伴随着电子器件微型化和轻柔化的发展趋势，聚合物基复合电介质因其在高储能密度方面的巨大潜力而备受瞩目。在考量复合电介质的储能密度时，击穿场强的贡献举足轻重。然而，对于介电击穿机理缺乏深入系统的理解，成为复合电介质设计时的薄弱环节。受限于实验上难以对高能瞬态的击穿过程进行原位表征分析，本文采用相场模拟等手段搭建了以“组分-结构-性能-设计”为线索的计算流程框架，基于多物理场的能量层面，将各击穿机制关联整合，时空解析了材料属性、微观结构和物理激励等因素对复合电介质击穿过程的影响，为复合电介质及器件设计提供了理论指导。随后针对非本征界面空间电荷效应，以结构为线索研究复合电介质的局域特性和外场响应等介电性能。首先构建静电击穿相场模型，动态剖析了介电击穿过程中的结构效应。进而以结构与性能的关联为导向，借助高通量计算研究了填料长径比和取向与击穿场强和介电常数的内在关联，最后设计并优化一种三明治叠层结构，可提升2.44倍的储能密度。其次，构造考虑热效应的电-热耦合模型，阐明了焦耳热对击穿过程的贡献。随后推算了微观结构与电导率和热导率关联的相图，并基于卷绕式薄膜电容器模型，探究高温高场下其内部温度及相应介电性能的稳定性，继而提出了一种高温复合电介质结构设计的新思路，即降低电介质薄膜面外电导率较之提升面内热导率对消减热效应更有效。为将各击穿理论有机结合，本工作提出了电-力-热协同击穿模型，并归纳总结了不同复合电介质的击穿机制。而后结合高通量计算和机器学习，获得了可快速预测复合电介质击穿场强的解析表达式，筛选出可提高击穿场强的填料类型，即低介电常数、高杨氏模量和低电导率的陶瓷填料，例如Al2O3和TiO2等，为复合电介质击穿场强提升及性能优化提供了参考。此外该计算框架也可拓展到热电材料和固态电解质等功能复合材料的筛选和优化设计。最后，构造并整合电荷输运和响应模型，探究了由杂质离子和电子注入形成的非本征空间电荷效应。结果表明复合电介质中界面空间电荷能够导致局域电场畸变，在低频区增大介电常数的同时，也带来了介电损耗等性能的上升，且填料的团聚会增强空间电荷效应。

Polymer-based composite dielectrics have gained increasing attention due to the enormous potential of high energy density under the trends of microminiaturization and flexibility of electronic components. The breakdown strength is a crucial factor of determining the energy density of composite dielectrics. However, poor understand of breakdown mechanisms becomes weaknesses in designing composite dielectrics. Limited by the unrealizable in-situ characterization of the drastic and momentary breakdown process, this thesis combines phase-field simulations and other calculation methods to bulid a computational framework with the clue of “component-structure-peoperty-design”. From the perspective of energies, different breakdown mechanisms are linked and integrated, then the effects of microstructures, material properties and physics stimuli on the breakdown process of composite dielectrics are investigated spatially and temporally, which can give theoretical guidance on design of composite dielectrics and devices. Furthermore, space charge effects, regarding as extrinsic factors, are considered to study local features and dielectric responses under different electric fields and structures.First, an electrostatic breakdown model was established to dynamically investigate the microstructure effect on dielectric breakdown process. Then, based on the relationship of microstructures and properties, the underlying relations between the aspect ratio and orientation of fillers and dielectric constant and breakdown strength were studied by high-throughput calculations. Following, a new sandwich structure was designed and optimized to improve energy density by 2.44 times. Second, an electric-thermal coupling breakdown model was built to consider the contribution of Joule heating to the breakdown process. Taking the winding film capacitor as the model, we investigated the changes of internal temperature and corresponding dielectric properties in capacitors under high applied electric field and high temperature, based on the phase diagarms of microstructure and electrical conductivity and thermal conductivity. It has found that reducing the out-of-plane electrical conductivity is much more effective to mitigate the thermal effect than increasing the in-plane thermal conductivity, which is a new idea of designing high-temperature composite dielectrics. To combine different breakdown mechanisms, an electric-thermal-mechanical synergetic breakdown model was constructed, which is able to predict and summrize the breakdown mechanisms of different composite dielectrics. With the help of high-throughput calculations and machine learning, we obtained an analytical expression to quickly predict the breakdown strength of composite dielectrics. It has found that the addition of oxides with lower dielectric constant and electrical conductivity such as Al2O3,and TiO2 into polymer matrix could enhance the breakdown strength, which provides fundamental insights for design and optimization of dielectric properties of composite dielectrics. It also can potentially be extended to optimize the performances of a wide variety of other types of materials such as thermoelectrics and solid electrolytesFinally, the extrinsic effect of space charge from impurity ions and electron injection were considered by integrating the charge transport and response model. The space charge at interfaces could distort the local electric field and increase dielectric constant in low frequency region but also bring about the increase of dielectric loss, and the agglomeration of fillers can enhance space charge effect.