Localized Electric Field-Activated Charge Transport in PEO:LiTFSI

Solid polymer electrolytes in battery systems can experience highly localized electric fields at heterogeneous interfaces, yet their nanoscale transport response under such field confinement remains insufficiently characterized. Here, conductive atomic force microscopy is used to probe electric field-activated transport in PEO:LiTFSI (EO:Li = 18:1) by comparing amorphous and crystalline regions while varying probe size, applied force, bias history, and bias duration. Measured currents reach the nanoampere range and do not scale with the nominal contact area, indicating strongly confined transport pathways. The current magnitude far exceeds that expected for purely ionic conduction, suggesting mixed transport behavior in which field-assisted electronic contributions may become substantial under high electric-field concentration. Cyclic voltammetry reveals bias-history dependence and distinct Faradaic peaks, demonstrating ionic redistribution and localized electrochemical activation. Localized biasing further induces polarity-dependent electrochemomechanical responses, including pronounced adhesion enhancement and surface depression or swelling after biasing. These results demonstrate that nanoscale field concentration drives coupled charge transport, electrochemical reaction, and mechanical responses in PEO:LiTFSI, underscoring the importance of local field heterogeneity and microstructure in governing electrolyte behavior under electrical polarization.