Pole piece and preparation method thereof, battery monomer, battery and power utilization device

Abstract

The invention discloses a pole piece and a preparation method thereof, a battery monomer, a battery and an electric device, and belongs to the technical field of batteries. The pole piece comprises a current collector and a first insulating layer, the current collector comprises a main body part and a tab, the tab extends from a first end of the main body part, the first end is one end of the main body part along a first direction, the tab comprises a first part and a second part, and the first part is close to the main body part relative to the second part; first insulating layers are arranged on the surfaces of the two sides of the first part, and the ratio L of the thickness of the first insulating layers to the thickness of the first part is smaller than or equal to 1.3. According to the technical scheme, the reliability of the single battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a pole piece and a preparation method thereof, a battery cell, a battery, and an electrical device. Background Art

[0002] As environmental pollution becomes increasingly serious, the new energy industry has attracted more and more attention. In the new energy industry, battery technology is an important factor related to its development.

[0003] The development of battery technology needs to consider many design factors, such as energy density, cycle life, reliability, etc. The design of the pole piece in the battery cell is crucial to the reliability of the battery cell. Therefore, how to provide a pole piece to improve the reliability of the battery cell is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a pole piece to improve the reliability of a battery cell.

[0005] In order to achieve the above-mentioned objectives, the present application provides a pole piece and a preparation method thereof, a battery cell, a battery, and an electrical device.

[0006] In a first aspect, a pole piece is provided, comprising a current collector and a first insulating layer, wherein the current collector comprises a main body and a pole ear, the pole ear extending from a first end of the main body, the first end being an end of the main body along the first direction, the pole ear comprising a first part and a second part, the first part being close to the main body relative to the second part, the first insulating layer being provided on surfaces on both sides of the first part, and a ratio L of a thickness of the first insulating layer to a thickness of the first part satisfies: L≤1.3.

[0007] An embodiment of the present application provides a pole piece, which includes a current collector and a first insulating layer. The current collector includes a main body and a pole ear, the pole ear extending from a first end of the main body, and the first end is an end of the main body along a first direction. The pole ear includes a first part and a second part, the first part is closer to the main body relative to the second part, and the surfaces on both sides of the first part are provided with a first insulating layer, so that the risk of the first part overlapping with the electrode of opposite polarity can be reduced. The ratio L of the thickness of the first insulating layer to the thickness of the first part satisfies: L≤1.3, so that the first insulating layer has a smaller thickness, and the total thickness of the first insulating layer and the first part is smaller, so that it is easy to bend the pole ear. In this way, the risk of short circuit caused by the electrode assembly inserted into the battery cell after the pole ear is bent can be reduced, which is conducive to improving the reliability of the battery cell.

[0008] In a possible implementation, the ratio L of the thickness of the first insulating layer to the thickness of the first portion satisfies: L≤1. In this way, the first insulating layer has a smaller thickness, which is conducive to further reducing the risk of short circuit caused by the electrode assembly of the battery cell when the tab is bent and part of the tab is inserted into the battery cell.

[0009] In a possible implementation, L satisfies: 1 / 30≤L≤1. In this way, the first insulating layer has a suitable thickness, thereby facilitating the preparation of the first insulating layer. In addition, when the first insulating layer includes a thermoplastic polymer, L is greater than or equal to 1 / 30, and the first insulating layer has a relatively large amount of thermoplastic polymer, so that a relatively suitable content of thermoplastic polymer melts and flows to the end surface, thereby forming a relatively uniform and dense second insulating layer at the end surface.

[0010] In a possible implementation, L satisfies: 4 / 13≤L≤6 / 13. In this way, the preparation of the first insulating layer can be facilitated, and the risk of inserting the tab into the electrode assembly after bending can be further reduced.

[0011] In a possible implementation, the thickness d1 of the first insulating layer satisfies: d1≤10 μm, so that the thickness of the first insulating layer is small, which facilitates bending the first part of the pole ear. In a battery cell including the above-mentioned pole piece, the risk of short circuit caused by the electrode assembly inserted into the battery cell after the pole ear is bent can be reduced, which is conducive to improving the reliability of the battery cell.

[0012] In a possible implementation, d1 satisfies: 0.5 μm ≤ d1 ≤ 10 μm. When the thickness d1 of the first insulating layer is not less than 0.5 μm, it is helpful to reduce the difficulty of preparing the first insulating layer; when the thickness d1 of the first insulating layer is not more than 10 μm, the first insulating layer has a smaller thickness, which can further reduce the difficulty of bending the tab.

[0013] In a possible implementation, d1 satisfies: 4μm≤d1≤6μm. When the thickness d1 of the first insulating layer is not less than 4μm, it is helpful to further reduce the difficulty of preparing the first insulating layer; when the thickness d1 of the first insulating layer does not exceed 6μm, the first insulating layer has a smaller thickness, which can further reduce the difficulty of bending the tab.

[0014] In a possible implementation, the first insulating layers on both side surfaces of the first part have the same thickness. The two insulating layers on both side surfaces have the same thickness, so that the forces on both sides of the first part are relatively uniform and the preparation of the first insulating layer is also convenient.

[0015] In a possible implementation, the main body includes a coating area and a transition area, the transition area is arranged between the coating area and the tab, and the first insulating layer is arranged on the surfaces of both sides of the transition area. By providing the first insulating layer on the surface of the transition area, it is helpful to reduce the risk of short circuit caused by the transition area overlapping with the electrode of opposite polarity.

[0016] In a possible implementation, the pole piece further includes an active material layer, and the active material layer is disposed on the surface of at least one side of the coating area. The active material layer is located on the surface of at least one side of the coating area, and the active material layer will not be cut during the cutting process, which can reduce the risk of the active material layer falling off. In addition, through the provision of the active material layer, the battery cell can be charged and discharged, which is conducive to the normal operation of the battery cell.

[0017] In a possible implementation manner, the first insulating layer includes a thermoplastic polymer.

[0018] In the above technical solution, during the process of cutting the current collector to prepare the pole ear, the thermoplastic polymer in the first insulating layer changes from a solid state to a fluid state, and then flows to the exposed end surface of the current collector produced by cutting. The fluid thermoplastic polymer solidifies after cooling, and can cover the burrs and exposed end surfaces produced by cutting, thereby reducing the risk of burrs or exposed end surfaces overlapping electrodes of opposite polarity, which is beneficial to further improve the reliability of the battery cell.

[0019] In a possible implementation, the maximum particle size D of the thermoplastic polymer is 1 max Satisfaction: D 1 max ≤10μm; optionally, D 1 max Satisfaction: D 1 max In this way, the risk of scratches in the process of preparing the first insulating layer due to the large maximum particle size of the thermoplastic polymer can be reduced, and it is also beneficial to obtain a first insulating layer with a suitable thickness, thereby facilitating the preparation of the first insulating layer.

[0020] In a possible implementation, the first insulating layer also includes a binder. By setting the binder, the thermoplastic polymer can be bonded to the current collector, thereby reducing the risk of the thermoplastic polymer falling off the current collector. Optionally, based on the total mass of the first insulating layer, the mass content A of the thermoplastic polymer satisfies: 40wt%≤A≤80wt%, and the mass content B of the binder satisfies: 20wt%≤B≤40wt%. In this way, the thermoplastic polymer and the binder have a suitable mass ratio. On the one hand, the binder has a suitable mass content, and the first insulating layer will not fall off the current collector; on the other hand, the thermoplastic polymer has a suitable mass content, which is convenient for forming a uniform and dense second insulating layer on the exposed end face after cutting.

[0021] In a possible implementation, the first insulating layer further includes inorganic particles; optionally, the inorganic particles include insulating inorganic particles; optionally, the insulating inorganic particles include: at least one of boehmite and alumina. By setting the inorganic particles, the surface tension of the insulating slurry can be reduced when the thickness of the first insulating layer is small, thereby reducing the risk of the current collector being exposed. The insulating inorganic particles are non-conductive, so that the first insulating layer has good insulation. Boehmite and alumina have good heat resistance and insulation. By selecting boehmite or alumina as insulating inorganic particles and adding them to the first insulating layer, the first insulating layer has good heat resistance and insulation.

[0022] In a possible implementation, based on the total mass of the first insulating layer, the mass content C of the inorganic particles satisfies: 0<C≤40wt%; optionally, C satisfies: 30wt%≤B≤40wt%. By properly setting the mass content of the inorganic particles, it is helpful to reduce the surface tension of the insulating slurry, thereby reducing the risk of current collector exposure.

[0023] In a possible implementation, the maximum particle size D of the inorganic particles is 2 max Satisfaction: D 2 max ≤10μm; optionally, D 2 max Satisfaction: D 2 max ≤6μm. In this way, the inorganic particles have a suitable particle size, which can reduce the risk of scratches in the process of preparing the first insulating layer, and is also conducive to obtaining a first insulating layer with a suitable thickness, thereby facilitating the preparation of the first insulating layer.

[0024] In a possible implementation, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 6 μm; optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 2 μm. In this way, in the process of preparing the first insulating layer, the slurry of the first insulating layer has a suitable viscosity, which is convenient for coating the first insulating layer; and the slurry of the first insulating layer has a relatively suitable solid content, which is convenient for drying the first insulating layer.

[0025] In one possible implementation, the melting point of the thermoplastic polymer is 100°C to 200°C; in the above technical solution, the thermoplastic polymer has a suitable melting point. During the process of cutting the current collector provided with the first insulating layer, under the action of the heat generated by the cutting, the thermoplastic polymer changes from a solid state to a fluid state. The fluid thermoplastic polymer can flow to the end face of the current collector exposed after cutting and the burrs generated by the cutting, thereby facilitating the preparation of the second insulating layer.

[0026] In a possible implementation, the melting point of the thermoplastic polymer is 100° C. to 130° C. In this way, it is convenient to prepare the second insulating layer under the action of relatively low heat.

[0027] In a possible implementation, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers; optionally, the polyolefin includes polyethylene wax. By using the above thermoplastic polymer, it is beneficial to form a uniform and dense coating on the end surface and burrs of the exposed current collector after cutting.

[0028] In a possible implementation, the binder includes: at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, and sodium alginate. The above binder has good bonding properties, which facilitates bonding the thermoplastic polymer to the surface of the current collector. Optionally, the binder includes polyacrylonitrile, which has good leveling properties, which is conducive to uniformly coating the first insulating layer on the surface of the current collector.

[0029] In a possible implementation, the bonding force F between the first insulating layer and the current collector satisfies: 20 N / m ≤ F ≤ 100 N / m; optionally, F satisfies: 60 N / m ≤ F ≤ 90 N / m. In this way, the bonding between the first insulating layer and the current collector is relatively strong, which can reduce the risk of the first insulating layer falling off the current collector.

[0030] In a possible implementation, along the first direction, the ratio of the size k1 of the first insulating layer to the sum of the sizes k2 of the first insulating layer and the second portion satisfies: 0.3≤k1:k2≤0.5. When k1:k2 is not less than 0.3, it is helpful to reduce the risk of short circuit caused by the first portion overlapping with the electrode of opposite polarity; when k1:k2 is not more than 0.5, it is helpful to connect the second portion of the tab with the end cap assembly of the battery cell.

[0031] In a possible implementation, the pole piece further includes a second insulating layer, which is disposed on the first end surface, and the first end surface is the end surface of the main body at the first end. In this way, the second insulating layer can cover the first end surface, reducing the risk of the first end surface being exposed, thereby reducing the risk of a short circuit caused by the first end surface overlapping with an electrode of opposite polarity; in addition, the second insulating layer can also cover burrs generated during the cutting process, reducing the risk of the burrs overlapping with an electrode of opposite polarity.

