875 resultados para LITHIUM-ION BATTERY


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Manipulation of matter at the nanoscale is a way forward to move beyond our current choices in electrochemical energy storage and conversion technologies with promise of higher efficiency, environmental benignity, and cost-effectiveness. Electrochemical processes being basically surface phenomena, tailored multifunctional nanoarchitecturing can lead to improvements in terms of electronic and ionic conductivities, diffusion and mass transport, and electron transfer and electrocatalysis. The nanoscale is also a domain in which queer properties surface: those associated with conversion electrodes, ceramic particles enhancing the conductivity of polymer electrolytes, and transition metal oxide powders catalyzing fuel cell reactions, to cite a few. Although this review attempts to present a bird's eye view of the vast literature that has accumulated in this rather infant field, it also lists a few representative studies that establish the beneficial effects of going `nano'. Investigations on nanostructuring and use of nanoparticles and nanoarchitectures related to lithium-ion batteries (active materials and electrolytes), supercapacitors (electrical double-layer capacitors, supercapacitors based on pseudo-capacitance, and hybrid supercapacitors), and fuel cells (electrocatalysts, membranes and hydrogen storage materials) are highlighted. (C) 2012 John Wiley & Sons, Ltd.

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The high computational cost of correlated wavefunction theory (WFT) calculations has motivated the development of numerous methods to partition the description of large chemical systems into smaller subsystem calculations. For example, WFT-in-DFT embedding methods facilitate the partitioning of a system into two subsystems: a subsystem A that is treated using an accurate WFT method, and a subsystem B that is treated using a more efficient Kohn-Sham density functional theory (KS-DFT) method. Representation of the interactions between subsystems is non-trivial, and often requires the use of approximate kinetic energy functionals or computationally challenging optimized effective potential calculations; however, it has recently been shown that these challenges can be eliminated through the use of a projection operator. This dissertation describes the development and application of embedding methods that enable accurate and efficient calculation of the properties of large chemical systems.

Chapter 1 introduces a method for efficiently performing projection-based WFT-in-DFT embedding calculations on large systems. This is accomplished by using a truncated basis set representation of the subsystem A wavefunction. We show that naive truncation of the basis set associated with subsystem A can lead to large numerical artifacts, and present an approach for systematically controlling these artifacts.

Chapter 2 describes the application of the projection-based embedding method to investigate the oxidative stability of lithium-ion batteries. We study the oxidation potentials of mixtures of ethylene carbonate (EC) and dimethyl carbonate (DMC) by using the projection-based embedding method to calculate the vertical ionization energy (IE) of individual molecules at the CCSD(T) level of theory, while explicitly accounting for the solvent using DFT. Interestingly, we reveal that large contributions to the solvation properties of DMC originate from quadrupolar interactions, resulting in a much larger solvent reorganization energy than that predicted using simple dielectric continuum models. Demonstration that the solvation properties of EC and DMC are governed by fundamentally different intermolecular interactions provides insight into key aspects of lithium-ion batteries, with relevance to electrolyte decomposition processes, solid-electrolyte interphase formation, and the local solvation environment of lithium cations.

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制备了化学稳定的Er^3+/Yb^3+共掺的磷酸盐玻璃,并在其中制作了用于光放大器和激光器的平面光波导.这种磷酸盐玻璃的失重速率为4.7×10^-5g·cm^-2·hr^-1,小于Kigre公司商业化的磷酸盐玻璃QX/Er的失重速率.采用Ag^+-Li^+交换技术制作了平面光波导并用m-线光谱在632.8nm测量了平面光波导的有效折射率.根据反WKB法得到折射率形貌,计算了离子交换参数如:离子交换深度、表面折射率,折射率改变和扩散系数等.

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The ocean represents a huge energy reservoir since waves can be exploited to generate clean and renewable electricity; however, a hybrid energy storage system is needed to smooth the fluctuation. In this paper a hybrid energy storage system using a superconducting magnetic energy system (SMES) and Li-ion battery is proposed. The SMES is designed using Yttrium Barium Copper Oxide (YBCO) tapes, which store 60 kJ electrical energy. The magnet component of the SMES is designed using global optimization algorithm. Mechanical stress, coupled with electromagnetic field, is calculated using COMSOL and Matlab. A cooling system is presented and a suitable refrigerator is chosen to maintain a cold working temperature taking into account four heat sources. Then a microgrid system of direct drive linear wave energy converters is designed. The interface circuit connecting the generator and storage system is given. The result reveals that the fluctuated power from direct drive linear wave energy converters is smoothed by the hybrid energy storage system. The maximum power of the wave energy converter is 10 kW. © 2012 IEEE.

