Electrode tab, method of manufacturing the same, secondary battery, battery module, and battery pack

Abstract

The application provides an electrode tab, a preparation method thereof, a secondary battery, a battery module and a battery pack. The electrode tab comprises a main area and isolation areas. The isolation areas are arranged on both sides of the main area along the width direction of the electrode tab. The isolation areas are provided with insulating strip-shaped coating layers, and the main area is provided with an active material layer. The outer edge of the active material layer is limited at the junction between the main area and the isolation area, and the contact angle between the slurry forming the active material layer and the insulating strip-shaped coating layer is greater than 90°. The problem of diffusion of the active material slurry along the width direction of the electrode tab is improved, thereby reducing the defective rate of the electrode tab.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to an electrode sheet and its preparation method, a secondary battery, a battery module, and a battery pack. Background Technology

[0002] Secondary batteries (lithium-ion batteries) have the characteristics of high specific energy, high operating voltage, low self-discharge rate, small size, and light weight, and are widely used in electric vehicles, electronic devices and other products.

[0003] The applicant has discovered that the width of the active material layer in existing electrode sheets is easily altered by the diffusion of the active material slurry along its width direction, resulting in misalignment due to inconsistent widths of the active material layers on both sides of the electrode sheet. This leads to an increased defect rate of the electrode sheets and affects the quality of secondary batteries. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to improve the width uniformity of the active material layer in the electrode sheet, thereby reducing the defect rate of the electrode sheet.

[0005] To achieve the above objectives, this application provides an electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device.

[0006] The first aspect of this application provides an electrode sheet, including a main body region and an isolation region. Along the width direction of the electrode sheet, the isolation region is disposed on both sides of the main body region. The isolation region is provided with an insulating strip coating, and the main body region is provided with an active material layer. The outer edge of the active material layer is confined at the boundary between the main body region and the isolation region. Furthermore, the contact angle between the slurry forming the active material layer and the insulating strip coating is greater than 90°, optionally greater than 125°. Therefore, the large contact angle between the slurry of the active material layer and the insulating strip coating reduces adhesion and migration between the active material and the insulating strip coating, improving the diffusion of the active material slurry along the width direction of the electrode sheet. This effectively improves the width consistency of the active material layer in the electrode sheet, reduces the risk of misalignment due to inconsistent widths of the active material layer on both sides of the electrode sheet, and thus reduces the defect rate of the electrode sheet.

[0007] In any embodiment, the insulating strip coating comprises a functional material. The slurry forming the active material layer is an aqueous slurry, and the insulating strip coating comprises a hydrophobic material; or the slurry forming the active material layer is an oil-based slurry, and the insulating strip coating comprises an oleophobic material. This serves to inhibit the diffusion of the aqueous or oil-based active material slurry to the edge of the electrode sheet.

[0008] In any embodiment, the hydrophobic material comprises at least one selected from polyolefin, polycarbonate, polyamide, and polyacrylonitrile. The aforementioned hydrophobic materials exhibit excellent hydrophobic properties.

[0009] In any embodiment, the oleophobic material comprises at least one of polytetrafluoroethylene and nano-SiO2. The aforementioned oleophobic material exhibits excellent oleophobic properties.

[0010] In any embodiment, the thickness H1 of the insulating strip coating is less than the thickness H2 of the active material layer, which enables the isolation region to have a good inhibitory effect on the diffusion of the active material layer, and also enables the electrode sheet with excellent quality to be obtained.

[0011] In any embodiment, the thickness H1 of the insulating strip coating is 5 μm to 30 μm, and the thickness H2 of the active material layer is 30 μm to 150 μm, which enables the insulating strip coating to have a good inhibitory effect on the diffusion of the active material layer, resulting in an electrode sheet with excellent quality.

[0012] In any embodiment, the thickness H1 of the insulating strip coating and the thickness H2 of the active material layer satisfy the following relationship: 1 / 5 ≤ H1 ∶ H2 ≤ 2 / 3. This reduces the risk of the electrode sheet being damaged during cold pressing due to the excessive thickness H1 of the insulating strip coating, which is beneficial to further improving the quality of the electrode sheet.

[0013] In any embodiment, the width of the insulating strip coating is 1 mm to 20 mm, which can produce electrode sheets with excellent quality.

