电介质储能薄膜的研究现状及提高储能密度的方法

Research Progress of Dielectric Energy Storage Thin Films and Methods for Improving Energy Storage Density

随着能源危机和环境污染问题的日益突出,新能源的研发是当前人们密切关注的重要研究领域之一。除新能源的收集外,能量的存储也日益受到人们的重视。常见的储能器件有电池、燃料电池、超级电容器和电介质电容器等。其中电池和燃料电池的能量密度高,但功率密度低;传统电介质电容器的功率密度高,但储能密度低;超级电容器的功率密度和能量密度介于电池和传统电容器之间。电介质电容器具有介电常数高、介电损耗低、功率密度高、充/放电速度快、工作电压/电流大、可靠性好、温度稳定性好等优点,已经被应用于脉冲功率器件领域。双轴拉伸聚丙烯(BOPP)已经实现了商业化应用。但电介质电容器固有的储能密度较低,限制了其应用范围。如何提高电容器的储能密度成为亟待解决的一个关键问题,也是目前人们研究的重点。与块体材料相比,薄膜电容器的耐压强度高,因此其储能密度高。本文的关注点就是无机储能薄膜的研究现状及提高其储能密度的方法。目前已经对储能薄膜开展了大量的研究,其结构体系有很多,如钙钛矿结构、铋层状结构、焦绿石结构、单金属氧化物薄膜等。其中钙钛矿结构薄膜是研究最早、最多的一类。目前,用磁控溅射或激光脉冲沉积制备的无铅钙钛矿结构薄膜的储能密度达100 J/cm 3以上。然而,由于薄膜制备方法多、工艺复杂,会产生很多因素影响其性能,特别是储能密度。薄膜工艺的可重复性和性能的稳定性是非常重要的。综合文献资料可知,提高储能密度的方法主要有:(1)元素掺杂或多相复合形成固溶体,可以提高极化和耐压强度,从而提高储能密度,该方法是一种比较简单易行的常见方法;(2)制备工艺的改进也可以提高薄膜的储能密度,改进的方法有退火工艺、局域场工程、取向、应力、电极等方面的调控;(3)叠层结构等异质结构界面调控是近年来兴起的一种提高薄膜储能密度的方法,已取得明显效果。本文概述了评价电介质储能特性的主要参数,简要介绍了电介质的分类,归纳了钙钛矿结构、焦绿石结构、氧化物结构等几类储能薄膜的研究现状,分析总结了提高薄膜储能密度的方法,最后对无机储能薄膜的发展趋势进行了展望,以期对无机储能薄膜的研发提供一定的参考。

Due to the energy crisis and environmental pollution,the research and development of new energy is one of the important research issues and has attracted much attention nowadays.Besides the collection of new energy sources,the storage of energy has also received increasing attention.Usually,energy storage devices are batteries,fuel cells,super-capacitors,and dielectric capacitors.Among them,the batteries and fuel cells have high energy density,but the power density is low;the conventional dielectric capacitor has high power density,but the storage density is low;the power density and energy density of the super-capacitor are between the battery and the conventional capacitor.Dielectric capacitors have the advantages of high dielectric constant,low dielectric loss,high power density,fast charge/discharge speed,large operating voltage/current,good reliability,and good temperature stability,and have been applied in the field of pulse power devices.Bia-xially oriented polypropylene(BOPP)has already been commercialized.However,dielectric capacitors have inherent shortage of low energy storage densities,which limits their applications range.As one focus of current research,it is a key issue to improve the energy storage density of capacitors.Compared with bulk materials,film capacitors have high electrical breakdown strength,and therefore have excellent energy storage densities.The focus of this paper is on the research status of inorganic energy storage films and methods to increase their energy storage density.At present,a lot of researches have been carried out on energy storage thin films,and there are many structural systems,such as perovskite structure,strontium layer structure,pyrochlore structure,single metal oxide film,etc.Among them,perovskite structure film is the earliest and most common studied.Nowadays,the energy storage density of the lead-free perovskite structure film prepared by magnetron sputtering or laser pulse deposition is as high as 100 J/cm 3 or more.However,due to the many methods of preparing the film and the complicated process,many factors can affect the performance of thin films,especially the energy storage density.The repeatability of the film process and the stability of the performance are very important.Based on the summary and analysis of literature,there are three methods to improve the energy storage density:element doping or multiphase solid solution is a relatively simple and common method,which can increase the polarization and breakdown strength,thereby increasing the energy storage density.Optimized preparation process can also improve the storage density of films.The modification methods include annealing process,local field engineering,orientation,stress,electrode and other aspects.The interface structure control of heterostructures is emerging in recent years and is a method for significantly increasing the energy storage density of a film capacitor.In this paper,first the key parameters for evaluating the energy storage performance of dielectric materials are introduced.Secondly,a brief introduction about the classification of dielectrics is presented and the research status of several types of energy storage thin films(such as perovskite structure,pyrochlore structure and oxide structure,etc.)are summarized.Then,the methods for improvement in the energy storage density of thin films are analyzed.Finally,the research trend of ceramic thin films for energy storage is proposed,which would be beneficial for the deve-lopment of inorganic energy storage films.