Local Concentration Effect-Derived Heterogeneous Li2S2/Li2S Deposition on Dual-Phase MWCNT/Cellulose Nanofiber/NiCo2S4 Self-Standing Paper for High Performance of Lithium Polysulfide Batteries.

Abstract

Lithium-sulfur (Li-S) batteries are highly attractive for their theoretical energy density and natural abundance, but the drawbacks of low sulfur utilization and rapid capacity fade in high-sulfur-loading cathodes still retard their practical use. To enhance kinetics in high-sulfur-loading Li-S cells, it is important to first understand and control the deposition of Li2S/Li2S from highly soluble lithium polysulfide (LiPS) during discharge processes. Here, we presented a series of multiphase-derived self-standing papers with diverse electronic conductivity and LiPS affinity for highly concentrated LiPS discharge processes and explained the Li2S/Li2S deposition behavior in detail. We demonstrated that high rate capacity and long cycle life of as-assembled paper-LiPS cathodes can be greatly depended on their phase material with high conductivity and LiPS affinity. A high-performance self-standing LiPS host-multiwalled carbon nanotube (MWCNT)/cellulose nanofiber (CNF)/NiCo2S4 (3.5 mg cm-2) can catalyze 2.85 mg cm-2 (based on sulfur) loaded LiPS to deliver a high specific capacity of 1154 mAh g-1 at 0.1C and a high rate performance of 963 mAh g-1 at 1C. We suggest that the insulating phase defect of nano-CNF and both highly electronic conductive (above 50 S cm-1) and LiPS adsorptive NiCo2S4 can promote the local concentration effect of LiPS, thus contributing to fast and stable heterogeneous particle-shaped deposition of Li2S2/Li2S and leading to high kinetics of the LiPS cathode.