A coal-based composite negative electrode material and its preparation method and application

Abstract

The present invention provides a coal-based composite negative electrode material and its preparation method and application. The method first uses high-temperature calcination in an air atmosphere to remove organic volatiles and a portion of low-melting-point inorganic impurities in anthracite, converting it into a porous coal-based negative electrode material with a high degree of graphitization, and then further purifying it to obtain a high-purity coal-based negative electrode material. Then, using vacuum and pressure impregnation technology, a slurry containing a silicon source and an organic carbon source is diffused into the pores of the high-purity coal-based negative electrode material, so that the silicon source is evenly distributed in the pores and optionally on the surface of the surface layer of the coal-based negative electrode material. The negative electrode material prepared by the method can retain the overall structural characteristics of anthracite, and fill the silicon source into the pores of the coal-based negative electrode material. The coal-based negative electrode material can effectively alleviate the volume expansion effect of the silicon source and provide a good conductive network, thereby improving the reversible capacity of the negative electrode material and significantly improving the cycle stability of the silicon-carbon negative electrode material used in lithium-ion batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery negative electrode materials, and specifically relates to a coal-based composite negative electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries offer a host of advantages, including high specific capacity, stable operating voltage, excellent safety, and no memory effect. Consequently, they are widely used in a wide range of portable electronic devices, including laptops, mobile phones, and instrumentation. With the rapid development of various electronic devices and electric vehicles, the demand for the energy density and cycle life of lithium-ion batteries is increasing. Anode materials are a crucial component of batteries. Together with cathode materials, they determine key performance characteristics such as cycle life, capacity, and safety, making them a key research focus worldwide.

[0003] Currently, commercial negative electrode materials are still mainly graphite-based, including natural graphite, petroleum coke, coal coke, asphalt carbon, etc. Natural graphite is a non-renewable resource. With the large-scale exploration and development of natural graphite mines in my country in recent years, some high-quality graphite mineral resources have gradually been depleted. Currently, artificial graphite is synthesized by high-temperature graphitization using high-quality petroleum coke or coal-based needle coke as raw materials. However, this technology route faces two major problems. First, the raw materials are uncontrollable. The high-quality petroleum coke and coal-based needle coke raw materials required by domestic synthetic graphite companies mostly need to be imported from the United States, Japan, South Korea, etc., and the import prices fluctuate greatly, and they are heavily dependent on petroleum resources. Second, it is energy-intensive. The temperature required for artificial graphite is as high as 2500-3000℃, and the electricity consumption during the production process is extremely high.

[0004] Anthracite is a plentiful and inexpensive resource, but currently most anthracite is burned directly, resulting in low added value. Even if existing technologies successfully graphitize anthracite to produce graphite, this is achieved at high temperatures (above 2500°C). Therefore, how to utilize anthracite to produce high-performance anode materials remains a pressing technical challenge in the lithium-ion battery field. Summary of the Invention

[0005] In order to improve the deficiencies of the prior art, the present invention provides a method for preparing a coal-based composite negative electrode material, the method comprising the following steps:

[0006] (1) calcining anthracite in an air atmosphere to obtain a coal-based negative electrode material;

[0007] (2) purifying the coal-based negative electrode material of step (1) to obtain a high-purity coal-based negative electrode material;

[0008] (3) mixing a silicon source, an organic carbon source, and a solvent to obtain a slurry;

[0009] (4) mixing the high-purity coal-based negative electrode material of step (2) and the slurry of step (3) and performing pressure impregnation;

[0010] (5) Carbonizing the impregnated material of step (4) to prepare the coal-based composite negative electrode material.

[0011] According to the present invention, in step (1), the mass content of fixed carbon in the anthracite is ≥90.0%.

[0012] According to the present invention, in step (1), the average particle size of the anthracite is 40 mm to 100 mm, for example, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm or 100 mm.

[0013] According to the present invention, in step (1), the calcination equipment is, for example, an electric furnace, the calcination temperature is 1800-2200° C., and the calcination time is 3-12 hours. Exemplarily, the calcination temperature is 1850° C., 1900° C., 1950° C., 2000° C., 2050° C., or 2150° C. The calcination time is 3 hours, 4 hours, 5 hours, 6 hours, 8 hours, 10 hours, or 12 hours.

