Phosphorus-Doped Metal-Organic Framework-Derived CoS2 Nanoboxes with Improved Adsorption-Catalysis Effect for Li-S Batteries.

Abstract

Lithium-sulfur (Li-S) batteries are regarded as one of the most promising next-generation battery technologies owing to their ultrahigh energy density up to 2600 W h kg-1 and low cost. However, major challenges still remain in the application of Li-S batteries, such as shuttle effect and sluggish redox kinetics. Herein, it is demonstrated that phosphorus doping can not only significantly improve the polysulfide adsorption but also enhance the catalysis effects of metal-organic framework-derived CoS2 nanoboxes in Li-S batteries. Consequently, a modified separator integrated with P-CoS2 and carbon nanotubes effectively suppresses the polysulfide shuttle and propels the redox kinetics of polysulfides, thus promising higher specific discharge capacity, better rate, and stable cycle performance. Even under the high sulfur loading condition (4.8 mg cm-2), the areal discharge capacity of the cell with the functional separator can still remain at 4.5 mA h cm-2 after 100 cycles at 0.2 C. More importantly, this work may encourage more effort on anion doping for engineering the polar surface of transition-metal compounds to further mediate the interfacial redox chemistry between transition-metal compounds and polysulfides in Li-S batteries.