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Study on production technology of spherical graphite

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Update time : 2020-05-06 16:32:01
The formation of natural flake graphite is formed under extremely high temperature and high pressure. Therefore, the crystallinity is often very good, the degree of graphitization is high, and the capacity of the processed negative electrode material can reach 365mAH / g or more The capacity of artificial graphite. This provides a resource guarantee for the mass production of lithium-ion anode materials. In the past ten years, in China's graphite industry, the production and processing of spherical graphite products have developed rapidly, and there is an increasing trend.
 
Spherical graphite is made of high-quality high-carbon natural flake graphite as raw material and adopts advanced processing technology to modify the surface of graphite. It produces graphite products with different fineness, which resemble elliptical spherical shape.
                       
Spherical graphite adopts advanced processing technology to modify its surface to produce graphite products with different fineness and oval shape. Spherical graphite is also processed from flake graphite, and the processing technology of spherical graphite is relatively high.
1. Recombination of fine particles.
 
Fine particle compounding is the use of fine particle compounding equipment to spheroidize powder particles.
 
2. Wet grinding.
 
Wet grinding ore preparation of spherical graphite can simplify the production process, reduce production costs, and increase the yield of spherical graphite.
 
3. High-energy ball milling, special crushing and classification process.
 
Both high-energy ball milling and special crushing and grading processes have a certain promotion effect on the spheroidization of cryptocrystalline graphite. The graphite spheres formed are fine and uniform, but there are certain differences.
 
Spherical graphite processing mechanism: First of all, the natural flake graphite powder is crushed to a suitable particle size, and then the processing of de-cornerization is carried out, so that it finally forms an ellipsoid or spherical-like shape, and at the same time, the grading device is used to de-angle the spherical particles The fine powder peeled off in the process is separated to obtain spherical graphite with normal distribution.
First, the choice of graphite raw materials.
 
On the one hand, the particle size of the raw materials should be appropriate. If it is too coarse, the cost will be higher; if it is too fine, the output rate of spherical graphite will be affected. Too many auxiliary products will also increase the raw material cost. Studies have shown that it is more appropriate to produce spherical graphite using raw materials with a particle size of -100 mesh.
 
On the other hand, carbon content is also a very important factor. The higher the carbon content, the higher the raw material cost. The lower the carbon content, the more purification passes will increase the wear of the equipment and the total cost will also increase. Accumulated through practice, containing 95% to 96% of raw materials, the overall cost is the most economical.
                             
Secondly, regarding the choice of spherical graphite processing equipment.
 
(1) The air flow vortex crusher is widely used in the spherical process, which has both the crushing performance and the effect of chamfering. In addition, the quality of the grading equipment will directly affect the yield of spheroidized graphite and the control of the technical indicators of spheroidal graphite, so attention should be paid to the selection.
 
(2) The purity requirements of graphite anode materials used in lithium ion batteries are often above 99.95%. Therefore, the purification process is essential and crucial in the entire production process. At present, the production of high-purity spherical graphite is generally produced by chemical purification methods. The chemical raw materials used are all strong acid substances, so the purification equipment must be acid-resistant and corrosion-resistant equipment. At the same time, because the chemical purification is done at a certain temperature, the equipment also has a certain high temperature resistance.
 
(3) After the chemical reaction is completed, the impurities in the spherical graphite are dissolved in the reaction solution, and the impurities can be taken away only by washing. The washing equipment used in the process is mainly two kinds of filter press and centrifuge. The advantages of the filter press are high recovery rate, less running material, low labor intensity, safety and easy operation. The disadvantage is that the washing effect is relatively poor, and there is no dead angle to wash. The advantage of the centrifuge is that the washing is sufficient and the effect is good, but the disadvantages are also more, such as more running material, greater waste, labor intensity at the time of discharge, safety and ease of inferiority to the filter press, and more waste of water. It is effective to use the two together.
 
(4) Dry the spherical graphite after purification and washing to remove moisture, and control the moisture below 0.5%. In the drying process, the most prone problem is secondary pollution, that is, the spherical graphite becomes unqualified due to the inclusion of impurities after drying, mainly manifested as unqualified indicators of carbon content and trace elements. More drying equipment is used, including drying kiln, microwave dryer and drying furnace.

 
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