Positive current collector, positive electrode sheet, manufacturing method, and battery

Abstract

This application relates to a positive electrode current collector, a positive electrode sheet and a manufacturing method thereof, and a battery. The positive electrode current collector has a foil material and a protective layer provided on the surface of the foil material. The protective layer contains inorganic particles, and the ratio of the thickness of the protective layer to the thickness of the foil material is 0.05 to 0.7. In this application, by controlling the thickness of the protective layer containing inorganic particles, the thickness ratio between the protective layer and the foil material is ensured, whereby a current collector having an ultra-thin protective layer is obtained. Due to the ultra-thin structure of the protective layer, wrinkles and bulges do not occur when the current collector is wound, enabling the winding and storage of the current collector. Furthermore, a process of stepwise coating during the manufacturing process of the positive electrode sheet is realized, avoiding the problem of a decrease in the gram capacity of the electrode sheet caused by the simultaneous coating of the active material layer and the protective layer.

Description

Technical Field

[0001] The present application belongs to the technical field of current collector manufacturing, and relates to, for example, a positive current collector, a positive electrode sheet and a manufacturing method, and a battery.

Background Art

[0002] A current collector is a structure or component for collecting current in a lithium-ion battery. Its main function is to collect the current generated from the active material of the battery, provide an electron passage, accelerate the charge transfer, and improve the charge-discharge Coulomb efficiency. As a current collector, it is necessary to satisfy characteristics such as high electrical conductivity, good mechanical performance, light mass, and low resistance when contacting the internal resistance and the active material surface.

[0003] Currently, commonly used current collectors are aluminum current collectors, copper current collectors, composite aluminum current collectors, and composite copper current collectors. Aluminum current collectors are usually manufactured by rolling, copper current collectors are manufactured by rolling or electroplating, and composite current collectors are manufactured by plating an aluminum or copper layer on a polymer material.

[0004] In order to improve the processing performance of the electrode sheet and the safety of the battery, as a positive electrode sheet, the surface of its current collector is coated with an active coating, and in addition, ceramic protection layers are applied on both sides of the active coating.

[0005] Specifically, while applying an active slurry to the current collector, a ceramic protection layer is applied to the current collector by extrusion coating. However, when applying simultaneously, some ceramics will fuse with the active slurry, resulting in a decrease in the gram capacity of the active coating. It is necessary to quickly solve the problem of providing a current collector that satisfies the electrochemical performance and has excellent processing effects.

Summary of the Invention

[0006] The following presents an overview of the subject matter to be described in detail in this specification. This overview does not limit the scope of protection of the claims.

[0007] In view of the problems existing in the related art, the present application provides a positive electrode current collector, a positive electrode sheet and a manufacturing method, and a battery. By controlling the thickness of the protective layer containing inorganic particles, it is ensured that the thickness ratio between the protective layer and the foil material is within the range of 0.05 to 0.7. Thereby, a current collector with an ultra-thin protective layer is obtained, enabling the winding and storage of the current collector. According to the current collector, a process of stepwise coating during the manufacturing process of the electrode sheet is realized, and the problems caused by simultaneous coating in the related art are avoided.

[0008] Also, due to the ultra-thin protective layer structure, it is difficult for wrinkles to occur on the electrode sheet during the winding process, and the problem of bulging protrusions is avoided, and furthermore, the production quality is improved.

[0009] To achieve the above object, the following technical aspects are used in the present application.

[0010] According to a first aspect, in an embodiment of the present application, there is provided a positive electrode current collector having a foil material and a protective layer provided on the surface of the foil material, and the protective layer contains inorganic particles. The ratio of the thickness of the protective layer to the thickness of the foil material is 0.05 to 0.7. For example, it may be 0.05, 0.08, 0.1, 0.2, 0.5 or 0.7, but it is not limited to the listed numerical values, and numerical values within the numerical range but not listed are also applicable.

[0011] In the embodiments of the present application, by controlling the thickness of the protective layer containing inorganic particles, it is ensured that the thickness ratio of the protective layer to the foil material is within the range of 0.05 to 0.7, whereby a current collector with an ultra-thin protective layer is obtained, enabling the winding and storage of the positive electrode current collector. According to the positive electrode current collector, a process of stepwise coating during the manufacturing process of the electrode sheet is realized, and problems caused by simultaneous coating in related technologies are avoided. In addition, due to the ultra-thin protective layer structure, wrinkles are less likely to occur on the electrode sheet during the winding process, and the problem of bulges protruding is avoided, and furthermore, the production quality is improved.

[0012] The positive electrode current collector according to the embodiments of the present application can be applied to a positive electrode sheet having any positive electrode active material.

[0013] The ratio of the thickness of the protective layer to the thickness of the foil material is 0.0625 to 0.625, and may be, for example, 0.0625, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5 or 0.625, but is not limited to the listed numerical values, and numerical values within the range but not listed are also applicable.

[0014] The current collector obtained by setting the ratio of the thickness of the protective layer to the thickness of the foil material to 0.625 or less has a protective layer with an ultra-thin structure applied thereto. Due to the ultra-thin structure of the protective layer, no wrinkles or bulges occur when the current collector is wound, enabling the winding and storage of the current collector. Furthermore, a process of stepwise coating during the manufacturing process of the positive electrode sheet is realized, and the problem of a decrease in the gram capacity of the electrode sheet caused by simultaneous coating of the active material layer and the protective layer is avoided.

[0015] In one embodiment, the thickness of the protective layer is in the range of 0 to 5 μm but not 0, and may be, for example, 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, but is not limited to the listed numerical values, and numerical values within the range but not listed are also applicable, and preferably 1 to 3 μm.

[0016] In one embodiment, the material of the protective layer contains a binder and inorganic particles.

[0017] In one embodiment, with respect to the mass of the protective layer, the mass of the binder is 70 to 100 wt%, but not 100 wt%. For example, it may be 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt% or 95 wt%, but is not limited to the recited values, and values within the numerical range but not recited are also applicable. Preferably, it is 70 to 95 wt%.

[0018] The ratio of the binder to the mass of the protective layer is at least 70 wt%. Different from the related art in which a small amount of binder is used in the protective layer, in the embodiments of the present application, by increasing the content of the binder, it is ensured that the ratio of the thickness of the protective layer to the thickness of the foil material is 0.0625 to 0.625. By controlling the mass occupancy rate of the binder, the thickness of the protective layer can be effectively reduced, thereby reducing the total usage amount of the protective layer material and further reducing the production cost of the current collector. If the mass occupancy rate of the binder is less than 70 wt%, the ratio of the thickness of the protective layer to the thickness of the foil material cannot be made 0.625 or less.

[0019] In one embodiment, the binder is a first binder and a second binder. The first binder is used in an aqueous slurry, while the second binder is used in an oil-based slurry.

