Pole piece and battery

Abstract

The utility model relates to the technical field of lithium batteries, and provides a pole piece and a battery. When the pole piece is a positive pole piece, the internal resistance of the active material coatings of the second edge area and the third edge area is larger than the internal resistance of the active material coating of the main body area, so that the lithium removal speed of the edge areas of the positive pole piece is slowed down, and the phenomenon that the lithium precipitation potential of a negative pole is too low due to the fact that the concentration of overhang edge electrolyte salt is too high in the rapid charging process is reduced; and the problem of lithium separation on the edge of the corresponding negative electrode edge area is not easy to occur. When the pole piece is a negative pole piece, the impedance of the active material coating of the marginal area b and the marginal area c is smaller than that of the active material coating of the main body area, so that the diffusion speed of lithium ions in the marginal areas of the negative pole piece is increased, and lithium ions separated from the positive pole side can be quickly embedded into the edge of the negative pole; and the problem of lithium separation on the edge of the corresponding negative electrode edge area is not easy to occur.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium batteries, in particular to a pole piece and a battery. Background Art

[0002] Lithium-ion batteries have many advantages, such as high energy density, low self-discharge, no memory effect, wide operating temperature range, superior cycle performance, good rate performance, high output power, and long service life. They are widely used in 3C consumption, power, energy storage and other fields. In particular, the large-scale popularization of new energy vehicles and high-rate fast-charging lithium-ion batteries have always been the main goals and directions of major lithium battery companies. However, due to the inherent structure of lithium-ion batteries, the negative electrode needs to be designed to be larger than the positive electrode. The part beyond the edge of the positive electrode is called the Overhang area (OH area for short) in the industry to meet process requirements. Lithium accumulation often occurs in the corresponding negative electrode graphite at the edge of the positive electrode relative to the negative electrode due to high-rate charge and discharge. The main reason is that the presence of OH causes transitional delithiation at the edge of the positive electrode, but lithium insertion cannot be completed quickly on the negative electrode side. After the positive electrode is transitionally delithiated, the electrolyte salt concentration in the local area within a certain distance from OH increases. Secondly, rapid charge and discharge cause the lithium ions in the negative electrode to diffuse to the Overhang area, and they cannot quickly escape from the negative electrode during discharge. When rapid charging is performed again, the negative electrode was not emptied in the previous cycle, resulting in insufficient lithium insertion space at this position. Therefore, the combined effect of multiple factors increases the risk of OH lithium precipitation.

[0003] Therefore, it is of great significance to develop a battery that alleviates the problem of lithium plating at the edge of the negative electrode. Utility Model Content

[0004] The present utility model has found that when designing lithium-ion batteries, the negative electrode sheet always needs to have a larger size than the positive electrode sheet. Due to the existence of Overhang, the positive electrode will transition to delithiation, thereby forming a lithium salt concentration difference at the edge of the negative electrode OH, and the lithium ions will diffuse to the Overhang position during the charging and discharging process of the lithium-ion battery (primary battery principle). When the discharge rate of the lithium-ion battery is low, the lithium salt concentration difference is small and the lithium ions in the Overhang will also diffuse and return to the positive electrode, and a large amount of lithium ions will not be stored inside the negative electrode. In fast-charge batteries, due to the large charge and discharge rate, the lithium salt concentration difference becomes larger, the negative electrode potential is more negative, and the lithium ions that are superimposed and diffused to the Overhang have no time to be put back into the positive electrode, which will cause the negative electrode at this position to be more prone to lithium precipitation in the next charge and discharge. Most of the existing technologies achieve the purpose of increasing the margin of the negative electrode edge by increasing the Overhang width, but ignore the problem that the wider the Overhang, the farther the lithium ions diffuse, which makes the lithium precipitation more serious, and the larger Overhang increases the battery volume, loses the volume energy density, and the gain does not outweigh the loss.

[0005] The purpose of the utility model is to overcome the above-mentioned problems existing in the prior art and provide a pole piece and a battery. When the pole piece is a positive pole piece, the internal resistance of the active material coating of the second edge area and the third edge area of ​​the positive pole piece is greater than the internal resistance of the active material coating of the main area, so that the lithium desorption speed of the edge area of ​​the positive pole piece is slowed down, and the positive and negative electrode potentials at the edge of the battery are increased so that the lithium deposition potential cannot be reached, so that the corresponding negative electrode edge area is not prone to edge lithium deposition. When the pole piece is a negative pole piece, the impedance of the active material coating of the edge area b and the edge area c of the negative pole piece is smaller than the impedance of the active material coating of the main area, so that the lithium ion diffusion speed of the edge area of ​​the negative pole piece is increased, and the lithium ions released from the positive electrode side can be quickly embedded in the negative electrode edge, so that the corresponding negative electrode edge area is not prone to edge lithium deposition.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the utility model provides a pole piece, which includes a current collector, and the surface of at least one side of the current collector includes a main area and at least two edge areas, and the main area and the edge area are both provided with an active material layer; wherein the internal resistance of the active material layer provided in the main area is greater than or less than the internal resistance of the active material layer in the edge area.

[0007] In some embodiments, when the electrode sheet is a positive electrode sheet, the positive electrode sheet includes a positive electrode collector, and the surface of at least one side of the positive electrode collector includes a first main area, at least one second edge area and at least one third edge area, and the second edge area and the third edge area are respectively located on both sides of the first main area; the first main area is provided with a first positive electrode active material layer, and the internal resistance of the first positive electrode active material layer is recorded as R1; the second edge area is provided with a second positive electrode active material layer, and the internal resistance of the second positive electrode active material layer is recorded as R2; the third edge area is provided with a third positive electrode active material layer, and the internal resistance of the third positive electrode active material layer is recorded as R3; wherein, R2>R1, R3>R1, R2 and R3 are the same or different.

[0008] In some embodiments, when the electrode sheet is a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector, and the surface of at least one side of the negative electrode current collector includes a main area a, at least one edge area b and at least one edge area c, and the edge area b and the edge area c are respectively located on both sides of the main area a; the main area a is provided with a first negative electrode active material layer, and the impedance of the first negative electrode active material layer is recorded as R a The edge region b is provided with a second negative electrode active material layer, and the impedance of the second negative electrode active material layer is denoted as R b The edge region c is provided with a third negative electrode active material layer, and the impedance of the third negative electrode active material layer is denoted as R c ; Among them, R b <R a , Rc <R a , R b With R c Same or different.

[0009] The second aspect of the utility model provides a battery, which includes the pole piece described in the first aspect of the utility model.

[0010] The utility model adopts the above technical solution to achieve the following beneficial effects:

[0011] (1) When the utility model provides a positive electrode sheet, the internal resistance of the edge area is larger, and the lithium desorption rate of the edge area is slowed down, which increases the positive and negative electrode potentials at the edge of the battery and makes it impossible to reach the lithium deposition potential, making it less likely for the corresponding negative electrode edge area to have edge lithium deposition problems.

[0012] (2) Furthermore, the internal resistance of the edge area of ​​the positive electrode provided by the utility model is greater, so that the corresponding negative electrode edge is in a state of shallow charge and shallow discharge for a long time. Even if lithium ions are accumulated on the edge of the negative electrode due to high-rate charge and discharge, since its charging energy density is always in an unsatisfactory state, the conditions for lithium deposition cannot be met, thereby improving the cycle life and safety of high-rate charge and discharge lithium-ion batteries.

[0013] (3) When the utility model provides a negative electrode sheet, the impedance of the edge area is smaller, the diffusion rate of lithium ions is increased, and the edge of the negative electrode can quickly diffuse and release lithium during discharge. The lithium ions released from the positive electrode side can be quickly embedded in the edge of the negative electrode, making it less likely for the corresponding edge area of ​​the negative electrode to have edge lithium deposition problems.

[0014] (3) Furthermore, the impedance of the edge area of ​​the negative electrode sheet provided by the utility model is smaller, the lithium concentration in the OH area is reduced, the edge effect is reduced, and the edge lithium insertion potential is increased, so that the edge of the negative electrode is in a state of shallow charge and discharge for a long time, and the conditions for lithium deposition are not met, thereby improving the cycle life and safety of high-rate charge and discharge lithium-ion batteries.

[0015] The endpoints and any values ​​of the range disclosed in this article are not limited to the precise range or value, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Herein, in the absence of special instructions, data ranges include endpoints. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shown is a schematic diagram of the planar structure of a positive electrode sheet in one embodiment of the utility model.

[0017] Figure 2 Shown is a schematic diagram of the planar structure of a positive electrode sheet in one embodiment of the utility model.

[0018] Figure 3 Shown is a schematic diagram of the planar structure of a positive electrode sheet in one embodiment of the utility model.

[0019] Figure 4 Shown is a schematic diagram of the planar structure of a negative electrode sheet in one embodiment of the utility model.

[0020] Figure 5 Shown is a schematic diagram of the planar structure of a negative electrode sheet in one embodiment of the utility model.

