A tin disulfide-helical carbon nanofiber composite material and its preparation method and application

Abstract

The present invention belongs to the field of electrode material technology, and in particular to a tin disulfide-helical carbon nanofiber composite material and its preparation method and application. The present invention mixes spiral carbon nanofibers, a tin source, an organic precipitant, an organic dispersant and an organic solvent to carry out a solvent thermal reaction, and then calcines the reaction product to obtain a tin dioxide-helical carbon nanofiber composite material, and then vulcanizes it in a sulfur vapor atmosphere to finally obtain a tin disulfide-helical carbon nanofiber composite material. The sulfide product prepared by the present invention not only has high purity and high crystallinity, but also has excellent structural stability and electrochemical performance under high current and long-term charge and discharge working conditions. At the same time, the method provided by the present invention does not need to wash and dry the sulfide product when preparing the sulfide product, the operating steps are relatively simple and easy to control, the production cost is greatly reduced, and it has a prospect for large-scale application.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and in particular relates to a tin disulfide-helical carbon nanofiber composite material and a preparation method and application thereof. Background Art

[0002] Currently, all electrical devices, from emerging new energy electric vehicles and portable wearable devices to cutting-edge space exploration equipment and military equipment, require high-performance, safe, and low-cost energy storage batteries to safeguard their operation. The rational design and utilization of energy storage batteries is a key constraint on the development of these industries. Among the numerous battery technologies being developed, lithium-ion secondary batteries are widely used in various energy storage devices due to their advantages, such as long cycle life, high discharge capacity, high operating voltage, low self-discharge, and minimal memory effect. Existing lithium-ion batteries are produced in a wide variety of types and appearances. Electrode materials are the primary factor limiting their development, directly determining the performance of the battery system. The anode material, in turn, is a key factor in determining battery performance. Currently, the commercially available anode material for lithium-ion batteries is graphite, which is widely distributed in nature and inexpensive. However, it suffers from drawbacks such as low initial charge and discharge coulombic efficiency and organic solvent co-intercalation during battery operation. Furthermore, graphite has a theoretical specific capacity of only 372 mAh / g, significantly limiting the energy density of lithium-ion batteries using graphite as anode material. Therefore, the development of new negative electrode materials has become one of the important directions for the development and innovation of the energy storage battery industry.

[0003] In recent years, with the in-depth study of negative electrode materials for lithium-ion batteries, tin dioxide (SnO2) and tin disulfide (SnS2) have attracted widespread attention due to their electrochemical advantages such as high theoretical specific capacity and relatively low redox reaction potential. Compared with SnO2 with a lattice spacing of 0.34nm, SnS2 has a lattice spacing of up to 0.59nm, which is beneficial to Li + Rapid intercalation / deintercalation between SnS2 nanocrystalline lattices. In addition, SnO2 has a theoretical specific capacity of 782 mAh / g, while SnS2 has a theoretical specific capacity of up to 1232 mAh / g. At the same time, SnO2 undergoes a two-step energy storage reaction process during lithium storage, while SnS2 undergoes a three-step energy storage reaction process during lithium storage, indicating that SnS2 has potential and excellent long cycle life and high capacity discharge performance.

[0004] However, pure SnS2 still has many shortcomings when used as a negative electrode material for lithium-ion batteries. For example, there is a certain degree of first irreversible reaction, which results in low initial charge and discharge efficiency; during the charge and discharge process, serious volume expansion, structural collapse and damage occur, causing the SnS2 active component to pulverize. What is more serious is that the active material falls off and collapses from the electrode sheet, which will lead to deterioration of cycle stability and seriously limit its large-scale application.

[0005] Chinese patent CN201610192008.1 discloses a method for preparing SnO2 / SnS2 / CNTS electrode material for lithium-ion battery negative electrode, wherein SnO2 and SnS2 are loaded on carbon fiber (CNTS) to improve the electrochemical properties of SnO2 and SnS2. The method mainly comprises three steps: (1) using ultrasonic treatment to thoroughly mix CNTs and SnCl2·2H2O; (2) transferring the mixed suspension to a hydrothermal reactor, and using hydrothermal reaction to graft SnO2 onto the surface of CNTs to obtain a SnO2 / CNTs composite material; (3) grinding and mixing the SnO2 / CNTs composite material with sublimated sulfur, and placing it in a vacuum tube furnace for sulfurization, thereby obtaining a SnO2 / SnS2 / CNTS electrode material. This patented technology grinds and mixes the SnO2 / CNTs composite material with sublimated sulfur and then performs vulcanization. Subsequently, a large amount of water and anhydrous ethanol are required to wash the powder and then dry it, which greatly increases the preparation cost. In addition, the prepared SnS2 has a low crystallinity, which is not conducive to improving the structural stability and electrochemical performance when used as a negative electrode material for lithium-ion batteries. Summary of the Invention

[0006] The purpose of the present invention is to provide a tin disulfide-helical nanocarbon fiber composite material, a preparation method and application thereof. The tin disulfide-helical nanocarbon fiber composite material provided by the present invention has high structural stability and excellent electrochemical properties under high current and long-term charge and discharge working conditions when used as a negative electrode material for lithium-ion batteries, and has great application potential as a negative electrode material for lithium-ion batteries.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a tin disulfide-helical carbon nanofiber composite material, comprising the following steps:

[0009] mixing the spiral carbon nanofibers, a tin source, an organic precipitant, an organic dispersant and an organic solvent to obtain a mixed liquid;

[0010] subjecting the mixed liquid to a solvothermal reaction to obtain a precursor mixture;

[0011] calcining the precursor mixture to obtain a tin dioxide-helical carbon nanofiber composite material; the tin dioxide-helical carbon nanofiber composite material comprises helical carbon nanofibers and tin dioxide nanoparticles loaded on the surface of the helical carbon nanofibers;

[0012] The tin dioxide-helical carbon nanofiber composite material is vulcanized in a sulfur vapor atmosphere to obtain a tin disulfide-helical carbon nanofiber composite material; the tin disulfide-helical carbon nanofiber composite material includes helical carbon nanofibers and tin disulfide nanoparticles loaded on the surface of the helical carbon nanofibers.

