Method for preparing carbon nanotube / nano-metal composite material by melting method and application thereof

Abstract

The application discloses a method for preparing carbon nanotube / nano metal composite material by a melting method and application, and belongs to the technical field of lithium battery negative electrode materials. The preparation method of the composite material is as follows: Fe-Ni-Cu-Sn quaternary alloy is used as a catalyst, the catalyst is completely melted into a liquid state under temperature rising in inert gas protection, methane gas is introduced into the liquid alloy, and a catalytic cracking reaction is carried out at 870-920 DEG C; after the reaction is completed, natural cooling is continued under inert gas protection, a black fluffy solid product is collected, and after purification treatment, the carbon nanotube / nano metal composite material is obtained. The composite material can be used as an active material to prepare a lithium ion battery negative electrode sheet, and can be further assembled to form a button cell. The application integrates tin-based active phase nanodispersion, carbon nanotube conductive network construction, Fe3C catalytic enhancement and inert skeleton buffer multiple functions into one, and cooperatively improves the comprehensive electrochemical performance of the carbon nanotube / nano metal composite material.

Description

Technical Field

[0001] This invention relates to the field of lithium battery anode material technology, and in particular to a method for preparing carbon nanotube / nanometal composite materials by melt method and its application. Background Technology

[0002] The anode material for lithium-ion batteries is one of the key factors determining the battery's energy density. Currently, the theoretical specific capacity of commercially available graphite anodes is 372 mAh / g, which is insufficient to meet the ever-increasing demand for high energy density. Tin-based materials, with their theoretical specific capacity as high as 994 mAh / g, are considered important candidates for next-generation anode materials. However, tin-based materials exhibit significant volume expansion during charge and discharge, resulting in extremely poor cycle stability, which severely limits their practical application.

[0003] To improve the cycling stability of tin-based anodes, researchers have proposed several strategies. Introducing inert elements to form multi-component alloys can effectively buffer volume changes, but these inert elements are mostly introduced externally, and their synergistic effect with the active tin phase is limited. Carbon material composites are another effective method, as the carbon matrix can provide a conductive network and inhibit the agglomeration of active particles, but this usually requires a step-by-step process, making the preparation process complex. Summary of the Invention To address the problems of poor cycle stability, complex preparation processes, and weak interfacial bonding between the carbon matrix and the active tin phase in existing tin-based anode materials, this invention provides a method for preparing carbon nanotube / nanometal composite materials via a melt process. This carbon nanotube / nanometal composite material is used as an anode material for lithium-ion batteries.

[0004] The method for preparing carbon nanotube / nanometal composite materials by melt method provided by the present invention comprises the following steps: Step S1: Prepare Fe-Ni-Cu-Sn quaternary alloy; The atomic ratio of Fe:Ni:Cu:Sn in the Fe-Ni-Cu-Sn quaternary alloy is (18-22):(6-10):(1.5-3):(65-75). Preferably, the atomic ratio of Fe:Ni:Cu:Sn is 20:8:2:70.

[0005] The preparation method of quaternary alloys is as follows: Iron, nickel, copper, and tin sources are added to deionized water and mixed evenly under stirring and / or ultrasonic conditions to form a slurry. The slurry is then dried at 110-200℃ to remove moisture, yielding precursor powder. The precursor powder is calcined and reduced at 850-900℃ in a reducing atmosphere for 4-12 hours, and finally cooled naturally in the furnace or rapidly under an inert atmosphere to obtain a blocky Fe-Ni-Cu-Sn quaternary alloy.

[0006] The iron source is selected from at least one of iron oxide, iron(II,III) oxide, iron nitrate, iron chloride, and iron acetate, preferably iron oxide and / or iron nitrate.

[0007] The nickel source is selected from at least one of nickel oxide, nickel nitrate, nickel chloride, and nickel acetate, preferably nickel oxide and / or nickel nitrate.

[0008] The copper source is selected from at least one of copper oxide, cuprous oxide, copper nitrate, copper chloride, and copper acetate, preferably copper oxide and / or copper nitrate.

[0009] The tin source is selected from at least one of tin oxide, tin dioxide, tin powder, and stannous chloride, preferably tin oxide and / or tin dioxide.

[0010] The original atmosphere is hydrogen or a mixture of hydrogen and nitrogen.

