CN102324497A - A kind of preparation method of lithium battery negative electrode material of graphene supported carbon coating tin antimony - Google Patents

Abstract

The invention discloses a kind of graphene-supported carbon and coat the preparation method of tin pewter particle as cathode material of lithium-ion power battery; Be to be raw material with stannic chloride, antimony chloride, sodium borohydride, natural graphite powder; Peel off legal system through chemical oxidation and be equipped with graphene oxide; Vapour deposition process coats the Sn-Sb alloy particle, finally forms graphene-supported carbon and coats the tin pewter particle composite material, and this method key is at first to form graphene oxide load Sn-Sb alloy particle presoma; Again through acetylene gas reduction graphene oxide; Coat one deck carbon on Sn-Sb alloy particle surface simultaneously, belong to the coating of vapour deposition process and carbon and carry out simultaneously, can know that through electro-chemical test this novel graphite alkene load carbon coats the tin pewter particle composite material and has the potentiality that are applied to lithium-ion-power cell.

Description

A kind of preparation method of lithium battery negative electrode material of graphene supported carbon coating tin antimony

technical field

The present invention relates to a chemical oxidation exfoliation method and a vapor deposition method. Specifically, graphene oxide is prepared by a chemical oxidation exfoliation method, and Sn-Sb alloy particles are coated by a vapor deposition method to finally form a graphene-loaded Sn-SbC composite material. The key to this method is to firstly form a graphene oxide-supported Sn-Sb alloy particle precursor, then reduce the graphene oxide by acetylene gas, and at the same time coat a layer of carbon on the surface of the Sn-Sb alloy particles; vapor deposition and carbon coating At the same time, the new graphene composite material was finally prepared. The invention belongs to the technical field of preparation of negative electrode materials for lithium ion power batteries.

Background technique

    In recent years, the new generation of hybrid electric vehicles (HEV) and pure electric vehicles (EV) have attracted increasing attention, and lithium-ion batteries as their power have also become a technical hotspot. In order to meet the needs of high-power electric vehicles, the preparation of corresponding high-current The material for charging and discharging has become a key technology. To be able to be used as a power material, it must have the advantages of high electrical conductivity, large specific surface area, fast Li ⁺ diffusion rate and structural stability. Transition metals and their oxides, such as cobalt, tin, antimony, nickel, etc., have always attracted attention due to their high specific energy, but these metal materials will cause a sharp change in their volume due to the lithium ion intercalation and extraction process. , such as tin can reach up to about 3 times the original volume, which will cause the structure of the entire electrode material to collapse rapidly during the cycle. In order to limit this drawback, other materials such as carbon nanotube packaging, carbon coating, core-shell Or template limitation method and other techniques to limit the buffer volume change, and can improve the cycle performance of electrode materials.

Graphene (Graphene nanosheets, GNS) is a two-dimensional carbon material discovered in 2004 that can exist stably. It has high specific surface area, electrical conductivity and thermal stability, and has the potential to be applied to lithium-ion batteries. There are many studies on tin-antimony alloy materials. Different control methods are used to improve the cycle performance and lithium storage capacity of tin-antimony alloys. SA Needham et al. use NaBH ₄ to reduce Sn-Sb alloy particles with a size of 50-100 nm, and then combine them with carbon black Mixing, it is found that when the carbon black content reaches 50%, the reversible specific capacity of the active material reaches 800 mAh/g, and after 50 cycles, it stabilizes at about 580 mAh/g (Journal of Alloys and Compounds, 2005, 40, 234–238); Min-Sik Park et al. supported Sn-Sb alloy materials through carbon nanotubes, and its reversible specific capacity remained at 480 mAh/g after 50 cycles (Chemistry of Materials, 2007, 19, 2406-2410), which has a good Cycling performance, carbon nanotubes play a role in buffering and limiting the volume expansion of Sn-Sb alloys; Zhong Wang et al. prepared Sn-Sb nanospheres with a particle size between 100-300 nm (Journal of Alloys and Compounds, 2007, 439,350 –354), the first reversible specific capacity was 701 mAh/g, and it remained at 566 mAh/g after 20 cycles; the reversible specific capacity of the electrode material obtained by Wei Xiang Chen et al. by encapsulating SnSb _0.5 with carbon nanotubes was 518 mAh/g, After 30 cycles, it still maintains the original 67.2% (Carbon, 2003, 41,959–966); in addition, the energy density of carbon electrode materials can be further improved by loading metal alloy materials, and various carbon materials can significantly improve the energy density of metal alloy materials. Cycle performance, first charge and discharge coulombic efficiency, etc. The conditions of the vapor deposition method are easy to control, the material is uniform, and it has the potential for mass production, and it also promotes the further application of lithium-ion power batteries.

Contents of the invention

The purpose of the present invention is to use tin chloride, antimony chloride, sodium borohydride, and natural graphite powder as raw materials to prepare graphene oxide by chemical oxidation stripping method, and to coat Sn-Sb alloy particles by vapor deposition to finally form graphene-supported For Sn-SbC composite materials, the key to this method is to first form a graphene oxide-supported Sn-Sb alloy particle precursor, then reduce the graphene oxide by acetylene gas, and at the same time coat a layer of carbon on the surface of the Sn-Sb alloy particles.

