β-MnO2withprotonconversionmechanisminrechargeablezincionbattery

Rechargeable aqueous zinc ion battery(RAZIB) is a promising energy storage system due to its high safety, and high capacity. Among them, manganese oxides with low cost and low toxicity have drawn much attention.However, the under-debate proton reaction mechanism and unsatisfactory electrochemical performance limit their applications. Nanorod b-MnO 2 synthesized by hydrothermal method is used to investigate the reaction mechanism. As cathode materials for RAZIB, the Zn//b-MnO 2 delivers 355 mA h gà1(based on cathode mass) at0.1 A gà1, and retain 110 mA h gà1 after 1000 cycles at 0.2 A gà1. Different from conventional zinc ion insertion/extraction mechanism, the proton conversion and Mn ion dissolution/deposition mechanism of b-MnO 2 is proposed by analyzing the evolution of phase, structure, morphology, and element of b-MnO 2 electrode, the pH change of electrolyte and the determination of intermediate phase MnO OH. Zinc ion, as a kind of Lewis acid, also provides protons through the formation of ZHS in the proton reaction process. This study of reaction mechanism provides a new perspective for the development of Zn//MnO 2 battery chemistry.