Preparation and application of nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material

Abstract

The invention relates to preparation and application of a nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material, and belongs to the technical field of electrode material preparation, and the preparation method mainly comprises the following steps: preparing porous SiO2 nanospheres by a template method, mixing with a reducing agent, calcining, and washing to obtain porous silicon nanospheres; then, adding the polymer coating precursor into a solvent, mixing the polymer coating precursor with the polymer coating precursor, and adjusting the pH value to 8-9 to prepare a polymer coating material; and finally, adding transition metal ions such as nickel, cobalt and manganese into the material, stirring for 6-12 hours, and calcining in an argon-hydrogen mixed atmosphere to obtain the nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material. When the nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon nano-particles are applied to a silicon-carbon negative electrode of a lithium ion battery, through the synergistic effect of the carbon layer and the alloy nano-particles, the conductivity is improved, the volume expansion of silicon in the charging and discharging process is buffered, and the cycling stability and the electrochemical performance are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of electrode materials, and specifically relates to the preparation and application of a carbon-coated porous silicon-carbon composite material enhanced with nickel-cobalt-manganese alloy. Background Art

[0002] In recent years, the rapid growth in the demand for electric vehicles has driven the progress of high-energy-density lithium-ion battery (LIB) technology. To further improve its energy density, research has focused on developing new electrode materials with higher specific capacities. Silicon has attracted much attention due to its extremely high theoretical capacity (about 4200 mAh / g, 11 times higher than that of commercial graphite anodes), low lithium intercalation voltage, and low polarization characteristics.

[0003] However, its application faces three core challenges: insufficient suppression of volume expansion, poor electrical conductivity, and low cycle stability. Silicon has a volume expansion rate of up to 300% during charge and discharge, resulting in continuous shrinkage and expansion during lithium intercalation and deintercalation, which leads to electrode pulverization and loss of electrical contact between silicon fragments and the current collector, resulting in rapid capacity decay. Existing technologies mainly improve performance through nanosizing, carbon coating, and pore-forming technologies. However, traditional graphite or carbon nanotube coating layers have a weak inhibitory effect on silicon volume expansion, and it is necessary to additionally introduce a porous structure (such as a self-assembly of silicon nanosheets) to provide a buffer space, but the preparation process of the porous structure is complex and costly.

[0004] In addition, after the silicon anode is pulverized, its surface is continuously exposed to the electrolyte, forming an unstable solid electrolyte interface, irreversibly consuming a large amount of lithium. At the same time, the relatively low ionic and electronic conductivities of silicon (especially amorphous silicon) also limit the actual utilization of its capacity. Therefore, how to enhance the structural stability and electrical conductivity of the silicon anode has become a key direction for application and is of great significance.

[0005] Based on the above, the present invention provides a preparation and application of a carbon-coated porous silicon-carbon composite material enhanced with nickel-cobalt-manganese alloy. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation and application of a carbon-coated porous silicon-carbon composite material enhanced with nickel-cobalt-manganese alloy to solve the problems raised in the background art.

[0007] The purpose of the present invention can be achieved by the following technical solutions: A preparation method of a carbon-coated porous silicon-carbon composite material enhanced with nickel-cobalt-manganese alloy specifically includes the following steps: Step (1): Prepare porous SiO 2 nano-spheres using the template method, and then mix and calcine them with a reducing agent, and wash the product to obtain porous silicon nano-spheres; During the above reaction process, the porous SiO 2The nanospheres are mixed with a reducing agent and calcined to reduce SiO 2 to Si, and a porous silicon nanosphere is obtained in a ratio of two.

[0008] Step (2): Add the porous silicon nanospheres into a solvent, mix them with a polymer coating precursor, and adjust the pH value of the system to 8-9 to obtain a polymer-coated material; Step (3): Add transition metal ions to the polymer-coated material, stir for 6-12 hours, and then calcine in a mixed atmosphere of argon and hydrogen to obtain a nickel cobalt manganese alloy-reinforced carbon-coated porous silicon carbon composite material; Among them, the transition metal ions are at least one of nickel, cobalt, and manganese ions.

[0009] Preferably, in step (1), the reducing agent is magnesium powder.

[0010] Further, in step (1), the porous SiO 2 nanospheres are specifically prepared by the following steps: Add the nanosphere template into an ethanol solution, stir for 20-30 minutes, then add a SiO 2 precursor solution to the system, continue to stir for 4-8 hours, then filter, wash the product and calcine it at 500-700 °C for 2-6 hours to obtain porous SiO 2 nanospheres.

