Low-Temperature and High-Rate Rechargeable Aluminum Batteries Enabled by Ternary Eutectic Electrolytes

Rechargeable aluminum batteries (RABs) have garnered extensive scientific attention as a promising alternative chemistry due to the inherent advantages associated with aluminum (Al) metal anodes, including their high theoretical capacities, cost-effectiveness, environmental friendliness, and inherent non-flammable properties. Nonetheless, the practical energy density of RABs is constrained by the electrolytes that support lower operational voltage windows. Herein, we report a ternary eutectic electrolyte composed of 1-ethyl-3-methylimidazolium chloride ([C₂C₁im]Cl):1-butyl-3-methylimidazolium chloride ([C₄C₁im]Cl):aluminum chloride (AlCl₃) for the application of RABs. The electrolyte exhibits a high operational potential window (~3 V vs. Al/Al³⁺ on SS 316) and high ionic conductivity (~8.3 mS cm⁻¹) while exhibiting only a low temperature glass transition at −65 °C suitable for all-climate conditions. Al||graphene nanoplatelets cell delivers a high capacity of ~117 mAh/g, and ~43 mAh/g at a very high current densities of 1 A/g and 5 A/g, respectively. The cells render a reversible capacity of 20 mAh/g at −20 °C and 17 mAh/g at −40 °C, indicating their suitability for operation under extreme environmental conditions. We comprehensively evaluated the design and optimization of carbon paper-based battery systems. The ternary eutectic electrolyte demonstrates exceptional electrochemical performance, thus signifying its substantial potential for utilization in high-performance energy storage systems in all climates.