the first positive electrode active coating in the third edge region is greater than the width of the first positive electrode active coating in the fourth edge region.

[0017] In the above-mentioned optional technical solutions for the positive electrode sheet, the first positive electrode active coating is continuously coated on the entire length direction of the third edge region and / or the fourth edge region; and / or the third edge region and the fourth edge region are located on both sides of the width direction of the positive electrode sheet.

[0018] On the other hand, the present invention also provides a battery cell, the battery cell comprising a positive electrode, a separator and a negative electrode as described in any of the above embodiments, wherein the separator is disposed between the positive electrode and the negative electrode.

[0019] On the other hand, the present invention also provides a battery cell, the battery cell comprising a negative electrode, a separator and a positive electrode as described in any of the above embodiments, wherein the separator is disposed between the positive electrode and the negative electrode.

[0020] In the above-mentioned optional technical solutions for the battery cell, the first negative electrode active coating in the first edge region of the negative electrode sheet is opposite to the first positive electrode active coating in the third edge region of the positive electrode sheet, and the first negative electrode active coating in the second edge region of the negative electrode sheet is opposite to the first positive electrode active coating in the fourth edge region of the positive electrode sheet.

[0021] In the above-mentioned optional technical solutions for the battery cell, the positive electrode and the negative electrode are the same size, and the edges of the positive electrode and the negative electrode are aligned in both the length and width directions.

[0022] In the above-mentioned optional technical solutions for the battery cell, the width of the first negative electrode active coating in the first edge region is the same as the width of the first positive electrode active coating in the third edge region; and / or the width of the first negative electrode active coating in the second edge region is the same as the width of the first positive electrode active coating in the fourth edge region.

[0023] On the other hand, the present invention also provides a battery comprising a housing and a cell as described in any of the above embodiments disposed within the housing.

[0024] Those skilled in the art will understand that the negative electrode sheet of this utility model has a first edge region, a negative electrode body region, and a second edge region. The first edge region and the second edge region are arranged opposite to each other, and the negative electrode body region is located between the first edge region and the second edge region. Both the first edge region and the second edge region are coated with a first negative electrode active coating, and the negative electrode body region is coated with a second negative electrode active coating. The first negative electrode active coating is a coating with a potential higher than that of the second negative electrode active coating.

[0025] During the charging process of a lithium-ion battery, lithium ions insert from the positive electrode into the negative electrode, causing the negative electrode potential to drop. When the negative electrode potential drops to the deposition potential of lithium metal, lithium plating occurs. In conventional negative electrode sheets, the NP ratio (the ratio of negative electrode capacity to positive electrode capacity) at the edges is smaller than that of the main negative electrode area, leading to increased current density in these areas. Simultaneously, their capacity density per unit area or specific capacity is also lower, resulting in the potential at the edges of the negative electrode sheet often being lower than that of the main negative electrode area, thus becoming high-risk areas for lithium plating. Therefore, this invention coats both the first and second edge areas on both sides of the main negative electrode area with a first negative electrode active coating. This first negative electrode active coating has a higher potential than the second negative electrode active coating, which can even out the overall potential distribution of the negative electrode sheet, effectively reducing the impedance of the first and second edge areas, allowing lithium ions to insert more smoothly and quickly, and suppressing the risk of localized lithium plating. Furthermore, the first negative electrode active coating of this invention is applied to the first edge region and the second edge region, forming a continuous ion migration interface, which can uniformly increase the electrode potential of the edge regions on both sides of the negative electrode sheet, and more comprehensively and effectively reduce the risk of lithium plating.

[0026] In terms of manufacturing process, a zebra coating method can be used to achieve one-time coating. Specifically, by designing the coating mold, the first negative electrode active coating slurry and the second negative electrode active coating slurry can be simultaneously coated on the corresponding areas of the current collector in a single coating process according to a preset pattern. This not only comprehensively reduces the risk of lithium plating, but also allows the coating of the first and second edge areas to be completed simultaneously in a single coating process. Compared with the complex multi-step processing of traditional micro-via solutions, which involves etching and perforating first and then filling, this method not only greatly simplifies the production process and improves manufacturing efficiency, but also avoids damage to the current collector substrate, thereby improving the yield of subsequent cell manufacturing.

