Negative electrode current collector, manufacturing method therefor and use thereof

Abstract

Provided in the present application are a negative electrode current collector, a manufacturing method therefor and the use thereof. The negative electrode current collector comprises a metal substrate and a carbon fiber layer provided on the surface of the metal substrate, the carbon fiber layer comprising a plurality of metal-coated carbon fibers. In the negative electrode current collector provided in the present application, the carbon fiber layer is composited on the surface of the metal substrate. On one hand, the carbon fibers can reduce the mass of the current collector and increase the energy density of a battery, and have high strength and are resistant to corrosion, prolonging the service life of the negative electrode current collector. On the other hand, coating the carbon fibers with metal can effectively increase the bonding force between the carbon fiber layer and the metal substrate, improving the conductivity of the negative electrode current collector.

Description

Negative electrode current collector, and preparation method and application thereof

[0001] Cross-reference to related applications

[0002] The present application claims priority from the Chinese patent application No. 202410869085.0 filed on June 28, 2024, and entitled "Negative electrode current collector, and preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the field of batteries, in particular to a negative electrode current collector, and preparation method and application thereof. BACKGROUND

[0004] The electrode pole 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 electrode current collector because it has good electrical conductivity and low cost. Some technologies use copper plating layer on the surface of carbon fiber cloth to reduce the mass of the negative electrode current collector, but the interface bonding force between the carbon fiber cloth and the copper plating layer is weak, and it is easy to fall off and separate. Therefore, it is necessary to provide a negative electrode current collector which has relatively small mass and high structural stability.

[0005] SUMMARY

[0006] In view of this, the present application provides a negative electrode current collector, and preparation method and application thereof. The negative electrode 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, and the carbon fiber has high strength and corrosion resistance, which can prolong the service life of the negative electrode current collector. On the other hand, metal coating 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 electrode current collector.

[0007] In a first aspect, the present application provides a negative electrode current collector, which 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.

[0008] Optionally, the metal substrate is selected from any one of a copper substrate, a nickel substrate, a titanium substrate and a stainless steel substrate.

[0009] Optionally, 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.

[0010] Optionally, the metal-coated carbon fibers in the carbon fiber layer are randomly oriented.

[0011] 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.

[0012] Optionally, the thickness of the metal cladding layer is 0.5 μm-2 μm.

[0013] Optionally, the carbon fiber layer comprises a pore structure, and the porosity of the carbon fiber layer is 20%-60%; and the pore diameter of the pore structure is 10 μm-100 μm.

[0014] Optionally, the thickness of the metal substrate is 3 μm-10 μm, and the thickness of the carbon fiber layer is 10 μm-1000 μm.

[0015] Optionally, the density of the negative electrode current collector is 1.4 g / cm3-5.7 g / cm3.

[0016] Optionally, the negative electrode 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.

[0017] Optionally, 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.

[0018] In a second aspect, the present application provides a preparation method of the negative electrode current collector provided in the first aspect, comprising:

[0019] carrying out metal cladding on the carbon fiber to obtain metal cladded carbon fiber;

[0020] pressing the metal cladded carbon fiber on a metal substrate and then carrying out sintering treatment to obtain a carbon fiber layer, thereby preparing the negative electrode current collector.

[0021] Optionally, the method further comprises coating an electrically conductive paste on the carbon fiber layer and obtaining an electrically conductive layer after drying treatment.

[0022] Optionally, the solid content of the electrically conductive paste is 10wt%-20wt%, and the viscosity of the electrically conductive paste is 100 mPa·s-500 mPa·s.

[0023] Optionally, the metal cladding method comprises one or more of electroplating, electroless plating, thermal reduction plating, magnetron sputtering, and vacuum evaporation.

[0024] Optionally, the metal cladding method is electroplating, and the current density of the electroplating is 2 A / dm2-3.5 A / dm2, and the electroplating time is 10 min-30 min.

[0025] In a third aspect, the present application 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, and the negative electrode current collector comprises the negative electrode current collector provided in the first aspect or the negative electrode current collector prepared by the preparation method provided in the second aspect.

[0026] In a fourth aspect, the present application 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 comprises the negative electrode sheet provided in the third aspect.

