A Variety Of Methods Were Used To Improve The Electrochemcal Performance Of Manganese Dioxide For The Cathode Of Zinc-ion Batteries

Manganese dioxide has broad application prospects as an anode material for aqueous zinc-ion batteries,but it has problems of poor stability and low conductivity.In this paper,starting from improving the conductivity and stability of manganese dioxide as the positive electrode of aqueous zinc-ion batteries,the electrochemical performance of manganese dioxide was improved.Al³⁺pre-embeddedα-MnO₂ nanorods（AMO）were prepared by hydrothermal method,and the effects of reaction time,reaction temperature and aluminum content on the electrochemical properties of the material were explored.The optimum temperature was 140°C,and the optimum reaction time was 12 h,the optimum Al³⁺dosage is 8 mmol.After that,poly-3,4-ethylenedioxythiophene（PEDOT）was coated on AMO by water bath method,and PEDOT-coated Al³⁺pre-embedded MnO₂ nanorods（PAMO）were obtained.The high-resolution transmission and XPS tests showed that Al³⁺was successfully intercalated into MnO₂ and Increased lattice spacing.Morphological characterization and specific surface area tests show that Al³⁺pre-embedding and PEDOT coating will not change the morphology of the material,and will not change the specific surface area.Refined XRD shows that the tunnel size of the nanorods becomes larger due to the pre-intercalation of Al³⁺.GITT tests show that Al³⁺pre-embedding will increase the ion diffusion coefficient:the H⁺diffusion coefficient of AMO is 10^-12,and the Zn²⁺diffusion coefficient is 10^-13.Compared with MnO₂,the diffusion coefficients are respectively increased by about an order of magnitude.When the current density is 0.1 A g^-1,the specific capacity of MnO₂ is 262m Ah g^-1,the specific capacity of AMO is 332 m Ah g^-1,and the specific capacity of PAMO is 340 m Ah g^-1;after 2000 cycles at a current density of 1 A g^-1,MnO₂ The retention rate of AMO is 26%;the retention rate of AMO is 47%;the retention rate of PAMO is 61%.MnO₂ nanosheets（GMO）were grown on pre-reduced graphene oxide substrates by a hydrothermal method.Afterwards,Al³⁺pre-embedded GMO nanosheets（GAMO）were prepared,and SEM showed that Al³⁺pre-embedded would change the morphology of the material from nanosheets to nanospheres.High-resolution transmission and XPS showed that Al³⁺was successfully intercalated and Increased lattice spacing;BET test showed that the intercalation of Al³⁺increased the specific surface area of the material:the specific surface area of GMO was 128 m² g^-1,and the specific surface area of GAMO was 399 m²g^-1.GITT tests show that the ion diffusion rate is increased due to the intercalation of Al³⁺:the H+diffusion coefficient of GAMO is 10^-11.5,and the Zn²⁺diffusion coefficient is 10^-13.5,which are respectively increased by about an order of magnitude compared with GMO.The GAMO was then coated with PEDOT（PGAMO）.At a current density of 0.1 A g^-1,the specific capacity of GMO is 195 m Ah g^-1,the specific capacity of GAMO is 309 m Ah g^-1,and the specific capacity of PGAMO is 318 m Ah g^-1;after 1000 cycles at a current density of 1A g^-1,the specific capacity of GMO The capacity retention rate is 46%;the capacity retention rate of GAMO is 65%;the capacity retention rate of PGAMO is 73%.