Hydrothermal modification of natural graphite as an anode material for lithium secondary batteries

A natural graphite powder was modified by a low-temperature (98 °C) hydrothermal reaction in a mixed solution of inorganic acid. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and particle sedimentation method were employed to evaluate the structural modification. It is found that such hydrothermal treatment can lead to the disintegration of big particles and the formation of a less-conducting dense layer on the particle surface. When used as an electrode for rechargeable lithium batteries, the treated graphite exhibits improved reversible capacity in comparison with the original graphite powder and especially the compatibility with the electrolyte captaining propylene carbonate (PC).