Designing Pitch-Derived Spherical Hard Carbon via Catalytic Aerobic Oxidation and Closed-Pore Regulation

Pitch-derived hard carbon emerges as an anode material for sodium-ion batteries, but its performance still suffers from the trade-offs among plateau capacity, rate capability, and compaction density. Herein, a catalytic aerobic oxidation strategy that enables controllable oxidation of pitch is employed to fabricate spherical hard carbon with tunable pore structures, realizing simultaneous enhancement of these abovementioned metrics. The spherical hard carbon achieves charging of 126.5 mAh g–1 within about 50 s and sustains sodium storage over continuous 1000 cycles at 9 A g–1. Under an increased areal loading, the anode maintains an areal capacity of 1.65 mAh cm–2, a volumetric capacity up to 332.6 mAh cm–3 and endures 100 charge–discharge cycles at a current density of nearly 3 mA cm–2. This work provides a strategy to design hard carbon anodes with enhanced volumetric capacity and rate performance for space-constrained energy storage scenarios.