[0014] A second aspect of this application also provides a method for preparing an electrode sheet, comprising the following steps: preparation of an insulating strip coating: mixing a functional material, an insulating material, and a first binder, and adding a first solvent to form a first slurry; coating the first slurry on both sides of the current collector surface along the length direction of the current collector, and drying to form two insulating strip coatings; the current collector surface between the two insulating strip coatings, where the first slurry is not coated, forms a main region, wherein the functional material is selected from hydrophobic or oleophobic materials; preparation of an active material layer: mixing an electrode active material, a conductive agent, and a second binder, and adding a second solvent to form a second slurry; coating the second slurry on the surface of the main region, and drying to form an active material layer. Wherein, the contact angle between the second slurry and the insulating strip coating is greater than 90°, and optionally greater than 125°.

[0015] Therefore, the preparation method of this application has the advantages of simple preparation process and wide availability of functional materials, which is suitable for large-scale production and helps to reduce production costs.

[0016] In any embodiment, based on the total mass of the insulating strip coating, the mass percentage of the functional material is 40% to 70%, the mass percentage of the insulating material is 20% to 30%, and the mass percentage of the first binder is 10% to 30%. By synergistically controlling the contents of the functional material, insulating material, first binder, and first solvent within the above ranges, the insulating strip coating can effectively inhibit the diffusion of the active material layer.

[0017] In any embodiment, the functional material is selected from hydrophobic materials, the first solvent is selected from oily solvents, and the second solvent is selected from aqueous solvents; or the functional material is selected from oleophobic materials, the first solvent is selected from aqueous solvents, and the second solvent is selected from oily solvents.

[0018] In any embodiment, the aqueous solvent is selected from at least one of deionized water, ethylene glycol, and ethanol; the oily solvent is selected from at least one of N-methylpyrrolidone, N-dimethylamide, and dimethyl sulfoxide.

[0019] In any embodiment, the first adhesive and the second adhesive each independently comprise polyvinylidene fluoride or styrene-butadiene rubber. The aforementioned adhesives exhibit excellent interfacial bonding properties.

[0020] In any embodiment, the insulating material comprises at least one of aluminum oxide and boehmite. The aforementioned insulating material possesses excellent insulating properties, thereby giving the insulating strip coating excellent insulating performance and improving the performance of the electrode sheet.

[0021] A third aspect of this application provides a secondary battery, including the electrode plates of the first aspect of this application.

[0022] A fourth aspect of this application provides a battery module including the secondary battery of the third aspect of this application.

[0023] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0024] A sixth aspect of this application provides an electrical device comprising at least one selected from the third aspect of this application, the fourth aspect of this application, or the fifth aspect of this application.

[0025] The beneficial effects of this application are:

[0026] This application provides an electrode sheet and its preparation method, a secondary battery, a battery module, and a battery pack. The electrode sheet includes a main region and isolation regions located on both sides of the main region. The isolation regions are provided with an insulating strip coating, thereby confining the outer edge of the active material layer at the boundary between the main region and the isolation region. Furthermore, the contact angle between the slurry forming the active material layer and the insulating strip coating is greater than 90°. This large contact angle reduces adhesion and migration between the active material and the insulating strip coating, improving the diffusion of the active material slurry along the width direction of the electrode sheet. This effectively improves the width consistency of the active material layer in the electrode sheet, reduces the risk of misalignment due to inconsistent widths of the active material layer on both sides of the electrode sheet, and thus reduces the defect rate of the electrode sheet. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of an electrode sheet according to one embodiment of this application.

[0028] Figure 2 This is a schematic diagram of the electrode sheet of one embodiment of this application, viewed along the thickness direction.

[0029] Figure 3 This is a schematic diagram of the electrode sheet of one embodiment of this application, viewed along the thickness direction.

[0030] Figure 4 This is a schematic diagram of the structure of an electrode sheet according to one embodiment of this application.

[0031] Figure 5 This is a schematic diagram of the electrode sheet of one embodiment of this application, viewed along the thickness direction.

[0032] Figure 6 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0033] Figure 7 yes Figure 6 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0034] Figure 8 This is a schematic diagram of a battery module according to one embodiment of this application.

[0035] Figure 9 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0036] Figure 10 yes Figure 9 An exploded view of a battery pack according to one embodiment of this application is shown.

[0037] Figure 11 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0038] Figure 12 This is a photograph of the electrode sheet in Example 1-1.

[0039] Figure 13 This is a photograph of the electrode sheet in Comparative Example 1-1.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate; 11 Main body area; 12 Isolation area; 13 Reservoir area; 14 Current collector; 111 Active material layer; 121 Insulating strip coating Detailed Implementation

[0042] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the electrode plates, secondary batteries, battery modules, battery packs, and electrical devices of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0043] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is understood that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, characterized in that a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0046] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0047] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0048] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0049] During its research on secondary batteries, the applicant discovered that in existing secondary battery electrode sheets, the active material slurry diffuses outward along the width of the electrode sheet. This may be due to a deviation between the width of the active material layer on the A and B sides of the electrode sheet and the designed width during the coating of the active material slurry onto the current collector surface. This width deviation makes the A and B sides of the electrode sheet more prone to misalignment, resulting in an increased defect rate for the electrode sheets.

