Composite current collector and preparation method thereof, pole piece, battery and electric device

Abstract

The invention discloses a composite current collector and a preparation method thereof, a pole piece, a battery and an electric device. The composite current collector comprises a current collector base material and a coating arranged on at least one side of the current collector base material, the coating comprises a carbon fluoride material, and the mass percentage content of fluorine in the carbon fluoride material is 2%-20%. Therefore, the coating containing the carbon fluoride material is formed on the current collector base material, and the strong electronegativity of the carbon fluoride material is utilized, so that corrosion of corrosive substances in electrolyte to the current collector can be effectively blocked, and the corrosion resistance of the current collector is enhanced; the mass percentage content of fluorine in the carbon fluoride material is within the range, and the conductivity of the coating is good, so that the composite current collector with both conductivity and corrosion resistance is formed.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a composite current collector and a preparation method thereof, a pole piece, a battery and an electrical device. Background Art

[0002] The current collector is the electron transfer center of the active material inside the battery (such as a lithium-ion battery), used for efficient collection and conduction of current, and physically supports the active material to ensure effective contact between particles. Therefore, its characteristic properties are closely related to the battery's internal resistance and energy conversion efficiency, affecting the battery's rapid charge and discharge capabilities and safety performance. Currently, traditional current collectors are mainly faced with two types of problems: First, due to the limited contact area between the current collector and the active material, the adhesion is insufficient, resulting in high interfacial contact resistance. In addition, when the structure collapses during the charge and discharge process, the active material is very easy to fall off from the current collector, resulting in capacity loss; second, the current collector is severely corroded by the attack of HF, a decomposition product of the electrolyte salt (such as LiPF6) (F - It has strong coordination and penetrating properties), affecting charge transfer.

[0003] Therefore, the current current collector and its preparation method, electrode, battery and electrical device still need to be improved. Summary of the Invention

[0004] The present application aims to alleviate or solve at least one of the above-mentioned problems to at least some extent.

[0005] In one aspect of the present application, a composite current collector is proposed. In some embodiments of the present application, the composite current collector includes a current collector substrate and a coating disposed on at least one side of the current collector substrate, wherein the coating includes a fluorinated carbon material, and the mass percentage of fluorine in the fluorinated carbon material is 2% to 20%. Thus, by forming a coating containing a fluorinated carbon material on the current collector substrate, the strong negative charge of the fluorinated carbon material can be utilized to effectively block the corrosion of the current collector by corrosive substances in the electrolyte, thereby enhancing the corrosion resistance of the current collector; when the mass percentage of fluorine in the fluorinated carbon material is within the above range, the coating has good conductivity, thereby forming a composite current collector with both electrical conductivity and corrosion resistance.

[0006] In some embodiments of the present application, the fluorinated carbon material includes one or more of fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, and fluorinated graphite.

[0007] In some embodiments of the present application, the coating has a thickness of 0.2 μm to 1 μm; and / or the current collector substrate comprises aluminum or copper. A coating thickness within this range can avoid foil exposure (part of the substrate not covered by the coating) due to a thin coating, and a reduction in battery energy density due to a thick coating. Aluminum or copper current collector substrates have high electrical conductivity, enabling rapid electron transport and improving battery performance.

[0008] In some embodiments of the present application, the coating further comprises a binder, thereby enhancing the bonding strength between the coating and the current collector substrate, and between the coating and the electrode active material layer.

[0009] In some embodiments of the present application, the binder includes one or more of the following materials: polyvinylidene fluoride, carboxymethyl cellulose and its sodium salt, potassium salt, calcium salt, ammonium salt, polyacrylic acid and its sodium salt, potassium salt, calcium salt, ammonium salt, styrene-butadiene rubber, copolymers of acrylic acid and its sodium salt, potassium salt, calcium salt or ammonium salt and acrylonitrile; and / or, the mass ratio of the carbon fluoride material to the binder is 1: (0.8-1.8). The above-mentioned binders all have good bonding properties, which can make the coating firmly adhere to the current collector substrate; when the mass ratio of the carbon fluoride material to the binder is within the above range, the coating can maintain good conductivity and maintain strong adhesion between the coating and the current collector substrate, and between the coating and the active material layer of the electrode.

