Production method of high-rate artificial graphite negative electrode material

Abstract

The invention relates to a production method of a high-magnification artificial graphite negative electrode material, which comprises the following steps: (1) calcining green coke at 900-1200 DEG C to obtain pretreated calcined coke; (2) performing vacuum crushing on the pre-treated calcined coke to obtain a crushed material; (3) graphitizing the crushed material to obtain graphite powder; (4) mixing the graphite powder and the adhesive, and mechanically stirring to uniformly mix the graphite powder and the adhesive to obtain a mixture; and (5) loading the mixture into a carbonization furnace filled with inert gas for carbonization treatment, and finally sieving and packaging to obtain the high-magnification artificial graphite negative electrode material. The raw material selected by the invention is the pretreated calcined coke, compared with green coke used in a traditional process, the processes of shaping, coating, carbonizing and the like are omitted before the graphitization process, and the method has the advantages that the process is simple, the powder preparation cost is low, the environmental pollution is reduced, the calcination heat value of the green coke can be utilized, the graphitization charge quantity is increased and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a production method of a high-rate artificial graphite anode material. Background Art

[0002] Lithium-ion batteries have the characteristics of high capacity, long service life, low consumption, no memory effect, small volume, small internal resistance, etc., and have been widely used in people's production and life. However, with the continuous improvement of people's living standards, the requirement for the battery charging time is getting higher and higher. As an important component of lithium batteries, the anode material has a great influence on the charge and discharge performance of the battery. Therefore, it is of great significance to improve the fast charging performance of the anode material and maintain the performance of long cycle life and small internal resistance. At present, most of the high-rate anode materials mass-produced in the domestic market (as shown in Figure 8 Figure 8 ) are secondary particle graphitization after calcined coke crushing, shaping and coating, and then high-temperature carbonization, which have the disadvantages of high cost, complex process, low calorific value utilization rate, environmental unfriendliness, etc.

[0003] Therefore, it is necessary to further research and develop the production process of high-rate artificial graphite anode materials. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a production method of a high-rate artificial graphite anode material. The raw material selected by this method is pretreated calcined coke. Compared with the green coke used in the traditional process, before the graphitization process, the processes of shaping, coating, carbonization, etc. are omitted, which has the advantages of simple process, low powder-making cost, reduced environmental pollution, utilization of the calcination heat value of green coke, and improvement of the graphitization furnace loading amount.

[0005] The present invention provides a production method of a high-rate artificial graphite anode material, including the following steps:

[0006] (1) Calcine green coke at 900°C - 1200°C to obtain pretreated calcined coke; wherein, the volatile content of the obtained calcined coke is controlled below 3%, and the true density is 1.9 - 2.1 g / cm 3 3 ;

[0007] (2) Vacuum crush the pretreated calcined coke to obtain crushed material;

[0008] (3) Graphitize the above crushed material to obtain graphite powder;

[0009] (4) Mix the above graphite powder with a binder and mechanically stir to make the two evenly mixed to obtain a mixed material;

[0010] (5) Load the above mixed material into a carbonization furnace filled with inert gas for carbonization treatment, and finally screen and package to obtain a high-rate artificial graphite anode material.

[0010]

[0011] Preferably, the particle size D50 of the crushed material in step (2) is 2-13 μm.

[0012] Preferably, the vacuum pulverization uses the vacuum pulverizer of ZL201610661794.5.

[0013] Preferably, the graphitization temperature in step (3) is 2500-3000 °C.

[0014] Preferably, the mass ratio of graphite powder to binder in step (4) is 90:10-99:1.

[0015] Preferably, the binder is asphalt or resin with a softening point of 100-200 °C.

[0016] Preferably, the mechanical stirring speed in step (4) is 100-300 rpm and the time is 10-30 min.

[0017] Preferably, the carbonization treatment time in step (5) is 4-15 h and the temperature is 900-1300 °C.

[0018] Beneficial effects

[0019] (1) The raw material selected in the present invention is calcined coke after pretreatment. Compared with the green coke used in the traditional process, before the graphitization process, processes such as shaping, coating, and carbonization are omitted, which has the advantages of simple process, low powder-making cost, reduced environmental pollution, utilization of the calorific value of green coke calcination, and increased charging amount of graphite.

