Nickel-coated graphite composite particles and a method for producing the same

Abstract

The application discloses a kind of nickel-coated graphite composite particles and its preparation method, its preparation method includes: oil is removed to graphite, then washes to neutral;Then graphite is placed in SnCl2 solution and stirs 5~10min, then filters, washes;Then graphite is placed in PdCl2 solution and stirs 5~10min, then filters, washes;Again, graphite is placed in plating solution, and graphite powder mixed plating solution is obtained, the plating solution includes complexing agent, nickel salt, pH stabilizer, sodium hydroxide and reducing agent, the concentration C of sodium hydroxide in plating solution is: 0.2 mol / L<C<3 mol / L;Graphite powder mixed plating solution is placed in oil bath and stirred to react, after solution color becomes colorless, after filtration, washing and drying, nickel-coated graphite composite particles are obtained.The preparation method can effectively control the morphology of nickel on the surface of graphite, prepare nickel-coated graphite composite particles with different nickel morphology, and the process is simple, which is conducive to industrial production.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, and relates to nickel-coated graphite composite particles, and particularly to a nickel-coated graphite composite particle and its preparation method. Background Technology

[0002] Nickel-coated graphite particles are a type of metal-coated composite powder with graphite as the core and a nickel metal layer as the surface coating. They are widely used as catalysts, conductive fillers, electromagnetic shielding materials, and microwave absorbing materials. Furthermore, nickel-coated graphite coatings possess excellent abrasion resistance, oxidation resistance, and a low coefficient of friction, making them suitable for abrasion-resistant sealing coatings on low- and medium-temperature components of gas turbines.

[0003] Currently, there are many methods for preparing nickel-coated graphite particles, such as hydrothermal reduction, ion plating, vacuum evaporation, chemical vapor deposition, sol-gel method, and electroless plating. Compared with other preparation processes, electroless plating has advantages such as simple preparation process, low preparation cost, good plating uniformity, reusable plating solution, and wide applicability, and has become a commonly used method for preparing nickel-coated graphite particles. For example, Chinese patent CN202110301151.0 discloses a method for preparing nickel-coated graphite composite powder material for conductive silicone, using electroless plating to prepare nickel-coated graphite for conductive silicone; Chinese patent CN202010198093.9 discloses a method for preparing nickel-coated graphite composite particles, preparing nickel-coated graphite through palladium-free electroless plating; and Chinese patent 201310753540.2 discloses a method for preparing nickel-coated graphite composite particles, successfully preparing a nickel coating layer on the graphite surface using a pre-planted nickel seed method.

[0004] Currently, most studies on nickel-coated graphite preparation focus on the uniformity of nickel coating on graphite, with very few reports on the control of nickel morphology on the graphite surface. As nickel-coated graphite can be used as a catalyst, microwave absorbing material, and electromagnetic shielding material, the morphology of nickel on its surface inevitably affects its key properties (such as adsorption characteristics for pollutants and absorption rate of electromagnetic waves). Therefore, effectively controlling the nickel morphology on the graphite surface through process control during the preparation of nickel-coated graphite particles is of great practical significance for improving the comprehensive performance of nickel-coated graphite powder materials and expanding their industrial applications. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a nickel-coated graphite composite particle and its preparation method. This preparation method can effectively control the nickel morphology on the graphite surface, prepare nickel-coated graphite composite particles with different nickel morphologies, and the process is simple and conducive to industrial production.

[0006] The technical solution of this invention is implemented as follows:

[0007] The preparation method of the first nickel-coated graphite composite particles specifically includes the following steps:

[0008] S1: Degrease the graphite and then wash it until it is neutral;

[0009] S2: Place the graphite from S1 into a SnCl2 solution and stir for 5–10 min, then filter and wash; wherein the concentration of SnCl2 in the SnCl2 solution is 0.09–0.1 mol / L;

[0010] S3: Place the graphite from S2 into a PdCl2 solution and stir for 5–10 min, then filter and wash; wherein the concentration of PdCl2 in the PdCl2 solution is 0.001–0.002 mol / L;

[0011] S4: Place the graphite from S3 into the plating solution to obtain a graphite powder mixed plating solution. The plating solution includes a complexing agent, nickel salt, pH stabilizer, sodium hydroxide, and reducing agent. The concentration C of sodium hydroxide in the plating solution is: 0.2 mol / L < C ≤ 0.75 mol / L.

