Development of graphite purification efficient chemical technology for lithium-ion battery anodes

Graphite is a key material for many high-tech industries, in particular for production of lithium-ion batteries. Ukraine has significant reserves of natural graphite, but domestic enterprises don’t have necessary technologies for its extraction in a highly purified state. Since graphite for the manufacture of lithium-ion batteries anode masses must contain more than 99.95% carbon material, the use of effective methods for its purification is especially important. In addition to ensuring the required degree of graphite сleanliness, the purification method must be economically viable and environmentally safe. Development of this method will significantly increase competitiveness of domestic products in the international market.The promising method for purifying graphite is treatment with a mixture of sulfuric acid and ammonium fluoride. Because of acid treatment, the degree of purification of graphite grades GUPG-92, GEO-94, GTO-95 ranged from 99.4% to 99.8%, which is insufficient for use in lithium-ion batteries, while the purity of battery graphite GAK-2 was increased to the required level of 99.95 %.Electrochemical investigations of purified graphite grade GAK-2 confirmed its compliance with requirements for lithium-ion batteries anode materials. Its capacity was approximately 350 mAh/g, which is a competitive value among modern graphite-based anode materials. The initial coulombic efficiency of the anodes (89–91%) approaches characteristics of commercial graphite materials. Studies of the cyclic stability of chemically purified graphite by analyzing the dependence of the specific capacity on the number of cycles demonstrate high stability of the material during long-term cycling. Electrochemical investigations confirm suitability of purified GAK-2 graphite for use in lithium-ion batteries. Electrical characteristics of graphite can be significantly improved after graphite particles spheroidization and coating them with carbon material to reduce the specific surface area.