Method for preparing energy storage negative electrode by briquetting and molding natural graphite spheroidized tailings

Abstract

The method comprises the following steps: mixing the natural graphite spheroidized tailings, an organic carbon source A and distilled water, carrying out briquetting molding, and tightly combining the natural graphite spheroidized tailings with the organic carbon source through mechanical force, so that the reaction contact area of the natural graphite spheroidized tailings and the organic carbon source is increased; then, the formed particles are added into a carbonization furnace for high-temperature carbonization, and after moisture is evaporated to dryness, the soft-melted organic carbon source and the spheroidized tailings are cross-linked, so that the surface defects of the spheroidized tailings are improved; the carbonized material is placed in a shaping machine to be crushed, shaped and graded, a graded material with the particle size D50 being 15-20 microns is obtained, the particle size of the spheroidized tailings is increased, and meanwhile the tap density of the spheroidized tailings is increased; and the graded material is fully mixed with an organic carbon source B for secondary carbonization, so that the specific surface area of the particles is reduced, and meanwhile, the cycling stability is enhanced. The spheroidized tailings coated and modified by the steps are long in cycle life and high in first charge-discharge efficiency, and can meet commercial requirements in the field of energy storage.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, and in particular to a method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings. Background Art

[0002] Lithium-ion batteries are mainly composed of negative electrodes, positive electrodes, electrolytes and separators. Currently on the market, lithium-ion battery materials include lithium iron phosphate, ternary lithium and lithium cobalt oxide, and negative electrode materials are mainly graphite. The reason why graphite is used as the negative electrode of lithium-ion batteries is because it has the characteristics of stable structure, high reversible capacity, easy access, low cost and environmental friendliness. However, graphite sheets mainly rely on van der Waals forces. Lithium ions are intercalated and deintercalated between graphite layers, and electrolytes will also enter the graphite layers to generate lithium salts and produce gases, reducing the reversible capacity and cycle life of the battery. Therefore, graphite negative electrodes are modified in industrial production, including spheroidization, surface modification, doping and other means. Among them, spherical graphite is widely praised for its advantages such as good conductivity, high isotropy, high crystallinity, controllable particle size, round particles and smooth surface. However, the preparation process of spherical graphite will produce about 50% of tailings. These tailings have low tap density and large specific surface area. Therefore, this part of spheroidized tailings can only be used to produce low-value-added lubricants and refractory materials, which greatly reduces the high-value utilization of natural graphite.

[0003] Therefore, there is an urgent need to provide a method for preparing energy storage negative electrodes by pressing and molding natural graphite spheroidized tailings to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings and defects of the prior art and provide a method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings, which can improve the tap density of the spheroidized tailings and reduce their specific surface area through briquetting and carbonization coating, and improve their electrochemical properties through the carbonization coating layer, so that the method can be applied to energy storage battery materials.

[0005] The objective of the present invention is achieved through the following technical solutions: A method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings, comprising the following steps: S1. Place the natural graphite spheroidization tailings, organic carbon source A and distilled water into a powerful mixer and mix them evenly to obtain a mixture; S2, placing the obtained mixture into a briquetting machine and pressing it into cylindrical large particles, then loading it into an alumina crucible, and placing it in a carbonization furnace; S3, a certain amount of inert gas is filled into the carbonization furnace, and the temperature is heated to 900-1200°C at a constant heating rate A, and carbonization treatment is performed after the heating is completed, and the carbonization time is B; after cooling to room temperature, the carbonized particles are taken out; S4, putting the carbonized particles obtained in S3 into a shaping machine for crushing, shaping and classification to obtain a classified material with a D50 of 15 μm to 20 μm; S5, placing the classified materials and the organic carbon source B into a powerful mixer to mix them evenly, then placing the mixture into an alumina crucible and placing it in a carbonization furnace; S6, a certain amount of inert gas is charged into the carbonization furnace, and heated to 300°C at a constant heating rate C for preheating, and the preheating time is D; then heated to 600-1000°C at a constant heating rate E, and carbonization treatment is performed after the heating is completed, and the carbonization time is F; after cooling to room temperature, the carbonized material is taken out; S7. Put the carbonized material into a ball mill for ball milling, and obtain the negative electrode material after screening and separation.

[0006] As a preferred technical solution of the present invention, the mass percentage of natural graphite spheroidization tailings in S1 is 65-75%, the mass percentage of organic carbon source A is 5-10%, the mass percentage of distilled water is 15-25%, and the mixing time is 10-30 min.

[0007] As a preferred technical solution of the present invention, the organic carbon source A in S1 is one of starch, glucose, epoxy resin, phenolic resin, polystyrene and polyvinyl chloride.

[0008] As a preferred technical solution of the present invention, the pressure of the briquetting machine in S2 is 1~5MPa.