[0021] Figure 6 Shown is a schematic diagram of the planar structure of a negative electrode sheet in one embodiment of the utility model.

[0022] Figure 7 The figure shows a cross-sectional schematic diagram of the positive electrode sheet of the utility model and the conventional negative electrode sheet when combined.

[0023] Figure 8 The figure shows a cross-sectional schematic diagram of the combination of the negative electrode sheet of the utility model and the conventional positive electrode sheet.

[0024] Fig. 9 Shown is a cross-sectional schematic diagram of the positive electrode sheet of the utility model and the negative electrode sheet of the utility model when combined. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is described in detail below. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0026] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention relates.

[0027] The first aspect of the utility model provides a pole piece, which includes a current collector, and the surface of at least one side of the current collector includes a main area and at least two edge areas, and the main area and the edge area are both provided with an active material layer; wherein the internal resistance of the active material layer provided in the main area is greater than or less than the internal resistance of the active material layer in the edge area.

[0028] It should be noted that the internal resistance mentioned in the present invention refers to ohmic resistance unless otherwise specified, and impedance refers to the obstruction of the current caused by resistance, inductance and capacitance when alternating current passes through the system. The internal resistance mentioned in the positive electrode sheet is ohmic resistance, which is usually obtained by testing with an electrode internal resistance tester; the impedance mentioned in the negative electrode sheet is usually used to describe Rsei (membrane impedance) and Rct (charge transfer impedance).

[0029] Positive electrode

[0030] When the electrode sheet is a positive electrode sheet, the positive electrode sheet includes a positive electrode collector, and the surface of at least one side of the positive electrode collector includes a first main area, at least one second edge area and at least one third edge area, and the second edge area and the third edge area are respectively located on both sides of the first main area; the first main area is provided with a first positive electrode active material layer, and the internal resistance of the first positive electrode active material layer is recorded as R1; the second edge area is provided with a second positive electrode active material layer, and the internal resistance of the second positive electrode active material layer is recorded as R2; the third edge area is provided with a third positive electrode active material layer, and the internal resistance of the third positive electrode active material layer is recorded as R3; wherein, R2>R1, R3>R1, R2 and R3 are the same or different.

[0031] In the present invention, the internal resistance in the positive electrode refers to the ohmic resistance. The testing method adopts four-probe testing of the electrode resistance. The electrode is placed on the resistance tester, the probes are used to press the electrode, and the device is started. The device will run at the set current, calculate the resistance value, and read the test result.

[0032] In the utility model, the internal resistance of the active material coating of the second edge area and the third edge area of ​​the positive electrode is greater than the internal resistance of the active material coating of the main area. On the one hand, the lithium desorption speed of the edge area (including the second edge area and the third edge area) of the positive electrode is slowed down, and the positive and negative electrode potentials at the edge of the battery are increased so that the lithium deposition potential cannot be reached, so that the corresponding edge area of ​​the negative electrode is not prone to edge lithium deposition. On the other hand, the internal resistance of the edge area of ​​the positive electrode is greater, so that the corresponding negative electrode edge is in a state of shallow charge and discharge for a long time. Even if the negative electrode edge has lithium ions accumulated due to high-rate charge and discharge, its charging energy density is always in an unsatisfactory state and cannot meet the conditions for lithium deposition, thereby improving the cycle life and use safety of high-rate charge and discharge lithium-ion batteries.

[0033] In some embodiments, the second positive electrode active material layer is disposed on the surface of the second edge region close to the positive electrode current collector, and / or the second positive electrode active material layer is disposed on the surface of the second edge region away from the positive electrode current collector. That is, the second positive electrode active material layer may be disposed only partially in the second edge region, the second positive electrode active layer may be disposed only on the surface close to the positive electrode current collector, or the second positive electrode active layer may be disposed only on the surface away from the positive electrode current collector, or the second positive electrode active layer may be disposed on both the surface close to the positive electrode current collector and the surface away from the positive electrode current collector, and the rest of the second edge region is disposed on the same positive electrode active material layer as the first main region.

[0034] In some embodiments, the third positive electrode active material layer is disposed on the surface of the third edge region close to the positive electrode current collector, and / or the third positive electrode active material layer is disposed on the surface of the third edge region away from the positive electrode current collector. That is, the third positive electrode active material layer may be disposed only partially in the third edge region, the third positive electrode active layer may be disposed only on the surface close to the positive electrode current collector, or the third positive electrode active layer may be disposed only on the surface away from the positive electrode current collector, or the third positive electrode active layer may be disposed on both the surface close to the positive electrode current collector and the surface away from the positive electrode current collector, and the rest of the third edge region is disposed on the same positive electrode active material layer as the first main region.

[0035] Arranging the second positive electrode active material layer and the third positive electrode active material layer with higher internal resistance on the surface of the second edge area and the third edge area can alleviate the problem of edge lithium plating. At the same time, arranging the positive electrode active material layer with higher internal resistance on the surface of the edge area can reduce the use of fillers and increase the overall content of positive electrode active material in the edge area, thereby reducing the loss of battery energy density.

[0036] Preferably, the second positive electrode active material layer is arranged in the entire second edge region, and / or the third positive electrode active material layer is arranged in the entire third edge region. The second edge region and the third edge region are all provided with the second positive electrode active material layer and the third positive electrode active material layer with higher internal resistance, which can better suppress edge lithium deposition and better improve the cycle life and use safety of the battery.

[0037] In some embodiments, Figure 1 As shown, one side surface or both sides surface (preferably two opposite surfaces) of the positive electrode current collector (not shown) includes a first main body region, a second edge region and a third edge region, and the second edge region and the third edge region are respectively located on both sides of the first main body region. The first main body region is provided with a first positive electrode active material layer 1, the second edge region is entirely provided with a second positive electrode active material layer 2, and the third edge region is entirely provided with a third positive electrode active material layer 3. This type of positive electrode sheet is suitable for wound batteries and can effectively solve the problem of lithium deposition at the negative electrode edge of wound batteries.

[0038] In some embodiments, Figure 2 As shown, one side surface or both sides surface (preferably two opposite surfaces) of the positive electrode current collector (not shown) includes a first main body area, two second edge areas and two third edge areas, and the two second edge areas and the two third edge areas are respectively located on opposite sides of the first main body area. The first main body area is entirely provided with a first positive electrode active material layer 1, the two second edge areas are respectively provided with a second positive electrode active material layer 2, and the two third edge areas are respectively provided with a third positive electrode active material layer 3. This type of positive electrode sheet is suitable for laminated batteries and can effectively solve the problem of lithium deposition at the negative electrode edge of laminated batteries.

[0039] In some embodiments, the values of R1, R2, and R3 are not limited and need to be adjusted according to the battery model and type. When the relationship R2 > R1 and R3 > R1 can be satisfied, the problem of lithium deposition at the negative electrode edge of the battery can be solved, and the cycle life and usage safety of the high-rate charge-discharge lithium-ion battery are improved.

[0040] In order to better solve the problem of lithium deposition at the negative electrode edge of the lithium battery, the present utility model also proposes the following preferred solutions:

[0041] In some embodiments, the ratio of R2 to R1 is (1.05 - 2.0):1, for example, it can be 1.05:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1; preferably (1.1 - 1.7):1.

[0042] In some embodiments, the ratio of R3 to R1 is (1.05 - 2.0):1, for example, it can be 1.05:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1; preferably (1.1 - 1.7):1.

[0043] When the ratio of R2 to R1 and the ratio of R3 to R1 are within the above ranges, the internal resistance ratio of the positive electrode active material layer in the edge region to the main body region can be controlled within a suitable range, avoiding excessive internal resistance in the edge region causing excessive self-heat loss of the battery and affecting the working voltage and discharge time of the battery; and it can also avoid too small internal resistance, which cannot effectively increase the positive and negative electrode potentials at the edge of the battery and affect the effect of improving lithium deposition at the edge.

[0044] R2 and R3 are the same or different, preferably R2 and R3 are the same. When R2 and R3 are the same, the second positive electrode active material layer and the third positive electrode active material layer can be the same, that is, the same positive electrode slurry can be used in the slurry coating stage, reducing the operation of ingredient preparation and saving processing time.

[0045] In some embodiments, the area of the second positive electrode active material layer is S2, the area of the third positive electrode active material layer is S3, and they satisfy the following relationship with the area S1 of the first positive electrode active material layer: 2% < S2 / S1 ≤ 10%, 2% < S3 / S1 ≤ 10%. Preferably, 2% < S2 / S1 ≤ 5%, 2% < S3 / S1 ≤ 5%. When the area ratio of the three positive electrode active material layers is within the above range, the energy density of the battery can be increased while alleviating the problem of lithium deposition at the edge.

[0046] In some embodiments, such as Figure 1As shown, when the second positive electrode active material layer 2 and the third positive electrode active material layer 3 are located at the two side edges of the surface of the positive electrode collector along the length direction, the lengths of the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer can be the same. At this time, the area ratio can be used as the width ratio. At this time, the length refers to the distance parallel to the length direction of the positive electrode collector, and the width refers to the distance parallel to the width direction of the positive electrode collector.

