Preparation And Modification Of Manganese Oxides Cathode For Aqueous Zinc-ion Batteries

The rapid development of attention to environmental crises and energy shortages has promoted the exploration of renewable and clean energy.Aqueous zinc ion batteries have received extensive attention in recent years owing to their low cost,high safety,and acceptable rate performance.Manganese-based oxides have become the most widely used cathode material in aqueous zinc-ion batteries due to their considerable capacity and output voltage.However,their low initial capacity,dissolution of manganese,and instability of performance at high current densities still limit their practicality application development.This article uses two different methods to modify the manganese oxide:1.During the charging and discharging process of the zinc ion battery,the manganese dioxide cathode usually dissolves,resulting in a serious decrease in cycle performance.After coating with titanium dioxide（Mn O₂@Ti O₂）,the amount of manganese dissolved in the reaction process can be greatly reduced,and its cycle stability can be effectively improved.The results show that the button battery assembled with Mn O₂@Ti O₂ has considerable cycle performance,which can be maintained at 80 m Ah/g for 1000 cycles of stable charge and discharge at a higher current density.At the same time,by calculating the battery reaction kinetics,the manganese dioxide material is mainly controlled by the capacitance behavior during the charging and discharging process.The high capacitance control contribution rate proves that Mn O₂ can store more charges and has a good rate performance.2.The development of Mn O cathodes in aqueous zinc-ion batteries is troubled by low specific capacity caused by slow reaction kinetics and rapid capacity decay caused by structural collapse.Here,based on simple electrospinning technology,the combination of Mn O_1-x rich in oxygen defects and carbon nanofiber(Mn O_1-x@CNF)membrane is designed.According to DFT calculation,oxygen defects reduce the H⁺diffusion barrier to promote electrode reaction kinetics.CNF provides a flexible and lightweight electronic transmission network to ensure fast reaction kinetics.Therefore,Mn O_1-x@CNF can reach a high discharge specific capacity of 260 m Ah/g at 0.1 A/g and can cycle stably for 2500 times at a high current density.At the same time,the results of in-situ X-ray diffraction and X-ray photoelectron spectroscopy showed that the Mn O_1-x@CNF positive electrode experienced reversible H⁺insertion/extraction during the cycle without phase inversion.In addition to the carbon fiber conductive network,Mn O_1-x@CNF also has excellent flexibility.After assembling it as a cathode material into a flexible full battery,its specific capacity remains above 200 m Ah/g,and cycles up to 500 times at 2 A/g.When the battery is bent 180 degrees,its capacity retention rate is still close to 100%,and it can also light up the light-emitting device.