Method for preparing negative electrode material using super-pure carbon and apparatus therefor

Abstract

The present application relates to the technical field of negative electrode material preparation, and more particularly to a method for preparing negative electrode material by using ultra-pure carbon and an apparatus thereof.S1: crushing ultra-pure carbon and pitch powder;S2: mixing the ultra-pure carbon powder and alkali solution and electrolyzing;S3: pressure filtering the ultra-pure carbon slurry into filter cake;S4: drying the filter cake;S5: mixing the dried ultra-pure carbon powder and pitch powder, pyrolyzing in a low-temperature pyrolysis furnace, and then slowly heating and coating;S6: carbonizing the pyrolyzed material;S7: graphitizing the carbonized material;S8: collecting the graphitized material, and then sequentially performing batch mixing and iron removal processes, and finally packaging the product.The present application uses pressurized pyrolysis and coating processes, which strengthens the quality of coating and improves the specific capacity of the negative electrode material;the electrochemical oxidation is used to pre-oxidize the ultra-pure carbon, which can remove the irregular structure on the surface of the ultra-pure carbon particles and increase the nano-pore channels for lithium ion diffusion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode material preparation, and more particularly to a method for preparing negative electrode material using ultra-pure carbon and an apparatus thereof. BACKGROUND

[0002] There are also more aromatic and hydrogen aromatic functional groups in anthracite composition, which are composed of short aliphatic and ether bonds, in addition, anthracite itself also contains some metal impurities (Fe, Al, Mg, Ca, Si, etc.) and other compounds, which are helpful for its graphitization at high temperature.

[0003] The ultra-pure carbon comes from the by-product of coal slime in the coal washing process after anthracite mining, and the coal slime can be separated into ultra-pure carbon powder with a particle size of less than 20 microns after being treated by a flotation machine, a cyclone, a filter and other equipment, and after further processing, nanometer ultra-pure carbon with a carbon content of more than 97% and an ash content of 0.5% to 3.0% can be produced. The properties and various indicators of nanometer ultra-pure carbon can be comparable to the so-called "coal treasure" of Taixi coal in Ningxia.

[0004] Today, energy storage materials are essential for the operation and development of electric vehicles. Among various energy storage technologies, high-energy-density rechargeable lithium-ion batteries are considered as an effective method to solve the range anxiety of electric vehicles, however, due to the limitation of specific capacity of negative electrode materials, current lithium-ion batteries cannot meet the more demanding requirements of large capacity and long life. So far, many methods have been reported for developing new negative electrode materials such as alloy, silicon and metal oxide-based negative electrode materials. Among them, graphite is the most widely used negative electrode material for lithium-ion batteries. In general, there are two kinds of graphite materials widely used as negative electrode materials for lithium-ion batteries: natural graphite and synthetic graphite. Natural graphite has anisotropic structural characteristics, which limits the random transport and diffusion of lithium ions in the graphite structure during charging and discharging, resulting in poor rate capability. Artificial graphite has higher comprehensive performance than natural graphite, so most of the negative electrode materials in recent years are produced from artificial graphite. Artificial graphite is mainly made of petroleum coke and needle coke as raw materials, which has high cost. Ultra-pure carbon is a by-product of anthracite production, which cannot be sold as a power coal product, but can be applied to negative electrode materials, achieving the effect of waste utilization.

[0005] Chinese invention publication number CN10931757A, entitled "A method for preparing hollow open onion carbon lithium ion battery negative electrode material", uses coal material as raw material, mixes with nickel salt or nickel element as catalyst, heats to make nickel salt or nickel element uniformly distributed on the surface of coal-based material particles, forms open graphite onion carbon layer on the surface of the spherical particles after cooling, and finally obtains graphite onion carbon with hollow open spherical structure after purification by acid-base treatment. The reversible specific capacity of the coal-based negative electrode material is close to 400 mAh / g. The disadvantages of this process are that the coating process is not used, the specific capacity can be further improved by using soft carbon coating, and the acid-base method used in this process has a large amount of wastewater, which has a large environmental pressure.

[0006] Chinese invention publication number CN111774147A, entitled "Carbon negative electrode material precursor and preparation method thereof", the carbon negative electrode material precursor is obtained by heat treatment of a mixture of high-rank bituminous coal, coal-based binder, coal-based inert agent and additives, wherein the high-rank bituminous coal has an average reflectivity of vitrinite > 1.3%, the coal-based binder is at least one of coal tar high temperature pitch, coal tar medium temperature pitch, coal-based mesophase pitch, coal tar refined pitch and coal liquefaction residual oil pitch, the coal-based inert agent is at least one of anthracite, pitch coke and petroleum coke, and the additives include optional aluminum silicate, optional iron powder and silicon carbide. The ash content of the bituminous coal in this patent is about 8%, and the ash content of the graphitized product is high.

[0007] Chinese invention publication number CN111244453A, entitled "Preparation method of artificial composite graphite negative electrode material", the preparation method includes the following steps: carbonizing a block-shaped mixture containing anthracite powder, needle coke coke powder, graphitization catalyst and binder capable of graphitization, and then high-temperature catalytic graphitization to obtain a negative electrode material. The discharge capacity of the button cell made of the material is above 360 mAh / g. The disadvantages of the above patent are that the ash and volatile matter of anthracite cannot be separated, which affects the electrochemical performance of the coal-based graphite. SUMMARY

[0008] The present application aims to at least solve one of the technical problems existing in the prior art, and therefore, one aspect of the present application aims to provide a method for preparing a negative electrode material using ultra-pure carbon, the specific steps of the preparation method being as follows:

[0009] S2. Mix the crushed ultra-pure carbon powder in S1 with alkaline solution, add the mixed coal slurry to the anode chamber, and place it in the electrolytic cell. Sodium hydroxide solution is introduced into the cathode chamber of the electrolytic cell, and after placing the anode plate, electrolysis is carried out. Maintain the circulation of the coal slurry between the anode chamber and the coal slurry tank, and the circulation of the alkaline solution between the cathode chamber and the alkaline solution tank.

