Computational discovery of Mg-based garnet structures with enhanced battery performance

In the burgeoning landscape of power source technologies, Mg-ion batteries have emerged as a promising alternative to the widely used Li-ion batteries due to the large natural abundance and divalence of magnesium. As an attempt to develop working Mg-ion batteries, for which securing efficient cathode materials with high energy density and ion mobility is crucial, we carry out electronic structure calculations based on density functional theory (DFT) to uncover high-performance garnet-type cathode materials, Mg 3 V 1.5 Cr 3.5 O 12 (MVCO) and Mg 3 V 3 Mn 2 O 12 (MVMO), for efficient Mg-ion batteries. Our DFT calculations demonstrate that MVCO (MVMO) not only achieves a high average voltage of 2.79V (2.69V) and energy density of 856 Wh/kg (821 Wh/kg) but also presents small volume change of 4.5 % (4 %) and low ion migration barrier of 395 meV (190 meV). It is further found out that although oxygen atoms participate in the redox reaction during the (de)intercalation process, the strong orbital hybridization between oxygen and transition metal elements prevents forming (O-O) n− dimers and thus oxygen release is likely to be suppressed, ensuring structural stability. Combined with high likelihood of successful synthesizability as is evidenced through comparison with the amorphous limits, these materials properties make the proposed garnet-structured magnesium compounds appealing candidates for post-Li energy storage solutions.