Preparation And Research On Electrochemistry Of Porous Transition Metal Compounds By Template Method

Transition metal compounds have received extensive attention due to their good electrical conductivity and structural stability,and cycling stability is one of the most important factors to evaluate the practical application value of secondary batteries,however,the electrode pulverization caused by volume expansion during electrochemical reaction greatly destroys the cycling stability.Moreover,the issue of poor electrochemical kinetics of the traditional block electrode materials also hinder their commercial application.Based on this,combined with the characteristics of nanomaterials and porous structures,three kinds of porous nano-positive materials were prepared by hard template method and their electrochemical properties were invetigated.The main research contents and results are as follows:Two kinds of composite transition metal oxide porous materials were prepared by hard template method,namely spinel structure nickel ferrite hollow sphere macroporous material and perovskite barium titanate mesoporous material,these two materials were used as the carrier of sulfur for cathode material of lithium-sulfur batteries to investigate electrochemical performance.Under the combination of physical limitation and polar adsorption of Ni Fe₂O₄ hollow spheres,h-Ni Fe₂O₄@S composites exhibit excellent electrochemical performance:the initial discharge specific capacity is 948.7 m A h g^-1,showing a large specific capacity;after 200cycles,the capacity is attenuated to 519.9 m A h g^-1,the capacity retention rate is54.80%,showing good cycle stability;and when the current densities are 200,500,1000,3000 m A g^-1,respectively,the discharge specific capacities were 1047,841.6,651.7,373.6 m A h g^-1,finally,when the current density returned to 200 m A g^-1 again,the discharge specific capacity recovered to 1042.1 m A h g^-1,showing excellent rate performance.Under the combined action of physical and spontaneous polarization of BaTiO₃ mesoporous materials,the composite exhibits more excellent cycling stability,rate performance and electrochemical reversibility,compared to the C/S composite under the same conditions.The discharge specific capacity of P-BaTiO₃/S cathode materials was 891,624.1,561.8,498.9 and 474.5 m A h g^-1 at current densities of 0.1,0.2,0.5,1 and 2 C,respectively.When the current density returns to0.1 C,the discharge specific capacity recovers to 525.1 m A h g^-1.CMK-3 ordered mesoporous carbon material was prepared by hard template method,and it was combined with transition metel selenide Cu₂Se nanoparticles by immersion deposition method for sodium ion battery to explore its electrochemical performance.The physical confinement effect of CMK-3 ordered mesoporous carbon material accommodates the volume expansion during electrochemical reaction and enhances the conductivity of the electrode material.The sodium ion battery using Cu₂Se@CMK-3 composite as the cathode exhibits good electrochemical performance:After 100 cycles at 0.1 C,the average capacity attenuation per time is only 0.33%,showing excellent cycling stability,and it also has good rate performance.The discharge capacities are 227,177,127,108,97 m A h g^-1 at current rates of 0.1,0.2,0.5,1,2 C,respectively.