Positive electrode 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] This application belongs to the technical field of current collector manufacturing, and relates, for example, to positive electrode current collectors, positive electrode sheets and manufacturing methods, and batteries. [Background technology]

[0002] A current collector is a structure or component used to collect electric current in a lithium-ion battery. Its main function is to collect the current generated from the battery's active material, provide an electron pathway, accelerate charge transfer, and improve charge-discharge Coulomb efficiency. Current collectors must meet certain characteristics, such as high electrical conductivity, good mechanical performance, low mass, and low internal resistance and resistance when in contact with the active material surface.

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

[0004] To improve the processing performance of the electrode sheet and the safety of the battery, the positive electrode sheet has an active coating on the surface of its current collector, and in addition, ceramic protective layers are applied to both sides of the active coating.

[0005] Specifically, an activated slurry is applied to the current collector, and at the same time, a ceramic protective layer is applied to the current collector by extrusion coating. However, because the coatings are applied simultaneously, some of the ceramics fuse with the activated slurry, reducing the gram capacity of the activated coating. Providing a current collector that satisfies electrochemical performance while also exhibiting excellent processing effects must be resolved as soon as possible. [Overview of the Initiative]

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

[0007] In view of the problems present in related technologies, this application provides a positive electrode current collector, a positive electrode sheet, a manufacturing method, and a battery. 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, thereby obtaining a current collector having an ultra-thin protective layer, enabling winding and storage of the current collector, and realizing a process of stepwise coating during the manufacturing of the electrode sheet, thereby avoiding problems caused by simultaneous coating in related technologies.

[0008] Furthermore, the ultra-thin protective layer structure makes it less likely for wrinkles to form in the electrode sheet during the winding process, avoiding the problem of bulging and protrusions, and ultimately improving production quality.

[0009] To achieve the above-mentioned objectives, the following technical aspects are employed in this application.

[0010] In a first embodiment of the present application, a positive electrode current collector is provided, comprising 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, and may be, for example, 0.05, 0.08, 0.1, 0.2, 0.5, or 0.7, but is not limited to the values ​​listed, and values ​​within the range that are not listed may also be applied.

[0011] In the embodiments of this invention, the thickness ratio of the protective layer to the foil material is ensured to be within the range of 0.05 to 0.7 by controlling the thickness of the protective layer containing inorganic particles, thereby obtaining a current collector having an ultra-thin protective layer, enabling winding and storage of the positive electrode current collector, and allowing a stepwise coating process during the manufacturing of the electrode sheet to be realized, thus avoiding problems caused by simultaneous coating in related technologies. Furthermore, the ultra-thin protective layer structure makes it less likely for wrinkles to form in the electrode sheet during the winding process, avoiding the occurrence of problems such as bulging and protrusion, and further improving production quality.

[0012] The positive electrode current collector according to the embodiment 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. However, it is not limited to the values ​​listed, and values ​​within the range that are not listed may also be applied.

[0014] A 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. Due to the ultra-thin structure of the protective layer, wrinkles and bulges do not occur when the current collector is wound up, making it possible to store the current collector in a wound state. Furthermore, a process of applying the protective layer in stages during the manufacturing process of the positive electrode sheet is realized, avoiding the problem of reduced gram capacity of the electrode sheet caused by the simultaneous application of the active material layer and the protective layer.

[0015] In one embodiment, the thickness of the protective layer is between 0 and 5 μm, but not zero. For example, it may be 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm. However, it is not limited to the values ​​listed, and values ​​within the range but not listed are also applicable. Preferably, it is between 1 and 3 μm.

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

[0017] In one embodiment, the mass of the binder relative to the mass of the protective layer is 70 to 100 wt%, but not necessarily 100 wt%, and may be, for example, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, or 95 wt%, but is not limited to the values ​​listed, and values ​​within the range but not listed may also be applied, preferably 70 to 95 wt%.

[0018] The proportion of the binder to the mass of the protective layer is at least 70 wt%, and unlike related technologies in which only a small amount of binder is used in the protective layer, the present embodiment ensures that the ratio of the thickness of the protective layer to the thickness of the foil is 0.0625 to 0.625 by increasing the binder content. By controlling the mass occupancy of the binder, the thickness of the protective layer can be effectively reduced, thereby reducing the total amount of protective layer material used and further reducing the production cost of the current collector. If the mass occupancy of the binder is less than 70 wt%, the ratio of the thickness of the protective layer to the thickness of the foil cannot be reduced to 0.625 or less.

