Expediting Polysulfide Evolution Kinetics via Porous Carbon Microspheres Embedded with Fe3Se4 Nanoparticles as a Separator Modifier for Lithium–Sulfur Batteries

As a prospective substitution for conventional lithium-ion batteries, lithium–sulfur batteries have been propelled into the spotlight on account of their merits, such as high energy density and ecofriendliness, among other things. Their commercialization, however, has run up against thorny impediments, with them primarily embodying sluggish evolution kinetics of sulfur species, the adverse shuttle effect of soluble polysulfide ions, and insufficient electronic conductivity of S 8 /Li 2 S 2 /Li 2 S. Herein, a multifunctional separator modifier based on porous carbonaceous microspheres inlaid with Fe 3 Se 4 nanoparticles (Fe 3 Se 4 /PCM) is proposed to surmount these hurdles. The porous carbon skeleton offers a wealth of adsorption sites for the physical immobilization of polysulfides in tandem with excellent electrical conductivity. Beyond chemically fixing polysulfide intermediates, the embedded Fe 3 Se 4 can facilitate the conversion reaction from Li 2 S 2 to Li 2 S. Attributed to the superiority of Fe 3 Se 4 /PCM, the final batteries deliver a high utilization rate of sulfur (1179.2 mAh·g –1 at 0.1 C), a superb rate capability of 486.4 mAh·g –1 at 3 C, and prolonged cycling stability (a low degradation rate of 0.04% per cycle over 500 cycles at 1 C). This work may provide a novel formula for designing a string of transition-metal selenides/porous carbon composites as separator modifiers to achieve robust lithium–sulfur batteries.