[0047] In some embodiments, Figure 2 As shown, the two second positive electrode active material layers 2 and the two third positive electrode active material layers 3 are respectively located on opposite sides of the first positive electrode active material layer 1. The area S2 of the second positive electrode active material layer is the area of ​​one side, not the sum of the areas of the two second positive electrode active material layers. Similarly, the area S3 of the third positive electrode active material layer is also the area of ​​one side.

[0048] In some embodiments, Figure 3 As shown, the surface of at least one side of the positive electrode current collector may include multiple second edge regions and multiple third edge regions, for example, three second edge regions and three third edge regions are respectively located on both sides of the first main region, and the length directions of the second positive electrode active material layer 2 of the three second edge regions and the third positive electrode active material layer 3 of the three third edge regions are parallel to the length direction of the positive electrode current collector. Among them, in the direction along the width of the positive electrode current collector and away from the first main region, the internal resistance gradient of the second positive electrode active material layer in the three second edge regions increases, and the internal resistance gradient of the third positive electrode active material layer in the three third edge regions increases. With this arrangement, an active material layer with a large internal resistance can be processed and set in the most edge region, which further effectively solves the problem of edge lithium deposition, and can reduce the overall internal resistance of the battery and improve the overall performance of the battery.

[0049] In some embodiments, the thicknesses of the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer on a single side are independently distributed between 20 μm and 60 μm, and the thicknesses of the active material layers in the three zones may be equal or unequal according to the design, or the second positive electrode active material layer may be equal to the third positive electrode active material layer.

[0050] In some embodiments, the total width of the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer (the sum of the widths of the three, the width refers to the distance along the width direction of the current collector) is between 3 mm and 600 mm. The widths of the three active materials can be equal or unequal according to the design, and the second positive electrode active material layer can also be equal to the third positive electrode active material layer. Preferably, the width of the first positive electrode active material layer is greater than the width of the second positive electrode active material layer, and preferably, the width of the first positive electrode active material layer is greater than the width of the third positive electrode active material layer.

[0051] In some embodiments, the width of the second positive electrode active material layer and the third positive electrode active material layer is independently ≥ 2 mm, preferably 2 mm to 5 mm. It is possible to avoid the edge zone width being too small, which will not effectively increase the potential of the positive and negative electrode edges and affect the effect of inhibiting edge lithium deposition, and to avoid the edge zone width being too large, which will increase the area of ​​the edge coating and significantly reduce the energy density of the battery.

[0052] In the present invention, the internal resistance of the corresponding coating can be adjusted by changing the content of the conductive agent in the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer. For example, the following schemes can be selected: (1) only reducing the content of the conductive agent in the second positive electrode active material layer and the third positive electrode active material layer, and the content of the conductive agent in the first positive electrode active material layer remains unchanged; (2) only increasing the content of the conductive agent in the first positive electrode active material layer, and the content of the conductive agent in the second positive electrode active material layer and the third positive electrode active material layer remains unchanged; (3) increasing the content of the conductive agent in the first positive electrode active material layer and reducing the content of the conductive agent in the second positive electrode active material layer and the third positive electrode active material layer at the same time.

[0053] Taking the battery performance into consideration, the above-mentioned solution (1) is selected to only change the internal resistance of the second positive electrode active material layer and the third positive electrode active material layer, that is, to increase the internal resistance by reducing the amount of conductive agent, and try not to change the amount of conductive agent in the main area, so as to avoid increasing the amount of conductive agent and causing the content of active material to decrease, which will affect the battery energy density, thereby improving the overall performance of the battery.

[0054] In some embodiments, the first positive electrode active material layer includes a first positive electrode conductive agent. Preferably, in the first positive electrode active material layer, the content of the first positive electrode conductive agent is 0.3wt% to 5wt%, for example, it can be 0.3wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, preferably 0.5wt% to 2wt%. When the content of the first positive electrode conductive agent is within the above range, the first positive electrode active material layer of the first main body region can have a suitable internal resistance, so that the overall internal resistance of the battery is within an appropriate range, and the internal resistance is too large to affect the cycle performance and service life of the battery.

[0055] In some embodiments, the second positive electrode active material layer includes a second positive electrode conductor; preferably, in the second positive electrode active material layer, the content of the second positive electrode conductor is 0.1wt% to 3wt%, for example, it can be 0.1wt%, 0.5wt%, 0.8wt%, 1wt%, 2wt%, 3wt%, preferably 0.5wt% to 1wt%.

[0056] In some embodiments, the third positive electrode active material layer includes a third positive electrode conductor; preferably, in the third positive electrode active material layer, the content of the third positive electrode conductor is 0.1wt% to 3wt%, for example, it can be 0.1wt%, 0.5wt%, 0.8wt%, 1wt%, 2wt%, 3wt%, preferably 0.5wt% to 1wt%.

[0057] When the content ratio of the second positive electrode conductive agent and the third positive electrode conductive agent is within the above range, the internal resistance of the second and third positive electrode active material layers can be made larger than the internal resistance of the first positive electrode active material coating, which can further effectively solve the problem of lithium plating at the edge of the negative electrode of the battery, thereby improving the cycle life and safety of high-rate charge and discharge lithium-ion batteries.

[0058] In some embodiments, the first positive electrode conductive agent, the second positive electrode conductive agent and the third positive electrode conductive agent may be the same or different. There is no limitation on the specific type of the positive electrode conductive agent, and the conductive agent may be freely selected from the conductive agents used in the field of lithium batteries. Exemplarily, the first positive electrode conductive agent, the second positive electrode conductive agent and the third positive electrode conductive agent independently include at least one or more of superconducting carbon, acetylene black, carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0059] In some embodiments, the second positive electrode active material layer and / or the third positive electrode active material layer independently include a filler. Preferably, both the second positive electrode active material layer and the third positive electrode active material layer include a filler. In the present invention, the internal resistance of the corresponding coating layer can be adjusted by adding a filler to the second positive electrode active material layer and the third positive electrode active material layer.

[0060] In the present utility model, "filler" refers to a substance that does not participate in the electrochemical reaction of the battery, for example, the filler includes at least one of lithium-containing phosphates such as lithium iron phosphate, lithium iron manganese phosphate, and lithium titanate, lithium-free inorganic substances such as alumina, zirconium oxide, boehmite, lithium titanate, silicon dioxide, silicon nitride, silicon carbide, and modified substances of the above substances. The addition of fillers reduces the energy density ratio of the active material in the second positive electrode active material layer and the third positive electrode active material layer, and increases the internal resistance of the active material coating.

[0061] In some embodiments, in the second positive electrode active material layer and / or the third positive electrode active material layer, the content of the filler is independently 1wt% to 50wt%, for example, 1wt%, 5wt%, 8wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, preferably 5wt% to 20wt%. When the content of the filler is within the above range, the internal resistance of the second positive electrode active material layer and the third positive electrode active material layer can be effectively increased, so that the lithium removal rate of the active material layer in the edge area is slower, the corresponding positive electrode potential is higher, and the problem of lithium precipitation at the edge is more effectively alleviated; the problem that the content of the filler is too small to effectively increase the internal resistance can be avoided, and the content is too large to significantly reduce the content of the active material in the edge area, affecting the overall energy density of the battery.

[0062] In some embodiments, the Dv50 of the filler is 0.1 μm to 1 μm, for example, 0.1 μm, 0.2 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm. Dv50 can be tested using a laser particle size analyzer. When the Dv50 of the filler is within the above range, the specific surface area of ​​the second positive electrode active material layer and the third positive electrode active material layer can be significantly increased, and the liquid retention capacity of the second positive electrode active material layer and the third positive electrode active material layer can be improved.

[0063] In some embodiments, the specific surface area of ​​the second positive electrode active material layer and / or the third positive electrode active material layer is independently greater than 50 m 2 / g, preferably the specific surface areas of the second positive electrode active material layer and the third positive electrode active material layer are both greater than 50m 2 / g. When the specific surface area of ​​the second positive electrode active material layer and the third positive electrode active material layer is greater than 50m 2 / g, it is possible to avoid the size of the specific surface area affecting the electrolyte's liquid retention capacity, and can significantly improve the liquid retention capacity of the active material particles in the positive electrode edge area, thereby increasing the lithium deintercalation capacity of the positive and negative electrodes corresponding to the positive electrode edge area, increasing the ion transfer rate and reducing the edge effect, thereby reducing the problem of lithium precipitation due to insufficient electrolyte at the edge.

[0064] Furthermore, by reducing the amount of conductive agent and adding filler, the internal resistance in the second edge and the third edge area can be increased, and the capacity in the second edge and the third edge area can be reduced, which can not only reduce the lithium desorption rate at the positive electrode edge, but also reduce the amount of lithium desorption. Under the combined effect, the problem of lithium deposition at the edge can be more effectively solved.

