Synthesis-Structure-Property Relations in Layered, "Li-excess" Oxides Electrode Materials Li[Li1/3-2x/3NixMn2/3-x/3]O2 (x=1/3, 1/4, and 1/5)
Synthesis-Structure-Property Relations in Layered, "Li-excess" Oxides Electrode Materials Li[Li1/3-2x/3NixMn2/3-x/3]O2 (x=1/3, 1/4, and 1/5)
复制标题
DOI：
10.1149/1.3473830
复制
发表时间：
2010-01-01
影响因子：
3.9
通讯作者：
Meng, Ying Shirley
中科院分区：
文献类型：
--
作者：
Fell, Christopher R.;Carroll, Kyler J.;Meng, Ying Shirley
通过X射线衍射、扫描电子显微镜(EELS)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)和电子能量损失谱分析，结合电化学性能测量，研究了过量锂层状氧化物Li[Ni(x)Li(1/3-2x/3)Mn(2/3-x/3)]O(2)(0 < x < 1/2)的合成条件、详细晶体结构和电化学性能之间的关系，包括恒电位间歇滴定技术（PITT）。化学计量样品在空气中 1000 摄氏度下烧结，然后炉冷，获得了最佳合成条件。当 x = 1/5、1/4 和 1/3 时，材料在 2-4.8 V 放电电压范围内分别表现出类似于 250、230 和 200 mAh/g 的容量。电化学循环电极材料的衍射数据显示，c/a 晶格比扩大，Li/Ni 层间混合发生变化，表明结构中存在特殊的阳离子迁移。高分辨率TEM图像和XPS光谱显示，化学计量和过量LiOH合成的样品的表面特性存在明显差异，表明表面特性是电化学性能差异的影响因素之一。我们的结果表明，第一个循环的不可逆容量受到原始材料的体积和表面特性的影响，这受到前驱体化学的强烈影响。 PITT结果表明，充电/放电过程中的阳离子重排对锂化学扩散率有显着影响。 (C) 2010 年电化学协会。 [DOI：10.1149/1.3473830] 保留所有权利。
Relations between synthesis conditions, detailed crystal structures, and electrochemical properties of the Li-excess layered oxides Li[Ni(x)Li(1/3-2x/3)Mn(2/3-x/3)]O(2)(0 < x < 1/2) are studied by X-ray diffraction, scanning electron microscopy (EELS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electron energy-loss spectrometry, combined with electrochemical property measurements including potentiostatic intermittent titration technique (PITT). Optimal synthesis conditions are obtained for stoichiometric samples sintered at 1000 degrees C in air followed by furnace cooling. The materials exhibit capacities of similar to 250, 230, and 200 mAh/g within a voltage range of 2-4.8 V on discharge for x = 1/5, 1/4 and 1/3, respectively. Diffraction data of electrochemically cycled electrode materials show an expanded c/a lattice ratio and changing Li/Ni interlayer mixing indicating peculiar cation migration in the structures. High resolution TEM images and XPS spectra show obvious differences in the surface characteristics of the samples synthesized with stoichiometric and excess amount of LiOH, suggesting that surface characteristics is one of the contributing factors to the difference in electrochemical properties. Our results suggest that the first cycle irreversible capacity is affected by both the bulk and surface characteristics of pristine materials, which is strongly influenced by precursor chemistry. The PITT results suggest that cation rearrangement during the charge/discharge has a significant impact on the lithium chemical diffusivity. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3473830] All rights reserved.