Tuning the Local Coordination of CoP1–x S x between NiAs- and MnP-Type Structures to Catalyze Lithium–Sulfur Batteries

摘要

The slow conversion and rapid shuttling of polysulfides remain major challenges that hinder the practical application of lithium–sulfur (Li–S) batteries. Efficient catalysts are needed to accelerate the conversion and suppress the shuttling. However, the lack of a rational understanding of catalysis poses obstacles to the design of catalysts, thereby limiting the rapid development of Li–S batteries. Herein, we theoretically analyze the modulation of the electronic structure of CoP1–x S x caused by the NiAs-to-MnP-type transition and its influence on catalytic activity. We found that the interacting d-orbitals of the active metal sites play a determining role in adsorption and catalysis, and the optimal d z 2 -, d xz -, and d yz -orbitals in an appropriately distorted five-coordinate pyramid enable higher catalytic activity compared with their parent structures. Finally, rationally designed catalysts and S were electrospun into carbonized nanofibers to form nanoreactor chains for use as cathodes. The resultant Li–S batteries exhibited superior properties over 1000 cycles with only a decay rate of 0.031 per cycle and demonstrated a high capacity of 887.4 mAh g–1 at a high S loading of 10 mg cm–2. The structural modulation and bonding analyses in this study provide a powerful approach for the rational design of Li–S catalysts.