Anionic redox is a double-edged sword for Li-ion cathodes because it offers a transformational increase in energy density that is also negated by several detrimental drawbacks to its practical implementation. Among them, voltage hysteresis is the most troublesome because its origin is still unclear and under debate. Herein, we tackle this issue by designing a prototypical Li-rich cation-disordered rock-salt compound Li_1.17Ti_0.33Fe_0.5O₂ that shows anionic redox activity and exceptionally large voltage hysteresis while exhibiting a partially reversible Fe migration between octahedral and tetrahedral sites. Through combined in situ and ex situ spectroscopic techniques, we demonstrate the existence of a non-equilibrium (adiabatic) redox pathway enlisting Fe³⁺/Fe⁴⁺ and O redox as opposed to the equilibrium (non-adiabatic) redox pathway involving sole O redox. We further show that the charge transfer from O(2p) lone pair states to Fe(3d) states involving sluggish structural distortion is responsible for voltage hysteresis. This study provides a general understanding of various voltage hysteresis signatures in the large family of Li-rich rock-salt compounds.

阴离子氧化还原对锂离子正极来说是一把双刃剑，因为它提供了能量密度的转变性增加，但也被其实际应用中的几个不利缺点所抵消。其中，电压迟滞是最令人头疼的问题，因为它的起源尚不明确，尚在争论中。在此，我们通过设计原型富锂阳离子无序岩盐化合物 Li _1.17 Ti _0.33 Fe _0.5 O _{2来解决这个问题}它显示出阴离子氧化还原活性和异常大的电压滞后，同时在八面体和四面体位点之间表现出部分可逆的 Fe 迁移。^{通过结合原位}和非原位光谱技术，我们证明了^与仅涉及 O氧化还原。我们进一步表明，从 O(2 p ) 孤对状态到 Fe(3 d ) 状态的电荷转移涉及缓慢的结构畸变是造成电压滞后的原因。这项研究提供了对大族富锂岩盐化合物中各种电压滞后特征的一般理解。