[0011] Preferably, in step (1), the porous SiO 2 nanospheres are specifically prepared by the following steps: Add the nanosphere template to a 50 wt% ethanol solution according to a mass-volume ratio of 1 g:20 mL, stir at a rate of 30-90 rpm at room temperature for 20-30 minutes, then add a SiO 2 precursor solution with a concentration of 0.1-0.8 mol / L to the system, continue to stir at room temperature for 4-8 hours, then filter, wash the product with deionized water and place it in a muffle furnace to raise the temperature to 500-700 °C at a heating rate of 10-20 °C / min in an air atmosphere and calcine for 2-6 hours to obtain porous SiO 2 nanospheres.

[0012] Further, the mass ratio of the nanosphere template to the SiO 2 precursor solution is (2-5):1.

[0013] Preferably, the nanosphere template is a polystyrene nanosphere.

[0014] Further, the SiO 2The precursor is at least one of methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrabutyl orthosilicate, and 3-aminopropyltriethoxysilane.

[0015] Further, in step (1), the porous silicon nanospheres are specifically prepared by the following steps: Mix the porous SiO2 nanospheres with a reducing agent, raise the temperature to 700 - 750 °C at a heating rate of 10 - 20 °C / min in an inert atmosphere, the calcination time is 2 - 6 hours, and after the calcination is completed, wash the product with 1 mol / L hydrochloric acid solution to obtain porous silicon nanospheres.

[0016] Further, porous SiO 2 The mass ratio of the nanospheres to the reducing agent is 1:(3 - 5).

[0017] Further, in step (2), the polymer coating material is specifically prepared by the following steps: Add the porous silicon nanospheres to the solvent according to a mass - to - volume ratio of 1 g:(10 - 20) mL, stir at 30 - 90 rpm for 10 - 20 minutes at room temperature, then mix with the polymer coating precursor, adjust the pH value of the system to 8 - 9 with ammonia water, and continue to stir at room temperature for 10 - 15 hours to obtain the polymer coating material.

[0018] Further, the solvent is at least one of methanol solution, propanol solution, butanol solution, and ethanol solution, and the concentration is 50 - 80 wt%.

[0019] Further, in step (2), the mass ratio of the porous silicon nanospheres to the polymer coating precursor is (3 - 5):(20 - 40).

[0020] Further, the polymer coating precursor is at least one of L - dopa, 3,4 - dihydroxybenzylamine, dopamine hydrochloride, and tea polyphenols.

[0021] Further, in step (3), the dosage ratio of the polymer coating material to the transition metal ions is (50 - 100) g:(0.1 - 0.3) mol.

[0022] Further, in step (3), the transition metal ions are at least one of nickel, cobalt, and manganese ions.

[0023] Further, in step (3), the volume ratio of argon to hydrogen in the mixed atmosphere is (90 - 99):(1 - 10).

[0024] Further, in step (3), the specific operation of the calcination is: raise the temperature to 450 - 800 °C at a heating rate of 10 - 20 °C / min and calcine for 6 - 8 hours.

[0025] Advantages of the present invention: In the technical solution of the present invention, the template-assisted deposition method is adopted. Using polystyrene nanospheres as the hard template, the silicon source precursor is deposited into the pores of the template through the sol-gel process. After high-temperature calcination to remove the organic template, silica nanospheres with a hierarchical pore structure are obtained. Then, through the high-temperature reduction-etching composite process, the porous silica nanospheres are mixed and calcined with magnesium powder. The magnesium thermal reduction reaction is used to selectively remove the silicon element in the silica skeleton, and then the residual metal impurities are etched with dilute hydrochloric acid solution. Finally, highly porous silicon nanospheres with a high specific surface area are obtained. Subsequently, the solvent mixing and dispersion technology is adopted to uniformly disperse the porous silicon nanospheres in an organic-aqueous mixed solvent system. By adjusting the pH, an interfacial polymerization reaction of the polymer coating precursor is initiated to form a dense carbon-based polymer coating layer with a core-shell structure. Finally, transition metal ions such as nickel and cobalt are mixed with the polymer coating material, and the metal ions are uniformly loaded through electrostatic adsorption. Subsequently, high-temperature carbonization is carried out in a mixed atmosphere of argon and hydrogen, synchronously completing the pyrolysis carbonization of the polymer and the reduction of metal ions. By using the ion adsorption-in-situ reduction method, a composite structure in which nickel-cobalt-manganese alloy nanoparticles are dispersed in a carbon-coated porous silicon matrix is formed. The nickel-cobalt-manganese alloy nanoparticles are uniformly distributed in the carbon layer. When applied to the silicon-carbon negative electrode of a lithium-ion battery, through the synergistic effect of the carbon layer and the alloy nanoparticles, the conductivity is improved and the volume expansion of silicon during charge and discharge is buffered, enhancing the conductivity and cycle stability of the material, and the electrochemical performance of the negative electrode can be regulated through different compounding ratios. The preparation method of the present invention is simple and has a low manufacturing cost. By using the alloy to reinforce the carbon coating layer to limit the deformation of the silicon material during the cycling process, the specific capacity and cycle life of the lithium-ion battery are significantly improved, which is suitable for large-scale production, especially for application scenarios such as electric vehicles and high-end electronic devices that require high energy density and long cycle life. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 TEM image of nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon nanoparticles prepared in Example 1.

