Designing a Zn(BF4)2-Based Ionic Liquid Electrolyte to Realize Superior Energy Density in a Carbon-Based Zinc-Ion Hybrid Capacitor

Carbon-based zinc-ion hybrid capacitors (C-ZIHCs), inheriting the merits from supercapacitors and batteries, exhibit promise in energy-storage technologies. However, unsatisfactory energy density still hinders their practical applications for most reported C-ZIHCs. We report a novel Zn(BF4)(2)/[EMIM]BF4 electrolyte to construct C-ZIHCs with a high energy density. The Zn(BF4)(2)/[EMIM]BF4 electrolyte features high reductive/oxidative stability, which guarantees no significant dendrites and side reactions to corrode the Zn anode during the charging/discharging process, and achieves ultrafast Zn plating/stripping with a high coulombic efficiency (>99 %) and unprecedented cycling stability (over 1200 h). By virtue of the excellent properties of the electrolyte, C-ZIHCs is built to exhibit a high average output voltage (1.9 V), a high energy/power density (220 Wh kg(-1)/9.5 KW kg(-1)), and a long cycle life (95 % capacity retention after 20000 cycles). Herein, we report the use of Zn salt-based ionic liquid as an electrolyte to construct C-ZIHCs, which provides a new opportunity for the development of C-ZIHCs with excellent comprehensive performance.

Automated summary

This study demonstrates the use of a novel electrolyte to construct C-ZIHCs with high energy density, ensuring stability and long cycle life during charging/discharging processes.