Tuning interlayer environment of V2C MXene by cobalt ion intercalation to boost zinc ion transfer kinetics in aqueous zinc-ion hybrid capacitors

Abstract

Zn-ion hybrid capacitors (ZIHCs) combined the high energy density of battery-type electrodes with the high power density of capacitor-type electrodes have shown great potential for next-generation energy storage. However, the limited capacity of conventional carbon-based cathode materials does not meet the requirements of practical applications. In this study, a universal and effective electrostatic self-assembly strategy has been proposed and developed for synthesizing the Co2+ ions intercalated V2C cathodes to boost the kinetics of Zn2+ ion transport and achieve excellent electrochemical reversibility and chemical stability. By adjusting the amount of intercalated Co2+ ions, the optimal ratio of sample (2:1 V2C-Co) showed an excellent specific capacity of 333 mAh g−1 at a current density of 0.1 A g−1 and an admirable rate performance of 175 mAh g−1 at 5 A g−1. Furthermore, the specific capacity retains 67 % of the initial value after 3000 cycles at 5 A g−1. This work provides an effective method for developing high efficient V2C cathodes for advanced aqueous zinc-ion hybrid capacitors.