[0027] Furthermore, the positive electrode sheet of this utility model has a third edge region, a positive electrode body region and a fourth edge region. The third edge region and the fourth edge region are arranged opposite to each other. The positive electrode body region is located between the third edge region and the fourth edge region. The third edge region and the fourth edge region are coated with a first positive electrode active coating. The positive electrode body region is coated with a second positive electrode active coating. The first positive electrode active coating is a coating with a potential lower than that of the second positive electrode active coating.

[0028] During battery charging, due to the edge current density concentration effect, the potential of the positive electrode body region is usually lower than that of the third and fourth edge regions on both sides. Uneven potential distribution exacerbates the risk of lithium plating at the edges of the negative electrode. Therefore, the above-mentioned arrangement of this invention can average the potential of the positive electrode, thereby relatively weakening the intensity of the lithium ion flow extracted from the third and fourth edge regions of the positive electrode. This reduces the lithium supply pressure on the first and second edge regions of the facing negative electrode, helping to improve the NP ratio of this local area. Furthermore, the first positive electrode active coating of this invention is applied to the third and fourth edge regions, forming a complete ion transport interface, which can uniformly regulate the electrode potential of the third and fourth edge regions on both sides of the positive electrode, thus reducing the risk of lithium plating more comprehensively and effectively from the source.

[0029] In terms of manufacturing process, a zebra coating method can be used to achieve one-time coating. Specifically, by designing the coating mold, the first and second positive electrode active coating slurries can be simultaneously coated on the corresponding areas of the current collector in a single coating process according to a preset pattern. This not only more comprehensively and synergistically suppresses the risk of lithium plating, but also allows the coating of the third and fourth edge regions to be completed simultaneously in a single coating process. Compared with the complex multi-step processing of traditional microvia solutions, which involves etching and perforating first and then filling, this method not only greatly simplifies the production process and improves manufacturing efficiency, but also maintains the integrity of the current collector substrate, improving the yield and reliability of subsequent cell manufacturing. Attached Figure Description

[0030] The preferred embodiments of this utility model are described below with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of the negative electrode sheet of this utility model; Figure 2 This is a schematic diagram of the positive electrode sheet of this utility model.

[0031] Explanation of reference numerals in the attached figures: 1-Negative electrode sheet; 11-First edge region; 111-First negative electrode active coating; 12-Negative electrode main body region; 121-Second negative electrode active coating; 13-Second edge region; 14-Negative electrode tab; 2-Positive electrode sheet; 21-Third edge region; 211-First positive electrode active coating; 22-Positive electrode main body region; 221-Second positive electrode active coating; 23-Fourth edge region; 24-Positive electrode tab. Detailed Implementation

[0032] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0033] It should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0034] To address the problem that existing technologies, which involve setting micropores in the edge region of the electrode and filling the micropores with active material, cannot comprehensively suppress lithium plating, this invention provides a positive electrode 2, a negative electrode 1, and a battery cell.

[0035] like Figure 1 As shown, the negative electrode 1 of this utility model will be introduced first.

[0036] The negative electrode sheet 1 of this invention has a first edge region 11, a negative electrode main body region 12, and a second edge region 13. The first edge region 11 and the second edge region 13 are arranged opposite to each other. Specifically, the first edge region 11 and the second edge region 13 are located on both sides of the width direction of the negative electrode sheet 1, and the negative electrode main body region 12 is located between the first edge region 11 and the second edge region 13. Both the first edge region 11 and the second edge region 13 are coated with a first negative electrode active coating 111, and the negative electrode main body region 12 is coated with a second negative electrode active coating 121. The first negative electrode active coating 111 has a higher potential than the second negative electrode active coating 121. It should be noted that in this invention, the potentials of the first negative electrode active coating 111 and the second negative electrode active coating 121 refer to the potentials exhibited under the dynamic operating condition of battery charging.

