Boosted electrochemical performance of graphite anode enabled by polytetrafluoroethylene-derived F-doping

Pure graphite anode exhibits inferior rate performance and cyclability in lithium-ion batteries. Herein, graphite was mixed in polytetrafluoroethylene (PTFE) aqueous emulsion followed by heating the parched mixture at 400 °C for 5 h. The common lipophilic behavior of the two materials allows the melted PTFE to reveal good wettability to graphite, and the large concentration gradient of fluorine element between graphite and the melted PTFE drives fluorine diffusion into graphite to achieve F-doped graphite. The as-modified product with a PTFE/graphite mass ratio of 1.2% reveals a reversible capacity of 390.8 mAh g−1 after 60 cycles at 0.1C, and a capacity of 319.3 mAh g−1 after 100 cycles at 0.5C, markedly superior to the performance of the pristine graphite. The appreciable property of the PTFE-modified graphite is attributable to the uniform PTFE coating for avoiding the direct interaction of electrolyte with graphite and enhancing the coulombic efficiency of first lithiation/de-lithiation cycle, the F-doping for facilitating electron transfer, the augmented mesopore volume and specific surface area for Li-ion storage, and the enlarged lattice spacing of graphite for Li-ion diffusion.