Decoration of carbon nanofibers with bimetal sulfides as interlayer for high performance lithium-sulfur battery

Abstract

In order to obtain high-performance lithium-sulfur (Li-S) batteries, the rapid capacity loss caused by the notorious polysulfide shuttle effect is an urgent challenge to be solved. It is widely reported that polysulfides are trapped in electrolytes due to the strong chemisorption of polar materials in Li-S batteries. Here, a free-standing NiCo2S4 nanoparticles decorated carbon nanofibers (NiCo2S4-CNFs) interlayer is prepared via electrospinning and simple hydrothermal method for the application in Li-S batteries. Three-dimensional carbon fibers (CNFs) skeleton builds a highly conductive carbon network, which provides a large quantities of transmission paths for electrons and ions. Uniformly distributed NiCo2S4 nanoparticles act as an absorbent of the long-chain lithium polysulfides (LiPSs) and a catalyst to accelerate the conversion of sulfur species. Meticulous designed NiCo2S4-CNFs interlayer significantly improves the capacity retention rate and cycle stability of Li-S batteries. It supplies an initial specific capacity of 1421 mAh g−1 at 0.1 C, and its capacity remains at 918 mAh g−1 after 200 cycles at 0.2 C. Even at a high current density of 1 C, it still possesses a reversible specific capacity of 515 mAh g−1 after 500 cycles and extremely low capacity decay of 0.06% per cycle. More importantly, the NiCo2S4-CNFs interlayer still delivers excellent electrochemical performance with a higher sulfur loading of 4.5 mg cm−2, which verifies its huge commercial application potential.