The electrochemical properties and reaction mechanism of orthorhombic Mn2SiO4 cathode for aqueous rechargeable zinc ion batteries

Abstract

Manganese-based cathodes for aqueous rechargeable zinc ion batteries (ZIBS) are attracting extensive attention owing to high energy density, high safety of mild aqueous electrolyte, environmental friendly, facile battery assembly and low cost of sources materials. Here, a new manganese-based battery system for aqueous ZIBs by employed orthorhombic manganese silicate (Mn2SiO4) as cathode, Zn metal as anode, mild aqueous ZnSO4 + MnSO4 as electrolyte is reported for the first time. The Zn/Mn2SiO4 battery shows good Zn storage performance and can deliver reversible capacity of 154 mA h g−1 in the first cycle. Notably, the battery undergoes capacity deterioration in initial cycles, but exhibits superior cyclic stability after several cycles. A comprehensive study reveals the electrochemical reaction mechanism of this battery system is the irreversible phase transition from Mn2SiO4 to amorphous todorokite MnO2, amorphous SiO2 and crystalline phase occurs during the first charge, and followed by reversible conversion reaction between amorphous phase (todorokite MnO2 and SiO2) and crystalline phase (MnOOH, ZnxMnO2 and Zn2SiO4) in the subsequent cycles. Although the practical capacity and reaction mechanism needs to be clearly evaluated, this work could provide new insights into exploiting other advanced cathodes for aqueous rechargeable ZIBS.