[0037] During the charging process of a lithium-ion battery, lithium ions are inserted from the positive electrode into the negative electrode, causing the negative electrode potential to drop. When the negative electrode potential drops to the deposition potential of lithium metal, a lithium plating reaction occurs. In conventional negative electrode sheets 1, the NP ratio (the ratio of negative electrode capacity to positive electrode capacity) of the edge regions is smaller than that of the main negative electrode region 12, leading to an increase in current density in the edge regions. Simultaneously, the capacity density per unit area or specific capacity is also lower, resulting in the potential of the edge regions of the negative electrode sheet 1 often being lower than that of the main negative electrode region 12, thus becoming high-risk areas for lithium plating. Therefore, this invention coats the first edge region 11 and the second edge region 13 on both sides of the main negative electrode region 12 with a first negative electrode active coating 111. The first negative electrode active coating 111 has a higher potential than the second negative electrode active coating 121, which can even out the overall potential distribution of the negative electrode sheet 1, effectively reducing the impedance of the first edge region 11 and the second edge region 13, allowing lithium ions to insert more smoothly and quickly, and suppressing the risk of localized lithium plating. Furthermore, the first negative electrode active coating 111 of this invention is coated on the first edge region 11 and the second edge region 13, forming a continuous ion migration interface. This can uniformly increase the potential of the edge regions on both sides of the negative electrode sheet 1, thus reducing the risk of lithium plating more comprehensively and effectively. Further, the first negative electrode active coating 111 is continuously coated along the entire length of the first edge region 11 and the second edge region 13. It can be understood that the continuous coating of the first negative electrode active coating 111 on the first edge region 11 means that the first negative electrode active coating 111 is not broken on the first edge region 11, and the same applies to the second edge region 13.

[0038] In terms of manufacturing process, a zebra coating method can be used to achieve one-time coating. Specifically, through the design of the coating mold, the first negative electrode active coating 111 slurry and the second negative electrode active coating 121 slurry can be coated simultaneously on the corresponding areas of the current collector in a single coating process according to a preset pattern. This not only reduces the risk of lithium plating more comprehensively, but also allows the coating of the first edge region 11, the negative electrode main body region 12, and the second edge region 13 to be completed simultaneously in a single coating process. Compared with the complex multi-step processing of traditional micro-via solutions, which involves etching and perforating first and then filling, this method not only greatly simplifies the production process and improves manufacturing efficiency, but also avoids damage to the current collector substrate and improves the yield of subsequent cell manufacturing.

[0039] As one possible implementation, the specific capacity and / or conductive agent content of the active material in the first negative electrode active coating 111 is higher than that in the second negative electrode active coating 121, and / or the kinetic performance of the active material in the first negative electrode active coating 111 is better than that in the second negative electrode active coating, so as to average the overall potential distribution of the negative electrode sheet 1 and suppress the risk of local lithium plating. It is understood that the kinetic performance of the active material mainly refers to the rate of lithium ion insertion / extraction reactions inside and on the surface of the active material particles. The faster the insertion / extraction reaction, the better the kinetic performance. Specifically, it can be characterized by lithium ion diffusion coefficient, AC internal resistance, resistivity, or the phase structure and grain size of the material, etc. Among the above characterization parameters: the higher the lithium ion diffusion coefficient, the better the kinetic performance; the lower the AC internal resistance or resistivity, the better the kinetic performance; and the smaller the grain size (shortening the diffusion path of lithium ions in the solid), the better the kinetic performance.

[0040] Regarding the specific form of the first negative electrode active coating 111, this utility model does not impose specific restrictions, as long as the first negative electrode active coating 111 is a coating with a potential higher than that of the second negative electrode active coating 121.

[0041] For example, regarding the active material, the first negative electrode active coating 111 can be made of high-capacity graphite with a specific capacity of 350-360 mAh / g, preferably 355 mAh / g; correspondingly, the second negative electrode active coating 121 can be made of conventional graphite with a specific capacity of 325-335 mAh / g, preferably 330 mAh / g. Alternatively, the first negative electrode active coating 111 can be made of silicon-carbon composite material with a specific capacity of 400-500 mAh / g, preferably 450 mAh / g; correspondingly, the second negative electrode active coating 121 can be made of mesophase carbon microspheres with a specific capacity of 330-350 mAh / g, preferably 340 mAh / g.

[0042] For example, regarding the conductive agent content, the conductive agent content in the first negative electrode active coating 111 can be 2.0%-3.5% (weight percentage), preferably 2.8%; the conductive agent used includes, but is not limited to, one or more of acetylene black, carbon nanotubes, graphene, or carbon fibers. The conductive agent content in the second negative electrode active coating 121 can be 1.0%-1.8% (weight percentage), preferably 1.5%; the conductive agent used includes, but is not limited to, one or more of acetylene black, carbon nanotubes, graphene, or carbon fibers.

