RESUMEN
A dual redox process involving Ti3+/Ti4+ cation species and S2-/(S2)2- anion species is highlighted in oxygenated lithium titanium sulfide thin film electrodes during lithium (de)insertion, leading to a high specific capacity. These cathodes for all-solid-state lithium-ion microbatteries are synthesized by sputtering of LiTiS2 targets prepared by different means. The limited oxygenation of the films that is induced during the sputtering process favors the occurrence of the S2-/(S2)2- redox process at the expense of the Ti3+/Ti4+ one during the battery operation, and influences its voltage profile. Finally, a perfect reversibility of both electrochemical processes is observed, whatever the initial film composition. All-solid-state lithium microbatteries using these amorphous lithiated titanium disulfide thin films and operated between 1.5 and 3.0 V/Li+/Li deliver a greater capacity (210-270 mAh g-1) than LiCoO2, with a perfect capacity retention (-0.0015% cycle-1).
RESUMEN
CuO thin films were prepared by radio frequency magnetron sputtering using a copper target in a (Ar + O2) reactive mixture. Different sputtering parameters were varied including oxygen flow rate, total pressure, target-substrate distance, substrate temperature and target orientation. As expected, the thin film chemical composition is strongly dependent on the oxygen flow rate. CuO thin films having a good electronic conductivity (9.3 × 10(-1) S·cm(-1)) were obtained with an oxygen concentration of 12%. The texture and the columnar growth are amplified when the target is tilted. Preliminary electrochemical results highlight that CuO thin film performances in lithium systems are tightly related to their morphology and structure.