[0010] S3. The electrolysis of S2 is completed, and the ultra-pure carbon slurry is poured into a two-stage belt filter to produce an ultra-pure carbon filter cake;

[0011] S4. The ultra-pure carbon filter cake is dried in a drying machine, nitrogen is introduced into the drying machine for protection, and after drying, it is again added to a crushing and grading system to control the particle size;

[0012] S5. The ultra-pure carbon powder dried in S4 is mixed with pitch powder to obtain a mixture, which is added to a pyrolysis furnace, the pyrolysis furnace is evacuated to a vacuum state, low-temperature pyrolysis is performed, and then the pressure is increased, and after heating, it is coated;

[0013] S6. The material after pyrolysis in S5 is added to a pusher kiln for carbonization;

[0014] S7. The material after carbonization in S6 is loaded into a crucible of an Acheson graphitization furnace, and power is turned on to heat and graphitize;

[0015] S8. The material after graphitization in S7 is collected, and then subjected to batch mixing and iron removal processes and packaged as a finished product.

[0016] Preferably, the moisture content of the ultra-pure carbon in S1 is 5% to 20%, and the ash content is 0.5% to 3.0%

[0017] Preferably, the crushing time in S1 is 5 minutes to 10 minutes, the D90 particle size of the ultra-pure carbon powder is 20 μm to 40 μm, and the D90 particle size of the pitch powder is 20 μm to 40 μm.

[0018] Preferably, the slurry concentration after the ultra-pure carbon powder in S2 is added to the alkali solution is 20 g / L to 100 g / L; the concentration of the sodium hydroxide solution is 1% to 6%.

[0019] Preferably, the coal slurry electrochemical oxidation in S2 is performed by constant potential method, the electrolysis time is 0.5 hours to 1.5 hours, the current density is 3 A / cm 2 ~20A / cm 2 , the voltage is 1V to 5V, and the coal slurry flow rate is 1 m³ / h to 2 m³ / h.

[0020] Preferably, the drying time in S4 is 0.5 hours to 2 hours, the temperature is 120°C, the moisture content after drying is reduced to 1% to 5%, and the particle size is controlled to be 20 μm to 40 μm.

[0021] Preferably, the mass ratio of the ultra-pure carbon to the pitch powder in S5 is 80 to 90:10 to 20, which is added to a pyrolysis furnace, low-temperature pyrolysis is performed at 300°C to 500°C for 0.5 hours to 1 hour, the pressure is 2 kpa to 101 kpa; after pyrolysis, nitrogen is introduced as a protective gas, the pressure is increased to 1 Mpa to 2 Mpa, and slow heating is performed to 750°C to 950°C for 1 hour to 3 hours.

[0022] Preferably, the S6 is carbonized in the push plate kiln for 12-24 hours, and the carbonization temperature is 800-1000 DEG C.

[0023] Preferably, the S7 is graphitized by power heating to 2800-3000 DEG C, and the duration is 7-10 hours.

[0024] Another aspect of the present application aims to provide a device for preparing negative electrode material by using ultra-pure carbon, wherein the ultra-pure carbon is added into a mechanical pulverizer through a feeding tank I, and after being pulverized, the ultra-pure carbon powder is separated out from the ultra-pure carbon powder grading wheel into a cyclone separator I, and the ultra-pure carbon powder is collected into an ultra-pure carbon powder tank I, and other dust is collected by a bag dust collector I.

[0025] Meanwhile, the pitch is added into an air flow pulverizer through a feeding tank II, and after being pulverized, the pitch powder is separated out from the pitch grading wheel into a cyclone separator II, and the pitch powder is collected into a pitch tank, and other dust is collected by a bag dust collector II.

[0026] The ultra-pure carbon powder in the ultra-pure carbon powder tank I is mixed with an alkali solution and then put into an electrolytic cell for electrolysis.

[0027] The ultra-pure carbon powder after electrolysis is put into a two-stage belt filter press, and the ultra-pure carbon filter cake is produced, dried by a drying machine, and then classified by a pulverizing and classifying system, and the classified ultra-pure carbon powder is put into an ultra-pure carbon powder tank II.

[0028] The ultra-pure carbon powder in the ultra-pure carbon powder tank II and the pitch powder in the pitch tank are added into a mixing and stirring tank to obtain a mixture, and the mixture is added into a pyrolysis furnace for pyrolysis.

[0029] The material after pyrolysis is carbonized in a push plate kiln.

[0030] The material after carbonization is loaded into an Acheson graphitization furnace for graphitization.

[0031] The material after graphitization is collected, sequentially passed through a batch mixer, an iron remover and a packaging machine, and then packaged as a finished product.

