Mechanics of flexible and stretchable piezoelectrics for energy harvesting

As rapid development in wearable/implantable electronic devices benefit human life in daily health monitoring and disease treatment medically, all kinds of flexible and/or stretchable electronic devices are booming, together with which is the demanding of energy supply with similar mechanical property. Due to its ability in converting mechanical energy lying in human body into electric energy, energy harvesters based on piezoelectric materials are promising for applications in wearable/implantable device's energy supply in a renewable, clean and life-long way. Here the mechanics of traditional piezoelectrics in energy harvesting is reviewed, including why piezoelectricity is the choice for minor energy harvesting to power the implantable/wearable electronics and how. Different kinds of up to date flexible piezoelectric devices for energy harvesting are introduced, such as nanogenerators based on Zn O and thin and conformal energy harvester based on PZT. A detailed theoretical model of the flexible thin film energy harvester based on PZT nanoribbons is summarized, together with the in vivo demonstration of energy harvesting by integrating it with swine heart. Then the initial researches on stretchable energy harvesters based on piezoelectric material in wavy or serpentine configuration are introduced as well.     

新型联苯胺基窄带隙共轭聚合物的光学及电化学性能研究

随着化石燃料的日益枯竭,人类社会对能源的需求在不断增长。为了平衡能量应用需求并提升能量使用效率,开发高效能量转换材料与电化学储能材料成为当前研究的重要课题。导电聚合物基电极材料面临着相应储能器件能量密度、功率密度、循环性能不高的挑战,需进行结构改性提高电导率、改善界面性质。鉴于共轭高分子的电子结构、光学及电化学性质由共轭链骨架结构决定,对导电共轭聚合物进行结构修饰以提升其电荷传输性能和载流子迁移率,进而设计合成新型高迁移率导电聚合物基共轭聚合物是提高相应器件特性的关键所在。已有研究大多借助复杂的结构设计来实现提升迁移率,设计合成了结构简单,有助提升电荷迁移的新型窄带隙聚联苯胺基共轭聚合物聚物。通过光谱学及电化学方法对材料结构与性能进行了表征分析。采用核磁共振氢谱、红外光谱,X射线粉末衍射对单体及聚合物进行了结构表征,通过紫外光谱、紫外可见漫反射、循环伏安、计时电位、交流阻抗对其进行了光学及电化学性能测试。结果表明,成功制得具有预期结构的共轭聚合物,所得聚合物结晶性较佳,光学带隙E_g^opt为1.85eV,HOMO及LUMO能级分别为-5.44和...     

后锂电池时代新型电池的开发与展望

石油、天然气等化石能源的枯竭及人类生存环境的进一步恶化,迫使人们寻求和开发清洁可再生能源和高效绿色的储能装置.传统的锂离子电池等已难以满足将来电动汽车等大规模使用的电器对于大容量蓄电装置的要求.文章综述了日本产业技术综合研究所周豪慎教授课题组近年来的研究成果,介绍了组合型电解液的概念及原理,并重点讨论了锂-铜电池和锂-空气电池等基于组合型电解液的后锂离子电池的设计方法和电化学性能.文章指出,组合电解液技术将是开发高能量电化学储能装置的重要思路和有效方法.     

Surface structure evolution of cathode materials for Li-ion batteries

Lithium ion batteries are important electrochemical energy storage devices for consumer electronics and the most promising candidates for electrical/hybrid vehicles. The surface chemistry influences the performance of the batteries significantly. In this short review, the evolution of the surface structure of the cathode materials at different states of the pristine, storage and electrochemical reactions are summarized. The main methods for the surface modification are also introduced.     

可延展柔性无机微纳电子器件原理与研究进展

为适应下一代电子产品便携性、形状可变性、人体适用性等方面的进一步需求,近年来基于无机电子材料的可延展柔性电子技术成为全球电子产业界与学术界关注的新焦点.与有机柔性电子学器件不同,可延展柔性无机电子器件指的是建立在柔性基底上的无机电子组件.这种具有柔性的集成电路利用力学设计提供大变形,在保持无机脆性电子器件高性能和高可靠性的同时,具备形状可弯曲、可伸缩等柔性性能.本文综述了近年来无机柔性电子器件的进展,包括力学设计原理、基于界面黏附的转印集成方法以及柔性大变形下的失效机理等,并展望了未来的应用和发展.     

