Solid-state thin-film batteries using LiMnPO 4 thin films as positive electrodes were fabricated and the electrochemical properties were characterized. The LiMnPO 4 thin films were deposited on Pt coated glass substrates by pulsed laser deposition. In-plane X-ray diffraction revealed that the LiMnPO 4 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 100 Pa. The electrochemical measurements indicate that the LiMnPO 4 films show charge and discharge peaks at 4.3 V and 4.1 V, respectively. The electrical conductivity of the LiMnPO 4 film was measured by impedance spectroscopy to be 2 × 10 −11 S cm −1 at room temperature. The solid-state thin-film batteries that show excellent cycle stability were fabricated using the LiMnPO 4 thin film. Moreover, the chemical diffusion of the LiMnPO 4 thin film was studied by cyclic voltammetry. The chemical diffusion coefficient of the LiMnPO 4 thin film is estimated to be 3.0 × 10 −17 cm 2 s −1 , which is approximately four orders magnitude smaller than the LiFePO 4 thin films, and the capacity of the thin-film battery was gradually increased for 500 cycles.

LiMnPO4with olivinestructure which is the promising candidate for high voltage cathode material was synthesized by hydrothermal method. In order to synthesize high purity and well-defined LiMnPO4, several precursors for Li, Mn, and P sources and hydrothermal reaction parameters including temperature and [H2O]/[Mn] value are optimized. By analyzing the structure, Mn valence, morphology, and chemical ratio via XRD, XPS, Raman, SEM, and ICP LiMnPO4synthesized from manganese acetate tetrahydrate have single phase of LiMnPO4without impurity and showed charge and discharge reaction caused by Mn2+/Mn3+redox. Specific capacity of synthesized LiMnPO4grew up during cycling. Moreover, when hydrothermal temperature was set at 150°C and [H2O]/[Mn] value was set at 15, discharge capacity as high as 70 mAh/g was obtained at1/20  Crate.

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