CN112645305B - Preparation method of pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material - Google Patents

Preparation method of pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material Download PDF

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CN112645305B
CN112645305B CN202110090432.6A CN202110090432A CN112645305B CN 112645305 B CN112645305 B CN 112645305B CN 202110090432 A CN202110090432 A CN 202110090432A CN 112645305 B CN112645305 B CN 112645305B
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anthracite
carbon material
hard carbon
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CN112645305A (en
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孙飞
王桦
王坤芳
高继慧
赵广播
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Harbin Institute of Technology
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Abstract

A preparation method of a pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material belongs to the technical field of electrode material preparation. Aiming at the technical bottleneck that the sodium/potassium storage capacity of the anthracite-based carbon material prepared by traditional direct carbonization or activation is poor, the invention aims to inhibit the microcrystal growth of the anthracite high-temperature carbonization process, and the method comprises the following steps: grinding and selecting to obtain powder with target particle size; pre-activation: introducing an activating atmosphere under the protection of an inert atmosphere, and preserving heat for 1-6 hours; or adding an activating agent according to the mass ratio of 0.5-4: 1 of the activating agent to the powder for solid-phase premixing, and preserving the heat for 1-6 hours under the protection of inert atmosphere; under the protection of inert atmosphere, heating to 800-1800 ℃ at a heating rate of 2-20 ℃/min, and keeping the temperature for 0.5-10 h. Compared with the carbon material obtained by the process, the anthracite-based hard carbon obtained based on the concept of 'preactivation-post carbonization' has high reversible capacity and high first coulombic efficiency in sodium ion storage and transportation, and has important application prospects.

Description

Preparation method of pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material
Technical Field
The invention belongs to the technical field of electrode material preparation, and particularly relates to a preparation method of a pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material.
Background
Sodium/potassium ion batteries are considered to be an important choice for the next generation of secondary ion batteries. The method is an important direction for developing the low-cost sodium/potassium ion battery by using coal as a low-cost natural carbon source and directionally preparing a carbon cathode material with a low-voltage platform (widening a full battery voltage window), high first-loop coulombic efficiency and long cycle life from top to bottom.
The anthracite has the characteristics of high carbon content (> 90%), low cost, small pretreatment difficulty and the like, and is an important choice for developing high-performance carbon cathode materials. Research reports that anthracite coal is directly carbonized to prepare a sodium-ion battery cathode material (Energy storage mater.2016,5,191). However, the initial carbon skeleton of the anthracite has an initial graphite-like microcrystalline structure, which tends to be developed in a long-range manner in the direct high-temperature carbonization process, and is not beneficial to further improving the sodium/potassium ion embedding storage capacity and the rate capability, and the construction of the short-range ordered graphite-like microcrystalline structure is the key point of the rapid and high-density sodium ion embedding storage.
On the other hand, physical/chemical/catalytic activation and the like are common means for preparing the coal-based porous carbon material; however, the continuity of the porous carbon microchip layer obtained by direct activation is damaged to a great extent, a great number of edge defects are exposed at the interface between the electrode and the electrolyte, and although sodium/potassium ions can be stored through an adsorption mechanism, solvent molecules of the electrolyte are easy to generate irreversible decomposition at a high-activity pore wall with an unsaturated edge or generate irreversible adsorption and reaction with the sodium/potassium ions, so that the first-turn coulombic efficiency is low, and the porous carbon microchip layer is difficult to be applied to an actual secondary ion full battery.
Graphite-like crystals in the coal-based carbon material prepared by direct carbonization show long-range order, and are not beneficial to the improvement of ion diffusion storage capacity and speed; the microcrystal in the porous carbon material prepared by direct physical/chemical activation is seriously damaged, and a large number of edge structures cause a series of irreversible effects to cause low first effect; the existing carbonization and activation combined mode only has reports of 'pre-carbonization-post activation', essentially only improves the direct activation process, and the obtained carbon material is still typical porous carbon and is not suitable for the cathode of a sodium/potassium ion battery. From the above analysis, the traditional single carbonization or activation means can not satisfy the preparation of the high-performance anthracite-based hard carbon material.
