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, a first insulating layer and a second 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; a first insulating layer and a second insulating layer are arranged on the surfaces of the two sides of the first part respectively, and the thickness d2 of the second insulating layer is larger than the thickness d1 of the first insulating layer. 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, a first insulating layer and a second 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 and the second insulating layer being respectively provided on surfaces on both sides of the first part, and the thickness d2 of the second insulating layer being greater than the thickness d1 of the first insulating layer.

[0007] The embodiment of the present application provides a pole piece, which includes a current collector, a first insulating layer and a second insulating layer. The current collector includes a main body and a pole ear, and the pole ear extends 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, and the first part is closer to the main body relative to the second part. The surfaces of both sides of the first part are respectively provided with a first insulating layer and a second insulating layer, so that the risk of the first part overlapping with the electrode of opposite polarity can be reduced. The thickness d2 of the second insulating layer is greater than the thickness d1 of the first insulating layer. In this way, when the pole ear is bent, since the thickness of the second insulating layer is greater than the thickness of the first insulating layer, the side surface of the first part provided with the second insulating layer is more difficult to bend than the side surface of the first part provided with the first insulating layer. The second insulating layer can play a certain supporting role for the first insulating layer, and the space occupied by the bent pole ear in the height direction is smaller, thereby reducing the risk of self-discharge, short circuit, etc. caused by factors such as squeezing of the bent pole ear affecting the electrode assembly inserted into the battery cell, which is conducive to improving the reliability of the battery cell.

[0008] In a possible implementation, the ratio of the thickness d2 of the second insulating layer to the thickness d1 of the first insulating layer satisfies: d2 / d1≥2. In this way, the thickness of the first insulating layer and the thickness of the second insulating layer have a certain difference, and the side surface of the first part of the tab provided with the second insulating layer is more difficult to bend than the side surface of the first part provided with the first insulating layer, which is conducive to further reducing the risk of inserting the tab into the electrode assembly of the battery cell after bending.

[0009] In a possible implementation, L satisfies: the ratio of the thickness d2 of the second insulating layer to the thickness d1 of the first insulating layer satisfies: 2≤d2 / d1≤20. In this way, the difference in thickness between the first insulating layer and the second insulating layer is appropriate, which facilitates the bending of the tab.

[0010] In a possible implementation manner, the thickness d1 of the first insulating layer satisfies: 1 μm≤d1≤12 μm.

[0011] When d1 is not less than 1 μm, it is helpful to reduce the difficulty of preparing the first insulating layer; when the thickness d1 of the first insulating layer does not exceed 12 μm, the first insulating layer has a smaller thickness, which is convenient for bending the first part of the pole ear, and can further reduce the difficulty of bending the pole ear.

[0012] In a possible implementation, the thickness d2 of the second insulating layer satisfies: 10 μm≤d2≤24 μm. In this way, the second insulating layer has a suitable bending difficulty, so that the tab has a suitable shape after bending, reducing the risk of inserting the bent tab into the electrode assembly of the battery cell.

[0013] 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 surfaces of both sides of the transition area are respectively provided with the first insulating layer and the second insulating layer. By providing the first insulating layer and the second 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 with opposite polarity.

[0014] 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.

[0015] In a possible implementation manner, the first insulating layer and the second insulating layer include thermoplastic polymers.

[0016] In the above technical solution, in the process of cutting the current collector to prepare the pole ear, under the action of the heat generated by the cutting, the thermoplastic polymer in the first insulating layer and the second 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 the cutting. The fluid thermoplastic polymer solidifies after cooling, and can cover the burrs and exposed end surfaces produced by the cutting, thereby reducing the risk of burrs or exposed end surfaces overlapping electrodes of opposite polarity, which is conducive to further improving the reliability of the battery cell.

[0017] In a possible implementation, the maximum particle size D of the thermoplastic polymer is 1 max Satisfaction: D 1 max ≤12μm; 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.

[0018] In a possible implementation, based on the total mass of the first insulating layer, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%. In this way, the first insulating layer and / or the second insulating layer has a suitable mass content of the thermoplastic polymer, so that after cutting, a uniform and dense coating layer can be formed on the exposed end surface after cutting.

[0019] In a possible implementation, the melting point T of the thermoplastic polymer satisfies: 100°C ≤ T ≤ 200°C.

[0020] 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 and the second 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 formation of a coating layer at the exposed end face.

[0021] In a possible implementation, the melting point of the thermoplastic polymer is 100° C. to 130° C. In this way, it is convenient to form a coating layer on the exposed end surface under the action of relatively low heat.

[0022] In a possible implementation, the thermoplastic polymer includes: at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide and their respective modified polymers; optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; optionally, the polyamide includes polyaromatic amide; optionally, the polyolefin includes polyethylene wax. By using the above thermoplastic polymer, it is beneficial to form a uniform and dense coating layer on the end face of the exposed current collector after cutting and the burrs generated by cutting.

[0023] In a possible implementation, the first insulating layer and the second insulating layer further include inorganic particles. In this way, the first insulating layer and the second insulating layer have good wear resistance, which can reduce the risk of the first insulating layer and the second insulating layer falling off.

[0024] In a possible implementation, based on the total mass of the first insulating layer, the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%. By reasonably setting the mass content of the inorganic particles, the first insulating layer and the second insulating layer have good wear resistance, and the risk of the first insulating layer and the second insulating layer falling off from the current collector is small during the production, transportation, and use of the battery cell.

[0025] In a possible implementation, the maximum particle size D of the inorganic particles is 2 max Satisfaction: D 2 max ≤12μm; 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 and the second insulating layer, and is also conducive to obtaining the first insulating layer and the second insulating layer with a suitable thickness, thereby facilitating the preparation of the first insulating layer and the second insulating layer.

[0026] 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 and the second insulating layer, the slurry of the first insulating layer and the second insulating layer has a suitable viscosity, which is convenient for coating the first insulating layer and the second insulating layer; and the slurry of the first insulating layer and the second insulating layer has a relatively suitable solid content, which is convenient for drying the first insulating layer and the second insulating layer.

[0027] In a possible implementation, the inorganic particles include insulating inorganic particles. In this way, the first insulating layer and the second insulating layer have certain insulating properties.

[0028] In a possible implementation, the insulating inorganic particles include at least one of boehmite and alumina. Boehmite and alumina have good heat resistance and insulation. By selecting boehmite or alumina as the insulating inorganic particles, the first insulating layer and the second insulating layer have good heat resistance and insulation.

[0029] In a possible implementation, the first insulating layer and the second insulating layer further include a binder. By providing 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.

[0030] In a possible implementation, based on the total mass of the first insulating layer, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%. In this way, the binder has a suitable mass content, the first insulating layer and the second insulating layer have suitable bonding force with the current collector, and the risk of falling off from the current collector is low.

[0031] 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 is convenient for 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 and the second insulating layer on the surface of the current collector.

[0032] In a possible implementation, the first insulating layer and the second insulating layer have different colors, so that the first insulating layer and the second insulating layer can be easily identified and the subsequent preparation of the electrode assembly and the battery cell can be facilitated.

[0033] In a possible implementation, the bonding force F1 between the first insulating layer and the current collector satisfies: 80 N / m ≤ F1 ≤ 200 N / m; optionally, F1 satisfies: 80 N / m ≤ F1 ≤ 145 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.

[0034] In a possible implementation, the bonding force F2 between the second insulating layer and the current collector satisfies: 20 N / m ≤ F2 ≤ 100 N / m; optionally, F2 satisfies: 20 N / m ≤ F2 ≤ 65 N / m. In this way, the bonding between the second insulating layer and the current collector is relatively strong, which can reduce the risk of the second insulating layer falling off the current collector.

[0035] In a possible implementation, along the first direction, a size k1 of the first insulating layer is the same as a size k2 of the second insulating layer. This helps to reduce the complexity of preparing the first insulating layer and the second insulating layer.

[0036] 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 k3 of the first insulating layer and the second portion satisfies: 0.3≤k1:k3≤0.5. When k1:k3 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:k3 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.

[0037] In a possible implementation, the pole piece further includes a coating layer, and the coating layer 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 coating layer can cover the first end surface, reducing the risk of the first end surface being exposed, thereby reducing the risk of short circuit caused by the first end surface overlapping with the electrode of opposite polarity; in addition, the coating layer can also cover the burrs generated by the cutting process, reducing the risk of the burrs overlapping with the electrode of opposite polarity.

[0038] In a possible implementation, the thickness d3 of the coating layer satisfies: 100nm≤d3≤200nm, so that the coating layer can better cover the burrs and the exposed first end surface with a small thickness. Optionally, the thickness d3 of the coating layer satisfies: 140nm≤d3≤200nm. This is conducive to further improving the coating effect on the burrs and the first end surface.

[0039] In a possible implementation, the resistance R of the coating layer satisfies: R≥50Ω; optionally, R satisfies: 230Ω≤R≤500Ω. The resistance of the coating layer satisfies the above conditions, thus reducing the risk of short circuit of the battery cell caused by the end surface overlapping with the electrode of opposite polarity.

