Negative current collector and preparation method and application thereof

Abstract

The invention provides a negative electrode current collector and a preparation method and application thereof, the negative electrode current collector comprises a metal substrate and a carbon fiber layer arranged on the surface of the metal substrate, and the carbon fiber layer comprises a plurality of metal coated carbon fibers. According to the negative current collector provided by the invention, the carbon fiber layer is compounded on the surface of the metal substrate, on one hand, carbon fibers can reduce the mass of the current collector and improve the energy density of a battery, and the carbon fibers are high in strength and corrosion-resistant, so that the service life of the negative current collector can be prolonged; on the other hand, the binding force between the carbon fiber layer and the metal substrate can be effectively improved by performing metal coating on the carbon fibers, and the conductivity of the negative electrode current collector is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a negative current collector and a preparation method and application thereof. BACKGROUND

[0002] The electrode pole piece generally includes a current collector and an active material layer arranged on the surface of the current collector. Copper foil is selected as a commonly used negative current collector due to its good electrical conductivity and low cost. Some technologies adopt a copper plating layer on the surface of carbon fiber cloth to reduce the mass of the negative current collector. However, the interface bonding force between the carbon fiber cloth and the copper plating layer is weak, and the carbon fiber cloth is easy to fall off and separate. Therefore, it is necessary to provide a negative current collector which has relatively small mass and high structural stability. SUMMARY

[0003] In view of this, the present application provides a negative current collector and a preparation method and application thereof. The negative current collector is prepared by compounding a carbon fiber layer on the surface of a metal substrate. On the one hand, the carbon fiber can reduce the mass of the current collector and improve the energy density of the battery. The carbon fiber has high strength and corrosion resistance, which can prolong the service life of the negative current collector. On the other hand, metal coating on the carbon fiber can effectively improve the bonding force between the carbon fiber layer and the metal substrate, and improve the electrical conductivity of the negative current collector.

[0004] In a first aspect, the present application provides a negative current collector, which includes a metal substrate and a carbon fiber layer arranged on the surface of the metal substrate, and the carbon fiber layer includes a plurality of metal-coated carbon fibers.

[0005] Optionally, the metal substrate is selected from any one of a copper substrate, a nickel substrate, a titanium substrate, and a stainless steel substrate.

[0006] Optionally, the metal-coated carbon fiber includes a carbon fiber body and a metal coating layer arranged on the surface of the carbon fiber body, and the metal coating layer includes one or more of copper, nickel, titanium, and stainless steel.

[0007] Optionally, the metal-coated carbon fibers in the carbon fiber layer are randomly oriented.

[0008] Optionally, the length of the carbon fiber body is 0.1 mm-1 mm, and the diameter of the carbon fiber body is 5 μm-10 μm.

[0009] Optionally, the thickness of the metal coating layer is 0.5 μm-2 μm.

[0010] Optionally, the carbon fiber layer includes a pore structure, and the porosity of the carbon fiber layer is 20%-60%; the pore diameter of the pore structure is 10 μm-100 μm.

[0011] Optionally, the thickness of the metal substrate is 3-10 μm, and the thickness of the carbon fiber layer is 10-1000 μm.

[0012] Optionally, the density of the negative current collector is 1.4-2.5 g / cm 3 -5.7 g / cm 3 .

[0013] Optionally, the negative current collector further comprises a conductive layer disposed on the carbon fiber layer, and the thickness of the conductive layer is 0.5-2 μm.

[0014] Optionally, the conductive layer comprises a conductive agent, and the conductive agent comprises one or more of graphene, graphite, carbon black, acetylene black, and carbon nanotube.

[0015] In a second aspect, the application provides a preparation method of the negative current collector provided in the first aspect, comprising:

[0016] coating the carbon fiber with metal to obtain metal-coated carbon fiber;

[0017] pressing the metal-coated carbon fiber on a metal substrate and then performing sintering treatment to obtain a carbon fiber layer, thereby preparing the negative current collector.

[0018] Optionally, the method further comprises coating a conductive slurry on the carbon fiber layer and obtaining a conductive layer after drying treatment.

[0019] Optionally, the solid content of the conductive slurry is 10-20 wt%, and the viscosity of the conductive slurry is 100-500 mPa·s.

[0020] Optionally, the metal coating method comprises one or more of electroplating, electroless plating, thermal reduction plating, magnetron sputtering, and vacuum evaporation.

[0021] Optionally, the metal coating method is electroplating, and the current density of the electroplating is 2-3.5 A / dm 2 -3.5 A / dm 2 , and the electroplating time is 10-30 min.

[0022] In a third aspect, the application provides a negative electrode tab, comprising a negative current collector and a negative active material layer disposed on the surface of the negative current collector, and the negative current collector comprises the negative current collector provided in the first aspect or prepared by the preparation method provided in the second aspect.

[0023] In a fourth aspect, the application provides a battery, comprising a positive electrode tab and a negative electrode tab, and a separator disposed between the positive electrode tab and the negative electrode tab, and the negative electrode tab comprises the negative electrode tab provided in the third aspect.

[0024] In a fifth aspect, the present application provides a power consumption device comprising the battery of the fourth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. The specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0026] Figure 1 A cross-sectional structure schematic diagram of a negative electrode current collector according to an embodiment of the present application is provided.

[0027] Figure 2 A structure schematic diagram of a metal-coated carbon fiber in a negative electrode current collector according to an embodiment of the present application is provided.

[0028] Figure 3 A cross-sectional structure schematic diagram of a negative electrode current collector according to another embodiment of the present application is provided.

