Rational design of Co nano-dots embedded three-dimensional graphene gel as multifunctional sulfur cathode for fast sulfur conversion kinetics

Abstract

Abstract Lithium-sulfur (Li-S) batteries hold great promises to serve as next-generation energy storage devices because of their high theoretical energy density and environmental benignity. However, the shuttle effect of the soluble lithium polysulfides (LiPS) and intrinsic insulating nature of sulfur lead to low sulfur utilization and coulombic efficiency, leading to poor cycling performance. The impeded charge transportation and retard LiPS catalytic conversion also endows the Li-S batteries with sluggish redox reaction, leading to unsatisfied rate capability. In this study, Co-based MOF material ZIF-67 is used as the precursor to prepare Co nano-dots decorated three-dimensional graphene aerogel as sulfur immobilizer. This porous architecture establishes a highly conductive interconnected framework for fast charge/mass transportation. The exposed Co nano-dots serve as active sites to strongly trap LiPS, which endows Co-NDs@G with low decomposition energy barrier for fast LiPS conversion reaction and promote the completely Li2S catalytic transformation. Li-S cells based on the Co-NDs@G cathode exhibits excellent cyclability and a high capacity retention rate of 91.1% in 100 cycles. This strategy offers a new direction to design sulfur immobilizer for accelerated LiPS conversion kinetics of Li-S batteries.