Hard carbon negative electrode material and preparation method and application thereof

Abstract

The application belongs to the technical field of ion batteries, and particularly relates to a hard carbon negative electrode material and a preparation method and application thereof. The application provides a preparation method of a hard carbon negative electrode material, which comprises the following steps: (1) after ball milling treatment and impurity removal treatment of a coal-based material, a coal-based nanomaterial is obtained; (2) after mixing of the coal-based nanomaterial and an aliphatic compound containing S and / or N, spray granulation is performed to obtain a mixed material; (3) the mixed material is first subjected to pre-oxidation treatment, and then subjected to carbonization treatment under an inert atmosphere to obtain the hard carbon negative electrode material. In the application, the coal-based material and the aliphatic compound are used, and the coal-based material and the aliphatic compound are polymerized to form a polymer network composite precursor through spray granulation and pre-oxidation, and in a high-temperature carbonization process, graphitization can be inhibited, the hard carbon material has a larger interlayer spacing and a rich closed pore structure, which is beneficial to ion diffusion dynamics, and the specific capacity, the first efficiency and the cycle life of the hard carbon negative electrode material are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ion batteries, and particularly relates to a hard carbon negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] Among the numerous negative electrode materials of sodium ion batteries, carbon-based materials develop the fastest due to their wide sources, significant cost and commercial production advantages. Hard carbon negative electrodes with high disorder degree and large interlayer spacing have higher storage capacity, lower working voltage and excellent cycle stability. Common hard carbons include resin-based, coal-based materials and biomass hard carbons.

[0003] However, hard carbon has a large specific surface area and a large number of defects, and a large amount of irreversible reactions will occur during the first charge and discharge process, resulting in a decrease in the initial efficiency of the battery. The internal kinetic performance, including the electronic conductivity and ion diffusion rate, is poor, causing poor rate of the material. In addition, the structure of hard carbon may be damaged during the charge and discharge process, thereby affecting its cycle stability. These shortcomings of hard carbon materials need to be solved by material modification and structure design optimization to improve the performance and stability of sodium ion batteries.

[0004] Therefore, there is more and more attention on optimizing hard carbon materials to make them more suitable for sodium ion batteries. SUMMARY

[0005] The present application aims to at least solve one of the problems in the related art. To this end, the embodiments of the present application propose a preparation method of a hard carbon negative electrode material, which has a larger interlayer spacing (0.399 nm) and a rich closed pore structure, which is beneficial to ion diffusion kinetics, and improves the specific capacity, initial efficiency and cycle life of the hard carbon negative electrode material.

[0006] The preparation method of the hard carbon negative electrode material according to the embodiments of the present application comprises the following steps:

[0007] (1) After ball milling and impurity removal treatment of the coal-based material, a coal-based nanomaterial is obtained;

[0008] (2) After mixing the coal-based nanomaterial obtained in step (1) with an aliphatic compound containing S and / or N, spray granulation is performed to obtain a mixed material;

[0009] (3) The mixed material obtained in step (2) is first subjected to pre-oxidation treatment, and then carbonization treatment under an inert atmosphere to obtain a hard carbon negative electrode material.

[0010] The preparation method of the hard carbon negative electrode material has the following advantages and technical effects: 1. The method of the embodiment of the application can obtain a polymer network composite precursor by mixing a coal-based material and an aliphatic compound and through spray granulation and pre-oxidation treatment, and the composite precursor can inhibit graphitization in a high-temperature carbonization process, so that the hard carbon material has a larger interlayer spacing (0.399 nm) and a rich closed pore structure, which is beneficial to ion diffusion dynamics and improves the specific capacity, the first efficiency and the cycle life of the hard carbon negative electrode material; 2. The method of the embodiment of the application selects an aliphatic compound containing S and / or N; the aliphatic N-containing compound can make the polymer network composite precursor obtained through pre-oxidation treatment generate C-N free radicals in the carbonization process, and then a hard carbon material with rich defects and a large interlayer spacing can be constructed, which can greatly improve the rate performance and the cycle stability of the sodium ion battery; the aliphatic S-containing compound can provide more active sites for the storage of sodium ions in the hard carbon layer, and the hard carbon material can exhibit larger reversible capacity, excellent cycle performance and better cycle stability, and there are no vacancy defects; 3. The method of the embodiment of the application is simple, the prepared hard carbon negative electrode material has good comprehensive performance, and is convenient for popularization and application in industrial production.

