Understanding the Relationship between the Main Components of Precursor and the Structure and Performance of Biomass-Derived Hard Carbon

Biomass-derived hard carbon holds significant appeal for sodium-ion batteries due to its abundant availability and cost-effectiveness. However, the complex composition and structure of the precursor have led to inadequate understanding of the pyrolysis mechanism and the performance of hard carbon. In this study, we present a bottom-up strategy to understand the relationship between the main components of the precursor and the structure and performance of hard carbon. Microcrystalline cellulose, lignin, and xylan are chosen as model polymers to analyze the microcrystalline structure, pore structure, and sodium storage performance of hard carbons. The cellulose-derived hard carbon exhibited the highest specific capacity of 312.84 mAh g^-1 at 30 mA g^-1 and superior rate performance of 188.00 mAh g^-1 at 3000 mA g^-1, indicating cellulose is the dominant component. The outstanding sodium storage performance should be attributed to the lowest degree of disorder in cellulose-derived hard carbon. Among four precursors with distinctly different compositions, bamboo flesh contained the highest cellulose content (37.5%), and the derived hard carbon exhibited the lowest degree of disorder and the best sodium storage performance, further confirming that cellulose is the advantageous component. Identifying the advantageous components in the precursor provides guidance for the selection of precursors and the design of pretreatment processes.