A high-ratio coal-based hard carbon composite material, its preparation method and application

Abstract

This invention relates to the field of secondary battery technology, and particularly to a high-rate coal-based hard carbon composite material, its preparation method, and its application. The preparation method includes the following steps: S1. Mixing and reacting a coal-based material with an aqueous solution of an organic oxidant, filtering, and drying to obtain an oxidized coal-based material; S2. Mixing and grinding the oxidized coal-based material with lithium carboxymethyl cellulose to obtain a hard carbon precursor material; S3. Mixing the hard carbon precursor material, catalyst, and metal powder evenly, adding the mixture to a resin solution for even dispersion, drying, and carbonization to obtain the coal-based hard carbon composite material. Through chemical reaction, lithium doping of the coal-based material reduces irreversible capacity and improves initial efficiency and specific capacity; simultaneously, the carbonization of lithium carboxymethyl cellulose forms pores, increasing specific capacity, and its catalysis causes the carbon-based material to form an isotropic carbon structure, improving the material's power performance; and silver doping further improves the material's electronic conductivity and power performance.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and in particular to a high-rate coal-based hard carbon composite material, its preparation method, and its application. Background Technology

[0002] Hard carbon is considered the most promising anode material for sodium-ion / lithium-ion batteries due to its advantages such as high capacity, low operating potential, wide availability, and low cost. Currently, the raw materials for preparing hard carbon mainly come from biomass and coal-based materials. Biomass materials, such as shells, starch, sugars, resins, and lignin, suffer from problems such as low residual carbon content (approximately 20-30%), high cost of finished products, diverse material sources, significant variations between different origins, and poor material quality. Coal-based materials, with their high residual carbon content (approximately 65-70%), better material consistency, and low cost, have become one of the main raw materials for preparing hard carbon. However, the application of coal-based hard carbon is limited by its inherent defects, such as low specific capacity (≤300mAh / g) and poor power performance. Measures to improve the energy density and power performance of coal-based hard carbon are mainly through doping, coating, and pore formation. Summary of the Invention

[0003] The first aspect of the present invention provides a method for preparing a high-ratio coal-based hard carbon composite material, the method comprising the following steps:

[0004] S1. Mix and react the coal-based material with an aqueous solution of an organic oxidant, filter, and dry to obtain oxidized coal-based material;

[0005] S2. Mix and grind the coal oxide-based material with lithium carboxymethyl cellulose to obtain a hard carbon precursor material;

[0006] S3. Mix the hard carbon precursor material, catalyst, and metal powder evenly, add the mixture to the resin solution and disperse evenly, dry, and carbonize to obtain a coal-based hard carbon composite material.

[0007] Further, S1 includes mixing the coal-based material with an aqueous solution (1-10 wt%) of an organic oxidant, reacting at 50-100°C for 1-6 hours, filtering, and vacuum drying to obtain the oxidized coal-based material.

[0008] In some embodiments, the organic oxidant includes at least one of oxalic acid, ammonium acetate, citric acid, ammonium citrate, urea, tartaric acid, and ammonium tartrate.

[0009] In some embodiments, the mass ratio of the coal-based material to the organic oxidant is 100:(1-10).

[0010] Furthermore, S2 includes mixing coal oxide-based materials with lithium carboxymethyl cellulose, adjusting the online speed of the sand mill to 10-15 m / s for 6-24 h, heating to 250-400℃ for a crosslinking reaction for 6-24 h, and air-jet pulverizing to a particle size of 5-15 μm to obtain a hard carbon precursor material.

[0011] Furthermore, the mass ratio of the coal-based oxidized material to lithium carboxymethyl cellulose is 100:(1-10). The applicant discovered in experiments that the ratio of coal-based oxidized material to lithium carboxymethyl cellulose significantly affects the power performance of the coal-based hard carbon composite material. After carbonization, lithium carboxymethyl cellulose can form pores, further increasing the specific capacity of the material. After catalysis, it causes the carbon-based structure to form an isotropic carbon structure, further improving the power performance of the material. The amount of lithium carboxymethyl cellulose added has a significant impact on the effect; too little addition has no significant effect on improving the initial efficiency, while too much addition will reduce the specific capacity of the material.

[0012] Furthermore, step S3 involves uniformly mixing the hard carbon precursor material, catalyst, and metal powder, adding the mixture to a resin solution for uniform dispersion, spray drying, transferring it to a tube furnace, and carbonizing it for 1-6 hours at 700-1100℃ under an inert atmosphere. The carbonization product is then acid-washed with hydrochloric acid, filtered, and dried to obtain a coal-based hard carbon composite material.

[0013] In some embodiments, the catalyst includes at least one of anthracene, phenanthrene, and naphthalene.