[0020] In one embodiment, the first binder includes any one or at least a combination of two or more selected from polyacrylic acid or its modified polymer, polyacrylamide or its modified polymer, polyurethane or its modified polymer, polyethylene hydrocarbon or its modified polymer, carboxyvinyl polymer, polyacrylate, polyimide, polyamideimide, carbomer resin, hydroxypolyethylene, or polymer-bonded benzyl acrylate. Typical and non-limiting combinations include combinations of polyacrylic acid and its modified polymer with polyacrylamide, combinations of polyacrylic acid and its modified polymer with polyacrylamide and its modified polymer, combinations of polyacrylamide and its modified polymer with polyurethane and its modified polymer, combinations of polyurethane and its modified polymer with polyethylene hydrocarbon and its modified polymer, combinations of polyethylene hydrocarbon and its modified polymer with carboxyvinyl polymer and polyacrylate, combinations of carboxyvinyl polymer with polyacrylate and polyimide, combinations of polyimide with polyamideimide and carbomer resin, combinations of polyamideimide with carbomer resin and hydroxypolyethylene, and combinations of carbomer resin with hydroxypolyethylene and polymer-bonded benzyl acrylate.

[0021] In one embodiment, the second binder includes any one or at least a combination of two or more selected from polyvinylidene fluoride, polyimide-based polymer, polyacrylic acid polymer, or its modified compound. For example, combinations include combinations of polyvinylidene fluoride and polyimide-based polymer, combinations of polyimide-based polymer and polyacrylic acid polymer, combinations of polyacrylic acid polymer and its modified compound, combinations of polyvinylidene fluoride with polyimide-based polymer and polyacrylic acid polymer, and combinations of polyimide-based polymer with polyacrylic acid polymer and its modified compound.

[0022] In one embodiment, the mass percentage content of the inorganic particles relative to the mass of the protective layer is from 0 to 30 wt%, but not 0, and may be, for example, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt% or 29 wt%, but is not limited to the recited values, and values within the numerical range but not recited are also applicable, and preferably it is from 10 to 30 wt%.

[0023] In one embodiment, the inorganic particles include any one or at least a combination of two selected from alumina, boehmite, mica, glass fiber, titanium oxide, or magnesium oxide. Typical and non-limiting combinations include the combination of alumina and boehmite, the combination of boehmite and mica, the combination of mica and glass fiber, the combination of glass fiber and titanium oxide, the combination of titanium oxide and magnesium oxide, the combination of alumina and the combination of boehmite and mica, the combination of boehmite and the combination of mica and glass fiber, the combination of mica and the combination of glass fiber and titanium oxide, the combination of glass fiber and the combination of titanium oxide and magnesium oxide.

[0024] In one embodiment, the areal density of the protective layer is from 0.05 to 2 g / m 2 and may be, for example, 0.05 g / m 2 , 0.1 g / m 2 , 0.5 g / m 2 , 1 g / m 2 , 1.5 g / m 2 or 2 g / m 2 but is not limited to the recited values, and values within the numerical range but not recited are also applicable.

[0025] In one embodiment, the resistance value of the protective layer is from 0 to 1000 Ω, but not 0, and may be, for example, 1 mΩ, 5 mΩ, 10 mΩ, 500 mΩ, 1 Ω, 5 Ω, 10 Ω, 50 Ω, 100 Ω, 500 Ω or 1000 Ω, but is not limited to the recited values, and values within the numerical range but not recited are also applicable, and preferably it is from 100 mΩ to 400 Ω.

[0026] In one embodiment, the adhesion between the protective layer and the foil material is 100 N / m or more (it is 100 N / m or exceeds 100 N / m), for example, it may be 100 N / m, 200 N / m, 300 N / m, 400 N / m or 500 N / m, but it is not limited to the recited numerical values, and numerical values within the numerical range but not recited are also applicable. After electrolyte immersion, the adhesion between the protective layer and the foil material becomes 20 N / m or more, for example, it may be 20 N / m, 50 N / m, 70 N / m, 80 N / m or 100 N / m, but it is not limited to the recited numerical values, and numerical values within the numerical range but not recited are also applicable.

[0027] In one embodiment, the foil material is an aluminum foil or a composite aluminum foil.

[0028] The protective layer may be disposed on one side of the foil material or on both sides of the foil material according to the requirements of the electrochemical characteristics of the positive current collector and the positive electrode sheet, and is not particularly limited in the embodiments of the present application.

[0029] In one embodiment, a blank area is disposed on the surface of the foil material, and protective layers are disposed on both sides of the blank area respectively. The blank area does not contain inorganic particles and is for manufacturing a positive electrode sheet by coating an active material. The blank area and the protective layer spatially divide the surface of the positive current collector.

[0030] In one embodiment, the width of the blank area is 10 to 1400 mm, for example, it may be 10 mm, 50 mm, 100 mm, 500 mm, 1000 mm or 1400 mm, but it is not limited to the recited numerical values, and numerical values within the numerical range but not recited are also applicable.

[0031] In one embodiment, the width of the protective layer is 0 to 20 mm but not 0, for example, it may be 0.5 mm, 1 mm, 5 mm, 10 mm, 15 mm or 20 mm, but it is not limited to the recited numerical values, and numerical values within the numerical range but not recited are also applicable.

[0032] In one embodiment, a conductive coating or a safety layer is disposed in the blank region. The conductive coating reduces the contact resistance between the current collector and the active material.

[0033] In one embodiment, the ratio of the thickness of the protective layer to the thickness of the conductive coating is 0.5 to 10, and may be, for example, 0.5, 1, 3, 5, 8, or 10, but is not limited to the recited values, and values within the numerical range that are not recited are also applicable.

[0034] In one embodiment, the conductive coating contains a conductive carbon material and a binder.

[0035] In one embodiment, based on the mass of the conductive coating, the mass percentage content of the conductive carbon material is 40 to 60 wt%, and may be, for example, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 60 wt%, but is not limited to the recited values, and values within the numerical range that are not recited are also applicable.

[0036] In one embodiment, based on the mass of the conductive coating, the mass percentage content of the binder in the conductive coating is 40 to 60 wt%, and may be, for example, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 60 wt%, but is not limited to the recited values, and values within the numerical range that are not recited are also applicable.

[0037] In one embodiment, the ratio of the thickness of the protective layer to the thickness of the safety layer is 0.08 to 5, and may be, for example, 0.08, 0.1, 0.5, 1, 2, 2.5, or 5, but is not limited to the recited values, and values within the numerical range that are not recited are also applicable.

[0038] In one embodiment, the material of the safety layer contains a positive electrode active material and a binder. The positive electrode active material includes lithium iron manganese phosphate and / or lithium iron phosphate.

[0039] The binders in the conductive coating and the safety layer are each independently any one or at least a combination of two selected from polyacrylic acid or its modified polymer, polyacrylamide or its modified polymer, polyurethane or its modified polymer, polyethylene hydrocarbon or its modified polymer, carboxyvinyl polymer, polyacrylate, polyimide, polyamideimide, carbomer resin, hydroxy polyethylene or polymer-bonded benzyl acrylate.

[0040] In the examples of the present application, the purpose of disposing the conductive coating in the blank region is to enhance the conductivity of the electrode sheet, while the purpose of disposing the safety layer is to enhance the thermal stability of the active material.