[0014] According to the present invention, in step (1), during the calcination process, the volatile organic matter (including C and H) in the anthracite reacts with oxygen in the air atmosphere to produce gases (CO2, CO, H2O) and are removed. Simultaneously, a portion of low-melting-point inorganic impurities are also volatilized. Furthermore, after the calcination is completed, the resulting product is allowed to cool naturally to room temperature and then pulverized to obtain a coal-based negative electrode material.

[0015] According to the present invention, in step (1), the coal-based negative electrode material is a porous coal-based negative electrode material, and the average pore size of the coal-based negative electrode material is 0.9 μm-1.5 μm, for example, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm.

[0016] According to the present invention, in step (1), the median particle size of the coal-based negative electrode material is 12-25 μm, exemplified by 14 μm, 16 μm, 20 μm or 25 μm.

[0017] According to the present invention, in step (1), the graphitization degree of the coal-based negative electrode material is 88%-94%, for example, 88%, 89%, 90%, 91%, 92%, 93% or 94%.

[0018] According to the present invention, in step (2), the purification treatment is an acid method or an alkali method, preferably an acid method.

[0019] According to the present invention, the steps of purification treatment by acid method are as follows: adding the coal-based negative electrode material to a mixed acid solution of hydrofluoric acid and sulfuric acid (the mass ratio of hydrofluoric acid to sulfuric acid is 1-10:10-1), controlling the liquid-solid ratio at 3-5:1, adjusting the total acid concentration to a pH value of 3-4, stirring the reaction at room temperature for 2-5 hours, filtering, washing to neutrality, and obtaining a high-purity coal-based negative electrode material.

[0020] According to the present invention, in step (2), the mass content of fixed carbon in the high-purity coal-based negative electrode material is ≥99.0%.

[0021] According to the present invention, in step (2), the purification treatment can further remove high melting point impurities in the coal-based negative electrode material in step (1).

[0022] According to the present invention, in step (2), the average pore size of the high-purity coal-based negative electrode material is 0.9 μm-1.5 μm.

[0023] According to the present invention, in step (3), the mixing is to place the silicon source, the organic carbon source and the solvent in a planetary ball mill for ball milling mixing, the ball milling uses corundum balls as the ball milling medium, the ball-to-material ratio is 1:1, the ball milling speed is 100-500r / min, and the ball milling time is 6-12h.

[0024] According to the present invention, in step (3), the mass ratio of the silicon source, the organic carbon source and the solvent is 1:(0.05-0.15):(5-15), for example, 1:0.05:5, 1:0.05:10, 1:0.05:15, 1:0.1:5, 1:0.1:10, 1:0.1:15, 1:0.15:5, 1:0.15:10 or 1:0.15:15.

[0025] According to the present invention, in step (3), the organic carbon source is selected from at least one of asphalt, epoxy resin, and phenolic resin. The solvent is selected from at least one of ethanol, propanol, and acetone. The silicon source is selected from elemental silicon or silicon dioxide.

[0026] According to the present invention, in step (3), the particle size of the silicon source in the slurry is 50 nm to 1.0 μm, for example, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1.0 μm. Preferably, the particle size of the silicon source in the slurry is smaller than the average particle size of the coal-based negative electrode material to ensure that more silicon source can penetrate into the pores under pressurized impregnation conditions.

[0027] According to the present invention, in step (4), the pressure impregnation is, for example, placing the high-purity coal-based negative electrode material of step (2) into a reactor, evacuating the reactor, and then adding the slurry of step (3) for pressure impregnation.

[0028] The vacuuming time is 10 to 60 minutes, that is, the vacuum degree is maintained for 10 to 60 minutes.

[0029] Among them, the vacuum degree of the reactor is 0.07~0.09MPa.

[0030] Exemplarily, the pressure impregnation is as follows: the high-purity coal-based negative electrode material of step (2) is placed in a reactor, vacuumed, and then the slurry suction valve is opened to suck the slurry of step (3) into the reactor. After the liquid is added, the suction valve is closed and the vacuuming is stopped.

