Room-Temperature Aluminum-Sulfur Batteries with a Lithium-Ion-Mediated Ionic Liquid Electrolyte

Summary Aluminum-sulfur (Al-S) chemistry is attractive for the development of future-generation electrochemical energy storage technologies. However, to date, only limited reversible Al-S chemistry has been demonstrated. This paper demonstrates a highly reversible room-temperature Al-S battery with a lithium-ion (Li + -ion)-mediated ionic liquid electrolyte. Mechanistic studies with electrochemical and spectroscopic methodologies revealed that the enhancement in reversibility by Li + -ion mediation is attributed to the chemical reactivation of aluminum polysulfides and/or sulfide by Li + during electrochemical cycling. The results obtained with X-ray photoelectron spectroscopy and density functional theory calculations suggest the presence of a Li 3 AlS 3 -like product with a mixture of Li 2 S- and Al 2 S 3 -like phases in the discharged sulfur cathode. With Li + -ion mediation, the cycle life of room-temperature Al-S batteries is greatly improved. The cell delivers an initial capacity of ∼1,000 mA hr g −1 and maintains a capacity of up to 600 mA hr g −1 after 50 cycles.