Synergistic Molecular Engineering of Crosslinked Polymer Dielectrics for High-Temperature Capacitive Energy Storage.

He, Yan; Sun, Quan; Xue, Rui; Wang, Qi; Guan, Aijiao; Zhang, Pingxia; Xu, Jingcheng; Ran, Zhaoyu et al. · Adv Mater · 2026

basic_science · Level V

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Abstract

Polymer dielectric capacitors are critical for high-temperature energy storage, yet current materials face a trade-off between thermal stability and capacitive performance due to conduction loss or insufficient polarization. Here, a modular molecular engineering to simultaneously optimize molecular polarity, topological crosslinking, and free volume in alicyclic polymers is designed. By incorporating thermally crosslinkable benzocyclobutene (BCB) and sulfone-methyl (─SO<sub>2</sub>CH<sub>3</sub>) groups into norbornene-based monomers via ring-opening metathesis polymerization (ROMP), crosslinked networks with decoupled non-conjugated backbones and polar moieties are constructed. The polymers exhibit a wide optical bandgap (E<sub>g</sub> > 3.7 eV), high thermal stability (T<sub>g</sub> > 350 °C), and suppressed dissipation (D<sub>f</sub> ≈ 0.0006). Optimized P50-B250 delivers an exceptional discharged energy density (U<sub>d</sub>) of 8.00 J cm<sup>-3</sup> at 150 °C (≥90% efficiency), while fully crosslinked P0-B300 retained U<sub>d</sub> of 7.34 J cm<sup>-3</sup> at 200 °C and 4.65 J cm<sup>-3</sup> at 250 °C, outperforming conventional dielectrics. Molecular dynamics (MD) simulations revealed that crosslinking increases free volume fraction by ≈40%, inhibiting interchain charge transfer complexes (CTCs). Density functional theory (DFT) calculations confirm that sulfonyl-enhanced polarization and crosslinking collectively restrict charge migration. This work establishes a general framework for designing polymer dielectrics by integrating structural modularity and topological control, offering pathways for next-generation energy storage applications under extreme conditions.