Vanadium atom modulated electrocatalyst for accelerated Li S chemistry

Abstract

Extensive efforts have been made to attain practically viable Li–S batteries. Nevertheless, issues mainly pertaining to the notorious polysulfide shuttle and the sluggish sulfur redox kinetics remain in enhancing the energy density and cycling lifespan of batteries. Herein, we propose an atom-level modulation engineering strategy to design a new model electrocatalyst of V-N-C delicately integrating twinborn isolated vanadium atoms and ultra-small-sized vanadium nitride (VN) nanoparticles in a carbonaceous framework for Li–S chemistry. Combining results from synchrotron X-ray three-dimensional nano-computed tomography (X-ray 3D Nano-CT), operando Raman and first-principles calculations, we conclude that, such a V-N-C electrocatalyst system synergizes the merits of highly efficient single atom V-N-C coordination (SAV-N-C) as well as site-rich VN centers, and thus effectively promotes both the formation and decomposition of Li 2 S during discharge and charge procedures, respectively. As a result, the highly active V-N-C electrocatalyst can enable superior rate capability and long-term cycling stability with a low decay of 0.052% per cycle up to 1000 cycles at 2 C. Furthermore, the designed S/V-N-C cathode still affords favorable electrochemical performances even under the scenarios of elevated sulfur loading (8.1 mg cm –2 ) and flexible pouch cell configurations, holding great promise in future practical implementation. • Proposing V-N-C electrocatalyst model for Li–S chemistry by atom-level modulation. • Probing the electrocatalytic mechanism of V-N-C electrocatalyst model for Li–S chemistry. • Developing synchrotron X-ray 3D imaging technique to reveal Li–S chemistry.