[0041] According to a second aspect, in the examples of the present application, a method for manufacturing a positive current collector according to the first aspect is provided, and the manufacturing method includes: a step of preparing a protective layer slurry; a step of applying the prepared protective layer slurry to the surface of the foil material, drying it, and then obtaining the positive current collector and winding and storing the manufactured one.

[0042] In the examples of the present application, the thickness of the protective layer is controlled, an ultra-thin protective layer structure is used, and a process method of applying the protective layer slurry and the active material layer slurry step by step is realized. First, the protective layer is applied to manufacture the current collector, and then the active material slurry is applied to manufacture the positive electrode sheet. Thus, the manufactured current collector can be wound and stored, and wrinkles and bulges are less likely to occur in the wound current collector.

[0043] In one example, the method for preparing the protective layer slurry includes mixing a binder, inorganic particles, and a solvent, and stirring to obtain the protective layer slurry.

[0044] In one example, the solvent includes deionized water and an oily solvent, preferably deionized water.

[0045] In the embodiments of the present application, the purpose of arranging an ultra-thin protective layer structure can be achieved by using either an aqueous slurry or an oil-based slurry. Compared with the oil-based slurry, the aqueous slurry is environmentally friendly and has low pollution. At the same time, in the method of applying the aqueous slurry step by step, the adhesion between the slurry and the foil material is good, and even if it is wiped off after electrolyte immersion, the powder is not likely to fall off.

[0046] In one embodiment, the protective layer slurry also contains a surfactant. By adding the surfactant, the wettability of the ceramic slurry on the foil material is improved, the coating leakage rate is reduced, and the coating efficiency is improved.

[0047] In one embodiment, the surfactant includes any one or at least a combination of two selected from a-[3,5-dimethyl-1-(2-methylpropyl)hexyl]-w-hydroxy-poly(oxy-1,2-ethanediyl), polyoxyethylene 2,6,8-trimethyl-4-nonyl ether, or polyoxyethylene trimethyl nonyl ether. Typical and non-limiting combinations include the combination of a-[3,5-dimethyl-1-(2-methylpropyl)hexyl]-w-hydroxy-poly(oxy-1,2-ethylenediyl) and polyoxyethylene 2,6,8-trimethyl-4-nonyl ether, the combination of polyoxyethylene 2,6,8-trimethyl-4-nonyl ether and polyoxyethylene trimethyl nonyl ether, and the combination of a-[3,5-dimethyl-1-(2-methylpropyl)hexyl]-w-hydroxy-poly(oxy-1,2-ethylenediyl) and polyoxyethylene trimethyl nonyl ether.

[0048] In one embodiment, the mass of the surfactant is 1 wt% or less of the mass of the protective layer slurry. For example, it may be 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt% or 0.9 wt%, but it is not limited to the listed values, and values within the numerical range but not listed are also applicable.

[0049] In one embodiment, as the mixing method, the binder is added to the solvent under the agitation of two planetary rotations with a revolution speed of 20 to 30 rpm and a rotation speed of 700 to 900 rpm, and after stirring for 15 to 40 minutes, inorganic particles are added, and then stirred with two planetary rotations at a revolution speed of 20 to 30 rpm and a rotation speed of 2200 to 2600 rpm for 250 to 350 minutes.

[0050] In one embodiment, a surfactant and a binder are added simultaneously during the mixing process.

[0051] In one embodiment, the viscosity of the protective layer slurry is in the range of 0 to 500 mPa·s, but not 0. For example, it may be 50 mPa·s, 100 mPa·s, 200 mPa·s, 300 mPa·s, 400 mPa·s or 500 mPa·s. However, it is not limited to the listed values, and values within the numerical range but not listed are also applicable.

[0052] In one embodiment, the solid content of the protective layer slurry is in the range of 0 to 20%, but not 0. For example, it may be 5%, 10%, 15%, 18% or 20%. However, it is not limited to the listed values, and values within the numerical range but not listed are also applicable, and preferably it is 5 to 15%.

[0053] In one embodiment, the coating speed is from 0.5 to 100, for example, it may be 0.5 m / min, 1 m / min, 5 m / min, 10 m / min, 20 m / min, 50 m / min or 100 m / min. However, it is not limited to the listed values, and values within the numerical range but not listed are also applicable.

[0054] In one embodiment, the drying temperature is 80 to 120 °C. For example, it may be 80 °C, 90 °C, 100 °C, 110 °C or 120 °C. However, it is not limited to the listed values, and values within the numerical range but not listed are also applicable.

[0055] In one embodiment, a blank area is arranged on the surface of the foil material, and the protective layers are arranged on both sides of the blank area respectively.

[0056] In one embodiment, a conductive coating or a safety layer is disposed in the blank area.

[0057] In one embodiment, the method for manufacturing the positive current collector further includes applying a conductive coating slurry or a safety layer slurry to the blank area.

[0058] As an alternative technical aspect of the manufacturing method according to the second aspect of the present application, the manufacturing method adds a binder to a solvent according to a ratio, stirs for 15 to 40 minutes with a two-planet rotation at a revolution speed of 20 to 30 rpm and a rotation speed of 700 to 900 rpm, then adds inorganic particles, and then stirs for 250 to 350 minutes with a two-planet rotation at a revolution speed of 20 to 30 rpm and a rotation speed of 2200 to 2600 rpm to obtain a protective layer slurry having a viscosity of 0 to 500 mPa·s but not 0 and a solid content of 0 to 20% but not 0; applying the obtained protective layer slurry to the surface of the foil material, applying a conductive coating slurry or a safety layer slurry to the blank area on the surface of the foil material, disposing protective layer slurries on both sides of the blank area, setting the coating speed to 0.5 to 100 m / min, drying at 80 to 120°C, and then obtaining the positive current collector.

[0059] According to a third aspect, a positive electrode sheet is provided in the present application. The positive electrode sheet contains a positive current collector according to the first aspect and an active material layer disposed on the surface of the positive current collector, and the protective layers are disposed on both sides of the active material layer, respectively.

[0060] According to a fourth aspect, in an embodiment of the present application, a method for manufacturing the positive electrode sheet according to the third aspect is provided. The manufacturing method includes preparing an active material layer slurry; applying the prepared active material layer slurry to the positive current collector obtained by the manufacturing method according to the second aspect, drying, and then obtaining the positive electrode sheet.

[0061] In one embodiment, the method for manufacturing the positive electrode sheet includes: preparing a protective layer slurry, applying the prepared protective layer slurry onto the surface of a foil material, drying it to obtain a positive electrode current collector, where the positive electrode current collector includes a protective layer; and preparing an active material layer slurry, applying the prepared active material layer slurry between adjacent protective layers of the positive electrode current collector, and drying it to obtain the positive electrode sheet.

[0062] In related technologies, an electrode sheet is directly manufactured after one-step coating by a process of simultaneously coating a ceramic slurry having a safety protection function and an active material slurry. However, during the one-step coating process, the protective layer slurry and the active material slurry belong to two types of slurries with significant differences in characteristics, and there are significant differences in their viscosities and solid content, etc. Therefore, the simultaneous coating speed is greatly limited. In addition, the instability of the coating surface density also increases, and furthermore, the consistency of the battery deteriorates.

