Silver chalcogenides (Ag₂X, X=S, Se) nanoparticles embedded in carbon matrix for facile magnesium storage via conversion chemistry

Despite intensive studies for the last several decades, the progress in the development of efficient cathode materials for rechargeable magnesium batteries is slow. In particular, most intercalation-based materials demonstrate lethargic reaction kinetics owing to a large activation barrier for Mg²⁺ migration. Here, for the first time, we evaluate silver chalcogenides as efficient cathode materials based on a conversion reaction mechanism. Simple one-pot ball milling is employed to produce silver chalcogenide nanoparticles embedded in a carbon matrix, which exhibits excellent electrochemical activity with Mg²⁺ at room temperature. Particularly, the Ag₂Se composite delivers a theoretical magnesium storage capacity of 182 ​mA ​h g⁻¹ at a 0.1-C rate and 79 ​mA ​h g⁻¹ at a 1-C with an adequate stability up to 500 cycles. Structural analyses during cycling confirm that silver chalcogenides operate via a conversion reaction route. This investigation provides an opportunity to develop a new class of viable cathode materials utilizing conversion chemistry.