[0014] Compared to the infinitely variable catalysts used in existing technologies, the present invention selects anthracene, phenanthrene, and naphthalene as catalysts. The amorphous carbon and other materials left after catalysis will not introduce impurities, and can further improve the storage performance and recycling performance of the materials.

[0015] In some embodiments, the particle size of the metal powder is 100-500 nm.

[0016] In some embodiments, the metal powder includes at least one of silver powder, iron powder, copper powder, aluminum powder, zinc powder, and tin powder.

[0017] In some embodiments, the mass ratio of the hard carbon precursor material, catalyst, and metal powder is 100:(1-5):(1-5).

[0018] This invention further defines the proportions of hard carbon precursor material, catalyst, and metal powder. When the content of catalyst and metal powder is too high, it will lead to a decrease in specific capacity and tap density. When the amount added is small, the improvement in the power performance of the material is not obvious.

[0019] To improve the electronic conductivity of the composite material, silver powder with a purity of ≥99.99% is preferred.

[0020] Compared to other metal powders, silver powder has better electronic conductivity.

[0021] In some embodiments, the coal-based material includes at least one of anthracite, lignite, and bituminous coal, with a particle size of 10-50 μm.

[0022] Coal-based materials with excessively large particle sizes have high specific capacity but also large expansion, resulting in poor power performance and reduced fast-charging performance. On the other hand, excessively small particle sizes result in a large specific surface area, leading to more side reactions and reduced high-temperature performance. Therefore, selecting coal-based materials with a particle size of 10-50μm can better balance specific capacity and power performance.

[0023] In some embodiments, the resin solution is an aqueous resin solution, and more specifically, an aqueous solution of a thermosetting resin, such as an aqueous solution of phenolic resin. The addition of the resin solution can achieve uniform dispersion and uniform coating on the surface of the coal-based material, improving the material's consistency.

[0024] A second aspect of the present invention provides a high-ratio coal-based hard carbon composite material obtained by the preparation method described above.

[0025] A third aspect of the present invention provides the application of the preparation method described herein or the high-rate coal-based hard carbon composite material described herein in the field of secondary battery preparation.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) By chemically reacting lithium to reduce irreversible capacity and improve first efficiency and specific capacity in coal-based materials, lithium is doped to form pores to improve specific capacity and catalyze the formation of isotropic carbon structures in carbon-based materials to improve power performance. Simultaneously, silver doping improves the electronic conductivity of materials and improves power performance.

[0028] (2) The use of organic catalysts such as anthracene, phenanthrene, and naphthalene, compared with inorganic catalysts, will not introduce impurities such as amorphous carbon left after organic catalysis, thus improving the storage performance and recycling performance of the materials. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 The image shows a SEM image of the high-ratio coal-based hard carbon composite material prepared in Example 1. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] The first aspect of this embodiment provides a method for preparing a high-ratio coal-based hard carbon composite material, the method comprising the following steps:

[0034] S1. Mix 100g of coal-based material with 400g of an aqueous solution (10wt%) of organic oxidant and react at 80℃ for 3h. Filter and vacuum dry at 80℃ for 24h to obtain oxidized coal-based material.

[0035] S2. Mix 100g of coal oxide-based material with 5g of lithium carboxymethyl cellulose, adjust the online speed of the sand mill to 15m / s and sand mill for 12h, raise the temperature to 300℃ for crosslinking reaction for 12h, and air-jet pulverize to a particle size of 10μm to obtain hard carbon precursor material.

[0036] S3. Mix 100g of hard carbon precursor material, 3g of anthracene catalyst, and 3g of silver powder evenly. Add the mixture to 400g of phenolic resin aqueous solution (5wt%) and disperse evenly. After spray drying, transfer to a tube furnace and carbonize at 900℃ for 3h under an argon inert atmosphere. The carbonization product is acid-washed with 0.1mol / L hydrochloric acid, filtered, and vacuum dried at 80℃ for 24h to obtain coal-based hard carbon composite material.

[0037] The coal-based material is anthracite with a particle size of 20 μm; the aqueous solution of the organic oxidant is an oxalic acid aqueous solution (5 wt%).

[0038] The second aspect of this embodiment provides a high-ratio coal-based hard carbon composite material obtained by the preparation method described above.

[0039] The third aspect of this embodiment provides an application of the aforementioned high-rate coal-based hard carbon composite material in the field of secondary battery preparation.

[0040] Example 2

[0041] The first aspect of this embodiment provides a method for preparing a high-ratio coal-based hard carbon composite material, the method comprising the following steps:

[0042] S1. Mix 100g of coal-based material with 100g of an aqueous solution (10wt%) of organic oxidant and react at 50℃ for 6h. Filter and vacuum dry at 80℃ for 24h to obtain oxidized coal-based material.

