Precise Proton Redistribution for Two-Electron Redox in Aqueous Zinc/Manganese Dioxide Batteries

The liquid electrolyte in conventional zinc/manganese dioxide (Zn/MnO2) batteries conduces to the capacity limitation of one-electron redox from MnO2 to MnOOH, as well as undesired Mn loss with capacity deterioration. Herein, to conquer these challenges, a new idea is proposed on the precise proton redistribution in the hydrogel electrolyte for the preferred two-electron redox reaction. Specifically, an acidic layer in the hydrogel adjoins the MnO2 cathode to maintain the two-electron redox, a neutral layer adjoins the zinc anode to inhibit the dendrite growth, which is separated by a mildly alkaline layer to immobilize the proton distribution. The two-electron redox of MnO2/Mn2+ and anode protection are demonstrated to play key roles in battery performance. Such a battery presents specific capacities of 516 mA h g(-1) at 0.05 A g(-1), as well as a capacity retention of 93.18% at 5 A g(-1) after 5000 cycles without extra Mn2+ addition in the electrolyte. More importantly, fibrous Zn/MnO2 batteries using the tri-layer electrolyte can sustain 2000 cycles with high initial capacity of 235 mAh g(-1) at 1 A g(-1). After 6000 times folding in 180 degrees, it can maintain 99.54% capacity. When integrated into user's clothing or portable accessories, the fibrous battery is demonstrated as a great potential in wearable electronics.

Automated summary

The study proposes a new idea for achieving preferred two-electron redox reactions through the precise proton redistribution in the hydrogel electrolyte, demonstrating key roles of MnO2/Mn2+ two-electron redox and anode protection in battery performance. Such batteries show specific capacities and high retention rates without additional Mn2+ in the electrolyte, as well as potential for wearable electronics.