Layered Sulfides with Anionic Redox Chemistry for Mg Cathodes

Rechargeable Mg batteries (RMBs), which are considered one of the most promising candidates for post‐lithium‐ion batteries, are primarily hindered by a lack of high‐energy cathode materials. Sulfides, albeit with faster reaction kinetics than oxides, suffer from low capacities and energy densities due to the solely cationic redox chemistry. Herein, a series of layered solid‐solution sulfides, V 1‐ x Cr x S 2 (0 ≤ x < 1), are designed to realize anionic redox chemistry, in which the transition metal–ligand energy levels are discreetly regulated to achieve the strong covalent interaction and trigger the charge compensation of sulfur. The V 0.5 Cr 0.5 S 2 sample is highlighted to yield a specific energy of 255 Wh kg −1 with the high output voltage of 1.5 V and decent cycling stability. The intercalation of Mg 2+ into layered V 0.5 Cr 0.5 S 2 is demonstrated to be facilitated by a 2‐methoxyethylamine molecule and basically involves the cationic (V 2+/4+ ) and anionic (S 2−/ n − , n < 2) redox. The achievement of anionic redox chemistry in layered sulfides will pioneer a way to develop high‐energy cathode materials for RMBs.