Porous N-Doped Carbon Decorated with Atomically Dispersed Independent Dual Metal Sites from Energetic Zeolite Imidazolate Frameworks as Bidirectional Catalysts for Lithium-Sulfur Batteries.

Abstract

Lithium-sulfur (Li-S) batteries have ultrahigh theoretical specific capacity and energy density, which are considered to be very promising energy storage devices. However, the slow redox kinetics of polysulfides are the main reason for the rapid capacity decay of Li-S batteries. A reasonable electrocatalyst for the Li-S battery should reduce the reaction barrier and accelerate the reaction kinetics of the bidirectional catalytic conversion of lithium polysulfides (LiPSs), thereby reducing the cumulative concentration of LiPSs in the electrolyte. In this report, porous N-doped carbon nanofibers decorated with independent dual metal sites as catalysts for Li-S batteries were fabricated in one step using a fusion-foaming method. Experimental and theoretical analyses demonstrate that the synergistic effect of independent dual metal sites provides strong LiPS affinity, improved electronic conductivity, and enhanced redox kinetics of polysulfides. Therefore, the assembled Li-S battery exhibits high rate performance (discharge specific capacity of 771 mA h g-1 at 2C) and excellent cycle stability (capacity decay rate of 0.51% after 1000 cycles at 1C).