Preparation And Electrochemical Performance Of Fe-based Metal Organic Framework Electrode Material

Nowadays,the energy crisis is becoming more and more serious,so it is urgent to develop environmentally friendly,low-cost and reliable renewable energy storage devices.Supercapacitor is a future energy device with high power density,excellent cycle stability and fast charge-discharge process.However,low energy density limits the development of supercapacitors.It is well known that the electrochemical properties of SCs are strongly dependent on the electrode material.However,traditional electrode materials cannot meet its development due to high cost,low capacitance and poor stability.Therefore,it is urgent to develop new electrode materials.Metal-organic frameworks（MOFs）is a candidate for SCs electrode materials due to their high specific surface area and adjustable pore size,but it has disadvantages such as low electrical conductivity and poor structural stability.Therefore,we expect to develop MOF-based electrode materials with high electrical conductivity and good cycling stability.In this paper,iron-based metal-organic framework electrode material（Fe-MOF）is used as the research object,and it is modified by different methods to solve the problems of low conductivity and poor stability.Meanwhile,the application and development of Fe-MOF in the field of SCs are explored.The specific research contents are as follows:（1）Fe-MOF nanorods were synthesized by solvothermal method,and then Ni（OH）₂was deposited on the surface of Fe-MOF by deposition method at room temperature to construct conductive pathways,and Fe-MOF@Ni（OH）₂-X composites were prepared.The composite material not only maintains the inherent advantages of Fe-MOF,but also effectively improves the conductivity of Fe-MOF.At the same time,the electrochemical properties of Fe-MOF@Ni（OH）₂-X at different deposition times were explored.The experimental results show that Fe-MOF@Ni（OH）₂-20 exhibits a high specific capacity of188 m Ah g^-1.The energy density of Fe-MOF@Ni（OH）₂-20//AC is as high as 67.1 Wh kg^-1when the Fe-MOF@Ni（OH）₂-20 composite material is applied to the asymmetric supercapacitor.（2）MIL-88A@Co（OH）₂ composites with hollow structure were prepared by introducing Co（OH）₂ onto MIL-88A（Fe-MOF）by solvothermal method.Through characterization technology analysis,it is found that the hierarchical porous structure of the material provides a high specific surface area,which is conducive to electrolyte storage and ion diffusion,thus significantly improving the reaction kinetics of the active material.In addition,hollow structures can expose more active sites and improve mass diffusion efficiency.The synergistic effect of MIL-88A and Co（OH）₂ makes it possess excellent energy storage performance.The specific capacity of MIL-88A@Co（OH）₂ is 275 m Ah g^-1at current density of 1 A g^-1.At the same time,MIL-88A@Co（OH）₂//AC asymmetric supercapacitors exhibit high energy density(73.1 Wh kg^-1)and power density(800 W kg^-1).（3）Firstly,Co Fe-MOF/NF was grown on the conductive substrate,and then the Co Fe-MOF@Mn O₂ nanocomposite was synthesized by a hydrothermal method.The composite material combines the structural advantages of Co Fe-MOF and Mn O₂ to improve the contact area between electrolyte and electrode material,and shorten the electron transport and ion diffusion path.Therefore,the specific capacity of Co Fe-MOF@Mn O₂ can reach 671.1 m Ah cm^-2 at the current density of 1 A g^-1,and it exhibits excellent cycling characteristics.The assembled asymmetric supercapacitor Co Fe-MOF@Mn O₂//AC can achieve an energy density of 65.87 Wh kg^-1 when power density is 800 W kg^-1.