[0012] S5: Place the graphite powder mixed plating solution in an oil bath and stir to react. After the solution turns colorless, filter, wash and dry to obtain nano needle-shaped nickel-coated graphite composite particles.

[0013] The second method for preparing nickel-coated graphite composite particles specifically includes the following steps:

[0014] S1: Degrease the graphite and then wash it until it is neutral;

[0015] S2: Place the graphite from S1 into a SnCl2 solution and stir for 5–10 min, then filter and wash; wherein the concentration of SnCl2 in the SnCl2 solution is 0.09–0.1 mol / L;

[0016] S3: Place the graphite from S2 into a PdCl2 solution and stir for 5–10 min, then filter and wash; wherein the concentration of PdCl2 in the PdCl2 solution is 0.001–0.002 mol / L;

[0017] S4: Place the graphite from S3 into the plating solution to obtain a graphite powder mixed plating solution. The plating solution includes a complexing agent, a nickel salt, a pH stabilizer, sodium hydroxide, and a reducing agent. The concentration C of sodium hydroxide in the plating solution is: 0.75 mol / L < C < 1.5 mol / L.

[0018] S5: Place the graphite powder mixed plating solution in an oil bath and stir to react. After the solution turns colorless, filter, wash and dry to obtain nano-filament nickel-coated graphite composite particles.

[0019] The third method for preparing nickel-coated graphite composite particles specifically includes the following steps:

[0020] S1: Degrease the graphite and then wash it until it is neutral;

[0021] S2: Place the graphite from S1 into a SnCl2 solution and stir for 5–10 min, then filter and wash; wherein the concentration of SnCl2 in the SnCl2 solution is 0.09–0.1 mol / L;

[0022] S3: Place the graphite from S2 into a PdCl2 solution and stir for 5–10 min, then filter and wash; wherein the concentration of PdCl2 in the PdCl2 solution is 0.001–0.002 mol / L;

[0023] S4: Place the graphite from S3 into the plating solution to obtain a graphite powder mixed plating solution. The plating solution includes a complexing agent, nickel salt, pH stabilizer, sodium hydroxide, and reducing agent. The concentration C of sodium hydroxide in the plating solution is: 1.5 mol / L ≤ C < 3 mol / L.

[0024] S5: Place the graphite powder mixed plating solution in an oil bath and stir to react. After the solution turns colorless, filter, wash and dry to obtain nano-spherical nickel-coated graphite composite particles.

[0025] Furthermore, the specific method in S1 of the above three methods for preparing nickel-coated graphite composite particles is as follows: placing graphite in a 5wt% NaOH aqueous solution at 40-50℃ to remove oil, stirring continuously during the oil removal process, the oil removal time is 20-30 minutes, and after the oil removal is completed, filtering and washing with water until neutral.

[0026] Furthermore, in the above three methods for preparing nickel-coated graphite composite particles, the complexing agent is one or more of sodium citrate, sodium tartrate, tetrasodium ethylenediaminetetraacetate, or tetrasodium glutamate diacetate, and the mass ratio of the complexing agent to the nickel salt in the plating solution is 0.005 to 0.02:1.

[0027] Furthermore, in the above three methods for preparing nickel-coated graphite composite particles, the nickel salt is nickel sulfate or nickel chloride, and the mass ratio of the nickel salt to the graphite in S3 is 0.285 to 0.388:1.

[0028] Furthermore, in the above three methods for preparing nickel-coated graphite composite particles, the pH stabilizer is ammonium chloride or hydrochloric acid.

[0029] Furthermore, in the above three methods for preparing nickel-coated graphite composite particles, the reducing agent is hydrazine, and the concentration of the reducing agent in the plating solution is 0.6–0.8 mol / L.

[0030] Furthermore, in the above three methods for preparing nickel-coated graphite composite particles, the oil bath temperature in S5 is 92–106°C.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention controls the nickel morphology on the surface of nickel-coated graphite by adjusting the amount of sodium hydroxide used. - The adsorption on different Ni crystal planes varies. (111) The Ni crystal plane has a larger surface energy, OH - It is easier for adsorption to occur on this crystal plane, which leads to an increase in the growth barrier of the (111)Ni crystal plane during electroless nickel plating, inhibiting the preferential growth of the (111)Ni crystal plane during electroless nickel plating. With the increase of OH in the plating solution... - With increasing concentration, the morphology of Ni particles on the surface of nickel-coated graphite changes from nanoneedle-like to nanofilament-like to nanosphere-like.

