Interfacial Dielectric Pinning for Engineering High-Rate Ion Transport in MnCo 2 O 4 -Reinforced PVA/PVP Polymer Separators

Regulating ion-relaxation kinetics and structural stability in hydrated polymer separators remains a critical challenge for high-power aqueous electrochemical systems. Herein, we introduce a “polymer pinning” strategy to engineer a high-performance composite separator by embedding surfactant-assisted MnCo2O4 nanocubes into a PVA/PVP binary matrix. Strong interfacial coordination between mixed-valence metal centers and polymer functional moieties establishes a stabilized dielectric interphase that suppresses Maxwell–Wagner–Sillars (MWS) polarization. Thermomechanical analyses confirm restricted segmental mobility, evidenced by an 18 °C increase in glass transition temperature (Tg) and a reduction in swelling from 80 to 13%. Distribution of relaxation time (DRT) analysis reveals a 20-fold acceleration in ionic relaxation kinetics, with τ reduced to 1.6 × 10–4 s for the optimized Mn0.75@PPF separator. When evaluated in an asymmetric supercapacitor, the engineered separator enables 94% surface-controlled charge storage, delivering 263 F g–1 with 96% retention over 10,000 cycles and suppressed self-discharge. This work establishes dielectric regulation via polymer pinning as a scalable materials engineering strategy for stabilizing ion transport in aqueous energy storage systems.