Tailoring pseudo-graphitic carbons from pitch via molecular matched-crosslinking toward advanced sodium-ion batteries

Abstract

The development of high-performance carbon anodes from coal liquefaction pitch for sodium-ion batteries (SIBs) remains challenging due to insufficient functional groups, uncontrollable graphitization, and the lack of precise molecular-level regulation, which collectively lead to inadequate Na+ storage sites, restricted interlayer spacing, and sluggish ion transport kinetics. To address these limitations, we propose a molecular structure-oriented strategy that integrates solvent fractionation, pre-oxidation, and structure-matched cross-linking to precisely tailor the architecture of pitch-derived carbons. The toluene-soluble (TS) fraction of pitch, which is rich in small aromatic cores and abundant aliphatic side chains, is selectively pre-oxidized to introduce carbonyl groups. These groups subsequently undergo esterification with hydroxyl-rich chitin, constructing a three-dimensional cross-linked network via -C(O)-O- linkages. This molecularly designed network imposes spatial confinement, effectively inhibiting graphitic layer rearrangement during pyrolysis and resulting in pseudo-graphitic carbons with expanded interlayer spacing and abundant closed ultramicropores. As an anode for SIBs, the resulting carbon (OTSCC) delivers a high reversible capacity of 318 mAh g- 1, an initial Coulombic efficiency of 76.1%, and remarkable cycling stability with 82.5% capacity retention after 500 cycles at a current density of 500 mA g- 1. This work underscores the critical role of precursor fraction control and molecular-matched cross-linking in designing advanced carbon materials for energy storage, providing a rational synthesis pathway toward highperformance SIB anodes.