Pole piece, battery and electric device

Abstract

The present disclosure relates to the field of lithium ion batteries, and particularly relates to a pole piece, a battery and a power device, the pole piece comprising a current collector, an active layer and a conductive layer; the current collector is provided with a first region, a second region and a third region along the length direction, the first region and the second region are distributed on both sides of the third region; the active layer is arranged on the surface of the third region; the conductive layer is arranged on the surface of the first region and the surface of the second region on at least one side of the current collector along the thickness direction; one side of the conductive layer is attached to the active layer, and the other side is gradually thinned in a slope shape and close to the end of the current collector; the thickness of the side of the conductive layer attached to the active layer is the same as the thickness of the active layer; the active layer comprises a first active material layer arranged on the surface of the third region and a second active material layer arranged on the surface of the first active material layer away from the surface of the third region; the surface of at least one side of the current collector along the thickness direction is provided with a plurality of recess structures. The pole piece of the present disclosure can enhance the rate performance of the battery.

Description

Technical Field

[0001] This disclosure relates to the field of lithium-ion batteries, and more specifically, to an electrode, a battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries possess numerous advantages, including high energy density, long cycle life, high voltage, and low self-discharge rate, leading to their widespread application in 3C products, electric vehicles, and energy storage systems. In recent years, with the rapid development of large-scale energy storage and the electric vehicle industry, higher demands have been placed on the energy density of lithium-ion batteries.

[0003] In the field of lithium-ion battery technology, multi-layer coating allows electrodes to have multiple layers of active material. Compared to single-layer active material, this method enables lithium-ion batteries to have higher energy density and better rate performance. However, under the same conditions, thicker electrodes cause lithium ions to migrate a longer distance during charging and discharging, which affects the electronic conductivity of the electrode coating and thus the final conductivity of the battery. Utility Model Content

[0004] In view of this, this disclosure aims to provide an electrode, a battery, and an electrical device to solve the problems of high internal resistance and contact impedance in the prior art, while overcoming the influence of thick-coated electrode on the electronic conductivity of the battery coating and on the final conductivity of the battery.

[0005] To solve the above-mentioned technical problems, this disclosure is implemented as follows: A first aspect of this disclosure provides an electrode sheet comprising a current collector, an active layer, and a conductive layer; the current collector is provided with a first region, a second region, and a third region along its length, the first region and the second region being distributed on both sides of the third region; the active layer is disposed on the surface of the third region on at least one side of the current collector along its thickness direction; the conductive layer is disposed on the surfaces of the first region and the second region on at least one side of the current collector along its thickness direction. Wherein, one side of the conductive layer is attached to the active layer, and the other side is close to the end of the current collector and gradually thins out in a slope shape; the thickness of the side of the conductive layer that is attached to the active layer is the same as the thickness of the active layer; The active layer includes a first active material layer disposed on the surface of at least one third region along the thickness direction of the current collector and a second active material layer disposed on the surface of the third region away from the current collector of the first active material layer. At least one side surface of the current collector in the thickness direction is provided with a plurality of recessed structures.

[0006] Optionally, the area of ​​the first region and the area of ​​the second region are equal; the length of the first region accounts for 2.7 to 4.5% of the total length of the electrode; and / or, the length of the second region accounts for 2.7 to 4.5% of the total length of the electrode.

[0007] Optionally, the conductive layer includes a conductive agent; the conductive agent includes at least one of carbon black, carbon nanotubes, carbon fibers, and graphene.

[0008] Optionally, the thickness of the conductive layer at its thinnest point is 2-4 mm.

[0009] Optionally, the thickness of the first active material layer is 80~100μm; and / or, the thickness of the second active material layer is 80~100μm.

[0010] Optionally, the electrode further includes a third active material layer disposed on the surface of a third region on the side of the second active material layer away from the first active material layer; the thickness of the third active material layer is 80~100μm.