[0011] The obtained bulk Fe-Ni-Cu-Sn quaternary alloy still needs to undergo surface purification treatment to remove residual organic matter and adsorbed impurities from the alloy surface, so as to obtain a clean bulk alloy that can be directly used in subsequent methane cracking reactions.

[0012] The surface impurity removal method is as follows: The bulk Fe-Ni-Cu-Sn quaternary alloy is immersed in an organic solvent that does not chemically react with Fe, Ni, Cu, and Sn. It is then cleaned under ultrasonic or stirring conditions. After removal, it is rinsed with deionized water and vacuum dried to complete the surface pretreatment. The organic solvent is selected from at least one of anhydrous ethanol, acetone, isopropanol, and n-hexane, preferably anhydrous ethanol or acetone. The ultrasonic cleaning time is 10-30 minutes, and the ultrasonic power is 50-150W. The vacuum drying temperature is 50-70℃, and the drying time is 2-4 hours.

[0013] Step S2: Using a Fe-Ni-Cu-Sn quaternary alloy as a catalyst, the catalyst is heated under inert gas protection to completely melt into a liquid state; then methane gas is introduced into the liquid alloy, and a catalytic cracking reaction is carried out at 870-920℃.

[0014] Specifically, the surface-treated blocky Fe-Ni-Cu-Sn quaternary alloy is placed at the bottom of a tubular furnace reactor and heated to 880-920℃ under inert gas protection at a rate of 4-6℃ / min, and held for 20-40 minutes to ensure complete melting and uniform temperature of the quaternary alloy, forming a liquid alloy pool. Then, methane gas (flow rate of 20-50 mL / min) is introduced from the bottom of the reactor to the bottom of the liquid alloy for catalytic cracking at 870-920℃ for 5-10 hours. During this process, methane is catalytically cracked into carbon atoms and hydrogen on the surface of the liquid alloy. Carbon atoms undergo a dissolution-precipitation mechanism to grow carbon nanotubes in situ on the surface of the liquid alloy, while some carbon atoms diffuse into the alloy and react with Fe to form Fe3C.

[0015] The inert gas is one of neon, argon, or helium.

[0016] Step S3: After the methane cracking reaction is completed, the methane supply is stopped, and the mixture is allowed to cool naturally under an inert gas atmosphere. During the cooling process, Fe and Sn dissolved in the liquid alloy precipitate due to decreased solubility, forming FeSn2 nanoparticles. Simultaneously, Fe3C nanoparticles also precipitate. The precipitated FeSn2 and Fe3C nanoparticles are then in situ coated by the generated carbon nanotube network. After cooling to room temperature, the black, fluffy solid product is collected. After purification, a carbon nanotube-coated FeSn2 / Fe3C tin-based composite material is obtained, which is a carbon nanotube / nanometallic composite material.

[0017] The specific method for purifying the black, fluffy solid product is as follows: The black, fluffy solid product was added to anhydrous ethanol and ultrasonically dispersed to form a black suspension. Unreacted residual metal precipitated at the bottom. The upper suspension was taken and filtered. The filter cake was collected and vacuum dried. After drying, it was ball-milled under inert gas (argon or helium) protection to finally obtain carbon nanotube / nanometal composite material.

[0018] The ultrasonic power is 100~200W, and the ultrasonic time is 15~30 minutes. The vacuum drying temperature is 60~80℃, and the drying time is 6~12 hours.

[0019] This invention also provides a method for applying a carbon nanotube / nanometal composite material: the carbon nanotube / nanometal composite material is used as a negative electrode material for lithium-ion batteries. The carbon nanotube / nanometal composite material is mixed and ground with a conductive agent, and a binder is added to form a uniform slurry. The slurry is coated onto the surface of a copper foil, and the vacuum-dried copper foil is cut into circular electrode sheets with a diameter of 14 mm, then compacted to obtain a lithium-ion battery negative electrode sheet. This lithium-ion battery negative electrode sheet is further assembled to form a button cell.

