Sulfur-assisted thermal reduction synthesis of MoO2/Mo4O11 materials as high-performance cathodes for aqueous zinc-ion batteries

Abstract

A MoO₂/Mo₄O₁₁ hetero-junction material prepared by a simple sulfur-assisted thermal reduction technique as the cathode of a water-based zinc-ion battery is reported. Density functionals theories (DFT) calculations reveals that the combining of Mo₄O₁₁slab and MoO₂slab aids the performance of the material in three aspects. Firstly, the facile 3D diffusion network in the case of Mo₄O₁₁slab offers the alternate Zn²⁺ diffusion passageway when the one dimensional diffusion channel of MoO₂ is blocked either by the adsorbed S-species or the stuck Zn²⁺. Secondly, the formation of MoO₂/Mo₄O₁₁ hetero-junction expands the interface area from MoO₂ side by ca. 3.1 % and this reduces the energy barrier from Zn2c to Zn2d in the MoO₂ slab to 0.14 eV. Thirdly, less volume expansion is observed in the case of MoO₂ slab with the intercalation of Zn²⁺ compared with bulk MoO₂, indicating more structural stability. Based on the synergistic effect of MoO₂ and Mo₄O₁₁, the prepared MoO₂/Mo₄O₁₁ hetero-junction material provides an amazing specific capacity of 260 mAh g⁻¹ after 500 cycles at the current density of 0.5A g⁻¹. During the long cycle (3000 cycles), the specific capacity of 184.1mAh g⁻¹ can be maintained even if the current is as high as 2A g⁻¹.