[0029] Figure 4 A flow chart of a preparation method of a negative electrode current collector according to an embodiment of the present application is provided.

[0030] BRIEF DESCRIPTION OF DRAWINGS

[0031] 100-negative electrode current collector; 10-metal substrate; 11-carbon fiber layer; 110-metal-coated carbon fiber; 1101-carbon fiber body; 1102-metal coating layer; 12-conductive layer. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0033] Currently, some technologies adopt a copper plating layer arranged on the surface of the carbon fiber cloth to achieve the purpose of reducing the mass of the negative electrode current collector. However, the carbon fiber surface has few polar groups, is chemically inert, has small surface energy and specific surface area, and has weak interfacial bonding force with the copper plating layer, which is easy to fall off and separate. In addition, the elastic modulus of the carbon fiber cloth and the copper plating layer is quite different, and in the process of battery charging and discharging, the negative electrode active material will expand and shrink in volume, which will cause the carbon fiber cloth and the copper plating layer to peel off. Therefore, it is necessary to provide a negative electrode current collector which has relatively small mass and high structural stability at the same time.

[0034] To solve the above problems, the negative electrode current collector provided in the application is prepared by compounding a carbon fiber layer on the surface of a metal substrate. On the one hand, the carbon fiber can reduce the mass of the current collector, improve the energy density of the battery, and has high strength and corrosion resistance, thereby prolonging the service life of the negative electrode current collector. On the other hand, the metal coating on the carbon fiber can effectively improve the bonding force between the carbon fiber layer and the metal substrate, thereby improving the structural stability and conductivity of the negative electrode current collector.

[0035] Figure 1 A cross-sectional structure schematic diagram of the negative electrode current collector 100 provided in an embodiment of the application is shown in FIG. 1. The negative electrode current collector 100 includes a metal substrate 10 and a carbon fiber layer 11 arranged on the surface of the metal substrate 10. The carbon fiber layer 11 includes a plurality of metal-coated carbon fibers 110. Figure 2 As shown in the figure, in the application, the metal-coated carbon fiber 110 includes a carbon fiber body 1101 and a metal coating layer 1102 coated on the surface of the carbon fiber. The negative electrode current collector is used to collect and output the current generated by the negative electrode active material and input the negative electrode current to the negative electrode active material. The negative electrode current collector 100 provided in the application is prepared by compounding the carbon fiber layer 11 on the surface of the metal substrate 10. The carbon fiber body 1101 in the carbon fiber layer 11 can reduce the mass of the current collector, improve the proportion of the active material layer in the negative electrode sheet, and thus improve the energy density of the battery. In addition, the carbon fiber body 1101 has good mechanical properties, high strength, and resistance to electrolyte corrosion, thereby prolonging the service life of the negative electrode current collector and improving the cycle service life of the electrode sheet. In addition, the carbon fiber body 1101 also has a high elastic modulus and a low expansion coefficient. The metal coating layer 1102 on the surface of the carbon fiber body 1101 is made of metal, which effectively improves the bonding force between the carbon fiber layer 11 and the metal substrate 10, prevents the peeling of the carbon fiber layer 11 and the metal substrate 10 caused by the volume expansion and contraction of the negative electrode active material layer during the charging and discharging process of the battery. The metal coating layer 1102 can also effectively improve the surface properties of the carbon fiber body 1101, improve the chemical inertness of the carbon fiber, and thus improve the interfacial bonding force between the carbon fiber layer and the metal substrate.

[0036] In an embodiment of the application, the metal substrate 10 is selected from any one of a copper substrate, a nickel substrate, a titanium substrate, and a stainless steel substrate. In an embodiment of the application, the shape of the metal substrate 10 is not limited, including but not limited to a foil, a mesh, a foamed metal, and the like.

[0037] In some embodiments of the present application, the metal substrate 10 is a copper substrate, and the metal cladding layer 1102 comprises copper. By selecting copper as the metal substrate and the metal cladding layer, the conductivity of the negative current collector can be further improved while further improving the bonding force between the metal substrate and the metal cladding layer.

[0038] In some embodiments of the present application, the metal substrate 10 is a copper substrate, and the metal cladding layer 1102 comprises copper. By selecting copper as the metal substrate and the metal cladding layer, the conductivity of the negative current collector can be further improved while further improving the bonding force between the metal substrate and the metal cladding layer.

[0039] In some embodiments of the present application, the metal-coated carbon fibers 110 in the carbon fiber layer 11 are randomly oriented, i.e., the metal-coated carbon fibers 110 are randomly arranged in the carbon fiber layer 11, which is a non-oriented distribution. Random arrangement of metal-coated carbon fibers in the carbon fiber layer can make the carbon fiber layer have good mechanical properties, and compared with carbon fiber cloth with anisotropy, it can effectively improve the isotropy of the carbon fiber layer, thereby effectively preventing the negative current collector from being broken or peeled off due to uneven stress when coating the negative active material layer or rolling.

[0040] In some embodiments of the present application, the carbon fiber layer 11 is a three-dimensional porous structure constructed by interlaced stacking of a plurality of metal-coated carbon fibers 110, the plurality of metal-coated carbon fibers 110 are randomly oriented in the carbon fiber layer 11, and the carbon fiber layer 11 comprises a pore structure. The three-dimensional network structure can effectively improve the specific surface area and surface energy of the carbon fiber layer, further improve the bonding force between the carbon fiber layer and the metal substrate and the negative active material layer, also can relieve the stress and strain generated during the charging and discharging process of the battery, improve the service life of the negative electrode sheet, also can accelerate the electron transmission rate, further improve the electrical conductivity of the negative current collector. Generally speaking, the shorter the length of the carbon fibers, the more carbon fibers per unit area in the carbon fiber layer, and the smaller the pores in the obtained carbon fiber layer.

