Heat-treatment of synthetic graphite under argon and effect on Li-ion electrochemistry

The novel use of heat-treatment in flowing Ar to systematically affect particle and crystallite dimensions of synthetic graphite LK-702 is reported. Samples were characterized by percent mass loss, X-ray powder diffraction, scanning electron microscopy, Brunauer-Emmett-Teller (BET) surface area, and methylene blue adsorption surface area measurements. The treated graphites were studied as possible electrode materials for Li-ion cells. The BET and methylene blue surface areas increased for treatment times up to 48 h, then remained constant. For times up to 48 h, Ar treatment was demonstrated to break apart larger graphite particles, narrowing the particle size distribution. The irreversible capacity of the graphite decreased substantially with increased Ar treatment time, while the reversible capacity remained unchanged.