Color-controllable carbon-coated current collector and preparation method therefor and application thereof

Abstract

A color-controllable carbon-coated current collector, comprising a current collector substrate (1) and a carbon-coated layer (2) disposed on the surface of at least one side of the current collector substrate (1), wherein a color layer (3) is disposed on the surface of the carbon-coated layer (2) away from the current collector substrate (1). The color layer (3) is prepared from the following raw materials: SiO2@Fe2O3 nano powder, an oil-soluble pigment dye, and a surfactant. The carbon-coated layer (2) can improve the current collection intensity of the current collector; the color layer (3) is favorable for monitoring the coverage rate during electrode sheet coating; moreover, SiO2 coats Fe2O3, so that the structure of Fe2O3 can be stabilized, and when the color-controllable carbon-coated current collector is used for preparing a battery, lithium can be effectively stored, and the capacity can be increased. The color-controllable carbon-coated current collector also has good hydrophobicity.

Description

A color-controllable carbon-coated current collector and its preparation method and application Technical Field

[0001] The embodiments of the present application relate to the field of current collector technology, such as a color-controllable carbon-coated current collector and its preparation method and application. Background Art

[0002] During the manufacturing process of lithium-ion batteries and sodium-ion batteries, in order to improve the current collection intensity of the current collector for the active material and the adhesion performance of the active material to the electrode, a layer of black conductive material is first applied to the surface of the current collector, and then the active material is directly applied to the surface of the current collector with the conductive material when manufacturing the electrode.

[0003] The existing current collector coating conductive materials are basically black conductive carbon materials, which appear as a thin black coating on the current collector surface, and the positive and negative electrode slurries are also black. When the carbon-coated current collector and the positive and negative electrode slurries are coated to manufacture the electrode sheets, it is impossible to quickly identify the missing coating points and the falling-off areas.

[0004] Therefore, in the art, it is desired to develop a color-controllable carbon-coated current collector.

[0005] Summary of the Invention

[0006] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0007] The present invention provides a color-controllable carbon-coated current collector, its preparation method, and application. This invention employs a double-layer coating method, first applying a carbon slurry to the current collector substrate to form a carbon coating layer, and then applying a color-controllable nano-iron oxide coating on the carbon coating layer, resulting in a carbon-coated current collector with a color completely different from the black positive and negative electrode slurries.

[0008] In a first aspect, embodiments of the present application provide a color-controllable carbon-coated current collector, comprising a current collector substrate and a carbon coating layer disposed on at least one surface of the current collector substrate, wherein a color layer is disposed on a side of the carbon coating layer away from the current collector substrate;

[0009] The raw materials for preparing the color layer include SiO2@Fe2O3 nano powder, oil-soluble pigment dye and surfactant.

[0010] In this application, the carbon coating layer can improve the current collection intensity of the current collector for the active material, improve the rate performance, and reduce the resistance; the color layer is conducive to monitoring the poor coverage during the electrode coating process; and the introduction of the SiO2 coating core-shell structure can stabilize the Fe2O3 nanostructure. When using the color-controllable carbon coating current collector provided by this application to prepare a battery, it can effectively store lithium and increase the capacity. Specifically, Fe2O3 has high theoretical capacity, good reversibility and is environmentally friendly. The lithium storage mechanism enables it to completely separate from Li + However, Fe2O3 has poor cycling stability due to its easy structural collapse. Therefore, a core-shell structure in which SiO2 is coated on Fe2O3 stabilizes the Fe2O3 structure. When batteries are prepared using the color-controllable carbon-coated current collector provided in this application, lithium can be effectively stored, increasing capacity.

[0011] In addition, the color-controllable carbon-coated current collector provided by the present application also has good hydrophobicity. This is because the SiO2@Fe2O3 nanopowder layer (color layer) is poorly soluble in water and will not be affected by water molecules in the air.

[0012] In the present application, the oil-soluble pigment dye may be, for example, oil-soluble yellow pigment and oil-soluble pigments of other colors.

[0013] The present application does not impose any specific restrictions on the preparation method of SiO2@Fe2O3 nanopowders. SiO2@Fe2O3 nanopowders can be obtained by coating SiO2 on Fe2O3 using the Stober method.

