Transformed Akhtenskite MnO₂ from Mn₃O₄ as Cathode for a Rechargeable Aqueous Zinc Ion\nBattery

Abstract

Low\ncost, safety, and environmental benignity make rechargeable\naqueous Zn/MnO₂ batteries promising candidates for large-scale\nenergy storage. However, the synthesis of MnO₂ with excellent\nelectrochemical performance is limited to the traditional hydrothermal\nmethod, which is difficult to scale up for mass production. Herein,\na ball-milling approach is developed to rapidly obtain Mn₃O₄ nanoparticles in large quantity. As the cathode material\nof aqueous zinc ion battery, Mn₃O₄ gradually\ntransforms to ε-MnO₂ in 1 M ZnSO₄ + 1\nM MnSO₄ aqueous electrolyte with increasing cycles. Benefiting\nfrom the unexpected phase transition from Mn₃O₄ to ε-MnO₂, the cathode delivers a specific capacity\nof 221 mAh g^–1 at a current density of 100 mA g^–1 and a good long-term cyclic stability over 500 cycles\nwith 92% capacity retention at a high rate of 500 mA g^–1. The excellent battery performance combined with the cost-effective\npreparation procedure, the good safety of aqueous mild electrolyte,\nand the easy cell assembly are believed to promote the practical use\nof the Zn/MnO₂ battery in large-scale energy storage.