[0013] Preferably, the vulcanization comprises the following steps:

[0014] A double-layer container is provided, comprising a first container with a lid and a second container disposed within the first container, a gap being left between the first container and the second container, and the height of the first container being greater than the height of the second container;

[0015] The tin dioxide-helical carbon nanofiber composite material is placed in the second container; and sulfur is placed in the interlayer;

[0016] In a protective gas, the first container is covered and heated to obtain sulfur vapor, so that the tin dioxide-helical carbon nanofiber composite material is vulcanized in the sulfur vapor atmosphere.

[0017] Preferably, the heating rate of the heating is 3 to 5° C. / min; the holding temperature of the vulcanization is 500 to 600° C., and the holding time is 1 to 3 hours.

[0018] Preferably, the mass ratio of the tin dioxide-helical carbon nanofiber composite material to the sulfur element is (1-3): (5-25); the ratio of the mass of the sulfur element to the volume of the first container is (5-25) g: 120000 mm 2 .

[0019] Preferably, the tin source is anhydrous stannous chloride; the mass ratio of the spiral carbon nanofibers to the tin source is (1-3):(1-3).

[0020] Preferably, the organic precipitant is an alkali metal acetate; and the mass ratio of the tin source to the organic precipitant is (1-3):(2-6).

[0021] The organic dispersant is polyvinyl pyrrolidone; the mass ratio of the tin source to the organic dispersant is (1-3):(2-10).

[0022] The organic solvent is ethanol; the ratio of the mass of the tin source to the volume of the organic solvent is (1-3) g: (40-70) mL.

[0023] Preferably, the solvent thermal reaction is carried out in a closed reaction container, and the volume of the mixed liquid accounts for 40-70% of the volume of the closed reaction container; the temperature of the solvent thermal reaction is 80-120° C., and the insulation time is 4-8 hours.

[0024] The present invention provides a tin disulfide-helical carbon nanofiber composite material prepared by the preparation method described in the above technical solution, comprising helical carbon nanofibers and tin disulfide nanoparticles loaded on the surface of the helical carbon nanofibers.

[0025] Preferably, the particle size of the tin disulfide nanoparticles is 5 to 20 nm; and the spiral diameter of the spiral nanocarbon fibers is 60 to 90 nm.

[0026] The present invention provides the use of the tin disulfide-helical carbon nanofiber composite material described in the above technical solution as a negative electrode material for a lithium ion battery.

[0027] The invention provides a preparation method of a tin disulfide-helical carbon nanofiber composite material, comprising the following steps: mixing helical carbon nanofibers, a tin source, an organic precipitant, an organic dispersant and an organic solvent to obtain a mixed liquid; subjecting the mixed liquid to a solvent thermal reaction to obtain a precursor mixture; calcining the precursor mixture to obtain a tin dioxide-helical carbon nanofiber composite material; the tin dioxide-helical carbon nanofiber composite material comprises helical carbon nanofibers and tin dioxide nanoparticles supported on the surface of the helical carbon nanofibers; and vulcanizing the tin dioxide-helical carbon nanofiber composite material in a sulfur vapor atmosphere to obtain a tin disulfide-helical carbon nanofiber composite material; the tin disulfide-helical carbon nanofiber composite material comprises helical carbon nanofibers and tin disulfide nanoparticles supported on the surface of the helical carbon nanofibers. The present invention does not require any acid-base surface modification, vacuum heat treatment or other pretreatment of the spiral nanocarbon fibers. The solvent thermal method can be used to graft uniformly attached tin dioxide nanoparticles on the surface of the spiral nanocarbon fibers. Subsequently, only a simple sulfurization method in a sulfur vapor atmosphere is required to obtain a composite material of in-situ growth of tin disulfide nanoparticles on the surface of the spiral nanocarbon fibers. The sulfurized product (tin disulfide) prepared by the method provided by the present invention is not only of high purity and high crystallinity, but also has high crystallinity. The high crystallinity helps to improve the structural stability and electrochemical performance of the lithium-ion battery, thereby having high structural stability and excellent electrochemical performance under large current and long-term charge and discharge working conditions. At the same time, compared with the prior art solution in which the precursor mixture is ground and mixed with sublimated sulfur and then sulfurized and the sulfurized product is repeatedly washed with deionized water and anhydrous ethanol after the sulfurization is completed, the sulfurized product prepared by the method provided by the present invention does not need to be washed and dried, thereby making the preparation method provided by the present invention relatively simple in operation steps, easy to control, and the production cost is greatly reduced, with huge potential for large-scale application.

[0028] The present invention provides a tin disulfide-helical nanocarbon fiber composite material prepared by the preparation method described in the above technical solution, comprising helical nanocarbon fibers and tin disulfide nanoparticles loaded on the surface of the helical nanocarbon fibers. The present invention uses helical nanocarbon fibers (HCNFs) as a matrix support material. HCNFs is a carbon nanomaterial with a helical structure. It exhibits a nanometer-sized three-dimensional helical structure and has a large specific surface area. It can fully contact with SnS2 nanoparticles as electrochemically active substances. In addition, a large number of active groups such as carboxyl and hydroxyl groups on the surface can promote the independent and uniform dispersion of SnS2 nanoparticles on the surface of the carbon matrix, thereby enhancing the wettability of the electrolyte to the active substance and improving the electronic conductivity and ion transport capacity. At the same time, the nanosized SnS2 particles are uniformly attached to the surface of the HCNFs in situ, and the HCNFs reserve a suitable three-dimensional expansion space for the SnS2 nanoparticles, which can effectively inhibit the occurrence of particle pulverization and volume expansion of the SnS2 nanoparticles during electrode operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the XRD spectrum of the electrode materials in Comparative Example 1 and Comparative Example 2;

[0030] Figure 2 XRD spectra of the SnS2@HCNFs composite negative electrode materials obtained in Examples 1 to 4;

[0031] Figure 3 2 are SEM images of the composite materials in Example 2 and Comparative Example 2;

[0032] Figure 4 2 is a comparison chart of the electrochemical performance of the negative electrode materials obtained in Example 2 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0033] The present invention provides a method for preparing a tin disulfide-helical carbon nanofiber composite material, comprising the following steps:

[0034] mixing the spiral carbon nanofibers, a tin source, an organic precipitant, an organic dispersant and an organic solvent to obtain a mixed liquid;

[0035] subjecting the mixed liquid to a solvothermal reaction to obtain a precursor mixture;

[0036] calcining the precursor mixture to obtain a tin dioxide-helical carbon nanofiber composite material; the tin dioxide-helical carbon nanofiber composite material comprises helical carbon nanofibers and tin dioxide nanoparticles loaded on the surface of the helical carbon nanofibers;

[0037] The tin dioxide-helical carbon nanofiber composite material is vulcanized in a sulfur vapor atmosphere to obtain a tin disulfide-helical carbon nanofiber composite material; the tin disulfide-helical carbon nanofiber composite material includes helical carbon nanofibers and tin disulfide nanoparticles loaded on the surface of the helical carbon nanofibers.

