High Coulombic efficiency aluminum-ion battery using an AlCl3-urea ionic liquid analog electrolyte

To relieve humanity's dependence on fossil fuels, grid-scale storage of renewable energy must be implemented. This requires cheap, high-rate, and long cycle life energy storage mechanisms. This work presents the development of an Al-ion battery using earth-abundant aluminum and graphite as anode and cathode, respectively, and an ionic liquid analog electrolyte composed of AlCl₃ and urea that is very low-cost and eco-friendly. The battery exhibits ∼99.7% Coulombic efficiency and a substantial rate capability, with a cathode capacity of 73 mA g^-1 at 100 mA g^-1 (1.4 C).