[0040] In a possible implementation, the coating layer is disposed on the first end surface and the second end surface, the second end surface being the end surfaces of the first portion at both ends 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 coating layer can coat the second end surface exposed due to cutting, thereby reducing the risk of the second end surface overlapping with an electrode of opposite polarity.

[0041] In a possible implementation, the coating layer includes a thermoplastic polymer, and the material of the thermoplastic polymer in the coating layer is the same as the material of the thermoplastic polymer in the first insulating layer and the second insulating layer. This is conducive to simplifying the preparation steps of the pole piece and speeding up the production rhythm.

[0042] In a possible implementation, the thermoplastic polymer in the coating layer is in the form of a film layer. Thus, the coating layer is formed by melting and solidifying the thermoplastic polymers in the first insulating layer and the second insulating layer. This helps to simplify the preparation steps of the pole piece, and the coating layer can be formed while cutting.

[0043] In a possible implementation, the thickness d4 of the first portion of the tab satisfies: 10 μm≤d4≤15 μm. In this way, the tab has a suitable thickness.

[0044] 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.

[0045] 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 layered transition metal oxide, a spinel material, and an olivine structured phosphate material; optionally, the olivine structured phosphate material includes lithium iron phosphate; optionally, the layered transition metal oxide includes: LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0046] 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.

[0047] In a second aspect, a method for preparing a pole piece in the first aspect and any possible implementation thereof is provided, comprising: coating a first insulating slurry and a second insulating slurry on surfaces on both sides of at least a first portion of a pole ear of a current collector, respectively, to prepare a first insulating layer and a second insulating layer, the thickness of the second insulating layer being greater than the thickness of the first insulating layer; and cutting the current collector provided with the first insulating layer and the second insulating layer to prepare the pole piece.

[0048] In the pole piece prepared by the above technical solution, the risk of short circuit and self-discharge caused by the electrode assembly inserted into the battery cell after the pole ear is bent is low, which is beneficial to improving the reliability of the battery cell.

[0049] In a possible implementation, the first insulating slurry and the second insulating slurry are respectively applied to the surfaces of both sides of the first part of the electrode tab of the current collector to prepare the first insulating layer and the second insulating layer, including: the first insulating slurry and the second insulating slurry are respectively applied to the surfaces of both sides of the transition region between the first part and the main body of the current collector to prepare the first insulating layer and the second insulating layer. In this way, in the prepared pole piece, the transition region of the main body and the first part of the electrode tab are both provided with the first insulating layer and the second insulating layer.

[0050] In a possible implementation, the first insulating slurry and the second insulating slurry are respectively coated on the surfaces of both sides of the first part of the current collector's pole ear to prepare the first insulating layer and the second insulating layer, including: coating the first insulating slurry on the surface of one side of the first part by gravure coating to prepare the first insulating layer; coating the second insulating slurry on the surface of the other side of the first part by gravure coating or extrusion coating to prepare the second insulating layer. The gravure coating method facilitates the preparation of a first insulating layer with a smaller thickness; the second insulating layer can select a suitable coating method according to actual needs or thickness.

[0051] In a possible implementation, the method further includes: coating an active material on a coating region of a main body of the current collector to prepare an active material layer.

[0052] In a possible implementation, the cutting of the current collector provided with the first insulating layer and the second insulating layer includes: controlling a laser processing tool to cut the current collector provided with the first insulating layer and the second insulating layer.

[0053] 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 polymers in the first insulating layer and the second insulating layer to become fluid and flow to the end surface, thereby facilitating the formation of the coating layer.

[0054] In a possible implementation, the first insulating paste is the same as the second insulating paste, so as to simplify the preparation process of the first insulating layer and the second insulating layer.

[0055] In a possible implementation manner, a ratio of a thickness d2 of the second insulating layer to a thickness d1 of the first insulating layer satisfies: d2 / d1≥2.

[0056] In a possible implementation manner, a ratio of a thickness d2 of the second insulating layer to a thickness d1 of the first insulating layer satisfies: 2≤d2 / d1≤20.

[0057] In a possible implementation manner, the thickness d1 of the first insulating layer satisfies: 1 μm≤d1≤12 μm.

[0058] In a possible implementation, the thickness d2 of the second insulating layer satisfies: 10 μm≤d2≤24 μm.

[0059] In a possible implementation manner, the first insulating paste and the second insulating paste include a thermoplastic polymer, a binder, and inorganic particles.

[0060] In a possible implementation, the maximum particle size D of the thermoplastic polymer is 1 max Satisfaction: D 1 max ≤12μm; Optionally, D 1 max Satisfaction: D 1 max ≤6μm.

[0061] In a possible implementation, based on the total mass of the first insulating paste, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%.

[0062] In a possible implementation, the melting point T of the thermoplastic polymer satisfies: 100°C ≤ T ≤ 200°C.

[0063] In a possible implementation, the melting point of the thermoplastic polymer is 100°C to 130°C.

[0064] In one possible implementation, the thermoplastic polymer includes: at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide and their respective modified polymers; optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; optionally, the polyamide includes polyaromatic amide; optionally, the polyolefin includes polyethylene wax.

[0065] In one possible implementation, based on the total mass of the first insulating paste, the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%.

[0066] In a possible implementation, the maximum particle size D of the inorganic particles is 2 max Satisfaction: D 2max ≤12μm; Optionally, D 2 max Satisfaction: D 2 max ≤6μm.

[0067] 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.

[0068] In a possible implementation, the inorganic particles include insulating inorganic particles.

[0069] In a possible implementation, the insulating inorganic particles include at least one of boehmite and alumina.

[0070] In a possible implementation, based on the total mass of the first insulating paste, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%.

[0071] 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.

[0072] 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.

[0073] In one possible implementation, the battery cell includes an electrode assembly, which includes an electrode assembly body and an electrode ear portion extending from the electrode assembly body, the surface where the second insulating layer is located faces the electrode assembly body, and the surface where the first insulating layer is located faces away from the electrode assembly body.

[0074] The thickness of the second insulating layer is greater than that of the first insulating layer, and the surface of the second insulating layer faces the electrode assembly body. In this way, the second insulating layer has a certain supporting effect. When the electrode assembly expands or the battery cell is shaken, collided or squeezed, the risk of the pole ear being inserted into the electrode assembly body is low, which is beneficial to improving the reliability of the battery cell.

[0075] In a possible implementation, the pole ear portion includes a plurality of pole ears, and the sum of the number of layers of the plurality of pole ears is greater than or equal to 50. In this way, the number of layers of the pole ears is large, the number of pole sheets is also large, the battery cell has a higher energy density, and the risk of the pole ear portion being inserted into the electrode assembly body is low.

[0076] In a fourth aspect, a battery is provided, comprising the battery cell described in the third aspect and any possible implementation manner thereof.

[0077] In a fifth aspect, an electrical device is provided, comprising the battery described in the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] 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.

[0079] Figure 1 It is a schematic diagram of a pole piece before processing the pole lug according to an embodiment of the present application;

[0080] Figure 2 A schematic diagram of a pole piece according to an embodiment of the present application;

[0081] Figure 3 for Figure 2 The cross-sectional view along the AA direction in FIG.

[0082] Figure 4 for Figure 2 The cross-sectional view along the BB direction;

[0083] Figure 5 A schematic diagram of a method for preparing a pole piece according to an embodiment of the present application;

[0084] Figure 6 A schematic diagram of a battery cell according to an embodiment of the present application;

[0085] Figure 7 A schematic diagram of a tab portion of a battery cell according to an embodiment of the present application;

[0086] Figure 8 A schematic diagram of a pole ear portion of a battery cell in the related art;

[0087] Fig. 9 A schematic diagram of inserting the electrode assembly into the pole ear portion;

[0088] Fig.10 A schematic diagram of a battery according to an embodiment of the present application;

[0089] Fig.11 A schematic diagram of an electrical device according to an embodiment of the present application;

[0090] Fig.12 A CT image of a pole ear portion of a battery cell according to an embodiment of the present application;

[0091] Fig.13 CT image of the pole ear portion of the battery cell in the comparative example of the present application;

[0092] Fig.14 This is a CT image of the electrode ear portion inserted into the electrode assembly body in the comparative example of the present application.

[0093] Reference numerals:

[0094] 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

[0095] 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.

[0096] "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.

[0097] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0098] 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.

[0099] 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.

[0100] 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 an electrode assembly, and then bend the pole pieces' ears to save the space occupied by the pole pieces, thereby increasing the energy density of the battery cells. However, during the preparation and use of battery cells, the bent pole pieces are easily squeezed and may be inserted into the electrode assembly (for example, the non-pole ear part of the pole piece in the electrode assembly), resulting in self-discharge or even short circuit, which is not conducive to improving the reliability of battery cells.

