Preparation And Performance Of Manganese Oxides Compound As Cathode Materials For Aqueous Zinc Ion Batteries

The high cost of lithium-ion batteries and the high reactivity limit their development in large-scale energy storage applications.Therefore,it is necessary to look for alternative batteries.Aqueous zinc ion batteries（ZIBs）have attracted the attention of many researchers because of their environmental benignity,low price and high safety.In addition,the ZIBs that replace the traditional organic electrolyte with aqueous electrolyte are expected to further reduce the production cost of the batteries and improve the safety.So far,researchers have found many materials suitable for ZIB cathode,such as manganese-based materials,vanadium-based materials,Prussian blue analogues.Mn O₂ is widely used as cathode material due to its rich source,non-toxic and high electrode potential.However,the reduction of layer spacing caused by phase change during charging/discharging process and the dissolution of Mn²⁺are the main problems that cause its structural failure.Therefore,the capacity and cycle performance of Mn O₂ aqueous battery can be effectively improved by coating and pre-insertion of cations.This paper focuses on the following two parts:（1）Attach C₆H₁₂O₆×H₂O to the surface of MnO₂ by stirring,and carbonize after centrifugal drying to obtain core-shell structure ofε-Mn O₂@C.The dissolution of Mn²⁺resulting from the disproportionation of Mn³⁺is slowed down by reducing the side reaction between the electrode and the electrolyte,thus improving the long cycle performance of the battery.At the current density of 0.2 A g^-1,the specific capacity of 280 m Ah g^-1 can be reached.In addition,at a high current density of 1 A g^-1,the capacity retention rate is about 91%(172 m Ah g^-1)after 1700 cycles,showing excellent electrochemical performance.（2）Co-K_0.27Mn O₂×0.54H₂O was prepared by one-step hydrothermal method.An appropriate amount of Co²⁺is conducive to the increase of crystal water,which is not only conducive to promoting the construction of loose 3D morphology,improving the stability of layered structure,but also conducive to the dissolution/deposition reaction mechanism combined with H⁺/Zn²⁺.At the current density of 1 A g^-1,a capacity of 192.5 m Ah g^-1 can be obtained,with a capacity retention rate of approximately 82%after 800 cycles,effectively increasing its capacity performance.