叠层结构MXene@氟化石墨烯/铁电聚合物复合薄膜的构筑及其介电储能增强机理研究

Polymer film capacitors are of great importance as power energy storage devices. The energy density (Ue) of the state-of-the-art capacitor film represented by biaxially oriented polypropylene (BOPP) has been restricted by its low dielectric constant. Conductive filler/ferroelectric polymer composites with relatively high εr have been regarded as one of the most promising dielectric materials for flexible high-Ue film capacitors, yet suffering from low breakdown strength and high loss. Therefore, it is critical to improve their breakdown strength and loss. In this project, a novel fluorine-free MXene is prepared as conductive filler and P(VDF-HFP) is used as matrix to develop flexible high-Ue composite dielectric film. In order to achieve high dielectric constant with maintenance of high breakdown strength and low loss in MXene/P(VDF-HFP) composite film, the MXene-polymer interface is tailored by encapsulating MXene with an electrical insulating fluorographene shell, while a multilayer spatial structure of composite film with anisotropy in each layer is constructed via electrospinning and hot pressing process. Then, a systematically study on the influence of interface structure, filler orientation, gradient distribution and laminated structure on the dielectric energy storage performance of composite film is conducted to reveal the synergistic enhancement mechanism of comprehensive structural design. This research will provide theoretical basis and technical guidance for the development of novel flexible high-Ue dielectric films and high-performance film capacitors.

聚合物薄膜电容器是极其重要的功率型储能器件。当前以BOPP为代表的商用电介质薄膜受其低介电常数限制而储能密度（Ue）很低。导电填料/铁电聚合物复合薄膜凭其极高的介电常数被誉为最具潜力的柔性高Ue电介质薄膜材料之一，但当前饱受击穿场强低和损耗高的困扰，因此如何改善其击穿强度和损耗成为该领域亟需解决的关键问题。本项目拟以新型二维无氟MXene为导电填料来发展柔性高Ue聚偏氟乙烯-六氟丙烯（P(VDF-HFP)）基复合介电薄膜，采用高电绝缘性氟化石墨烯包覆MXene为全新界面调控手段，借助“静电纺丝+叠层热压”法构建各层各向异性的叠层互补结构，以期通过上述结构调控实现介电常数、损耗及击穿强度的协同改善，通过系统研究界面结构、填料取向、梯度分布及叠层结构对复合薄膜介电储能性能的影响，揭示基于综合结构设计的介电储能增强机理。本项目预期成果将为开发新型柔性高Ue电介质薄膜提供理论依据和技术指导。

目前商用电介质薄膜受其低介电常数限制而储能密度（Ue）很低，严重制约薄膜电容器发展和应用。导电填料/铁电聚合物复合薄膜因具有较高的介电常数被认为是极具潜力的柔性高Ue薄膜介质材料，其面临的关键问题是如何实现介电常数和击穿强度的协同改善。本项目研究引入导电性Ti3C2Tx（MXene）和高绝缘性氟化石墨烯（FG）作为新型二维填料来发展柔性高Ue铁电聚合物基复合薄膜，研究了MXene的制备工艺对其形貌和结构的影响规律，探究了FG包覆MXene的制备条件，并以此为基础研究了MXene结构及其表面包覆改性、FG以及填料取向结构对复合薄膜介电性能的影响规律，揭示了相应复合薄膜的介电储能增强机理，主要的研究成果包括：（1）实现了形貌良好的无氟MXene（Ti3C2Tx，T = Cl, O）的可控制备，通过自组装法制备了MXene@FG二维异质复合填料；（2）查明了FG的高电绝缘性、沿面取向及其氢键诱导形成的界面是FG填充铁电聚合物薄膜获得高击穿场强和低损耗的关键成因；（3）揭示了无氟MXene固有结构缺陷带来的低电导率是制约无氟MXene填充铁电聚合物薄膜的介电常数显著提升的桎梏；（4）基于含氟MXene理清了FG表面包覆和填料取向分布对复合薄膜介电常数提升的影响规律和机理。上述研究成果为发展新型高性能柔性聚合物复合介电薄膜提供了参考经验和理论依据。