Carbon-coated current collector and preparation method thereof, pole piece and battery

Abstract

The invention relates to the technical field of current collectors, and provides a carbon-coated current collector, a preparation method thereof, a pole piece and a battery. The carbon-coated current collector comprises a substrate and a carbon-coated layer arranged on at least one side surface of the substrate. Wherein the carbon coating layer comprises a carbon nanotube array and a sheet-shaped conductive material. The carbon nanotube array comprises a plurality of first carbon nanotubes and a plurality of second carbon nanotubes, one end of each first carbon nanotube is connected with the substrate, and the other end of each first carbon nanotube is far away from the substrate; and one end of the second carbon nanotube is connected with the side wall of the first carbon nanotube. The space between the adjacent first carbon nanotubes is filled with the sheet-shaped conductive material. According to the invention, the carbon nanotube array and the sheet-shaped conductive material are cooperatively matched, and point-line-surface combination is utilized to form a three-dimensional conductive network with anisotropy, so that the longitudinal resistance of the pole piece is remarkably reduced, and the rate capability and the cycling stability of the battery are further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current collectors, in particular to a carbon-coated current collector, a preparation method thereof, a pole piece and a battery. BACKGROUND

[0002] At present, in order to improve the interface contact between the current collector and the active material layer, a carbon coating layer is usually arranged on the current collector. The carbon coating layer is usually formed by mixing a conductive agent (such as carbon black, graphite) and a binder to form a random conductive network. Since the conductive agent in the traditional carbon coating layer is randomly distributed, the anchoring effect on the active material layer is weak, and there is no significant difference in conductivity in the direction parallel and perpendicular to the current collector, which is difficult to meet the requirement of efficient transmission of current in the direction perpendicular to the current collector, i.e. the main direction of lithium ion insertion / extraction of the active material. Especially in the application of high-rate charging or thick electrode, the large longitudinal resistance of the pole piece represents the increase of the comprehensive resistance of the pole piece, thereby causing the performance of the battery to decrease. SUMMARY

[0003] Therefore, it is necessary to provide a carbon-coated current collector capable of reducing the longitudinal resistance of the pole piece, a preparation method thereof, a pole piece and a battery.

[0004] In a first aspect, the present application provides a carbon-coated current collector, comprising:

[0005] a substrate;

[0006] a carbon coating layer arranged on at least one side surface of the substrate, comprising a carbon nanotube array and a sheet-shaped conductive material; the carbon nanotube array comprises a plurality of first carbon nanotubes and a plurality of second carbon nanotubes, one end of the first carbon nanotube is connected to the substrate, and the other end is away from the substrate; one end of the second carbon nanotube is connected to the side wall of the first carbon nanotube; and the sheet-shaped conductive material is filled between adjacent first carbon nanotubes.

[0007] In some embodiments, the carbon coating layer satisfies at least one of the following conditions:

[0008] (1) the average included angle between the length direction of the first carbon nanotube and the surface of the substrate is 45°-90°;

[0009] (2) the average sheet diameter of the sheet-shaped conductive material is 1-5 times the interval distance between adjacent first carbon nanotubes;

[0010] (3) the length of the first carbon nanotube is 1-6 μm, the diameter is 10-20 nm, and the interval distance between adjacent first carbon nanotubes is 100-1000 nm;

[0011] (4) the length of the second carbon nanotube is 0.5-2 μm, and the diameter is 1-3 nm;

[0012] (5) The average flake diameter of the flaky conductive material is 100 nm-2000 nm, and the thickness is 0.4 nm-200 nm.

[0013] In some embodiments, the carbon coating layer further satisfies at least one of the following conditions:

[0014] (1) The ratio of the mass of the carbon nanotube array to the mass of the flaky conductive material in the carbon coating layer is 1:(1-4);

[0015] (2) The carbon nanotube array accounts for 5%-30% of the mass of the carbon coating layer;

[0016] (3) The flaky conductive material accounts for 10%-40% of the mass of the carbon coating layer;

[0017] (4) The carbon coating layer further comprises a binder filled between adjacent first carbon nanotubes, and the binder accounts for 10%-30% of the mass of the carbon coating layer.

[0018] In some embodiments, the surface of the substrate is distributed with a plurality of first catalyst layers, and the first carbon nanotubes are arranged on the first catalyst layers.

[0019] And / or, the sidewall of the first carbon nanotube is distributed with a plurality of second catalyst layers, and the second carbon nanotubes are arranged on the second catalyst layers.

[0020] In some embodiments, the carbon coating layer further satisfies at least one of the following conditions:

[0021] (1) The thickness of the first catalyst layer is 1 nm-5 nm, and the average diameter of the first catalyst layer is 20 nm-50 nm;

[0022] (2) The thickness of the second catalyst layer is 1 nm-5 nm, and the average diameter of the second catalyst layer is 5 nm-20 nm;

[0023] (3) The material of the first catalyst layer and the material of the second catalyst layer each independently comprises at least one of iron, cobalt and nickel.

[0024] In a second aspect, the present application provides a preparation method of a carbon-coated current collector, which comprises:

[0025] Growing the first carbon nanotubes on at least one side surface of the substrate, and the growth direction of the first carbon nanotubes is away from the substrate; then growing the second carbon nanotubes on the sidewall of the first carbon nanotubes to form a carbon nanotube array on the surface of the substrate;

[0026] Coating a slurry containing flaky conductive material to the surface of the substrate with the carbon nanotube array, so that the flaky conductive material is filled between adjacent first carbon nanotubes to form a carbon coating layer on the surface of the substrate.

[0027] In some embodiments, the method for growing the first carbon nanotubes comprises:

[0028] depositing a first catalyst layer on a surface of a substrate; and using a first carbon source to perform chemical vapor deposition on a surface of the first catalyst layer to form a plurality of first carbon nanotubes arranged on the first catalyst layer.

[0029] In some embodiments, the method for growing the first carbon nanotubes satisfies at least one of the following conditions:

[0030] (1) the volume concentration of the first carbon source in the chemical vapor deposition is 5% to 15%, the temperature is 700°C to 800°C, and the time is 2 min to 5 min;

[0031] (2) the first carbon source comprises at least one of acetylene, methane, and ethylene.

