Challenges and perspectives for manganese-based oxides for advanced aqueous zinc-ion batteries

Li-ion batteries(LIBs)with excellent cycling stability and high-energy densities have already occupied the commercial rechargeable battery market.Unfortunately,the high cost and intrinsic insecurity induced by organic electrolyte severely hinder their applications in large-scale energy storage.In contrast,aqueous Zn-ion batteries(ZIBs)are being developed as an ideal candidate because of their cheapness and high security.Benefiting from high operating voltage and acceptable specific capacity,recently,manganese-based oxides with different various crystal structures have been extensively studied as cathode materials for aqueous ZIBs.This review presents research progress of manganese-based cathodes in aqueous ZIBs,including various manganese-based oxides and their zinc storage mechanisms.In addition,we also discuss some optimization strategies that aim at improving the electrochemical performance of manganese-based cathodes,and the design of flexible aqueous ZIBs based on manganese-based cathodes(MZIBs).Finally,this review summarizes some valuable research directions,which will promote the further development of aqueous MZIBs.