Disclosure of Invention
The invention provides a method for preparing anthracite-based hard carbon material by combining pre-activation pore-forming and high-temperature carbonization, which aims at the technical bottleneck that the sodium/potassium storage capacity of the anthracite-based carbon material prepared by traditional direct carbonization or activation is poor and aims at inhibiting the microcrystal growth process of the anthracite high-temperature carbonization process. The purpose of the "pre-carbonization-post-activation" process is to regulate the pore structure. The invention aims at optimizing the structure of the smokeless coal-based hard carbon microcrystal and improving the sodium/potassium storage capacity, and provides the technical idea of combining pre-activation pore-forming and post-carbonization regulation and control microcrystal: the hard carbon material with the short-range ordered graphite-like crystal structure is obtained by manufacturing pores through physical/chemical activation in advance and then inhibiting the long-range development of microcrystals in the anthracite during the high-temperature carbonization process by utilizing the preset pore structure.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a preparation method of a pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material comprises the following steps:
the method comprises the following steps: grinding and selecting: crushing and screening raw coal to obtain powder with a target particle size;
step two: pre-activation: for physical activation, under the carrying of inert gas, the activating gas is introduced, and the total flow rate should be controlled within 0.6-4.5L/(m)3Min), the flow ratio of the activated gas to the inert gas is 1: 4-0, the temperature is raised to 700-1000 ℃ according to the temperature rise rate of 2-20 ℃/min, and the temperature is kept for 1-6 hours, so that a pre-activated product is obtained; for chemical activation, adding an activating agent according to the mass ratio of 0.5-4: 1 of the activating agent to the powder for solid-phase premixing, heating to 700-1000 ℃ at the heating rate of 2-20 ℃/min under the protection of inert atmosphere, and preserving heat for 1-6 hours to obtain a pre-activated product; the second step also comprises an acid washing step, specifically, hydrochloric acid, hydrofluoric acid and water are sequentially used for cleaning before or after the pre-activation is started, and drying is carried out;
step three: carbonizing: and (3) under the protection of inert atmosphere, heating the powder preactivation product obtained in the second step to 800-1800 ℃ at a heating rate of 2-20 ℃/min, and preserving heat for 0.5-10 hours to obtain the anthracite-based hard carbon material.
Compared with the prior art for preparing the coal-based carbon material, the invention has the beneficial effects that:
(1) compared with the carbon material obtained by the process, the anthracite-based hard carbon obtained based on the concept of preactivation-post carbonization has high reversible capacity and high first coulombic efficiency in sodium ion storage and transportation, and has important application prospect. Specifically, compared with the conventional method for preparing the coal-based hard carbon material by direct carbonization or preparing the coal-based porous carbon material by a direct activation and pre-carbonization-post-activation process, the method has the advantages that the pre-activation step is added before the conventional carbonization step, and the pores are preset in the coal coke structure to inhibit the growth of graphite-like crystals in the high-temperature carbonization process, so that the prepared anthracite-based hard carbon material has a short-range ordered graphite-like crystal structure, and the problems of low reversible capacity and low initial coulombic efficiency of the anthracite-based hard carbon cathode material can be synergistically improved.
(2) Compared with a direct carbonization material, the anthracite-based carbon cathode prepared by inhibiting the growth of coal-based microcrystals through physical or chemical pre-activation has the advantages that the reversible capacity is greatly improved, and the initial coulombic efficiency is still kept at 75-85%.
(3) Aiming at the problem that the reversible capacity of the coal-based carbon material is low, the method takes high-rank coal as a raw material, particularly coal types such as anthracite and the like with coal microcrystals which are fully developed or easily graphitized at high temperature, adopts the preparation idea of the combination of pre-activation pore-forming and high-temperature carbonization for inhibiting the growth of the microcrystals, and obtains the coal-based hard carbon material through the steps of grinding, acid washing, pre-activation, carbonization and the like. According to the preparation method, through pre-activation treatment, the amorphous region near the coal microcrystal is ablated by using the gas diffusion etching effect, the growth/recombination of the coal microcrystal is inhibited, the reversible capacity of the coal smokeless coal-based carbon material used as the cathode of the sodium/potassium ion battery can be effectively improved, and the increment is 60-75 mAh/g.
