Preparation method of coal-based onion-like fullerene with high lithium storage performance

Abstract

The invention relates to a preparation method of coal-based onion-like fullerene with high lithium storage performance, which comprises the following steps: by taking anthracite as a carbon source, performing impurity removal treatment by hydrofluoric acid, performing high-temperature carbonization in an inert atmosphere to obtain carbonized coal powder, loading a ferric salt catalyst, putting the carbonized coal powder and the loaded ferric salt catalyst into an arc plasma device, and performing high-voltage discharge reaction to obtain a reaction crude product; and purifying to obtain the coal-based onion-like fullerene. The coal-based onion-like fullerene prepared by the method has high lithium storage specific capacity, shows remarkable lithium storage performance advantage superior to that of a traditional graphite negative electrode when being used as a negative electrode material of a lithium ion battery, and greatly improves the cycling stability and rate capability of the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanocarbon materials, and relates to a preparation method of coal-based onion-like fullerenes. BACKGROUND

[0002] Onion-like fullerenes (OLFs) are quasi-spherical carbon nanomaterials composed of multiple concentrically nested sp 2 hybrid graphene sheets, which have unique "core-shell-mesoporous" composite structures and combine the characteristics of zero-dimensional nanoparticles and the advantages of three-dimensional conductive networks.

[0003] As a new generation of energy storage battery negative electrode material, OLFs construct three-dimensional electron transmission channels through continuous sp 2 carbon layers to form a high-conductive network, and the mesopores of 2-5 nm between the layers provide efficient diffusion paths and significantly improve the ion kinetic performance. + Compared with traditional carbon materials, the multi-layer buffer structure of OLFs can control the volume expansion rate during the charging and discharging process below 5%, effectively inhibit the deformation of the electrode structure by the mechanical stability of the concentric spherical graphite shell layer, and further shorten the diffusion distance of ions by the smaller particle size (usually nanoscale). In addition, OLFs can also be used as a conductive agent to enhance the rate performance of the electrode, relieve the electrode cracking problem by dispersing stress, and exhibit the comprehensive advantages of synergistic optimization of conductivity, structural stability and ion diffusion efficiency.

[0004] However, the traditional OLFs preparation methods generally face the problems of low yield (<30%), limited specific capacity (<500 mAh g -1 ), complex process, etc., and the root cause lies in the difficulty of precisely controlling the carbon layer number and structural uniformity of OLFs by existing synthesis technologies (such as chemical vapor deposition method, nano-diamond annealing method and heat treatment method), which makes it difficult to break through the stability of specific surface area, electrical conductivity and lithium storage performance.

[0005] In contrast, the plasma method can dissociate the carbon source by a high-energy plasma source and controllably cool and assemble OLFs, and has the comprehensive advantages of high yield, environmental friendliness and controllable microstructure, especially in the field of coal-based carbon source preparation, which has more application potential. Among them, the arc plasma method excites electron flow between high-voltage electrodes, and under the action of electric field acceleration, gas molecules are ionized to form high-temperature plasma (temperature up to 10 3 ~ 10 4The high-energy electrons, ions, and free radicals abundant in OLFs (on the order of kiloliters) can efficiently drive carbon atom reconstruction. By precisely controlling plasma parameters (such as power, atmosphere, and cooling rate), it is possible not only to achieve directional control of the number of OLF layers, mesopore size, and degree of graphitization, but also to promote the deep graphitization of coal-based precursors using ultra-high temperature environments. This simultaneously optimizes the lithium storage capacity and structural stability of the material, providing an innovative solution for the large-scale preparation of high-performance OLFs.

[0006] Liu et al. (Onion-like carbon coated Fe3C nanocapsules embedded in porouscarbon for the stable lithium-ion battery anode[J]. Applied Surface Science (2019, 479: 318-325.) A one-pot method was used to prepare an onion-like carbon-encapsulated Fe3C nanoparticle / porous carbon composite material by arc discharge of iron-graphite in an argon-hydrogen mixed atmosphere. The synergistic effect of the Fe3C nanoparticles, the carbon coating layer, and the porous matrix significantly improved the cycle stability (0.2 A g) of the lithium-ion battery anode. -1 After 500 cycles, the capacity remains at 582mAh g. -1 ) and rate performance (0.2~16A g) -1 (Capacity retention rate is nearly 100%).

