MXene derivative Ta4C3-Ta2O5 heterostructure as bi-functional barrier for Li-S batteries

The shuttle effect of polysulfides during the charging and discharging of lithium-sulfur (Li-S) batteries and the growth of Li dendrites are crucial obstacles to hinder the commercialization of Li-S batteries. Heterostructure engineering is an effective strategy to accelerate catalytic conversion and suppress the dissolution of polysulfides. Herein, we report a Ta4C3-Ta2O5 heterostructure composite as a bi-functional modified separator that not only achieves effective protection for lithium metal but also accelerates the polysulfides redox kinetics process. This heterostructure possesses efficient chemical anchoring and abundant active sites to immobilize polysulfides by synergistic effect, which endows a stable long cycling performance for Li-S batteries. This corresponds to an initial high capacity of 801.9 mAh g–1 at 1 C with a decay rate of 0.086% for 500 cycles. Due to its high Young's modulus (up to 384 GPa), Ta4C3 contributes to forming a protective layer on the Li metal surface to inhibit the growth of Li dendrites. Accordingly, the symmetrical cell has a stable overpotential for 700 cycles at 20 mA cm–2/20 mAh cm–2. So, this “one stone two birds” design affords a novel perspective for high-energy Li-S battery storage system design and Li metal protection.