Preparation And Properties Of Metal-organic Frameworks And Derived Metal Phosphate

The electrode material of the supercapacitor is a vital part of the entire device,which directly affects the capacity and cycle life of the supercapacitor.As the material for supercapacitors,conditions such as large effective specific surface area and good conductivity are required.Although the metal-organic frameworks materials have large specific surface area and high porosity,the shortcomings of their poor electrical conductivity limit their application in supercapacitors.The introduction of the second metal element into the single metal-organic frameworks can adjust the original electronic structure of the material,increase the electron transfer rate,and achieve the purpose of improving the electrochemical performance of the metal-organic frameworks and their derivatives.In the experiment,bimetallic organic framework materials with different ratios were prepared according to the mixing method,the prepared metal organic framework materials were used as raw materials to synthesize metal phosphate materials through hydrothermal reaction.The prepared metal organic framework materials and metal phosphate materials were characterized by X-ray diffraction,scanning electron microscope,transmission electron microscope,X-ray photoelectron spectroscopy and other physical methods.Using the cyclic voltammetry,constant current charge and discharge,AC impedance Chemical methods to study the electrochemical properties of materials.The calculation was used to simulate the changes of the state density and energy band of the La-doped phosphate.Then studied the properties of metal-organic frameworks and metal phosphates doped with rare earth elements and compare the effects of different conductive agents on the electrochemical performance of electrode materials.The experimental results show that the Ni/Co bimetallic phosphate derived from the Ni/Co bimetallic organic framework has better electrochemical performance than the metal organic framework,and the metal element ratio n(Ni):n(Co)=8:1 sample has the best specific capacitance.The calculated capacitance value is 895.29 F·g^-1 at a sweep speed of 5 m V·s^-1 and 808.89 F·g^-1 at the charge and discharge current density of 1 A·g^-1.It can provide a specific energy of 22.75?11.00 Wh·kg^-1 at the specific power of 225?4500 W·kg^-1 specific power.The results of calculation and simulation found that doping La element can reduce the band gap and increase the conductivity of the system,and the experimental results of doping rare earth element found that when the ratio of doping La element is 0.2,it is obtained by hydrothermal reaction at 150?for15 h The phosphate material has the best electrochemical performance.At the same time,the use of Super P as a conductive agent will further improve the electrochemical performance of the material.The capacitance calculated at a sweep speed of 5 m V·s^-1is 1406.38 F·g^-1 and the calculated capacitance value under the charge and discharge current density of 1 A·g^-1 is 1397.78 F·g^-1,It can provide a specific energy of39.3125?19.25 Wh·kg^-1 at the specific power of 225?4500 W·kg^-1 specific power.