[0009] As a preferred technical solution of the present invention, the heating rate A of the S3 carbonization is 2-5°C / min, and the carbonization time B is 120-180min.

[0010] As a preferred technical solution of the present invention, the mass percentage of the classified material in S5 is 85-95%, and the mass percentage of the organic carbon source B is 5-15%.

[0011] As a preferred technical solution of the present invention, the organic carbon source B in S5 is one of rice husk powder, coconut shell powder, coke, asphalt, melamine and citric acid.

[0012] As a preferred technical solution of the present invention, the heating rate C of the S6 carbonization is 2~5°C / min, the preheating time D is 45~90min, the heating rate E is 2~5°C / min, and the carbonization time F is 120~180min.

[0013] As a preferred technical solution of the present invention, the ball milling time in S7 is 30 to 60 minutes.

[0014] As a preferred technical solution of the present invention, in S7, a sieve is used to screen and separate the carbonized raw materials after ball milling, and the aperture of the sieve is 0.038 mm.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention is to mix natural graphite spheroidized tailings, organic carbon source A, and distilled water, and carry out briquetting, and closely combine the natural graphite spheroidized tailings with the organic carbon source through mechanical force to increase the reaction contact area. Then, the formed particles are placed in a carbonization furnace for high-temperature carbonization. After the water is evaporated, the soft-melted organic carbon source is cross-linked with the spheroidized tailings to improve the surface defects of the spheroidized tailings. The carbonized material is placed in a shaping machine for crushing, shaping, and grading to obtain a graded material with a particle size D50 of 15 μm to 20 μm, thereby increasing the particle size of the spheroidized tailings and increasing its tap density. The graded material is fully mixed with the organic carbon source B for secondary carbonization, reducing the specific surface area of ​​the particles and enhancing its cycle stability. Through the above steps, the shortcomings of the spheroidized tailings such as fine particle size, large specific surface area, and many surface defects can be improved, and the spheroidized tailings after coating and modification have a long cycle life and high first charge and discharge efficiency, which can meet the commercial needs in the field of energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a process flow chart of the present invention.

[0017] Figure 2 This is the particle size distribution diagram of the raw material of Example 1 of the present invention.

[0018] Figure 3 This is the particle size distribution diagram of the material after being processed in Example 1 of the present invention.

[0019] Figure 4 This is a schematic diagram of the battery cycle performance of Example 1 of the present invention.

[0020] Figure 5 This is a schematic diagram of the battery cycle performance of Example 2 of the present invention.

[0021] Figure 6 This is a schematic diagram of the battery cycle performance of Example 3 of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0023] The specific implementation process of the present invention is as follows: like Figure 1 As shown, a method for preparing an energy storage negative electrode by pressing and molding natural graphite spheroidized tailings, comprises the following steps: S1. Place the natural graphite spheroidization tailings, organic carbon source A and distilled water into a powerful mixer and mix them evenly to obtain a mixture; S2, placing the obtained mixture into a briquetting machine and pressing it into cylindrical large particles, then loading it into an alumina crucible, and placing it in a carbonization furnace; S3, a certain amount of inert gas is filled into the carbonization furnace, and the temperature is heated to 900-1200°C at a constant heating rate A, and carbonization treatment is performed after the heating is completed, and the carbonization time is B; after cooling to room temperature, the carbonized particles are taken out; S4, putting the carbonized particles obtained in S3 into a shaping machine for crushing, shaping and classification to obtain a classified material with a particle size D50 of 15 μm to 20 μm; S5, placing the classified materials and the organic carbon source B into a powerful mixer to mix them evenly, then placing the mixture into an alumina crucible and placing it in a carbonization furnace; S6, a certain amount of inert gas is charged into the carbonization furnace, and heated to 300°C at a constant heating rate C for preheating, and the preheating time is D; then heated to 600-1000°C at a constant heating rate E, and carbonization treatment is performed after the heating is completed, and the carbonization time is F; after cooling to room temperature, the carbonized material is taken out; S7. Put the carbonized material into a ball mill for ball milling, and obtain the negative electrode material after screening and separation.

