【摘要】 随着器件小型化与多功能化的蓬勃发展,柔性储能装置在电子电力系统中的地位日益突出,电介质电容器由于寿命长、功率密度高,深受人们青睐,但是低的储能密度阻碍其广泛应用。有机-无机复合材料将有机介质的柔韧性和高击穿场强与无机介质的高介电常数相结合,是柔性储能材料的一大关注焦点,特别是基于聚偏氟乙烯(PVDF)的有机-无机复合储能介质受到广泛关注。首先,就无机填料类型而言,PVDF基有机-无机复合介质中无机填料的种类有陶瓷粉体、半导体粉体与导体粉体。陶瓷粉体填料的介电常数高、损耗小,但是与PVDF的相容性差,一般需要通过表面改性来改善其与有机介质的相容性;半导体粉体与导体粉体作为PVDF的填料可以显著提升复合材料的介电常数,从而提升其储能密度,但是填料添加量略大容易形成导电通路致使介电储能材料制备失败。其次,就无机填料的形貌而言,同一种材料不同的形貌对复合材料的储能性能有不同影响。零维纳米颗粒在有机基质中易于形成均匀分散的体系,一般随纳米颗粒添加量的增加复合材料的储能密度有一极值,且填料颗粒尺寸减小更有利于电场均匀分布,从而可以进一步提高复合材料的击穿场强和储能密度;采用一维纳米纤维和二维纳米片填料有利于增强复合材料的极化、改变电场的击穿路径,从而增强复合材料的击穿强度,提高其储能密度。最后,采用层状结构设计对提高复合材料的储能密度和储能效率十分有效。单层结构的复合材料以牺牲其击穿强度来提高介电常数,储能密度的提升有限;双层、三层和多层结构将高介电常数的极化层和高击穿强度的绝缘层相堆叠,可同时实现高介电常数与高击穿强度,有效促进复合材料储能密度的提升。有机-无机复合储能材料的研究对解决柔性设备的储能问题十分重要,未来需要寻找更优的复合体系,降低成本,提高工艺可控性,开发适合大规模生产的工艺流程。更多还原

【Abstract】 With the development of miniaturized and multifunctional devices, flexible energy storage devices play an important role in electronic power systems. Dielectric capacitors have attracted immense interest due to their long cycle life and high-power density. However, low energy density limits their wide applications. Organic-inorganic composite, one of the most important flexible energy storage materials, combines the flexibility of organic dielectrics with the high dielectric constant of inorganic dielectrics. Particularly, polyvinylidene fluoride(PVDF)-based organic-inorganic composite energy storage dielectrics have received extensive attention. Firstly, in terms of the types of inorganic fillers, the inorganic fillers in PVDF-based composite materials include ceramic powders, semiconductor powders and conductor powders. Ceramic fillers have high dielectric constant, low dielectric loss, but poor compatibility with PVDF, therefore, the interface compatibility generally needs be improved by surface mo-dification. Semiconductor and conductor fillers can significantly enhance the dielectric constant of PVDF-based composites, thereby improving energy density. However, conductive path is easily formed by an improper conductor filler adding amount, leading to the preparation failure of dielectric energy storage materials. Secondly, as to the filler morphology, different morphologies for the one filler material have different effects on the energy storage of composites. 0 D nanoparticles facilitate to form a uniform dispersed system in polymer matrix. Generally, there is a maximum value of the energy storage density of composites with the increased filler amount. With the decrease of particle size, the electric field distribution is more uniform, which can further improve the breakdown strength and the energy storage density of composites. The use of 1 D nanofibers and 2 D nanosheets is beneficial to increase polarization, and the breakdown strength of composite can be enhanced by varying breakdown path in electric field, thus improving energy storage density. Eventually, the layer design of composite structure is very effective to improve energy storage density and energy storage efficiency. Monolayer composite has to sacrifice breakdown strength to increase its dielectric constant, resulting in a limited improvement of energy storage density. Bilayer, sandwich and multilayer structure can simultaneously realize high dielectric constant and high breakdown strength depending on the stack of the high polarization layer with high dielectric constant and the insulation layer with high breakdown strength, which effectively improves energy storage density. It’s significant for energy storage of flexible devices to research organic-inorga-nic composite. In the future we need to develop some composites with high energy storage density and low cost. The improvement of process controllability and development of technological process are also necessary to mass production.更多还原