Rechargeable Mg/Li, Mg/Na, and Mg/K Hybrid Batteries Based on Layered VS.

Rechargeable Mg batteries have great potential in next-generation scalable energy-storage applications, but the electrochemical performance is limited by the Mg-intercalation cathodes. Hybrid batteries based on dual-cation (Mg and alkali metal cations) electrolytes would not only improve the electrochemical performance but also induce the co-intercalation of Mg with alkali metal cations. As previous reports overwhelmingly focus on Mg/Li hybrid batteries, in this work, Mg/Na and Mg/K hybrid batteries are constructed using a typical layered VS cathode and studied in comparison with Mg/Li batteries. It is observed that Mg could co-intercalate into VS with Li, Na, or K. However, Mg-intercalation is irreversible in the Mg/Li system, and co-intercalation of Mg and K would cause a collapse of VS. Comparatively, the co-intercalation of Mg and Na into VS exhibits the highest reversibility, and the Mg/Na hybrid battery shows the best cycling stability without capacity fading within 1000 cycles. Our work highlights the co-intercalation reversibility of a non-pre-expanded layered disulfide cathode and delivers insights for the development of high-performance rechargeable Mg metal batteries.