Water exposure of layered nickel-rich transition metal oxide electrodes, widely used in high-energy lithium-ion batteries, has detrimental effects on the electrochemical performance, which complicates electrode handling and prevents implementation of environmentally benign aqueous processing procedures. Elucidating the degradation mechanisms in play may help rationally mitigate/circumvent key challenges. Here, the bulk structural consequences of long-term (>2.5 years) deuterated water (D₂O) exposure of intercalation materials with compositions Li_xNi_0.5Co_0.2Mn_0.3O₂ (NCM523) and Li_xNi_0.8Co_0.1Mn_0.1O₂ (NCM811) are studied by neutron powder diffraction (NPD). Detailed inspection of the NPD data reveals gradual formation of a secondary crystalline phase in all exposed samples, not previously reported for this system. This unknown phase forms faster in liquid- compared to vapor-exposed compounds. Structural modelling of the NPD data shows a stable level of Li/Ni anti-site defects and does not indicate any significant changes in lattice parameters or hydrogen-lithium (D⁺/Li⁺) exchange in the structure. Consequently, the secondary phase formation must take place via transformation rather than modification of the parent material. X-ray photoelectron spectroscopy data indicate formation of LiHCO₃/Li₂CO₃ at the surface and a Li-deficient oxide in the sub-surface region of the pristine compounds, and the presence of adsorbed water and transition metal hydroxides at the exposed sample surfaces.

高能量锂离子电池中广泛使用的层状富镍过渡金属氧化物电极的水暴露会对电化学性能产生不利影响，这会使电极处理复杂化，并妨碍执行对环境有益的水处理程序。阐明运行中的降级机制可能有助于合理缓解/规避关键挑战。在此，长期（> 2.5年）氘化水（D ₂ O）暴露于组成为Li _x Ni _0.5 Co ₀的插层材料的总体结构后果_。2 Mn _{0 。3} O ₂（NCM523）和Li _x Ni _0.8Co _{0 。1} Mn _{0 。}通过中子粉末衍射（NPD）研究了₁ O ₂（NCM811）。对NPD数据的详细检查表明，在所有暴露的样品中都逐渐形成了第二晶相，这是该系统先前未报告的。与蒸气接触的化合物相比，这种未知相在液体中的形成速度更快。NPD数据的结构建模显示稳定水平的Li / Ni反位缺陷，并且未表明结构中晶格参数或氢-锂（D ⁺ / Li ⁺）交换的任何显着变化。因此，次级相的形成必须通过转换而不是修改母材。X射线光电子能谱数据表明，在原始化合物的表面形成了LiHCO ₃ / Li ₂ CO ₃，在次表面的次表面区域形成了缺锂的氧化物，并且在暴露的样品中存在吸附的水和过渡金属氢氧化物表面。