Synergistic Co-Blending of Low- and High-Rank Coals: A Strategy for Engineering High-Performance Porous Carbons for Supercapacitors

Owing to the inherent limitations of a single coalification degree, precursors derived from a single-rank coal often struggle to simultaneously fulfill the requirements of composition, structure, and performance. To address this, a blended-coal strategy combining oxygen-rich low-rank Baishihu coal and aromatic-rich high-rank Yicheng coal is proposed to overcome the reactivity–stability trade-off during KOH/KCl activation. The optimized sample, BYCM-40, delivers a high specific surface area of 2556.53 m2·g−1, a hierarchical porosity with 75% micropores and 25% mesopores, and 22.77 at% surface oxygen, achieving a specific capacitance of 357.8 F·g−1 and remarkable cycling stability with 99.2% retention after 20,000 cycles. This work is expected to open a sustainable pathway for valorizing low-rank coals into high-performance porous carbons for advanced supercapacitors.