[0020] (2) The powder-making process in the present invention uses vacuum powder-making technology, which protects the microstructure of precursor particles, reduces the internal stress of particles, and improves the service life. Compared with the traditional mechanical pulverization method, it can effectively protect the microstructure of particles and the particle morphology is neat. Compared with air-flow pulverization, the particle size distribution is reasonable, the material utilization rate is high, the production capacity is large, and the energy consumption is low.

[0021] (3) The negative electrode material prepared by the present invention through high-temperature modification and blending process, during the pole piece rolling process, the composite particle structure is decomposed into single-particle structure by the rolling pressure and the stress generated during the rolling process is eliminated, thereby optimizing the lithium-ion migration channel, shortening the migration path, reducing the internal resistance, and effectively improving the battery rate performance. During the rolling process, the composite particles are decomposed into single particles, absorbing the stress generated by rolling, thereby reducing the pole piece rebound, improving the compaction density and energy density; the pole piece is flatter, which can effectively protect the diaphragm, thereby improving the safety performance of the battery. Description of the Drawings

[0022] Figure 1 It is the electron microscope image of the coke powder after being pulverized by the vacuum pulverizer.

[0023] Figure 2 It is the electron microscope image of coke powder after being crushed by a roller press mill.

[0024] Figure 3 It is the electron microscope image of coke powder after being crushed by a mechanical mill.

[0025] Figure 4 It is the electron microscope image of the electrode sheet of Example 1 of the high-rate artificial graphite anode material of the present invention.

[0026] Figure 5 It is the electron microscope image of the electrode sheet of Example 2 of the high-rate artificial graphite anode material of the present invention.

[0027] Figure 6 It is the electron microscope image of the electrode sheet of Example 3 of the high-rate artificial graphite anode material of the present invention.

[0028] Figure 7 It is the cross-sectional electron microscope image of the electrode sheet of the high-rate artificial graphite anode material of the present invention.

[0029] Figure 8 It is the electron microscope image of the electrode sheet of a commercially available high-rate anode material. Detailed implementation manners

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0031] Example 1

[0032] (1) Calcine green coke at 1000 °C to obtain calcined coke after pretreatment;

[0033] (2) Select calcined coke after pretreatment with a volatile content of 0.8% and a true density of 1.9 g / cm 3 and perform vacuum crushing to obtain two crushed materials with different particle sizes, with particle size D50 = 11 um and 13 um;

[0034] (3) Graphitize the above-mentioned crushed materials to obtain graphite powder, and the graphitization temperature is 2800 °C;

[0035] (4) Mix the graphite powder with D50 = 11 um and binder pitch in a mass ratio of 96:4 and perform mechanical stirring; mix the graphite powder with D50 = 13 um and binder pitch in a mass ratio of 98:2 and perform mechanical stirring; the mechanical stirring speed is 150 rpm, the time is 20 min, and the softening point of the pitch is 180 °C;

[0036] (5) Charge the two mixtures into a carbonization furnace filled with inert gas and carbonize for 10 h at a carbonization temperature of 1100 °C;

[0037] (6) Mix the two carbonized materials in a mass ratio of 50:50 and conduct mechanical stirring at a mechanical stirring speed of 100 rpm for 30 min, and then perform sieving and packaging to obtain the high-rate artificial graphite anode material.

[0038] Example 2

[0039] (1) Calcinate the green coke at 900 °C to obtain the pretreated calcined coke;

[0040] (2) Select the pretreated calcined coke with a volatile content of 2.5% and a true density of 2.05 g / cm 3 and conduct vacuum pulverization to obtain a pulverized material with a particle size D50 of 4 μm;

[0041] (3) Graphitize the above pulverized material to obtain graphite powder at a graphitization temperature of 3000 °C;

[0042] (4) Mix the graphite powder and the binder pitch in a mass ratio of 90:10 and conduct mechanical stirring to make them evenly mixed to obtain a mixture; the mechanical stirring speed is 300 rpm, the time is 20 min, and the softening point of the pitch is 150 °C;

[0043] (5) Charge the mixture into a carbonization furnace filled with inert gas and carbonize for 6 h at a carbonization temperature of 900 °C;

[0044] (6) Sieve and package the carbonized material to obtain the high-rate artificial graphite anode material.

