Electrochemical Properties Of Mg-Al-Sn And Mg-Al-Pb Alloys As Sea-water Activated Battery

Abstract:Because of low electrode potential, steady discharge process, rapid activation and high power density capability, magnesium anode have arise great attention in many countries. This technology is mature in foreign countries but have a large space for development in domestic research on sea-water activated cell. The prospect of develop new magnesium anode to fit new equipment is bright. Therefore, two series of magnesium anode material Mg-Al-Pb alloy and Mg-Al-Sn alloy were prepared in this study. They are expected to be applied to underwater propulsion battery.The potentiodynamic polarization, galvanostatic discharge and electrochemical impedance spectroscopy are used to study the electrochemical properties of the prepared alloys; The scanning electron microscopy, energy disperse spectroscopy, optical microscope were used to study the effect of alloy elements, heat treatment, processing on the magnesium anode.The results show that the effect of aluminum in Mg-Al-Pb series alloy is to keep the discharge potential negative. The optimal mass fraction of aluminum in Mg-Al-Pb alloy is6%.The discharge process maintain steady when the alloys are annealed at473K.The discharge potential can reach-1.5V (vs.SCE).For the Mg-Al-Sn series alloys, The effect of aluminum is to keep the discharge process steady especially when the Mg-6%Al-1%Sn alloy were discharged under high current density such as200mA/cm2. This result is get by comparing to the result of Mg-1%Sn alloy. The heat treatment results show that the discharge process is steady when the alloys are annealed at473K. The discharge potential shifts from-1.1V to-0.9V when the alloys are annealed at673K. This is because the fine grains become coarse which results in polarization of the alloys. The AC impedance studies reveal that the alloy/seawater interface process is determined by an activation-controlled reaction for both Mg-Al-Pb and Mg-Al-Sn series alloys. The charge transfer-resistance (Rct) of Mg-6%Al-5%Pb alloy is smaller than that of Mg-6%Al-1%Sn alloy. This means the Mg-6%Al-5%Pb alloy can obtain a more negative discharge potential.In order to optimize the electrochemical properties of Mg-Al-Pb series alloys, the element zinc (Mass Fraction<1%) was added to Mg-6%Al-5%Pb alloy. The results show that the discharge potential of APZ65is-1.1V when the alloys are discharged under current density of330mA/cm2. This value is negative than that of AP65which means the element Zinc is benefit to the galvanostatic discharge property of Mg-Al-Pb alloys.