[0007] Zhang et al. (P doped onion-like carbon layers coated FeP nanoparticles for anode materials in lithium ion batteries[J]. Journal of Alloys and Compounds (2019, 777: 860-865.) P-doped onion-like carbon-coated FeP core-shell nanoparticles (FeP@(P,OLC)) prepared via a one-pot method using an argon / hydrogen / ethanol mixed atmosphere arc discharge exhibited high initial efficiency (79.8%) and long cycle stability (0.1 A g) as a lithium-ion battery anode, thanks to the synergistic effect of the P-OLC shell in inhibiting FeP aggregation, enhancing conductivity, and buffering volume expansion. -1 After 1500 cycles, the capacity is 915mAh g. -1 ) and excellent rate performance (8.0 / 10.0A g) -1 Lower capacity 379 / 237mAh g -1 ). Summary of the Invention

[0008] The purpose of the present application is to provide a preparation method of coal-based onion-like fullerene which can be used as anode material of lithium ion battery, so as to quickly and efficiently prepare coal-based onion-like fullerene with high lithium storage specific capacity.

[0009] The preparation method of coal-based onion-like fullerene according to the present application is specifically prepared by using anthracite as carbon source according to the following steps:

[0010] 1. Hydrofluoric acid impurity removal treatment is performed on the anthracite to obtain impurity-removed anthracite;

[0011] 2. High-temperature carbonization of the impurity-removed anthracite is performed under inert atmosphere to obtain carbonized coal powder;

[0012] 3. The carbonized coal powder is uniformly dispersed in anhydrous ethanol solution of water-soluble iron salt, and the anhydrous ethanol is evaporated to obtain iron salt catalyst-loaded coal powder;

[0013] 4. The iron salt catalyst-loaded coal powder is placed in an electric arc plasma device, and high-voltage discharge reaction is performed in argon atmosphere under the condition of current 25-35 A and voltage 20 V to obtain reaction crude product;

[0014] 5. The reaction crude product is purified by hydrochloric acid solution, and washed with water to neutral to obtain coal-based onion-like fullerene target product.

[0015] In the preparation method according to the present application, the anthracite is preferably crushed into coal powder with particle size below 200 mesh.

[0016] The hydrofluoric acid impurity removal treatment of anthracite according to the present application is not particularly limited, and various conventional methods for removing silicates and other inorganic minerals in coal by hydrofluoric acid can be used. Preferably, the present application uses mixed acid solution of hydrofluoric acid and hydrochloric acid for impurity removal treatment of anthracite.

[0017] More preferably, the mixed acid solution of hydrofluoric acid and hydrochloric acid is a mixed acid solution prepared by mixing hydrofluoric acid with a concentration of 10 wt% and 4M hydrochloric acid solution at a volume ratio of 4:5.

[0018] Further, the present application preferably adds the anthracite coal powder to 10 times the volume of the mixed acid solution for impurity removal treatment.

[0019] Further, after stirring the anthracite coal powder in the mixed acid solution at room temperature for not less than 12 h, the anthracite coal powder is washed with water to neutral and dried to obtain impurity-removed anthracite.

[0020] Specifically, the present application heats the impurity-removed anthracite to 600-900 DEG C under inert atmosphere for high-temperature carbonization to obtain carbonized coal powder, and the preferred high-temperature carbonization time is 2-6 h.

[0021] Further, the mass of the loaded iron salt in the prepared iron salt loaded catalyst coal powder is preferably 0.4-1.0 times the mass of the carbonized coal powder.

[0022] Further, the present application preferably uses 4-6M hydrochloric acid solution to purify the crude product of the arc plasma reaction.

[0023] The present application uses arc plasma technology, uses anthracite as a low-cost carbon source, and obtains coal-based onion-like fullerenes (OLFs) materials with suitable specific surface area and high structural stability by accurately adjusting the preparation process parameters, which are used as lithium ion battery negative materials and exhibit significant lithium storage performance advantages over traditional graphite negative materials.