[0032] In a possible implementation, the thickness d2 of the second insulating layer is 10 nm to 400 nm, so that the second insulating layer can better cover the burrs and the exposed first end surface with a smaller thickness. Optionally, the thickness d2 of the second insulating layer is 100 nm to 200 nm. This is conducive to further improving the covering effect of the burrs and the first end surface.

[0033] In a possible implementation, the resistance R of the second insulating layer satisfies: R≥1Ω; optionally, R satisfies: 50Ω≤R≤500Ω. The resistance of the second insulating layer satisfies the above condition, thus reducing the risk of short circuit of the battery cell caused by the end surface overlapping with the electrode of opposite polarity.

[0034] In a possible implementation, the second insulating layer is disposed on the first end surface and the second end surface, the second end surface being the end surfaces at both ends of the first part along a second direction, the second direction being different from the first direction; optionally, the second direction is perpendicular to the first direction. In this way, the second insulating layer can cover the second end surface exposed due to cutting, and the risk of the second end surface overlapping with an electrode of opposite polarity can be reduced.

[0035] In a possible implementation, the material of the second insulating layer is the same as the material of the thermoplastic polymer in the first insulating layer. This is helpful to simplify the preparation steps of the pole piece and speed up the production rhythm.

[0036] In a possible implementation, the thermoplastic polymer in the second insulating layer package is in the form of a film layer. Thus, the first insulating layer is formed by melting and solidifying the thermoplastic polymer in the second insulating layer. This helps to simplify the preparation steps of the pole piece, and the first insulating layer can be formed while cutting.

[0037] In a possible implementation, the number of layers of the pole tab is greater than or equal to 50; optionally, the thickness d3 of the first portion of each layer of the pole tab satisfies: 10 μm≤d3≤15 μm.

[0038] In a possible implementation, the pole piece includes a positive pole piece; optionally, the current collector includes aluminum foil. This is conducive to reducing the risk of overlapping of the positive pole piece and the negative pole piece, and is conducive to improving the reliability of the battery cell. In addition, it is also conducive to reducing the risk of overlapping of lithium dendrites precipitated from the positive pole piece and the negative pole piece. The current collector includes aluminum foil, so that the current collector has a relatively simple structure, which is conducive to simplifying the preparation process of the current collector.

[0039] In a possible implementation, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes at least one of a lithium transition metal oxide and an olivine structured lithium-containing phosphate; optionally, the olivine structured lithium-containing phosphate includes lithium iron phosphate; optionally, the lithium transition metal oxide includes: LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0040] In a possible implementation, the current collector includes a metal foil or a composite current collector; optionally, the metal foil includes aluminum foil or copper foil; optionally, the composite current collector includes: a polymer material base and a metal layer located on at least one surface of the polymer material base; optionally, the current collector includes aluminum foil. In this way, it is convenient to select a suitable current collector according to actual needs.

[0041] In a second aspect, a method for preparing a pole piece is provided, comprising: coating an insulating slurry on a first region of a current collector to form a first insulating layer in the first region, wherein a ratio L of a thickness d1 of the first insulating layer to a thickness of the first portion satisfies: L≤1.3; and cutting the current collector provided with the first insulating layer along a cutting line, wherein at least part of the cutting line is provided in the first region.

[0042] In the above technical solution, the thickness of the first insulating layer is relatively small, so that the portion of the pole ear produced after cutting the current collector and provided with the first insulating layer has a relatively small thickness, thereby reducing the difficulty of bending the pole ear, and can reduce the risk of short circuit and self-discharge caused by the electrode assembly inserted into the battery cell after the pole ear is bent, which is beneficial to improving the reliability of the battery cell.

[0043] In a possible implementation, L satisfies: L≤1; optionally, L satisfies: 1 / 30≤L≤1; optionally, 4 / 13≤L≤6 / 13.

[0044] In a possible implementation, the thickness d1 of the first insulating layer satisfies: d1≤10μm; optionally, d1 satisfies: 0.5μm≤d1≤10μm; optionally, d1 satisfies: 4μm≤d1≤6μm. In this way, it is easy to reduce the difficulty of preparing the first insulating layer and further reduce the difficulty of bending the tab.

[0045] In a possible implementation, the insulating slurry includes a thermoplastic polymer emulsion and a binder. Optionally, based on the total mass of the insulating slurry, the mass content A of the thermoplastic polymer in the thermoplastic polymer emulsion in the insulating slurry satisfies: 40wt%≤A≤80wt%, and the mass content B of the binder satisfies: 20wt%≤B≤40wt%. By reasonably setting the mass content of the thermoplastic polymer, it is beneficial to form a uniform and dense second insulating layer at the exposed section of the current collector produced by cutting; by reasonably setting the mass content of the binder, it is beneficial to reduce the risk of the first insulating layer falling off from the current collector.

[0046] In a possible implementation, the maximum particle size D of the thermoplastic polymer is 1 max Satisfaction: D 1 max ≤10μm; optionally, D 1 max Satisfaction: D 1 max ≤6μm. In this way, the risk of scratches in the process of preparing the first insulating layer due to the large maximum particle size of the thermoplastic polymer can be reduced, which facilitates the preparation of the first insulating layer.

[0047] In a possible implementation, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 6 μm; optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 2 μm. In this way, in the process of preparing the first insulating layer, the slurry of the first insulating layer has a suitable viscosity, which is convenient for coating the first insulating layer; and the slurry of the first insulating layer has a relatively suitable solid content, which is convenient for drying the first insulating layer.

[0048] In a possible implementation, the insulating slurry further includes inorganic particles. Inorganic particles are added to the insulating slurry, and the surface tension of the insulating slurry can be reduced during the coating process of the insulating slurry, thereby reducing the risk of the current collector being exposed due to the rupture of the insulating slurry when the coating thickness of the insulating slurry is small. Optionally, the inorganic particles include insulating inorganic particles; optionally, the insulating inorganic particles include at least one of boehmite and alumina.

[0049] In a possible implementation, based on the total mass of the insulating slurry, the mass content C of the insulating inorganic particles in the insulating slurry satisfies: 0<C≤40wt%; optionally, C satisfies: 30wt%≤B≤40wt%. By reasonably setting the mass content of the insulating inorganic particles, the risk of surface exposure of the current collector is reduced.

[0050] In a possible implementation, the maximum particle size D of the inorganic particles is 2 max Satisfaction: D 2 max ≤10μm; optionally, D 2 max Satisfaction: D 2 max ≤6μm.

[0051] In a possible implementation, the solid content E of the thermoplastic polymer emulsion satisfies: 30 wt% ≤ E ≤ 50 wt%. This facilitates the preparation of the thermoplastic polymer emulsion.

[0052] In a possible implementation, the melting point T of the thermoplastic polymer in the thermoplastic polymer emulsion is 100°C to 200°C; optionally, the melting point T is 100°C to 130°C.

[0053] In a possible implementation, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers; optionally, the polyolefin includes polyethylene wax.

[0054] In the above technical solution, the thermoplastic polymer has a suitable melting point. In the process of cutting the current collector provided with the first insulating layer, under the action of the heat generated by the cutting, the thermoplastic polymer changes from a solid state to a fluid state, and the fluid thermoplastic polymer can flow to the end face of the current collector exposed after cutting and the burrs generated by the cutting, thereby facilitating the preparation of the second insulating layer. By using the above thermoplastic polymer, it is conducive to forming a uniform and dense coating on the end face and burrs of the exposed current collector after cutting.

[0055] In a possible implementation, the binder includes at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, and sodium alginate. The above binder has good bonding properties and is convenient for bonding the thermoplastic polymer to the surface of the current collector.

[0056] In a possible implementation, coating the insulating slurry on the first region of the current collector to form the first insulating layer in the first region includes: coating the insulating slurry on the first region of the current collector by gravure coating to form the first insulating layer in the first region. The gravure coating method facilitates the preparation of a first insulating layer with a smaller thickness.

[0057] In a possible implementation, the method further includes: coating the insulating slurry on the first region of the current collector to form the first insulating layer in the first region, and then coating the active material on the second region of the current collector to form the active material layer in the second region. In this way, the influence of the thicker active material layer on the preparation of the first insulating layer can be reduced, and the first insulating layer with a smaller thickness can be prepared by gravure coating.

[0058] In a possible implementation, cutting the current collector provided with the first insulating layer along a cutting line includes: controlling a laser processing tool to cut the current collector provided with the first insulating layer along the cutting line.

[0059] In the above technical solution, the current collector is cut by laser, and more heat can be generated during the cutting process, which is conducive to the thermoplastic polymer in the first insulating layer to become a fluid state and flow to the end surface, thereby facilitating the formation of the second insulating layer.

[0060] In a third aspect, a battery cell is provided, comprising the pole piece in the first aspect and any possible implementation thereof, and / or the pole piece prepared by the method in the second aspect and any possible implementation thereof.

[0061] In a fourth aspect, a battery is provided, comprising the battery cell described in the third aspect.

[0062] In a fifth aspect, an electrical device is provided, comprising the battery described in the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0064] Figure 1 It is a schematic diagram of a pole piece before processing the pole lug according to an embodiment of the present application;

[0065] Figure 2 A schematic diagram of a pole piece according to an embodiment of the present application;

[0066] Figure 3 for Figure 2 The cross-sectional view along the AA direction in ;

[0067] Figure 4 for Figure 2 The cross-sectional view along the BB direction;

[0068] Figure 5 A schematic diagram of a method for preparing a pole piece according to an embodiment of the present application;

[0069] Figure 6 A schematic diagram of a current collector according to an embodiment of the present application;

[0070] Figure 7 A schematic diagram of a current collector coated with a first insulating layer according to an embodiment of the present application;

[0071] Figure 8 A schematic diagram of a current collector showing a cutting line according to an embodiment of the present application;

[0072] Fig. 9 A schematic diagram of a current collector coated with an active material layer according to an embodiment of the present application;

[0073] Fig.10 A schematic diagram of a battery cell according to an embodiment of the present application;

[0074] Fig.11 A schematic diagram of a battery according to an embodiment of the present application;

[0075] Fig.12 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application.

[0076] Reference numerals:

[0077] 1: pole piece; 124: cutting line; 10: current collector; 11: active material layer; 121: first insulating layer; 1211: first sub-portion; 1212: second sub-portion; 122: second insulating layer; 101: main body; 102: pole ear; 1021: first portion; 1022: second portion; 1011: coating area; 1012: transition area; 1011a: first end face; 1222a: second end face. DETAILED DESCRIPTION

[0078] The detailed description of the pole piece and its preparation method, battery cell, battery, and electrical device of the present application is specifically disclosed with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0079] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0080] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0081] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0082] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0083] The development of battery technology must consider many design factors at the same time, such as energy density, cycle life, discharge capacity, charge and discharge rate, reliability, etc. Energy density, as an important performance, is crucial for battery cells. High-capacity battery cells usually have higher energy density, and high-capacity battery cells require more pole pieces. In the process of preparing battery cells, it is necessary to wind or stack multiple layers of pole pieces (including positive pole pieces and negative pole pieces) and isolation films into electrode assemblies, and then weld and bend the pole pieces' tabs to save the space occupied by the tabs, thereby increasing the energy density of the battery cells. The pole pieces include a current collector and an active material layer and an insulating layer coated on different areas of the current collector. After the corresponding active material layer and insulating layer are coated on the current collector, the current collector coated with the active material layer and the insulating layer needs to be cut to cut out the pole pieces. After the cutting is completed, an insulating layer is set on part of the pole piece. However, the thickness of the insulating layer on the pole ear is relatively large. When there are many layers of the pole ear, the thickness of the insulating layer on the pole ear is too thick, which will make it difficult to bend the pole ear. As a result, part of the pole ear will be inserted into the electrode assembly (for example, the non-pole ear part of the pole sheet in the electrode assembly) after bending, causing short circuit and other phenomena, which is not conducive to improving the reliability of the battery cell.