[0027] In a fifth aspect, the present application provides an electric device, which comprises the battery provided in the fourth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0028] 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 description of the embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0029] FIG. 1 is a schematic diagram of the cross-sectional structure of the negative electrode current collector provided in an embodiment of the present application;

[0030] FIG. 2 is a schematic diagram of the structure of the metal-coated carbon fiber in the negative electrode current collector provided in an embodiment of the present application;

[0031] FIG. 3 is a schematic diagram of the cross-sectional structure of the negative electrode current collector provided in another embodiment of the present application;

[0032] FIG. 4 is a flowchart of the preparation method of the negative electrode current collector provided in an embodiment of the present application.

[0033] Explanation of reference numerals 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

[0034] 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 any creative effort fall within the scope of protection of the present application.

[0035] At present, some technologies adopt a copper plating layer on the surface of the carbon fiber cloth to reduce the mass of the negative current collector, but the carbon fiber surface has few polar groups, is chemically inert, has small surface energy and specific surface area, and has weak interface bonding force with the copper plating layer, which is easy to fall off and separate; and the elastic modulus of the carbon fiber cloth and the copper plating layer is quite different, and during the charging and discharging process of the battery, the negative 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 current collector which has relatively small mass while having high structural stability.

[0036] To solve the above problems, the application provides a negative current collector, which is obtained 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, and 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 structural stability and conductivity of the negative current collector.

[0037] Figure 1 is a schematic diagram of the cross-sectional structure of the negative current collector 100 provided by an embodiment of the application, which includes a metal substrate 10 and a carbon fiber layer 11 arranged on the surface of the metal substrate 10, and the carbon fiber layer 11 includes a plurality of metal-coated carbon fibers 110. As shown in Figure 2, in the present 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 current collector is used to collect and output the current generated by the negative active material, and input the negative current to the negative active material. The negative current collector 100 provided by the present application is obtained by compounding a carbon fiber layer 11 on the surface of a 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. Moreover, the carbon fiber body 1101 has good mechanical properties, high strength and resistance to electrolyte corrosion, which prolongs the service life of the negative current collector and thus improves the cycle service life of the electrode sheet. In addition, the carbon fiber body 1101 also has high elastic modulus and low expansion coefficient. The metal coating layer 1102 on the surface of the carbon fiber body 1101 is made of metal material, which effectively improves the bonding force between the carbon fiber layer 11 and the metal substrate 10, and prevents the carbon fiber layer 11 and the metal substrate 10 from peeling off due to the volume expansion and shrinkage of the negative 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 interface bonding force between the carbon fiber layer and the metal substrate.

[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 binding force between the metal substrate and the metal cladding layer.

[0039] 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 binding force between the metal substrate and the metal cladding layer.

[0040] 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 binding force between the metal substrate and the metal cladding layer.

[0041] 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 binding force between the metal substrate and the metal cladding layer.

[0042] 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 binding force between the metal substrate and the metal cladding layer.

[0043] 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 within 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 in the current collector density caused by too large pore structure, the penetration of the negative active material into the current collector, and avoiding too large density of the carbon fiber layer caused by too small pore structure. 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.

[0044] 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 of 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 the coating of the negative active material layer or the rolling, and in addition, the porosity of the carbon fiber layer 11 can be controlled 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, or 10 μm.

[0045] 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, or 2 μm.

[0046] In some embodiments of the present application, the density of the negative current collector is 1.4 g / cm3-5.7 g / cm3. Specifically, the negative current collector can be but is not limited to 1.4 g / cm3, 1.5 g / cm3, 2 g / cm3, 2.5 g / cm3, 3 g / cm3, 3.5 g / cm3, 4 g / cm3, 4.5 g / cm3, 5 g / cm3, 5.5 g / cm3, 5.7 g / cm3. The present application obtains a negative current collector with a density much smaller than that of a pure metal current collector by special design of the negative current collector.

[0047] In an embodiment of the present application, the thickness of the metal substrate 10 is 3 μm-10 μm. Controlling the metal substrate 10 at an appropriate thickness can ensure that the negative current collector has excellent electrical conductivity while minimizing the mass of the negative current collector as much as possible. Specifically, the thickness of the metal substrate can be adjusted according to the actual battery requirements for electrical conductivity and energy density. Specifically, the thickness of the metal substrate can be but is not limited to 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, etc.

