Synthesis and electrochemical property of LiCoO2 thin films composed of nanosize compounds synthesized via nanosheet restacking method

LiCoO2 thin films with nanosize particles were synthesized on Au substrates by nanosheet restacking method and subsequent hydrothermal reaction which needs less cost than the vacuum deposition methods. The grain size of LiCoO2 films estimated by XRD reflection was about 15 nm that was independent of the thickness of precursor cobalt hydroxide film. Comparing the rate performance of the thin films with various thickness, the optimum performance was obtained by the thin film with 5 min deposition time: 62% of the capacity was held at 400 C-rate compared with that at 20 C-rate. The results of AC-impedance analysis of electrode reaction indicate that the high rate capability of the LiCoO2 film is obtained by the small grain size and large surface area of LiCoO2 thin film with nano size particles.