[0019] In one embodiment, the binder consists of a first binder and a second binder, the first binder being used in an aqueous slurry, and the second binder being used in an oily 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, hydroxy polyethylene 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 hydroxy polyethylene, combinations of carbomer resin with hydroxy polyethylene 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 of polyvinylidene fluoride with polyimide-based polymer, combinations of polyimide-based polymer with polyacrylic acid polymer, combinations of polyacrylic acid polymer with its modified compound, combinations of polyvinylidene fluoride with combinations of polyimide-based polymer and polyacrylic acid polymer, combinations of polyimide-based polymer with combinations of polyacrylic acid polymer and its modified compound are included.

[0022] In one embodiment, with respect to the mass of the protective layer, the mass percentage content of the inorganic particles 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 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 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 100 mΩ to 400 Ω.

[0026] In one embodiment, the bonding force between the protective layer and the foil material is 100 N / m or more (100 N / m or greater than 100 N / m), for example 100 N / m, 200 N / m, 300 N / m, 400 N / m or 500 N / m, but is not limited to the values ​​listed, and values ​​within the range but not listed are also applicable. After immersion in the electrolyte, the bonding force between the protective layer and the foil material becomes 20 N / m or more, for example 20 N / m, 50 N / m, 70 N / m, 80 N / m or 100 N / m, but is not limited to the values ​​listed, and values ​​within the range but not listed are also applicable.

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

[0028] The protective layer may be placed on one side of the foil material or on both sides of the foil material, depending on the requirements of the electrochemical properties of the positive electrode current collector and the positive electrode sheet, and is not particularly limited in the embodiments of this application.

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

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

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

[0032] In one embodiment, a conductive coating or safety layer is placed in the blank area. 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. However, it is not limited to the values ​​listed, and values ​​within the range but not listed may also be applied.

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

[0035] In one embodiment, the mass percentage content of the conductive carbon material relative to the mass of 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 values ​​listed, and values ​​within the numerical range but not listed may also be applied.

[0036] In one embodiment, the mass percentage content of the binder in the conductive coating is 40 to 60 wt% relative to the mass of the conductive coating, and may be, for example, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 60 wt%, but is not limited to the values ​​listed, and values ​​within the range but not listed may also be applied.

[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. However, it is not limited to the values ​​listed, and values ​​within the range but not listed may also be applied.

[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 each independently comprise one or at least two selected from polyacrylic acid or a modified polymer thereof, polyacrylamide or a modified polymer thereof, polyurethane or a modified polymer thereof, polyethylene hydrocarbon or a modified polymer thereof, carboxyvinyl polymer, polyacrylate, polyimide, polyamide-imide, carbomer resin, hydroxypolyethylene, or polymer-bound benzyl acrylate.

[0040] In the embodiments of this invention, the purpose of placing a conductive coating in the blank area is to enhance the conductivity of the electrode sheet, while the purpose of placing a safety layer is to enhance the thermal stability of the active material.

[0041] In a second aspect, a method for manufacturing a positive electrode current collector according to the first aspect is provided in the embodiment of the present application, and the manufacturing method is The steps include preparing a protective layer slurry, The process includes the steps of applying the prepared protective layer slurry to the surface of the foil material, drying it to obtain the positive electrode current collector, and winding and storing the manufactured product.

[0042] In the embodiments of this invention, the thickness of the protective layer is controlled, an ultra-thin protective layer structure is used, and a process method is realized in which the protective layer slurry and the active material layer slurry are applied in stages. 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. As a result, the manufactured current collector can be stored after winding, and wrinkles and bulges are less likely to occur in the current collector after winding.

[0043] In one embodiment, the method for preparing the protective layer slurry includes mixing a binder, inorganic particles, and a solvent, stirring, and then obtaining the protective layer slurry.

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

[0045] In the embodiments of this invention, the objective of creating an ultrathin protective layer structure can be achieved by using either an aqueous slurry or an oil-based slurry. Compared to oil-based slurries, aqueous slurries are more environmentally friendly and less polluting. At the same time, in the method of applying aqueous slurries in stages, the adhesion between the slurry and the foil material is good, and powder is less likely to fall off even when wiped after immersion in the electrolyte solution.

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

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

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

[0049] In one embodiment, the mixing method involves adding the binder to the solvent under two planetary stirring conditions with an orbital speed of 20-30 rpm and a rotational speed of 700-900 rpm, stirring for 15-40 minutes, then adding inorganic particles, and finally stirring for 250-350 minutes under two planetary stirring conditions with an orbital speed of 20-30 rpm and a rotational speed of 2200-2600 rpm.

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

[0051] In one embodiment, the viscosity of the protective layer slurry is between 0 and 500 mPa·s, but not zero. 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 values ​​listed, and values ​​within the range but not listed may also be applied.