[0048] In an embodiment of the present application, the thickness of the carbon fiber layer 11 is 10 μm-1000 μm. Controlling the thickness of the carbon fiber layer within an appropriate range can effectively reduce the mass of the negative current collector and thus improve the energy density of the battery while ensuring that the carbon fiber layer and the metal substrate have strong bonding force, avoiding detachment of the two during the preparation of the current collector or the use of the battery. Specifically, the thickness of the carbon fiber layer can be but is not limited to 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm.

[0049] In an embodiment of the present application, as shown in FIG. 3, the negative current collector 100 further comprises a conductive layer 12 disposed on the carbon fiber layer 11, and the conductive layer 12 comprises a conductive agent. The conductive layer disposed on the carbon fiber layer can further improve the electrical conductivity of the negative current collector, and the three-dimensional porous network structure of the carbon fiber layer is conducive to increasing the bonding force between the conductive layer 12 and the carbon fiber layer 11, obtaining a negative current collector with a tightly bonded laminated structure. The conductive layer can also improve the peel strength between the negative current collector and the negative active material layer and reduce the interface impedance, thereby improving the cycle life and electrochemical performance of the battery. In an embodiment of the present application, the conductive agent comprises one or more of graphene, graphite, carbon black, acetylene black, and carbon nanotubes.

[0050] In an embodiment of the present application, the thickness of the conductive layer 12 is 0.5-2 μm, and the conductive layer with a suitable thickness can further improve the conductivity of the negative current collector while ensuring the bonding force between the layers of the negative current collector. 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.

[0051] In an embodiment of the present application, the conductive layer 12 further comprises 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 current collector. In an embodiment of the present application, the binder can include, but is not limited to, one or more of carboxymethyl cellulose, styrene butadiene rubber, polyamide, and polyvinylidene fluoride; and the dispersant can include, 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 dodecyl benzene sulfonate.

[0052] The negative current collector provided by the present application has a light weight, which can effectively improve the energy density of the battery. In addition, the negative current collector has good corrosion resistance and no obvious anisotropy. In the process of battery preparation or use, the bonding performance between the negative current collector and the negative active material layer is good, and the cycle service life is long.

[0053] Referring to FIG. 4, the preparation method of the negative current collector provided by an embodiment of the present application is shown in the flow chart, which comprises the following steps:

[0054] S101: coating the carbon fibers with metal to obtain metal-coated carbon fibers;

[0055] S102: pressing the metal-coated carbon fibers on a metal substrate and then performing sintering treatment to obtain a carbon fiber layer, thereby preparing the negative current collector.

[0056] 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 the present application, the metal coating method is electroplating. In an embodiment of the present application, the current density of electroplating is 2 A / dm2-3.5 A / dm2, and the electroplating time is 10 min-30 min. Controlling the relevant parameters of electroplating within an appropriate range can further control the thickness of the metal coating layer on the surface of the carbon fiber. Specifically, the current density of electroplating can include but is not limited to 2 A / dm2, 2.2 A / dm2, 2.4 A / dm2, 2.5 A / dm2, 2.6 A / dm2, 2.8 A / dm2, 3 A / dm2, 3.2 A / dm2, 3.4 A / dm2, 3.5 A / dm2, and the electroplating time can include but is not limited to 10 min, 15 min, 20 min, 25 min, 30 min.

[0057] In some specific embodiments of the present application, the electroplating can be chemical electroplating. In some embodiments of the present application, the components of the plating solution for chemical electroplating can be CuSO4 and H2SO4, or CuSO4, HCHO, and NaKC4H4O6, or Cu2P2O7 and K4P2O7. In an embodiment of the present application, the chemical electroplating process further includes adding a dispersant, which 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, the chemical electroplating process further includes stirring treatment. By adding a dispersant and stirring treatment, the carbon fibers can be dispersed, further improving the uniformity of the metal coating layer.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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℃.

[0065] 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.

[0066] The application further 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.

[0067] The application further 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.

[0068] 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, etc. 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.

[0069] The application further 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, etc., wherein the electronic device may be, for example, a mobile phone, a tablet computer, a watch, a VR glasses, etc. 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, etc.