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本论文分为两个部分研究了铿离子电池和生物燃料电池中的关键材料,主要的创新点和结论如下。采用聚合物电解质是提高铿二次电池性能的有效方法之一。聚合物电解质良好电导率、高铿离子迁移数、宽电化学窗口以及好的机械性能是其应用于铿二次电池中的关键。论文的第一部分主要讨论了聚合物、增塑剂和无机纳米粒子等对复合电解质体系的化学和物理性质的影响。我们采用溶液浇注一浸渍法制备了各种纳米复合聚合物电解质,例如开发出基于PVDFHFP或梳状聚合物基体的全固态以及聚合物和碳酸醋形成的胶体聚合物电解质体系。首次制备了具有较高离子电导率的单离子聚合物电解质。考察了两类纳米粒子填充物对体系的影响:一种是“惰性”发烟硅;另一种是“活性”蒙脱土。比较了全固态和胶体聚合物电解质体系电化学性质的不同之处。采用电化学交流阻抗,示差扫描量热法,X衍射,拉曼光谱,红外光谱,扫描电镜,循环伏安等方法详细研究了聚合物电解质中各组分对体系离子电导率和机械性能的影响。研究结果表明,纳米复合物为开发具有特定电化学和机械性能的电解质提供了一种有效的途径,它对聚合物电解质的物理性质影响明显。纳米粒子的加入增强了体系的机械性能,同时也使体系对溶剂的吸附能力增加。在全固态聚合物电解质中加入增塑剂,形成胶体态聚合物电解质,体系的电导率大大增加。所制备的胶体复合物电解质的室温电导率可以达到10-3s cm-1的数量级,机械强度好,阳离子迁移数高。指出选择合适的添加剂及复合方法,控制界面的结构和形态,形成尽可能多的高导电的界面,是获得电导率高和机械性能良好的聚合物电解质的有效途径。并讨论了聚合物电解质在铿离子电池中的应用。 近年来,针对生物燃料电池的研究得到了广泛关注,其中实现蛋白质酶分子和电极之间的直接电子传递是研究中的热点。论文的第二部分主要研究了生物燃料电池中的酶电极。通过对碳纳米管(MWNTs)进行预处理,使其表面带有功能性官能团,从而可以实现酶分子在碳纳米管表面的固定,同时还保持了其生物活性。采用吸附法将微过氧化物酶-11(MP-11)或葡萄糖氧化酶(GOx)等生物分子固定到MWNTs上制成酶修饰电极,研究MWNTs对酶和电极之间电子传递的促进作用。当酶分子(MP-11,GOX)固定到MWNTs表面后,循环伏安结果显示出一对可逆的氧化还原峰,对应酶分子的直接电子转移。研究结果表明这种方法可以扩展到固定其他生物酶分子以及实现蛋白质酶分子和电极之间的直接电化学,可以获得一系列氧化还原酶分子的电化学参数,如反应速率常数等。同时,我们还研究了酶修饰电极对其底物的电催化反应。研究结果表明,该修饰电极对底物的电化学反应表现出较好的催化活性。我们还研究了酶分子在MWNTs修饰铂微电极上的电化学行为。这些研究为研制生物燃料电池提供了一种固定酶以及制备电极材料较好的方法。

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In this present work, a polymer electrolyte based on polymer/clay nanocomposite has been developed. Montmorillonite (MMT) clay was used as the filler. due to its special size in length and thickness, and its sandwich type structure. The obtained gel polymer electrolytes have high ionic conductivity up to 2.5 mS cm(-1) with high cationic transference number (about 0.64) at room temperature. The influences of the filler on the membrane morphology. the solvent uptake, the ionic conductivity, and the cation transport number were investigated, and thus the significant contribution from the exfoliated organophilic MMT was identified.

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In an attempt to increase the interface stability of carbon used in Li-ion batteries, a thin conducting polyaniline (PANI) film was fabricated on the surface of carbon by in situ chemical polymerization. The chemical and electrochemical properties of the composite material were characterized using X-ray diffraction, Raman spectroscopy, scanning electron microscope, cyclic voltammetry, and electrochemical impedance spectroscopy. It was confirmed that the PANI film has an obvious effect on the morphology and the electrochemical performance of carbon. The results could be attributed to the electronic and electrochemical activity of the conducting PANI films.

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A series of compounds, La2/3 - xLi3xMoO4, were first prepared. Their structures are tetragonal scheelites with the cationic defects. The cell parameters a, c and values of c/a decrease with the increasing of the substitution amount (3x) of lithium ion. Cationic vacancies are getting more as Li+ concentration is lower. The diffusion of lithium ion is predominant. The concentration of charge carriers increases with increasing the substitution amount (3x) of lithium ion, meanwhile, the concentration of cationic vacancies decreases. The conductivity approaches the best when the substitution amount (3x) of lithium ion is about 0.3. The conductivity of La0.567Li0.3MoO4 is 6.5 x 10(-6) S . cm(-1) at room temperature.