[0084] In view of this, the present application provides a pole piece, which includes a current collector and a first insulating layer, wherein the first insulating layer is disposed on a portion of the surface of the pole ear of the current collector, and the ratio L of the thickness of the first insulating layer to the thickness of the current collector (the portion of the pole ear disposed with the first insulating layer) satisfies: L≤1.3. In this way, the thickness of the first insulating layer is small, and the difficulty of bending the pole ear is reduced, thereby reducing the risk of short circuit caused by inserting the pole ear into the electrode assembly, which is conducive to improving the reliability of the battery cell.

[0085] [Pole piece]

[0086] Figure 1 This is a schematic diagram of a pole piece before processing the pole lug according to an embodiment of the present application. Figure 2 is a schematic diagram of a pole piece according to an embodiment of the present application, Figure 3 for Figure 2 The cross-sectional view along the AA direction in Figure 4for Figure 2 Cross-sectional view along BB direction.

[0087] Combination Figure 1 and Figure 2 As shown, Figure 1 This is a schematic diagram of the processing of the pole piece before the pole ear. Figure 2 This is a schematic diagram of the electrode after the electrode ear is processed. Figure 1 As shown, the black dotted line is the cutting line 124 for cutting the tab. After cutting along the cutting line 124, the tab is obtained as shown in FIG. Figure 2 The pole piece 1 is shown.

[0088] Combination Figures 1 to 4 As shown, the pole piece 1 includes a current collector 10 and a first insulating layer 121 .

[0089] The current collector 10 includes a main body 101 and a tab 102 . The tab 102 extends from a first end of the main body 101 . The first end is one end of the main body 101 along a first direction.

[0090] The first direction is parallel to the plane where the current collector 10 is located, and the first direction is the direction in which the tab 102 protrudes relative to the main body 101. For example, the first direction is Figure 2 y direction in .

[0091] The tab 102 includes a first portion 1021 and a second portion 1022 . The first portion 1021 is closer to the main body 101 than the second portion 1022 . The first insulating layer 121 is disposed on surfaces of both sides of the first portion 1021 .

[0092] The first portion 1021 is connected to the second portion 1022 , and the second portion 1022 is not provided with the first insulating layer 121 , that is, the second portion 1022 is exposed.

[0093] The surfaces on both sides of the current collector 10 refer to two surfaces opposite to each other along the thickness direction of the current collector 10. The surfaces on both sides of the first portion 1021 are provided with a first insulating layer 121, that is, the first insulating layer 121 is provided on both opposite surfaces of the first portion 1021 of the tab 102 along the thickness direction.

[0094] A ratio L of the thickness d1 of the first insulating layer 121 to the thickness d3 of the first portion 1021 satisfies: L≤1.3.

[0095] L can be 1.3, 1.29, 1, 0.8, 0.6, 0.3, 0.1 or any value within the above range.

[0096] The thickness d3 of the first portion 1021 may also be referred to as the thickness of the current collector 10 .

[0097] The thickness d1 of the first insulating layer 121 is the thickness of the first insulating layer 121 on one side surface of the first portion 1021. The total thickness of the first insulating layer is the sum of the thicknesses of the first insulating layer 121 on both side surfaces. For example, the thicknesses of the first insulating layer 121 on both side surfaces of the first portion 1021 may be the same or different.

[0098] The thickness d1 of the first insulating layer 121 may refer to the average thickness of the first insulating layer 121 on one side surface of the first portion 1021. For example, the average thickness is the average of the maximum dimension and the minimum dimension in the thickness direction of the first insulating layer 121. Similarly, the thickness d3 of the first portion 1021 refers to the average thickness of the first portion 1021.

[0099] When L does not exceed 1.3, the first insulating layer 121 has a relatively small thickness, and the total thickness of the first insulating layer 121 and the first portion 1021 is also relatively small. In this way, when the number of layers of the tab 102 is large, the difficulty of bending the tab 102 can be reduced, thereby reducing the risk of inserting the tab 102 into the electrode assembly after bending, and further reducing the risk of short circuit caused by inserting the tab into the electrode assembly.

[0100] The embodiment of the present application provides a pole piece 1, which includes a current collector 10 and a first insulating layer 121. The current collector 10 includes a main body 101 and a pole ear 102, and the pole ear 102 extends from a first end of the main body 101, and the first end is an end of the main body 101 along a first direction. The pole ear 102 includes a first part 1021 and a second part 1022, and the first part 1021 is closer to the main body 101 than the second part 1022, and the first insulating layer 121 is provided on the surface of both sides of the first part 101, so that the risk of the first part 1021 overlapping with the electrode of opposite polarity can be reduced. The ratio L of the thickness d1 of the first insulating layer 121 to the thickness d3 of the first part 1021 satisfies: L≤1.3, so that the thickness of the first insulating layer 121 is small, and the total thickness of the first insulating layer 121 and the first part 1021 is also small, so that it is easy to bend the first part 1021 of the pole ear 102. In a battery cell including the pole piece 1 described above, the risk of self-discharge, short circuit, etc. caused by the electrode assembly inserted into the battery cell after the pole ear 102 is bent can be reduced, which is beneficial to improving the reliability of the battery cell.

[0101] In some embodiments, the ratio L of the thickness d1 of the first insulating layer 121 to the thickness d3 of the first portion 1021 satisfies: L≤1. In this way, the first insulating layer 121 has a smaller thickness, which is conducive to further reducing the risk of short circuit caused by the electrode assembly of the battery cell when the tab 102 is bent and part of the tab is inserted into the battery cell.

[0102] In some embodiments, L satisfies: 1 / 30≤L≤1. In this way, the first insulating layer 121 has a suitable thickness, thereby facilitating the preparation of the first insulating layer 121. In addition, when the first insulating layer 121 includes a thermoplastic polymer, L is greater than or equal to 1 / 30, and the first insulating layer 121 has a large amount of thermoplastic polymer, so that a relatively suitable amount of thermoplastic polymer melts and flows to the end surface, thereby forming a relatively uniform and dense second insulating layer at the end surface.

[0103] In some embodiments, L satisfies: 4 / 13≤L≤6 / 13. In this way, the preparation of the first insulating layer 121 can be facilitated, and the risk of bending the tab 102 and inserting it into the electrode assembly can be further reduced.

[0104] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: d1≤10 μm, for example, d1 is 0.5 μm, 1 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm or any value within the above range.

[0105] When the thickness d1 of the first insulating layer 121 does not exceed 10 μm, the total thickness of the first insulating layer 121 is relatively small. In this way, when the number of layers of the tab 102 is relatively large, the difficulty of bending the tab 102 can be reduced, thereby reducing the risk of inserting the tab 102 into the electrode assembly after bending, and further reducing the risk of short circuit caused by inserting the tab into the electrode assembly.

[0106] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: 0.5 μm≤d1≤10 μm.

[0107] When the total thickness d1 of the first insulating layer 121 is not less than 0.5 μm, the first insulating layer 121 has a certain thickness, which can reduce the difficulty of preparing the first insulating layer 121, is conducive to preparing a more uniform first insulating layer 121, and reduces the risk of partial surface exposure of the first part 1021 of the tab 102.

[0108] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: 4 μm≤d1≤6 μm. For example, d1 is 4 μm, 5 μm, 6 μm or any value within the above range.

[0109] When the thickness d1 of the first insulating layer 121 is not less than 4 μm, it is helpful to reduce the difficulty of preparing the first insulating layer 121 ; when the thickness d1 of the first insulating layer 121 does not exceed 6 μm, the first insulating layer 121 has a smaller thickness, which can further reduce the difficulty of bending the tab 102 .

[0110] In some embodiments, the first insulating layer 121 has the same thickness on both sides of the first portion 1021. The two insulating layers 121 on both sides have the same thickness, so that the forces on both sides of the first portion 1021 are relatively uniform, and the preparation of the first insulating layer 121 is also convenient.

[0111] In some embodiments, the main body 101 includes a coating area 1011 and a transition area 1012 . The transition area 1012 is disposed between the coating area 1011 and the tab 102 . The first insulating layer 121 is disposed on surfaces of both sides of the transition area 1012 .

[0112] The first insulating layer 121 may include a first sub-portion 1211 and a second sub-portion 1212 . The first sub-portion 1211 is located on a surface of the transition region 1012 of the body portion 101 , and the second sub-portion 1212 is located on a surface of the first portion 1021 of the tab 102 .

[0113] Optionally, in some embodiments, a first insulating layer 121 is disposed on a surface of one side of the transition region 1012 .

[0114] In the above embodiment, by providing the first insulating layer 121 on the surface of the transition region 1012 , it is helpful to reduce the risk of short circuit caused by the transition region 1012 overlapping with the electrode with opposite polarity.

[0115] In some embodiments, the pole piece 1 further includes an active material layer 11, and the active material layer 11 is disposed on the surface of at least one side of the coating area 1011. In this way, the active material layer 11 will not be cut during the cutting process, which can reduce the risk of the active material layer 11 falling off. In addition, through the provision of the active material layer 11, the battery cell can be charged and discharged, which is conducive to the normal operation of the battery cell.

[0116] In some embodiments, the active material layer 11 is disposed on surfaces of both sides of the coating area 1011 .

[0117] Optionally, in some embodiments, the active material layer 11 is disposed on a surface of one side of the coating area 1011 .

[0118] In some embodiments, the first insulating layer 121 includes a thermoplastic polymer.

[0119] Thermoplastic polymers may refer to polymers that soften when heated, solidify when cooled, and can soften again. For example, when heated to a certain temperature, a thermoplastic polymer changes from solid particles to a flowable state, and when cooled, it can become a layered or film-like thermoplastic polymer.

[0120] When the thermoplastic polymer in the first insulating layer 121 is heated to a certain condition, it will change from a solid state to a fluid state. In this way, in the process of cutting the current collector 10 provided with the first insulating layer 121, the fluid thermoplastic polymer can flow to the burrs generated by the cutting and the exposed end surface of the current collector 10 after cutting. After the temperature is lowered, the fluid thermoplastic polymer solidifies at the burrs and the exposed end surface to cover the burrs and the exposed end surface, thereby reducing the risk of the burrs and the exposed end surface overlapping with the electrodes of opposite polarity, which is conducive to further improving the reliability of the battery cell.

[0121] In some embodiments, the maximum particle size D of the thermoplastic polymer is 1 max Satisfaction: D 1 max ≤10μm; optionally, D 1 max Satisfaction: D 1 max ≤6μm.

[0122] D 1 max It can be 3 μm, 5 μm, 7 μm, 8 μm, 9 μm, 10 μm or any value within the above range.

[0123] In this way, the risk of scratches during the preparation of the first insulating layer 121 due to the large maximum particle size of the thermoplastic polymer can be reduced, and it is also beneficial to obtain the first insulating layer 121 with a suitable thickness, thereby facilitating the preparation of the first insulating layer 121.

[0124] In some embodiments, due to factors such as the preparation process of the thermoplastic polymer, the maximum particle size D of the thermoplastic polymer is 1 max There is a certain corresponding relationship with the volume particle size distribution Dv50 of the thermoplastic polymer, for example, the two satisfy the normal distribution or slightly deviate from the normal distribution.

[0125] In some embodiments, the first insulating layer 121 further includes a binder. In this way, during the preparation of the first insulating layer 121 , the thermoplastic polymer in the insulating slurry of the first insulating layer 121 is easily bonded to the surface of the current collector 10 , thereby reducing the risk of the thermoplastic polymer falling off from the current collector 10 .

[0126] Optionally, based on the total mass of the first insulating layer 121 , the mass content A of the thermoplastic polymer satisfies: 40 wt % ≤ A ≤ 80 wt %, and the mass content B of the binder satisfies: 20 wt % ≤ B ≤ 40 wt %.

