Enhanced Corrosion Resistance and Discharge Performance of Mg-MnO2 Battery by Na2SiO3 Additive

Corrosion resistance and delayed action are major obstacles that severely limit the practical application of Mg alloy in battery fields. In this work, the effects of Na2SiO3 on the electrochemical behavior of the AZ31B Mg alloy in MgSO4-Mg(NO3)(2) composite solution[0.14 mol/L MgSO4, 1.86 mol/L Mg(NO3)(2)] were investigated. Electrochemical tests were carried out using electrochemical impedance spectroscopy, galvanostatic discharge, and linear sweep voltammograms. The results indicate that the impedance value increases by nearly fourfold, and the delayed time decreases from 2.1 s to 0.6 s. 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 were studied by scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy( FTIR), respectively. The SEM images of the AZ31B Mg alloys in composite solution with or without Na2SiO3 additive have an evident distinction due to the formation of new insoluble compound. FTIR result confirms that the corrosion products accumulated on the alloy surface in the electrolyte containing Na2SiO3 are mainly composed of Mg(OH)(2), MgCO3, and MgSiO3.