Submicron-size primary particles of Li_xNi_0.88Co_0.08Mn_0.04O₂ cathode material for next-generation lithium-ion-battery (LIB) application were prepared and annealed in-situ from room temperature (RT) to 200 and 400 ̊C, respectively, and their space-resolved Ni L₃-, Co L₃-, Mn L₃-and O K-edge x-ray absorption spectra were acquired by scanning transmission x-ray microscopy (STXM). The aim was to investigate the local phase changes and oxidation-state changes of the cations within each of the primary particles, in order to understand the annealing-induced degradation mechanism of the material. Compared with the Co L₃-and Mn L₃-edge spectra, the Ni L₃-and O K-edge spectra showed clear changes manifesting as a reduction of Ni ions when annealed, especially from 200 to 400 ̊C. The average oxidation numbers of the Co and Mn ions showed negligible changes. On the other hand, the Ni ions showed clear changes: when averaged over the particle areas, the number was +3 at RT and 200 ̊C, and +2.6 at 400 ̊C. For smaller particles (~100 nm in diameter), the values were smaller: +2.8 at RT, +2.7 at 200 ̊C, and +2.2 at 400 ̊C. In the O K-edge spectrum, the intensity of the O 2p – Ni 3d hybridization peaks decreased and a NiO-related peak appeared at 400 ̊C. These observations imply that at 400 ̊C, Ni ions are predominantly reduced, to a lower average oxidation number, as the annealing temperature reaches 400 ̊C, and that the reduction of Ni ions occurs mainly in the edge area and in smaller particles. The overall results suggest that preparation of larger-size primary particles and proper capping of each primary particle can improve the lifetime and stability of the LIB.

准备了用于下一代锂离子电池（LIB）的Li _x Ni _0.88 Co _0.08 Mn _0.04 O ₂阴极材料的亚微米级一次颗粒，并从室温（RT）现场退火至200和400°C，分别通过扫描透射X射线显微镜（STXM）获得其空间分辨的Ni L _3-，Co L _3-，Mn L _3-和O K-edge X射线吸收光谱。目的是研究每个初级粒子中阳离子的局部相变和氧化态变化，以了解退火引起的材料降解机理。与Co L ₃相比和Mn L _3-边缘光谱，Ni L ₃-和O K边缘光谱显示出明显的变化，表现为退火时Ni离子的减少，尤其是从200到400°C时。Co和Mn离子的平均氧化数变化可忽略不计。另一方面，Ni离子显示出明显的变化：当平均颗粒区域时，在室温和200°C时，离子数为+3，在400°C下为+2.6。对于较小的粒子（直径约为100 nm），其值较小：在RT下为+2.8，在200°C下为+2.7，在400°C下为+2.2。在O K边缘光谱中，O 2p-Ni 3d杂交峰的强度降低，并且在400°C处出现NiO相关峰。这些观察结果表明，在退火温度达到400°C时，在400°C时，Ni离子主要被还原至较低的平均氧化数，并且Ni离子的还原主要发生在边缘区域和较小的颗粒中。