[0063] In the embodiments of the present application, by first coating a protective layer to manufacture a current collector and then coating an active material slurry to manufacture a positive electrode sheet, the time for manufacturing the positive electrode sheet is shortened, the consistency of battery production is improved, and moreover, the manufactured current collector can be stored after winding.

[0064] In one embodiment, the active material layer slurry contains an active material, a conductive agent, a binder, and a solvent.

[0065] In one embodiment, the solid content of the active material layer slurry is 45% to 80%, for example, it may be 45%, 50%, 60%, 70%, or 80%, but it is not limited to the recited values, and values within the numerical range but not recited are also applicable.

[0066] In one embodiment, the viscosity of the active material layer slurry is 2,000 to 3,000 mPa·s, and may be, for example, 2,000 mPa·s, 2,200 mPa·s, 2,400 mPa·s, 2,600 mPa·s, 2,800 mPa·s, or 3,000 mPa·s. However, it is not limited to the recited values, and values within the numerical range but not recited are also applicable.

[0067] In one embodiment, the coating speed is 0.5 to 100 m / min, and may be, for example, 0.5 m / min, 1 m / min, 5 m / min, 10 m / min, 20 m / min, 50 m / min, or 100 m / min. However, it is not limited to the recited values, and values within the numerical range but not recited are also applicable.

[0068] In one embodiment, the active material layer slurry is applied to the blank area of the positive electrode current collector.

[0069] In one embodiment, the drying temperature is 80 to 120 °C, and may be, for example, 80 °C, 90 °C, 100 °C, 110 °C, or 120 °C. However, it is not limited to the recited values, and values within the numerical range but not recited are also applicable.

[0070] As an alternative technical aspect of the method for manufacturing a positive electrode sheet according to the fourth aspect of the present application, the manufacturing method includes the following steps.

[0071] Add the binder to the solvent according to the ratio, stir for 15 - 40 min with a two - planet stirrer at a revolution speed of 20 - 30 rpm and a rotation speed of 700 - 900 rpm, then add inorganic particles, and then stir for 250 - 350 min with a two - planet stirrer at a revolution speed of 20 - 30 rpm and a rotation speed of 2200 - 2600 rpm to obtain a protective layer slurry with a viscosity in the range of 0 - 500 mPa·s (but not 0) and a solid content in the range of 0 - 20% (but not 0); Apply the obtained protective layer slurry to the surface of the foil material, apply the conductive coating slurry or the safety layer slurry to the blank area on the surface of the foil material, arrange the protective layer slurry on both sides of the blank area respectively, set the coating speed at 0.5 - 100 m / min, dry at 80 - 120 °C to obtain the positive current collector, and the positive current collector includes a protective layer; The method of applying the protective layer slurry and the conductive coating slurry, or the protective layer slurry and the safety layer slurry is step - by - step coating or simultaneous coating;

[0072] Mix the active material, conductive agent and binder according to the ratio to prepare an active material layer slurry with a viscosity of 2000 - 3000 mPa·s and a solid content of 45 - 80%. Apply the prepared active material layer slurry at a speed of 0.5 - 100 m / min between the adjacent protective layers of the positive current collector, and dry at 80 - 120 °C to obtain the positive electrode sheet.

[0073] According to the fifth aspect, in the embodiments of the present application, a battery having the positive current collector according to the first aspect or the positive electrode sheet according to the third aspect is provided.

[0074] According to the sixth aspect, in the embodiments of the present application, an electrical utilization device having the battery according to the fifth aspect is provided.

[0075] The beneficial effects brought by the above technical aspects to the present application are shown below.

[0076] In the present application, by controlling the thickness of the protective layer containing inorganic particles, it is ensured that the thickness ratio of the protective layer to the foil material is within the range of 0.05 to 0.7, whereby a current collector having an ultra-thin protective layer is obtained. Due to the ultra-thin structure of the protective layer, wrinkles or bulges do not occur when the current collector is wound, enabling the winding and storage of the current collector. Furthermore, a process of stepwise coating during the manufacturing process of the positive electrode sheet is realized, avoiding the problem of a decrease in the gram capacity of the electrode sheet caused by the simultaneous coating of the active material layer and the protective layer in related technologies.

[0077] In addition, the protective layer has a strong adhesion force with the foil material, is difficult to detach from the foil material, has a thin thickness, and does not become brittle even after being baked twice (when the active material layer is coated first, the active material layer must be baked twice, resulting in a small weight reduction rate of the electrode sheet, excessive evaporation of the solvent, brittleness of the electrode sheet, and a decrease in the use performance of the electrode sheet).

[0078] After reading and understanding the drawings and the detailed description, other aspects can be understood.

Brief Description of the Drawings

[0079] The drawings provide a further understanding of the technical aspects of this specification and are used to explain the technical aspects of this specification together with the embodiments of the present application as part of the specification, and do not limit the technical aspects of this specification.

Figure 1

Figure 2

Figure 3

[0080] 1 - Foil material, 2 - Blank area, 3 - Protective layer, 4 - Conductive coating, 5 - Safety layer.

Modes for Carrying Out the Invention

[0081] Hereinafter, the technical aspects of the present application will be further described with reference to the drawings in specific embodiments. However, the following examples are merely simple examples of the present application and do not represent or limit the scope of the rights of the present application. The protection scope of the present application shall comply with the scope of the claims.

[0082] Example 1 In this example, a positive electrode current collector (the schematic diagram of its structure is as shown in Figure 1) is provided. The positive electrode current collector has a foil material 1, a blank region 2 provided on one surface of the foil material 1, and a protective layer 3. The foil material 1 is an aluminum foil. Protective layers 3 are respectively arranged on both sides of the blank region 2. The width of the blank region 2 is 178 mm, and the width of the protective layer 3 is 8 mm.

[0083] The thickness of the aluminum foil 1 is 16 μm, the thickness of the protective layer 3 is 1 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the aluminum foil 1 is 0.625.

[0084] The material of the protective layer 3 contains polyacrylic acid and boehmite. The mass of polyacrylic acid is 90 wt% of the mass of the protective layer 3, and the mass of boehmite is 10 wt% of the mass of the protective layer 3. The surface density of the protective layer 3 is 0.48 g / m 2 is.

[0085] The manufacturing method of the positive electrode current collector includes the following.

[0086] The binder was added to deionized water at a mass ratio of the binder to inorganic particles, stirred for 30 min with a two-planet stirrer at a revolution speed of 25 pm and a rotation speed of 800 rpm, then inorganic particles were added, and then stirred for 300 min with a vacuum two-planet stirrer at a revolution speed of 25 rpm and a rotation speed of 2500 rpm to obtain a protective layer slurry with a solid content of 10%.

[0087] The obtained protective layer slurry was applied to the surface of the foil material at an application speed of 100 m / min. The manufacturing time required for 2000 m of application was 20 min, and after drying at 90 °C, the positive electrode current collector was obtained and wound up for storage.

[0088] Example 2 In this example, a positive electrode current collector (the schematic diagram of its structure is as shown in Fig. 1) is provided. Compared with Example 1, for the positive electrode current collector, the mass of polyacrylic acid is 80 wt% of the mass of the protective layer 3, the mass of boehmite is 20 wt% of the mass of the protective layer 3, and the areal density of the protective layer 3 is 1.41 g / m 2 2, and the thickness of the foil material 1 is 13 μm, the thickness of the protective layer 3 is 3 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.231, which are different points.