[0014] Exemplarily, the SiO2@Fe2O3 nanopowder is prepared by the following method:

[0015] Weigh 0.5g of Fe2O3 and 200mL of anhydrous ethanol, mix them ultrasonically for 10 minutes, then add 100mL of water and 1mL of NH3·H2O and stir mechanically until uniform. Weigh 1mL of TEOS (ethyl silicate) and dissolve it in 25mL of anhydrous ethanol. After mixing the two solutions, stir them mechanically at room temperature for 6 hours at a speed of 4000 rpm. 1 After centrifugation for 5 minutes, the supernatant was removed, the precipitate was washed with water three times until the pH was 7, the precipitate was transferred to a three-necked flask, NH3·H2O was added to adjust the pH value of the solution to 11, and then 1 mL of oleic acid was added and stirred at room temperature for 30 minutes. After stirring, the supernatant was removed by centrifugation, the precipitate was washed with water three times, and vacuum dried at 60°C for 4 hours to obtain the SiO2@Fe2O3 nanopowder.

[0016] Preferably, the thickness of the carbon coating layer is less than 800 nm, for example, 750 nm, 700 nm, 600 nm, 500 nm, or 400 nm. The thickness of the carbon coating layer refers to the thickness of a single carbon coating layer. For example, when the upper and lower surfaces of the current collector substrate are both provided with carbon coating layers, the thickness of each carbon coating layer is less than 800 nm.

[0017] Preferably, the thickness of the color layer is less than 600 nm, for example, 550 nm, 500 nm, 400 nm, 300 nm, or 200 nm. The thickness of the color layer refers to the thickness of a single color layer. For example, when the upper and lower surfaces of the current collector substrate are both provided with carbon coating layers, the thickness of the two color layers (i.e., each carbon coating layer is provided with a color layer on a side away from the current collector substrate) is less than 600 nm.

[0018] Preferably, the mass ratio of the SiO2@Fe2O3 nanopowder to the oil-soluble pigment dye is 1:(8-20), and 8-20 can be, for example, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20.

[0019] Preferably, the mass ratio of the SiO2@Fe2O3 nanopowder to the surfactant is 1:(0.03-0.08), and 0.03-0.08 can be, for example, 0.03, 0.04, 0.05, 0.06, 0.07 or 0.08.

[0020] Preferably, the surfactant comprises oleic acid.

[0021] Preferably, the raw materials for preparing the carbon coating layer include the following components by weight: 5-8% (e.g., 5%, 6%, 7%, or 8%) of conductive carbon material, 7-22% (e.g., 7%, 10%, 13%, 15%, 18%, 20%, or 22%) of binder, 3-20% (e.g., 3%, 5%, 8%, 10%, 13%, 15%, 18%, or 20%) of wetting agent, and the balance being solvent. The solid content of the conductive paste for the carbon coating layer prepared from the above raw materials is 5-10%.

[0022] Preferably, the pH of the conductive paste is 4 to 9, such as 4, 5, 6, 7, 8 or 9.

[0023] Preferably, the conductive carbon material includes any one of conductive carbon black, conductive graphite, carbon nanotubes, carbon nanofibers or graphene, or a combination of at least two of them.

[0024] Preferably, the adhesive comprises acrylic resin.

[0025] Preferably, the wetting agent includes any one of isopropyl alcohol, propylene glycol, n-octanol, polyethylene glycol or polyoxyethylene ether, or a combination of at least two thereof.

[0026] Preferably, the solvent comprises deionized water.

[0027] Preferably, the current collector matrix includes any one of aluminum foil, PET / PP composite aluminum foil, copper foil, PET / PP composite copper foil, titanium foil or iron foil, or a combination of at least two of them.