[0065] In some embodiments, the first positive electrode active material layer further includes first positive electrode active material particles, the second positive electrode active material layer further includes second positive electrode active material particles, and the third positive electrode active material layer further includes third positive electrode active material particles. The first positive electrode active material particles, the second positive electrode active material particles, and the third positive electrode active material particles may be the same or different, and conventional lithium ion battery positive electrode materials in the art may be selected.

[0066] In some embodiments, the first positive electrode active material particles, the second positive electrode active material particles and the third positive electrode active material particles independently include lithium transition metal oxides and / or lithium-containing phosphates. Preferably, the lithium transition metal oxide includes one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof. The lithium-containing phosphate includes one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon and modified compounds thereof.

[0067] In some embodiments, the Dv50 of the first positive electrode active material particles, the second positive electrode active material particles and the third positive electrode active material particles are independently between 1 μm and 40 μm. The Dv50 of the first positive electrode active material particles, the second positive electrode active material particles and the third positive electrode active material particles may be equal or unequal according to the design, and the second positive electrode active material particles may also be equal to the third positive electrode active material particles.

[0068] In some embodiments, in the first positive electrode active material layer, the content of the first positive electrode active material particles accounts for 80 wt% to 99 wt%. In the second positive electrode active material layer, the content of the second positive electrode active material particles accounts for 50 wt% to 90 wt%. In the third positive electrode active material layer, the content of the third positive electrode active material particles accounts for 50 wt% to 90 wt%.

[0069] Preferably, the content ratio of the second positive electrode active material particles and the third positive electrode active material is lower than the content ratio of the first positive electrode active material particles. This can reduce the capacity of the active materials on both sides of the positive electrode and increase the lithium insertion potential of the corresponding area on the negative electrode side, thereby meeting the condition that the lithium deposition potential cannot be reached and effectively solving the problem of edge lithium deposition.

[0070] In some embodiments, the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer independently include a binder and a dispersant. The binder and the dispersant may be selected from the binders and dispersants used in conventional lithium-ion batteries in the art. Exemplarily, the binder includes one or more of polyvinylidene fluoride, styrene-butadiene rubber, and aluminate coupling agent; the dispersant includes polyvinyl pyrrolidone and / or polyethylene oxide.

[0071] In some embodiments, the content ratio of the binder in the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer is independently 0.5wt% to 5wt%, and the content ratio of the binder in the three positive electrode active material layers may be the same or different, preferably the same.

[0072] In some embodiments, the content ratio of the dispersant in the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer is independently 1wt% to 20wt%, and the content ratio of the dispersant in the three positive electrode active material layers may be the same or different, preferably the same.

[0073] The utility model also provides a method for preparing the positive electrode sheet, comprising the following steps:

[0074] (1) preparing an active material slurry 1 for a first positive electrode active material layer, an active material slurry 2 for a second positive electrode active material layer, and an active material slurry 3 for a third positive electrode active material layer, wherein the slurry 2 and the slurry 3 may be the same;

[0075] (2) The active material slurry 1 is placed in the coating system 1, and the active material positive electrode slurries 2 and 3 are placed in the coating systems 2 and 3, and the active material slurries 1 and the active material slurries 2 and 3 are respectively coated on the middle main area and the edge areas on both sides of the surface of one side of the positive electrode current collector, referring to Figure 1 The coating widths of coating zones 1, 2 and 3 can be changed according to the design.

[0076] (3) The positive electrode current collector coated on one side is coated on the other side of the opposite side, and the positive electrode sheet is obtained after drying in an oven. Optionally, the rolled positive electrode sheet is unwound and cut by an unwinding device to obtain small pieces of designed size, and the pole ears of designed size are cut by laser die, and the positive electrode sheet is obtained after gluing according to the designed size.

[0077] Negative plate

[0078] When the electrode sheet is a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector, and the surface of at least one side of the negative electrode current collector includes a main area a, at least one edge area b and at least one edge area c, and the edge area b and the edge area c are respectively located on both sides of the main area a; the main area a is provided with a first negative electrode active material layer, and the impedance of the first negative electrode active material layer is recorded as R a The edge region b is provided with a second negative electrode active material layer, and the impedance of the second negative electrode active material layer is denoted as R b The edge region c is provided with a third negative electrode active material layer, and the impedance of the third negative electrode active material layer is denoted as R c ; Among them, R b <R a , R c <R a , R b With R c Same or different.

[0079] The impedance in the negative electrode sheet mainly refers to Rsei (membrane impedance) and Rct (charge transfer impedance). The test method includes cutting a 2cm×2cm long and wide negative electrode sheet, making a negative-to-negative symmetrical battery, injecting an equal amount of electrolyte, and then testing it using a Zahner electrochemical workstation. The test frequency range is 0.5mHz to 10Mhz.

[0080] In the utility model, the impedance of the active material coating in the edge area b and the edge area c of the negative electrode sheet is smaller than the impedance of the active material coating in the main area. On the one hand, the diffusion speed of lithium ions in the edge area (including the edge area b and the edge area c) of the negative electrode sheet is increased, and the edge of the negative electrode can quickly diffuse and de-lithium during discharge, and the lithium ions released from the positive electrode side can be quickly embedded in the edge of the negative electrode, so that the corresponding edge area of ​​the negative electrode is not prone to edge lithium precipitation. On the other hand, the impedance of the edge area of ​​the negative electrode sheet is smaller, the lithium concentration in the OH area is reduced, the edge effect is reduced, and the edge lithium insertion potential is increased, so that the edge of the negative electrode is in a state of shallow charge and shallow discharge for a long time. Even if the edge of the negative electrode has accumulated lithium ions due to high-rate charge and discharge, because its charging energy density is always in an unsatisfactory state, it cannot meet the conditions for lithium precipitation, thereby improving the cycle life and use safety of high-rate charge and discharge lithium-ion batteries.

[0081] In some embodiments, Figure 4As shown, one side surface or both sides surface (preferably two opposite surfaces) of the negative electrode current collector (not shown) includes a main region a, an edge region b and an edge region c, and the edge region b and the edge region c are respectively located on both sides of the main region a. The main region a is provided with a first negative electrode active material layer 4, the edge region b is entirely provided with a second negative electrode active material layer 5, and the edge region c is entirely provided with a third negative electrode active material layer 6. This type of negative electrode sheet is suitable for wound batteries and can effectively solve the problem of lithium deposition at the edge of the negative electrode of the wound battery.

[0082] In some embodiments, Figure 5 As shown, one side surface or both side surfaces (preferably two opposite surfaces) of the negative electrode current collector (not shown) include a main region a, two edge regions b and two edge regions c, and the two edge regions b and the two edge regions c are respectively located on opposite sides of the main region a. The main region a is provided with a first negative electrode active material layer 4, the two edge regions b are respectively provided with a second negative electrode active material layer 5, and the two edge regions c are respectively provided with a third negative electrode active material layer 6. This type of negative electrode sheet is suitable for laminated batteries and can effectively solve the problem of lithium deposition at the negative electrode edge of laminated batteries.

[0083] In some embodiments, R a , R b , R c The value range is not limited and needs to be adjusted according to the battery model and type to meet R b <R a , R c <R a When the relationship is achieved, the problem of lithium plating at the edge of the negative electrode of the battery can be solved, thereby improving the cycle life and safety of high-rate charge and discharge lithium-ion batteries.

[0084] In order to better solve the problem of lithium deposition at the edge of the negative electrode of the lithium battery, the utility model also proposes the following preferred solution:

[0085] In some embodiments, R b With R a The ratio is (0.5-0.95):1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 0.95:1; preferably (0.7-0.9):1.

[0086] In some embodiments, R c With R a The ratio is (0.5-0.95):1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 0.95:1; preferably (0.7-0.9):1.

[0087] R b With Ra The ratio of R c With R a When the ratio is within the above range, the impedance ratio of the negative electrode edge area to the negative electrode active material layer in the main area can be controlled within an appropriate range to avoid the impedance of the negative electrode edge area being too large, which cannot effectively increase the positive and negative electrode potentials at the edge of the battery and affect the effect of improving edge lithium deposition.

[0088] R b With R c The same or different, preferably R b With R c Same. b With R c Under the same circumstances, the second negative electrode active material layer and the third negative electrode active material layer can be made the same, that is, the same negative electrode slurry can be used in the slurry coating stage, which reduces the operation of batching and saves processing time.

[0089] In some embodiments, the area of ​​the second negative electrode active material layer is S b The area of ​​the third negative electrode active material layer is S c , and the area S of the first negative electrode active material layer a Satisfies the following relationship: 2% b / S a ≤10%, 2% c / S a ≤10%. When the area ratio of the three negative electrode active material layers is within the above range, the energy density of the battery can be improved while alleviating the problem of edge lithium deposition.

[0090] In some embodiments, Figure 4 As shown, when the second negative electrode active material layer 5 and the third negative electrode active material layer 6 are located at the two side edges of the negative electrode current collector surface along the length direction, the lengths of the first negative electrode active material layer 4, the second negative electrode active material layer 5 and the third negative electrode active material layer 6 can be the same. At this time, the area ratio can be used as the width ratio. At this time, the length refers to the distance parallel to the length direction of the negative electrode current collector, and the width refers to the distance parallel to the width direction of the negative electrode current collector.

