Construction of self-standing MnO2-based films for reversible and practical electrolytic Zn//MnO2 batteries in acidic environment

In acidic environment, electrolytic Zn//MnO2 batteries possess high potential to reach high energy density on the promise of high safety, low cost, and high power density. However, several serious challenges still need to be overcome, mainly including suitable current collector that can be stable in strong acidic and oxidizing environment, optimal cathode that can promote massive and uniform deposition of the MnO2, and Zn-plating efficiency and corrosion resistance improvement. Herein, a free-standing and binder-free film composed of graphene powder (GP) and MnSO4 (GP/MS-F) was developed and used as initial cathode frame. The film with a GP: MnSO4 mass ratio of 2:3 and a total areal mass of 13 mg cm−2 exhibits good conductivity and considerable flexibility without the using of any other additives. Matched with C coated ZnO (ZnO@C) modified anode frame and Carboxy Methyl Cellulose Sodium gelled acidic electrolyte, the film can deliver a high areal capacity of 1.4 mAh cm−2, corresponding to a specific capacity of 184 mAh g−1 based on the total mass of initial GP and deposited MnO2 (∼7.6 mg). At 5 mA cm−2, a high Coulombic efficiency of 92 % can be achieved and maintained for 2,100 cycles. At 30 mA cm−2, the cell can work well for 8,000 cycles. Meanwhile, discharge voltage of the cell can reach 1.9 V, exhibiting high practical application prospect.