Molecular Oxidative Cross-Linking Engineering of Low-Cost Pitch to Hard Carbon Anodes for High-Performance Sodium-Ion Batteries

Currently, pitch-derived hard carbon (HC) materials are regarded as promising anodes in sodium-ion batteries (SIBs). However, the rational regulation of pitch-based HC microstructures, including interlayer spacing and closed pores via a facile approach, still faces a huge challenge. Hence, a strategy combining facile calcium gluconate molecular cross-linking and preoxidation has been proposed for the first time to inhibit pitch melting and carbon atom rearrangement during carbonization. This strategy facilitates the transformation of graphitic soft carbon to a highly disordered HC with numerous closed pores and a large interlayer spacing. The optimized PCHC-300 as an anode delivers both high total capacity and plateau capacity of 345.4 and 202.7 mAh g –1 at 30 mA g –1, respectively. Even at 3 A g –1, it delivers a high specific capacity of 226.7 mAh g –1, which outperforms the most reported pitch-derived HCs. In addition, multiscale microstructural characterizations, including in situ and ex situ measurements, have been performed and have demonstrated that the low-voltage plateau capacity stems from Na + intercalation and filling of closed pores of the PCHC-300 anode. Furthermore, the as-assembled full cell delivers a high energy density of 204 Wh kg –1 at a rate of 21.4 W kg –1 . This work provides a new opportunity to design low-cost and high-performance pitch-based HC anodes for practical applications of SIBs.