An Aqueous Zn-Ion Hybrid Supercapacitor with High Energy Density and Ultrastability up to 80 000 Cycles

Integrating a battery-type electrode to build a hybrid supercapacitor is a promising approach to improve the overall energy density of a supercapacitor-type energy storage device without sacrificing its power output. However, this strategy is usually achieved at the expense of cycling lifespan. In this work, a hybrid supercapacitor comprising Zn foil and porous carbon derived from chemical activated graphene (aMEGO) is developed, and the trade-off between energy density and cycling life is well-balanced by the utilization of 3 _M Zn(CF₃SO₃)₂ electrolyte with high Zn stripping/plating efficiency. Such a hybrid supercapacitor demonstrates an energy density of 106.3 Wh kg^-1 and a power density of 31.4 kW kg^-1, and significantly a wide operation voltage of 1.9 V is achieved in aqueous electrolyte. Benefitting from the high Zn stripping/plating efficiency, the Zn-aMEGO hybrid-supercapacitor also exhibits an ultralong cycling life up to 80 000 cycles with capacity retention of 93%, which is comparable to that of conventional electrochemical double-layer capacitors.