[0032] The present application has the following beneficial effects:

[0033] The super-pure carbon used in the application has higher aromaticity, less oxygen-containing groups and side chain substituents than low-rank coal such as lignite and anthracite, and the oxygen-containing groups can be increased by activation in a certain way, and the structure of the oxygen-containing groups is beneficial to form a stable SEI and a dense passivation film to prevent the solvation reaction of electrolyte on graphite. In the application, a nickel plate is used as an anode, a graphite plate is used as a cathode, coal slurry is in the anode chamber, NaOH solution is in the cathode chamber, and the two chambers are separated by a diaphragm. The electrochemical oxidation of anthracite is carried out under a certain voltage and current. The application can open the aromatic structure and form oxygen-containing groups from the microstructure of anthracite.

[0034] The super-pure carbon is a kind of particle produced in the anthracite coal preparation process, has low ash content and low particle size, and can be oxidized and etched on the surface of the coal particle by liquid phase electrochemical oxidation to generate more micropores and nanochannels. After drying and graphitization, a negative electrode material with high specific capacity is produced.

[0035] The application uses super-pure carbon, a byproduct of anthracite production, as a raw material, greatly reducing the cost of the negative electrode material, and finding a route for the diversified utilization of anthracite in the future. The use of pressurized pyrolysis and coating process strengthens the quality of coating and improves the specific capacity of the negative electrode material. The use of electrochemical oxidation for pre-oxidation treatment of super-pure carbon can remove the irregular structure on the surface of the super-pure carbon particles and increase the lithium ion diffusion channels.

[0036] Additional aspects and advantages of the application will become apparent from the following description, or will be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0037] The above and / or additional aspects and advantages of the application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0038] Figure 1 is a production process flowchart of an embodiment of the application;

[0039] Figure 2 is a production process flowchart of a comparative example of the application;

[0040] Figure 3 is an XRD graph of the super-pure carbon raw material of the embodiment of the application;

[0041] Figure 4 is a SEM graph of the product of the third embodiment of the application;

[0042] Figure 5 is a SEM graph of the product of the fourth embodiment of the application;

[0043] Figure 6is a charge-discharge curve comparison chart of the present application comparative example 1, example 3 and example 4;

[0044] Wherein, 1 is a mechanical crusher; 2 is an air flow crusher; 3 is an ultra-pure carbon powder grading wheel; 4 is an asphalt grading wheel; 5-1 is a cyclone separator I; 5-2 is a cyclone separator II; 6-1 is a bag dust collector I; 6-2 is a bag dust collector II; 7 is an ultra-pure carbon powder tank; 7-1 is an ultra-pure carbon powder tank I; 7-2 is an ultra-pure carbon powder tank II; 8 is an asphalt tank; 9 is a mixing and stirring tank; 10 is a pyrolysis furnace; 11 is a push plate kiln; 12 is an Acheson graphitization furnace; 13 is an electrolytic cell; 14 is a belt filter press; 15 is a dryer; 16-1 is a feeding tank I; 16-2 is a feeding tank II; 17 is a batch mixer; 18 is a de-ironing device; 19 is a packaging machine. DETAILED DESCRIPTION

[0045] In order to enable persons skilled in the art to more clearly understand the above-mentioned objects, features and advantages of the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0046] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, however, the present application can also be implemented in other ways different from the description, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0047] As Figure 1 The production process flow chart of the embodiment of the present application is shown

[0048] Example 1

[0049] S1. 200 kg of ultra-pure carbon with moisture content of 14% and ash content of 1.9% is added to the mechanical crusher 1 through the feeding tank I 16-1, after crushing for 5 min, the ultra-pure carbon powder is separated out by the ultra-pure carbon powder grading wheel 3 into the cyclone separator I 5-1, the ultra-pure carbon powder enters the ultra-pure carbon powder tank I 7-1, and other dust is collected by the bag dust collector I 6-1, the D90 particle size range of the ultra-pure carbon powder is 20-40 μm; at the same time, 30 kg of asphalt with softening point of 220-270 ℃ is added to the air flow crusher 2 through the feeding tank II 16-2, after crushing, the asphalt powder is separated out by the asphalt grading wheel 4 into the cyclone separator II 5-2, the asphalt powder enters the asphalt tank 8, and other dust is collected by the bag dust collector II 6-2, the D90 particle size range of the asphalt powder is 20-40 μm;

[0050] S2. Add 150 kg of the pulverized ultra-pure carbon powder in S1 to the coal slurry tank containing 4% alkali solution, mix uniformly, and then add the mixture into the anode chamber of the electrolytic tank 13 in batches after forming a 50 g / L coal slurry. A 4% sodium hydroxide solution is introduced into the cathode chamber of the electrolytic tank, and the anode chamber and the cathode chamber are separated by a diaphragm. The electrolysis is carried out at a voltage of 1.5 V for 0.5 hours, and the flow rate of the coal slurry in the anode chamber is maintained at 1 m³ / h;

[0051] S3. The ultra-pure carbon slurry after electrolysis in S2 is added into the two-stage belt filter press 14, and the filtrate and washing liquid are discharged to produce the ultra-pure carbon filter cake;

[0052] S4. The ultra-pure carbon filter cake is dried in the drying machine 15 for 1-2 hours at a temperature of 120°C, and the moisture content is reduced to below 5%. Then, the ultra-pure carbon powder is placed in the ultra-pure carbon powder tank II 7-2;

