Preparation And Modification Of Cathode Materials For Zinc Secondary Battery

With the increasing demand for energy,the secondary battery,as an important device for energy storage,is playing an increasingly important role in people's daily life.Today,lithium-ion batteries have been widely applied in various electronic equipment,portable devices,as well as military system and other fields.However,lithium ion batteries are more expensive and unfriendly to the environment,so researchers have turned to developing more low-cost and environmentally friendly secondary cells.The zinc secondary cell uses the low price zinc as the main material.And zinc has the good electrochemical performance as well as the volu me energy density is higher,whicih is hopeful to replace the lithium ion battery service in the future.In this paper,several kinds of zinc secondary cells have been compared.Besides,the low–cost and environmentally friendly anode materials have been selected out,polyaniline and manganese dioxide.In this thesis,polyaniline and polyaniline/cobalt oxide composite materials with different sizes have been prepared by chemical oxidation and interfacial polymerization.XRD test shows that polyaniline and its composite prepared by interfacial polymerization have better crystallinity and better regularity.SEM test shows that the particles prepared by interfacial polymerization have smaller particle size and smaller aggregation phenomenon.The polyaniline's capacity reaches 20 m Ah/g prepared by chemical oxidation.The maximum specific discharge capacity of the polyaniline prepared by interfacial polymerization is 77.4 m Ah/g,and the cycle performance is better.Polyaniline/cobalt oxide composite material have the largest specific capacity of 122.9 m Ah/g,but its cycle performance is poor.In addition,the non-aqueous electrolyte consisting of Zn Cl2-urea ionic liquid and propylene carbonate?PC?or acetonitrile?AC?as additive is developed for zinc/polyaniline battery.When the volume ratio of PC or AC to Zn Cl2-urea is 1:1,cells shows best performance.The battery with AC as additive exhibits a discharge capacity of 114.3 m Ah/g at the second cycle at a current density of 50 m A/g comparing to 86.2 m Ah/g with PC as additive.MnO₂ has been prepared by hydrothermal method as cathode material of Zn/MnO₂ secondary battery.The effects of process parameters on crystal shape,morphology and crystallinity of MnO₂ have been investigated.MnO₂ has high capacity but poor cycle performance.In order to improve the stability of the material,MnO₂/GO,MnO₂/Co3O4 composite materials have been prepared.The results shows that the discharge performance of the composite has obviously improved.When the 300 mg GO is added,the discharge capacity of the battery is as high as 190.5 m Ah/g,and the discharge performance tends to be stable after 60 cycles.The MnO₂/Co3O4 composite material reaches discharge capacity as high as 235.5 m Ah/g,and the discharge capacity remains at 100 m Ah/g after the 40 cycles.Finally,the economic analysis of Polyaniline and manganese dioxide as cathode materials for zinc secondary batteries is carried out.Polyaniline and manganese dioxide and their composite materials have the advantages of low cost and environmental friendliness,and have broad application prospects.