为了缓解人类所面临的化石能源枯竭与环境恶化等问题所带来的压力，介电电容器因其卓越的功率密度和超快的充放电速率而在新能源的存储领域获得了广泛青睐。高击穿强度的柔性聚合物基电介质是基于电极化原理实现聚合物薄膜电容器储能的关键介质材料。然而在电动汽车和航空航天动力系统等先进电力设备中，迫切需要能够在高温下有效工作的介电材料。聚合物的低介电常数、高温下急剧增加的传导损耗和差的导热性限制了其在高温下的使用。全聚合物复合电介质和纳米聚合物复合材料是解决该问题的两个有希望的途径。

本文选用耐高温、低介电损耗的线性聚酰亚胺(PI)作为基体，通过借助聚合物链间的静电作用，控制宽带隙无机填料的形貌和设计具有介电常数和带隙梯度的核壳结构填料来调控PI复合电介质的界面，制备了具有高介电、低损耗、高储能密度且耐高温的全聚合物型及填料/聚合物型的PI基薄膜。主要的研究内容和结论如下：

(1) 选取高耐热性的聚醚砜(PES)与PI共混改性，然后采用溶液流延法制备了具有透明光泽、均一柔性和厚度约为10 μm的PES/PI共混膜。研究发现，在PI中引入PES提高了复合薄膜的介电常数，同时还保持着较低的介电损耗，得益于紧密排列的PI和PES聚合物链，这样增强了偶极子密度，并减少了纳米结构偶极域的摩擦。PES/PI共混膜也由于强链间静电相互作用具有减少的自由体积，在高温下实现了优异的击穿强度和储能密度。50/50 PES/PI共混膜在150 ℃能承受的场强提升至350 MV/m，储能密度达到2.3 J/cm³，分别是纯PES和纯PI储能密度的11.5倍和2.53倍，而充放电效率也保持在70%以上。此外，所制备的PES/PI膜具有良好的导热性，适合高温储能应用。

(2) 采用溶剂热法和熔盐法制备了二氧化锆纳米片(ZrO₂-NPs)并选购了球形纳米二氧化锆(ZrO₂)，将二者与PI复合分别制备了ZrO₂-NPs/PI和ZrO₂/PI纳米复合材料。高介电常数的ZrO₂-NPs和ZrO₂的掺杂显著提升了PI的介电常数，9 vol% ZrO₂-NPs/PI和9 vol% ZrO₂/PI复合薄膜介电常数分别达到3.95和3.77。具有高纵横比的ZrO₂-NPs填料相比球形ZrO₂更能抑制导电通路的形成，使得ZrO₂-NPs/PI在高温下实现了较低的介电损耗和更高的击穿场强及储能密度。3 vol% ZrO₂-NPs/PI复合薄膜在1000 Hz的介电损耗仅为0.004，在150 ℃下能承受的场强从纯PI的200 MV/m和ZrO₂/PI的275 MV/m提升至350 MV/m，储能密度达到2.89 J/cm³，是纯PI储能密度的3.18倍，充放电效率同时保持在70%以上。此外，在PI中掺杂ZrO₂-NPs相比掺杂球形ZrO₂更能使得复合材料实现良好的导热性能。

(3) 采用Stöber法在球形纳米ZrO₂表面制备了具有不同厚度的二氧化硅(SiO₂)壳，以组成的ZrO₂@SiO₂-5%和ZrO₂@SiO₂-10%核壳结构填料掺杂PI获得一系列ZrO₂@SiO₂/PI复合薄膜。SiO₂壳层的引入产生了额外的界面极化，增强了ZrO₂/PI的介电响应。同时由于SiO₂的高绝缘性抑制了电荷载流子的迁移，使得ZrO₂@SiO₂/PI实现较低的介电损耗。宽带隙SiO₂外壳还在复合材料中产生了深层陷阱来捕获载流子并降低了能量损耗。ZrO₂@SiO₂-5%/PI和ZrO₂@SiO₂-10%/PI在体积分数为5%时分别实现3.34 J/cm³和3.07 J/cm³ (@325 MV/m和150 ℃)的高储能密度。相比5 vol% ZrO₂/PI的储能密度(@225 MV/m和150 ℃)分别提高93%和77%，而充放电效率保持在70%以上。此外，在PI中掺杂ZrO₂@SiO₂实现了较好的导热性。本研究中制备的ZrO₂@SiO₂-5%/PI复合薄膜具有较为全面综合的性能，优于大多数已报道的介电纳米复合薄膜。

To mitigate the pressure brought by the consumption of fossil energy and environmental deterioration faced by mankind, dielectric capacitors have gained tremendous momentum in the field of new energy storage due to their excellent power density and ultra-fast charge and discharge rate. Flexible polymer-based dielectric with high breakdown strength is the key material to realize the energy storage of polymer film capacitors based on the principle of electric polarization. However, advanced power electronics such as electric vehicles and aerospace power systems demand polymer dielectrics able to operate availably at high temperatures, and the low dielectric constant, the drastically increased conduction losses at elevated temperatures, and poor thermal conductivity of polymers astrict the high temperature capacitive energy storage applications. All polymers and nanocomposites dielectrics are two viable pathways to tackle the problem.

