EQCM study during lithium insertion/deinsertion processes in Nb 2O 5 films prepared by polymeric precursor method

Abstract

The electrochemical quartz crystal microbalance (EQCM) technique was used to study two chemically distinct Nb 2O 5 electrochromic thin films (one pure and the other lithium-doped) during the lithium electroinsertion reaction. In the initial cycles, the electrode showed an irreversible mass variation greater than expected for Li + insertion/deinsertion processes, which was attributed to the wettability effect (allied to the porous morphology) that emerged as the dominant process in apparent electrode mass changes. As the cycles progressed, the mass variation stabilized and the changes in apparent mass became reversible, showing a good correlation with the charge variations. The results generally indicated that the Li + insertion/deinsertion process occurred more easily in the Nb 2O 5-doped film, which also displayed a greater capacity for Li + insertion. However, a total mass/charge balance analysis revealed that the stoichiometry of the Li + solid state insertion/deinsertion reaction was similar in the two electrodes under study.