Phase transformations and volume changes in spinel LixMn2O4
Phase transformations and volume changes in spinel LixMn2O4
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DOI：
10.1016/s0167-2738(00)00326-x
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发表时间：
2000-11-01
影响因子：
3.2
通讯作者：
Ceder, G
中科院分区：
文献类型：
--
作者：
Van der Ven, A;Marianetti, C;Ceder, G
采用第一性原理方法计算了尖晶石型LixMn 2 O 4的相图和体积膨胀随锂含量的变化关系。计算证实了实验观察到的两相区之间的x = 1和2和有序相在x = 1/2。此外，在x = 1处获得了预期的大电压阶跃。结果表明，这些现象是定性的相互作用的Li和Mn 2 O 4主机，只有定量影响更微妙的电子效应，如Jahn-Teller扭曲，电荷有序和磁激发。发现x = 1和2之间的两相区域是由占据相邻四面体8a和八面体16 c位置的锂离子之间的强排斥相互作用驱动的。从第一性原理出发，研究了LiMn_2O_4向Li_2Mn_2O_4转变过程中大体积变化的原因。体积变化的可能来源被确定为嵌入锂、Jahn-Teller扭曲以及反键e（g）电子引入到Mn d轨道中。后一种效果被认为是占主导地位的。提出了如何防止二氧化锰锂化后体积变化大的设想。(C)2000 Elsevier Science B.V，保留所有权利。
First-principles methods have been used to calculate the phase diagram and volume expansion of spinel LixMn2O4 as a function of lithium content. The calculations confirm the experimentally observed two phase region between x = 1 and 2 and the ordered phase at x = 1/2. In addition, the expected large step in voltage at x = 1 is obtained. It is shown that these phenomena are qualitatively determined by the interactions of Li with each other and the Mn2O4 host and only quantitatively influenced by the more subtle electronic effects such as Jahn-Teller distortions, charge ordering and magnetic excitations. The two-phase region between x = 1 and 2 is found to be driven by strong repulsive interactions between lithium ions occupying adjacent tetrahedral 8a and octahedral 16c sites. The origin of the large volume change upon transforming from LiMn2O4 to Li2Mn2O4 is also investigated from first principles. The possible sources of the volume change are identified to be the intercalated lithium, the Jahn-Teller distortion, and the introduction of anti-bonding e(g) electrons into the Mn d-orbitals. The latter effect is found to be dominant. Some speculation is offered on how the large volume change upon lithiation of manganese dioxide can be prevented. (C) 2000 Elsevier Science B.V, All rights reserved.