Quenching pretreated coal-derived hard carbon negative electrode material and preparation and application thereof

Abstract

The application discloses a kind of quenching pretreatment coal derived hard carbon negative material and its preparation and application.The method of the present application comprises: obtaining coal precursor;First-stage low-temperature pyrolysis is carried out to the coal particles to obtain carbon intermediate;Carbon intermediate is carried out second-stage high-temperature carbonization to obtain hard carbon;Wherein the coal precursor and / or carbon intermediate are respectively subjected to quenching pretreatment.Through the method, while ensuring that the pseudo-graphitized structure hard carbon has higher conductivity, it also provides new channels and sufficient sodium storage active sites for the effective diffusion and embedding of sodium ions, significantly improves the migration and storage of sodium ions, and ultimately obtains a coal-based sodium-ion battery hard carbon negative material with high efficiency and high capacity.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of sodium ion batteries, and particularly relates to a quenching pretreatment coal-derived hard carbon negative electrode material and a preparation and application thereof. BACKGROUND

[0002] With the increasing proportion of renewable energy in the power grid, large-scale and low-cost energy storage technology has become a bottleneck for the grid connection of renewable energy. In recent years, the price fluctuation of lithium resources, the limited lithium reserves and the burning and explosion of lithium ion batteries have highlighted the problems. Safe, low-cost and large-scale energy storage technology is urgently needed. Sodium ion batteries have abundant sodium resources, similar working principles to lithium ion batteries and no safety problems caused by dendrite growth, and are considered to be one of the ideal large-scale energy storage technologies. However, one of the main reasons for the lagging industrialization process of sodium ion batteries is the lack of high-performance and low-cost negative electrode materials that can be mass-produced. Hard carbon is considered to be the most promising sodium ion battery negative electrode material due to its rich precursor resources, high reversible capacity and high platform capacity in the low potential range. The precursors of hard carbon mainly include biomass, oxygen-containing resin, pitch and coal. Among them, coal is one of the ideal low-cost precursors for hard carbon due to its rich carbon content, easy control and abundant reserves. However, the high aromaticity of coal makes its structure dense during high-temperature carbonization, resulting in a decrease in porosity, which leads to a lack of sodium storage active sites, low capacity and poor rate performance of coal-derived hard carbon.

[0003] For the above problems, methods such as activation, oxidation and coating have been developed to improve the sodium storage performance of coal-based hard carbon, but there are certain problems in cost or effect. It is urgent to develop a cheap and efficient modification method to meet the commercialization requirements of sodium ion batteries. SUMMARY

[0004] To solve the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a preparation method of a quenching pretreatment coal-derived hard carbon negative electrode material.

[0005] Another purpose of the present application is to provide a quenching pretreatment coal-derived hard carbon negative electrode material prepared by the above preparation method.

[0006] Still another purpose of the present application is to provide the application of the above quenching pretreatment coal-derived hard carbon negative electrode material in sodium ion batteries.

[0007] The quenching pretreatment coal-derived hard carbon negative electrode material applied to the negative electrode of sodium ion batteries has the advantages of high sodium storage capacity, good rate performance and stable cycle performance.

[0008] The purposes of the present application are achieved by the following technical solutions:

[0009] A preparation method of a quenching pretreatment coal-derived hard carbon negative electrode material, comprising the following steps:

[0010] (1) crushing, sieving, washing and drying a coal raw material to obtain coal precursor particles;

[0011] (2) pyrolyzing the coal precursor particles at a low temperature to obtain a pyrolysis intermediate;

[0012] (3) carbonizing the pyrolysis intermediate at a high temperature to obtain a hard carbon material;

[0013] Preferably, the coal precursor particles obtained in step (1) and / or the pyrolysis intermediate obtained in step (2) are subjected to quenching pretreatment.

[0014] Preferably, the coal raw material in step (1) is at least one of lignite and bituminous coal.

[0015] Preferably, the coal raw material in step (1) is crushed and sieved to obtain raw coal particles with a particle size of 0.5-500 μm.