Flexible Graphene‐, Graphene‐Oxide‐, and Carbon‐Nanotube‐Based Supercapacitors and Batteries

Flexible energy‐storage devices increasingly attract attention owing to their advantages of providing lightweight, portable, wearable, or implantable capabilities. Many efforts are made to explore the structures and fabrication processes of flexible energy‐storage devices for commercialization. Here, the most recent advances in flexible energy‐storage devices based on graphene, graphene oxide (GO), and carbon nanotubes (CNTs), are described, including flexible supercapacitors and batteries. First, properties, synthesis methods, and possible applications of those carbon‐based materials are described. Then, the development of carbon‐nanotube‐based flexible supercapacitors, graphene/graphene‐oxide‐based flexible supercapacitors, and graphene‐ and carbon‐nanotube‐based flexible battery electrodes are discussed. Finally, the future trends and perspectives in the development of flexible energy‐storage devices are highlighted.     

Nanomaterials for electrochemical energy storage

The development of nanotechnology in the past two decades has generated great capability of controlling materials at the nanometer scale and has enabled exciting opportunities to design materials with desirable electronic, ionic, photonic, and mechanical properties. This development has also contributed to tile advance in energy storage, which is a critical technology in this century. In this article, we will review how the rational design of nanostructured materials has addressed the challenges of batteries and electrochemical capacitors and led to high-performance electrochemical energy storage devices. Four specific material systems will be discussed： i） nanostructured alloy anodes for Li-batteries, ii） nanostructured sulfur cathodes for Li-batteries, iii） nanoporous open- framework battery electrodes, and iv） nanostructured electrodes for electrochemical capacitors.     

离子导体载流子输运与存储的界面调控

离子导电材料既可以是载流子主要为离子的纯离子导体,也可以是载流子同时包括离子和电子的混合离子导体.这两类材料是电化学能量转换与储存、化学传感以及选择性透过膜等器件的关键材料.在这些器件中,均存在电极与电解质、颗粒与颗粒、不同晶粒之间的二维或三维的异质结界面.因此,离子与电子在异质结中的输运性质对器件性能有重要的影响.但...     

Pulse applications of electrochemical cells - materials aspects

There is a rapidly increasing need for energy sources that are optimized to provide electrical energy at high power for short times. The terms “ultracapacitor” and “supercapacitor” are often used to describe some types of such devices. Applications include the requirement for very short pulses for digital electronic devices, the somewhat longer power pulse demands of heart defibrillators and other implantable medical devices, and the much larger transient power needs in connection with electric vehicle traction. The several mechanisms that can be used to store and provide pulse energy in electrochemical systems are reviewed. Their fundamental characteristics, as well as their applicability to the different types of pulse output requirements, are discussed. The use of spreadsheet techniques to model transient transport behavior in solids under various conditions, as well as the use of Laplace transform methods to convert information about the physical mechanisms and parameters of individual components into the dynamic response of an electrochemical system are demonstrated. Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11 – 18 Sept. 1994     

基于中性水凝胶/取向碳纳米管阵列高电压柔性固态超级电容器

随着科技发展和时代进步,发展质轻便携、安全环保的高性能储能器件变得日趋重要,对柔性固态超级电容器的研究也应运而生.柔性电极材料及电解质的选用是设计柔性固态超级电容器的关键因素,近年来一直是研究的热点.考虑到环境污染及实际需求问题,本文采用中性凝胶电解质对具有高比表面积、良好导电性及取向性的碳纳米管阵列进行包埋处理,所形成的柔性复合薄膜作为电极材料,设计制备三明治结构的柔性超级电容器件.通过改变凝胶电解质中所加入的无机盐电解质种类,调控器件的电化学储能性质.最终在聚乙烯醇PVA-NaCl作为凝胶电解质时,整个器件比容量最高达104.5 mF·cm~(–3),远高于有机离子凝胶与碳管阵列形成的复合器件以及无规分布的碳纳米管与水凝胶形成的复合器件,同时获得了0.034 mW·h·cm~(–3)的最大能量密度,并且具有良好的倍率性能、循环稳定性及抑制自放电的效果,并在高电压1.6 V下依然保持良好的化学稳定性.这种中性凝胶/碳管阵列复合超级电容器件不仅满足了绿色安全、柔性便携的要求,未来在医学可植入器件等领域也具有很好的应用前景.     