[0053] S5. 150 kg of the ultra-pure carbon powder in the ultra-pure carbon powder tank II 7-2 after drying in S4 and 16.6 kg of pitch powder in the pitch tank 8 are added into the mixing and stirring tank 9 to obtain a mixture. The mixture is added into the pyrolysis furnace 10, which is vacuumed, heated to 300°C, and subjected to low-temperature pyrolysis for 1 hour. After the pyrolysis, nitrogen is filled as a protective gas, and the pressure is controlled at 2 kpa. The pressure is increased to 2 Mpa, and then the temperature is slowly increased to 500°C for 2 hours;

[0054] S6. The material after pyrolysis in S5 is added into the push plate kiln 11 and carbonized for 12 hours at a carbonization temperature of 1000°C;

[0055] S7. The material after carbonization in S6 is loaded into the crucible of the Acheson graphitization furnace 12, and the temperature is increased to 2800°C for graphitization for 7 hours;

[0056] S8. The material after graphitization in S7 is collected, and then sequentially passes through the batch mixer 17, the iron remover 18, and the packaging machine 19 to be packaged as a finished product.

[0057] Example Two

[0058] S1. Put 200 kg of ultra-pure carbon with moisture content of 14% and ash content of 1.9% into mechanical crusher 1 through feeding tank I 16-1, crush for 5 minutes, and then pass through ultra-pure carbon powder grading wheel 3 into cyclone separator I 5-1 to separate out ultra-pure carbon powder, and the ultra-pure carbon powder enters ultra-pure carbon powder tank I 7-1, and other dust is collected by bag dust collector I 6-1, and the D90 particle size of the ultra-pure carbon powder is in the range of 20 μm~40 μm; at the same time, 50 kg of pitch with softening point of 220℃~270℃ is added into jet mill 2 through feeding tank II 16-2, crushed, and then passed through pitch grading wheel 4 into cyclone separator II 5-2 to separate out pitch powder, and the pitch powder enters pitch tank 8, and other dust is collected by bag dust collector II 6-2, and the D90 particle size of the pitch powder is in the range of 20 μm~40 μm;

[0059] S2. Put 150 kg of crushed ultra-pure carbon powder in S1 into a coal slurry tank with 4% alkali solution, stir uniformly, mix into a coal slurry with a concentration of 50 g / L, and then batch into the anode chamber of electrolytic cell 13, a 4% sodium hydroxide solution is introduced into the cathode chamber, the anode chamber and the cathode chamber are separated by a diaphragm, electrolysis is carried out by power supply, the electrolysis time is 0.5 hours, the voltage is 1.5V, and the flow rate of the coal slurry in the anode chamber is maintained at 2 m³ / h;

[0060] S3. The ultra-pure carbon slurry after electrolysis in S2 is punched into two-stage belt filter press 14, and the filtrate and washing liquid are discharged to produce ultra-pure carbon filter cake;

[0061] S4. The ultra-pure carbon filter cake is dried by dryer 15, the drying time is 1~2 hours, the temperature is 120℃, and after drying, the moisture content is reduced to below 5%, and then the ultra-pure carbon powder is put into ultra-pure carbon powder tank II 7-2;

[0062] S5. Put 119.0 kg of ultra-pure carbon powder in ultra-pure carbon powder tank II 7-2 after drying in S4 and 13.2 kg of pitch powder in pitch tank 8 into mixing and stirring tank 9 to mix and obtain a mixture, put it into pyrolysis furnace 10, vacuumize the pyrolysis furnace 10, heat to 300℃ for low-temperature pyrolysis for 1 hour, after completion, fill in nitrogen as protective gas, and control the pressure at 2 kpa; adjust the pressure to 2Mpa, and slowly heat to 500℃ for 2 hours;

[0063] S6. Put the material after pyrolysis in S5 into push plate kiln 11 for carbonization for 12 hours, and the carbonization temperature is 1000℃;

[0064] S7. Put the material after carbonization in S6 into the crucible of Acheson graphitization furnace 12, heat to 2800℃ by power supply for graphitization for 7 hours;

[0065] S8. Collect the material after graphitization in S7, and then pass through batch mixer 17, iron remover 18 and packaging machine 19 in sequence to package into finished products.

[0066] Example Three

[0067] S1. 200 kg of ultra-pure carbon with moisture content of 14% and ash content of 1.9% is added to a mechanical crusher 1 through a feeding tank I 16-1, after being crushed for 5 minutes, the ultra-pure carbon powder is separated out by a cyclone separator I 5-1 through an ultra-pure carbon powder grading wheel 3, the ultra-pure carbon powder enters an ultra-pure carbon powder tank I 7-1, and other dust is collected by a bag dust collector I 6-1, the D90 particle size of the ultra-pure carbon powder is in the range of 20 μm to 40 μm; at the same time, 50 kg of pitch with a softening point of 220 ℃ to 270 ℃ is added to an air flow crusher 2 through a feeding tank II 16-2, after being crushed, the pitch powder is separated out by a cyclone separator II 5-2 through a pitch grading wheel 4, the pitch powder enters a pitch tank 8, and other dust is collected by a bag dust collector II 6-2, the D90 particle size of the pitch powder is in the range of 20 μm to 40 μm;

[0068] S2. 150 kg of the crushed ultra-pure carbon powder in S1 is added to a coal slurry tank containing 4% alkali solution, after being stirred uniformly, a 50 g / L coal slurry is formed and then is punched into an electrolytic tank 13 anode chamber in batches, a 4% sodium hydroxide solution is introduced into the cathode chamber, the anode chamber and the cathode chamber are separated by a diaphragm, electrolysis is carried out by power supply, the electrolysis time is 0.5 hours, the voltage is 2 V, and the flow rate of the coal slurry in the anode chamber is maintained at 2 m³ / h;