[0011] In some embodiments, in the step (1), the solution used in the impurity removal treatment includes at least one of an HF solution and / or an HCl solution.

[0012] In some embodiments, in the step (2), the mass ratio of the coal-based nanomaterial and the aliphatic compound is (5-15): 1.

[0013] In some embodiments, in the step (2), the particle size of the mixed material obtained after the spray granulation is 5-12 mu m.

[0014] In some embodiments, in the step (3), the temperature of the pre-oxidation treatment is 200-400 DEG C, and the time of the pre-oxidation treatment is 1-3 h.

[0015] In some embodiments, in the step (3), the temperature of the carbonization treatment is 1000-1600 DEG C, and the time of the carbonization treatment is 2-4 h.

[0016] And / or, the temperature of the pre-oxidation treatment is increased to the temperature of the carbonization treatment at a temperature increasing rate of 1-5 DEG C / min.

[0017] In some embodiments, in the step (3), the inert atmosphere includes at least one of argon or nitrogen.

[0018] The embodiment of the application further provides a hard carbon negative electrode material prepared by the above preparation method.

[0019] The embodiment of the present application also provides a negative pole piece comprising the hard carbon negative pole material prepared by the preparation method or the hard carbon negative pole material.

[0020] The embodiment of the present application also provides a sodium ion battery comprising the negative pole piece. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the first week charge-discharge curve of the battery prepared in Example 1. DETAILED DESCRIPTION

[0022] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0023] The preparation method of the hard carbon negative pole material of the embodiment of the present application comprises the following steps:

[0024] (1) After ball milling treatment and impurity removal treatment of the coal-based material, a coal-based nanomaterial is obtained;

[0025] (2) After mixing the coal-based nanomaterial obtained in step (1) and an aliphatic compound containing S and / or N, spray granulation is performed to obtain a mixed material;

[0026] (3) The mixed material obtained in step (2) is first subjected to pre-oxidation treatment, and then carbonization treatment under inert atmosphere to obtain a hard carbon negative pole material.

[0027] The preparation method of the hard carbon negative pole material of the embodiment of the present application mixes the coal-based material and the aliphatic compound and performs spray granulation and pre-oxidation treatment, so that a polymer network composite precursor can be obtained. The composite precursor can inhibit graphitization in the high-temperature carbonization process, so that the hard carbon material has a larger interlayer spacing (0.399 nm) and a rich closed pore structure, which is beneficial to ion diffusion dynamics and improves the specific capacity, the first efficiency and the cycle life of the hard carbon negative pole material. The method of the embodiment of the present application selects an aliphatic compound containing S and / or N. The aliphatic N-containing compound can make the polymer network composite precursor obtained by pre-oxidation treatment produce C-N free radicals in the carbonization process, and then a hard carbon material with rich defects and expanded interlayer spacing can be constructed, which can greatly improve the rate performance and cycle stability of the sodium ion battery. The aliphatic S-containing compound can provide more active sites for the storage of sodium ions in the hard carbon layer, so that the hard carbon material can exhibit larger reversible capacity, excellent cycle performance and better cycle stability, and there are no vacancy defects. The method of the embodiment of the present application is simple in process, the prepared hard carbon negative pole material has good comprehensive performance, and is convenient for popularization and application in industrial production.

[0028] In some embodiments, preferably, in the step (1), the impurity removal treatment employs a solution including at least one of an HF solution and / or an HC1 solution.

[0029] In some embodiments, preferably, in the step (2), the S and / or N containing aliphatic compound includes at least one of thiourea (CH4N2S), cysteine (C3H7NO2S), penicillamine (C5H11NO2S), an aminothiol compound or an aminothiol compound. 11 NO2S), an aminothiol compound or an aminothiol compound.

[0030] In some embodiments, preferably, in the step (2), the mass ratio of the coal-based nanomaterial and the aliphatic compound is (5-15): 1, such as 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, etc.

[0031] In the embodiments of the present application, the mass ratio of the aliphatic compound and the coal-based nanomaterial is preferred, which is beneficial to obtain a negative electrode material with good comprehensive performance; if the amount of the aliphatic compound is too low, the hard carbon material obtained has insufficient active sites and the interlayer spacing is reduced, thereby the rate performance and the cycle performance of the battery are reduced; if the amount of the aliphatic compound is too high, the conductivity of the hard carbon material obtained is reduced, the subsequent negative electrode sheet film resistance is increased, and the cycle performance of the battery is reduced.

[0032] In some embodiments, preferably, the particle size of the mixed material obtained after the spray granulation is 5-12 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc.

