Preparation method of hard carbon composite material, hard carbon composite material and application

Abstract

The application relates to the technical field of secondary battery material preparation, and discloses a preparation method of a hard carbon composite material, the hard carbon composite material and application. The preparation method of the hard carbon composite material comprises the following steps: S1, heating sodium chloride to melting, adding calcium carbide, metal oxide or sulfide, mixing uniformly, introducing carbon dioxide, and carrying out reaction to obtain a hard carbon precursor material; and S2, transferring the hard carbon precursor material to a container, introducing inert gas, and then introducing natural gas and bromide gas in sequence to modify, so as to obtain the hard carbon composite material. Through the technical scheme, the problem of poor battery performance of the hard carbon material prepared in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of secondary battery material preparation technology, specifically to a method for preparing a hard carbon composite material, the hard carbon composite material itself, and its applications. Background Technology

[0002] Hard carbon materials have a layered structure with a small number of randomly arranged crystallites. Even with high-temperature heat treatment, they cannot be transformed into a graphite structure, hence they are called non-graphitizable carbon materials. Compared with graphite and soft carbon materials, hard carbon materials have excellent cycle characteristics and are the most promising anode materials for commercial sodium-ion batteries. They have a large lattice spacing and many disordered structures, enabling reversible insertion and extraction of sodium ions.

[0003] Hard carbon materials are used as negative electrode materials for secondary batteries. The preparation method generally involves crushing shell materials, pre-carbonizing, curing, acid washing, and high-temperature carbonization. The resulting materials have problems such as low tap density, poor consistency, poor batch stability, and low energy density, which leads to unsatisfactory battery performance. Summary of the Invention

[0004] This invention proposes a method for preparing hard carbon composite materials, as well as the hard carbon composite materials and their applications, which solves the problem of poor battery performance in the preparation of hard carbon materials in related technologies.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a hard carbon composite material includes the following steps:

[0007] S1. Heat sodium chloride until it melts, add calcium carbide, metal oxides or sulfides and mix evenly, then introduce carbon dioxide to carry out the reaction and obtain hard carbon precursor material.

[0008] S2. The hard carbon precursor material is transferred to a container, and after inert gas is introduced, natural gas and bromide gas are introduced in sequence for modification to obtain a hard carbon composite material.

[0009] As a further technical solution, the reaction temperature in S1 is 850~1000℃, and the reaction time is 6~24h.

[0010] As a further technical solution, the mass ratio of sodium chloride, calcium carbide, and metal oxides or sulfides in S1 is 1000:100:1~5.

[0011] As a further technical solution, the flow rate of carbon dioxide introduced into S1 is 100~1000 mL / min.

[0012] As a further technical solution, after the reaction in S1 is completed, filtration, water washing, and acid washing are also included.

[0013] As a further technical solution, the temperature of natural gas introduced in S2 is 700~1000℃, and the time is 1~6h.

[0014] As a further technical solution, S2 contains one of the bromine gases: hydrogen bromide and bromomethane.

[0015] The temperature for introducing bromine gas is 1000~1500℃, and the time is 1~6h.

[0016] As a further technical solution, the metal in S1 includes one of Sn, Sb, Mo, and Ge.

[0017] The present invention also proposes a hard carbon composite material, which is prepared by the aforementioned preparation method.

[0018] The present invention also proposes a method for preparing a hard carbon composite material or the application of the hard carbon composite material in a secondary battery.

[0019] The working principle and beneficial effects of this invention are as follows:

[0020] 1. This invention uses the molten salt method to prepare a hard carbon composite material. The method involves dissolving the material in a salt solution and carrying out a liquid-phase reaction. This method has high reaction efficiency and completeness, and the resulting material has high density, which can improve the material's electrochemical properties such as energy density.