In this paper, linear polyimide (PI) with high temperature resistance and low dielectric loss was selected as the matrix. By utilizing electrostatic interactions between polymer chains, controlling the morphology of inorganic filler with wide band gap and designing the core-shell filler with dielectric constant and band gap gradient to regulate the interface of PI composite dielectric, and all polymers and filler/polymer dielectric films with high dielectric constant, low loss, high energy storage density and high temperature resistance were fabricated. The primary contents and conclusions are indicated below:

(1) Polyether sulfone (PES) with high heat resistance was blended with PI, and then the PES/PI all polymer blend film with transparent luster, uniform flexibility and thickness of about 10 μm was obtained by solution casting. It is found that the introduction of PES into PI improves the dielectric constant of the composite film, while maintaining a low dielectric loss thanks to the closely packed PI and PES polymer chains, which enhances the dipole density and reduces the friction in the nanostructured dipole domain. The PES/PI blend film is also endowed with a reduced free volume due to strong electrostatic interaction between chains, achieving excellent breakdown strength and energy storage density at high temperatures. The field strength of 50/50 PES/PI blend film at 150 ℃ increases to 350 MV/m, and the energy storage density reaches 2.3 J/cm³, which is 11.5 times and 2.53 times higher than that of PES and PI, respectively. The charge-discharge efficiency is also maintained above 70%. In addition, the prepared PES/PI film endows greater thermal conductivity, which is suitable for high-temperature energy storage applications.

(2) Zirconia nanosheets (ZrO₂-NPs) were prepared by solvothermal method and molten salt method and spherical nano zirconia (ZrO₂) was selected, and ZrO₂-NPs/PI and ZrO₂/PI nanocomposites were prepared by combining them with PI, respectively. The doping of ZrO₂-NPs and ZrO₂ with high dielectric constant significantly increases the permittivity of PI, and the permittivity of 9 vol% ZrO₂-NPs/PI and 9 vol% ZrO₂/PI composites reach 3.95 and 3.77, respectively. ZrO₂-NPs with high aspect ratio inhibits the formation of conductive pathways more than spherical ZrO₂, and significantly restrains dielectric loss, enhances the breakdown strength and energy storage density of the ZrO₂-NPs/PI, especially under high temperatures. The dielectric loss of 3 vol% ZrO₂-NPs/PI at 1000 Hz is only 0.004, and the field strength that can withstand at 150 °C is increased from 200 MV/m of pure PI and 275 MV/m of ZrO₂/PI to 350 MV/m, and the energy storage density as high as 2.89 J/cm³, which is 3.18 times that of PI, and concurrently an immense charge-discharge efficiency of above 70%. In addition, doped ZrO₂-NPs in PI can achieve better thermal conductivity compared with spherical ZrO₂.

(3) Silica (SiO₂) shells with different thicknesses were prepared on the surface of nano spherical ZrO₂ by Stöber method, and a series of ZrO₂@SiO₂/PI nanocomposites were obtained by doping PI with synthetic ZrO₂@SiO₂-5% and ZrO₂@SiO₂-10% core-shell structural fillers. The introduction of SiO₂ shells enhances the dielectric response of ZrO₂/PI due to the resulting interfacial polarization and inhibits the dielectric loss of ZrO₂@SiO_2/PI because high insulation of SiO₂ restrains the migration of charge carriers. The wide band gap SiO₂ shell also creates deep traps in the composites to capture carriers and thus yields a lower energy loss with respect to those with pristine ZrO₂ at high temperatures. Accordingly, 5 vol% ZrO₂@SiO₂-5%/PI and 5 vol% ZrO₂@SiO₂-10%/PI deliver high energy storage densities of 3.34 J/cm³ and 3.07 J/cm³ (@325 MV/m and 150 °C), respectively, which are enhanced by 93% and 77% relative to 5 vol% ZrO₂/PI (@225 MV/m and 150 °C), respectively, while the charge-discharge efficiency remains above 70%. Furthermore, a high thermal conductivity is achieved for doping ZrO₂@SiO₂ into PI. In conclusion, the ZrO₂@SiO₂-5%/PI composites prepared in this study produce a relatively comprehensive performance and outperform most of the reported dielectric nanocomposite films.