An understanding of the structural properties that allow for optimal cathode performance, and their origin, is necessary for devising advanced cathode design strategies and accelerating the commercialisation of next-generation cathodes. High-voltage, Fe- and Mg-substituted LiNi_0.5Mn_1.5O₄ cathodes offer a low-cost and cobalt-free, yet energy-dense alternative to commercial cathodes. In this work, we explore the effect of substituents on several important structure properties including Ni/Mn ordering, charge distribution and extrinsic defects. In the cation-disordered samples studied, we observe a correlation between increased Fe/Mg substitution, Li-site defects and Li-rich impurity phase formation – the concentrations of which are greater for Mg-substituted samples. We attribute this to the lower formation energy of Mg_Li defects when compared to Fe_Li defects. Li-site defect-induced impurity phases consequently alter the charge distribution of the system, resulting in increased [Mn³⁺] with Fe/Mg substitution. In addition to impurity phases, other charge compensators were also investigated to explain the origin of Mn³⁺ (extrinsic defects, [Ni³⁺], oxygen vacancies and intrinsic off-stoichiometry), although their effects were found to be negligible.

中文翻译：

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锂位缺陷诱导富锂杂质相的形成：对 LiNi0.5-xMxMn1.5O4 阴极的电荷分布和性能的影响（M = Fe 和 Mg；x = 0.05–0.2）

了解实现最佳阴极性能的结构特性及其起源，对于设计先进的阴极设计策略和加速下一代阴极的商业化是必要的。高电压、铁和镁取代的 LiNi _0.5 Mn _1.5 O ₄阴极为商业阴极提供了一种低成本、无钴且能量密集的替代品。在这项工作中，我们探讨了取代基对几个重要结构特性的影响，包括 Ni/Mn 排序、电荷分布和外在缺陷。在研究的阳离子无序样品中，我们观察到铁/镁取代增加、锂位缺陷和富锂杂质相形成之间的相关性——镁取代样品的浓度更高。我们将此归因于与铁_锂缺陷相比，镁_锂缺陷的形成能较低。 Li 位缺陷诱导的杂质相因此改变了系统的电荷分布，导致Fe/Mg 取代时[Mn ³⁺ ] 增加。除了杂质相之外，还研究了其他电荷补偿剂来解释 Mn ³⁺的起源（外在缺陷、[Ni ³⁺ ]、氧空位和内在非化学计量），尽管发现它们的影响可以忽略不计。