Structural and Electrochemical Study of the Li-Mn-Ni Oxide System within the Layered Single Phase Region
Structural and Electrochemical Study of the Li-Mn-Ni Oxide System within the Layered Single Phase Region
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DOI：
10.1021/cm503505b
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发表时间：
2014-12-23
影响因子：
8.6
通讯作者：
Dahn, J. R.
中科院分区：
文献类型：
--
作者：
Li, Jing;Camardese, John;Dahn, J. R.
Li-Mn-Ni氧化物伪三元体系1的相图被用作起点，以了解过渡金属组成和锂含量对具有以下组成的材料的结构和电化学的影响：Li 1 +x（NiyMn 1-y）（1-x）O-2（y = 0.2，0.33，0.4，0.5，0.6和0.7，0 = x = 0.34）。使用连续搅拌釜式反应器通过共沉淀法合成混合过渡金属氢氧化物前体。粉末X-射线衍射结果表明，当锂含量小于与参考文献1一致的单层相所需的锂含量时，观察到额外的尖晶石、岩盐和/或层状相。此外，在具有相对高的锂含量的样品的背散射扫描电子显微镜图像中检测到残留的Li 2CO 3。从而确定了单相区的边界，并绘制了单相区晶格常数与组成的等值线图。电化学测试表明，为了获得最高的容量，应避免相分离，并应制备单相样品。当0.5 < y < 0.7时，在单相区的中部附近发现最大可逆容量至4.6V，而当y < 0.7时，其在单相区的顶部（最小锂含量）。
The phase diagram of the Li-Mn-Ni-oxide pseudoternary system1 was used as a starting point to understand the influence of transition metal composition and lithium content on the structures and electrochemistry of materials with compositions: Li1+x(NiyMn1-y)(1-x)O-2 (y = 0.2, 0.33, 0.4, 0.5, 0.6, and 0.7, 0 = x = 0.34). Mixed transition metal hydroxide precursors were synthesized via coprecipitation using a continuously stirred tank reactor. Powder X-ray diffraction results showed that additional spinel, rocksalt and/or layered phases were observed when the lithium content was less than that required for a single layered phase in agreement with ref 1. Additionally, residual Li2CO3 was detected in the backscattered scanning electron microscopy images for samples with relatively high lithium content. The boundaries of the single phase region were therefore defined and the contour plots of the lattice constants versus composition in the single phase region were generated. Electrochemical measurements showed that phase separation should be avoided and single phase samples should be prepared in order to obtain the highest capacity. The maximum reversible capacity to 4.6 V was found near the middle of the single phase region when 0.5 < y < 0.7, whereas it was at the top (smallest lithium content) of the single phase region when y