[0032] In some embodiments, the method for growing the second carbon nanotubes comprises:

[0033] immersing the substrate with the first carbon nanotubes into a solution containing a catalyst raw material; and after taking out the substrate, drying the substrate to allow the catalyst raw material to crystallize on the sidewall of the first carbon nanotube; and using a second carbon source to perform chemical vapor deposition on a surface of the catalyst raw material to form a plurality of second carbon nanotubes.

[0034] In some embodiments, the method for growing the second carbon nanotubes satisfies at least one of the following conditions:

[0035] (1) the time for immersing the substrate into the solution is 5 s to 60 s;

[0036] (2) the concentration of the catalyst raw material in the solution is 0.01 mol / L to 0.1 mol / L;

[0037] (3) the solvent contained in the solution comprises at least one of ethanol, isopropyl alcohol, and ethylene glycol;

[0038] (4) the catalyst raw material comprises at least one of iron salt, cobalt salt, and nickel salt;

[0039] (5) the volume concentration of the second carbon source in the chemical vapor deposition is 3% to 10%, the temperature is 550°C to 650°C, and the time is 1 min to 3 min;

[0040] (6) the second carbon source comprises at least one of ethanol, methanol, and acetone.

[0041] In a third aspect, the present application provides a pole piece, the pole piece comprising a carbon-coated current collector of the first aspect or a carbon-coated current collector prepared by the method of the second aspect, and the carbon-coated current collector is provided with an active material layer on at least one side surface.

[0042] In a fourth aspect, the application provides a battery, the battery comprising the electrode tab of the third aspect.

[0043] Compared with the prior art, the application has at least the following beneficial effects:

[0044] In the carbon coating layer of the application, the first carbon nanotubes arranged on the surface of the substrate act as "conductive pillars", providing a direct and low-resistance vertical channel for the transmission of electrons from the substrate to the active material layer. Further, the second carbon nanotubes grown on the sidewalls of the first carbon nanotubes act as branch structures, not only increasing the specific surface area of the carbon coating layer, but also further improving the adhesion between the carbon coating layer and the active layer, and also cooperating with the sheet-shaped conductive material filled between the first carbon nanotubes to form an efficient horizontal conductive network, thereby connecting each "conductive pillar" into a whole and improving the conductive performance of the carbon coating layer. The application utilizes the combination of "point (carbon nanotube tip) - line (carbon nanotube body) - surface (sheet-shaped conductive material)", and cooperates to form a three-dimensional conductive structure far superior to the performance of the traditional random mixed conductive network, which can form a three-dimensional and anisotropic three-dimensional conductive network, significantly reducing the vertical resistance of the electrode tab, and further reducing the resistivity of the electrode tab as a whole, and improving the rate performance and cycle stability of the battery. DETAILED DESCRIPTION

[0045] The application will be further described in detail below in conjunction with the embodiments and examples. These embodiments and examples are only used to explain the application and not to limit the scope of the application. The purpose of providing these embodiments and examples is to make the disclosure of the application more thorough and comprehensive. It should also be understood that the application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or changes without departing from the spirit of the application, and the equivalent forms obtained thereby also fall within the protection scope of the application. In addition, in the following description, a large number of specific details are given in order to provide a more complete understanding of the application. It should be understood that the application can be implemented without one or more of these details.

[0046] In the application, "optionally", "optional" and "optional" mean that it can or can not be present, i.e. it means to select either of the two parallel schemes "yes" or "no". If there are multiple "options" in a technical solution, each "option" is independent of each other if there is no special description, and there is no contradictory relationship or mutual restriction.

[0047] In the present application, the terms "first", "second" and the like in the "first aspect", "second aspect" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second" and the like only serve the purpose of non-exhaustive enumeration description, and should be understood as not constituting a closed limitation on the quantity.

[0048] In the present application, "longitudinal resistance" refers to the resistance in the direction perpendicular to the surface of the substrate. Similarly, "lateral resistance" refers to the resistance in the direction parallel to the surface of the substrate.

[0049] In the conventional technology, different dimensional carbon materials such as carbon black, carbon nanotubes and graphite are directly mixed to build a carbon-coated layer with a three-dimensional conductive structure on the current collector. However, due to the random distribution of carbon nanotubes and graphite, i.e. carbon nanotubes and graphite are randomly arranged in the carbon-coated layer in parallel, inclined or vertical manner. Therefore, the longitudinal and lateral conductivities in the conventional carbon-coated layer are not much different, which is difficult to meet the application of high rate charging or thick electrode.

[0050] Based on this, the first aspect of the present application provides a carbon-coated current collector, comprising a substrate and a carbon-coated layer arranged on at least one side surface of the substrate.

[0051] The carbon-coated layer comprises a carbon nanotube array and a sheet-shaped conductive material. The carbon nanotube array comprises a plurality of first carbon nanotubes and a plurality of second carbon nanotubes, one end of the first carbon nanotube is connected to the substrate, and the other end is away from the substrate; one end of the second carbon nanotube is connected to the side wall of the first carbon nanotube. The sheet-shaped conductive material is filled between adjacent first carbon nanotubes.

[0052] In the carbon-coated layer of the present application, the first carbon nanotube arranged on the surface of the substrate serves as a "conductive pillar", providing a direct and low-resistance longitudinal channel for the transmission of electrons from the substrate to the active material layer. Further, the second carbon nanotube grown on the side wall of the first carbon nanotube serves as a branch structure, which not only increases the specific surface area of the carbon-coated layer, but also further improves the adhesion between the carbon-coated layer and the active layer, and can also cooperate with the sheet-shaped conductive material filled between the first carbon nanotubes to form an efficient lateral conductive network, thereby connecting each "conductive pillar" into a whole, improving the conductive performance of the carbon-coated layer. The present application utilizes the combination of "point (carbon nanotube tip) - line (carbon nanotube body) - surface (sheet-shaped conductive material)", which cooperates to form a three-dimensional conductive structure far superior to the performance of the traditional random mixed conductive network, can form a three-dimensional and anisotropic three-dimensional conductive network, significantly reducing the longitudinal resistance of the pole piece, and further reducing the resistivity of the whole pole piece, improving the rate performance and cycle stability of the battery.

