Synergistic Adsorption-Electrocatalysis of 2D/2D heterostructure toward high performance Li-S batteries

The shuttle effect of polysulfides and sluggish reaction kinetics have become current major obstacles for the development of lithium-sulfur (Li-S) batteries. Herein, a novel 2D/2D heterostructure, consisting of ultrathin Ni-Co MOFs with rich unsaturated metal sites and conductive Ti3C2Tx nanosheets (Ti3C2Tx/Ni-Co MOF), is developed as a multifunctional barrier coated on commercial separators for Li-S batteries. Based on the synergistic adsorption-electrocatalysis, the modified separators not only suppress the dissolution of polysulfides and promote their conversion effectively, but also accelerate the electron/ion transfer. Moreover, density functional theory results further confirm that the heterostructure has strong adsorption energy for polysulfides and low energy barriers for their conversion. Li-S batteries with the Ti3C2Tx/Ni-Co MOF heterostructure modified separators exhibit an excellent reversible capacity of 1260 mAh g−1 at 0.2C and a remarkable cycling stability with capacity retention of 91.1 % at 0.5C after 350 cycles. When equipped with high sulfur loading of 5.8 mg cm−2 and low electrolyte/sulfur ratio of 4 uL mg−1, the cell maintains a superior capacity. This work provides a new route to the design of modified separators for high performance Li-S batteries with especially remarkable cycling stability.