[0089] Example 3 In this example, a positive electrode current collector (the schematic diagram of its structure is as shown in Fig. 1) is provided. Compared with Example 1, for the positive electrode current collector, the mass of polyacrylic acid is 70 wt% of the mass of the protective layer 3, the mass of boehmite is 30 wt% of the mass of the protective layer 3, and the areal density of the protective layer 3 is 1.72 g / m 2 2, and the thickness of the foil material 1 is 8 μm, the thickness of the protective layer 3 is 5 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.625, which are different points.

[0090] Example 4 In this example, a positive electrode current collector (the schematic diagram of its structure is as shown in Fig. 1) is provided. Compared with Example 1, for the positive electrode current collector, polyacrylic acid is replaced by polyvinylidene fluoride, the mass of the polyvinylidene fluoride is 75 wt% of the mass of the protective layer 3, the mass of boehmite is 25 wt% of the mass of the protective layer 3, and the areal density of the protective layer 3 is 1.79 g / m 2 2, and the thickness of the foil material 1 is 12 μm, the thickness of the protective layer 3 is 5 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.417, which are different points.

[0091] When comparing the manufacturing method of the positive electrode current collector with that of Example 1, it is different in that deionized water as a solvent is replaced by an equal amount of N-methylpyrrolidone (NMP).

[0092] Example 5 In this example, a positive electrode current collector (the schematic diagram of its structure is as shown in Fig. 1) is provided. Compared with Example 1, in this positive electrode current collector, boehmite is replaced by alumina, the mass of polyacrylic acid is 78 wt% of the mass of the protective layer 3, the mass of alumina is 22 wt% of the mass of the protective layer 3, and the areal density of the protective layer 3 is 1.84 g / m 2 And the thickness of the foil material 1 is 13 μm, the thickness of the protective layer 3 is 5 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.386, which are different points.

[0093] Example 6 In this example, a positive electrode current collector (the schematic diagram of its structure is as shown in Fig. 1) is provided. Compared with Example 1, in this positive electrode current collector, boehmite is replaced by titanium oxide, polyacrylic acid is replaced by polyacrylamide, the mass of polyacrylamide is 82 wt% of the mass of the protective layer 3, the mass of titanium oxide is 18 wt% of the mass of the protective layer 3, and the areal density of the protective layer 3 is 1.34 g / m 2 And the thickness of the foil material 1 is 10 μm, the thickness of the protective layer 3 is 2 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.2, which are different points.

[0094] Example 7 In this example, a positive electrode current collector (the schematic diagram of its structure is as shown in Fig. 1) is provided. Compared with Example 1, in this positive electrode current collector, boehmite is replaced by magnesium oxide, polyacrylic acid is replaced by carboxyvinyl polymer, the mass of carboxyvinyl polymer is 85 wt% of the mass of the protective layer 3, the mass of magnesium oxide is 15 wt% of the mass of the protective layer 3, and the areal density of the protective layer 3 is 1.51 g / m 2 And the thickness of the foil material 1 is 15 μm, the thickness of the protective layer 3 is 3 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.2, which are different points.

[0095] Example 8 In this example, a positive electrode current collector (the schematic structure diagram thereof is as shown in FIG. 1) is provided. Compared with Example 1, in this positive electrode current collector, boehmite is replaced by mica and glass fiber, polyacrylic acid is replaced by hydroxy polyethylene, the mass of hydroxy polyethylene is 79 wt% of the mass of the protective layer 3, the mass of mica and glass fiber is 21 wt% of the mass of the protective layer 3, and the surface density of the protective layer 3 is 1.27 g / m 2 It is different in that, and the thickness of the foil material 1 is 12 μm, the thickness of the protective layer 3 is 2 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.167.

[0096] Example 9 In this example, a positive electrode current collector (the schematic structure diagram thereof is as shown in FIG. 1) is provided. Compared with Example 1, in this positive electrode current collector, aluminum foil is replaced by composite aluminum foil, the mass of polyacrylic acid is 73 wt% of the mass of the protective layer 3, the mass of boehmite is 27 wt% of the mass of the protective layer 3, and the surface density of the protective layer 3 is 1.9 g / m 2 It is different in that, and the thickness of the foil material 1 is 16 μm, the thickness of the protective layer 3 is 5 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.3125.

[0097] Example 10 In this example, a positive electrode current collector (the schematic structure diagram thereof is as shown in FIG. 1) is provided. Compared with Example 1, in this positive electrode current collector, polyacrylic acid is replaced by polyvinylidene fluoride, the mass of polyvinylidene fluoride is 95 wt% of the mass of the protective layer 3, the mass of boehmite is 5 wt% of the mass of the protective layer 3, and the surface density of the protective layer 3 is 0.55 g / m 2 It is different in that, and the thickness of the foil material 1 is 13 μm, the thickness of the protective layer 3 is 1 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.077.

[0098] Compared with Example 1, the manufacturing method of the positive electrode current collector is different in that deionized water as a solvent is replaced by an equal amount of NMP.

[0099] Example 11 In this example, a positive electrode current collector (a schematic diagram of its structure is as shown in FIG. 1) is provided. Comparing this positive electrode current collector with that of Example 1, in the manufacturing method of the positive electrode current collector, the protective layer slurry also contains polyoxyethylene trimethyl nonyl ether with a mass content of 1 wt% as a surfactant, which is different.

[0100] Example 12 In this example, a positive electrode current collector (its structure is as shown in FIG. 2) is provided. Comparing this positive electrode current collector with that of Example 1, a conductive coating 4 is disposed on the positive electrode current collector. The material of the conductive coating 4 includes conductive carbon black and a binder. The thickness of the conductive coating 4 is 1.2 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the conductive coating 4 is 0.9, which is different.

[0101] Example 13 In this example, a positive electrode current collector (its structure is as shown in FIG. 2) is provided. Comparing this positive electrode current collector with that of Example 2, a conductive coating 4 is disposed on the positive electrode current collector. The material of the conductive coating 4 is conductive carbon black and a binder with a mass ratio of 4:6. The thickness of the conductive coating 4 is 6 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the conductive coating 4 is 0.5, which is different.

[0102] Example 14 In this example, a positive electrode current collector (its structure is as shown in FIG. 2) is provided. Comparing this positive electrode current collector with that of Example 3, a conductive coating 4 is disposed on the positive electrode current collector. The material of the conductive coating 4 is conductive carbon black and a binder with a mass ratio of 6:4. The thickness of the conductive coating 4 is 0.5 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the conductive coating 4 is 10, which is different.

[0103] Example 15 In this example, a positive electrode current collector (whose structure is as shown in FIG. 2) is provided. Compared with Example 12, the difference lies in that the conductive coating slurry and the protective layer slurry are applied simultaneously.