[0053] In some embodiments, the average angle between the length direction of the first carbon nanotube and the surface of the substrate is 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, or 90°. Optionally, the average angle is 60°-90°. Further optionally, the average angle is 90°. In addition, the second carbon nanotube can be perpendicular to the sidewall of the first carbon nanotube, or can be inclined to the sidewall of the first carbon nanotube, so that the first carbon nanotube with the second carbon nanotube presents a tree structure. That is, the first carbon nanotube is the trunk, and the second carbon nanotube is the branch. Similarly, the average angle between the sheet-shaped conductive material and the surface of the substrate is 0°-45°. Optionally, the average angle is 0°-15°.

[0054] In some embodiments, the sheet-shaped conductive material includes artificial graphite, natural sheet-shaped graphite, graphene nanosheet, and conductive carbon black with sheet-shaped or grape-shaped structure such as Ketjen black. The first carbon nanotube and the second carbon nanotube can each independently include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes. The substrate can include a copper foil or an aluminum foil.

[0055] In some embodiments, the average sheet diameter of the sheet-shaped conductive material is 1-5 times the spacing distance between adjacent first carbon nanotubes, for example, can be 1.0 times, 1.5 times, 2.0 times, 2.5 times, 3.0 times, 3.5 times, 4.0 times, 4.5 times, or 5.0 times. It can be understood that the shape of the sheet-shaped conductive material can be circular, oval, polygonal, etc. The average sheet diameter thereof refers to the average sheet diameter of the sheet-shaped structure equivalent to a circular shape.

[0056] The size of the sheet-shaped conductive material is selected as above to ensure that it can fill the gap between adjacent first carbon nanotubes and form a continuous transverse conductive surface, so that the carbon coating layer not only ensures the longitudinal conductive effect of the first carbon nanotube, but also ensures the transverse coverage of the sheet-shaped conductive material, and together realizes low impedance and high uniformity of current collection.

[0057] The length of the first carbon nanotube is 1-6 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or 6 μm; the diameter is 10-20 nm, for example, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm or 20 nm; and the interval distance between adjacent first carbon nanotubes is 100-1000 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1000 nm. The interval distance refers to the distance between the connecting position of the first carbon nanotube and the substrate. The size of the first carbon nanotube is selected as above, which effectively ensures the longitudinal conductive performance of the carbon coating layer. Controlling the interval distance between adjacent first carbon nanotubes can avoid the problem of difficulty in filling the flaky conductive material due to too small interval distance, and can also prevent the problem of fracture of the transverse conductive network due to too large interval distance.

[0058] Alternatively, the length of the second carbon nanotube is less than the length of the first carbon nanotube, and / or the diameter of the second carbon nanotube is less than the diameter of the first carbon nanotube. The length of the second carbon nanotube is 0.5-2 μm, for example, 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2.0 μm; and the diameter is 1-3 nm, for example, 1.0 nm, 1.5 nm, 2.0 nm, 2.5 nm or 3.0 nm. The size of the second carbon nanotube is selected as above, which can further improve the specific surface area of the carbon coating layer, thereby improving the bonding force with the active layer, and can further increase the contact point position of the flaky conductive material and the carbon nanotube array, and improve the conductive performance of the carbon coating layer. Controlling the length of the second carbon nanotube to be shorter than the length of the carbon nanotube can avoid the entanglement of the carbon nanotube when forming the “branch structure”, while ensuring the effect of improving the specific surface area of the carbon coating layer.

[0059] Further, the average flaky diameter of the flaky conductive material is 100-2000 nm, for example, 100 nm, 200 nm, 400 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm or 2000 nm; and the thickness is 0.4-200 nm, for example, 0.4 nm, 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm or 200 nm.

[0060] In some embodiments, the ratio of the mass of the array of carbon nanotubes to the mass of the sheet-like conductive material in the carbon-coated layer is 1:(1~4), which can be 1:1, 1:1.5, 1:2.0, 1:2.5, 1:3.0, 1:3.5, or 1:4.0, for example.

[0061] The present application selects the ratio of the mass of the array of carbon nanotubes to the mass of the sheet-like conductive material as above, which not only ensures the longitudinal conductivity of the array of carbon nanotubes, but also ensures the lateral coverage of the sheet-like conductive material, and cooperates to realize low impedance and high uniformity of current collection. Specifically, when the content of the sheet-like conductive material is close to the content of the array of carbon nanotubes, the skeleton effect of the array of carbon nanotubes is obvious, and the sheet-like conductive material can just fill into the array of carbon nanotubes, realizing the connection of the first array of carbon nanotubes, thereby forming a three-dimensional network dominated by longitudinal conductivity, which is particularly suitable for super-high rate batteries. With the increase of the content of the sheet-like conductive material, the array of carbon nanotubes can still provide key longitudinal conductive channels, and the lateral conductivity of the carbon-coated layer gradually improves, which is conducive to the uniform distribution of current in the active material layer, thereby reducing the local polarization of the pole piece, and is particularly suitable for high-load thick electrodes and long cycle life application scenarios.

[0062] If the mass proportion of the array of carbon nanotubes is relatively high, although the longitudinal conductivity of the carbon-coated layer can be ensured, the sheet-like conductive material is difficult to connect multiple carbon nanotubes, resulting in an imperfect lateral conductive network and poor conductive uniformity of the carbon-coated layer. If the mass proportion of the array of carbon nanotubes is relatively low, the sheet-like conductive material can cover the array of carbon nanotubes, weakening the longitudinal conductivity of the array of carbon nanotubes.

[0063] The mass proportion of the array of carbon nanotubes in the carbon-coated layer is 5%~30%, for example, which can be 5%, 10%, 15%, 20%, 25%, or 30%; the mass proportion of the sheet-like conductive material in the carbon-coated layer is 10%~40%, for example, which can be 10%, 15%, 20%, 25%, 30%, 35%, or 40%.