[0127] A can be 40wt%, 50wt%, 60wt%, 70wt%, 80wt% or any value within the above range, and B can be 20wt%, 30wt%, 35wt%, 40wt% or any value within the above range.

[0128] For example, the first insulating layer 121 only includes a thermoplastic polymer and a binder, the mass content A of the thermoplastic polymer is 60wt%, and the mass content B of the binder is 40wt%; for another example, the mass content A of the thermoplastic polymer is 80wt%, and the mass content B of the binder is 20wt%.

[0129] Optionally, the first insulating layer 121 may further include substances other than the thermoplastic polymer and the binder. As an example, in this case, A may be 40 wt % and B may be 20 wt %.

[0130] In the above embodiment, the binder has an appropriate mass content, and the first insulating layer 121 will not fall off the current collector 10; the thermoplastic polymer has an appropriate mass content, which facilitates the formation of a uniform and dense second insulating layer 122 on the exposed end surface after cutting.

[0131] In some embodiments, the first insulating layer 121 further includes inorganic particles. By providing the inorganic particles, the surface tension of the insulating slurry can be reduced when the thickness of the first insulating layer 121 is small, thereby reducing the risk of the current collector 10 being exposed.

[0132] The inorganic particles may be insulating inorganic particles, or inorganic particles that are non-conductive at the operating voltage of the battery (for example, non-conductive at a voltage of 5 V). For example, the inorganic particles may have a certain dielectric constant.

[0133] Inorganic particles have certain ion transport properties, but inorganic particles are insulating at least under the operating voltage of the battery.

[0134] Optionally, the inorganic particles include insulating inorganic particles.

[0135] Optionally, the insulating inorganic particles include at least one of boehmite (γ-AlOOH) and alumina. Boehmite and alumina have good heat resistance and insulation. By selecting boehmite or alumina as the insulating inorganic particles and adding them to the first insulating layer 121, the first insulating layer 121 has good heat resistance and insulation. In addition, boehmite and alumina are easy to obtain and have low cost.

[0136] For another example, the insulating inorganic particles may also be silicon oxide, etc. The embodiments of the present application include but are not limited to the above.

[0137] In some embodiments, the inorganic particles may also be inorganic particles having a dielectric constant of 3 or higher, and may include boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon oxide SiO x (0<x≤2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), hafnium dioxide (HfO2), cerium oxide (CeO2), zirconium titanate (ZrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0<m<1, 0<n<1) and Pb(Mg3Nb 2 / 3 )O3-PbTiO3 (abbreviated as PMN-PT).

[0138] In some embodiments, the inorganic particles have the ability to transport active ions and may include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y Glass (0<x<4, 0<y<13), lanthanum lithium titanate (Li x La y TiO3, 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (Li x N y , 0<x<4, 0<y<2), SiS2 type glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4) and P2S5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7).

[0139] In some embodiments, the maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤10μm; optionally, D 2 max Satisfaction: D 2 max In this way, the inorganic particles have a suitable particle size, which can reduce the risk of scratches in the process of preparing the first insulating layer 121 , and is also conducive to obtaining the first insulating layer 121 with a suitable thickness, thereby facilitating the preparation of the first insulating layer 121 .

[0140] In some embodiments, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 6 μm. For example, Dv50 is 0.5 μm, 1 μm, 2 μm, 4 μm, 5 μm, 6 μm, or any value within the above range.

[0141] In this way, during the preparation of the first insulating layer 121 , the slurry of the first insulating layer 121 has a suitable viscosity to facilitate coating of the first insulating layer 121 ; and the slurry of the first insulating layer 121 has a relatively suitable solid content to facilitate drying of the first insulating layer 121 .

[0142] Due to the influence of factors such as the preparation process, the volume particle size distribution Dv50 of the inorganic particles is related to the maximum particle size D 2 max For example, when the volume particle size distribution Dv50 of the inorganic particles is 0.5 μm, D 2 max is about 1 μm; when the volume particle size distribution Dv50 of the inorganic particles is 2 μm, D 2 max is about 5 μm; when the volume particle size distribution Dv50 of the inorganic particles is 6 μm, D 2 max It is about 10μm.

[0143] In some embodiments, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤2 μm. In this way, the particle size of the inorganic particles is small, which facilitates separation of some impurities in the slurry of the first insulating layer 121 from the inorganic particles, thereby facilitating filtering out the impurities.

[0144] In some embodiments, based on the total mass of the first insulating layer 121, the mass content C of the insulating inorganic particles satisfies: 0<C≤40wt%. For example, C is 10wt%, 30wt%, 35wt%, 40wt% or any value in the above range. By reasonably setting the mass content of the insulating inorganic particles, it is beneficial to reduce the surface tension of the insulating slurry when the thickness of the first insulating layer 121 is small, thereby reducing the risk of the current collector 10 being exposed.

[0145] For example, in the first insulating layer 121, the mass content A of the thermoplastic polymer is 40wt%, the mass content B of the binder is 40wt%, and the mass content C of the inorganic particles is 20wt%. For another example, A is 40wt%, B is 20wt%, and C is 40wt%. The values ​​of A, B, and C can be within the above ranges, and the embodiments of the present application include but are not limited to this.

[0146] Optionally, C satisfies: 30wt%≤B≤40wt%.

[0147] In some embodiments, the melting point T of the thermoplastic polymer is 100° C. to 200° C. For example, the melting point of the thermoplastic polymer is 100° C., 110° C., 130° C., 150° C., 200° C., or any value within the above range.

[0148] The melting point of a thermoplastic polymer is the temperature at which the thermoplastic polymer changes from a solid or semi-solid state to a liquid state.

[0149] The melting point of the thermoplastic polymer is not less than 100°C, so that the risk of the thermoplastic polymer melting or flowing due to the heating of the pole piece 1 during other processing can be reduced. The melting point of the thermoplastic polymer does not exceed 200°C, so that the risk of the thermoplastic polymer not being able to be transformed into a fluid state during the cutting process can be reduced, thereby reducing the risk of not being able to form the second insulating layer 122 at the exposed end surface of the current collector 10 after cutting or the second insulating layer 122 not being uniform and dense enough. In addition, the melting point of the thermoplastic polymer does not exceed 200°C, and the thermoplastic polymer can be transformed into a fluid state under less heat, which is conducive to reducing the energy consumed in cutting.

[0150] In the above embodiment, the thermoplastic polymer has a suitable melting point. During the process of cutting the current collector 10 provided with the first insulating layer 121, the thermoplastic polymer changes from a solid state to a fluid state under the action of the heat generated by the cutting. The fluid thermoplastic polymer can flow to the end surface of the current collector 10 exposed after cutting and the burrs generated by the cutting, thereby facilitating the preparation of the second insulating layer 122.

[0151] In some embodiments, the melting point T of the thermoplastic polymer is 100° C. to 130° C. In this way, it is convenient to prepare the second insulating layer under the action of relatively low heat.

[0152] Optionally, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate, and modified polymers thereof.

[0153] Polyolefins may refer to a class of thermoplastic resins obtained by polymerizing or copolymerizing α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and certain cycloolefins. For example, polyolefins include polyethylene wax.

[0154] For example, the thermoplastic polymer includes at least one of modified polymers of polystyrene, modified polymers of polyolefin, modified polymers of polyimide, modified polymers of polyester, modified polymers of polyphenylene sulfide, modified polymers of polyaramid, modified polymers of polyamide, and modified polymers of copolymers of butyl acrylate and ethyl methacrylate.

[0155] The melting point of a thermoplastic polymer is related to the molecular weight of the thermoplastic polymer. Generally speaking, the larger the molecular weight, the higher the melting point. For the same type of thermoplastic polymer, thermoplastic polymers with different molecular weights have different melting points.

[0156] By using the above-mentioned thermoplastic polymer, it is advantageous to form a uniform and dense coating on the end surface and burrs of the exposed current collector 10 after cutting.

[0157] In some embodiments, the binder includes at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, and sodium alginate.

[0158] The above-mentioned binder has good bonding properties, which facilitates bonding the thermoplastic polymer to the surface of the current collector 10 .

[0159] Optionally, the binder is polyacrylonitrile, which has good leveling properties and is conducive to uniformly coating the first insulating layer on the surface of the current collector 10 .

[0160] In some embodiments, the bonding force F between the first insulating layer 121 and the current collector 10 satisfies: 20 N / m to 100 N / m; optionally, F satisfies: 60 N / m≤F≤90 N / m.

[0161] F can be 20 N / m, 60 N / m, 80 N / m, 100 N / m or any value within the above range.

[0162] When the bonding force between the first insulating layer 121 and the current collector 10 is 20 N / m to 100 N / m, the bonding between the first insulating layer 121 and the current collector 10 is relatively strong, which can reduce the risk of the first insulating layer 121 falling off the current collector 10 .

[0163] In some embodiments, along the first direction, the ratio of the size k1 of the first portion 1021 to the sum k2 of the sizes of the first insulating layer 121 and the second portion 1012 satisfies: 0.3≤k1:k2≤0.5. For example, k1:k2 is 0.3, 0.4, 0.5 or any value within the above range.

[0164] k2 is the sum of the size of the first insulating layer 121 and the size of the second portion 1012 along the first direction.

[0165] When k1:k2 is not less than 0.3, it is helpful to reduce the risk of short circuit caused by the first part 1021 overlapping with the electrode of opposite polarity; when k1:k2 does not exceed 0.5, it is beneficial to connect the second part 1022 of the tab 102 with the end cover assembly of the battery cell.

[0166] In some embodiments, the pole piece 1 further includes a second insulating layer 122 , and the second insulating layer 122 is disposed on the first end surface 1011 a , and the first end surface 1011 a is the end surface of the main body 101 at the first end.

[0167] The first end surface 1011a is a surface parallel to the thickness direction of the current collector 10. Figure 3 As shown, the end surface 1011a is a surface parallel to the y-direction and the z-direction.

[0168] The first end surface 1011a may be formed by the following process: Figure 1 As shown, during the cutting process of the current collector 10, the current collector 10 is cut along the cutting line 124, and the first end surface 1011a is the cut end surface of the transition zone 1012. After cutting, the current collector 10 is exposed at the first end surface 1011a, and burrs may be generated.

[0169] In the above embodiment, the second insulating layer 122 can cover the first end surface 1011a, reducing the risk of the first end surface 1011a being exposed, thereby reducing the risk of a short circuit caused by the first end surface 1011a overlapping with an electrode of opposite polarity; in addition, the second insulating layer 122 can also cover the burrs generated by the cutting process, reducing the risk of the burrs overlapping with the electrode of opposite polarity.

[0170] In some embodiments, the thickness d2 of the second insulating layer 122 is 10 nm to 400 nm. For example, d2 is 10 nm, 30 nm, 100 nm, 120 nm, 160 nm, 200 nm, 300 nm, 350 nm, 400 nm or any value within the above range.

[0171] Optionally, the thickness d2 of the second insulating layer 122 is related to the thickness d1 of the first insulating layer 121. For example, when the first insulating layer 121 includes a thermoplastic polymer, the greater the thickness d1 of the first insulating layer 121, the more thermoplastic polymers there are in the first insulating layer 121, the greater the thickness d2 of the second insulating layer 122, and the more conducive it is to form a uniform and dense second insulating layer 122.

[0172] The thickness d2 of the second insulating layer 122 is an average thickness of the second insulating layer 122. For example, the thickness d2 is an average value of the maximum dimension and the minimum dimension of the second insulating layer 122 in the thickness direction.

[0173] The thickness d2 of the second insulating layer 122 can be measured in the following manner: photograph the first end surface 1011a of the pole piece 1 using a scanning electron microscope (SEM), and measure the thickness d2 of the second insulating layer 122 using the obtained image.

