Quinone/Ester-based Oxygen Functional Groups Enhanced Full Carbon Li-ion Capacitor
Lithium ion capacitors (LICs) are regarded as one of the most promising energy storage devices since they can bridge the gap between lithium ion batteries and supercapacitors. However, the mismatches in specific capacity, high-rate behavior, and cycling stability between the two electrodes are the most critical issues needed to be addressed, seriously limiting large energy density and long cycling life of LICs at the output of high-power density. Herein, quinone and ester-type oxygen-modified carbon is successfully obtained by chemical activation with alkali, beneficial to the absorption of the PF6- together with lithium ion, which would largely improve the electrode kinetics. Greatly, the cathode capacity is obviously enhanced with the increase of the amount of oxygen functional groups. Moreover, for the full carbon LIC device, an energy density of 144 Wh kg-1 is exhibited at the power density of 200 W kg-1. Surprisingly, even after 10000 cycle at 20000 W kg-1, a capacity retention of 70.8% is successfully achieved. These remarkable results could be ascribed to the enhancement of cathode capacity and the acceleration of anode kinetics. Furthermore, the density functional theory (DFT) calculations prove that the oxygen functional groups can deliver an enhanced electrochemical activity for lithium storage through surface-induced redox reactions. This elaborate work may open an avenue for resolving the imbalances for the electrode materials of LICs and deepen the understanding on the surface engineering strategies of oxygen-functional groups.
- This article is part of the themed collection: 2020 Nanoscale HOT Article Collection