Manganese cobalt sulfide-doped fibrous sulfurized polyacrylonitrile for high-rate and long-life lithium–sulfur batteries†

Abstract

Sulfurized polyacrylonitrile (SPAN) is regarded as a promising cathode material for next-generation lithium batteries. However, the insufficient electronic and ionic conductivity of the SPAN material leads to low rate-performance, unsatisfactory active material utilization, and limited cycling stability. Here, we propose a strategy to increase the electronic conductivity of SPAN by compositing PAN with manganese cobalt sulfide (MCS), which increases the graphitization degree during the subsequent vulcanization as manifested by higher graphitic nitrogen content. In addition, the incorporation of MCS promotes the formation of a thinner and uniform cathode electrolyte interface, which suppresses the dissolution of sulfur species into the electrolyte as revealed by in situ UV-vis spectroscopy. Together with an electrospun fibrous morphology that minimizes the migration path of Li⁺ inside the SPAN, the resulting SPAN composite displays fast reaction kinetics, high active material utilization and stable long-term cycling at high current density, achieving a high capacity retention of 437 mA h g⁻¹ (based on the composite) after 1500 cycles at 5C (1C = 600 mA g⁻¹) without obvious capacity fading, and 338 mA h g⁻¹ after 2000 cycles at 10C with a low fading rate of 0.01% per cycle.