[0038] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0039] The invention mixes spiral carbon nanofibers, a tin source, an organic precipitant, an organic dispersant and an organic solvent to obtain a mixed liquid.

[0040] In the present invention, the spiral diameter of the spiral nanocarbon fiber is preferably 60 to 90 nm, more preferably 80 nm. In the present invention, the spiral diameter of the spiral nanocarbon fiber refers to the cross-sectional width of a single spiral nanocarbon fiber. The fiber length of the spiral nanocarbon fiber is preferably 20 to 200 μm, more preferably 40 to 160 μm. In the present invention, the fiber length of the spiral nanocarbon fiber refers to the length of a single spiral nanocarbon fiber. In the present invention, the pitch of the spiral nanocarbon fiber is preferably 65 to 95 nm, more preferably 60 to 90 nm.

[0041] In the present invention, the spiral carbon nanofibers are preferably prepared by chemical vapor deposition, and the temperature of the chemical vapor deposition is preferably 290-300° C. The present invention has no special requirements on the specific implementation of the chemical vapor deposition method for preparing the spiral carbon nanofibers.

[0042] The preparation method provided by the present invention does not require any pretreatment of the spiral nanocarbon fibers such as acid-base surface modification or vacuum heat treatment. SnO2 nanoparticles can be grafted onto the surface of the carbon matrix using a solvent thermal method.

[0043] The present invention adopts HCNFs as the carbon matrix. HCNFs are carbon nanomaterials with a unique structure, which presents a nanometer-sized three-dimensional spiral structure. Within the above-mentioned spiral diameter, length and pitch parameter range, HCNFs have a large specific surface area and can fully contact with SnS2 nanoparticles as electrochemically active substances. In addition, the large number of active groups such as carboxyl and hydroxyl groups on the surface can promote the independent and uniform dispersion of SnS2 nanoparticles on the carbon matrix surface, enhance the wettability of the electrolyte to the active material, and improve the electronic conductivity and ion transport capacity. At the same time, HCNFs reserve suitable three-dimensional expansion space for SnS2 nanoparticles, which can effectively inhibit the occurrence of particle pulverization and volume expansion of SnS2 nanoparticles during electrode operation.

[0044] In the present invention, the tin source is preferably anhydrous stannous chloride. The present invention selects the anhydrous stannous chloride of stable chemical property as tin source, compared with the anhydrous tin tetrachloride or tin tetrachloride pentahydrate used in the prior art, anhydrous tin tetrachloride easily hydrolyzes and produces pungent odor, tin tetrachloride pentahydrate in crystallized block is not convenient for taking, and all need to add hydrolysis inhibitor before reaction, also need to introduce alkali lye in the reaction process, this makes the reaction process not convenient for operation, control, is difficult to control reaction rate and reaction end, causes the consistency of product to be poor. And the present invention adopts the anhydrous stannous chloride in powder state to be able to store for a long time under normal temperature conditions, is not easy to hydrolyze, does not need to additionally add inhibitor or stabilizer in chemical reaction system, can be directly dissolved in absolute ethanol or deionized water, and technical operation process is simpler and controllable is higher.

[0045] In the present invention, the mass ratio of the spiral carbon nanofibers to the tin source is preferably (1-3):(1-3), more preferably (1.5-2.5):(1.5-2.5).

[0046] In the present invention, the organic precipitant is preferably an alkali metal acetate, more preferably sodium acetate. In the present invention, sodium acetate is preferably used as the organic precipitant. During the solvent thermal reaction, the alkali metal acetate decomposes to produce hydroxide, which reacts with Sn in the mixed liquid. 2+ A precipitation reaction occurs, and Sn(OH)2 is generated in situ on the surface of the helical nanocarbon fibers.

[0047] In the present invention, the mass ratio of the tin source to the organic precipitant is preferably (1-3):(2-6), more preferably (1.5-2.5):(2.5-5.5).

[0048] In the present invention, the organic dispersant is preferably polyvinyl pyrrolidone. In the present invention, polyvinyl pyrrolidone is preferably used as the organic dispersant, which can better disperse the tin dioxide nanoparticles evenly and graft them on the surface of HCNFs.

[0049] In the present invention, the mass ratio of the tin source to the organic dispersant is preferably (1-3):(2-10), more preferably (1.5-2.5):(2.5-9).

[0050] In the present invention, the organic solvent is preferably ethanol. The present invention uses ethanol as the organic solvent to reduce costs.

[0051] In the present invention, the ratio of the mass of the tin source to the volume of the organic solvent is preferably (1-3) g: (40-70) mL, more preferably (1.5-2.5) g: (40-70) mL.

[0052] In the present invention, the mixing is preferably performed under ultrasonic conditions, with the ultrasonic temperature preferably being 25-30°C, the ultrasonic power preferably being 50-80W, and the ultrasonic duration preferably being 10-20 minutes. Ultrasonic mixing is preferred in the present invention to achieve a more uniform dispersion of HCNFs in the mixed liquid.

[0053] After obtaining the mixed liquid, the present invention performs a solvent thermal reaction on the mixed liquid to obtain a precursor mixture.

[0054] In the present invention, the solvothermal reaction is preferably carried out in a sealed reaction vessel, with the volume of the mixed liquid preferably accounting for 40-70%, preferably 45-65%, of the volume of the sealed reaction vessel. The solvothermal reaction temperature is preferably 80-120°C, more preferably 90-110°C; the holding time is preferably 4-8 hours, more preferably 4.5-7 hours. The solvothermal reaction pressure is preferably 2-3 MPa.

[0055] In the present invention, the volume of the mixed liquid preferably accounts for 40-70% of the volume of the closed reaction container, which can avoid the pressure in the closed container for the solvent thermal reaction from meeting 2-3 MPa and avoid excessive or insufficient pressure in the closed container.

