Preparation And Electrochemical Properties Of Cathode Material For Zinc-ion Battery

Aqueous rechargeable zinc ion batteries（ARZIBs）have been widely studied because of their many advantages,such as the transfer of two electrons in an electrochemical reaction,high theoretical specific capacity of zinc(820 mAh g^-1),high safety of zinc battery system,suitable redox potential（-0.76V vs.SHE）coupled with abundant zinc resources.Manganese oxide has become a promising cathode material for ARZIBs because of its the advantages such as environmentally friendly,low price,low toxicity and abundant valence states.However,there are still some problems in its commercial application,such as low intrinsic conductivity,dissolution and structure collapse during zinc ions insert/extract.In this paper,in order to solve the issues of manganese oxide above,the modification research was carried out by constructing nanostructured materials and carbon based composites.The main research contents are as follows:（1）To solve the problem of low conductivity of manganese dioxide electrodes,a novel array cathode material was prepared by anchoring ultrathin MnO₂nanosheets on metal organic framework-derived N-doped carbon nanowall array grown on carbon cloth（CC@CN@MnO₂）.The unique structure enables to improve the conductivity,furthermore,the ultrathin MnO₂nanosheets can provide shortened electronic/ion diffusion paths.The Zn//CC@CN@MnO₂ deliver admire capacity and superior rate capability,Which deliver310.5 mAh g^-1at 100 mA g^-1 and 115.6 mAh g^-1at 5 Ag^-1.（2）In order to solve the problem of manganous oxide electrodes conductivity are low and manganous oxide dissolved,the carbon coated manganous oxide（C@MnO）cathode materials are prepared by hydrothermal method.Then which are modified by adding carbon nanotube（CNT）to make the CNT can formed conductive network connect between C@MnO.This unique structure can not only improve the conductivity of the electrode material,but it can also inhibit the dissolution of manganese and provide shortened electronic/ion diffusion paths.As a result,the Zn//MnO@C NPS-18 exhibit high capacity,superior rate performance and excellent cycle performance.Which can deliver discharge specific capacity of 310 mAh g^-1 at 100 mA g^-1.When under a high current density of 2 A g^-1,which can also deliver admire discharge specific capacity of 179 mAh g^-1 and the capacity retention rate is up to 84%after 1200 cycles.（3）Hierarchical porous MnO₂ nanosheets（MnO₂ Ns）materials were prepared with bagasse as template.Compared with the Bulk MnO₂ materials prepared by template-free,the hierarchical porous MnO₂nanosheets not only have more uniform morphology of nanosheets,but they also have larger specific surface area(41.1 m²g^-1).Electrochemical data shows that they exhibit a specific capacity of 283/168 mAh g^-1 at 0.1/1 A g^-1for the hierarchical porous MnO₂ nanosheets electrode materials prepared at 550℃（MnO₂ Ns）,when under a high current density of 1 A g^-1,they show a specific capacity of 115.6 mAh g^-1 after 600 cycles.The electrochemical performance of the hierarchical porous MnO₂nanosheets electrode materials is superior to the Bulk MnO₂ electrode materials.