[0033] 2. The process of this invention is simple and beneficial for the industrial production of nickel-coated graphite composite particles with controllable Ni morphology on the surface. The plating solution in this invention includes a complexing agent, a nickel salt, a pH stabilizer, sodium hydroxide, and a reducing agent. The complexing agent maintains the stability of the reaction solution and prevents the nickel salt from self-decomposing in the solution; the nickel salt is the main salt in the reaction, providing nickel ions for the nickel-coated graphite; the pH stabilizer maintains the pH stability of the solution before the addition of sodium hydroxide; the reducing agent reduces nickel ions to nickel atoms, allowing nickel to deposit and grow on the graphite, and providing reaction kinetics for the experiment. Sodium hydroxide provides hydroxide ions to the solution. The main reaction in the experiment is: 2Ni 2+ +N₂H₄+4OH - = 2Ni + N2 + 4H2O. Attached Figure Description

[0034] Figure 1 - A schematic diagram of the mechanism of this invention.

[0035] Figure 2 - Surface morphology images of nickel-coated graphite particles obtained in Examples 1 to 4.

[0036] Figure 3 X-ray diffraction patterns and crystal plane intensity comparison diagrams of nickel-coated graphite particles obtained in Examples 1 to 4.

[0037] Figure 4 - Comparison of magnetic properties between pure nickel blocks and nickel-coated graphite particles obtained in Examples 1 to 4.

[0038] Figure 5 - Comparison of electromagnetic shielding and wave absorption performance of nickel-coated graphite particles obtained in Examples 1 to 4. Detailed Implementation

[0039] This invention uses 200-300 mesh graphite. The schematic diagram of the mechanism of this invention is shown below. Figure 1 As shown, under alkaline conditions, after sensitization and activation treatment, Pd deposited on the graphite surface is electrostatically adsorbed. 2+ Ni is reduced to Pd and becomes a catalytically active site. 2+ Nickel atoms diffuse around the active Pd sites and are reduced to Ni atoms by the reducing agent hydrazine. When the Ni atom concentration reaches the non-uniform nucleation potential energy, nickel nuclei form on the active Pd sites. Subsequently, Ni is deposited and grown on the nickel nuclei through autocatalysis. When the concentration C of sodium hydroxide in the plating solution is: 0.2 mol / L < C ≤ 0.75 mol / L, nano-needle-shaped nickel-coated graphite composite particles are obtained; when the concentration C of sodium hydroxide in the plating solution is: 0.75 mol / L < C < 1.5 mol / L, nano-filament-shaped nickel-coated graphite composite particles are obtained; when the concentration C of sodium hydroxide in the plating solution is: 1.5 mol / L ≤ C < 3 mol / L, nano-spherical nickel-coated graphite composite particles are obtained. The nickel-coated graphite composite particles obtained in this invention have a nickel mass fraction of 72-78%, with the remainder being graphite.

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] (1) Weigh 4g NaOH, add it to 200mL of deionized water and stir until fully dissolved. Mix well to prepare solution A for later use.

[0043] (2) Weigh 4g of graphite into solution A to remove oil, stir continuously for 20 minutes, filter and wash with water until pH=7 after oil removal is complete.

[0044] (3) Weigh 4g SnCl2, add it to 16mL HCl, stir to dissolve it completely, then add 200mL deionized water, stir to dissolve it completely, mix well to prepare solution B, and set aside.

[0045] (4) Place the graphite obtained in (2) into solution B and stir for 10 min, then filter and wash.

[0046] (5) Weigh 0.04g PdCl2, add it to 4mL HCl, stir to dissolve it completely, then add 200mL deionized water, stir to dissolve it completely, mix well to prepare solution C, and set aside.

[0047] (6) Place the graphite obtained in (4) into liquid C and stir for 5 min, then filter and wash.

[0048] (7) Weigh 100g of sodium citrate dihydrate, 60g of ammonium chloride, and 53.6g of nickel sulfate hexahydrate, add them to 1L of deionized water and stir to dissolve them completely. Mix them evenly to prepare solution D for later use.

[0049] (8) Weigh 60g NaOH, add it to 400mL of deionized water and stir until fully dissolved. Mix well to prepare solution E for later use.

