Fabrication of LiCoO₂ films for lithium rechargeable microbattery in an aqueous solution by electrochemical reflux method

LiCoO₂ films were directly deposited on electron-conducting substrates using electrochemical reflux method in an aqueous solution under ambient atmosphere at a fixed temperature between 100 and 200°C with a fixed current density between 0.1 and 1.0 mA cm^-2. The structural and compositional purities of the deposited LiCoO₂ film were confirmed by elemental analyses, X-ray diffraction pattern analyses, and Raman spectroscopy. According to the Raman spectroscopy and the voltage versus capacity profiles for the deposited LiCoO₂ film, it appears that the deposited film consists of layered LiCoO₂ phase (space group R̄3m). Although the deposited LiCoO₂ film was fabricated in a very economical and simple way, it exhibits an initial discharge capacity of 54.1 μAh/cm ² μm and the discharge capacity retention of 85.6% over 15 cycles.