Unlocking the potential of fossil fuel-derived hard carbons in sodium-ion batteries: Mechanistic insight and design strategies

Abstract

Sodium-ion batteries (SIBs) have garnered significant attention as an attractive energy storage complementary technology to lithium-ion batteries (LIBs) and could be critical in future electric vehicles and large-scale energy storage systems. The anode material, as an important component of SIBs, has a decisive influence on their electrochemical performances. Among available anode materials, hard carbons are regarded as the practical anode materials for SIBs. Suitable precursors are crucial for producing economical and high-quality hard carbons. Given the low cost, abundant availability, high carbon content, and specific organic structures, fossil fuels have been considered as an ideal carbon resource for hard carbons. However, the complex composition and high aromaticity of fossil fuels result in uncontrollable pyrolytic structural evolution and highly graphitized microstructure, which hinders the development of high-performance hard carbon anodes. In this review, we provide a comprehensive overview of the structural model evolution and classification of fossil fuels and hard carbon. Subsequently, we analyzed in depth the similarities and differences in the pyrolysis behavior of various fossil fuels. Based on these fundamental insights, we summarize the effects and limitations of various modification strategies on fossil fuel-derived hard carbons. Finally, we highlight the key challenges and future research directions for next-generation high-performance fossil fuel-derived carbon anodes, particularly in molecular design of fossil fuels, multiscale characterizations and big data analytics of hard carbons, and compatibility with other components of SIBs.