Propelling polysulfide conversion for high-loading lithium-sulfur batteries through highly sulfiphilic NiCo2S4 nanotubes

Li-S batteries have received unprecedented attention owing to their exceptionally high energy density and low cost. Nevertheless, the daunting challenges of insulating properties, soluble polysulfide shuttling, drastic volume change and sluggish polysulfide conversion kinetics, still hinder their application towards commercialization. Very recently, exciting progresses have been made on inorganic/organic polar hosts as either polysulfide immobilizers or polysulfide redox accelerators, targeting durable Li-S batteries. Herein, self-assembled NiCo2S4 granules comprising secondary open-hole tubular structures are first devised as highly-efficient host materials for high-sulfur-loading and durable Li-S batteries. NiCo2S4 hosts are featured with their large porosity, high electronic conductivity, rapid ion conduction, strong polysulfide immobilization capability and catalytic effect on polysulfide redox, thus greatly ameliorating the polysulfide-shuttle issue and accelerating the polysulfide conversion kinetics. Therefore, the NiCo2S4/S cathode shows a reversible capacity of 1387 mAh g(-1) at 0.2C and retains a value of 543 mAh g(-1) after 500 cycles at 2 C. Impressively, the NiCo2S4/S cathode with a sulfur loading of 8.9 mg cm(-2) exhibits high areal capacity of 8.3 mAh cm(-2), low polarization and high cycling stability. Moreover, the as-derived soft-package battery with a 4.5 mg cm(-2) sulfur loading can power 169 light-emitting diodes, verifying its great potential for practical application.