Preliminary Investigation\ninto the Feasibility of\nan Ambient-Temperature Gallium-Based Liquid Metal-Air Battery

Rechargeable metal-air batteries are of great interest,\nas they\ncan provide extremely high energy densities. Here, we describe our\npreliminary investigation into the feasibility of an ambient-temperature\nliquid metal-air battery based on gallium, which lays the groundwork\nfor an all-liquid-flow battery with an unprecedented energy density.\nCyclic voltammetry results confirm a reversible Ga–Ga<sub>2</sub>O<sub>3</sub> redox couple suitable for the negative electrode, with\na potential of −0.483 V vs the reversible hydrogen electrode\nunder strongly alkaline conditions. Thus, the resulting cell voltage\nfor the Ga-air battery is 1.72 V, in comparison to 1.67 V for conventional\nsolid Zn-air systems. The gallium liquid metal air battery (LMAB)\nshows superior polarization performance in comparison with a commercial\nZn-air battery, which is particularly attractive when coupled with\nthe natural benefits of the liquid state of the metal, such as the\nabsence of dendrite formation, self-healing nature, convenient refilling,\nor recharging, and the potential for a true flow metal air battery\n(MAB) with a flexible configuration. The button gallium LMAB cell\ntested here for proof of concept was set up as a nonrechargeable primary\nbattery; however, CV studies demonstrate the reversibility of the\nreaction chemistry. The lack of rechargeability in the current design\nis attributed to the detrimental drying of the thin electrolyte layer\nat a test temperature of 50 °C. A flowing electrolyte, for example,\ncan readily hydrate the thin electrolyte layer to overcome inadvertent\ndrying, and a flow battery configuration can enhance mixing to overcome\nthe transport limitations of the oxide at the interface.