High-capacity cathodes for magnesium lithium chlorine tri-ion batteries through chloride intercalation in layered MoS2: a computational study

Abstract

Rechargeable magnesium ion batteries (MIBs) have great potential as an alternative technology to substitute resource-limited lithium-ion batteries (LIBs), but rather difficult transportation of Mg²⁺ in cathodes and hence low cathode capacities loom as a major roadblock for their applications. Here we attempt to formulate high capacity cathodes for MIBs through theoretical simulation of the energetic and kinetic responses to the introduction of metallic ions (Mg²⁺ or Li⁺) or their chlorides into the inter-layered sites in the MoS₂ compound. We find that the layered structural feature of metal sulphides can be energetically and dynamically stable, when either metallic ions or their chlorides are accommodated. The latter is also effective in opening up the inter-layer spacing and thus bringing about significant enhancement in the transport of the active ions (Li⁺, Mg²⁺ and Cl⁻) together with highly increased capacity. The optimized new cathode material M_xMoS₂Cl_0.5 (M refers to Mg²⁺, Li⁺, or a mixture of both) is capable of sustaining a high chemical potential of 2.4 V above Mg/Mg²⁺, together with a high capacity of over 277.4 mA h g⁻¹ without experiencing considerable volumetric changes during charge–discharge cycles. The theoretical energy density is over 465 to 651 mW h g⁻¹, which is highly attractive for developing a new class of high-performance magnesium–lithium–chlorine tri-ion batteries, using environmentally friendly materials with sustainable resources and good chemical stability.