Construction of strong built-in electric field in binary metal sulfide heterojunction to propel high-loading lithium-sulfur batteries

Abstract

The practical application of lithium-sulfur (Li-S) batteries is greatly hindered by soluble polysulfides shuttling and sluggish sulfur redox kinetics. Rational design of multifunctional hybrid materials with superior electronic conductivity and high electrocatalytic activity, e.g., heterostructures, is a promising strategy to solve the above obstacles. Herein, a binary metal sulfide MnS-MoS2 heterojunction electrocatalyst is first designed for the construction of high-sulfur-loaded and durable Li-S batteries. The MnS-MoS2 p-n heterojunction shows a unique structure of MoS2 nanosheets decorated with ample MnS nanodots, which contributes to the formation of a strong built-in electric field at the two-phase interface. The MnS-MoS2 hybrid host shows strong soluble polysulfide affinity, enhanced electronic conductivity, and exceptional catalytic effect on sulfur reduction. Benefiting from the synergistic effect, the as-derived S/MnS-MoS2 cathode delivers a superb rate capability (643 mA h g−1 at 6 C) and a durable cyclability (0.048% decay per cycle over 1000 cycles). More impressively, an areal capacity of 9.9 mA h cm−2 can be achieved even under an extremely high sulfur loading of 14.7 mg cm−2 and a low electrolyte to sulfur ratio of 2.9 μL mg−1. This work provides an in-depth understanding of the interfacial catalytic effect of binary metal compound heterojunctions on sulfur reaction kinetics.