高储能密度聚合物基多层复合电介质的研究进展

薄膜电容器是现代电力装置与电子设备的核心电子元件,受限于薄膜介质材料的介电常数偏低,当前薄膜电容器难以获得高储能密度(指有效储能密度,即可释放电能密度),从而导致薄膜电容器体积偏大,应用成本过高。将具有高击穿场强的聚合物与高介电常数的纳米陶瓷颗粒复合,制备聚合物/陶瓷复合电介质,是实现薄膜电容器高储能密度的有效策略。对于单层结构的0-3型聚合物/陶瓷复合电介质,其介电常数与击穿场强难以同时获得有效提升,限制了储能密度的进一步提高。为了解决此矛盾,研究者们叠加组合高介电常数的复合膜与高击穿场强的复合膜,制备了2-2型多层复合电介质,能够协同调控极化强度与击穿场强来获取高储能密度。研究表明,调控多层复合电介质的介观结构与微观结构,可以实现优化电场分布、协同调控介电常数与击穿场强等目标。本文综述了近年来包括陶瓷/聚合物和全有机聚合物在内的多层聚合物基复合电介质的研究进展，重点阐述了多层结构调控策略对储能性能的提升作用，总结了聚合物基多层复合电介质的储能性能增强机制,并讨论了当前多层复合电介质面临的挑战和发展方向。     

聚合物-陶瓷纳米复合材料在电介质储能应用中的研究进展EI北大核心

电介质电容器因其极高的功率密度,近年来在工业生产、基础科研、航空航天、国防军工等领域发挥着越来越重要的作用。然而,电介质电容器较低的能量密度导致其体积普遍较大,难以满足未来器件的小型化需求。聚合物-陶瓷复合电介质材料可以将陶瓷材料的高介电常数与聚合物材料的高击穿场强联合起来,进而有望获得优异的储能特性。当前,发展具有高储能密度的聚合物-陶瓷复合电介质材料对于未来实现电介质电容器的小型化目标至关重要。本文主要从纳米填料调控、聚合物-陶瓷界面优化和多层复合结构设计三个角度出发,系统总结了目前聚合物-陶瓷复合电介质储能材料的研究进展,详细介绍了纳米填料的维度、尺寸、种类和多级结构,表面修饰改性和构筑核壳结构等界面优化方法以及三明治结构和梯度结构等多层复合结构设计对复合电介质材料的介电常数、击穿场强和储能密度的影响规律,分析探讨了复合电介质材料的微观结构与其储能特性之间的构效关系。最后,针对当前研究存在的挑战和不足,指出选用新型二维纳米填料、提升能量存储效率、采取多方式协同优化策略以及构筑相应的电容器件将是该领域未来的重点发展方向。     

聚合物-陶瓷纳米复合材料在电介质储能应用中的研究进展EI

电介质电容器因其极高的功率密度,近年来在工业生产、基础科研、航空航天、国防军工等领域发挥着越来越重要的作用。然而,电介质电容器较低的能量密度导致其体积普遍较大,难以满足未来器件的小型化需求。聚合物-陶瓷复合电介质材料可以将陶瓷材料的高介电常数与聚合物材料的高击穿场强联合起来,进而有望获得优异的储能特性。当前,发展具有高储能密度的聚合物-陶瓷复合电介质材料对于未来实现电介质电容器的小型化目标至关重要。本文主要从纳米填料调控、聚合物-陶瓷界面优化和多层复合结构设计三个角度出发,系统总结了目前聚合物-陶瓷复合电介质储能材料的研究进展,详细介绍了纳米填料的维度、尺寸、种类和多级结构,表面修饰改性和构筑核壳结构等界面优化方法以及三明治结构和梯度结构等多层复合结构设计对复合电介质材料的介电常数、击穿场强和储能密度的影响规律,分析探讨了复合电介质材料的微观结构与其储能特性之间的构效关系。最后,针对当前研究存在的挑战和不足,指出选用新型二维纳米填料、提升能量存储效率、采取多方式协同优化策略以及构筑相应的电容器件将是该领域未来的重点发展方向。     