[0056] In the present invention, the solvent thermal reaction is preferably carried out in a reactor lined with polytetrafluoroethylene.

[0057] In the present invention, the temperature of the solvent thermal reaction cannot be too high or too low. If the reaction temperature is too high, the decomposition rate of acetate will be too fast, and Sn(OH)2 will be generated too quickly, which is not conducive to the uniform dispersion and growth of Sn(OH)2 on the surface of HCNFs; if the reaction temperature is too low, the decomposition rate of acetate will be too slow, which is not conducive to the generation of Sn(OH)2.

[0058] In the present invention, after the solvothermal reaction is completed, a solvothermal reaction liquid is obtained. The present invention preferably post-treats the solvothermal reaction liquid after cooling to room temperature to obtain the precursor mixture. In the present invention, the post-treating preferably includes: solid-liquid separation of the solvothermal reaction liquid to obtain a precipitate; and sequentially washing and drying the precipitate to obtain the precursor mixture. In the present invention, the solid-liquid separation is preferably performed by suction filtration. The washing is preferably performed by deionized water; the drying is preferably performed by forced air drying, preferably at a temperature of 60 to 80°C, more preferably 60°C, and for a time of 10 to 12 hours. The drying is preferably performed in a forced air drying oven.

[0059] After obtaining the precursor mixture, the present invention calcines the precursor mixture to obtain a tin dioxide-helical nanocarbon fiber composite material; the tin dioxide-helical nanocarbon fiber composite material includes helical nanocarbon fibers and tin dioxide nanoparticles loaded on the surface of the helical nanocarbon fibers.

[0060] In the present invention, the calcination temperature is preferably 350-400°C, and the calcination time is preferably 1.5-2.5 hours. In the present invention, during the calcination process, the Sn(OH)2 grown in situ on the surface of the HCNFs decomposes into SnO2, thereby obtaining a tin dioxide-helical nanocarbon fiber composite material, which is referred to as SnO2@HCNFs in the present invention.

[0061] After obtaining the tin dioxide-helical carbon nanofiber composite material, the tin dioxide-helical carbon nanofiber composite material is vulcanized in a sulfur vapor atmosphere to obtain a tin disulfide-helical carbon nanofiber composite material (denoted as SnS2@HCNFs in the present invention); the tin disulfide-helical carbon nanofiber composite material includes helical carbon nanofibers and tin disulfide nanoparticles loaded on the surface of the helical carbon nanofibers.

[0062] In the present invention, the vulcanization preferably comprises the following steps:

[0063] A double-layer container is provided, comprising a first container with a lid and a second container disposed within the first container, a gap being left between the first container and the second container, and the height of the first container being greater than the height of the second container;

[0064] The tin dioxide-helical carbon nanofiber composite material is placed in the second container; and sulfur is placed in the interlayer;

[0065] In a protective gas, the first container is covered and then heated to obtain sulfur vapor, so that the tin dioxide-helical carbon nanofiber composite material is vulcanized in the sulfur vapor atmosphere.

[0066] The present invention provides a double-layer container, which includes a first container with a cover and a second container arranged in the first container, a gap interlayer is left between the first container and the second container, and the height of the first container is greater than that of the second container.

[0067] In a specific embodiment of the present invention, the first container is an alumina crucible porcelain boat with a cover, and the size of the first container is 100 mm×40 mm×30 mm.

[0068] In a specific embodiment of the present invention, the second container is an uncovered alumina crucible porcelain boat, and the size of the second container is 60 mm×30 mm×20 mm.

[0069] In a specific embodiment of the present invention, the second container is located at the center of the first container.

[0070] In the present invention, the tin dioxide-helical carbon nano-fiber composite material is placed in the second container; and elemental sulfur is placed in the interlayer.

[0071] In the present invention, the mass ratio of the tin dioxide-helical nano-carbon fiber composite material and the sulfur element is preferably (1-3): (5-25), more preferably (1.5-2.5): (4.5-25), further preferably 2: (10-25), and most preferably 1:5.

[0072] In the present invention, the mass ratio of the tin dioxide-helical carbon nanofiber composite material to the sulfur element should be neither too high nor too low. If the mass ratio is too low, the sulfur element cannot form sufficient sulfur vapor to completely sulfide the tin dioxide into tin sulfide, resulting in too low a crystallinity of the tin sulfide, which is detrimental to the structural stability and electrochemical performance of the lithium-ion battery. If the mass ratio is too high, the sulfur element forms excessive sulfur vapor, resulting in too low a purity of the tin sulfide, which is detrimental to the structural stability and electrochemical performance of the lithium-ion battery.

[0073] In the present invention, the ratio of the mass of the sulfur element to the volume of the first container is preferably (5-25) g:120000 mm 3 , more preferably (6-24) g: 120000 mm 3 .

[0074] In a protective gas, the first container is covered and then heated to obtain sulfur vapor, so that the tin dioxide-helical carbon nanofiber composite material is vulcanized in the sulfur vapor atmosphere.

[0075] The present invention preferably places the double-layer container in the center of the tube furnace and heats the first container in a protective gas. In the present invention, the protective gas is preferably Ar.

[0076] In the present invention, the heating rate is preferably 3-5°C / min, more preferably 5°C / min; the vulcanization holding temperature is preferably 500-600°C, more preferably 550-600°C; and the holding time is preferably 1-3h.

[0077] In the present invention, the vulcanization temperature is 500-600°C to ensure that the tin dioxide and sulfur vapor react completely to form tin disulfide. If the temperature is too low, the tin dioxide cannot be completely vulcanized. If the temperature is too high, the sulfur element will quickly decompose and volatilize, reducing the chance of contact between the sulfur and the tin dioxide. Furthermore, too high a temperature wastes energy.

[0078] During the vulcanization process, the SnO2@HCNFs composite material is separated from the sublimed sulfur and placed. Compared with the prior art solution in which the precursor mixture and the sublimed sulfur are ground and mixed before vulcanization, and the vulcanized product is repeatedly washed with deionized water and anhydrous ethanol after the vulcanization, the preparation method provided by the present invention not only prepares a vulcanized product with high purity without the need for any washing and drying of the vulcanized product, but also the vulcanization process is not affected by the flow rate of the Ar gas, the operation steps are relatively simple and easy to control, the production cost is greatly reduced, and the method has huge potential for large-scale application.

