阅读说明：本技术 一种氟掺杂硬碳材料的制备方法及其应用 (Preparation method and application of fluorine-doped hard carbon material ) 是由 封伟 周日新 李瑀 冯奕钰 彭聪 于 2019-09-03 设计创作，主要内容包括：本发明提供一种氟掺杂硬碳材料的制备方法及其应用,将梧桐树皮置于管式炉中,通入保护气体,700-1200℃下碳化4-6h,即得到硬碳材料；把硬碳材料置于80-150℃的真空干燥箱中,并在真空干燥箱底部放入干燥剂,以对硬碳材料进行有效的烘干干燥作业,干燥3-9h后取出,即得到干燥后的硬碳材料；将干燥后的硬碳材料置于反应器中并将该反应器抽至真空,待反应器升温到40-220℃后保温20-150min,然后再向抽至真空的反应器中通入氟气或者是氟气和惰性气体的混合气至-0.06-0Mpa,反应0.5-5h后,即得到氟掺杂硬碳材料。本方法操作简单,原料来源广,成本低,产量高,得到的氟掺杂硬碳材料的比容量和循环性能以及倍率性能都有所提升,价格低廉,性能优良,应用前景广阔。(The invention provides a preparation method and application of a fluorine-doped hard carbon material, wherein phoenix tree bark is placed in a tubular furnace, protective gas is introduced, and carbonization is carried out at 700-; putting the hard carbon material into a vacuum drying oven at the temperature of 80-150 ℃, putting a drying agent at the bottom of the vacuum drying oven to effectively dry the hard carbon material, and taking out the hard carbon material after drying for 3-9h to obtain the dried hard carbon material; and placing the dried hard carbon material in a reactor, vacuumizing the reactor, keeping the temperature for 20-150min after the temperature of the reactor is raised to 40-220 ℃, introducing fluorine gas or mixed gas of the fluorine gas and inert gas into the reactor which is vacuumized until the pressure is-0.06-0 MPa, and reacting for 0.5-5h to obtain the fluorine-doped hard carbon material. The method has the advantages of simple operation, wide raw material source, low cost, high yield, low price, excellent performance and wide application prospect, and the obtained fluorine-doped hard carbon material has improved specific capacity, cycle performance and rate capability.)

1. A preparation method of a fluorine-doped hard carbon material is characterized by comprising the following steps: the method comprises the following steps:

step 1, placing phoenix tree barks in a tube furnace, introducing protective gas, and carbonizing at 700-1200 ℃ for 4-6h to obtain a hard carbon material;

step 2, placing the hard carbon material prepared in the step 1 in a vacuum drying box at the temperature of 80-150 ℃, placing a drying agent at the bottom of the vacuum drying box to effectively dry the hard carbon material, drying for 3-9h, and taking out to obtain the dried hard carbon material;

and 3, placing the dried hard carbon material obtained in the step 2 into a reactor, vacuumizing the reactor, heating the reactor to 40-220 ℃, preserving the temperature for 20-150min, introducing fluorine gas or mixed gas of the fluorine gas and inert gas into the reactor which is vacuumized to-0.06-0 MPa, and reacting for 0.5-5h to obtain the fluorine-doped hard carbon material, wherein the volume ratio of the fluorine gas in the mixed gas is 10-60%.

2. The method for preparing a fluorine-doped hard carbon material according to claim 1, wherein the method comprises the following steps: in step 1, one of nitrogen, helium and argon is used as the protective gas.

3. The method for preparing a fluorine-doped hard carbon material according to claim 1, wherein the method comprises the following steps: in the step 1, the carbonization temperature is 800-.

4. The method for preparing a fluorine-doped hard carbon material according to claim 1, wherein the method comprises the following steps: in the step 2, the vacuum drying temperature is 90-120 ℃, the vacuum drying time is 4-8h, and the drying agent is one or more of anhydrous phosphorus pentoxide, molecular sieve and activated carbon.

5. The method for preparing a fluorine-doped hard carbon material according to claim 1, wherein the method comprises the following steps: in the step 3, one of nitrogen, helium and argon is used as the inert gas, and the volume ratio of the fluorine gas in the mixed gas is 20-50%.

6. The method for preparing a fluorine-doped hard carbon material according to claim 1, wherein the method comprises the following steps: in step 3, the temperature is raised to 50-200 ℃ and the heat preservation time is 30-120 min.

7. The method for preparing a fluorine-doped hard carbon material according to claim 1, wherein the method comprises the following steps: in step 3, fluorine gas or the mixed gas of fluorine gas and inert gas is introduced into the reactor which is vacuumized to-0.05-0 Mpa, and the reaction lasts for 1-4 h.

8. The use of the method of any one of claims 1 to 7 for the preparation of a fluorine-doped hard carbon material for the negative electrode material of a sodium ion battery.

9. Use according to claim 8, characterized in that: the crystal face spacing of the fluorine-doped hard carbon material is larger than that of the hard carbon material, and the increased interlayer spacing is beneficial to the embedding and the extraction of sodium ions.

