Lignin derived hard carbon for sodium ion batteries: Recent advances and future perspectives

Lignin-derived hard carbon (LHC) is considered one of the most promising anode materials for sodium-ion batteries (SIBs) due to its abundant and renewable feedstocks, tunable microstructure, and excellent electrochemical performance. In recent years, significant progress has been achieved in the development of LHCs. However, a comprehensive review and critical evaluation of the existing research remain lacking, hindering their further advancement. To address this gap, this review first introduces the fundamental properties of lignin and hard carbon to elucidate the microstructural formation processes of LHCs. Subsequently, the fabrication methods and key characteristics of LHCs, along with the effects of feedstock properties and operating parameters on their microstructure and performance, are systematically summarized and analyzed. Particular attention is given to optimization strategies, including feedstock pretreatment, preparation process regulation, and post-treatment, to provide practical guidance for enhancing the overall performance of LHCs. Finally, suggestions and future perspectives for advancing LHCs in SIB applications are proposed based on the current research landscape and practical demands. This review aims to offer scientific insights into the microstructural regulation and electrochemical performance optimization of LHCs, thereby promoting their broader application in SIBs.