Research On Mn/Ni Bimetallic Metal-Organic Frameworks Materials In Supercapacitors Electrodes

Supercapacitors are widely used in hybrid electric vehicles,microgrids,distributed power generation and consumer electronics because of their high power density,long cycle life,and environmental friendliness.As energy storage devices,they are faster to charge/discharge than batteries and have reversible storage capacity,and can also withstand a large number of charge/discharge cycles.Current research on supercapacitors is focused on how to increase their energy density while keeping the power density constant.The electrode is one of the most critical components affecting the performance of supercapacitors.Traditional electrode materials such as carbon,metal oxides and conductive polymers have been used,but supercapacitors prepared from these electrode materials can no longer meet the needs of the expanding energy storage scenarios,thus there is an urgent need to explore supercapacitors with high system stability,high capacity and high power density suitable for new energy storage applications such as integrated energy systems and energy internet.Metal-organic framework(MOF)are an emerging material developed in recent years consisting of organic ligands and inorganic metal units,whose pore size,shape and structure can usually be designed and adjusted by changing the type of organic ligand and metal ion.MOFs have been extensively studied in the fields of gas adsorption,catalytic reactions and hydrogen storage.MOFs are also considered to be one of the highly promising materials for energy storage electrodes due to their abundant redox-active metal ions as well as their porous structure.However,for practical industrial applications,technical bottlenecks such as their poor electrical conductivity,poor structural stability and susceptibility to hydrolysis still need to be addressed.In this paper,a new manganese nickel bimetallic metal-organic framework(Mn/Ni-MOF@MWCNTs)anchored on multi-walled carbon nanotubes was prepared by a one-step solvothermal method.The effects of different Mn/Ni mass ratios on the microscopic morphology,structure and electrochemical properties of the MWCNTs were investigated,and the support of the MWCNTs on the bimetallic metal-organic frameworks was analysed.These sites can enhance electron transfer and structural integrity with small contact and charge transfer resistances.Electrochemical test results show that the energy storage electrodes prepared from Mn/Ni-MOF@MWCNTs materials can achieve a specific capacitance of 793.6 F g^-1in 1 M Li OH aqueous solution,and the capacitance capacity remains above 74.92%of the original capacity after 1000 cycles at 1 A g^-1.The crystal structure and electronic information of the anchored Mn-Ni bimetallic organic framework are also investigated by density flooding(DFT)theory calculations in this paper.Finally,the bimetallic organic framework composite Mn/Ni-MOF@MWCNTs developed in this paper was assembled into a button-type symmetric supercapacitor and its practical electrochemical performance was investigated.The results show that it exhibits a specific capacitance of 119 F g^-1at 0.5 A g^-1and an energy density of 33.2 Wh kg^-1at a power density of 1198 W kg^-1,and the residual capacity remains above 78.3%of the original after 2000 cycles.These results provide reference data and theoretical basis for further research on the applicability of bimetallic organic framework materials to high-performance electrochemical energy storage.