[0043] For example, regarding the kinetic properties of the active material, the lithium-ion diffusion coefficient of the first negative electrode active coating 111 material can be 8.0×10⁻¹²-2.0×10⁻¹¹m² / s, preferably 1.2×10⁻¹¹m² / s; correspondingly, the lithium-ion diffusion coefficient of the second negative electrode active coating 121 material can be 5.0×10⁻¹³-3.0×10⁻¹²m² / s, preferably 1.0×10⁻¹²m² / s. The AC internal resistance of the first negative electrode active coating 111 is in the range of 18-25mΩ, preferably 20mΩ; correspondingly, the AC internal resistance of the second negative electrode active coating 121 is in the range of 25-35mΩ, preferably 30mΩ. The resistivity of the first negative electrode active coating 111 at a 1C rate can be 15-25 Ω·cm, preferably 20 Ω·cm; correspondingly, the resistivity of the second negative electrode active coating 121 can be 25-35 Ω·cm, preferably 30 Ω·cm.

[0044] In one possible implementation, the first edge region 11 is located on one side of the negative electrode tab 14 of the negative electrode sheet 1. The tab is the concentration point of current input and output. During charging and discharging, the area connected to the negative electrode tab 14 has the highest current density and the most intense lithium-ion insertion and extraction reactions. Therefore, this area is the core risk area where the potential on the negative electrode sheet 1 is most likely to drop to the lithium plating critical point. In addition, to avoid stress concentration at the root of the tab during winding or stacking, the first edge region 11 connected to the negative electrode tab 14 is usually thinned, which would exacerbate the risk of lithium plating. Therefore, by placing the first edge region 11 of the first negative electrode active coating 111 with high specific capacity, high conductivity, and / or superior kinetic performance on one side of the negative electrode tab 14, precise protection can be provided for this high-risk area.

[0045] In one possible implementation, the width of the first negative electrode active coating 111 in the first edge region 11 is greater than the width of the first negative electrode active coating 111 in the second edge region 13. The first edge region 11, which connects to the negative electrode tab 14, is a concentration point for current input and output, and its current density is much higher than other edge regions, making it the region with the lowest potential and the highest risk of lithium plating on the entire negative electrode sheet 1. By widening the first negative electrode active coating 111 in the first edge region 11 located on one side of the negative electrode tab 14, the overall potential of a larger area from the root of the negative electrode tab 14 inward can be more effectively increased, ensuring that the potential of this high-risk area is safely maintained above the lithium plating threshold.

[0046] As one possible implementation, the sum of the widths of the first negative electrode active coating 111 in the first edge region 11 and the second edge region 13 is h. The lithium-ion diffusion coefficient Ds of the first negative electrode active coating 111 material satisfies the following formula: f(h,Ds)=a×ln(h)+b+c×ln(Ds)+d, where h is in meters and Ds is in meters. 2 / s, a, b, c, d are preset coefficients, and f(h, Ds) is a preset value greater than 0.

[0047] When determining the sum h of the widths of the first negative electrode active coating 111 in the first edge region 11 and the second edge region 13, the lithium-ion diffusion coefficient Ds of the first negative electrode active coating 111 material can be measured first. Substituting the value of Ds, a, b, c, and d into the formula, the range of values ​​for the sum of widths h can be obtained. Among them, a, b, c, and d can be preset coefficients obtained by fitting a large amount of simulation data and / or experimental test results. The preferred ranges of values ​​for a, b, c, and d are: a = 0.002735 (0.00125, 0.00422), b = -0.1393 (-1.891e+13, 1.891e+13), c = 0.001109 (0.0008615, 0.001357), d = 0.2311 (-1.891e+13, 1.891e+13). The specific values ​​of the aforementioned coefficients a, b, c, and d are actually optimized solutions obtained based on specific design objectives (such as uniform potential of negative electrode 1) and a series of initial boundary conditions (such as areal density, capacity of the first negative electrode active coating 111 g, thickness of negative electrode 1, weight of the first negative electrode active coating 111 g, capacity of the first positive electrode active coating 211 g, thickness of positive electrode 2, weight of the first positive electrode active coating 211 g, etc.). Therefore, the values ​​of these coefficients are not fixed and can be adjusted by those skilled in the art according to specific product design requirements.

