Fabrication of solid-state thin-film batteries using LiMnPO4 thin films deposited by pulsed laser deposition

Solid-state thin-film batteries using LiMnPO4 thin films as positive electrodes were fabricated and the electrochemical properties were characterized. The LiMnPO4 thin films were deposited on Pt coated glass substrates by pulsed laser deposition. In-plane X-ray diffraction revealed that the LiMnPO4 thin films were well crystallized and may have a texture with a (020) orientation. The deposition conditions were optimized; the substrate temperature was 600°C and the argon pressure was 100Pa. The electrochemical measurements indicate that the LiMnPO4 films show charge and discharge peaks at 4.3V and 4.1V, respectively. The electrical conductivity of the LiMnPO4 film was measured by impedance spectroscopy to be 2×10−11Scm−1 at room temperature. The solid-state thin-film batteries that show excellent cycle stability were fabricated using the LiMnPO4 thin film. Moreover, the chemical diffusion of the LiMnPO4 thin film was studied by cyclic voltammetry. The chemical diffusion coefficient of the LiMnPO4 thin film is estimated to be 3.0×10−17cm2s−1, which is approximately four orders magnitude smaller than the LiFePO4 thin films, and the capacity of the thin-film battery was gradually increased for 500cycles.