Dual-Defect Engineering of Bidirectional Catalyst for High-Performing Lithium-Sulfur Batteries.

Abstract

Practical applications of lithium-sulfur (Li-S) batteries have been hindered by sluggish reaction kinetics and severe capacity decay during charge-discharge cycling due to the notorious shuttle effect of polysulfide and the unfavored deposition and dissolution of Li2 S. Herein, to address these issues, a double-defect engineering strategy is developed for preparing Co-doped FeP catalyst containing P vacancies on MXene, which effectively improves the bidirectional redox of Li2 S. Mechanism analysis indicates that P vacancy accelerates Li2 S nucleation via increased unsaturated sites, and Co doping generates local electric field to reduce the reaction energy barrier and accelerate Li2 S dissolution. MXene provides highly conductive channels for electron transport, and effectively captures polysulfide. The double-defect catalyst enables an impressive reversible specific capacity of 1297.9 mAh g-1 at 0.2 C, and excellent rate capability of 726.5mAhg-1 at 4C. Remarkably, it demonstrates excellent cycling stability with capacity retention of 533.3mAhg-1 after 500 cycles at 2C. The results can unlock the double-defect engineering of vacancy induction and heteroatomic doping towards practical Li-S batteries.