[0028] Figure 2 X-ray diffraction pattern of nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon nanoparticles prepared in Example 2.

[0029] Figure 3The figure shows the long cycle performance of a lithium-ion battery assembled with nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon nanoparticles as the anode material in Application Example 1.

[0030] Figure 4 The figure shows the rate performance of a lithium-ion battery assembled with nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon nanoparticles as the anode material in Application Example 1. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] The technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] The reagents involved in the specific implementation manners of this application are all of analytical grade. In addition: The nanosphere template uses polystyrene nanospheres, and the particle size is its preparation method, including the following steps: Take 13 g of styrene monomer, wash it three times with 0.1 mol / L NaOH solution, then wash it with deionized water until the pH value of the washing solution is neutral. Then mix it with 0.5 - 1.0 g of potassium persulfate and 150 mL of deionized water. Raise the temperature of the system to 80 °C in a nitrogen atmosphere, stir and react at a rate of 500 rpm for 8 - 12 hours. Then naturally cool the system to room temperature, centrifuge at a rate of 12,000 rpm for 15 minutes, filter, wash the filtered product with deionized water, and freeze-dry to obtain polystyrene nanospheres; In Example 1, the amount of potassium persulfate used for the nanosphere template is 0.5 g, and the reaction time is 8 hours; In Example 2, the amount of potassium persulfate used for the nanosphere template is 0.8 g, and the reaction time is 10 hours; In Example 3, the amount of potassium persulfate used for the nanosphere template is 1.0 g, and the reaction time is 12 hours.

[0034] Magnesium powder: The purity is 99.9%, and the average particle size is 5 μm.

[0035] Tea polyphenols: The CAS number is 84650 - 60 - 2, the purity is ≥ 98%, and it is provided by Xi'an Wanlv Biotechnology Co., Ltd.

[0036] Example 1 A preparation method of a nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon-carbon composite material specifically includes the following steps: Step (1): Prepare porous SiO 2 nanospheres by the template method, and then mix and calcine them with a reducing agent, and wash the product to obtain porous silicon nanospheres. The specific operation is as follows: Mix the porous SiO 2 nanospheres with a reducing agent, raise the temperature to 750 °C at a heating rate of 10 °C / min in an argon atmosphere, and the calcination time is 6 hours. After the calcination, wash the product 3 times with 1 mol / L hydrochloric acid solution to obtain porous silicon nanospheres; during the process, the mass ratio of the porous SiO 2 nanospheres to the reducing agent is 1:3, and the reducing agent used is magnesium powder; Among them, the porous SiO 2 nanospheres are specifically prepared by the following steps: Add the nanosphere template to a 50 wt% ethanol solution at a mass-to-volume ratio of 1 g:20 mL, stir at a rate of 60 rpm for 30 minutes at room temperature, then add a SiO 2 precursor solution with a concentration of 0.35 mol / L to the system, continue to stir at room temperature for 7 hours, then filter, wash the product with deionized water and place it in a muffle furnace to calcine at a heating rate of 10 °C / min in an air atmosphere to 700 °C for 6 hours to obtain porous SiO 2 nanospheres; during the process, the mass ratio of the nanosphere template to the SiO 2 precursor solution is 3:1; the SiO 2 precursor solution used is methyltriethoxysilane.