[0011] Optionally, the diameter of the recessed structure is 10~50μm, the depth of the recessed structure is 0.5~1.5μm; and / or, the total area of ​​the plurality of recessed structures accounts for 2~8% of the surface area of ​​the third region.

[0012] Optionally, the recessed structures are distributed in a vertical array on at least one side surface of the current collector in the thickness direction; or, the recessed structures are distributed in a ring array on at least one side surface of the current collector in the thickness direction.

[0013] A second aspect of this disclosure provides a battery comprising a battery assembly including a positive electrode and / or a negative electrode, wherein the positive electrode and / or negative electrode are the aforementioned electrodes.

[0014] A third aspect of this disclosure provides an electrical device comprising a battery, wherein the battery is the battery described above.

[0015] The beneficial technical effects of this disclosure through the above technical solution are as follows: In this disclosure, conductive layers are provided on the surfaces of the first and second regions located at both ends of the current collector, which can quickly conduct electrons between the active layer and the current collector. Multiple recessed structures provided on at least one side of the current collector's thickness direction can reduce wrinkling of the electrode during charging and discharging, increase the contact area between the coatings of the current collector, and accelerate electron transport. When the electrode of this disclosure is applied to lithium-ion batteries, it can reduce the battery's internal resistance and contact impedance, achieve high energy density, and enhance the battery's rate performance.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further understand the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof.

[0018] Figure 1 The diagram shown is a schematic of the electrode sheet of this disclosure.

[0019] Figure 2 The diagram shows the electron configuration of the electrode with a conductive layer in the current collector.

[0020] Figure 3 The diagram shows the electron configuration of the electrode with a conductive layer and a recessed structure in the current collector.

[0021] Explanation of reference numerals in the attached figures 1. Current collector 2. Active layer 3. Conductive layer 4. First Area 5. Second Zone 6. Third Zone Detailed Implementation This disclosure provides an electrode, a battery, and an electrical device. Those skilled in the art can refer to the content herein to appropriately modify process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this disclosure. The methods and applications of this disclosure have been described through preferred embodiments. Those skilled in the art will clearly be able to modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this disclosure to implement and apply the technology of this disclosure.

[0022] In the description of this disclosure, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] Unless otherwise specified, all embodiments and optional embodiments of this disclosure can be combined to form new technical solutions.

[0025] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions.

[0026] Unless otherwise specified, the terms "comprising" and "including" as used in this disclosure can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0027] To address the issues of high internal resistance and contact impedance in existing batteries, and to overcome the impact of thick-coated electrode sheets on the electronic conductivity of the battery coating and its final conductivity, this disclosure adopts the following technical solution: The first aspect of this disclosure provides an electrode, such as Figure 1 As shown, the electrode includes a current collector 1, an active layer 2, and a conductive layer 3; the current collector is provided with a first region 4, a second region 5, and a third region 6 along its length direction, with the first region 4 and the second region 5 distributed on both sides of the third region 6; the active layer 2 is disposed on the surface of the third region 6 on at least one side of the current collector along its thickness direction; the conductive layer 3 is disposed on the surface of the first region 4 and the second region 5 on at least one side of the current collector 1 along its thickness direction. In this embodiment, one side of the conductive layer 3 is attached to the active layer 2, and the other side is close to the end of the current collector 1 and gradually thins out in a sloping shape; the thickness of the side of the conductive layer 3 that is attached to the active layer 2 is the same as the thickness of the active layer 2. The active layer 2 includes a first active material layer disposed on the surface of at least one third region 6 along the thickness direction of the current collector 1 and a second active material layer disposed on the surface of the third region on the side of the first active material layer away from the current collector. At least one side surface of the current collector 1 in the thickness direction is provided with a plurality of recessed structures.

[0028] In this disclosure, conductive layers are provided on the surfaces of the first and second regions located at both ends of the current collector, which can quickly conduct electrons between the active layer and the current collector. Multiple recessed structures provided on at least one side of the current collector's thickness direction can reduce wrinkling of the electrode during charging and discharging, increase the contact area between the coatings of the current collector, and accelerate electron transport. When the electrode of this disclosure is applied to lithium-ion batteries, it can reduce the battery's internal resistance and contact impedance, achieve high energy density, and enhance the battery's rate performance.