[0043] S2. Mix 100g of coal oxide-based material with 1g of lithium carboxymethyl cellulose, adjust the online speed of the sand mill to 10m / s and sand mill for 24h, raise the temperature to 250℃ for crosslinking reaction for 24h, and air-jet pulverize to a particle size of 5μm to obtain hard carbon precursor material.

[0044] S3. Mix 100g of hard carbon precursor material, 1g of phenanthrene catalyst, and 1g of silver powder evenly. Add the mixture to 1000g of phenolic resin aqueous solution (1wt%) and disperse evenly. After spray drying, transfer to a tube furnace and carbonize at 700℃ for 6h under an argon inert atmosphere. The carbonization product is acid-washed with 0.1mol / L hydrochloric acid, filtered, and vacuum-dried at 80℃ for 24h to obtain a coal-based hard carbon composite material.

[0045] The coal-based material is lignite with a particle size of 10 μm; the aqueous solution of the organic oxidant is an ammonia acetic acid solution (1 wt%).

[0046] The second aspect of this embodiment provides a high-ratio coal-based hard carbon composite material obtained by the preparation method described above.

[0047] The third aspect of this embodiment provides an application of the aforementioned high-rate coal-based hard carbon composite material in the field of secondary battery preparation.

[0048] Example 3

[0049] The first aspect of this embodiment provides a method for preparing a high-ratio coal-based hard carbon composite material, the method comprising the following steps:

[0050] S1. Mix 100g of coal-based material with 10g of an aqueous solution (10wt%) of organic oxidant and react at 100℃ for 1h. Filter and vacuum dry at 80℃ for 24h to obtain oxidized coal-based material.

[0051] S2. Mix 100g of coal oxide-based material with 10g of lithium carboxymethyl cellulose, adjust the online speed of the sand mill to 15m / s and sand mill for 6h, heat to 400℃ for crosslinking reaction for 6h, and air-jet pulverize to a particle size of 15μm to obtain hard carbon precursor material.

[0052] S3. Mix 100g of hard carbon precursor material, 5g of naphthalene catalyst, and 5g of silver powder evenly. Add the mixture to 300g of phenolic resin aqueous solution (10wt%) and disperse evenly. After spray drying, transfer to a tube furnace and carbonize at 1100℃ for 1h under an argon inert atmosphere. The carbonization product is acid-washed with 0.1mol / L hydrochloric acid, filtered, and vacuum dried at 80℃ for 24h to obtain a coal-based hard carbon composite material.

[0053] The coal-based material is bituminous coal with a particle size of 30 μm; the aqueous solution of the organic oxidant is a citric acid aqueous solution (10 wt%).

[0054] The second aspect of this embodiment provides a high-ratio coal-based hard carbon composite material obtained by the preparation method described above.

[0055] The third aspect of this embodiment provides an application of the aforementioned high-rate coal-based hard carbon composite material in the field of secondary battery preparation.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing a high-ratio coal-based hard carbon composite material. The specific implementation method is the same as in Example 1, except that 0g of lithium carboxymethyl cellulose is used.

[0058] Comparative Example 2

[0059] This comparative example provides a method for preparing a high-ratio coal-based hard carbon composite material. The specific implementation method is the same as in Example 1, except that the anthracene catalyst and silver powder are both 0g.

[0060] Performance testing

[0061] The coal-based hard carbon composite materials prepared in the examples and comparative examples were subjected to the following tests.

[0062] (1) SEM testing

[0063] Figure 1 The image shows a SEM image of the coal-based hard carbon composite material prepared in Example 1. As can be seen from the image, the material exhibits a granular structure with a reasonable size distribution and a particle size between (5-10) μm.

[0064] (2) Physicochemical properties and button cell testing

[0065] The particle size, tap density, specific surface area, ash content and specific capacity, and initial efficiency of the coal-based hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested.

[0066] Test method: GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries":

[0067] The coal-based hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were used as negative electrode materials and assembled into button cells A1, A2, A3, B1, and B2, respectively. The preparation method was as follows: binder, conductive agent, and solvent were added to the negative electrode material, stirred and slurryed, coated on copper foil (single-sided thickness 120 μm), and dried and rolled. The binder used was LA132, the conductive agent was SP, and the solvent was double-distilled water. The ratio was negative electrode material: SP: LA132: double-distilled water = 90g: 4g: 6g: 220mL, and a negative electrode sheet was prepared. The electrolyte was LiPF6 / EC+DEC (volume ratio 1:1, concentration 1.3mol / L), the counter electrode was lithium metal sheet, and the separator was a composite membrane of polyethylene (PE) and polypropylene (PP) (PP / PE / PP). The simulated battery was assembled in an argon-filled glove box, and the electrochemical performance was tested on a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.005V to 2.0V, and the charge / discharge rate was 0.1C. The rate capability (3C, 0.1C) and cycle performance (0.5C / 0.5C, 100 cycles) of the coin cell were also tested. Detailed test data are shown in Table 1.

