Pyrolysis of hard carbon material and preparation method and application thereof

Abstract

The application discloses a pyrolytic hard carbon material and a preparation method and application thereof, and belongs to the technical field of hard carbon materials. First, hard carbon raw materials and nitrogen-containing compounds are heated to react to obtain liquid raw materials, then nano carbon fibers are added to the liquid raw materials to prepare a precursor material with uniform dispersion, and after the precursor material is solidified, pre-carbonization treatment is performed, and then temperature is increased for carbonization treatment to obtain the hard carbon material. The prepared hard carbon material has uniform pore distribution and suitable pore size structure, and the embedding and disembedding speed of sodium ions is improved. The hard carbon material can effectively avoid volume expansion caused by sodium ion embedding and disembedding, thereby protecting the stability of the electrode structure, and on the other hand, the micropore structure greatly improves the adsorption of sodium ions, thereby improving the capacity and cycle stability of the sodium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of hard carbon materials, and in particular to a pyrolytic hard carbon material and a preparation method and application thereof. Background Art

[0002] Sodium-ion batteries are secondary batteries that rely solely on the movement of sodium ions between the positive and negative electrodes to operate, similar to the working principle of lithium-ion batteries. Due to the long-term high price of lithium, the price advantage of sodium-ion battery raw materials has continued to emerge. Based on the above cost analysis, researchers have gradually turned their attention to sodium as a negative electrode material for batteries. Compared with lithium-ion batteries, sodium-ion batteries have higher energy density and lower cost. Compared with traditional lead-acid batteries and nickel-metal hydride batteries, sodium-ion batteries have lower environmental pollution and longer service life, and are more in line with the green and environmental protection requirements of modern society.

[0003] Sodium ion batteries are mainly composed of positive and negative electrode materials, positive and negative electrode shells, diaphragms and electrolytes. The positive electrode materials of sodium ion batteries include layered oxides, Prussian blue, tunnel-type oxides and polyanion-type oxides; the negative electrode materials of sodium ion batteries include carbon-based materials, titanium-based materials, alloy materials, organic compounds and other systems. The commonly used negative electrode material for lithium ion batteries is graphite. However, graphite has a small interlayer spacing and cannot meet the requirements of sodium ion embedding and de-embedding, so it is not suitable for use as a negative electrode material for sodium ion batteries. In addition, the volume change of existing sodium ion battery negative electrode materials during the process of sodium ion de-embedding / de-embedding leads to structural collapse, which will lead to poor cycle stability of sodium ion batteries. To this end, the present invention provides a pyrolytic hard carbon material and its preparation method and application. Summary of the Invention

[0004] The present invention provides a pyrolytic hard carbon material and its preparation method and application, which effectively solves the technical problems that graphite as a negative electrode material for sodium ion batteries cannot meet the requirements of sodium ion insertion and extraction, and that existing negative electrode materials for sodium ion batteries lead to poor cycle stability of sodium ion batteries. At the same time, it provides a pyrolytic hard carbon material with excellent performance.

[0005] The present invention provides a method for preparing a pyrolytic hard carbon material, which is characterized by comprising the following steps:

[0006] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0007] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 300-600° C. in a nitrogen atmosphere for 2-4 hours, heating to 800-1300° C., and carbonizing for 1-5 hours to obtain a hard carbon material.

[0008] Preferably, in S1, the hard carbon raw material is at least two of phenolic resin, epoxy resin, medium-temperature coal tar, anthracene oil, and washing oil.

[0009] Preferably, in S1, the nitrogen-containing compound is hydroxylamine, ethylenediamine, ethanolamine, butanediamine or 2-methylpentanediamine.

[0010] Preferably, in S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.005-0.03.

[0011] Preferably, in S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:10-60 mL.

[0012] Preferably, in S2, the cross-linking agent is chloroform, carbon tetrachloride or dimethoxymethane, and the mass percentage of the cross-linking agent in the precursor material is 5% to 8%.

[0013] Preferably, in S1, the heating is specifically: hydrothermal reaction at 80-130° C. for 5-12 hours.

[0014] The present invention also provides a pyrolytic hard carbon material prepared according to the above preparation method.