[0010] In another aspect of the present application, a method for preparing a composite current collector is provided. In some embodiments of the present application, the method for preparing the composite current collector includes forming a coating on at least one side of a current collector substrate, wherein the coating comprises a fluorinated carbon material, wherein the fluorinated carbon material has a fluorine content of 2% to 20% by weight. Thus, by forming a coating comprising a fluorinated carbon material on the current collector substrate and regulating the fluorine content within a suitable range, the corrosion resistance of the composite current collector can be enhanced while maintaining good electrical conductivity.

[0011] In some embodiments of the present application, forming a coating on at least one side of the current collector substrate includes the following steps: preparing a conductive paste comprising the carbon fluoride material and a solvent; applying the conductive paste to at least one side of the current collector substrate to form a conductive paste layer; and performing a drying process to remove the solvent from the conductive paste layer to form a coating. The composite current collector can be prepared through a simple dispersion-coating-drying process, significantly reducing technical barriers.

[0012] In some embodiments of the present application, the conductive paste also includes a binder, and the conductive paste satisfies at least one of the following conditions: the binder includes one or more of the following materials: polyvinylidene fluoride, carboxymethyl cellulose and its sodium salt, potassium salt, calcium salt, ammonium salt, polyacrylic acid and its sodium salt, potassium salt, calcium salt, ammonium salt, styrene-butadiene rubber, a copolymer of acrylic acid and its sodium salt, potassium salt, calcium salt or ammonium salt and acrylonitrile; in the conductive paste, the mass ratio of the carbon fluoride material to the binder is 1: (0.8~1.8).

[0013] In some embodiments of the present application, the method for preparing a composite current collector satisfies at least one of the following conditions: the current collector substrate includes aluminum or copper; the fluorinated carbon material includes one or more of fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, and fluorinated graphite; the solvent includes N-methylpyrrolidone or deionized water; the solid content of the conductive paste is 5% to 18%; the viscosity of the conductive paste is 50 mPa·s to 200 mPa·s; the temperature of the drying treatment is 100°C to 150°C; and the time of the drying treatment is 10 min to 60 min.

[0014] In some embodiments of the present application, the preparation of the conductive paste includes the following steps: placing the carbon fluoride material, the binder and the solvent in a mixing device, and treating them at a rotation speed of 300rpm to 1500rpm for 0.5h to 3h to obtain the conductive paste; or, the preparation of the conductive paste includes the following steps: mixing the binder with the solvent to obtain a mixture with a solid content of 15% to 35% and a pH of 3 to 9, and then placing the mixture, the carbon fluoride material and the solvent in a mixing device, and treating them at a rotation speed of 300rpm to 1500rpm for 0.5h to 3h to obtain the conductive paste.

[0015] In another aspect of the present application, a pole piece is provided. In some embodiments of the present application, the pole piece includes a composite current collector and an active material layer disposed on at least one side of the composite current collector. The composite current collector is the composite current collector described above or a composite current collector prepared using the method described above. Thus, the pole piece has all the features and advantages of the composite current collector described above, and no further details are given here.

[0016] In another aspect of the present application, a battery is provided. In some embodiments of the present application, the battery includes the aforementioned electrode sheet. Thus, the battery has all the features and advantages of the aforementioned electrode sheet, which will not be further elaborated here.

[0017] In another aspect of the present application, an electrical device is provided. In some embodiments of the present application, the electrical device includes the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be further elaborated here. DETAILED DESCRIPTION

[0018] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be understood as limiting the present application.

[0019] As mentioned above, the current traditional current collectors (such as copper foil, aluminum foil, etc.) are mainly faced with two types of problems. First, the contact area between the current collector and the active material is limited, resulting in insufficient adhesion, high interface contact resistance, and the active material is easy to fall off from the current collector; second, the current collector is easily corroded under HF attack, affecting charge transfer.

[0020] In the related art, the performance of the current collector is improved by forming a carbon coating on a substrate such as copper foil and aluminum foil. Taking aluminum foil as an example, carbon-coated aluminum foil (using carbon materials such as carbon black, carbon nanotubes, and graphene as the conductive component of the coating) is the positive electrode current collector widely used in current production. The carbon coating can significantly promote the charge transfer between the current collector and the active material, effectively reduce the interface impedance, and thus greatly improve the rate performance of the battery. However, the carbon coating has limitations in preventing HF from corroding the current collector. Since the carbon material itself has a high chemical stability and is difficult to form a strong interaction with other substances, the free F in the electrolyte - It can easily pass through the gaps between carbon material particles, penetrate the carbon coating and corrode the aluminum foil current collector. In addition, if the carbon coating is uneven or has defects, some parts of the aluminum foil may be exposed, making it more susceptible to F in the electrolyte. - corrosion.

