One of the biggest challenges for polyimide (PI) insulators is to achieve high breakdown strength compatible with low dielectric loss, which would significantly affect the operating power, energy loss and electric equipment ageing during application. Here, we successfully realized enhancement of breakdown strength of PI film from 2.37 MV/cm to 2.99 MV/cm by in-situ compositing fluorinated graphene (FG), and this is accompanied with a reduction of dielectric loss from 0.017 to 0.006. By combining solubility testing in concentrated sulfuric acid and in-situ Fourier transform infrared (FTIR) characterization, the “cross-linking” structure of PI/FG film was experimentally confirmed. Meanwhile, it was found that space charge accumulation of cross-linked PI film under an electric field was suppressed and uniformed, and the mobility of its molecular chain under an alternating-current (AC) electric field was found to be significantly constrained. Therefore, it was supposed that the cross-linking structure plays a determining role in optimizing the dielectric performance of PI/FG films, which provides a feasible strategy to optimize the overall insulating/dielectric performance of insulators and dielectrics.

聚酰亚胺 (PI) 绝缘体面临的最大挑战之一是实现与低介电损耗兼容的高击穿强度，这将显着影响应用过程中的工作功率、能量损耗和电气设备老化。在这里，我们通过原位复合氟化石墨烯 (FG)成功实现了 PI 薄膜的击穿强度从 2.37 MV/cm 提高到 2.99 MV/cm ，同时介电损耗从 0.017 降低到 0.006。通过将在浓硫酸中的溶解度测试和原位测试相结合傅里叶变换红外（FTIR）表征，实验证实了PI/FG薄膜的“交联”结构。同时发现交联PI薄膜在电场作用下的空间电荷积累受到抑制和均匀化，其分子链在交流(AC)电场作用下的迁移率受到显着限制。因此，可以认为交联结构在优化PI/FG薄膜的介电性能方面起着决定性的作用，为优化绝缘体和电介质的整体绝缘/介电性能提供了可行的策略。