[0091] In some embodiments, Figure 5 As shown, the two second negative electrode active material layers 5 and the two third negative electrode active material layers 6 are respectively located on opposite sides of the first negative electrode active material layer 4, and the area S of the second negative electrode active material layer is b is the area of ​​one side, not the sum of the areas of the two second negative electrode active material layers. Similarly, the area of ​​the third negative electrode active material layer S c It is also the area of ​​one side.

[0092] In some embodiments, Figure 6 ​​As shown, the surface of at least one side of the negative electrode current collector may include multiple edge regions b and multiple edge regions c, for example, three edge regions b and three edge regions c are respectively located on both sides of the main region a, and the length directions of the second negative electrode sheet active material layer 5 of the three edge regions b and the third negative electrode sheet active material layer 6 of the three edge regions c are parallel to the length direction of the negative electrode current collector. Among them, along the width of the negative electrode current collector and away from the main region a, the impedance gradient of the second negative electrode active material layer in the three edge regions b is reduced, and the impedance gradient of the third negative electrode active material layer in the three edge regions c is reduced. With such a setting, an active material layer with very small impedance can be processed and set in the most edge region, which further effectively solves the problem of edge lithium deposition, and can reduce the overall impedance of the battery and improve the overall performance of the battery.

[0093] In some embodiments, the thicknesses of the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer on a single side are independently distributed between 20 μm and 90 μm, and the thicknesses of the negative electrode active material layers in the three zones may be equal or unequal according to the design, or the second negative electrode active material layer may be equal to the third negative electrode active material layer.

[0094] In some embodiments, the total width of the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer (the sum of the widths of the three, the width refers to the distance along the width direction of the current collector) is distributed between 5 mm and 600 mm. The widths of the three negative electrode active materials can be equal or unequal according to the design, and the second negative electrode active material layer can also be equal to the third negative electrode active material layer. Preferably, the width of the first negative electrode active material layer is greater than the width of the second negative electrode active material layer, and preferably, the width of the first negative electrode active material layer is greater than the width of the third negative electrode active material layer.

[0095] In some embodiments, the width of the second negative electrode active material layer and the third negative electrode active material layer is independently ≥ 2 mm, preferably 2 to 6 mm. Avoiding too small a width of the edge region, which will not effectively increase the potential of the positive and negative electrode edges and affect the effect of inhibiting edge lithium precipitation, and avoiding too large a width of the edge region, which will accelerate the loss of positive electrode materials and lead to capacity decay, and avoiding doping of low-granularity materials in the negative electrode edge region, which will increase the consumption of lithium ions and reduce the initial charge and discharge efficiency of the battery.

[0096] In some embodiments, a better effect can be achieved when the size of the negative electrode edge area is greater than the size of the positive electrode edge area. The principle is that when the internal resistance of the positive electrode edge area increases and the negative electrode edge impedance decreases, the positive and negative electrode potentials at the edge of the battery can be significantly improved, thereby satisfying the condition that the lithium deposition potential cannot be reached, and more effectively solving the problem of edge lithium deposition.

[0097] In the present invention, the impedance of the corresponding coating can be adjusted by changing the content of the conductive agent in the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer. For example, the following schemes can be selected: (1) only increasing the content of the conductive agent in the second negative electrode active material layer and the third negative electrode active material layer, and the content of the conductive agent in the first negative electrode active material layer remains unchanged; (2) only reducing the content of the conductive agent in the first negative electrode active material layer, and the content of the conductive agent in the second negative electrode active material layer and the third negative electrode active material layer remains unchanged; (3) reducing the content of the conductive agent in the first negative electrode active material layer and increasing the content of the conductive agent in the second negative electrode active material layer and the third negative electrode active material layer at the same time.

[0098] Taking the battery performance into consideration, the above-mentioned solution (1) is selected to only change the impedance of the second negative electrode active material layer and the third negative electrode active material layer, that is, to reduce the impedance by increasing the amount of conductive agent, and try not to change the amount of conductive agent in the first negative electrode active material layer, so as to avoid reducing the amount of conductive agent, which will cause the overall impedance of the battery to be too large and affect the discharge current and service life of the battery.

[0099] In some embodiments, the first negative electrode active material layer includes a first negative electrode conductive agent. Preferably, in the first negative electrode active material layer, the content of the first negative electrode conductive agent is 0.3wt% to 5wt%, for example, 0.3wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, preferably 1wt% to 3wt%. When the content of the first negative electrode conductive agent is within the above range, the first negative electrode active material layer of the main area a can have a suitable impedance, so that the internal resistance of the battery as a whole is within an appropriate range, and the internal resistance is too large to affect the cycle performance and service life of the battery.

[0100] In some embodiments, the second negative electrode active material layer includes a second negative electrode conductive agent; preferably, in the second negative electrode active material layer, the content of the second negative electrode conductive agent is 0.5wt% to 8wt%, for example, it can be 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, preferably 2wt% to 6wt%.

[0101] In some embodiments, the third negative electrode active material layer includes a third negative electrode conductive agent; preferably, in the third negative electrode active material layer, the content of the third negative electrode conductive agent is 0.5wt% to 8wt%, for example, it can be 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, preferably 2wt% to 6wt%.

[0102] When the content ratio of the second negative electrode conductive agent and the third negative electrode conductive agent is within the above range, the impedance of the second and third negative electrode active material layers can be made smaller than the impedance of the first negative electrode active material coating, which can further effectively solve the problem of lithium plating at the negative electrode edge of the battery, thereby improving the cycle life and safety of high-rate charge and discharge lithium-ion batteries.

[0103] In some embodiments, the first negative electrode conductive agent, the second negative electrode conductive agent and the third negative electrode conductive agent may be the same or different. There is no limitation on the specific type of the negative electrode conductive agent, and it can be freely selected from the conductive agents used in the field of lithium batteries. Exemplarily, the first negative electrode conductive agent, the second negative electrode conductive agent and the third negative electrode conductive agent independently include at least one or more of superconducting carbon, acetylene black, carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0104] In the utility model, in addition to adjusting the impedance by changing the content of the conductive agent, the diffusion coefficient of the negative electrode active layer can also be adjusted so that the diffusion coefficient of the negative electrode active material particles in the main area a is smaller than the diffusion coefficient of the negative electrode active material particles in the edge areas b and c on both sides, that is, the diffusion coefficient in the middle is low and the diffusion coefficients on both sides are high.

[0105] In some embodiments, the diffusion coefficient of the first negative electrode active material layer is 10 -5 cm 2 / S~10 -10 cm 2 / S, for example, it can be 10 -5 cm 2 / S~10 -6 cm 2 / S, 10 -6 cm 2 / S~10 -7 cm 2 / S, 10 -7 cm 2 / S~10 -8 cm 2 / S, 10 -8 cm 2 / S~10- 9 cm 2 / S, 10 -9 cm 2 / S~10 -10 cm 2 / S, preferably 10 -5 cm 2 / S~10 -8 cm 2 / S.

[0106] In some embodiments, the diffusion coefficients of the second negative electrode active material layer and the third negative electrode active material layer are independently greater than 10 -5 cm 2 / S.

[0107] The diffusion coefficient of the negative electrode edge has been optimized to be higher, so that the lithium ions released from the positive electrode side can be quickly inserted into the negative electrode edge. During discharge, the negative electrode edge can quickly diffuse and de-lithium, reducing the lithium concentration in the OH area, reducing the edge effect, and increasing the edge lithium insertion potential, thereby meeting the purpose of shallow charge and discharge at the negative electrode edge, thereby improving the cycle life and safety of high-rate charge and discharge lithium-ion batteries.

[0108] In the utility model, the method of improving the diffusion coefficient of the two edges of the negative electrode sheet includes modification of the pure negative electrode active coating, the coating modification includes laser drilling of the edge coating, laser wire drawing of the edge coating, use of small-particle graphite in the edge coating, use of high-diffusion coefficient graphite in the edge coating, hard carbon coating, hard carbon doping, soft carbon coating, soft carbon doping, LTO coating, LTO doping and graphite doping of one or more of the above, etc., which can meet the implementation method of improving the diffusion coefficient of the edge coating.

[0109] In some embodiments, the method of improving the diffusion coefficient of the two edges of the negative electrode sheet also includes using modified graphite, for example, using some vapor deposition to etch pores perpendicular to the graphite intercalation on the graphite surface. This type of graphite will quickly intercalate lithium along the pores during the lithium insertion process, greatly reducing the energy barrier and lithium insertion distance required for lithium insertion, and has a higher diffusion capacity than conventional graphite.

[0110] In some embodiments, the first negative electrode active material layer includes first negative electrode active material particles, the second negative electrode active material layer includes second negative electrode active material particles, and the third negative electrode active material layer includes third negative electrode active material particles. The first negative electrode active material particles, the second negative electrode active material particles, and the third negative electrode active material particles may be the same or different, and conventional lithium ion battery negative electrode materials in the art may be selected, for example, natural graphite, artificial graphite, graphite derivatives, silicon and silicon modified materials, silicon and graphite mixed doping, LTO, and other conventional materials that can be used for negative electrode active materials.

