Preparation And Electrochemical Performance Of Ultra-fine Manganese Oxides By Spray Drying

Manganese oxides, especially manganese dioxide, are widely used in the field of battery and catalysis. Its quality is vital to battery performance and catalysis activity. Therefore, it is all-important to prepare the active manganese oxides. Based on the review of research and development of manganese oxides, spray drying was used to prepare the ultra-fine powders and Ni-MnO_x film electrode was made by mist spray for the first time. The electrochemical reduction of manganese oxides and electro-catalysis reduction of oxygen on some manganese oxides in alkaline solution were investigated by different material characterization methods and electrochemical techniques, such as SEM, XRD, TG, AFM, laser-granularity, linear polarization, cyclic voltammetry and electrochemical impedance spectroscopy.In the third chapter of this dissertation, ultra-fine manganese oxides was firstly prepared by spray drying, such as Mn₃O₄, Mn₂O₃, Mn₅O₈, α-MnO₂, β-MnO₂, γ-MnO₂ and λ-MnO-2. The component, structrue, morphology and electrochemical performance were studied. It is found that manganese oxides was formed at 300 °C by burning precursor. This burning process is propitious to obtain ultra-fine powders. The SEM showed global precursor was hollow. Being heat-treated, particle was formed conglomeration which was made up of smaller particle of 0.1 μm. Acid treating could offer the samples with high content MnO₂. The composition and purity of sample E, F and H was higher than commercial EMD. Particularly, electrochemical performance was good with an initial discharge capacity of 215 mAh·g^-1. The proton diffusion process in MnO₂ was studied by using the transmission block model of porous electrode.In the fourth chapter, the techniques of atom force microscope and potential steps were used to examine the texture and surface chemical area of Ni-MnO_x film electrode. The effect of reduction kinetics on discharged intermediate spieces was studied by fast cyclic voltammetry in alkaline solution. The experimental results...