Insoluble Polyquinonyl Sulfide as High-Capacity Cathode Material for Magnesium Battery

Organic magnesium storage materials are intriguing as cathode materials for rechargeable magnesium batteries (RMBs) because of their flexible structure and the potential of fast Mg-ion diffusion kinetics. However, the dissolution of these materials in the electrolytes of the RMBs limits their application. Herein, the pentacenetetrone (PT) and its polymer poly(pentacenetetrone sulfide) (PPTS) are developed as cathode materials for RMBs. Given the benefit of its insoluble property in the Mg-ion electrolyte, the as-prepared PPTS cathode exhibits significantly enhanced reversible capacity, coulombic efficiency, and rate performance compared to PT. For instance, the high capacities of 241 mAh g^-1 (100 mA g^-1) and 131 mAh g^-1 (2 A g^-1) are obtained for the PPTS cathode, demonstrating a competitive rate performance of PPTS compared to previously reported organic cathodes of RMBs. In contrast, the soluble PT cathode exhibits much lower capacities of 163 mAh g^-1 (100 mAh g^-1) and 31 mAh g^-1 (2 A g^-1).