Electrochemically reduced cobalt-graphite intercalation compound

The reactions occurring during electrochemical reduction within a lithium battery system have been studied using a cobalt chloride-graphite intercalation compound as positive electrode. The reduction mechanism is a semi-infinite diffusion of lithium between the graphite layers along with an irreversible charge transfer between lithium ions and graphite. A washing process, intended to remove impurities such as lithium chloride, leads to the cobalt-GIC. Its rough formula is Co0.7C11(CoCl2)0.3(LiC1)0.5 determined through elemental analysis. Structural theoretical calculations, X-ray diffraction (XRD),transmission electron microscopy (TEM) observations, extended X-ray absorption fine structure (EXAFS) and magnetic experiments have been carried out on this compound. The results indicate that the reduced compound is, in its major part, a first-stage cobalt-graphite phase CoC2 with an ABC commensurate structure, constituted of two-dimensional islands, randomly distributed in the graphite structure. The crystallographic parameters for this hexagonal structure are a = 0.248nm, and c = 1.68nm equal to three times the identity period. An elastic balls-elastic graphitic networks model can explain this structure.