[0015] The present invention also provides an application of the pyrolytic hard carbon material in preparing a negative electrode material for a sodium ion battery.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention first heats a hard carbon raw material and a nitrogen-containing compound to react to obtain a liquid raw material, then adds nano-carbon fibers to the liquid raw material to obtain a uniformly dispersed precursor material, solidifies the precursor material, first performs a pre-carbonization treatment, and then heats and carbonizes the material to obtain a hard carbon material. The hard carbon material prepared by the present invention has uniform pore distribution and a suitable pore structure, which improves the insertion and extraction speed of sodium ions. On the one hand, the hard carbon material of the present invention can effectively avoid the volume expansion caused by the insertion / extraction of sodium ions, thereby protecting the stability of the electrode structure. On the other hand, its microporous structure greatly improves the adsorption of sodium ions, thereby improving the capacity and cycle stability of the sodium ion battery.

[0018] (2) The negative electrode material prepared by the hard carbon material of the present invention is assembled into a button battery, which has better performance, and the sodium ion battery rate, electrochemical performance and battery specific capacity are all better; under different current densities, after 10 cycles, when the current density returns to 100 mA g -1 The specific capacity of the button cell of Example 3 still maintains 97.8% of the original capacity; at 0.5Ag -1At a current density of 1.5, after 150 cycles, the specific capacity of Example 3 still remained at 450 mAh g -1 . DETAILED DESCRIPTION

[0019] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples, but the examples are not intended to limit the present invention. The following experimental and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0020] Example 1

[0021] A method for preparing a pyrolytic hard carbon material comprises the following steps:

[0022] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0023] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 300° C. in a nitrogen atmosphere for 2 h, heating to 800° C., and carbonizing for 1 h to obtain a hard carbon material.

[0024] In S1, the hard carbon raw materials are phenolic resin and epoxy resin.

[0025] In S1, the nitrogen-containing compound is hydroxylamine.

[0026] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.005.

[0027] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:10 mL.

[0028] In S2, the cross-linking agent is chloroform, and the mass percentage of the cross-linking agent in the precursor material is 5%.

[0029] In S1, the heating is specifically: hydrothermal reaction at 80° C. for 5 hours.

[0030] Example 2

[0031] A method for preparing a pyrolytic hard carbon material comprises the following steps:

[0032] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0033] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 600° C. in a nitrogen atmosphere for 4 h, heating to 1300° C., and carbonizing for 5 h to obtain a hard carbon material.

[0034] In S1, the hard carbon raw materials are epoxy resin and medium-temperature coal tar.

[0035] In S1, the nitrogen-containing compound is ethylenediamine.

[0036] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.03.

[0037] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:60 mL.

[0038] In S2, the cross-linking agent is carbon tetrachloride, and the mass percentage of the cross-linking agent in the precursor material is 8%.

[0039] In S1, the heating is specifically: hydrothermal reaction at 130° C. for 12 hours.

[0040] Example 3

[0041] A method for preparing a pyrolytic hard carbon material comprises the following steps:

[0042] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0043] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 400° C. in a nitrogen atmosphere for 2.5 h, heating to 1000° C., and carbonizing for 4 h to obtain a hard carbon material.

[0044] In S1, the hard carbon raw materials are medium-temperature coal tar, anthracene oil and washing oil.

[0045] In S1, the nitrogen-containing compound is ethanolamine.

[0046] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.025.

[0047] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:30 mL.

[0048] In S2, the cross-linking agent is dimethoxymethane, and the mass percentage of the cross-linking agent in the precursor material is 7%.

[0049] In S1, the heating is specifically: hydrothermal reaction at 100° C. for 8 hours.

[0050] Example 4

[0051] A method for preparing a pyrolytic hard carbon material comprises the following steps:

[0052] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0053] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 500° C. in a nitrogen atmosphere for 3 h, heating to 1200° C., and carbonizing for 2 h to obtain a hard carbon material.

[0054] In S1, the hard carbon raw materials are phenolic resin, epoxy resin, anthracene oil and washing oil.

[0055] In S1, the nitrogen-containing compound is diaminobutane.

[0056] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.01.

[0057] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:40 mL.

[0058] In S2, the cross-linking agent is carbon tetrachloride, and the mass percentage of the cross-linking agent in the precursor material is 6.5%.

[0059] In S1, the heating is specifically: hydrothermal reaction at 120° C. for 10 hours.

