Co/Co₃O₄-embedded N-doped hollow carbon composite derived from a bimetallic MOF/ZnO core-shell template as a sulfur host for Li-S batteries

Abstract

Lithium-sulfur batteries are a promising next-generation energy storage technology. To meet the industrial requirements, however, effective sulfur host materials are highly desired for the enhanced sulfur loading and lithium polysulfides (LiPSs) trapping. Herein, we describe the synthesis of N-doped hollow carbon composite embedded with well-dispersed Co/Co₃O₄ nanoparticles (Co/Co₃O₄-NHC) via the carbonization of a Zn/Co bimetallic metal-organic frameworks/ZnO nanospheres core-shell structure. The Co/Co₃O₄-NHC features uniform N-doping, intertwined carbon nanotubes (CNTs), and dual types of pores. ZnO nanospheres employed as a template for hollow structure also contribute to the formation of CNTs and micro-pores. The S-infiltrated Co/Co₃O₄-NHC cathode delivers an excellent rate performance (specific capacity of 447.9 mA h g⁻¹ at 5 C-rate) and stability (553.4 mA h g⁻¹ after 500 cycles). With a high S loading (4 mg cm⁻²), 87.8% of specific capacity is retained after 250 cycles. This work can offer insights on designing the sulfur host materials for high-performance Li-S batteries.