Spherical graphite research progress in production technology
Spherical graphite is high-quality high carbon natural flake graphite as raw material, the use of advanced processing technology to modify the graphite surface, the production of different fineness, elliptic spherical graphite products.
Spherical graphite processing mechanism: first, the natural flake graphite powder crushed into appropriate size, and then to deal with the processing of edges and corners, to eventually become the ellipsoid or class of spherical shape, and grading device will go spherical particles with edges and corners to make use of the stripping down fine powder in the process of separation, the normal distribution can be got the spherical graphite.
Graphite raw materials selection.
On the one hand, the granularity of raw materials should be appropriate. Too thick cost is higher; Too fine will affect the yield of spherical graphite, and too many auxiliary products will increase the cost of raw materials. The results show that it is suitable to produce spherical graphite with -100 mesh particle size.
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 increase of purification times, will also aggravate the wear of equipment, the total cost will also increase. After practice accumulation, containing 95%~96% of raw materials, the comprehensive cost is the most economical.
About the choice of spherical graphite processing equipment.
(1) Spherical process is more used in the airflow vortex mill, which has both crushing performance and the effect of de-angular.In addition, the quality of grading equipment will directly affect the yield of spherical fossil ink and the technical index control of spherical graphite, so we should pay attention to the selection.
(2) The purity of graphite anode material used in lithium-ion batteries is often above 99.95%. Therefore, the purification process is essential and crucial in the whole production process. At present, the production of high purity spherical graphite is generally produced by the chemical purification method, the chemical raw materials used are strong acid substances, so the purification equipment must be acid and corrosion-resistant equipment. At the same time, because the chemical purification is completed at a certain temperature, so the equipment also has a certain high-temperature resistance.
(3) After the chemical reaction, the impurities in the spherical graphite are dissolved in the reaction solution, and the impurities can only be taken away by washing. The washing equipment used in the process is mainly filtered press and centrifuge. The advantages of the filter press are high recovery rate, less running material, low labor intensity, safety, and ease of operation, the disadvantage is that the washing effect is relatively poor, there is a dead Angle that can not wash. The advantage of the centrifuge is washing more fully, the effect is good, but there are also more shortcomings, such as running material, waste, discharge labor intensity, safety and ease as pressure filter, and more waste of water. Combining the two to use the effect is good.
(4) The spherical graphite after purification and washing is dried to remove moisture, and the moisture is controlled below 0.5%.In the drying process, the most likely problem is secondary pollution, that is, spherical graphite after drying because of mixed impurities and become unqualified products, mainly manifested as the index of carbon content and trace elements is not qualified. The use of more drying equipment is drying kiln, microwave dryer, and drying oven.
Although there are still some problems in the application of spherical graphite in lithium-ion batteries, such as safety problems, circulation problems, and fast charge and discharge with high current, domestic research is further improved. For example, Zhejiang Fengli's project of "Development of complete equipment and technology for spherification of lithium battery cathode materials" has been listed in Zhejiang Province's key technical innovation special plan. The products processed by the production line have good crystal alignment, high roundness, and stable quality. The production line adopts automatic control, is easy to operate, greatly reduces energy consumption, improves production efficiency. With the enhancement of the concept of environmental protection, people's demand for spherical graphite will increase exponentially or even 100 times in the future. Spherical graphite used as anode material for the lithium-ion battery will open up a broad prospect for the application of natural graphite in the field of new energy.
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