Characterization of Cu3N/CuO thin films derived from annealed Cu3N for electrode application in Li-ion batteries

Highlights: • Cu₃N/CuO thin film was prepared by simply anneal at low temperature in air. • The Cu₃N enhances the transport of Li⁺ ions and electrons in CuO thin film. • The prepared electrodes own high electrochemical performance. -- Abstract: Flexible lithium-ion batteries have attracted tremendous attention as a promising power source in the growing field of flexible electronic devices. CuO shows high theory specific capacity in Li-ion storage, but it also suffers poor electrochemical cycling stability arising from the low conductivity during the lithium uptaking/releasing process. In this work, we report a simple and binder free for the synthesis of flexible Cu₃N/CuO thin film electrodes directly on Ni foam by magnetron sputtering method followed with annealing in air at low temperature. This method is highly effective in improving the rate capability of the 300 °C treated Cu₃N/CuO (CNO-300) electrode with discharge capacity of 605 mAh g⁻¹ at 400 mA g⁻¹ after 300 cycles, which is close to the theoretical capacity. The CNO-300 thin film electrode also shows remarkable cyclic performance retaining about 100% of the initial capacity (534 mAh g⁻¹) after 1000 cycles at 1000 mA g⁻¹.