[0021] In order to improve the corrosion resistance of the carbon coating, a composite method is usually adopted in which a layer of anti-corrosion coating is first applied to the surface of the aluminum foil, and then a carbon coating is applied. The related art discloses a surface treatment method for an aluminum foil current collector and a battery pole piece, wherein a first treatment liquid is used to remove the oil and oxidation layer remaining on the surface of the aluminum foil during processing, and a second treatment liquid is used to form an anti-corrosion protective layer and an anti-oxidation protective layer on the surface of the aluminum foil and increase the affinity between the aluminum foil current collector and the active substance / carbon coating layer, and finally a carbon coating layer is applied. This method can effectively improve the adhesion between the aluminum foil and the active substance / carbon coating layer, prevent the active substance / carbon coating layer from falling off, and avoid the corrosion and oxidation of the current collector by the electrolyte inside the battery. However, the above method involves multi-layer coating, and the preparation process is complicated. In addition, the design method of the composite coating often has high technical barriers, such as magnetron sputtering and atomic layer deposition, resulting in high production costs.

[0022] From the perspective of materials, this application abandons the concept of multiple component composites and directly uses fluorinated carbon materials (fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, fluorinated graphite, etc.) as the main components of the coating. The selection of fluorinated carbon materials with a fluorine content within a certain range can enhance the corrosion resistance and antioxidant effect of the current collector, and the coating has good conductivity. This application can complete the preparation of the coating through a simple dispersion-coating-drying process, which can greatly reduce technical barriers. The CF bond in fluorinated carbon will greatly enhance the electronegativity of the material, and the F - Produce a repulsive effect, effectively inhibiting F - The diffusion and penetration of F can enhance the corrosion resistance and oxidation resistance of the coating. In addition, the presence of F can reduce the interfacial energy of carbon-based materials, which is conducive to their uniform dispersion during the pulping process.

[0023] One purpose of the present application is to at least to some extent solve the problem of limited corrosion resistance of a single carbon coating current collector. Another purpose of the present application is to at least to some extent solve the problem of high cost of preparing a composite coating.

[0024] In one aspect of the present application, a composite current collector is proposed. In some embodiments of the present application, the composite current collector includes a current collector substrate and a coating provided on at least one side of the current collector substrate, wherein the coating includes a fluorinated carbon material, and the mass percentage of fluorine in the fluorinated carbon material may be 2% to 20%. For example, the mass percentage of fluorine in the fluorinated carbon material may be 2%, 3%, 5%, 8%, 10%, 12%, 15%, 17% or 20%. When the content of fluorine in the fluorinated carbon material is within the above range, the coating has good conductivity, and the resistivity of the composite current collector is low. Using the current collector in an electrode or battery is beneficial to improving the performance of the electrode or battery; the CF bond in the fluorinated carbon material can greatly enhance the electronegativity of the material, and resists F in the electrolyte. - Produce a repulsive effect, effectively inhibiting F - The diffusion penetration of the composite current collector can enhance the corrosion resistance of the coating. In addition, the fluorinated carbon material can also enhance the oxidation resistance of the coating, thereby further improving the performance of the composite current collector.

[0025] In some embodiments of the present application, the current collector substrate may include aluminum or copper.

[0026] In some embodiments, the current collector substrate may be an aluminum foil. In some specific embodiments, the thickness of the aluminum foil may be 10 μm to 20 μm.

[0027] In other embodiments, the current collector substrate may be a copper foil. In some specific embodiments, the thickness of the copper foil may be about 6 μm.

[0028] In some embodiments of the present application, the fluorinated carbon material may include one or more of fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, and fluorinated graphite. In some embodiments, the fluorinated carbon material may include fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, or fluorinated graphite. In other embodiments, the fluorinated carbon material may include two or more of fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, and fluorinated graphite. The above materials all contain C—F bonds, which can enhance the corrosion resistance of the coating.

[0029] In some embodiments of the present application, the coating layer may be disposed on only one side of the current collector substrate. In other embodiments of the present application, the coating layer may be disposed on both sides of the current collector substrate.

[0030] In some embodiments of the present application, the coating may have a thickness of 0.2 μm to 1 μm, for example, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, or 1 μm. Coating thicknesses within these ranges are less likely to cause foil exposure and can effectively protect the current collector substrate from corrosion by the electrolyte. Furthermore, coatings of this thickness can maintain a high energy density in the battery.

