Engineering of Pore Structure and Ordered sp2 Carbon Layers in Pitch-Derived Carbons at Low Carbonization Temperature for High-Performance Sodium-Ion Batteries

Abstract

Low carbonization temperatures generally result in excessive open pores, abundant defects, and unstable interfaces in pitch-derived carbons (PDCs), thereby limiting the reversible sodium-storage capacity and initial Coulombic efficiency (ICE). Herein, a one-step thermoplastic-pitch-driven self-reconstruction strategy is proposed through solvent-free solid-phase compounding of oxidized pitch with thermoplastic pitch followed by low-temperature carbonization at 1100 °C, enabling simultaneous pore-structure regulation, ordered sp2-carbon-layer construction, and tuning of the sp2/sp3 ratio. During carbonization, oxygen-containing functional groups (OCFGs) and interfacial esterification collaboratively promote closed-pore formation, contributing to enhanced plateau capacity and reversible sodium storage. Meanwhile, thermoplastic pitch forms a continuous sp2-rich coating that seals nanoscale channels and stabilizes the electrode/electrolyte interface, thereby improving ICE and charge-transfer kinetics. Consequently, EP@10P-1100 achieves a high capacity of 346.1 mAh g−1 with an ICE of 88.8%, excellent rate capability (251.1 mAh g−1 at 2 A g−1), and 89.0% capacity retention after 1000 cycles at 1 A g−1. Notably, the slope/plateau capacity strongly correlates with the sp2/sp3 ratio, highlighting its critical role in sodium storage. This work provides a scalable strategy for developing high-performance PDC anodes under low-temperature carbonization conditions.