[0064] The carbon-coated layer also includes a binder filled between adjacent first carbon nanotubes. The mass proportion of the binder in the carbon-coated layer is 10%~30%, for example, which can be 10%, 15%, 20%, 25%, or 30%.

[0065] Optionally, the binder includes at least one of polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), and polyacrylic acid (PAA).

[0066] In some embodiments, the substrate has a plurality of first catalyst layers distributed on the surface of the substrate, and the first carbon nanotubes are disposed on the first catalyst layers. The first catalyst layers not only provide growth sites for the first carbon nanotubes, but also enhance the conductivity of the junction between the first carbon nanotubes and the substrate, thereby improving the current collection capability of the carbon-coated layer.

[0067] The first catalyst layer has a thickness of 1 nm to 5 nm, for example, 1 nm, 2 nm, 3 nm, 4 nm, or 5 nm. The first catalyst layer has an average diameter of 20 nm to 50 nm, for example, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm.

[0068] In some embodiments, the first carbon nanotubes have a plurality of second catalyst layers distributed on the sidewalls of the first carbon nanotubes, and the second carbon nanotubes are disposed on the second catalyst layers. The second catalyst layers not only provide growth sites for the second carbon nanotubes, but also enhance the conductivity of the first carbon nanotubes and the second carbon nanotubes, thereby improving the current collection capability of the carbon-coated layer.

[0069] Optionally, the second catalyst layer has an average diameter smaller than that of the first catalyst layer. The second catalyst layer has a thickness of 1 nm to 5 nm, for example, 1 nm, 2 nm, 3 nm, 4 nm, or 5 nm. The second catalyst layer has an average diameter of 5 nm to 20 nm.

[0070] Specifically, the size of the second catalyst layer is controlled as described above to match the small-diameter characteristic of the second carbon nanotubes (the size of the catalyst particles directly affects the diameter of the carbon nanotubes). A small second catalyst layer ensures the growth of small-diameter and highly dispersed second carbon nanotubes, thereby avoiding excessive agglomeration of the second carbon nanotubes and affecting the continuity of the conductive network.

[0071] Optionally, the material of the first catalyst layer and the material of the second catalyst layer each independently comprises at least one of iron, cobalt, and nickel.

[0072] In some embodiments, the substrate can be a copper foil or an aluminum foil.

[0073] In some embodiments, the carbon-coated layer has a thickness of 1 μm to 5 μm, for example, 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, or 5.0 μm. Further, the carbon-coated layer has a thickness of 2 μm to 3 μm, for example, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, or 3.0 μm.

[0074] The second aspect of the present application provides a method for preparing a carbon-coated current collector, the method comprising:

[0075] growing first carbon nanotubes on at least one side surface of the substrate, the growth direction of the first carbon nanotubes being away from the substrate; and growing second carbon nanotubes on the sidewall of the first carbon nanotubes to form a carbon nanotube array on the surface of the substrate;

[0076] applying a slurry containing flaky conductive material to the surface of the substrate having the carbon nanotube array, so that the flaky conductive material fills between adjacent first carbon nanotubes to form a carbon-coated layer on the surface of the substrate.

[0077] In some embodiments, the method for growing the first carbon nanotubes comprises: depositing a first catalyst layer on the surface of the substrate; and using a first carbon source to perform chemical vapor deposition on the surface of the first catalyst layer to form a plurality of first carbon nanotubes arranged on the first catalyst layer.

[0078] In the chemical vapor deposition, the volume concentration of the first carbon source is 5% to 15%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%; the temperature is 700°C to 800°C, for example, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, or 800°C; and the time is 2 minutes to 5 minutes, for example, 2.0 minutes, 2.5 minutes, 3.0 minutes, 3.5 minutes, 4.0 minutes, 4.5 minutes, or 5.0 minutes.

[0079] In the above-mentioned chemical vapor deposition process, the first catalyst layer will agglomerate to form larger nanoparticles (20nm to 50nm) due to surface tension during the temperature rising process, which serves as the basis for growing the first carbon nanotubes with larger diameters, smaller lengths, and moderate densities.

[0080] Optionally, the first carbon source comprises at least one of acetylene, methane, and ethylene.

[0081] Specifically, methane and ethylene are conventional carbon sources for chemical vapor deposition (CVD) growth of carbon nanotubes. Compared with acetylene, the decomposition temperature of methane is slightly higher, which is suitable for the growth temperature of 700°C to 800°C, and the reaction activity of ethylene is moderate. The combination of the three can control the growth rate and crystallinity of the first carbon nanotubes by adjusting the proportion.

[0082] Optionally, the thickness of the first catalyst layer is 1nm to 5nm. The first catalyst layer can be formed by at least one of magnetron sputtering, electron beam evaporation, and coating.

[0083] In some embodiments, the method for growing the second carbon nanotube comprises: immersing the substrate with the first carbon nanotube into a solution containing a catalyst precursor; drying after taking out the substrate, so that the catalyst precursor crystallizes on the sidewall of the first carbon nanotube; and using a second carbon source to perform chemical vapor deposition on the surface of the catalyst precursor to form the second carbon nanotube. It can be understood that, in the process of drying, the solvent volatilizes, the catalyst precursor nucleates and crystallizes on the surface of the first carbon nanotube, and then forms particles of the catalyst precursor on the surface of the first carbon nanotube, and after heat treatment, a second catalyst layer can be formed. For example, the heat treatment can be performed during the temperature rise of the chemical vapor deposition.

[0084] The substrate is immersed in the solution for 5s to 60s, for example, 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 60s.

[0085] The concentration of the catalyst precursor in the solution is 0.01mol / L to 0.1mol / L, for example, 0.01mol / L, 0.02mol / L, 0.03mol / L, 0.04mol / L, 0.05mol / L, 0.06mol / L, 0.07mol / L, 0.08mol / L, 0.09mol / L or 0.10mol / L.