[0050] Based on this, after in-depth research, the applicant discovered that by setting isolation zones on both sides of the main body area (the area where the active material layer is set) of the electrode sheet, and these isolation zones are equipped with insulating strip coatings, the outer edge of the active material layer is confined to the boundary between the main body area and the isolation zones. Furthermore, the slurry forming the active material layer and the insulating strip coating have large interfacial angles, reducing adhesion and migration between the active material and the insulating strip coating, thus improving the diffusion of the active material slurry along the width direction of the electrode sheet. This effectively improves the width consistency of the active material layer in the electrode sheet, reduces the risk of misalignment due to inconsistent widths of the active material layer on both sides of the electrode sheet, and thereby reduces the defect rate of the electrode sheet.

[0051] In order to effectively reduce the defect rate of electrode sheets and improve the quality of secondary batteries, this application provides an electrode sheet and its preparation method, a secondary battery, a battery module, and a battery pack.

[0052] In one embodiment of this application, an electrode sheet is provided, such as... Figure 1 and Figure 2 As shown, the electrode includes a main body region 11 and an isolation region 12. Along the width direction of the electrode sheet, the isolation region 12 is disposed on both sides of the main body region 11. The isolation region 12 is provided with an insulating strip coating 121, and the main body region 11 is provided with an active material layer 111. The outer edge of the active material layer 111 is confined at the boundary between the main body region 11 and the isolation region 12. Furthermore, the contact angle between the slurry forming the active material layer 111 and the insulating strip coating 121 is greater than 90°, and optionally greater than 125°.

[0053] In this application, the main body region 11 refers to the main body portion of the electrode sheet, and the main body region 11 is typically provided with an active material layer 111. Exemplarily, the active material layer 111 can be coated on the current collector surface in the main body region 11; the isolation region 12 refers to the portions located on both sides of the main body region 11 along the width direction of the electrode sheet, and the isolation region 12 is provided with an insulating strip coating 121. The electrode sheet of this application may include a positive electrode sheet and / or a negative electrode sheet.

[0054] In this application, the electrode sheet can be coated on one side or both sides. (Reference) Figure 2 In one example, when the electrode sheet is coated on one side only, the active material layer 111 and the insulating strip coating 121 can be disposed on one surface of the current collector 14; Reference Figure 3 In another example, when the electrode sheet is double-sided coated, the active material layer 111 and the insulating strip coating 121 can be disposed on both surfaces of the current collector 14.

[0055] Although the mechanism is not yet clear, the applicant unexpectedly discovered that the electrode sheet of this application includes a main region and isolation regions located on both sides of the main region. The isolation regions are provided with an insulating strip coating, which confines the outer edge of the active material layer to the boundary between the main region and the isolation region. Furthermore, the contact angle between the slurry forming the active material layer and the insulating strip coating is greater than 90°, improving the problem of diffusion of the active material slurry along the width direction of the electrode sheet. This effectively improves the width consistency of the active material layer in the electrode sheet, reduces the risk of misalignment due to inconsistent widths of the active material layer on both sides of the electrode sheet, and thus reduces the defect rate of the electrode sheet.

[0056] In some embodiments, the insulating strip coating includes a functional material. The functional material in this application may include a hydrophobic material or an oleophobic material.

[0057] In some embodiments, the slurry forming the active material layer is an aqueous slurry, and the insulating strip coating includes a hydrophobic material, resulting in a large contact angle between the insulating strip coating and the aqueous active material slurry. Thus, when the aqueous active material slurry comes into contact with the insulating strip coating, the aqueous active material slurry does not easily wet the insulating strip coating, thereby inhibiting the diffusion of the aqueous active material slurry to the edge of the electrode sheet.

[0058] In other embodiments, the slurry forming the active material layer is an oil-based slurry, and the insulating strip coating includes an oleophobic material, resulting in a large contact angle between the insulating strip coating and the oil-based active material slurry. Thus, when the oil-based active material slurry comes into contact with the insulating strip coating, the oil-based active material slurry does not easily wet the insulating strip coating, thereby inhibiting the diffusion of the oil-based active material slurry to the edge of the electrode sheet.

[0059] This application does not impose any particular limitation on the hydrophobic material, as long as it achieves the purpose of this application. In one embodiment, the hydrophobic material includes at least one selected from polyolefin, polycarbonate, polyamide, and polyacrylonitrile. This application does not impose any particular limitation on polyolefin, as long as it achieves the purpose of this application, it may include polypropylene.

