Superhierarchical Cobalt-Embedded Nitrogen-Doped Porous Carbon Nanosheets as Two-in-One Hosts for High-Performance Lithium-Sulfur Batteries

Abstract

Lithium-sulfur (Li-S) batteries, based on the redox reaction between elemental sulfur and lithium metal, have attracted great interest because of their inherently high theoretical energy density. However, the severe polysulfide shuttle effect and sluggish reaction kinetics in sulfur cathodes, as well as dendrite growth in lithium-metal anodes are great obstacles for their practical application. Herein, a two-in-one approach with superhierarchical cobalt-embedded nitrogen-doped porous carbon nanosheets (Co/N-PCNSs) as stable hosts for both elemental sulfur and metallic lithium to improve their performance simultaneously is reported. Experimental and theoretical results reveal that stable Co nanoparticles, elaborately encapsulated by N-doped graphitic carbon, can work synergistically with N heteroatoms to reserve the soluble polysulfides and promote the redox reaction kinetics of sulfur cathodes. Moreover, the high-surface-area pore structure and the Co-enhanced lithiophilic N heteroatoms in Co/N-PCNSs can regulate metallic lithium plating and successfully suppress lithium dendrite growth in the anodes. As a result, a full lithium-sulfur cell constructed with Co/N-PCNSs as two-in-one hosts demonstrates excellent capacity retention with stable Coulombic efficiency.

Keywords: DFT calculations; carbon nanosheets; lithium metal anodes; lithium-sulfur batteries; sulfur hosts.