In this paper, we report an electrochromic device (ECD) using novel porous TiO2@prussian blue core-shell nanostructures as electrodes. The core-shell nanostructures were formed by coating prussion blue (PB) on TiO2 nanorod templates through two-step soft chemical methods. The surface area of PB is remarkably enlarged and the diffusion length of ions is notably shortened due to the distinct porous morphology of the nanostructures, resulting in highly increased storage capacity of K+ ions in electrochromic process. Compared with the ECD based on dense PB film, higher optical contrast (48%) and faster response speed (t(c) = 6.2 s, t(b) =2.2 s) are realized in the TiO2@PB core-shell structures. In particular, the coloration efficiency of the ECD based on the core-shell nanostructures is significantly improved to 131.5 cm(2) C-1 at 700 nm. Moreover, a model of insertion/extraction of K+ ions was proposed to interpret the enhanced electrochromic performance of core-shell nanostructures. (C) 2016 Elsevier Ltd. All rights reserved.