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

[0053] In one embodiment, the coating speed is 0.5 to 100, 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 values ​​listed, and values ​​within the range but not listed may also be applied.

[0054] 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 values ​​listed, and values ​​within the range but not listed may also be applied.

[0055] In one embodiment, a blank area is provided on the surface of the foil material, and the protective layer is provided on both sides of the blank area.

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

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

[0058] As a selective technical embodiment of the manufacturing method according to the second aspect of this application, the manufacturing method is: The process involves adding a binder to the solvent in proportion, stirring for 15-40 minutes with two planets at an orbital speed of 20-30 rpm and a rotational speed of 700-900 rpm, then adding inorganic particles, and stirring for 250-350 minutes with two planets at an orbital speed of 20-30 rpm and a rotational speed of 2200-2600 rpm to obtain a protective layer slurry with a viscosity of 0-500 mPa·s but not 0, and a solid content of 0-20% but not 0. The process includes the steps of applying the obtained protective layer slurry to the surface of the foil material, applying a conductive coating slurry or safety layer slurry to the blank areas on the surface of the foil material, placing the protective layer slurry on both sides of the blank areas, applying at a rate of 0.5 to 100 m / min, drying at 80 to 120°C, and then obtaining the positive electrode current collector.

[0059] In a third aspect, the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector according to the first aspect and an active material layer disposed on the surface of the positive electrode current collector, the protective layer disposed on both sides of the active material layer.

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

[0061] In one embodiment, the method for manufacturing the positive electrode sheet is as follows: The process involves preparing a protective layer slurry, applying the prepared protective layer slurry to the surface of a foil material, drying it, and obtaining a positive electrode current collector, wherein the positive electrode current collector includes a protective layer. The process includes the steps of preparing an active material layer slurry, applying the prepared active material layer slurry between adjacent protective layers of the positive electrode current collector, drying it, and then obtaining the positive electrode sheet.

[0062] In related technologies, electrode sheets are directly manufactured after a one-step coating process by simultaneously coating a ceramic slurry with safety protection functions 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 properties, and because there are significant differences in their viscosity and solid content, the speed of simultaneous coating is greatly limited. In addition, the instability of the coated surface density increases, further worsening the consistency of the battery.

[0063] In the embodiment of the present invention, the current collector is manufactured by first applying a protective layer, and then the positive electrode sheet is manufactured by applying an active material slurry. This shortens the time required to manufacture the positive electrode sheet, improves the consistency of battery production, and allows the manufactured current collector to 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 45-80%, and may be, for example, 45%, 50%, 60%, 70%, or 80%, but is not limited to the values ​​listed, and values ​​within the range but not listed may also be applied.

[0066] In one embodiment, the viscosity of the active material layer slurry is 2000 to 3000 mPa·s, and may be, for example, 2000 mPa·s, 2200 mPa·s, 2400 mPa·s, 2600 mPa·s, 2800 mPa·s, or 3000 mPa·s. However, it is not limited to the values ​​listed, and values ​​within the range but not listed may also be applied.

[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 values ​​listed, and values ​​within the range but not listed may also be applied.

[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 values ​​listed, and values ​​within the range but not listed may also be applied.

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

[0071] The binder is added to the solvent in proportion, and the mixture is stirred for 15-40 minutes using two planetary systems with an orbital speed of 20-30 rpm and a rotational speed of 700-900 rpm. Then, inorganic particles are added, and the mixture is stirred for 250-350 minutes using two planetary systems with an orbital speed of 20-30 rpm and a rotational speed of 2200-2600 rpm to obtain a protective layer slurry with a viscosity of 0-500 mPa·s but not zero, and a solid content of 0-20% but not zero; the obtained protective layer slurry is then applied to the surface of the foil material. The positive electrode current collector is obtained by applying a conductive coating slurry or safety layer slurry to the blank areas on the surface of the foil material, placing protective layer slurry on both sides of the blank areas, applying at a rate of 0.5 to 100 m / min, and drying at 80 to 120°C, with the positive electrode current collector containing the 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, can be stepwise or simultaneous application;

[0072] An active material, conductive agent, and binder are mixed in proportion to prepare an active material layer slurry with a viscosity of 2000-3000 mPa·s and a solid content of 45-80%. The prepared active material layer slurry is applied between adjacent protective layers of the positive electrode current collector at a speed of 0.5-100 m / min, and the positive electrode sheet is obtained after drying at 80-120°C.

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

[0074] In the sixth aspect, an embodiment of the present application provides an electrical device having a battery according to the fifth aspect.