[0024] Specifically, when the onion-like fullerenes prepared by the present application are applied to lithium ion battery negative materials, a high reversible capacity of more than 650mAh / g -1 can be achieved under conventional charge and discharge conditions, and a capacity output of nearly 200mAh / g -1 can still be maintained at a high current density of 5A / g -1 , greatly improving the cycle stability and rate performance of the battery.

[0025] The OLFs prepared by the present application not only have high intrinsic electrical conductivity, excellent thermal / chemical stability, but also exhibit excellent electromagnetic response characteristics, which can be applied to electrode materials, energy storage devices, electronic sensors and other new functional material fields, realizing the high value-added transformation and upgrading of coal resources from traditional fuels to nanocarbon materials, and having broad application prospects in the fields of energy storage (lithium / sodium ion batteries), energy conversion (supercapacitors) and electromagnetic shielding.

[0026] The coal-based onion-like fullerenes preparation method provided by the present application has simple process and low raw material cost, breaks through the yield and capacity limitations of traditional synthesis technology, and provides a feasible path for the industrial production of coal-based OLFs. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 FIG. 1 is a scanning electron microscope image of the coal-based onion-like fullerenes prepared in Examples 1-5.

[0028] Figure 2 FIG. 2 is a transmission electron microscope image of the coal-based onion-like fullerenes prepared in Examples 1-5.

[0029] Figure 3 FIG. 3 is an X-ray diffraction pattern of the coal-based onion-like fullerenes prepared in Examples 1-5.

[0030] Figure 4 FIG. 4 is a Raman spectrum of the coal-based onion-like fullerenes prepared in Examples 1-5.

[0031] Figure 5 is the X-ray diffraction pattern of the carbon nanomaterial prepared in Comparative Example 1.

[0032] Figure 6 is the transmission electron microscope image of the carbon nanomaterial prepared in Comparative Example 2.

[0033] Figure 7 is the GCD curve of the coal-based onion-like fullerenes prepared in Examples 1-5.

[0034] Figure 8 is the GCD curve of the coal-based onion-like fullerenes prepared in Comparative Examples 3-4.

[0035] Figure 9 is the cycle life curve of the coal-based onion-like fullerenes prepared in Examples 1-5.

[0036] Figure 10 is the cycle life curve of the coal-based onion-like fullerenes prepared in Comparative Examples 3-4.

[0037] Figure 11 is the rate performance curve of the coal-based onion-like fullerenes prepared in Examples 1-5. Embodiments

[0038] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present application, so that those skilled in the art can well understand and utilize the present application, and are not intended to limit the protection scope of the present application.

[0039] The production process, experimental method or detection method involved in the embodiments of the present application, if not specifically stated, are all conventional methods in the prior art, and the name and / or abbreviation thereof all belong to the conventional name in the art, which are very clear and explicit in the related use field. Those skilled in the art can understand the conventional process steps and apply the corresponding equipment according to the name, and implement it according to the conventional conditions or the conditions suggested by the manufacturer.

[0040] The various instruments, equipment, raw materials or reagents used in the embodiments of the present application do not have special restrictions on the source, and are all conventional products that can be purchased through normal commercial channels, or can be prepared according to the conventional method well known to those skilled in the art.

[0041] The following examples of the present application are specifically prepared coal-based onion-like fullerenes using anthracite as the carbon source according to the following method:

[0042] S1: impurity removal treatment

[0043] The anthracite was crushed to 200 mesh, and then was added into mixed acid solution (10 wt% HF + 4 M HCl, v / v = 4:5) with a solid-liquid mass volume ratio (g / mL) of 1:10. The mixture was stirred at room temperature for no less than 12 h, and then was filtered and washed with deionized water until neutral. The anthracite powder was obtained by drying.

