A Class of Organopolysulfides As Liquid Cathode Materials for High-Energy-Density Lithium Batteries

Sulfur-based cathodes are promising to enable high-energy-density lithium–sulfur batteries; however, elemental sulfur as active material faces several challenges, including undesirable volume change (∼80%) when completely reduced and high dependence on liquid electrolyte wherein an electrolyte/sulfur ratio >10 μL mg–1 is required for high material utilization. These limit the attainable energy densities of these batteries. Herein, we introduce a new class of phenyl polysulfides C6H5SxC6H5 (4 ≤ x ≤ 6) as liquid cathode materials synthesized in a facile and scalable route to mitigate these setbacks. These polysulfides possess sufficiently high theoretical specific capacities, specific energies, and energy densities. Spectroscopic techniques verify their chemical composition and computation shows that the volume change when reduced is about 37%. Lithium half-cell testing shows that phenyl hexasulfide (C6H5S6C6H5) can provide a specific capacity of 650 mAh g–1 and capacity retention of 80% through 500 cycles ...