[0060] Example 5

[0061] A method for preparing a pyrolytic hard carbon material comprises the following steps:

[0062] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0063] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 450° C. in a nitrogen atmosphere for 3.5 hours, heating to 900° C., and carbonizing for 3 hours to obtain a hard carbon material.

[0064] In S1, the hard carbon raw materials are phenolic resin, epoxy resin, and washing oil.

[0065] In S1, the nitrogen-containing compound is 2-methylpentanediamine.

[0066] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.02.

[0067] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:20 mL.

[0068] In S2, the cross-linking agent is chloroform, and the mass percentage of the cross-linking agent in the precursor material is 6%.

[0069] In S1, the heating is specifically: hydrothermal reaction at 110° C. for 6 hours.

[0070] Example 6

[0071] A method for preparing a pyrolytic hard carbon material comprises the following steps:

[0072] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0073] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 550° C. in a nitrogen atmosphere for 4 h, heating to 1100° C., and carbonizing for 3.5 h to obtain a hard carbon material.

[0074] In S1, the hard carbon raw materials are phenolic resin, medium-temperature coal tar, anthracene oil and washing oil.

[0075] In S1, the nitrogen-containing compound is ethanolamine.

[0076] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.015.

[0077] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:50 mL.

[0078] In S2, the cross-linking agent is dimethoxymethane, and the mass percentage of the cross-linking agent in the precursor material is 7.5%.

[0079] In S1, the heating is specifically: hydrothermal reaction at 90° C. for 9 hours.

[0080] Example 7

[0081] A method for preparing a pyrolytic hard carbon material comprises the following steps:

[0082] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0083] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 350° C. in a nitrogen atmosphere for 2 h, heating to 850° C., and carbonizing for 4.5 h to obtain a hard carbon material.

[0084] In S1, the hard carbon raw materials are phenolic resin, epoxy resin, medium-temperature coal tar, anthracene oil and washing oil.

[0085] In S1, the nitrogen-containing compound is hydroxylamine.

[0086] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.02.

[0087] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:35 mL.

[0088] In S2, the cross-linking agent is dimethoxymethane, and the mass percentage of the cross-linking agent in the precursor material is 5.5%.

[0089] In S1, the heating is specifically: hydrothermal reaction at 100° C. for 7 hours.

[0090] In order to further illustrate the effect of the present invention, the present invention also provides a comparative example, as follows:

[0091] Comparative Example 1

[0092] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0093] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 400° C. in a nitrogen atmosphere for 2.5 h, heating to 1000° C., and carbonizing for 4 h to obtain a hard carbon material.

[0094] In S1, the hard carbon raw materials are medium-temperature coal tar, anthracene oil and washing oil.

[0095] In S1, the nitrogen-containing compound is ethanolamine.

[0096] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.025.

[0097] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 0.5 g:30 mL.

[0098] In S2, the cross-linking agent is dimethoxymethane, and the mass percentage of the cross-linking agent in the precursor material is 7%.

[0099] In S1, the heating is specifically: hydrothermal reaction at 100° C. for 8 hours.

[0100] Comparative Example 2

[0101] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0102] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor at 400° C. in a nitrogen atmosphere for 2.5 h, heating to 1000° C., and carbonizing for 4 h to obtain a hard carbon material.

[0103] In S1, the hard carbon raw materials are medium-temperature coal tar, anthracene oil and washing oil.

[0104] In S1, the nitrogen-containing compound is ethanolamine.

[0105] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.002.

[0106] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:30 mL.

[0107] In S2, the cross-linking agent is dimethoxymethane, and the mass percentage of the cross-linking agent in the precursor material is 7%.

[0108] In S1, the heating is specifically: hydrothermal reaction at 100° C. for 8 hours.

[0109] Comparative Example 3

[0110] S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating to obtain a precursor material;

[0111] S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, heating the cured precursor to 1000° C. in a nitrogen atmosphere, and carbonizing for 4 hours to obtain a hard carbon material.

[0112] In S1, the hard carbon raw materials are medium-temperature coal tar, anthracene oil and washing oil.

[0113] In S1, the nitrogen-containing compound is ethanolamine.

[0114] In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.025.

[0115] In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g:30 mL.

[0116] In S2, the cross-linking agent is dimethoxymethane, and the mass percentage of the cross-linking agent in the precursor material is 7%.

[0117] In S1, the heating is specifically: hydrothermal reaction at 100° C. for 8 hours.