[0069] S3. The ultra-pure carbon slurry after electrolysis in S2 is punched into a two-stage belt filter press 14, the filtrate and washing liquid are discharged, and the ultra-pure carbon filter cake is produced;

[0070] S4. The ultra-pure carbon filter cake is dried by a dryer 15, the drying time is 1 to 2 hours, the temperature is 120 ℃, after drying, the moisture content is reduced to below 5%, and then the ultra-pure carbon powder is placed in an ultra-pure carbon powder tank II 7-2;

[0071] S5. 119.0 kg of the ultra-pure carbon powder in the ultra-pure carbon powder tank II 7-2 after drying in S4 and 13.2 kg of the pitch powder in the pitch tank 8 are added to a mixing and stirring tank 9 to obtain a mixture, the mixture is added to a pyrolysis furnace 10, the pyrolysis furnace 10 is vacuumized, heated to 300 ℃, and low-temperature pyrolysis is carried out for 1 hour, after the end, nitrogen is filled as a protective gas, and the pressure is controlled at 2 kpa; the pressure is increased to 2 Mpa, and then slowly heated to 500 ℃ for 2 hours;

[0072] S6. The material after pyrolysis in S5 is added to a push plate kiln 11 for carbonization for 12 hours, and the carbonization temperature is 1000 ℃;

[0073] S7. The material after carbonization in S6 is loaded into a crucible of an Acheson graphitization furnace 12, power is supplied to heat to 2800 ℃ for graphitization for 7 hours;

[0074] S8. After collecting the graphitized material of S7, the material is sequentially passed through a batch mixer 17, an iron remover 18, and a packaging machine 19 to be packaged as a finished product.

[0075] Example Four

[0076] S1. 200 kg of ultra-pure carbon with a moisture content of 14% and an ash content of 1.9% is added to a mechanical crusher 1 through a feeding tank I 16-1, crushed for 5 minutes, and then passed through an ultra-pure carbon powder grading wheel 3 into a cyclone separator I 5-1 to separate out ultra-pure carbon powder. The ultra-pure carbon powder is collected in an ultra-pure carbon powder tank I 7-1, and other dust is collected by a bag dust collector I 6-1. The D90 particle size of the ultra-pure carbon powder is in the range of 20 μm to 40 μm. At the same time, 50 kg of pitch with a softening point of 220°C to 270°C is added to an air flow crusher 2 through a feeding tank II 16-2, crushed, and then passed through a pitch grading wheel 4 into a cyclone separator II 5-2 to separate out pitch powder. The pitch powder is collected in a pitch tank 8, and other dust is collected by a bag dust collector II 6-2. The D90 particle size of the pitch powder is in the range of 20 μm to 40 μm.

[0077] S2. 150 kg of the crushed ultra-pure carbon powder in S1 is added to a coal slurry tank containing 4% alkali solution, stirred uniformly, mixed into a coal slurry with a concentration of 50 g / L, and then punched into an anode chamber of an electrolytic tank 13 in batches. A 4% sodium hydroxide solution is introduced into a cathode chamber of the electrolytic tank. The anode chamber and the cathode chamber are separated by a diaphragm. The electrolysis is carried out by applying electricity. The electrolysis time is 0.5 hours, the voltage is 3.5 V, and the flow rate of the coal slurry in the anode chamber is maintained at 2 m³ / h.

[0078] S3. The ultra-pure carbon slurry after electrolysis in S2 is punched into a two-stage belt filter press 14, and filtrate and washing liquid are discharged to produce ultra-pure carbon filter cake.

[0079] S4. The ultra-pure carbon filter cake is dried by a drying machine 15 for 1 to 2 hours at a temperature of 120°C. The moisture content of the ultra-pure carbon powder after drying is reduced to below 5%. The ultra-pure carbon powder is then placed in an ultra-pure carbon powder tank II 7-2.

[0080] S5. 119.0 kg of the dried ultra-pure carbon powder in the ultra-pure carbon powder tank II 7-2 in S4 and 13.2 kg of pitch powder in the pitch tank 8 are added to a mixing and stirring tank 9 to obtain a mixture. The mixture is added to a pyrolysis furnace 10. The pyrolysis furnace 10 is vacuumed, heated to 300°C, and subjected to low-temperature pyrolysis for 1 hour. After the pyrolysis, nitrogen is filled as a protective gas, and the pressure is controlled at 2 kpa. The pressure is increased to 2 Mpa, and then slowly heated to 500°C for 2 hours.

[0081] S6. The pyrolyzed material in S5 is added to a push plate kiln 11 for carbonization for 12 hours at a carbonization temperature of 1000°C.

[0082] S7. The material after carbonization in S6 is loaded into the crucible of the Acheson graphitization furnace 12, and the temperature is raised to 2800℃ for graphitization for 7 hours;

[0083] S8. After the material in S7 is collected, it is sequentially passed through the batch mixer 17, the iron remover 18, and the packaging machine 19 to be packaged as a finished product.