[0104] Example 16 In this example, a positive electrode current collector (whose structure is as shown in FIG. 3) is provided. Compared with Example 1, a safety layer 5 is arranged on the positive electrode current collector. The material of the safety layer 5 includes a ternary material and a binder. The thickness of the safety layer 5 is 12.5 μm, and the difference lies in that the ratio of the thickness of the protective layer 3 to the thickness of the safety layer 5 is 0.08.

[0105] Example 17 In this example, a positive electrode current collector (whose structure is as shown in FIG. 3) is provided. Compared with Example 2, a safety layer 5 is arranged on the positive electrode current collector. The material of the safety layer 5 includes a ternary material and a binder. The thickness of the safety layer 5 is 2.15 μm, and the difference lies in that the ratio of the thickness of the protective layer 3 to the thickness of the safety layer 5 is 1.39.

[0106] Example 18 In this example, a positive electrode current collector (whose structure is as shown in FIG. 3) is provided. Compared with Example 3, a safety layer 5 is arranged on the positive electrode current collector. The material of the safety layer 5 includes a ternary material and a binder. The thickness of the safety layer 5 is 1 μm, and the difference lies in that the ratio of the thickness of the protective layer 3 to the thickness of the safety layer 5 is 5.

[0107] Comparative Example 1 In this comparative example, a positive electrode current collector is provided. Compared with Example 1, polyacrylic acid is replaced by polyvinylidene fluoride. The mass of the polyvinylidene fluoride is 15 wt% of the mass of the protective layer, and the mass of boehmite is 85 wt% of the mass of the protective layer. The areal density of the protective layer is 6.38 g / m 2 And the thickness of the aluminum foil is 16 μm, the thickness of the protective layer is 5 μm, and the difference lies in that the ratio of the thickness of the protective layer to the thickness of the aluminum foil is 0.938.

[0108] Since the protective layer according to the related art is usually coated simultaneously with the active material layer, the same solvent as that used for the active material layer, i.e., an oily solvent, must be used as the solvent for the protective layer according to the related art. Comparing the manufacturing method of the positive current collector with Example 1, it is different in that deionized water as the solvent is replaced with an equal amount of NMP.

[0109] Comparative Example 2 In this comparative example, a positive current collector is provided. Comparing the positive current collector with Example 1, the mass of polyacrylic acid is 12 wt% of the mass of the protective layer, the mass of boehmite is 88 wt% of the mass of the protective layer, and the areal density of the protective layer is 6.1 g / m 2 In that regard, and the thickness of the aluminum foil is 13 μm, the thickness of the protective layer is 20 μm, and the ratio of the thickness of the protective layer to the thickness of the aluminum foil is 1.538.

[0110] Comparing the manufacturing method of the positive current collector with Example 1, it is different in that deionized water as the solvent is replaced with an equal amount of NMP.

[0111] Comparative Example 3 In this comparative example, a positive current collector is provided. Comparing the positive current collector with Example 1, polyacrylic acid is replaced with polyvinylidene fluoride, the mass of the polyvinylidene fluoride is 20 wt% of the mass of the protective layer, the mass of boehmite is 80 wt% of the mass of the protective layer, and the areal density of the protective layer is 7.14 g / m 2 In that regard, and the thickness of the aluminum foil is 8 μm, the thickness of the protective layer is 20 μm, and the ratio of the thickness of the protective layer to the thickness of the aluminum foil is 2.5.

[0112] Comparing the manufacturing method of the positive current collector with Example 1, it is different in that deionized water as the solvent is replaced with an equal amount of NMP.

[0113] Comparative Example 4 In this comparative example, a positive electrode current collector is provided. Compared with Example 1, the mass of polyacrylic acid in the protective layer is 15 wt% of the mass of the protective layer, the mass of boehmite is 85 wt% of the mass of the protective layer, and the areal density of the protective layer is 6.62 g / m 2 and the thickness of the aluminum foil is 13 μm, the thickness of the protective layer is 12 μm, and the ratio of the thickness of the protective layer to the thickness of the aluminum foil is 0.923.

[0114] Example 19 In this example, a positive electrode sheet is provided. The positive electrode sheet includes the positive electrode current collector described in Example 2 and an active material layer disposed on the positive electrode current collector.

[0115] The method for manufacturing the positive electrode sheet includes the following.

[0116] Lithium iron phosphate (LiFePO 4 , LFP), a conductive agent (conductive carbon black), and a binder (polyvinylidene fluoride) were mixed at a mass ratio of 95.5%:2.5%:2.0% to prepare an active material layer slurry. NMP was selected as the solvent, and the solid content of the obtained active material layer slurry was 60% and the viscosity was 8500 mPa·s.

[0117] The obtained active material layer slurry was applied to the blank area of the foil material at a speed of 50 m / min. The active material coating time for 2000 m of coating was 40 min, and after drying at 90 °C, the positive electrode sheet was obtained.

[0118] Example 20 In this example, a positive electrode sheet is provided. Compared with Example 19, the difference is that the positive electrode current collector described in Example 2 is replaced by the positive electrode current collector described in Example 15.

[0119] Example 21 In this example, a positive electrode sheet is provided. Compared with Example 19, the difference is as follows.

[0120] The manufacturing method of the positive electrode sheet includes the following steps.

[0121] A ternary material (Li(NiCoMn)O 2 , NCM), a conductive agent (conductive carbon black), and a binder (polyvinylidene fluoride) were used to prepare an active material layer slurry with a mass ratio of 97%:1.5%:1.5%. NMP was selected as the solvent. The solid content of the obtained active material layer slurry was 74%, and the viscosity was 9500 mPa·s.

[0122] The obtained active material layer slurry was applied to the blank area of the foil material at a speed of 100 m / min. The active material coating time for 2000 m of coating was 20 min. After drying at 90 °C, the positive electrode sheet was obtained.

[0123] Example 22 In this example, a positive electrode sheet is provided. Compared with Example 21, the positive electrode current collector described in Example 2 is replaced by the positive electrode current collector described in Example 15.

[0124] Example 23 In this example, a positive electrode sheet is provided. Compared with Example 21, the positive electrode current collector described in Example 2 is replaced by the positive electrode current collector described in Example 17.

[0125] Comparative Example 5 In this comparative example, a positive electrode sheet is provided. Compared with Example 19, the positive electrode current collector is replaced by aluminum foil of the same thickness.

[0126] Compared with Example 19, in the manufacturing method of the positive electrode sheet, the obtained active material layer slurry was applied to the aluminum foil at a speed of 30 m / min. The active material coating time for 2000 m of coating was 66.7 min.

[0127] Comparative Example 6 In this comparative example, a positive electrode sheet is provided. Compared with Comparative Example 5, the difference lies in that a conductive coating is disposed on the aluminum foil.

[0128] Comparative Example 7 In this comparative example, a positive electrode sheet is provided. Compared with Comparative Example 5, in the manufacturing method of the positive electrode sheet, the active material slurry is replaced with one adjusted so that the mass ratio of the ternary material, conductive agent, and binder is 97%: 1.5%: 1.5%. The obtained active material layer slurry is applied to the aluminum foil at a speed of 50 m / min, and the difference lies in that the active material application time for 2000 m of coating is 40 min.

