In this work, we have been increasingly interested in the direct synthesis of the electro-active Cu0.5Fe0.5F2 thin films electrodes by Pulsed Laser Deposition approaches. Thin film depositions were performed from high purity LiF, Fe and Cu mixed targets (mol ratio 4:1:1) at room temperature. The initial electrochemical oxidation occurs at the first charge to form solid-solution Cu0.5Fe0.5F2 shown in the CV curve. During the delithiation process, the oxidation of Fe (Fe0 to Fe2+) occurs at 3.0 V, and further oxidation to higher valence state at 3.3 V. In the higher voltage region, the oxidation peak at 3.8 V indicated the conversion from Cu0 to Cu2+ and the forming of solid-solution Cu0.5Fe0.5F2. The lithiation process is quite different from the charge process. The CV curve clearly indicated the reduction of Fe and Cu presented overlap range from 3.7 V to 3.2 V, which may promoted the conversion to forma disordered rutile-like Cu–Fe–F phase. The final results may weaken the low hysteresis of Fe and the dissolution of Cu. The novel ternary metal fluoride is appealing for use in all-solid-state thin film Li-ion batteries.
Fig.1 The cyclic voltammetry curve of Cu0.5Fe0.5F2 at scan rate 0.1 mV/s.
Reference
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