Effect of an electrolyte additive hexamethylenetetramine on electrochemical behaviors of the Mg-11Li-3.5Al-2Zn-1.5Re-0.5Zr electrode

The electrochemical performance of the Mg-11Li-3.5Al-2Zn-1.5Re-0.5Zr electrode in a 0.7 mol L-1 NaCl solution, containing different concentrations of hexamethylenetetramine (C6H12N4) as an electrolyte additive was investigated by potentiodynamic polarization, potentiostatic current-time, electrochemical impedance spectra measurements and scanning electron microscopy (SEM). The potentiodynamic polarization curves show that the corrosion potential of the electrode increases with the concentration of C6H12N4 in the following order: 0.10 mmol L-1 < 0.05 mmol L-1 < 2.00 mmol L-1 < 0.50 mmol L-1 < 0.80 mmol L-1 < 1.00 mmol L-1 < 0.00 mmol L-1. The potentiostatic current-time curves indicate that the oxidation current density of the electrode in a 0.7 mol L-1 NaCl solution containing 0.10 mmol L-1 of C6H12N4 is the largest among the studied electrolyte solutions, and the polarization resistance of the Mg-11Li-3.5Al-2Zn-1.5Re-0.5Zr electrode in a 0.7 mol L-1 NaCl solution containing 0.10 mmol L-1 of C6H12N4 is smaller than that in a 0.7 mol L-1 NaCl solution. The scanning electron microscopy studies suggest that the presence of C6H12N4 in a 0.7 mol L-1 NaCl solution can loosen oxidation products and promote its coming off, consequently enhancing the discharging performance of the Mg-11Li-3.5Al-2Zn-1.5Re-0.5Zr electrode.