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Magnesium ion battery is one of the promising next-generation energy storage systems. Nevertheless, lack of appropriate cathode materials to ensure massive storage and efficient migration of Mg cations is a big obstacle for development of Mg-ion batteries. Herein, by means of first principles calculations, the geometric structure, electronic structure, Mg intercalation behavior and Mg diffusion behavior of the layered MoO2 and two MoOSe (MoOSe(I) and MoOSe(V)) were systematically investigated. Layered MoO2 shows semiconductor properties, while MoOSe displays metallic characteristics which ensure higher conductivity. The Mg cations tend to intercalate into octahedral sites for both MoO2 and MoOSe. The maximum Mg-storage phases of the layered MoO2, MoOSe(I) and MoOSe(V) correspond to Mg0.666MoO2, Mg0.666MoOSe(I) and Mg0.666MoOSe(V), with theoretical specific capacities of 279, 191 and 191 mAh g−1, respectively. The calculated discharge plateaus of MoO2 and two MoOSe are all about 1 V, which ensure that the layered MoO2 and MoOSe electrodes can act as cathodes for Mg-ion batteries in the early stage. Moreover, comparing with other cathodes, the diffusion barrier of Mg cations and volume expansion during Mg intercalation process are competitive. The results suggest that layered MoO2 and MoOSe are the promising cathode materials for Mg-ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • DFT for prediction of Li+, Na+ and Al3+ pre-intercalated V 2 O 5 cathodes for MIBs. • Investigation of Mg intercalation and migration behavior on pre-intercalated V 2 O 5. • Metal ions pre-intercalation strategy of layered structure cathode for Mg-ion batteries is proposed. Metal ions pre-intercalated layered structure materials are considered as potential high performance cathodes for Mg-ion batteries (MIBs). Herein, metal ions pre-intercalation strategy of layered cathode for MIBs by using Li, Na, Al pre-intercalated V 2 O 5 cathode as a carrier has been investigated and proposed based on first principle calculations. The pre-intercalation process is energetically favorable and metal ion pre-intercalation improves the electronic conductivity of V 2 O 5. The bondings of Li-V 2 O 5 , Na-V 2 O 5 and Al-V 2 O 5 all exhibit ionic characters, and the interaction between Al ion and V 2 O 5 is the strongest. The interlayer distance expansion of Na pre-intercalated V 2 O 5 is more trivial than that of Li, Al pre-intercalated V 2 O 5. The open circuit voltage of the V 2 O 5 cathode is dropped by pre-intercalated metal ions, and the voltage of Li and Na pre-intercalated V 2 O 5 is higher than that of Al pre-intercalated V 2 O 5. The diffusion barriers of Mg in the V 2 O 5 matrix are reduced by pre-intercalation. Overall, metal ion pre-intercalation with a large atomic radius and small atomic charges holds great potentials to expand interlayer distance, enhance electronic conductivity, maintain high discharge voltage and improve diffusion ability of layered cathode. We hope our work could provide a significant guidance to the practical design of layered cathodes for MIBs. [ABSTRACT FROM AUTHOR]

Three types of VS 2 as electrode for magnesium ion batteries were been studied by first-principle calculations. The average working voltages results suggest that monolayer-VS 2 can be employed as anode materials, while double-layer-VS 2 , bulk-VS 2 can be used as cathode materials for magnesium ion batteries. • DFT for prediction of three types of VS 2 as electrode materials for MIBs. • Investigation of the adsorption, charge transfer, bond stability of Mg on the VS 2. • M-VS 2 can be employed as anode, while D-VS 2 , B-VS 2 can be used as cathode for MIBs. Herein, by means of first-principle calculations based on density functional theory (DFT), the electrochemical properties of monolayer VS 2 (M-VS 2), double-layer VS 2 (D-VS 2) and bulk VS 2 (B-VS 2) as electrode materials for Mg-ion batteries (MIBs) were comprehensively explored. The computation results reveal that Mg atom can strongly bind with the three different forms of VS 2. All of the Mg adsorbed VS 2 systems demonstrate metallic characteristics, which indicates a good electronic conductivity. In addition, crystal orbital hamiltonian population shows that the stability of V-S bond is weakened after adsorption of Mg atom. The low diffusion barriers of Mg give rise to the high rate performance of VS 2 in MIBs. More interestingly, the three types of VS 2 display same storage ability for Mg cations, which can adsorb 0.5 Mg atoms for VS 2 , producing maximum theoretical capacity 233 mA h g−1 for MIBs. The average working voltages results suggest that M-VS 2 can be employed as anode materials, while D-VS 2 , B-VS 2 can be used as cathode materials for MIBs. [ABSTRACT FROM AUTHOR]