Insight into the intercalation problem of the Li/CuO cell by analytical electron spectroscopies

Abstract

CuO-based cathodes partially discharged using high-density current have been studied by analytical electron spectroscopies with the aim of elucidating the cell-discharge mechanism with particular reference to the formation of an Li_xCuO intercalation phase. The most interesting spectroscopic data of involved Cu species are reported and discussed. The disappearance of Cu^II at the cathode surface just at the beginning of the cell discharge and the formation of Cu^O and/or Cu^I were observed. The calculated modified Auger parameter values allowed characterization of Cu^I and Cu^O and distinction to be made between them when both were present. The presence of Cu^I has been rationalized on the base of an after-discharge solid-state reaction between electrochemically produced metallic copper and the underlying CuO. These results, together with the inhomogeneous depth profile of Li species concentration, seem to exclude the hypothesis of the formation of a genuine intercalation phase. At the same time an alternative explanation based on a ‘porous electrode’ model is suggested for the electroanalytical data reported by other authors and interpreted in terms of the formation of an intercalation phase.