[0048] f(h,Ds) represents the lowest potential of the first edge region 11 and the second edge region 13 after the first negative electrode active coating 111 is applied. This value must be at least greater than 0 to ensure that lithium plating does not occur. The higher the value of f(h,Ds), the lower the risk of lithium plating. However, if f(h,Ds) is applied too wide, it will result in material waste. Furthermore, since the first negative electrode active coating 111 has relatively high activity, applying it too wide will lead to greater battery loss, higher lithium consumption, and a reduced lifespan. Therefore, the value of f(h,Ds) can be related to C(Ds) and W(h). C(Ds) is the unit weight cost increment of the first negative electrode active coating 111 material relative to the second negative electrode active coating 121, which is positively correlated with Ds. W(h) is the weight of the first negative electrode active coating 111, which is linearly positively correlated with h. The preset value is C(Ds) × W(h). In this way, it is possible to pursue the improvement of the lowest negative electrode potential and the minimization of the total cost increment.

[0049] like Figure 2 As shown, the positive electrode 2 of this utility model will be described below.

[0050] The positive electrode sheet 2 of this invention has a third edge region 21, a positive electrode body region 22, and a fourth edge region 23. The third edge region 21 and the fourth edge region 23 are arranged opposite to each other, specifically, the third edge region 21 and the fourth edge region 23 are located on both sides in the width direction of the positive electrode sheet. Furthermore, the positive electrode body region 22 is located between the third edge region 21 and the fourth edge region 23. Both the third edge region 21 and the fourth edge region 23 are coated with a first positive electrode active coating 211, and the positive electrode body region 22 is coated with a second positive electrode active coating 221. The first positive electrode active coating 211 has a lower potential than the second positive electrode active coating 221. It should be noted that in this invention, the potentials of the first positive electrode active coating 211 and the second positive electrode active coating 221 refer to the potentials exhibited under the dynamic operating condition of battery charging.

[0051] During battery charging, due to the edge current density concentration effect, the potential of the positive electrode main region 22 is usually lower than that of the third edge region 21 and the fourth edge region 23 on both sides. Uneven potential distribution will exacerbate the risk of lithium plating at the edge of the negative electrode 1. Therefore, the above-mentioned arrangement of this utility model can average the potential of the positive electrode 2, so that the intensity of the lithium ion flow extracted from the third edge region 21 and the fourth edge region 23 of the positive electrode 2 is relatively weakened, reducing the lithium supply pressure on the first edge region 11 and the second edge region 13 of the facing negative electrode 1, which helps to improve the NP ratio of this local area. Moreover, the first positive electrode active coating 211 of this utility model is coated on the third edge region 21 and the fourth edge region 23, forming a complete ion transport interface, which can uniformly regulate the potential of the third edge region 21 and the fourth edge region 23 on both sides of the positive electrode 2, and more comprehensively and effectively reduce the risk of lithium plating from the source. Furthermore, the first positive electrode active coating 211 is continuously coated along the entire length of the third edge region 21 and the fourth edge region 23. It is understandable that the first positive electrode active coating 211 is continuously coated on the third edge region 21, meaning that the first positive electrode active coating 211 is not broken on the third edge region 21, and the same applies to the fourth edge region 23.

[0052] In terms of manufacturing process, a zebra coating method can be used to achieve one-time coating. Specifically, through the design of the coating mold, the first positive electrode active coating 211 slurry and the second positive electrode active coating 221 slurry can be coated simultaneously on the corresponding areas of the current collector in a single coating process according to a preset pattern. This not only more comprehensively and synergistically suppresses the risk of lithium plating, but also allows the coating of the third edge region 21, the positive electrode main body region 22, and the fourth edge region 23 to be completed simultaneously in a single coating process. Compared with the complex multi-step processing of traditional micro-via solutions, which involves etching and perforating first and then filling, this method not only greatly simplifies the production process and improves manufacturing efficiency, but also maintains the integrity of the current collector substrate, improving the yield and reliability of subsequent cell manufacturing.