[0101] In view of this, the present application provides a pole piece, which includes a current collector, a first insulating layer and a second insulating layer. The current collector includes a main body and a pole ear, the pole ear extends 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 respectively provided with a first insulating layer and a second insulating layer, and the thickness d2 of the second insulating layer is greater than the thickness d1 of the first insulating layer. In this way, when the pole ear is bent, since the thickness of the second insulating layer is greater than the thickness of the first insulating layer, the side surface of the first part provided with the second insulating layer is more difficult to bend than the side surface of the pole ear provided with the first insulating layer, so that the side surface of the first part provided with the second insulating layer can play a certain supporting role, and when squeezed, the risk of the bent pole ear being inserted into the electrode assembly in the battery cell is reduced, thereby reducing the risks of self-discharge, short circuit, etc., which is conducive to improving the reliability of the battery cell.

[0102] [Pole piece]

[0103] 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 4 for Figure 2 Cross-sectional view along BB direction.

[0104] 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 1As 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.

[0105] Combination Figures 1 to 4 As shown, the pole piece 1 includes a current collector 10 , a first insulating layer 121 and a second insulating layer 122 .

[0106] 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.

[0107] 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 .

[0108] 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 surfaces of both sides of the first portion 1021 are respectively provided with a first insulating layer 121 and a second insulating layer 122 .

[0109] 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 and the second insulating layer 122 , that is, the second portion 1022 is exposed.

[0110] The surfaces on both sides of the first part 1021 refer to two opposite surfaces of the first part 1021 along the thickness direction of the current collector 10. The surfaces on both sides of the first part 1021 are respectively provided with a first insulating layer 121 and a second insulating layer 122, that is, the surface on one side of the first part 1021 is provided with the first insulating layer 121, and the surface on the other side of the first part 1021 is provided with the second insulating layer 122.

[0111] The thickness d2 of the second insulating layer 122 is greater than the thickness d1 of the first insulating layer 121. In other words, the thickness of the second insulating layer 122 is different from the thickness of the first insulating layer 121.

[0112] The thickness d1 of the first insulating layer 121 may refer to the average thickness of the first insulating layer 121. 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 d2 of the second insulating layer 122 refers to the average thickness of the second insulating layer 122.

[0113] The thickness of the second insulating layer 122 is greater than that of the first insulating layer 121. Thus, when the tab 102 is bent, the side surface of the first portion 1021 provided with the second insulating layer 122 is more difficult to bend than the side surface of the first portion 1021 provided with the first insulating layer 121, because the thickness of the second insulating layer 122 is greater than that of the first insulating layer 121. The second insulating layer 122 also has a certain function of supporting the first insulating layer 121. Compared with the method in which the thickness of the second insulating layer 122 is the same as that of the first insulating layer 121, in the embodiment of the present application, the bent tab 102 occupies a smaller space in the height direction of the battery cell (the height direction of the battery cell may be the arrangement direction of the electrode assembly in the battery cell and the end cap provided with the electrode terminal in the battery cell).

[0114] During the use, transportation or preparation of the battery cell, the electrode assembly expands, which may cause the bent pole ear 102 to be squeezed, or the battery cell is subjected to external forces such as collision and shaking, and the bent pole ear 102 is squeezed by the end cap or the electrode assembly. Through the arrangement of the embodiment of the present application, after the bent pole ear 102 is squeezed, the bent pole ear 102 occupies a smaller space and the second insulating layer 122 supports the first insulating layer 121, so the risk of the bent pole ear 102 being inserted into the electrode assembly after being squeezed is smaller, which can reduce the risk of self-discharge, short circuit, etc. caused by the electrode assembly inserted into the battery cell after the pole ear is bent, which is conducive to improving the reliability of the battery cell.

[0115] The embodiment of the present application provides a pole piece 1, which includes a current collector 10, a first insulating layer 121 and a second insulating layer 122. 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 relative to the second part 1022, and the surfaces of both sides of the first part 101 are respectively provided with the first insulating layer 121 and the second insulating layer 122, so that the risk of the first part 1021 overlapping with the electrode of opposite polarity can be reduced. The thickness of the second insulating layer 122 is greater than that of the first insulating layer 121. The surface of one side of the first portion 1021 provided with the second insulating layer 122 is more difficult to bend than the surface of one side of the first portion 1021 provided with the first insulating layer 121. The second insulating layer 122 can play a certain supporting role for the first insulating layer 121. The space occupied by the bent pole ear 102 in the height direction is smaller, thereby reducing the risk of self-discharge, short circuit, etc. caused by factors such as the bent pole ear 102 being squeezed and affecting the electrode assembly inserted into the battery cell, which is beneficial to improving the reliability of the battery cell.

[0116] In some embodiments, the ratio of the thickness d2 of the second insulating layer 122 to the thickness d1 of the first insulating layer 121 satisfies: d2 / d1≥2. For example, d2 / d1 is 2, 3, 5, 8, 10, 20 or any other value within the above range.

[0117] When d2 / d1≥2, there is a certain difference between the thickness of the first insulating layer 121 and the thickness of the second insulating layer 122. The surface of the side of the first part 1021 of the tab 102 provided with the second insulating layer 122 is more difficult to bend than the surface of the side of the first part 1021 provided with the first insulating layer 121, which is beneficial to further reduce the risk of the electrode assembly inserted into the battery cell after the tab 102 is bent.

[0118] In some embodiments, L satisfies: the ratio of the thickness d2 of the second insulating layer 122 to the thickness d1 of the first insulating layer 121 satisfies: 2≤d2 / d1≤20. In this way, the difference in thickness between the first insulating layer 121 and the second insulating layer 122 is small, which facilitates the bending of the tab 102.

[0119] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: 1 μm≤d1≤12 μm. For example, d1 is 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm or any value within the above range.

[0120] When d1 is not less than 1 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 12 μm, the first insulating layer 121 has a smaller thickness, which is convenient for bending the first part 1021 of the pole ear 102, and can further reduce the difficulty of bending the pole ear 102.

[0121] In some embodiments, d1 satisfies: 4μm≤d1≤6μm, for example, 4μm, 5μm, 6μm or any value within the above range. In this way, it is helpful to further consider the difficulty of preparing the first insulating layer 121 and the difficulty of bending the first part 1021, which is convenient for preparing the first insulating layer 121 and bending the tab 102.

[0122] In some embodiments, the thickness d2 of the second insulating layer 122 satisfies: 10 μm≤d2≤24 μm. For example, d1 is 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 24 μm or any value within the above range.

[0123] When d2 is not less than 10 μm, the second insulating layer 122 is more difficult to bend than the first insulating layer 121, which is conducive to the tab 102 having a more suitable shape after bending, and reduces the risk of the bent tab 102 being inserted into the electrode assembly in the battery cell. When d2 does not exceed 24 μm, it is convenient to reduce the risk of the second insulating layer 122 being difficult to bend due to the large thickness of the second insulating layer 122 itself. In this way, when 10 μm ≤ d2 ≤ 20 μm, the second insulating layer 122 has a suitable bending difficulty, so that the tab 102 has a suitable shape after bending, and reduces the risk of the bent tab 102 being inserted into the electrode assembly in the battery cell.

[0124] In some embodiments, d2 satisfies: 16 μm≤d2≤18 μm. In this way, the second insulating layer 122 has a suitable thickness, which is convenient for bending the tab 102 and can reduce the space occupied by the second insulating layer 122, thereby facilitating both the reliability and volume energy density of the battery cell.

[0125] In some embodiments, d1 is 5 μm, and d2 is 10 μm. Alternatively, d1 is 6 μm, and d2 is 12 μm. d1 and d2 may also be other values ​​satisfying the above range, and the embodiments of the present application include but are not limited to these.

[0126] 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 surfaces on both sides of the transition area 1012 are respectively provided with a first insulating layer 121 and a second insulating layer 122 .

[0127] A first insulating layer 121 is disposed on a surface of one side of the transition region 1012 and the first portion 1021 , and a second insulating layer 122 is disposed on a surface of the other side of the transition region 1012 and the first portion 1021 .

[0128] The first insulating layer 121 may include a first sub-portion 1211 and a second sub-portion 1212, wherein the first sub-portion 1211 is located on the surface of the transition zone 1012 of the main body 101, and the second sub-portion 1212 is located on the surface of the first portion 1021 of the tab 102. Similarly, the second insulating layer 122 includes two sub-portions, one sub-portion is located on the surface of the transition zone 1012 of the main body 101, and the other sub-portion is located on the surface of the transition zone 1012 of the main body 101.

[0129] In the above embodiment, by respectively providing the first insulating layer 121 and the second insulating layer 122 on the surfaces of both sides of the transition region 1012 , it is helpful to reduce the risk of short circuit caused by the transition region 1012 overlapping with electrodes of opposite polarity.

[0130] 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.

[0131] In some embodiments, the active material layer 11 is disposed on surfaces of both sides of the coating region 1011 .

[0132] Optionally, in some embodiments, the active material layer 11 is disposed on a surface of one side of the coating area 1011 .

[0133] In some embodiments, the first insulating layer 121 and the second insulating layer 122 include a thermoplastic polymer.

[0134] 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.