[0111] In some embodiments, in the first negative electrode active material layer, the content of the first negative electrode active material particles accounts for 80wt% to 99wt%. In the second negative electrode active material layer, the content of the second negative electrode active material particles accounts for 80wt% to 95wt%. In the third negative electrode active material layer, the content of the third negative electrode active material particles accounts for 80wt% to 95wt%.

[0112] In some embodiments, the second negative electrode active material layer and the third negative electrode active material layer can be high-capacity graphite coating, pure silicon coating, silicon-doped graphite coating, pure hard carbon or hard carbon doped coating, pure soft carbon or soft carbon doped coating, etc., which are sufficient to improve the capacity of the edge coating. After the negative electrode edge capacity is improved, the positive and negative electrode potentials at the edge of the battery can be significantly improved, thereby meeting the condition that the lithium deposition potential cannot be reached, and effectively alleviating the problem of edge lithium deposition.

[0113] In some embodiments, the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer independently include a binder and a dispersant. The binder and the dispersant may be selected from the binders and dispersants used in conventional lithium ion batteries in the art.

[0114] In some embodiments, the content ratio of the binder in the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer is independently 1wt% to 10wt%, and the content ratio of the binder in the three negative electrode active material layers may be the same or different, preferably the same.

[0115] In some embodiments, the content of the dispersant in the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer is independently 1 wt% to 20 wt%, and the content of the dispersant in the three negative electrode active material layers may be the same or different, preferably the same.

[0116] The utility model also provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps:

[0117] (i) preparing an active material slurry a1 for a first negative electrode active material layer, an active material slurry a2 for a second negative electrode active material layer, and an active material slurry a3 for a third negative electrode active material layer, wherein the slurry a2 and the slurry a3 may be the same;

[0118] (2) The active material slurry a1 is placed in the coating system 1, and the active material negative electrode slurries a2 and a3 are placed in the coating systems 2 and 3, and the negative electrode active material slurries a1 and a2, a3 are respectively coated on the middle main area and the edge areas on both sides of the surface of one side of the negative electrode current collector, referring to Figure 1 The coating widths of coating zones 1, 2 and 3 can be changed according to the design.

[0119] (3) The negative electrode current collector coated on one side is coated on the other side of the opposite side, and the negative electrode sheet is obtained after drying in an oven. Optionally, the rolled negative electrode sheet is unwound and cut by an unwinding device to obtain small pieces of designed size, and the pole ears of designed size are cut by laser die, and the negative electrode sheet is obtained after gluing according to the designed size.

[0120] Battery

[0121] The third aspect of the present invention provides a battery, which includes the positive electrode sheet of the present invention, and / or includes the negative electrode sheet of the present invention. Preferably, the battery includes the positive electrode sheet of the present invention, and the negative electrode sheet of the present invention.

[0122] In some embodiments, Figure 7 As shown, when the battery is the positive electrode sheet a with a conventional negative electrode sheet c, the positive electrode sheet a and the negative electrode sheet c are separated by a separator b, and 7 is the Overhang area. When the battery is the positive electrode sheet a with a conventional negative electrode sheet, the internal resistance of the active material layer in the edge area of ​​the positive electrode sheet is greater, the lithium desorption rate is slowed down, and the positive and negative electrode potentials at the edge of the battery are increased so that the lithium deposition potential cannot be reached. In addition, in the preferred embodiment, the filler added to the edge area of ​​the positive electrode sheet can increase the electrolyte retention capacity of the edge, and then the use of the positive electrode sheet of the utility model alone will also produce an effective gain in the potential of the edge of the battery, solving the problem of lithium deposition at the edge.

[0123] In some embodiments, Figure 8 As shown, when the battery is the negative electrode sheet c and the conventional positive electrode sheet a, the positive electrode sheet a and the negative electrode sheet c are separated by the separator b, and 7 is the Overhang area. When the battery is the negative electrode sheet and the conventional positive electrode sheet, the impedance of the negative electrode edge is reduced, so that the lithium ion diffusion rate of the edge area of ​​the negative electrode sheet is increased, and the lithium ions released from the positive electrode side can be quickly inserted into the negative electrode edge, so that the corresponding negative electrode edge area is not prone to edge lithium precipitation; and the increase of the negative electrode edge diffusion coefficient alone can quickly reduce the lithium concentration of the negative electrode edge during charging and discharging, thereby weakening the influence of the edge effect.

[0124] In some preferred embodiments, Fig. 9 As shown, when the battery is the positive electrode sheet a and the negative electrode sheet c, the positive electrode sheet a and the negative electrode sheet c are separated by the separator b, and 7 is the Overhang area. When the battery is the positive electrode sheet and the negative electrode sheet of the utility model, on the one hand, the lithium insertion potential of the corresponding area on the negative electrode side can be improved, and the lithium ions released from the positive electrode side can be quickly inserted into the edge of the negative electrode, so that the corresponding edge area of ​​the negative electrode is not prone to edge lithium precipitation; on the other hand, the electrolyte retention amount at the edge of the positive electrode and the corresponding negative electrode edge can be increased, so that the electrolyte in this area is always in a more sufficient state, reducing the risk of large resistance to deintercalation at the edge due to small amount of electrolyte.

[0125] In some embodiments, in the lithium-ion battery of the utility model, the N / P (capacity per unit area of ​​the negative electrode sheet to the capacity per unit area of ​​the positive electrode sheet) ratio of the active material coating of the first main area and the main area a is between 1.01 and 1.2. In some embodiments, the NP ratio of the active material coating of the second edge area and the third edge area to the edge area b and the edge area c needs to meet> the N / P of the active material coating of the first main area and the main area a, and is between 1.1 and 1.5. The lithium-ion battery prepared under this condition satisfies that when charging at a high rate, the negative electrode position corresponding to the high NP ratio has less lithium embedded, which improves the lithium embedding potential and / or ion diffusion capacity of the fully charged state of the negative electrode, making the negative electrode edge potential higher and the lithium ion diffusion faster to meet the condition that the negative electrode does not precipitate lithium, further reducing the capacity of the positive electrode edge, so that the corresponding negative electrode edge is in a state of shallow charge and shallow discharge for a long time, even if the negative electrode edge has lithium ions accumulated due to high-rate charging and discharging, because its charging capacity is always in an unsatisfactory state and the negative electrode edge has a higher diffusion coefficient, it does not meet the conditions for lithium precipitation.

[0126] In some embodiments, the negative electrode Overhang width is between 0.1 and 3 mm. When the negative electrode Overhang width is in the range of 0.5 to 1.5 mm, the utility model can achieve the best effect in suppressing edge lithium deposition. In this range, it can meet the process requirements and ensure that the Li diffusion path embedded in the OH position is not too far, so that most of the lithium ions in the Overhang can quickly undergo lithium deintercalation reaction during the cycle.

[0127] The utility model provides a lithium-ion battery, which comprises the positive electrode sheet of the utility model, the negative electrode sheet of the utility model, and a separator known in the industry. The positive electrode sheet, the negative electrode sheet and the separator are wound according to the design size, and the positive electrode sheet, the negative electrode sheet and the separator are combined into a lithium-ion battery cell by stacking and the like. Then, the corresponding packaging method is selected according to the design size, and the electrolyte is injected. The lithium-ion battery is prepared by hot pressing, forming, secondary sealing, etc. According to the design, the structure type of the lithium-ion battery of the utility model includes a winding structure, a cylindrical structure or a stacking structure. According to the classification of the pole ear structure, the lithium-ion battery of the utility model can be a multi-pole ear structure or a single pole ear structure.

[0128] It should be noted that the numerical expressions such as "first", "second", and "third" in the present invention are only used to distinguish different substances or usage methods, and do not represent the difference in order.

[0129] The following will be combined with the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0130] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0131] The present invention is described in detail below in conjunction with specific embodiments, which are used to understand rather than limit the present invention.

[0132] A Group A Positive Plate

[0133] The positive electrode sheets of the embodiments and comparative examples in the following group A are all prepared according to the following method, and the only difference is the components or contents in the positive electrode sheets. The specific differences are shown in Table 1.

[0134] A method for preparing a positive electrode sheet comprises the following steps:

[0135] (1) After mixing lithium cobalt oxide at a ratio of 97.5wt% + carbon nanotubes at a ratio of 1.1wt% + polyvinylidene fluoride at a ratio of 1.4wt%, an appropriate amount of NMP was added, and the mixture was fully stirred in a stirring tank to prepare positive electrode slurry 1. After mixing the second positive electrode active material particles (or the third positive electrode active material particles, both of which are the same) in the edge region, the second conductive agent carbon nanotubes (or the third conductive agent, both of which are the same) and the binder polyvinylidene fluoride (the contents of the above three components are 100wt%, wherein the content percentage of the positive electrode active material particles and the content percentage of the conductive agent are shown in Table 1, and the content percentage of the polyvinylidene fluoride can be calculated and will not be repeated) and the filler, an appropriate amount of NMP was added, and the mixture was fully stirred in a stirring tank to prepare positive electrode slurries 2 and 3 (positive electrode slurries 2 and positive electrode slurries 3 are the same).