[0028] In a second aspect, an embodiment of the present application provides a method for preparing a color-controllable carbon-coated current collector as described in the first aspect, the preparation method comprising the following steps:

[0029] (1) mixing a conductive carbon material, a binder, a wetting agent, and a solvent to obtain a conductive slurry, coating the conductive slurry on at least one surface of a current collector substrate, and drying the mixture to form a carbon coating layer;

[0030] (2) dissolving SiO2@Fe2O3 nanopowder in n-heptane to obtain an n-heptane solution of SiO2@Fe2O3 nanopowder, mixing engine oil and n-heptane to obtain a mixed solution, adding the mixed solution to the n-heptane solution of SiO2@Fe2O3 nanopowder, then adding a surfactant, raising the temperature, and then adding an oil-soluble pigment dye to obtain dyed SiO2@Fe2O3 nanopowder;

[0031] (3) The dyed SiO2@Fe2O3 nanopowder is added to an organic solvent and dispersed to obtain a SiO2@Fe2O3 nanopowder suspension, and then the SiO2@Fe2O3 nanopowder suspension is coated on the surface of the carbon-coated layer in step (1). After the organic solvent is dried and evaporated, the SiO2@Fe2O3 nanopowder particles are thoroughly and evenly spread on the surface of the carbon-coated layer to form a color layer, thereby obtaining the color-controllable carbon-coated current collector.

[0032] As a preferred technical solution of the present application, the mixing in step (1) specifically includes the following steps:

[0033] 1) adding a binder to a solvent and stirring to obtain a binder solution;

[0034] The stirring is carried out in a double planetary mixer at a stirring speed of 10 to 30 rpm, a dispersion speed of 2000 to 4000 rpm, a temperature of 15 to 30° C., and a time of 15 to 30 minutes.

[0035] 2) adding the conductive carbon material to the binder solution in the previous step in equal portions and stirring to obtain a conductive carbon material aqueous solution;

[0036] The stirring is carried out in a double planetary mixer at a stirring speed of 40 to 80 rpm, a dispersion speed of 3000 to 6000 rpm, a temperature of 15 to 30° C., and a total time of 30 to 90 minutes.

[0037] 3) slowly adding the wetting agent to the conductive carbon material aqueous solution in the previous step and stirring to obtain a mixed solution;

[0038] The stirring is carried out in a double planetary mixer at a stirring speed of 40 to 80 rpm, a dispersion speed of 3000 to 6000 rpm, a temperature of 15 to 30° C., and a time of 20 to 60 minutes.

[0039] Preferably, the solid content of the conductive paste in step (1) is 5-10%, for example, 5%, 6%, 7%, 8%, 9% or 10%.

[0040] Preferably, the mixing in step (1) further includes the steps of particle size treatment and vacuuming.

[0041] Preferably, the particle size treatment can be achieved using a grinder or a homogenizer. In the following specific embodiments, a homogenizer is used to achieve the particle size treatment described in this application, but the present invention is not limited to the homogenizer used in the embodiments of this application. After the particle size treatment, the D50 of the dispersed mixed solution is less than 1.2 μm and the D90 is less than 5 μm.

[0042] Preferably, the vacuum degree of the vacuuming is less than -0.07 KPa.

[0043] Preferably, the coating speed in step (1) is 60 to 120 m / min, for example, 60 m / min, 80 m / min, 100 m / min, or 120 m / min. Prior to coating in step (1), the current collector substrate foil is first subjected to a corona treatment or a preheating oven, or both, to remove surface oil from the foil and increase the dyne value of the foil, wherein the corona power is not less than 6 kW and the preheating oven temperature is 85 to 120°C.

[0044] Preferably, the drying temperature in step (1) is 80-120°C, for example, 80°C, 90°C, 100°C, 110°C or 120°C.

[0045] Preferably, in the n-heptane solution of the SiO2@Fe2O3 nanopowder, the mass ratio of SiO2@Fe2O3 nanopowder to n-heptane is 1:(10-20), and 10-20 can be, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20.

[0046] Preferably, in the mixed liquid, the mass ratio of engine oil to n-heptane is (15-8):1, and 15-8 can be, for example, 15, 14, 13, 12, 11, 10, 9 or 8.

[0047] Preferably, the mass ratio of the SiO2@Fe2O3 nanopowder to the engine oil is 1:(30-50), and 30-50 can be, for example, 30, 33, 35, 38, 40, 43, 45, 48 or 50.

[0048] Preferably, the mass ratio of the SiO2@Fe2O3 nanopowder to the surfactant is 1:(0.03-0.08), and 0.03-0.08 can be, for example, 0.03, 0.04, 0.05, 0.06, 0.07 or 0.08.

