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°, 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. © 2021 Wiley-VCH GmbH