[0050] (9) Weigh 64 mL of hydrazine monohydrate, add it to 400 mL of deionized water and stir to dissolve it completely. Mix well to prepare solution F for later use.

[0051] (10) Take E and F respectively and add them to D in sequence to dissolve them completely and mix them evenly to obtain electroplating solution G.

[0052] (11) Take the graphite from (6) and add it to liquid G and stir for 5 minutes. Mix it evenly to obtain a graphite powder mixed plating solution with [NaOH] = 0.75 mol / L.

[0053] (12) The graphite powder mixed plating solution obtained in (11) was placed in an oil bath at 92-106℃ for reaction. During the reaction, the mixture was stirred continuously. When the solution color turned colorless, the solution was taken out, the reaction product was filtered and washed, and then placed in an oven to dry. Finally, nickel-coated graphite particles were obtained.

[0054] Example 2

[0055] This example is the same as Example 1, except that in this example, the mass of NaOH in solution E is 72g, resulting in a graphite powder mixed plating solution with [NaOH] = 0.9mol / L.

[0056] Example 3

[0057] This example is the same as Example 1, except that the mass of NaOH in Solution E in this example is 80g, resulting in a graphite powder mixed plating solution with [NaOH] = 1mol / L.

[0058] Example 4

[0059] This example is the same as Example 1, except that in this example, the mass of NaOH in solution E is 120g, resulting in a graphite powder mixed plating solution with [NaOH] = 1.5mol / L.

[0060] 1. Surface morphology images of nickel-coated graphite particles with different NaOH concentrations obtained in Examples 1 to 4 are shown below. Figure 2 As shown. Among them. Figure 2 The concentrations of 0.75 mol / L, 0.9 mol / L, 1 mol / L, and 1.5 mol / L correspond to Examples 1 through 4, respectively. Figure 2It can be seen that when [NaOH] = 0.75 mol / L, the morphology of Example 1 is characterized by nickel uniformly coating the graphite surface to form a nickel layer, which consists of numerous long nickel needles. When [NaOH] = 0.9 mol / L, the morphology of Example 2 is similar to that of Example 1, with the graphite coated by a nickel layer, and a certain amount of nickel growing outward into whiskers with a diameter of 100 nm and a length of 500 nm. When [NaOH] = 1 mol / L, the morphology of Example 3 is characterized by graphite being covered by longer and denser whiskers, which consist of spiky nickel with a length of less than 100 nm. When [NaOH] = 1.5 mol / L, the morphology of Example 4 is characterized by anemone-shaped nickel-coated graphite particles formed by a large number of nickel whiskers formed by the agglomeration of quasi-spherical nickel with a diameter of 400 nm coating the graphite surface. This indicates that as the NaOH concentration increases, the morphology of nickel growth changes from needle-like to quasi-spherical, and the growth rate of nickel also increases accordingly.

[0061] 2. X-ray diffraction patterns and crystal plane intensity comparison diagrams of the nickel-coated graphite particles obtained in Examples 1 to 4 are shown below. Figure 3 As shown. Figure 3 (a) is the X-ray diffraction pattern of nickel-coated graphite particles. Figure 3 (b) shows the trend of different crystal plane intensities as a function of NaOH concentration. Figure 3 (a) It can be seen that nickel-coated graphite was successfully prepared in Examples 1 to 4 without other impurities. In the X-ray diffraction patterns, the diffraction peaks near 44.5°, 51.8°, and 76.4° correspond to the (111), (200), and (220) crystal planes of Ni, respectively, while the remaining diffraction peaks correspond to the crystal planes of graphite. Figure 3 (b) It can be seen that at a low concentration of [NaOH] = 0.75 mol / L, (111) / (002) > (200) / (002) > (220) / (002), and the difference is obvious. As the NaOH concentration increases, the difference gradually decreases. When the NaOH concentration further increases to 1.5 mol / L, the strength ratios of each are close to 0. This indicates that under different NaOH concentrations, the nickel in nickel-coated graphite particles always preferentially grows along the (111) crystal plane. Moreover, as the NaOH concentration increases, the strength ratios of different crystal planes of nickel and the (002) plane of graphite decrease from large to small, eventually becoming consistent. This shows that the growth rate of nickel along different crystal planes tends to be consistent with the increase of NaOH concentration.

[0062] 3. The specific surface areas of nickel-coated graphite particles obtained at different concentrations in Examples 1 to 4 are shown in Table 1.