[0041] In some embodiments of the present application, the porosity of the carbon fiber layer 11 is 20%-60%, and the pore size of the pore structure in the carbon fiber layer 11 is 10-100 μm. By adding carbon fibers of a suitable length and content to the carbon fiber layer, the present application can further improve the pore structure of the carbon fiber layer, and controlling the porosity of the carbon fiber layer and the pore size of the pore structure in the above suitable range can further inhibit the volume expansion of the negative electrode sheet during the charging and discharging process, and further improve the electrical conductivity of the negative electrode current collector, effectively avoiding the decrease of the current collector density caused by too large pore structure, the penetration of the negative electrode active material into the current collector, and avoiding too small pore structure causing too large density of the carbon fiber layer. Specifically, the porosity of the carbon fiber layer 11 can be but is not limited to 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, and the pore size of the pore structure in the carbon fiber layer 11 can be but is not limited to 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm.

[0042] In some embodiments of the present application, the length of the carbon fiber body 1101 is 0.1-1 mm, and the diameter of the carbon fiber body 1101 is 5-10 μm. By selecting chopped carbon fibers with a length less than or equal to 1 mm to prepare the carbon fiber layer, compared with carbon fiber cloth with anisotropy, the isotropy of the carbon fiber layer can be further improved, thereby effectively preventing the fracture or peeling of the negative electrode current collector caused by uneven stress during coating of the negative electrode active material layer or rolling, and further controlling the porosity of the carbon fiber layer 11 within a suitable range. Specifically, the length of the carbon fiber body 1101 can be but is not limited to 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, and the diameter of the carbon fiber body 1101 can be but is not limited to 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm.

[0043] In some embodiments of the present application, the thickness of the metal coating layer 1102 is 0.5-2 μm, and controlling the thickness of the metal coating layer within a suitable range can further improve the electrical conductivity with as small mass as possible. Specifically, the thickness of the metal coating layer 1102 can be but is not limited to 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm.

[0044] In some embodiments of the present application, the density of the negative electrode current collector is 1.4-5.7 g / cm 3 3 . Specifically, the density of the negative electrode current collector can be but is not limited to 1.4 g / cm 3 ​1.5g / cm 3 2g / cm 3 2.5g / cm 3 3g / cm 3 3.5g / cm 3 4g / cm 3 4.5g / cm 3 5g / cm 3 5.5g / cm 3 5.7g / cm 3 This application achieves a negative electrode current collector with a density much lower than that of a pure metal current collector through a special design.

[0045] In one embodiment of this application, the thickness of the metal substrate 10 is 3μm-10μm. Controlling the metal substrate 10 to an appropriate thickness can ensure excellent conductivity of the negative electrode current collector while minimizing its mass. The specific thickness of the metal substrate can be adjusted according to the actual battery's requirements for conductivity and energy density. Specifically, the thickness of the metal substrate can be, but is not limited to, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, or 10μm.

[0046] In one embodiment of this application, the thickness of the carbon fiber layer 11 is 10μm-1000μm. Controlling the thickness of the carbon fiber layer within an appropriate range can effectively reduce the mass of the negative electrode current collector, thereby improving the energy density of the battery, while ensuring a strong bond between the carbon fiber layer and the metal substrate, preventing them from detaching during current collector fabrication or battery use. Specifically, the thickness of the carbon fiber layer can be, but is not limited to, 10μm, 20μm, 50μm, 80μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, or 1000μm.

[0047] In one embodiment of this application, as Figure 3 As shown, the negative electrode current collector 100 further includes a conductive layer 12 disposed on the carbon fiber layer 11, the conductive layer 12 comprising a conductive agent. Disposing of the conductive layer on the carbon fiber layer can further improve the conductivity of the negative electrode current collector, and the three-dimensional porous network structure of the carbon fiber layer helps to increase the bonding force between the conductive layer 12 and the carbon fiber layer 11, resulting in a tightly bonded layered negative electrode current collector. The conductive layer can also improve the peel strength between the negative electrode current collector and the negative electrode active material layer and reduce the interfacial impedance, thereby improving the cycle life and electrochemical performance of the battery. In one embodiment of this application, the conductive agent includes one or more of graphene, graphite, carbon black, acetylene black, and carbon nanotubes.

[0048] In one embodiment of this application, the thickness of the conductive layer 12 is 0.5 μm-2 μm. A conductive layer of suitable thickness can further improve the conductivity of the negative electrode current collector while ensuring the bonding force between the layers. Specifically, the thickness of the conductive layer 12 can be, but is not limited to, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, or 2 μm.

[0049] In one embodiment of this application, the conductive layer 12 further includes a binder and a dispersant. The binder can improve the bonding ability between the components in the conductive layer, and the dispersant can make the conductive agent uniformly dispersed in the conductive layer, thereby improving the conductivity uniformity of the negative electrode current collector. In one embodiment of this application, the binder may include, but is not limited to, one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyamide, and polyvinylidene fluoride; the dispersant may include, but is not limited to, one or more of fatty alcohol polyoxyethylene ether, polyacrylic acid, polyethylene glycol monomethyl ether ester, polyvinylpyrrolidone (PVP), sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate.