[0044] S2: High-temperature carbonization

[0045] The impurity-removed anthracite powder was placed in a tube furnace, and the air in the tube furnace was replaced with argon for 30 min. The temperature was raised to 600-900 °C at a rate of 5 °C / min, and the carbonization was carried out for 2-6 h. The carbonized coal powder was obtained by cooling to room temperature.

[0046] S3: Catalyst loading

[0047] The carbonized coal powder was dispersed in anhydrous ethanol solution of FeCl3 with a concentration of 0.01-0.03 g / mL, and was ultrasonically treated for 30 min. The mixture was stirred in a water bath at 60-80 °C until the anhydrous ethanol was completely evaporated, and the FeCl3-loaded catalyst coal powder was obtained.

[0048] S4: Arc plasma reaction

[0049] The FeCl3-loaded catalyst coal powder was placed in an arc plasma device, and the high-voltage discharge reaction was carried out by setting the current at 25-35 A and the voltage at 20 V, and by introducing argon at a flow rate of 30 mL / min. The reaction was continuously carried out for 5 min, and the reaction crude product was obtained.

[0050] S5: Product purification

[0051] The reaction crude product was purified by treatment with 4-6 M HCl solution, and was washed with water until neutral. The coal-based onion-like fullerene target product was obtained.

[0052] In the following specific examples, the measurement parameters of the raw material components may have slight deviations within the weighing accuracy range, unless otherwise specified. The temperature and time parameters allow for acceptable deviations caused by instrument testing accuracy or operation accuracy. Examples

[0053] Example 1

[0054] 1.5 g of impurity-removed anthracite powder was weighed and added to 60 mL of anhydrous ethanol. Then, 1.217 g (7.5 mmol) of FeCl3 was added, and the mixture was heated in a water bath at 80 °C until the anhydrous ethanol was completely evaporated.

[0055] The FeCl3-loaded coal powder was dried and ground, and was placed in an arc plasma device. The high-voltage discharge of arc plasma was carried out in an argon atmosphere by setting the current of the device at 25 A and the voltage at 20 V. 1 g of reaction crude product was obtained.

[0056] The reaction crude product was collected and purified by placing it in 60 mL of a 5 M HC1 solution. After stirring at room temperature for 6 h, it was washed to neutral to obtain the target product, which was named AC-OLFs.

[0057] Example 2

[0058] The purified anthracite was placed in a tube furnace and carbonized at 600°C for 2 h under an argon atmosphere. After cooling, the carbonized coal powder was obtained.

[0059] 1.5 g of the carbonized coal powder was weighed and added to 60 mL of anhydrous ethanol. Then, 1.217 g (7.5 mmol) of FeCl3 was added and mixed uniformly. The mixture was heated on an 80°C water bath until the anhydrous ethanol was completely evaporated.

[0060] The FeCl3-loaded coal powder was dried and ground, and then placed in an electric arc plasma device. The current and voltage of the device were set to 25 A and 20 V, respectively. High-voltage discharge of the electric arc plasma was performed in an argon atmosphere to obtain 1 g of the reaction crude product.

[0061] The reaction crude product was collected and purified by placing it in 60 mL of a 5 M HC1 solution. After stirring at room temperature for 6 h, it was washed to neutral to obtain the target product, which was named 600AC-OLFs.

[0062] Example 3

[0063] The purified anthracite was placed in a tube furnace and carbonized at 700°C for 2 h under an argon atmosphere. After cooling, the carbonized coal powder was obtained.

[0064] 1.5 g of the carbonized coal powder was weighed and added to 60 mL of anhydrous ethanol. Then, 1.217 g (7.5 mmol) of FeCl3 was added and mixed uniformly. The mixture was heated on an 80°C water bath until the anhydrous ethanol was completely evaporated.

[0065] The FeCl3-loaded coal powder was dried and ground, and then placed in an electric arc plasma device. The current and voltage of the device were set to 25 A and 20 V, respectively. High-voltage discharge of the electric arc plasma was performed in an argon atmosphere to obtain 1 g of the reaction crude product.

[0066] The reaction crude product was collected and purified by placing it in 60 mL of a 5 M HC1 solution. After stirring at room temperature for 6 h, it was washed to neutral to obtain the target product, which was named 700AC-OLFs.