[0174] In the above embodiment, the second insulating layer 122 can better cover the burrs and the first end surface 1011 a with a relatively small thickness.

[0175] Optionally, the thickness d2 of the second insulating layer 122 is 100 nm to 200 nm. In this way, the second insulating layer 122 has a relatively large thickness, which is beneficial to further improve the covering effect on the burrs and the first end surface 1011 a.

[0176] In some embodiments, the resistance R of the second insulating layer 122 satisfies: R≥1Ω. For example, R is 1Ω, 5Ω, or 10Ω.

[0177] When the resistance of the second insulating layer 122 is greater than 1Ω, even in some extreme cases, when the first end face 1011a overlaps with the electrode of opposite polarity, the battery cell will not have an internal short circuit due to the second insulating layer 122 having a certain resistance, thereby reducing the risk of short circuit or even explosion caused by the internal short circuit.

[0178] Optionally, the resistance R of the second insulating layer 122 satisfies: 50Ω≤R≤500Ω. In this way, when the second insulating layer 122 has a small thickness, the risk of short circuiting the battery cell due to the overlap of the first end surface 1011a with the electrode of opposite polarity can be reduced.

[0179] In some embodiments, the second insulating layer 122 is disposed on the first end surface 1011a and the second end surface 1222a. The second end surface 1222a is the end surfaces at both ends of the first portion 1021 along a second direction, and the second direction is different from the first direction.

[0180] In the case where the pole piece 1 includes a plurality of pole tabs 102, the second direction may be the arrangement direction of the plurality of pole tabs 102. Figure 2 As shown, the second direction is the x direction.

[0181] In the process of cutting the current collector 10 along the cutting line 124 to prepare the tab 102, the cutting tool passes through the area of ​​the second sub-portion 1212 of the first insulating layer 121 (also referred to as the area of ​​the first portion 1021 of the tab 102), and after cutting, the second end surface 1222a is exposed. By providing the first insulating layer 121 at the second end surface 1222a, the risk of the second end surface 1222a overlapping with the electrode of opposite polarity can be reduced.

[0182] Optionally, the second direction is perpendicular to the first direction.

[0183] In the above embodiment, the second insulating layer 122 can cover the second end surface 1222a exposed due to cutting, which can reduce the risk of the second end surface 1222a overlapping with the electrode with the opposite polarity.

[0184] Optionally, the resistance of the second end surface 1222 a provided with the second insulating layer 122 is the same as the resistance of the first end surface 1011 a provided with the second insulating layer 122 .

[0185] In some embodiments, the material of the second insulating layer 122 is the same as the material of the thermoplastic polymer in the first insulating layer 121. This is helpful to simplify the preparation steps of the pole piece 1 and speed up the production rhythm.

[0186] For example, the current collector 10 coated with the active material layer 11 may be cut first, and then a hot melt tool (such as a hot melt gun, a hot melt coater, etc.) may be used to prepare the second insulating layer 122 at the first end face 1011a and the second end face 122a, and the first insulating layer 121 may be prepared at the transition region 1012 and the first portion 1021 of the tab 102. In this way, the first insulating layer 121 and the second insulating layer 122 may be prepared simultaneously in one step.

[0187] For another example, the active material layer 11 and the first insulating layer 121 are first prepared on the current collector 10, and the second insulating layer 122 is simultaneously prepared during the cutting process. In this way, the tab 102 can be produced by cutting in one step, and the second insulating layer 122 can be simultaneously prepared.

[0188] In some embodiments, the thermoplastic polymer in the second insulating layer 122 is in the form of a film layer. In other words, the second insulating layer 122 includes a thermoplastic polymer in the form of a film layer.

[0189] In the above embodiment, the second insulating layer 122 is formed by melting and solidifying the thermoplastic polymer in the first insulating layer 121. After the thermoplastic polymer in the first insulating layer 121 becomes fluid, it flows to the first end face 1011a and the second end face 1222a, and solidifies at the first end face 1011a and the second end face 1222a to form the second insulating layer 122. In this way, it is helpful to simplify the preparation steps of the pole piece 1, and the second insulating layer 122 can be formed while cutting.

[0190] In the first insulating layer 121, at least some of the granular thermoplastic polymers are retained, for example, at a position away from the cutting line, the thermoplastic polymers are particles protruding from the current collector. In the second insulating layer 122, the thermoplastic polymers are in the form of a film layer and have almost no particle shape.

[0191] The particulate thermoplastic polymer may have various shapes, such as sphere, rod, or lamellar. The particulate thermoplastic polymer herein means that the thermoplastic polymer has not become a fluid state, but is in a solid state.

[0192] Before cutting the first insulating layer 121, the thermoplastic polymer in the first insulating layer 121 is in a granular state. During the cutting process of the first insulating layer 121, part of the thermoplastic polymer in the first insulating layer 121 changes from a solid state to a fluid state (for example, the thermoplastic polymer near the cutting line 124 changes to a fluid state), and the other part of the thermoplastic polymer remains in a solid granular state.

[0193] In some embodiments, the number of layers of the tab 102 is greater than or equal to 50. Optionally, the thickness d3 of the first portion 1021 of each layer of the tab 102 satisfies: 10 μm ≤ d3 ≤ 15 μm. In this way, the total thickness of the tab is not less than 500 μm. Although the total thickness of the tab is relatively thick, due to the small thickness of the first insulating layer 121, after being prepared into a battery cell, the probability of the tab being bent and inserted into the electrode assembly is greatly reduced.

[0194] The number of layers of the tabs 102 may be 50, 60, 80, 100 or a greater number. As the number of layers of the tabs 102 increases, the capacity of the battery cell also increases.

[0195] In some embodiments, the electrode sheet 1 includes a positive electrode sheet. Optionally, the current collector includes aluminum foil. In this way, the electrode sheet 1 is a positive electrode sheet, which is conducive to reducing the risk of overlapping the positive electrode sheet and the negative electrode sheet, and is conducive to improving the reliability of the battery cell. In addition, it is also conducive to reducing the risk of overlapping the lithium dendrites precipitated from the positive electrode sheet and the negative electrode sheet.

[0196] In some embodiments, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes at least one of a lithium transition metal oxide and an olivine-structured lithium-containing phosphate.

[0197] Optionally, the lithium-containing phosphate with an olivine structure includes lithium iron phosphate. In this way, the battery cell prepared from the pole piece has higher reliability.

[0198] The general formula of the lithium-containing phosphate with olivine structure can be Li a A x Mn 1-y B y P 1-z C z O 4-n D n , wherein 0<a≤1.1, 0.001≤x≤0.1, 0.001≤y<0.5, 0.001≤z≤0.1, 0.001≤n≤0.1, A includes one or more of Zn, Al, Na, K, Mg, Nb, Mo and W, B includes one or more of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, C includes one or more of B, S, Si and N, and D includes one or more of S, F, Cl and Br.

[0199] The olivine-structured lithium-containing phosphate may further include at least one of lithium manganese phosphate and lithium manganese iron phosphate.

[0200] Optionally, the lithium transition metal oxide includes: LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811). In this way, the battery cell prepared from the pole piece can have a higher capacity.

[0201] The lithium transition metal oxide may also include other ternary materials, such as NCM622. The lithium-containing transition metal oxide may also include lithium-rich manganese-based materials and the like.

[0202] The battery will be accompanied by the deintercalation and consumption of Li during the charging and discharging process. The molar content of Li is different when the battery is discharged to different states. The above definition of a includes the molar content of Li under different charging and discharging states of the battery (usually the battery voltage is between 2-5V). In the enumeration of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after the charge and discharge cycle. In the enumeration of positive electrode materials in this application, the molar content of O is only a theoretical state value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0203] In some embodiments, the current collector 10 includes a metal foil or a composite current collector, so that the material of the current collector 10 can be easily set according to actual needs.

[0204] Optionally, the metal foil includes aluminum foil or copper foil.

[0205] Optionally, the composite current collector includes: a polymer material base layer and a metal layer located on at least one surface of the polymer material base layer.

[0206] Combination of the above Figures 1 to 4 The technical solution of the pole piece is explained below. Figure 5 The preparation method of the pole piece is described below, wherein the parts corresponding to the pole piece can be referred to above and will not be described in detail here.

[0207] [Method for preparing electrode]

[0208] Figure 5 Schematic diagram of a method for preparing a pole piece according to an embodiment of the present application. The method 200 can be used to prepare the pole piece 1 in the above embodiment. The method 200 includes the following steps.

[0209] Figure 6 Schematic diagram of a current collector according to an embodiment of the present application. Figure 6 As shown, the shape of the current collector 10 is a sheet or a rectangle. The shape and size of the current collector 10 can be set according to actual needs, and the embodiments of the present application include but are not limited to this.

[0210] Step 210 , coating an insulating paste on the first region of the current collector 10 to form a first insulating layer 121 in the first region, wherein a ratio L of a thickness d1 of the first insulating layer 121 to a thickness d3 of the first portion 1021 satisfies: L≤1.3.

[0211] Specifically, the insulating slurry is coated on surfaces of both sides of the first region of the current collector 10 .

[0212] Figure 7 Schematic diagram of a current collector coated with a first insulating layer according to an embodiment of the present application. Figure 7 As shown, an insulating slurry is coated on the first region of the current collector 10 to obtain the current collector 10 provided with the first insulating layer 121 .

[0213] The size of the first area can be set according to actual needs. In the embodiment of the present application, the first area corresponds to the transition area 1012 of the main body 101 of the pole piece 1 and the first part 1021 of the pole ear 102 .

[0214] Step 220 , cutting the current collector 10 provided with the first insulating layer 121 along the cutting lines 124 , wherein at least a portion of the cutting lines 124 are provided in the first region.

[0215] Figure 8 FIG. 1 is a schematic diagram of a current collector showing a cutting line according to an embodiment of the present application. Figure 8 As shown, the current collector 10 is cut along the cutting line 124 to obtain Figures 2 to 4 The pole piece 1 is shown.

[0216] In the above technical solution, the thickness of the first insulating layer 121 is relatively small, so that the portion of the pole ear 102 provided with the first insulating layer 121 produced after cutting the current collector 10 has a relatively small thickness, so that the difficulty of bending the pole ear 102 is reduced, and the risk of short circuit and self-discharge caused by the electrode assembly of the battery cell after the pole ear 102 is bent and inserted into the battery cell can be reduced, which is beneficial to improving the reliability of the battery cell.

[0217] In some embodiments, L satisfies: L≤1; optionally, L satisfies: 1 / 30≤L≤1; optionally, L satisfies: 4 / 13≤L≤6 / 13.

[0218] In some embodiments, the thickness d1 of the first insulating layer satisfies: d1≤10μm; optionally, d1 satisfies: 0.5μm≤d1≤10μm; optionally, d1 satisfies: 4μm≤d1≤6μm. In this way, the difficulty of preparing the first insulating layer 121 and the difficulty of bending the tab 102 are further reduced.

[0219] In some embodiments, the insulating paste includes a thermoplastic polymer emulsion and a binder.

[0220] The thermoplastic polymer emulsion may be a solution of a thermoplastic polymer mixed with water.

[0221] The thermoplastic polymer emulsion and the binder are liquids, and the liquid thermoplastic polymer emulsion and the binder can be evenly mixed in a relatively short time, which is beneficial to reducing the preparation time of the insulating slurry.

[0222] Optionally, the insulating paste only includes a thermoplastic polymer emulsion and a binder. In this way, the insulating paste has a relatively simple formula, which is convenient for reducing the complexity of production.