[0060] This application does not impose any particular limitation on the oleophobic material, as long as it achieves the purpose of this application. In one embodiment, the oleophobic material includes at least one of polytetrafluoroethylene and nano-SiO2. This application does not impose any particular limitation on the particle size of the nano-SiO2, for example, its particle size range is 10 nm to 1000 nm.

[0061] In some implementations, reference Figure 2 and Figure 3The thickness H1 of the insulating strip coating 121 is less than the thickness H2 of the active material layer 111, thereby avoiding the following situations: if the thickness of the insulating strip coating is too small, it may affect the inhibition effect of the isolation region on the diffusion of the active material layer; if the thickness of the insulating strip coating is too large, it may affect the die-cutting quality of the electrode sheet, thus affecting the quality of the electrode sheet. Therefore, the thickness of the insulating strip coating in this application is less than the thickness of the active material layer, which enables the isolation region to have a good inhibition effect on the diffusion of the active material layer, and also enables the obtaining of electrode sheets with excellent quality.

[0062] In some embodiments, the thickness H1 of the insulating strip coating is 5 μm to 30 μm, and the thickness H2 of the active material layer is 30 μm to 150 μm. By controlling the thickness H1 of the insulating strip coating and the thickness H2 of the active material layer within the above ranges, the insulating strip coating can effectively inhibit the diffusion of the active material layer, resulting in an electrode sheet with excellent quality. This application does not impose any particular limitation on the width of the active material layer; electrode sheets with different active material layer widths can be prepared as needed. Of course, the design of the active material layer widths on surfaces A and B of the electrode sheet is usually the same.

[0063] In some embodiments, the thickness H1 of the insulating strip coating and the thickness H2 of the active material layer satisfy the following relationship: 1 / 5 ≤ H1 ∶ H2 ≤ 2 / 3. This can reduce the risk of the electrode sheet being damaged during cold pressing due to the excessive thickness H1 of the insulating strip coating, which is beneficial to further improving the quality of the electrode sheet.

[0064] In some embodiments, the width of the insulating strip coating is 1 mm to 20 mm, thereby avoiding the following situations: if the width of the insulating strip coating is too wide, it will affect the welding effect of the tabs and be detrimental to improving the yield of the electrode sheet; if the width of the insulating strip coating is too narrow, it will affect the inhibitory effect of the isolation region on the diffusion of the active material layer. Therefore, by controlling the width of the insulating strip coating within the above range, this application can obtain electrode sheets with excellent quality.

[0065] In some implementations, reference Figure 4 and Figure 5 The electrode sheet of this application also includes a blank area 13, which is located on the side of the isolation region 12 away from the main body region 11 along the width direction of the electrode sheet. The blank area 13 in this application can refer to the area located at the edge of the electrode sheet. The surface of the blank area is a current collector, and the blank area can reserve space for the tab, thereby collecting electrons. In some embodiments, the width of the blank area is 10mm to 60mm.

[0066] In one embodiment of this application, a method for preparing an electrode sheet is also provided, comprising the following steps:

[0067] Preparation of insulating strip coating: Functional material, insulating material and first binder are mixed and then a first solvent is added to form a first slurry. The first slurry is coated on both sides of the current collector surface along the length direction of the current collector. After drying, two insulating strip coatings are formed. The current collector surface between the two insulating strip coatings, where the first slurry is not coated, forms the main area.

[0068] Preparation of the active material layer: The electrode active material, conductive agent and second binder are mixed and then a second solvent is added to form a second slurry; the second slurry is coated on the surface of the main area and dried to form an active material layer; wherein, the contact angle between the second slurry and the insulating strip coating is greater than 90°, and can be greater than 125°.

[0069] During the preparation process, even if the active material slurry is accidentally applied to the surface of the insulating strip coating, the active material slurry on the surface of the insulating strip coating can be easily peeled off after drying due to the large contact angle between the active material layer slurry and the insulating strip coating, which is beneficial to improving the yield of electrode sheets.

[0070] In this application, the functional material is selected from hydrophobic or oleophobic materials. In some embodiments, when the functional material is selected from hydrophobic materials, the first solvent is selected from an oil-based solvent, and the second solvent is selected from an aqueous solvent. It is understood that in the process of preparing the negative electrode active material layer, the second solvent in the negative electrode active material slurry (second slurry) is usually an aqueous solvent, such as deionized water, and correspondingly, the first solvent is an oil-based solvent. Based on this, this embodiment can be adopted when preparing the negative electrode sheet.