[0067] Example 4

[0068] The purified anthracite was placed in a tube furnace and carbonized at 800°C for 2 h under an argon atmosphere. After cooling, the carbonized coal powder was obtained.

[0069] Take 1.5 g of carbonized coal powder, add to 60 mL of anhydrous ethanol, then add 1.217 g (7.5 mmol) of FeCl3 and mix well, heat to 80°C water bath until the anhydrous ethanol is completely evaporated.

[0070] Dry and grind the FeCl3-loaded coal powder, place it in an arc plasma device, set the current of the device to 25 A and the voltage to 20 V, and perform arc plasma high-voltage discharge in an argon atmosphere to obtain 1 g of the reaction crude product.

[0071] Collect the reaction crude product, place it in 60 mL of 5M HCl solution for purification treatment, stir at room temperature for 6 h, then wash to neutral to obtain the target product, named 800AC-OLFs.

[0072] Example 5

[0073] Place the impurity-removed anthracite in a tube furnace, carbonize at 900°C for 2 h under argon atmosphere, cool and take out to obtain carbonized coal powder.

[0074] Take 1.5 g of carbonized coal powder, add to 60 mL of anhydrous ethanol, then add 1.217 g (7.5 mmol) of FeCl3 and mix well, heat to 80°C water bath until the anhydrous ethanol is completely evaporated.

[0075] Dry and grind the FeCl3-loaded coal powder, place it in an arc plasma device, set the current of the device to 25 A and the voltage to 20 V, and perform arc plasma high-voltage discharge in an argon atmosphere to obtain 1 g of the reaction crude product.

[0076] Collect the reaction crude product, place it in 60 mL of 5M HCl solution for purification treatment, stir at room temperature for 6 h, then wash to neutral to obtain the target product, named 900AC-OLFs.

[0077] Comparative Example 1

[0078] Directly take the non-impurity-removed anthracite, place it in a tube furnace, carbonize at 600°C for 2 h under argon atmosphere, cool and take out to obtain carbonized coal powder.

[0079] Take 1.5 g of carbonized coal powder, add to 60 mL of anhydrous ethanol, then add 1.217 g (7.5 mmol) of FeCl3 and mix well, heat to 80°C water bath until the anhydrous ethanol is completely evaporated.

[0080] Dry and grind the FeCl3-loaded coal powder, place it in an arc plasma device, set the current of the device to 25 A and the voltage to 20 V, and perform arc plasma high-voltage discharge in an argon atmosphere to obtain 1 g of the reaction crude product.

[0081] The crude product was collected and purified in 60 mL of 5 M HCl solution. After stirring at room temperature for 6 h, the solution was washed until neutral to obtain the target product, which was named CNM1.

[0082] Comparative Example 2

[0083] The purified anthracite was placed in a tubular furnace and carbonized at 600°C for 2 hours under an argon atmosphere. After cooling, it was removed to obtain carbonized coal powder.

[0084] The carbonized coal powder was ground and placed in an electric arc plasma device. The device was set with a current of 25A and a voltage of 20V. High-voltage discharge of electric arc plasma was carried out in an argon atmosphere to obtain 1g of crude reaction product.

[0085] The crude product was collected and purified in 60 mL of 5 M HCl solution. After stirring at room temperature for 6 h, the solution was washed until neutral to obtain the target product, which was named CNM2s.

[0086] Comparative Example 3

[0087] According to the literature AMA Mohamed, et.al., A comparison of the electrochemical performance of graphitized coal prepared by high-temperature heating and flash Joule heating as an anode material for lithium and potassium ionbatteries[J]. Chemical Physics Letters The method described in , 2023, 815: 140362, uses high-temperature heating to catalytically graphitize coal, transforming the amorphous structure of coal into a crystalline structure.

[0088] Anthracite pulverized coal was used as raw material and carbonized at 600℃ for 6 hours in a tubular furnace, followed by natural cooling.

