Graphitization Induction Effect of Hard Carbon for Sodium‐Ion Storage

Abstract Hard carbon (HC) is regarded as the leading anode material for sodium ion batteries (SIBs), owing to its low sodium storage potential, high reversible specific capacity, abundant precursor sources, and cost‐effectiveness. Nevertheless, the randomly oriented amorphous structure and large number of defects in HC result in low initial Coulombic efficiency, inadequate rate performance, and limited cycling stability when utilized as an anode material for SIBs. Therefore, optimizing the microstructure of HC material to obtain both a low defect ratio and large sodium ion transport channels is essential for better sodium storage/release kinetics and cycling stability. This review focuses on the graphitization induction effect on HC. It highlights the key methods and mechanisms of graphitized HC, along with the structure‐activity relationship between its microstructure and sodium storage behaviors. Additionally, the advantages, disadvantages, and application feasibility of various induction methods are systematically evaluated. Ultimately, this review discusses the challenges and development directions for designing and constructing HC material with an appropriate level of local graphitization. It offers a novel perspective on the rational design of HC microstructure and scientific theoretical guidance for accelerating the industrial application of HC anode material in SIBs.