Influences of surface fluorination and carbon coating with furan resin in natural graphite as anode in lithium-ion batteries

Graphite and carbonaceous materials are promising as the anode for lithium-ion batteries. Although natural graphite exhibits a high specific capacity, violent irreversible capacity occurs after a few charge/discharge cycles. Carbon coating from furan resin pyrolysis on natural graphite surface can enhance graphite surface structure and promote the electrochemical properties by increasing C–C bonding. In this research, electrochemical characteristics of surface fluorination natural graphite and fluorination carbon-coated graphite are investigated. The C–F bonds formed at a temperature of around 500 °C heat treatment under 5 at% fluorine gas can improve lithium-ion intercalation and de-intercalation during charge/discharge. Both methods of carbon coating and surface fluorination can increase the first charge capacity and decrease the irreversibility of natural graphite. The analysis on surface properties is investigated by Raman spectroscopy and the bulk is analyzed by X-ray diffraction measurements.