核-壳结构纳米填料/聚偏二氟乙烯复合电介质的制备及储能性能

在薄膜电容器领域,开发高储能密度(U)和高放电能量效率(η)的聚合物复合电介质仍然是一大挑战。文中将银纳米粒子(AgNP)负载到钛酸钡(BT)纳米颗粒上,再将其表面改性制得被二氧化硅(SiO_2)壳层包覆的负载AgNP的BT纳米填料(SiO_2@Ag@BT)。AgNP赋予材料较大的电位移,而绝缘的SiO_2壳层充当缓冲层限制了漏电流,防止了材料的电击穿及空间电荷的渗透。当SiO_2@Ag@BT质量分数为3%时,聚偏二氟乙烯(PVDF)纳米复合电介质的介电常数为10.0,介电损耗(tanδ)低至0.024,击穿场强为329 MV/m。在200 MV/m的电场下,与BT/PVDF相比,SiO_2@Ag@BT/PVDF纳米复合电介质的储能密度提高了13.7%,达到2.72 J/cm~3,且放电能量效率达到78.0%。经SiO_2改性的含AgNP核-壳结构填料在低添加量下即可实现聚合物复合电介质储能密度的提高并保持高放电能量效率,这为设计新型聚合物电介质材料提供了一种简单而有效的思路。     

高储能密度介电材料的研究进展

介绍了电介质材料储能密度的概念和测量方法,分别对陶瓷材料、聚合物材料和陶瓷-聚合物复合介电材料的研究进展进行了概述.在此基础上指出,在复相介电材料制备方法、组分优选、表面改性和加工工艺等方面进行深入研究是进一步提高电介质材料储能密度的有效途径.     

介电陶瓷／聚合物复合材料

介电陶瓷/聚合物复合材料是介质材料的新领域,它的综合性能远优于各单独组分。本文在回顾其开发概况的基础上评述了BaTiO_3/PVDF介电复合材料的研究进展。据报道,70(wt)%BaTiO_3的BaTiO_3/PVDF复合材料有较高的介电常数和热释电系数等。对材料的XRD行为、在不同温度和不同频率的介电性变化亦有详细研究。表明介电陶瓷/聚合物复合材料是值得研究的、介电陶瓷和介电聚合物的理想替代材料。     

分子量对α相聚偏氟乙烯介电性能与储能特性的影响

制备了4种不同分子量的α相聚偏氟乙烯(PVDF)膜,研究了PVDF分子量对其介电性能与储能特性的影响。研究结果表明,低分子量PVDF膜具有更窄的电滞回线,其充放电效率达到了73.05%,是高分子量薄膜的2.27倍。进一步的研究发现,在1 000kV/cm电场下,低分子量PVDF膜的漏导电流为0.07175μA,远低于高分子量PVDF膜,并体现出较高的电阻率(22.7TΩ·m),更适合作为储能电容器的电介质材料。     

聚偏氟乙烯基复合材料的制备及介电性能

为有效改善聚合物基复合材料的介电性能,兼顾高介电常数和低填料量同时并存,采用以聚偏氟乙烯(PVDF)为基体树脂,钛酸钡(BT)和石墨烯(GNP)分别为介电填料和导电填料,在BT-GNP/PVDF复合体系内部构建微电容器结构。采用溶液法和热压法制备GNP/PVDF薄膜和BT-GNP/PVDF复合薄膜。结果表明,BT和GNP填料在BT-GNP/PVDF复合薄膜中能够均匀分散,在薄膜内能形成明显的微电容器结构。陶瓷填料BT的引入,使微电容器结构更有利于提高BT-GNP/PVDF复合薄膜的介电常数。BT含量大于50wt%的BT-GNP/PVDF复合薄膜介电常数均不低于GNP/PVDF薄膜。BT含量为50wt%的BT-GNP/PVDF复合薄膜的介电常数高于BT含量分别为35wt%、60wt%和70wt%的BT-GNP/PVDF复合薄膜,最大值约为43,相当于GNP含量为0.8wt%的GNP/PVDF薄膜的1.5倍;BT含量为50wt%的BT-GNP/PVDF复合薄膜损耗角正切均小于其他体系薄膜,最大不超过0.09,最小约为0.02。BT-GNP/PVDF复合薄膜的电导率变化趋势基本一致,没有明显差异。      

