Surface-Phosphided Metal Oxide Microspheres as Catalytic Host of Sulfur to Enhance the Performance of Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are one of the most promising high-energy density secondary batteries due to their high theoretical energy density of 2600 Wh kg. However, the sluggish kinetics and severe "shuttle effect" of polysulfides are the well-known barriers that hinder their practical applications. A carefully designed catalytic host of sulfur may be an effective strategy that not only accelerates the conversion of polysulfides but also limit their dissolution to mitigate the "shuttle effect." Herein, surface-phosphided NiCoMnO (p-NCMO) oxide microspheres are prepared via gas-phase phosphidation as a catalytic host of sulfur. The as-prepared unique heterostructured microspheres, with enriched surface-coated metal phosphide, exhibit superior synergistic effect of catalytic conversion and absorption of the otherwise soluble intermediate polysulfides. Correspondingly, the sulfur cathode exhibits excellent electrochemical performance, including a high initial discharge capacity (1162 mAh g at 0.1C), long cycling stability (491 mAh g after 1000 cycles at 1C), and excellent rate performance (565 mAh g at 5C). Importantly, the newly prepared sulfur cathode shows a high areal capacity of 4.0 mAh cm and long cycle stability under harsh conditions (high sulfur loading of 5.3 mg cm and lean electrolyte/sulfur ratio of 5.8 μL mg). This work proposes an effective strategy to develop the catalytic hosts of sulfur for achieving high-performance Li-S batteries via surface phosphidation.