Progress in Solid-State NMR Studies of Electrode Materials for Lithium Ion Batteries

对于研究材料的结构变化和考察原子所处的化学环境 ,固体核磁共振技术是一种有效的手段。通过6 Li和7Li核磁共振谱的变化 ,可以清楚地了解锂离子电池电极材料中 Li与邻近金属或碳原子的配位情况及在充放电过程中对应于锂离子嵌 /脱过程中材料的结构变化 ,对于研究电极材料的电化学性能有重要的意义。本文综述了固体 NMR技术在研究锂离子电池电极材料的结构及嵌锂机理方面的一些进展Solid-state NMR is the effective technique for the study of local structural changes and chemical environment around the atoms which monitor atomic environments by varying adjacent metal or carbon content. Based on the changes of the 6Li, 7Li NMR spectrum, the coordinating condition of lithium with the neighbor metal atoms and the structural changes of the materials during the charge/discharge cycle can be clearly identified. The developments in the micro-structural analysis of the electrode materials and mechanistic study of Li + intercalation into a various of materials by using solid NMR techniques were reviewed.国家杰出青年科学基金 ( 2 992 5 3 10 )资助课

Fabrication and Characteristics of GaN-based Blue VCSEL

利用金属有机物气相沉积技术(MOCVD)在(0001)蓝宝石衬底上生长了Ga N基垂直腔面发射激光器(VCSEL)的多量子阱腔层结构。X射线衍射测量显示该多量子阱具有良好周期结构和平整界面。运用键合及激光剥离技术将该外延片制作成VCSEL,顶部和底部反射镜为极高反射率的介质膜分布布拉格反射镜(DBR)。在室温、紫外脉冲激光的泵浦条件下,观察到了VCSEL明显的激射现象,峰值波长位于447.7 nm,半高宽为0.11 nm,自发辐射因子约为6.0×10-2,阈值能量密度约为8.8 m J/cm2。在大幅度降低制作难度的情况下,得到目前国际最好结果同样数量级的激射阈值。降低器件制作难度有利于制备的重复性,有利于器件的产品化。Ga N-based multiple quantum wells( MQWs) were epitaxially grown on( 0001)-oriented sapphire substrate by metal organic chemical vapor deposition( MOCVD) technique. X-ray diffraction measurements indicated that the MQWs had good periodic structure and smooth interface. By employing bonding and laser lift-off techniques,the MQW structure was sandwiched between two high reflectivity dielectric distributed Bragg reflectors( DBRs),forming a vertical-cavity surfaceemitting laser( VCSEL). Under optical pumping,the VCSEL achieved laser action at room temperature with a threshold pumping energy density of about 8. 8 m J / cm2. The laser emitted a blue light at 447. 7 nm with a narrow linewidth of 0. 11 nm,and had a high spontaneous emission factor of about 6. 0 × 10- 2.国家自然科学基金(61307115);; 福建省教育厅A类科技项目(JA12249);; 厦门理工学院高校高层次人才基金(YKJ11026R);; 福建省自然科学基金(2013J05104)资助项

黄河三角洲自然保护区鹤类南迁迁徙规律初步研究

黄河三角洲国家级自然保护区是鹤类重要的迁徙中转站,在鹤类保护中具有重要意义。在中国9种鹤类资源中,保护区有7种。2006年鹤类南迁期,作者于10月初至12月初,采用定点观察法,对保护区内的鹤类进行观察,并对鹤类南迁的迁徙规律进行分析

New progress in studies of lithium nickel oxide as positive electrode materials of lithium ion batteris

[中文摘要] 锂镍氧化物是目前高容量大功率锂离子电池正极材料的主要候选材料之一 .本文详细介绍了锂镍氧化物作为锂离子电池正极材料的实用化困难与其结构的内在联系 ,以及解决这些困难所进行的合成方法和掺杂改性研究的概况 .探索新的合成方法以及多组分掺杂改性应是今后锂镍氧化物的研究方向。[英文文摘]Lithium nickel oxide as the positive electrode of lithium ion batteries has aroused more and more interests.This paper reviews the recent reserches on synthesis and element_substitution of LiNiO 2 cathode material,and summarizes the intrinsical relationship between properties and sturcture of the material.The developments of new synthesis methods and mutil_substitution of the material are expecting to be studied in the future research

Rietveld refinement of powder XRD and its application on the studies of lithium nickel oxide cathode materials

简要介绍了粉末衍射Rietveld结构精修方法的基本原理,实验数据的收集和应用软件的情况,并将其应用于锂离子蓄电池正极材料锂镍氧化物的研究中。通过理论模拟采用不同原子分数坐标的两种LiNiO2模型的XRD谱图,证明Li-3 a,Ni-3 b模型是正确的;通过结构精修分析不同合成条件下LiNi0.8Co0.2O2电极材料的微结构信息,优化了该材料的合成条件;通过结构精修分析不同掺杂离子含量的LiNi0.8-yTiyCo0.2O2电极材料的微结构信息,揭示了钛离子的掺杂作用机理;通过Rietveld方法多物相定量分析在空气中贮存一年后的LiNiO2电极材料,发现贮存过程中生成了Li2CO3以及Ni2+含量增大,促进了对LiNiO2电极材料贮存后性能下降现象的理解。实验结果表明,Rietveld方法是获取固体电极材料微结构信息的一种强有力工具。In this paper, the basic principle, data collection and analysis programs of Rietveld refinement, which is a useful tool for the structure characterization of solid state materials,were introduced briefly and applied to the studies on lithium nickel oxide as ahode materials for lithium ion battery. Some of the refinement results also were reported , including calculat-ing XRD patterns according to the structure models, optimizing synthesis conditions by comparing the structure parameters, exploring the mechanism of doping by analyzing the cation distribution, and enhancing the comprehension for the perfor-mance of eloectrode materials by quantitative analysis of multiphase materials.国家自然科学基金资助课题(29925310

To switch or not to switch?Cognitive and neural mechanisms of card switching behavior

决策是每个人每天都会进行的活动。二择一时,有人择一而终,有人变换不定。这种个体差异可能与坚持性人格和认知灵活性有关。本研究旨在探讨这种行为特征背后的认知神经机制,以便进一步理解决策变换中存在的个体差异。本研究采用了单变量和多变量体素形态学分析的方法分析了350名大学生(其中女性194人,平均年龄19.97岁)在随机猜牌任务中的换牌频率与大脑灰质体积的相关情况,探讨了坚持性人格特质和认知灵活性与换牌频率的关系,并考察了两者在大脑灰质体积与换牌频率中的中介作用。单变量和多变量体素形态学分析结果都表明,左侧后扣带回、右侧额中回、右侧额极和右侧脑岛区域的灰质体积可以预测被试的换牌频率;坚持性人格和认知灵活性在其中起到了中介作用。这些结果阐释了换牌频率个体差异的认知机制和神经基础,对理解为何有的人一味坚持,而有的人灵活变换背后的原因提供了理论基础,同时为开发改善非理性决策行为的方法提供了重要的参考价值。</p