[0031] It should be noted that in this application, the thickness of the coating refers to the thickness of the single-sided coating. When a coating is provided on both sides of the current collector substrate, the thickness of the coating is the same and is in the range of 0.2 μm to 1 μm.

[0032] In some embodiments of the present application, in addition to the carbon fluoride material, the coating also includes a binder. The binder can bind the substances in the coating and adhere the coating to the current collector substrate, thereby forming a strong adhesion between the coating and the current collector substrate, thereby improving the stability of the composite current collector.

[0033] In some embodiments of the present application, the binder may include one or more of the following materials: polyvinylidene fluoride, carboxymethyl cellulose and its sodium salt, potassium salt, calcium salt, ammonium salt, polyacrylic acid and its sodium salt, potassium salt, calcium salt, ammonium salt, styrene-butadiene rubber, copolymers of acrylic acid and its sodium salt, potassium salt, calcium salt or ammonium salt and acrylonitrile. The above binders have good bonding properties and can serve to bond the coating layer to the current collector substrate. In some specific embodiments, the binder may include polyvinylidene fluoride, sodium carboxymethyl cellulose, or sodium polyacrylate.

[0034] In some embodiments of the present application, the mass ratio of the carbon fluoride material to the binder in the coating can be 1:(0.8-1.8). For example, the mass ratio of the carbon fluoride material to the binder can be 1:0.8, 1:1, 1:1.3, 1:1.5, or 1:1.8. When the mass ratio of the carbon fluoride material to the binder is within the above range, the coating can maintain good conductivity and stability, and the coating can also be firmly bonded to the current collector substrate, and the coating is not easy to fall off or powder.

[0035] When the binder contains fluorine, different methods can be used to determine the fluorine content of the carbon fluoride in the coating. The following uses polyvinylidene fluoride (PVDF) as the binder to illustrate the test method for the fluorine content of the carbon fluoride in the product end:

[0036] Method 1: Immerse the composite current collector in N-methylpyrrolidone (NMP) and accelerate the dissolution of PVDF by heating and / or ultrasound. Centrifuge to separate the insoluble carbon fluoride material and the dissolved PVDF solution, and determine the F content by ion chromatography / XRF.

[0037] Method 2: Through XPS testing, the chemical environments of F in PVDF and fluorinated carbon are different, and the corresponding binding energies are different. Finally, the F content is determined by peak fitting.

[0038] In another aspect of the present application, a method for preparing a composite current collector is provided. In some embodiments of the present application, the method for preparing the composite current collector includes forming a coating on at least one side of a current collector substrate. The coating includes a fluorinated carbon material, wherein the mass percentage of fluorine in the fluorinated carbon material may be 2% to 20%. As a result, the coating has good corrosion resistance and electrical conductivity, and the composite current collector can maintain good electrical conductivity and is not easily corroded or oxidized by the electrolyte.

[0039] In this application, a highly electronegative carbon fluoride material is used as the primary coating material to block the corrosion of the current collector by corrosive substances in the electrolyte, ensuring the current collector's working state under harsh conditions. Although the presence of fluorine can enhance the corrosion resistance of the coating, the presence of excessive C-F bonds will change the electron arrangement around the C-C bonds, which is not conducive to intrinsic electron transfer. Therefore, the fluorine content in the carbon fluoride material needs to be controlled within a reasonable range.

[0040] In some embodiments of the present application, the fluorinated carbon material may include one or more of fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, and fluorinated graphite.

[0041] The specific preparation method of the carbon fluoride material is not particularly limited in this application. Those skilled in the art can select or set it according to actual needs, or directly purchase a carbon fluoride material with a fluorine content that meets the use requirements. In some embodiments, the carbon fluoride required for this application can be synthesized by common industrial methods for producing carbon fluoride, such as direct fluorine gas fluorination, fluorination with a fluorinating agent, electrolytic fluorination, electrochemical fluorination, liquid phase stripping, and mechanical stripping. The fluorine content in the carbon fluoride material can be adjusted by controlling the reaction conditions such as the amount of fluorine source, reaction temperature, and time to ensure that the fluorine content in the carbon fluoride material meets the use requirements.

[0042] The characteristics of the current collector substrate, such as the material and thickness, have been described in detail above and will not be repeated here.

[0043] In some embodiments of the present application, forming a coating on at least one side of the current collector substrate may include the following steps:

[0044] S10: preparing a conductive paste, wherein the conductive paste includes a carbon fluoride material and a solvent.