[0070] The effects of the technical solutions of the application are further described below through specific examples.

[0071] Embodiment 1

[0072] First, the carbon fiber with length of 0.6mm and diameter of 7μm is pretreated, including carbon fiber surface degumming, surface roughening, sensitization and activation, the specific operation is: to put the carbon fiber in isopropyl alcohol solution for 24h, then use magnetic stirrer high speed stirring for 2h, stirring speed is 1000rpm, to remove the surface protective film, then use deionized water to clean, put into drying oven at 100℃ for 3h; after degumming, the carbon fiber is soaked in the mixed solution of sulfuric acid and ammonium persulfate and ultrasonic for 20min-60min for surface roughening, then use deionized water to clean, put into drying oven at 100℃ for 3h; after surface roughening, the carbon fiber is put into sensitization solution for 5min for sensitization treatment, the sensitization solution is stannous chloride and dilute hydrochloric acid mixed solution, the content of stannous chloride in the sensitization solution is 4g / L-6g / L, then use deionized water to clean, put into drying oven at 100℃ for 3h; after sensitization treatment, the carbon fiber is put into activation solution for 5min for activation treatment, the activation solution is silver ammonia solution prepared by nitric acid silver and ammonia water, the content of nitric acid silver in the activation solution is 150g / L-250g / L, then use deionized water to clean, put into drying oven at 100℃ for 3h. Then the carbon fiber is electroplated with copper, the plating solution is CuSO4 and H2SO4, 50mg of carbon fiber and 1mg of dispersant sodium pyrophosphate are added into 100ml of plating solution, the carbon fiber and dispersant are dispersed uniformly by using magnetic stirrer, then copper foil substrate and copper plated copper sheet are put into the plating solution, copper foil is connected to negative electrode and copper plated copper sheet is connected to positive electrode, the plating current density is adjusted to 3A / dm2, the plating time is 20min, and a metal coating layer with thickness of 1μm is obtained on the surface of carbon fiber. A copper foil substrate with thickness of 4μm and area of 3cm*3cm is placed at the bottom of the mold, 40mg of metal coated carbon fiber is filled into the mold cavity, and the convex mold is assembled and tightened by bolt; then sintering treatment is carried out, the sintering temperature is 800℃, the heating rate is 5℃ / min, and the holding time is 1h, a carbon fiber layer with thickness of 30μm is obtained on the surface of copper foil substrate, the pore size of the pore structure of the carbon fiber layer is 40μm, the porosity is 40%, and the negative electrode current collector is obtained.

[0073] Example 2

[0074] The difference from example 1 is that after obtaining the carbon fiber layer on the surface of the copper foil substrate, a conductive layer is coated on the metal coated carbon fiber current collector, including: adding deionized water, polyacrylic acid, sodium carboxymethyl cellulose and carbon black with mass ratio of 61:51:1:7 into the sanding machine, sanding for 3h to obtain conductive slurry with solid content of 15wt% and viscosity of 300mPa·s; the obtained conductive slurry is coated on the carbon fiber layer to obtain a conductive layer with thickness of 1μm, and the negative electrode current collector is obtained after drying at 100℃ for 30s.

[0075] Example 3

[0076] The difference from Example 2 is that the length of the carbon fiber is 0.05 mm, the pore diameter of the pore structure of the carbon fiber layer is 5 μm, and the porosity is 10%.

[0077] Example 4

[0078] The difference from Example 2 is that the length of the carbon fiber is 0.1 mm, the pore diameter of the pore structure of the carbon fiber layer is 10 μm, and the porosity is 40%.

[0079] Example 5

[0080] The difference from Example 2 is that the length of the carbon fiber is 1 mm, the pore diameter of the pore structure of the carbon fiber layer is 100 μm, and the porosity is 40%.

[0081] Example 6

[0082] The difference from Example 2 is that the length of the carbon fiber is 5 mm, the pore diameter of the pore structure of the carbon fiber layer is 300 μm, and the porosity is 70%.

[0083] Example 7

[0084] The difference from Example 2 is that the thickness of the carbon fiber layer is 10 μm, the pore diameter of the pore structure of the carbon fiber layer is 40 μm, and the porosity is 20%.

