Molten salt-assisted fabrication of hierarchical porous carbon derived from lignite for Zn-ion hybrid supercapacitors

Zn-ion hybrid supercapacitors (ZIHCs) are considered as the most potential energy storage device. Herein, a hierarchical porous carbon was prepared by molten salt-assisted one-pot activation strategy. The molten salt synthesized lignite-derived porous carbon (MLPC) has high specific surface area (3035 m2 g−1) and unique architecture with dual majority pores of size in 1–3 nm. The assembled ZIHC delivers a high specific capacitance of 570.6 F g−1 at 0.1 A g−1 and a remarkable energy density of 82.8 W h kg−1 at a power density of 16 kW kg−1. The cell achieves good long-term cycling stability with 82.2 % capacity retention at 2 A g−1 after 5000 cycles. This study provides a facile approach to utilize lignite to fabricate superior carbon cathode for high-performance aqueous ZIHCs.