Dependence on lithium-ion batteries for automobile applications is rapidly increasing. The emerging use of anionic redox can boost the energy density of batteries, but the fundamental origin of anionic redox is still under debate. Moreover, to realize anionic redox, many reported electrode materials rely on manganese ions through π-type interactions with oxygen. Here, through a systematic experimental and theoretical study on a binary system of Li₃NbO₄–NiO, we demonstrate for the first time the unexpectedly large contribution of oxygen to charge compensation for electrochemical oxidation in Ni-based materials. In general, for Ni-based materials, e.g., LiNiO₂, charge compensation is achieved mainly by Ni oxidation, with a lower contribution from oxygen. In contrast, for Li₃NbO₄–NiO, oxygen-based charge compensation is triggered by structural disordering and σ-type interactions with nickel ions, which are associated with a unique environment for oxygen, i.e., a linear Ni–O–Ni configuration in the disordered system. Reversible anionic redox with a small hysteretic behavior was achieved for LiNi_2/3Nb_1/3O₂ with a cation-disordered Li/Ni arrangement. Further Li enrichment in the structure destabilizes anionic redox and leads to irreversible oxygen loss due to the disappearance of the linear Ni–O–Ni configuration and the formation of unstable Ni ions with high oxidation states. On the basis of these results, we discuss the possibility of using σ-type interactions for anionic redox to design advanced electrode materials for high-energy lithium-ion batteries.

中文翻译：

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结构无序引发的氧对电荷补偿的贡献出乎意料的大：Li3NbO4-NiO 二元系统的详细实验和理论研究

汽车应用对锂离子电池的依赖正在迅速增加。阴离子氧化还原的新兴用途可以提高电池的能量密度，但阴离子氧化还原的基本起源仍在争论中。此外，为了实现阴离子氧化还原，许多报道的电极材料通过与氧的 π 型相互作用依赖锰离子。_{在这里，通过对 Li 3} NbO ₄ -NiO二元体系的系统实验和理论研究，我们首次证明了氧对镍基材料电化学氧化的电荷补偿具有出人意料的巨大贡献。一般来说，对于镍基材料，例如，LiNiO ₂，电荷补偿主要通过Ni氧化实现，氧气的贡献较低。相比之下，对于 Li ₃ NbO ₄ -NiO，氧基电荷补偿是由结构无序和与镍离子的 σ 型相互作用触发的，这与氧的独特环境有关，即线性 Ni-O-Ni无序系统中的配置。_{LiNi 2/3} Nb _1/3 O ₂实现了具有小滞后行为的可逆阴离子氧化还原具有阳离子无序的 Li/Ni 排列。由于线性 Ni-O-Ni 构型的消失和具有高氧化态的不稳定 Ni 离子的形成，结构中进一步的 Li 富集使阴离子氧化还原不稳定并导致不可逆的氧损失。在这些结果的基础上，我们讨论了使用 σ 型相互作用进行阴离子氧化还原来设计用于高能锂离子电池的先进电极材料的可能性。