[0050] The negative electrode current collector provided in this application is lightweight, which can effectively improve the energy density of the battery. In addition, the negative electrode current collector has good corrosion resistance and no obvious anisotropy. During the battery preparation or use, the negative electrode current collector has good bonding performance with the negative electrode active material layer and has a long cycle life.

[0051] Please see Figure 4 The flowchart below shows a method for preparing a negative electrode current collector according to an embodiment of this application, including:

[0052] S101: Metal coating is applied to carbon fibers to obtain metal-coated carbon fibers;

[0053] S102: The metal-coated carbon fiber is placed on a metal substrate, pressed, and then sintered to obtain a carbon fiber layer, thereby preparing a negative electrode current collector.

[0054] In step S101, the metal coating method includes one or more of electroplating, electroless plating, thermal reduction plating, magnetron sputtering, and vacuum evaporation. In some embodiments of this application, the metal coating method is electroplating. In one embodiment of this application, the electroplating current density is 2 A / dm³. 2 -3.5A / dm 2 The electroplating time is 10-30 minutes. Controlling the electroplating parameters within a suitable range allows for control over the thickness of the metallic coating on the carbon fiber surface. Specifically, the electroplating current density can be, but is not limited to, 2 A / dm³. 2 2.2A / dm 2 2.4A / dm2 2.5 A / dm 2 2.6 A / dm 2 2.8 A / dm 2 3 A / dm 2 3.2 A / dm 2 3.4 A / dm 2 3.5 A / dm 2 The plating time can include, but is not limited to, 10 min, 15 min, 20 min, 25 min, 30 min.

[0055] In some embodiments of the present application, the plating can be, for example, electroless plating. In some embodiments of the present application, the components of the plating solution for electroless plating can be, for example, CuSO4 and H2SO4, or CuSO4, HCHO and NaKC4H4O6, or Cu2P2O7 and K4P2O7. In an embodiment of the present application, a dispersing agent can be added during the electroless plating process. The dispersing agent can include, but is not limited to, one or more of sodium pyrophosphate, alkyl aryl phosphate, trimethyl stearamide chloride, polyoxyethylene alkyl phenol ether, and polycarboxylate. In an embodiment of the present application, stirring can be performed during the electroless plating process. The carbon fibers can be dispersed by adding the dispersing agent and performing the stirring, and the uniformity of the metal coating layer can be further improved.

[0056] In an embodiment of the present application, the length of the carbon fiber is 0.1 mm-1 mm. Specifically, the length of the carbon fiber can be, but is not limited to, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm. In an embodiment of the present application, the carbon fiber is further subjected to surface pretreatment before being subjected to the metal coating treatment, including: removing glue, surface roughening, sensitization and activation of the surface of the carbon fiber. The surface of the untreated carbon fiber is attached with a thin organic glue protective film, which makes it difficult to disperse in water due to poor wettability in aqueous solution. Therefore, the surface of the carbon fiber needs to be subjected to glue removal treatment. The specific operation of glue removal can be: the carbon fiber is immersed in isopropyl alcohol solution for 24 h, then high-speed stirring is performed using a magnetic stirrer for 2 h, the stirring speed is 1000 rpm, then the surface protective film is removed, then deionized water is used for cleaning, and then the carbon fiber is placed in a drying oven at 100°C for drying for 3 h. The surface roughening treatment can increase the roughness of the surface of the carbon fiber, thereby enhancing the bonding force between the metal coating layer and the carbon fiber. The specific operation of surface roughening can be: the carbon fiber after glue removal is immersed in a mixed solution of sulfuric acid and ammonium persulfate and is subjected to surface roughening by ultrasonic for 20 min-60 min, then deionized water is used for cleaning, and then the carbon fiber is placed in a drying oven at 100°C for drying for 3 h. The sensitization treatment and the activation treatment can make the carbon fiber surface adsorb noble metals with catalytic ability, which can act as a catalytic center for inducing reducing agents in chemical electroplating, so that the chemical electroplating can be spontaneously carried out. The specific operation of sensitization and activation can be: the carbon fiber after surface roughening is immersed in a sensitization solution for 5 min for sensitization treatment, the sensitization solution is a mixed solution of stannous chloride and dilute hydrochloric acid, the content of stannous chloride in the sensitization solution is 4 g / L-6 g / L, then deionized water is used for cleaning, and then the carbon fiber is placed in a drying oven at 100°C for drying for 3 h; after the sensitization treatment, the carbon fiber is immersed in an activation solution for 5 min for activation treatment, the activation solution is a silver ammonia solution prepared from silver nitrate and ammonia water, the content of silver nitrate in the activation solution is 150 g / L-250 g / L, then deionized water is used for cleaning, and then the carbon fiber is placed in a drying oven at 100°C for drying for 3 h. The carbon fiber after surface pretreatment has better bonding force with the metal coating layer, and the metal coating layer is more uniform and dense.

[0057] In step S102, the metal-coated carbon fibers can be pressed on the metal substrate in the following manner: the metal substrate is placed on the bottom of a mold, an appropriate amount of metal-coated carbon fibers is weighed and filled into the mold to cover the surface of the metal substrate, a punch is then placed on the metal-coated carbon fibers, and the punch is tightened with a bolt. In an embodiment of the present application, the mass of the metal-coated carbon fibers per square centimeter of the metal substrate is 1 mg-130 mg. In some specific embodiments, the mass of the metal-coated carbon fibers per square centimeter of the metal substrate can be, for example, 1 mg, 5 mg, 10 mg, 20 mg, 30 mg, 40 mg, 50 mg, 60 mg, 70 mg, 80 mg, 90 mg, 100 mg, 110 mg, 120 mg, or 130 mg. By adjusting the amount of the metal-coated carbon fibers according to the area of the metal substrate to control the content of the metal-coated carbon fibers per unit area of the metal substrate, the pore structure of the carbon fiber layer can be improved. The more the number of the metal-coated carbon fibers per unit area, the denser the three-dimensional network structure formed by the metal-coated carbon fibers, and the smaller the pore structure.