[0129] Comparative Example 8 In this comparative example, a positive electrode sheet is provided. Compared with Comparative Example 7, the difference lies in that a conductive coating is disposed on the aluminum foil.

[0130] Comparative Example 9 In this comparative example, a positive electrode sheet is provided. Compared with Comparative Example 7, the difference lies in that a safety layer is disposed on the aluminum foil.

[0131] Application Example 1 In this application example, a lithium ion battery is provided, and the lithium ion battery has the positive electrode sheet described in Example 19.

[0132] Application Example 2 In this application example, a lithium ion battery is provided, and the lithium ion battery has the positive electrode sheet described in Example 20.

[0133] Application Example 3 In this application example, a lithium ion battery is provided, and the lithium ion battery has the positive electrode sheet described in Example 21.

[0134] Application Example 4 In this application example, a lithium-ion battery is provided, and the lithium-ion battery has a positive electrode sheet described in Example 22.

[0135] Application Example 5 In this application example, a lithium-ion battery is provided, and the lithium-ion battery has a positive electrode sheet described in Example 23.

[0136] Comparative Application Example 1 In this comparative application example, a lithium-ion battery is provided, and the lithium-ion battery has a positive electrode sheet described in Comparative Example 5.

[0137] Comparative Application Example 2 In this comparative application example, a lithium-ion battery is provided, and the lithium-ion battery has a positive electrode sheet described in Comparative Example 6.

[0138] Comparative Application Example 3 In this comparative application example, a lithium-ion battery is provided, and the lithium-ion battery has a positive electrode sheet described in Comparative Example 7.

[0139] Comparative Application Example 4 In this comparative application example, a lithium-ion battery is provided, and the lithium-ion battery has a positive electrode sheet described in Comparative Example 8.

[0140] Comparative Application Example 5 In this comparative application example, a lithium-ion battery is provided, and the lithium-ion battery has a positive electrode sheet described in Comparative Example 9.

[0141] The positive electrode current collector and the positive electrode sheet obtained as described above were measured, and after being further assembled into a lithium-ion battery, electrochemical performance measurement was performed. The measurement methods and results are shown below.

[0142] Thickness measurement method: Using a Mitutoyo micrometer 293-100-10 (resolution 0.0001 mm, high-precision micrometer, measurement range 0 - 25 mm) imported from Japan, measure the thickness at at least 20 different points on the protective layer, with the interval between each point being 10 cm, and record the average value of the thickness of all measurement points as the thickness of the coating.

[0143] Areal density measurement method: A CY-MRX-CP60 button cell press is used. Press dimensions of Φ0 mm to Φ100 mm are selected. Press at least 20 different points on the protective layer onto small wafers, with the interval between each point being 10 cm. Ensure that the edges of the small wafers are smooth, without burrs or chips. Record the weights of all small wafers and take the average value. Areal density = weight average value / area of the small wafer.

[0144] Adhesion measurement: Measure the adhesion between the protective layer and the current collector using a Shimadzu tensile testing machine by the 180° angle peel method: Cut the protective layer into a rod-shaped sample of 10 mm × 80 mm, and its longitudinal and transverse values can be proportionally adjusted according to the actual situation. Along the longitudinal direction of the sample, bond one end of the insulating layer surface of the sample to a steel plate with double-sided tape, with the bonding length being 80 mm or more. Then, fix the steel plate at the corresponding position of the tensile testing machine, and pull the other end of the sample that is not bonded to the steel plate. Place the electrode sheet sample into the clamp head either through a connector or directly, and make the angle formed by the pulled sample part and the steel plate spatially 180°.

[0145] Separate the protective layer and the current collector by pulling the electrode sheet at a speed of 15 mm / min with the clamp head, and finally record the average value of the tensile force in the smooth region of 20 - 60 mm as the adhesion between the protective layer and the current collector.

[0146] Immersion in electrolyte: The protective layer was cut into rod-shaped samples of 10 mm × 80 mm, and the vertical and horizontal values could be proportionally adjusted according to the actual situation. It was immersed in the electrolyte with the electrolyte components EC (ethylene carbonate): DEC (diethyl carbonate): DMC (dimethyl carbonate) = 1:1:1, placed in an oven at 45°C for 7 days, taken out, and after gently wiping off the electrolyte, the adhesion after electrolyte immersion was immediately measured by the adhesion measurement method.

[0147] Measurement of swelling: The dried positive current collector with a length of 2000 m was wound to obtain a cylindrical current collector winding. The current collector winding was fixed on a shelf, and by going around the circumferential surface of the current collector winding with a film ruler (accuracy: 1 mm), the circumferential length of the protective layer of the wound positive current collector and the circumferential length of the blank area of the wound positive current collector were respectively obtained. Specifically, for the measurement of each area, 5 points were selected for measurement, and the average value of the measurement results was taken to obtain the circumferential length of the measurement area.

[0148] Definition: When the height of the protrusion = the circumferential length of the protective layer - the circumferential length of the blank area, and if the height of the protrusion is 2 mm or less, it is determined that there is no swelling in the current collector. For the current collector coated with a conductive coating or a safety layer, when the height of the protrusion = the circumferential length of the protective layer - the circumferential length of the conductive coating / safety layer area, and if the height of the protrusion is 2 mm or less, it is determined that there is no swelling in the current collector.

[0149] Measurement method of gram capacity: For LFP - the voltage was 2.5~3.65 V and the current was 0.33 C. For NCM - the voltage was 2.8~4.3 V and the current was 0.33 C. The gram capacity was calculated based on the total battery capacity combined with the negative electrode sheet and the actual areal density. The gram capacity satisfies the formula: gram capacity = (capacity × 1000) / (areal density × S × loading), where the unit of gram capacity is mAh / g, the unit of capacity is Ah, and the unit of areal density is g / m 2 is calculated based on the actual coating material, S is the coating area of the active material, and the unit is m 2where loading- is the occupancy rate of the positive electrode main material. The total battery capacity refers to the first capacity calibrated at 0.33C after the core is assembled with the negative electrode sheet and then undergoes formation and capacity grading.

[0150] The manufacturing parameters and measurement results of each example, application example, and comparative example are shown in Tables 1 to 5 below.

[0151]

Table 1

[0152]

Table 2

[0153]

Table 3

[0154]

Table 4

[0155]

Table 5

[0156] As is clear from Table 1 described above, the conventional current collector according to the related art swelled after winding. However, in the present application, by controlling the thickness of the protective layer containing inorganic particles, it is ensured that the thickness ratio of the protective layer to the foil material is within the range of 0.05 to 0.7. As a result, a positive electrode current collector with an ultra-thin protective layer is obtained. Due to the ultra-thin structure of the protective layer, wrinkles and swelling do not occur when the positive electrode current collector is wound, enabling the winding and storage of the positive electrode current collector. Furthermore, a process of stepwise coating during the manufacturing process of the positive electrode sheet is realized.

[0157] As is clear from Tables 2 and 3, in the present application, after the conductive coating and the safety layer are additionally provided, even when the positive electrode current collector is wound, no swelling occurs.

