A Rechargeable Al–Te Battery

Rechargeable aluminum based batteries attract particular attention due to their high anode capacity, safety, and cost advantage. Recently, high discharge voltage, ultrahigh rate performance, and long cycle life of aluminum ion batteries have been reported. However, the capacity of these Al-based batteries is limited, and it is of great value to explore novel cathodes with high reversible capacity that can rival a rechargeable lithium ion battery. In this work, we present the redox process of a tellurium electrode in a Lewis acidic AlCl₃/[EMIm]Cl room temperature ionic liquid and disclose, for the first time, that the tellurium not only can be reduced to Te^2– but also can be oxidized to TeCl₃⁺, and the whole process is reversible. Subsequently, we successfully construct a rechargeable Al–Te battery with an initial reversible capacity of ∼913 mAh/g, which is close to the theoretical capacity of tellurium of ∼1260.27 mAh/g and an obvious discharge voltage plateau at ∼1.5 V, already approaching that of a Li–Te battery (1.7 V). Significantly, this work brings a new way to reconsider the reaction mechanism and the theoretical capacities of chalcogen and its compounds as the cathode of the aluminum based batteries in room temperature chloroaluminate melts. For instance, the theoretical capacity of the sulfur is an unprecedented 5015.09 mAh/g when it undergoes a similar reversible redox process from S^2– to SCl₃⁺.