[0063] Table 1. Specific surface area of ​​nickel-coated graphite particles obtained at different concentrations in Examples 1-4

[0064] NaOH concentration 0.75 mol / L 0.9 mol / L 1mol / L 1.5 mol / L Specific surface area <![CDATA[5.7m 2 / g]]> <![CDATA[10.8m 2 / g]]> <![CDATA[28.4m 2 / g]]> <![CDATA[67.7m 2 / g]]>

[0065] As shown in Table 1, when [NaOH] = 0.75 mol / L, the specific surface area of ​​Example 1 is 5.7 m². 2 / g, when [NaOH]=0.9mol / L, the specific surface area of ​​Example 2 is 10.8m². 2 / g, when [NaOH]=1mol / L, the specific surface area of ​​Example 3 is 28.4m². 2 / g, when [NaOH]=1.5mol / L, the specific surface area of ​​Example 1 is 67.7m². 2 / g. As the NaOH concentration increases, the nickel on the surface of the nickel-coated graphite particles gradually changes from long needle-like shapes to quasi-spherical shapes, with the length continuously decreasing, and the specific surface area of ​​the nickel-coated graphite increases.

[0066] 4. Comparison of magnetic properties between pure nickel blocks and nickel-coated graphite particles obtained at different concentrations in Examples 1 to 4 is shown in the figure below. Figure 4 As shown. By Figure 4 It can be seen that the specific saturation magnetization of pure nickel block is 55 emu / g, the specific saturation magnetization of Example 1 is 25.4 emu / g, the specific saturation magnetization of Example 2 is 41.3 emu / g, the specific saturation magnetization of Example 3 is 34.2 emu / g, and the specific saturation magnetization of Example 4 is 32.4 emu / g. This indicates that changing the NaOH concentration in the experimental conditions can effectively change the magnetic properties of nickel-coated graphite particles. The specific saturation magnetization of the material is proportional to the number of Bohr magnetons. The number of Bohr magnetons for nickel is 0.604 μB, while the number of Bohr magnetons for graphite, being a non-magnetic material, is nearly 0, thus reducing the ferromagnetism of nickel-coated graphite. At the same time, the high specific surface area of ​​nickel increases the spin disorder and antiferromagnetic oxidation of the material surface, further reducing the ferromagnetism of the material.

[0067] 5. Comparison of electromagnetic shielding and wave absorption performance of nickel-coated graphite particles obtained in Examples 1 to 4 is shown in the figure below. Figure 5 As shown. Figure 5 (a) and Figure 5 (b) Comparison of electromagnetic shielding and wave absorption performance of nickel-coated graphite particles. Figure 5 It can be seen that Example 2 exhibits excellent performance in both electromagnetic shielding and wave absorption, and its SE T and SE A The average values ​​for 1–18 GHz are 37 dB and 25.9 dB, respectively, both of which are suitable for commercial applications. Figure 5 (a) It can be seen that the effectiveness of electromagnetic shielding first increases and then decreases with increasing NaOH concentration. Example 1: At 1–4.9 GHz, 10 dB ≤ SE T ≤20dB, at 4.9~18GHz, SE T >20dB; Example 2 at 1–18 GHz, SE TAll are greater than 35.8 dB; Example 3 at 1–18 GHz, SE T All are greater than 25 dB; in Example 4, 10 dB ≤ SE in the range of 1–8.7 GHz. T ≤20dB, in 8.7~18GHz, SE T >20dB. (By) Figure 5 (b) It can be seen that in Example 1, at 2–5.5 GHz, 10 dB ≤ SE A ≤15dB, at 11–18 GHz, SE A >20dB; Example 2 at 1–18 GHz, SE A All are greater than 25.5 dB; Example 3 at 14.3–18 GHz, SE A >20dB; Example 4 at 3.9–9.7 GHz, 10dB≤SE A ≤15dB, at 15–18GHz, SE A >20dB. This indicates that changing the concentration of NaOH in the experiment can effectively improve the electromagnetic shielding and absorption performance of nickel-coated graphite particles. Both electromagnetic shielding and absorption performance are related to the material's composition, morphology, and thickness. Adding nickel to graphite effectively improves the material's electrical conductivity, and nickel's strong magnetism effectively enhances the material's magnetic loss performance. Because high-frequency electromagnetic waves have shorter wavelengths and higher frequencies, they undergo strong electromagnetic coupling and eddy current dissipation with the nickel particles in the absorbing material. When electromagnetic waves pass through the absorbing material, the magnetic powder particles in the material are excited by the electromagnetic waves, generating heat and causing the internal temperature of the material to rise, ultimately absorbing the electromagnetic waves. Nickel, due to its eddy current loss, exhibits strong absorption in the high-frequency region.

