Surface anisotropy of spinel LiMn₂O₄ crystal is of significance for strengthening the lithium storage. In this work, we investigate the evolutions of surface orientations and oxygen vacancies in the LiMn₂O₄ cathode materials by the spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) technique. Firstly, the {111} lattice planes appear in the formed LiMn₂O₄ octahedra, and then the {110} and {001} crystal planes are observed in the subsequent truncated octahedral at a higher temperature or a longer annealing time. The LiMn₂O₄ crystals with dominated {111} and {110} planes and an appropriate amount of oxygen vacancies exhibits a superior cycling performance and rate performance, suggesting a synergistic effect of surface orientation and concentration of oxygen vacancies achieves an enhanced electrochemical performance. The introduction of oxygen vacancies can accelerate the diffusion of lithium-ions along {110} plane and strengthen the rate performance of LiMn₂O₄, as elucidated by the combination of Cs-STEM observation, X-ray photoelectronic spectra analysis and property measurements.

尖晶石型LiMn ₂ O ₄晶体的表面各向异性对于增强锂的储存具有重要意义。在这项工作中，我们通过球差校正扫描透射电子显微镜（Cs-STEM）技术研究了LiMn ₂ O ₄正极材料中表面取向和氧空位的演变。首先，{111}晶面出现在形成的LiMn ₂ O ₄八面体中，然后在更高温度或更长的退火时间下，在随后的截短的八面体中观察到{110}和{001}晶面。LiMn ₂ O ₄具有{111}和{110}面为主且适量的氧空位的晶体显示出优异的循环性能和速率性能，表明表面取向和氧空位浓度的协同效应实现了增强的电化学性能。结合Cs-STEM观察，X射线光电子能谱分析和性能测量可以看出，引入氧空位可以加速锂离子沿{110}面的扩散并增强LiMn ₂ O ₄的速率性能。