[0071] In other embodiments, the functional material is selected from oleophobic materials, the first solvent is selected from an aqueous solvent, and the second solvent is selected from an oil-based solvent. It is understood that during the preparation of the positive electrode active material layer, the second solvent in the positive electrode active material slurry (second slurry) is typically an oil-based solvent, such as N-methylpyrrolidone (NMP), and correspondingly, the first solvent is an aqueous solvent. Based on this, this embodiment can be used when preparing the positive electrode sheet.

[0072] In some embodiments, based on the total mass of the insulating strip coating, the mass percentage of the functional material is 40% to 70%, the mass percentage of the insulating material is 20% to 30%, and the mass percentage of the first binder is 10% to 30%. By synergistically controlling the contents of the functional material, insulating material, first binder, and first solvent within the above ranges, the insulating strip coating can effectively inhibit the diffusion of the active material layer.

[0073] This application does not impose any particular limitation on aqueous and oil-based solvents, as long as they can achieve the purpose of this application. In some embodiments, the aqueous solvent is selected from at least one of deionized water, ethylene glycol, and ethanol, and has good dispersibility for oleophobic materials; the oil-based solvent is selected from at least one of N-methylpyrrolidone, N-dimethylamide, and dimethyl sulfoxide, and has good dispersibility for hydrophobic materials.

[0074] This application does not impose any particular limitations on the first and second adhesives, as long as they achieve the purpose of this application. In some embodiments, the first and second adhesives each independently comprise polyvinylidene fluoride or styrene-butadiene rubber. The aforementioned adhesives exhibit good interfacial bonding properties.

[0075] In some embodiments, the insulating material of this application includes at least one of aluminum oxide and boehmite. These insulating materials possess excellent insulating properties, thereby giving the insulating strip coating excellent insulating performance and improving the performance of the electrode sheet. This application does not impose any particular limitation on the particle size of the insulating material, as long as it achieves the purpose of this application.

[0076] In some embodiments, a blank area is formed on the surface of the current collector between the outer edge of each insulating strip coating away from the main area and the long edge of the current collector that is closer to it. For example, a first slurry can be applied at a certain distance from the long edge of the current collector to form a blank area.

[0077] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0078] In one embodiment of this application, a secondary battery is provided.

[0079] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0080] [Positive electrode plate]

[0081] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.

[0082] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0083] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0084] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. The lithium transition metal oxide is characterized by including, but is not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0085] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0086] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0087] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0088] [Negative electrode plate]

[0089] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0090] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0091] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0092] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. 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, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional 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.

[0093] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0094] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0095] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0096] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0097] [Electrolytes]

[0098] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0099] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0100] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0101] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0102] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0103] [Isolation membrane]

[0104] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0105] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0106] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0107] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0108] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0109] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 6 This is an example of a square-structured secondary battery 5.

[0110] In some implementations, refer to Figure 7 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0111] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0112] Figure 8 This is battery module 4, used as an example. (See reference...) Figure 8 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0113] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0114] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0115] Figure 9 and Figure 10 This is battery pack 1 as an example. (See reference...) Figure 9 and Figure 10 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0116] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0117] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0118] Figure 11 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0119] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0120] Example

[0121] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0122] Example 1-1

[0123] <Preparation of Insulating Strip Coating>

[0124] The functional material nano-SiO2 (average particle size 500nm), the insulating material aluminum oxide (Al2O3), and the first binder styrene-butadiene rubber (SBR) were mixed at a mass ratio of 60:30:10. Then, deionized water was added as the first solvent, and the mixture was stirred under vacuum until homogeneous, yielding a first slurry with a solid content of 30wt%. A 12μm aluminum foil was selected as the current collector. The first slurry was applied to both sides of the current collector surface along its length using an extrusion coating method. After drying at 90℃, two insulating strip-shaped coatings were formed. A blank area was formed on the current collector surface between the outer edge of each insulating strip-shaped coating furthest from the main area and the long edge of the current collector closest to it. Correspondingly, the current collector surface between the two insulating strip-shaped coatings, without the first slurry coating, formed the main area. The insulating strip-shaped coatings had a thickness of 24μm and a width of 10mm, and the blank area had a width of 10mm.

[0125] <Preparation of Active Material Layer>

[0126] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (a conductive agent), and PVDF (a second binder) are mixed at a mass ratio of 96:2:2. Then, N-methylpyrrolidone (NMP) is added as a second solvent, and the mixture is stirred under vacuum until homogeneous, yielding a second slurry with a solid content of 60 wt%. The second slurry is then coated onto the surface of the main body area using an extrusion coating method, dried at 120°C, and cold-pressed to obtain a positive electrode sheet with a positive active material layer thickness of 35 μm. The above steps are then repeated on the other surface of this positive electrode sheet to obtain a positive electrode sheet with an insulating strip coating and an active material layer on both sides. This positive electrode sheet is then formed by tab molding and slitting processes.

