Molecular Weaving of Biomass Precursors: Engineering Hard Carbon With Synergistic sp2/sp3-C and Closed-Pore Structures for High-Performance Sodium-Ion Batteries.

Hard carbon is regarded as one of the most promising anode materials for sodium-ion batteries (SIBs). However, its practical application is hindered by the incompatibility of the contradiction between rate performance, capacity, and initial coulombic efficiency. Herein, we propose a biomass-derived molecular weaving carbon strategy that enables precise control over the precursor structure at the molecular scale by controlling the pre-carbonization temperature. The hydroxyl-rich starch chains are woven with aromatic lignin skeletons to construct a starch-lignin-derived hard carbon (SLHC) interpenetrating polymer network. In the prepared SLHC, the appropriate proportion of sp2/sp3-C enhances both conductivity and additional active sites, whereas abundant andlarge-sized closed pores provide sufficient space for Na+ storage. The synergistic effect enables SLHC to achieve faster Na+ diffusion kinetics and higher storage capacity. The SLHC electrode delivers a high reversible capacity of 346.0 mAh g-1 at 30 mA g-1 and retains 190.0 mAh g-1 after 500 cycles at 500 mA g-1. Additionally, the assembled full-cell achieves a high energy density of 227.6 Wh kg-1. Through in situ/ex situ characterization techniques, the intrinsic mechanisms of charge storage and interface dynamics are revealed. This work constructs a molecular engineering strategy for the rational design of high-performance hard carbon anodes in SIBs.