[0049] Preferably, the mass ratio of the SiO2@Fe2O3 nanopowder to the oil-soluble pigment dye is 1:(8-20), and 8-20 can be, for example, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20.

[0050] Preferably, the heating in step (2) is to 105-115°C, such as 105°C, 110°C or 115°C.

[0051] Preferably, the organic solvent in step (3) comprises any one of alcohols, ethers, alkanes or halogenated derivatives thereof having a boiling point below 100°C.

[0052] Preferably, in the SiO2@Fe2O3 nanopowder suspension, the mass percentage of SiO2@Fe2O3 nanopowder is 5-8%, for example, 5%, 6%, 7% or 8%.

[0053] Preferably, the dispersion in step (3) includes ultrasonic dispersion, and the ultrasonic dispersion conditions are 10KHz to 150KHz.

[0054] Preferably, the coating in step (3) comprises blade coating.

[0055] Preferably, the coating speed in step (3) is 10 to 80 m / min, for example, 10 m / min, 30 m / min, 50 m / min or 80 m / min.

[0056] Preferably, the drying temperature in step (3) is 80-100°C, such as 80°C, 90°C or 100°C.

[0057] In a third aspect, an embodiment of the present application provides an application of a color-controllable carbon-coated current collector as described in the first aspect in a lithium-ion battery and / or a sodium-ion battery.

[0058] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0059] In the embodiments of this application, the carbon coating layer can enhance the current collection strength of the current collector for the active material, improve rate performance, and reduce resistance. The color layer facilitates monitoring of poor coverage during the electrode coating process. Furthermore, the introduction of a SiO2-coated core-shell structure stabilizes the Fe2O3 nanostructure. When batteries are fabricated using the color-controllable carbon-coated current collector provided by this application, effective lithium storage and increased capacity are achieved. Furthermore, the color-controllable carbon-coated current collector provided by this application also exhibits good hydrophobicity.

[0060] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0062] FIG1 is a schematic structural diagram of a color-controllable carbon-coated current collector provided in Example 1.

[0063] Among them, 1-current collector substrate, 2-carbon coating layer, 3-color layer.

[0064] FIG2 is a graph showing the contact angle test results of the color-controllable carbon-coated current collector provided in Example 1. DETAILED DESCRIPTION

[0065] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0066] The SiO2@Fe2O3 nanopowder used in the examples of this application was prepared by the following method:

[0067] Weigh 0.5g of Fe2O3 and 200mL of anhydrous ethanol, mix them ultrasonically for 10 minutes, then add 100mL of water and 1mL of NH3·H2O and stir mechanically until uniform. Weigh 1mL of TEOS and dissolve it in 25mL of anhydrous ethanol. After mixing the two solutions, stir them mechanically at room temperature for 6 hours at a speed of 4000 rpm. -1 After centrifugation for 5 minutes, the supernatant was removed, the precipitate was washed with water three times until the pH was 7, the precipitate was transferred to a three-necked flask, NH3·H2O was added to adjust the pH value of the solution to 11, and then 1 mL of oleic acid was added and stirred at room temperature for 30 minutes. After stirring, the supernatant was removed by centrifugation, the precipitate was washed with water three times, and vacuum dried at 60°C for 4 hours to obtain the SiO2@Fe2O3 nanopowder.

[0068] Example 1

[0069] In this embodiment, a color-controllable carbon-coated current collector is provided, and a schematic structural diagram thereof is shown in Figure 1. The color-controllable carbon-coated current collector includes a current collector substrate 1 and a carbon-coated layer 2 arranged on the upper and lower surfaces of the current collector substrate 1. The carbon-coated layer 2 is provided with a color layer 3 on the side away from the current collector substrate 1. The thickness of the single-layer carbon-coated layer is 700nm (that is, the thickness of the carbon-coated layer on the upper and lower surfaces of the carbon-coated layer is 700nm), and the thickness of the single-layer color layer is 500nm (that is, the thickness of the two color layers is 500nm).

[0070] The raw materials for preparing the color layer include SiO2@Fe2O3 nanopowder, oil-soluble yellow pigment and surfactant (oleic acid).

