溶胶-凝胶法制备LiFePO_4/C及其电化学性能

以硝酸铁、磷酸二氢铵、氢氧化锂为原料,以聚乙二醇PEG-4000为螯合剂和碳源,采用溶胶-凝胶法制备了LiFePO4/C。利用XRD、SEM、电化学性能测试等手段对LiFePO4/C的物相结构、形貌、电化学性能进行表征。结果表明:PEG-4000作为螯合剂和碳源,使得样品的粒径较小且分布均匀。650℃烧结18h所合成的样品具有最佳的电化学性能,0.1C首次充、放电容量分别为152.7、150.6 mAh/g;循环30次后容量为146 mAh/g,容量衰减率为3.05%。     

基于LabVIEW的三相异步电机变频调速策略

为了降低成本,减少系统的复杂性,将变频调速技术与虚拟仪器技术相结合,基于虚拟仪器灵活、开放的特点,以及计算机强大的处理能力,用简洁易懂的图形化编程语言LabVIEW实现SPWM的信号发生,并通过数据采集卡输出给逆变电路控制三相异步电机,以此来取代传统的控制系统.经验证该系统稳定可靠,且大大降低了开发成本,缩短了开发周期,提高了系统的灵活性.     

带钢表面图像缺陷区域的分割方法

主要研究了一种适用于带钢表面图像的缺陷区域分割方法．首先,对传统的基于边缘检测和全局阈值的缺陷区域分割方法进行研究和比较,然后根据带钢表面缺陷图像的灰度特点,提出了一种基于灰度级形态学增强和自适应阈值的缺陷区域分割方法．采用本文方法对常见的带钢表面图像进行缺陷区域分割实验,结果表明本文方法的分割效果要优于传统的分割方法．因此,提出的基于灰度级形态学增强和自适应阈值的缺陷区域分割方法具有一定的实际应用价值．     

Synthesis and characterization of triclinic structural LiVPO4F as possible 4.2 V cathode materials for lithium ion batteries

A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction （CTR） process. Firstly, V2O5, NH4H2PO4 and acetylene black are reacted under an Ar atmosphere to yield VPO4. The transition-metal reduction is facilitated by the CTR based on C→CO transition. These CTR conditions favor stabilization of the vanadium as V^3＋ as well as leaving residual carbon, which is useful in the subsequent electrode processing. Secondly, VPO4 reacts with ElF to yield LiVPO4F product. The property of the LiVPO4F was investigated by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurement. XRD studies show that LiVPO4F synthesized has triclinic structure（space group p I ）, isostructural with the naturally occurring mineral tavorite, EiFePO4-OH. SEM image exhibits that the particle size is about 2μm together with homogenous distribution. Electrochemical test shows that the initial discharge capacity of LiVPO4F powder is 119 mA·h/g at the rate of 0.2C with an average discharge voltage of 4.2V （vs Ei/Li^＋）, and the capacity retains 89 mA·h/g after 30 cycles.     

Preparation and electrochemical studies of Y-doped LiVPO<Subscript>4</Subscript>F cathode materials for lithium-ion batteries

Y-doped LiVPO₄F cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped LiVPO₄F samples were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies show that the Y-doped LiVPO₄F samples have the same triclinic structure as the undoped LiVPO₄F. The Li extraction/insertion performances of Y-doped LiVPO₄F samples were investigated through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Y is x=0.04 in LiY _x V_1−x PO₄F system. The Y-doped LiVPO₄F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVPO₄F cathode materials are attributed to the addition of Y³⁺ ion by stabilizing the triclinic structure. Funded by the Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning(GuiJiaoRen [2007]71), Guangxi Natural Science Foundation(No.0832259), the Research Funds of the Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment Program to Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning(GuiJiaoRen [2007]71)     

锂离子电池Li2FeP2O7正极材料的制备及其电化学性能

采用固相球磨法制备了Li2FeP2O7/C正极材料,研究了烧结温度、碳包覆含量以及碳源对其结构、形貌以及电化学性能的影响。结果表明: 高温固相烧结合成样品的适宜温度为680 ℃,以柠檬酸为碳源、碳包覆量为5%时,合成的Li2FeP2O7/C晶型完整,晶粒较小且均匀,0.1C倍率下的放电比容量可达102.6 mAh/g,0.5C倍率下的初次放电比容量可达83.4 mAh/g,循环30次后放电比容量为80.7 mAh/g,展现了较好的循环性能以及倍率性能。     

湿法机械活化法提高磷酸铁锂均一性的实验研究

采用湿法机械活化混料、喷雾干燥、固相烧结法制备了磷酸铁锂。实验结果表明, 在合适的球料比、液固比下, 经过3 h机械活化的物料烧结后, 产品的0.2C首次放电容量为151.8 mAh/g, 30次循环衰减为0.80%, 明显优于干法混料产品的电性能。     

不同方法合成的LiVPO4F/C的电化学性能（英文）

通过一步固相反应和两步固相反应分别合成LiVPO4F/C,采用XRD、SEM和电化学性能测试对LiVPO4F/C进行性能表征。XRD研究表明一步固相反应合成的LiVPO4F/C与两步固相反应合成的样品一样,均属于三斜晶系结构。SEM研究表明:一步固相反应合成的LiVPO4F/C颗粒比两步固相反应合成的样品颗粒小,一步固相反应合成的 LiVPO4F/C 样品电化学性能得到提高是由于草酸作为还原剂和碳源合成的样品颗粒变小。交流阻抗研究表明步固相反应合成的LiVPO4F/C样品电化学阻抗减小。     

锂离子电池橄榄石结构正极材料LiMnPO_4的研究进展

LiMnPO4是一种新型的橄榄石结构的锂离子电池正极材料。相比于其他橄榄石结构的磷酸盐,LiM-nPO4以其原料成本低,合成条件温和,电压平台高达4.1V的特点更具有应用潜力。本文介绍了LiMnPO4的结构及电化学特征,全面综述了采用不同方法制备LiMnPO4的研究现状以及改性方法。     

球磨对LiVPO4F的合成及性能的影响

通过碳热还原法合成了正极材料LiVPO4F,利用XRD、SEM和充放电测试研究了球磨对LiVPO4F的合成和电化学性能的影响,结果表明:没有球磨的样品不能合成单相的LiVPO4F;球磨1 h和2 h合成的LiVPO4F样品的首次放电比容量分别为117 mAh/g和130 mAh/g,库仑效率分别为84.8%和87.2%,50次循环后,容量衰减率分别为16.2%和14.6%。