Electrochemical characteristics of graphite coated with tin-oxide and copper by fluidised-bed chemical vapour deposition

Anodes for a lithium secondary battery are prepared with synthetic graphite (meso-phase carbonaceous microbead: MCMB) which is coated with tin-oxide and copper by fluidised-bed chemical vapour deposition (FCVD). In the present study, three different samples was prepared, and their electrochemical characteristics are examined by using X-ray diffraction, electrochemical voltage spectroscopy (EVS), scanning electron micrography, ac impedance measurements, and galvanostatic charge-discharge experiments. The electrode coated with tin-oxide gives higher capacity than uncoated MCMB, but the capacity decreases with cycling. This is probably due to severe volume changes. The cycleability is improved, however, by coating copper on the surface of the carbonaceous material coated with tin-oxide. The copper plays an important role as an inactive matrix which provides a buffer against volume changes.