Metal-oxidized graphite composite electrodes for lithium-ion batteries

The electrochemical behavior of composite electrodes obtained by mixing graphite (Timrex KS-15 by Timcall), partially oxidized by thermal treatment, with nanometric metal particles (Au, Ag, Ni, Cu, Al, Sn) at about 1% (w/o) is presented. The charge-discharge properties of the composite electrodes have been studied in the temperature range 20 to -30 degrees C in 1 M LiPF6 EC-DEC-DMC (1:1:1). The main effect is a general improvement of the cycling behavior at any temperature. In particular, at -30 degrees C about 30% of the theoretical intercalation capacity is retained by electrodes containing Cu, Al and Sn. At the same temperature, the composites containing the above metals show evidences of lithium staging. This may indicate that certain metals affect the kinetics of phase transformation that, together with other effects including charge transfer resistance, lithium diffusion coefficient and polarization due to SEI and solvent conductivities, seems to be the main cause of the poor intercalation capacity of graphite anodes at low temperature. (C) 2005 Elsevier Ltd. All rights reserved.