Bio derived deep eutectic solvents for rechargeable Aluminum batteries

Existing literature on Al rechargeable batteries is promising but the technology is far from optimized. There are currently no commercially available rechargeable aluminum batteries, though the literature in the past few years has been very active. Beyond lithium-based rechargeable battery systems based on Na, K, Mg, Ca, Zn, and Al, have been proposed as alternatives. Among all these, battery systems based on Al harbor the potential of being environmentally sustainable and low cost, as Al is the most abundant metal in the Earth’s crust (8.2 wt %) and its raw material cost is also lowest (1.9 USD kg−1). From an energy storage perspective, Al metal exhibits the highest theoretical volumetric capacity at 8,046 mAh cm−3 and its theoretical specific capacity (2,981 Ah kg−1) is only second to that of Li metal (3,861 Ah kg−1). These exceptionally high theoretical capacities of metallic Al signal the possibility of achieving electrochemical energy storage devices with considerably high energy density. Unlike, for example Pb acid batteries, Al electrodeposition in aqueous electrolyte is hindered due to the lower reduction potential of Al3+/Al redox couple relative to that of H2O/H2 making an alternative solvent necessary. We have identified a potentially bio-derived deep eutectic solvent suitable for this application. Deep eutectic solvents allow plating and deplating of aluminum, a crucial part of use of a metal in batteries. These solvents vary considerably in properties. Part of our aim is to leverage existing work at CAER using machine learning to aid in this.