Bidirectional electrocatalysis of polysulfides via synergistic P-doping and Te vacancies for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are highly promising next-generation energy storage systems due to their high energy density and environmental benignity, but their practicality is severely limited by the lithium polysulfide (LiPSs) shuttle effect and sluggish bidirectional conversion kinetics. A key solution is to develop electrocatalysts with well-defined, synergistically complementary catalytic sites to accelerate LiPSs redox reactions. Herein, we construct a P-CoTe2−x/MXene electrocatalyst via dual-defect engineering, where P-doped CoTe2 nanosheets with Te vacancies are anchored on MXene to boost bidirectional LiPSs conversion. Theoretical and experimental results confirm that P-doping increases the electron density of Co sites and reduces the nucleation barrier of Li2S in the sulfur reduction reaction, whereas Te vacancies form electron-deficient Co sites and lower the dissociation barrier of Li2S in the sulfur oxidation reaction. This synergistic design endows the catalyst with robust bidirectional catalytic activity. The S/P-CoTe2−x/MXene-based LSBs exhibit a low capacity decay rate of 0.069% per cycle over 1000 cycles at 1 C and a high areal capacity of 16.7 mAh cm−2 under a sulfur loading of 13.7 mg cm−2. Furthermore, the pouch cell delivers 7.57 mAh cm−2 at 6.9 mg cm−2 with a lean electrolyte/sulfur ratio of 6 μL mg−1. This work offers novel perspectives for designing LSB electrode materials integrating strong adsorption and efficient bidirectional catalysis.