Orchestrating Charge‐Trap and Oxygen‐Barrier Synergy in XLPE via Grafting Voltage Stabilizer: A Multiscale Blueprint for Multi‐Stress‐Resistant Dielectrics
Abstract
Crosslinked polyethylene (XLPE) is the benchmark insulation for high‐voltage direct‐current (HVDC) cables, yet its amorphous phase remains the Achilles' heel—vulnerable to space charge accumulation, oxygen permeation, and thermo‐oxidative degradation that synergistically trigger premature failure. Here, we report a multiscale molecular design strategy that covalently grafts a tailored voltage stabilizer, 3‐amino‐5‐chloro‐3′‐fluorobenzophenone (ACFM), onto XLPE chains to concurrently engineer deep charge traps, dense amorphous‐phase packing, and oxidative resistance. First‐principles calculations and atomistic simulations reveal that the grafted ACFM introduces localized π‐conjugated states within the XLPE band gap, forming deep electron traps (0.9–2.2 eV) and hole traps (0.5–1.7 eV) that suppress carrier transport and dissipate hot‐electron kinetic energy via phonon coupling. Simultaneously, multi‐dipolar ACFM side chains enhance cohesive energy density, reduce fractional free volume, and diminish thermodynamic compatibility with O 2 , thereby lowering oxygen solubility and self‐diffusion coefficients across the 300–400 K operational window. Oxidation pathway calculations further demonstrate that the grafted ACFM moiety reduces reaction exothermicity by ~50% and elevates activation energy relative to pristine XLPE segments, conferring sacrificial antioxidant protection. Experimentally, 1.0 wt% ACFM grafting increases DC dielectric breakdown strength by 13.6% (from 368.5 to 418.7 kV/mm) and achieves an unprecedented 88.0% retention after 504 h of thermo‐oxidative aging at 135°C, substantially outperforming conventional stabilizers and representing the first demonstration of a grafted voltage stabilizer maintaining effectiveness under standardized severe aging conditions. These findings establish a “charge trap–dense aggregation–anti‐oxidation” synergistic paradigm and offer a transferable molecular blueprint for fortifying polyolefin dielectrics against multi‐stress degradation in advanced HVDC systems.