A new superstructure of layered pristine LiNiO2 (LNO) was obtained optimizing a large supercell of the 166 space group, the one observed experimentally by XRD, and relaxing both cell parameters and internal positions. The crystal structure shows size and charge disproportionation of the NiO6 octahedra instead of the Jahn-Teller distortion. The decrease of the internal energy obtained with the structural optimization of the supercell relative to the same structure in its primitive unit cell is much larger than the one obtained by relaxing similarly dimensioned supercells of monoclinic symmetry relative to their primitive unit cells, although the monoclinic phase remains more stable. The Ni-O bond length distribution of the new structure agree well with the experiments. Our results show that the choice of the simulation cell is important for determining the energetics of this class of oxide materials, proposed for cathodes in lithium ion batteries (LIBs). We used this new structure as a template for the study of the structural and electronic changes induced by the delithiation and Mn for Ni cation substitution, originating the solid solutions LiNiyMn(1-y)O2 (LNMO). Our results, surprisingly, agree well with the existing experiments and explain observed trends better than previous studies.

中文翻译：

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锂离子电池用富镍氧化物的结构和电子态

通过优化 166 空间群的大型超级电池（通过 XRD 实验观察到的超级电池），并松弛电池参数和内部位置，获得了一种新的层状原始 LiNiO2 (LNO) 超结构。晶体结构显示 NiO6 八面体的尺寸和电荷歧化，而不是 Jahn-Teller 畸变。通过超晶结构优化获得的内能相对于其原始晶胞中相同结构的内能的减少远大于通过弛豫类似尺寸的单斜对称超晶胞相对于其原始晶胞所获得的内能的减少，尽管单斜晶相保持更加稳定。新结构的Ni-O键长分布与实验吻合良好。我们的结果表明，模拟电池的选择对于确定此类氧化物材料的能量非常重要，这些材料建议用于锂离子电池（LIB）的阴极。我们使用这种新结构作为模板，研究脱锂和 Mn 取代 Ni 阳离子引起的结构和电子变化，从而产生固溶体 LiNiyMn(1-y)O2 (LNMO)。令人惊讶的是，我们的结果与现有的实验非常吻合，并且比以前的研究更好地解释了观察到的趋势。