[0079] The preparation method provided by the present invention uses HCNFs as a carbon matrix, anhydrous stannous chloride as a tin source, sodium acetate as a precipitant, and polyvinyl pyrrolidone as a dispersant. A simple and efficient solvent thermal method is used to directly graft tin dioxide nanoparticles (hereinafter referred to as SnO2) onto the surface of HCNFs to obtain a SnO2@HCNFs composite material; then, the present invention uses a sulfur vapor vulcanization method to in-situ phase-transform the SnO2 nanoparticles on the surface of HCNFs into SnS2 nanoparticles, thereby preparing a SnS2@HCNFs composite negative electrode material in which SnS2 nanoparticles are in-situ grown on the surface of spiral nanocarbon fibers, which greatly reduces the preparation cost and the prepared SnS2 nanoparticles have high crystallinity and purity.

[0080] The present invention provides a tin disulfide-helical carbon nanofiber composite material prepared by the preparation method described in the above technical solution, comprising helical carbon nanofibers and tin disulfide nanoparticles loaded on the surface of the helical carbon nanofibers.

[0081] In the present invention, the particle size of the tin disulfide nanoparticles is preferably 5 to 30 nm, more preferably 5 to 20 nm. In the present invention, the spiral diameter of the spiral nanocarbon fibers is preferably 60 to 90 nm, more preferably 80 nm.

[0082] In the present invention, SnS2 nanoparticles are discretely and uniformly loaded on the surface of HCNFs. HCNFs provide suitable three-dimensional expansion space for SnS2 nanoparticles, effectively suppressing particle pulverization and volume expansion during electrode operation.

[0083] The present invention provides the use of the tin disulfide-helical carbon nanofiber composite material described in the above technical solution as a negative electrode material for a lithium ion battery.

[0084] The present invention provides a lithium ion battery negative electrode active material, comprising the tin disulfide-helical carbon nanofiber composite material described in the above technical solution, a conductive agent and an adhesive.

[0085] In the present invention, the conductive agent is preferably conductive carbon black (SuperP).

[0086] In the present invention, the adhesive is preferably sodium carboxymethylcellulose (CMC).

[0087] In the present invention, the mass ratio of the tin disulfide-helical carbon nanofiber composite material, the adhesive and the conductive agent is preferably 7:1:2.

[0088] The present invention provides a method for preparing a lithium ion battery negative electrode from the lithium ion battery negative electrode material described in the above technical solution, comprising the following steps:

[0089] The tin disulfide-helical carbon nanofiber composite material, a conductive agent, a binder and deionized water are mixed to obtain a negative electrode slurry;

[0090] The negative electrode slurry is coated on the surface of the current collector and then dried, and the negative electrode sheet of the lithium ion battery is obtained after the electrode sheet is cut into pieces.

[0091] In the present invention, the current collector is preferably copper foil. The present invention has no special requirements on the coating thickness and the specific implementation process of the coating, and the conventional coating thickness and operation familiar to those skilled in the art can be adopted; in the present invention, the drying is preferably vacuum drying, and the drying temperature is preferably 70-120°C, more preferably 80-100°C; the drying time is preferably 12h.

[0092] The present invention provides a lithium-ion battery comprising a counter electrode sheet, an electrolyte, a separator, and a negative electrode sheet. The counter electrode sheet is preferably a metallic lithium sheet, and the electrolyte preferably comprises LiPF6 and additives, wherein the additives comprise ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC). The molar concentration of LiPF6 in the electrolyte is preferably 1 mol / L, and the volume ratio of EC, DEC, and DMC is preferably 1:1:1.

[0093] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0094] Example 1

[0095] (1) HCNFs with a size of 60 nm were prepared as the carbon matrix material by low-temperature chemical vapor deposition (CVD) at 290°C. 0.1 g of HCNFs, 0.1 g of anhydrous stannous chloride, 0.2 g of sodium acetate, and 0.4 g of polyvinylpyrrolidone were weighed and placed in a 100 mL beaker. 40 mL of anhydrous ethanol was added to the beaker and ultrasonically dispersed for 10 min to obtain a black suspension.

[0096] (2) The black suspension obtained above was transferred to a reactor lined with polytetrafluoroethylene, with the liquid filling degree of the reactor being 40%, and then reacted at a temperature of 90°C for 6 hours. After the reaction was completed, the tank was allowed to cool naturally to room temperature to obtain a black precipitate;

[0097] (3) collecting the black precipitate in step (2) by suction filtration, washing with deionized water, drying the filter cake in a forced air drying oven at 60° C. for 10 h, and finally calcining at 350° C. to obtain a SnO2@HCNFs composite material;

[0098] (4) Weigh 0.1 g of the SnO2@HCNFs composite material obtained above and place it in an uncovered alumina crucible boat (small boat) with dimensions of 60 mm × 30 mm × 20 mm (length × width × height). The boat is then placed in the center of another covered alumina crucible boat (large boat) with dimensions of 100 mm × 40 mm × 30 mm. Then weigh 0.25 g of sublimated sulfur powder and spread it on the bottom area of ​​the large boat between the inner wall of the large boat and the outer wall of the small boat. Finally, cover the large boat with a lid.

[0099] (5) The large porcelain boat was placed in the center of a tube furnace, and Ar gas was used as the protective gas. The temperature was raised to 550°C at a rate of 4°C / min and kept at 550°C for 2 h. Finally, the SnS2@HCNFs composite negative electrode material was prepared, in which the average particle size of the SnS2 nanoparticles was about 5 nm.

[0100] Example 2

[0101] (1) HCNFs with a size of 80 nm were prepared as the carbon matrix material by low-temperature chemical vapor deposition (CVD) at 295°C. 0.1 g of HCNFs, 0.15 g of anhydrous stannous chloride, 0.3 g of sodium acetate, and 0.6 g of polyvinylpyrrolidone were weighed and placed in a 100 mL beaker. 50 mL of anhydrous ethanol was added to the beaker and ultrasonically dispersed for 15 min to obtain a black suspension.

