Structure and electron density analysis of electrochemically and chemically delithiated LiCoO2 single crystals
Structure and electron density analysis of electrochemically and chemically delithiated LiCoO2 single crystals
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DOI：
10.1016/j.jssc.2006.10.018
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发表时间：
2007-01-01
影响因子：
3.3
通讯作者：
Akimoto, Junji
中科院分区：
文献类型：
--
作者：
Takahashi, Yasuhiko;Kijima, Norihito;Akimoto, Junji
以LiCoO₂单晶为母体化合物，通过电化学和化学脱锂过程首次成功合成了Li₀.₆₈CoO₂、Li₀.₄₈CoO₂和Li₀.₃₅CoO₂单晶。单晶X射线衍射研究证实，Li₀.₆₈CoO₂属于三方R - 3m空间群，六方晶格参数a = 2.8107(5)埃，c = 14.2235(6)埃，c/a = 5.060；Li₀.₄₉CoO₂的a = 2.8090(15)埃，c = 14.3890(17)埃，c/a = 5.122；Li₀.₃₅CoO₂的a = 2.8070(12)埃，c = 14.4359(14)埃，c/a = 5.143。晶体结构精修到常规值，Li₀.₆₈CoO₂的R = 1.99%，wR = 1.88%；Li₀.₄₈CoO₂的R = 2.40%，wR = 2.58%；Li₀.₃₅CoO₂的R = 2.63%，wR = 2.56%。确定CoO₆八面体中的氧 - 氧接触距离因脱锂从LiCoO₂中的2.6180(9)埃缩短到Li₀.₃₅CoO₂中的2.5385(15)埃。利用300 K下的单晶X射线衍射数据，通过最大熵方法（MEM）分析了这些LiₓCoO₂晶体的电子密度分布。从单晶MEM的结果来看，在这些化合物中，Co和O原子之间明显存在强共价键，而在Li原子周围未发现键合。可以精确分析脱锂时Li位点电子密度的逐渐降低。（c）2006 Elsevier Inc.保留所有权利。
Single crystals of Li(0.68)CoO(2), Li(0.48)CoO(2) and Li(0.35)CoO(2) were successfully synthesized for the first time by means of electrochemical and chemical delithiation processes using LiCoO(2) single crystals as a parent compound. A single-crystal X-ray diffraction study confirmed the trigonal R (3) over barm space group and the hexagonal lattice parameters a = 2.8107(5) angstrom, c = 14.2235(6) angstrom, and c/a = 5.060 for Li(0.68)CoO(2); a = 2.8090(15) angstrom, c = 14.3890(17) angstrom, and c/a = 5.122 for Li(0.49)CoO(2); and a = 2.8070(12) angstrom, c = 14.4359(14) angstrom, and c/a 5.143 for Li(0.35)CoO(2). The crystal structures were refined to the conventional values R = 1.99% and wR = 1.88% for Li(0.68)CoO(2); R = 2.40% and wR = 2.58% for Li(0.48)CoO(2); and R = 2.63% and wR = 2.56% for Li(0.35)CoO(2). The oxygen-oxygen contact distance in the CoO(6) octahedron was determined to be shortened by the delithiation from 2.6180(9) angstrom in LiCoO(2) to 2.5385(15) angstrom in Li(0.35)CoO(2)). The electron density distributions of these Li(x)CoO(2) crystals were analyzed by the maximum entropy method (MEM) using the present single-crystal X-ray diffraction data at 300 K. From the results of the single-crystal MEM, strong covalent bonding was clearly visible between the Co and O atoms, while no bonding was found around the Li atoms in these compounds. The gradual decrease in the electron density at the Li site upon delithiation could be precisely analyzed. (c) 2006 Elsevier Inc. All rights reserved.