High-energy asymmetric electrochemical capacitors based on oxides functionalized hollow carbon fibers electrodes

By Li, Ting; Zhang, Wenliang; Zhi, Lei; Yu, Hang; Dang, Liqin; Shi, Feng; Xu, Hua; Hu, Fangyuan; Liu, Zonghuai; Lei, Zhibin; Qiu, Jieshan
Published in Nano Energy NULL 2016

Abstract

Abstract Asymmetric supercapacitors (ASC) using traditional porous carbon as negative electrode usually suffer from low energy density. Herein, we report a high-performance negative electrode by growing columnar Fe2O3 nanorods vertically on activated hollow yet conductive carbon fiber (aCF), featuring bundled nanorods with a diameter of 50-70 nm and a length of 200-300 nm. The porous nature originated from the unique assembly of these Fe2O3 nanorods results in large electrochemically active surface area, yielding a high specific capacitance of 988 F g?1 in 2.0 M {KOH} electrolyte. An asymmetric capacitor with aCF-Fe2O3 as negative electrode and nickel-cobalt double hydroxide (NiCo-DH) grown on aCF as positive electrode showed an extended working voltage window up to 1.6 V in aqueous KOH, thus delivering a maximum energy density of 83.7 Wh kg?1 at the power density of 392.3 W kg?1. Interestingly, the {ASC} exhibits remarkable cycling stability with 94.6% capacitance retention even after 10000 cycles of charge-discharge. These performances are far superior to most of previous {ASCs} with respect to energy density, rate capability or cycling stability. It has been demonstrated that two {ASCs} connected in series are able to power various electronic devices, including a red light-emitting diode indicator, toy car, a fun and an electronic timer.

Read » Back