[0135] The thermoplastic polymer in the first insulating layer 121 and the second insulating layer 122 will change from a solid state to a fluid state when heated to certain conditions. Thus, in the process of cutting the current collector 10 provided with the first insulating layer 121 and the second insulating layer 122, the fluid thermoplastic polymer can flow to the burrs produced by the cutting and the exposed end faces of the current collector 10 after cutting. After the temperature is lowered, the fluid thermoplastic polymer solidifies at the burrs and the exposed end faces to cover the burrs and the exposed end faces, thereby reducing the risk of the burrs and the exposed end faces overlapping with electrodes of opposite polarities, which is beneficial to further improve the reliability of the battery cells.

[0136] In some embodiments, the maximum particle size D of the thermoplastic polymer is 1 max Satisfaction: D 1 max ≤12μm; Optionally, D 1 max Satisfaction: D 1 max ≤6μm.

[0137] D 1 max It can be 3μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm or any value within the above range.

[0138] In this way, the risk of scratches during the preparation of the first insulating layer 121 and the second insulating layer 122 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 and the second insulating layer 122 with a suitable thickness, thereby facilitating the preparation of the first insulating layer 121 and the second insulating layer 122.

[0139] 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.

[0140] In some embodiments, based on the total mass of the first insulating layer 121, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A1≤40wt%; and / or, based on the total mass of the second insulating layer 122, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%.

[0141] A1 can be 30wt%, 35wt%, 40wt% or any value within the above range, A2 can be 30wt%, 35wt%, 40wt% or any value within the above range. A1 and A2 can be the same value or different values.

[0142] As an example, A1 and A2 are the same value. The slurry of the first insulating layer 121 and the slurry of the second insulating layer 122 have the same formula, which is helpful to reduce the complexity of preparation.

[0143] In the above embodiment, when 30wt%≤A1≤40wt%, the first insulating layer 121 has a suitable mass content of thermoplastic polymer; when 30wt%≤A2≤40wt%, the second insulating layer 122 has a suitable mass content of thermoplastic polymer; in this way, a uniform and dense coating layer can be formed on the exposed end surface of the current collector 10 after cutting.

[0144] In some embodiments, the melting point T of the thermoplastic polymer satisfies: 100°C≤T≤200°C.

[0145] For example, the melting point T of the thermoplastic polymer is 100° C., 110° C., 130° C., 150° C., 200° C., or any value within the above range.

[0146] 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.

[0147] 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 a coating layer at the exposed end surface of the current collector 10 after cutting or the coating layer 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.

[0148] 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 and the second insulating layer 122, 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 face of the current collector 10 exposed after cutting and the burrs generated by the cutting, thereby facilitating the preparation of a coating layer covering the exposed end face.

[0149] In some embodiments, the melting point T of the thermoplastic polymer is 100° C. to 130° C. In this way, it is convenient to form a coating layer on the exposed end surface under the action of relatively low heat.

[0150] In some embodiments, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide and their respective modified polymers. Optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; optionally, the polyamide includes polyaromatic amide; optionally, the polyolefin includes polyethylene wax. By using the above thermoplastic polymer, it is beneficial to form a uniform and dense coating layer on the end surface of the exposed current collector 10 after cutting and the burrs generated by cutting.

[0151] 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.

[0152] For example, the thermoplastic polymer includes at least one of a modified polymer of polystyrene, a modified polymer of polyolefin, a modified polymer of polyimide, a modified polymer of polyester, a modified polymer of polyphenylene sulfide, and a modified polymer of polyamide.

[0153] 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.

[0154] In some embodiments, the first insulating layer 121 and the second insulating layer 122 further include inorganic particles.

[0155] The first insulating layer 121 and the second insulating layer 122 include inorganic particles, which are beneficial to improving the wear resistance of the first insulating layer 121 and the second insulating layer 122. For example, during the use, transportation or preparation of the battery cell, the first insulating layer 121 contacts with the end cap, adapter, etc. of the battery cell and wears, and the second insulating layer 122 contacts with the electrode assembly of the battery cell and wears; due to the presence of the inorganic particles, the wear resistance of the first insulating layer 121 and the second insulating layer 122 is improved, and the risk of falling off from the current collector 10 is reduced.

[0156] In some embodiments, based on the total mass of the first insulating layer 121 , the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating layer 122 , the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%.

[0157] B1 can be 30wt%, 35wt%, 40wt% or any value within the above range, B2 can be 30wt%, 35wt%, 40wt% or any value within the above range. B1 and B2 can be the same value or different values.

[0158] By reasonably setting the mass content of the inorganic particles, the first insulating layer 121 and the second insulating layer 122 have good wear resistance. During the production, transportation, and use of the battery cell, the risk of the first insulating layer 121 and the second insulating layer 122 falling off from the current collector 10 is relatively small.

[0159] In some embodiments, the maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤12μm; 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 during the preparation of the first insulating layer 121 and the second insulating layer 122, and is also conducive to obtaining the first insulating layer 121 and the second insulating layer 122 with a suitable thickness, thereby facilitating the preparation of the first insulating layer 121 and the second insulating layer 122.

[0160] D 2 max It can be 3μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm or any value within the above range.

[0161] 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.

[0162] In this way, in the process of preparing the first insulating layer 121 and the second insulating layer 122, the slurry of the first insulating layer 121 and the second insulating layer 122 has a suitable viscosity, which is convenient for coating the first insulating layer 121 and the second insulating layer 122; and the slurry of the first insulating layer 121 and the second insulating layer 122 has a relatively suitable solid content, which is convenient for drying the first insulating layer 121 and the second insulating layer 122.

[0163] 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.

[0164] 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 and the second insulating layer 122 from the inorganic particles, thereby facilitating filtering out the impurities.

[0165] In some embodiments, the inorganic particles include insulating inorganic particles. Thus, the first insulating layer 121 and the second insulating layer 122 have certain insulating properties.

[0166] 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 insulating inorganic particles and adding them to the first insulating layer 121 and the second insulating layer 122, the first insulating layer 121 and the second insulating layer 122 have good heat resistance and insulation. In addition, boehmite and alumina are easy to obtain and have low cost.

[0167] The inorganic particles may also be inorganic particles that are not conductive at the operating voltage of the battery (for example, not conductive at a voltage of 5 V). For example, the inorganic particles may have a certain dielectric constant.

[0168] Inorganic particles have certain ion transport properties, but inorganic particles are insulating at least under the operating voltage of the battery.

[0169] 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.

[0170] 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).

[0171] 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).

[0172] In some embodiments, the first insulating layer 121 and the second insulating layer 122 further include a binder. In this way, in the process of preparing the first insulating layer 121 and the second insulating layer 122, it is convenient to bond the thermoplastic polymer in the insulating slurry of the first insulating layer 121 and the second insulating layer 122 to the surface of the current collector 10, thereby reducing the risk of the thermoplastic polymer falling off from the current collector 10.

[0173] In some embodiments, based on the total mass of the first insulating layer 121, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating layer 122, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%.

[0174] C1 can be 20wt%, 30wt%, 35wt%, 40wt% or any value in the above range, and C2 can be 20wt%, 30wt%, 35wt%, 40wt% or any value in the above range. C1 and C2 can be the same value or different values.

[0175] In the above embodiment, the binder has an appropriate mass content, and the first insulating layer 121 and the second insulating layer 122 have an appropriate bonding force with the current collector 10 , and the risk of falling off from the current collector 10 is low.

[0176] 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.

[0177] The above-mentioned binder has good bonding properties, which facilitates bonding the thermoplastic polymer to the surface of the current collector 10 .

[0178] Optionally, the binder is polyacrylonitrile, which has good leveling properties and is conducive to uniformly coating the first insulating layer 121 and the second insulating layer 122 on the surface of the current collector 10 .

[0179] In some embodiments, the bonding force F1 between the first insulating layer 121 and the current collector 10 satisfies: 80 N / m≤F1≤200 N / m; optionally, F1 satisfies: 80 N / m≤F1≤145 N / m.

[0180] F1 can be 80 N / m, 100 N / m, 120 N / m, 150 N / m, 180 N / m, 200 N / m or any value within the above range.

[0181] When the bonding force between the first insulating layer 121 and the current collector 10 is 80 N / m to 200 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 .

[0182] In some embodiments, the bonding force F2 between the second insulating layer 122 and the current collector 10 satisfies: 20 N / m≤F2≤100 N / m; optionally, F2 satisfies: 20 N / m≤F2≤65 N / m.

[0183] F2 can be 20 N / m, 60 N / m, 65 N / m, 80 N / m, 90 N / m, 100 N / m or any value within the above range.

[0184] When the bonding force between the second insulating layer 122 and the current collector 10 is 20 N / m to 100 N / m, the bonding between the second insulating layer 122 and the current collector 10 is relatively strong, which can reduce the risk of the second insulating layer 122 falling off the current collector 10 .

[0185] In some embodiments, along the first direction, the size k1 of the first insulating layer 121 is the same as the size k2 of the second insulating layer 122. This helps to reduce the complexity of manufacturing the first insulating layer 121 and the second insulating layer 122.