Drawings
Fig. 1 is an XRD spectrum of the 1300 c carbonized anthracite-based hard carbon material as described in comparative example 1.
FIG. 2 is an XRD partial peak spectrum of the 1300 ℃ carbonization-treated anthracite-based hard carbon material described in comparative example 1.
FIG. 3 is a graph showing the charge and discharge curves of the anthracite-based hard carbon material carbonized at 1300 ℃ as described in comparative example 1.
FIG. 4 is a graph of rate capability of the 1300 ℃ carbonized-treated anthracite-based hard carbon material described in comparative example 1.
Fig. 5 is an XRD spectrum of the anthracite-based porous carbon activated with steam at 900 c as described in comparative example 2.
Fig. 6 is an XRD peak profile of the anthracite-based porous carbon activated with 900 ℃ water vapor as described in comparative example 2.
Fig. 7 is a graph of the rate capability of the anthracite-based porous carbon activated with water vapor at 900 ℃ as described in comparative example 2.
Fig. 8 is a graph showing the charge and discharge curves of the anthracite-based porous carbon activated with steam at 900 c as described in comparative example 2.
Fig. 9 is a graph of the rate capability of the anthracite-based porous carbon activated with 700 ℃ KOH as described in comparative example 3.
Fig. 10 is a charge-discharge graph of the anthracite-based porous carbon activated with 700 ℃ KOH as described in comparative example 3.
Figure 11 is an XRD spectrum of the anthracite-based hard carbon as described in example 1, pre-activated with water vapor at 900 c, carbonized at 1300 c.
Figure 12 is an XRD peak profile of the anthracite-based hard carbon as described in example 1 after pre-activation with 900 c water vapor and carbonization at 1300 c.
Fig. 13 is a graph showing the charging and discharging curves of the anthracite-based hard carbon pre-activated by water vapor at 900 ℃ and carbonized at 1300 ℃ as described in example 1.
Fig. 14 is a graph of rate capability of the anthracite-based hard carbon as described in example 1, pre-activated with 900 c steam and carbonized at 1300 c.
FIG. 15 is a graph of the charge and discharge curves for the anthracite-based hard carbon as described in example 3, pre-activated with KOH at 700 ℃ and carbonized at 1300 ℃.
FIG. 16 is a graph of rate capability of the anthracite-based hard carbon as described in example 3, pre-activated with KOH at 700 ℃ and carbonized at 1300 ℃.
Detailed Description
The technical solutions of the present invention are further described below with reference to the drawings and the embodiments, but the present invention is not limited thereto, and modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
The first embodiment is as follows: the embodiment describes a method for preparing a anthracite-based hard carbon material by combining pre-activation pore-forming and high-temperature carbonization, which comprises the following steps:
the method comprises the following steps: grinding and selecting: crushing and screening raw coal to obtain powder with a target particle size;
step two: pre-activation: for physical activation, under the carrying of inert gas, the activating gas is introduced, and the total flow rate should be controlled to be 0.6-4.5L/(m)3Min), the flow ratio of the activated gas to the inert gas is 1: 4-0, the temperature is raised to 700-1000 ℃ according to the temperature rise rate of 2-20 ℃/min, and the temperature is kept for 1-6 hours, so that a pre-activated product is obtained; for chemical activation, adding an activating agent according to the mass ratio of 0.5-4: 1 of the activating agent to the powder for solid-phase premixing, heating to 700-1000 ℃ at the heating rate of 2-20 ℃/min under the protection of inert atmosphere, and preserving heat for 1-6 hours to obtain a pre-activated product; the second step also comprises an acid washing step, specifically, hydrochloric acid, hydrofluoric acid and water are sequentially used for cleaning before or after the pre-activation is started, and drying is carried out;
step three: carbonizing: and (3) under the protection of inert atmosphere, heating the powder preactivation product obtained in the step two to 800-1800 ℃ at a heating rate of 2-20 ℃/min, and preserving heat for 0.5-10 h to obtain the anthracite-based hard carbon material.
