Yolk-shell-structured zinc-cobalt binary metal sulfide @ N-doped carbon for enhanced lithium-ion storage

Abstract

Owing to high capacity, low cost, and environmental benignity, transition-metal sulfides have attracted increasing attention as potential anode materials for lithium-ion batteries (LIBs). However, their practical application is impeded by poor cycling stability and rate capability due to large volume change and sluggish kinetics. Here, a yolk-shell structured zinc-cobalt binary metal sulfide @ N-doped carbon composite (Zn-Co-S@N-C) with enhanced lithium storage is reported. In this composite, unique porous yolk-shell structure provides short Li+/e− diffusion distance and offers sufficient void space to accommodate volume variation during the Li+ insertion/extraction process. The presence of N-doped carbon matrix not only enhances electron transfer kinetics, but also improves structural stability. Moreover, bimetallic sulfides enhance electrochemical reactivity for superior lithium storage and mitigate the formation of by-products. The resulting Zn-Co-S@N-C anode exhibits significantly enhanced cycling stability (667.7 mAh g−1 after 300 cycles at 1000 mA g−1) and rate capability (332.2 mAh g−1 at 5000 mA g−1).