Achieving balanced behavior between polysulfides adsorption and catalytic conversion from heterostructure Fe3C-Fe3P promotor for high-performance lithium-sulfur batteries

Abstract

Although rechargeable lithium-sulfur batteries (LSBs) are next generation energy storage devices, severe shuttle effect and sluggish multi-electron redox reactions compromise the practical application of LSBs. To address these issues and enable the manufacture of robust LSBs, here the use of Fe3C-Fe3P heterostructure encapsulated in nitrogen–doped carbon nanotubes (FeCP@NCNT) was synthesized. The tubular geometry of FeCP@NCNT provided buffering void to suppress volume change, and afforded conductive network to expedite the diffusion of Li+, as well as endowed plenteous active sites to absorb and catalyze the transformation of LiPSs during charge–discharge cycles. Experimental data proved that FeCP@NCNT could strengthen the “anchoring of lithium polysulfides (LiPSs)” (by Fe3P) and expedite the “diffusion of intermediate” (by CNT) as well as accelerate the “catalytic phase conversion” (by Fe3C), resulting in balanced “trapping-diffusion-conversion” dynamic process. Notably, FeCP-3 h@NCNT/G/S attained an initial capacity of 1127 mAh/g with a low decay rate of 0.12 % at 1C for 300 cycles Moreover, FeCP-3 h@NCNT/G/S delivered excellent battery performances under high currents of 2 and 5C for 500 cycles. This work felicitously proposed the strategy to fabricate metal carbide-phosphide heterostructure electrocatalyst for high-performance LSBs.