[0058] In an embodiment of the present application, the heating rate of the sintering process is 5 ℃ / min-30 ℃ / min, the temperature of the sintering process is 700 ℃-900 ℃, and the time of the sintering process is 1 h-2 h. Specifically, the heating rate of the sintering process can be, but is not limited to, 5 ℃ / min, 10 ℃ / min, 15 ℃ / min, 20 ℃ / min, 25 ℃ / min, or 30 ℃ / min, the temperature of the sintering process can be, but is not limited to, 700 ℃, 750 ℃, 800 ℃, 850 ℃, or 900 ℃, and the time of the sintering process can be, but is not limited to, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min.

[0059] In an embodiment of the present application, step S102 further comprises: coating a conductive paste on the carbon fiber layer to obtain a conductive layer after drying treatment. In an embodiment of the present application, the conductive paste comprises a conductive agent, a binder, a dispersing agent, and a solvent, and the mass ratio of the conductive agent, the binder, the dispersing agent, and the solvent can be, for example, 7:51:1:61. In an embodiment of the present application, the conductive agent can comprise, but is not limited to, one or more of graphene, graphite, carbon black, acetylene black, and carbon nanotubes; the binder can comprise, but is not limited to, one or more of carboxymethyl cellulose, butadiene-styrene rubber, polyamide, and polyvinylidene fluoride; the dispersing agent can comprise, but is not limited to, one or more of fatty alcohol polyoxyethylene ether, polyacrylic acid, maleic acid monopropylene glycol monomethyl ether ester, polyvinylpyrrolidone (PVP), sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate; and the solvent can comprise, but is not limited to, one or more of deionized water, ethanol, isopropyl ketone, N-methyl pyrrolidone, and N-dimethylformamide.

[0060] In an embodiment of the present application, the conductive slurry can be obtained by sanding treatment, but is not limited thereto. A certain proportion of the conductive agent, the binder, the dispersing agent and the solvent are mixed and then added to a sanding machine for sanding treatment. The rotation speed of the sanding treatment is 1000 rpm-1500 rpm, and the sanding treatment time is 2 h-5 h. Specifically, the rotation speed of the sanding treatment can be, but is not limited to, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm or 1500 rpm, and the sanding treatment time can be, but is not limited to, 2 h, 3 h, 4 h or 5 h.

[0061] In an embodiment of the present application, the solid content of the conductive slurry is 10wt%-20wt%, and the viscosity of the conductive slurry is 100 mPa·s-500 mPa·s. Controlling the solid content and the viscosity of the conductive slurry within a suitable range can be more conducive to the coating of the conductive slurry on the surface of the carbon fiber layer, further improve the bonding force between the conductive layer and the carbon fiber layer, and also facilitate the subsequent coating of the negative active slurry on the conductive layer. Specifically, the solid content of the conductive slurry can be, but is not limited to, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%, etc.; and the viscosity of the conductive slurry can be, but is not limited to, 100 mPa·s, 150 mPa·s, 200 mPa·s, 250 mPa·s, 300 mPa·s, 350 mPa·s, 400 mPa·s, 450 mPa·s or 500 mPa·s, etc.

[0062] In an embodiment of the present application, after the conductive slurry is coated on the surface of the carbon fiber layer, drying treatment is further required. The drying treatment time is 30 s-60 s, and the drying treatment temperature is 80℃-120℃. Specifically, the drying treatment time can be, but is not limited to, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s or 60 s, and the drying treatment temperature can be, but is not limited to, 80℃, 90℃, 100℃, 110℃ or 120℃.

[0063] The preparation method provided by the present application is novel, the preparation process is simple, and the negative electrode current collector with high electrical conductivity, strong bonding capacity and good cycle stability can be prepared.

[0064] The application also provides a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, wherein the negative electrode current collector comprises the negative electrode current collector of any one of the above embodiments or the negative electrode current collector prepared by the preparation method of any one of the above embodiments. In the application, the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material is a commonly used negative electrode active material in the field, which can include, but is not limited to, at least one of modified or unmodified artificial graphite, natural graphite, hard carbon, soft carbon and graphene. In an embodiment of the application, the negative electrode active material layer further comprises a conductive agent and a binder, the conductive agent is a commonly used conductive agent in the field, which can include, but is not limited to, one or more of graphene, graphite, carbon black, acetylene black and carbon nanotubes; and the binder is a commonly used binder in the field, which can include, but is not limited to, one or more of carboxymethyl cellulose, butadiene rubber, polyamide and polyvinylidene fluoride. In an embodiment of the application, the negative electrode active material layer is formed by coating the negative electrode active material paste on the negative electrode current collector described above, and the negative electrode active material sheet is obtained after rolling. The negative electrode active material layer is tightly combined with the conductive layer or the carbon fiber layer in the negative electrode current collector, and is not easy to fall off, which is conducive to improving the structural stability and service life of the negative electrode sheet.

