An interface consisting of Li4Ti5O12 film electrode and Li1+xAlxTi2-x(PO4)(3)-based NASICON (sodium superionic conductor)-type solid electrolyte (LTP) was prepared by a sol-gel coating method. The prepared solid-solid electrochemical interface was evaluated by cyclic voltammetry, galvanostatic discharge-charge test, and ac impedance method. The measured impedance of the interface between Li4Ti5O12 and LTP was about 1000-2000 Omega cm(-2), and compressed semicircles were observed at all electrode potentials, indicating a presence of potential distribution at the electrochemical interface due to poor solid-solid contact between Li4Ti5O12 and LTP. In cyclic voltammograms of this electrochemical interface, a highly reversible sharp redox peak was observed at around 1.55 V. From discharge-charge tests, Li4Ti5O12 thin-film electrode on LTP showed high reversibility during discharge and charge cycles, and it exhibited discharge capacities of 160 mAh g(-1) at 0.1 C rate and 106 mAh g(-1) at 5 C rate, respectively. (c) 2005 The Electrochemical Society.