[0127] Examples 1-2 to 1-6

[0128] Except for adjusting the types of functional materials, insulating materials, and first solvents in the first slurry, as shown in Table 1, and the mass ratio between each component, everything else is the same as in Examples 1-1.

[0129] Examples 1-7 to Examples 1-8

[0130] Except for adjusting the amount of the first solvent added, thereby adjusting the solid content of the first slurry as shown in Table 1, the rest is the same as in Example 1-1.

[0131] Example 2-1

[0132] <Preparation of Insulating Strip Coating>

[0133] Functional material polyolefin (polypropylene), insulating material aluminum oxide (Al2O3), and first binder PVDF are mixed at a mass ratio of 60:30:10. Then, the first solvent NMP is added, and the mixture is stirred under vacuum until homogeneous, yielding a first slurry with a solid content of 30 wt%. An 8 μm copper foil is selected as the current collector. The first slurry is applied to both sides of the current collector surface along its length using an extrusion coating method. After drying at 90°C, two insulating strip-shaped coatings are formed. A blank area is formed on the current collector surface between the outer edge of each insulating strip-shaped coating furthest from the main area and the long edge of the current collector closest to it. Correspondingly, the current collector surface between the two insulating strip-shaped coatings, without the first slurry coating, forms the main area. The insulating strip-shaped coatings have a thickness of 24 μm and a width of 5 mm, while the blank area has a width of 10 mm.

[0134] <Preparation of Active Material Layer>

[0135] Artificial graphite (negative electrode active material), conductive carbon black (conductive agent), and SBR (second binder) were mixed at a mass ratio of 96:2:2. Then, deionized water (second solvent) was added, and the mixture was stirred under vacuum until homogeneous, yielding a second slurry with a solid content of 60 wt%. The second slurry was coated onto the surface of the main body area using an extrusion coating method, dried at 120°C, and cold-pressed to obtain a negative electrode sheet with a negative electrode active material layer thickness of 35 μm. The above steps were then repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with an insulating strip coating and an active material layer on both sides. This negative electrode sheet was then processed through tab forming and slitting to obtain the final negative electrode sheet.

[0136] Examples 2-2 to 2-9

[0137] Except for adjusting the types of functional materials, insulating materials, and first solvents in the first slurry, as shown in Table 2, and the mass ratio between each component, everything else is the same as in Example 2-1.

[0138] Examples 2-10 to 2-11

[0139] Except for adjusting the amount of the first solvent added, thereby adjusting the solid content of the first slurry as shown in Table 2, the rest is the same as in Example 2-1.

[0140] Examples 3-1 to 3-7

[0141] Except for adjusting the thickness and width of the insulating strip coating and the thickness and width of the active material layer as shown in Table 3, the rest is the same as in Example 1-1.

[0142] Examples 4-1 to 4-7

[0143] Except for adjusting the thickness and width of the insulating strip coating and the thickness and width of the active material layer as shown in Table 4, the rest is the same as in Example 2-1.

[0144] Comparative Example 1-1

[0145] Except that the first slurry does not contain functional materials and the mass ratios of the components are adjusted as shown in Table 1, the rest is the same as in Example 1-1.

[0146] Comparative Example 2-1

[0147] Except that the first slurry does not contain functional materials and the mass ratios between the components are adjusted as shown in Table 2, the rest is the same as in Example 2-1.

[0148]

[0149]

[0150] The relevant parameters of Examples 3-1 to 3-7 are shown in Table 3 below.

[0151] Table 3

[0152]

[0153] In the table, " / " indicates that the relevant parameter does not exist.

[0154] The relevant parameters of Examples 4-1 to 4-7 are shown in Table 4 below.

[0155] Table 4

[0156]

[0157] In the table, " / " indicates that the relevant parameter does not exist.

[0158] Contact angle test between active material slurry and insulating strip coating:

[0159] The contact angle between the active slurry and the insulating strip layer was tested using a contact angle meter.

[0160] Measurement of the thickness H1 of the edge-band coating and the thickness H2 of the active material layer:

[0161] Use a micrometer to measure the thickness H1 of the edge banding coating and the thickness H2 of the active material layer.

[0162] Electrode defect rate test:

[0163] Due to the significant color difference between the active material and the insulating strip coating, a charge-coupled device (CCD) displays grayscale values ​​to distinguish the boundary between the active material layer and the insulating strip coating. One hundred electrode sheets from each embodiment and comparative example were taken, and the presence of a clear interface between the insulating strip coating and the active material layer in each electrode sheet was determined using a CCD device according to the following method:

[0164] If the active material layer and the insulating strip coating are not fused, a clear grayscale transition will be observed, indicating a clear interface, and the product will be considered good. If the active material layer and the insulating strip coating are fused, an unclear grayscale transition will be observed, indicating a lack of a clear interface, and the product will be considered defective.