[0086] The concentration of the catalyst precursor in the solution is selected as above to form catalyst particles with appropriate particle size and density on the sidewall of the first carbon nanotube, so as to ensure the growth of the second carbon nanotube with small size and high density. If the concentration of the catalyst precursor is relatively low, the catalyst particles formed on the sidewall of the first carbon nanotube have small size and low density, resulting in sparse distribution of the second carbon nanotube, and even the second carbon nanotube cannot be grown. If the concentration of the catalyst precursor is relatively high, the crystallization speed of the catalyst precursor is fast, and catalyst particles with large size and uneven structure are formed on the first carbon nanotube, which can grow into thick and disordered second carbon nanotube, and even the second carbon nanotube can fall off due to its large size.

[0087] Optionally, the solvent contained in the solution comprises at least one of ethanol, isopropyl alcohol and ethylene glycol. Optionally, the solvent is ethanol.

[0088] Specifically, the solvent isopropanol, ethylene glycol, and ethanol are all polar solvents, which can effectively dissolve iron salt / cobalt salt / nickel salt, and the volatility of isopropanol is close to that of ethanol, which can avoid excessive agglomeration of catalyst particles during drying, and the viscosity of ethylene glycol is slightly high, which can improve the adhesion of the catalyst raw material on the first carbon nanotube sidewall. Secondly, the volume concentration of the second carbon source is lower than that of the first carbon source, and is suitable for a low-temperature growth environment of 550-650°C, so that the carbon source can slowly decompose in a low-temperature environment, and the lower concentration of the second carbon source can avoid excessive carbon deposition leading to structural defects of the second carbon nanotube. In addition, methanol and acetone are carbon sources with easy volatilization and low decomposition temperature, which are suitable for growing fine-diameter second carbon nanotubes at low temperature, and can optimize the stability of carbon source supply in cooperation with ethanol.

[0089] The present application selects a solvent with low surface tension as described above, which not only can infiltrate the surface of the first carbon nanotube, but also can absorb the solution into the interior of the first carbon nanotube through capillary action, thereby improving the infiltration amount of the catalyst raw material on the first carbon nanotube. In addition, the volatility of solvents such as ethanol is strong during the drying process, which can prevent the catalyst particles from growing too large, and further ensure that the second carbon nanotubes with smaller size can be formed on the surface of the first carbon nanotube.

[0090] Alternatively, the catalyst raw material includes at least one of iron salt, cobalt salt and nickel salt. For example, the catalyst raw material includes at least one of ferric nitrate, ferric sulfate, ferric chloride, cobalt sulfate, cobalt chloride, cobalt nitrate, nickel sulfate, nickel chloride and nickel nitrate.

[0091] The volume concentration of the second carbon source in the chemical vapor deposition is 3%-10%, for example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%; the temperature is 550-650°C, for example, it can be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C or 650°C; the time is 1-3 minutes, for example, it can be 1.0 minute, 1.2 minutes, 1.4 minutes, 1.6 minutes, 1.8 minutes, 2.0 minutes, 2.2 minutes, 2.4 minutes, 2.6 minutes, 2.8 minutes or 3.0 minutes.

[0092] The present application selects the growth temperature of the second carbon nanotube as described above, which ensures the stable growth of the second carbon nanotube on the basis of avoiding damaging the first carbon nanotube. Further, a shorter growth time is adopted to grow the second carbon nanotube with small structure and random direction on the sidewall of the first carbon nanotube, to form a first carbon nanotube structure with dense branches (second carbon nanotubes) on the surface, so that the carbon nanotube array has a secondary structure similar to a forest.

[0093] Optionally, the second carbon source includes at least one of ethanol, methanol and acetone. The second carbon source can be ethanol. The use of ethanol and other easily decomposable carbon sources can further ensure the formation of second carbon nanotubes with small structure and random direction.

[0094] In some embodiments, the method for preparing the slurry containing the flaky conductive material includes: dispersing the flaky conductive material and the binder in a solvent, and stirring to form the slurry. It can be understood that the viscosity of the slurry can be adjusted according to the coating needs. The solvent can be selected according to the type of the binder, for example, N-methyl pyrrolidone can be used to dissolve polyvinylidene fluoride (PVDF), and deionized water can be used to dissolve styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC).

[0095] Optionally, the mass concentration of the flaky conductive material in the slurry is 8% to 15%, for example, it can be 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0096] Optionally, the slurry is coated on the surface of the substrate by at least one of a doctor blade coating, a micro-gravure coating and a spraying. During the coating process, the slurry penetrates and fills into the gaps of the carbon nanotube array, so that the flaky conductive agent is randomly laid or overlapped between the carbon nanotubes.

[0097] In some embodiments, after the slurry layer is formed on the surface of the substrate, the slurry layer is vacuum infiltrated and dried. Optionally, the drying temperature can be 80°C to 120°C. By vacuum infiltration, the slurry is ensured to fully penetrate into the carbon nanotube array, avoiding the formation of voids in the carbon coating layer.

[0098] Exemplarily, a method for preparing the carbon-coated current collector is provided, including the following steps:

[0099] A first catalyst layer with a thickness of 1 nm to 5 nm is deposited on the surface of the substrate; a plurality of first carbon nanotubes arranged on the first catalyst layer are formed by chemical vapor deposition of a first carbon source on the surface of the first catalyst layer. During the heating process of the chemical vapor deposition, the first catalyst layer agglomerates to form a plurality of nanoparticles with larger diameters due to surface tension, serving as the growth basis of the first carbon nanotubes. In the chemical vapor deposition, the volume concentration of the first carbon source is 5% to 15%, the temperature is 700°C to 800°C, and the time is 2 min to 5 min.

[0100] The substrate with the first carbon nanotubes is immersed in a solution with a catalyst raw material concentration of 0.01 mol / L to 0.1 mol / L for 5 s to 60 s; after the substrate is taken out, drying is performed, and after the solvent is volatilized, the catalyst raw material is crystallized on the side wall of the first carbon nanotubes; a second carbon source is used for chemical vapor deposition on the surface of the catalyst raw material to form a second carbon nanotube, so as to form a carbon nanotube array on the surface of the substrate. In the chemical vapor deposition, the volume concentration of the second carbon source is 3% to 10%, the temperature is 550°C to 650°C, and the time is 1 min to 3 min.

