Electron-Deficient Cobalt Centers Realized by Rational p─π Conjugation Regulation for High-Performance Li─S Batteries

Rational design of the coordination environment of single-atom catalysts (SACs) can enhance their catalytic activity, which is of great significance for high-loading and lean-electrolyte lithium-sulfur (Li─S) batteries. Inspired by the Lewis acid-base theory, we design a unique coordination environment for constructing electron-deficient Co SACs on carbon nanotubes (named as CNT@f-CoNC), which function as a Lewis acid, to enhance the chemisorption and catalytic activity towards polysulfides (Lewis base). Compared with porphyrin-like Co SACs, electron-deficient Co SACs (Lewis acid) exhibit much stronger binding affinity towards polysulfides (Lewis base) and a significantly lower energy barrier of the rate-determining step in the sulfur reduction reaction. As expected, even with a high sulfur loading (6.9 mg cm^-2) and lean electrolyte to sulfur (E/S) ratio (4.0 µL mg^-1), the areal capacity still reaches 7.7 mAh cm^-2. Moreover, a 1.6 Ah-class pouch cell is successfully assembled under the harsh conditions and delivers an energy density of 422 Wh kg^-1. This work provides novel insights into enhancing the electrochemical performance of Li─S batteries by modulating the local electronic density of metal sites through the rational design of the coordination environment.