Abstract:

High-temperature dielectric energy storage materials are essential for next-generation power electronics and electrical systems operating in extreme environments. However, achieving high-energy storage in polymer dielectrics at ultrahigh temperatures (e.g., 200°C) remains a critical challenge, chiefly owing to the marked enhancement of molecular chain thermal motion, which gives rise to elevated charge conduction losses and diminished breakdown strength. Here, we propose a rigid-flexible synergistic multiple crosslinked network strategy that simultaneously suppresses inter/intra-chain charge transport while inhibiting thermal molecular motion. This rigid crosslinked architecture supports adjacent polymer chains, enhancing local segmental stability while also reducing interchain π-π stacking and dipole interactions. Further, enabled by the thermodynamic annealing of flexible segments, the homogenously distributed interchain rigid scaffolds strike a balance between local structural rigidity and global deformability, thereby efficiently mitigating bulk charge conduction and boosting energy storage capabilities under extreme conditions. The resulting material exhibits an exceptional energy storage performance at 200°C, with a discharge energy density of 6.91 J cm-3 at 90% efficiency. Moreover, it demonstrates outstanding cycling stability, maintaining performance over 50,000 charge-discharge cycles at 500 MV m-1. This study presents a new design strategy for high-temperature dielectric materials, showcasing the potential of multiple crosslinked structures to meet the demanding requirements of ultrahigh-temperature applications.