Aluminium Deposition in EMImCl-AlCl <sub>3</sub> Ionic Liquid and Ionogel for Improved Aluminium Batteries
Theresa Schoetz, Oi Man Leung, Carlos Ponce de León, C. Zaleski, Igor Efimov
Abstract
Aluminium batteries with non-aqueous electrolyte have initially focused on Lewis acidic ionic liquid systems with heavy Al 2 Cl 7 − anions that limit the specific capacity, energy and power. In order to develop the secondary aluminium batteries further for future energy storage beyond lithium-ion, high performance electrolytes that enable efficient aluminium deposition/dissolution must be developed. This work studied the electrodeposition of aluminium from both 1-ethyl-3-methylimidazolium chloride aluminium chloride (EMImCl-AlCl 3 ) ionic liquids with different Lewis acidities, and their gel form- the ionogel . Thereby, cyclic voltammetry, in-operando atomic force microscopy and scanning electron microscopy coupled with energy dispersive X-ray diffraction measurements were used to determine the characteristics of aluminium deposition in the ionic liquid depending on the ratio of AlCl 3 to EMImCl. Based on these insights, Lewis acidic and neutral ionic liquids were gelified with polyethylene oxide. The focus was on the feasibility of aluminium deposition in Lewis neutral ionogels containing only lightweight AlCl 4 − anions. It was proven for the first time that aluminium can be deposited from a Lewis neutral ionogel without any dendrite growth within a very wide potential stability window of 5 V but at a low coulombic efficiency of ≤60%.