Purification mechanism of microcrystalline graphite and lithium storage properties of purified graphite

Abstract

In order to improve the application value of natural microcrystalline graphite with carbon content of 49.5%, high-purity microcrystalline graphite was prepared by emulsifying kerosene flotation firstly, and then purifying hydrofluoric acid and hexafluorosilicic acid. Then the purified microcrystalline graphite was prepared for the lithium-ion battery anode material, its microstruture and electrochemical properties were analyzed, the purification mechanism and lithium storage mechanism were discussed. The research results show that carbon content of microcrystalline graphite after emulsified kerosene flotation and mixed acid purification are 93.5% and 99.0% respectively. After pickling, high-purity microcrystalline graphite shows the largest layer spacing, which is 0.351 5 nm and is 0.001 4 nm higher than that of natural microcrystalline graphite. Size disparity of acid washing sample is larger, layered structure is more obvious, cycle performance and magnification performance are better than those of floation sample. The pickled sample has the highest initial reversible specific capacity of 477.4 mAh/g, and the first Coulomb efficiency is 61.3%. Charge transfer impedance, interface impedance and SEI membrane impedance, and lithium ion diffusion impedance in electrode material are significantly lower than those of microcrystalline graphite after flotation.

Hydroxyl Removal in Muscovite by Heating for Low-Fluoride Purification of Natural Flake Graphite

“…Chemical or high-temperature purification is required to further improve the purity of natural graphite. These methods include high-temperature purification, alkali-melting acid leaching, , chlorination roasting, , hydrofluoric acid method, etc. Under high temperatures and the protection of the inert atmosphere, 99.99% high-purity graphite can be obtained by heating graphite to 2300–3000 °C using high-temperature purification equipment and expelling impurities from graphite .…”

Enhancement of the mechanical and tribological properties of carboxylated acrylonitrile butadiene rubber filled with cryptocrystalline graphite by different preparation methods

“…[3][4][5] Most notably, graphite, a solid lubricant with a unique lamellar structure, can improve the mechanical, anti-friction, and wear-resistance performance of polymers. [6][7][8] Graphite materials generally include flake graphite, 9 expandable graphite, 10,11 graphene, 12,13 and graphene oxide. [14][15][16] They have been used as multifunctional additives endowed with excellent electrical/thermal conductivity, heat aging and tribological properties, etc.…”

“…The rapid development of mineral purification processes and the deepened understanding of mineralogy characteristics lead to a growing focus on the application of anode materials for lithium-ion batteries and nuclear and high purity graphite. [13][14][15]18 It is promising for CG, a cost-effective and environmentally friendly natural mineral, to be used as a functional filler. Unfortunately, the research and application of CG in polymers, especially rubber materials, remain extremely insufficient.…”

“…Graphite materials generally include flake graphite, 9 expandable graphite, 10,11 graphene, 12,13 and graphene oxide 14–16 . They have been used as multifunctional additives endowed with excellent electrical/thermal conductivity, heat aging and tribological properties, etc.…”

“…CG was usually ignored and hardly studied on account of its difficulty in purification and low added value in the past. The rapid development of mineral purification processes and the deepened understanding of mineralogy characteristics lead to a growing focus on the application of anode materials for lithium‐ion batteries and nuclear and high purity graphite 13–15,18 . It is promising for CG, a cost‐effective and environmentally friendly natural mineral, to be used as a functional filler.…”