[0016] Preferably, the washing in step (1) comprises acid washing followed by water washing to neutral.

[0017] More preferably, the acid washing is performed using a 0.1-5 mol / L hydrochloric acid solution for 1-120 h.

[0018] Preferably, the pyrolysis in step (2) is performed at a temperature of 200-900 °C; more preferably, 300-800 °C; most preferably, 600-800 °C.

[0019] Preferably, the pyrolysis in step (2) is performed for 1-6 h; more preferably, 1-2 h; most preferably, 2 h.

[0020] Preferably, the pyrolysis in step (2) is performed at a heating rate of 1-50 °C / min; more preferably, 5-20 °C / min; most preferably, 10 °C / min.

[0021] Preferably, the pyrolysis in step (2) and the carbonization in step (3) are performed in an inert atmosphere, which is at least one of nitrogen, argon and helium.

[0022] Preferably, the carbonization in step (3) is performed at a temperature of 900-1800 °C; more preferably, 1100-1400 °C; most preferably, 1200-1400 °C.

[0023] Preferably, the carbonization in step (3) is performed for 1-30 h; more preferably, 2-3 h; most preferably, 2 h.

[0024] Preferably, the carbonization in step (3) is performed at a heating rate of 1-50 °C / min; more preferably, 2-5 °C / min; most preferably, 2 °C / min.

[0025] Preferably, the temperature of the quenching pretreatment is -300 to 0℃; more preferably -300 to -180℃; most preferably liquid nitrogen quenching pretreatment.

[0026] Preferably, the time of the quenching pretreatment is 1 min to 3000 min; more preferably 10 to 30 h; most preferably 15 to 30 h.

[0027] The application provides a quenching pretreated coal-derived hard carbon negative electrode material prepared by the preparation method.

[0028] The application also provides application of the quenching pretreated coal-derived hard carbon negative electrode material in a sodium ion battery.

[0029] Generally, coal is prone to carbon layer rearrangement and accumulation in the direct high-temperature carbonization process, resulting in that the coal-based carbon material exhibits a highly ordered microcrystalline structure, a small interlayer spacing and a low porosity, which limits the embedding of sodium ions. At present, most researchers have proposed methods such as activation, oxidation and coating to improve the electrochemical properties of the coal-based carbon material, but these improvement processes are complex and time-consuming, and it is difficult to meet the commercialization requirements of the sodium ion battery. The temperature difference of more than 200℃ between liquid nitrogen (-196℃) and coal can cause a strong "cold impact" on the coal, induce the expansion of the interlayer spacing and pore structure, and inhibit the high graphitization in the subsequent carbonization process, thereby bringing high sodium storage performance.

[0030] Compared with the prior art, the application has the following advantages and beneficial effects:

[0031] (1) The application provides a method for preparing a quenching pretreated coal-derived sodium ion battery hard carbon negative electrode material. First, the precursor particles and / or pyrolysis intermediates are immersed in liquid nitrogen, which forms many cracks and pores on the surface of the material and changes the microstructure. Second, the carbon layer is rearranged, and part of the open pores is closed to form closed pores through low-temperature pyrolysis and high-temperature carbonization processes, respectively, which shows more pseudo-graphite domain structure and surface defects, provides new channels and sodium storage sites for the effective diffusion and embedding of sodium ions, is beneficial to the rapid migration and storage of sodium ions, and thus improves the initial efficiency, reversible capacity and cycle performance of the sodium ion battery.

[0032] (2) The application respectively performs quenching pretreatment on the precursor particles and the pyrolysis intermediates, compares the influence of the "cold impact" of different stages on the structure of the final carbon material, and shows that the immersion of the intermediates is more conducive to the formation of pseudo-graphite domain structure and closed pore structure.

[0033] (3) The preparation process provided by the application is relatively simple and green, and is suitable for large-scale industrial production; the product has relatively good performance and has certain competitive advantage. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Scanning electron microscope image of the hard carbon material obtained in Example 4.

[0035] Figure 2 X-ray diffraction pattern of the hard carbon material obtained in Example 4.

