Fabrication of thin-film batteries composed of LiCoO2, Li3PO4, and Li layers

This paper reports the fabrication of thin film batteries which are composed of three stacking layers; LiCoO2, Li3PO4, and Li. First, a LiCoO2 layer is constructed on an electron-conductive substrate by pulsed laser deposition as a cathode. Crystallinity of LiCoO2 layer is mainly controlled by cationic ratio of Li and Co. Subsequently, an amorphous Li3PO4 layer with a high ionic conductivity is further deposited on the cathode LiCoO2 layer by radio frequency magnetron sputtering as a solid electrolyte. To avoid any possible damage which causes the formation of resistive species between LiCoO2 and Li3PO4, bias control of the substrate during Li3PO4 deposition is essential. Finally, a Li metal layer is deposited as an anode/current collector on the Li3PO4/LiCoO2 bilayer by resistive heating evaporation in vacuum at elevated temperature for the formation of low resistive interface. The fabricated three-layer thin film battery shows a high-rate capability when LiCoO2 layer is (104) oriented epitaxial film.