Dual Cation- and Anion-Based Redox Process in Lithium Titanium Oxysulfide Thin Film Cathodes for All-Solid-State Lithium-Ion Batteries

A dual redox process involving Ti³⁺/Ti⁴⁺ cation species and S^2–/(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 S^2–/(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)

Thorough Characterization of Sputtered CuO Thin Films Used as Conversion Material Electrodes for Lithium Batteries

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

Iron(III) Phosphates Obtained by Thermal Treatment of the Tavorite-Type FePO₄·H₂O Material: Structures and Electrochemical Properties in Lithium Batteries

Thermal treatment of the Tavorite-type material FePO₄·H₂O leads to the formation of two crystallized iron phosphates, very similar in structure. Their structural description is proposed taking into account results obtained from complementary characterization tools (thermal analyses, diffraction, and spectroscopy). These structures are similar to that of the pristine material FePO₄·H₂O: iron atoms are distributed between the chains of corner-sharing FeO₆ octahedra observed in FePO₄·H₂O and the octahedra from the tunnels previously empty, in good agreement with the formation of a Fe_4/3PO₄(OH)-type phase. The formation of an extra disordered phase was also proposed. These samples obtained by thermal-treatment of FePO₄·H₂O also intercalate lithium ions through the reduction of Fe³⁺ to Fe²⁺ at an average voltage of ∼2.6 V (vs Li⁺/Li), with a good cyclability and a reversible capacity around 120 mA h g^–1 (>160 mA h g^–1 during the first discharge)