High Performance Lithium Sulfur Batteries Via MoS₂-Protected Lithium Metal Anode

Abstract

It is no secret that lithium (Li) metal is considered an optimal anode material for the next-generation lithium (Li) metal-based batteries such lithium-sulfur (Li-S). However, challenges have hindered the progress in achieving practical rechargeable batteries based on the Li anode including: the formation of poor-quality interphases on the surface of Li when in contact with any electrolytes; high chemical reactivity of Li with other active species in the electrolyte (i.e. polysulfides); and the difficulty in controlling the morphology of Li electrodeposits (i.e. Li dendrites) during battery operation. In attempt to solve all those issues, we introduce an atomic layer two-dimensional MoS 2 as a protective layer for Li metal anode. With the Li-intercalated atomic layer of MoS 2 formed, stable Li electrodeposition is realized with the nucleation sites for dendrite growth inhibited. In addition to the prevention of Li dendrites, MoS 2 -protected Li anode has been demonstrated to prevent polysulfides from corroding the anode while facilitating reversibility of active materials without decomposing the electrolyte. Here, we report the mechanistic study of Li-ion transport in the atomic layer of MoS 2 with varying microstructure of MoS 2 , and the performance of Li-S batteries utilizing MoS 2 -protected Li anodes. The full cell performance was characterized with different sulfur loading amounts from 4 to 7 mg cm -2 while tuning the electrolyte/sulfur (E/S) ratio from 10 to 6. The results have demonstrated the E/S ratio of 6 (42 µL electrolyte to 7 mg cm -2 sulfur) with reversible specific capacity of ~1068 mAh g -1 at 0.5C rate (~1.4mA cm -2 ) for up to 1000 cycles. The exceptional performance in Li-S battery that utilizes 2D MoS 2 anode without reducing the sulfur amount opens a new pathway towards the realization of high energy density and safe Li-metal based batteries.