According to the invention, the pre-activation step is carried out before the carbonization step, and the growth of microcrystals in the carbonization process of the anthracite is inhibited through presetting pores, so that the reversible capacity and the first coulombic efficiency of the anthracite-based hard carbon negative electrode material can be synergistically improved.
The second embodiment is as follows: in the first step of the preparation method of the anthracite-based hard carbon material combining pre-activation pore-forming and high-temperature carbonization, in consideration of the actual effect of the "pre-activation-post-carbonization" process on the regulation and control of the coal-based microcrystalline structure, the raw coal is one or more of anthracite No. one to No. three.
The third concrete implementation mode: in the first step, in order to ensure the activation depth in the pre-activation step and facilitate the production of a carbon electrode after the carbonization step is finished, the target particle size is 80 to 400 meshes.
The fourth concrete implementation mode: in the second and third steps of the preparation method of the anthracite-based hard carbon material combining pre-activated pore-forming and high-temperature carbonization, the inert gas is one or more of nitrogen and argon.
The fifth concrete implementation mode is as follows: in the second step, the activated gas is one or a mixture of water vapor, carbon dioxide, ammonia gas or oxygen gas, and is used for etching to form a sub-nanometer to nanometer-scale microporous structure, wherein the ammonia gas can be introduced with nitrogen atoms at the same time.
The sixth specific implementation mode: in the second step of the preparation method of the anthracite-based hard carbon material combining pre-activation pore-forming and high-temperature carbonization in the specific embodiment, the pre-activation effect needs to be controlled in consideration of the structural regulation strength of the subsequent carbonization step and the electrochemical performance when the material is applied to a carbon cathode, and the specific surface area of the material after pre-activation treatment is controlled to be 300-900 m2Between/g.
The seventh embodiment: in the second step of the preparation method of the anthracite-based hard carbon material combining pre-activation pore-forming and high-temperature carbonization, in order to ensure the beneficial effect on the anthracite-based hard carbon negative electrode material during the chemical pre-activation, the activating agent is KOH or K2CO3、CH3COOK or K2FeO4One or more of (a).
The specific implementation mode eight: in the second step, the concentration of hydrochloric acid is 2 to 5M, the concentration of hydrofluoric acid is 5 to 20 wt%, and the ratio of the volume of acid to the mass of the powder is 20 to 40: 1.
The specific implementation method nine: in the second step of the preparation method of the anthracite-based hard carbon material combining pre-activated pore-forming and high-temperature carbonization, the water is distilled water or deionized water with the resistivity of not less than 10M Ω · cm, and the final effect of water washing is that the supernatant of the solution is neutral or weakly acidic.
Comparative example 1:
the preparation method of the anthracite-based hard carbon material provided by the comparative example is carried out according to the following steps:
grinding and selecting: and (3) crushing and screening the anthracite raw coal to obtain powder of 80-100 meshes.
Acid washing: and (3) carrying out 4M hydrochloric acid pickling, water washing, 20% hydrofluoric acid pickling, water washing and drying on the powder.
Carbonizing: and under the protection of argon atmosphere, heating the acid-washing product to 1300 ℃ at the speed of 5 ℃/min, and preserving heat for 1h to obtain the anthracite-based hard carbon material.
The microcrystalline structure of the smokeless coal-based hard carbon material is characterized by an X-ray diffraction (XRD) technology (figure 1), and the calculated microcrystalline interlayer spacing is 0.365nm and the microcrystalline width is 4.72nm by performing peak separation treatment on a spectral line (figure 2). When the hard carbon material is used as a sodium ion battery negative electrode, the reversible capacity is 154.7mAh/g under 0.1C (1C-300 mA/g), the first coulombic efficiency is 73% (figure 3), but the rate capability is poor (figure 4). The reversible capacity of the hard carbon material when used in a potassium ion battery is only 87 mAh/g.
Comparative example 2:
the preparation method of the anthracite-based porous carbon material provided by the comparative example is carried out according to the following steps:
grinding and selecting: and (3) crushing and screening the anthracite raw coal to obtain powder of 80-100 meshes.
Acid washing: and (3) carrying out 4M hydrochloric acid pickling, water washing, 20% hydrofluoric acid pickling, water washing and drying on the powder.