[0165] Then, count the number of good and bad electrodes out of 100 electrodes. The defect rate of the electrodes is calculated as: (Number of bad electrodes / 100) × 100%.

[0166] The electrode sheets prepared in each embodiment and comparative example were tested for defect rate according to the electrode sheet defect rate test method provided in this application. The results are as follows.

[0167] Table 5: Performance test results of Examples 1-1 to 1-8 and Comparative Example 1-1

[0168] CCD determines the number of defective products. CCD determines the number of good products defect rate Example 1-1 2 98 2％ Examples 1-2 0 100 0％ Examples 1-3 0 100 0％ Examples 1-4 0 100 0％ Examples 1-5 0 100 0％ Examples 1-6 0 100 0％ Examples 1-7 0 100 0％ Examples 1-8 0 100 0％ Comparative Example 1-1 100 0 100％

[0169] Based on the above results, it can be seen that the electrode sheets of Examples 1-1 to 1-8 have a low defect rate. It is evident that the electrode sheets with the insulating strip coating of this application reduce the defect rate of the electrode sheets, giving them excellent quality, reducing the scrap of electrode sheets, and lowering production costs.

[0170] In contrast, the electrode sheet of Comparative Example 1-1, since the first slurry does not contain the functional material of this application, is prone to the problem of the active material slurry diffusing outward along the width direction of the electrode sheet, resulting in a high defect rate, and the high defect rate is not conducive to reducing production costs.

[0171] Table 6: Performance test results of Examples 2-1 to 2-11 and Comparative Example 2-1

[0172] CCD determines the number of defective products. CCD determines the number of good products defect rate Example 2-1 0 100 0％ Example 2-2 0 100 0％ Example 2-3 0 100 0％ Examples 2-4 0 100 0％ Examples 2-5 0 100 0％ Examples 2-6 0 100 0％ Examples 2-7 0 100 0％ Examples 2-8 0 100 0％ Examples 2-9 0 100 0％ Example 2-10 0 100 0％ Example 2-11 0 100 0％ Comparative Example 2-1 100 0 100％

[0173] Based on the above results, it can be seen that the electrode sheets of Examples 2-1 to 2-11 have a low defect rate. It is evident that the electrode sheets with the insulating strip coating of this application reduce the defect rate of the electrode sheets, giving them excellent quality, reducing the scrap of electrode sheets, and lowering production costs.

[0174] In contrast, the electrode sheet of Comparative Example 2-1, since the first slurry does not contain the functional material of this application, is prone to the problem of the active material slurry diffusing outward along the width direction of the electrode sheet, resulting in a high defect rate, and the high defect rate is not conducive to reducing production costs.

[0175] Table 7: Performance test results of Examples 3-1 to 3-7

[0176]

[0177]

[0178] The thickness H1 of the insulating strip coating and the thickness H2 of the active material layer typically affect the defect rate of the electrode sheet. As can be seen from Examples 1-1 and 3-1 to 3-5, the defect rate of the electrode sheet can be further reduced by adjusting the thickness H1 of the insulating strip coating and the thickness H2 of the active material layer.

[0179] It can also be seen from Examples 3-1 to 3-3 that by adjusting the ratio between the thickness H1 of the insulating strip coating and the thickness H2 of the active material layer, the defect rate of the electrode sheet can be further reduced.

[0180] The width of the insulating strip coating also has a certain impact on the defect rate of the electrode sheet. As can be seen from Examples 3-1 to 3-7, by adjusting the width of the insulating strip coating, the defect rate of the electrode sheet can be further reduced.

[0181] Table 8: Performance test results of Examples 4-1 to 4-7

[0182] CCD determines the number of defective products. CCD determines the number of good products defect rate Example 2-1 0 100 0％ Example 4-1 2 98 2％ Example 4-2 0 100 0％ Example 4-3 0 100 0％ Example 4-4 20 80 20％ Examples 4-5 31 69 31％ Examples 4-6 26 74 26％ Examples 4-7 19 81 19％

[0183] The thickness H1 of the insulating strip coating and the thickness H2 of the active material layer typically affect the defect rate of the electrode sheet. As can be seen from Examples 2-1 and 4-1 to 4-7, the defect rate of the electrode sheet can be further reduced by adjusting the thickness H1 of the insulating strip coating and the thickness H2 of the active material layer.