[0186] In some embodiments, along the first direction, the ratio of the size k1 of the first portion 1021 to the sum k3 of the sizes of the first insulating layer 121 and the second portion 1012 satisfies: 0.3≤k1:k3≤0.5. For example, k1:k3 is 0.3, 0.4, 0.5 or any value within the above range.

[0187] k3 is the sum of the size of the first insulating layer 121 and the size of the second portion 1012 along the first direction.

[0188] When k1:k3 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:k3 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.

[0189] In some embodiments, the pole piece 1 further includes a coating layer 123 , and the coating layer 123 is disposed on the first end surface 1011 a , and the first end surface 1011 a is an end surface of the main body 101 at the first end.

[0190] 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 x-direction and the z-direction.

[0191] 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.

[0192] In the above embodiment, the coating layer 123 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 coating layer 123 can also cover the burrs generated by the cutting process, reducing the risk of the burrs overlapping with the electrode of opposite polarity.

[0193] In some embodiments, the thickness d3 of the coating layer 123 satisfies: 100 nm≤d3≤200 nm. For example, d3 is 100 nm, 120 nm, 160 nm, 200 nm or any value within the above range.

[0194] Optionally, the thickness of the coating layer 123 is related to the thickness of the first insulating layer 121 and the second insulating layer 122. For example, in the case where the first insulating layer 121 and the second insulating layer 122 include thermoplastic polymers, the greater the thickness of the first insulating layer 121 and the second insulating layer 122, the more thermoplastic polymers there are in the first insulating layer 121 and the second insulating layer 122, the greater the thickness of the coating layer 123, and the more conducive to forming a uniform and dense coating layer 123.

[0195] The thickness d3 of the coating layer 123 is the average thickness of the coating layer 123. For example, the thickness d3 is the average value of the maximum dimension and the minimum dimension of the coating layer 123 in the thickness direction.

[0196] The thickness d3 of the coating layer 123 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 d3 of the coating layer 123 using the obtained image.

[0197] In the above embodiment, the coating layer 123 can better coat the burrs and the first end surface 1011 a with a relatively small thickness.

[0198] In some embodiments, the resistance R of the coating layer 123 satisfies: R≥50Ω. For example, R is 50Ω, 100Ω, or 200Ω.

[0199] When the resistance of the coating layer 123 is greater than 50Ω, 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 certain resistance of the coating layer 123, thereby reducing the risk of short circuit or even explosion caused by internal short circuit.

[0200] Optionally, the resistance R of the coating layer 123 satisfies: 230Ω≤R≤500Ω. In this way, the risk of short circuit of the battery cell caused by the first end surface 1011a overlapping with the electrode of opposite polarity can be reduced.

[0201] In some embodiments, the coating layer 123 is disposed on the first end surface 1011a and the second end surface 1222a. The second end surface 1222a is the end surface of the first portion 1021 at both ends along the second direction, and the second direction is different from the first direction.

[0202] 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.

[0203] 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 coating layer 123 at the second end surface 1222a, the risk of the second end surface 1222a overlapping with the electrode of opposite polarity can be reduced.

[0204] Optionally, the second direction is perpendicular to the first direction.

[0205] In the above embodiment, the coating layer 123 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.

[0206] In some embodiments, the coating layer 123 includes a thermoplastic polymer, and the material of the thermoplastic polymer in the coating layer 123 is the same as the material of the thermoplastic polymer in the first insulating layer 121 and the second insulating layer 122. This is conducive to simplifying the preparation steps of the pole piece 1 and speeding up the production rhythm.

[0207] 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 coating layer 123 at the first end surface 1011a and the second end surface 122a, and the first insulating layer 121 and the second insulating layer 122 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 coating layer 123 may be prepared simultaneously in one step.

[0208] For another example, the active material layer 11, the first insulating layer 121 and the second insulating layer 122 are first prepared on the current collector 10, and the coating layer 123 is simultaneously prepared during the cutting process. In this way, the tab 102 can be cut in one step and the coating layer 123 can be prepared at the same time.

[0209] In some embodiments, the thermoplastic polymer in the coating layer 123 is in the form of a film layer. In other words, the coating layer 123 includes a thermoplastic polymer in the form of a film layer.

[0210] In the above embodiment, the coating layer 123 is formed by melting and solidifying the thermoplastic polymer in the first insulating layer 121 and the second insulating layer 122. After the thermoplastic polymer in the first insulating layer 121 and the second insulating layer 122 becomes a fluid state, it flows to the first end surface 1011a and the second end surface 1222a, and solidifies at the first end surface 1011a and the second end surface 1222a to form the coating layer 123. In this way, it is helpful to simplify the preparation steps of the pole piece 1, and the coating layer 123 can be formed while cutting.

[0211] In the first insulating layer 121 and the second insulating layer 122, at least some granular thermoplastic polymers are retained. For example, at a position away from the cutting line 124, the thermoplastic polymers are particles protruding from the current collector 10. In the coating layer 123, the thermoplastic polymers are in the form of films and have almost no particle shape.

[0212] 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.

[0213] In some embodiments, the thickness d4 of the first portion 1021 of the tab 102 satisfies: 10 μm≤d4≤15 μm. Thus, after the first insulating layer 121 and the second insulating layer 122 are provided, the tab 102 has a suitable thickness.

[0214] The thickness d4 may be 10 μm, 12 μm, 15 μm or any value within the above range. The thickness d4 of the first portion 1021 may also be the thickness of the current collector 10 .

[0215] 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.

[0216] In some embodiments, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes at least one of a layered transition metal oxide, a spinel material, and an olivine structured phosphate material.

[0217] Optionally, the phosphate material with an olivine structure includes a lithium-containing phosphate with an olivine structure, such as lithium iron phosphate. In this way, the battery cell prepared from the pole piece has higher reliability.

[0218] 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.

[0219] The olivine-structured lithium-containing phosphate may further include at least one of lithium manganese phosphate and lithium manganese iron phosphate.

[0220] The layered transition metal oxide includes a layered lithium transition metal oxide or a layered sodium transition metal oxide.

[0221] 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.

[0222] Lithium transition metal oxides can also include other ternary materials, such as LiNi 0.6 Co 0.2 Mn 0.2O2 (NCM622). The lithium-containing transition metal oxide may also include lithium-rich manganese-based materials and the like.

[0223] The spinel material includes spinel lithium manganese oxide and the like.

[0224] The positive electrode active material in this embodiment may be a sodium salt used in a sodium ion battery or a sodium metal battery, or may be a lithium salt used in a lithium ion battery or a lithium metal battery.

[0225] 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.

[0226] 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.

[0227] Optionally, the metal foil includes aluminum foil or copper foil.

[0228] 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.

[0229] 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.

[0230] [Method for preparing electrode]

[0231] 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.

[0232] Step 210 , coating the first insulating slurry and the second insulating slurry on the surfaces of at least both sides of the first portion 1021 of the tab 102 of the current collector 10 , respectively, to prepare a first insulating layer 121 and a second insulating layer 122 , wherein the thickness of the second insulating layer 122 is greater than the thickness of the first insulating layer 121 .

[0233] Step 220 , cutting the current collector 10 provided with the first insulating layer 121 and the second insulating layer 122 to prepare the pole piece 1 .

[0234] Specifically, the current collector 10 provided with the first insulating layer 121 and the second insulating layer 122 is cut along the cutting line 124 .

[0235] In the pole piece 1 prepared by the above technical solution, the risk of short circuit and self-discharge caused by the electrode assembly after the pole ear 102 is bent and inserted into the battery cell is low, which is conducive to improving the reliability of the battery cell.

[0236] In some embodiments, step 210 includes: coating the first insulating slurry and the second insulating slurry on the surfaces of the first portion 1021 and the transition region 1012 of the main body 101 of the current collector 10 on both sides, respectively, to prepare the first insulating layer 121 and the second insulating layer 122. In this way, in the prepared pole piece 1, the transition region 1012 of the main body 101 and the first portion 1021 of the pole tab 102 are both provided with the first insulating layer 121 and the second insulating layer 122.

[0237] In some embodiments, step 210 includes: coating a first insulating slurry on the surface of one side of the first part 1021 by gravure coating to prepare a first insulating layer 121; coating a second insulating slurry on the surface of the other side of the first part 1021 by gravure coating or extrusion coating to prepare a second insulating layer 122. The gravure coating method facilitates the preparation of a first insulating layer 121 with a smaller thickness; the second insulating layer 122 can be coated in a suitable manner according to actual needs or thickness.

[0238] For example, the first insulating layer 121 and the second insulating layer 122 are both prepared by gravure coating. In this way, the first insulating layer 121 and the second insulating layer 122 can be prepared by the same process, which is conducive to reducing the complexity of the process.

[0239] After the first insulating layer 121 and the second insulating layer 122 are prepared, an active material is coated on the coating area 1011 of the current collector 10 to form an active material layer 11. 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. Since the thickness of the active material layer 11 is greater than the thickness of the first insulating layer 121, the active material layer 11 is prepared after the first insulating layer 121 is prepared, which can reduce the influence of the thicker active material layer 11 on the preparation of the first insulating layer 121, and facilitate the preparation of the first insulating layer 121 with a smaller thickness by gravure coating.

