The course of the conversion reaction during the electrochemical
insertion/deinsertion of lithium in CuO thin film electrodes was surveyed
by cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS).
The electrochemical processes were studied through the comprehensive
acquisition and interpretation of XPS and Auger spectra (Cu 2p, O
1s, Cu LMM) recorded at different stages of the first cycle of a Li/CuO
cell. The reduction process consisting of three main steps leads successively
to Cu+ and Cu0 and involves a Li2O2 peroxide type phase as an intermediate, whereas Li2O is the main lithiated oxide at the end of the discharge.
Only the two last steps appear reversible in charge. No evidence of
Cu2+ was found at the end of the charge at 3.5 V/Li+/Li, showing the irreversibility of the first step in our
experimental conditions. Complementary XPS depth profile analyses
were performed to check the evolution of the active material composition
over the thickness of the electrode.
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