Technical Field

The invention relates to the technical field of carbon composite materials, in particular to a preparation method and application of a fluorine-doped hard carbon material.

Background

Since the invention, the lithium ion battery has good capacity and rate performance, so that the lithium ion battery almost occupies the whole river and mountain in the battery field, but the content of lithium metal on the earth is not as rich as sodium, a large amount of sodium chloride is contained in seawater resources distributed all over the earth, and the sodium chloride can be obtained by electrolyzing and melting the sodium chloride, thereby solving the problem that the price of the lithium ion battery is raised and does not drop because the price of the lithium metal is high. However, the radius of the sodium ions is larger than that of the lithium ions, the interlayer spacing of the graphite serving as the traditional lithium ion battery negative electrode material is small and is not enough to accommodate a large amount of sodium ions, the specific capacity of the graphite negative electrode sodium ion battery is limited, the intercalation and deintercalation of the sodium ions are also influenced, and the rate performance is greatly reduced, so that a layered material with the radius equivalent to that of the sodium ions must be found to meet the requirement.

At present, researchers put their own research interests on biomass-derived hard carbon materials, carbon-containing organic matters with abundant reserves in the nature provide a large amount of carbon sources, and the hard carbon materials with different graphitization degrees can be obtained from nut shells, shaddock peel, banana peel, kelp and organic precursors with different shapes and colors through high-temperature carbonization treatment. Hard carbon is used as a sodium ion battery cathode material, a highly disordered structure provides sites for storing a large amount of sodium ions, the specific capacity can be higher than that of graphite, and meanwhile, the movement of the sodium ions is promoted by a larger interlayer spacing, so that the improvement of the electrochemical performance of the battery is facilitated.

Disclosure of Invention

The invention overcomes the defects in the prior art and provides a preparation method and application of a fluorine-doped hard carbon material.

The purpose of the invention is realized by the following technical scheme.

A preparation method of a fluorine-doped hard carbon material comprises the following steps:

step 1, placing phoenix tree barks in a tube furnace, introducing protective gas, and carbonizing at 700-1200 ℃ for 4-6h to obtain a hard carbon material;

step 2, placing the hard carbon material prepared in the step 1 in a vacuum drying box at the temperature of 80-150 ℃, placing a drying agent at the bottom of the vacuum drying box to effectively dry the hard carbon material, drying for 3-9h, and taking out to obtain the dried hard carbon material;

and 3, placing the dried hard carbon material obtained in the step 2 into a reactor, vacuumizing the reactor, heating the reactor to 40-220 ℃, preserving the temperature for 20-150min, introducing fluorine gas or mixed gas of the fluorine gas and inert gas into the reactor which is vacuumized to-0.06-0 MPa, and reacting for 0.5-5h to obtain the fluorine-doped hard carbon material, wherein the volume ratio of the fluorine gas in the mixed gas is 10-60%.

In step 1, one of nitrogen, helium and argon is used as the protective gas.

In the step 1, the carbonization temperature is 800-.

In the step 2, the vacuum drying temperature is 90-120 ℃, the vacuum drying time is 4-8h, and the drying agent is one or more of anhydrous phosphorus pentoxide, molecular sieve and activated carbon.

In the step 3, one of nitrogen, helium and argon is used as the inert gas, and the volume ratio of the fluorine gas in the mixed gas is 20-50%.

In step 3, the temperature is raised to 50-200 ℃ and the heat preservation time is 30-120 min.

In step 3, fluorine gas or the mixed gas of fluorine gas and inert gas is introduced into the reactor which is vacuumized to-0.05-0 Mpa, and the reaction lasts for 1-4 h.

The invention has the beneficial effects that: the method provided by the invention has the advantages of simple operation, wide raw material source, low cost, high yield, simple post-treatment and capability of preparing the fluorine-doped hard carbon material by one-step reaction, wherein the yield can reach dozens of milligrams or even hundreds of grams. Fluorine gas is used as a fluorine source for fluorine doping at low temperature to obtain hard carbon with different doping degrees, and the hard carbon is used as a sodium ion battery cathode for testing.

Drawings

FIG. 1 is a scanning electron micrograph of a hard carbon material and a fluorine doped hard carbon material of the present invention;

FIG. 2 is an XRD pattern of a hard carbon material at different doping temperatures;

fig. 3 is a graph showing negative charge and discharge curves of a hard carbon material and a fluorine-doped hard carbon material according to the present invention, wherein a is the hard carbon material and B is the fluorine-doped hard carbon material according to the present invention;

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples.

Example 1

(1) Placing 2g of the treated phoenix tree bark tube into a tube furnace, introducing argon, and carbonizing for 5 hours at 800 ℃;

(2) putting 30mg of the hard carbon prepared in the step (1) into a vacuum drying oven at 90 ℃, putting anhydrous phosphorus pentoxide at the bottom of the vacuum drying oven, taking out after 4 hours, and sealing for later use;

(3) and (3) placing 30mg of the dried hard carbon obtained in the step (2) in a reactor, vacuumizing, keeping the temperature for 30min after the temperature of the reactor is raised to 50 ℃, vacuumizing, introducing a mixed gas of 20% fluorine gas and nitrogen gas to-0.05 Mpa, and reacting for 1h to obtain the fluorine-doped hard carbon material.