And (3) activation: under the protection of nitrogen atmosphere, the temperature is raised to 900 ℃ at the speed of 10 ℃/min, then 40mL of water vapor is introduced under the carrying of 160mL of nitrogen atmosphere, and the temperature is kept for 2h, so that the anthracite-based porous carbon material is obtained.
The microcrystalline structure of the smokeless coal-based porous carbon material is characterized by an X-ray diffraction (XRD) technology (figure 5), and the microcrystalline interlayer spacing is 0.370nm and the microcrystalline width is 2.26nm by calculating through peak separation processing on a spectral line (figure 6). When the smokeless coal-based porous carbon material is used as a sodium ion battery negative electrode, the rate stability is good (figure 7), but the reversible capacity is only 52.3mAh/g under 0.1C (1C-300 mA/g), and the first coulombic efficiency is 22.9% (figure 8).
Comparative example 3:
the preparation method of the anthracite-based porous carbon material provided by the comparative example comprises the following steps:
grinding and selecting: and (3) crushing and screening the anthracite raw coal to obtain 100-200 mesh powder.
And (3) activation: uniformly mixing coal powder and KOH according to the mass ratio of 1:1, heating the uniform mixture to 700 ℃ at the speed of 10 ℃/min under the protection of nitrogen atmosphere, and preserving heat for 1h to obtain a chemically activated product.
Acid washing: and (3) carrying out 5M hydrochloric acid pickling, water washing, 10% hydrofluoric acid pickling, water washing and drying on the product after chemical activation to obtain the anthracite-based porous carbon.
When the smokeless coal-based porous carbon material is used as a sodium ion battery negative electrode, the rate charge-discharge performance is good (figure 9), the reversible capacity is 151mAh/g under 0.1C (1C-300 mA/g), and the first coulombic efficiency is only 51% (figure 10).
Example 1:
the preparation method of the anthracite-based carbon material provided by the embodiment is carried out according to the following steps:
grinding and selecting: and (3) crushing and screening the anthracite raw coal to obtain powder of 80-100 meshes.
Pre-activation: raising the temperature to 900 ℃ at the speed of 10 ℃/min under the protection of nitrogen atmosphere, then introducing 40mL of water vapor under the carrying of 160mL of nitrogen atmosphere, and preserving the temperature for 2h to obtain a preactivated product.
Acid washing: and (3) carrying out 4M hydrochloric acid pickling, water washing, 20% hydrofluoric acid pickling, water washing and drying on the powder.
Carbonizing: under the protection of nitrogen atmosphere, heating the preactivated product to 1300 ℃ at the speed of 5 ℃/min, and preserving heat for 1h to obtain the anthracite-based hard carbon material.
The microcrystalline structure of the anthracite-based hard carbon material is characterized by an X-ray diffraction (XRD) technology (figure 11), and the spectral line is subjected to peak separation treatment (figure 12), so that the interlayer spacing of the microcrystalline is 0.375nm and the width of the microcrystalline is 3.01 nm. When the anthracite-based hard carbon material is used as a sodium ion battery negative electrode, the reversible capacity at 0.1C (1C 300mA/g) is 230.6mAh/g, and the reversible capacity is increased by 75.8mAh/g compared with the direct carbonized anthracite-based hard carbon material described in comparative example 1. When the hard carbon material is used as a potassium ion battery cathode, the reversible capacity is 200mAh/g, and is increased by 121mAh/g compared with that of comparative example 1.
Example 2:
the preparation method of the anthracite-based carbon material provided by the embodiment is carried out according to the following steps:
grinding and selecting: and (3) crushing and screening the anthracite raw coal to obtain powder of 80-100 meshes.
Pre-activation: under the protection of nitrogen atmosphere with the flow rate of 200mL/min, the temperature is increased to 900 ℃ at the speed of 10 ℃/min, then the temperature is switched to carbon dioxide atmosphere with the flow rate of 200mL/min, and the temperature is kept for 2h, so that a preactivation product is obtained.
Acid washing: the powder was subjected to 4M hydrochloric acid pickling, water washing, 20% hydrofluoric acid pickling, water washing, and drying in this order.
