Sputter-Deposited Amorphous Li 3 PO 4 Solid Electrolyte Films.

This paper reports the thin-film synthesis of Li 3 PO 4 solid electrolytes by RF magnetron sputtering. A relatively high ionic conductivity of more than 1 × 10 -6 S cm -1 is achieved. It is revealed that the crystallization of Li 3 PO 4 impedes ionic conduction, and a moderate amount of O 2 addition to Ar suppresses the crystallization and guarantees long-term deposition. Another important finding in this study is that when Li 3 PO 4 is deposited on a LiCoO 2 film to construct a thin-film battery, the LiCoO 2 film can be damaged depending on the substrate bias potential relative to the cathode potential propagated through the sputtering plasma. Active control of the bias potential to avoid the damage realizes negligible interface resistance in the thin-film battery.