Monoclinic MoO2 Terminated with Enriched (-2 -1 1) Facets Enabling −80 °C Operation in Zinc-Ion Batteries

Abstract

Polar research stations, high-altitude unmanned systems, and aerospace platforms, among others, require rechargeable batteries that can function reliably at extremely low temperatures, yet electrode materials capable of sustaining such frigid operation are exceedingly rare. This work reports a monoclinic MoO2 material that features enriched (-2-1 1) facets and consists of primary crystallites as small as 3−7 nm. Density functional theory calculations reveal that this facet offers a more accessible interfacial migration pathway for zinc ions entering from the surface into the bulk, with an energy barrier of 1.3 eV, significantly lower than the 3.6 eV required on the conventional (0 1 1) facetthe thermodynamically preferred surface in bulk MoO2. When evaluated as zinc-ion battery electrode material at −80 °C, the material can deliver discharge/charge capacities of 92.2/92.5 mAh g−1 at 0.05 A g−1; and at 0.1 A g−1, it sustains discharge/charge capacities of 76.8/76.7 mAh g−1 after 1200 cycles, with Coulombic efficiency approaching 100%. Notably, when benchmarked against the limited literature on zinc-ion storage at or below −70 °C, the oxide presented here delivers high specific capacities and excellent cycling stability, ranking among the best reported for ultra-low-temperature zinc-ion storage.