Corncob-Derived Hierarchical Porous Activated Carbon for High-Performance Lithium-Ion Capacitors
Shuhua Yang, Le Zhang, Jing Sun, Kui Li, Songfang Zhao, Degang Zhao, Jieqiang Wang, Chao Yang, Xiutong Wang, Bingqiang Cao
Abstract
Lithium-ion capacitors (LICs) are hybrid energy storage devices with a capacitor-type cathode and battery-type anode, which bridge the gap between conventional high-energy lithium-ion batteries and high-power capacitors. It is still a challenge for high energy density at high power density. In this article, corncob-derived hierarchical porous activated carbons (ACs-X) are prepared through a H2SO4-assisted hydrothermal treatment with subsequent activation and are used as a capacitor-type cathode. The amount of H2SO4 plays significant roles on the microstructures of the ACs-X during the process of hydrothermal treatment. Specifically, the optimized ACs-1.5 exhibits rationally hierarchical porous structures with huge specific surface area, improved graphitization degree, and enough pore volume. Consequently, the enhanced specific capacitance of 251 F g–1 at 0.3 A g–1 and outstanding rate capability are realized. ACs-1.5//Fe3O4/G LICs are constructed, exhibiting a splendid energy density of 118 Wh kg–1 at a large power density of 3726 W kg–1, comparable or excelling to previously reported LICs. Furthermore, the ACs-1.5//Fe3O4/G LICs exhibited long cycling stability with a capacitance retention of 88.7% after 5 000 cycles at 2 A g–1 within the voltage range of 1–4.0 V.