Zn2+ intercalation/de-intercalation-based aqueous electrochromic titanium dioxide electrode with Zn-ion storage

The popularity of intelligent electronic products demands suitable smart electrodes with high specific capacitance, superior durability, and intrinsic safety. Herein, a bifunctional titanium dioxide (TiO 2 ) electrode with electrochromic energy storage in the Zn-ion aqueous electrolyte was demonstrated. The color of the electrode can be changed according to its charging state by Zn 2+ intercalation/de-intercalation, to realize the noticeable judgment and prediction of the energy contained. Direct growth of TiO 2 by the hydrothermal method effectively increases the bonding force between the active TiO 2 material and the substrate. Electrochemical results show that the TiO 2 electrode has high specific capacitance of 139.8 mF·cm −2 at 1.5 mA·cm −2 , and retains 93% of the initial areal specific capacitance after 100 CV cycles. In addition, it exhibits high transmittance contrast of 45% at a wavelength of 980 nm in the near-infrared region, short bleaching time (6.5 s) and coloration time (18.0 s) at an alternating potential between 0 and − 1.1 V. These superior electrochemical and electrochromic performances can be attributed to the fast Zn 2+ diffusion facilitated by the porous structure and short ion diffusion distance of the TiO 2 electrode.