Study On The Preparation Of Manganese Dioxide Anode Material And Additives In The Electrolyte For Mercury-free Rechargeable Alkaline Manganese Dioxide Battery

The preparation, modification and application of cathode active materials MnO2 were studied in this paper for developing mercury-free rechargeable manganese dioxide electrode material with practical prospects. These samples prepared by KMnO4 oxidation of MnCl2 solution and MnCO3 thermal decomposition were studied by chemical analysis , X-ray diffraction (XRD), scanning electron microscope(SEM), potential dynamic sweep, galcanostatic cycles method and other chemical methods in combination with modern spectrum techniques. The mechanism and disciplinarian of charge-discharge characteristic were also analyzed and discussed theoretically. The additives in electrolyte were primarily studied.The method of preparing chemical manganese dioxides by KMnO4 oxidation of MnCl2 salts in HNO3 solution had the merits of brief flow, low energy consume and simple technical condition. The optimum factors concluded from experiments were as following: reaction temperature was 85 C; reaction time was 1 hour; concentration of HNO3 was 0.5~1mol/L; manganese salt was MnCl2; dopant was Bi(NO)3; Mn:Bi was about 6~10. The experiment results showed that the accumulative capacities of 10 cycles of Bi-MnO2 were 300% higher than that of ordinary MnO2. XRD indicated that the samples mainly belonged to mixed crystal of -MOOH as the main phase. But the samples of KMnO4 oxidation had low density.The optimum factors concluded from experiments of MnCO3 thermal decomposition were as following: deposition temperature was 40 C ; deposition time were 1.5 hours; thermal temperature was 375C~390C; thermal time were 8 hours and so on. The tapped density of the MnO2 powder could be increased more than 1.7g/cm3 and therechargeability was also excellent. XRD indicated that the samples mainly belonged to crystal of -type structure. SEM indicated that the samples were the global granule microstrure.The effects of additives in electrolyte on the electrochemical performances of zinc electrode were investigated, through the hydrogen collection experiment, short circuit experiment and cyclic voltammetry method. The experiment results showed that the rechargeability of the alkaline zinc-manganese battery with 0.1% TEA in electrolyte was improved obviously and additives inhibited corrosion and dendrite of zinc electrode.Through the theoretical analysis and discussion, the reasons for excellent electrochemical behavior of modified MnO2 was like that the component and structure of modified MnO2 was changed, so that the MnO2 had a good rechargeability both in deep and shallow discharge regions.