Boric Acid Tailored Pre-Oxidation Crosslinking and Suppressed Molecular Rearrangement Toward Pitch-Derived Carbon Anodes for Sodium-Ion Batteries

Abstract

Pitch-derived carbon is a promising sodium-ion battery anode but has inadequate sodium storage capacity due to high graphitization and limited active sites from polycyclic aromatic structure polycondensation/stacking during carbonization. Herein, a strategy of enhancing pre-oxidation crosslinking and suppressing molecular rearrangement of pitch by employing boric acid to construct a boron and oxygen co-crosslinking carbon precursor structure, further regulating the carbon texture, is proposed. In situ FTIR and subsequent analyses confirmed that B─C─O bonds suppress molecular rearrangement, leading to the formation of a disordered carbon framework, ultimately resulting in a disordered carbon framework. Meanwhile, the borate species derived from the thermal decomposition of boric acid serve as a dual-functional template and dopant, facilitating the development of a hierarchical mesoporous carbon architecture alongside the incorporation of diverse boron-doped carbon configurations during high-temperature carbonization. By tuning boric acid to pitch ratio and carbonization temperature, the pitch-derived carbon reaches 317 mAh g−1 reversible capacity dominated by a reversible Na⁺ adsorption/intercalation mechanism, 84% initial coulombic efficiency, and excellent cycling stability with 94.3% retention after 5000 cycles at 1 A g−1. Separately, the 1.5 Ah Na4Fe3(PO4)2P2O7||BHC-1.5-800 pouch cell maintains 94% capacity retention after 300 cycles at a 0.5C rate.