第25回 GREENオープンセミナー

In this talk, fabrication technique of solid-state thin-film batteries (TFBs) using pulsed laser deposition (PLD) is reported. TFBs are fabricated by depositing layers of cathode, electrolyte and anode. We use several transition metal oxides (LiCoO2, LiMn2O4, and LiCoMnO4) as a cathode layer. As a solid electrolyte, amorphous lithium phosphate is deposited from ceramic Li3PO4 target. Although the oxide electrolytes show lower ionic conductivity than sulfides, the resistance of the electrolyte layer is small enough to operate thin-film batteries. The anode layer is selected by the electrochemical stability of electrolyte. Lithium metal can be used for L-P-O electrolyte.

　TFBs are also applied to a fundamental study of lithium intercalation in solid-state batteries. We use in situ Raman spectroscopy to measure the structural change of cathode materials (LiCoO2 and LiMn2O4) in TFBs. Detailed information of the phase transition is obtained related to lithium insertion/extraction in TFBs. Very slow movement of phase-boundary is also observed in solid-state batteries.