Fine‐Grain Strengthened Vanadium‐Based Electrocatalysts via Recrystallization Maneuver for Lithium‐Sulfur Batteries

Abstract The rational design of abundant and efficient active sites for lithium‐sulfur electrocatalysis remains a long‐standing challenge, wherein the optimization of catalyst activity by manipulating their sizes has stimulated extensive exploration. Herein, a fine‐grain strengthening strategy is proposed for a vanadium‐nitrogen‐carbon (VNC) catalyst comprising active vanadium (V)‐based units, throughout modulating the size and surface energy via salt‐template recrystallization. The recrystallization frequency is dictated to precisely tune the fine‐grain strengthening effect. Through a rigorous procedure of 5‐time recrystallization, V‐based units realize the size reduction from 209 to 99 Å, the surface energy increase from 0.16 to 0.32 eV Å −2 , along with the specific surface area adjustment from 41.5 to 206.3 m 2 g −1 . Accordingly, the fine‐grain strengthening effect effectively activates the V‐based units in i) enhancing sulfur species adsorption and propelling Li 2 S nucleation/decomposition reaction kinetics; ii) guiding high‐flux and uniform lithium‐ions and thus promoting lithium plating/stripping behaviors. Consequently, the battery demonstrates an initial discharge capacity of 1236.4 mA h g −1 at 0.2 C. Even after 600 cycles at 2.0 C, the cycle‐to‐cycle attenuation is merely 0.048%. Furthermore, a pouch cell with a fine‐grain strengthened VNC catalyst can proceed a stable cycling operation at 1.0 C, ensuring a reliable and consistent power supply for electronic gadgets.