[0101] The slurry containing the flaky conductive material is coated to the surface of the substrate to form a slurry layer, vacuum infiltration and drying are sequentially performed on the slurry layer, and then the flaky conductive material is filled between adjacent first carbon nanotubes, so as to form a carbon-coated layer on the surface of the substrate.

[0102] The third aspect of the present application provides a pole piece, which comprises the carbon-coated current collector of the first aspect or the carbon-coated current collector prepared by the preparation method of the second aspect, and the carbon-coated current collector is provided with an active material layer on at least one side surface.

[0103] In the present application, the pole piece can be a positive pole piece or a negative pole piece. In the positive pole piece, the substrate of the carbon-coated current collector can be an aluminum foil. The positive electrode material can be a ternary positive electrode material or a lithium iron phosphate positive electrode material. In the negative pole piece, the substrate of the carbon-coated current collector can be a copper foil. The negative electrode material can be at least one of artificial graphite, natural graphite, silicon-carbon, hard carbon and lithium titanate.

[0104] It can be understood that the pole piece needs to be rolled after the active material layer is prepared. In the rolling process, the carbon nanotube array and the flaky conductive material in the carbon-coated layer will be partially broken, but the structure of the carbon-coated layer for longitudinal conduction will still be maintained.

[0105] The fourth aspect of the present application provides a battery, which comprises the pole piece of the third aspect.

[0106] It should be noted that the battery of the present application can be assembled from a positive pole piece, a negative pole piece, a separator and an electrolyte. The current collector in the positive pole piece and the negative pole piece can be the carbon-coated current collector described above. The separator can be a material with a polypropylene base material, and the electrolyte can be a commonly used electrolyte in the art, which is composed of an organic solvent, a lithium salt and an additive.

[0107] The embodiments of the present application will be described in detail below with reference to the examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods in the following examples without specific conditions are preferred to refer to the instructions given in the present application, and can also be performed according to the experimental manual or conventional conditions in the art, or according to the conditions suggested by the manufacturer, or by referring to the experimental methods known in the art.

[0108] Example 1

[0109] A 3nm-thick iron catalyst layer is deposited on the surface of an aluminum foil; acetylene is used as a first carbon source to form a plurality of first carbon nanotubes arranged on the iron catalyst layer by chemical vapor deposition on the surface of the iron catalyst layer, the average angle between the length direction of the first carbon nanotubes and the surface of the substrate is about 90°, the length of the first carbon nanotubes is 3μm, the diameter is 15nm, and the interval distance is 500nm. In the chemical vapor deposition, the volume concentration of acetylene is 10%, the temperature is 750℃, and the time is 3min.

[0110] The aluminum foil with the first carbon nanotubes is immersed in an ethanol solution with a concentration of 0.05mol / L of ferric nitrate for 30s; after the aluminum foil is taken out, it is dried, and after the solvent is volatilized, the ferric nitrate is crystallized on the side wall of the first carbon nanotubes; ethanol vapor is used as a second carbon source to form second carbon nanotubes on the surface of the ferric nitrate crystals by chemical vapor deposition, the length of the second carbon nanotubes is 1μm, the diameter is 2nm, and a carbon nanotube array is formed on the surface of the substrate. In the chemical vapor deposition, the volume concentration of the second carbon source is 6%, the temperature is 600℃, and the time is 2min.

[0111] Graphite, carboxymethyl cellulose, and water are mixed to form a slurry, the mass concentration of graphite in the slurry is 10%, the average flake diameter of the graphite is 1000nm, and the thickness is 100nm. The above-mentioned slurry is coated onto the surface of the aluminum foil with the carbon nanotube array to form a slurry layer, and after vacuum infiltration and 100℃ drying of the slurry layer are sequentially performed, the graphite is filled into the carbon nanotube array to form a carbon coating layer with a thickness of 5μm on the surface of the aluminum foil. In the carbon coating layer, the mass proportion of the carbon nanotube array is 18%, and the mass proportion of the graphite is 32%.

[0112] Example 2

[0113] A 1nm-thick iron catalyst layer is deposited on the surface of an aluminum foil; acetylene is used to form a plurality of first carbon nanotubes arranged on the iron catalyst layer by chemical vapor deposition on the surface of the iron catalyst layer, the average angle between the length direction of the first carbon nanotubes and the surface of the substrate is about 60°, the length of the first carbon nanotubes is 1μm, the diameter is 10nm, and the interval distance is 100nm. In the chemical vapor deposition, the volume concentration of acetylene is 5%, the temperature is 700℃, and the time is 2min.

[0114] The aluminum foil with the first carbon nanotubes is immersed in an ethanol solution with a concentration of 0.01 mol / L of ferric nitrate for 60 s; after the aluminum foil is taken out, it is dried, and after the solvent is volatilized, the ferric nitrate is crystallized on the side wall of the first carbon nanotube; a second carbon nanotube is formed on the surface of the ferric nitrate crystal by chemical vapor deposition of ethanol vapor, the length of the second carbon nanotube is 0.5 μm, and the diameter is 1 nm, so as to form a carbon nanotube array on the surface of the substrate. In the chemical vapor deposition, the volume concentration of the second carbon source is 3%, the temperature is 550°C, and the time is 1 min.

[0115] Graphite, carboxymethyl cellulose and water are mixed to form a slurry, the mass concentration of graphite in the slurry is 8%, the average flake diameter of graphite is 100 nm, and the thickness is 0.4 nm. The above slurry is coated onto the surface of the aluminum foil with the carbon nanotube array to form a slurry layer, and the slurry layer is sequentially subjected to vacuum infiltration and drying at 100°C, so that the graphite is filled into the carbon nanotube array to form a carbon coating layer on the surface of the aluminum foil. The mass proportion of the carbon nanotube array in the carbon coating layer is 8%, and the mass proportion of the graphite is 15%.

[0116] Example 3

[0117] An iron catalyst layer with a thickness of 5 nm is deposited on the surface of the aluminum foil; a plurality of first carbon nanotubes arranged on the iron catalyst layer are formed by chemical vapor deposition of acetylene on the surface of the iron catalyst layer, the average included angle between the length direction of the first carbon nanotube and the surface of the substrate is about 45°, the length of the first carbon nanotube is 6 μm, the diameter is 20 nm, and the interval distance is 1000 nm. In the chemical vapor deposition, the volume concentration of acetylene is 15%, the temperature is 800°C, and the time is 5 min.

