Study On The Preparation Of Manganese Dioxide Particles Doped With Rare Earth Elements

As a new kind of storage device,super capacitor has attracted much attention due to its high power density,high energy density and excellent circulation performance.The source of manganese oxides is abundant,the capacity is high and the environment is friendly.In recent years,it has been the research hotspot of the electrode materials of super capacitor,but its mechanical stability is low and the conductivity is small,so that its actual capacity is far below the theoretical value.It is the main research area to explore appropriate preparation processes to improve the properties of materials.In this paper,the high purity manganese dioxide particles were prepared with citric acid and manganese acetate through high temperature roasting and acidification.The effects of acid treatment,doping content and temperature on the crystal form and electrical properties of modified manganese dioxide were studied by doping rare earth elements Ce and La.The morphology,structure and electrochemical properties of the samples were characterized by scanning electron microscope(SEM),X ray diffraction(XRD)and electrochemical workstation,and the optimum process conditions and the optimum doping amount were determined by experiments.Research shows:The manganese dioxide prepared is spherical and granular,and its crystal form is a-Mn02,the average grain size is about 91nm and the capacitance value is 151.62 F·g-1.The crystal shape of the sample is changed after Ce doping,which is s-MnO2 phase,The crystal form is single and the purity is high.When the molar ratio of manganese acetate and ammonium ceric nitrate is 1:0.06,the specific capacitance of the electrode is the largest,up to 226.12 F·g-1,and the electrode has good capacitance and power characteristics.Acid treatment of Mn02-Ce was performed,the charging and discharging time of samples before and after acidification are 79s and 117s respectively,and the dispersity of the particles is good after acidification,indicating that the acid treatment can improve the capacitance of the sample;The crystal type of lanthanum doped manganese dioxide is Ca-MnO2 crystal consistent with pure MnO2,proved that did not generate a new phase after La doping,but the peak shape of the team should be widened and the peak strength weakened.When the molar ratio of the manganese acetate and lanthanum nitrate is 1:0.09,the electrode material has a maximum capacity of 323.02 F·g-1,which is twice as high as the pure manganese dioxide.The acid treatment results of MnO2-La show that the composite materials with acid treatment are not only small in size,loose in structure,but also can greatly improve the electrochemical properties of the electrode.Through the study of the preparation process parameters of MnO2-La composites,the optimum process conditions for preparing MnO2-La are that the molar ratio of manganese acetate and lanthanum nitrate is 1:0.09,the calcination temperature was 350 C,and after sintering 10h,2h was treated in acid bath at 90C.