[0024] Optionally, in the present embodiment, a certain amount of natural graphite spheroidization tailings, organic carbon source A, and distilled water are weighed and placed in a strong mixer for mixing. After adding distilled water, it is helpful for the briquetting of graphite and its mechanical strength is enhanced. The mixture is placed in a briquetting machine and pressed into cylindrical large particles. The cylindrical large particles are then loaded into a crucible made of alumina material, placed in a carbonization furnace and a certain amount of inert gas is passed through, and heated to 900~1200℃ at a constant heating rate A, and the temperature is maintained to continue carbonization for a period of time, and then taken out after cooling to room temperature; the carbonized raw material is placed in a shaping machine for crushing, shaping, and grading. By shaping, it is possible to crush large particles, polish particle edges, compact particles, and obtain a controllable particle size distribution. After that, the graded material is mixed with the organic carbon source B and then subjected to secondary carbonization. A certain amount of inert gas is filled into the carbonization furnace, and heated to 300°C at a constant heating rate C for a period of preheating; then heated to 600~1000°C at a constant heating rate E, and carbonized for F after heating; after cooling to room temperature, the carbonized material is taken out; the carbonized material is added to the ball mill for ball milling, and after ball milling, the desired negative electrode material is obtained by screening with a sieve. The obtained negative electrode material is coated with a layer of organic carbon source B on the outside, and the internal spheroidized tail material is closely combined with the organic carbon source A, which greatly improves the structural stability and ion transfer rate; at the same time, the raw material particle size is increased and the specific surface area is reduced.

[0025] The present invention will be further described below in conjunction with specific embodiments. Example 1

[0026] The natural graphite spheroidization tailings, phenolic resin and distilled water were respectively placed in a high-power mixer at a mass ratio of 70%:5%:25% for efficient mixing, and the mixing time was 10 minutes to obtain a mixture; wherein the particle size D50 of the natural graphite spheroidization tailings was 3μm; the mixture was placed in a briquetting machine with a pressure of 1MPa to obtain large cylindrical particles, and the large cylindrical particles were loaded into an alumina crucible and placed in a carbonization furnace; a certain amount of inert gas was filled into the carbonization furnace, and the temperature was heated to 900℃ at a heating rate of 5℃ / min. After the temperature reached 900℃, this temperature was maintained to continue carbonization, and the carbonization time was 60min; after the carbonization was completed, it was allowed to cool to room temperature, and then the raw material was taken out and placed in a shaping machine for crushing, shaping and grading to obtain particles with a particle size D50 of 15μm, and then the graded particles were mixed with asphalt The raw materials are mixed with 2% cyanide in a mass ratio of 95%:5% for secondary carbonization; a certain amount of inert gas is filled into the carbonization furnace, and the furnace is heated to 300°C at a constant heating rate of 2°C / min for preheating, and the preheating time is 60 minutes; the furnace is then heated to 600°C at a constant heating rate of 5°C / min, and carbonization is performed after the heating is completed, and the carbonization time is 60 minutes; after the carbonization is completed, the raw materials are placed to cool to room temperature, and then the raw materials are taken out; the carbonized raw materials are placed in a ball mill for ball milling, and the ball milling time is 60 minutes. After the ball milling is completed, the negative electrode material is sieved with a vibration screen with a mesh size of 0.038mm to obtain the negative electrode material, and the electrochemical performance of the obtained negative electrode material is tested, and the first efficiency is 91%, the first discharge specific capacity is 423mAh / g, and the capacity retention rate is 85% after 200 cycles of charge and discharge tests. Figure 4 shown. Example 2

[0027] The natural graphite spheroidization tailings, glucose and distilled water were respectively placed in a high-power mixer at a mass ratio of 75%:10%:15% for efficient mixing, and the mixing time was 10 minutes to obtain a mixture; the particle size D50 of the natural graphite spheroidization tailings was 3μm; the mixture was placed in a briquetting machine with a pressure of 3MPa to obtain large cylindrical particles, and the large cylindrical particles were loaded into an alumina crucible and placed in a carbonization furnace; a certain amount of inert gas was filled into the carbonization furnace, and the temperature was heated to 1200℃ at a heating rate of 2℃ / min. After the temperature reached 900℃, this temperature was maintained to continue carbonization for 60 minutes; after the carbonization was completed, it was allowed to cool to room temperature, and then the raw material was taken out and placed in a shaping machine for crushing, shaping and grading to obtain particles with a particle size D50 of 17μm, and then the graded particles were mixed with trimer The cyanamide was mixed in a mass ratio of 85%:15% and subjected to secondary carbonization; a certain amount of inert gas was filled into the carbonization furnace, and the mixture was heated to 300°C at a constant heating rate of 2°C / min for preheating, and the preheating time was 60 minutes; the mixture was heated to 800°C at a constant heating rate of 2°C / min, and carbonization was performed after the heating was completed, and the carbonization time was 60 minutes; after the carbonization was completed, the mixture was allowed to cool to room temperature, and then the raw materials were taken out; the carbonized raw materials were placed in a ball mill for ball milling, and the ball milling time was 60 minutes. After the ball milling was completed, the negative electrode material was sieved with a vibrating screen with a mesh size of 0.038 mm to obtain the negative electrode material, and the electrochemical performance of the obtained negative electrode material was tested, and the first efficiency was 86%, the first discharge specific capacity was 441 mAh / g, and the capacity retention rate was 81% after 200 cycles of charge and discharge tests. Figure 5 shown. Example 3

