Investigation Of ?-MnO₂ Nanomaterial As Cathode For Aqueous Znic Ion Batteries

With the serious environmental pollution caused by fossil fuels and the continuous expansion of energy demand,the development of clean and renewable energy has become more urgent.Aqueous zinc ion batteries(ZIBs)are considered to be very promising energy storage devices due to their low cost,simple preparation process,environmental protection and safety.As the core component of aqueous zinc ion batteries,positive electrode materials have made rapid progress in related research.Among them,manganese dioxide(MnO₂)has the advantages of low toxicity,low cost,and environmental friendliness.It is a relatively widely studied cathode material for aqueous zinc ion batteries.In this paper,two manganese dioxide nanomaterials with different morphologies and structures were synthesized by a simple preparation process,so as to achieve the improvement of the electrochemical performance of the anode material of the aqueous zinc ion battery.The main research contents are as follows(1)Synthesis and properties of one-dimensional nanowire-shaped manganese dioxide.Firstly,the precursor basic manganese oxide nanowires were synthesized by hydrothermal method using KMnO₄and CH₂CH₃OH as raw materials,and then annealed to prepare one-dimensional manganese based cathode nanomaterials?-MnO₂.?-MnO₂nanowires were characterized by XRD,SEM,TEM,XPS and other means.Furthermore,using?-MnO₂nanomaterials as cathode materials to assemble an aqueous zinc-ion battery for electrochemical performance testing.The results show that at a current density of 100 m A g^-1,the specific discharge capacity of the first lap is 35.4 mAh g^-1,and the specific discharge capacity of the second lap is 102 mAh g^-1.The specific discharge capacity can reach250 mAh g^-1,and the specific discharge capacity still remains 227 mAh g^-1after 150 cycles of stable cycles.It can circulate5000 cycles at a large current density of 5000 m A g^-1,and the specific capacity retention rate is 95%,showing excellent long-term cycle stability.(2)Study on the synthesis and properties of nanorod-shaped manganese dioxide.First,the pure phase MnOOH nanowire precursor was synthesized by a simple hydrothermal method.Then,MnOOH nanowires are used as the substrate to grow parallel pieces of nanosheets.The growth mechanism includes two steps:the formation of crystal nuclei at room temperature and the growth of nanorods during high-temperature hydrothermal processes.The nanorod-shaped?-MnO₂was characterized and assembled into a battery for electrochemical performance testing.The results show that at a current density of 100 m A g^-1,the specific discharge capacity reaches 160 mAh g^-1,which can be cycled stably for 150 cycles.After 150cycles,the specific discharge capacity of?-MnO₂is 157 mAh g^-1;Under the high current density of 2000 m A g^-1,the specific capacity retention rate reached 93%after cycling 1000 cycles at 88 mAh g^-1.