Electrode/electrolyte interface was studied for all solid-state batteries using inorganic solid electrolyte with the crystalline thio-LISICON and glassy Li-Si-P-S-O systems. The formation of the interfacial phase depends on the electrolyte. The thio-LISICON (Li3.25Ge0.2.5P0.75S4) and the Li-Al negative electrode provided the best electrode/electrolyte interface for fast charge-discharge characteristics, while the SEI phase formed at the Li-Al/Li3PO4-Li2S-SiS2 glass boundary caused high interfacial resistance. The formation of the SEI phase is general behavior at the electrode/electrolyte interface of solid-state batteries, and the fast electrochemical reaction is attained as a result of optimization of the electrode/electrolyte combination. (C) 2008 Elsevier Ltd. All rights reserved.