[0031] According to the present invention, in step (4), after the pressure impregnation is completed, filtration and drying are performed.

[0032] According to the present invention, in step (4), the pressure of the pressurized impregnation is 1 MPa to 3 MPa, and the time of the pressurized impregnation is 1 to 5 hours.

[0033] According to the present invention, in step (5), the carbonization temperature is 700-900°C, exemplified by 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, and 900°C. Furthermore, the carbonization time is 1-6 hours, for example, 2-5 hours, exemplified by 4 hours and 6 hours. The carbonization is carried out under the protection of an inert atmosphere, such as a nitrogen atmosphere or an argon atmosphere. Furthermore, after the carbonization is completed, the obtained product is naturally cooled to room temperature to obtain a coal-based composite negative electrode material.

[0034] The present invention also provides a coal-based composite negative electrode material prepared by the above method.

[0035] According to the present invention, the median particle size of the coal-based composite negative electrode material is 12.5-26 μm, exemplified by 14.5 μm, 16.8 μm or 20 μm.

[0036] According to the present invention, the graphitization degree of the coal-based composite negative electrode material is 88%-94%.

[0037] According to the present invention, the mass percentage of the silicon source in the coal-based composite negative electrode material is 3-12%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11% or 12%.

[0038] According to the present invention, the coal-based composite negative electrode material includes a coal-based material and amorphous carbon and a silicon source that permeate the pores of the coal-based material. The amorphous carbon is formed by carbonization of an organic carbon source, and the amorphous carbon firmly fixes the silicon source in the pores of the coal-based material.

[0039] According to the present invention, the amorphous carbon and silicon source penetrate into the pores of the surface layer of the coal-based material, forming a core-shell structure, wherein the core is the coal-based material that has not been penetrated by the amorphous carbon and silicon source, and the shell is the coal-based material that has been penetrated by the amorphous carbon and silicon source.

[0040] According to the present invention, the coal-based composite negative electrode material includes an outer shell layer, which includes amorphous carbon and a silicon source. The outer shell layer is coated on the surface of the coal-based material (preferably, coated on the outer surface of the outer shell layer). The amorphous carbon is formed by carbonization of an organic carbon source, and the amorphous carbon firmly fixes the silicon source on the surface of the coal-based material.

[0041] According to the present invention, the coal-based material is a coal-based material with a graphitized structure formed by calcining anthracite at 1800-2200° C. for 3-12 hours in an air atmosphere.

[0042] According to the present invention, the first charging capacity of the coal-based composite negative electrode material is ≥400 mAh / g, for example ≥449 mAh / g.

[0043] According to the present invention, the first charge and discharge efficiency of the coal-based composite negative electrode material is ≥88.0%.

[0044] According to the present invention, the capacity retention rate of the coal-based composite negative electrode material after 500 cycles of 0.2C charge and discharge at room temperature is above 90%.

[0045] The present invention also provides use of the above-mentioned coal-based composite negative electrode material in lithium-ion batteries, preferably as a negative electrode material for lithium-ion batteries.

[0046] Beneficial effects of the present invention:

[0047] The present invention provides a coal-based composite negative electrode material and its preparation method and application. The method first uses high-temperature calcination (1800-2200°C) in an air atmosphere to remove organic volatiles (including C and H) and a portion of low-melting-point inorganic impurities in anthracite, converting it into a porous coal-based negative electrode material with a high degree of graphitization, and then further purifying it to obtain a high-purity coal-based negative electrode material. Then, using vacuum and pressure impregnation technology, a slurry containing a silicon source and an organic carbon source is diffused into the pores of the high-purity coal-based negative electrode material, so that the silicon source is evenly distributed in the pores and optionally on the surface of the surface layer of the coal-based negative electrode material. The negative electrode material prepared by the method can retain the overall structural characteristics of anthracite and fill the silicon source into the pores of the coal-based negative electrode material. The coal-based negative electrode material can effectively alleviate the volume expansion effect of the silicon source and provide a good conductive network. Because the silicon source has a high theoretical specific capacity, introducing a small amount of silicon source into the coal-based negative electrode material can greatly improve the reversible capacity of the negative electrode material, significantly improving the cycle stability of the silicon-carbon negative electrode material used in lithium-ion batteries. By adjusting the silicon source content in the negative electrode material, the resulting finished product capacity can be adjusted between 400-800 mAh / g, with an initial coulombic efficiency of ≥88%. Furthermore, the method significantly increases the added value of anthracite, achieving rational resource utilization and possessing significant commercial value. DETAILED DESCRIPTION

[0048] The preparation method of the present invention will be described in further detail below with reference to specific examples. It should be understood that the following examples are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection intended by the present invention.

