Hard carbon composite material for sodium ion battery and preparation method thereof

Abstract

The application relates to the technical field of battery negative electrode materials, and discloses a hard carbon composite material for a sodium ion battery and a preparation method of the hard carbon composite material. The preparation method of the hard carbon composite material for the sodium ion battery comprises the following steps: S1, uniformly mixing oxidized pitch, a pore-forming agent and a crosslinking agent, pre-carbonizing, and obtaining a precursor material; S2, placing the precursor material in a reactor, introducing water vapor, and obtaining a sodium-doped hard carbon precursor material; and S3, carbonizing the sodium-doped hard carbon precursor material, and obtaining a hard carbon composite material. The pore-forming agent in S1 comprises one or both of sodium hydride and sodium borohydride. Through the technical scheme, the problems of low specific capacity, low first efficiency, poor rate performance and poor cycle performance of the hard carbon material in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery negative electrode materials, in particular to a hard carbon composite material for sodium ion batteries and a preparation method thereof. BACKGROUND

[0002] Hard carbon is the main raw material of sodium ion battery negative electrode material. It is the first choice because of its abundant resources, wide material sources and simple preparation process. However, it has problems such as low specific capacity and low compactness, which further causes low energy density of sodium ion batteries. At present, there are many methods to improve the specific capacity of hard carbon material, such as raw material optimization, material doping pore forming, optimization of heat treatment temperature, precursor crosslinking to form more pores, etc. Among them, adding crosslinking agent is the simplest and most effective method.

[0003] Patent application No. CN202011018024.1 discloses a kind of hard carbon material and its preparation method and application. By introducing conductive additives into the precursor of hard carbon material to improve the conductivity of the obtained material, and combining with variable speed temperature pre-oxidation to introduce a large number of oxygen-containing functional groups, the crosslinking degree of the material skeleton is increased, thereby improving the strength and specific capacity of the material. However, the pores formed by crosslinking reaction are few, and the specific capacity of the material is limited, and the first efficiency is low. SUMMARY

[0004] The present application provides a kind of hard carbon composite material for sodium ion batteries and a preparation method thereof, which solves the problems of low specific capacity, low first efficiency, poor rate performance and poor cycle performance of hard carbon material in related technology.

[0005] The technical scheme of the present application is as follows:

[0006] A preparation method of a hard carbon composite material for sodium ion batteries, comprising the following steps:

[0007] S1, uniformly mix oxidized pitch, pore forming agent and crosslinking agent, and pre-carbonize to obtain a precursor material;

[0008] S2, place the precursor material in a reactor and introduce water vapor to obtain a sodium-doped hard carbon precursor material;

[0009] S3, carbonize the sodium-doped hard carbon precursor material to obtain a hard carbon composite material.

[0010] As a further technical solution, the pore forming agent in S1 includes one or both of sodium hydride and sodium borohydride.

[0011] As a further technical solution, the pre-carbonization temperature in S1 is 300-400℃, and the time is 1-6h.

[0012] As a further technical solution, the cross-linking agent in S1 includes one or more of m-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, trioxane, and 4-hydroxy-3-methoxybenzaldehyde.

[0013] As a further technical solution, the mass ratio of the oxidized pitch, the pore-forming agent, and the cross-linking agent in S1 is 100:0.5-6:10-20.

[0014] As a further technical solution, the mass ratio of the oxidized pitch, the pore-forming agent, and the cross-linking agent in S1 is 100:1-5:10-20.

[0015] As a further technical solution, the mixing in S1 is performed by ball milling, and the ball milling time is 0.5-2 h.

[0016] As a further technical solution, the ball milling is performed in a ball mill with a rotation speed of 100-500 r / min.

[0017] As a further technical solution, the preparation method of the oxidized pitch in S1 includes the following steps: uniformly mixing pitch, a conductive agent, and an acid anhydride, and performing an oxidation reaction to obtain the oxidized pitch.

[0018] As a further technical solution, the mass ratio of the pitch, the conductive agent, and the acid anhydride is 80-95:1-5:1-5.

[0019] As a further technical solution, the conductive agent includes one or more of carbon nanotubes, iron powder, nickel powder, and cobalt powder.

