Highly efficient electro-optically tunable smart-supercapacitors using an oxygen-excess nanograin tungsten oxide thin film

Inamdar, AI and Kim, J and Jo, Y and Woo, H and Cho, S and Pawar, SM and Lee, S and Gunjakar, JL and Cho, Y and Hou, B and Cha, SN and Kwak, J and Park, Y and Kim, H and Im, H (2017) Highly efficient electro-optically tunable smart-supercapacitors using an oxygen-excess nanograin tungsten oxide thin film. Solar Energy Materials and Solar Cells, 166. pp. 78-85. ISSN 0927-0248

Abstract

A smart supercapacitor shares the same electrochemical processes as a conventional energy storage device while also having electrochromic functionality. The smart supercapacitor device can sense the energy storage level, which it displays in a visually discernible manner, providing increased convenience in everyday applications. Here, we report an electro-optically tunable smart supercapacitor based on an oxygen-rich nanograin WO electrode. The nanostructured WO electrode is dark blue in color in the charged state and becomes transparent in its discharged state with a high optical modulation of 82%. The supercapacitor has a specific capacitance of 228 F g at 0.25 Ag with a large potential window (1.4 V). It is highly durable, exhibits good electrochemical stability over 2000 cycles, retains 75% of its initial capacitance, and exhibits high coloration efficiency (~170 cm /C). The excellent electrochromic and electrochemical supercapacitor properties of the electrode is due to the synergetic effect between nanograin morphology and excess oxygen. A smart-supercapacitor fabricated with an oxygen-rich nanograin WO electrode exhibits a superb combination of energy storage and highly-efficient electrochromic features in one device that can monitor the energy storage level through visible changes in color. 3 3 3 −1 −1 2