Fast charge-transfer at the self-assembled solid electrolyte interface (SEI) has been obtained in an all-solid-state ceramic lithium battery. The SEI phase was formed between a Li-Al anode and the thio-LISICON (Li3.25Ge0.25P0.75S4) solid electrolyte by applying current though the cell. After the spontaneous formation of the SEI phase, the interfacial resistance fluctuated and decreased to constant values during the charge-and-discharge process. The breathing interface effectively makes a close contact at the electrolyte/electrode boundary and promotes fast charge transfer at the solid-interface. The self-assembled SEI phase is a general concept of interfacial design and will play a crucial role in the development of all solid-state batteries. (C) 2004 The Electrochemical Society.