轴向压缩下圆柱形动力锂离子电池的性能

动力电池的安全问题制约了电动汽车的推广和发展,轴向压缩是锂离子电池的一种重要的破坏工况。通过实验方法,研究了18650锂离子电池在轴向压缩载荷下的安全性能,探讨了荷电状态分别为60%、80%、100%时电池的载荷、电压、温度的变化特征,分析了轴向压缩载荷下电池的失效过程。研究表明:轴向压缩过程中电压均出现特有的台阶式下降,极限载荷和温度骤升几乎同时发生;电池正极的凹槽结构诱导电池在靠近正极的侧面破裂。对比轴向压缩实验和径向平板压缩实验发现,动力电池轴向压缩热失控程度弱于径向平板压缩。     

电动汽车锂离子电池热管理系统研究进展

锂离子电池作为电动汽车最广泛使用的动力源,对工作温度高度敏感,为保证其高性能和安全运行,电池热管理系统必不可少.本文综述了近年来锂离子电池热管理系统的研究进展.首先讨论了由高低温环境和电池温度不均匀引起的临界热问题.在此基础上,对设计原则和现有的电池热管理系统进行了广泛的介绍和阐述.然后进一步分析了用于未来电池热管理系统的热电器件和内部加热方法等新兴技术.分析表明,被动和主动冷却/加热方法的组合有望满足苛刻的热要求,特别是在功率波动剧烈的动态条件下.此外,电池在变工况下所输出的电流、电压等均不相同,因此建议对电动汽车动力电池进行动态性能实时管理,从而延长电池使用寿命。     

增程式电动汽车动力总成参数匹配设计

增程式电动汽车作为一种新型节能环保型汽车,是传统内燃机汽车向纯电动汽车过渡的一种车型;根据动力传动系统的设计原则和设计目标,基于铃木奥拓燃油汽车改装设计了增程式电动汽车的动力传动系统的参数匹配方法,根据电动汽车基本参数及其控制目标,对动力总成系统的关键零部件进行了匹配设计;匹配结果表明:电动机的额度电压为60 V,最高转速为4 000 r/min,额定功率为8 kW,额定转矩为40.43 N·m,峰值功率为11 kW,最大扭矩为80.86 N·m;增程器采用马勒增程器和两缸直列四冲程发动机;动力电池组采用磷酸铁锂子电池,单组额定容量为80 Ah、总电压为96 V;对于指导增程式电动汽车的开发、提高汽车性能和安全性,以及对于电动汽车底盘集成控制系统的开发都具有重要的工程应用意义。     

基于无烟煤软碳负极材料的低成本钠离子电池开发成功

正环境污染问题日益突出,风能、太阳能等清洁能源的利用越来越受到人们的关注,但是这些能源是间隙性的,限制了其发展和广泛应用,大规模储能技术是解决可再生能源高效利用瓶颈的关键技术。锂离子电池是一种非常重要的储能技术,广泛应用于便携电子设备和新能源汽车上,随着电动汽车、智能电网时代的到来,锂离子电池大规模发展受到锂资源短缺的     

超大容量圆柱形单体400A·h锂离子电池投产

随着国内外汽车厂家全电动汽车在今春北京第十一届国际车展上集体亮相,“新能源汽车元年”悄然揭开了时代的序幕．日前天津大学和北京天路能源有限公司通过产学研合作,探索了电动汽车动力供给、安全稳定与绿色环保之间完美结合的新途径,开发的超大容量圆柱形单体400A·h“巨无霸”锂离子电池在全球锐开先河,成功投入小批量生产．该产品具有超高容量、安全性好、     

锂离子电池中的物理问题及其研究进展

锂离子电池作为一种性能优越的新型可充放电池已经或将要在移动通信、手提式计算机和电动汽车等诸多领域获得广泛的应用 .然而与锂离子电池相关的物理问题却往往被人们忽视 .例如 ,如何从本质上来提高正极材料的体相电子电导率 ,而不是在正极活性物质中添加炭黑之类的电子导电材料 .文章将着重针对与锂离子电池相关的物理问题 ,介绍近年来的主要进展 ,以期待对锂离子电池有更深入的了解 .     

基于扩展单粒子模型的锂离子电池参数识别策略

为了精确识别电动汽车锂离子动力电池的关键状态参数,基于多孔电极理论和浓度理论,建立了一种考虑液相动力学行为的锂离子电池扩展单粒子模型.相较于传统单粒子模型,该模型增加了对负电极表面固体电解质界面膜参数的描述,并考虑了温度和液相浓度变化对锂离子电池关键参数的耦合影响.基于所建立的扩展单粒子模型,提出一种简化的参数灵敏度分析方法和有效的锂电池参数识别策略,用以确定特定工况下的高灵敏度待识别参数,进而利用遗传算法实现参数的优化求解.最后,通过对比分析本文模型和传统单粒子模型的仿真输出电压和相同工况下电池的实验输出电压验证了提出模型和参数识别方法的有效性和可行性,为电池管理系统的健康状态估计提供了理论基础.     

基于相变材料的动力电池热管理数值模拟

锂离子动力电池经过多次充放电循环后,不可避免出现老化现象,单体电池局部温差增大,成组效应更加明显.本文建立了非均匀产热动力电池组三维模型,采用数值模拟的方法,模拟分析了基于相变材料的圆柱形LiFePO_4动力电池模块(4×6)的降温与均温性能。结果表明,相比没有填充PCM情况,填充PCM后,最高温度随时间呈现先明显增加后逐渐平缓的趋势,放电结束时明显降低,但随着导热系数的增加,最高温度降低不明显。在单体电池固有较大温差情况下,采用StyleⅠ方式排列电池正负极,降低相变温度和增加导热系数均难很好地控制电池模块温度均匀性。对于正负极出现产热不均匀的老化电池组,采用styleⅡ或styleⅢ排列方式是必要的。     

向前“充”——电动车充电新方案

正自从亨利·福特1908年推出的T型汽车成为第一款真正意义上面向大众的汽车以来,内燃机车一直主宰着道路。结果是运输业的温室气体排放量几乎占欧洲的三分之一,其中约90%来自道路交通。显然,电动交通是大势所趋。随着价格的降低和电池技术的革新,越来越多的人开始选择购买插电式混合动力汽车或全电动汽车。国际能源协会(IEA)报告称,今年3月,英国电动汽车在新车销量中达到了破纪录的13%。     

Li电池原材料的穆斯堡尔谱及分析

穆斯堡尔效应的发现与X射线衍射和电子显微技术的发现具有同样重要的意义。它的能量分辨率极高,能够清晰地观察到原子核能级的跃迁。锂离子电池因其高工作电压和高能量密度广泛应用于便携式电子产品、电动工具和电动汽车等领域。电极材料是决定锂离子电池性能的重要因素之一。相对于负极材料,正极材料研究遇到更多的挑战,如高电压窗口、高比容量、良好的倍率性能、循环寿命、价廉和安全性等。但是,随着锂离子电池应用领域的不断拓宽,迫切需要研制新型的电极材料来满足日益增长的应用需求。以FeSO_4·H_2O和LiF为原料,用离子液体EMI-TFSI作反应媒介,300℃反应5 h得到产品。并通过穆斯堡尔谱仪测量并分析样品的成分。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.