Structural, magnetic, and electrochemical studies on lithium insertion materials LiNi1−xCoxO2 with 0≤x≤0.25
Structural, magnetic, and electrochemical studies on lithium insertion materials LiNi1−xCoxO2 with 0≤x≤0.25
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DOI：
10.1016/j.jssc.2010.05.019
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发表时间：
2010-07
影响因子：
3.3
通讯作者：
K. Mukai;J. Sugiyama;Y. Aoki
中科院分区：
文献类型：
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作者：
K. Mukai;J. Sugiyama;Y. Aoki
通过粉末X射线衍射分析、磁化率（χ）测量和非水锂电池充放电测试，研究了x= 0、0.05、0.1和0.25的LiNi 1 − xCoxO 2样品的结构、磁性和电化学性能.根据使用Rietveld方法的结构分析，对于所有样品，Ni离子在Li层中的占有率估计为低于0.01，并且最终与x无关。在磁场H= 10 kOe时，x − 1随温度的变化表明，在100 K以下，所有样品都是居里-外斯顺磁体。在低T下，所有样品在低于Tf时进入自旋玻璃状相。Tf的大小被发现几乎与x线性下降，在这种情况下的晶格参数的ah-和ch-轴，韦斯温度，和有效磁矩的x依赖性。因此，发现磁性随x的变化可以简单地解释为由于Co ~（3+）离子量的增加而产生的稀释效应。另一方面，电化学测量表明，在初始循环的不可逆容量急剧下降的少量的钴离子。此外，x=0.05和0.1的样品的放电容量（Qdis）大于x=0的样品的放电容量;即，对于x=0，Qdis= 180 mAhg − 1，对于x=0.05，Qdis= 217 mAhg − 1，并且对于x=0.1，Qdis= 206 mAhg − 1。与过去的结果相比，发现Li层中Ni离子的量对决定LiNi 1 − xCoxO 2的磁性和电化学性质起着重要作用。
The structural, magnetic, and electrochemical properties of the LiNi1−xCoxO2samples with x= 0, 0.05, 0.1, and 0.25 have been investigated by powder X-ray diffraction analyses, magnetic susceptibility (χ) measurements, and electrochemical charge and discharge test in non-aqueous lithium cell. According to the structural analyses using a Rietveld method, the occupancy of the Ni ions in the Li layer was estimated to be below 0.01 for all the samples and was eventually independent of x. The temperature (T) dependence of χ−1obtained with the magnetic field H=10kOe indicated that all the samples are a Curie–Weiss paramagnet down to ∼100K. At low T, all the samples entered into a spin-glass-like phase below Tf. The magnitude of Tfwas found to decrease almost linearly with x, as in the case for the x dependences of the lattice parameters of ah- and ch-axes, Weiss temperature, and effective magnetic moment. It is, therefore, found that the change of the magnetic properties with x is simply explained by a dilution effect due to the increase of the quantity of Co3+ions. On the other hand, the electrochemical measurements demonstrated that the irreversible capacity at the initial cycle is drastically decreased by the small amount of Co ions. Furthermore, the discharge capacity (Qdis) for the x=0.05 and 0.1 samples are larger than that for the x=0 sample; namely, Qdis=180mAhg−1for x=0, Qdis=217mAhg−1for x=0.05, and Qdis=206mAhg−1for x=0.1. Comparing with the past results, the amount of Ni ions in the Li layer is found to play a significant role for determining the magnetic and electrochemical properties of LiNi1−xCoxO2.