[0053] As one possible implementation, the specific capacity and / or conductive agent content of the active material in the first positive electrode active coating 211 is lower than that in the second positive electrode active coating 221, and / or the kinetic performance of the active material in the second positive electrode active coating 221 is better than that in the first positive electrode active coating 211. This averages the overall potential distribution of the positive electrode 2, resulting in a more uniform distribution of lithium ions extracted from the positive electrode 2, further synergistically reducing the risk of local lithium plating at the edge of the negative electrode 1. It is understood that the kinetic performance of the active material mainly refers to the rate of lithium ion insertion / extraction reactions within and on the surface of the active material particles. The faster the insertion / extraction reaction, the better the kinetic performance. Specifically, it can be characterized by lithium ion diffusion coefficient, AC internal resistance, resistivity, or the phase structure and grain size of the material, etc. Among the above characterization parameters: a higher lithium ion diffusion coefficient indicates better kinetic performance; a lower AC internal resistance or resistivity indicates better kinetic performance; and a smaller grain size (shortening the diffusion path of lithium ions in the solid) indicates better kinetic performance.

[0054] This utility model does not impose specific restrictions on the specific form of the first positive electrode active coating 211, as long as the first positive electrode active coating 211 is a coating with a potential lower than that of the second positive electrode active coating 221.

[0055] For example, regarding the specific capacity of the active material, the first positive electrode active coating 211 can be made of lithium iron phosphate material with a specific capacity of 130-150 mAh / g, preferably 140 mAh / g; correspondingly, the second positive electrode active coating 221 can be made of lithium iron phosphate material with a specific capacity of 155-170 mAh / g, preferably 160 mAh / g. Alternatively, both can be made of ternary materials (NCM), wherein the specific capacity of the first positive electrode active coating 211 is 160-175 mAh / g, preferably 168 mAh / g; correspondingly, the specific capacity of the second positive electrode active coating 221 is 180-190 mAh / g, preferably 182 mAh / g.

[0056] For example, regarding the conductive agent content, the total conductive agent content in the first positive electrode active coating 211 can be 1.0%-1.8% (weight percentage), preferably 1.4%; correspondingly, the total conductive agent content in the second positive electrode active coating 221 can be 2.0%-3.0% (weight percentage), preferably 2.5%. The conductive agents used include, but are not limited to, one or more of carbon nanotubes, acetylene black, carbon black, and graphene.

[0057] For example, in terms of kinetic performance, the first positive electrode active coating 211 has a lithium-ion diffusion coefficient of 5.0 × 10⁻¹. 4 The first positive electrode active coating 211 has a resistivity of -2.0 × 10⁻¹³ m² / s, preferably 1.0 × 10⁻¹³ m² / s; correspondingly, the lithium-ion diffusion coefficient of the second positive electrode active coating 221 is 1.0 × 10⁻¹³ - 5.0 × 10⁻¹³ m² / s, preferably 3.0 × 10⁻¹³ m² / s. The resistivity of the first positive electrode active coating 211 at a 1C rate can be 90-110 Ω·cm, preferably 100 Ω·cm; correspondingly, the resistivity of the second positive electrode active coating 221 can be 50-70 Ω·cm, preferably 60 Ω·cm.

[0058] In one possible implementation, the third edge region 21 is located on one side of the positive electrode tab 24 of the positive electrode plate 2. The third edge region 21, connected to the positive electrode tab 24, is a critical area for current release. This region experiences a significant potential increase at the end of charging, thereby exacerbating the risk of lithium plating towards the edge of the negative electrode plate 1. Therefore, by placing the third edge region 21 of the first positive electrode active coating 211, which has low specific capacity, low conductive agent content, and / or inferior kinetic performance compared to the second positive electrode active coating 221, on one side of the positive electrode tab 24, the potential peak in this high-risk region can be specifically suppressed, reducing the lithium-ion extraction rate, alleviating the lithium-ion supply pressure on the edge of the negative electrode plate 1, and thus improving the lithium plating phenomenon of the negative electrode plate 1.

[0059] In one possible implementation, the width of the first positive active coating 211 in the third edge region 21 is greater than the width of the first positive active coating 211 in the fourth edge region 23. The third edge region 21, which connects to the positive electrode tab 24, is also a concentration point for current input and output; this region experiences a sharp potential rise due to extremely high current density at the end of charging. Excessively high positive electrode potential increases the lithium supply pressure on the first edge region 11 of the facing negative electrode 1, thereby exacerbating the risk of lithium plating on the negative electrode 1. By widening the first positive active coating 211 in this area, the potential peak at the end of charging can be more effectively suppressed, reducing the lithium-ion supply intensity to the most dangerous region of the negative electrode from the source.

[0060] The battery cell of this utility model is described below.

