Hard carbon negative electrode material and preparation method thereof

Abstract

The application discloses a kind of hard carbon negative electrode material and preparation method thereof, belong to lithium ion, sodium ion battery technical field, the application is carried out graphitization carbon coating to hard carbon surface using plasma method, step 1: with anthracite as reactant, using ball milling process to the mixture is ball milled, the obtained product is soaked with hydrochloric acid and hydrofluoric acid to remove impurities, then washed with water to neutral;Step 2: precursor obtained in step 1 is heated in air and pre-oxidized;Then, high-temperature carbonization is carried out under argon atmosphere;Step 3: with alcohol as carbon source, the product obtained in step 2 is placed in radio frequency inductive coupled plasma, liquid alcohol is heated to gaseous state and carrier gas is introduced into discharge cavity together, and plasma discharge is carried out, and finally hard carbon negative electrode material is obtained.The hard carbon negative electrode material obtained by step 3 plasma treatment has higher coulomb efficiency and specific capacity than the hard carbon negative electrode without carbon layer coating obtained in step 2.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion and sodium-ion battery technology, and particularly relates to a hard carbon anode material and its preparation method. Background Technology

[0002] Hard carbon is widely used as an anode material in sodium-ion and lithium-ion batteries. However, in practical applications, hard carbon materials suffer from low specific capacity, low initial coulombic efficiency, and low rate performance. To address these issues, this invention uses vaporized alcohols as plasma discharge gases to modify their surface. The carbon active groups decomposed in the alcohol plasma coat the surface with a graphitized carbon layer, thereby improving the initial coulombic efficiency and discharge specific capacity of the hard carbon anode material. Summary of the Invention

[0003] To address the problems in the background art, this invention proposes a hard carbon anode material and its preparation method.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing a hard carbon anode material includes the following steps:

[0006] (1) Precursor treatment: After milling the anthracite balls, soak them in a mixed solution of hydrochloric acid and hydrofluoric acid to remove impurities, and wash them with water until neutral;

[0007] (2) Segmented carbonization: The product described in step (1) is pre-oxidized in air at a temperature range of 200~500℃ and a heating rate of 2~20℃ / min; then carbonized at high temperature under argon at a temperature range of 1100~1500℃ and a heating rate of 2~20℃ / min to obtain uncoated hard carbon.

[0008] (3) Plasma coating: Using alcohol as carbon source, the hard carbon described in step (2) is placed in a radio frequency inductively coupled plasma cavity. The liquid alcohol is heated to a gaseous state and introduced into the discharge cavity together with the carrier gas to perform plasma discharge, thereby obtaining a hard carbon anode material.

[0009] In the above technical solution, the ball milling time in step (1) is 0.5~5h, and the ball-to-powder mass ratio is 10:1~100:1.

[0010] In the above technical solution, the concentrations of hydrochloric acid and hydrofluoric acid in step (1) are both 1~5 mol / L, the concentration ratio is 10:1~1:10, and the soaking time is 2~6h.

[0011] In the above technical solution, the pre-oxidation temperature in step (2) is 200~400℃, the reaction time is 0.5~5h, and the high-temperature carbonization reaction time is 0.5~10h.

[0012] In the above technical solution, the plasma discharge power in step (3) is 100~1000W, the discharge time is 0.2h~3h, and the gas pressure is 10~300Pa.

[0013] In the above technical solution, in step (3), the alcohol is one or a mixture of ethanol, methanol or propanol, and the heating temperature is 200~500℃; the carrier gas is one or a mixture of nitrogen, argon or hydrogen; the volume ratio of alcohol to carrier gas is 1:100~100:1.

[0014] A hard carbon anode material is prepared by the above method, and its surface is coated with a graphitized carbon layer with a thickness of 3-10 nm.

[0015] In the above technical solution, the initial coulombic efficiency is improved by 10%~20% compared with uncoated hard carbon, and the specific capacity is increased by 20~50mAh / g.

[0016] The aforementioned hard carbon anode material is used in sodium-ion batteries or lithium-ion batteries as the anode material.

[0017] Beneficial effects:

[0018] 1. After plasma alcoholization: After step (3), a graphitized carbon layer is formed by plasma, with a carbon layer thickness of 3~10nm.

[0019] 2. Performance improvement: After the hard carbon is modified by ethanol plasma in step (3), its initial coulombic efficiency is increased by 10%~20%, and the battery specific capacity is increased by 20~50mAh / g. Attached Figure Description

[0020] Figure 1 The image shows the transmission electron microscope (TEM) morphology of the hard carbon prepared in Example 1.