柔性PDMS基介电复合材料的电场及击穿损伤形貌演变规律研究

与其它储能设备相比,由介电复合材料制得的介质电容器在快速充放电能力与高功率密度方面极具优势,如何提高介电复合材料能量密度与优化其击穿性能已成为当前研究热点之一。为进一步调控并兼顾介电常数与击穿性能,本工作基于DBM(DielectricBreakdownModel,介电击穿模型),采用有限元数值模拟,研究了无机填料的分布对柔性聚二甲硅氧烷(PDMS)基介电复合材料体系的电场与发生介电击穿时击穿损伤形貌演变的具体影响。研究结果表明:填料与基体边界处存在较大的介电差异,可以使用较大介电常数的聚合物基体或较小介电常数的无机填料来减小其界面处的高电场区域,继而提高复合材料的耐击穿能力；同时发现当无机填料分散更均匀时,其树状损伤通道更容易产生分支,此种情况将使介电击穿的树状损伤通道的损伤位点增多,延缓其损伤速度,继而提高复合材料的耐击穿性能。该研究结果将为开发高储能密度且具有优异击穿性能的有机-无机复合电介质材料提供坚实的理论依据。     

提高PVDF基有机-无机柔性复合膜储能密度的研究新进展

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.     

Recent progress in dielectric nanocomposites

The rapid development of modern capacitor devices has raised an urgent need of high performance dielectric materials with superior electrical and mechanical properties with low fabrication costs. By now, individual ceramic or polymer dielectrics cannot meet these criteria. Recently, dielectric nanocomposites have shown very promising dielectric and mechanical properties, which combines both advantages of ceramic and polymers. In this review, the recent progress in dielectric nanocomposites has been systematically addressed. The key parameters which determine the performance of nanocomposites, such as dielectric constants, dielectric loss and breakdown strength have been discussed. The fabrication methods of ceramic nanopowders have been reviewed, including sol–gel, hydrothermal and molten salt method are some common techniques to synthesise nanoparticles. For fabrication of electronic device, printing techniques are utilised. Organic light-emitting diode and sensors from nanocomposite thin film capacitors have also been discussed. The review provides a guideline for designing flexible, printable capacitors from nanocomposites.     

Negatively Charged Nanosheets Significantly Enhance the Energy-Storage Capability of Polymer-Based Nanocomposites

Polymer-based dielectric materials play a key role in advanced electronic devices and electric power systems. Although extensive research has been devoted to improve their energy-storage performances, it is a great challenge to increase the breakdown strength of polymer nanocomposites in terms of achieving high energy density and good reliability under high voltages. Here, a general strategy is proposed to significantly improve their breakdown strength and energy storage by adding negatively charged Ca₂Nb₃O₁₀ nanosheets. A dramatically enhanced breakdown strength (792 MV m⁻¹) and the highest energy density (36.2 J cm⁻³) among all flexible polymer-based dielectrics are observed in poly(vinylidene fluoride)-based nanocomposite capacitors. The strategy generalizability is verified by the similar substantial enhancements of breakdown strength and energy density in polystyrene-based nanocomposites. Phase-field simulations demonstrate that the further enhanced breakdown strength is ascribed to the local electric field, produced by the negatively charged Ca₂Nb₃O₁₀ nanosheets sandwiched with the positively charged polyethyleneimine, which suppresses the secondary impact-ionized electrons and blocks the breakdown path in nanocomposites. The results demonstrate a new horizon of high-energy-density flexible capacitors.     

