Mesoporous Thorn-Covered Core-Shell Cathode and 3D Reduced Graphene Oxide Aerogel Composite Anode with Conductive Multivalence Metal Sulfides for High-Performance Aqueous Hybrid Capacitors

Abstract

Aqueous hybrid capacitors (AHCs) are very promising electrochemical energy devices due to their being safe, cheap, and environmentally friendly, but their low energy and power densities are yet to be overcome for prolonged operation in a single fast charging device. Herein, a strategy to realize high-energy density and ultrafast rechargeable AHCs is reported. A thorn-covered core-shell conductive multivalence metal sulfide is synthesized as a cathode material that achieves high capacity via multivalence Ni and Co states and contains multiple mesoporous channels for fast ion transfer and ultrafine nanoparticles for efficient contact with electrolyte ions. Moreover, the multivalence metal states of the Fe1-xS anode units loaded on a three-dimensional carbon structure with the mesoporous holes attain high capacity even at a very fast charging rate (20 A g(-1), approximate to 86.4 C rate). The proposed AHC exploits the advantages of capacitive and diffusion-controlled reactions. This is demonstrated by its high-energy density (up to 120.5 Wh kg(-1)) surpassing that of state-of-the-art AHCs and the ultrafast rechargeable power density (up to 23,998 W kg(-1)) that exceeds those of battery-type reactions more than 100-fold and provides long-life stability for over 50 000 charge-discharge cycles.