Hydrothermal synthesis of β-MnO2 nanorods for highly efficient zinc-ion storage

Rechargeable aqueous Zn/MnO2 battery with mild electrolyte is exceedingly suitable for massive electrochemical applications due to its eco-friendliness and high safety. However, cycle stability is a crucial question in the practical application. Besides, the mechanism involved in energy storage is still controversial. Here, we show a Zn/MnO2 battery with excellent cycle stability and provide the reasonable explanation of the operating mechanism. In this battery, the mild aqueous ZnSO4 solution containing MnSO4 and Na2SO4 additives serves as the electrolyte and the β-MnO2 nanorods serve as the cathode. As presented in the electrochemical tests, the specific capacity of β-MnO2 nanorods is as high as 323.5 mA h g−1, and its capacity retention is 94% after 1000 cycles at 3 A g−1. The proposed energy storage mechanism is related to the reversible conversion reaction between β-MnO2 and MnOOH. Therefore, the application of β-MnO2 nanorods in aqueous Zn-ion battery has broad development prospects.Graphical abstract