[0223] Optionally, based on the total mass of the insulating paste, the mass content A of the thermoplastic polymer in the thermoplastic polymer emulsion in the insulating paste satisfies: 40wt%≤A≤80wt%, and the mass content B of the binder in the insulating paste satisfies: 20wt%≤B≤40wt%. For example, A is 40wt%, 60wt%, 80wt% or any value within the above range, and B is 20wt%, 35wt%, 40wt% or any value within the above range.

[0224] By properly setting the mass content of the thermoplastic polymer, it is helpful to form a uniform and dense second insulating layer 122 at the exposed end surface of the current collector produced by cutting; by properly setting the mass content of the binder, it is helpful to reduce the risk of the first insulating layer 121 falling off from the current collector 10.

[0225] In some embodiments, the maximum particle size D of the thermoplastic polymer is 1 max Satisfaction: D 1 max ≤10μm; optionally, D 1 max Satisfaction: D 1 max ≤6μm.

[0226] In some embodiments, the insulating paste further includes inorganic particles.

[0227] Adding inorganic particles to the insulating slurry can reduce the surface tension of the insulating slurry during the coating process of the insulating slurry, thereby reducing the risk of the current collector 10 being exposed due to rupture of the insulating slurry when the coating thickness of the insulating slurry is small.

[0228] Optionally, based on the total mass of the insulating paste, the mass content C of the inorganic particles in the insulating paste satisfies: 0<C≤40wt%, and C may be 20wt%, 30wt%, 40wt% or any value within the above range.

[0229] By properly setting the mass content of the insulating inorganic particles, the risk of surface exposure of the current collector 10 can be reduced.

[0230] In some embodiments, the maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤10μm; optionally, D 2 max Satisfaction: D 2 max In this way, the inorganic particles have a suitable particle size, which can reduce the risk of scratches in the process of preparing the first insulating layer 121 and facilitate the first insulating layer 121 to have a suitable thickness, thereby facilitating the preparation of the first insulating layer 121.

[0231] For example, when the maximum particle size of the inorganic particles is greater than 10 μm and the thickness of the first insulating layer 121 to be prepared is less than 10 μm, some inorganic particles protrude from the first insulating layer 121 , which is not conducive to controlling the thickness of the first insulating layer 121 .

[0232] Optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 6 μm; Optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 2 μm. In this way, in the process of preparing the first insulating layer 121, the insulating slurry has a suitable viscosity, which is convenient for coating the insulating slurry; and the insulating slurry has a relatively suitable solid content, which is convenient for drying the first insulating layer 121.

[0233] In some embodiments, the volume particle size distribution Dv50 of the inorganic particles is 1 μm, so that the insulating slurry has a relatively suitable fineness, which facilitates obtaining a first insulating layer with a suitable thickness.

[0234] In some embodiments, the fineness of the insulating paste is about 10 μm, so that a relatively uniform first insulating layer 121 with a suitable thickness can be obtained.

[0235] In some embodiments, the solid content E of the thermoplastic polymer emulsion satisfies: 30 wt % ≤ E ≤ 50 wt %.

[0236] Solid content can refer to the mass percentage of the remaining part of the emulsion after drying under specified conditions. For example, the solid content can be measured by drying the emulsion to constant weight at 100°C using a solid content meter. In the process of preparing a thermoplastic polymer emulsion, the solid content of the thermoplastic polymer emulsion can be calculated by the mass of the thermoplastic polymer and the mass of the added solvent.

[0237] Setting the solid content E of the thermoplastic polymer emulsion to meet the above conditions facilitates the preparation of the thermoplastic polymer emulsion.

[0238] In some embodiments, the melting point of the thermoplastic polymer in the thermoplastic polymer emulsion is 100°C to 200°C; optionally, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers.

[0239] In the above technical solution, the thermoplastic polymer has a suitable melting point. In the process of cutting the current collector 10 provided with the first insulating layer 121, under the action of the heat generated by the cutting, the thermoplastic polymer changes from a solid state to a fluid state, and the fluid thermoplastic polymer can flow to the end face of the current collector 10 exposed after cutting and the burrs generated by cutting, thereby facilitating the preparation of the second insulating layer 122. By using the above thermoplastic polymer, it is beneficial to form a uniform and dense coating on the end face and burrs of the exposed current collector 10 after cutting.

[0240] In some embodiments, the binder includes at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, and sodium alginate. The above binder has good bonding properties, which facilitates bonding the thermoplastic polymer to the surface of the current collector 10.

[0241] Optionally, the binder is polyacrylonitrile, which has good leveling properties and is conducive to uniformly coating the first insulating layer on the surface of the current collector 10 .

[0242] In some embodiments, step 210 includes: coating the insulating slurry on the first region of the current collector 10 by gravure coating to form the first insulating layer 121 in the first region. The gravure coating method facilitates the preparation of the first insulating layer 121 with a smaller thickness.

[0243] As an example, a gravure coater may be used for gravure coating, for example, the gravure coater includes a gravure roller, a pressure roller and a scraper, and the first insulating layer 121 is coated by the cooperation of the gravure roller, the pressure roller and the scraper.

[0244] In some embodiments, the method 200 further includes: after step 210 , coating an active material on the second region of the current collector 10 to form an active material layer 11 on the second region.

[0245] Specifically, the active material is coated on the surfaces of both sides of the second region.

[0246] Fig. 9 Schematic diagram of a current collector coated with an active material layer according to an embodiment of the present application. Fig. 9 As shown, an active material is coated in the second region of the current collector 10 to obtain a current collector 10 provided with an active material layer 11 .

[0247] The second region of the current collector 10 may be a region set according to actual needs. In the embodiment of the present application, the second region corresponds to the coating region 1011 of the main body 101 of the pole piece 1 .

[0248] The thickness of the active material layer 11 may be several tens of micrometers, which is greater than the thickness of the first insulating layer 121 .

[0249] In the above embodiment, since the thickness of the active material layer 11 is greater than the thickness of the first insulating layer 121, preparing the active material layer 11 after step 220 can reduce the impact of the thicker active material layer 11 on the preparation of the first insulating layer 121, making it easier to prepare the thinner first insulating layer 121 by gravure coating.

[0250] In some embodiments, step 230 includes: controlling a laser processing tool to cut the current collector provided with the first insulating layer 121 along a cutting line 124 .

[0251] In the above embodiment, the current collector 10 is cut by laser, and more heat can be generated during the cutting process, which is conducive to the thermoplastic polymer in the first insulating layer 121 to become a fluid state and flow to the exposed end surface of the current collector 10, thereby facilitating the formation of the second insulating layer 122.

[0252] The operating parameters of the laser processing tool can be set according to actual needs. For example, different powers, frequencies, and feed speeds can be set according to the type of thermoplastic polymer.

[0253] [Positive electrode]

[0254] The electrode sheet 1 in the embodiment of the present application may be a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector.

[0255] The positive electrode current collector may be a metal foil or a composite current collector. For example, the positive electrode current collector may be an aluminum foil.

[0256] The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0257] The positive electrode film layer includes a positive electrode active material. The positive electrode active material can be a positive electrode active material for a battery known in the art. For example, the positive electrode active material is lithium iron phosphate, a ternary material, a lithium-rich manganese-based material, and the like.

[0258] The positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0259] The positive electrode film layer may also optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0260] [Negative electrode]

[0261] The electrode sheet 1 in the embodiment of the present application may be a negative electrode sheet, and the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector.

[0262] The negative electrode current collector may be a metal foil or a composite current collector. The negative electrode current collector may be a copper foil. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0263] The negative electrode film layer includes a negative electrode active material. The negative electrode active material may be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0264] The negative electrode film layer may also optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0265] [Electrolytes]

[0266] The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode. The present application embodiment has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0267] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0268] The electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0269] The solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0270] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and may also include performance additives that can improve certain battery properties, such as improving battery overcharge performance, improving battery high temperature or low temperature performance, etc.

[0271] [Isolation film]

[0272] The separator is used to separate the positive electrode sheet from the negative electrode sheet. The embodiment of the present application has no particular limitation on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0273] The material of the isolation membrane may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0274] The positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly through a winding process or a lamination process.

[0275] [Battery Cell]

[0276] An embodiment of the present application provides a battery cell, including the pole piece 1 in the above embodiment, and / or a pole piece prepared by the method in the above embodiment.

[0277] The embodiment of the present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. The battery cell may be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, a magnesium-ion battery, etc.

[0278] Fig.10 Schematic diagram of a battery cell according to an embodiment of the present application. Fig.10 As shown, the battery cell 3 is a square battery cell and includes a housing 31 , an end cap assembly 32 and an electrode assembly 33 disposed in the housing 31 .

[0279] The electrode assembly 33 can be made of a positive electrode sheet, a negative electrode sheet and a separator by a winding process or a lamination process. In some embodiments, the positive electrode sheet is the electrode sheet 1 in the embodiment of the present application.

[0280] The end cap assembly 32 includes an electrode terminal 322, such as Fig.10 As shown, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0281] The battery cell 3 further includes a current collecting member 34, which is used to connect the pole ear portion 331 of the electrode assembly 33 and the electrode terminal 322. For example, when the pole piece 1 of the embodiment of the present application is a positive pole piece, one current collecting member 34 is used to connect the positive pole ear (which may also be the pole ear 102 of the pole piece 1) and the positive electrode terminal, and the other current collecting member 34 is used to connect the negative pole ear and the negative electrode terminal.

[0282] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more. The specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0283] [Battery]

[0284] An embodiment of the present application provides a battery, comprising the battery cell in the above embodiment. Fig.11 Schematic diagram of a battery according to an embodiment of the present application. Fig.11 As shown, the battery 5 may include a plurality of battery cells (not shown in the figure).

[0285] The battery cells 3 can directly form the battery 5 , or can first form a battery module, and then multiple battery modules form the battery 5 .

[0286] [Electrical devices]

[0287] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0288] Fig.12 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application. Fig.12 As shown, the present application provides an electrical device 6, including the battery in the above embodiment.

[0289] Optionally, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc. The embodiments of the present application include but are not limited to these.

[0290] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0291] [Example]

[0292] Example 1

[0293] In Example 1, the structure of the pole piece 1 can be seen in Figure 2 As shown. The first insulating layer 121 includes a thermoplastic polymer and a binder. The insulating paste of the first insulating layer 121 includes a thermoplastic polymer emulsion and a binder. Based on the total mass of the insulating paste, the mass content A of the thermoplastic polymer in the thermoplastic polymer emulsion in the insulating paste is 70wt%, and the mass content B of the binder in the insulating paste is 30wt%. The thickness d1 of the first insulating layer 121 is 4μm, the thickness d3 of the first part 1021 of the tab 102 is 13μm, and the material of the thermoplastic polymer is polyethylene wax with a melting point of 130°C.

[0294] Embodiment 2-7

[0295] The difference between Embodiment 2-7 and Embodiment 1 is that the total thickness of the first insulating layer 121 is different; accordingly, the thickness of the second insulating layer 122 is different. Specific parameters can be seen in Table 1.

[0296] Embodiment 8-9

[0297] The difference between Embodiments 8-9 and Embodiment 1 is that the mass content A of the thermoplastic polymer in the insulating paste of the first insulating layer 121 is different. Accordingly, the mass content B of the binder in the insulating paste is also different.

[0298] Examples 10-12

[0299] The difference between Examples 10-12 and Example 1 is that the thermoplastic polymer in the thermoplastic polymer emulsion is different. The thermoplastic polymer in Example 12 is polyester, and the melting point of polyester is 220°C.

[0300] Examples 13-15

[0301] The difference between Examples 13 to 15 and Example 1 is that the insulating paste of the first insulating layer 121 further includes insulating inorganic particles.

[0302] Example 16

[0303] The difference between Example 16 and Example 1 is that the adhesive is different.

