Can Atomic Layer Deposition of Surface Coatings Suppress Structural Fatigue in Ni-Rich Lithium-Ion Battery Cathodes?

Abstract

The high-voltage (more than 4.2 V versus graphite) electrochemical degradation of layered nickel-rich lithium 3d transition metal oxide (LiNi_{x}Mn_{y}Co_{1−x−y}O_{2}, where x ≥ 0.6) cathodes currently limits their practical energy densities. The degradation primarily stems from surface oxygen loss and its consequent effects, which leads to rapid capacity fade and voltage hysteresis. Addressing this necessitates not only novel material engineering approaches but also a deeper comprehension of how it leads to performance enhancement. Here, using in-house operando x-ray diffraction studies of ∼3.4 mA h/cm^{2} polycrystalline LiNi_{0.8}Mn_{0.1}Co_{0.1}O_{2} (NMC811)-graphite pilot-line-built pouch cells cycled between 3 and 4.4 V, we show that particle atomic layer deposition (ALD) of an aluminum phosphate surface layer on the NMC811 cathode particles suppresses the formation of electrochemically fatigued phases within the cathode bulk, leading to notable performance enhancements. This study contributes to our growing understanding of how scalable ALD processing is essential for stabilizing the high-voltage performance of Ni-rich layered oxide cathodes.