[0118] The aluminum foil with the first carbon nanotubes is immersed in an ethanol solution with a concentration of 0.01 mol / L of ferric nitrate for 60 s; after the aluminum foil is taken out, it is dried, and after the solvent is volatilized, the ferric nitrate is crystallized on the side wall of the first carbon nanotube; a second carbon nanotube is formed on the surface of the ferric nitrate crystal by chemical vapor deposition of ethanol vapor, the length of the second carbon nanotube is 0.5 μm, and the diameter is 1 nm, so as to form a carbon nanotube array on the surface of the substrate. In the chemical vapor deposition, the volume concentration of the second carbon source is 3%, the temperature is 550°C, and the time is 1 min.

[0119] Graphite, carboxymethyl cellulose and water are mixed to form a slurry, the mass concentration of graphite in the slurry is 8%, the average flake diameter of graphite is 100 nm, and the thickness is 0.4 nm. The above slurry is coated onto the surface of the aluminum foil with the carbon nanotube array to form a slurry layer, and the slurry layer is sequentially subjected to vacuum infiltration and drying at 100°C, so that the graphite is filled into the carbon nanotube array to form a carbon coating layer on the surface of the aluminum foil. The mass proportion of the carbon nanotube array in the carbon coating layer is 8%, and the mass proportion of the graphite is 15%.

[0120] Example 4

[0121] The carbon-coated current collector was prepared according to the method of Example 1, except that the average flake diameter of the graphite was 80 nm.

[0122] Example 5

[0123] The carbon-coated current collector was prepared according to the method of Example 1, except that the average flake diameter of the graphite was 2500 nm.

[0124] Example 6

[0125] The carbon-coated current collector was prepared according to the method of Example 1, except that the content of the graphite in the slurry was adjusted so that the mass fraction of the graphite in the carbon-coated layer was 8%.

[0126] Example 7

[0127] The carbon-coated current collector was prepared according to the method of Example 1, except that the content of the graphite in the slurry was adjusted so that the mass fraction of the graphite in the carbon-coated layer was 45%.

[0128] Example 8

[0129] The carbon-coated current collector was prepared according to the method of Example 1, except that the concentration of the iron nitrate in the iron nitrate solution was 0.008 mol / L.

[0130] Example 9

[0131] The carbon-coated current collector was prepared according to the method of Example 1, except that the concentration of the iron nitrate in the iron nitrate solution was 0.12 mol / L.

[0132] Comparative Example 1

[0133] The carbon-coated current collector was prepared according to the method of Example 1, except that the second carbon nanotubes were not grown on the surface of the first carbon nanotubes.

[0134] Comparative Example 2

[0135] The carbon-coated current collector was prepared according to the method of Example 1, except that the first carbon nanotubes and the second carbon nanotubes were not grown on the surface of the foil, and carbon nanotubes with a length of 3 μm and a diameter of 15 nm were directly mixed into the slurry to form a carbon-coated layer on the surface of the foil.

[0136] The carbon-coated current collectors prepared in the above examples and comparative examples were subjected to performance testing, and the testing method included:

[0137] Comprehensive resistance test: four-probe method was used to measure conductivity. The probes were symmetrically pressed on the surface of the carbon coating layer and the corresponding area of the substrate at a distance of 2 mm. A constant current of 1 mA was applied, and the overall conductivity of the carbon coating layer was tested to comprehensively reflect the transverse and longitudinal conductivity, with the unit of mΩ·cm;

[0138] Rate performance test: the carbon-coated current collector was prepared into a positive electrode sheet. The active material was LiNi 0.8 Co 0.1 Mn 0.1 O2, and a graphite negative electrode, a PP separator, and 1 mol / L LiPF6 electrolyte were assembled into a button cell. At 25°C, the cell was charged to 4.3V at 0.5C and discharged to 3.0V at 1C and 3C, respectively. The discharge capacity retention rate at 1C and 3C was recorded, i.e., the percentage relative to the 0.5C discharge capacity.

[0139] Cycle stability test: the above button cell was charged and discharged at 1C at 25°C, with a voltage range of 4.3V~3.0V. After 100 cycles, the capacity retention rate was recorded, i.e., the percentage relative to the first 1C discharge capacity.

[0140] Table 1

[0141]

[0142] Table 2

[0143]

[0144] In combination with Tables 1 and 2, it can be seen from Comparative Examples 1-9 and Comparative Examples 1-2 that the application utilizes the combination of "point (carbon nanotube tip) - line (carbon nanotube body) - surface (sheet-shaped conductive material)", which synergistically forms a three-dimensional conductive structure far superior to the performance of traditional random mixed conductive networks, can form a three-dimensional and anisotropic three-dimensional conductive network, significantly reduces the longitudinal resistance of the electrode sheet, and further improves the rate performance and cycle stability of the battery.

[0145] As can be seen from Comparative Example 1 and Examples 4-5, as the size of the sheet-shaped conductive material increases, it will affect the planar conductive network formed by the sheet-shaped conductive material, thereby affecting the comprehensive conductivity. Therefore, the application controls the distance between the sheet-shaped conductive material and the first carbon nanotube, thereby forming a continuous planar conductive network in the carbon coating layer without affecting the longitudinal conductivity of the first carbon nanotube.

[0146] As can be seen from Comparative Example 1 and Examples 6-7, as the mass of the carbon nanotube array increases, it will affect the planar conductive network formed by the sheet-shaped conductive material, thereby affecting the comprehensive conductivity. Therefore, the application controls the mass ratio of the carbon nanotube array and the sheet-shaped conductive material, which can balance the longitudinal conductivity and transverse conductivity of the carbon coating layer.

[0147] As can be seen from Comparative Example 1 and Examples 8-9, with the increase of the concentration of the catalyst raw material during the growth of the second carbon nanotubes, the size of the second catalyst layer on the sidewall of the second carbon nanotubes is affected, and thus the size of the second carbon nanotubes is affected. Therefore, the concentration of the catalyst raw material solution used in the growth of the second carbon nanotubes is controlled to ensure the size and distribution of the second carbon nanotubes, and thus the conductive performance of the carbon coating layer is improved.