[0089] Weigh 5 mmol of nickel chloride and 1 g of anthracite powder, add them to 100 ml of ethanol, stir at 600 rpm for 1 h to mix evenly, dry at 80 °C for 24 h to obtain nickel-impregnated anthracite powder, catalytically graphitize it in a high-temperature furnace at 1400 °C for 10 h, cool to room temperature, collect the graphitization product, wash with HCl to remove the Ni catalyst, wash with water until neutral, and vacuum dry at 60 °C for 24 h to obtain graphitized carbon nanomaterials, named HTC.

[0090] Comparative Example 4

[0091] According to the literature of Comparative Example 3, the coal was catalytically graphitized by flash joule heating (FJH), and the amorphous structure of the coal was successfully converted into a crystal structure.

[0092] The anthracite powder was carbonized in a tube furnace at 600℃ for 6h and naturally cooled.

[0093] The carbon black and carbonized coal powder were mixed at a mass ratio of 10:90, 100mg of which was placed in a quartz tube, and a graphite rod was used as the electrode on both sides and connected to the FJH device. A capacitor bank with a capacitance of 60mF was used to provide a direct current discharge current with a maximum voltage of up to 400V, which heated the sample to 3000℃ within a few seconds, and then the amorphous carbon was converted into graphite carbon, and then a pulse of 300V was applied to the sample for about 5s under a slight vacuum of 10mmHg.

[0094] After 5min of FJH reaction, the sample was cooled to room temperature, removed and ground, and washed repeatedly with HCl and deionized water, and dried at 60℃ under vacuum for 24h to obtain graphitized carbon nanomaterials, named FHC.

[0095] Application Example 1

[0096] Figure 1 and Figure 2 The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the OLFs prepared in Examples 1-5 are shown, respectively.

[0097] It can be observed from Figure 1 that the carbonization temperature has no significant effect on the morphology of the material. As the carbonization temperature increases, the morphology of the material does not have a significant trend, and is mainly irregular block-shaped, and the particle size of each material is relatively not uniform, and the particle size range is about 2-10μm, indicating that the carbonization temperature has little effect on the particle size of the material.

[0098] The morphology and structure of the OLFs were further analyzed by TEM, and the specific results are shown in Figure 2 It can be seen that the prepared OLFs have a typical onion-like multilayer carbon shell structure, including OLFs with Fe core inside and hollow OLFs.

[0099] Figure 3 X-ray diffraction (XRD) analysis was performed on the five materials to further investigate the structural changes of the materials.

[0100] The five materials all have diffraction peaks corresponding to the graphite (002) crystal face near 26°, accompanied by sharp peaks representing Fe2O3 phase, indicating that Fe2O3 may be reduced to elemental Fe during the catalysis process, thereby playing a catalytic role. With the carbonization temperature increasing to 800℃, the half peak width of the material presents a trend of first increasing and then decreasing, and the 900AC-OLFs have the largest half peak width, indicating that the graphitization degree of the 900AC-OLFs is the lowest. At the same time, with the increase of the carbonization temperature, it can be seen that the (002) face peak of the material around 26° slightly shifts to the left, indicating that the average carbon layer spacing of the material increases.

[0101] The proportion of graphite structure and amorphous structure in the material is analyzed by Raman spectrum test, and the specific results are shown in Figure 4 .

[0102] The D peak of Raman spectrum at 1350cm -1 around corresponds to the defects, impurities or sp 3 hybridization of diamond structure in the material, while the G peak at 1580cm -1 around corresponds to the sp 2 hybridization in the material, that is, the number of graphite structures, so the graphitization degree of the product can be judged. I D / I G The graphitization degrees of the five OLFs are 0.76, 0.69, 0.83, 0.87 and 0.94 respectively, indicating that the number of internal defects of the material increases with the increase of the carbonization temperature. I D / I G The X-ray diffraction pattern of the carbon nanomaterial prepared in Comparative Example 1 is shown in

[0103] Figure 5 It can be seen that the product prepared from the non-impurity anthracite as the raw material is greatly affected by silicate impurities.

