Recent progress on hard carbon-based anode for sodium-ion battery

In recent years, hard carbon (HC) has been considered as a potential anode material for sodium-ion batteries due to its ideal internal structure (pore structure, defect, etc.) and large carbon layer spacing. This paper summarizes the work in recent years and expounds the development trend of HC anode, hoping to help more scholars cope with the opportunities and challenges of HC materials in the future. In this paper, the mechanism and different model of Na+ storage in HC are described in detail to guide the structural design of HC. In addition, the classification, electrochemical performance and synthesis mechanism of advanced HC materials are discussed comprehensively. Finally, the challenges and future development direction of HC are concluded, which can provide reference for the commercialization of sodium-ion batteries.