Abstract:
Cation additives can efficiently enhance the total electrochemical capabilities of zinc-ion hybrid capacitors (ZHCs). However, their energy storage mechanisms in zinc-based systems are still under debate. Herein, we modulate the electrolyte and achieve dual-ion storage by adding magnesium ions. And we assemble several Zn//activated carbon devices with different electrolyte concentrations and investigate their electrochemical reaction dynamic behaviors. The zinc-ion capacitor with Mg
2+ mixed solution delivers 82 mAh·g
−1 capacity at 1 A·g
−1 and maintains 91% of the original capacitance after 10000 cycling. It is superior to the other assembled zinc-ion devices in single-component electrolytes. The finding demonstrates that the double-ion storage mechanism enables the superior rate performance and long cycle lifetime of ZHCs.