[0148] As can be seen from Comparative Example 1 and Comparative Examples 1-2, the first carbon nanotubes arranged on the surface of the substrate in the carbon coating layer of the present application serve as "conductive pillars", providing a direct and low-resistance vertical channel for the transmission of electrons from the substrate to the active material layer. Further, the second carbon nanotubes grown on the sidewall of the first carbon nanotubes serve as branch structures, which not only increase the specific surface area of the carbon coating layer, but also further improve the adhesion between the carbon coating layer and the active layer, and can also cooperate with the sheet-shaped conductive material filled between the first carbon nanotubes to form an efficient horizontal conductive network, thereby connecting each "conductive pillar" into a whole, and improving the conductive performance of the carbon coating layer.

[0149] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present disclosure.

[0150] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A carbon-coated current collector, characterized by, The carbon coating layer comprises a carbon nanotube array and a sheet-shaped conductive material. The carbon coating layer satisfies at least one of the following conditions: (1) the average included angle between the length direction of the first carbon nanotube and the surface of the substrate is 45°-90°; (2) the average sheet diameter of the sheet-shaped conductive material is 1-5 times the spacing distance between adjacent first carbon nanotubes; 2. The carbon-coated current collector of claim 1, wherein (3) the length of the first carbon nanotube is 1-6 μm, the diameter is 10-20 nm, and the spacing distance between adjacent first carbon nanotubes is 100-1000 nm; (4) the length of the second carbon nanotube is 0.5-2 μm, and the diameter is 1-3 nm; (5) the average sheet diameter of the sheet-shaped conductive material is 100-2000 nm, and the thickness is 0.4-200 nm. The carbon coating layer further satisfies at least one of the following conditions: (1) the mass ratio of the carbon nanotube array to the sheet-shaped conductive material in the carbon coating layer is 1:(1-4); (2) the mass percentage of the carbon nanotube array in the carbon coating layer is 5%-30%; 3. The carbon-coated current collector of claim 1, wherein (3) the mass percentage of the sheet-shaped conductive material in the carbon coating layer is 10%-40%; (4) the carbon coating layer further comprises a binder filled between adjacent first carbon nanotubes, and the mass percentage of the binder in the carbon coating layer is 10%-30%. The surface of the substrate is distributed with a plurality of first catalyst layers, and the first carbon nanotubes are arranged on the first catalyst layers; And / or, the sidewall of the first carbon nanotube is distributed with a plurality of second catalyst layers, and the second carbon nanotubes are arranged on the second catalyst layers. The carbon coating layer further satisfies at least one of the following conditions:

4. The carbon-coated current collector according to any one of claims 1 to 3, wherein (1) the thickness of the first catalyst layer is 1-5 nm, and the average diameter of the first catalyst layer is 20-50 nm; (2) the thickness of the second catalyst layer is 1-5 nm, and the average diameter of the second catalyst layer is 5-20 nm; 5. The carbon-coated current collector of claim 4, wherein (3) the material of the first catalyst layer and the material of the second catalyst layer independently comprise at least one of iron, cobalt and nickel. The preparation method comprises: growing first carbon nanotubes on at least one side surface of a substrate, wherein the growth direction of the first carbon nanotubes is away from the substrate; then growing second carbon nanotubes on the sidewall of the first carbon nanotubes to form a carbon nanotube array on the surface of the substrate; applying a slurry containing a sheet-shaped conductive material to the surface of the substrate having the carbon nanotube array, so that the sheet-shaped conductive material is filled between adjacent first carbon nanotubes to form a carbon coating layer on the surface of the substrate.

6. A method for producing a carbon-coated current collector, characterized by, ​ ​ ​ 7. The method of producing a carbon-coated current collector according to claim 6, wherein The method for growing the first carbon nanotubes comprises: depositing a first catalyst layer on a surface of the substrate; and using a first carbon source to perform chemical vapor deposition on a surface of the first catalyst layer to form a plurality of the first carbon nanotubes arranged on the first catalyst layer.

8. The method of claim 7, wherein the carbon-coated current collector is prepared by the steps of: The method for growing the first carbon nanotubes satisfies at least one of the following conditions: (1) the volume concentration of the first carbon source in the chemical vapor deposition is 5% to 15%, the temperature is 700°C to 800°C, and the time is 2 min to 5 min; (2) the first carbon source comprises at least one of acetylene, methane, and ethylene.

9. The method of producing a carbon-coated current collector according to any one of claims 6 to 8, wherein The method for growing the second carbon nanotubes comprises: immersing the substrate with the first carbon nanotubes in a solution containing a catalyst raw material; and after taking out the substrate, drying to crystallize the catalyst raw material on a side wall of the first carbon nanotube; and using a second carbon source to perform chemical vapor deposition on a surface of the catalyst raw material to form the second carbon nanotube.

10. The method of claim 9, wherein the carbon-coated current collector is prepared by the steps of: The method for growing the second carbon nanotube satisfies at least one of the following conditions: (1) the time for immersing the substrate in the solution is 5 s to 60 s; (2) the concentration of the catalyst raw material contained in the solution is 0.01 mol / L to 0.1 mol / L; (3) the solvent contained in the solution comprises at least one of ethanol, isopropyl alcohol, and ethylene glycol; (4) the catalyst raw material comprises at least one of iron salt, cobalt salt, and nickel salt; (5) the volume concentration of the second carbon source in the chemical vapor deposition is 3% to 10%, the temperature is 550°C to 650°C, and the time is 1 min to 3 min; (6) the second carbon source comprises at least one of ethanol, methanol, and acetone.

11. A pole piece characterized by, The electrode plate comprises the carbon-coated current collector according to any one of claims 1 to 5 or the carbon-coated current collector prepared by the method according to any one of claims 6 to 10, and at least one side surface of the carbon-coated current collector is provided with an active material layer.

12. A battery, characterized by The battery comprises the electrode plate according to claim 11.

Images