[0075] The beneficial effects that the above technical embodiments bring to the present application are shown below.

[0076] In this invention, 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, thereby obtaining a current collector with an ultra-thin protective layer. Due to the ultra-thin structure of the protective layer, wrinkles and bulges do not occur when the current collector is wound up, enabling winding and storage of the current collector. Furthermore, a process of applying the protective layer in stages during the manufacturing process of the positive electrode sheet is realized, avoiding the problem of reduced gram capacity of the electrode sheet caused by the simultaneous application of the active material layer and protective layer in related technologies.

[0077] Furthermore, the protective layer has strong adhesion to the foil material, is difficult to detach from the foil material, is thin, and does not become brittle even after two baking processes (if the active material layer is applied first, the active material layer must be baked twice, resulting in a small reduction in the weight of the electrode sheet, excessive evaporation of the solvent, embrittlement of the electrode sheet, and a decrease in the performance of the electrode sheet).

[0078] After reading and understanding the drawings and detailed descriptions, other aspects can be understood. [Brief explanation of the drawing]

[0079] The drawings are provided to further illustrate the technical aspects of this specification, together with the embodiments of the application, as part of the specification, and do not limit the technical aspects of this specification. [Figure 1] This is a schematic diagram of the structure of the positive electrode current collector described in Examples 1 to 11. [Figure 2] This is a schematic diagram of the structure of the positive electrode current collector described in Examples 12 to 15. [Figure 3] This is a schematic diagram of the structure of the positive electrode current collector described in Examples 16-18.

[0080] 1- Foil material, 2- Blank area, 3- Protective layer, 4- Conductive coating, 5- Safety layer. [Modes for carrying out the invention]

[0081] The technical aspects of this application will be further described below with reference to the drawings and specific embodiments. However, the following examples are merely simplified representations of this application and do not represent or limit the scope of protection of this application; the scope of protection of this application is subject to the claims.

[0082] Example 1 In this embodiment, a positive electrode current collector (a schematic diagram of its structure is shown in Figure 1) is provided, which comprises a foil material 1, a blank area 2 provided on the surface of one side of the foil material 1, and a protective layer 3, wherein the foil material 1 is aluminum foil, and protective layers 3 are arranged on both sides of the blank area 2, with the width of the blank area 2 being 178 mm and the width of the protective layer 3 being 8 mm.

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

[0084] The protective layer 3 comprises polyacrylic acid and boehmite, with the mass of polyacrylic acid being 90 wt% of the mass of the protective layer 3, the mass of boehmite being 10 wt% of the mass of the protective layer 3, and the surface density of the protective layer 3 being 0.48 g / m² 2 That is the case.

[0085] The method for manufacturing the positive electrode current collector includes the following:

[0086] Add the binder to deionized water in a mass ratio of binder to inorganic particles, and revolve at 25 r After stirring for 30 minutes in a two-planetary system with a rotation speed of 800 rpm, inorganic particles were added, and then the mixture was stirred for 300 minutes in a vacuum two-planetary system with an orbital 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 a coating speed of 100 m / min, with a manufacturing time of 20 mins for coating 2000 m, and after drying at 90°C, the positive electrode current collector was obtained and stored after winding.

[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 this 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 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 this 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 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 this 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 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 the solvent is replaced by an equal amount of N-methylpyrrolidone (NMP).

[0092] Example 5 In this embodiment, a positive electrode current collector (its schematic structure is shown in Figure 1) is provided. Compared to Example 1, this positive electrode current collector has boehmite replaced with alumina, the mass of polyacrylic acid is 78 wt% of the mass of protective layer 3, the mass of alumina is 22 wt% of the mass of protective layer 3, and the surface density of the protective layer 3 is 1.84 g / m². 2 It differs in that 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.

[0093] Example 6 In this embodiment, a positive electrode current collector (its schematic structure is shown in Figure 1) is provided. Compared to Example 1, this positive electrode current collector has the following characteristics: boehmite is replaced with titanium oxide, polyacrylic acid is replaced with polyacrylamide, the mass of polyacrylamide is 82 wt% of the mass of protective layer 3, the mass of titanium oxide is 18 wt% of the mass of protective layer 3, and the surface density of the protective layer 3 is 1.34 g / m². 2 It differs in that 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.

