Rechargeable Mg2+/Li+, Mg2+/Na+, and Mg2+/K+ Hybrid Batteries Based on Layered VS2

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 (Mg2+ and alkali metal cations) electrolytes would not only improve the electro-chemical performance but also induce the co-intercalation of Mg2+ with alkali metal cations. As previous reports overwhelmingly focus on Mg2+/Li+ hybrid batteries, in this work, Mg2+/Na+ and Mg2+/K+ hybrid batteries are constructed using a typical layered VS2 cathode and studied in comparison with Mg2+/Li+ batteries. It is observed that Mg2+ could co-intercalate into VS2 with Li+, Na+, or K+. However, Mg-intercalation is irreversible in the Mg2+/Na+ system, and co-intercalation of Mg2+ and K+ would cause a collapse of VS2. Comparatively, the co-intercalation of Mg2+ and Na+ into VS2 exhibits the highest reversibility, and the Mg2+/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.