Pitch-derived hard carbon anodes for sodium-ion batteries

Sodium-ion batteries (SIBs) are widely regarded as a promising technology for large-scale energy storage owing to the abundance of sodium, low production cost, and intrinsically stable electrochemical performance. The realization of commercially viable SIBs, however, critically depends on the development of high-performance anode materials. Among various anode precursors, pitch-derived hard carbon (HC) has attracted considerable attention because of its wide availability, low cost, and high carbon yield. This review provides a comprehensive and systematic overview of optimization strategies and recent advances in pitch-derived anode materials for SIBs, and summarizes four representative Na-storage mechanisms in HC. Particular emphasis is placed on pitch heteroatom doping, pre-oxidation, pore-structure engineering, molecular cross-linking, and electrode-electrolyte interface regulation, with the aim of offering guidance for the rational design of high-performance SIB anodes. These modification strategies collectively show great potential for further improving capacity, rate capability, and cycling stability. Furthermore, we highlight the need to develop greener, more scalable preparation routes and to employ advanced characterization techniques, theoretical calculations, and molecular-/machine-dynamics simulations to achieve precise regulation of pitch molecular structure and microstructure. Such efforts are expected to further enhance the performance of pitch-derived SIBs and accelerate their eventual commercialization.