Revealing the energy storage mechanism of coal-derived graphite-like porous carbon in high-performance aqueous zinc-ion hybrid capacitors

Developing porous carbon cathodes with optimized pore structures and high conductivity is critical for advancing zinc-ion hybrid capacitors (ZHCs) that achieve high energy and power densities. This work reports a reliable method for synthesizing graphite-like porous carbon using low-cost anthracite as the precursor. The resultant material combines the advantages of high conductivity and stability from graphite-like domains, as well as a high specific surface area and efficient ion transport pathways from its porous network. When employed as the cathode in aqueous ZHCs, the optimized sample CMC-6 exhibits outstanding electrochemical performance: a high specific capacity of 239.5 mAh g−1 at a current density of 0.1 A g−1, a remarkable energy density of 91.79 Wh kg−1 even at a high power density of 3798.11 W kg−1, and undetectable capacity decay after 10,000 cycles at 1 A g−1. A systematic investigation of the pore size effect reveals that ∼0.7 nm low-energy-barrier micropores promote ion diffusion, whereas ∼0.4 nm ultra-micropores tend to hinder it. Combined experimental and theoretical analysis demonstrates that the highly ordered structure within the carbon framework is critical to achieving high energy density. This work provides fundamental insights into the structure-performance relationship of coal-derived carbon materials for advanced energy storage applications.