[0033] In some embodiments, preferably, in the step (3), the temperature of the pre-oxidation treatment is 200-400°C, such as 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, etc.; the time of the pre-oxidation treatment is 1-3 h, such as 1 h, 1.5 h, 2 h, 2.5 h, 3 h, etc.

[0034] In some embodiments, preferably, in the step (3), the temperature of the carbonization treatment is 1000-1600°C, such as 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, etc.; the time of the carbonization treatment is 2-4 h, such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc.

[0035] and / or, the temperature of the pre-oxidation treatment is increased to the temperature of the carbonization treatment at a temperature increasing rate of 1-5℃ / min, for example, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, etc.

[0036] In some embodiments, preferably, in the step (3), the inert atmosphere comprises at least one of argon or nitrogen.

[0037] The embodiment of the present application also provides a hard carbon negative electrode material prepared by the above preparation method.

[0038] The embodiment of the present application also provides a negative electrode sheet comprising the hard carbon negative electrode material prepared by the above preparation method or the hard carbon negative electrode material.

[0039] The embodiment of the present application also provides a sodium ion battery comprising the negative electrode sheet.

[0040] The technical solutions of the present application are described in detail below in combination with specific embodiments and drawings.

[0041] Embodiment 1

[0042] (1) A certain mass of coal-based material is weighed, and the mass ratio of the coal-based material to the ball milling beads is 1:20; the ball milling is performed in a ball mill at a speed of 1200 rpm for 4 h, and the material after ball milling is taken out and washed with 1M HCl, and then dried to obtain a coal-based nanomaterial;

[0043] (2) The coal-based nanomaterial and thiourea (CH4N2S) are added into a solvent ethanol in a mass ratio of 10:1 and uniformly mixed, and then spray granulated to obtain a mixed material with a particle size of 8 μm;

[0044] (3) The mixed material is placed into a muffle furnace and pre-oxidized at 300℃ in air for 1 h to obtain a polymer network composite precursor; the temperature is increased to 1400℃ at a temperature increasing rate of 2℃ / min, and then the polymer network composite precursor is kept at 1400℃ in an inert atmosphere of argon for 2 h to obtain a hard carbon negative electrode material HC-1400 after high-temperature carbonization;

[0045] (4) The HC-1400, Super P, CMC and SBR are uniformly slurried in a mass ratio of 94:1:1.8:3.2, and an appropriate amount of deionized water is added during the uniform slurry, and then the uniformly mixed slurry is coated on an aluminum foil current collector substrate to obtain a negative electrode sheet; and then a CR2032 button-type half cell is formed together with a sodium sheet, and the electrolyte used is NaClO4 (EC+DEC+5% FEC).

[0046] Embodiment 2

[0047] The preparation method of this example is the same as that of Example 1, except that the high-temperature carbonization temperature in step (3) is 1200°C.

[0048] Example 3

[0049] The preparation method of this example is the same as that of Example 1, except that the high-temperature carbonization temperature in step (3) is 1600°C.

[0050] Example 4

[0051] The preparation method of this example is the same as that of Example 1, except that in step (2), the mass ratio of the coal-based nanomaterial to the aliphatic compound is 5:1.

[0052] Example 5

[0053] The preparation method of this example is the same as that of Example 1, except that in step (2), the mass ratio of the coal-based nanomaterial to the aliphatic compound is 15:1.

[0054] Comparative Example 1

[0055] (1) A certain mass of coal-based material was weighed, and the mass ratio of the coal-based material to the ball milling beads was 1:20; the ball milling was carried out in a ball mill at a speed of 1200 rpm for 4 h, and the material after ball milling was taken out and washed with 1M HCl, and then dried to obtain a coal-based nanomaterial;

[0056] (2) The coal-based nanomaterial was mixed uniformly in a solvent ethanol, and after spray granulation, a mixed material was obtained;

[0057] (3) The mixed material was placed in a muffle furnace and pre-oxidized at 300°C for 1 h in air, and then heat-treated at 1400°C for 2 h in an inert atmosphere of argon to obtain a hard carbon negative electrode material HC-C after high-temperature carbonization;

[0058] (4) The battery assembly was the same as that of Example 1.

