Construction of Oxygen-Deficient La(OH)3 Nanorods Wrapped by Reduced Graphene Oxide for Polysulfide Trapping toward High-Performance Lithium/Sulfur Batteries.

Abstract

Despite the high theoretical capacity (2600 Wh kg-1) of a sulfur cathode, lithium/sulfur (Li/S) batteries still face several serious challenges on the road to commercial success. Herein, a unique three-dimensional hierarchical microsphere architecture assembled by oxygen-deficient La(OH)3 and reduced graphene oxide (rGO), as the sulfur host material for Li/S batteries, has been rationally designed using a facile spray-drying method for the first time. The robust microsphere architecture can reduce ion diffusion pathways and provide adequate space to modulate volume variation during cycling. It is noted that the abundant inner void spaces in the microspheres formed by rGO and oxygen-deficient La(OH)3 nanorod stacking provide physical adsorption for polysulfides. Meanwhile, the hydroxyl groups and defective sites on the surface of polar La(OH)3 nanorods provide strong chemical adsorption to lithium polysulfides, which was confirmed by density functional theory calculations. Additionally, rich oxygen-deficient La(OH)3 nanorods as an effective electrocatalyst promote the reversibility and conversion kinetics of polysulfides. The fast polysulfide conversion reactions can prevent accumulation in the cathode and loss in the electrolyte. Consequently, a sulfur cathode with rGO-La(OH)3 exhibits a high initial specific capacity of 1160.4 mAh g-1 at 0.2C and retains long-term stability for a capacity of 541.7 mAh g-1 after 600 cycles at 1C.