高抗电强度高功率密度金属氧化物电介质的自修复效应及其应用研究

The top preference of capacitors for high energy storage applications in the next generation is multilayer capacitor from laminating metal oxide films. The dielectric constant and working temperature of metal oxides are higher than those of the polymer films used to wind traditional capacitors. The major disadvantage of the metal oxide films is their low dielectric strength (100-300 MV/m), which is much lower than that of the polymer films (600-700 MV/m). In the past a few years, our research group discovered a self-repairing phenomenon of defects under applied electric field from the sol-gel derived aluminum oxide and strontium titanate films, which substantially enhanced the dielectric strength of the films (400-550 MV/m). .This project intends to expand the research scope from simple metal oxides to complex perovskite oxides such as PLZST, from amorphous films to microcrystalline films, from linear dielectrics to nonlinear dielectrics. The focused attention of the studies on self-repairing phenomena will be the ionic transportation characteristics, space charge polarization and interface polarization mechanism under high electric field. Taking the dielectric and impedance frequency spectra, using the equivalent circuit modulation, the major physical and chemical characteristics of the self-healing phenomena can be identified. The project will try to generalize the favorable factors to enhance the self-repairing phenomena comprehensively and to modulate the phenomena by means of composition and structure adjustment. As a result of the work, we are trying to explore a few thin and thick metal oxide films with excellent self-repairing effect for practical applications, pushing forward the research on self-repairing dielectrics entering the frontier of the arena worldwide.

多层结构的金属氧化物薄膜电容器是新一代高密度储能电容器的首选方案。金属氧化物的介电常数和工作温度要比传统卷绕型聚合物薄膜储能电容器高，主要缺点是抗电强度远低于聚合物薄膜。本课题组在溶胶-凝胶法合成的氧化铝和钛酸锶薄膜中发现了材料和电极体系在电场下的缺陷自修复效应，大幅度提高了薄膜材料的抗电强度（400-550 MV/m）。本项申请拟将研究工作从氧化铝等简单金属氧化物扩展到锆钛锡酸铅等复合钙钛矿氧化物，从非晶薄膜扩展到微晶薄膜，从线性电介质扩展到非线性电介质。自修复现象的研究则主要关注强场作用下的离子输运，空间电荷与界面极化过程，测定介电频谱与阻抗谱，通过等效电路的模拟计算来获取材料物理与化学过程的主要参数，综合考察强化材料自修复效应的因素，研究通过组成和结构来调控自修复功能的途径，开发出几种具有自修复功能的薄膜，以期在自修复效应的研究领域率先进入前沿阵地。

本项目研究用溶胶-凝胶以及流延等软化学方法制备高抗电强度有自修复功能的电介质薄膜。主研氧化铝、钛酸锶以及锆锡钛酸铅(PLZST)等三大类单元和多元金属氧化物及其固溶体和复合体；研究重点是材料的非晶和纳米微晶复合膜的抗电强度及其在强场作用下的自修复功能和机理，优化材料的组成、制备与结构，开发高抗电强度有自修复功能的高性能电介质薄膜，为绿色能源技术、军工技术急需的高性能储能材料做出贡献。. 本项目首先采用了交流阻抗法测定无定型氧化铝薄膜的宏观频率响应，通过等效电路模拟计算了材料的电学参数，获得了无定型氧化铝薄膜在强场下自修复效应的可靠数据，发现薄膜的自修复效应来源于铝电极的阳极氧化导致的宏观缺陷自修补和非晶电介质的离子输运导致的微观缺陷自修复两种机制，并建立了相应的物理模型。同时首次发现了以铜和钛等阀金属作为顶电极也同样表现出优异的自修复功能，薄膜的抗电强度和储能密度均大幅提高，为开发以金属氧化物为介质，以铜或钛为电极的超高储能密度多层陶瓷电容器奠定了坚实的基础。. 用溶胶-凝胶或流延等软化学方法制备高抗电强度有自修复功能的电介质工艺简单，效果明显，与传统陶瓷工艺兼容，产业化前景十分广阔。本项目在自修复效应的应用开发方面开展了一系列工作。（1）在非晶氧化铝薄膜中引入纳米晶氧化锆粉体以及在非晶钛酸锶薄膜中引入纳米氧化铝粉体形成1-3型纳米复合膜，其界面区域中载流子迁移率大幅提高，促进了铝电极与复合膜之间的电化学反应。抗电强度提高了1.4倍。（2）非晶钛酸锶薄膜与非晶氧化铝薄膜复合形成2-2型多重复合膜，此多重复合膜的抗电强度和介电常数同时提高，储能密度也相应大幅提高。（3）在研究氧化铝介质膜的阳极氧化效应和自修复现象中，发现氧化铝溶胶包覆PLZST陶瓷粉体的软化学杂化工艺这种材料复合方式可以更有效地大幅度提高介质膜的击穿强度和储能性能，可以使有效释放的储能密度提高一倍，这对于脉冲MLCC陶瓷电容器意义重大。