Preparation And Electrochemical Performance Of Lanthanide Perovskite Oxide Materials

With the massive consumption of fossil energy and the increasingly serious environmental pollution problem,the research of new energy development and high-efficiency energy storage devices has attracted extensive attention from researchers.Supercapacitors are favored for their excellent properties such as high-power density,fast charging and discharging,and long service life.The electrochemical performance of supercapacitors is mainly determined by the electrode materials.Therefore,the search for new transition metal oxide materials to improve the electrochemical performance of supercapacitors poses a new challenge to researchers.With their unique structure and rich physicochemical properties,perovskite structural oxides are used as electrode materials for supercapacitors by in situ reversible redox reactions in ionic solutions through oxygen insertion mechanism to generate Faraday pseudo-capacitance to store charge,and become a new research direction for the preparation of high energy and high-power density supercapacitors.Based on this,LaBO₃（B=Cr,Mn,Co and Al）perovskite oxides were selected as the object of study in this paper to improve the electrochemical properties of perovskite oxide materials by changing the morphology and elemental doping through different material preparation methods to increase the number of oxygen vacancies.The main research contents are as follows:（1）LaCrO₃,LaMn O₃and LaCoO₃ nanoparticles were prepared by sol-gel method.X-ray diffractometer（XRD）,scanning electron microscope（SEM）,transmission electron microscope（TEM）and specific surface tester（BET）were used to characterize the microscopic morphology and structure of the samples.The elemental valence and elemental content of the samples were determined using X-ray photoelectron spectroscopy（XPS）.The electrochemical properties of the three materials were tested:the maximum specific capacitance of LaCr O₃,LaMn O₃ and LaCoO₃ nanoparticle samples were 54,62 and 74 F/g in 3M KOH solution,respectively,with LaCoO₃ having the largest specific capacitance.（2）Preparation of La_1-xA_xCoO₃（A=Sr,Ca,x=0,0.1,0.15,0.2）series nanoparticles and nanofiber samples by sol-gel method and electrostatic spinning method.Characterize the microstructure,lattice structure,specific surface area and elemental valence of the samples on XRD,SEM,TEM,BET and XPS devices.The test results show that elemental doping can increase the specific surface area and oxygen vacancy concentration of the material.The electrochemical test results show that the doping of Ca elements with small ionic radius is more prominent compared with Sr elements doping,in which La_0.85Ca₀.₁₅CoO₃ sample has the best electrochemical performance.The La_1-xA_xCoO₃ nanofiber samples prepared by electrostatic spinning method have better electrochemical properties because of their unique nanotube structure,in which La_0.85Ca_0.15CoO₃ nanofiber has the largest specific capacitance of 211 F/g.（3）La_1-xCa_xAl O₃（x=0,0.05,0.1,0.15）nanofiber samples were prepared by electrostatic spinning method,and the microstructure and electrochemical test results showed that:The Ca element doping can increase the material specific surface area and enhance the oxygen vacancy concentration,and significantly improve the electrochemical properties of the LaAl O₃ system,in which La_0.9Ca_0.1Al O₃ has the largest specific capacitance of 157 F/g.The cyclic stability test showed that the stability of La_0.9Ca_0.1Al O₃ electrode was good.