Low-content core–shell-structured TiO2 nanobelts@SiO2 doped with poly(vinylidene fluoride) composites to achieve high-energy storage density

Polymer film capacitors have a high power density and great application potential in high-power electronic devices; however, high-energy storage density of polymer composites is usually obtained via doping high-content ceramic filler. An efficient approach to solve this issue is to dope polymers with an ultralow-content ceramic filler to improve their energy storage density. In this work, one-dimensional (1D) TiO₂ nanobelts@SiO₂ (TO nb@SO) are prepared via the hydrothermal reaction, muffle calcination, and hydrolysis. Extremely low-content TO nb@SO/poly(vinylidene fluoride) (TO nb@SO/PVDF) composites are prepared. The microstructure, crystalline structure, dielectric properties, electric breakdown strength, and discharge energy density are systematically investigated. The results show that the nanobelts have a width of 250 nm, a length of 1–2 μm, and a uniform shell layer at the edge with a thickness of ～25 nm. The relative dielectric constant of the composites is significantly enhanced; it reaches 11 for PVDF at 100 Hz, and 12.03 for 0.5 wt% TO nb@SO/PVDF. The theoretical dielectric constant is calculated based on a mathematical model and compared with the measured value. 1D materials with a large aspect ratio are beneficial in the improvement of the dielectric properties. The Weibull breakdown field strength is 381.3 MV/m for 0.5 wt% TO nb@SO/PVDF. A discharge energy density of 8.86 J/cm³ is obtained at 390 MV/m, while a high charge/discharge efficiency of 66.28% is achieved. To conclude, this work provides a valuable method for increasing the energy storage density and charge/discharge efficiency of dielectric capacitors.

     

Superior Energy Storage Capability and Stability in Lead-Free Relaxors for Dielectric Capacitors Utilizing Nanoscale Polarization Heterogeneous Regions

The development of high-performance lead-free dielectric ceramic capacitors is essential in the field of advanced electronics and electrical power systems. A huge challenge, however, is how to simultaneously realize large recoverable energy density (W_rec), ultrahigh efficiency (η), and satisfactory temperature stability to effectuate next-generation high/pulsed power capacitors applications. Here, a strategy of utilizing nanoscale polarization heterogeneous regions is demonstrated for high-performance dielectric capacitors, showing comprehensive properties of large W_rec (≈6.39 J cm⁻³) and ultrahigh η (≈94.4%) at 700 kV cm⁻¹ accompanied by excellent thermal endurance (20–160 °C), frequency stability (5–200 Hz), cycling reliability (1–105 cycles) at 500 kV cm⁻¹, and superior charging-discharging performance (discharge rate t_0.9 ≈ 28.4 ns, power density PD ≈161.3 MW cm⁻³). The observations reveal that constructing the polarization heterogeneous regions in a linear dielectric to form novel relaxor ferroelectrics produces favorable microstructural characters, including extremely small polar nanoregions with high dynamics and multiphase coexistence and stable local structure symmetry, which enables large breakdown strength and ultralow polarization switching hysteresis, hence synergistically contributing to high-efficient capacitive energy storage. This study thus opens up a novel strategy to design lead-free dielectrics with comprehensive high-efficient energy storage performance for advanced pulsed power capacitors applications.     

Alkali-free glass as a high energy density dielectric material

One of the greatest challenges in the development of new high energy density materials is to increase dielectric permittivity while maintaining high breakdown strength. The dielectric breakdown behavior of an alkali-free barium boroaluminosilicate glass is shown to have remarkably high DC dielectric breakdown strength (12 MV/cm) and reasonably high permittivity (~ 6), equating to energy densities in excess of 35 J/cm³. This behavior is attributed to highly polarizable Ba ions enhancing the real part of complex permittivity, the low loss due to the alkali-free composition, and the substantially defect-free quality of the glass and its surfaces. To our knowledge, this is the highest breakdown strength reported for a bulk glass, and rivals the breakdown strength more typically observed in pristine thin films of SiO₂. These findings indicate that alkali-free multicomponent glasses may be strong candidates for next-generation high energy density storage capacitors for portable or pulsed power applications.     

Nonlinear dielectric thin films for high-power electric storage with energy density comparable with electrochemical supercapacitors

Although batteries possess high energy storage density, their output power is limited by the slow movement of charge carriers, and thus capacitors are often required to deliver high power output. Dielectric capacitors have high power density with fast discharge rate, but their energy density is typically much lower than electrochemical supercapacitors. Increasing the energy density of dielectric materials is highly desired to extend their applications in many emerging power system applications. In this paper, we review the mechanisms and major characteristics of electric energy storage with electrochemical supercapacitors and dielectric capacitors. Three types of in-house-produced ferroic nonlinear dielectric thin film materials with high energy density are described, including (Pb(0.97)La(0.02))(Zr(0.90)Sn(0.05)Ti(0.05))O(3) (PLZST) antiferroelectric ceramic thin films, Pb(Zn(1/3)Nb(2/3))O(3-)Pb(Mg(1/3)Nb(2/3))O(3-)PbTiO(3) (PZN-PMN-PT) relaxor ferroelectric ceramic thin films, and poly(vinylidene fluoride) (PVDF)-based polymer blend thin films. The results showed that these thin film materials are promising for electric storage with outstandingly high power density and fairly high energy density, comparable with electrochemical supercapacitors.     

