From graphite to hard carbon: multifaceted sodium storage reactions and future perspectives of carbon anode materials for sodium-ion batteries

The increasing demand for lithium-ion batteries, driven by the rapid expansion of electronics and electric vehicles, may face limitations due to the finite supply of lithium resources. Recently, significant advancements have been made in anode materials, which have long restricted the progress of sodium-ion batteries. Carbon-based anodes for SIBs have attracted considerable interest due to their potential for high energy density, cost-effectiveness, and environmental sustainability. This review focuses on research progress related to the sodium storage capabilities of carbon materials used as SIB anodes, such as graphite, amorphous carbon, and biomass-derived carbon. The sodium storage mechanisms in these materials, particularly hard carbon, are examined in depth, with attention to structural characteristics, pore morphology, and surface functionalization to enhance the understanding of sodium storage behavior. Furthermore, this paper reviews the current state of SIB material research, assesses potential future developments, and provides essential insights into scientific and practical challenges in advancing SIB technology.