Two-dimensional montmorillonite-based heterostructure for high-rate and long-life lithium-sulfur batteries

Abstract

In lithium-sulfur batteries, the polysulfide redox reaction kinetics is obstructed by unfavorable electron conduction and ion transportation. To address this issue, a two-dimensional (2D) heterostructure with fast ion/electron transport bi-pathways is designed herein by well integrating monolayer lithium-montmorillonite (MMT) and nitrogen-doped reduced graphene oxide (RGO). The low diffusion barrier on the Li-MMT contributes to the fast lithium ion transport, and the nearby RGO builds high electron conduction network, which enables high-efficiency adsorption-diffusion-conversion for polysulfides and achieves fast electrochemical reaction kinetics. Consequently, the lithium-sulfur batteries using the heterostructure interlayer show effective suppression towards the notorious “shuttle effect” of polysulfides, as well as deliver high initial specific capacity of 1317 mAh g−1 at 0.2 C, high rate capability of 848 mAh g−1 even at 3 C, and low capacity decay rate of 0.011% per cycle at 1 C over 200 cycles and 0.067% per cycle at 2 C over 600 cycles. The corresponding pouch cell shows high initial discharge capacity of 1542 mAh g−1 at 0.05 C. This work exhibits the potential application of the low-cost and environmentally-friendly clay as the 2D heterostructure interlayer material for realizing high-energy-density, long-lasting, and high-rate Li-S batteries.