[0068] Table 1

[0069]

[0070] As can be seen from Table 1, the coal-based hard carbon composite material prepared in Example 1 has high specific capacity and first-pass efficiency. This is because silver doping in the hard carbon material increases the electronic conductivity of the material, thereby increasing the specific capacity and improving the rate performance; at the same time, lithium doping in the coal-based material reduces the irreversible capacity and improves the first-pass efficiency.

[0071] (3) Pouch battery

[0072] The coal-based hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were used as negative electrode materials, and ternary materials (LiNi) were used. 1 / 3 Co 1 / 3 Mn 1 / 3 Using O2 as the positive electrode, LiPF6 (solvent EC+DEC, volume ratio 1:1, concentration 1.3mol / l) as the electrolyte, and Celegard 2400 as the separator, 2Ah soft-pack batteries C1, C2, C3 and D1, D2 were prepared, thus obtaining ternary lithium batteries.

[0073] 3.1 Ratio Performance:

[0074] The rate performance of the soft-pack battery was then tested. The charge and discharge voltage range was 2.75 to 4.2V, the temperature was 25±3.0℃, and the battery was charged at 1.0C, 3.0C, 5.0C, and 10.0C, and discharged at 1.0C. The charge ratio and constant current ratio of the battery were tested. The test results are detailed in Table 2.

[0075] Table 2

[0076]

[0077] As shown in Table 2, the rate charging performance of the soft-pack batteries in Examples 1-3 is significantly better than that in Comparative Examples 1-2, i.e., the charging time is shorter. The reason for this is that lithium ions need to migrate during the battery charging process, and the lithium compounds doped in the materials of the examples increase the lithium ion insertion and extraction rate during the charging and discharging process, further improving the constant current ratio of the materials; at the same time, silver doping improves the electronic conductivity of the materials and improves the power performance.

[0078] 3.2 Cyclic Performance Test:

[0079] The cycle performance test method is as follows: charge / discharge current 2C / 2C, voltage range 2.75-4.2V, number of cycles 500; the test results are shown in Table 3.

[0080] Table 3

[0081] project Initial capacity retention (%) Retention rate (%) after 300 cycles Retention rate (%) after 500 cycles Example 1 100 98.46 97.36 Example 2 100 98.36 96.15 Example 3 100 98.97 97.95 Comparative Example 1 100 94.76 92.45 Comparative Example 2 100 95.46 93.03

[0082] As shown in Table 3, the lithium-ion batteries prepared using the coal-based hard carbon composite materials obtained in Examples 1-3 exhibit significantly better cycle performance than the comparative examples at all stages. Experimental results indicate that the doped lithium salt compounds in the materials of this invention can increase the number of lithium ions during charging and discharging, and improve cycle performance; simultaneously, the materials in the examples have a high specific surface area, further enhancing the liquid retention and cycle performance of the materials.

[0083] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-rate coal-based hard carbon composite material, characterized in that, The preparation method includes the following steps: S1. Mix and react the coal-based material with an aqueous solution of an organic oxidant, filter, and dry to obtain oxidized coal-based material; S2. Mix and grind the coal-based oxidized material with lithium carboxymethyl cellulose to obtain a hard carbon precursor material; S3. Mix the hard carbon precursor material, catalyst, and metal powder evenly, add the mixture to the resin solution and disperse evenly, dry, and carbonize to obtain a coal-based hard carbon composite material; Organic oxidants include at least one of oxalic acid, ammonium acetate, citric acid, ammonium citrate, urea, tartaric acid, and ammonium tartrate. The catalyst includes at least one of anthracene, phenanthrene, and naphthalene.

2. The method for preparing a high-ratio coal-based hard carbon composite material according to claim 1, characterized in that, The mass ratio of the coal-based material to the organic oxidant is 100:(1-10).

3. The method for preparing a high-ratio coal-based hard carbon composite material according to claim 1, characterized in that, The particle size of the metal powder is 100-500 nm.

4. The method for preparing a high-ratio coal-based hard carbon composite material according to claim 1, characterized in that, The metal powder includes at least one of silver powder, iron powder, copper powder, aluminum powder, zinc powder, and tin powder.

5. The method for preparing a high-ratio coal-based hard carbon composite material according to claim 1, characterized in that, The mass ratio of the hard carbon precursor material, catalyst, and metal powder is 100:(1-5):(1-5).

6. The method for preparing a high-ratio coal-based hard carbon composite material according to claim 1, characterized in that, The coal-based material includes at least one of anthracite, lignite, and bituminous coal, with a particle size of 10-50 μm.

7. A high-ratio coal-based hard carbon composite material obtained by the preparation method according to any one of claims 1-6.

8. The application of a preparation method according to any one of claims 1-6 or the high-rate coal-based hard carbon composite material according to claim 7 in the field of secondary battery preparation.

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