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

Abstract

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 electrochemical 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⁺/Li⁺ 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.