[0104] Figure 6 The transmission electron microscope image of the carbon nanomaterial prepared in Comparative Example 2 is shown in

[0105] According to the characterization in Figures 1-4 , the 800AC-OLFs have moderate defects, which not only have many lithium storage sites, but also are beneficial to the reversible storage of lithium ions.

[0106] Application Example 2

[0107] The five OLFs prepared in Examples 1-5 were used as negative active materials of lithium ion batteries, NMP was used as solvent, and electrode slurry was prepared according to the mass ratio of active material: PVDF binder: acetylene black conductive agent = 8:1:1, and then was applied on copper foil to prepare working electrode, and was assembled into CR2032 type half battery together with metal lithium counter electrode, 1M LiPF6 / (EC:DEC:EMC = 1:1:1) electrolyte and PP separator.

[0108] The electrochemical performance test was performed using a new battery tester, and the galvanostatic charge-discharge curve (GCD) was tested at 0.05A g -1 , the cycle life was tested at 0.1A g -1 , and the rate performance was tested at 0.05-5A g -1 .

[0109] Figure 7 In the GCD graph of the five materials, the specific capacity of the five materials at a current density of 0.05A g -1 was 474, 652, 507, 678 and 427mAh g -1 , respectively, and the initial coulombic efficiency (ICE) was 42%, 67%, 69%, 81% and 60%, respectively. It can be seen that the initial coulombic efficiency (ICE) of the product after carbonization treatment is significantly improved. The specific capacity of the remaining samples also has a significant increase, and although the specific capacity of 900AC-OLFs is slightly lower, it is not significant.

[0110] While Figure 8 Comparative Examples 3 and 4 showed that the initial charge and discharge specific capacity of HTC was 322.5 and 463mAh g -1 , respectively, and the initial charge and discharge specific capacity of FHC was 321.3 and 450.6mAh g -1 , respectively, at a current density of 0.1C (1C = 372mAh g -1 ); the initial coulombic efficiency (ICE) of HTC and FHC was about 70% and 71.3%, respectively.

[0111] After comparison, it can be seen that although the same carbonization treatment is performed, the coal-based carbon nanomaterials prepared by high-temperature pyrolysis and flash pyrolysis have much lower performance as negative electrodes of lithium ion batteries than the product obtained by arc plasma, that is, the specific capacity of the material for storing lithium is lower at a smaller current density, and the product obtained by arc plasma has higher ICE while maintaining high specific capacity.

[0112] According to the cycle life curve of Figure 9 , it can be seen that the five materials have a current density of 0.1A g -1The initial discharge / charge specific capacities of the five materials were 458 / 432, 440 / 419, 422 / 408, 572 / 546 and 414 / 399 mAh g -1 , and the initial coulombic efficiencies (ICE) were 94%, 95%, 97%, 95% and 96%, respectively. In addition, after 100 cycles, the charge specific capacities of the five materials were 462, 409, 439, 626 and 433 mAh g -1 .

[0113] It can be seen that the five materials all maintained a high ICE. Except for the 600AC-OLFs, the charge specific capacities of the other materials after 100 cycles were all improved compared with the initial charge specific capacities, indicating that different degrees of electrochemical activation occurred.

[0114] In addition, Figure 10 The cycle behavior and coulombic efficiency of the HTC and FHC electrodes after 100 cycles at a current rate of 2C are shown. During the initial charge cycle, the capacity of the HTC was 215.8 mAh g -1 , and after 100 cycles, the capacity was still 199.2 mAh g -1 , with a capacity retention rate of about 99%; the initial charge capacity of the FHC was 179.6 mAh g -1 , and after 100 cycles, the capacity was 166.1 mAh g -1 , with a coulombic efficiency close to 99%.

[0115] Application Example 3

[0116] The output current of a lithium ion battery during use is often not constant, so it is necessary to investigate the rate performance of the material at different current densities, and the specific results are shown in Figure 11 .