[0021] 2. This invention involves reacting calcium carbide with carbon dioxide in a molten sodium chloride solution: 2CaC₂ + 3CO₂ = 2CaCO₃ + 5C, to generate amorphous carbon with high density and good uniformity, thus obtaining a hard carbon precursor material. This process offers advantages such as high preparation efficiency, good uniformity, and high tap density. Furthermore, the uniform internal pores of the resulting amorphous carbon enhance the material's sodium storage capacity. In addition, this invention uses vapor deposition to deposit amorphous carbon on the surface of the hard carbon precursor material, reducing surface defects, improving electronic conductivity, and enhancing rate performance. The outer surface is then brominated to further reduce defects, and the bromination treatment improves the compatibility between the material surface and the electrolyte, thus enhancing storage performance. Attached Figure Description

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1 This is a SEM image of the hard carbon composite material obtained in Example 1 of the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] S1. Heat 1000g of sodium chloride to 950℃ to form a liquid, add 100g of calcium carbide and 3g of antimony trioxide and disperse evenly. Then, introduce carbon dioxide at a flow rate of 500mL / min and react at this temperature for 12h. After filtration, wash with water and acid wash three times with 1000mL of 0.1mol / L hydrochloric acid to obtain hard carbon precursor material.

[0027] S2. The hard carbon precursor material obtained in S1 is transferred to a rotary tube furnace. First, argon inert gas is introduced to purge the air in the tube, and the rotation function in the tube furnace is turned on. The temperature is raised to 800°C and natural gas is introduced for 3 hours. Then, the temperature is raised to 1200°C and hydrogen bromide gas is introduced for 3 hours for modification. Finally, the temperature is lowered to room temperature in an argon atmosphere to obtain the hard carbon composite material.

[0028] Example 2

[0029] S1. Heat 1000g of sodium chloride to 850℃ to form a liquid, add 100g of calcium carbide and 1g of molybdenum trioxide and disperse evenly. Then, introduce carbon dioxide at a flow rate of 100mL / min and react at this temperature for 24h. After filtration, wash with water and acid wash three times with 1000mL of 0.1mol / L hydrochloric acid to obtain hard carbon precursor material.

[0030] S2. The hard carbon precursor material obtained in S1 is transferred to a rotary tube furnace. First, argon inert gas is introduced to purge the air in the tube, and the rotation function in the tube furnace is turned on. The temperature is raised to 700°C and natural gas is introduced for 6 hours. Then, the temperature is raised to 1000°C and bromomethane gas is introduced for 6 hours for modification. Finally, the temperature is lowered to room temperature in an argon atmosphere to obtain the hard carbon composite material.

[0031] Example 3

[0032] S1. Heat 1000g of sodium chloride to 1000℃ to form a liquid, add 100g of calcium carbide and 5g of tin dioxide and disperse evenly. Then, introduce carbon dioxide at a flow rate of 1000mL / min and react at this temperature for 6h. After filtration, wash with water and acid wash three times with 1000mL of 0.1mol / L hydrochloric acid to obtain hard carbon precursor material.

[0033] S2. The hard carbon precursor material obtained in S1 is transferred to a rotary tube furnace. First, argon inert gas is introduced to purge the air inside the tube, and the rotation function in the tube furnace is turned on. The temperature is raised to 1000℃ and natural gas is introduced for 1 hour. Then, the temperature is raised to 1500℃ and hydrogen bromide gas is introduced for 1 hour for modification. Finally, the temperature is lowered to room temperature in an argon atmosphere to obtain the hard carbon composite material.

[0034] Example 4

[0035] The only difference from Example 1 is that antimony oxide is replaced with an equal amount of antimony trisulfide; otherwise, they are the same as in Example 1.

[0036] Comparative Example 1

[0037] The only difference from Example 1 is that antimony trioxide is not added; otherwise, it is the same as Example 1.

[0038] Comparative Example 2

[0039] The only difference from Example 1 is that hydrogen bromide gas is not introduced; otherwise, it is the same as Example 1.

[0040] Performance testing:

[0041] (1) SEM test: The hard carbon composite material obtained in Example 1 was subjected to SEM test, and the test results are as follows. Figure 1 As shown.

[0042] from Figure 1 As can be seen, the hard carbon composite material has a uniform size distribution and a small amount of adsorbed fine powder on the surface, with a particle size between 5 and 10 μm.

[0043] (2) Physical and chemical performance test: The specific surface area and powder conductivity of the hard carbon composite material obtained by the examples and comparative examples were tested according to the method in the national standard GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". The diffusion coefficient of the material was tested by GITT and its particle size La was tested by XRD. The test results are shown in Table 1.