[0304] Examples 17-18

[0305] The difference between Embodiments 17-18 and Embodiment 1 is that along the first direction, the ratio k1:k2 of the size k1 of the first portion 1021 of the pole tab 102 to the size k2 of the pole tab 102 is different.

[0306] Embodiment 19

[0307] The difference between Example 19 and Example 1 is that the insulating paste of the first insulating layer 121 does not include a thermoplastic polymer, the first insulating layer includes a binder and insulating inorganic particles, the thickness of the first insulating layer 121 is 4 μm, and the pole piece does not include the second insulating layer 122 .

[0308] Examples 20-21

[0309] The difference between Example 20 and Example 21 and Example 14 is that the thickness of the first insulating layer is different, and the particle size of the inorganic particles is different. In Example 20 and Example 21, the thickness of the first insulating layer is increased, and the particle size of the inorganic particles that can be selected is also increased.

[0310] Examples 22-23

[0311] The difference between Examples 22-23 and Example 1 is that the single-layer thickness of the tab and the number of tab layers are different.

[0312] Embodiment 24

[0313] The difference between Example 24 and Example 7 is that the single-layer thickness of the tab and the number of tab layers are different.

[0314] Embodiment 25

[0315] The difference between Example 25 and Example 1 is that the thickness of the first insulating layer and the single-layer thickness of the tab are different.

[0316] Embodiment 26

[0317] The difference between Example 26 and Example 2 is that the single layer thickness of the tab is different.

[0318] Embodiment 27

[0319] The difference between Example 27 and Example 5 is that the particle size of the thermoplastic polymer is different.

[0320] Embodiment 28

[0321] The difference between Example 28 and Example 6 is that the particle size of the thermoplastic polymer is different.

[0322] In Examples 1-28, the first insulating layer 121 on both side surfaces of the current collector has the same thickness.

[0323] Comparative Example 1

[0324] The difference between Comparative Example 1 and Example 1 is that the insulating paste of the first insulating layer 121 does not include a thermoplastic polymer, the thickness of one side of the first insulating layer 121 is 20 μm (the total thickness is 40 μm), and the pole piece does not include the second insulating layer 122. The insulating paste includes boehmite and a binder, the mass ratio of boehmite to the binder is 70:30, and the binder is polyvinylidene fluoride (PVDF).

[0325] Comparative Example 2

[0326] The difference between Comparative Example 2 and Example 1 is that the thickness of one side of the first insulating layer 121 is 20 μm (the total thickness is 40 μm).

[0327] Comparative Example 3

[0328] The difference between Comparative Example 3 and Comparative Example 1 is that the single-layer thickness of the tab is different.

[0329] In Table 1, d1 is the thickness of the first insulating layer 121, T is the melting point of the thermoplastic polymer in the first insulating layer 121, A is the mass content of the thermoplastic polymer in the insulating paste of the first insulating layer 121, B is the mass content of the binder in the insulating paste of the first insulating layer 121, C is the mass content of the insulating inorganic particles in the insulating paste of the first insulating layer 121, F is the bonding force between the first insulating layer 121 and the current collector 10, d2 is the thickness of the second insulating layer 122, R is the resistance of the second insulating layer 122, and k1:k2 is the ratio of the size k1 of the first insulating layer along the first direction to the sum k2 of the size of the first insulating layer and the size of the second part 1012.

[0330] In Table 2, whether there is a short circuit can reflect the state of the thermoplastic polymer at the end surface, that is, whether the second insulating layer is completely provided at the end surface, and the short circuit is not caused by the insertion of the tab into the electrode assembly.

[0331]

[0332]

[0333] Table 2 Experimental results of comparative examples and embodiments

[0334]

[0335]

[0336] [Preparation of battery cells]

[0337] (1) Prepare insulation slurry

[0338] Thermoplastic polymer emulsion, insulating inorganic particles (optional) and binder are mixed in a certain proportion, and the solvent is added and stirred evenly. The slurry viscosity is about 300mPa·s. The solvent is water. The specific thermoplastic polymer and the ratio of thermoplastic polymer emulsion, dispersant (or insulating inorganic particles) and binder can be seen in Table 1.

[0339] (2) Coating and drying

[0340] The insulating slurry was coated on the aluminum foil by gravure coating, with a coating width of 10 mm, and a width of 30 μm was reserved for preparing the tab blank foil. After oven drying at 100°C, the thickness of the first insulating layer after drying is shown in Table 1. The positive electrode slurry was then evenly coated on the aluminum foil, and dried in an oven at 100°C to obtain a positive electrode active material layer. Among them, the positive electrode active material in the positive electrode slurry is lithium iron phosphate.

[0341] (3) Laser die cutting

[0342] The above product is rolled and cut by using laser to obtain positive electrode sheets, wherein the laser power is 20W, the frequency is 100kHz, and the tape speed is 30m / min.

[0343] (4) Preparation of battery cells

[0344] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order so that the separator is located between the positive electrode sheet and the negative electrode sheet and can separate the positive electrode sheet from the negative electrode sheet; then the stacked components are wound up and placed in a shell, and after drying, the electrolyte is injected, and after packaging, a lithium-ion battery cell is obtained.

[0345] It should be noted that, for Example 19 and Comparative Example 1, the insulating slurry does not include a thermoplastic polymer emulsion. For Comparative Example 1, Comparative Example 2 and Comparative Example 3, the first insulating layer is not prepared by gravure coating, but by extrusion coating.

[0346] [Confirmation of the first insulating layer]

[0347] Use a scanning electron microscope to observe the surface of the pole piece to check whether there is a first insulating layer on the surface. Cut the pole piece open, use a scanning electron microscope to photograph the cross section of the pole piece, and observe the thickness of the first insulating layer based on the photographed photos.

[0348] [Confirmation of the second insulating layer]

[0349] A scanning electron microscope (SEM) is used to observe the end face to check whether there is a second insulating layer at the end face; in addition, the thickness of the second insulating layer can also be observed through photos taken by the scanning electron microscope.

[0350] [Overlapping Fully Charged Anode Test]

[0351] Use the laser die-cut end face to overlap the fully charged anode and observe whether there is a short circuit.

[0352] [Test of inserting the tab into the electrode assembly]

[0353] Computed tomography (CT) is used to detect whether the tabs in the battery cells are inserted into the electrode assembly.

[0354] [Test of Adhesion]

[0355] Select a plate-like material with a flat surface as the first substrate, stick one side of the double-sided tape on the surface of the first substrate, and stick the other side of the double-sided tape on the first insulating layer on one side of the pole piece. Select a plate with a sticky coating area as the second substrate, and stick the second substrate to the first insulating layer on the other side of the pole piece. At this time, the pole piece is located between the first substrate and the second substrate. Fix the same side of the first substrate and the second substrate on the lower and upper ends of the universal tensile testing machine for tensile testing. After the force-relative displacement curve displayed on the universal tensile testing machine runs smoothly, record the tension value and displacement value, and select a relatively stable section of the curve to calculate the bonding force, bonding force = tension / displacement.

[0356] [Test of resistance of the second insulating layer]

[0357] The resistance of the second insulating layer can be measured using an ohmmeter.

[0358] For example, one end of the ohmmeter is connected to the tab of the positive electrode sheet in the embodiment (specifically, the portion of the tab not coated with the first insulating layer), and the other end is connected to the tab of the negative electrode sheet, and the negative electrode sheet overlaps the end surface of the positive electrode sheet.

[0359] [Particle size test]

[0360] The volume particle size distribution Dv50 can be determined by a particle size analyzer-laser diffraction method. Specifically, the standard GB / T19077-2016 can be referred to, and a laser diffraction scattering particle size analyzer can be used for measurement according to the manufacturer's instructions. For example, before preparing the slurry, take an appropriate amount of inorganic particles or thermoplastic polymers, and use the Malvern 2000 (MasterSizer 2000) laser particle size analyzer to test the average volume particle size of the material. Take an appropriate amount of the sample to be tested (the sample concentration is sufficient to ensure 8-12% shading), add 20 ml of deionized water, and at the same time, ultraviolet for 5 minutes (53KHz / 120W) to ensure that the sample is completely dispersed, and then measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard. Afterwards, DV50 can be calculated or obtained according to the instrument max .

[0361] For another example, a scanning electron microscope may be used to test the pole piece to obtain an image of the region of the first insulating layer of the pole piece, and the particle size of the thermoplastic polymer or the inorganic particle may be measured based on the image.

[0362] [Confirmation of Melting Point of Thermoplastic Polymer]

[0363] The melting point of a thermoplastic polymer can be determined by a differential scanning calorimeter (DSC) device. Specifically, as an example, 8 mg of a sample is placed in a DSC device, and the temperature is increased under an N2 atmosphere and a flow rate of 50 ml / min, a heating rate of 10°C / min, and a cutoff temperature of 400°C, thereby testing the melting point of the thermoplastic polymer.

[0364] For another example, the melting point of a thermoplastic polymer can be determined according to the specific type of thermoplastic polymer. As an example, for a crystalline thermoplastic polymer, the melting point refers to the melting point of the crystalline thermoplastic polymer; for an amorphous thermoplastic polymer, the melting point refers to the glass transition temperature of the amorphous thermoplastic polymer.

[0365] [Mass ratio of thermoplastic polymer, inorganic particles and binder]

[0366] The above mass ratio can be obtained according to the mass of the thermoplastic polymer emulsion, the mass of the inorganic particles and the mass of the binder added during the preparation process.

[0367] In addition, the thermoplastic polymer, binder and inorganic particles in the pole piece can also be determined in the following way.

[0368] Scrape off the first insulating layer with a knife to form powder or block. Place about 1g of the film sample in a mold and heat it to the melting point of the thermoplastic polymer, then it can be made into a film and tested by infrared (FTIR), and the type of polymer in it can be determined by the characteristic peak. You can also use thermogravimetric infrared (TG-FTIR) to heat the film sample from room temperature to 600℃, and determine the composition of the film by its thermal decomposition temperature, weight loss ratio and product composition.

[0369] As shown in Example 1-28 and Comparative Example 1-2, when the ratio of the thickness of the first insulating layer to the thickness of the first portion of the tab is less than or equal to 1.3, the thickness of the first insulating layer is small, and the sum of the thickness of the first insulating layer and the first portion is small. When the number of tabs is large, the tab will not be inserted into the electrode assembly. Therefore, the embodiment of the present application can reduce the risk of the tab being inserted into the electrode assembly.

[0370] As shown in Examples 1-7, as the thickness of the first insulating layer increases, the thickness of the second insulating layer also gradually increases, and the bonding force between the current collector and the first insulating layer gradually decreases. By reasonably setting the thickness of the first insulating layer, a second insulating layer with a relatively suitable thickness can be obtained, and the second insulating layer has a suitable resistance. In addition, when the thickness of the first insulating layer is not less than 0.5 μm, the preparation of the first insulating layer is facilitated, and the risk of the current collector being exposed due to the first insulating layer being too thin can be reduced; and a relatively uniform second insulating layer can also be obtained, reducing the risk of the second insulating layer being present at the end surface. In addition, as shown in Examples 25-26 and 1-7, the preparation of the first insulating layer is facilitated by reasonably setting the particle size of the thermoplastic polymer.

[0371] As shown in Examples 8-9, as the mass content of the thermoplastic polymer increases, more thermoplastic polymer melts and flows to the end surface during cutting, so that the second insulating layer has a greater thickness. As the mass content of the thermoplastic polymer increases, the mass content of the binder that can be added decreases. When the mass content of the binder decreases, the bonding force between the current collector and the first insulating layer decreases. The mass content of the thermoplastic polymer is reasonably set, and the second insulating layer has a suitable thickness; the mass content of the binder is reasonably set, and the current collector has a suitable bonding force with the first insulating layer.