[0037] Step (2): Add the porous silicon nanospheres to a solvent and mix them with a polymer coating precursor, and adjust the pH value of the system to 8.5 to obtain a polymer-coated material. The specific operation is as follows: Add the porous silicon nanospheres obtained in step (1) to a solvent at a mass-to-volume ratio of 1 g:15 mL, stir at a rate of 60 rpm for 20 minutes at room temperature, then mix with a polymer coating precursor, adjust the pH value of the system to 8.5 with ammonia water, and continue to stir at room temperature for 12 hours to obtain a polymer-coated material; among them, the solvent used is a methanol solution with a concentration of 50 wt%; the mass ratio of the porous silicon nanospheres to the polymer coating precursor is 4:30; the polymer coating precursor used is L-dopa.

[0038] Step (3): Add transition metal ions to the polymer-coated material, stir for 10 hours, and then calcine at a heating rate of 10 °C / min to 650 °C for 6 hours in a mixed atmosphere of argon and hydrogen to obtain a nickel cobalt manganese alloy-reinforced carbon-coated porous silicon carbon composite material; Among them, the dosage ratio of the polymer coating material to the transition metal ions is 80 g:0.2 mol; the volume ratio of argon to hydrogen in the mixed atmosphere is 95:5; the transition metal ions used are cobalt chloride hexahydrate.

[0039] Now, the sample prepared in Example 1 was observed using a transmission electron microscope. The specific observation results are as Figure 1 shown.

[0040] From Figure 1 the results in, it can be seen that after calcination, the template was completely removed, a large number of pores existed on the surface of the nanospheres, and a porous structure with a high specific surface area was formed. Some "dark rings" and gray-scale changes were observed, which confirmed that L-dopa formed a thin layer to wrap the nanospheres after carbonization. Through several regions with local high contrast, it was proved that the nanoparticles generated by cobalt reduction were uniformly loaded on the surface of the porous silicon.

[0041] Example 2 A preparation method of a nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon-carbon composite material specifically includes the following steps: Step (1): Use the template method to prepare porous SiO 2 nanospheres, and then mix and calcine them with a reducing agent, and wash the product to obtain porous silicon nanospheres. The specific operation is as follows: Mix the porous SiO2 nanospheres with a reducing agent, and raise the temperature to 750 °C at a heating rate of 15 °C / min in an argon atmosphere. The calcination time is 5 hours. After the calcination is completed, wash the product 3 times with 1 mol / L hydrochloric acid solution to obtain porous silicon nanospheres; during the process, the mass ratio of the porous SiO 2 nanospheres to the reducing agent is 1:4, and the reducing agent used is magnesium powder; Among them, the porous SiO 2 nanospheres are specifically prepared by the following steps: Add the nanosphere template to a 50 wt% ethanol solution according to a mass-volume ratio of 1 g:20 mL, stir at a rate of 90 rpm for 30 minutes at room temperature, then add a SiO 2 precursor solution with a concentration of 0.2 mol / L to the system, continue to stir at room temperature for 6 hours, then filter, wash the product with deionized water and place it in a muffle furnace to raise the temperature to 625 °C at a heating rate of 10 °C / min in an air atmosphere and calcine for 2 hours to obtain porous SiO 2 nanospheres; during the process, the mass ratio of the nanosphere template to the SiO 2 precursor solution is 3:1; the SiO 2 precursor solution used is tetraethoxysilane.

[0042] Step (2): Add the porous silicon nanospheres into a solvent and mix them with the polymer coating precursor, and adjust the pH value of the system to 8.5 to obtain the polymer-coated material. The specific operation is as follows: Add the porous silicon nanospheres obtained in step (1) into the solvent according to the mass-volume ratio of 1 g:15 mL, stir at 90 rpm for 20 minutes at room temperature, then mix with the polymer coating precursor, adjust the pH value of the system to 8.5 using ammonia water, and continue to stir at room temperature for 15 hours to obtain the polymer-coated material. Among them, the solvent used is an ethanol solution with a concentration of 70 wt%; the mass ratio of the porous silicon nanospheres to the polymer coating precursor is 5:30; the polymer coating precursor used is 3,4-dihydroxybenzylamine.

[0043] Step (3): Add transition metal ions to the polymer-coated material, stir for 12 hours, and then raise the temperature to 625 °C at a heating rate of 20 °C / min under a mixed atmosphere of argon and hydrogen and calcine for 6 hours to obtain a nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon-carbon composite material; Among them, the dosage ratio of the polymer-coated material to the transition metal ions is 80 g:0.2 mol; the volume ratio of argon to hydrogen in the mixed atmosphere is 95:5; the transition metal ions used are nickel chloride hexahydrate.

