A Low-Cost Al-Graphite Battery with Urea and Acetamide-Based Electrolytes

Al-ion batteries employing natural graphite cathodes have been proposed as a valid alternative to Li-ion systems due to their low-cost and sustainability, as well as a stable long-term cycle life. In contrast to commonly used but typically expensive ionic-liquid-based electrolytes, our reported Al-graphite batteries use AlCl3/urea and AlCl3/acetamide deep eutectic solvents (DES, also known as ionic liquid analogues) as low-cost alternative. By carefully selecting amide composition, Al speciation in the DES electrolyte can be modified, as confirmed by Raman, NMR and IR spectroscopy. We correlate the speciation changes to resulting battery performance by systematic electrochemical investigations of Al-graphite batteries employing urea and acetamide eutectics of different compositions. The practical applicability was demonstrated using long-term cycling experiments with >8000 cycles, exhibiting a specific capacity of around 50 mAh/g at a current rate of 2 A/g.