Corrosion Resistance and Discharge Performance of Mg-MnO2 Battery by Sodium Silicate Additive

Abstract： The corrosion resistance and delayed action are major obstacles severely limit the practical application of magnesium (Mg) alloy in battery fields. In this paper, the effects of sodium silicate (Na2SiO3) on electrochemical behavior of AZ31B Mg alloy are investigated in MgSO4-Mg(NO3)2 composite solution (0.14 mol L-1 MgSO4, 1.86 mol L-1 Mg(NO3)2). The electrochemical tests are carried out by using electrochemical impedance spectroscopy (EIS), galvanostatic discharge (GD) and linear sweep voltammograms (LSV). The results indicate that the impedance value increases nearly 4 times and the delayed time decreases from 2.1 s to 0.6 s. Furthermore, the battery performance test reveals that the addition of Na2SiO3 significantly improves the discharge specific capacity of Mg-MnO2. The surface morphology and composition of corrosion products from Mg alloys are studied by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The SEM images of AZ31B Mg alloys in composite solution with or without Na2SiO3 additive have an obvious distinction due to the formation of new insoluble compound. FT-IR result confirms that the corrosion products accumulated on the alloy surface in the electrolyte containing Na2SiO3 are mainly composed of magnesium hydroxide, magnesium carbonate and magnesium silicate.