Layered Li(Ni,Mn,Co,)O$_2$ (NMC) presents an intriguing ternary alloy design space for optimization as a cathode material in Li-ion batteries. Recently, the high cost and resource limitations of Co have added a new design constraint and high Ni-containing NMC alloys have gained enormous attention despite possible performance trade-offs. It is not fully understood if this material space is a disordered solid solution at room temperature and any arbitrary combination can be used or if there exist distinct transition metal orderings to which meta-stable solid solutions will decay during cycling and affect performance. Here, we present a high fidelity computational search of the ternary phase diagram with an emphasis on high-Ni, and thus low Co, containing compositional phases to understand the room temperature stability of the ordered and disordered solid solution phases. This is done through the use of density functional theory training data fed into a reduced order model Hamiltonian that accounts for effective electronic and spin interactions of neighboring transition metal atoms at various lengths in a background of fixed composition and position lithium and oxygen atoms. This model can then be solved to include finite temperature thermodynamics into a convex hull analysis to understand the regions of ordered and disordered solid solution as well the transition metal orderings within the ordered region of the phase diagram. We find that for the majority of transition metal compositions of the layered material, specifically medium to high-Ni content, prefer transition metal ordering and predict the collection of preferred compositions in the ordered region.

中文翻译：

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迈向超低钴阴极：层状 Li-Ni-Mn-Co 氧化物的高保真计算相搜索

层状 Li(Ni,Mn,Co,)O$_2$ (NMC) 为锂离子电池正极材料的优化提供了一个有趣的三元合金设计空间。最近，Co 的高成本和资源限制增加了新的设计约束，尽管可能存在性能权衡，但含 Ni 含量高的 NMC 合金获得了极大的关注。尚不清楚该材料空间是否在室温下是无序的固溶体并且可以使用任何任意组合，或者是否存在不同的过渡金属有序性，亚稳态固溶体将在循环过程中衰变并影响性能。在这里，我们提出了三元相图的高保真计算搜索，重点是高镍，因此低钴，包含组成相以了解有序和无序固溶体相的室温稳定性。这是通过使用密度泛函理论训练数据输入降阶模型哈密顿量来完成的，该模型解释了在固定组成和位置的锂和氧原子的背景下，不同长度的相邻过渡金属原子的有效电子和自旋相互作用。然后可以求解该模型，将有限温度热力学纳入凸包分析，以了解有序和无序固溶体的区域以及相图有序区域内的过渡金属有序性。我们发现，对于层状材料的大多数过渡金属成分，特别是中到高 Ni 含量，