[0020] Compared with the prior art, the advantages of the present invention are: (1) This invention provides a novel method for preparing tin-based anode materials, resulting in a novel carbon nanotube-coated nano-FeSn2 / Fe3C tin-based composite material. The preparation method employs an alloy system with FeSn as the main component and Ni and Cu as auxiliary elements. Utilizing the catalytic activity of Ni for methane cracking and the promoting effect of Cu on carbon graphitization, efficient in-situ growth of carbon nanotubes is achieved at temperatures of 870-920℃, significantly reducing reaction energy consumption and enabling precise control of the morphology of the carbon products. Simultaneously, the liquid alloy environment allows FeSn2 and Fe3C nanoparticles to precipitate synchronously and be in-situ coated during carbon nanotube growth, forming a tightly bonded chemical interface. Furthermore, a small amount of Ni forms the Ni3Sn4 phase, which acts as an auxiliary buffer framework, further enhancing the structural stability of the electrode. Therefore, this invention integrates multiple functions, including nano-dispersion of the tin-based active phase, construction of a carbon nanotube conductive network, Fe3C catalytic enhancement, and inert framework buffering, synergistically improving the comprehensive electrochemical performance of the composite material. Among them, nano-sized FeSn2 alleviates volume expansion, carbon nanotubes provide fast conductive channels and elastic buffers, Fe3C catalyzes the reversible transformation of the SEI film to contribute additional capacity, and Ni3Sn4 assists in enhancing structural stability.

[0021] (2) Electrochemical tests showed that the carbon nanotube / nanometal composite material was effective in the charge-discharge voltage range of 0.01~1.2V and the current density of 100mA·g. -1 After 200 cycles, the specific capacity remained stable at over 550 mAh / g, far exceeding that of commercial carbon nanotubes (approximately 110 mAh / g) and Ni / Cu binary alloy derivatives (below 150 mAh / g), fully demonstrating the significant advantages of the method of this invention in improving the overall performance of lithium battery anodes.

[0022] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0023] Figure 1 The XRD patterns are of the materials prepared in Example 1 and different comparative examples.

[0024] Figure 2 The images show the microstructure and elemental analysis results of the material prepared in Example 1. (a) is a SEM image, (b)-(f) are EDS spectra, and (g) is an elemental distribution map.

[0025] Figure 3 A comparison graph showing the cycling performance of material samples prepared in different embodiments and comparative examples. Detailed Implementation

[0026] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0027] Example 1 A method for preparing carbon nanotube / nanometallic composite materials by melt processing is as follows: S1. Preparation of alloy materials: Iron oxide, nickel oxide, copper oxide, and tin dioxide powders were weighed according to the atomic ratio Fe:Ni:Cu:Sn = 20:8:2:70. The various powders were added to deionized water, mixed under stirring at 500 r / min, and ultrasonically dispersed to form a slurry. The slurry was dried at 150℃ to obtain precursor powder. The precursor powder was placed in an alumina boat and heated to 880℃ at a heating rate of 5℃ / min under a hydrogen atmosphere, calcined and reduced for 8 h, and then naturally cooled to room temperature in the furnace. The resulting bulk Fe-Ni-Cu-Sn quaternary alloy was obtained.

[0028] The prepared Fe-Ni-Cu-Sn quaternary alloy was immersed in anhydrous ethanol and ultrasonically cleaned for 20 minutes under an ultrasonic power of 100W. After being removed, it was rinsed with deionized water and vacuum dried at 60℃ for 3 hours to complete the surface impurity removal treatment.

[0029] S2. Place the surface-cleaned blocky Fe-Ni-Cu-Sn quaternary alloy at the bottom of a tubular furnace reactor. Introduce argon gas into the reactor for 30 minutes to purge air. Then, under argon protection, heat the alloy to 900°C at a rate of 5°C / min and hold for 30 minutes, at which point the alloy completely melts to form a liquid alloy pool. Introduce methane gas into the liquid alloy from the bottom of the reactor at a flow rate of 30 mL / min and maintain the reaction at 900°C for 8 hours. Methane molecules decompose into carbon atoms and hydrogen gas, and carbon nanotubes grow in situ on the surface of the liquid alloy through a dissolution-precipitation mechanism.

[0030] S3. After the reaction is complete, stop the methane supply and allow the mixture to cool naturally to room temperature under argon protection. During cooling, Fe and Sn dissolved in the liquid alloy precipitate due to decreased solubility, forming FeSn2 nanoparticles. Simultaneously, Fe3C nanoparticles formed by the reaction of some carbon atoms with Fe also precipitate. The precipitated nanoparticles are in situ coated by the already formed carbon nanotube network. Due to the density difference, the black, fluffy solid product floats on the alloy surface. After cooling to room temperature, open the reactor and collect the black, fluffy solid product, which is the carbon nanotube / nanometal composite material (crude product).