[0094] Example 7 In this embodiment, a positive electrode current collector (its schematic structure is shown in Figure 1) is provided. Compared to Example 1, this positive electrode current collector has the following characteristics: boehmite is replaced with magnesium oxide, polyacrylic acid is replaced with carboxyvinyl polymer, the mass of the carboxyvinyl polymer is 85 wt% of the mass of the protective layer 3, the mass of the magnesium oxide is 15 wt% of the mass of the protective layer 3, and the surface density of the protective layer 3 is 1.51 g / m². 2 It differs in that the foil material 1 has a thickness of 15 μm, the protective layer 3 has a thickness of 3 μm, and the ratio of the thickness of the protective layer 3 to the thickness of the foil material 1 is 0.2.

[0095] Example 8 In this embodiment, a positive electrode current collector (its schematic structure is shown in Figure 1) is provided. Compared to Example 1, this positive electrode current collector has boehmite replaced with mica and glass fiber, polyacrylic acid replaced with hydroxypolyethylene, the mass of hydroxypolyethylene is 79 wt% of the mass of protective layer 3, the mass of mica and glass fiber is 21 wt% of the mass of protective layer 3, and the surface density of the protective layer 3 is 1.27 g / m². 2 It differs in that 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 embodiment, a positive electrode current collector (its schematic structure is shown in Figure 1) is provided. Compared to Example 1, this positive electrode current collector has the aluminum foil replaced with composite aluminum foil, the mass of polyacrylic acid is 73 wt% of the mass of protective layer 3, the mass of boehmite is 27 wt% of the mass of protective layer 3, and the surface density of the protective layer 3 is 1.9 g / m². 2 It differs in that 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 embodiment, a positive electrode current collector (its schematic structure is shown in Figure 1) is provided. Compared to Example 1, this positive electrode current collector has polyacrylic acid replaced with polyvinylidene fluoride, the mass of polyvinylidene fluoride is 95 wt% of the mass of protective layer 3, the mass of boehmite is 5 wt% of the mass of protective layer 3, and the surface density of the protective layer 3 is 0.55 g / m². 2 It differs in that 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] The method for manufacturing the positive electrode current collector differs from that of Example 1 in that the deionized water used as the solvent is replaced with an equal amount of NMP.

[0099] Example 11 In this embodiment, a positive electrode current collector (its schematic structure is shown in Figure 1) is provided. Compared to the positive electrode current collector in Example 1, the manufacturing method of the positive electrode current collector differs in that the protective layer slurry also contains polyoxyethylene trimethyl nonyl ether as a surfactant at a mass content of 1 wt%.

[0100] Example 12 In this embodiment, a positive electrode current collector (its structure is shown in Figure 2) is provided. This positive electrode current collector differs from that of Embodiment 1 in that a conductive coating 4 is placed 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.

[0101] Example 13 In this embodiment, a positive electrode current collector (its structure is shown in Figure 2) is provided. This positive electrode current collector differs from that of Embodiment 2 in that a conductive coating 4 is placed on the positive electrode current collector, the material of the conductive coating 4 is conductive carbon black and a binder in 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.

[0102] Example 14 In this embodiment, a positive electrode current collector (its structure is as shown in Figure 2) is provided. This positive electrode current collector differs from that of Embodiment 3 in that a conductive coating 4 is placed on the positive electrode current collector, the material of the conductive coating 4 is conductive carbon black and a binder in 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.

[0103] Example 15 In this embodiment, a positive electrode current collector (whose structure is shown in Figure 2) is provided, which differs from that of Example 12 in that a conductive coating slurry and a protective layer slurry are applied simultaneously.

[0104] Example 16 In this embodiment, a positive electrode current collector (its structure is as shown in Figure 3) is provided. This positive electrode current collector differs from that of Embodiment 1 in that a safety layer 5 is placed 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 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 embodiment, a positive electrode current collector (its structure is as shown in Figure 3) is provided. This positive electrode current collector differs from that of Embodiment 2 in that a safety layer 5 is placed 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 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 embodiment, a positive electrode current collector (its structure is as shown in Figure 3) is provided. This positive electrode current collector differs from that of Embodiment 3 in that a safety layer 5 is placed 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 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 to Example 1, the polyacrylic acid in this positive electrode current collector is replaced with polyvinylidene fluoride, the mass of the polyvinylidene fluoride is 15 wt% of the mass of the protective layer, the mass of the boehmite is 85 wt% of the mass of the protective layer, and the surface density of the protective layer is 6.38 g / m². 2 It differs in that the aluminum foil has a thickness of 16 μm, the protective layer has a thickness of 5 μm, and the ratio of the thickness of the protective layer to the thickness of the aluminum foil is 0.938.

[0108] Since the protective layer using related technologies is usually coated simultaneously with the active material layer, the solvent used for the protective layer using related technologies must be the same as that used for the active material layer, i.e., an oily solvent. The method for manufacturing the positive electrode current collector differs from that of Example 1 in that the deionized water used as the solvent is replaced with an equal amount of NMP.

