Water soluble graphene as electrolyte additive in magnesium-air battery system

• WSG was successfully synthesized and utilized as a catalyst to improve Mg-Air system.
• High specific capacity of 1030.71 mAh g−1 and current density of 19.33 mA cm−2 achieved.
• Mg anode breakdown during self-discharge cycle was circumvented.
• Reduction in Hydrogen gas evolution at Mg anode in WSG based NaCl electrolyte.

Magnesium-air (Mg-air) batteries are an important energy source used to power electronic equipment and automobiles. Metal-air batteries give more energy density due to surplus air involved in reduction reaction at air cathode. In this study, the scope of improvements in the efficiency of Metal-air batteries is investigated through addition of water soluble graphene (WSG) as inhibitor in NaCl electrolyte. The discharge performance, corrosion behaviour and electrochemical impedance are studied for (i) the conventional Mg-air battery using 3.5% NaCl and (ii) Mg-air battery with WSG-based 3.5% NaCl electrolyte. X-ray diffraction analysis for WSG is carried out and it shows the crystalline nature of WSG by an intense sharp peak at 26.3°. Scanning electron microscope study is also performed and shows the flake-like structure of WSG denoted by thin layers of carbon. The immersion of WSG in 3.5% NaCl electrolyte increased the current density from 13.24 to 19.33 mA cm−2. Meanwhile, the WSG-based Mg-air battery was found to hold specific discharge capacity of 1030.71 mAh g−1, which was higher than that obtained in 3.5% NaCl electrolyte (i.e., 822.85 mAh g−1). The WSG-based Mg-air battery shows good self-discharge capacity and higher electrochemical activity during discharge.