[0184] It can also be seen from Examples 4-1 to 4-3 that by adjusting the ratio between the thickness H1 of the insulating strip coating and the thickness H2 of the active material layer, the defect rate of the electrode sheet can be further reduced.

[0185] The width of the insulating strip coating also has a certain impact on the defect rate of the electrode sheet. As can be seen from Examples 4-1 to 4-7, by adjusting the width of the insulating strip coating, the defect rate of the electrode sheet can be further reduced.

[0186] Figure 12The image shows a photograph of the electrode sheet prepared in Example 1-1 (the main body region is not fully shown in the image due to its width). As can be seen from the image, a clear interface is formed between the main body region and the isolation region of the electrode sheet, indicating that the active material in the main body region does not diffuse along the width of the electrode sheet.

[0187] Figure 13 The image shows a photograph of the electrode sheet prepared in Comparative Example 1-1 (the main body region is not fully shown in the image due to its width). As can be seen from the image, an indistinct interface forms between the main body region and the isolation region of this electrode sheet, indicating that the active material in the main body region has diffused along the width of the electrode sheet.

[0188] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrode sheet, characterized in that, The electrode includes a main body region and an isolation region. Along the width direction of the electrode sheet, the isolation region is disposed on both sides of the main body region and has an insulating strip-shaped coating. The main body region has an active material layer. The outer edge of the active material layer is confined at the junction between the main body area and the isolation area, and the contact angle between the slurry forming the active material layer and the insulating strip coating is greater than 90°. The insulating strip coating includes a functional material; the slurry forming the active material layer is an oil-based slurry, and the insulating strip coating includes an oleophobic material; the oleophobic material includes at least one of polytetrafluoroethylene and nano-SiO2.

2. The electrode sheet according to claim 1, characterized in that, The contact angle between the slurry forming the active material layer and the insulating strip coating is greater than 125°.

3. The electrode sheet according to claim 1 or 2, characterized in that, The thickness H1 of the insulating strip coating is less than the thickness H2 of the active material layer.

4. The electrode sheet according to claim 3, characterized in that, The thickness H1 of the insulating strip coating is 5 μm to 30 μm, and the thickness H2 of the active material layer is 30 μm to 150 μm.

5. The electrode sheet according to claim 4, characterized in that, The thickness H1 of the insulating strip coating and the thickness H2 of the active material layer satisfy the following relationship: 1 / 5 ≤ H1 ∶ H2 ≤ 2 / 3.

6. The electrode sheet according to claim 1, characterized in that, The width of the insulating strip coating is 1mm to 20mm.

7. A method for preparing an electrode sheet, characterized in that, Includes the following steps: Preparation of insulating strip coating: A functional material, an insulating material, and a first binder are mixed, and a first solvent is added to form a first slurry. The first slurry is coated on both sides of the current collector surface along the length of the current collector. After drying, two insulating strip coatings are formed. The current collector surface between the two insulating strip coatings, where the first slurry is not coated, forms the main area. The functional material is selected from oleophobic materials; the oleophobic material includes at least one of polytetrafluoroethylene and nano-SiO2. Preparation of the active material layer: The electrode active material, conductive agent and second binder are mixed and then a second solvent is added to form a second slurry; the second slurry is coated on the surface of the main body area and dried to form an active material layer; wherein the contact angle between the second slurry and the insulating strip coating is greater than 90°.

8. The preparation method according to claim 7, characterized in that, The contact angle between the second slurry and the insulating strip coating is greater than 125°.

9. The preparation method according to claim 7, characterized in that, Based on the total mass of the insulating strip coating, the functional material has a mass percentage of 40% to 70%, the insulating material has a mass percentage of 20% to 30%, and the first adhesive has a mass percentage of 10% to 30%.

10. The preparation method according to claim 7, characterized in that, The functional material is selected from oleophobic materials, the first solvent is selected from aqueous solvents, and the second solvent is selected from oily solvents.

11. The preparation method according to claim 7, characterized in that, The first adhesive and the second adhesive each independently comprise polyvinylidene fluoride or styrene-butadiene rubber.

12. The preparation method according to claim 7, characterized in that, The insulating material includes at least one of aluminum oxide and boehmite.

13. A secondary battery, characterized in that, It includes at least one of the electrode sheets selected from any one of claims 1 to 6 and the electrode sheets prepared by the preparation method of any one of claims 7 to 12.

14. A battery module, characterized in that, Includes the secondary battery as described in claim 13.

15. A battery pack, characterized in that, Includes the battery module as described in claim 14.

16. An electrical appliance, characterized in that, It includes at least one selected from the secondary battery of claim 13, the battery module of claim 14, or the battery pack of claim 15.

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