[0036] Figure 3 Raman pattern of the hard carbon material obtained in Example 4.

[0037] Figure 4 Charge-discharge curve of the hard carbon material obtained in Example 4.

[0038] Figure 5 Long cycle graph of the hard carbon material obtained in Example 4. DETAILED DESCRIPTION

[0039] The present application will be further described in detail by reference to the following examples and drawings, but the embodiments of the present application are not limited thereto.

[0040] In the embodiments of the present application, unless specific conditions are specified, the operations are performed according to the conventional conditions or the conditions recommended by the manufacturers. The raw materials, reagents, etc. used, which are not specified by the manufacturers, are all conventional products that can be purchased on the market.

[0041] The preparation method of the coal precursor particles described in the examples and comparative examples of the present application is as follows:

[0042] (1) The lignite is crushed and sieved by a crushing device to obtain lignite particles with a particle size of 74 μm;

[0043] (2) The raw coal particles after the crushing and sieving operations are subjected to a washing treatment, and after being pickled with 2 mol / L hydrochloric acid for 12 h, they are washed with water until neutral;

[0044] (3) The coal after the pickling is subjected to a drying operation to obtain precursor particles.

[0045] Comparative Example 1

[0046] (1) Preparation of coal precursor particles.

[0047] (2) The coal precursor particles are placed in a tube furnace under a nitrogen atmosphere, and the coal precursor particles are heated from room temperature to 600℃ at a heating rate of 10℃ / min, and held for 2 h to obtain a pyrolysis intermediate.

[0048] (3) The above sample is placed in a tube furnace under a nitrogen atmosphere, and heated to 1300℃ at a heating rate of 2℃ / min, and held for 2 h to obtain a hard carbon material.

[0049] Example 1

[0050] (1) Preparation of coal precursor particles.

[0051] (2) The coal precursor particles were immersed in liquid nitrogen for 10 h, then dried in an oven at 80℃ to obtain the quenching pretreated coal precursor.

[0052] (3) The dried quenching pretreated coal precursor was placed in a tube furnace under nitrogen atmosphere, and the first stage pyrolysis treatment was performed. The coal precursor particles were heated from room temperature to 800℃ at a heating rate of 10℃ / min, and held for 2.5 h to obtain a carbon intermediate.

[0053] (4) The above sample was placed in a tube furnace under nitrogen atmosphere, and the second stage carbonization was performed. The temperature was increased to 1100℃ at a heating rate of 2℃ / min, and held for 3 h to obtain a hard carbon material.

[0054] Example 2

[0055] (1) Preparation of coal precursor particles.

[0056] (2) The coal precursor particles were immersed in liquid nitrogen for 10 h, then dried in an oven at 80℃ to obtain the quenching pretreated coal precursor.

[0057] (3) The dried quenching pretreated coal precursor was placed in a tube furnace under nitrogen atmosphere, and the first stage pyrolysis treatment was performed. The coal precursor particles were heated from room temperature to 600℃ at a heating rate of 5℃ / min, and held for 2.5 h to obtain a carbon intermediate.

[0058] (4) The above sample was placed in a tube furnace under nitrogen atmosphere, and the second stage carbonization was performed. The temperature was increased to 1300℃ at a heating rate of 2℃ / min, and held for 2 h to obtain a hard carbon material.

[0059] Example 3

[0060] (1) Preparation of coal precursor particles.

[0061] (2) The coal precursor particles were placed in a tube furnace under nitrogen atmosphere, and the temperature was increased to 700℃ at a heating rate of 5℃ / min. The particles were held for 2.5 h to obtain a pyrolysis intermediate.

[0062] (3) The pyrolysis intermediate was immersed in liquid nitrogen for 15 h, then dried in an oven at 80℃ to obtain a quenching pretreated intermediate.

[0063] (4) The quenching pretreated intermediate was placed in a tube furnace under nitrogen atmosphere, and the temperature was increased to 1300℃ at a heating rate of 3℃ / min. The particles were held for 2 h to obtain a hard carbon material.

