Atomic layer deposition (ALD) has emerged as a promising technology for applying ultrathin protective coatings on lithium-ion battery (LIB) cathode surfaces to improve their cycling stability. While there have been numerous reports evaluating the electrochemical performance of these surface-modified cathode materials, the chemical changes induced on the surface of the cathode materials upon ALD coating are not fully studied. This paper describes a systematic investigation to understand the interfacial changes of 12 different cathode materials upon coating with aluminum oxide (Al₂O₃) using trimethylaluminum (TMA) and H₂O, and aluminum fluoride (AlF₃) using TMA and hydrogen fluoride pyridine (HFPy). The surface composition of these cathode materials, which range from simple transition metal oxides (e.g., NiO and MnO) to complex multielement cathode materials (e.g., LiNi_xMn_1–x–yCo_yO₂, NMC), was studied via X-ray photoelectron spectroscopy (XPS). The XPS measurements reveal that the transition metals in the cathode materials undergo selective oxidation/reduction depending upon the nature of the precursor, the coating, and the cathode material. The ability to chemically modify the surface of cathode materials via vapor-phase precursor adsorption will open new avenues to systematically control the interface of the cathode materials in LIBs that are not possible by conventional coating methods.

中文翻译：

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阐明锂离子电池正极材料原子层沉积过程中的氧化还原行为

原子层沉积 (ALD) 已成为在锂离子电池 (LIB) 阴极表面应用超薄保护涂层以提高其循环稳定性的一种有前途的技术。虽然已经有许多评估这些表面改性正极材料的电化学性能的报道，但并未充分研究在 ALD 涂层上正极材料表面引起的化学变化。本文描述了系统的调查在与氧化铝（Al涂覆理解的12个不同的阴极材料的界面的变化₂ ö ₃使用三甲基铝（TMA））和H ₂ O，和氟化铝（ALF ₃) 使用 TMA 和氟化氢吡啶 (HFPy)。这些正极材料的表面组成，从简单的过渡金属氧化物（例如 NiO 和 MnO）到复杂的多元素正极材料（例如 LiNi _x Mn _{1– x – y} Co _y O ₂, NMC)，通过 X 射线光电子能谱 (XPS) 进行研究。XPS 测量表明，阴极材料中的过渡金属根据前体、涂层和阴极材料的性质进行选择性氧化/还原。通过气相前体吸附对正极材料表面进行化学改性的能力将为系统地控制 LIB 中正极材料的界面开辟新的途径，这是传统涂层方法无法实现的。