陶瓷基高储能复合材料关键问题的研究

This proposal is based on a famous US patent granted to the EEStor Inc. According to the patent, the dielectric constant of alumina coated compositional modified barium titanate powder could be kept as high as 20,000 under 500 V/μm electric field, which would result in the capability of extraordinary high energy storage density. Most experts of electronic ceramics would think the feature unbelievable. After careful deliberation，we believe that the alumina films and their self-healing behavior under high electric field are one of the core issues in the study of dielectrics with high energy storage density. The previous studies on alumina films are mostly focused on their filtration and seperation, abrassive and corrosive resistance and optical applications. There are only very few works on their dielectric behavior under high electric field. We propose to shift our emphases from ferroelectric dielectrics with high dielectric constant to alumina films with high dielectric breakdown strength. We suggest to study the following key issues in this project: 1. To develop a reasonable way to prepare alumina films with dense structure and high electric breakdown strength, which can be used to coat ceramic powders by means of optimizing the wet chemistry sol-gel method and the electrochemistry method and combining the merit of the both methods; 2. To study the Current-Voltage characteristics of the alumina films under high electric field to achieve high electric breakdown strength; 3. To study the self-healing phenomenum of the alumina films under high electric field; 4. To introduce solid inorganic/organic electrolytes into the alumina film configuration to enhance their self healing behaviors and achieve higher energy storage density and better safty performance.

本项申请是基于EEStor的一个著名专利。该专利声称由氧化铝包覆的钛酸钡粉体的介电常数即使在高达500伏/微米的电场下，仍可维持在约2万的水平，从而使其具有很高的储能密度。这一成果使许多电子陶瓷专家觉得不可思议。我们认为氧化铝包覆膜及其在强电场下的自修复功能对于获得高介电常数和高储能密度起了最关键的作用。以往对氧化铝膜的研究主要集中在分离、耐磨、抗蚀和光学等应用，甚少对其强场介电行为进行研究。为此我们把研究重点从高介电常数的铁电陶瓷转移到高抗电强度的氧化铝膜上来，提出以下几个关键问题进行研究：1.研究结构致密、抗电强度高并能够用于粉体包覆的氧化铝膜的制备方法；2.研究氧化铝膜在强场下的电流-电压特性, 提高其抗电强度；3.深入研究氧化铝膜在强场下的自修复特性；4.引入无机或有机电解质，强化氧化铝膜在强场下的自修复功能，进一步提高其储能密度和运行安全性。

本项目针对氧化物薄膜电介质的强场击穿现象和自修复机制开展研究，以氧化铝线性电介质薄膜为典型，考察分析其击穿前的发展过程和击穿现象以及相关的物理和化学变化、击穿现象与环境条件、电极因素、材料在不同层次上的结构以及样品的构型等因素的影响，对材料击穿过程取得了比较全面的认识。引用电介质在弱场下介电性能掺杂改性和结构调控方式来提高材料的抗电强度。发现了多种元素、化合物、纳米掺杂的有效体系，为进一步发展这一技术开拓了道路。.. 此项研究取得了氧化物电介质薄膜在强场下自修复效应的可靠实验证据，提出了阳极氧化宏观缺陷的自修补和离子输运微观缺陷的自修复两种机制，发现溶胶-凝胶方法制备的水合氧化物薄膜是一种优异的电介质,具有很高的抗电强度和化学活性，同时还能起到固态电解质的作用，并同时能有效地保障电极材料及氧化物介质的结构组成元素,实现阳极氧化反应，实现缺陷结构的自修补与自修复，大幅度地提高了材料的抗电强度和储能密度。这种电介质-电解质双向复合特性过去并不多见，知之甚少，是一种适合于开发全固态高电压电解电容器的新型电介质，无需再额外地引入其他电解质，为进一步产业化和推广应用创造了条件。.. 通过本项目,对氧化物薄膜电介质的强场击穿现象和自修复机制有了较为深入全面的认识，取得了一些突破，大幅度提高了材料的击穿场强，使其接近材料的本征击穿场强，引起了国内外同行的关注，推动了薄膜电介质强场击穿和自修复现象研究，在一定程度上弥补了电介质击穿理论的薄弱环节，使其成为电介质领域的一个新的前沿研究方向，为进一步发展这一学术方向开了一个好头。

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