Conformal coating of nm-thick Al₂O₃ layers on electrode material is an effective strategy for improving the longevity of rechargeable batteries. However, solid understanding of how and why surface coatings work the way they do has yet to be established. In this article, we report on low-temperature atomic layer deposition (ALD) of Al₂O₃ on practical, ready-to-use composite cathodes of NCM622 (60% Ni), a technologically important material for lithium-ion battery applications. Capacity retention and performance of Al₂O₃-coated cathodes (≤10 ALD growth cycles) are significantly improved over uncoated NCM622 reference cathodes, even under moderate cycling conditions. Notably, the Al₂O₃ surface shell is preserved after cycling in full-cell configuration for 1400 cycles as revealed by advanced electron microscopy and elemental mapping. While there are no significant differences in terms of bulk lattice structure and transition-metal leaching among the coated and uncoated NCM622 materials, the surface of the latter is found to be corroded to a much greater extent. In particular, detachment of active material from the secondary particles and side reactions with the electrolyte appear to lower the electrochemical activity, thereby leading to accelerated capacity degradation.

在电极材料上共形涂覆nm厚的Al ₂ O ₃层是提高可充电电池寿命的有效策略。然而，尚未建立对表面涂层如何以及为什么起作用的扎实理解。在本文中，我们报告了在实用且可立即使用的NCM622（60％Ni）复合阴极上Al ₂ O ₃的低温原子层沉积（ALD），NCM622是锂离子电池应用中的技术上重要的材料。即使在适度的循环条件下，与未涂层的NCM622参比阴极相比，Al ₂ O ₃涂层的阴极（≤10 ALD生长周期）的容量保持率和性能也得到了显着改善。值得注意的是，铝如高级电子显微镜和元素图谱所示，以全细胞配置循环1400个循环后，将₂ O ₃表面壳保存下来。尽管在涂覆和未涂覆的NCM622材料之间，在体晶格结构和过渡金属浸出方面没有显着差异，但发现后者的表面受到了更大程度的腐蚀。特别地，活性物质与次级颗粒的分离以及与电解质的副反应似乎降低了电化学活性，从而导致加速的容量降低。