A Chlorine-Free and Water-Free Ternary Eutectic Electrolyte Enabling High-Performance Aluminum-Ion Batteries

Abstract

Aluminum-ion batteries (AIBs) have garnered significant attention as promising candidates for large-scale energy storage systems. However, the widespread adoption of AIBs has been impeded by the limitations of conventional AlCl₃-based ionic liquid electrolytes, which are characterized by high cost, corrosiveness, and sensitivity to moisture. In this study, we present a novel ternary eutectic electrolyte system for AIBs that addresses these challenges, offering enhanced stability, reduced corrosivity, and cost efficiency. The proposed electrolyte is composed of aluminum trifluoromethanesulfonate, ethylene glycol (EG), and N-methylacetamide (NMA) with an optimized ratio. Through comprehensive spectroscopic analyses, we demonstrate that the coordination structure of metal cations in the electrolyte is effectively modulated by interactions with EG and NMA molecules, and the synergistic combination of EG and NMA with Al³⁺ can reduce hydrogen evolution corrosion and side reaction of free ligands, effectively promoting the reaction kinetics and enhancing the stability of the Al electrode. Furthermore, the assembled AIB achieves a remarkable discharge capacity of 91 mAh g^–1 while exhibiting exceptional cycling stability. Moreover, the energy storage mechanism of the AIBs has been systematically investigated and elucidated. This study provides fundamental insights into the design of efficient AIB systems and offers valuable guidance for developing next-generation metal-ion batteries.