[0029] In the embodiments of this disclosure, in order to ensure that the current conduction speed at both ends of the current collector is uniform, the area of ​​the first region and the area of ​​the second region are equal.

[0030] In this disclosure, the appropriate lengths of the first and second regions enhance the conductivity of the electrode material, ensuring effective charge transfer and thus improving the battery's charge-discharge efficiency and cycle life. An excessively long conductive layer increases the battery's internal resistance, affecting its rate performance. Conversely, if the conductive layer is too short, it may lead to poor connection between the electrode and the current collector, affecting charge transfer efficiency and consequently reducing battery performance and stability. In embodiments of this disclosure, the length of the first region may account for 2.7 to 4.5% of the total length of the electrode; and / or, the length of the second region may account for 2.7 to 4.5% of the total length of the electrode. For example, the length of the first region can be any value among 2.7%, 3%, 3.3%, 3.7%, 4.0%, 4.2%, and 4.5% of the total length of the electrode, or any value within the range of any two of the above values; the length of the second region can be any value among 2.7%, 3%, 3.3%, 3.7%, 4.0%, 4.2%, and 4.5% of the total length of the electrode, or any value within the range of any two of the above values.

[0031] In this disclosure, the conductive layer may include a conductive agent; exemplarily, the conductive agent includes at least one of carbon black, carbon nanotubes, carbon fibers, and graphene.

[0032] In some embodiments of this disclosure, the conductive layer may further include a conductive dispersant and a binder. Exemplarily, the dispersant may include at least one of carboxymethyl cellulose, polyvinylpyrrolidone, sodium polyacrylate, and polyethylene glycol octylphenyl ether; the binder may include at least one of polyvinylidene fluoride, styrene-butadiene rubber, polyacrylic acid, and polyamides.

[0033] According to this disclosure, the thickness of the thinnest part of the conductive layer can be 2-4 mm. If the thinnest part of the conductive layer is too thin, it may lead to a decrease in conductivity, making it unable to effectively carry large currents, resulting in increased resistance and causing heat generation problems, thus affecting the stability and reliability of the battery. If the thinnest part of the conductive layer is too thick, it may lead to the formation of additional resistance paths, hindering the effective transport of electrons and lithium ions, especially at high current densities, which will affect the cycle performance of the battery. For example, the thinnest part of the conductive layer can be any value selected from 2 mm, 2.5 mm, 3 mm, 3.5 mm, and 4 mm, or any value within the range formed by any two of the above values.

[0034] In this disclosure, suitable thicknesses of the first and second active material layers can achieve the technical effect of ensuring electrochemical performance while maintaining high capacity. As one embodiment of this disclosure, the thickness of the first active material layer can be 80-100 μm; and / or, the thickness of the second active material layer can be 80-100 μm. Exemplarily, the thickness of the first active material layer can be any value selected from 80 μm, 85 μm, 90 μm, 95 μm, and 100 μm, or any value within the range formed by any two of the aforementioned values; the thickness of the second active material layer can be any value selected from 80 μm, 85 μm, 90 μm, 95 μm, and 100 μm, or any value within the range formed by any two of the aforementioned values.

[0035] In a preferred embodiment of this disclosure, the electrode may further include a third active material layer disposed on the surface of a third region on the side of the second active material layer away from the first active material layer; optionally, the thickness of the third active material layer is 80-100 μm; exemplaryly, the thickness of the third active material layer can be any value selected from 80 μm, 85 μm, 90 μm, 95 μm, and 100 μm, or any value within the range formed by any pair of the above values. By setting three active material layers in this disclosure, not only can the energy density of the battery be improved, but also the ion transport efficiency can be improved, and the cycle performance and rate performance of the battery can be enhanced, thereby obtaining a more efficient and stable battery system.