[0084] Example Five

[0085] S1. 200 kg of ultra-pure carbon with a moisture content of 14% and an ash content of 1.9% is added to the mechanical pulverizer 1 through the feeding tank I 16-1, and after being pulverized for 5 minutes, the ultra-pure carbon powder is separated out by the ultra-pure carbon powder grading wheel 3 into the cyclone separator I 5-1. The ultra-pure carbon powder is collected in the ultra-pure carbon powder tank I 7-1, and the dust is collected by the bag dust collector I 6-1. The D90 particle size of the ultra-pure carbon powder is in the range of 20 μm to 40 μm. At the same time, 50 kg of pitch with a softening point of 220℃ to 270℃ is added to the jet mill 2 through the feeding tank II 16-2, and after being pulverized, the pitch powder is separated out by the pitch grading wheel 4 into the cyclone separator II 5-2. The pitch powder is collected in the pitch tank 8, and the dust is collected by the bag dust collector II 6-2. The D90 particle size of the pitch powder is in the range of 20 μm to 40 μm;

[0086] S2. 150 kg of the pulverized ultra-pure carbon powder in S1 is added to the coal slurry tank containing 4% alkali solution, and after being stirred uniformly, it is mixed into a coal slurry with a concentration of 50 g / L, and then it is punched into the anode chamber of the electrolytic tank 13 in batches. A 4% sodium hydroxide solution is introduced into the cathode chamber of the electrolytic tank. The anode chamber and the cathode chamber are separated by a diaphragm. The electrolysis is carried out by applying a voltage of 1.5 V for 2 hours, and the flow rate of the coal slurry in the anode chamber is maintained at 2 m³ / h.

[0087] S3. The ultra-pure carbon slurry after electrolysis in S2 is punched into the two-stage belt filter press 14, and the filtrate and washing liquid are discharged to produce ultra-pure carbon filter cake;

[0088] S4. The ultra-pure carbon filter cake is dried by the dryer 15 for 1 to 2 hours at a temperature of 120℃, and the moisture content is reduced to below 5%. Then, the ultra-pure carbon powder is placed in the ultra-pure carbon powder tank II 7-2.

[0089] S5. 119.0 kg of the ultra-pure carbon powder in the ultra-pure carbon powder tank II 7-2 after drying in S4 and 13.2 kg of the pitch powder in the pitch tank 8 are added to the mixing and stirring tank 9 to obtain a mixture. The mixture is added to the pyrolysis furnace 10, which is vacuumed, heated to 300℃, and subjected to low-temperature pyrolysis for 1 hour. After the pyrolysis is completed, nitrogen is filled as a protective gas, and the pressure is controlled at 2 kpa. The pressure is increased to 2 Mpa, and then the temperature is slowly increased to 500℃ for 2 hours.

[0090] S6. The material after pyrolysis in S5 is added into the push plate kiln 11 for carbonization for 12 hours at a carbonization temperature of 1000℃;

[0091] S7. The material after carbonization in S6 is loaded into the crucible of the Acheson graphitization furnace 12, and is heated to 2800℃ for graphitization for 7 hours;

[0092] S8. The material after graphitization in S7 is collected, and is sequentially passed through the batch mixer 17, the iron remover 18 and the packaging machine 19 to be packaged into a finished product.

[0093] As shown in Figure 2 the production process flowchart of the comparative example of the present application

[0094] Comparative Example 1

[0095] S1. 200kg of ultra-pure carbon with moisture content of 14% and ash content of 1.9% is added into the mechanical pulverizer 1 through the feeding tank I 16-1, and is pulverized for 5min, and then is passed through the ultra-pure carbon powder grading wheel 3 into the cyclone separator I 5-1 to separate out the ultra-pure carbon powder, and the ultra-pure carbon powder is passed into the ultra-pure carbon powder tank 7 and other dust is collected by the bag dust collector I 6-1, and the D90 particle size range of the ultra-pure carbon powder is 20μm~40μm; at the same time, 50kg of pitch with softening point of 220℃~270℃ is added into the jet pulverizer 2 through the feeding tank II 16-2, and is pulverized, and then is passed through the pitch grading wheel 4 into the cyclone separator II 5-2 to separate out the pitch powder, and the pitch powder is passed into the pitch tank 8 and other dust is collected by the bag dust collector II 6-2, and the D90 particle size range of the pitch powder is 20μm~40μm;

[0096] S2. 150kg of the ultra-pure carbon powder in the ultra-pure carbon powder tank 7 and 16.6kg of the pitch powder in the pitch tank 8 in S1 are added into the mixing and stirring tank 9 to obtain a mixture, and are added into the pyrolysis furnace 10, and under the condition of slow stirring, the pyrolysis furnace 10 is vacuumized, is heated to 300℃ for low-temperature pyrolysis for 1 hour, and after the end, nitrogen is filled in as a protective gas, is pressurized to 2Mpa, and is heated to 500℃ for coating for 2 hours;

[0097] S3. The material after pyrolysis in S2 is added into the push plate kiln 11 for carbonization for 12 hours at a carbonization temperature of 1000℃;

[0098] S4. The material after carbonization in S3 is loaded into the crucible of the Acheson graphitization furnace 12, and is heated to 3100℃ for graphitization for 7 hours;

[0099] S5. The material after graphitization in S4 is collected, and is sequentially passed through the batch mixer 17, the iron remover 18 and the packaging machine 19 to be packaged into a finished product.

