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High electrochemical performance and lithiation–delithiation phase evolution in CuO thin films for Li-ion storage

Chen, Wenhao, Zhang, Hong, Ma, Zhiyuan, Yang, Bao, Li, Zhicheng
Journal of materials chemistry A 2015 v.3 no.27 pp. 14202-14209
copper, cupric oxide, cuprous oxide, electrochemistry, electrodes, films (materials)
Magnetron sputtered CuO thin films with a hierarchical structure and large specific surface were prepared, and their electrochemical properties and reaction characteristics as the Li-ion storage electrodes were investigated. The nanostructured CuO thin film showed a high capacity, good cycling stability and excellent rate performance and exhibited discharge capacities of 703 mA h g⁻¹ at 100 mA g⁻¹ and 465 mA h g⁻¹ at 1000 mA g⁻¹ even after 100 electrochemical cycles. Transmission electron microscopy was applied to investigate the phase evolution of the CuO thin film after being electrochemically induced at various stages in the 3ʳᵈ lithiation–delithiation cycle. An intermediate phase of Cu₄O₃, besides Cu and Cu₂O products, was identified in the CuO electrode during the electrochemical process. The investigation of phase evolution revealed that the CuO active materials were partially reduced to Cu₄O₃, followed by being reduced to Cu₂O and Cu during the discharge process, whereas the reversible electrochemical reactions Cu → Cu₂O → Cu₄O₃ → CuO took place during the charging process.