[0036] In this disclosure, the recessed structure on the current collector surface can be formed by laser etching. The recessed structure reduces wrinkles on the electrode during charging and discharging, increases the contact area between the current collector and the active material layer, and the recessed structure and conductive layer can synergistically achieve rapid electron conduction, improving the conductivity of the thick electrode battery. As one embodiment of this disclosure, the diameter of the recessed structure can be 10~50μm, and the depth of the recessed structure can be 0.5~1.5μm. Exemplarily, the diameter of the recessed structure can be any value from 10μm, 20μm, 30μm, 40μm, and 50μm, or any value within the range of any two of the above values; the depth of the recessed structure can be any value from 0.5μm, 0.8μm, 1.0μm, 1.2μm, and 1.5μm, or any value within the range of any two of the above values.

[0037] In this disclosure, if the total area of ​​the recessed structures is too large, the current collector may be subjected to greater local stress during charging and discharging, thereby causing interfacial cracking or detachment between the current collector and the active material layer, affecting the cycle stability of the battery. If the total area of ​​the recessed structures is too small, the contact area between the current collector and the active material layer may be reduced, thereby reducing the electron conduction efficiency and affecting the rate performance of the battery. As one embodiment of this disclosure, the total area of ​​the plurality of recessed structures can account for 2 to 8% of the surface area of ​​the third region. Exemplarily, the total area of ​​the plurality of recessed structures can account for any value among 2%, 4%, 6%, and 8% of the surface area of ​​the third region, or any value within the range of any pair of the above values.

[0038] In some embodiments of this disclosure, the recessed structures are arranged in a vertical array on at least one surface in the thickness direction of the current collector; or, the recessed structures are arranged in a ring array on at least one surface in the thickness direction of the current collector. In this disclosure, a vertical array of recessed structures on at least one surface in the thickness direction of the current collector means that the recessed structures are arranged in a direction perpendicular to the surface of the active material layer; a ring array of recessed structures on at least one surface in the thickness direction of the current collector means that the recessed structures are arranged in a ring or concentric circles on the surface of the active material layer.

[0039] A second aspect of this disclosure provides a battery comprising a battery assembly including a positive electrode and / or a negative electrode, wherein the positive electrode and / or negative electrode are the aforementioned electrodes.

[0040] A third aspect of this disclosure provides an electrical device comprising a battery, wherein the battery is the battery described above.

[0041] In some embodiments of this application, the battery further includes an electrolyte and a separator. That is, the battery includes a positive electrode, a negative electrode, an electrolyte, and a separator.

[0042] In this embodiment, the specific material or type of the separator is not limited, and any separator known in the art that can be used in secondary batteries can be selected.

[0043] It should also be noted that the battery in this application does not limit the specific material or type of electrolyte. Any components and types known in the art that can be used in secondary batteries can be selected, as long as the purpose of this application can be achieved.

[0044] Since the battery provided in this application adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0045] The present application will be described in detail below with reference to the accompanying drawings and examples. However, the implementation and protection of the present application are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application. Figure 2 The diagram shows the electron configuration of the electrode with a conductive layer on the current collector; Figure 3 A schematic diagram showing the electron configuration of the electrode with a conductive layer and a recessed structure in the current collector is shown.

[0046] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0047] Example 1 (1) Preparation of positive electrode sheet A laser-etched aluminum foil is used as the positive electrode current collector. The positive electrode current collector has a first region, a second region, and a third region along its length, with the first and second regions distributed on either side of the third region. A coating structure is formed on the surface of the third region. Conductive layers are formed on the surfaces of the first and second regions. One side of the conductive layer is attached to the coating structure, while the other side gradually thins towards the end of the current collector in a sloping manner. The thickness of the conductive layer on the side attached to the active layer is the same as the thickness of the coating structure. In this embodiment, the conductive layer is prepared by mixing a conductive agent (conductive carbon black), a binder (polyvinylidene fluoride (PVDF)), and a dispersant (polyphosphate) in a mass ratio of 76:9:15 to obtain a mixed material. The mixed material is then thoroughly and rapidly stirred in N-methylpyrrolidone (NMP) to obtain a conductive layer slurry. The conductive layer slurry is coated onto the surfaces of the first and second regions and then dried.