[0240] 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 and the second insulating layer 122 are coated by the cooperation of the gravure roller, the pressure roller and the scraper.

[0241] For another example, the first insulating layer 121 is prepared by gravure coating, and the second insulating layer 122 is prepared by extrusion coating.

[0242] In some embodiments, the method 200 further includes: coating an active material on the coating region 1011 of the main body 101 of the current collector 10 to prepare an active material layer 11 .

[0243] In some embodiments, step 230 includes: controlling a laser processing tool to cut the current collector 10 having the first insulating layer 121 and the second insulating layer 122 .

[0244] 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 and the second insulating layer 122 to become a fluid state and flow to the exposed end surface of the current collector 10, thereby facilitating the formation of the coating layer 123.

[0245] 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.

[0246] In some embodiments, the first insulating paste is the same as the second insulating paste, so as to simplify the preparation process of the first insulating layer 121 and the second insulating layer 122 .

[0247] In some embodiments, a ratio of a thickness d2 of the second insulating layer 122 to a thickness d1 of the first insulating layer 121 satisfies: d2 / d1≥2; optionally, 2≤d2 / d1≤20.

[0248] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: 1 μm≤d1≤12 μm; optionally, 4 μm≤d1≤6 μm.

[0249] In some embodiments, the thickness d2 of the second insulating layer 122 satisfies: 10 μm≤d2≤24 μm.

[0250] In some embodiments, the insulating paste includes a thermoplastic polymer, inorganic particles, and a binder.

[0251] In some embodiments, the maximum particle size D of the thermoplastic polymer is 1 max Satisfaction: D 1 max ≤12μm; Optionally, D1 max Satisfaction: D 1 max ≤6μm.

[0252] In some embodiments, based on the total mass of the first insulating paste, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%.

[0253] In some embodiments, the melting point T of the thermoplastic polymer satisfies: 100°C≤T≤200°C.

[0254] In some embodiments, the thermoplastic polymer has a melting point of 100°C to 130°C.

[0255] In some embodiments, the thermoplastic polymer includes: at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide and their respective modified polymers; optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; optionally, the polyamide includes polyaramid; optionally, the polyolefin includes polyethylene wax.

[0256] In some embodiments, based on the total mass of the first insulating paste, the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%.

[0257] In some embodiments, the maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤12μm; Optionally, D 2 max Satisfaction: D 2 max ≤6μm.

[0258] In some embodiments, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 6 μm; alternatively, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 2 μm.

[0259] In some embodiments, the inorganic particles include insulating inorganic particles.

[0260] In some embodiments, the insulating inorganic particles include at least one of boehmite and alumina.

[0261] In some embodiments, based on the total mass of the first insulating paste, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%.

[0262] 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.

[0263] As an example, a thermoplastic polymer is first mixed with water to form a thermoplastic polymer emulsion, and then the polymer emulsion is mixed with a binder and inorganic particles. The thermoplastic polymer emulsion and the binder are liquids, and the liquid thermoplastic polymer emulsion and the binder can be mixed uniformly in a short time, which is conducive to reducing the preparation time of the insulating slurry.

[0264] [Positive electrode]

[0265] 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.

[0266] 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.

[0267] 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.).

[0268] 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.

[0269] 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.

[0270] 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.

[0271] [Negative electrode]

[0272] 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.

[0273] 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.).

[0274] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can 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.

[0275] 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.

[0276] [Electrolytes]

[0277] 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.

[0278] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0279] 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.

[0280] 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.

[0281] 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.

[0282] [Isolation film]

[0283] 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.

[0284] 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.

[0285] 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.

[0286] [Battery Cell]

[0287] An embodiment of the present application provides a battery cell, comprising the pole piece 1 in the above embodiment, and / or the pole piece 1 prepared by the method in the above embodiment.

[0288] 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.

[0289] Figure 6 is a schematic diagram of a battery cell according to an embodiment of the present application, Figure 7 Schematic diagram of a pole ear portion of an embodiment of the present application. In some embodiments, Figure 6 and Figure 7 As shown, the battery cell includes an electrode assembly 33, which includes an electrode assembly body 331 and an electrode ear portion 332 extending from the electrode assembly body 331, the surface where the second insulating layer 122 is located faces the electrode assembly body 331, and the surface where the first insulating layer 121 is located faces away from the electrode assembly body 331.

[0290] 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. As an example, the positive electrode sheet is the sheet 1 in the embodiment of the present application.

[0291] The battery cell 3 further includes a shell 31 and an end cover assembly 32 , and the electrode assembly 33 is disposed in the shell 31 .

[0292] The pole ear portion 332 is formed by bending the pole ears 102 of the plurality of pole pieces 1. After the pole ears 102 are bent, the surface where the second insulating layer 122 is located faces the electrode assembly body 331, and the surface where the first insulating layer 121 is located faces the end cap assembly 32. The pole ear portion 332 can be formed by bending the pole ears 102 of the plurality of pole pieces 1. Figure 7 Not shown, please refer to Figure 6 ) is connected to the end cover assembly 32.

[0293] The thickness of the second insulating layer 122 is greater than that of the first insulating layer 121, and the surface of the second insulating layer 122 faces the electrode assembly body. In this way, the second insulating layer 122 has a certain supporting effect, and the size of the pole ear 332 in the height direction z of the battery cell 3 is relatively small. When the electrode assembly expands or the battery cell is shaken, collided or squeezed, the risk of the pole ear 332 inserting into the electrode assembly body 331 is relatively low, which is beneficial to improving the reliability of the battery cell 3.

[0294] In some embodiments, the pole lug portion 332 includes a plurality of pole lugs 102 , and the sum of the number of layers of the plurality of pole lugs 102 is greater than or equal to 50.

[0295] For example, see Figure 6 As shown, the battery cell 3 includes four electrode assemblies, and the tabs in two electrode assemblies are stacked and bent together to form a tab portion 332. In one tab portion 332, the total number of tabs 102 layers is greater than or equal to 50.

[0296] The number of layers of the tabs 102 may be 50, 60, 80, 100 or a greater value. As the number of layers of the tabs 102 increases, the capacity and energy density of the battery cell also increase.

[0297] In this embodiment, the battery cell 1 has a higher energy density. At the same time, due to the arrangement of the first insulating layer 121 and the second insulating layer 122 in the pole piece, after the pole ear portion 332 is bent, the risk of being inserted into the electrode assembly body 331 in the event of extrusion or the like is reduced.

[0298] Figure 8 is a schematic diagram of a pole ear portion of a battery cell in the related art, Fig. 9 Schematic diagram of inserting the electrode assembly into the lug. Figure 8 and Fig. 9 As shown, Figure 8 In the battery cell shown, the first insulating layer 121 and the second insulating layer 122 of the pole piece 1 have the same thickness. After the pole ear is bent, the shape of the bent pole ear portion 332 is close to a C shape, such as Figure 8 When the pole ear portion 332 is squeezed, one pole ear portion 332 may be bifurcated, for example, a portion of the pole ear of the pole ear portion 332 is separated from another portion of the pole ear from the middle, and a portion of the pole ear is inserted into the electrode assembly body 331 .

[0299] In some embodiments, the end cap assembly 32 includes an electrode terminal 322, such as Figure 6 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.

[0300] 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 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.

[0301] 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.

[0302] [Battery]

[0303] An embodiment of the present application provides a battery, comprising the battery cell in the above embodiment. Fig.10 Schematic diagram of a battery according to an embodiment of the present application. Fig.10 As shown, the battery 5 may include a plurality of battery cells (not shown in the figure).

[0304] 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 .

[0305] [Electrical devices]

[0306] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0307] Fig.11 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application. Fig.11 As shown, the present application provides an electrical device 6, including the battery in the above embodiment.

[0308] 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.

[0309] 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.

[0310] [Example]

[0311] Example 1

[0312] In Example 1, the structure of the pole piece 1 can be seen in Figure 2 As shown. The slurry of the first insulating layer 121 and the second insulating layer 122 is the same. The thickness d1 of the first insulating layer 121 is 5 μm, and the thickness d2 of the second insulating layer 122 is 15 μm. The first insulating layer 121 and the second insulating layer 122 are prepared by gravure coating.

[0313] In the slurry of the first insulating layer 121 and the second insulating layer 122, based on the total mass of the slurry, the mass contents of the thermoplastic polymer A1 and A2 are both 40wt%, the mass contents of the inorganic particles B1 and B2 are both 30wt%, and the mass contents of the binder C1 and C2 are both 30wt%. The material of the thermoplastic polymer is polyethylene wax with a melting point of 130°C; the inorganic particles are boehmite; and the binder is polyacrylonitrile.

[0314] Embodiment 2-8

[0315] The difference between Example 2-8 and Example 1 is that the thickness d1 of the first insulating layer 121 and the thickness d2 of the second insulating layer 122 are different; accordingly, d2 / d1 also changes accordingly, wherein the specific parameters can be seen in Table 1.