[0136] (2) If an aluminum foil with a width of 100 mm is used as the positive electrode current collector, the positive electrode slurry 1 is placed in the coating system 1, and the positive electrode slurries 2 and 3 are placed in the coating systems 2 and 3 respectively. According to the design of the coating system, the active material slurry 1 and the active material slurries 2 and 3 can be coated on the surface of the current collector at one time through a special knife pad. The knife pad includes three coating areas, namely, the middle coating area: the positive electrode slurry 1 is coated, and the edge coating areas 2 and 3 are coated with positive electrode slurries 2 and 3 respectively. The positive electrode slurry 1 with a width of 60-90 mm is coated on the first main area of ​​the first and second surfaces of the aluminum foil and dried to obtain the first positive electrode active material layer, and the positive electrode slurry 2 with a width greater than 2 mm is coated on the second edge area and the third edge area of ​​the first and second surfaces and dried to obtain the second positive electrode active material layer and the third positive electrode active material layer respectively. The coating length is 890 mm and the coating thickness is 79 μm. The roller pressing device is used for one-time calendering to a compaction density of 4.05. The empty foil at the edge is cut off, and the pole ear is welded in the middle empty foil area, and insulating tape is affixed to prepare a rolled positive electrode sheet.

[0137] The positive electrode sheet resistance (ohmic resistance) is tested using four probes. The test method uses four probes to test the electrode sheet resistance. The electrode sheet is placed on the resistance tester, and the probe is used to press the electrode sheet. The device is started. The device will run at the set current and calculate the internal resistance value. The test results are read out. Three center positions are selected in the first main body area, the second edge area, and the third edge for three measurements, and the average value is taken to record the internal resistance value. The internal resistance of the first positive active material layer is recorded as R1, the internal resistance of the second positive active material layer is recorded as R2, and the internal resistance of the third positive active material layer is recorded as R3.

[0138] The configurations of Examples A1 to A6 are shown in Table 1 below.

[0139] Table 1

[0140]

[0141]

[0142] Note: In Table 1, "same as A1" means the same as Example A1, and "same as A2" means the same as Example A2.

[0143] Example A5

[0144] Referring to Example A1, a positive electrode active material layer with large internal resistance is arranged on the surface of the second edge region and the third edge region away from the current collector, and the opening position of the ceramic glue path of the coating knife pad is designed to realize coating of the doped coating (the second positive electrode active material layer and the third positive electrode active material layer) on the surface of the edge region, that is, when the opening is located on the surface of the positive electrode sheet, the coating layer is located on the surface of the positive electrode sheet with a thickness of 20 μm, and the bottom layer is a conventional active material coating (the first positive electrode active material layer).

[0145] Example A6

[0146] Referring to Example A2, an active layer with a large internal resistance is arranged on the surface of the second edge area and the third edge area close to the current collector, and the opening position of the ceramic glue path of the coating knife pad is designed to realize the coating of the doped coating (the second positive electrode active material layer and the third positive electrode active material layer) on the bottom layer of the edge area, that is, when the opening is located at the bottom layer of the electrode sheet, the coating layer is located at the bottom layer of the positive electrode sheet, with a thickness of 20 μm, and the surface layer is a conventional active coating (the first positive electrode active material layer).

[0147] Comparative Example A1

[0148] The method is carried out in accordance with Example A1, except that the positive electrode sheets are all coated with the positive electrode slurry 1, so as to obtain positive electrode sheets having completely the same positive electrode active material layer.

[0149] Comparative Example A2

[0150] Refer to Example A1, except that the formula of positive electrode slurry 2 and positive electrode slurry 3 in the positive electrode sheet is 96.1wt% lithium cobalt oxide + 2.5wt% carbon nanotubes + 1.4wt% polyvinylidene fluoride, and the amount of conductive agent of the active material layer in the edge area is increased so that the internal resistance of the edge area is smaller than that of the main area.

[0151] The positive electrode sheet in the above-mentioned Group A embodiment and comparative example is matched with a conventional negative electrode sheet, and the formula of the active material layer in the negative electrode sheet is artificial graphite: carbon nanotube: styrene-butadiene rubber: carboxymethyl cellulose lithium 96%: 1.5%: 1.5%; 1%. The positive electrode sheet, the negative electrode sheet and the separator (a ceramic coating with a thickness of 2 μm is coated on both sides of a 5 μm polyethylene separator) are wound to form a winding core, which is packaged with an aluminum-plastic film, baked to remove moisture, and then injected with an electrolyte (propylene carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate are mixed in a weight ratio of 1:1:0.5:1, and 1 mol / L LiPF6 is added and mixed evenly), and a battery is obtained by hot pressing.

[0152] The performance of the above battery is tested as follows:

[0153] (1) Cycle disassembly phenomenon: During the battery cycle, a group of batteries are removed from the stage every 50T for disassembly and observation. During the disassembly process, the battery needs to be charged to 100% SOC state. After disassembly, it is necessary to observe the lithium metal deposition on the surface of the negative electrode and the diaphragm of the battery. If the size range of lithium metal deposition on the surface of the negative electrode and the diaphragm does not exceed 1 / 10 of the total length of the electrode, it is considered to be slight lithium deposition. If the size range of lithium metal deposition on the surface of the negative electrode and the diaphragm exceeds 1 / 10 of the total length of the electrode, it is considered to be severe lithium deposition. Further, according to the earliest cycle number and the size range of lithium deposition, when lithium deposition occurs before 300T or severe lithium deposition is defined, it is defined as poor lithium deposition improvement, when lithium deposition occurs between 300T and 600T and is relatively mild, it is defined as moderate lithium deposition improvement, when lithium deposition occurs between 600T and 1000T and is relatively mild, it is defined as better improvement, and when there is no lithium deposition after 1000T, it is defined as excellent lithium deposition improvement. The test results are recorded in Table 2.

[0154] (2) Fast charging performance: The fast charging performance test method is based on 5C direct charging, 0.05C cut-off / 0.7C discharge as the basic charging and discharging conditions. Under this charging and discharging condition, the cycle is set to 1000T as the observation period. During the observation period, a group of batteries are removed every 50T for disassembly and observation of lithium deposition status. The test results are recorded in Table 2.

[0155] Table 2

[0156]

[0157]

[0158] It can be seen from the results in Table 2 that in the positive electrode sheet provided by the present invention, the greater internal resistance in the edge area can effectively solve the problem of edge lithium deposition and improve the fast charging performance of the battery.

[0159] Group B Example Negative Plate

[0160] The negative electrode sheets of the examples and comparative examples in the following group A are all prepared according to the following method, and the only difference is the components or contents in the negative electrode sheets. The specific differences are shown in Table 1.

[0161] A method for preparing a negative electrode sheet comprises the following steps:

[0162] (1) After mixing graphite at a ratio of 96.7 wt% + carbon nanotubes at a ratio of 0.8 wt% + styrene-butadiene rubber at a ratio of 2.5 wt%, an appropriate amount of water was added, and the mixture was fully stirred in a stirring tank to prepare negative electrode slurry 1. After mixing the second negative electrode active material particles graphite (or the third negative electrode active material particles, both of which are the same) in the edge region + the second negative electrode conductive agent carbon nanotubes (or the third negative electrode conductive agent, both of which are the same) + styrene-butadiene rubber (the contents of the above three components are 100 wt%, wherein the content ratio of the negative electrode active material particles graphite and the content ratio of the conductive agent are shown in Table 2, and the content of styrene-butadiene rubber can be calculated and will not be repeated), an appropriate amount of water was added, and the mixture was fully stirred in a stirring tank to prepare negative electrode slurries 2 and negative electrode slurries 3 (negative electrode slurries 2 and negative electrode slurries 3 are the same).

[0163] (2) If a copper foil with a width of 100 mm is used as the negative electrode current collector, the negative electrode slurry 1 is placed in the coating system 1, and the negative electrode slurries 2 and 3 are placed in the coating systems 2 and 3 respectively. According to the design of the coating system, the active material slurry 1 and the active material slurries 2 and 3 can be coated on the surface of the current collector at one time through a special knife pad. The knife pad includes three coating areas, namely the middle coating area: coating the negative electrode slurry 1, and the edge coating areas 2 and 3 are coated with negative electrode slurries 2 and 3 respectively. The negative electrode slurry 1 with a width of 60-90 mm is coated on the first main area of ​​the first and second surfaces of the copper foil and dried to obtain the first negative electrode active material layer, and the negative electrode slurry 2 with a width greater than 2 mm is coated on the second edge area and the third edge area of ​​the first and second surfaces and dried to obtain the second negative electrode active material layer and the third negative electrode active material layer respectively, and the coating length is 890 mm. The compaction is usually between 1 and 4. Unreasonable compaction may cause damage to the negative electrode active material or lithium precipitation. The negative electrode sheet is obtained by cutting along the edge of the hollow foil, the pole ear is welded on the negative electrode sheet, and the insulating tape is attached to the edge of the positive electrode to prepare the negative electrode sheet.