[0102] (2) The black suspension obtained above was transferred to a reactor lined with polytetrafluoroethylene, with the liquid filling degree of the reactor being 50%, and then reacted at a temperature of 90°C for 6 hours. After the reaction was completed, the tank was allowed to cool naturally to room temperature to obtain a black precipitate;

[0103] (3) collecting the black precipitate in step (2) by suction filtration, washing with deionized water, drying the filter cake in a forced air drying oven at 60° C. for 10 h, and finally calcining at 350° C. to obtain a SnO2@HCNFs composite material;

[0104] (4) Weigh 0.2 g of the SnO2@HCNFs composite material obtained above and place it in an uncovered alumina crucible boat (small boat) with dimensions of 60 mm × 30 mm × 20 mm (length × width × height). The boat is then placed in the center of another covered alumina crucible boat (large boat) with dimensions of 100 mm × 40 mm × 30 mm. Then weigh 1.0 g of sublimated sulfur powder and spread it on the bottom area of ​​the large boat between the inner wall of the large boat and the outer wall of the small boat. Finally, cover the large boat with a lid.

[0105] (5) The large porcelain boat was placed in the center of a tube furnace, and Ar gas was used as the protective gas. The temperature was raised to 550°C at a rate of 4°C / min and kept at 550°C for 2 h. Finally, the SnS2@HCNFs composite negative electrode material was prepared, in which the average particle size of the SnS2 nanoparticles was about 10 nm.

[0106] Example 3

[0107] (1) HCNFs with a size of 80 nm were prepared as the carbon matrix material by low-temperature chemical vapor deposition (CVD) at 295°C. 0.2 g of HCNFs, 0.2 g of anhydrous stannous chloride, 0.4 g of sodium acetate, and 0.6 g of polyvinylpyrrolidone were weighed and placed in a 100 mL beaker. 60 mL of anhydrous ethanol was added to the beaker and ultrasonically dispersed for 20 min to obtain a black suspension.

[0108] (2) The black suspension obtained above was transferred to a reactor lined with polytetrafluoroethylene, with the liquid filling degree of the reactor being 60%, and then reacted at a temperature of 100°C for 5 hours. After the reaction was completed, the tank was allowed to cool naturally to room temperature to obtain a black precipitate;

[0109] (3) collecting the black precipitate in step (2) by suction filtration, washing with deionized water, drying the filter cake in a forced air drying oven at 80° C. for 8 h, and finally calcining at 350° C. to obtain a SnO2@HCNFs composite material;

[0110] (4) Weigh 0.2 g of the SnO2@HCNFs composite material obtained above and place it in an uncovered alumina crucible boat (small boat) with dimensions of 60 mm × 30 mm × 20 mm (length × width × height). The boat is then placed in the center of another covered alumina crucible boat (large boat) with dimensions of 100 mm × 40 mm × 30 mm. Then, weigh 1.75 g of sublimated sulfur powder and spread it on the bottom area of ​​the large boat between the inner wall of the large boat and the outer wall of the small boat. Finally, cover the large boat with a lid.

[0111] (5) The large porcelain boat was placed in the center of a tube furnace, and Ar gas was used as the protective gas. The temperature was heated to 575°C at a heating rate of 6°C / min and kept at 575°C for 3 h. Finally, the SnS2@HCNFs composite negative electrode material was prepared, in which the average particle size of the SnS2 nanoparticles was about 15 nm.

[0112] Example 4

[0113] (1) HCNFs with a size of 90 nm were prepared as the carbon matrix material by low-temperature chemical vapor deposition (CVD) at 300°C. 0.2 g of HCNFs, 0.25 g of anhydrous stannous chloride, 0.5 g of sodium acetate, and 0.8 g of polyvinylpyrrolidone were weighed and placed in a 100 mL beaker. 60 mL of anhydrous ethanol was added to the beaker and ultrasonically dispersed for 20 min to obtain a black suspension.

[0114] (2) The black suspension obtained above was transferred to a reactor lined with polytetrafluoroethylene, with the liquid filling degree of the reactor being 60%, and then reacted at a temperature of 100°C for 5 hours. After the reaction was completed, the tank was allowed to cool naturally to room temperature to obtain a black precipitate;

[0115] (3) collecting the black precipitate in step (2) by suction filtration, washing with deionized water, and finally drying the filter cake in a forced air drying oven at 80° C. for 8 h to obtain a SnO2@HCNFs composite material;

[0116] (4) Weigh 0.2 g of the SnO2@HCNFs composite material obtained above and place it in an uncovered alumina crucible boat (small boat) with dimensions of 60 mm × 30 mm × 20 mm (length × width × height). The boat is then placed in the center of another covered alumina crucible boat (large boat) with dimensions of 100 mm × 40 mm × 30 mm. Then, weigh 2.5 g of sublimated sulfur powder and spread it on the bottom area of ​​the large boat between the inner wall of the large boat and the outer wall of the small boat. Finally, cover the large boat with a lid.

[0117] (5) The large porcelain boat was placed in the center of a tube furnace, and Ar gas was used as the protective gas. The temperature was heated to 575°C at a heating rate of 6°C / min and kept at 575°C for 3 h. Finally, the SnS2@HCNFs composite negative electrode material was prepared, in which the average particle size of the SnS2 nanoparticles was about 20 nm.

[0118] Application Example 1

[0119] The SnS2@HCNFs negative electrode active material prepared in Example 1, Example 2, Example 3, or Example 4 was ground and mixed with sodium carboxymethyl cellulose (CMC) and conductive carbon black (SuperP) in a mass ratio of 7:1:2 to form a negative electrode slurry. This slurry was then evenly coated on the bright side of a copper foil current collector. After the water in the coating slurry evaporated, the resulting coated sheet was placed in a vacuum drying oven at 80°C for 12 hours. The coated sheet was cut into circular electrode sheets with a diameter of 12 mm using an MSK-T10 electrode sheet cutter. Coin-type cells were assembled in a glove box with a water and oxygen content of less than 0.1 ppm using a lithium metal sheet as the counter electrode, a 1 mol / L LiPF6 mixture (with additives including EC, DEC, and DMC in a 1:1:1 volume ratio) as the electrolyte, and a polypropylene microporous membrane as the separator. The cells were tested for constant current charge and discharge using a CT-4000Tn battery tester produced by Shenzhen Xinweier Electronics Co., Ltd. Test conditions: room temperature 25°C, atmospheric environment, charge and discharge voltage range 0.01~3V, and 100 cycles of charge and discharge at a current density of 200mA / g.

