Synergy of single atoms and sulfur vacancies for advanced polysulfide-iodide redox flow battery.

Wang, Zhigui; Lu, Guolong; Wei, Tianran; Meng, Ge; Cai, Haoxiang; Feng, Yanhong; Chu, Ke; Luo, Jun et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Aqueous redox flow batteries (RFBs) incorporating polysulfide/iodide chemistries have received considerable attention due to their safety, high scalability, and cost-effectiveness. However, the sluggish redox kinetics restricted their output energy efficiency and power density. Here we designed a defective MoS<sub>2</sub> nanosheets supported Co single-atom catalyst that accelerated the transformation of S<sup>2-</sup>/S<sub>x</sub><sup>2-</sup> and I<sup>-</sup>/I<sub>3</sub><sup>-</sup> redox couples, hence endow the derived polysulfide-iodide RFB with an initial energy efficiency (EE) of 87.9% and an overpotential of 113 mV with an average EE 80.4% at 20 mA cm<sup>-2</sup> and 50% state-of-charge for 50 cycles, and a maximal power density of 95.7 mW cm<sup>-2</sup> for an extended cycling life exceeding 850 cycles at 10 mA cm<sup>-2</sup> and 10% state-of-charge. In situ experimental and theoretical analyses elucidate that Co single atoms induce the generation of abundant sulfur vacancies in MoS<sub>2</sub> via a phase transition process, which synergistically contributed to the enhanced adsorption of reactants and key reaction intermediates and improved charge transfer, resulting in the enhanced RFB performance.