Sulfur-deficient MoS₂-carbon hollow nanospheres for synergistic trapping and electrocatalytic conversion of...

Lithium-sulfur battery is one of the most promising candidates for next-generation energy storage systems, but the serious shuttle effect and sluggish reaction kinetics of polysulfides impair its practical applications. Herein, sulfur-deficient MoS₂/carbon hollow nanospheres (MoS₂-CHNs) are firstly synthesized by a NaCl-template pyrolysis and employed as sulfur host for lithium-sulfur batteries. TEM analysis reveals that carbon hollow nanospheres existing in the composite are the backbones that help to immobilize the ultrathin MoS₂ nanosheets and ensure their large specific surface area. The MoS₂ nanosheets consist of 5-10 layers of MoS₂ with rich sulfur vacancies. The first principle calculation demonstrates that sulfur vacancy led to an intensively enhanced binding energy (-4.70 eV) towards Li₂S₆ compared to the pristine MoS₂ (-1.57 eV). It suppressed the shuttle effect efficiently. The catalytic experiments reveal that MoS₂-CHNs have a superior ability for the nucleation of Li₂S and bidirectional electrocatalytic capability for the conversion of polysulfide. The large storage space inside MoS₂-CHNs can work as a reservoir for intermediate polysulfides to substantially reduce the concentration overpotential. Due to this advantageous structural design of MoS₂-CHNs electrode, its reversible capacity remains 1139 mAh g^-1 after 100 cycles at 0.2C, and 600 mAh g^-1 after 500 cycles at 5C with a sulfur loading of 5 mg cm^-2. Even though the sulfur loading increases to 10 mg cm^-2, the Li-S battery delivers a stable capacity of 978 mAh g^-1 after 50 cycles at 0.2C. So the MoS₂-CHNs demonstrate a promising application for high-energy Li-S batteries.