[0044] Now, perform XRD analysis on the sample prepared in Example 2, and the specific results are as Figure 2 shown.

[0045] From Figure 2 the results in, it can be seen that in addition to the characteristic peaks of silicon, there are two other characteristic peaks at the positions of 44.5° and 51.8°. These two characteristic peaks belong to the (111) and (200) crystal planes of cubic nickel respectively, verifying the conversion of nickel ions into the metallic state and alloying.

[0046] Example 3 A preparation method of a nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon-carbon composite material specifically includes the following steps: Step (1): Use the template method to prepare porous SiO 2 nanospheres, and then mix them with a reducing agent and calcine, and wash the product to obtain porous silicon nanospheres. The specific operation is as follows: Mix the porous SiO2 nanospheres with the reducing agent, raise the temperature to 725 °C at a heating rate of 15 °C / min under an argon atmosphere, and the calcination time is 5 hours. After the calcination, wash the product 3 times with 1 mol / L hydrochloric acid solution to obtain porous silicon nanospheres. During the process, the mass ratio of the porous SiO 2 nanospheres to the reducing agent is 1:3, and the reducing agent used is magnesium powder; Among them, the porous SiO 2The nanospheres are specifically prepared by the following steps: Add the nanosphere template to a 50 wt% ethanol solution at a mass-to-volume ratio of 1 g:20 mL. After stirring at a rate of 90 rpm for 30 minutes at room temperature, add a SiO 2 precursor solution with a concentration of 0.4 mol / L to the system. Continue stirring at room temperature for 8 hours, then filter, wash the product with deionized water, and place it in a muffle furnace. Raise the temperature to 700 °C at a heating rate of 20 °C / min in an air atmosphere and calcine for 2 hours to obtain porous SiO 2 nanospheres; during the process, the mass ratio of the nanosphere template to the SiO 2 precursor solution is 3:1; the SiO 2 precursor solution used is 3-aminopropyltriethoxysilane.

[0047] Step (2): Add the porous silicon nanospheres to a solvent and mix with the polymer coating precursor, and adjust the pH value of the system to 8.5 to obtain a polymer-coated material. The specific operation is as follows: Add the porous silicon nanospheres obtained in step (1) to a solvent at a mass-to-volume ratio of 1 g:20 mL. After stirring at 90 rpm for 20 minutes at room temperature, mix with the polymer coating precursor, adjust the pH value of the system to 8.5 using ammonia water, and continue stirring at room temperature for 15 hours to obtain a polymer-coated material; among them, the solvent used is a methanol solution with a concentration of 70 wt%; the mass ratio of the porous silicon nanospheres to the polymer coating precursor is 4:30; the polymer coating precursor used is tea polyphenols.

[0048] Step (3): Add transition metal ions to the polymer-coated material. After stirring for 8 hours, raise the temperature to 650 °C at a heating rate of 20 °C / min in a mixed atmosphere of argon and hydrogen and calcine for 8 hours to obtain a nickel-cobalt-manganese alloy-reinforced carbon-coated porous silicon-carbon composite material; Among them, the dosage ratio of the polymer-coated material to the transition metal ions is 80 g:0.2 mol; the volume ratio of argon to hydrogen in the mixed atmosphere is 95:5; the transition metal ions used are obtained by mixing nickel chloride hexahydrate, cobalt chloride hexahydrate, and manganese chloride hexahydrate in a molar ratio of 1:0.5:0.5.

[0049] Application Example 1: Use the sample prepared in Example 3 in a button battery. The specific preparation method is as follows: Using N-methylpyrrolidone as a solvent, the active material (the sample prepared in Example 3), the conductive agent (conductive graphite), and the binder (polyvinylidene fluoride) were uniformly mixed and stirred into a slurry, where the mass ratio of the active material, the conductive agent, and the binder was 8:1:1. Then, the prepared slurry was uniformly coated on a copper foil and dried at a temperature of 70 °C for 12 hours. After that, the dried negative electrode sheet was compacted using a roll press, and the compaction pressure was 30 MPa to ensure that the loading amount of the active material reached 1.8 mg / cm². Finally, lithium metal was used as the counter electrode, a polypropylene membrane was used as the separator, and 1 mol / L LiPF 5 dissolved in ethylene carbonate / dimethyl carbonate (volume ratio 1:1) was used as the electrolyte to assemble a CR2032 coin cell.

[0050] Now, the coin cell prepared in Application Example 1 was tested for its capacity density, capacity efficiency, and Coulomb efficiency. The specific test results are as Figure 3 and Figure 4 shown.