[0031] S4. Purification of the carbon nanotube / nanometal composite material (crude product): 0.5 g of the product collected in step S3 was placed in a beaker, and 200 ml of anhydrous ethanol was added. The mixture was ultrasonically dispersed at 150 W for 20 min to form a black suspension. Because the metal has a higher density, it precipitated at the bottom of the beaker after ultrasonication. The upper part of the suspension was vacuum filtered, and the lower precipitated metal was discarded. The filter cake obtained by vacuum filtration was vacuum dried at 70 °C for 10 h. The dried material powder was placed in a ball mill jar and subjected to planetary ball milling under argon protection. The ball milling media was agate balls, the ball-to-material ratio was 8:1, the ball milling speed was 300 rpm, and the ball milling time was 2 h, finally obtaining a uniformly dispersed carbon nanotube / nanometal composite material powder.

[0032] Battery Assembly and Electrochemical Testing: Weigh 35 mg of the carbon nanotube / nanometallic composite powder obtained in step S4, mix it with the conductive agent acetylene black at a mass ratio of 7:2 and grind it evenly. Add the binder solution (4 wt% PVDF NMP solution) to make the mass ratio of composite material, conductive agent and binder 7:2:1, and continue grinding until the slurry is uniform. Coat the slurry onto the surface of copper foil with a coating thickness of 100 μm, and vacuum dry it at 60 °C for 12 h. Cut the dried copper foil into circular electrode sheets with a diameter of 14 mm, wrap them with weighing paper and press them on a mold to obtain the negative electrode sheet. Before battery assembly, weigh the obtained electrode sheets and seal them for later use. In a glove box filled with argon (oxygen and water content are both less than 1 ppm), assemble the button cell in the following order: positive electrode shell - electrode sheet - separator - electrolyte - lithium sheet - stainless steel gasket - spring sheet - negative electrode shell. The assembled battery was subjected to constant current charge-discharge cycle testing, with a charge-discharge voltage range of 0.01~1.2V and a current density of 100mA·g. -1 The cycle count was 200 times to evaluate the cycling performance of the electrode material.

[0033] Example 2 Based on Example 1, the preparation method was adjusted as follows: In step S1, the raw material powders are weighed according to the atomic ratio Fe:Ni:Cu:Sn = 18:10:2:70. The calcination reduction temperature is 850℃, and the calcination reduction time is 12h.

[0034] In step S2, the temperature for both alloy melting and methane cracking reaction is 920℃, the methane gas flow rate is 50mL / min, and the holding time is 10h.

[0035] In step S4, the ball-to-material ratio is 5:1, the ball milling speed is 350 rpm, and the ball milling time is 1.5 h.

[0036] The remaining steps and parameters are the same as in Example 1.

[0037] Example 3 Based on Example 1, the preparation method was adjusted as follows: In step S1, each raw material powder is weighed according to the atomic ratio Fe:Ni:Cu:Sn = 21:7:2.5:69.5. The calcination reduction temperature is 900℃, and the calcination reduction time is 4h.

[0038] In step S2, the temperature for both alloy melting and methane cracking reaction is 870℃, the methane gas flow rate is 20mL / min, and the holding time is 5h.

[0039] In step S4, the ball-to-material ratio is 5:1, the ball mill speed is 400 rpm, and the ball milling time is 1 hour.

[0040] The remaining steps and parameters are the same as in Example 1.

[0041] Comparative Example 1 Commercial multi-walled carbon nanotubes were used directly as the active material. Electrodes were prepared and batteries were assembled using the same method as in Example 1 for electrochemical testing.

[0042] Comparative Example 2 The difference from Example 1 is that in step S1, no nickel or copper source is added, and iron oxide and tin dioxide powders are weighed according to the atomic ratio Fe:Sn = 22:78. The calcination reduction temperature is 880℃, and the calcination reduction time is 8 hours. In step S3, the heating temperature is 920℃ to ensure that the Fe-Sn binary alloy melts completely at a higher temperature. The remaining steps and parameters are the same as in Example 1.

