NaTi2(PO4)(3) (NTP) thin-film electrode was synthesized by sol-gel method. The thin-film consisted of NTP single phase and the morphology was dispersion of nano-particles, rather than flat film. The electrochemical behavior in aqueous solution was studied by cyclic voltammetry and A. C. impedance spectroscopy. Cyclic voltammogram showed the clear redox current pair corresponding to the Na+- ion insertion and extraction. From the impedance plot, a semi-circle ascribed to the charge transfer resistance (Rct) was observed. The interfacial activation energy estimated from the temperature dependency of Rct was 26 kJ mol(-1), which was much smaller than that of Li+- ion in lithium-ion batteries. These results indicated that aqueous sodium-ion batteries with NTP electrode would promise to deliver the extensive high power. (C) The Author(s) 2016. Published by ECS.