Mechanical vs. electrical failure mechanisms in high voltage,high energy density multilayer ceramic capacitors

Causes of breakdown, both mechanical and electrical, in high voltage, high energy density, BaTiO₃ capacitors were studied. The flexural strength of the capacitors was 96 MPa. Failure was due to surface defects or pores close to the surfaces of the samples. The dielectric breakdown strength of the samples was 181 kV/cm. The causes of breakdown were either electrode end effects or pores between the dielectric and electrode layers. Weibull statistics were used to determine if there was a correlation between mechanical failure and dielectric breakdown. A strong correlation between the two types of failure was not found in the study, in contrast to earlier studies of single dielectric layer capacitor materials.     

Carboxylated Poly (p-Phenylene Terephthalamide) Reinforced Polyetherimide for High-Temperature Dielectric Energy Storage

Dielectric energy storage polymers play a vital role in advanced electronics and electrical systems, due to their high breakdown strength, excellent reliability, and easy fabrication. However, the low dielectric constant and poor thermal resistance of dielectric polymers limit their energy storage density and working temperatures, making them less versatile for broader applications. In this work, a novel carboxylated poly (p-phenylene terephthalamide) (c-PPTA) is synthesized and employed to simultaneously enhance the dielectric constant and thermal resistance of polyetherimide (PEI), leading to a discharged energy density of 6.4 J cm⁻³ at 150 °C. The introduction of c-PPTA molecules effectively reduces the Π Π stacking effect and increases the average chain spacing between polymer molecules, which is conducive to improving the dielectric constant. Additionally, c-PPTA molecules with stronger positive charges and high dipole moments can capture electrons, resulting in reduced conduction loss and enhanced breakdown strength at high temperatures. The coiled capacitor fabricated with the PEI/c-PPTA film exhibits superior capacitance performances and higher working temperatures compared to commercial metalized PP capacitors, demonstrating great potential for dielectric polymers in high-temperature electronic and electrical energy storage systems.     

陶瓷电介质储能材料研究进展EI北大核心CSCD

为了更好地推动高储能密度和高效率无铅陶瓷介质电容器的研究与发展,本文综合介绍了陶瓷电介质储能材料的储能原理及分类,比较分析了近年来线性电介质、铁电体、弛豫铁电体和反铁电体储能材料的研究进展,主要研究体系和性能优劣。总结了陶瓷储能材料目前面临的挑战以及改善其储能性能的策略,展望了其未来在5G通信、新能源汽车、消费电子等工业应用中的发展及小型化、高耐电压性、高可靠性的技术发展趋势。     

Investigation of charge trapping and breakdown characteristics of sputtered-Y2O3 on n-GaAs substrates

Metal-oxide-semiconductor (MOS) capacitors fabricated by depositing yttrium oxide (Y₂O₃) using radio frequency sputtering system on top of n-GaAs substrates have been investigated. To study the interface properties, charge trapping behavior and breakdown characteristics of Y₂O₃ gate dielectric, the MOS capacitors were subjected to constant current stress, high pulse voltage stress and high constant voltage stress. The average value of the cross section of generated traps during electrical stress has been determined from our experimental data. Further the trap charge density, its distribution and location have been investigated by measurements on application and subsequent withdrawal of high pulse voltage stress. Additionally, stress induced leakage current density and time dependent dielectric breakdown characteristics have been obtained and time-to-breakdown exceeding 840 s is observed for Y₂O₃ gate dielectrics directly deposited on n-GaAs. Our experimental results have been analyzed with simple analytical formulae available in the literature.