Preparation And Electrochemical Performance Of Manganese/Vanadiumbased Cathode Materials For Zinc-ion Batteries

Aqueous zinc-ion battery is one of the hotspots in the field of energy storage.It has low cost and abundant resources in nature,especially the electrolyte used is water-based electrolyte,which is non-flammable and has good safety.It is expected to become one of the favorable candidates for the next generation of rechargeable batteries and has attracted wide attention from researchers.However,due to the large hydrated ion radius of zinc ions,it is difficult for zinc ions to be embedded in the cathode material,which affects the improvement of electrochemical performance.Therefore,researching suitable cathode materials is one of the keys to the practical application of aqueous zinc-ion batteries.In this paper,two kinds of cathode materials are prepared,one is Ag doped Mn O₂,the other is N-doped C-coated V₂O₃ nanometer material.The synthesized materials are physically characterized,and the battery is tested by constant current charge and discharge method.The energy storage mechanism is studied by XRD and XPS test method in charge and discharge state.A simple hydrothermal method is used to prepare Ag-doped manganese dioxide material.The synthetic material has a morphology similar to the shape of a sea urchin,and surrounded by the nanowire structure.This unique structure can increase the contact area with the electrolyte,and the structure of the synthetic material has a certain effect on preventing particle aggregation.At the same time,Ag doping further enhances the conductivity of the material,which is conducive to the improvement of the electrochemical performance of the material.The initial discharge specific capacity at 1 A g^-1 is 153.4 m Ah g^-1.After 500 cycles,the discharge specific capacity remains at 135.5 m Ah g^-1,and the capacity retention rate is 88.3%.The mechanism of charge/discharge reaction is studied by ex-situ XRD and XPS.The mechanism of reversible intercalation of Zn²⁺in Mn O₂ is explained.N-doped C-coated V₂O₃ nanomaterial is successfully prepared by hydrothermal technique and heat treatment using metal organic framework as precursor.Nanowire structure can increase the contact area between electrode and electrolyte,thus providing more active sites.C-coated structure can enhance the conductivity of the material and prevent the dissolution of vanadium in electrolyte solution.In the first charging process,V₂O₃ is oxidized to V₂O_5-x·n H₂O by electrochemical pre oxidation,which has larger interlayer spacing and ion diffusivity.The prepared material has outstanding electrochemical properties.The initial discharge capacity is 274.6 m Ah g^-1 at 5 A g^-1.After 2000 cycles,the discharge capacity remains at 259.0 m Ah g^-1,the capacity retention rate is 94%,and the charge discharge efficiency is close to 100%.The reaction mechanism of Zn²⁺reversible intercalation between hydrated layered vanadium pentoxide layers is explained by ex-situ XPS and XRD.