[0045] The conductive paste contains fluorinated carbon materials. The presence of fluorine can reduce the interfacial energy of the carbon-based material, which is beneficial to its uniform dispersion during the slurrying process, thereby forming a uniformly dispersed conductive paste, which is beneficial to improving the uniformity of the coating.

[0046] In some embodiments of the present application, the solvent may include N-methylpyrrolidone (NMP) or deionized water. In some specific embodiments, the solvent may be NMP or deionized water.

[0047] In some embodiments, the carbon fluoride material and the solvent may be placed in a mixing device and stirred or ground to form a uniformly dispersed conductive paste.

[0048] In some embodiments, in addition to the carbon fluoride material and the solvent, the conductive paste further includes a binder. In some embodiments, the binder may include one or more of the following materials: polyvinylidene fluoride, carboxymethyl cellulose and its sodium salt, potassium salt, calcium salt, and ammonium salt, polyacrylic acid and its sodium salt, potassium salt, calcium salt, and ammonium salt, styrene-butadiene rubber, and a copolymer of acrylic acid and its sodium salt, potassium salt, calcium salt, or ammonium salt and acrylonitrile.

[0049] In some embodiments of the present application, the mass ratio of the carbon fluoride material to the binder in the conductive paste can be 1:(0.8-1.8). For example, the mass ratio of the carbon fluoride material to the binder can be 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6, or 1:1.8. Thus, the prepared coating has a suitable mass ratio of the carbon fluoride material to the binder, which is beneficial for improving the performance of the composite current collector.

[0050] In some embodiments of the present application, the solid content of the conductive paste may be 5% to 18%, for example, the solid content of the conductive paste may be 5%, 8%, 10%, 12%, 15%, or 18%. As a result, the conductive paste is easy to apply and is conducive to forming a coating with uniform thickness and uniform composition.

[0051] In some embodiments of the present application, the viscosity of the conductive paste can be 50 mPa·s to 200 mPa·s. For example, the viscosity of the conductive paste can be 50 mPa·s, 80 mPa·s, 100 mPa·s, 120 mPa·s, 150 mPa·s, 180 mPa·s, or 200 mPa·s. When the viscosity of the paste is within the above range, the conductive paste is neither too thin nor too thick, which facilitates the formation of a conductive paste layer of uniform thickness through coating.

[0052] In the present application, the conductive paste can be prepared by using different steps, which are described in detail below.

[0053] In some specific embodiments of the present application, preparing the conductive paste may include the following steps: placing a carbon fluoride material, a binder, and a solvent in a mixing device and processing at a rotation speed of 300 rpm to 1500 rpm for 0.5 h to 3 h to obtain the conductive paste. In some embodiments, the rotation speed may be 300 rpm, 500 rpm, 700 rpm, 1000 rpm, 1200 rpm, or 1500 rpm, and the processing time may be 0.5 h, 0.8 h, 1 h, 1.5 h, 2 h, 2.5 h, or 3 h.

[0054] In other specific embodiments of the present application, the preparation of the conductive paste may include the following steps: mixing a binder with a solvent to obtain a mixture with a solid content of 15% to 35% and a pH of 3 to 9, and then placing the mixture, a fluorinated carbon material, and a solvent in a mixing device, and processing at a speed of 300 rpm to 1500 rpm for 0.5 h to 3 h to obtain a conductive paste. In some embodiments, the solid content of the mixture may be 15%, 18%, 20%, 23%, 25%, 27%, 30%, 32% or 35%, and the pH may be 3, 4, 5, 6, 7, 8 or 9. The solid content and pH of the mixture meet the above conditions, and a conductive paste with suitable viscosity and uniform dispersion can be obtained. Moreover, when the pH of the mixture is within the above range, the adhesion between the conductive coating formed and the current collector substrate and between the active material layers of the electrode is stronger.

[0055] In some embodiments, the mixing device may be a sand mill, in which various materials may be placed and sand milled at a rotation speed of 300 rpm to 1500 rpm for 0.5 to 3 hours to ensure that there is no obvious agglomeration of particles in the conductive paste.

[0056] S20: coating a conductive paste on at least one side of the current collector substrate to form a conductive paste layer.

[0057] In some embodiments, the conductive paste can be applied to one side of the current collector substrate to form a conductive paste layer. In other embodiments, the conductive paste can be applied to both sides of the current collector substrate to form a conductive paste layer on each side of the current collector substrate. In some specific embodiments, a conductive paste layer can be first formed on one side of the current collector substrate and dried to form a coating layer. Subsequently, the conductive paste can be applied to the other layer of the current collector substrate and dried to form a second coating layer.