[0100] Comparative Example 2

[0101] S1. 200 kg of ultra-pure carbon containing 14% moisture and 1.9% ash is added to a mechanical crusher 1 through a feeding tank I 16-1, and after being crushed for 5 minutes, the ultra-pure carbon powder is separated out by a cyclone separator I 5-1 through an ultra-pure carbon powder grading wheel 3, and the ultra-pure carbon powder is collected in an ultra-pure carbon powder tank I 7-1, while other dust is collected by a bag dust collector I 6-1, and the D90 particle size of the ultra-pure carbon powder is in the range of 20-40 μm; at the same time, 50 kg of pitch with a softening point of 220-270℃ is added to an air flow crusher 2 through a feeding tank II 16-2, and after being crushed, the pitch powder is separated out by a cyclone separator II 5-2 through a pitch grading wheel 4, and the pitch powder is collected in a pitch tank 8, while other dust is collected by a bag dust collector II 6-2, and the D90 particle size of the pitch powder is in the range of 20-40 μm;

[0102] S2. 150 kg of the crushed ultra-pure carbon powder in S1 is added to a coal slurry tank containing 4% alkali solution, and after being stirred uniformly, a coal slurry with a concentration of 50 g / L is prepared and then is punched into an anode chamber of an electrolytic tank 13 in batches, a 4% sodium hydroxide solution is introduced into a cathode chamber of the electrolytic tank, the anode chamber and the cathode chamber are separated by a diaphragm, and electrolysis is carried out by power supply, the electrolysis time is 0.5 hours, the voltage is 2.5 V, and the flow rate of the coal slurry in the anode chamber is maintained at 2 m³ / h;

[0103] S3. The ultra-pure carbon slurry after electrolysis in S2 is punched into a two-stage belt filter press 14, and filtrate and washing liquid are discharged, and an ultra-pure carbon filter cake is produced;

[0104] S4. The ultra-pure carbon filter cake is dried by a dryer 15, the drying time is 1-2 hours, the temperature is 120℃, and after drying, the moisture content is reduced to below 5%, and then the ultra-pure carbon powder is placed in an ultra-pure carbon powder tank II 7-2;

[0105] S5. 119.0 kg of the ultra-pure carbon powder in the ultra-pure carbon powder tank II 7-2 after drying in S4 and 13.2 kg of the pitch powder in the pitch tank 8 are added to a mixing and stirring tank 9 to obtain a mixture, and the mixture is added to a pyrolysis furnace 10, the pyrolysis furnace 10 is vacuumized, and is heated to 500℃ for coating for 3 hours;

[0106] S6. The material after pyrolysis in S5 is added to a push plate kiln 11 for carbonization for 12 hours, and the carbonization temperature is 1000℃;

[0107] S7. The material after carbonization in S6 is loaded into a crucible of an Acheson graphitization furnace 12, and is heated to 2800℃ for graphitization for 7 hours by power supply;

[0108] S8. The material after graphitization in S7 is collected, and is sequentially subjected to batch mixing by a batch mixer 17, iron removal by an iron remover 18, and packaging by a packaging machine 19 to obtain a finished product.

[0109] The products of example one to example five and comparative example one and comparative example two are sampled for experiments, and the experimental results are shown in Table 1 as follows:

[0110] Table 1. Experimental results

[0111] As can be seen from Table 1, compared with comparative example one, examples one to five use electrochemical oxidation to open aromatic groups of the lower coal in the microcosmic level, and eliminate part of aliphatic hydrocarbon structure or other defects, and manufacture a certain amount of pore structure on the surface of the coal particles, which can provide sufficient active sites for lithium ion in and out of the negative electrode material, indicating that the electrochemical performance of the ultra-pure carbon can be enhanced by electrochemical oxidation treatment.

[0112] The data comparison of example one and comparative example one shows that the electrochemical oxidation of the ultra-pure carbon before being coated with pitch can improve the specific capacity of the negative electrode material made of the ultra-pure carbon.

[0113] The data of example two to example four shows that the voltage of the electrolytic cell needs to be in a certain range to ensure that the specific capacity of the negative electrode material is above 340 mAh / g, and increasing the voltage has a side effect on improving the specific capacity of the negative electrode material, and the specific capacity of the ultra-pure negative electrode material obtained in example three is the highest.

[0114] The comparison of example two and comparative example two shows that the pressurized pyrolysis has a certain influence on the specific capacity data, and the pressurized pyrolysis makes the pyrolysis gas with a large internal pressure, and the porosity of the ultra-pure carbon particles is increased in the release process of the pyrolysis gas.

[0115] Example five prolongs the electrolysis time, and the data shows that the prolongation of the electrolysis time has a great influence on the specific capacity, and the electrolysis time should be in a certain range.

[0116] The XRD graph of the ultra-pure carbon used in the examples of the present application is shown in Figure 3 The SEM graphs of the products of example three and example four are shown in Figure 4 and Figure 5 The comparison graph of the 5th charge-discharge curve of comparative example one, example three and example four is shown in Figure 6 .