The present invention is achieved through the following technical solutions.

The present invention is a preparation method of lithium battery negative electrode material of graphene-loaded carbon-coated tin-antimony alloy particles, which is characterized in that it has the following process and steps:

a. Weigh a certain amount of natural graphite powder in an ice-water bath and keep it under magnetic stirring at 0 ℃, first add a certain amount of HNO ₃ with a concentration of 65% and H ₂ SO ₄ with a concentration of 98%, then add a certain amount of KMnO ₄ , and heat up to 30-40 ℃ for 2-3 h; then raise the temperature to 70-90 ℃ for 1-2 h; add 300-500 ml of ultrapure water to dilute the concentrated acid to obtain a black colloidal substance; then add 10-20 ml of 30% H ₂ O ₂ and 100-150 ml of 10% HCl to wash to obtain a brownish-yellow solution; centrifuge and wash to neutral; dry at 50-60°C in air to obtain graphene oxide; the amount of natural graphite powder is between 1-2 g, At the same time, the mass ratio of natural graphite powder and KMnO ₄ is between 1:4-1:6; the amount of concentrated HNO ₃ is between 80-100 ml, and the concentration of 65% HNO ₃ and 98% H ₂ SO ₄ The dosage volume ratio is between 1:1-1:3;

b. Take a certain amount of tin chloride and antimony chloride respectively to prepare a certain volume of ethanol solution, stir well and mix to obtain a colorless and clear solution; at the same time, take a certain amount of the above-mentioned graphene oxide and ultrasonically disperse it in the aqueous solution for 1-2 h , to obtain a gel-like black solution, and add it to the above colorless and clear mixed solution to obtain a uniform black solution; prepare NaBH ₄ aqueous solution and add it to the above precursor solution; keep the temperature in an ice-water bath at 0-5 °C React for 1-2 hours, centrifuge and wash with water until neutral after the reaction; vacuum-dry at 50-60°C to obtain a black powder;

c. Put the above black powder in a tube furnace with a heating rate of 5-10 ℃/min, an airflow of 50-100 sccm, and a reduction of C ₂ H ₂ gas at 500-550 ℃ for 1-3 h to obtain the final product; The molar ratio of tin chloride to antimony chloride is between 3:1-4:1; the mass ratio of tin chloride to graphene oxide is between 1:1-1:6; The concentrations of antimony ethanol solution and _NaBH4 aqueous solution were between 0.006-0.01 M, 0.001-0.005 M and 0.008-0.015 M, respectively.

Description of drawings

Figure 1 is the X-ray diffraction (XRD) pattern of graphene-supported Sn-SbC composites.

Figure 2 is a scanning electron microscope (SEM) photo of graphene-loaded Sn-SbC composites.

Figure 3 is a transmission electron microscope (TEM) photo of graphene-loaded Sn-SbC composites.

Figure 4 is the charge-discharge specific capacity cycle performance graph of graphene-loaded Sn-SbC composites at different current rates (0.1C, 0.5C, 1C, 2C, 5C).

Detailed ways

Specific embodiments of the present invention are now described in the following.

Example 1

Take 2g of natural graphite powder and put it into a 1000mL flask, place the flask in ice water, keep the temperature in the ice water bath at about 0°C, add 80ml of HNO ₃ (65%) first, then carry out magnetic stirring for 10min, then add 120ml of H ₂ SO ₄ (98 %), stir for 1 hour, the temperature is about 20°C, slowly add 10g KMnO ₄ to avoid a sharp rise in temperature, keep the temperature at 35°C, stir magnetically for 2 hours after adding KMnO ₄ , then add 400ml of ultrapure water to obtain a black colloidal substance, Then add 40ml of 30% H ₂ O ₂ , the solution is brownish yellow, add 100ml of 10% HCl to wash, centrifuge at a speed of about 15000-18000rpm, wash with ultrapure water for 3 times until the sample is neutral, and finally carry out Dry to obtain graphene oxide.

According to the final theory, the mass ratio of Sn-Sb alloy and graphene in the graphene-loaded Sn-SbC product is 2:1 to prepare the reaction raw materials. Prepare solution A first: dissolve 0.009M SnCl ₄ in 20 ml of absolute ethanol and stir magnetically to fully dissolve. Reconstitute B solution: dissolve 0.003M SbCl ₃ in 20 ml of absolute ethanol, stir magnetically, and fully dissolve. Then add B dropwise to A with magnetic stirring to obtain a clear solution. In addition, ultrasonically disperse 0.056 g of the above-mentioned graphene oxide into 10 ml of deionized water, and add it to the above-mentioned A:B mixed solution; stir for 1 hour, and ultrasonically dissolve it for 30 minutes to form a slurry; then prepare C solution: add 0.012M Dissolve NaBH ₄ in 20ml of ultrapure water, and add it dropwise to the slurry solution obtained above; stir in an ice-water bath, keep the temperature below 3°C (under the condition of not exceeding 5°C), and add dropwise within 30min , stirred for 2 hours. Then centrifuge, wash with water, until neutral; vacuum dry at 65°C for 12h; then place the sample in a tube furnace with a heating rate of 5-10°C/min, C ₂ H ₂ air flow of 50-100 sccm, and use C at 500°C ₂ H ₂ gas reduction for 2 hours, the graphene supported Sn-SbC composite material was obtained.