[0044] (3) Button cell battery test: The hard carbon composite materials obtained in Examples 1-4 and Comparative Examples 1-2 were used as negative electrode materials for lithium-ion batteries to assemble button cells. The specific preparation method of the negative electrode material was as follows: the negative electrode sheet was prepared by mixing hard carbon composite material, binder CMC, binder SBR, conductive agent SP, and H2O in a mass ratio of 95:2.5:1.5:1:150; a sodium sheet was used as the counter electrode; the electrolyte was NaPF6 (solvent volume ratio of EC:DEC:PC:propylene glycol polyoxypropylene ether = 1:2:1:0.05, concentration 1.3mol / L); the separator was a composite membrane of polyethylene (PE), polypropylene (PP), and polyethylene propylene (PEP). The button cells were assembled in an argon-filled glove box. Electrochemical performance was tested using a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.00V to 2.0V, and the charge / discharge rate was 0.1C. The initial discharge capacity and initial efficiency, charge DCR (50% SOC, 0.1C), and cycle performance (0.5C / 0.5C, 100 cycles) of the coin cells were tested. The test results are shown in Table 1.

[0045] Table 1 Physicochemical properties of hard carbon composites

[0046]

[0047] As shown in Table 1, the hard carbon anode composite materials obtained in Examples 1-4 are superior to those in Comparative Examples 1-2 in terms of diffusion coefficient, tap density, and specific capacity. This is because amorphous carbon is deposited on the surface of the hard carbon precursor material using vapor deposition, which reduces surface defects, improves electronic conductivity, reduces DCR, and improves first-pass efficiency. Simultaneously, the metal and sodium form an alloy, further enhancing the specific capacity and first-pass efficiency of the material.

[0048] (4) Rate performance test: The hard carbon composite materials obtained in Examples 1-4 and Comparative Examples 1-2 were slurried and coated to prepare negative electrode sheets, using layered oxides (NaFe) 1 / 3 Mn 1 / 3 Ni 1 / 3 A 5Ah soft-pack battery was prepared using O2 as the positive electrode and NaPF6 (solvent volume ratio EC:DEC:PC:propylene glycol polyoxypropylene ether = 1:2:1:0.05, concentration 1.3mol / L) as the electrolyte.

[0049] Test method: Charge and discharge voltage range 1~4.0V, temperature 25±3.0℃, charging at 1.0C and 3.0C, discharging at 1.0C, the test results are shown in Table 2.

[0050] Table 2 Rate performance of hard carbon composite materials

[0051]

[0052] As can be seen from Table 2, the rate charging performance of the pouch batteries in Examples 1 to 4 is significantly better than that of the comparative examples, that is, the charging time is shorter. The reason for this is that the materials in the examples have excellent diffusion coefficients and low La values, which improve the insertion and extraction rate of sodium ions and thus improve the rate performance.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hard carbon composite material, characterized in that, Includes the following steps: S1. Heat sodium chloride until it melts, add calcium carbide, metal oxides or sulfides and mix evenly, then introduce carbon dioxide to carry out the reaction and obtain hard carbon precursor material. S2. The hard carbon precursor material is transferred to a container, and after an inert gas is introduced, natural gas and bromide gas are introduced in sequence for modification to obtain a hard carbon composite material. The mass ratio of sodium chloride, calcium carbide, and metal oxides or sulfides in S1 is 1000:100:1~5. The metal in S1 includes one of Sn, Sb, Mo, and Ge; The bromine gas in S2 includes one of hydrogen bromide and bromomethane. The temperature for introducing bromine gas is 1000~1500℃, and the time is 1~6h.

2. The method for preparing a hard carbon composite material according to claim 1, characterized in that, The reaction temperature in S1 is 850~1000℃, and the reaction time is 6~24h.

3. The method for preparing a hard carbon composite material according to claim 1, characterized in that, The flow rate of carbon dioxide introduced into S1 is 100~1000 mL / min.

4. The method for preparing a hard carbon composite material according to claim 1, characterized in that, After the reaction in S1 is completed, the process also includes filtration, water washing, and acid washing.

5. The method for preparing a hard carbon composite material according to claim 1, characterized in that, The temperature of the natural gas introduced into S2 is 700~1000℃, and the time is 1~6h.

6. A hard carbon composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing a hard carbon composite material as described in any one of claims 1 to 5, or the application of the hard carbon composite material as described in claim 6 in a secondary battery.

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