Metal-Organic Framework-Derived Nitrogen-Doped Cobalt Nanocluster Inlaid Porous Carbon as High-Efficiency Catalyst for Advanced Potassium-Sulfur Batteries.

Abstract

Despite high theoretical capacity and earth-abundant resources, the potential industrialization of potassium-sulfur (K-S) batteries is severely plagued by poor electrochemical reaction kinetics and a parasitic shuttle effect. Herein, a facile low-temperature pyrolysis strategy is developed to synthesize N-doped Co nanocluster inlaid porous N-doped carbon derived from ZIF-67 as catalytic cathodes for K-S batteries. To maximize the utilization efficiency, the size of Co nanoparticles can be tuned from 7 nm to homogeneously distributed 3 nm clusters to create more active sites to regulate affinity for S/polysulfides, improving the conversion reaction kinetics between captured polysulfides and K₂S₃/S, fundamentally suppressing the shuttle effect. Cyclic voltammetry curves, Tafel plots, electrochemical impedance spectroscopy, and density functional theory calculations ascertain that 3 nm Co clusters in S-N-Co_s-C cathodes exhibit superior catalytic activity to ensure low charge transfer resistance and energy barriers, enhanced exchange current density, and improved conversion reaction rate. The constructed S-N-Co_s-C cathode delivers a superior reversible capacity of 453 mAh g^-1 at 50 mA g^-1 after 50 cycles, a dramatic rate capacity of 415 mAh g^-1 at 400 mA g^-1, and a long cycling stability. This work provides an avenue to make full use of high catalytic Co nanoclusters derived from metal-organic frameworks.