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AMR在科研和军事方面的应用决定了其需要一个能够准确、实时估计出锂电池SOC的估计值。由于AMR工作中的放电具有很强的动态性,使得传统估计方法用于锂电池SOC的动态估计效果很不理想。本文描述了EKF方法在AMR锂电池SOC动态估计中的应用。模拟AMR工况进行动态放电试验。试验结果表明,该估计方法能够实时而准确地得到SOC值。

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准确估计剩余电量(state of charge,SOC)关系到自主移动机器人(AMR)的生存与安全,是AMR研究中所面临的主要挑战之一。针对广义卡尔曼滤波估计SOC的不足,本文给出基于无色卡尔曼滤波(UKF)估计AMR锂电池SOC的新方法。通过试验对UKF和EKF进行了比较。试验验证了同样条件下,UKF比EKF具有更好的滤波估计精度。

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Two complementary wireless sensor nodes for building two-tiered heterogeneous networks are presented. A larger node with a 25 mm by 25 mm size acts as the backbone of the network, and can handle complex data processing. A smaller, cheaper node with a 10 mm by 10 mm size can perform simpler sensor-interfacing tasks. The 25mm node is based on previous work that has been done in the Tyndall National Institute that created a modular wireless sensor node. In this work, a new 25mm module is developed operating in the 433/868 MHz frequency bands, with a range of 3.8 km. The 10mm node is highly miniaturised, while retaining a high level of modularity. It has been designed to support very energy efficient operation for applications with low duty cycles, with a sleep current of 3.3 μA. Both nodes use commercially available components and have low manufacturing costs to allow the construction of large networks. In addition, interface boards for communicating with nodes have been developed for both the 25mm and 10mm nodes. These interface boards provide a USB connection, and support recharging of a Li-ion battery from the USB power supply. This paper discusses the design goals, the design methods, and the resulting implementation.

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Three-dimensional vanadium pentoxide (V2O5) material architectures in the form of inverse opals (IOs) were fabricated using a simple electrodeposition process into artificial opal templates on stainless steel foil using an aqueous solution of VOSO4.χH2O with added ethanol. The direct deposition of V2O5 IOs was compared with V2O5 planar electrodeposition and confirms a similar progressive nucleation and growth mechanism. An in-depth examination of the chemical and morphological nature of the IO material was performed using X-ray crystallography, X-ray photoelectron spectroscopy, Raman scattering and scanning/transmission electron microscopy. Electrodeposition is demonstrated to be a function of the interstitial void fraction of the artificial opal and ionic diffusivity that leads to high quality, phase pure V2O5 inverse opals is not adversely affected by diffusion pathway tortuosity. Methods to alleviate electrodeposited overlayer formation on the artificial opal templates for the fabrication of the porous 3D structures are also demonstrated. Such a 3D material is ideally suited as a cathode for lithium ion batteries, electrochromic devices, sensors and for applications requiring high surface area electrochemically active metal oxides.

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Three-dimensional ordered mesoporous (3DOM) ZnCo2O4 materials have been synthesized via a hard template and used as bifunctional electrocatalysts for rechargeable Li-O2 batteries. The as-prepared ZnCo2O4 nanoparticles possess a high specific surface area of 127.2 m2 g-1 and a spinel crystalline structure. The Li-O2 battery utilizing 3DOM ZnCo2O4 shows a higher specific capacity of 6024 mAh g-1 than that with pure Ketjen black (KB). Moreover, the ZnCo2O4-based electrode enables much enhanced cyclability with a smaller discharge-recharge voltage gap than that of the carbon-only cathode. Such excellent catalytic performance of ZnCo2O4 could be associated with its larger surface area and 3D ordered mesoporous structure

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In this study we investigated the influence of five different cations on the physical-chemical properties of protic ionic liquids (PILs) based on bis(trifluoromethanesulfonyl)imide (TFSI-). We showed that the viscosities, ionic conductivities, densities and thermal properties of these PIL are strongly affected by the structure of the protic cation. Furthermore, the influence of the cation structure on the lithium coordination was investigated by Raman spectroscopy for all investigated PIL-based electrolytes for lithium-ion batteries (LIBs). This investigation clearly demonstrates, that the lithium average coordination number in PIL-based electrolytes is strongly affected by (ring) size and the number of protons on the cations structure and, more importantly, it might be significantly lower (more than 60 of that of electrolytes containing aprotic ionic liquids (AILs). Electrochemical performances of these PILs-based electrolytes were then also investigated to dress some conclusion on their applicability for LIB.