[0048] The length of the first region accounts for 3.0% of the total length of the electrode, and the length of the second region accounts for 3.0% of the total length of the electrode; the thickness of the thinnest part of the conductive layer is 3.0 mm.

[0049] The surface of the positive electrode current collector has a recessed structure, and the recessed structure is distributed in a vertical array on at least one side of the current collector in the thickness direction; the diameter of the pit is about 30 μm, the depth of the pit is 1.0 μm, and the area of ​​the pit accounts for 5% of the total area of ​​the current collector.

[0050] The coating structure comprises, from the inside out, a first positive electrode active material layer, a second positive electrode active material layer, and a third positive electrode active material layer. The thickness of the first active material layer is 85 μm, the thickness of the second active material layer is 90 μm, and the thickness of the third active material layer is 95 μm. The preparation method of the first positive electrode active material layer, the second positive electrode active material layer, and the third positive electrode active material layer includes: mixing the positive electrode active material (ternary nickel cobalt manganese oxide material), the conductive agent (conductive carbon black), and the binder (PVDF) in a mass ratio of 93:5:2 to obtain a mixed material; thoroughly and rapidly stirring the mixed material in NMP to obtain a positive electrode slurry; and applying the positive electrode slurry to the surface of the third region in three layers.

[0051] (1) Preparation of negative electrode sheet A laser-etched copper foil is used as the negative electrode current collector. The negative electrode current collector has a first region, a second region, and a third region along its length. The first and second regions are distributed on both sides of the third region. A coating structure is formed on the surface of the third region. Conductive layers are formed on the surfaces of the first and second regions. One side of the conductive layer is attached to the coating structure, and the other side gradually thins down in a slope shape near the end of the current collector. The thickness of the conductive layer on the side attached to the active layer is the same as the thickness of the coating structure.

[0052] The length of the first region accounts for 3.0% of the total length of the electrode, and the length of the second region accounts for 3.0% of the total length of the electrode; the thickness of the conductive layer at its thinnest point is 3 mm.

[0053] The surface of the negative electrode current collector has a concave structure, and the concave structure is distributed in a vertical array on at least one side of the current collector surface in the thickness direction; the diameter of the pit is about 30 μm, the depth of the pit is 1.0 μm, and the area of ​​the pit accounts for 5% of the total area of ​​the current collector.

[0054] The coating structure comprises, from the inside out, a first negative electrode active material layer, a second negative electrode active material layer, and a third negative electrode active material layer. The thickness of the first active material layer is 80 μm, the thickness of the second active material layer is 85 μm, and the thickness of the third active material layer is 90 μm. The preparation method of the first negative electrode active material layer, the second negative electrode active material layer, and the third negative electrode active material layer includes: mixing the negative electrode active material (graphite), the conductive agent (conductive carbon black), and the binder (PVDF) in a mass ratio of 93:5:2 to obtain a mixed material; thoroughly and rapidly stirring the mixed material in NMP to obtain a negative electrode slurry; and applying the negative electrode slurry to the surface of the third region in three layers.

[0055] (3) Battery preparation Ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare an electrolyte.

[0056] After weighing, the electrode sheets are directly used as the negative electrode of the lithium-ion battery. The assembly of the 2032 coin cell is carried out in a glove box filled with Ar. The specific assembly method includes: arranging the positive electrode sheet, separator and negative electrode sheet in sequence and assembling them by winding; injecting the electrolyte into the dry cell, soaking for 24 hours, and then completing the cell manufacturing process after formation, aging and other processes.