[0120] Comparative Example 1

[0121] The method is basically the same as that of Application Example 1, except that the pure HCNFs prepared in Example 2 are used instead of the SnS2@HCNFs composite material prepared in Example 1, Example 2, Example 3 or Example 4 as the negative electrode material, and the battery assembly and testing methods are the same as those in Application Example 1.

[0122] Comparative Example 2

[0123] The method is basically the same as that of Application Example 1, except that the SnO2@HCNFs composite material prepared in Example 2 is used instead of the SnS2@HCNFs composite material prepared in Example 1, Example 2, Example 3 or Example 4 as the negative electrode material, and the battery assembly and testing implementation methods are the same as those in Application Example 1.

[0124] Figure 1 The XRD patterns of the HCNFs carbon matrix material and the SnO2@HCNFs composite material prepared in Example 2 are shown. Comparing the XRD characteristic peaks of HCNFs and SnO2@HCNFs composite materials, it can be seen that the latter has obvious characteristic peaks at 26.611°, 33.893°, 37.949°, and 51.780° compared with the former. These peaks have a high degree of match with the standard characteristic peaks of the standard material card JCPDS.No.41-1445, corresponding to the (110), (101), (200), and (211) crystal planes of SnO2, respectively. This shows that the material prepared in Example 2 is a SnO2@HCNFs composite material with a confirmed physical phase. Figure 3(a) is the SEM image of the SnO2@HCNFs composite material prepared in Example 2. Figure 3 It can be seen from (a) that the surface of the SnO2@HCNFs composite material is relatively rough and a large number of nanoparticles loaded on the surface can be clearly observed. At the same time, there is no free nanoparticles distributed in the fiber matrix or agglomeration, indicating that Example 2 prepared a SnO2@HCNFs composite material with good SnO2 nanoparticle loading and uniform distribution. This is not only beneficial for the SnO2 nanoparticles on the HCNFs surface in the SnO2@HCNFs composite material obtained in Example 2 to be converted into SnS2 nanoparticles in an in situ phase transformation during the vulcanization process, but also ensures that the SnS2 grown on the HCNFs surface has good independent distribution.

[0125] Figure 2(a) to (d) are the XRD patterns of the composite materials obtained in Example 1, Example 2, Example 3 and Example 4, respectively. From the analysis of the XRD pattern results, it can be seen that for the composite material prepared in Example 1, there are characteristic peaks of two phases. The characteristic peaks of the first phase appear at 26.611°, 33.893°, 37.949°, 51.780°, 54.757°, 64.717° and 65.937°, which have a high degree of match with the standard characteristic peak positions of the standard material card JCPDS.No.41-1445. This result corresponds to the (110), (101), (200), (211), (220), (112) and (301) crystal planes of SnO2. The characteristic peaks of another phase appear at 15.029°, 28.199°, 30.262°, 32.124°, 41.886°, 49.960° and 52.451°, which have a high degree of match with the standard characteristic peaks of the standard material card JCPDS.No.23-0677. This result corresponds to the (001), (100), (002), (101), (102), (110) and (111) crystal planes of SnS2, indicating that there is an incomplete phase transition in the sulfurization process in Example 1, that is, there is some SnO2 in the composite material that does not participate in the sulfurization reaction. The XRD diffraction peaks of the SnS2@HCNFs composite materials prepared in Example 2, Example 3 and Example 4 are all located at 15.029°, 28.199°, 30.262°, 32.124°, 41.886°, 46.121°, 49.960°, 52.451°, 54.960°, 58.351°, 59.509°, 60.619°, 62.968°, 67.152°, 70.333°, 77.442°, 82.307°, 84.384°, 88.196° and 88.387°, which are consistent with the standard The standard characteristic peaks of the quality card JCPDS.No.23-0677 are consistent, and the results correspond to the (001), (100), (002), (101), (102), (003), (110) and (111), (103), (200), (112), (201), (004), (202), (113), (203), (211), (114), (212), (105) crystal planes of SnS2, indicating that the materials synthesized in Example 2, Example 3 and Example 4 are all SnS2@HCNFs composite materials with clear phase composition. Figure 2 (b) and Figure 1 It can be seen that the SnO2 on the surface of HCNFs has been completely converted into SnS2 in situ, thus obtaining a SnS2@HCNFs composite anode material with high crystallinity. Figure 3(b) is the SEM image of the SnS2@HCNFs composite negative electrode material obtained in Example 2. Figure 3 As shown in (b), a layer of nanoparticles with a particle size of about 10 nm is attached to the surface of the material, and no obvious agglomerated particles are found free between the fiber matrix, indicating that the SnS2 nanoparticles on the surface of the SnS2@HCNFs composite negative electrode material originate from the in situ phase transformation of the SnO2 nanoparticles on the surface of the SnO2@HCNFs precursor composite material, indirectly proving that the conversion process is carried out in the form of in situ phase transformation.

[0126] Figure 4 The cycle performance test curves of the negative electrode materials prepared in Example 2 and Comparative Examples 1 and 2 in Application Example 1 are shown. Figure 4 It can be seen that at a current density of 200 mA / g, the negative electrode material obtained from the SnS2@HCNFs composite material prepared in Example 2 in Application Example 1 has the best electrochemical performance, with its initial charge and discharge specific capacities reaching 962.61 mAh / g and 1276.32 mAh / g, respectively. The discharge specific capacity after 100 cycles is still as high as 706.62 mAh / g, indicating that the composite material prepared by the method of Example 2 has a stable structure, better electrochemical performance, and is more suitable for use as a negative electrode material for lithium-ion batteries. It is particularly noteworthy that the HCNFs negative electrode material prepared in Comparative Example 1 using Example 2 has an initial discharge capacity of 549.47 mAh / g at a current density of 200 mA / g, and the discharge capacity after 100 cycles is only maintained at 203.40 mAh / g. Although the discharge capacity is low, as a pure carbon matrix material, it continues to maintain relatively stable discharge performance during the fourth and subsequent cycles. The negative electrode material obtained from the SnO2@HCNFs composite material prepared in Comparative Example 2 using Example 2 has an initial discharge capacity of 769.13 mAh / g, but its discharge capacity continues to decay during the cycle. After the 100th cycle, its discharge capacity is only 198.01 mAh / g. This undesirable phenomenon is caused by the huge volume effect and pulverization phenomenon of the active substance (SnO2) in the negative electrode material during the operation of the battery, and its own conductivity is poor, resulting in poor overall electrochemical performance of the electrode. The test results show that converting the SnO2 phase on the HCNFs surface into SnS2 can significantly enhance the overall electrochemical performance of the electrode material.