As shown in FIG. 1, the hard carbon derived from French karaya bark is in the form of particles with a size distribution of 4-25 μm, the bulk surface is more porous and the surface is rougher, and when doped with fluorine gas, the edges of the bulk become dull, indicating that fluorine atoms are successfully attached to the surface of the hard carbon material and the inter-layer spacing increases.

As shown in fig. 2, the blunt peak located in the vicinity of 23 ° represents the 002 crystal plane, the diffraction angle thereof is shifted to the left, and the interplanar spacing of the fluorine-doped hard carbon material is increased according to the bragg equation.

As shown in fig. 3, the constant current charge-discharge curve shows that there is a large capacity loss during the first cycle of charge-discharge of the hard carbon material, which indicates that the SEI film is formed in the first cycle of the hard carbon material, resulting in an irreversible capacity loss; the specific capacity of the fluorine-doped hard carbon material after doping modification is improved, and the increase of the interlayer spacing of the fluorine-doped hard carbon material is proved to be beneficial to the embedding and the separation of sodium ions.

Example 2

(1) Placing 2g of the treated phoenix tree bark tube into a tube furnace, introducing argon, and carbonizing at 900 ℃ for 5 hours;

(2) putting 40mg of the hard carbon prepared in the step (1) into a vacuum drying oven at 100 ℃, putting anhydrous phosphorus pentoxide at the bottom of the vacuum drying oven, taking out after 5 hours, and sealing for later use;

(3) and (3) placing 40mg of the dried hard carbon obtained in the step (2) in a reactor, vacuumizing, keeping the temperature for 60min after the temperature of the reactor is raised to 100 ℃, vacuumizing, introducing a 30% mixed gas of fluorine gas and nitrogen gas to-0.04 MPa, and reacting for 2h to obtain the fluorine-doped hard carbon material.

Example 3

(1) Placing 2g of the treated phoenix tree bark tube into a tube furnace, introducing argon, and carbonizing for 5 hours at 1000 ℃;

(2) putting 50mg of the hard carbon prepared in the step (1) into a vacuum drying oven at 110 ℃, putting anhydrous phosphorus pentoxide at the bottom of the vacuum drying oven, taking out after 6 hours, and sealing for later use;

(3) and (3) placing 50mg of the dried hard carbon obtained in the step (2) in a reactor, vacuumizing, keeping the temperature for 90min after the temperature of the reactor is raised to 150 ℃, vacuumizing, introducing 40% of mixed gas of fluorine gas and nitrogen gas to-0.03 MPa, and reacting for 3h to obtain the fluorine-doped hard carbon material.

Example 4

(1) Placing 2g of the treated phoenix tree bark tube into a tube furnace, introducing argon, and carbonizing at 1100 ℃ for 5 hours;

(2) putting 70mg of the hard carbon prepared in the step (1) into a vacuum drying oven at 120 ℃, putting anhydrous phosphorus pentoxide at the bottom of the vacuum drying oven, taking out after 7 hours, and sealing for later use;

(3) and (3) placing 60mg of the dried hard carbon obtained in the step (2) in a reactor, vacuumizing, keeping the temperature for 120min after the temperature of the reactor is raised to 200 ℃, vacuumizing, introducing a mixed gas of 50% fluorine gas and argon gas to 0MPa, and reacting for 4h to obtain the fluorine-doped hard carbon material.

Example 5

(1) 2g of the treated phoenix tree bark tube is put into a tube furnace, nitrogen is introduced, and carbonization is carried out for 6 hours at 700 ℃;

(2) putting 30mg of the hard carbon prepared in the step (1) into a vacuum drying oven at 80 ℃, putting a molecular sieve at the bottom of the vacuum drying oven, taking out after 9 hours, and sealing for later use;

(3) and (3) placing 30mg of the dried hard carbon obtained in the step (2) in a reactor, vacuumizing, keeping the temperature for 150min after the temperature of the reactor is raised to 40 ℃, vacuumizing, introducing 10% of mixed gas of fluorine gas and nitrogen gas to-0.06 MPa, and reacting for 0.5h to obtain the fluorine-doped hard carbon material.

Example 6

(1) Putting 2g of the treated phoenix tree bark tube into a tube furnace, introducing helium, and carbonizing for 4 hours at 1200 ℃;

(2) putting 30mg of the hard carbon prepared in the step (1) into a vacuum drying oven at 150 ℃, putting active carbon into the bottom of the vacuum drying oven, taking out after 3 hours, and sealing for later use;

(3) and (3) placing 30mg of the dried hard carbon obtained in the step (2) in a reactor, vacuumizing, keeping the temperature for 20min after the temperature of the reactor is raised to 220 ℃, vacuumizing, introducing 60% of mixed gas of fluorine gas and helium gas to-0.035 Mpa, and reacting for 6h to obtain the fluorine-doped hard carbon material.

The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.