Exploration of Amorphous V₂O₅ as Cathode for Magnesium Batteries

Development of energy storage technologies that can exhibit higher energy densities, better safety, and lower supply-chain constraints than the current state-of-the-art Li-ion batteries is crucial for our transition into sustainable energy use. In this context, Mg batteries offer a promising pathway to achieve superior volumetric energy densities than Li-ion but require the development of positive electrodes (cathodes) that exhibit high energy densities at a reasonable power performance. Notably, amorphous materials that lack long range order can exhibit "flatter" potential energy surfaces than crystalline frameworks, possibly resulting in faster Mg²⁺ motion. Here, we use a combination of ab initio molecular dynamics (AIMD), and machine learned interatomic potential based calculations is used to explore amorphous-V₂O₅ as a potential cathode for Mg batteries. Using an AIMD-generated dataset, we train and validate moment tensor potentials that can accurately model amorphous-V₂O₅ Importantly, we find a ≈7 (5) orders of magnitude higher Mg²⁺ diffusivity in amorphous-MgV₂O₅ than crystalline-Mg_xV₂O₅ (thiospinel-Mg_xTi₂S₄), which is directly attributable to the amorphization of the structure, along with a 10-14% drop in the average Mg intercalation voltage. Our work highlights the potential of amorphous-V₂O₅ as a cathode that can exhibit both high energy and power densities, resulting in the practical deployment of Mg batteries.