[0127] Table 1 shows the electrochemical performance test results of the corresponding negative electrode materials obtained from Examples 1-4 and Comparative Examples 1-2 in Application Example 1. The results in Table 1 show that during the sulfurization process, the relative amounts of sublimated sulfur and SnO2@HCNFs composite material directly affect the electrochemical performance of the resulting SnS2@HCNFs composite negative electrode material. When the mass ratio of SnO2@HCNFs composite material to sublimated sulfur is 0.2:1 (i.e., the amount of SnO2@HCNFs composite material is 0.2g and the amount of sublimated sulfur is 1.0g), the resulting SnS2@HCNFs composite negative electrode material exhibits the best electrochemical performance.

[0128] Table 1 Electrochemical properties of the negative electrode materials obtained in Examples 1 to 4 and Comparative Examples 1 to 2

[0129]

[0130] Table 2 shows the electrochemical performance results of the materials obtained in comparative example 2 and the materials obtained in the prior art. The SnS2@MWCNTs in Table 2 were prepared according to “Zhai C, DuN, Zhang H, et al. Multiwalled carbon nanotubesanchored with SnS2 nanosheets as high-performance anode materials of lithium-ion batteries[J]. ACS applied materials&interfaces, 2011, 3(10): 4067-4074.”; the SnS2@MWCNTs in Table 2 were prepared according to “Sun H, Ahmad M, Luo J, et al. SnS2 nanoflakesdecorated multiwalled carbon nanotubes as high performance anode materialsfor lithium-ion batteries[J]. Materials Research Bulletin, 2014, 49: 319-324.”; the SnS2@CNFs in Table 2 were prepared according to “ChengY, Xie H, Zhou L, et al. In-situ liquid-phase transformation of SnS2 / CNTs composite from SnO2 / CNTs for high performance lithium-ion battery anode[J].Applied Surface Science, 2021,566:150645." was prepared; in Table 2, SnS2@GO was prepared according to "Li K, Yan S, Lin Z, et al. Preparation and lithium ionbatteries properties of SnS2nanoparticle / reduced graphene oxide nanosheetnanocomposites using supercritical carbon dioxide[J].Synthetic Metals,2016,217:138-143.The SnS2@CNTs in Table 2 were prepared according to the method disclosed in Example 1 of the specification of Chinese patent CN107394129A; the SnS2 / rGO in Table 2 were prepared according to the method disclosed in Example 1 of the specification of Chinese patent CN105428609A; and the SnS2 / C in Table 2 were prepared according to the method disclosed in Example 1 of the specification of Chinese patent CN108281625A. The results in Table 2 show that compared with the anode materials disclosed in the prior art, the SnS2@HCNFs composite anode material obtained in Example 2 of the present invention exhibits the best electrochemical performance.

[0131] Table 2 Electrochemical properties of the materials obtained in Example 2 and the materials obtained in the prior art

[0132]

[0133] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a tin disulfide-helical carbon nanofiber composite material, characterized in that: The following steps are involved: The spiral carbon nanofibers, a tin source, an organic precipitant, an organic dispersant, and an organic solvent are mixed to obtain a mixed liquid, wherein the tin source is anhydrous stannous chloride, the organic precipitant is an alkali metal acetate, the mass ratio of the tin source to the organic precipitant is (1-3):(2-6), the organic dispersant is polyvinyl pyrrolidone, and the organic solvent is ethanol; The mixed liquid is subjected to a solvothermal reaction to obtain a precursor mixture, wherein the solvothermal reaction temperature is 80-120° C. and the holding time is 4-8 hours; the solvothermal reaction is carried out in a closed reaction vessel, and the volume of the mixed liquid occupies 40-70% of the volume of the closed reaction vessel; calcining the precursor mixture to obtain a tin dioxide-helical carbon nanofiber composite material; the tin dioxide-helical carbon nanofiber composite material comprises helical carbon nanofibers and tin dioxide nanoparticles loaded on the surface of the helical carbon nanofibers; The tin dioxide-helical nanocarbon fiber composite material is vulcanized in a sulfur vapor atmosphere, the vulcanization holding temperature is 500-600°C, the holding time is 1-3h, the mass ratio of the tin dioxide-helical nanocarbon fiber composite material to sulfur is (1-3):(5-25), and a tin disulfide-helical nanocarbon fiber composite material is obtained; the tin disulfide-helical nanocarbon fiber composite material includes spiral nanocarbon fibers and tin disulfide nanoparticles loaded on the surface of the spiral nanocarbon fibers, and the particle size of the tin disulfide nanoparticles is 5-20 nm.

2. The preparation method according to claim 1, characterized in that The vulcanization comprises the following steps: A double-layer container is provided, comprising a first container with a lid and a second container disposed within the first container, a gap being left between the first container and the second container, and the height of the first container being greater than the height of the second container; The tin dioxide-helical carbon nanofiber composite material is placed in the second container; the sulfur element is placed in the interlayer; In a protective gas, the first container is covered and heated to obtain sulfur vapor, so that the tin dioxide-helical carbon nanofiber composite material is vulcanized in the sulfur vapor atmosphere.

3. The preparation method according to claim 2, characterized in that The heating rate is 3-5°C / min.

4. The preparation method according to claim 2 or 3, characterized in that The ratio of the mass of the sulfur element to the volume of the first container is (5-25) g:120000 mm 3 .

5. The preparation method according to claim 1, characterized in that The mass ratio of the spiral carbon nanofibers to the tin source is (1-3):(1-3).

6. The preparation method according to claim 1, characterized in that The mass ratio of the tin source to the organic dispersant is (1-3):(2-10); The ratio of the mass of the tin source to the volume of the organic solvent is (1-3) g: (40-70) mL.

7. The tin disulfide-helical carbon nanofiber composite material obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The invention comprises spiral nano-carbon fibers and tin disulfide nano-particles loaded on the surface of the spiral nano-carbon fibers.

8. The tin disulfide-helical carbon nanofiber composite material according to claim 7, characterized in that: The spiral diameter of the spiral nanocarbon fiber is 60-90 nm.

9. Use of the tin disulfide-helical carbon nanofiber composite material according to claim 7 or 8 as a negative electrode material for lithium-ion batteries.

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