[0109] Comparative Example 2 In this comparative example, a positive electrode current collector is provided. Compared to Example 1, this positive electrode current collector has a polyacrylic acid mass of 12 wt% of the protective layer mass, a boehmite mass of 88 wt% of the protective layer mass, and a surface density of 6.1 g / m² of the protective layer. 2 It differs in that the aluminum foil has a thickness of 13 μm, the protective layer has a thickness of 20 μm, and the ratio of the thickness of the protective layer to the thickness of the aluminum foil is 1.538.

[0110] The method for manufacturing the positive electrode current collector differs from that of Example 1 in that the deionized water used as the solvent is replaced with an equal amount of NMP.

[0111] Comparative Example 3 In this comparative example, a positive electrode current collector is provided. Compared to Example 1, the polyacrylic acid in this positive electrode current collector is replaced with polyvinylidene fluoride, the mass of the polyvinylidene fluoride is 20 wt% of the mass of the protective layer, the mass of the boehmite is 80 wt% of the mass of the protective layer, and the surface density of the protective layer is 7.14 g / m². 2 It differs in that the aluminum foil has a thickness of 8 μm, the protective layer has a thickness of 20 μm, and the ratio of the thickness of the protective layer to the thickness of the aluminum foil is 2.5.

[0112] The method for manufacturing the positive electrode current collector differs from that of Example 1 in that the deionized water used 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 to Example 1, this positive electrode current collector has a polyacrylic acid mass of 15 wt% of the protective layer mass, a boehmite mass of 85 wt% of the protective layer mass, and a surface density of 6.62 g / m² of the protective layer. 2 It differs in that the aluminum foil has a thickness of 13 μm, the protective layer has a thickness of 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 embodiment, a positive electrode sheet is provided, which includes a positive electrode current collector as 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] An active material layer slurry was prepared using lithium iron phosphate (LiFePO4, LFP), a conductive agent (conductive carbon black), and a binder (polyvinylidene fluoride) in a mass ratio of 95.5%:2.5%:2.0%. NMP was selected as the solvent, and the resulting active material layer slurry had a solid content of 60% and a viscosity of 8500 mPa·s.

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

[0118] Example 20 In this embodiment, a positive electrode sheet is provided, and this positive electrode sheet differs from that in Example 19 in that the positive electrode current collector described in Example 2 is replaced with the positive electrode current collector described in Example 15.

[0119] Example 21 In this embodiment, a positive electrode sheet is provided, which differs from that of Example 19 in the following respects.

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

[0121] An active material layer slurry was prepared using a mass ratio of ternary material (Li(NiCoMn)O2, NCM), conductive agent (conductive carbon black), and binder (polyvinylidene fluoride) of 97%:1.5%:1.5%. NMP was selected as the solvent, and the resulting active material layer slurry had a solid content of 74% and a viscosity of 9500 mPa·s.

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

[0123] Example 22 In this embodiment, a positive electrode sheet is provided. This positive electrode sheet differs from that in Example 21 in that the positive electrode current collector described in Example 2 is replaced with the positive electrode current collector described in Example 15.

[0124] Example 23 In this embodiment, a positive electrode sheet is provided. This positive electrode sheet differs from that of Example 21 in that the positive electrode current collector described in Example 2 is replaced with the positive electrode current collector described in Example 17.

[0125] Comparative Example 5 In this comparative example, a positive electrode sheet is provided, and compared to Example 19, this positive electrode sheet differs in that the positive electrode current collector is replaced with aluminum foil of the same thickness.

[0126] The method for manufacturing the positive electrode sheet differs from that of Example 19 in that the obtained active material layer slurry is applied to the aluminum foil at a speed of 30 m / min, and the active material application time for 2000 m of application is 66.7 min.

[0127] Comparative Example 6 In this comparative example, a positive electrode sheet is provided, and this positive electrode sheet differs from that of Comparative Example 5 in that a conductive coating is placed on the aluminum foil.

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

[0129] Comparative Example 8 In this comparative example, a positive electrode sheet is provided, and this positive electrode sheet differs from that in Comparative Example 7 in that a conductive coating is placed on the aluminum foil.

[0130] Comparative Example 9 In this comparative example, a positive electrode sheet is provided, and this positive electrode sheet differs from that of Comparative Example 7 in that a safety layer is placed on the aluminum foil.

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

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

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

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

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

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

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

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

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

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

[0141] The positive electrode current collector and positive electrode sheet obtained as described above were measured, and after assembling them into a lithium-ion battery, electrochemical performance measurements were performed. The measurement method and results are shown below.

