PNNL

Abstract

Recently, mild aqueous rechargeable Zn-MnO2 batteries have attracted increasing interest for energy storage due to the appealing attributes of low cost of Zn and Mn resource and high safety and environmental benignity. Despite extensive types of MnO2 have been proposed for cathodes, the different reported performance, complex synthesis methods and lacking a thorough understanding of reactions in MnO2 cathodes greatly hinder their practical applications for long life energy storage. Here we demonstrate the low cost and commercially available electrolytic manganese dioxide (EMD) as a promising and reversible cathode for mild aqueous rechargeable Zn-MnO2 batteries through a rational manipulation of redox reactions in EMD cathode. In optimal Zn(TFSI)2-based electrolyte, the EMD cathode exhibits a mixed diffusion controlled conversation relation between EMD and H+ and diffusion-free pseudocapacitance-like reactions without phase change. This mechanism enables EMD cathode with excellent cycling stability over 5000 cycles with a capacity retention of 94%. This study provides new opportunity to develop mild aqueous Zn-MnO2 batteries with low cost and high-performance cathode materials by a rational control of the reaction mechanisms.