[0372] As shown in Examples 10-11, the embodiments of the present application can be applicable to different thermoplastic polymers; as shown in Example 12, when the melting point of the thermoplastic polymer is relatively high, it is more difficult for the thermoplastic polymer to melt completely and more heat is required to melt it; therefore, there is thermoplastic polymer at some positions of the end surface, and when it is overlapped with the negative electrode plate, a short circuit occurs at some positions.

[0373] As shown in Examples 13-15, inorganic particles are added to the insulating slurry and the mass content of the inorganic particles is reasonably set, so that the current collector will not be exposed due to the first insulating layer being too thin. By reasonably setting the particle size of the inorganic particles, the preparation of the first insulating layer is facilitated.

[0374] As shown in Example 16, the present application embodiment is applicable to a variety of binders. By properly matching the binder and the thermoplastic polymer, the preparation and coating of the slurry of the first insulating layer are facilitated, and the preparation of the first insulating layer is facilitated.

[0375] As shown in Examples 17-18, the embodiments of the present application are suitable for pole pieces with k1:k2 of 0.3 to 0.5.

[0376] As shown in Example 19, although no thermoplastic polymer is added, the tab will not be inserted into the electrode assembly due to the small thickness of the first insulating layer.

[0377] As shown in Examples 20-21, the maximum particle size of the inorganic particles does not exceed the thickness of the first insulating layer, which can reduce the risk of scratches in the process of preparing the first insulating layer due to excessively large inorganic particles. By reasonably setting the particle size of the inorganic particles, the preparation of the first insulating layer is facilitated.

[0378] As the number of tab layers increases, the total thickness of the tab gradually increases, and the difficulty of bending the tab increases, so the risk of partially inserting the tab into the electrode assembly after the tab is bent increases. In the embodiments of the present application, combined with embodiments 22-24 and embodiments 27-28, when the number of tab layers is large, the tabs in the embodiments of the present application will not be inserted into the electrode assembly.

[0379] It should be noted that the above embodiments and comparative examples are described with the positive electrode sheet whose current collector is aluminum foil. The embodiments of the present application can also be applied to the positive electrode sheet whose current collector is other materials, and the negative electrode sheet. In addition, although the data is described only by taking the first insulating layer on both sides of the current collector as an example with the same thickness, the scheme of the present application is still applicable when the thickness is different. The table only shows the values ​​of part of L. When the thickness of the first insulating layer and the thickness of the first part of the pole ear (or the current collector) change, the ratio of L also changes accordingly.

[0380] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A pole piece, characterized in that: include: a current collector and a first insulating layer, in, The current collector includes a main body and a tab, the tab extends from a first end of the main body, the first end is an end of the main body along a first direction, the tab includes a first part and a second part, the first part is close to the main body relative to the second part, the first insulating layer is provided on the surfaces of both sides of the first part, and a ratio L of the thickness of the first insulating layer to the thickness of the first part satisfies: L≤1.

3.

2. The pole piece according to claim 1, characterized in that: A ratio L of the thickness of the first insulating layer to the thickness of the first portion satisfies: L≤1; optionally, L satisfies: 1 / 30≤L≤1; Optionally, L satisfies: 4 / 13≤L≤6 / 13.

3. The pole piece according to claim 1 or 2, characterized in that: The thickness d1 of the first insulating layer satisfies: d1≤10 μm; optionally, d1 satisfies: 0.5 μm≤d1≤10 μm; optionally, d1 satisfies: 4 μm≤d1≤6 μm.

4. The pole piece according to any one of claims 1 to 3, characterized in that: The thickness of the first insulating layer on both side surfaces of the first portion is the same.

5. The pole piece according to any one of claims 1 to 4, characterized in that: The main body includes a coating area and a transition area, wherein the transition area is arranged between the coating area and the tab, and the first insulating layer is arranged on surfaces of both sides of the transition area.

6. The pole piece according to claim 5, characterized in that: The pole piece further includes an active material layer, and the active material layer is disposed on a surface of at least one side of the coating area.

7. The pole piece according to any one of claims 1 to 6, characterized in that: The first insulating layer includes a thermoplastic polymer.

8. The pole piece according to claim 7, characterized in that: The maximum particle size D of the thermoplastic polymer 1 max Satisfaction: D 1 max ≤10μm; optionally, D 1 max Satisfaction: D 1 max ≤6μm.

9. The pole piece according to claim 7 or 8, characterized in that: The first insulating layer further comprises a binder; optionally, based on the total mass of the first insulating layer, a mass content A of the thermoplastic polymer satisfies: 40wt%≤A≤80wt%, and a mass content B of the binder satisfies: 20wt%≤B≤40wt%.

10. The pole piece according to any one of claims 7 to 9, characterized in that: The first insulating layer further comprises inorganic particles; optionally, the inorganic particles comprise insulating inorganic particles; optionally, the insulating inorganic particles comprise at least one of boehmite and alumina.

11. The pole piece according to claim 10, characterized in that: Based on the total mass of the first insulating layer, the mass content C of the inorganic particles satisfies: 0<C≤40wt%; optionally, C satisfies: 30wt%≤B≤40wt%.

12. The pole piece according to claim 10 or 11, characterized in that: The maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤10μm; optionally, D 2 max Satisfaction: D 2 max ≤6μm.

13. The pole piece according to any one of claims 10 to 12, characterized in that: The volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤6 μm; optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤2 μm.

14. The pole piece according to any one of claims 7 to 13, characterized in that: The melting point T of the thermoplastic polymer satisfies: 100°C≤T≤200°C; optionally, T satisfies: 100°C≤T≤130°C.

15. The pole piece according to any one of claims 7 to 14, characterized in that: The thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers; optionally, the polyolefin includes polyethylene wax.

16. The pole piece according to any one of claims 7 to 15, characterized in that: The binder comprises at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan and sodium alginate.

17. The pole piece according to any one of claims 1 to 16, characterized in that: The bonding force F between the first insulating layer and the current collector satisfies: 20 N / m≤F≤100 N / m; optionally, F satisfies: 60 N / m≤F≤90 N / m.

18. The pole piece according to any one of claims 1 to 17, characterized in that: Along the first direction, a ratio of a size k1 of the first insulating layer to a sum k2 of sizes of the first insulating layer and the second portion satisfies: 0.3≤k1:k2≤0.

5.

19. The pole piece according to any one of claims 1 to 18, characterized in that: The pole piece further includes a second insulating layer, and the second insulating layer is disposed on a first end surface, and the first end surface is an end surface of the main body at the first end.

20. The pole piece according to claim 19, characterized in that: The thickness d2 of the second insulating layer is 10 nm to 400 nm; optionally, the thickness d2 of the second insulating layer is 100 nm to 200 nm.

21. The pole piece according to claim 18 or 19, characterized in that: The resistance R of the second insulating layer satisfies: R≥1Ω; optionally, R satisfies: 50Ω≤R≤500Ω.

22. The pole piece according to any one of claims 19 to 21, characterized in that: The second insulating layer is arranged on the first end surface and the second end surface, the second end surface is the end surfaces at both ends of the first part along a second direction, and the second direction is different from the first direction; optionally, the second direction is perpendicular to the first direction.

23. The pole piece according to any one of claims 19 to 22, characterized in that: The material of the second insulating layer is the same as the material of the thermoplastic polymer in the first insulating layer.

24. The pole piece according to any one of claims 19 to 23, characterized in that: The thermoplastic polymer in the second insulating layer is in the form of a film layer.

25. The pole piece according to any one of claims 1 to 24, characterized in that: The number of layers of the pole tab is greater than or equal to 50; optionally, the thickness d3 of the first portion of each layer of the pole tab satisfies: 10 μm≤d3≤15 μm.

26. The pole piece according to any one of claims 1 to 25, characterized in that: The electrode sheet includes a positive electrode sheet; optionally, the current collector includes aluminum foil.

27. The pole piece according to claim 26, characterized in that: The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes at least one of a lithium transition metal oxide and an olivine structured lithium-containing phosphate; optionally, the olivine structured lithium-containing phosphate includes lithium iron phosphate; optionally, the lithium transition metal oxide includes: LiNi 0.8 Co 0.1 Mn 0.1 O2.

28. A method for preparing a pole piece, characterized in that: include: Coating an insulating paste on a first region of the current collector to form a first insulating layer in the first region, wherein a ratio L of a thickness d1 of the first insulating layer to a thickness of the first portion satisfies: L≤1.3; The current collector provided with the first insulating layer is cut along cutting lines, and at least a portion of the cutting lines are provided in the first region.

29. The method according to claim 28, characterized in that A ratio L of the thickness d1 of the first insulating layer to the thickness of the first portion satisfies: L≤1; optionally, L satisfies: 1 / 30≤L≤1; Optionally, L satisfies: 4 / 13≤L≤6 / 13.

30. The method according to claim 28 or 29, characterized in that The thickness d1 of the first insulating layer satisfies: d1≤10 μm; optionally, 0.5 μm≤d1≤10 μm; optionally, d1 satisfies: 4 μm≤d1≤6 μm.

31. The method according to any one of claims 28 to 30, characterized in that The insulating paste comprises a thermoplastic polymer emulsion and a binder; optionally, based on the total mass of the insulating paste, the mass content A of the thermoplastic polymer in the thermoplastic polymer emulsion in the insulating paste satisfies: 40wt%≤A≤80wt%, and the mass content B of the binder satisfies: 20wt%≤B≤40wt%.

32. The method according to claim 31, characterized in that The maximum particle size D of the thermoplastic polymer in the thermoplastic polymer emulsion is 1 max Satisfaction: D 1 max ≤10μm; optionally, D 1 max Satisfaction: D 1 max ≤6μm.

33. The method according to claim 31 or 32, characterized in that The insulating slurry further comprises inorganic particles; optionally, the inorganic particles comprise insulating inorganic particles; optionally, the insulating inorganic particles comprise at least one of boehmite and alumina.

34. The method according to claim 33, characterized in that The mass content C of the inorganic particles in the insulating paste satisfies: 0<C≤40wt%; optionally, C satisfies: 30wt%≤B≤40wt%.

35. The method according to claim 33 or 34, characterized in that The maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤10μm; optionally, D 2 max Satisfaction: D 2 max ≤6μm.

36. The method according to any one of claims 33 to 35, characterized in that The volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤6 μm; optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤2 μm.

37. The method according to any one of claims 31 to 36, characterized in that The melting point T of the thermoplastic polymer in the thermoplastic polymer emulsion satisfies: 100°C≤T≤200°C; optionally, T satisfies: 100°C≤T≤130°C.

38. The method according to any one of claims 31 to 37, characterized in that The thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers; optionally, the polyolefin includes polyethylene wax.

39. The method according to any one of claims 31 to 38, characterized in that The binder comprises at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan and sodium alginate.

40. The method according to any one of claims 28 to 39, characterized in that The step of coating an insulating slurry on a first region of the current collector to form a first insulating layer on the first region includes: The insulating slurry is coated on the first region of the current collector by gravure coating to form the first insulating layer in the first region.

41. The method according to any one of claims 28 to 40, characterized in that The method further comprises: After coating the insulating slurry on the first region of the current collector to form a first insulating layer in the first region, coating the active material on the second region of the current collector to form an active material layer in the second region.

42. The method according to any one of claims 28 to 41, characterized in that The method of cutting the current collector provided with the first insulating layer along the cutting line comprises: The laser processing tool is controlled to cut the current collector provided with the first insulating layer along the cutting line.

43. A battery cell, characterized in that: Comprising a pole piece as described in any one of claims 1-27, and / or a pole piece prepared by the method as described in any one of claims 28-42.

44. A battery, characterized in that: Comprising a battery cell as claimed in claim 43.

45. An electrical device, characterized in that: Comprising a battery as claimed in claim 44.

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