[0043] Comparative Example 3 Based on Example 1, in step S4, the filter cake obtained by vacuum filtration is dried at 70°C for 10 hours, and then, without ball milling, the dried material powder is directly used to prepare electrodes and assemble batteries for electrochemical testing. The remaining steps and parameters are the same as in Example 1.

[0044] Comparative Example 4 The difference from Example 1 is as follows: In step S1, no tin source is added, and iron oxide, nickel oxide, and copper oxide powders are weighed according to the atomic ratio Fe:Ni:Cu = 70:20:10. The calcination reduction temperature is 880℃, and the calcination reduction time is 8h, obtaining a Fe-Ni-Cu ternary alloy block. In step S2, due to the high melting point of the Fe-Ni-Cu ternary alloy, the alloy remains solid at the reaction temperature of 900℃. The specific operation is as follows: The surface-cleaned block alloy is placed at the bottom of the reactor and heated to 900℃ under argon protection and held at this temperature. At this temperature, the alloy remains in a solid block form. Subsequently, methane gas (30mL / min) is introduced from the bottom of the reactor to carry out the reaction, and the reaction time is 8h. After the reaction is completed, the carbon material obtained after the reaction is collected. The remaining steps and parameters are the same as in Example 1.

[0045] Comparative Example 5 The difference from Example 1 is as follows: In step S1, no iron source is added, and tin dioxide, nickel oxide, and copper oxide powders are weighed according to the atomic ratio Sn:Ni:Cu = 70:20:10. The calcination reduction temperature is 880℃, and the calcination reduction time is 8 hours to obtain a Sn-Ni-Cu ternary alloy block. In step S2, the alloy melting and methane cracking reaction temperatures are both 900℃, at which temperature the alloy is in a liquid state. Methane is introduced and reacted for 8 hours using the same process. After the reaction is complete, the carbon material obtained after the reaction is collected. The remaining steps and parameters are the same as in Example 1.

[0046] Comparative Example 6 Commercially available multi-walled carbon nanotubes (CNTs), FeSn2 nanoparticles, and Fe3C nanoparticles were used directly as raw materials. FeSn2 nanoparticles were prepared using the most common chemical reduction method (polyol method), which involves a one-pot reduction of a metal salt precursor in a polyol solvent. Each raw material was weighed according to a mass ratio of CNTs:FeSn2:Fe3C = 2:5:3. The three powders were then placed directly into a ball mill jar and subjected to planetary ball milling under argon protection. The milling media were agate balls, the ball-to-material ratio was 8:1, the milling speed was 300 rpm, and the milling time was 2 h, resulting in a physically mixed composite powder. Subsequently, this physically mixed powder was used as the active material to prepare electrodes and assemble batteries according to the same method as in Example 1 for electrochemical testing.

[0047] Figure 1 The figures show the XRD patterns of the materials prepared in Example 1 and different comparative examples (Comparative Examples 2, 4, and 5). As can be seen from the figures, Example 1 successfully prepared the target phases FeSn2, Fe3C, and Ni3Sn4 using a one-step Fe-Ni-Cu-Sn quaternary alloy method. Due to the high atomic percentage content of Sn in the catalyst, a large amount of Sn remains in the product. Comparative Example 2 lacks Ni and therefore does not have the Ni3Sn4 phase; Comparative Example 4 only has the Fe3C phase; and Comparative Example 5 has both Ni3Sn4 and Sn phases, but no Fe3C phase.

[0048] Figure 2 The images show the microstructure and elemental analysis results of the material prepared in Example 1. (a) is the SEM image, (b)-(f) are the EDS spectra, and (g) is the elemental distribution map. The SEM image confirms the successful preparation of carbon nanotubes. The EDS spectra and elemental distribution map confirm the successful preparation of carbon nanotube-coated FeSn2 / Fe3C tin-based composite materials.

[0049] Figure 3The figures show the cycling performance of different embodiments and comparative samples. The results indicate that the materials prepared in Examples 1-3 exhibit good cycling performance in the charge / discharge voltage range of 0.01–1.2 V and at a current density of 100 mA·g. -1 After 200 cycles, the specific capacity remained stable at over 550 mAh / g, far exceeding that of the commercial carbon nanotubes in Comparative Example 1 (below 100 mAh / g) and the material obtained using the physical mixing method in Comparative Example 6 (below 200 mAh / g). The cycling performance of the materials obtained in Comparative Examples 2, 4, and 5 was significantly lower than that of Examples 1-3 due to changes in the alloy composition. The cycling performance of the material obtained in Comparative Example 3 was also significantly lower than that of Examples 1-3 because the ball milling step was omitted. This fully demonstrates the significant advantages of the composite material prepared in this invention in improving the overall performance of lithium-ion battery anodes.

