Preparation And Electrochemical Properties Of Silver Based Three-element Compounds

Conventional alkaline electrochemical cells have an anode comprising zinc and a cathode comprising manganese dioxide. They have been widely used in our everyday life due to their advantages on discharge capacity, specific energy and low-temperature performance etc. Although such alkaline cells are in widespread commercial use there is a need to improve the cell or develop a new type of cell that exhibits reliable performance and longer service life for normal applications and performs even better than conventional zinc/MnO₂ cells.This thesis consists of four parts. The first one aims to survey the background of the research work. It comprises of the overview of the present status of chemical power sources, the introduction of zinc/MnO₂ cell, the fundamental electrochemical reaction mechanism, characteristics of MnO₂ electrode, the knowledge related to Ag₃BiO_x,Ag₅Pb₂O₆,AgNiO₂.The second chapter expresses the preparation of Ag₃BiO_x and its modifying effect for MnO₂ electrodes. Firstly Ag₃BiO_x powder was prepared by chemical coprecipitation method and characterized by XRD, SEM techniques. Its electrochemical properties were studied by means of constant current discharge and linear sweep voltammetry experiments. Ag₃BiO_x shows the better discharge property than that of electrolytic manganese dioxide (EMD) in alkaline electrolyte. The electrochemical properties of EMD cathodes doped with Ag₃BiO_x were studied by galvanostatic charge/discharge and cyclic voltammetry. The results indicated that the electrochemical performance of EMD electrode was effectively improved by doping of Ag₃BiO_x. EMD electrode doped with Ag₃BiO_x possessed remarkably higher discharge voltage, larger capacity and better reversibility than that of pure EMD electrode.The third chapter shows the preparation of Ag₅Pb₂O₆ and its modifying effect for MnO₂ electrodes. Firstly Ag₅Pb₂O₆ powder was prepared by chemical coprecipitation method and characterized by XRD, SEM techniques. The samples Ag₅Pb₂O₆ had good electrochemical activity at the certain potential in 9M KOH solution. Ag₅Pb₂O₆ was used as the additive for manganese dioxide electrodes in aqueous electrolyte (9M) at room temperature. The influence of the additive on the discharge and charge performance of MnO₂ was discussed by galvanostatic charge/discharge and cyclic voltammetry. The results indicated that Ag₅Pb₂O₆ involved in electrode reaction of the modified MnO₂ electrodes. Ag₅Pb₂O₆ formed a series of complexes, which stabled electrode' s structure and caused a better utilization of manganese dioxide. In the presence of Ag₅Pb₂O₆ the discharge/charge cycle ability of MnO₂ was clearly improved.The fourth chapter studies the preparation of AgNiO₂ and its modifying effect for MnO₂ electrodes. Firstly AgNiO₂ powder was prepared by chemical coprecipitation method and characterized by XRD, SEM techniques. The samples AgNiO₂ had good electrochemical activity in 9M KOH solution. The electrochemical properties of EMD cathodes doped with AgNiO₂ were studied by galvanostatic charge/discharge and cyclic voltammetry. The results indicated that AgNiO₂ was effective to heavy load discharge than to that of MnO₂.