[0065] The application also provides a battery, which comprises a positive electrode sheet and a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet is prepared by the negative electrode sheet of any one of the above embodiments or the preparation method of any one of the above embodiments. The negative electrode sheet provided by the application has strong bonding force, high electrical conductivity and good cycle stability, which is conducive to improving the service life and electrochemical performance of the battery.

[0066] In an embodiment of the application, the separator can be ion-exchanged to form a complete ion conduction path. Specifically, the separator can include, but is not limited to, a woven film, a non-woven fabric, a microporous film, a composite film, a calendered film or a separator paper. In an embodiment of the application, the battery further comprises an electrolyte. At least part of the positive electrode sheet and at least part of the negative electrode sheet are soaked in the electrolyte. The electrolyte of the application is not particularly limited, and various substances capable of being used as a battery electrolyte in the art can be used.

[0067] The application also provides a power-using device, which comprises the battery described in any one of the above embodiments. The power-using device provided by the application has good cycle performance, high safety performance, and strong market competitiveness. The power-using device includes a vehicle, an electronic device, an energy storage system, and the like. The electronic device may, for example, include a mobile phone, a tablet, a watch, a VR glasses, and the like. In an embodiment of the application, the battery can be used in a vehicle, which can improve the service life and charging rate of the vehicle, improve the wide application of new energy vehicles, and be conducive to the construction of a green and environmentally friendly environment. In another embodiment of the application, the battery can also be applied to a mobile phone, which can reduce the preparation cost of the battery and improve the safety of the battery. The above battery of the application can be arranged in a power-using device in the form of a single battery, a battery module, a battery pack, or the like.

[0068] The effects of the technical solutions of the application are further described below through specific examples.

[0069] Embodiment 1

[0070] First, the carbon fibers with a length of 0.6 mm and a diameter of 7 μm are pretreated, including carbon fiber surface degumming, surface roughening, sensitization and activation. The specific operation is as follows: the carbon fibers are placed in an isopropyl alcohol solution and soaked for 24 h, and then a magnetic stirrer is used for high-speed stirring for 2 h, the stirring speed is 1000 rpm, the surface protective film is removed, then deionized water is used for cleaning, and the carbon fibers are placed in a drying oven and dried at 100 ℃ for 3 h; the carbon fibers after degumming are soaked in a mixed solution of sulfuric acid and ammonium persulfate and ultrasonically roughened for 20 min-60 min, then deionized water is used for cleaning, and the carbon fibers are placed in a drying oven and dried at 100 ℃ for 3 h; the carbon fibers after surface roughening are placed in a sensitization solution for sensitization treatment for 5 min, the sensitization solution is a mixed solution of stannous chloride and dilute hydrochloric acid, the content of stannous chloride in the sensitization solution is 4 g / L-6 g / L, then deionized water is used for cleaning, and the carbon fibers are placed in a drying oven and dried at 100 ℃ for 3 h; after the sensitization treatment, the carbon fibers are placed in an activation solution for activation treatment for 5 min, the activation solution is a silver ammine solution prepared from silver nitrate and ammonia water, the content of silver nitrate in the activation solution is 150 g / L-250 g / L, then deionized water is used for cleaning, and the carbon fibers are placed in a drying oven and dried at 100 ℃ for 3 h. Then the carbon fibers are subjected to chemical copper plating, the plating solution is CuSO4 and H2SO4, 50 mg of carbon fibers and 1 mg of dispersant sodium pyrophosphate are added to 100 ml of the plating solution, the carbon fibers and the dispersant are uniformly dispersed by using a magnetic stirrer, then a copper foil substrate and a copper-plated copper sheet are placed in the plating solution, the copper foil is connected to the negative electrode, the copper-plated copper sheet is connected to the positive electrode, the plating current density is adjusted to 3 A / dm 2Electroplating time was 20 min, resulting in a 1 μm thick metal coating layer on the carbon fiber surface. A 4 μm thick copper foil substrate with an area of ​​3 cm * 3 cm was placed at the bottom of the mold. 40 mg of metal-coated carbon fiber was weighed and filled into the mold cavity. A punch was installed and tightened with bolts. Then, sintering was performed at a temperature of 800℃, a heating rate of 5℃ / min, and a holding time of 1 h, resulting in a 30 μm thick carbon fiber layer on the copper foil substrate surface. The pore size of the carbon fiber layer was 40 μm, and the porosity was 40%, thus obtaining the negative electrode current collector.

[0071] Example 2

[0072] The difference from Example 1 is that after obtaining the carbon fiber layer on the copper foil substrate, a conductive layer is also coated on the metal-coated carbon fiber current collector. This includes: adding deionized water, polyacrylic acid, sodium carboxymethyl cellulose, and carbon black in a mass ratio of 61:51:1:7 to a sand mill, and sanding for 3 hours to obtain a conductive slurry with a solid content of 15 wt% and a viscosity of 300 mPa·s; coating the obtained conductive slurry onto the carbon fiber layer to obtain a conductive layer with a thickness of 1 μm, and drying at 100°C for 30 seconds to obtain a negative electrode current collector.

[0073] Example 3

[0074] The difference from Example 2 is that the length of the carbon fiber is 0.05 mm, the pore size of the carbon fiber layer is 5 μm, and the porosity is 10%.

[0075] Example 4

[0076] The difference from Example 2 is that the length of the carbon fiber is 0.1 mm, the pore size of the carbon fiber layer is 10 μm, and the porosity is 40%.

