Construction of Coal Tar-Derived 3D Porous Carbon with KOH–K₂CO₃ Synergistic Activation for Advanced Zinc Ion Capacitors

High carbon content, good liquidity, and low cost endow coal tar with great potential in the field of advanced carbon cathode materials. Herein, honeycomb porous carbon nanosheet cathodes were prepared by the synergistic activation method of an alkali- and salt-coupled system. The obtained coal tar-derived carbon (CTPC) with a unique porous honeycomb-like microstructure significantly enhances the migration rate of electrolyte ions and electron conduction within the cathode. Besides, the valence bond variation on the CTPC has been detected via in situ infrared spectroscopy to demonstrate the mechanism of reversible chemisorption and desorption of Zn2+. The constructed zinc ion capacitors with the CTPC4 cathode can achieve a high discharge capacity of 104.9 mA h g–1 at 0.05 A g–1 and an impressive energy density up to 80.6 W h kg–1 at a power density of 93.1 W kg–1. Notably, CTPC4 maintains excellent performance stability during 10,000 cycles. The novel alkali- and salt-coupled synergistic activation method can provide a new perspective for the preparation of advanced carbon materials.