[0117] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and the present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a negative electrode material using ultra-pure carbon, characterized by: The specific steps of the preparation method are as follows: S1. Add ultra-pure carbon into a pulverizer, and separate the ultra-pure carbon powder from the pulverized ultra-pure carbon through a cyclone separator; meanwhile, pulverize and classify the pitch to obtain pitch powder; S2. Mix the ultra-pure carbon powder pulverized in S1 with an alkali solution, and add the mixed coal slurry into an anode chamber, and then place the coal slurry into an electrolytic cell, and introduce sodium hydroxide solution into a cathode chamber of the electrolytic cell, and place an anode plate, and then electrolyze, and keep the coal slurry circulation between the anode chamber and the coal slurry tank and the alkali solution circulation between the cathode chamber and the alkali solution tank; S3. Punch the ultra-pure carbon slurry electrolyzed in S2 into a two-stage belt filter, and obtain ultra-pure carbon filter cake; S4. Dry the ultra-pure carbon filter cake through a drying machine, introduce nitrogen into the drying machine for protection, and then add the ultra-pure carbon filter cake into a pulverizing and classifying system again to control the particle size; S5. Mix the ultra-pure carbon powder dried in S4 with the pitch powder to obtain a mixture, and then add the mixture into a pyrolysis furnace, and then perform low-temperature pyrolysis on the mixture in a vacuum state, and then increase the pressure, and then coat the mixture after heating; S6. Add the material pyrolyzed in S5 into a push plate kiln for carbonization; S7. Place the material carbonized in S6 into a crucible of an Acheson graphitization furnace, and then perform graphitization on the material after heating by electricity; S8. Collect the material graphitized in S7, and then sequentially perform batching and iron removal processes on the material, and then package the material as a finished product.

2. The method for preparing a negative electrode material using ultra-pure carbon according to claim 1, characterized in that: The moisture content of the ultra-pure carbon in S1 is 5% to 20%, and the ash content is 0.5% to 3.0%.

3. The method for preparing a negative electrode material using ultra-pure carbon according to claim 1, characterized in that: The pulverizing time in S1 is 5 minutes to 10 minutes, the D90 particle size of the ultra-pure carbon powder is 20 μm to 40 μm, and the D90 particle size of the pitch powder is 20 μm to 40 μm.

4. The method for preparing a negative electrode material using ultra-pure carbon according to claim 1, characterized in that: The concentration of the slurry after the ultra-pure carbon powder in S2 is added into the alkali solution is 20 g / L to 100 g / L, and the concentration of the sodium hydroxide solution is 1% to 6%.

5. The method for preparing a negative electrode material using ultra-pure carbon according to claim 1, characterized in that: The coal slurry electrochemical oxidation in the S2 is carried out by using the constant potential method, the electrolysis time is 0.5-1.5 hours, the current density is 3-20 A / cm 2 , the voltage is 1-5 V, and the flow rate of the coal slurry is 1-2 m³ / h. 2 , the voltage is 1-5 V, and the flow rate of the coal slurry is 1-2 m³ / h.

6. The method for preparing a negative electrode material using ultra-pure carbon according to claim 1, characterized in that: The drying time in S4 is 0.5 hours to 2 hours, the temperature is 120°C, the moisture content after drying is reduced to 1% to 5%, and the particle size is controlled to be 20 μm to 40 μm.

7. The method for preparing a negative electrode material using super-pure carbon according to claim 1, characterized in that: The mass ratio of the ultra-pure carbon to the pitch powder in S5 is 80 to 90:10 to 20, the mixture is added into a pyrolysis furnace, low-temperature pyrolysis is performed on the mixture at 300°C to 500°C for 0.5 hours to 1 hour, the pressure is 2 kPa to 101 kPa, nitrogen is introduced as a protective gas after pyrolysis, the pressure is increased to 1 MPa to 2 MPa, and the mixture is slowly heated to 750°C to 950°C for coating for 1 hour to 3 hours. 8.The method for preparing a negative electrode material using ultra-pure carbon according to claim 1, characterized in that: The carbonization time in S6 is 12 hours to 24 hours in the push plate kiln, and the carbonization temperature is 800°C to 1000°C. 9.The method for preparing a negative electrode material using ultra-pure carbon according to claim 1, characterized in that: The temperature is increased to 2800°C to 3000°C for graphitization in S7 by electricity, and the duration is 7 hours to 10 hours.

10. A device for preparing an anode material by using ultra-pure carbon, the device being used for the preparation method as claimed in any one of claims 1 to 9, and characterized in that: ultra-pure carbon is added into a mechanical pulverizer (1) through a feeding tank I (16-1), and the ultra-pure carbon powder is separated from the pulverized ultra-pure carbon through an ultra-pure carbon powder classifying wheel (3) and introduced into a cyclone separator I (5-1), and the ultra-pure carbon powder is introduced into an ultra-pure carbon powder tank I (7-1), and other dust is collected by a bag dust collector I (6-1); At the same time, the asphalt is added into the jet mill (2) through the feeding tank II (16-2), and after being crushed, the asphalt is separated from the dust through the asphalt grading wheel (4) and the cyclone separator II (5-2), and the asphalt powder is collected into the asphalt tank (8), and the dust is collected by the bag dust collector II (6-2); The ultrapure carbon powder in the ultrapure carbon powder tank I (7-1) is mixed with the alkali solution and then is put into the electrolytic tank (13) for electrolysis; The ultrapure carbon powder after electrolysis is put into the two-stage belt filter press (14) to produce the ultrapure carbon filter cake, which is dried by the drying machine (15) and then is classified by the crushing and grading system, and the classified ultrapure carbon powder is put into the ultrapure carbon powder tank II (7-2); The ultrapure carbon powder in the ultrapure carbon powder tank II (7-2) and the asphalt powder in the asphalt tank (8) are added into the mixing and stirring tank (9) to obtain a mixture, and the mixture is added into the pyrolysis furnace (10) for pyrolysis; The material after pyrolysis is added into the push plate kiln (11) for carbonization; The material after carbonization is loaded into the Acheson graphitization furnace (12) for graphitization; The material after graphitization is collected and is sequentially subjected to the batch mixer (17), the iron remover (18) and the packaging machine (19) to be packaged into a finished product.

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