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0050] Example 1:

[0051] (1) Anthracite (fixed carbon content 90.0%) was crushed into particles with a particle size of 50 mm, and then calcined at 1850°C in an electric calciner (air atmosphere) for 6 hours. After naturally cooling to room temperature, the particles were pulverized to obtain a coal-based negative electrode material (particle size 14 μm). The coal-based negative electrode material was added to a mixed acid solution of hydrofluoric acid and sulfuric acid with a mass ratio of 10:4, the liquid-solid ratio was controlled at 3.5:1, the total acid concentration was adjusted to a pH of 3, and the mixture was stirred and reacted at room temperature for 5 hours. After filtering and washing until neutral, a high-purity coal-based negative electrode material (fixed carbon content 99.2%, average pore size 0.9 μm) was obtained.

[0052] (2) 100g of silicon powder, 8g of asphalt and 500g of ethanol were placed in a planetary ball mill and ball milled for 6 hours, wherein corundum balls were used as the ball milling medium, the ball-to-material ratio was 1:1, and the ball mill speed was 200r / min to obtain a slurry. The particle size of the silicon powder in the slurry was 50nm-300nm. The high-purity coal-based negative electrode material was placed in a reactor, vacuumed (vacuum degree was 0.07MPa), and the slurry suction valve was opened to suck the slurry into the reactor. After the liquid was added, the suction valve was closed and the vacuum was stopped. The slurry was pressurized and impregnated at 3MPa for 3 hours. After the pressurized impregnation was completed, it was filtered and dried. The dried coal-based negative electrode material was carbonized at 900℃ for 2 hours under nitrogen protection and cooled to room temperature to obtain a coal-based composite negative electrode material.

[0053] The coal-based composite negative electrode material includes a coal-based material and amorphous carbon and silicon powder infiltrated into the pores of the surface layer of the coal-based material, forming a core-shell structure. The core is a coal-based material that is not infiltrated by amorphous carbon and silicon powder, and the shell is a coal-based material infiltrated by amorphous carbon and silicon powder. The coal-based composite negative electrode material includes an outer shell layer, which includes amorphous carbon and silicon powder, and the outer shell layer is coated on the surface of the above-mentioned shell layer. The amorphous carbon is formed by carbonization of an organic carbon source, and the amorphous carbon firmly fixes the silicon powder in the pores of the coal-based material and on the surface of the coal-based material. The degree of graphitization of the coal-based composite negative electrode material is 88%, and the mass percentage of silicon in the coal-based composite negative electrode material is 5.6%.

[0054] Example 2:

[0055] (1) Anthracite (fixed carbon content 92.0%) was crushed into particles with a particle size of 80 mm, and then calcined at 2000°C in an electric calciner (air atmosphere) for 4 hours. After naturally cooling to room temperature, the particles were pulverized to obtain a coal-based negative electrode material (particle size 16 μm); the coal-based negative electrode material was added to a mixed acid solution of hydrofluoric acid and sulfuric acid with a mass ratio of 10:2, the liquid-solid ratio was controlled at 3.5:1, the total acid concentration was adjusted to a pH of 3, and the mixture was stirred and reacted at room temperature for 5 hours. After filtering and washing to neutrality, a high-purity coal-based negative electrode material (fixed carbon content 99.3%, average pore size 1.5 μm) was obtained.

