Lithium electrochemical intercalation into mechanically and chemically treated Sri Lanka natural graphite

Abstract

Graphite is a host material for lithium intercalation and can be used as an active anode material in rechargeable lithium cells. The battery performances and cycling depends on the type and morphology of graphite. The advantage of natural graphite is the possibility of enhancing the electrochemical intercalation by simple mechanical or chemical treatments. Sri Lanka natural graphite is found in various morphologies with different structural and physical characteristics. The most abundant morphology, the shiny–slippery–fibrous graphite found in Kahatagaha/Kolongaha mines, has a very high purity of over 98% and high crystallinity. Lithium has been electrochemically intercalated into different morphologies of pure natural graphite as well as into treated graphite. The ball milling facilitates partial conversion of hexagonal into rhombohedral phase, which increases structural defects lowering the tendency to solvent co-intercalation and exfoliation and increasing the reversible capacity. Chemical treatments on graphite show improvements in reversible capacity. The mechanical ball milling and the chemical oxidation in air and (NH4)2S2O8 are simple and effective methods to enhance the electrochemical intercalation of lithium ions into natural graphite.