Supercritical CO₂-Induced Quinone Confinement and Interfacial Polarization in Microporous Carbon Electrodes for Aqueous All-Organic Batteries

Aqueous organic batteries provide a sustainable and metal-free alternative to conventional electrochemical storage, with performance often limited by modest active material loading and incomplete utilization inside porous carbon hosts. We report a simple all-organic full cell in which supercritical CO₂ (scCO₂) impregnation loads halogenated quinones into activated carbon (AC) and reorganizes the interface in a way that accelerates charge transfer. Using a minimal formulation, 1,5-dichloroanthraquinone is incorporated at approximately 38 wt % loading in the quinone/AC composite (prior to binder addition) with full electrochemical utilization, corresponding to high-density filling of the micropores rather than a high overall active-mass fraction, and serving as evidence of effective pore accessibility. Micropore analysis indicates about 90% of a micropore-limited upper bound. Small-angle X-ray scattering shows an increase in the high-q electron density correlation length, consistent with strengthened π-π stacking and denser intrapore packing under supercritical conditions. We extracted interfacial electronic state information that can change with the impregnation route: comparative C K-edge X-ray absorption and X-ray photoelectron spectroscopy reveal core-level shifts consistent with a modified electronic environment and enhanced interfacial polarization in the scCO₂-impregnated samples relative to liquid-impregnated controls; confinement- and packing-related effects may also contribute. In aqueous full cells, the supercritical route gives a 60% increase in energy density and a clearly improved rate response relative to liquid-phase impregnation, while retaining 95% of the capacity after 1000 cycles; electrochemical impedance spectroscopy likewise shows a lower apparent charge transfer resistance for electrodes fabricated via supercritical impregnation, indicating faster interfacial kinetics. Taken together, these results demonstrate that scCO₂ impregnation promotes π-π-stacking-driven intrapore ordering and near-complete utilization in porous carbon quinone electrodes, translating nanoscale organization into device-level gains in a simple metal-free aqueous system.