[0057] Example 2 The preparation methods of the positive and negative electrode sheets in this embodiment are generally the same as those in Embodiment 1, except that the thickness of the thinnest part of the conductive layer of the positive electrode sheet is 2 mm, and the thickness of the thinnest part of the conductive layer of the negative electrode sheet is 2 mm.

[0058] The battery preparation method in this embodiment is the same as in Embodiment 1.

[0059] Example 3 The preparation methods of the positive and negative electrode sheets in this embodiment are generally the same as those in Embodiment 1, except that the thickness of the thinnest part of the conductive layer of the positive electrode sheet is 4 mm, and the thickness of the thinnest part of the conductive layer of the negative electrode sheet is 4 mm.

[0060] The battery preparation method in this embodiment is the same as in Embodiment 1.

[0061] Example 4 The preparation methods of the positive and negative electrode sheets in this embodiment are the same as those in Embodiment 1, except that the diameter of the pits on the current collector surface of the positive electrode sheet is 10 μm, and the diameter of the pits on the current collector surface of the negative electrode sheet is 10 μm.

[0062] The battery preparation method in this embodiment is the same as in Embodiment 1.

[0063] Example 5 The preparation methods of the positive and negative electrode sheets in this embodiment are the same as those in Embodiment 1, except that the diameter of the pits on the current collector surface of the positive electrode sheet is 50 μm, and the diameter of the pits on the current collector surface of the negative electrode sheet is 50 μm.

[0064] The battery preparation method in this embodiment is the same as in Embodiment 1.

[0065] Example 6 The preparation methods of the positive and negative electrode sheets in this embodiment are generally the same as those in Embodiment 1, except that the depth of the pits on the current collector surface of the positive electrode sheet is 0.5 μm, and the depth of the pits on the current collector surface of the negative electrode sheet is 0.5 μm.

[0066] The battery preparation method in this embodiment is the same as in Embodiment 1.

[0067] Example 7 The preparation methods of the positive and negative electrode sheets in this embodiment are generally the same as those in Embodiment 1, except that the depth of the pits on the current collector surface of the positive electrode sheet is 1.5 μm, and the depth of the pits on the current collector surface of the negative electrode sheet is 1.5 μm.

[0068] The battery preparation method in this embodiment is the same as in Embodiment 1.

[0069] Comparative Example 1 (1) Preparation of positive electrode sheet Aluminum foil after laser etching is used as the positive electrode current collector. The surface of the positive electrode current collector is provided with a coating structure and a recessed structure. The recessed structure is distributed in a vertical array on at least one side of the surface in the thickness direction of the current collector. The diameter of the pit is about 30 μm, the depth of the pit is 1.0 μm, and the area of ​​the pit accounts for 5% of the total area of ​​the current collector.

[0070] The coating structure comprises, from the inside out, a first positive electrode active material layer, a second positive electrode active material layer, and a third positive electrode active material layer. The thickness of the first active material layer is 85 μm, the thickness of the second active material layer is 90 μm, and the thickness of the third active material layer is 95 μm. The preparation method of the first positive electrode active material layer, the second positive electrode active material layer, and the third positive electrode active material layer includes: mixing the positive electrode active material (ternary nickel cobalt manganese oxide material), the conductive agent (conductive carbon black), and the binder (PVDF) in a mass ratio of 93:5:2 to obtain a mixed material; thoroughly and rapidly stirring the mixed material in NMP to obtain a positive electrode slurry; and applying the positive electrode slurry to the surface of the third region in three layers.

[0071] (1) Preparation of negative electrode sheet A copper foil after laser etching is used as the negative electrode current collector, and a coating structure is provided on the surface of the negative electrode current collector. The surface of the negative electrode current collector has a concave structure, and the concave structure is distributed in a vertical array on at least one side of the surface in the thickness direction of the current collector. The diameter of the concave is about 30 μm, the depth of the concave is 1.0 μm, and the area of ​​the concave is 5% of the total area of ​​the current collector.

