Stepwise De-solvation and Diffusion Kinetics of Hydrated Zn-ion in Hierarchical Porous Carbon Anode for Improved EDLC...

Porous carbon (PC) is widely recognized as a promising anode material for zinc-ion hybrid supercapacitors (ZiHSCs), but its practical deployment is hindered by sluggish ion diffusion kinetics and poor rate performance. In this study, a stepwise de-solvation of hydrated Zn-ion is observed during migration within the hierarchical micropore channels characterized by dominated dimension of 0.74 and 1.54 nm. This phenomenon mitigates the free energy dissipation of hydrated Zn-ion diffusion, accelerates charge transfer kinetics, and substantially enhances the EDLC generation. In situ Raman, ex situ FT-IR and XPS analysis reveal an intensive removal of bound water from [Zn (H₂O)₆]²⁺ and rapid micropore filling at the discharge state. The optimized anode delivers a specific capacitance of 224.1 mAh/g at 0.2 A/g, an impressive energy density of 179.6 Wh/kg (active materials basis), and exceptional cycling stability (99.1% capacity retention over 100,000 cycles). This dimension design paradigm establishes a generalizable framework for optimizing porous carbons in energy storage, bridging the gap between fundamental ion-solvent-pore interactions.