Research On The Synthesis Of Manganese Oxides And Electrochemical Properties

Manganese oxides are currently attracting a lot of interest due to the relatively lowcost,lowtoxicity,excellent electrochemical performance,environmentally friendly character in compare with other transition metal oxides.Manganese oxides have unique chemical and physical properties and now are widely used in catalysis,ion exchange,molecular adsorption,biosensor,and particularly,energy storage. The structures, properties and morphologies of resultant manganese oxides are very sensitive to the synthetic routes and synthetic conditions.As the operating properties of a battery depend not only on the manganese oxidation state but also on the MnO₂ structure type,as well as particle size and shape,effort has been made to prepare MnO₂ with different structures.In this thesis,manganese oxide of different crystallographic types and crystal morphologies have been selectively synthesized and electrochemically investigated as electrode materials in Li/MnO₂ batteries.1.Manganese oxides withα-,γ- andδ-type structures were prepared by treating KMnO4 in hydrochloric acid solutions at room temperature. the acidity of the solution have a certain effect on the crystal structures,morphologies and electrochemical characterization of the resulted MnO₂. When the concetration of HCl was 4%, MnO₂ was uniform size thorn sphere,the electrochemical experiments showed that the initial discharge capacity of the material was 172mAh g^-1,even after 50 cycles was 100mAh g^-1, indicating a promising application.2 . Ion doping influenced on manganese oxides was investigated . The morphologies of the as-obtained samples were characterized by scanning electron microscopy (TEM).The results showed that the additives cause the transformation of morphology and the charge-discharge property of MnO₂ was enhanced after ion doping.3.Microemulsions as reaction medium, Mn2O3 nanoparticles are synthesized via thermal reaction.The charge and discharge characteristics of the prepared Mn2O3 in the rechargeable lithium batteries were studied,the initial discharge capacity of the material was 432 mAh g^-1.