[0085] Example 8

[0086] The difference from Example 2 is that the thickness of the carbon fiber layer is 1 mm, the pore diameter of the pore structure of the carbon fiber layer is 40 μm, and the porosity is 60%.

[0087] Example 9

[0088] The difference from Example 2 is that the thickness of the copper foil substrate is 3 μm.

[0089] Example 10

[0090] The difference from Example 2 is that the thickness of the copper foil substrate is 10 μm.

[0091] Example 11

[0092] 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 diameter of the pore structure of the carbon fiber layer is 80 μm, and the porosity is 50%.

[0093] Example 12

[0094] 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 diameter of the pore structure of the carbon fiber layer is 15 μm, and the porosity is 30%.

[0095] Example 13

[0096] The difference from Example 2 is that the thickness of the metal coating layer on the surface of the carbon fiber is 0.1 μm.

[0097] Example 14

[0098] The difference from Example 2 is that the thickness of the metal coating layer on the surface of the carbon fiber is 4 μm.

[0099] Comparative Example 1

[0100] The difference from Example 2 is that the carbon fiber is not subjected to electrochemical copper plating treatment.

[0101] Comparative Example 2

[0102] The same copper foil as in Example 1 is used as the negative current collector.

[0103] Performance test

[0104] Density test

[0105] The negative current collectors prepared in Examples 1-14 and Comparative Examples 1-2 are subjected to a density test, the test procedure being as follows: using a 10000 mm2sampler (accuracy ±0.1 mm), two samples are taken from the left and right sides 20 mm apart on the same straight line in the width direction of the sample of the negative current collector to be tested, one sample is taken at the center, and two samples are taken at a distance of 200 mm from the center on the left and right sides, respectively, to give five samples, the mass m of each 10000 mm2negative current collector is weighed in order using a balance (accuracy 0.1 mg), and the mass per unit area of each negative current collector is calculated: m x 100 (g / m2); the thickness h of each negative current collector is measured using a screw micrometer, and the density of the negative current collector is calculated: m x 100 / h (g / cm3), five sets of test results are recorded and averaged, and the results are shown in Table 1.

[0106] Mechanical property test

[0107] The negative current collectors prepared in Examples 1-14 and Comparative Examples 1-2 are subjected to a mechanical test, the test procedure being as follows: five longitudinal samples each having a width of 15 mm are cut from the negative current collectors prepared in Examples 1-14 and Comparative Example 1, the samples being ensured to be smooth, free of burrs and free of obvious mechanical damage, a tensile testing machine is calibrated and zeroed, the tensile speed is set to 50 mm / min, the gauge length is set to 50 mm, the sample is clamped and the displacement is zeroed, the test is started, and five sets of tensile strength and elongation data are recorded, and the average of the five sets of data is calculated, and the results are shown in Table 1.

[0108] Resistivity test

[0109] The negative current collector prepared in the above-mentioned examples 1-14 and comparative examples 1-2 was cut into a negative current collector disc with a diameter of 30 mm by a sampler, and placed on a surface resistance tester. The test pressure was 25 MPa. After the probe was lowered to be in good contact with the flexible negative current collector, the "start test button" was pressed. Three sets of test results were recorded and averaged to obtain the results shown in Table 1.

[0110] Peeling force test

[0111] The negative current collector prepared in the above-mentioned examples 1-14 and comparative examples 1-2 was subjected to a tab peeling force test. The active material was coated on the surface of the negative current collector, and the adhesive tape was pasted on the surface of the active material of the tab, so that the active material could be peeled off from the current collector. Then, the tab was cut into a sample with a length of 100 mm and a width of 40 mm, which was pasted and fixed on a flat steel plate with double-sided tape. The free end of the tab and the steel plate were clamped in the upper and lower clamps of a peeling force tester, respectively, and were subjected to 180° peeling at a peeling speed of 50 mm / min. Three sets of test results were recorded and averaged to obtain the results shown in Table 1.

[0112] Table 1: Test results of negative current collector performance

[0113] As can be seen from Table 1, the negative current collector of the present application has a smaller density, while significantly improving its compressive strength and elongation, and has better mechanical properties, compared with the pure copper foil current collector of comparative example 2 and the composite carbon fiber current collector of comparative example 1. In addition, the resistivity is also significantly reduced, and the conductivity is better. Compared with comparative example 1 without electrochemical copper plating treatment of the carbon fiber, the present application improves the conductivity of the carbon fiber by plating copper, and also improves the bonding force between the carbon fiber and the metal substrate.

