Hierarchically porous nanofibers comprising multiple core–shell Co3O4@graphitic carbon nanoparticles grafted within N-doped CNTs as functional interlayers for excellent Li–S batteries

Abstract

Hierarchically porous nanofibers (NFs) comprising multiple core–shell Co3O4@graphitic carbon (GC) nanoparticles grafted within N-doped carbon nanotubes (CNTs) (Co3O4@GC/N-CNT NF) were rationally designed as functional interlayers for excellent Li–S batteries (LSBs). The well-grafted N-doped CNTs (N-CNTs) and high-conductivity GC layer coated on Co3O4 nanoparticles provided conductive channels for fast ionic/electronic transfer during charging–discharging. The Co3O4 nanoparticles inside the GC layer served as active polar sites for efficient anchoring of dissolved lithium polysulfides and ensured their reuse during redox reactions via fast charge transfer processes. Consequently, the assembled Li–S cell featuring a Co3O4@GC/N-CNT NF-coated separator and a pure sulfur electrode (70 wt% and 2.0 mg cm−2 loading) presented an excellent electrochemical performance, namely a high-rate capability and stable cycling performance at C-rates of 0.1, 0.5, and 1.0C. In addition, the Li-ion diffusion coefficient of the assembled Li–S cell (10−8 cm2 s−1) was one order of magnitude higher than those of the assembled Li–S cells featuring bare Co3O4 NF-coated and pristine separators (10−9 cm2 s−1). The remarkable overall cell performance was attributed to the combination of highly conductive N-CNTs, GC layer, and polar Co3O4 nanoparticles, which effectively trapped polysulfides. Therefore, we believe that the proposed unique nanostructure synthesis method can provide new insights into the development of sustainable and highly conductive polar materials as functional interlayers for advanced LSBs.