[0071] The carbon coating is prepared from the following raw materials, calculated by weight: 5% conductive carbon material (SP-Li), 7% binder (acrylic resin, brand Derby 611), 15% wetting agent (isopropyl alcohol), and the balance solvent (deionized water). The resulting conductive slurry has a solids content of 8.7% and a pH of 6.1.

[0072] The method for preparing a color-controllable carbon-coated current collector comprises the following steps:

[0073] (1) A conductive carbon material, a binder, a wetting agent, and a solvent are mixed to obtain a conductive slurry, which is then coated on a double-sided smooth aluminum foil using a coating machine. The aluminum foil is pre-treated with a corona machine at a coating speed of 60 m / min and dried in an oven at 80°C to form a carbon coating layer.

[0074] The preparation of the conductive paste specifically includes the following steps:

[0075] 1) Prepare a binder aqueous solution according to the formula, add acrylic resin to the remaining solvent water, and stir and disperse. The stirring speed of the double planetary mixer is 15 rpm, the dispersion speed is 2000 rpm, the temperature is 25°C, and the time is 15 minutes;

[0076] 2) adding the conductive carbon material SP-Li to the binder aqueous solution prepared in step 1) in two equal portions, stirring and dispersing the mixture. The stirring speed of the dual planetary mixer was 60 rpm, the dispersion speed was 4000 rpm, the temperature was 25° C., and each time was for 15 minutes to obtain a conductive carbon material aqueous solution.

[0077] 3) slowly adding isopropyl alcohol as a wetting agent to the conductive carbon material aqueous solution in step 2) and stirring and dispersing the mixture. The stirring speed of the dual planetary mixer is 60 rpm, the dispersion speed is 4000 rpm, the temperature is 25° C., and the time is 30 min to obtain a mixed solution.

[0078] 4) The mixed solution in step 3) was subjected to a homogenizer to obtain a dispersed mixed solution having a D50 of 0.789 μm and a D90 of 4.12 μm;

[0079] 5) The dispersed mixed solution in step 4) was subjected to vacuum treatment with a double planetary mixer at a reverse stirring speed of 10 rpm, a vacuum degree of <-0.07 KPa, a temperature of 25° C., and a time of 30 min to obtain a conductive paste.

[0080] (2) 0.65 g of SiO2@Fe2O3 nanopowder was dissolved in 10 mL of n-heptane and stirred at 100 °C. At the same time, 30 mL of engine oil was added to 4 mL of n-heptane and heated to make the n-heptane evenly distributed in the engine oil. The engine oil with n-heptane was poured into the n-heptane solution containing SiO2@Fe2O3 nanopowder. Then, 0.032 g of oleic acid was added as a surfactant. The temperature was raised to 110 °C and mechanical stirring was continued until no small bubbles emerged in the solution. Then, 8 g of oil-soluble yellow pigment (brand name: Luchuan Curcumin E40) was added for dyeing to obtain yellow SiO2@Fe2O3 nanopowder.

[0081] (3) The yellow SiO2@Fe2O3 nanopowder is placed in anhydrous ethanol solvent and ultrasonically dispersed at 100 kHz for 30 minutes to disperse and suspend the yellow SiO2@Fe2O3 nanopowder in the anhydrous ethanol solvent to form a yellow SiO2@Fe2O3 nanopowder suspension (the mass percentage of the yellow SiO2@Fe2O3 nanopowder is 8%). The suspension is then evenly scraped onto the surface of the carbon-coated layer in step (1) at a coating speed of 30 m / min and dried at 80°C to form a color layer (yellow), thereby obtaining the color-controllable carbon-coated current collector.

[0082] Example 2

[0083] The only difference between this embodiment and embodiment 1 is that the thickness of the single color layer is 400 nm.

[0084] Example 3

[0085] In this embodiment, a color-controllable carbon-coated current collector is provided, which includes a current collector substrate and a carbon-coated layer arranged on the upper surface of the current collector substrate. A color layer is provided on the side of the carbon-coated layer away from the current collector substrate. The thickness of the carbon-coated layer is 700 nm, and the thickness of the color layer is 500 nm.