[0316] Examples 9-11

[0317] The difference between Examples 9-11 and Example 1 is that the thermoplastic polymer is different. The thermoplastic polymer in Example 12 is polyester, and the melting point of polyester is 220°C.

[0318] Examples 12-14

[0319] The difference between Examples 12 to 14 and Example 1 is that the mass content of the thermoplastic polymer, the mass content of the inorganic particles, and the mass content of the binder in the slurry of the first insulating layer 121 and the second insulating layer 122 are different.

[0320] Examples 15-16

[0321] The difference between Example 15 and Example 6 is that the particle sizes of the thermoplastic polymer and the inorganic particles are different.

[0322] The difference between Example 16 and Example 1 is that the thicknesses of the first insulating layer 121 and the second insulating layer 122 are different, and the particle sizes of the thermoplastic polymer and the inorganic particles are different.

[0323] In Example 15 and Example 16, the thickness of the first insulating layer 121 and the second insulating layer 122 is thicker than that of Examples 6 and 1, and the particle sizes of the thermoplastic polymer and inorganic particles that can be selected are also larger.

[0324] Examples 17-18

[0325] The difference between Embodiments 17-18 and Embodiment 1 is that along the first direction, the ratio k1:k3 of the size k1 of the first portion 1021 of the pole tab 102 to the size k3 of the pole tab 102 is different.

[0326] Examples 19-21

[0327] The difference between Examples 19-21 and Example 1 is that the single-layer thickness of the tab and the number of tab layers are different.

[0328] Comparative Example 1

[0329] The difference between Comparative Example 1 and Example 1 is that the thickness of the insulating layer on both sides of the first part of the tab is the same, and the insulating slurry of the insulating layer does not include a thermoplastic polymer. The insulating slurry includes boehmite and a binder, the mass ratio of boehmite to the binder is 70:30, and the binder is polyvinylidene fluoride (PVDF).

[0330] Comparative Examples 2-3

[0331] The difference between Comparative Example 2-3 and Example 1 is that the thickness of the first insulating layer 121 and the second insulating layer 122 are the same.

[0332] In Table 1, d1 is the thickness of the first insulating layer 121, d2 is the thickness of the first insulating layer 122, T is the melting point of the thermoplastic polymer, A1 and A2 are the mass contents of the thermoplastic polymer in the slurry of the first insulating layer 121 and the second insulating layer 122, respectively, B1 and B2 are the mass contents of the inorganic particles in the slurry of the first insulating layer 121 and the second insulating layer 122, C1 and C2 are the mass contents of the binder in the slurry of the first insulating layer 121 and the second insulating layer 122, F1 is the bonding force between the first insulating layer 121 and the current collector 10, F2 is the bonding force between the second insulating layer 122 and the current collector 10, d3 is the thickness of the coating layer 123, R is the resistance of the coating layer 123, and k1:k3 is the ratio of the size k1 of the first insulating layer along the first direction to the sum k3 of the size of the first insulating layer and the size of the second part 1012.

[0333] In Table 2, whether there is a short circuit can reflect the state of the thermoplastic polymer at the end face, that is, whether the end face is completely provided with a coating layer, and the short circuit is not caused by the insertion of the tab into the electrode assembly. "10% insertion" means that the CT images of the obtained battery cells are statistically analyzed and sampled, and there is a 10% frequency of the tab being inserted into the electrode assembly. "10% unqualified" means that the battery cells are tested for self-discharge, and there is a 10% frequency of abnormal self-discharge of the battery cells.

[0334] Table 1 Parameters of Examples and Comparative Examples

[0335]

[0336]

[0337] Table 2 Experimental results of comparative examples and embodiments

[0338]

[0339]

[0340] [Preparation of battery cells]

[0341] (1) Prepare slurry

[0342] Thermoplastic polymer, inorganic particles and binder are mixed in a certain proportion, and a solvent is added and stirred evenly. The slurry viscosity is about 50-500 mPa·s. The solvent is water. The specific proportion of thermoplastic polymer, inorganic particles and binder can be seen in Table 1.

[0343] (2) Coating and drying

[0344] The slurry was coated on aluminum foil with a coating width of 10 mm, leaving a width of 30 μm for preparing the tab blank. After drying in an oven at 100°C, the thickness of the first insulating layer and the second insulating layer after drying are 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. The positive electrode active material in the positive electrode slurry is lithium iron phosphate.

[0345] (3) Laser die cutting

[0346] 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.

[0347] (4) Preparation of battery cells

[0348] 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.

[0349] It should be noted that, for Comparative Examples 1 and 3, the first insulating layer and the second insulating layer were prepared by extrusion coating.

[0350] [Confirmation of the first and second insulating layers]

[0351] Use a scanning electron microscope to observe the surface of the pole piece to check whether there is a first insulating layer and a second 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 and the second insulating layer based on the photographed photos.

[0352] [Confirmation of coating layer]

[0353] A scanning electron microscope (SEM) is used to observe the end face to check whether there is a coating layer at the end face; in addition, the thickness of the coating layer can also be observed through photos taken by the scanning electron microscope.

[0354] [Overlapping Fully Charged Anode Test]

[0355] Use the laser die-cut end face to overlap the fully charged anode and observe whether there is a short circuit.

[0356] [Test of inserting the tab into the electrode assembly]

[0357] Computed tomography (CT) is used to detect whether the tabs in the battery cells are inserted into the electrode assembly.

[0358] In the embodiment of the present application, multiple battery cells with the same configuration may be tested, and the risk of the tab being inserted into the electrode assembly may be determined based on the multiple test results. For example, 10% insertion may mean that among multiple battery cells with the same configuration, 10% of the battery cells have the tab inserted into the electrode assembly in the CT images captured.

[0359] [Test of Adhesion]

[0360] 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 sides of the first substrate and the second substrate at 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.

[0361] [Test of resistance of coating layer]

[0362] The resistance of the coating can be measured using an ohmmeter.

[0363] 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.

[0364] [Particle size test]

[0365] 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 .

[0366] For another example, a scanning electron microscope may be used to test the pole piece to obtain images of the first insulating layer and the second insulating layer of the pole piece, and the particle size of the thermoplastic polymer or the inorganic particle may be measured based on the images.

[0367] [Confirmation of Melting Point of Thermoplastic Polymer]

[0368] 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.

[0369] 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.

[0370] [Mass ratio of thermoplastic polymer, inorganic particles and binder]

[0371] 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.

[0372] In addition, the thermoplastic polymer, binder and inorganic particles in the pole piece can also be determined in the following way.

[0373] 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.

[0374] [Self-discharge test]

[0375] The battery was adjusted to 80% SOC and stored for 48 hours. The voltage before storage was V1, and the voltage after storage was V2. k = (V1-V2) / 48.

[0376] Among them, k is used to characterize the self-discharge performance of the battery. When k≤0.2mV / h, it means that the self-discharge test has passed.

[0377] In the embodiment of the present application, multiple battery cells with the same configuration may be tested, and whether the self-discharge is qualified or not may be determined based on the multiple test results. For example, 10% failure may mean that among multiple battery cells with the same configuration, 10% of the battery cells fail the self-discharge test.

[0378] It should be noted that the tab inserted into the electrode assembly in the embodiment of the present application refers to the tab being inserted into the non-tab portion of the electrode assembly, that is, the tab being inserted into the main body of the electrode assembly.

[0379] Fig.12 This is a CT image of the pole ear portion of a battery cell according to an embodiment of the present application. Fig.13 CT image of the pole ear of the battery cell in the comparative example of the present application, Fig.14 This is a CT image of the electrode ear portion inserted into the electrode assembly body in the comparative example of the present application.

[0380] Fig.13 and Fig.14 CT schematic diagram of the electrode ear and electrode assembly of Comparative Example 3. Fig.13 and Fig.14 As shown, when the thickness of the second insulating layer is the same as that of the first insulating layer, or when the thickness of the second insulating layer and the first insulating layer are both large, the risk of the pole ear portion bifurcating from the middle and inserting into the electrode assembly body increases. Fig.12 As shown in Examples 1-21, when the number of tab layers is large, the tab will not be inserted into the electrode assembly or the risk of inserting into the electrode assembly is reduced. Therefore, the embodiments of the present application can reduce the risk of the tab inserting into the electrode assembly.

[0381] As shown in Examples 2-7, as the thickness of the first insulating layer and the thickness of the second insulating layer increase, the thickness of the coating layer also gradually increases, and the bonding force between the current collector and the first insulating layer and the second insulating layer gradually decreases. By reasonably setting the thickness of the first insulating layer and the second insulating layer, a coating layer with a suitable thickness can be obtained, and the coating layer has a suitable resistance.

[0382] As shown in Examples 1-7 and 8, when d2 / d1 is greater than or equal to 2, the risk of the tab being inserted into the electrode assembly is further reduced. In addition, as shown in Examples 15-16 and 1-8, by reasonably setting the particle size of the thermoplastic polymer and the inorganic particles, the preparation of the first insulating layer and the second insulating layer is facilitated. 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 during the preparation of the first insulating layer due to excessive inorganic particles. By reasonably setting the particle size of the inorganic particles, the preparation of the first insulating layer is facilitated.