[0056] (2) 100g of silicon oxide powder, 10g of asphalt and 1000g of ethanol were placed in a planetary ball mill and ball milled for 12 hours, wherein corundum balls were used as the ball milling medium, the ball-to-material ratio was 1:1, and the ball mill speed was 500r / min to obtain a slurry. The particle size of silicon oxide powder in the slurry was 500nm-1.0μm. The high-purity coal-based negative electrode material was placed in a reactor, vacuumed (vacuum degree was 0.09MPa), and the slurry suction valve was opened to suck the slurry into the reactor. After the liquid was added, the suction valve was closed and the vacuum was stopped. The slurry was pressurized and impregnated at 2MPa for 2 hours. After the pressurized impregnation was completed, it was filtered and dried. The dried coal-based negative electrode material was carbonized at 750℃ for 2 hours under nitrogen protection and cooled to room temperature to obtain a coal-based composite negative electrode material.

[0057] The coal-based composite negative electrode material includes a coal-based material and amorphous carbon and silicon dioxide powder that penetrate into the pores of the surface layer of the coal-based material, forming a core-shell structure. The core is a coal-based material that is not penetrated by amorphous carbon and silicon dioxide powder, and the shell is a coal-based material that is penetrated by amorphous carbon and silicon dioxide powder. The coal-based composite negative electrode material includes an outer shell layer, which includes amorphous carbon and silicon dioxide powder, and the outer shell layer is coated on the surface of the above-mentioned shell layer. The amorphous carbon is formed by carbonization of an organic carbon source, and the amorphous carbon firmly fixes the silicon dioxide powder in the pores of the coal-based material and on the surface of the coal-based material. The degree of graphitization of the coal-based composite negative electrode material is 91%, and the content of silicon dioxide in the coal-based composite negative electrode material is 12%.

[0058] Example 3:

[0059] (1) Anthracite (fixed carbon content of 94.0%) was crushed into particles with a particle size of 100 mm, and then calcined at 2200°C in an electric calciner (air atmosphere) for 5 hours. After naturally cooling to room temperature, the particles were pulverized to obtain a coal-based negative electrode material (particle size of 20 μm). The coal-based negative electrode material was added to a mixed acid solution of hydrofluoric acid and sulfuric acid with a mass ratio of 10:1, the liquid-solid ratio was controlled at 3.5:1, the total acid concentration was adjusted to a pH of 3, and the mixture was stirred and reacted at room temperature for 5 hours. The mixture was filtered and washed to neutrality to obtain a high-purity coal-based negative electrode material (fixed carbon content of 99.4%, average pore size of 1.2 μm).

[0060] (2) 100g of silicon powder, 12g of asphalt and 1200g of ethanol were placed in a planetary ball mill and ball milled for 8 hours, wherein corundum balls were used as the ball milling medium, the ball-to-material ratio was 1:1, and the ball mill speed was 400r / min to obtain a slurry. The particle size of the silicon powder in the slurry was 200nm-800nm. The high-purity coal-based negative electrode material was placed in a reactor, vacuumed (vacuum degree was 0.07MPa), and the slurry suction valve was opened to suck the slurry into the reactor. After the liquid was added, the suction valve was closed and the vacuum was stopped. The slurry was pressurized and impregnated at 1MPa for 3 hours. After the pressurized impregnation was completed, it was filtered and dried. The dried coal-based negative electrode material was carbonized at 850℃ for 4 hours under nitrogen protection and cooled to room temperature to obtain a coal-based composite negative electrode material.

[0061] The coal-based composite negative electrode material includes a coal-based material and amorphous carbon and silicon powder infiltrated into the pores of the surface layer of the coal-based material, forming a core-shell structure. The core is a coal-based material that is not infiltrated by amorphous carbon and silicon powder, and the shell is a coal-based material infiltrated by amorphous carbon and silicon powder. The coal-based composite negative electrode material includes an outer shell layer, which includes amorphous carbon and silicon powder, and the outer shell layer is coated on the surface of the above-mentioned shell layer. The amorphous carbon is formed by carbonization of an organic carbon source, and the amorphous carbon firmly fixes the silicon powder in the pores of the coal-based material and on the surface of the coal-based material. The graphitization degree of the coal-based composite negative electrode material is 94%, and the silicon content in the coal-based composite negative electrode material is 10.6%.