[0077] Example 5

[0078] The difference from Example 2 is that the length of the carbon fiber is 1 mm, the pore size of the carbon fiber layer is 100 μm, and the porosity is 40%.

[0079] Example 6

[0080] The difference from Example 2 is that the length of the carbon fiber is 5 mm, the pore size of the carbon fiber layer is 300 μm, and the porosity is 70%.

[0081] Example 7

[0082] The difference from Example 2 is that the thickness of the carbon fiber layer is 10 μm, the pore size of the carbon fiber layer is 40 μm, and the porosity is 20%.

[0083] Example 8

[0084] The difference from Example 2 is that the thickness of the carbon fiber layer is 1 mm, the pore size of the carbon fiber layer is 40 μm, and the porosity is 60%.

[0085] Example 9

[0086] The difference from Example 2 is that the thickness of the copper foil substrate is 3 μm.

[0087] Example 10

[0088] The difference from Example 2 is that the thickness of the copper foil substrate is 10 μm.

[0089] Example 11

[0090] The difference from Example 2 is that the amount of metal-coated carbon fiber added is 9 mg; the thickness of the carbon fiber layer is 10 μm; the pore size of the carbon fiber layer is 80 μm; and the porosity is 50%.

[0091] Example 12

[0092] The difference from Example 2 is that the amount of metal-coated carbon fiber added is 90 mg; the thickness of the carbon fiber layer is 100 μm; the pore size of the carbon fiber layer is 15 μm; and the porosity is 30%.

[0093] Example 13

[0094] The difference from Example 2 is that the thickness of the metal cladding layer on the carbon fiber surface is 0.1 μm.

[0095] Example 14

[0096] The difference from Example 2 is that the thickness of the metal cladding layer on the carbon fiber surface is 4 μm.

[0097] Comparative Example 1

[0098] The difference from Example 2 is that the carbon fiber is not subjected to electrochemical copper plating.

[0099] Comparative Example 2

[0100] The same copper foil as in Example 1 was used as the negative electrode current collector.

[0101] Performance testing

[0102] Density test

[0103] The negative electrode current collectors prepared in Examples 1-14 and Comparative Examples 1-2 were subjected to density testing. The testing process involved using a 10000mm² water tank. 2Using a sampler (accuracy ±0.1mm), take two samples 20mm from each side of the negative electrode current collector sample along the same straight line in the width direction. Take one sample from the center, and two more samples 200mm to the left and right of the center point. Take five samples in total. Weigh each sample sequentially using a balance (accuracy 0.1mg) to measure its 10000mm diameter. 2 The mass m of the negative electrode current collector is calculated as follows: Mass per unit area of ​​each negative electrode current collector = m × 100 (g / m²) 2 Then, use a micrometer screw gauge to measure the thickness h of each negative electrode current collector, and calculate: the density of the negative electrode current collector = m × 100 / h (g / cm³) 3 Five sets of test results were recorded and the average value was taken. The results are shown in Table 1.

[0104] Mechanical property testing

[0105] The negative electrode current collectors prepared in Examples 1-14 and Comparative Examples 1-2 were subjected to mechanical testing. The testing process was as follows: five longitudinal specimens with a width of 15 mm were cut from each of the negative electrode current collectors prepared in Examples 1-14 and Comparative Example 1. The specimens were ensured to be smooth, burr-free, and free from obvious mechanical damage. The universal testing machine was calibrated and zeroed. The tensile speed was set to 50 mm / min and the gauge length was set to 50 mm. After clamping the specimens, the displacement was zeroed and the test was started. Five sets of tensile strength and elongation data were recorded, and the average value of the five sets of data was taken. The results are shown in Table 1.

[0106] resistivity test

[0107] The negative electrode current collectors prepared in Examples 1-14 and Comparative Examples 1-2 were cut into 30mm diameter discs using a sampler and placed on a surface resistivity tester. The test pressure was 25MPa. After the probe descended to make good contact with the flexible negative electrode current collector, the "Start Test" button was pressed. Three sets of test results were recorded and the average value was taken. The results are shown in Table 1.

[0108] Peel force test

[0109] The negative electrode current collectors prepared in Examples 1-14 and Comparative Examples 1-2 were subjected to electrode peel force tests. An active material was coated on the surface of the negative electrode current collector, and adhesive tape was attached to the surface of the active material of the electrode, which enabled the active material to be peeled off from the current collector. Then, the electrode was cut into samples with a length of 100 mm and a width of 40 mm, and fixed to a flat thin steel plate with double-sided tape. The free end of the electrode and the steel plate were clamped in the upper and lower clamps of the peel force tester, and 180° peeling was performed at a peeling speed of 50 mm / min. Three sets of test results were recorded and the average value was taken. The results are shown in Table 1.

[0110] Table 1 Test Results of Negative Electrode Current Collector Performance

[0111]

[0112] As shown in Table 1, the embodiments of this application, through a special design of the negative electrode current collector, compared with the pure copper foil current collector of Comparative Example 2 and the composite carbon fiber current collector of Comparative Example 1, have a lower density while significantly improving its compressive strength and elongation, resulting in better mechanical properties. Furthermore, the resistivity is also significantly reduced, leading to better conductivity. Moreover, compared with Comparative Example 1, which did not undergo electrochemical copper plating treatment on the carbon fiber, the embodiments of this application, by plating copper on the carbon fiber, significantly improve its conductivity and also enhance the bonding force between the carbon fiber and the metal substrate.