[0383] As shown in Examples 9-10, the embodiments of the present application can be applicable to different thermoplastic polymers; as shown in Example 11, when the melting point of the thermoplastic polymer is relatively high, it is more difficult for the thermoplastic polymer to melt completely and requires more heat to melt; 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, and there is a 5% possibility of failing the self-discharge test.

[0384] As shown in Examples 12-14, as the mass content of the thermoplastic polymer increases, more thermoplastic polymer melts and flows to the end surface during cutting, so that the coating 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 coating 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 and the second insulating layer.

[0385] As shown in Examples 17-18, the embodiments of the present application are suitable for pole pieces with k1:k3 being 0.3 to 0.5.

[0386] 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 1-21, when the number of tab layers is large, the risk of inserting the tab into the electrode assembly in the embodiments of the present application is low.

[0387] It should be noted that the above embodiments and comparative examples are described with the positive electrode sheet whose current collector is aluminum foil, and the embodiments of the present application can also be applied to the positive electrode sheet and negative electrode sheet whose current collector is other materials. In addition, although the data is described only with the example that the slurry of the first insulating layer and the second insulating layer is the same, the scheme of the present application is still applicable when the slurry is different.

[0388] 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: It includes: a current collector, a first insulating layer and a second insulating layer, in, The current collector includes a main body and a tab, the tab extending from a first end of the main body, the first end being an end of the main body along a first direction, the tab including 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 and the second insulating layer being respectively provided on surfaces on both sides of the first part, the thickness d2 of the second insulating layer being greater than the thickness d1 of the first insulating layer.

2. The pole piece according to claim 1, characterized in that: A ratio of a thickness d2 of the second insulating layer to a thickness d1 of the first insulating layer satisfies: d2 / d1≥2.

3. The pole piece according to claim 1 or 2, characterized in that: A ratio of a thickness d2 of the second insulating layer to a thickness d1 of the first insulating layer satisfies: 2≤d2 / d1≤20.

4. The pole piece according to any one of claims 1 to 3, characterized in that: The thickness d1 of the first insulating layer satisfies: 1 μm≤d1≤12 μm.

5. The pole piece according to any one of claims 1 to 4, characterized in that: The thickness d2 of the second insulating layer satisfies: 10 μm≤d2≤24 μm.

6. The pole piece according to any one of claims 1 to 5, 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 surfaces on both sides of the transition area are respectively provided with the first insulating layer and the second insulating layer.

7. The pole piece according to claim 6, 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.

8. The pole piece according to any one of claims 1 to 7, characterized in that: The first insulating layer and the second insulating layer include a thermoplastic polymer.

9. The pole piece according to claim 8, characterized in that: The maximum particle size D of the thermoplastic polymer 1 max Satisfaction: D 1 max ≤12μm; Optionally, D 1 max Satisfaction: D 1 max ≤6μm.

10. The pole piece according to claim 8 or 9, characterized in that: Based on the total mass of the first insulating layer, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%.

11. The pole piece according to any one of claims 8 to 10, 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.

12. The pole piece according to any one of claims 8 to 11, characterized in that: The thermoplastic polymer includes: at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide and their respective modified polymers; optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; optionally, the polyamide includes polyaromatic amide; optionally, the polyolefin includes polyethylene wax.

13. The pole piece according to any one of claims 8 to 12, characterized in that: The first insulating layer and the second insulating layer further include inorganic particles.

14. The pole piece according to claim 13, characterized in that: Based on the total mass of the first insulating layer, the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%.

15. The pole piece according to claim 13 or 14, characterized in that: The maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤12μm; Optionally, D 2 max Satisfaction: D 2 max ≤6μm.

16. The pole piece according to any one of claims 8 to 15, characterized in that: The first insulating layer and the second insulating layer further include an adhesive.

17. The pole piece according to claim 16, characterized in that: Based on the total mass of the first insulating layer, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%.

18. The pole piece according to claim 16 or 17, 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.

19. The pole piece according to any one of claims 1 to 18, characterized in that: The first insulating layer and the second insulating layer have different colors.

20. The pole piece according to any one of claims 1 to 19, characterized in that: The bonding force F1 between the first insulating layer and the current collector satisfies: 80 N / m≤F1≤200 N / m; optionally, F1 satisfies: 80 N / m≤F1≤145 N / m.

21. The pole piece according to any one of claims 1 to 20, characterized in that: The bonding force F2 between the second insulating layer and the current collector satisfies: 20 N / m≤F2≤100 N / m; optionally, F2 satisfies: 20 N / m≤F2≤65 N / m.

22. The pole piece according to any one of claims 1 to 21, characterized in that: Along the first direction, a size k1 of the first insulating layer is the same as a size k2 of the second insulating layer.

23. The pole piece according to any one of claims 1 to 22, characterized in that: Along the first direction, a ratio of a size k1 of the first insulating layer to a sum k3 of sizes of the first insulating layer and the second portion satisfies: 0.3≤k1:k3≤0.

5.

24. The pole piece according to any one of claims 1 to 23, characterized in that: The pole piece further includes a coating layer, and the coating 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.

25. The pole piece according to claim 24, characterized in that: The thickness d3 of the coating layer satisfies: 100nm≤d3≤200nm; optionally, the thickness d3 of the coating layer satisfies: 140nm≤d3≤200nm.

26. The pole piece according to claim 24 or 25, characterized in that: The resistance R of the coating layer satisfies: R≥50Ω; optionally, R satisfies: 230Ω≤R≤500Ω.

27. The pole piece according to any one of claims 24 to 26, characterized in that: The covering layer includes a thermoplastic polymer, and a material of the thermoplastic polymer in the covering layer is the same as a material of the thermoplastic polymer in the first insulating layer and the second insulating layer.

28. The pole piece according to claim 27, characterized in that: The thermoplastic polymer in the coating layer is in the form of a film layer.

29. The pole piece according to any one of claims 1 to 28, characterized in that: A thickness d4 of the first portion of the tab satisfies: 10 μm≤d4≤15 μm.

30. The pole piece according to any one of claims 1 to 29, characterized in that: The electrode sheet includes a positive electrode sheet; optionally, the current collector includes aluminum foil.

31. The pole piece according to claim 30, 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 layered transition metal oxide, a spinel material, and an olivine structure phosphate material.

32. A method for preparing a pole piece as claimed in any one of claims 1 to 31, characterized in that: include: Coating a first insulating slurry and a second insulating slurry respectively on surfaces of at least both sides of the first portion of the electrode tab of the current collector to prepare a first insulating layer and a second insulating layer, wherein the thickness of the second insulating layer is greater than the thickness of the first insulating layer; The current collector provided with the first insulating layer and the second insulating layer is cut to prepare the pole piece.

33. The method according to claim 32, characterized in that The method comprises: coating the first insulating slurry and the second insulating slurry on the surfaces of at least both sides of the first part of the electrode ear of the current collector to prepare the first insulating layer and the second insulating layer, comprising: The first insulating slurry and the second insulating slurry are respectively coated on surfaces of both sides of the transition region between the first portion and the main body of the current collector to prepare the first insulating layer and the second insulating layer.

34. The method according to claim 32 or 33, characterized in that The method comprises: coating the first insulating slurry and the second insulating slurry on the surfaces of at least both sides of the first part of the electrode ear of the current collector to prepare the first insulating layer and the second insulating layer, comprising: Coating the first insulating slurry on a surface of one side of the first portion by gravure coating to prepare the first insulating layer; The second insulating slurry is coated on the surface of the other side of the first portion by gravure coating or extrusion coating to prepare the second insulating layer.

35. The method according to any one of claims 32 to 34, characterized in that The method further comprises: An active material is coated on the coating region of the main body portion of the current collector to prepare an active material layer.

36. The method according to any one of claims 32 to 35, characterized in that The step of cutting the current collector provided with the first insulating layer and the second insulating layer to prepare the pole piece comprises: The laser processing tool is controlled to cut the current collector provided with the first insulating layer and the second insulating layer.

37. The method according to any one of claims 32 to 36, characterized in that The first insulating paste is the same as the second insulating paste.

38. A battery cell, characterized in that: Comprising a pole piece as described in any one of claims 1-31, and / or a pole piece prepared by the method as described in any one of claims 32-37.

39. The battery cell according to claim 38, characterized in that The battery cell includes an electrode assembly, which includes an electrode assembly body and an electrode ear portion extending from the electrode assembly body, a surface where the second insulating layer is located faces the electrode assembly body, and a surface where the first insulating layer is located faces away from the electrode assembly body.

40. The battery cell according to claim 39, characterized in that The pole lug portion includes a plurality of pole lugs, and a sum of the number of layers of the plurality of pole lugs is greater than or equal to 50.

41. A battery, characterized in that: Comprising a battery cell as claimed in any one of claims 38 to 40.

42. An electrical device, characterized in that: Comprising a battery as claimed in claim 41.

Images