Se as eutectic accelerator in sulfurized polyacrylonitrile for high performance all-solid-state lithium-sulfur battery

Abstract

Replacing liquid electrolyte by solid electrolyte to construct all-solid-state Li-S battery can overcome the safety issue, polysulfide dissolution and presumably lithium dendrite formation, but usually lead to poor rate performance and low S utilization due to the poor Li-ion/electronic conduction resulting from solid-solid interfacial problems. Sulfurized polyacrylonitrile (S@pPAN) is a good sulfur cathode candidate showing excellent results in liquid electrolytes but still limited performance in all-solid-state batteries. Herein, selenium is used in S@pPAN as a eutectic accelerator which can be uniformly distributed into the composite at molecular level through Se-S bonding and accelerate reaction kinetics while contributing capacity at the same time. It is shown that the Li ion diffusion and electronic conduction are tremendously improved by 5 mol% Se-doping in all-solid-state lithium-sulfur batteries. At room temperature, the Se0.05S0.95@pPAN with 5 mg cm-2 cathode loading (1 mg cm-2 Sulfur loading) deliveres an initial reversible capacity of 840 mA h g-1 at current density of 167.5 mA g-1 and high capacity retention of 81% for 150 cycles, and significantly improved rate performance comparing to traditional S@pPAN. The good Li ion and electronic conductivity of Se0.05S0.95@pPAN is pivotal for high performance all-solid-state Li-S battery and the use of the eutectic accelerator is a general and promising way to improve sulfur cathode performance in all-solid-state batteries.