[0064] Example 4

[0065] (1) Preparation of coal precursor particles.

[0066] (2) The coal precursor particles were placed in a tube furnace under nitrogen atmosphere, and heated from room temperature to 600°C at a heating rate of 10°C / min, and kept for 2h to obtain the pyrolysis intermediate.

[0067] (3) The pyrolysis intermediate was immersed in liquid nitrogen for 15h, and then dried in an oven at 80°C to obtain the quenching pretreatment intermediate.

[0068] (4) The quenching pretreatment intermediate was placed in a tube furnace under nitrogen atmosphere, and heated to 1200°C at a heating rate of 2°C / min, and kept for 2h to obtain the hard carbon material.

[0069] Example 5

[0070] (1) Coal precursor particles were prepared.

[0071] (2) The coal precursor particles were placed in a tube furnace under nitrogen atmosphere, and heated from room temperature to 400°C at a heating rate of 5°C / min, and kept for 2h to obtain the pyrolysis intermediate.

[0072] (3) The pyrolysis intermediate was immersed in liquid nitrogen for 15h, and then dried in an oven at 80°C to obtain the quenching pretreatment intermediate.

[0073] (4) The quenching pretreatment intermediate was placed in a tube furnace under nitrogen atmosphere, and heated to 1500°C at a heating rate of 2°C / min, and kept for 2h to obtain the hard carbon material.

[0074] Example 6

[0075] (1) Coal precursor particles were prepared.

[0076] (2) The coal precursor particles were placed in a tube furnace under nitrogen atmosphere, and heated from room temperature to 600°C at a heating rate of 10°C / min, and kept for 2h to obtain the pyrolysis intermediate.

[0077] (3) The pyrolysis intermediate was immersed in liquid nitrogen for 30h, and then dried in an oven at 80°C to obtain the quenching pretreatment intermediate.

[0078] (4) The quenching pretreatment intermediate was placed in a tube furnace under nitrogen atmosphere, and heated to 1400°C at a heating rate of 2°C / min, and kept for 2h to obtain the hard carbon material.

[0079] Example 7

[0080] (1) Coal precursor particles were prepared.

[0081] (2) The coal precursor particles were placed in a tube furnace under a nitrogen atmosphere, and heated from room temperature to 600°C at a heating rate of 10°C / min, and held for 2 h to obtain a pyrolysis intermediate.

[0082] (3) The pyrolysis intermediate was immersed in liquid nitrogen for 30 h, and then dried in an oven at 80°C to obtain a quenching pretreatment intermediate.

[0083] (4) The quenching pretreatment intermediate was placed in a tube furnace under a nitrogen atmosphere, and heated to 1300°C at a heating rate of 2°C / min, and held for 2 h to obtain a hard carbon material.

[0084] Example 8

[0085] (1) Coal precursor particles were prepared.

[0086] (2) The coal precursor particles were placed in a tube furnace under a nitrogen atmosphere, and heated from room temperature to 300°C at a heating rate of 3°C / min, and held for 2 h to obtain a pyrolysis intermediate.

[0087] (3) The pyrolysis intermediate was immersed in liquid nitrogen for 30 h, and then dried in an oven at 80°C to obtain a quenching pretreatment intermediate.

[0088] (4) The quenching pretreatment intermediate was placed in a tube furnace under a nitrogen atmosphere, and heated to 1200°C at a heating rate of 2°C / min, and held for 2 h to obtain a hard carbon material.

[0089] Electrochemical performance test

[0090] The hard carbon negative electrode materials prepared in Comparative Example 1 and Examples 1-8 were used as working electrodes, sodium was used as the counter electrode, and the electrolyte was a sodium hexafluorophosphate solution (the concentration of sodium hexafluorophosphate was 0.8 mol / L, and the solvent was a mixed solution of ethylene carbonate EC and diethyl carbonate DEC at a volume ratio of 1:1), and a coin cell was assembled. A blue electric tester was used for testing, at a current density of 20 mA / g, and the voltage range was 0.001-2.5 V, and the test results are shown in Table 1.

