Constructing long‐cycling crystalline C₃N₄‐based carbonaceous anodes for sodium‐ion battery via N configuration control

Abstract Carbon nitrides with two‐dimensional layered structures and high theoretical capacities are attractive as anode materials for sodium‐ion batteries while their low crystallinity and insufficient structural stability strongly restrict their practical applications. Coupling carbon nitrides with conductive carbon may relieve these issues. However, little is known about the influence of nitrogen (N) configurations on the interactions between carbon and C₃N₄, which is fundamentally critical for guiding the precise design of advanced C₃N₄‐related electrodes. Herein, highly crystalline C₃N₄ (poly (triazine imide), PTI) based all‐carbon composites were developed by molten salt strategy. More importantly, the vital role of pyrrolic‐N for enhancing charge transfer and boosting Na⁺ storage of C₃N₄‐based composites, which was confirmed by both theoretical and experimental evidence, was spot‐highlighted for the first time. By elaborately controlling the salt composition, the composite with high pyrrolic‐N and minimized graphitic‐N content was obtained. Profiting from the formation of highly crystalline PTI and electrochemically favorable pyrrolic‐N configurations, the composite delivered an unusual reverse growth and record‐level cycling stability even after 5000 cycles along with high reversible capacity and outstanding full‐cell capacity retention. This work broadens the energy storage applications of C₃N₄ and provides new prospects for the design of advanced all‐carbon electrodes.