Cooperative Electronic Structure Modulator of Fe Single-Atom Electrocatalyst for High Energy and Long Cycle Li-S Pouch Cell.

High-energy and long cycle lithium-sulfur (Li-S) pouch cells are limited by the insufficient capacities and stabilities of their cathodes under practical electrolyte/sulfur (E/S), electrolyte/capacity (E/C), and negative/positive (N/P) ratios. Herein, an advanced cathode comprising highly active Fe single-atom catalysts (SACs) are reported to form 320.2 W h kg -1 multi-stacked Li-S pouch cells with total capacity of ∼1 A h level, satisfying low E/S (3.0), E/C (2.8), N/P (2.3) ratios, and high sulfur loadings (8.4 mg cm -2 ). The high-activity Fe SAC was designed by manipulating their local environments using electron-exchangeable binding (EEB) sites. Introducing EEB sites comprising two different types of S species, namely, thiophene-like-S (-S) and oxidized-S (-SO 2 ), adjacent to Fe SACs, promoted the kinetics of the Li 2 S redox reaction by providing additional binding sites and modulating the Fe d-orbital levels via electron exchange with Fe. The -S donates the electrons to the Fe SACs, whereas -SO 2 withdraws electrons from the Fe SACs. Thus, the Fe d-orbital energy level can be modulated by the different -SO 2 /-S ratios of the EEB site, controlling the electron donating/withdrawing characteristics. This desirable electrocatalysis is maximized by the intimate contact of the Fe SACs with the S species, which are confined together in porous carbon. This article is protected by copyright. All rights reserved.