[0062] Comparative Example 1:

[0063] (1) Anthracite (fixed carbon content 94.0%) was crushed into particles with a particle size of 100 mm, and then graphitized at 2200°C in a graphitization furnace (nitrogen atmosphere) for 5 hours. After naturally cooling to room temperature, the particles were crushed to obtain a coal-based negative electrode material (particle size 20 μm). The coal-based negative electrode material was added to a mixed acid solution of hydrofluoric acid and sulfuric acid with a mass ratio of 10:1, the liquid-solid ratio was controlled at 3.5:1, the total acid concentration was adjusted to a pH of 3, and the mixture was stirred and reacted at room temperature for 5 hours. After filtering and washing until neutral, a high-purity coal-based negative electrode material (fixed carbon content 99.4%, average pore size 0.5 μm) was obtained.

[0064] (2) 100g of silicon powder, 8g of asphalt and 500g of ethanol were placed in a planetary ball mill and ball milled for 6 hours, wherein corundum balls were used as the ball milling medium, the ball-to-material ratio was 1:1, and the ball mill speed was 200r / min to obtain a slurry. The particle size of the silicon powder in the slurry was 200nm-400nm. The high-purity coal-based negative electrode material was placed in a reactor, vacuumed (vacuum degree was 0.07MPa), and the slurry suction valve was opened to suck the slurry into the reactor. After the liquid was added, the suction valve was closed and the vacuum was stopped. The pressure impregnation was carried out at 1MPa for 3 hours. After the pressure impregnation was completed, it was filtered and dried. The dried coal-based negative electrode material was carbonized at 850℃ for 4 hours under nitrogen protection and cooled to room temperature to obtain a coal-based composite negative electrode material.

[0065] The coal-based composite negative electrode material includes a coal-based material and a shell layer covering the outer surface of the coal-based material. The shell layer includes amorphous carbon and silicon powder. The amorphous carbon is formed by carbonization of an organic carbon source, and the amorphous carbon firmly fixes the silicon powder to the surface of the coal-based material.

[0066] The graphitization degree of the coal-based composite negative electrode material is 94%, and the silicon content in the coal-based composite negative electrode material is 0.5%.

[0067] Electrochemical performance test

[0068] Semi-electric test method: The negative electrode materials prepared in Examples 1-3 and Comparative Example 1 were mixed uniformly in a ratio of conductive carbon black (SP): carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) = 95:1:1.5:2.5 (mass ratio) and coated on copper foil. The coated electrode was placed in a vacuum drying oven at 120°C and dried for 12 hours. Simulated battery assembly was performed in an argon-protected Braun glove box. The electrolyte consisted of 1M LiPF6 + EC:DEC:DMC (volume ratio of 1:1:1). A metal lithium sheet served as the counter electrode. Simulated battery testing was performed in a 5V, 10mA Xinwei battery test cabinet with a charge and discharge voltage of 0.01-1.5V and a charge and discharge rate of 0.2C. The obtained initial discharge specific capacity, initial charge specific capacity, and initial charge and discharge efficiency were measured.

[0069] Full battery test method:

[0070] A full battery was assembled using the materials prepared in Examples 1-3 and Comparative Example 1 as the negative electrode, lithium cobalt oxide as the positive electrode, and 1M-LiPF6+EC:DEC:DMC (volume ratio 1:1:1) solution as the electrolyte. The battery was charged and discharged at room temperature at a rate of 0.2C and a voltage range of 3.0-4.2V. The capacity retention rate after 500 charge and discharge cycles was tested.

[0071] Table 1. Electrochemical performance test results

[0072]

[0073] The test results show that the coal-based composite negative electrode material prepared by the present invention as a negative electrode material for lithium-ion batteries has good comprehensive electrochemical properties, a specific capacity ≥449 mAh / g, an initial charge and discharge efficiency >88%, and a capacity retention rate ≥90% after 500 cycles; while the negative electrode material prepared by graphitizing anthracite has a low initial charge specific capacity and poor cycle performance.