[0117] According to the rate performance curves of the five materials at current densities of 0.05-5 A g -1 , it can be seen that the 800AC-OLFs can maintain the highest specific capacity at low current densities (0.05 and 0.1 A g -1 ). As the current density increased to 5 A g -1 , the specific capacities of the five materials were 39, 138, 163, 197 and 161 mAh g -1 , and the capacity retention rates were 8%, 21%, 32%, 29% and 38%, respectively, which may be due to the problem of large volume change within the material at a high current density. In addition, it can also be seen that carbonization treatment plays an important role in improving the capacity retention rate of the material at high rates.

[0118] As the current density increased from 5 A g -1Recovery to 0.05A g -1 The specific capacity of the five materials can be effectively recovered, and the discharge specific capacity before and after recovery is 474 / 445, 652 / 455, 507 / 430, 678 / 560 and 427 / 403mAh g -1 at 0.05A g -1 , indicating that the material has practical application prospect.

[0119] In combination with the above test conclusions, carbonization treatment has a significant influence on the lithium storage performance of the coal-based OLFs prepared by the arc plasma method, and too high carbonization temperature can lead to a decrease in the lithium storage performance of the OLFs, the coal-based OLFs prepared under 800 DEG C carbonization treatment have the highest lithium storage specific capacity, and have practical application prospect.

[0120] The above embodiments of the present application do not describe all the details, and the present application is not limited to the above described embodiments. Various changes, modifications, replacements and variations of the embodiments made by those skilled in the art without departing from the principles and purposes of the present application shall be included in the protection scope of the present application.

Claims

1. A preparation method of coal-based onion-like fullerene with high lithium storage performance, which is prepared by using anthracite as a carbon source according to the following steps: 1) performing hydrogen fluoride acid impurity removal treatment on the anthracite to obtain impurity-removed anthracite; 2) performing high-temperature carbonization on the impurity-removed anthracite under an inert atmosphere to obtain carbonized coal powder; 3) uniformly dispersing the carbonized coal powder in an anhydrous ethanol solution of a water-soluble iron salt, and evaporating the anhydrous ethanol to obtain iron salt catalyst-loaded coal powder; 4) placing the iron salt catalyst-loaded coal powder in an electric arc plasma device, and performing high-voltage discharge reaction under an argon atmosphere at a current of 25-35 A and a voltage of 20 V to obtain a reaction crude product; and 5) performing purification treatment on the reaction crude product with a hydrochloric acid solution, and washing to neutral to obtain the coal-based onion-like fullerene target product. The anthracite is crushed into coal powder with a particle size of 200 mesh or less. The anthracite is subjected to impurity removal treatment with a mixed acid solution of hydrofluoric acid and hydrochloric acid. The mixed acid solution of hydrofluoric acid and hydrochloric acid is prepared by mixing 10 wt% hydrofluoric acid and 4 M hydrochloric acid solution at a volume ratio of 4:

5. The anthracite coal powder is added to 10 times the volume of the mixed acid solution, and stirred at room temperature for no less than 12 h. The impurity-removed anthracite is subjected to high-temperature carbonization treatment at 600-900 ℃ under an inert atmosphere for 2-6 h.

2. The method for preparing coal-based onion-like fullerenes according to claim 1, characterized in that: The iron salt loaded in the iron salt catalyst-loaded coal powder is 0.4-1.0 times the mass of the carbonized coal powder.

3. The method of claim 1, wherein the coal-based onion-like fullerene is prepared by the process of claim 1, wherein the process is characterized by The reaction crude product of the electric arc plasma reaction is subjected to purification treatment with a 4-6 M hydrochloric acid solution.

4. The method of claim 3, wherein the coal-based onion-like fullerene is prepared by the process of claim 1 or 2.

9. The coal-based onion-like fullerene material prepared by the preparation method of any one of claims 1-8.

5. The method of claim 3, wherein the coal-based onion-like fullerene is prepared by the process of claim 1 or 2.

10. Use of the coal-based onion-like fullerene material of claim 9 as a negative electrode material for lithium ion batteries.

6. The method for preparing coal-based onion-like fullerenes according to claim 1, characterized in that: ​ 7. The method for preparing coal-based onion-like fullerenes according to claim 1, characterized in that: ​ 8. The method of claim 1, wherein the coal-based onion-like fullerene is prepared by ​ ​ ​

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