Pore structure in hard carbon: From recognition to regulation

Abstract

Hard carbon (HC) has garnered significant attention as the most commercially promising anode material for sodium-ion batteries (SIBs), owing to its wide distribution, low cost, and abundant resources. However, challenges have arisen in recent years regarding its application in SIBs due to variations in Na storage mechanisms and performance resulting from its diverse microstructure. The diversity of microstructures in HC, resulting from different precursor systems, presents a formidable challenge to the elucidation of the mechanism and regulation of Na storage in HC. A comprehensive understanding of the diverse pore structures in HC is pivotal for rational modulation of its structure and performance, as well as for comprehending its Na storage mechanism. This review initially discusses the classification, structure, and characterization methods of nanopores in HC. Subsequently, it elucidates the relationship between these nanopores and their electrochemical properties, encompassing open pores, closed pores, and sieving pores. Finally, it introduces and prospects common approaches for manipulating disordered carbon multi-structure. This review is anticipated to offer a viable research direction for the field of HC, facilitating the rational design of high-capacity carbon anodes, and accelerating the industrialization process of SIBs.