Bi-Cation Electrolyte for a 1.7 V Aqueous Zn Ion Battery.

Rechargeable aqueous zinc-ion batteries (ZIBs) are receiving increased attention because of their high safety and low cost. However, their practical application is plagued by their low energy density as a result of low output voltage and a narrow voltage window of aqueous electrolytes. Here, we explored a ZIB with a wider potential window using bication (1 M Al(CFSO)/1 M Zn(CFSO)) as the electrolyte and α-MnO as the cathode, obtaining a discharge voltage of 1.7 V, ∼0.3 V higher than the value reported earlier. The resultant cell delivers a record high energy density of 448 W h kg (based on MnO mass) and retains 100% capacity over 1000 cycles. The ion-storage mechanism and the role of Al in enlarging the output voltage were elucidated. This research indicates the important role of using bications in improving the electrochemical performance of aqueous ZIBs, opening a new way to increase the energy density of aqueous energy storage devices.