[0020] As a further technical solution, the acid anhydride includes one or more of glycine anhydride, maleic anhydride, glutaric anhydride, and succinic anhydride.

[0021] As a further technical solution, the oxidation reaction specifically involves flowing oxygen at a flow rate of 100-1000 mL / min to perform the oxidation reaction.

[0022] As a further technical solution, the oxidation reaction is performed at a temperature of 200-300℃ for 30-300 min.

[0023] As a further technical solution, the temperature is increased to 200-300℃ at a rate of 1-5℃ / min.

[0024] As a further technical solution, the flow rate of the water vapor in S2 is 100-500 mL / min, and the time is 30-300 min.

[0025] As a further technical solution, the carbonization in S3 is performed at a temperature of 1800-2200℃ for 1-6 h.

[0026] As a further technical solution, the carbonization in S3 further includes cooling, washing and drying.

[0027] The application further provides a hard carbon composite material for a sodium ion battery, which is prepared by the preparation method.

[0028] The working principle and beneficial effects of the application are as follows:

[0029] 1. In the application, one or both of sodium hydride and sodium borohydride are used as a pore-forming agent. By adding the pore-forming agent into oxidized pitch and introducing water vapor to react, larger pores are formed. Then, the pore structure is regulated by high-temperature carbonization, so that suitable nano / micropore structures are formed, the sodium storage function of the material is improved, and the specific capacity is improved. At the same time, the doping of sodium in the hard carbon reduces defects, improves the initial efficiency, rate performance and cycle performance.

[0030] 2. In the application, by adding a conductive agent and an acid anhydride into the pitch, the conductivity of the oxidized pitch is improved, and more hydrogen / carboxyl chemical groups are formed on the surface, thereby improving the specific capacity of the oxidized pitch under the action of the crosslinking agent in the subsequent process. BRIEF DESCRIPTION OF DRAWINGS

[0031] The application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Figure 1 FIG. 1 is a SEM image of the hard carbon composite material obtained in Example 1 of the application. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0034] The oxidized pitch in the following examples and comparative examples is prepared by the following method:

[0035] 90g of pitch (coal pitch with a softening point of 200℃), 3g of carbon nanotubes (multi-walled carbon nanotubes with an inner diameter of 3-5nm, an outer diameter of 8-15nm, a length of 3-12μm and a specific surface area of >233m 2 / g, purchased from Suzhou Carbon Graphene Technology Co., Ltd., model CNTS-010-0), and 3g of glycine anhydride are added to a mixer, heated to 250℃ at a heating rate of 3℃ / min, oxygen is introduced at a flow rate of 500mL / min, and an oxidation reaction is carried out for 120min to obtain oxidized pitch.

[0036] Example 1

[0037] S1, 100 g of oxidized pitch, 3 g of sodium hydride, and 15 g of m-hydroxybenzaldehyde were added to a planetary ball mill with a rotation speed of 300 r / min and ball-milled for 1 h, and then pre-carbonized at 400 DEG C for 3 h to obtain a precursor material;

[0038] S2, the precursor material was transferred to a vacuum furnace, water vapor was introduced at a flow rate of 300 mL / min for 120 min, and then the temperature was lowered to room temperature to obtain a sodium-doped hard carbon precursor material;

[0039] S3, the sodium-doped hard carbon precursor material was carbonized at 2000 DEG C for 3 h, and then the temperature was lowered to room temperature, washed with 0.1 mol / L dilute hydrochloric acid, and vacuum dried at 80 DEG C for 24 h to obtain a hard carbon composite material.

[0040] Example 2

[0041] S1, 100 g of oxidized pitch, 1 g of sodium hydride, and 10 g of 3-hydroxybenzaldehyde were added to a planetary ball mill with a rotation speed of 100 r / min and ball-milled for 2 h, and then pre-carbonized at 300 DEG C for 6 h to obtain a precursor material;

[0042] S2, the precursor material was transferred to a vacuum furnace, water vapor was introduced at a flow rate of 100 mL / min for 300 min, and then the temperature was lowered to room temperature to obtain a sodium-doped hard carbon precursor material;

[0043] S3, the sodium-doped hard carbon precursor material was carbonized at 1800 DEG C for 6 h, and then the temperature was lowered to room temperature, washed with 0.1 mol / L dilute hydrochloric acid, and vacuum dried at 80 DEG C for 24 h to obtain a hard carbon composite material.