[0061] The battery cell of this invention includes the aforementioned negative electrode 1 and positive electrode 2, and also includes a separator disposed between the positive electrode 2 and the negative electrode 1. Specifically, the first negative electrode active coating 111 of the first edge region 11 faces the first positive electrode active coating 211 of the third edge region 21, and the first negative electrode active coating 111 of the second edge region 13 faces the first positive electrode active coating 211 of the fourth edge region 23. It is understood that the first negative electrode active coating 111 of the first edge region 11 facing the first positive electrode active coating 211 of the third edge region 21 means that when the negative electrode 1 is projected orthogonally onto the positive electrode 2, the first negative electrode active coating 111 of the first edge region 11 and the first positive electrode active coating 211 of the third edge region 21 at least partially overlap. The first negative electrode active coating 111 of the second edge region 13 and the first positive electrode active coating 211 of the fourth edge region 23 are opposite to each other, meaning that when the negative electrode 1 is projected onto the positive electrode 2, the first negative electrode active coating 111 of the second edge region 13 and the first positive electrode active coating 211 of the fourth edge region 23 at least partially overlap.

[0062] The above configuration can synergistically optimize the NP ratio of the edge regions on both sides of the battery cell. It achieves a better match between the weak lithium-ion extraction at the edge of the positive electrode 2 and the stronger lithium-ion absorption capacity at the edge of the negative electrode 1, resulting in a better balance between the potential and current distribution at the electrode edges. This leads to a more comprehensive and effective suppression of lithium plating. Furthermore, the width of the first negative electrode active coating 111 in the first edge region 11 is the same as the width of the first positive electrode active coating 211 in the third edge region 21, and / or the width of the first negative electrode active coating 111 in the second edge region 13 is the same as the width of the first positive electrode active coating 211 in the fourth edge region 23. This improves material utilization and reduces costs while suppressing lithium plating.

[0063] Due to the above-mentioned design of the positive electrode 2 and negative electrode 1 of this utility model, there is no need to worry about lithium plating. Therefore, the positive electrode 2 and negative electrode 1 can be designed to have the same size, and the edges of the positive electrode 2 and negative electrode 1 are aligned in both the length and width directions.

[0064] In this design, the positive electrode 2 and the negative electrode 1 are the same size, and their edges are aligned in both the length and width directions. Compared to the OH design (Overhang: the negative electrode size exceeds the positive electrode size), this arrangement has the following advantages: First, since the negative electrode 1 has no excess capacity, it does not occupy extra capacity, thus increasing the energy density of the cell. Second, it reduces the amount of negative electrode 1 used, and the positive electrode does not need to use a ceramic coating to reduce the risk of short circuits, reducing manufacturing costs. Third, since there is no need to control the OH to meet specifications, the winding efficiency or stacking efficiency is improved, reducing manufacturing costs. Fourth, there is no need to discard cells with small OH during winding and stacking, improving yield. Fifth, it reduces the risk of the positive electrode directly contacting the negative electrode, enhancing safety. Sixth, it improves storage and cycle life, as lithium ions embedded in the negative electrode 1 can return to the positive electrode 2 in a timely manner during discharge, avoiding the accumulation of lithium ions in the negative electrode.

[0065] On the other hand, the present invention also provides a battery comprising a housing and a cell of the above-described embodiment disposed within the housing.

[0066] The technical solution of this utility model has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the protection scope of this utility model is obviously not limited to these specific embodiments. Without departing from the principle of this utility model, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of this utility model.

Claims

1. A negative electrode (1), characterized in that, The negative electrode sheet (1) has a first edge region (11), a negative electrode body region (12), and a second edge region (13). The first edge region (11) and the second edge region (13) are arranged opposite to each other. The negative electrode body region (12) is located between the first edge region (11) and the second edge region (13). The first edge region (11) and the second edge region (13) are both coated with a first negative electrode active coating (111). The negative electrode body region (12) is coated with a second negative electrode active coating (121). The first negative electrode active coating (111) is a coating with a potential higher than that of the second negative electrode active coating (121).

2. The negative electrode (1) according to claim 1, characterized in that, The specific capacity of the active material and / or the content of the conductive agent in the first negative electrode active coating (111) are higher than those in the second negative electrode active coating (121); and / or The kinetic properties of the active material in the first negative electrode active coating (111) are better than those in the second negative electrode active coating (121).

