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

Abstract

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.