Water-based asymmetric supercapacitors with 2.5 V wide potential and high energy density based on Na0.6CoO2 nanoarray formed via electrochemical oxidation
Zhiqiang Liu, Yanling Qiu, Liang Cui, Rongkun Zheng, Wenrong Yang, Colin J. Barrow, Joselito M. Razal, Jingquan Liu
Abstract
The voltage limit of water-based asymmetric supercapacitors is usually 2 V, which prevents further improvement of energy density. Na0.6CoO2 nanoarrays with high Na content are formed on carbon cloth (CC) by cyclic electrochemical oxidation (EO) and can work stably in 0–1.2 V wide potential, and the specific capacitance is up to 575.98C g−1 at 1 A g−1. Using carbon coated Fe2O3 nanoarrays on CC as the negative electrode and Na0.6CoO2/CC as the positive electrode, a water-based asymmetric supercapacitor (ASC) which can operate stably in 0–2.5 V wide voltage window is assembled. The Na0.6CoO2/CC//Fe2O3@C/CC ASC exhibits an energy density of 133.92 Wh kg−1 at a power density of 1250 W kg−1, which is better than previously reported Co-based supercapacitors. This study provides a scheme for the working voltage of water-based ASCs to be further expanded to more than 2 V. Utilizing cationic pre-inserted Co3O4 nanoarray to construct high operating voltage composite electrode should have broad application prospect.