[0058] In some embodiments, the method of coating the conductive paste may include but is not limited to at least one of blade coating and roller coating. Of course, those skilled in the art may also select a specific coating method of the conductive paste according to actual conditions.

[0059] S30: performing a drying process to remove the solvent in the conductive paste layer to obtain a coating.

[0060] In some embodiments of the present application, the drying temperature may be 100° C. to 150° C., for example, 100° C., 110° C., 120° C., 130° C., 140° C., or 150° C. Drying at the above temperature can remove the solvent in the conductive paste layer to obtain a coating with a smooth surface.

[0061] In some embodiments of the present application, the drying time may be 10 to 60 minutes, for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes. When the drying time is within the above range, the solvent can be completely removed to obtain a coating.

[0062] In some embodiments, the drying process may be performed using a forced air drying oven. In other embodiments, the current collector substrate coated with the conductive paste layer may be dried using vacuum drying.

[0063] In some embodiments, the thickness of the coating formed after drying may be 0.2 μm to 1 μm.

[0064] In general, the method for preparing the composite current collector proposed in this application is simple in process, easy to implement, conducive to reducing the preparation cost, and suitable for large-scale industrial application. Using a strongly negatively charged carbon fluoride material as a coating material can effectively block the F in the electrolyte. -The erosion of the current collector can enhance the corrosion resistance and oxidation resistance of the coating. The presence of fluorine can reduce the interfacial energy of the carbon-based material, which is beneficial to the uniform dispersion of the slurry, thereby improving the uniformity and stability of the coating. The coating is prepared by the method of the present application. The fluorine content of the fluorinated carbon material is controllable and the conductivity is good. When coated on the current collector substrate, it can ensure that the conductive performance of the coating on the current collector substrate is not affected, forming a composite current collector with both conductivity and corrosion resistance.

[0065] In another aspect of the present application, a pole piece is provided. In some embodiments of the present application, the pole piece may include a composite current collector and an active material layer disposed on at least one side of the composite current collector, wherein the composite current collector is the composite current collector described above or a composite current collector prepared using the method described above. As a result, the composite current collector in the pole piece has strong corrosion resistance and good electrical conductivity, thereby improving the electrical conductivity of the pole piece as well as the stability and safety during the charge and discharge process.

[0066] In some embodiments, the active material layer may be disposed only on one surface of the composite current collector. In other embodiments, an active material layer may be disposed on each of two surfaces of the composite current collector. The thickness of the active material layer is not particularly limited in this application and can be configured and adjusted as needed by those skilled in the art.

[0067] In some embodiments of the present application, the electrode sheet may be a positive electrode sheet. In some specific embodiments, the current collector substrate of the composite current collector may be aluminum foil, and a positive electrode active material layer may be formed on at least one side of the composite current collector to obtain a positive electrode sheet. In some embodiments, the positive electrode active material layer may include a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The thickness of the positive electrode active material layer, the specific material of the positive electrode active material, the specific material of the positive electrode conductive agent, and the specific material of the positive electrode binder are not particularly limited in this application, and those skilled in the art may select and set them according to actual needs.

[0068] In other embodiments of the present application, the electrode sheet may be a negative electrode sheet. In some specific embodiments, the current collector substrate of the composite current collector may be copper foil, and a negative electrode active material layer may be formed on at least one side of the composite current collector to obtain a negative electrode sheet. In some embodiments, the negative electrode active material layer may include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. The thickness of the negative electrode active material layer, the specific material of the negative electrode active material, the specific material of the negative electrode conductive agent, and the specific material of the negative electrode binder are not particularly limited in this application, and those skilled in the art may select and configure them according to actual needs.

[0069] In another aspect of the present application, the present application provides a battery. In some embodiments of the present application, the battery may include the aforementioned pole piece.

[0070] In some embodiments, the battery may include a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The current collector in the positive electrode sheet and / or the negative electrode sheet may use the composite current collector described above.

[0071] In some specific embodiments of the present application, the battery may be a lithium-ion battery. In some embodiments, the electrolyte of the lithium-ion battery may be an electrolyte solution, and the electrolyte solution may include an electrolyte salt LiPF6.

[0072] In other specific embodiments of the present application, the battery may be a sodium ion battery.