[0114] The above describes the preferred embodiments of the present application, but should not be construed as limiting the scope of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered within the scope of protection of the present application.

Claims

1. A negative electrode current collector (100), characterized in that, The negative electrode current collector (100) includes a metal substrate (10) and a carbon fiber layer (11) disposed on the surface of the metal substrate (10), wherein the carbon fiber layer (11) includes multiple metal-coated carbon fibers (110).

2. The negative electrode current collector (100) as described in claim 1, characterized in that, The metal substrate (10) is selected from any one of copper substrate, nickel substrate, titanium substrate and stainless steel substrate.

3. The negative electrode current collector (100) as described in claim 1, characterized in that, The metal-coated carbon fiber (110) includes a carbon fiber body (1101) and a metal cladding layer (1102) covering the surface of the carbon fiber body (1101). The metal cladding layer (1102) includes one or more of copper, nickel, titanium and stainless steel.

4. The negative electrode current collector (100) as described in any one of claims 1-3, characterized in that, The metal-coated carbon fibers (110) in the carbon fiber layer (11) are randomly oriented.

5. The negative electrode current collector (100) as described in any one of claims 3 or 4, characterized in that, The carbon fiber body (1101) has a length of 0.1mm-1mm and a diameter of 5μm-10μm; the metal cladding layer (1102) has a thickness of 0.5μm-2μm.

6. The negative electrode current collector (100) as described in any one of claims 1-5, characterized in that, The carbon fiber layer (11) includes a porous structure, and the porosity of the carbon fiber layer (11) is 20%-60%; the pore size of the porous structure is 10μm-100μm.

7. The negative electrode current collector (100) as described in any one of claims 1-6, characterized in that, The thickness of the metal substrate (10) is 3μm-10μm, and the thickness of the carbon fiber layer (11) is 10μm-1000μm.

8. The negative electrode current collector (100) as described in any one of claims 1-7, characterized in that, The density of the negative electrode current collector (100) is 1.4 g / cm3-5.7 g / cm3.

9. The negative electrode current collector (100) as described in any one of claims 1-8, characterized in that, The negative electrode current collector (100) further includes a conductive layer (12) disposed on the carbon fiber layer (11), the thickness of the conductive layer (12) being 0.5μm-2μm; the conductive layer (12) includes a conductive agent, the conductive agent including one or more of graphene, graphite, carbon black, acetylene black, and carbon nanotubes.

10. A method for preparing the negative electrode current collector (100) as described in any one of claims 1-9, characterized in that, include: Metal coating was applied to carbon fibers to obtain metal-coated carbon fibers (110); The metal-coated carbon fiber (110) is placed on a metal substrate (10), pressed, and then sintered to obtain a carbon fiber layer (11), thus preparing a negative electrode current collector (100).

11. The preparation method according to claim 10, characterized in that, The method also includes coating the carbon fiber layer (11) with a conductive slurry and drying it to obtain a conductive layer (12); the solid content of the conductive slurry is 10wt%-20wt%, and the viscosity of the conductive slurry is 100mPa·s-500mPa·s.

12. The preparation method according to claim 10 or 11, characterized in that, Metal coating methods include one or more of electroplating, electroless plating, thermal reduction plating, magnetron sputtering, and vacuum evaporation.

13. The preparation method according to claim 12, characterized in that, The metal coating method is electroplating, and the current density of the electroplating is 2A / dm2-3.5A / dm2, and the electroplating time is 10min-30min.

14. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative electrode current collector (100) and a negative electrode active material layer disposed on the surface of the negative electrode current collector (100). The negative electrode current collector (100) includes the negative electrode current collector (100) according to any one of claims 1-9 or the negative electrode current collector (100) prepared by the preparation method according to any one of claims 10-13.

15. A battery, characterized in that, The battery includes a positive electrode and a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the negative electrode includes the negative electrode as described in claim 14.

16. An electrical appliance, characterized in that, The electrical device includes the battery as described in claim 15.

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