[0072] The coating structure comprises, from the inside out, a first negative electrode active material layer, a second negative electrode active material layer, and a third negative electrode active material layer. The thickness of the first active material layer is 80 μm, the thickness of the second active material layer is 85 μm, and the thickness of the third active material layer is 90 μm. The preparation method of the first negative electrode active material layer, the second negative electrode active material layer, and the third negative electrode active material layer includes: mixing the negative electrode active material (graphite), the conductive agent (conductive carbon black), and the binder (PVDF) in a mass ratio of 93:5:2 to obtain a mixed material; thoroughly and rapidly stirring the mixed material in NMP to obtain a negative electrode slurry; and applying the negative electrode slurry to the surface of the third region in three layers.

[0073] (3) Battery preparation The battery in this comparative example is prepared using the same method as in Example 1.

[0074] Comparative Example 2 The preparation methods of the positive and negative electrode sheets in this comparative example are generally the same as those in Example 1, except that the current collector of the positive electrode sheet is made of ordinary aluminum foil without laser etching, and the current collector of the negative electrode sheet is made of ordinary copper foil without laser etching.

[0075] The battery in this comparative example is prepared using the same method as in Example 1.

[0076] Comparative Example 3 (1) Preparation of positive electrode sheet Ordinary aluminum foil is used as the positive electrode current collector, and a coating structure is formed on the surface of the positive electrode current collector. The coating structure consists of a first positive electrode active material layer, a second positive electrode active material layer, and a third positive electrode active material layer from the inside out. The thickness of the first active material layer is 85 μm, the thickness of the second active material layer is 90 μm, and the thickness of the third active material layer is 95 μm. The preparation method of the first positive electrode active material layer, the second positive electrode active material layer, and the third positive electrode active material layer includes: mixing the positive electrode active material (ternary nickel cobalt manganese oxide material), the conductive agent (conductive carbon black), and the binder (PVDF) at a mass ratio of 93:5:2 to obtain a mixed material; thoroughly stirring the mixed material at high speed in NMP to obtain a positive electrode slurry; and applying the three-layer coating of the positive electrode slurry to the surface of the third region.

[0077] (1) Preparation of negative electrode sheet Ordinary copper foil is used as the negative electrode current collector, and a coating structure is formed on the surface of the negative electrode current collector. The coating structure consists of a first negative electrode active material layer, a second negative electrode active material layer, and a third negative electrode active material layer from the inside out. The thickness of the first active material layer is 80 μm, the thickness of the second active material layer is 85 μm, and the thickness of the third active material layer is 90 μm. The preparation method of the first negative electrode active material layer, the second negative electrode active material layer, and the third negative electrode active material layer includes: mixing the negative electrode active material (graphite), the conductive agent (conductive carbon black), and the binder (PVDF) in a mass ratio of 93:5:2 to obtain a mixed material; thoroughly stirring the mixed material at high speed in NMP to obtain a negative electrode slurry; and applying the negative electrode slurry to the surface of the third region in three layers.

[0078] (3) Battery preparation The battery in this comparative example is prepared using the same method as in Example 1.

[0079] Test Example 1 The performance of the batteries prepared in the examples and comparative examples was tested, and the test results are shown in Table 1.

[0080] The testing methods include: (1) Film resistance test: Test the film resistance of the electrode on a resistance tester.

[0081] (2) DCR test: The resistance values ​​of different groups of batteries are obtained by DCR performance test. The specific test method is as follows: At 25℃, the battery is charged to 50% SOC (State of Charge) at 0.33C constant current and constant voltage. The voltage at this time is recorded as U0. After 30 minutes, it is discharged at 2C constant current for 30 seconds. The voltage is recorded as U1. DCR=(U0-U1) / I (I is 0.33C).