[0045] Example 3

[0046] (1) Calcinate the green coke at 950 °C to obtain the pretreated calcined coke;

[0047] (2) Select the pretreated calcined coke with a volatile content of 1% and a true density of 2.0 g / cm 3 and conduct vacuum pulverization to obtain a pulverized material with a particle size D50 of 8 μm;

[0048] (3) Graphitize the above pulverized material to obtain graphite powder at a graphitization temperature of 2800 °C;

[0049] (4) Mix the graphite powder and the binder resin in a mass ratio of 92:8 and conduct mechanical stirring to make them evenly mixed to obtain a mixture; the mechanical stirring speed is 200 rpm, the time is 15 min, and the softening point of the resin is 100 °C;

[0050] (5) Charge the mixture into a carbonization furnace filled with inert gas and carbonize it for 8 h at a carbonization temperature of 1200 °C;

[0051] (6) Screen and package the carbonized material to obtain the high-rate artificial graphite anode material.

[0052] As can be seen from Figures 1 - 3 , for the coke powder crushed by the vacuum crusher, the particle morphology is neat, the surface is relatively smooth, there are fewer edges and corners, and the strength of the particle structure is well protected.

[0053] As can be seen from Figures 4 - 6 , compared with the domestic mass-produced high-rate anode materials, the surface of the anode sheet of the high-rate artificial graphite anode material of the present invention is flatter and has fewer pores. The lithium-ion migration channels are more optimized, and the separator can be effectively protected.

[0054] Table 1 Comparison results of rate charging between Example 1 and the comparative example

[0055]

[0056]

[0057] Remarks: 1. The comparative example is a commercially available high-rate anode material.

[0058] 2. Both are discharged at 1C and charged at 0.5C, 1C, 2C, 3C, 4C, and 5C respectively to compare the charging capacity ratios at different rates.

[0059] As can be seen from Table 1, when charging at a high rate above 3C, Example 1 has an obvious fast-charging advantage.

[0060] Table 2 Comparison results of 1C / 1C cycle between Example 1 and the comparative example

[0061] Name C300 C546 C900 C1200 Example 1 98.48％ 97.41％ 94.57％ 92.49％ Comparative example 92.45％ 79.91％ / /

[0062] As can be seen from Table 2, in the 1C / 1C cycle, the capacity retention rate of the comparative example drops to 79.91% after 546 cycles, while according to the trend, the capacity retention rate of Example 1 can still be above 80% after about 2800 cycles.

[0063] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the above embodiments are only exemplary and not restrictive, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A method for producing a high-rate artificial graphite negative electrode material, comprising the following steps: (1) calcining green coke at 900°C-1200°C to obtain pre-treated calcined coke; wherein: The volatile matter of the calcined coke is controlled below 3%, and the true density is 1.9-2.1g / cm 3 ; (2) vacuum crushing the pretreated calcined coke to obtain a crushed material; (3) graphitizing the crushed material to obtain graphite powder; (4) mixing the graphite powder and the adhesive and then mechanically stirring them to make them uniformly mixed to obtain a mixture; (5) The mixed material is placed in a carbonization furnace filled with inert gas for carbonization treatment, and finally sieved and packaged to obtain a high-rate artificial graphite negative electrode material.

2. The preparation method according to claim 1, characterized in that: The particle size D50 of the crushed material in step (2) is 2 to 13 μm.

3. The preparation method according to claim 1, characterized in that: The graphitization temperature in step (3) is 2500-3000°C.

4. The preparation method according to claim 1, characterized in that: The mass ratio of graphite powder to adhesive in step (4) is 90:10 to 99:

1.

5. The preparation method according to claim 1 or 4, characterized in that: The adhesive is asphalt or resin with a softening point of 100-200°C.

6. The preparation method according to claim 1, characterized in that: The mechanical stirring speed in step (4) is 100-300 rpm, and the time is 10-30 min.

7. The preparation method according to claim 1, characterized in that: The carbonization treatment time in step (5) is 4-15 hours, and the temperature is 900-1300°C.

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