[0044] Example 3

[0045] S1, 100 g of oxidized pitch, 5 g of sodium hydride, and 20 g of trioxymethylene were added to a planetary ball mill with a rotation speed of 500 r / min and ball-milled for 0.5 h, and then pre-carbonized at 350 DEG C for 1 h to obtain a precursor material;

[0046] S2, the precursor material was transferred to a vacuum furnace, water vapor was introduced at a flow rate of 500 mL / min for 30 min, and then the temperature was lowered to room temperature to obtain a sodium-doped hard carbon precursor material;

[0047] S3, the sodium-doped hard carbon precursor material was carbonized at 2200 DEG C for 1 h, and then the temperature was lowered to room temperature, washed with 0.1 mol / L dilute hydrochloric acid, and vacuum dried at 80 DEG C for 24 h to obtain a hard carbon composite material.

[0048] Example 4

[0049] S1, 100 g of oxidized pitch, 1 g of sodium borohydride and 10 g of 3-hydroxybenzaldehyde were added to a planetary ball mill with a rotation speed of 100 r / min and ball milled for 2 h, then pre-carbonized at 300 DEG C for 6 h to obtain a precursor material;

[0050] S2, the precursor material was transferred to a vacuum furnace, water vapor was introduced at a flow rate of 100 mL / min for 300 min, and then cooled to room temperature to obtain a sodium-doped hard carbon precursor material;

[0051] S3, the sodium-doped hard carbon precursor material was carbonized at 1800 DEG C for 6 h, then cooled to room temperature, washed with 0.1 mol / L dilute hydrochloric acid, and vacuum dried at 80 DEG C for 24 h to obtain a hard carbon composite material.

[0052] Example 5

[0053] S1, 100 g of oxidized pitch, 0.5 g of sodium hydride and 15 g of m-hydroxybenzaldehyde were added to a planetary ball mill with a rotation speed of 300 r / min and ball milled for 1 h, then pre-carbonized at 400 DEG C for 3 h to obtain a precursor material;

[0054] S2, the precursor material was transferred to a vacuum furnace, water vapor was introduced at a flow rate of 300 mL / min for 120 min, and then cooled to room temperature to obtain a sodium-doped hard carbon precursor material;

[0055] S3, the sodium-doped hard carbon precursor material was carbonized at 2000 DEG C for 3 h, then cooled to room temperature, washed with 0.1 mol / L dilute hydrochloric acid, and vacuum dried at 80 DEG C for 24 h to obtain a hard carbon composite material.

[0056] Example 6

[0057] S1, 100 g of oxidized pitch, 6 g of sodium hydride and 15 g of m-hydroxybenzaldehyde were added to a planetary ball mill with a rotation speed of 300 r / min and ball milled for 1 h, then pre-carbonized at 400 DEG C for 3 h to obtain a precursor material;

[0058] S2, the precursor material was transferred to a vacuum furnace, water vapor was introduced at a flow rate of 300 mL / min for 120 min, and then cooled to room temperature to obtain a sodium-doped hard carbon precursor material;

[0059] S3, the sodium-doped hard carbon precursor material was carbonized at 2000 DEG C for 3 h, then cooled to room temperature, washed with 0.1 mol / L dilute hydrochloric acid, and vacuum dried at 80 DEG C for 24 h to obtain a hard carbon composite material.

[0060] Comparative Example 1

[0061] The difference from Example 1 is only that sodium hydride is not added.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that the oxidized asphalt is replaced with an equal amount of asphalt.

[0064] Performance testing:

[0065] (1) SEM test: The hard carbon composite material obtained in Example 1 was subjected to SEM test, and the results are as follows. Figure 1 As shown.

[0066] Depend on Figure 1 As can be seen, the hard carbon composite material prepared in Example 1 of the present invention exhibits a granular structure with uniform size distribution and local porous structure, with a particle size between 10 and 15 μm.