[0028] The natural graphite spheroidization tailings, citric acid and distilled water were respectively placed in a high-power mixer at a mass ratio of 80%:5%:15% for efficient mixing, and the mixing time was 30 minutes to obtain a mixture; wherein the particle size D50 of the natural graphite spheroidization tailings was 3μm; the mixture was placed in a briquetting machine with a pressure of 5MPa to obtain large cylindrical particles, and the large cylindrical particles were loaded into an alumina crucible and placed in a carbonization furnace; a certain amount of inert gas was filled into the carbonization furnace, and the temperature was heated to 1100℃ at a heating rate of 5℃ / min. After the temperature reached 900℃, this temperature was maintained to continue carbonization, and the carbonization time was 60min; after the carbonization was completed, it was allowed to cool to room temperature, and then the raw material was taken out and placed in a shaping machine for crushing, shaping and grading to obtain particles with a particle size D50 of 16μm, and then the graded particles were mixed with starch at 90%:10% mass ratio is mixed for secondary carbonization; a certain amount of inert gas is filled into the carbonization furnace, and heated to 300℃ at a constant heating rate of 2℃ / min for preheating, and the preheating time is 60min; then heated to 1000℃ at a constant heating rate of 5℃ / min, and carbonization treatment is carried out after heating, and the carbonization time is 120min; after carbonization, it is placed to cool to room temperature, and then the raw materials are taken out; the carbonized raw materials are placed in a ball mill for ball milling, and the ball milling time is 60min. After ball milling, the negative electrode material is sieved with a vibration screen with a mesh size of 0.038mm to obtain the negative electrode material, and the electrochemical performance of the obtained negative electrode material is tested, the first efficiency is 88%, the first discharge specific capacity is 405mAh / g, and the capacity retention rate is 80% after 200 cycles of charge and discharge test. Figure 6 shown.

[0029] The above-mentioned embodiments only express the implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings, characterized in that: The following steps are involved: S1. Place the natural graphite spheroidization tailings, organic carbon source A and distilled water into a powerful mixer and mix them evenly to obtain a mixture; S2, placing the obtained mixture into a briquetting machine and pressing it into cylindrical large particles, then loading it into an alumina crucible, and placing it in a carbonization furnace; S3, a certain amount of inert gas is filled into the carbonization furnace, and the temperature is heated to 900-1200°C at a constant heating rate A, and carbonization treatment is performed after the heating is completed, and the carbonization time is B; after cooling to room temperature, the carbonized particles are taken out; S4, putting the carbonized particles obtained in S3 into a shaping machine for crushing, shaping and classification to obtain a classified material with a D50 of 15 μm to 20 μm; S5, placing the classified materials and the organic carbon source B into a powerful mixer to mix them evenly, then placing the mixture into an alumina crucible and placing it in a carbonization furnace; S6, a certain amount of inert gas is charged into the carbonization furnace, and heated to 300°C at a constant heating rate C for preheating, and the preheating time is D; then heated to 600-1000°C at a constant heating rate E, and carbonization treatment is performed after the heating is completed, and the carbonization time is F; after cooling to room temperature, the carbonized material is taken out; S7. Put the carbonized material into a ball mill for ball milling, and obtain the negative electrode material after screening and separation.

2. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 1, characterized in that: The mass percentage of natural graphite spheroidization tailings in S1 is 65-75%, the mass percentage of organic carbon source A is 5-10%, the mass percentage of distilled water is 15-25%, and the mixing time is 10-30 minutes.

3. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 2, characterized in that: The organic carbon source A in S1 is one of starch, glucose, epoxy resin, phenolic resin, polystyrene and polyvinyl chloride.

4. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 1, characterized in that: The pressure of the briquetting machine in S2 is 1~5MPa.

5. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 1, characterized in that: The heating rate A of the S3 carbonization is 2-5°C / min, and the carbonization time B is 120-180min.

6. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 1, characterized in that: The mass percentage of the classified material in S5 is 85-95%, and the mass percentage of the organic carbon source B is 5-15%.

7. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 1, characterized in that: The organic carbon source B in S5 is one of rice husk powder, coconut shell powder, coke, asphalt, melamine and citric acid.

8. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 1, characterized in that: The heating rate C of the S6 carbonization is 2-5°C / min, the preheating time D is 45-90min, the heating rate E is 2-5°C / min, and the carbonization time F is 120-180min.

9. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 1, characterized in that: The ball milling time in S7 is 30 to 60 minutes.

10. The method for preparing an energy storage negative electrode by briquetting natural graphite spheroidized tailings according to claim 1, characterized in that: In S7, a screen is used to screen and separate the carbonized raw materials after ball milling, and the aperture of the screen is 0.038 mm.

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