[0164] The impedance in the negative electrode sheet mainly refers to Rsei (membrane impedance) and Rct (charge transfer impedance). The test method includes cutting a conventional negative electrode sheet with a length and width of 2cm×2cm to make a conventional negative electrode-conventional negative electrode symmetrical battery; preparing and cutting the negative electrode sheets of the above embodiment and the comparative example with a length and width of 2cmx2cm to make a doped negative electrode-doped negative electrode symmetrical battery respectively. After injecting equal amounts of electrolyte, the battery is tested using a Zahner electrochemical workstation. The test frequency range is 0.5mHz~10Mhz. After testing three symmetrical batteries in each group, the average value is taken and the internal resistance value is recorded. The impedance of the first negative electrode active material layer is recorded as R a The impedance of the second negative electrode active material layer is denoted as R b The impedance of the third negative electrode active material layer is denoted as R c .

[0165] The configurations of Example B1 to Example B3 are shown in Table 3 below.

[0166] Table 3

[0167]

[0168]

[0169] Note: In Table 3, "same as B1" means the same as Example B1, and "same as B2" means the same as Example B2.

[0170] Comparative Example B1

[0171] The method is carried out in accordance with Example B1, except that all negative electrode sheets are coated with negative electrode slurry 1 to obtain negative electrode sheets having completely the same negative electrode active material layer.

[0172] Comparative Example B2

[0173] Refer to Example B1, except that the formula of negative electrode slurry 2 and negative electrode slurry 3 in the negative electrode sheet is 97wt% graphite + 0.5wt% carbon nanotubes + 2.5wt% styrene-butadiene rubber, and the amount of conductive agent in the active material layer in the edge area is reduced, so that the internal resistance of the edge area is greater than the internal resistance of the main area.

[0174] The negative electrode sheets in the above Group B embodiments and comparative examples were matched with conventional positive electrode sheets, and the formula of the active material layer in the positive electrode sheet was 97.5wt% of lithium cobaltate + 1.1wt% of carbon nanotubes + 1.4wt% of polyvinylidene fluoride. The positive electrode sheet, the negative electrode sheet and the separator (a ceramic coating with a thickness of 2μm is coated on both sides of a 5μm polyethylene separator) were wound to form a winding core, which was packaged with an aluminum-plastic film, baked to remove moisture, and then injected with an electrolyte (propylene carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate were mixed in a weight ratio of 1:1:0.5:1, and 1mol / L of LiPF6 was added and mixed evenly), and a battery was obtained by hot pressing.

[0175] The performance of the above battery was tested. The test method was based on the method of Group A embodiment. The test results are recorded in Table 4.

[0176] Table 4

[0177]

[0178]

[0179] It can be seen from the results in Table 4 that the impedance of the edge area of ​​the negative electrode sheet provided by the present invention is smaller, which can effectively solve the problem of edge lithium deposition and improve the fast charging performance of the battery.

[0180] Group C Example

[0181] Combine the positive electrode sheet in the above group A with the positive electrode sheet in the group B, with the negative electrode overhang width of 1 mm, and assemble the battery with reference to the battery preparation process of group A or group B in Example.

[0182] Table 5

[0183]

[0184] The lithium ion battery of Example C1 is a positive electrode sheet prepared in Example A1 matched with a negative electrode sheet prepared in Example B1, the lithium ion battery prepared in Example C4 is a positive electrode sheet prepared in Example A2 matched with a conventional negative electrode sheet), the lithium ion battery prepared in Example C5 is a negative electrode sheet prepared in Example B2 matched with a conventional positive electrode sheet, and the lithium ion battery prepared in the conventional structure in Comparative Example C1. It can be seen from the data in Table 5 that when the positive electrode sheet in the utility model is matched with the negative electrode sheet, the effect of suppressing lithium precipitation is the best, and the fast charging performance is also relatively good.

[0185] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0186] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A pole piece, characterized in that: The pole piece includes a current collector, and the surface of at least one side of the current collector includes a main region and at least two edge regions, and the main region and the edge region are both provided with an active material layer; wherein the internal resistance of the active material layer provided in the main region is greater than or less than the internal resistance of the active material layer in the edge region; The electrode sheet is a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector, the surface of at least one side of the positive electrode current collector includes a first main body area, at least one second edge area and at least one third edge area, the second edge area and the third edge area are respectively located on both sides of the first main body area; the first main body area is provided with a first positive electrode active material layer, the internal resistance of the first positive electrode active material layer is recorded as R1; the second edge area is provided with a second positive electrode active material layer, the internal resistance of the second positive electrode active material layer is recorded as R2; the third edge area is provided with a third positive electrode active material layer, the internal resistance of the third positive electrode active material layer is recorded as R3; wherein R2>R1, R3>R1, R2 and R3 are the same or different; And / or, the electrode sheet is a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector, the surface of at least one side of the negative electrode current collector includes a main area a, at least one edge area b and at least one edge area c, the edge area b and the edge area c are respectively located on both sides of the main area a; the main area a is provided with a first negative electrode active material layer, and the impedance of the first negative electrode active material layer is recorded as R a The edge region b is provided with a second negative electrode active material layer, and the impedance of the second negative electrode active material layer is denoted as R b The edge region c is provided with a third negative electrode active material layer, and the impedance of the third negative electrode active material layer is denoted as R c ; Among them, R b <R a , R c <R a , R b With R c Same or different.

2. The pole piece according to claim 1, characterized in that: The area of ​​the second positive electrode active material layer is S2, and the area of ​​the third positive electrode active material layer is S3, which satisfies the following relationship with the area S1 of the first positive electrode active material layer: 2% <S2 / S1≤10%,2%<S3 / S1≤10%; And / or, the area of ​​the second negative electrode active material layer is S b The area of ​​the third negative electrode active material layer is S c , and the area S of the first negative electrode active material layer a Satisfies the following relationship: 2% b / S a ≤10%, 2% c / S a ≤10%.​​ 3. The pole piece according to claim 1, characterized in that: The second positive electrode active material layer is arranged on a surface of the second edge region close to the positive electrode current collector, and / or the second positive electrode active material layer is arranged on a surface of the second edge region away from the positive electrode current collector; And / or, the third positive electrode active material layer is arranged on the surface of the third edge region close to the positive electrode current collector, and / or the third positive electrode active material layer is arranged on the surface of the third edge region away from the positive electrode current collector.

4. The pole piece according to claim 1, characterized in that: The second positive electrode active material layer is disposed in the entire second edge region; and / or the third positive electrode active material layer is disposed in the entire third edge region; And / or, the second negative electrode active material layer is disposed in the entire edge region b; and / or, the third negative electrode active material layer is disposed in the entire edge region c.

5. The pole piece according to any one of claims 1 to 4, characterized in that: One side surface or both sides of the positive electrode current collector comprises a first main body region, a second edge region and a third edge region, and the second edge region and the third edge region are respectively located on both sides of the first main body region; And / or, one side surface or both sides surface of the positive electrode current collector comprises a first main body region, two second edge regions and two third edge regions, and the two second edge regions and the two third edge regions are respectively located on two opposite sides of the first main body region.

6. The pole piece according to any one of claims 1 to 4, characterized in that: One side surface or both sides of the negative electrode current collector comprises a main region a, an edge region b and an edge region c, and the edge region b and the edge region c are respectively located on both sides of the main region a; And / or, one side surface or both sides surface of the negative electrode current collector includes a main region a, two edge regions b and two edge regions c, and the two edge regions b and the two edge regions c are respectively located on two opposite sides of the main region a.

7. The pole piece according to any one of claims 1 to 4, characterized in that: The width of the first positive electrode active material layer is greater than the width of the second positive electrode active material layer; and / or the width of the first positive electrode active material layer is greater than the width of the third positive electrode active material layer; the width of the second positive electrode active material layer is the same as or different from the width of the third positive electrode active material layer; And / or, the width of the first negative electrode active material layer is greater than the width of the second negative electrode active material layer, and / or, the width of the first negative electrode active material layer is greater than the width of the third negative electrode active material layer, and the widths of the second negative electrode active material layer and the third negative electrode active material layer are the same or different.

8. The pole piece according to any one of claims 1 to 4, characterized in that: The widths of the second positive electrode active material layer and the third positive electrode active material layer are independently ≥ 2 mm; And / or, the widths of the second negative electrode active material layer and the third negative electrode active material layer are independently ≥ 2 mm.

9. The pole piece according to any one of claims 1 to 4, characterized in that: The thickness of the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer on one side are independently distributed between 20 μm and 60 μm; And / or, the thicknesses of the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer on one side are independently distributed between 20 μm and 90 μm.

10. A battery, characterized in that: A pole piece comprising any one of claims 1 to 9.

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