[0086] The raw material selection and dosage for preparing the carbon coating layer and the color layer are the same as those in Example 1.

[0087] The difference between the preparation method and Example 1 is that the conductive slurry is adaptively coated only on the upper surface of the current collector substrate to form a carbon coating layer, and a yellow SiO2@Fe2O3 nanopowder suspension is scraped on the side of the carbon coating layer away from the current collector substrate to form a color layer.

[0088] Example 4

[0089] In this embodiment, a color-controllable carbon-coated current collector is provided, which includes a current collector substrate and a carbon-coated layer arranged on the upper and lower surfaces of the current collector substrate. A color layer is provided on the side of the carbon-coated layer away from the current collector substrate. The thickness of a single carbon-coated layer is 600 nm, and the thickness of a single color layer is 300 nm.

[0090] The raw materials for preparing the color layer include SiO2@Fe2O3 nanopowder, oil-soluble yellow pigment and surfactant (oleic acid).

[0091] The specific selection and amount of raw materials for preparing the carbon coating layer are the same as those in Example 1.

[0092] The method for preparing a color-controllable carbon-coated current collector comprises the following steps:

[0093] (1) A conductive carbon material, a binder, a wetting agent, and a solvent are mixed to obtain a conductive slurry, which is then coated on a double-sided smooth aluminum foil using a coating machine. The aluminum foil is pre-treated with a corona machine at a coating speed of 60 m / min and dried in an oven at 80°C to form a carbon coating layer.

[0094] (2) 0.56 g of SiO2@Fe2O3 nanopowder was dissolved in 10 mL of n-heptane and stirred at 100 °C. At the same time, 30 mL of engine oil was added to 3 mL of n-heptane and heated to make the n-heptane evenly distributed in the engine oil. The engine oil with n-heptane was poured into the n-heptane solution containing SiO2@Fe2O3 nanopowder. Then, 0.028 g of oleic acid was added as a surfactant. The temperature was raised to 110 °C and mechanical stirring was continued until no small bubbles emerged in the solution. Then, 6 g of oil-soluble yellow pigment (brand name: Luchuan Curcumin E40) was added for dyeing to obtain yellow SiO2@Fe2O3 nanopowder.

[0095] (3) The yellow SiO2@Fe2O3 nanopowder is placed in anhydrous ethanol solvent and ultrasonically dispersed at 100 kHz for 30 minutes to disperse and suspend the yellow SiO2@Fe2O3 nanopowder in the anhydrous ethanol solvent to form a yellow SiO2@Fe2O3 nanopowder suspension (the mass percentage of the yellow SiO2@Fe2O3 nanopowder is 8%). The suspension is then evenly scraped onto the surface of the carbon-coated layer in step (1) at a coating speed of 30 m / min and dried at 80°C to form a color layer (yellow), thereby obtaining the color-controllable carbon-coated current collector.

[0096] Example 5

[0097] The only difference between this embodiment and embodiment 1 is that the thickness of the single color layer is 700 nm.

[0098] Comparative Example 1

[0099] In this comparative example, a carbon-coated current collector is provided. The carbon-coated current collector includes a current collector substrate and carbon coating layers disposed on the upper and lower surfaces of the current collector substrate. The thickness of a single carbon coating layer is 700 nm.

[0100] The carbon coating is prepared from the following raw materials, calculated by weight: 5% conductive carbon material (SP-Li), 7% binder (acrylic resin, brand Derby 611), 15% wetting agent (isopropyl alcohol), and the balance solvent (deionized water). The resulting conductive slurry has a solids content of 8.7% and a pH of 6.1.

[0101] The preparation method of the carbon-coated current collector comprises the following steps:

[0102] (1) A conductive carbon material, a binder, a wetting agent, and a solvent are mixed in a prescribed amount to obtain a conductive slurry, which is then coated on a double-sided smooth aluminum foil using a coating machine. The aluminum foil is pretreated with a corona machine at a coating speed of 60 m / min and dried in an oven at 80° C. to form a carbon coating layer, thereby obtaining a carbon-coated current collector.