Carbonizing: and under the protection of argon atmosphere, heating the preactivated product to 1300 ℃ at the speed of 5 ℃/min, and preserving heat for 2 hours to obtain the smokeless coal-based hard carbon material.
When the anthracite-based hard carbon material is used as a sodium ion battery negative electrode, the reversible capacity is 254.4mAh/g under 0.1C (1C-300 mA/g), the first coulombic efficiency reaches 80%, and the reversible capacity is increased by 99.3mAh/g compared with the directly carbonized anthracite-based hard carbon material described in comparative example 1.
Example 3:
the preparation method of the anthracite-based carbon material provided by the embodiment is carried out according to the following steps:
grinding and selecting: and (3) crushing and screening the anthracite raw coal to obtain 100-200 mesh powder.
Pre-activation: uniformly mixing the coal powder and KOH according to the mass ratio of 1:1, heating the uniform mixture to 700 ℃ at the speed of 10 ℃/min under the protection of nitrogen atmosphere, and preserving heat for 1h to obtain a chemically activated product.
Acid washing: and (3) carrying out 5M hydrochloric acid pickling, water washing, 10% hydrofluoric acid pickling, water washing and drying on the product after chemical activation to obtain the anthracite-based porous carbon.
Carbonizing: and under the protection of nitrogen atmosphere, heating the preactivated product to 1300 ℃ at the speed of 5 ℃/min, and preserving heat for 2 hours to obtain the smokeless coal-based hard carbon material.
When the smokeless coal-based hard carbon material is used as a sodium ion battery cathode, the reversible capacity is 301mAh/g under 0.1C (1C-300 mA/g), and the reversible capacity is increased by 145mAh/g compared with the direct carbonization smokeless coal-based carbon material in comparative example 1; the reversible capacity was increased by 150mAh/g compared to the anthracite-based porous carbon material described in comparative example 3.
Example 4:
the preparation method of the anthracite-based carbon material provided by the embodiment is carried out according to the following steps:
grinding and selecting: the anthracite raw coal is crushed and screened to obtain powder of 80-100 meshes.
Pre-activation: under the protection of argon atmosphere, heating to 900 ℃ at the speed of 10 ℃/min, then introducing 40ml/min of water vapor under the carrying of 160ml/min of nitrogen atmosphere, preserving heat for 1h, replacing the atmosphere with 200ml/min of carbon dioxide gas, and continuously preserving heat for 2h to obtain a preactivated product.
Acid washing: the powder was subjected to 4M hydrochloric acid pickling, water washing, 20% hydrofluoric acid pickling, water washing, and drying in this order.
Carbonizing: and under the protection of argon atmosphere, heating the preactivated product to 1500 ℃ at the speed of 5 ℃/min, and preserving heat for 2 hours to obtain the smokeless coal-based porous hard carbon material.
The specific surface area of the smokeless coal-based porous hard carbon material is 821m2And/g, when used as a sodium ion battery negative electrode, has a reversible capacity of 140mAh/g at 0.1C (1C-300 mA/g).
Example 5:
the preparation method of the anthracite-based carbon material provided by the embodiment is carried out according to the following steps:
grinding and selecting: and (3) crushing and screening the anthracite raw coal to obtain 100-200 mesh powder.
Pre-activation: raising the temperature to 900 ℃ at the speed of 10 ℃/min under the protection of nitrogen atmosphere, then introducing 40mL of water vapor under the carrying of 160mL of nitrogen atmosphere, and preserving the temperature for 3h to obtain a preactivated product.
Acid washing: and (3) carrying out 4M hydrochloric acid pickling, water washing, 20% hydrofluoric acid pickling, water washing and drying on the powder.
Carbonizing: and under the protection of nitrogen atmosphere, heating the preactivated product to 1400 ℃ at the speed of 5 ℃/min, and preserving heat for 1h to obtain the anthracite-based hard carbon material.
When the smokeless coal-based hard carbon material is used as a negative electrode of a sodium ion battery, the reversible capacity is 211mAh/g under 0.1C (1C-300 mA/g).