[0073] In another aspect of the present application, an electrical device is provided. In some embodiments of the present application, the electrical device may include the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be further elaborated here.

[0074] In some embodiments of the present application, the power-consuming device may be a portable electronic device (eg, a mobile phone, a laptop computer, etc.), an electric car, an electric bicycle, a hybrid electric vehicle, etc.

[0075] The present application will be described below by specific examples, and it will be appreciated by those skilled in the art that the following specific examples are merely for illustrative purposes and are not intended to limit the scope of the present application in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment employed are all commercially available. If, in the following examples, specific processing conditions and treatment methods are not clearly described, then conditions and methods well known in the art may be used to process.

[0076] Example 1

[0077] S1: Add fluorinated carbon black with a fluorine element mass percentage of 2% and a binder slurry (the binder is sodium polyacrylate, the solvent in the binder slurry is deionized water, the solid content of the binder slurry is 20%, and the pH is 7-7.5) to the solvent (deionized water), the mass ratio of fluorinated carbon black to binder is 1:1.2, and sand grind at a speed of 400 rpm for 2 hours to form a conductive slurry with a solid content of 8%.

[0078] S2: The conductive paste prepared in S1 was evenly coated on both sides of an aluminum foil with a thickness of 13 μm, and then placed in a forced air drying oven and dried at 100° C. for 10 min to obtain a composite current collector.

[0079] Example 2

[0080] The difference between this embodiment and embodiment 1 is that in this embodiment, the mass percentage of fluorine element in the fluorinated carbon black is 5%. The remaining parameters and steps are the same as those in embodiment 1.

[0081] Example 3

[0082] The difference between this embodiment and embodiment 1 is that in this embodiment, the mass percentage of fluorine element in the fluorinated carbon black is 10%. The remaining parameters and steps are the same as those in embodiment 1.

[0083] Example 4

[0084] The difference between this embodiment and embodiment 1 is that in this embodiment, the mass percentage of fluorine element in the fluorinated carbon black is 20%. The remaining parameters and steps are the same as those in embodiment 1.

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, the mass percentage of fluorine element in the fluorinated carbon black is 30%. The remaining parameters and steps are the same as those in Example 1.

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the mass percentage of fluorine element in the fluorinated carbon black is 50%. The remaining parameters and steps are the same as those in Example 1.

[0089] Comparative Example 3

[0090] The difference between Comparative Example 3 and Example 1 is that the carbon black is not subjected to fluorination treatment, but is directly prepared into a conductive slurry and coated on the current collector aluminum foil. The rest is the same as Example 1.

[0091] Comparative Example 4

[0092] The difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, the mass percentage of fluorine element in the fluorinated carbon black is 1%. The remaining parameters and steps are the same as those in Example 1.

[0093] Performance tests were performed on the composite current collectors in various embodiments and comparative examples, including electrolyte immersion tests and resistivity tests.

[0094] Electrolyte Immersion Test: Cut the composite current collector into 5cm×8cm samples, weigh them, and completely immerse them in an electrolyte solution consisting of 1M LiPF6 / EC:DMC (the solvent is EC and DMC in a 1:1 volume ratio). The electrolyte temperature is 60°C. Immerse for 7 days. Remove the sample and quickly wipe off the electrolyte on the surface. Weigh the sample after immersion and calculate the weight change of the composite current collector after immersion. The weight of the sample before immersion is V1, and the weight of the sample after immersion is V2. Weight change = (V1-V2) / V1×100%. The test results are recorded in Table 1.

[0095] Table 1

[0096]

[0097] It should be noted that the lower the weight change rate of the sample after immersion in the electrolyte, the stronger the ability of the composite current collector sample to resist electrolyte corrosion.

[0098] Resistivity test: A multifunctional electrode resistance meter was used to test the resistivity of samples (5cm×8cm) before and after immersion in the electrolyte. The test used a continuous test method, constant pressure test (25MPa), and a pressure holding time of 30s.

[0099] Table 2

[0100]

[0101] From the data in Table 1 and Table 2, it can be seen that the composite current collectors prepared in Examples 1 to 4 of the present application have both good resistance to electrolyte corrosion and good electrical conductivity. Among them, the composite current collector prepared in Example 3 has both the best resistance to electrolyte corrosion and electrical conductivity. The overall performance of the composite current collector in Example 3 is the best. Compared with Comparative Examples 3 and 4, the composite current collector in Example 3 has significantly improved resistance to electrolyte corrosion. The fluorine content of the fluorinated carbon material has a significant effect on the resistance to electrolyte corrosion and electrical conductivity of the composite current collector. As the fluorine content in the fluorinated carbon material increases, the resistance to electrolyte corrosion of the composite current collector improves, but the electrical conductivity decreases. It can be seen that regulating the content of fluorine in the fluorinated carbon material is crucial for preparing a composite current collector with both excellent resistance to electrolyte corrosion and electrical conductivity.