[0091] Table 1

[0092]

[0093] As can be seen from Table 1, the hard carbon negative electrode prepared in Example 4 exhibits the best charge-discharge specific capacity and first coulombic efficiency. The use of liquid nitrogen for quenching pretreatment causes many cracks and pores to form on the surface of the material, changing its microstructure. Secondly, after the low-temperature pyrolysis and high-temperature carbonization processes, respectively, the carbon layer is rearranged, part of the open pores is closed to form closed pores, more pseudo-graphite domain structures and surface defects are exhibited, new channels are provided for the effective diffusion of sodium ions, additional active sites are provided for the storage of sodium ions, and the rate capability, capacity and cycle performance of the sodium-ion battery negative electrode are comprehensively improved.

[0094] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A method for preparing a quench pretreated coal-derived hard carbon negative electrode material, characterized in that, The preparation method comprises the following steps: (1) crushing, screening, washing and drying a coal raw material to obtain coal precursor particles; (2) pyrolyzing the coal precursor particles at 200-900 ℃ to obtain a pyrolysis intermediate; (3) carbonizing the pyrolysis intermediate at 900-1800 ℃ to obtain a hard carbon material; The coal precursor particles obtained in step (1) and / or the pyrolysis intermediate obtained in step (2) need to be subjected to quenching pretreatment. The quenching pretreatment is liquid nitrogen quenching pretreatment. The quenching pretreatment time is 10-30 h.

2. The method of claim 1, wherein the method of preparing a quench pretreated coal-derived hard carbon negative electrode material is characterized by, The coal raw material in step (1) is at least one of lignite and bituminous coal.

3. The method of claim 2, wherein the method of preparing a quench pretreated coal-derived hard carbon negative electrode material is characterized by, The quenching pretreatment time is 15-30 h.

4. The method of claim 1 or 2, wherein the method of preparing a quench pretreated coal-derived hard carbon negative electrode material is characterized by, The pyrolysis temperature in step (2) is 300-800 ℃; And / or, the pyrolysis time in step (2) is 1-6 h; And / or, the pyrolysis temperature rising rate in step (2) is 1-50 ℃ / min.

5. The method of claim 4, wherein the method of preparing a quench pretreated coal-derived hard carbon negative electrode material is characterized by, The pyrolysis temperature in step (2) is 600-800 ℃; And / or, the pyrolysis time in step (2) is 1-2 h; And / or, the pyrolysis temperature rising rate in step (2) is 5-20 ℃ / min.

6. The method of claim 1 or 2, wherein the method of preparing a quench pretreated coal-derived hard carbon negative electrode material is characterized by, The carbonization temperature in step (3) is 1100-1400 ℃; And / or, the carbonization time in step (3) is 1-30 h; And / or, the carbonization temperature rising rate in step (3) is 1-50 ℃ / min.

7. The method of claim 6, wherein the method of preparing a quench pretreated coal-derived hard carbon negative electrode material is characterized by, The carbonization temperature in step (3) is 1200-1400 ℃; And / or, the carbonization time in step (3) is 2-3 h; And / or, the carbonization temperature rising rate in step (3) is 2-5 ℃ / min.

8. The method of claim 1 or 2, wherein the method of preparing a quench pretreated coal-derived hard carbon negative electrode material is characterized by, The particle size of the raw coal particles obtained after crushing and screening in step (1) is 0.5-500 μm; And / or, the washing in step (1) refers to acid washing followed by water washing to neutral; And / or, the acid washing refers to acid washing with 0.1-5 mol / L hydrochloric acid solution for 1-120 h; And / or, the pyrolysis in step (2) and the carbonization in step (3) are carried out in an inert atmosphere, and the inert atmosphere is at least one of nitrogen, argon and helium.

9. A quenching pretreated coal-derived hard carbon negative electrode material prepared by the preparation method in any one of claims 1-8.

10. Application of the quenching pretreated coal-derived hard carbon negative electrode material in claim 9 in a sodium ion battery.

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