[0067] (2) Physical and chemical properties and button cell performance testing: The hard carbon composite materials obtained in Examples 1-6 and Comparative Examples 1-2 were tested for tap density, specific surface area, specific capacity and initial efficiency according to the methods in GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries", and the interlayer spacing of the materials was tested by XRD.

[0068] The hard carbon composite materials obtained in Examples 1-6 and Comparative Examples 1-2 were assembled into button cells. The preparation method was as follows: hard carbon composite material, LA132 binder, conductive agent SP, and double-distilled water were mixed, stirred to form a slurry, coated onto copper foil, and dried and rolled to obtain the negative electrode sheet. The ratio of hard carbon composite material: conductive agent SP: LA132 binder: double-distilled water = 94g: 2g: 4g: 220mL; the electrolyte was NaPF6 / EC+DEC (volume ratio 1:1, concentration 1.1mL). The battery was constructed using sodium metal sheets as the counter electrode and polyethylene membrane as the separator. The simulated battery was assembled in an argon-filled glove box. Electrochemical performance was tested using a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.00V~2.0V, and the charge / discharge rate was 0.1C. Simultaneously, the rate performance (2C / 0.1C) and cycle performance (0.2C / 0.2C, 200 cycles) of the coin cell were tested. The OI value of the negative electrode was measured by XRD. The test results are shown in Table 1 below.

[0069] Table 1. Physicochemical properties and button cell performance of hard carbon composite materials

[0070]

[0071] As shown in Table 1, compared with Comparative Examples 1 and 2, the hard carbon composite material obtained in Example 1 has higher initial discharge capacity, initial efficiency, rate performance (2C / 0.1C), and cycle performance than Comparative Examples 1 and 2. The reason is that sodium hydride is added to oxidized asphalt, and after water vapor is introduced, the sodium hydride reacts with water to generate hydrogen gas, leaving a large number of nano- and micro-sized pores. The pores are regulated by high-temperature carbonization, thereby improving the sodium storage function of the hard carbon composite material and increasing the specific capacity. At the same time, sodium doping in hard carbon reduces defects and improves initial efficiency, rate performance, and cycle performance.

[0072] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hard carbon composite material for sodium-ion batteries, characterized in that, Includes the following steps: S1. Mix the oxidized asphalt, pore-forming agent and crosslinking agent evenly, and pre-carbonize to obtain the precursor material; S2. Place the precursor material in a reactor and introduce water vapor to obtain sodium-doped hard carbon precursor material. S3. Carbonize the sodium-doped hard carbon precursor material to obtain a hard carbon composite material. The pore-forming agent in S1 includes one or both of sodium hydride and sodium borohydride. The method for preparing oxidized asphalt in S1 includes the following steps: mixing asphalt, conductive agent, and acid anhydride evenly, and carrying out an oxidation reaction to obtain oxidized asphalt; The mass ratio of the asphalt, conductive agent, and acid anhydride is 80~95:1~5:1~5.

2. The method for preparing a hard carbon composite material for a sodium-ion battery according to claim 1, characterized in that, The pre-carbonization temperature in S1 is 300~400℃ and the time is 1~6h.

3. The method for preparing a hard carbon composite material for a sodium-ion battery according to claim 1, characterized in that, The crosslinking agent in S1 includes one or more of m-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, trioxymethylene, and 4-hydroxy-3-methoxybenzaldehyde.

4. The method for preparing a hard carbon composite material for a sodium-ion battery according to claim 1, characterized in that, The mass ratio of oxidized asphalt, pore-forming agent, and crosslinking agent in S1 is 100:0.5~6:10~20.

5. The method for preparing a hard carbon composite material for a sodium-ion battery according to claim 1, characterized in that, The oxidation reaction is carried out at a temperature of 200-300℃ for a time of 30-300 minutes.

6. The method for preparing a hard carbon composite material for a sodium-ion battery according to claim 1, characterized in that, The flow rate of water vapor introduced in S2 is 100~500mL / min, and the time is 30~300min.

7. The method for preparing a hard carbon composite material for a sodium-ion battery according to claim 1, characterized in that, The carbonization temperature in S3 is 1800~2200℃ and the time is 1~6h.

8. A hard carbon composite material for sodium-ion batteries is prepared by the preparation method described in any one of claims 1 to 7.

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