Electrode preparation and testing

The preparation of the electrode is to set the weight ratio of the above-mentioned composite material active material, conductive agent (carbon black) and binder (polyvinylidene fluoride-PVDF) to 8:1:1, and use N, N-dimethylpyrrolidone (NMP) is used as a solvent to make the electrode material into a slurry, apply it on a bright copper sheet, and dry it under vacuum at 85°C for 10h. A lithium sheet is used as the counter electrode, the electrolyte is 1M lithium hexafluorophosphate (LiPF ₆ ), and the solvent is a mixture of ethylene carbonate and divinyl carbonate with a weight ratio of 1:1. The test current density is 0.1C, 0.5C, 1C, 2C and 5C, where 1C is equal to 800 mA/g, and the test voltage range is 0.005-3V.

As shown in Figure 1: After analysis, the product is a graphene-loaded Sn-SbC composite material with high crystallinity (Sn phase, corresponding to the standard sample JCPDS 04-0673 and SnSb phase, corresponding to the standard sample JCPDS 33-0018). Accompanying drawing 2 is its SEM photo: It can be seen that graphene supports Sn-SbC composite material, graphene presents a nearly transparent film, Sn-Sb alloy is evenly dispersed on the inner and outer surfaces of graphene, and the particle size is between 50-150nm . Figure 3 is a transmission electron microscope (TEM) photo of the graphene-supported Sn-SbC composite material prepared in this implementation. Covered with a layer of carbon, which is obtained by vapor deposition. Figure 4 is a diagram of the charge-discharge specific capacity of the graphene-supported Sn-SbC composite material in the first 30 cycles at different current density ratios. It can be seen from Figure 4 that the specific capacity remains at 897 mAh/g after 30 cycles at a current density of 80 mA/g; the specific capacity remains at 408 mAh/g after 30 cycles at a current density of 4000 mA/g, still The theoretical capacity of 372 mAh/g is higher than that of natural graphite; it can be seen that this material still has superior performance under high current, excellent cycle performance, and has the potential to be applied to lithium-ion battery electric vehicles.

Claims (1)

1. a kind of preparation method of the negative electrode material of lithium battery of graphene supported carbon coating tin-antimony alloy particle, it is characterized in that having following technological process and step: a. Weigh a certain amount of natural graphite powder in an ice-water bath and keep it under magnetic stirring at 0 ℃, first add a certain amount of HNO ₃ with a concentration of 65% and H ₂ SO ₄ with a concentration of 98%, then add a certain amount of KMnO ₄ , and heat up to 30-40 ℃ for 2-3 h; then raise the temperature to 70-90 ℃ for 1-2 h; add 300-500 ml of ultrapure water to dilute the concentrated acid to obtain a black colloidal substance; then add 10-20 ml of 30% H ₂ O ₂ and 100-150 ml of 10% HCl to wash to obtain a brownish-yellow solution; centrifuge and wash to neutral; dry at 50-60°C in air to obtain graphene oxide; the amount of natural graphite powder is between 1-2 g, At the same time, the mass ratio of natural graphite powder and KMnO ₄ is between 1:4-1:6; the amount of concentrated HNO ₃ is between 80-100 ml, and the concentration of 65% HNO ₃ and 98% H ₂ SO ₄ The dosage volume ratio is between 1:1-1:3; b. Take a certain amount of tin chloride and antimony chloride respectively to prepare a certain volume of ethanol solution, stir well and mix to obtain a colorless and clear solution; at the same time, take a certain amount of the above-mentioned graphene oxide and ultrasonically disperse it in the aqueous solution for 1-2 h , to obtain a gel-like black solution, and add it to the above colorless and clear mixed solution to obtain a uniform black solution; prepare NaBH ₄ aqueous solution and add it to the above precursor solution; keep the temperature in an ice-water bath at 0-5 °C React for 1-2 hours, centrifuge and wash with water until neutral after the reaction; vacuum-dry at 50-60°C to obtain a black powder; c. Put the above black powder in a tube furnace with a heating rate of 5-10 ℃/min, an airflow of 50-100 sccm, and a reduction of C ₂ H ₂ gas at 500-550 ℃ for 1-3 h to obtain the final product; The molar ratio of tin chloride to antimony chloride is between 3:1-4:1; the mass ratio of tin chloride to graphene oxide is between 1:1-1:6; The concentrations of antimony ethanol solution and _NaBH4 aqueous solution were between 0.006-0.01 M, 0.001-0.005 M and 0.008-0.015 M, respectively.

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