[0021] Figure 2 The specific surface area of ​​the hard carbon synthesized in Example 1 after being coated with ethanol and argon plasma is given.

[0022] Figure 3 The specific surface area is the hard carbon synthesized without plasma encapsulation in Example 1.

[0023] Figure 4 The charge-discharge curves are those of the hard carbon and uncoated carbon materials prepared in Example 1. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0025] Example 1:

[0026] Using 500g of anthracite as reactant, the material was ball-milled for 3 hours. The resulting product was then immersed in a 100ml solution of 1mol / L hydrochloric acid and hydrofluoric acid for 3-4 hours. The precursor was heated to 500℃ in air at a rate of 5℃ / min and held for 3 hours. Subsequently, it was heated to 1300℃ under an argon atmosphere at a rate of 5℃ / min for 5 hours. The resulting product was placed in a radio frequency inductively coupled plasma discharge chamber. Ethanol gas was heated to 300℃ and introduced into the discharge chamber along with argon gas for plasma discharge at a power of 300W, a discharge time of 20 minutes, and a pressure of 50Pa, ultimately yielding a carbon-coated hard carbon anode material. The hard carbon prepared in the above example was tested by TEM, and the results are as follows: Figure 1 As shown, the carbon layer thickness is approximately 10 nm. Figure 2 and Figure 3 As shown, after being coated with alcohol plasma, the specific surface area of ​​hard carbon increased from 89.97 m². 2 / g decreased to 52.61 m 2 / g, the reduction in specific surface area effectively improves the initial coulombic efficiency. The hard carbon prepared in the above steps was subjected to battery performance testing, and the results are as follows: Figure 4 As shown, the charge / discharge specific capacities of the uncoated carbon are 380 mAh / g and 272.9 mAh / g, respectively, with a charge / discharge efficiency of 71.8%. The charge / discharge specific capacities of the uncoated carbon after plasma coating are 338 mAh / g and 305.4 mAh / g, respectively, with a charge / discharge efficiency of 90.4%. Therefore, after carbon coating, the specific capacitance and initial charge / discharge efficiency are increased by 32.5 mAh / g, and the charge / discharge efficiency is increased by 18.6%.

[0027] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a hard carbon anode material, characterized in that, Includes the following steps: (1) Precursor treatment: After milling the anthracite balls, soak them in a mixed solution of hydrochloric acid and hydrofluoric acid to remove impurities, and wash them with water until neutral; (2) Segmented carbonization: The product described in step (1) is pre-oxidized in air at a temperature range of 200~500℃ and a heating rate of 2~20℃ / min; then carbonized at high temperature under argon at a temperature range of 1100~1500℃ and a heating rate of 2~20℃ / min to obtain uncoated hard carbon. (3) Plasma coating: Using alcohol as the carbon source, the hard carbon described in step (2) is placed in the radio frequency inductively coupled plasma cavity. The liquid alcohol is heated to a gaseous state and introduced into the discharge cavity together with the carrier gas to perform plasma discharge, and finally the hard carbon anode material is obtained.

2. The preparation method according to claim 1, characterized in that, In step (1), the ball milling time is 0.5 to 5 hours and the ball-to-powder mass ratio is 10:1 to 100:

1.

3. The preparation method according to claim 1, characterized in that, In step (1), the concentrations of hydrochloric acid and hydrofluoric acid are both 1~5 mol / L, the concentration ratio is 10:1~1:10, and the soaking time is 2~6h.

4. The preparation method according to claim 1, characterized in that, In step (2), the pre-oxidation temperature is 200~400℃, the reaction time is 0.5~5h, and the high-temperature carbonization reaction time is 0.5~10h.

5. The preparation method according to claim 1, characterized in that, In step (3), the plasma discharge power is 100~1000W, the discharge time is 0.2h~3h, and the gas pressure is 10~300Pa.

6. The preparation method according to claim 1, characterized in that, In step (3), the alcohol is one or more of ethanol, methanol, propanol, and isopropanol, and the alcohol is heated at a temperature of 200~500℃. The carrier gas is one or more of nitrogen, argon, and hydrogen. The volume ratio of alcohol to carrier gas is 1:100~100:

1.

7. A hard carbon anode material, characterized in that, Prepared by any one of claims 1-6, the surface of which is coated with a graphitized carbon layer with a thickness of 3-10 nm.

8. The hard carbon anode material according to claim 7, characterized in that, The initial coulombic efficiency is 10%~20% higher than that of uncoated hard carbon, and the discharge specific capacity is increased by 20~50mAh / g.

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