二维原子层谷电子学材料和器件

人为操控电子的内禀自由度是现代电子器件的核心和关键.如今电子的电荷和自旋自由度已经被广泛地应用于逻辑计算与信息存储.以二维过渡金属硫属化合物为代表的二维原子层材料由于其具有独特的谷自由度和优异的物理性质,成为了新型谷电子学器件研究的优选材料体系.本文介绍了能谷的基本概念、谷材料的基本物理性质、谷效应的调控和谷电子学器件...     

Nitrogen-Doped Porous Graphene Coated with Fe3O4 Nanoparticles for Advanced Supercapacitor Electrode Material with Improved Electrochemical Performance

With the increasing demand for high-performance energy storage devices, single materials of ordinary structures for electrode materials have become increasingly difficult to meet people's needs. Therefore, composites of inimitable structures have drawn considerable attention. In this work, nitrogen-doped porous graphene coated with Fe₃O₄ nanoparticles (NPGF) is prepared by an efficient and green pyrolysis method. Structural and compositional characterizations confirm that the NPGF nanohybrids possess uniformly distributed pore structure and quite pure composition which is free of any impurities. In addition, electrochemical characterization verifies the excellent electrochemical performance, such as high-specific capacitance (713 F g⁻¹ at 1 A g⁻¹), prominent rate capability (capacitance retention of 77.3% and 67.9% when the current density is increased respectively from 1 to 10 and 20 A g⁻¹), and outstanding cycling stability (capacitance retention of 94.3% after 3000 cycles). Such promising results suggest that the NPGF nanohybrids have great application prospects in future high-performance supercapacitors.     

Potassium‐Sodium‐Niobate‐Based Thin Films: Lead Free for Micro‐Piezoelectrics

Extensive research and great progress of (K,Na)NbO₃ (KNN)‐based lead‐free piezoelectric films have been driven by the current legislation and the requirement for sustainable development of society and environment in the applications of microelectromechanical systems. A comprehensive discussion of the recent achievement in KNN‐based films is presented herein. First, the available synthetic techniques, chemical modification, the ferroelectric and piezoelectric properties of KNN‐based films are reviewed, followed by an introduction of the crystal structures and electrical properties of KNN‐based epitaxial films in comparison with the bulk ceramics. Finally, the applications of KNN‐based films for the sensors, the energy harvesters, and energy storage devices are addressed, and current challenges and prospects for future work are discussed.     

纳米材料和技术在可再生能源方面的应用

纳米光子学,产生于纳米技术和光子学的交界处,处理光和物质在纳米尺度的相互作用,可以被用来产生新的效果和发展纳米尺度的器件。世界在迎接未来能源需求方面正面临巨大挑战。纳米光子学为太阳能转换提供了新的进展。在太阳能转换领域,我们正加速开展新的基于纳米光子学让太阳光子在整个光谱范围从紫外到红外有效率地被吸收和转换,并且有效率地转换为电能方面的研究（比如直接或者电化学的转换）。纳米技术也为热电和能量储存方面的研究提供了新的途径,我们正追求把它们和太阳能获取整合在一起从而提供广泛的能源解决方案。     

Fabrication,properties, and applications of flexible magnetic films

Flexible magnetic devices, i.e., magnetic devices fabricated on flexible substrates, are very attractive in applications such as detection of magnetic field in an arbitrary surface, non-contact actuators, and microwave devices, due to their stretchable, biocompatible, light-weight, portable, and low cost properties. Flexible magnetic films are essential for the realization of various functionalities of flexible magnetic devices. To give a comprehensive understanding for flexible magnetic films and related devices, recent advances in the study of flexible magnetic films are reviewed, including fabrication methods, magnetic and transport properties of flexible magnetic films, and their applications in magnetic sensors, actuators, and microwave devices. Our aim is to foster a comprehensive understanding of these films and devices. Three typical methods have been introduced to prepare the flexible magnetic films, by deposition of magnetic films on flexible substrates, by a transfer and bonding approach or by including and then removing sacrificial layers. Stretching or bending the magnetic films is a good way to apply mechanical strain to them, so that magnetic anisotropy, exchange bias, coercivity, and magnetoresistance can be effectively manipulated. Finally, a series of examples is shown to demonstrate the great potential of flexible magnetic films for future applications.     