[0158] As is clear from Table 4, in the present application, by arranging the ultra-thin protective layer structure, even when the stepwise coating method is adopted during manufacturing, there is no significant difference in the total manufacturing time of the positive electrode sheet compared to the synchronous coating method. In addition, the problem of the decrease in the gram capacity of the positive electrode sheet caused by the simultaneous coating of the active material layer and the protective layer according to the related art is avoided.

[0159] As is clear from Table 5, when the positive electrode current collector and the positive electrode sheet manufactured according to the present application are applied to a battery, they are excellent in conductivity and cyclicity, and the electrochemical performance of the battery is further ensured by arranging the safety layer or the conductive coating.

[0160] In the present application, since the thickness of the protective layer is controlled and the ultra-thin protective layer structure is used, the process method of stepwise coating is realized. First, the protective layer is coated to manufacture the current collector, and then the active material slurry is coated to manufacture the positive electrode sheet, thereby improving the coating speed, improving the consistency of battery production, and moreover, the manufactured current collector can be stored after winding.

[0161] In the present application, an aqueous slurry is used. Compared with an oily slurry, the aqueous slurry is environmentally friendly and has low pollution. At the same time, in the method of stepwise coating the aqueous slurry, the adhesion between the slurry and the foil material is good, and even when wiped off after electrolyte immersion, the powder does not easily fall off.

[0162] Although the detailed structural features of the present application have been described by the above embodiments, the present application is not limited to the above-described detailed structural features. In other words, the present application does not mean that it cannot be implemented without relying on the above-described detailed structural features. It should be understood by those skilled in the art that any improvement to the present application, equivalent substitution of the components selected in the present application, increase of auxiliary components, selection of specific methods, etc. are all included within the protection scope and the disclosure scope of the present application.

Claims

1. A positive current collector having a foil material and a protective layer provided on the surface of the foil material, wherein the protective layer contains inorganic particles, the ratio of the thickness of the protective layer to the thickness of the foil material is 0.05 to 0.7, positive current collector.

2. the ratio of the thickness of the protective layer to the thickness of the foil material is 0.0625 to 0.625, optionally, the thickness of the protective layer is 0 to 5 μm but not 0, preferably 1 to 3 μm, optionally, the protective layer contains a binder and inorganic particles, optionally, based on the mass of the protective layer, the mass percentage content of the binder is 70 to 100 wt% but not 100 wt%, preferably 70 to 95 wt%, optionally, the binder is a first binder or a second binder, optionally, the first binder includes any one or at least a combination of two selected from polyacrylic acid or its modified polymer, polyacrylamide or its modified polymer, polyurethane or its modified polymer, polyethylene hydrocarbon or its modified polymer, carboxyvinyl polymer, polyacrylate, polyimide, polyamideimide, carbomer resin, hydroxy polyethylene, or polymer-bonded benzyl acrylate, optionally, the second binder includes any one or at least a combination of two selected from polyvinylidene fluoride, polyimide-based polymer, polyacrylic acid polymer or its modified compound, optionally, based on the mass of the protective layer, the mass percentage content of the inorganic particles is 0 to 30 wt% but not 0, preferably 10 to 30 wt%, optionally, the inorganic particles include any one or at least a combination of two selected from alumina, boehmite, mica, glass fiber, titanium oxide, or magnesium oxide, Optionally, the areal density of the protective layer is 0.05 to 2 g / m 2 and optionally, the resistance value of the protective layer is 0 to 1000 Ω but not 0, preferably 100 mΩ to 400 Ω, optionally, the adhesion between the protective layer and the foil material is 100 N / m or more, and after immersion in the electrolyte, the adhesion between the protective layer and the foil material becomes 20 N / m or more, optionally, the foil material is an aluminum foil or a composite aluminum foil, The positive current collector according to Claim 1.

3. A blank area is arranged on the surface of the foil material, and protective layers are arranged on both sides of the blank area respectively, Optionally, the width of the blank area is 10 to 1400 mm, Optionally, the width of the protective layer is from 0 to 20 mm but not 0, The positive electrode current collector according to claim 1 or 2.

4. A conductive coating or a safety layer is disposed in the blank area, Optionally, the ratio of the thickness of the protective layer to the thickness of the conductive coating is 0.5 to 10, Optionally, the conductive coating contains a conductive carbon material and a binder, Optionally, based on the mass of the conductive coating, the mass percentage content of the conductive carbon material is 40 to 60 wt%, Optionally, the ratio of the thickness of the protective layer to the thickness of the safety layer is 0.08 to 5, Optionally, the safety layer contains a positive electrode active material and a binder, The positive electrode current collector according to claim 3.

5. A method for manufacturing a positive electrode current collector according to any one of claims 1 to 4, Preparing a protective layer slurry; Applying the prepared protective layer slurry onto the surface of the foil material, and drying to obtain the positive electrode current collector. Manufacturing method.

6. The method for preparing the protective layer slurry includes mixing a binder, inorganic particles and a solvent, and stirring to obtain the protective layer slurry, Optionally, the solvent includes deionized water or an oily solvent, Optionally, as the mixing method, the binder is added to the solvent under two-planet stirring with a revolution speed of 20 to 30 rpm and a rotation speed of 700 to 900 rpm, stirred for 15 to 40 min, then inorganic particles are added, and then stirred with two planets at a revolution speed of 20 to 30 rpm and a rotation speed of 2200 to 2600 rpm for 250 to 350 min, Optionally, the viscosity of the protective layer slurry is from 0 to 500 mPa·S but not 0, Optionally, the solid content of the protective layer slurry is from 0 to 20% but not 0, preferably 5 to 15%, Optionally, the coating speed is 0.5 to 100 m / min, Optionally, the drying temperature is 80 to 120 °C, Optionally, a blank area is disposed on the surface of the foil material, and protective layers are disposed on both sides of the blank area, Optionally, a conductive coating or a safety layer is disposed in the blank area, Optionally, the method for manufacturing the positive electrode current collector further includes applying a conductive coating slurry or a safety layer slurry to the blank area, The manufacturing method according to claim 5.

7. A positive electrode sheet, wherein the sheet includes the positive electrode current collector according to any one of claims 1 to 4 and an active material layer disposed on the surface of the positive electrode current collector, and the protective layers are disposed on both sides of the active material layer, Positive electrode sheet.

8. A method for manufacturing the positive electrode sheet according to claim 7, comprising: a step of preparing an active material layer slurry; a step of applying the prepared active material layer slurry to the positive electrode current collector obtained by the manufacturing method according to claim 5 or 6, drying the slurry, and obtaining the positive electrode sheet, Manufacturing method.

9. The active material layer slurry contains an active material, a conductive agent, a binder, and a solvent, optionally, the solid content of the active material layer slurry is 45 to 80%, optionally, the viscosity of the active material layer slurry is 2000 to 3000 mPa·s, optionally, the active material layer slurry is applied to the blank region of the positive electrode current collector, optionally, the application speed is 0.5 to 100 m / min, optionally, the drying temperature is 80 to 120 °C, The manufacturing method according to claim 8.

10. A battery having the positive electrode current collector according to any one of claims 1 to 4 or the positive electrode sheet according to claim 7, Battery.

11. An electrical utilization device having the battery according to claim 10.

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