[0113] The above description represents the preferred embodiments of this application, but should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A negative electrode current collector, characterized by, The negative current collector comprises a metal substrate and a carbon fiber layer arranged on the surface of the metal substrate, and the carbon fiber layer comprises a plurality of metal-coated carbon fibers.

2. The negative current collector according to claim 1, wherein The metal substrate is selected from any one of a copper substrate, a nickel substrate, a titanium substrate, and a stainless steel substrate.

3. The negative current collector according to claim 1, wherein The metal-coated carbon fiber comprises a carbon fiber body and a metal coating layer arranged on the surface of the carbon fiber body, and the metal coating layer comprises one or more of copper, nickel, titanium, and stainless steel.

4. The negative current collector according to any one of claims 1 to 3, wherein The metal-coated carbon fibers in the carbon fiber layer are randomly oriented.

5. The negative current collector according to any one of claims 3 or 4, wherein The length of the carbon fiber body is 0.1 mm-1 mm, and the diameter of the carbon fiber body is 5 μm-10 μm; the thickness of the metal coating layer is 0.5 μm-2 μm.

6. The negative current collector according to any one of claims 1 to 5, wherein The carbon fiber layer comprises a pore structure, and the porosity of the carbon fiber layer is 20%-60%; the pore diameter of the pore structure is 10 μm-100 μm.

7. The negative current collector according to any one of claims 1 to 6, wherein The thickness of the metal substrate is 3 μm-10 μm, and the thickness of the carbon fiber layer is 10 μm-1000 μm.

8. The negative current collector according to any one of claims 1 to 7, wherein The density of the negative current collector is 1.4 g / cm 3 -5.7 g / cm 3 .

9. The negative current collector according to any one of claims 1 to 8, wherein The negative current collector further comprises an electrically conductive layer arranged on the carbon fiber layer, and the thickness of the electrically conductive layer is 0.5 μm-2 μm; the electrically conductive layer comprises an electrically conductive agent, and the electrically conductive agent comprises one or more of graphene, graphite, carbon black, acetylene black, and carbon nanotubes.

10. A method of producing the negative electrode current collector according to any one of claims 1 to 9, characterized by, Comprising: metal-coating carbon fibers are obtained; the metal-coated carbon fibers are placed on a metal substrate and pressed and then sintered to obtain a carbon fiber layer, thereby preparing a negative current collector.

11. The production method according to claim 10, wherein Further comprising coating an electrically conductive slurry on the carbon fiber layer, and obtaining an electrically conductive layer after drying treatment; the solid content of the electrically conductive slurry is 10 wt%-20 wt%, and the viscosity of the electrically conductive slurry is 100 mPa·s-500 mPa·s.

12. The production method according to claim 10 or 11, characterized by, The metal-coating method comprises one or more of electroplating, electroless plating, thermal reduction plating, magnetron sputtering, and vacuum evaporation.

13. The production method according to claim 12, wherein The metal coating is by electroplating, the current density of which is 2 A / dm 2 - 3.5 A / dm 2 and the plating time is 10 min - 30 min.

14. A negative electrode sheet characterized by comprising: The negative electrode sheet comprises a negative current collector and a negative active material layer arranged on the surface of the negative current collector, and the negative current collector comprises the negative current collector of any one of claims 1-9 or the negative current collector prepared by the preparation method of any one of claims 10-13.

15. A battery, characterized by The battery comprises a positive electrode sheet and a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet comprises the negative electrode sheet of claim 14.

16. An electrical device, characterized by The electric device comprises the battery of claim 15. The metal-coated carbon fiber comprises a carbon fiber body and a metal coating layer arranged on the surface of the carbon fiber body, and the metal coating layer comprises one or more of copper, nickel, titanium, and stainless steel. The metal substrate is selected from any one of a copper substrate, a nickel substrate, a titanium substrate, and a stainless steel substrate. The length of the carbon fiber body is 0.1 mm-1 mm, and the diameter of the carbon fiber body is 5 μm-10 μm; the thickness of the metal coating layer is 0.5 μm-2 μm. The carbon fiber layer comprises a pore structure, and the porosity of the carbon fiber layer is 20%-60%; the pore diameter of the pore structure is 10 μm-100 μm. The thickness of the metal substrate is 3 μm-10 μm, and the thickness of the carbon fiber layer is 10 μm-1000 μm. The negative current collector further comprises an electrically conductive layer arranged on the carbon fiber layer, and the thickness of the electrically conductive layer is 0.5 μm-2 μm; the electrically conductive layer comprises an electrically conductive agent, and the electrically conductive agent comprises one or more of graphene, graphite, carbon black, acetylene black, and carbon nanotubes. Comprising: metal-coating carbon fibers are obtained; the metal-coated carbon fibers are placed on a metal substrate and pressed and then sintered to obtain a carbon fiber layer, thereby preparing a negative current collector. Further comprising coating an electrically conductive slurry on the carbon fiber layer, and obtaining an electrically conductive layer after drying treatment; the solid content of the electrically conductive slurry is 10 wt%-20 wt%, and the viscosity of the electrically conductive slurry is 100 mPa·s-500 mPa·s. The metal-coating method comprises one or more of electroplating, electroless plating, thermal reduction plating, magnetron sputtering, and vacuum evaporation. The negative electrode sheet comprises a negative current collector and a negative active material layer arranged on the surface of the negative current collector, and the negative current collector comprises the negative current collector of any one of claims 1-9 or the negative current collector prepared by the preparation method of any one of claims 10-13. The battery comprises a positive electrode sheet and a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet comprises the negative electrode sheet of claim 14. The electric device comprises the battery of claim 15.

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