Oxides As Cathode Materials for Mg-Ion Batteries
Despite these attractive properties, implementation of Mg-ion batteries has been hindered by several challenges. Most significantly, 1) electrolytes which allow for reversible Mg deposition have limited stability, and 2) reversible intercalation of Mg2+in cathode materials is kinetically slow and often irreversible. Thus, future Mg-ion batteries must incorporate stable high voltage and capacity cathode materials with fast and reversible Mg intercalation kinetics.
Mg battery prototypes have used Chevrel phase cathodes, Mo6S8, and its derivatives. These cathodes incorporate a delocalized framework to accommodate the charge and diffusion of hard Mg2+ ions. The multiple Mo ions allow for a diffuse charge network to accommodate intercalated Mg2+ ions. However, Chevrel phase cathodes suffer from low voltages (~1.1 V vs Mg/Mg2+) and only partial reversibility, where the total capacity drops by ~40% after the first discharge cycle.For Mg batteries to be realized commercially, the cathode’s voltage and reversibility must be improved.
In this talk we discuss our efforts using transition-metal oxides with open and delocalized structures as cathode materials for Mg-ion batteries. We investigate various bronzes and polyoxometalates, which have known magnesiated forms and high redox potentials. We find that these oxides exhibit reversible electrochemical behavior in various non-aqueous electrolytes and report on our efforts at confining these materials to electrode surfaces.
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