Dipentamethylene Thiuram Tetrasulfide-Based Cathodes For Rechargeable Magnesium Batteries

Rechargeable Mg batteries (RMBs) represent a possible route for low-cost energy storage applications, but they are lacking a satisfactory cathode material. Conventional sulfur (S-8) cathodes have shown promise, yet they suffer from poor cycling stability and low reversibility. Her; we investigate the organosulfur compound dipentamethylene thiuram tetrasulfide (PMTT) as the source of redox active sulfur. In its pristine form with carbon black as a conductive additive, an initial discharge capacity of 295 mA h g(-1) is reported, which is one of the highest capacities reported for an organosulfur compound for RMBs. A reaction mechanism is proposed, supported by density functional theory calculations. Through a mild heat treatment, a PMTT-derived sulfur/mesoporous carbon composite is investigated. PMTT's unique chemistry and the resulting molecular mixture of active and inactive components enable a high cycling stability (76% capacity retention in the 100th cycle after one formation cycle) and excellent rate performance (185 mA h g(-1) at 500 mA g(-1)) for an RMB. The PMTT-derived sulfur/mesoporous carbon composite outperforms reference cells with a conventional S-8 composite and, combining with further electrolyte development, may open up for cost-competitive RMBs.