[0068] Finally, it should be noted that the above embodiments of the present invention are merely illustrative examples and not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for producing a nickel-coated graphite composite particle, characterized by comprising: Specifically comprising the following steps: ​ S1: oil removal of graphite, then washing to neutral; S2: the graphite in S1 is placed in SnCl2 solution and stirred for 5-10 min, then filtered and washed; the concentration of SnCl2 in the SnCl2 solution is 0.09-0.1 mol / L; S3: the graphite in S2 is placed in PdCl2 solution and stirred for 5-10 min, then filtered and washed; the concentration of PdCl2 in the PdCl2 solution is 0.001-0.002 mol / L; S4: the graphite in S3 is placed in a plating solution to obtain a graphite powder mixed plating solution, the plating solution comprising a complexing agent, a nickel salt, a pH stabilizer, sodium hydroxide and a reducing agent, the concentration C of sodium hydroxide in the plating solution being 0.75 mol / L S5: the graphite powder mixed plating solution is placed in an oil bath and stirred to react, after the solution color becomes colorless, filtration, washing and drying to obtain nanometer wire-shaped nickel-coated graphite composite particles.

2. A method for producing a nickel-coated graphite composite particle, characterized by comprising: Specifically comprising the following steps: S1: oil removal of graphite, then washing to neutral; S2: the graphite in S1 is placed in SnCl2 solution and stirred for 5-10 min, then filtered and washed; the concentration of SnCl2 in the SnCl2 solution is 0.09-0.1 mol / L; S3: the graphite in S2 is placed in PdCl2 solution and stirred for 5-10 min, then filtered and washed; the concentration of PdCl2 in the PdCl2 solution is 0.001-0.002 mol / L; S4: the graphite in S3 is placed in a plating solution to obtain a graphite powder mixed plating solution, the plating solution comprising a complexing agent, a nickel salt, a pH stabilizer, sodium hydroxide and a reducing agent, the concentration C of sodium hydroxide in the plating solution being 1.5 mol / L S5: the graphite powder mixed plating solution is placed in an oil bath and stirred to react, after the solution color becomes colorless, filtration, washing and drying to obtain nanometer wire-shaped nickel-coated graphite composite particles.

3. The method of claim 1 or 2, wherein the nickel-coated graphite composite particles are prepared by the steps of: The specific method in S1 is: the graphite is placed in a 5wt% NaOH aqueous solution at 40-50 ℃ for oil removal, the oil removal process is continuously stirred, the oil removal time is 20-30 min, and after the oil removal is completed, the graphite is filtered and washed with clean water to neutral. ​ 4. The method of claim 1 or 2, wherein the nickel-coated graphite composite particles are prepared by the steps of: The complexing agent is one or more of sodium citrate, sodium tartrate, tetrasodium ethylenediaminetetraacetate or tetrasodium glutamate diacetate, and the mass ratio of the complexing agent to the nickel salt in the plating solution is 0.005-0.02:

1. ​ 5. The method of claim 1 or 2, wherein the nickel-coated graphite composite particles are prepared by the steps of: The nickel salt is nickel sulfate or nickel chloride, and the mass ratio of the nickel salt to the graphite in S3 is 0.285-0.388:

1. ​ 6. The method of claim 1 or 2, wherein the nickel-coated graphite composite particles are prepared by the steps of: The pH stabilizer is ammonium chloride or hydrochloric acid. ​ 7. The method of claim 1 or 2, wherein the nickel-coated graphite composite particles are prepared by the steps of: The reducing agent is hydrazine, and the concentration of the reducing agent in the plating solution is 0.6-0.8 mol / L. ​ 8. The method of claim 1 or 2, wherein the nickel-coated graphite composite particles are prepared by the steps of: The oil bath temperature in S5 is 92-106 ℃. ​ 9. A nickel-coated graphite composite particle, characterized by, Prepared by the preparation method of the nickel-coated graphite composite particles according to any one of claims 1-8.

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