[0050] In summary, this invention innovatively introduces highly catalytically active Ni and graphitization-promoting Cu, enabling the Fe-Ni-Cu-Sn quaternary alloy to efficiently catalyze methane cracking and grow high-quality carbon nanotubes at 870-920℃, significantly reducing reaction energy consumption and achieving precise control over the morphology of carbon products. Simultaneously, this invention utilizes the simultaneous precipitation of nano-FeSn2 and Fe3C particles during the cooling process of this liquid alloy, which are then tightly coated by the in-situ grown carbon nanotube network. This completes the construction of a carbon-based conductive network, the generation of the active phase, and in-situ composite in one step, greatly simplifying the complex step-by-step preparation process of traditional tin-based anode materials. Furthermore, the chemical bonding interface effectively solves the problems of high contact resistance and weak bonding caused by physical mixing, resulting in a multi-functional carbon nanotube / nano-metal composite material for preparing lithium-ion battery anodes.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing carbon nanotube / nanometallic composite materials by melt processing, characterized in that, A Fe-Ni-Cu-Sn quaternary alloy was used as a catalyst. The catalyst was heated under inert gas protection to completely melt it into a liquid state. Then, methane gas was introduced into the liquid alloy, and a catalytic cracking reaction was carried out at 870-920℃. After the reaction was completed, the mixture was allowed to cool naturally under inert gas protection. The black, fluffy solid product was collected and purified to obtain a carbon nanotube / nanometal composite material. The atomic ratio of Fe:Ni:Cu:Sn in the Fe-Ni-Cu-Sn quaternary alloy was (18-22):(6-10):(1.5-3):(65-75).

2. The method for preparing carbon nanotube / nanometal composite materials by melt method as described in claim 1, characterized in that, The preparation method of the Fe-Ni-Cu-Sn quaternary alloy is as follows: Iron, nickel, copper, and tin sources are added to deionized water and mixed evenly. The mixed slurry is then dried to obtain precursor powder. The precursor powder is calcined and reduced at 850-900℃ for 4-12 hours in a reducing atmosphere. After cooling, Fe-Ni-Cu-Sn quaternary alloy is obtained.

3. The method for preparing carbon nanotube / nanometal composite materials by melt method as described in claim 1, characterized in that, The Fe-Ni-Cu-Sn quaternary alloy is heated to a melting temperature of 880~920℃ and held for 20~40 minutes to ensure that the quaternary alloy is completely melted into a liquid state and that the temperature is uniform.

4. The method for preparing carbon nanotube / nanometal composite materials by melt method as described in claim 1, characterized in that, The catalytic cracking reaction takes 5-10 hours.

5. The method for preparing carbon nanotube / nanometal composite materials by melt method as described in claim 1, characterized in that, The inert gas is one of neon, argon, or helium.

6. The method for preparing carbon nanotube / nanometal composite materials by melt method as described in claim 1, characterized in that, The method for purifying the black, fluffy solid product is as follows: The black, fluffy solid product was added to anhydrous ethanol and ultrasonically dispersed to form a black suspension. Unreacted residual metal precipitated at the bottom. The upper suspension was taken and filtered. The filter cake was collected and vacuum dried. After drying, it was ball-milled under inert gas protection to finally obtain a carbon nanotube / nanometal composite material.

7. A carbon nanotube / nanometal composite material prepared by the method according to any one of claims 1-6.

8. A method for applying the carbon nanotube / nanometal composite material as described in claim 7, characterized in that, The composite material is used as a negative electrode material for lithium-ion batteries. The carbon nanotube / nano-metal composite material is mixed and ground with a conductive agent, and a binder is added to form a uniform slurry. The slurry is coated onto the surface of a copper foil, and the copper foil is cut into circular electrode sheets with a diameter of 14 mm after vacuum drying. Then it is compacted to obtain the negative electrode sheet for lithium-ion batteries.

9. The application method as described in claim 8, characterized in that, The lithium-ion battery negative electrode sheet is used to assemble button batteries.

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