[0103] The preparation of the conductive paste specifically includes the following steps:

[0104] 1) Prepare a binder aqueous solution according to the formula, add acrylic resin to the remaining solvent water, and stir and disperse. The stirring speed of the double planetary mixer is 15 rpm, the dispersion speed is 2000 rpm, the temperature is 25°C, and the time is 15 minutes;

[0105] 2) adding the conductive carbon material SP-Li to the binder aqueous solution in step 1) in two equal portions, stirring and dispersing the mixture, using a dual planetary mixer at a stirring speed of 60 rpm, a dispersion speed of 4000 rpm, and a temperature of 25° C. for 15 minutes each time to obtain a conductive carbon material aqueous solution;

[0106] 3) slowly adding isopropyl alcohol as a wetting agent to the conductive carbon material aqueous solution in step 2) and stirring and dispersing the mixture. The stirring speed of the dual planetary mixer is 60 rpm, the dispersion speed is 4000 rpm, the temperature is 25° C., and the time is 30 min to obtain a mixed solution.

[0107] 4) The mixed solution in step 3) was subjected to a homogenizer to obtain a dispersed mixed solution having a D50 of 0.789 μm and a D90 of 4.12 μm;

[0108] 5) The dispersed mixed solution in step 4) was subjected to vacuum treatment with a double planetary mixer at a reverse stirring speed of 10 rpm, a vacuum degree of <-0.07 KPa, a temperature of 25° C., and a time of 30 min to obtain a conductive paste.

[0109] The performance of the carbon-coated current collectors provided in Examples 1-5 and Comparative Example 1 was tested using the following method:

[0110] (1) Surface resistance: tested using a four-probe resistance tester;

[0111] (2) Number of water-resistant wipes: Fix the carbon-coated current collector on the table, press a 25g weight + a 55g adjustment rod (80g in total) on a cotton swab soaked in pure water, apply a force F to pull the weight and the adjustment rod back and forth to make the cotton swab wipe the coating surface of the carbon-coated current collector, observe whether the coating changes color and falls off, and record the number of wipes performed when the coating changes color and falls off.

[0112] The performance test results are shown in Table 1.

[0113] Table 1

[0114] It can be seen from Table 1 that the carbon-coated current collectors provided in Examples 1-4 of the present application are provided with a color layer, but the surface resistance thereof is not much different from that of the carbon-coated current collector provided in Comparative Example 1. The thickness of the color layer of the carbon-coated current collector provided in Example 5 is too large, exceeding the preferred range, and therefore the surface resistance is too high. Compared with the carbon-coated current collector provided in Comparative Example 1 which has only the original carbon layer, the carbon-coated current collectors provided in Examples 1-5 of the present application are provided with a color layer, which has excellent water resistance, and the color layer is conducive to monitoring poor coverage during the electrode coating process.

[0115] The color-controllable carbon-coated current collector provided in Example 1 was subjected to a contact angle test using deionized water as the test solvent. The test results are shown in FIG2 . As can be seen from the figure, the contact angle is greater than 90°, indicating low wettability to deionized water, further verifying that its water resistance is significantly improved.

[0116] The applicant declares that while the above-mentioned embodiments are used to illustrate the color-controllable carbon-coated current collector, its preparation method, and its application, this application is not limited to the above-mentioned embodiments, and does not necessarily rely on the above-mentioned embodiments for implementation. Persons skilled in the art should understand that any improvements to this application, equivalent replacements for the raw materials used, addition of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of this application.

Claims

1. A color-controllable carbon-coated current collector, wherein: The color-controllable carbon-coated current collector comprises a current collector substrate and a carbon-coated layer disposed on at least one side of the current collector substrate, wherein a color layer is disposed on a side of the carbon-coated layer away from the current collector substrate; The raw materials for preparing the color layer include SiO2@Fe2O3 nano powder, oil-soluble pigment dye and surfactant.

2. The color-controllable carbon-coated current collector according to claim 1, wherein: The thickness of the carbon coating layer is less than 800 nm.

3. The color-controllable carbon-coated current collector according to claim 1 or 2, wherein: The thickness of the color layer is less than 600 nm.

4. The color-controllable carbon-coated current collector according to any one of claims 1 to 3, wherein: The mass ratio of the SiO2@Fe2O3 nano powder to the oil-soluble pigment dye is 1:(8-20).

