Porous NiCo2S4 Nanoneedle Arrays with Highly Efficient Electrocatalysis Anchored on Carbon Cloths as Self-Supported Hosts for High-Loading Li-S Batteries.

Lithium-sulfur (Li-S) batteries have attracted all-time attention because of their supernormal high energy density and low cost, whereas they are still plagued by the severe polysulfide shuttling and sluggish sulfur redox reaction kinetics. Moreover, poor sulfur electrochemical utilization and rapid capacity degradation are top concerns in the high-loading Li-S batteries, which severely hinder their practical applications. Herein, a completely novel porous nanoneedle array NiCo2S4 electrocatalyst grown on a nitrogen-sulfur-doped carbon cloth (NSCC) (NiCo2S4@NSCC) is constructed as a 3D self-supported sulfur host for high-loading Li-S batteries, in which the highest sulfur loading reaches 4.9 mg cm-2. The as-prepared NiCo2S4@NSCC with a typical sulfur loading of around 2.0 mg cm-2 provides a high discharge capacity of 1223 mA h g-1 at 0.2 C and long-term cycle stability with a low capacity decay of 0.046% per cycle over 500 cycles at 1 C. Additionally, NiCo2S4@NSCC/S with a high sulfur loading of 4.9 mg cm-2 delivers an excellent reversible areal capacity of 4.4 mA h cm-2 g over 50 cycles. Noting that such superior electrochemical performance of NiCo2S4@NSCC/S with high-loading sulfur is mainly attributed to high electronic conductivity and the abundant porous structure of NSCC to transport electrons and ions fastly and accommodate sulfur as well as robust absorbability and the outstanding catalytic effect of NiCo2S4 to accelerate the capture and conversion of the polysulfide intermediate. Predictably, this work can provide a guideline to efficiently and rationally design the structure of metal-based compounds with catalytic functions for various applications.