[0051] From Figure 3 and Figure 4 the results, it can be seen that in the capacity density test results, in the 0-80 cycle range, the initial cycle capacity was close to 3500 mAh / g, verifying that the porous structure of the material provided abundant active sites, and the formed carbon coating layer further anchored lithium ions through π-π conjugation and functional group interactions, reducing the initial polarization. After 80 cycles, the capacity remained good and the decay rate showed a stable trend, indicating that the carbon coating layer effectively buffered the volume expansion during the charge and discharge of silicon, inhibited particle agglomeration and pulverization, and at the same time verified that transition metal ions were loaded on the surface of the carbon coating layer, acting as an electron conductor and a lithium ion diffusion channel to prevent the repeated loss of active sites due to oxidation / reduction.

[0052] In the capacity efficiency and Coulomb efficiency test results, the red discharge capacity curve gradually decreased from the initial value (about 2500 mAh / g) and still remained above about 500 mAh / g after 700 cycles, showing good stability. The black Coulomb efficiency curve was always close to 100%, and even remained higher than 95% after 700 cycles, verifying that the conductivity of the carbon coating layer and the buffering effect of the porous silicon structure could effectively inhibit the problems of volume expansion and ion migration blockage.

[0053] Moreover, the battery was charged and discharged at different current densities, achieving a rate performance of 1200 mAh / g at a cycle of 8.0 A / g. At the same time, after cycling 700 times at a current density of 5 A / g, the average reversible capacity reached 1500 mAh / g. From the above conclusions, it can be known that the prepared sample has good structural stability and exhibits good conductivity.

[0054] In the description of the specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0055] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the specific embodiments described or use similar methods for substitution, as long as they do not deviate from the concept of the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material, characterized in that: The specific steps include: Step (1): preparing porous SiO2 nanospheres by using a template method, then mixing with a reducing agent, calcining, and washing the product to obtain porous silicon nanospheres; Step (2): adding porous silicon nanospheres into a solvent, and mixing with a polymer coating precursor, adjusting the pH value of the system to 8-9, to obtain a polymer coating material; Step (3): adding transition metal ions to the polymer coating material, stirring for 6-12 hours, and calcining in a mixed atmosphere of argon and hydrogen to obtain a nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material; Wherein, the transition metal ion is at least one of nickel, cobalt and manganese ions.

2. The nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material according to claim 1, characterized in that: In step (1), the porous SiO2 nanospheres are specifically prepared by the following steps: Add the nanosphere template to the ethanol solution, stir for 20-30 minutes, add the SiO2 precursor solution to the system, continue stirring for 4-8 hours, then filter, wash the product and calcine at 500-700°C for 2-6 hours to obtain porous SiO2 nanospheres.

3. The nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material according to claim 2, characterized in that: The mass ratio of the nanosphere template to the SiO2 precursor solution is (2-5):

1.

4. The nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material according to claim 1, characterized in that: In step (1), the porous silicon nanospheres are prepared by the following steps: The porous SiO2 nanospheres are mixed with a reducing agent, and the temperature is increased to 700-750°C at a heating rate of 10-20°C / min in an inert atmosphere. The calcination time is 2-6 hours. After the calcination, the product is washed to obtain porous silicon nanospheres.

5. The nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material according to claim 4, characterized in that: The mass ratio of the porous SiO2 nanospheres to the reducing agent is 1:(3-5).

6. The nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material according to claim 1, characterized in that: In step (2), the polymer coating material is specifically prepared by the following steps: The porous silicon nanospheres are added to the solvent, stirred for 10-20 minutes and then mixed with the polymer coating precursor, the pH value of the system is adjusted to 8-9 with ammonia water, and the stirring is continued for 10-15 hours to obtain the polymer coating material.

7. The nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material according to claim 1, characterized in that: In step (2), the mass ratio of porous silicon nanospheres to polymer coating precursor is (3-5):(20-40).

8. The nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material according to claim 1, characterized in that: In step (3), the ratio of the polymer coating material to the transition metal ion is (50-100) g: (0.1-0.3) mol.

9. The nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material according to claim 1, characterized in that: In step (3), the specific operation of calcination is: raising the temperature to 450-800° C. at a heating rate of 10-20° C. / min and calcining for 6-8 hours.

10. Use of the nickel-cobalt-manganese alloy reinforced carbon-coated porous silicon-carbon composite material as claimed in any one of claims 1 to 9 in electrode materials.

Images