Curvature Effect on Compressible Turbulent Flow over a Wavy Wall

A fully developed compressible turbulent flow in a channel with a lower wavy wall and a upper plane wall is studied using large eddy simulation. We mainly attempt to deal with the curvature effect on compressible turbulent flow over the wavy wall. Some typical quantities including the mean turbulence statistics, dilatation and baroclinic terms in the enstrophy equation, turbulent kinetic energy budgets and the near-wall turbulent structures are analysed. The results obtained in this study provide physical insight into the understanding of the effects of curvature and compressibility on wall-bounded compressible turbulent flow.     

Atomically thin two-dimensional materials for functional electrodes of electrochemical devices

The development of atomically thin semiconductor nanocrystals for electrodes of various electrochemical devices is probably one of the fastest growing fields in the modern condensed conductive matter research. Two-dimensional (2D) nanocrystals have been established as a large class of nanostructures with unusual properties. In this study, specific characteristic, features and technologies of making the 2D nanocrystals including graphene for composite nanostructured electrodes of electrochemical devices are reviewed.     

Producing terahertz coherent synchrotron radiation at the Hefei Light Source

This paper theoretically proves that an electron storage ring can generate coherent radiation in the THz region using a quick kicker magnet and an AC sextupole magnet. When the vertical chromaticity is modulated by the AC sextupole magnet, the vertical beam collective motion excited by the kicker produces a wavy spatial structure after a number of longitudinal oscillation periods. The radiation spectral distribution was calculated from the wavy bunch parameters at the Hefei Light Source(HLS). When the electron energy is reduced to 400 Me V, extremely strong coherent synchrotron radiation(CSR) at 0.115 THz should be produced.     

Hierarchical nanowires for high-performance electrochemical energy storage

Nanowires are promising candidates for energy storage devices such as lithium-ion batteries, su- per（：apa.citors and lithium-air batteries. However, simple-structured nanowires have some limitations hence the strategies to make improvements need to be explored and investigated. Hierarchical nanowires with enhanced periormanee have been considered as an ideal candidate for energy storage due to the novel structures and/or synergistic properties. This review describes some of the recent progresses in the hierarchical nanowire merits, classification, synthesis and performance in energy storage applieat, ions. Herein we discuss the hierarchical nanowires based on their structural design from three major categories, including exterior design, interior design and aligned nanowire assembly. This review also briefly outlines the prospects of hierarchical nanowires in morphology control, property enhancement and application versatility.     

Direct numerical simulation of a fully developed compressible wall turbulence over a wavy wall

Compressible turbulent channel flow over a wavy surface is investigated by direct numerical simulations using high-resolution finite difference schemes. The Reynolds number considered in the present paper is 3380 based on the bulk velocity, the channel half-width and the kinetic viscosity at the wall. Four test cases are simulated and analysed at Ma_m = 0.33, 0.8, 1.2, 1.5 based on the bulk velocity and the speed of sound at the wall. We mainly focus on the curvature and the Mach number effects on the compressible turbulent flows. Numerical results show that although the wavy wall has effects on the mean and fluctuation quantities, log law still exists in the distribution of the wave-averaged streamwise velocity if the roughness effects are taken into consideration in the scaling of it. Near-wall streaks are broken by the wavy surface and near-wall quasi-streamwise vortices mostly begin at the upslope of the wave and pass over the crest of it. The wavy wall makes the turbulence more active and the flow easier to be blended. From the viewpoint of turbulent kinetic budgets, curvature effects strengthen both the diffusion terms and the dissipation terms. At the same time, they change the properties of the compressibility-related terms and promote more inner energy transferring into turbulent kinetic energy. As the Mach number increases, the reattachment of the mean flow is delayed, which indicates the mean separation bubble becomes larger. Concerning the near-wall coherent structures, the vortices are more sparsely distributed with the increasing of the Mach number. For the supersonic cases, shock waves appear. Though they have little effects on the mean turbulent quantities, they change the structures of the flow fields and induce local separations at the upper wall of the channel.