3. The negative electrode sheet (1) according to claim 1 or 2, characterized in that, The first edge region (11) is located on one side of the negative electrode tab (14) of the negative electrode sheet (1).

4. The negative electrode sheet (1) according to claim 3, characterized in that, The width of the first negative electrode active coating (111) in the first edge region (11) is greater than the width of the first negative electrode active coating (111) in the second edge region (13).

5. The negative electrode sheet (1) according to claim 1, characterized in that, The first negative electrode active coating (111) is continuously coated along the entire length of the first edge region (11) and / or the second edge region (13); and / or The first edge region (11) and the second edge region (13) are located on both sides of the width direction of the negative electrode (1).

6. The negative electrode (1) according to claim 1, characterized in that, The sum of the widths of the first negative electrode active coating (111) in the first edge region (11) and the second edge region (13) is h, and h satisfies the following formula with respect to the lithium-ion diffusion coefficient Ds of the first negative electrode active coating (111) material: f(h,Ds)=a×ln(h)+b+c×ln(Ds)+d, where h is in meters and Ds is in meters. 2 / s, a, b, c, d are preset coefficients, and f(h,Ds) is a preset value greater than 0.

7. A positive electrode (2), characterized in that, The positive electrode sheet (2) has a third edge region (21), a positive electrode body region (22) and a fourth edge region (23). The third edge region (21) and the fourth edge region (23) are arranged opposite to each other. The positive electrode body region (22) is located between the third edge region (21) and the fourth edge region (23). The third edge region (21) and the fourth edge region (23) are both coated with a first positive electrode active coating (211). The positive electrode body region (22) is coated with a second positive electrode active coating (221). The first positive electrode active coating (211) is a coating with a potential lower than that of the second positive electrode active coating (221).

8. The positive electrode (2) according to claim 7, characterized in that, The specific capacity of the active material and / or the content of the conductive agent in the first positive electrode active coating (211) are lower than those in the second positive electrode active coating (221); and / or The kinetic properties of the active material in the second positive electrode active coating (221) are better than those of the first positive electrode active coating (211).

9. The positive electrode (2) according to claim 7 or 8, characterized in that, The third edge region (21) is located on one side of the positive electrode tab (24) of the positive electrode plate (2).

10. The positive electrode (2) according to claim 9, characterized in that, The width of the first positive electrode active coating (211) in the third edge region (21) is greater than the width of the first positive electrode active coating (211) in the fourth edge region (23).

11. The positive electrode (2) according to claim 7, characterized in that, The first positive electrode active coating (211) is continuously coated along the entire length of the third edge region (21) and / or the fourth edge region (23); and / or The third edge region (21) and the fourth edge region (23) are located on both sides of the width direction of the positive electrode sheet.

12. A battery cell, characterized in that, The battery cell includes a positive electrode, a separator, and a negative electrode (1) according to any one of claims 1 to 6, wherein the separator is disposed between the positive electrode and the negative electrode (1).

13. A battery cell, characterized in that, The battery cell includes a negative electrode, a separator, and a positive electrode (2) according to any one of claims 7 to 11, wherein the separator is disposed between the positive electrode (2) and the negative electrode.

14. The battery cell according to claim 13, characterized in that, The negative electrode is the negative electrode (1) according to any one of claims 1 to 6, wherein the first negative electrode active coating (111) of the first edge region (11) of the negative electrode (1) is opposite to the first positive electrode active coating (211) of the third edge region (21) of the positive electrode (2), and the first negative electrode active coating (111) of the second edge region (13) of the negative electrode (1) is opposite to the first positive electrode active coating (211) of the fourth edge region (23) of the positive electrode (2).

15. The battery cell according to claim 14, characterized in that, The positive electrode (2) and the negative electrode (1) are the same size, and the edges of the positive electrode (2) and the negative electrode (1) are aligned in both the length and width directions.

16. The battery cell according to claim 14, characterized in that, The width of the first negative electrode active coating (111) in the first edge region (11) is the same as the width of the first positive electrode active coating (211) in the third edge region (21); and / or The width of the first negative electrode active coating (111) of the second edge region (13) is the same as that of the first positive electrode active coating (211) of the fourth edge region (23).

17. A battery, characterized in that, The battery includes a housing and a cell disposed within the housing as described in any one of claims 12 to 16.

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