[0059] The batteries prepared in Examples 1-5 and Comparative Example 1 were subjected to performance testing, and the results are shown in Table 1: wherein the first week of charge-discharge curve of the battery prepared in Example 1 is shown in Figure 1

[0060] Table 1

[0061] Initial efficiency (%) Capacity (mAh / g) Capacity retention rate (%) after 1C cycling for 50 cycles Example 1 91.6 311.1 97.5 Example 2 87.3 310.5 95.9 Example 3 91.2 299.7 95.3 Example 4 90.1 294.1 97.0 Example 5 87.8 270.5 96.6 Comparative Example 1 84.2 260.2 97.2

[0062] ​The sodium ion battery prepared by the embodiment of the present application has higher initial efficiency, capacity and excellent capacity retention rate. As can be seen from the data of examples 1-3, with the increase of carbonization temperature, the initial efficiency and capacity of the battery both show a trend of first increasing and then decreasing. This is because there are more heteroatoms in the hard carbon material obtained by carbonization at a lower temperature, and there are a large number of defects, high-energy defects adsorb to form dead sodium and form SEI film by side reaction with electrolyte, so the initial coulombic efficiency is lower when carbonization at a lower temperature. With the increase of carbonization temperature, the specific surface area of the prepared hard carbon material decreases, and the pore size increases. High-temperature treatment causes the structure of the graphite crystallite to change. In this process, a large amount of deoxygenation and denitrification increases the degree of graphitization, and the specific surface area of the hard carbon material decreases sharply. Part of the poorly stacked amorphous carbon changes to order, resulting in the collapse and disappearance of part of the micropores, and the growth of part of the micropores to form mesopores, resulting in a decrease in capacity.

[0063] In example 4 and example 5, the mass ratio of coal-based material to aliphatic compound is adjusted. In example 4, the amount of aliphatic compound is more than that in example 1, and the initial efficiency is basically unchanged, but the capacity decreases. If too much aliphatic compound is added, it will occupy the active sites in the hard carbon material, so the initial efficiency is basically unchanged, and the capacity decreases. In example 5, the amount of aliphatic compound is less than that in example 1, and the content of N / S elements in the generated hard carbon material is less, so the initial efficiency and capacity of the prepared hard carbon material are reduced, and the capacity retention rate decreases.

[0064] In comparative example 1, only coal-based material is used to prepare hard carbon material, and not only the initial efficiency can be maintained at 84.2%, but also the capacity is reduced to 260.2 mAh / g.

[0065] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the present specification and the features of different embodiments or examples can be combined and modified by those skilled in the art without contradiction.

[0066] Although the above embodiments have been shown and described, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and the changes, modifications, replacements and variations of the above embodiments made by those skilled in the art are within the protection scope of the present application.

Claims

1. A method for preparing a hard carbon anode material, characterized in that, Includes the following steps: (1) Coal-based nanomaterials are obtained by ball milling and impurity removal of coal-based materials; (2) The coal-based nanomaterials obtained in step (1) are mixed with an aliphatic compound containing S and N, and then spray-granulated to obtain a mixed material; the mass ratio of the coal-based nanomaterials to the aliphatic compound is (5~15):1; the aliphatic compound containing S and N includes at least one of thiourea, cysteine, penicillamine, aminothiol compounds or aminothiophenol compounds. (3) The mixed material obtained in step (2) is first subjected to pre-oxidation treatment, and then carbonized under an inert atmosphere to obtain hard carbon anode material; The temperature of the pre-oxidation treatment is 200~400℃, and the time of the pre-oxidation treatment is 1~3h; The carbonization treatment temperature is 1000~1600℃, and the carbonization treatment time is 2~4h.

2. The method for preparing the hard carbon anode material according to claim 1, characterized in that, In step (1), the solution used for the impurity removal process includes at least one of HF solution and / or HCl solution.

3. The method for preparing the hard carbon anode material according to claim 1, characterized in that, In step (2), the particle size of the mixed material obtained after spray granulation is 5~12μm.

4. The method for preparing the hard carbon anode material according to claim 1, characterized in that, In step (3), the temperature of the pre-oxidation treatment is increased to the temperature of the carbonization treatment at a heating rate of 1~5℃ / min.

5. The method for preparing the hard carbon anode material according to claim 1, characterized in that, In step (3), the inert atmosphere includes at least one of argon or nitrogen.

6. A hard carbon anode material, characterized in that, It is prepared by any one of claims 1 to 5.

7. A negative electrode sheet, characterized in that, Includes the hard carbon anode material prepared by the preparation method of any one of claims 1 to 5 or the hard carbon anode material as described in claim 6.

8. A sodium-ion battery, characterized in that, Includes the negative electrode sheet as described in claim 7.

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