Example 6:
the preparation method of the anthracite-based carbon material provided by the embodiment is carried out according to the following steps:
grinding and selecting: and (3) crushing and screening the anthracite raw coal to obtain 100-200 mesh powder.
Acid washing: and (3) carrying out 4M hydrochloric acid pickling, water washing, 20% hydrofluoric acid pickling, water washing and drying on the powder.
Pre-activation: under the protection of nitrogen atmosphere, heating to 900 ℃ at the speed of 10 ℃/min, then introducing 40ml/min of water vapor under the carrying of 160ml/min of nitrogen atmosphere, preserving heat for 1h, replacing the water vapor with carbon dioxide gas, and continuously preserving heat for 1h to obtain a preactivated product.
Carbonizing: and under the protection of nitrogen atmosphere, heating the preactivated product to 1600 ℃ at the speed of 5 ℃/min, and preserving heat for 2 hours to obtain the smokeless coal-based hard carbon material.
When the smokeless coal-based hard carbon material is used as a negative electrode of a sodium ion battery, the reversible capacity is 218mAh/g under 0.1C (1C-300 mA/g).

Claims (7)

1. A preparation method of a pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: grinding and selecting: crushing and screening raw coal to obtain powder with a target particle size; the raw coal is one or a mixture of more of anthracite I to anthracite III;
step two: pre-activation: for physical activation, under the carrying of inert gas, the activating gas is introduced, and the total flow rate should beControlling the flow rate of the activating gas to the inert gas to be 0.6-4.5L/min, wherein the flow rate of the activating gas to the inert gas is 1: 4-0, heating to 700-1000 ℃ at a heating rate of 2-20 ℃/min, and preserving heat for 1-6 hours to obtain a preactivated product; for chemical activation, according to the mass ratio of an activating agent to powder of 0.5-4: 1, adding an activating agent for solid-phase premixing, heating to 700-1000 ℃ at a heating rate of 2-20 ℃/min under the protection of inert atmosphere, and preserving heat for 1-6 hours to obtain a preactivated product; the specific surface area of the material after the pre-activation treatment is controlled to be 300-900 m2Between/g; the second step also comprises an acid washing step, specifically, hydrochloric acid, hydrofluoric acid and water are sequentially used for cleaning before or after the pre-activation is started, and drying is carried out;
step three: carbonizing: and (3) under the protection of inert atmosphere, heating the powder preactivation product obtained in the step two to 800-1800 ℃ at a heating rate of 2-20 ℃/min, and preserving heat for 0.5-10 h to obtain the anthracite-based hard carbon material.
2. The method for preparing the anthracite-based hard carbon material by combining the pre-activated pore-forming and the high-temperature carbonization according to the claim 1, is characterized by comprising the following steps: in the first step, the target particle size is 80-400 meshes.
3. The method for preparing the anthracite-based hard carbon material by combining the pre-activated pore-forming and the high-temperature carbonization according to the claim 1, is characterized by comprising the following steps: in the second step and the third step, the inert gas is one or more of nitrogen and argon.
4. The method for preparing the anthracite-based hard carbon material by combining pre-activated pore-forming and high-temperature carbonization according to claim 1, which is characterized in that: in the second step, the activated gas is one or a mixture of water vapor, carbon dioxide, ammonia gas or oxygen.
5. The method for preparing the anthracite-based hard carbon material by combining pre-activated pore-forming and high-temperature carbonization according to claim 1, which is characterized in that: in the second step, the activating agent is KOH or K2CO3、CH3COOK or K2FeO4One or more of (a).
6. The method for preparing the anthracite-based hard carbon material by combining the pre-activated pore-forming and the high-temperature carbonization according to the claim 1, is characterized by comprising the following steps: in the second step, the concentration of the hydrochloric acid is 2-5M, the concentration of the hydrofluoric acid is 5-20 wt%, and the ratio of the volume of the acid to the mass of the powder is 20-40: 1.
7. The method for preparing the anthracite-based hard carbon material by combining the pre-activated pore-forming and the high-temperature carbonization according to the claim 1, is characterized by comprising the following steps: in the second step, the water is distilled water or deionized water, and the final effect of water washing is that the supernatant of the solution is neutral or weakly acidic.
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