[0074] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a coal-based composite negative electrode material, the method comprising the following steps: (1) calcining anthracite in an air atmosphere to obtain a coal-based negative electrode material; (2) purifying the coal-based negative electrode material of step (1) to obtain a high-purity coal-based negative electrode material; (3) mixing a silicon source, an organic carbon source, and a solvent to obtain a slurry; (4) mixing the high-purity coal-based negative electrode material of step (2) and the slurry of step (3) and performing pressure impregnation; (5) carbonizing the impregnated material of step (4) to prepare the coal-based composite negative electrode material; In step (1), the calcination temperature is 1800-2200°C; In step (1), the coal-based negative electrode material is a porous coal-based negative electrode material, and the average pore size of the coal-based negative electrode material is 0.9 μm-1.5 μm; In step (1), the median particle size of the coal-based negative electrode material is 12-25 μm; In step (3), the particle size of the silicon source in the slurry is 50 nm-1.0 μm; The coal-based composite negative electrode material comprises a coal-based material and amorphous carbon and a silicon source infiltrated into pores of the coal-based material.

2. The preparation method according to claim 1, wherein In step (1), the calcination treatment time is 3-12 hours; And / or, in step (1), the graphitization degree of the coal-based negative electrode material is 88%-94%.

3. The preparation method according to claim 1, wherein In step (2), the purification treatment is an acid method or an alkali method; the steps of using the acid method for purification are: adding the coal-based negative electrode material to a mixed acid solution of hydrofluoric acid and sulfuric acid, and controlling the liquid-solid ratio to 3 5:1, total acid concentration adjusted to pH 3 4. Stir the reaction at room temperature for 2 5 hours, filtering and washing to neutrality to obtain a high-purity coal-based negative electrode material; wherein the mass ratio of hydrofluoric acid to sulfuric acid is 1-10:10-1.

4. The preparation method according to claim 1, wherein In step (3), the mixing is to place the silicon source, the organic carbon source and the solvent in a planetary ball mill for ball milling, wherein the ball milling uses corundum balls as the ball milling medium, the ball-to-material ratio is 1:1, the ball milling speed is 100-500 r / min, and the ball milling time is 6-12h; And / or, in step (3), the mass ratio of the silicon source, the organic carbon source and the solvent is 1:(0.05-0.15):(5-15); And / or, in step (3), the organic carbon source is selected from at least one of asphalt, epoxy resin and phenolic resin; the solvent is selected from at least one of ethanol, propanol and acetone; and the silicon source is selected from elemental silicon or silicon monoxide.

5. The preparation method according to claim 1, wherein In step (4), the pressure impregnation is as follows: the high-purity coal-based negative electrode material of step (2) is placed in a reactor, vacuumed, and then the slurry of step (3) is added and pressure impregnation is performed; And / or, in step (4), the pressure of the pressurized impregnation is 1 MPa to 3 MPa, and the time of the pressurized impregnation is 1 to 5 hours.

6. The preparation method according to claim 1, wherein In step (5), the carbonization temperature is 700-900°C, and the carbonization time is 1-6 hours; And / or, the carbonization is carried out under the protection of an inert atmosphere.

7. A coal-based composite negative electrode material prepared by the method according to any one of claims 1 to 6.

8. The coal-based composite negative electrode material according to claim 7, wherein: The median particle size of the coal-based composite negative electrode material is 12.5-26 μm; And / or, the degree of graphitization of the coal-based composite negative electrode material is 88%-94%; And / or, the mass percentage of the silicon source in the coal-based composite negative electrode material is 3-12%.

9. The coal-based composite negative electrode material according to claim 7 or 8, wherein: The coal-based composite negative electrode material comprises a coal-based material and amorphous carbon and a silicon source infiltrated into pores of the coal-based material.

10. The coal-based composite negative electrode material according to claim 9, wherein: The amorphous carbon and silicon source penetrate into the pores of the surface layer of the coal-based material to form a core-shell structure; the core is the coal-based material not penetrated by the amorphous carbon and silicon source, and the shell is the coal-based material penetrated by the amorphous carbon and silicon source.

11. The coal-based composite negative electrode material according to claim 9, wherein: The coal-based composite negative electrode material comprises an outer shell layer, which comprises amorphous carbon and a silicon source, and the outer shell layer is coated on the surface of the coal-based material.

12. Use of the coal-based composite negative electrode material according to any one of claims 7 to 11 in lithium-ion batteries.

13. The use according to claim 12, wherein The coal-based composite negative electrode material is used as a negative electrode material for lithium-ion batteries.

Images