Oxygen-anion redox in lithium-rich layered oxides can boost the capacity of lithium-ion battery cathodes. However, the over-oxidation of oxygen at highly charged states aggravates irreversible structure changes and deteriorates cycle performance. Here, we investigate the mechanism of surface degradation caused by oxygen oxidation and the kinetics of surface reconstruction. Considering Li₂MnO₃, we show through density functional theory calculations that a high energy orbital (lO_2p’) at under-coordinated surface oxygen prefers over-oxidation over bulk oxygen, and that surface oxygen release is then kinetically favored during charging. We use a simple strategy of turning under-coordinated surface oxygen into polyanionic (SO₄)²⁻, and show that these groups stabilize the surface of Li₂MnO₃ by depressing gas release and side reactions with the electrolyte. Experimental validation on Li_1.2Ni_0.2Mn_0.6O₂ shows that sulfur deposition enhances stability of the cathode with 99.0% capacity remaining (194 mA h g⁻¹) after 100 cycles at 1 C. Our work reveals a promising surface treatment to address the instability of highly charged layered cathode materials.

富锂层状氧化物中的氧负离子氧化还原可以提高锂离子电池阴极的容量。然而，在高电荷状态下氧的过氧化加剧了不可逆的结构变化并恶化了循环性能。在这里，我们研究了由氧氧化引起的表面降解的机理和表面重建的动力学。考虑到Li ₂ MnO ₃，我们通过密度泛函理论计算表明，在配位不足的表面氧处的高能轨道（lO _{2 p '}）比整体氧更倾向于过度氧化，因此在充电过程中动力学上有利于释放表面氧。我们采用一种简单的策略，将配位不足的表面氧转变为聚阴离子（SO_图4）^2-，表明这些基团通过抑制气体释放和与电解质的副反应来稳定Li ₂ MnO ₃的表面。在Li _1.2 Ni _0.2 Mn _0.6 O ₂上进行的实验验证表明，硫沉积可提高阴极的稳定性，在1 C循环100次后，剩余容量为99.0％（194 mA hg ^-1）。我们的工作揭示了解决不稳定性的有前途的表面处理方法高电荷的分层阴极材料。