5. The color-controllable carbon-coated current collector according to any one of claims 1 to 4, wherein: The mass ratio of the SiO2@Fe2O3 nanopowder to the surfactant is 1:(0.03-0.08); Preferably, the surfactant comprises oleic acid.

6. The color-controllable carbon-coated current collector according to any one of claims 1 to 5, wherein: The raw materials for preparing the carbon coating layer include the following components by weight percentage: 5-8% of conductive carbon material, 7-22% of binder, 3-20% of wetting agent, and the balance of solvent; Preferably, the conductive carbon material includes any one or a combination of at least two of conductive carbon black, conductive graphite, carbon nanotubes, carbon nanofibers or graphene; Preferably, the binder comprises acrylic resin; Preferably, the wetting agent includes any one or a combination of at least two of isopropyl alcohol, propylene glycol, n-octanol, polyethylene glycol or polyoxyethylene ether; Preferably, the solvent comprises deionized water.

7. The color-controllable carbon-coated current collector according to any one of claims 1 to 6, wherein: The current collector matrix includes any one of aluminum foil, PET / PP composite aluminum foil, copper foil, PET / PP composite copper foil, titanium foil or iron foil, or a combination of at least two of them.

8. A method for preparing a color-controllable carbon-coated current collector as claimed in any one of claims 1 to 7, comprising the following steps: (1) mixing a conductive carbon material, a binder, a wetting agent, and a solvent to obtain a conductive slurry, coating the conductive slurry on at least one side of a current collector substrate, and drying the slurry to form a carbon coating layer; (2) dissolving SiO2@Fe2O3 nanopowder in n-heptane to obtain an n-heptane solution of SiO2@Fe2O3 nanopowder, mixing engine oil and n-heptane to obtain a mixed solution, adding the mixed solution to the n-heptane solution of SiO2@Fe2O3 nanopowder, then adding a surfactant, heating, and then adding an oil-soluble pigment dye to obtain a dyed SiO2@Fe2O3 nanopowder; (3) Adding the dyed SiO2@Fe2O3 nanopowder into an organic solvent and dispersing it to obtain a SiO2@Fe2O3 nanopowder suspension, and then coating the SiO2@Fe2O3 nanopowder suspension on the surface of the carbon-coated layer in step (1), drying it to form a color layer, thereby obtaining the color-controllable carbon-coated current collector.

9. The preparation method according to claim 8, wherein: The solid content of the conductive paste in step (1) is 5-10%.

10. The preparation method according to claim 8 or 9, wherein: After the mixing in step (1), the step further includes the steps of particle size treatment and vacuuming; Preferably, the particle size processing is achieved by a grinder or a homogenizer.

11. The preparation method according to any one of claims 8 to 10, wherein The coating speed in step (1) is 60 to 120 m / min; Preferably, the drying temperature in step (1) is 80-120°C.

12. The preparation method according to any one of claims 8 to 11, wherein In the n-heptane solution of the SiO2@Fe2O3 nanopowder, the mass ratio of the SiO2@Fe2O3 nanopowder to n-heptane is 1:(10-20); Preferably, in the mixed liquid, the mass ratio of engine oil to n-heptane is (15-8):1; Preferably, the mass ratio of the SiO2@Fe2O3 nanopowder to the engine oil is 1:(30-50); Preferably, the mass ratio of the SiO2@Fe2O3 nanopowder to the surfactant is 1:(0.03-0.08); Preferably, the mass ratio of the SiO2@Fe2O3 nanopowder to the oil-soluble pigment dye is 1:(8-20); Preferably, the heating in step (2) is to be increased to 105-115°C.

13. The preparation method according to any one of claims 8 to 12, wherein In the SiO2@Fe2O3 nano powder suspension, the mass percentage of SiO2@Fe2O3 nano powder is 5-8%; Preferably, the coating in step (3) comprises blade coating; Preferably, the coating speed in step (3) is 10 to 80 m / min; Preferably, the drying temperature in step (3) is 80-100°C.

14. Use of the color-controllable carbon-coated current collector according to any one of claims 1 to 7 in a lithium-ion battery and / or a sodium-ion battery.

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