[0102] In the description of this specification, the reference terms "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0103] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A composite current collector, characterized in that: The invention comprises a current collector substrate and a coating arranged on at least one side of the current collector substrate. The coating comprises a fluorinated carbon material. The mass percentage of fluorine element in the fluorinated carbon material is 2% to 20%.

2. The composite current collector according to claim 1, characterized in that The fluorinated carbon material includes one or more of fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, and fluorinated graphite.

3. The composite current collector according to claim 1 or 2, characterized in that: The thickness of the coating is 0.2 μm to 1 μm; And / or, the current collector substrate includes aluminum or copper.

4. The composite current collector according to any one of claims 1 to 3, characterized in that The coating also includes a binder.

5. The composite current collector according to claim 4, characterized in that: The binder comprises one or more of the following materials: polyvinylidene fluoride, carboxymethyl cellulose and its sodium salt, potassium salt, calcium salt, ammonium salt, polyacrylic acid and its sodium salt, potassium salt, calcium salt, ammonium salt, styrene-butadiene rubber, copolymer of acrylic acid and its sodium salt, potassium salt, calcium salt or ammonium salt and acrylonitrile; And / or, the mass ratio of the carbon fluoride material to the binder is 1:(0.8-1.8).

6. A method for preparing a composite current collector, characterized in that: include: A coating is formed on at least one side of the current collector substrate. The coating comprises a fluorinated carbon material. The mass percentage of fluorine element in the fluorinated carbon material is 2% to 20%.

7. The method according to claim 6, characterized in that Forming a coating on at least one side of the current collector substrate comprises the following steps: preparing a conductive paste comprising the carbon fluoride material and a solvent; coating the conductive paste on at least one side of the current collector substrate to form a conductive paste layer; A drying process is performed to remove the solvent in the conductive paste layer to obtain a coating.

8. The method according to claim 7, characterized in that The conductive paste further includes a binder, and the conductive paste satisfies at least one of the following conditions: The binder comprises one or more of the following materials: polyvinylidene fluoride, carboxymethyl cellulose and its sodium salt, potassium salt, calcium salt, ammonium salt, polyacrylic acid and its sodium salt, potassium salt, calcium salt, ammonium salt, styrene-butadiene rubber, copolymer of acrylic acid and its sodium salt, potassium salt, calcium salt or ammonium salt and acrylonitrile; In the conductive paste, the mass ratio of the carbon fluoride material to the binder is 1:(0.8-1.8).

9. The method according to claim 7 or 8, characterized in that At least one of the following conditions is met: The current collector substrate comprises aluminum or copper; The fluorinated carbon material includes one or more of fluorinated carbon black, fluorinated carbon nanotubes, fluorinated graphene, and fluorinated graphite; The solvent includes N-methylpyrrolidone or deionized water; The solid content of the conductive paste is 5% to 18%; The viscosity of the conductive paste is 50mPa·s to 200mPa·s; The drying temperature is 100°C to 150°C; The drying time is 10 min to 60 min.

10. The method according to claim 8, characterized in that The preparation of the conductive paste comprises the following steps: placing the carbon fluoride material, the binder and the solvent in a mixing device, and treating them at a rotation speed of 300 rpm to 1500 rpm for 0.5 h to 3 h to obtain the conductive paste; Alternatively, the preparation of the conductive paste includes the following steps: mixing the binder with a solvent to obtain a mixture with a solid content of 15% to 35% and a pH of 3 to 9, and then placing the mixture, the carbon fluoride material, and the solvent in a mixing device, and processing at a rotation speed of 300 rpm to 1500 rpm for 0.5 h to 3 h to obtain the conductive paste.

11. A pole piece, characterized in that: The invention comprises a composite current collector and an active material layer arranged on at least one side of the composite current collector, wherein the composite current collector is the composite current collector according to any one of claims 1 to 5 or a composite current collector prepared by the method according to any one of claims 6 to 10.

12. A battery, characterized in that: Including the pole piece according to claim 11.

13. An electrical device, characterized in that: Including the battery according to claim 12.

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