基于热压工艺的耐高温聚合物基储能电介质材料研究

目前，商业化双轴拉伸聚丙烯（BOPP）薄膜电容器因其室温下超高击穿场强和极低介电损耗，在电磁脉冲系统、混合动力电动汽车、航空航天等领域有着广泛应用。然而当温度超过105 °C后，其性能将会明显恶化，无法满足日益增长的高温高场下对电能存储和转换的需求。本论文从自由体积和库仑阻塞效应两个角度出发，分别设计了以下两个实验来提升聚合物电介质的高温电容性能。

我们通过调控热压参数改变了全有机耐高温聚合物——聚酰亚胺（PI）分子链间的自由体积，并进一步探究了其对材料高温电容性能的影响。研究结果表明，提升热压压强和温度会使PI的自由体积逐渐减少，从而导致其在高温下击穿场强、储能密度和充放电效率的提高。我们还通过离子溅射法结合热压法得到了低体积分数掺杂且纳米填料不连续的聚碳酸酯-金纳米点-聚碳酸酯异质结复合材料。结果表明，由于库仑阻塞效应，金纳米点可在层间界面引入局部深陷阱，在高温和高场下有效地捕获电荷并阻止电荷在聚合物内的传输，从而提高了复合材料在高温下的击穿强度，在获得超高储能密度（6.25 J/cm³）的同时保持了较高的效率（86.6%）。

相比于引入超声分散、表面改性等复杂步骤的高体积分数纳米掺杂聚合物，全有机耐高温聚合物和低体积分数纳米掺杂耐高温复合材料以其简单的制备工艺获得了显著提升的充放电效率和储能密度，因此更满足工业化大规模制备以及高温集成化和小型化的应用需求。

Currently, commercial biaxially oriented polypropylene (BOPP) film capacitors have a wide range of applications in electromagnetic pulse systems, hybrid electric vehicles, and aerospace due to their ultra-high breakdown field strength and extremely low dielectric loss at room temperature. However, when the temperature exceeds 105 °C, the performance deteriorates significantly and can’t meet the increasing demand for electrical energy storage and conversion at high temperatures and high electric fields. In this thesis, the following two experiments are designed to improve the high-temperature capacitive performance of polymer dielectrics from two perspectives: free volume and Coulomb blocked effect, respectively.

We modified the free volume between the molecular chains of the polyimide (PI), the all-organic high-temperature resistant polymer, by regulating the hot-pressing parameters, and further investigated its effect on the high-temperature capacitive performance of the material. The results show that increasing the hot-pressure pressure and hot-pressure temperature leads to a gradual decrease in the free volume of PI, which gives rise to an increase in breakdown strength, energy storage density, and charge-discharged efficiency at high temperatures. We also obtained polycarbonate-gold nanodot-polycarbonate heterojunction composites with low volume fraction doping and discontinuous nanofillers by ion sputtering combined with hot pressing. The results show that the gold nanodots can introduce localized deep traps at the interlayer due to the Coulomb blocked effect, which effectively traps the charge and prevents the charge transport within the polymer at high temperature and high fields, thus improving the breakdown strength of the composites and maintaining a high efficiency (86.6%) while obtaining an ultra-high energy storage density (6.25 J/cm³) at high temperature.

Compared with high volume fraction nano-doped polymers that introduce complex steps such as ultrasonic dispersion and surface modification, the all-organic high-temperature resistant polymers and low volume fraction nano-doped high-temperature resistant composites achieve significantly improved charge-discharged efficiency and energy storage density with simple preparation process, and thus better meet the demands of industrial large-scale preparation as well as high-temperature integration and miniaturization applications.

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