Study On The Preparation And Properties Of Positive Electrode Materials For Water-based Zinc Ion Batteries

The water-based rechargeable battery is considered to be a kind of promising battery because of its low cost,simple preparation process,safety and environmental protection.Among them,water-based zinc ion battery?ZIBs?is a new type of secondary battery developed in recent years,which has an energy density of up to 320Wh/kg and a power density of 12 k W/kg.Compared with other metal anodes,zinc has high active chemical properties,and the redox potential of Zn²⁺/Zn is lower.Common positive materials of zinc ion battery include manganese oxide,vanadium oxide and prussian blue analogue.Among the positive materials,Prussian blue analogue has low specific capacity and cycle life and vanadium oxide has low working voltage and specific capacity,while manganese oxide is easily soluble in electrolyte,so it is very important to develop new cathode materials of ZIBs.In this paper,firstly,the molybdenum based anode material Zn Mo O₄ was prepared by coprecipitation method,then the manganese based anode material Zn Mn₂O₄ was synthesized by hydrothermal method,finally,the magnesium doped Zn Mg_xMn_2-xO₄ also was prepared by simple hydrothermal method and the electrochemical performances of the three prepared cathode materials in aqueous ZIBs were investgaed.The details are as follows:?1?The positive electrode material Zn Mo O₄ was prepared by coprecipitation method.The effects of calcination temperature and time on the properties of Zn Mo O₄were investigated.The results show that the Zn Mo O₄ synthesized by calcining at600°C for 3 hours has good properties.XRD results show that the main diffraction peak intensity of the material is high,indicating that Zn Mo O₄ has good purity and crystallinity.SEM analysis shows that the material has uniform sheet structure and smooth surface.BET results show that the material has large specific surface area and small pore size.The electrochemical performance test results show that in the voltage range of 0.1-2 V,when the current density is 100 m A·g^-1,the specific discharge capacity of the material for the first time is 124.34 m Ah·g^-1,the specific discharge capacity after 150 charge-discharge cycles is still as high as 118.40 m Ah·g^-1.?2?The positive electrode material Zn Mn₂O₄ was prepared by hydrothermal method.The effects of hydrothermal temperature and time on the properties of Zn Mn₂O₄ were investigated.The results of XRD and SEM show that the Zn Mn₂O₄samples synthesized by hydrothermal treatment at 160°C for 16 hours have good purity,crystallinity and uniform morphology.The material was electrochemically tested,and the charge-discharge voltage range was 0.8-1.9 V.When the current density is 100 m A·g^-1,the first discharge specific capacity of the material is 130.47m Ah·g^-1,the specific discharge capacity after 100 charge discharge cycles is 128.00m Ah·g^-1.?3?The cathode material Zn Mg_xMn_2-xO₄ was prepared by hydrothermal method.The effect of doping different proportion of Mg ions on the properties of Zn Mn₂O₄was investigated.The results of XRD and SEM show that when molar ratio of Mg is0.05,the Zn Mg_0.05Mn_1.95O₄ sample has small particle size and large specific surface area.A series of electrochemical tests show that the material has excellent electrochemical properties.The first discharge specific capacity is as high as 149.55m Ah·g^-1,and the specific discharge capacity after 100 charge-discharge cycles is142.00 m Ah·g^-1.