[0142] Thickness measurement method: Using a Mitoyo 293-100-10 micrometer (resolution 0.0001 mm, high-precision micrometer, measuring range 0-25 mm) imported from Japan, the thickness of at least 20 different points on the protective layer is measured, with a spacing of 10 cm between each point. The average value of the thicknesses of all measured points is recorded as the thickness of the coating.

[0143] Method for measuring surface density: A CY-MRX-CP60 button battery press machine is used, with press dimensions of Φ0mm to Φ100mm selected. At least 20 different points on the protective layer are pressed onto a small wafer, with a spacing of 10cm between each point. The edges of the small wafers are smooth and free of burrs and chips. The weight of all the small wafers is recorded and the average value is taken. Surface density = average weight / area of ​​the small wafer.

[0144] Measurement of bonding force: The bonding force between the protective layer and the current collector is measured using the 180° angle peeling method with a Shimadzu tensioning machine. The protective layer is cut into a rod-shaped sample measuring 10 mm x 80 mm, and its length and width can be proportionally adjusted according to the actual situation. The insulating layer surface at one end of the sample is bonded to a steel plate with double-sided tape along the longitudinal direction of the sample, with a bonding length of 80 mm or more. Next, the steel plate is fixed to the corresponding position on the tensioning machine, and the other end of the sample that is not bonded to the steel plate is pulled. The electrode sheet sample is then clamped by placing it in the clamp head either via a connector or directly, and the spatial angle between the pulled portion of the sample and the steel plate is set to 180°.

[0145] The electrode sheet is pulled at a speed of 15 mm / min using a clamp head to separate the protective layer from the current collector. The average value of the tensile force measured in the calm region of 20-60 mm is recorded as the bonding force between the protective layer and the current collector.

[0146] Immersion in electrolyte: The protective layer was cut into 10mm x 80mm rod-shaped samples, and its length and width could be proportionally adjusted according to the actual conditions. The samples were immersed in an electrolyte with an electrolyte composition of EC (ethylene carbonate):DEC (diethyl carbonate):DMC (dimethyl carbonate) = 1:1:1, and left in a 45°C oven for 7D. After removal, the electrolyte was lightly wiped off, and the bonding strength after electrolyte immersion was immediately measured using a bonding strength measurement method.

[0147] Measurement of swelling: A 2000m length of dried positive electrode current collector was wound up to obtain a cylindrical winding. The winding was fixed to a shelf, and a film ruler (accuracy: 1mm) was used to run around the circumference of the winding, thereby obtaining the circumference of the protective layer of the wound positive electrode current collector and the circumference of the blank area of ​​the wound positive electrode current collector. Specifically, for the measurement of each area, five points were selected and measured, and the average value of the measurement results was taken to obtain the circumference of the measurement area.

[0148] Definition: If the height of the protrusion satisfies the condition that the circumference of the protective layer minus the circumference of the blank area, and the height of the protrusion is 2 mm or less, the current collector is judged to have no bulge. For current collectors coated with a conductive coating or safety layer, if the height of the protrusion satisfies the condition that the height of the protrusion satisfies the condition that the circumference of the protective layer minus the circumference of the conductive coating / safety layer area, and the height of the protrusion is 2 mm or less, the current collector is judged to have no bulge.

[0149] Gram capacity measurement method: LFP - voltage set to 2.5~3.65V, current to 0.33C. NCM - voltage set to 2.8~4.3V, current to 0.33C. Gram capacity was calculated using the total battery capacity combined with the negative electrode sheet and the actual surface density. The formula gram capacity = (capacity × 1000) / (surface density × S × loading) satisfies the equation, where the unit of gram capacity is mAh / g, the unit of capacity is Ah, and the unit of surface density is g / m 2 This is calculated based on the actual coating material, S is the coating area of ​​the active material, in units of m 2Here, "loading-" is the occupancy rate of the positive electrode main material. Total battery capacity refers to the first capacity measured at 0.33C after the core is assembled with the negative electrode sheet, undergoes chemical formation and capacity grading.

[0150] The manufacturing parameters and measurement results for 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 above, conventional current collectors using related technologies bulged after winding. However, in this invention, 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. This results in a positive electrode current collector having an ultra-thin protective layer. Due to the ultra-thin structure of the protective layer, wrinkles and bulges do not occur when the positive electrode current collector is wound, enabling winding and storage of the positive electrode current collector. Furthermore, a process of applying the protective layer in stages during the manufacturing process of the positive electrode sheet is realized.

[0157] As is clear from Tables 2 and 3, in this invention, after the conductive coating and safety layer are added, bulging will not occur even when the positive electrode current collector is wound up.