[0082] (3) Capacity retention test: At 25℃, the battery is charged at a constant current of 0.33C to 4.25V, and then charged at a constant voltage of 4.25V until the current I ≤ 0.05C. The battery charging capacity is recorded as C0. After resting for 5 minutes, it is discharged at a constant current of 0.33C to 2.65V and then rested for 30 minutes. The above process is repeated 300 times to record the battery discharge capacity, which is recorded as C1. The capacity retention rate of the 300th cycle is calculated as C1 / C0. Calculations are performed with 100% accuracy.

[0083] Table 1 Based on the test results of the examples and comparative examples, the battery film fabricated with a core having a conductive layer and a current collector recess structure has lower resistance and DCR resistance, and better conductivity. Optimal conductivity and capacity retention are achieved under moderate conductive layer thickness (3mm), moderate etched pit diameter (30μm), and moderate pit depth (1.0μm). The thickness of the conductive layer and the diameter and depth of the pits affect the electronic conduction between the coating and the current collector. Small thickness / diameter / shallow depth result in less significant electronic conduction and poorer conductivity; large thickness / diameter / depth leads to a large specific surface area, which increases the electron diffusion path, causing slow lithium-ion diffusion kinetics and poorer conductivity.

[0084] It can be seen that the conductive layer of this disclosure can promote electron conduction between the coating and the current collector; the etched recessed structure on the current collector can reduce the wrinkling phenomenon of the electrode during charging and discharging, increase the contact area between the coatings of the current collector, and accelerate electron transport.

[0085] The above description is only a preferred embodiment of this disclosure. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principles of this disclosure, and these improvements and modifications should also be considered within the scope of protection of this disclosure.

Claims

1. An electrode sheet, characterized in that, The electrode includes a current collector, an active layer, and a conductive layer; the current collector is provided with a first region, a second region, and a third region along its length, with the first region and the second region distributed on both sides of the third region; the active layer is disposed on the surface of the third region on at least one side of the current collector along its thickness direction; the conductive layer is disposed on the surfaces of the first region and the second region on at least one side of the current collector along its thickness direction. Wherein, one side of the conductive layer is attached to the active layer, and the other side is close to the end of the current collector and gradually thins out in a slope shape; the thickness of the side of the conductive layer that is attached to the active layer is the same as the thickness of the active layer; The active layer includes a first active material layer disposed on the surface of at least one third region along the thickness direction of the current collector and a second active material layer disposed on the surface of the third region away from the current collector of the first active material layer. At least one side surface of the current collector in the thickness direction is provided with a plurality of recessed structures.

2. The electrode sheet according to claim 1, characterized in that, The area of ​​the first region is equal to the area of ​​the second region; The length of the first region accounts for 2.7 to 4.5% of the total length of the electrode; and / or, the length of the second region accounts for 2.7 to 4.5% of the total length of the electrode.

3. The electrode sheet according to claim 1, characterized in that, The thickness of the conductive layer at its thinnest point is 2-4 mm.

4. The electrode sheet according to claim 1, characterized in that, The thickness of the first active material layer is 80~100μm; and / or, The thickness of the second active material layer is 80~100μm.

5. The electrode sheet according to claim 1, characterized in that, The electrode also includes a third active material layer disposed on the surface of a third region on the side of the second active material layer away from the first active material layer; The thickness of the third active material layer is 80~100μm.

6. The electrode sheet according to claim 1, characterized in that, The diameter of the recessed structure is 10~50μm, and the depth of the recessed structure is 0.5~1.5μm; And / or, The total area of ​​the plurality of said recessed structures accounts for 2 to 8% of the surface area of ​​the third region.

7. The electrode sheet according to claim 1 or 6, characterized in that, The recessed structures are arranged in a vertical array on at least one surface in the thickness direction of the current collector; or, The recessed structures are distributed in a ring array on at least one side of the surface in the thickness direction of the current collector.

8. A battery, characterized in that, The battery includes a battery assembly, which includes a positive electrode and / or a negative electrode, wherein the positive electrode and / or negative electrode is the electrode as described in any one of claims 1 to 7.

9. An electrical device, characterized in that, The electrical device includes a battery, which is the battery described in claim 8.

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