[0118] The hard carbon materials prepared in the above Examples 1 to 7 and Comparative Examples 1 to 3 were used to prepare negative electrode materials for sodium ion batteries, and their performance was tested in the following manner: The preparation method of the button batteries used for the test was as follows: the negative electrode materials for sodium ion batteries prepared in Examples 1-7 and Comparative Examples 1-3 were respectively mixed with a conductive agent and SBR in the ratio of 82:10:2, applied on a copper foil, and vacuum dried to serve as the negative electrode. Lithium metal was used as the counter electrode, and the electrolyte was a mixture of 1M LiPF6, ethylene carbonate (EC) and dimethyl carbonate (DMC) in a mass ratio of 1:1. The diaphragm was a PE / PP / PE composite film, and the batteries were assembled into button batteries.

[0119] The rate of button batteries made of the hard carbon materials of Examples 1 to 7 and Comparative Examples 1 to 3 was tested. Since the performance of Examples 1 to 7 is similar, only Example 3 is used as an example for illustration. The cycle performance of four sodium ion button batteries (Example 3, Comparative Examples 1 to 3) was tested. After 10 cycles at different current densities, when the current density returned to 100 mA g -1 The button battery capacity of Example 3 still maintains 97.8% of the original capacity; in contrast, the hard carbon materials of Comparative Examples 1 to 3 have poor capacity after cycling without current, which confirms that the synergistic effect of the hard carbon material structure of the present invention has a great promoting effect on the rate performance of sodium ion batteries.

[0120] The electrochemical performance of button cells made from the hard carbon materials of Example 3 and Comparative Examples 1 to 3 was tested. The results showed that at 0.5 A g -1 At a current density of 1.5, after 150 cycles, the specific capacity of Example 3 still remained at 450 mAh g -1 In contrast, the hard carbon materials of Comparative Examples 1 to 3 have a capacity of only 263 mAh g after 150 cycles. -1 , 220mAh g -1 , 130mAh g -1 It is confirmed that the synergistic effect of the hard carbon material structure of the present invention has greatly improved the electrochemical performance of sodium ion batteries.

[0121] In summary, the hard carbon material prepared by the present invention has uniform pore distribution and appropriate pore structure, which improves the insertion and extraction speed of sodium ions. On the one hand, the hard carbon material of the present invention can effectively avoid the volume expansion caused by the insertion / extraction of sodium ions, thereby protecting the stability of the electrode structure. On the other hand, its microporous structure greatly improves the adsorption of sodium ions, thereby increasing the capacity of the sodium ion battery.

[0122] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a pyrolytic hard carbon material, characterized in that: The following steps are involved: S1, mixing a hard carbon raw material with a nitrogen-containing compound, heating the mixture to obtain a liquid raw material, adding carbon nanofibers to the liquid raw material, and ultrasonicating the mixture to obtain a precursor material; the hard carbon raw material is at least two of phenolic resin, epoxy resin, medium-temperature coal tar, anthracene oil, and washing oil; and the nitrogen-containing compound is hydroxylamine, ethylenediamine, ethanolamine, butanediamine, or 2-methylpentanediamine; S2, adding a crosslinking agent to the precursor material of S1, curing to obtain a cured precursor, pre-carbonizing the cured precursor in a nitrogen atmosphere at 300-600° C. for 2-4 hours, heating to 800-1300° C., and carbonizing for 1-5 hours to obtain a pyrolytic hard carbon material.

2. The preparation method according to claim 1, characterized in that In S1, the mass ratio of the hard carbon raw material to the nitrogen-containing compound is 1:0.005-0.

03.

3. The preparation method according to claim 1, characterized in that In S1, the size of the carbon nanofiber is 10-20 nm, and the material-liquid ratio of the carbon nanofiber to the liquid raw material is 1 g: 10-60 mL.

4. The preparation method according to claim 1, characterized in that In S2, the cross-linking agent is chloroform, carbon tetrachloride or dimethoxymethane, and the mass percentage of the cross-linking agent in the precursor material is 5% to 8%.

5. The preparation method according to claim 1, characterized in that In S1, the heating is specifically: hydrothermal reaction at 80-130° C. for 5-12 hours.

6. The pyrolytic hard carbon material prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the pyrolytic hard carbon material according to claim 6 in preparing a negative electrode material for sodium ion batteries.