[0158] As is clear from Table 4, in this invention, by arranging an ultrathin protective layer structure, even if a stepwise coating method is adopted during manufacturing, there is no significant difference in the total manufacturing time of the positive electrode sheet compared to a synchronous coating method. In addition, the problem of reduced gram capacity of the positive electrode sheet caused by simultaneous coating of the active material layer and protective layer using related technologies is avoided.

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

[0160] In this invention, the thickness of the protective layer is controlled, and an ultra-thin protective layer structure is used, enabling a stepwise coating process. 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. This improves the coating speed, enhances the consistency of battery production, and allows the manufactured current collector to be stored after winding.

[0161] In this application, an aqueous slurry is used. Compared to oil-based slurries, aqueous slurries are more environmentally friendly and less polluting. At the same time, in the method of applying the aqueous slurry in stages, the adhesion between the slurry and the foil material is good, and powder does not easily fall off even when wiped after immersion in the electrolyte solution.

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

Claims

1. A positive electrode current collector comprising a foil material and a protective layer provided on the surface of the foil material, wherein the protective layer contains inorganic particles and a binder, The ratio of the thickness of the protective layer to the thickness of the foil material is 0.05 to 0.

7. The thickness of the aforementioned protective layer is 0 to 5 μm, but not 0. With respect to the mass of the protective layer, the mass percentage content of the binder is 70 to 100 wt%, but not 100 wt%, and the mass percentage content of the inorganic particles is 0 to 30 wt%, but not 0. A blank area is provided on the surface of the foil material, and protective layers are provided on both sides of the blank area, the width of the blank area is 10 to 1400 mm, and the width of the protective layer is 0 to 20 mm but not 0. Positive electrode 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. The thickness of the protective layer is 1 to 3 μm. The positive electrode current collector according to claim 1.

3. The binder is a first binder or a second binder, The first binder comprises one or at least 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, polyamide-imide, carbomer resin, hydroxypolyethylene, or polymer-bound benzyl acrylate. The second binder comprises one or at least two selected from polyvinylidene fluoride, polyimide polymers, polyacrylic acid polymers, or modified compounds thereof. The positive electrode current collector according to claim 1.

4. The inorganic particles include one or at least two selected from alumina, boehmite, mica, glass fiber, titanium oxide, or magnesium oxide. The positive electrode current collector according to claim 1.

5. The surface density of the protective layer is 0.05 to 2 g / m² 2 And, The resistance of the aforementioned protective layer is 0 to 1000 Ω, but not 0. The bonding force between the protective layer and the foil material is 100 N / m or more, and after immersion in the electrolyte, the bonding force between the protective layer and the foil material becomes 20 N / m or more. The aforementioned foil material is aluminum foil or composite aluminum foil. The positive electrode current collector according to claim 1.

6. A conductive coating is placed in the blank area. The ratio of the thickness of the protective layer to the thickness of the conductive coating is 0.5 to 10. The conductive coating contains a conductive carbon material and a binder. The mass percentage content of the conductive carbon material relative to the mass of the conductive coating is 40 to 60 wt%. The positive electrode current collector according to claim 1.

7. A safety layer is provided in the blank area. The ratio of the thickness of the protective layer to the thickness of the safety layer is 0.08 to 5. The safety layer contains a positive electrode active material and a binder. The positive electrode current collector according to claim 1.

8. A method for manufacturing a positive electrode current collector according to any one of claims 1 to 7, The steps include preparing a protective layer slurry, The process includes the steps of applying the prepared protective layer slurry to the surface of the foil material, drying it, and then obtaining the positive electrode current collector. Manufacturing method.

9. The method for preparing the protective layer slurry includes mixing a binder, inorganic particles, and a solvent, stirring, and then obtaining the protective layer slurry. The solvent comprises deionized water or an oily solvent. The aforementioned mixing method involves adding the binder to the solvent under two planetary agitation with an orbital speed of 20-30 rpm and a rotational speed of 700-900 rpm, stirring for 15-40 minutes, then adding inorganic particles, and then stirring for 250-350 minutes under two planetary agitation with an orbital speed of 20-30 rpm and a rotational speed of 2200-2600 rpm. The manufacturing method according to claim 8.

10. The viscosity of the protective layer slurry is 0 to 500 mPa·s, but not 0. The solid content of the protective layer slurry is 0-20%, but not 0. The coating speed is 0.5 to 100 m / min. The drying temperature is 80 to 120°C. Apply a conductive coating slurry or safety layer slurry to the blank area. The manufacturing method according to claim 8.

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