纳米金红石二氧化钛基复合介电材料的多界面极化增强机制和储能性质研究

The trend in the development of high energy density and miniaturization for electrostatic capacitors requires nano-based dielectric composites (nanostructured material (filler)/polymer). However, the energy storage performances of nanocomposites are quite sensitive to the filler itself and nanocomposites’structures, which result in many issues to date such as: the effective way to enhance energy density is still lacking; the overall performance is not stable; the involved mechanisms are not yet clear, etc. . To this end, this project, based on the nanoscale controllable synthesis and interfacial capacitors model studied previously, proposes a new principle i.e. fabrication of multi-interfacial structures for enhancing multi-interfacial polarization. Well-defined (uniform in sizes and specific dimensions) rutile TiO2 nanostructures (nano particles, nanorods and nanowires growing along crystallographic c axis) will be synthesized by multi-scale control over the solution chemistry dynamics. The as-prepared rutile TiO2 nanostructures will be functionalized by surface coating of SiO2 to form core/shell structures and further, to fabricate nanocomposites with multiple interfaces with combing polymer PVDF, i.e. rutile-TiO2/PVDF and rutile-TiO2@SiO2/PVDF by well-controlled solution casting method. During the nanocomposites fabrication, the multi-interface structures will be well designed, tuned and optimized to enhance the multi-interfacial polarizations, giving rise to high energy density. This project will also illuminate how the multi-interface structures affect and contribute to the interfacial polarizations and what the role in energy storage the multi-interface structures play, in order to undercover and create the correlations between structure and property. This project is thus helpful for the exploration of new dielectric nanocomposites with high energy density.

物理电容器高储能密度和器件小型化发展亟需纳米/聚合物复合介质材料，但复合介质材料的储能性能对填料（纳米材料）属性和结构模型极其敏感，导致储能密度不能有效提高、不稳定和机制不清晰等诸多问题。. 本项目在前期纳米调控和界面电容器研究基础上，提出“构筑多界面结构以增强多界面极化”原理，选取高介电常数金红石二氧化钛（rutile TiO2）为基材料，多尺度调控溶液化学生长动力学，制备尺寸均一和维度可控的rutile TiO2纳米相（纳米颗粒，沿c轴生长的纳米棒和纳米线）；包覆二氧化硅（SiO2）构筑初级界面，采用溶液浇筑提高填料均匀性和分散性，复合PVDF构筑多界面；优化调控多界面结构以增强界面极化，制备出高能量密度rutile TiO2/PVDF和rutile TiO2@SiO2/PVDF复合材料。最后，阐明多界面结构对于界面极化和能量存储的增强机制和调控规律，建立模型指导新材料开发。

1、研究背景. 高储能密度静电电容器在高功率电磁器件领域具有重要应用。无机-有机复合介电薄膜因同时兼具高介电常数和高击穿场强、工艺简单和柔性等特点而备受关注。在无机纳米填料-聚合物复合薄膜材料领域，一直存在三个重要基础问题：一是热处理工艺对于聚合物物相的调控规律及其储能性质影响；二是纳米填料自身属性（晶体结构、取向、表面、维度和组装等）对于复合薄膜储能性质的影响规律；三是界面结构对于复合薄膜储能性质的调控规律。解决这些问题，有利于获得高储能密度复合薄膜，同时指导开发新材料体系。.2、研究内容. 本项目针对上述三个重要问题，提出纳米填料调控合成与层级界面构筑制备复合薄膜的研究思路，优化薄膜制备工艺技术，全面研究电学和介电储能性质。开展了金红石二氧化钛（r-TiO2）的合成调控、表面功能化及其r-TiO2@PVDF复合薄膜以及铌酸钾（KNb3O8）的电学、介电和储能性质研究；通过对晶体结构、界面结构、微结构等系统探测表征（XRD、SEM、HRTEM、EDX、FT-IR、Raman等）以及介电、铁电、耐电压等电学性质分析，阐明静电储能性质的结构调控的起源和关联性，探索得到具有高储能密度的介电复合薄膜的工艺技术，揭示多界面结构对于能量存储调控和增强的本质规律。.3、研究结果.1）通过溶液化学调控，制备合成金红石二氧化钛（r-TiO2）纳米材料（纳米颗粒、纳米纺锤体、纳米棒、纳米片、纳米线阵列）、铌酸钾（KNb3O8）纳米材料（纳米颗粒、纳米棒、纳米线、纳米片），并进行表面修饰和功能化包覆SiO2和多巴胺（PDA）。这些作为填料进一步与聚合物PVDF制备复合薄膜，深入研究结构、微结构、界面结构、电学、介电和储能性质的关联。.2）优化获得具有高储能密度的无机填料-有机聚合物复合薄膜：其中，r-TiO2纳米棒的储能密度为29 J/cm-3，r-TiO2纳米片的储能密度为33 J/cm-3，KNb3O8纳米棒和纳米片的储能密度均大于28 J/cm-3，是目前储能密度最高的复合薄膜之一。.3）薄膜退火处理以及PDA包覆有利于构筑界面极化增强效应，获得储能高性能。.4、科学意义.1）获得纳米材料可控合成新方法、高储能密度复合薄膜新方法和工艺技术，对材料设计和应用提供重要指导。.2）揭示界面多级结构对于静电储能的作用原理和规律，为材料设计提供重要依据。