Operando and in situ APXPS investigation of the atomic layer deposition of a metal oxide coating on a Ni-rich cathode

The expansion of the electric vehicle industry is driving increased demand for lithium-ion batteries (LIBs), which in turn creates challenges in material availability and waste management that more durable LIBs could address. Electrode surface coating helps extend LIB lifespan, with atomic layered deposition (ALD) as the preferred method due to its precise thickness control and ability to coat various substrates. However, despite the extensive research on cathode modification via ALD, there is limited work on understanding the reaction mechanisms between precursors and unconventional substrates, such as composite electrodes. In this study, synchrotron-based ambient pressure X-ray photoelectron spectroscopy (APXPS) is employed to investigate the surface evolution of a LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathode during the initial stages of TiO 2 formation via ALD. The operando and in situ APXPS data suggest that a hydroxylation step is essential for the initiation of TiO 2 growth on a NMC811 composite electrode. The persistent appearance of –CF 2 peaks implies that the deposition does not occur on the polymer binder. The findings of this study offer a deeper understanding of the surface chemistry during ALD half-cycles on cathode substrates, aiding in the optimization of the deposition process. • Synchrotron-based operando and in situ APXPS of TiO 2 ALD on NMC811 electrode. • Insights into NMC811 and TTIP/H 2 O precursor reactions during ALD-half cycles. • Hydroxyl-functionalized surfaces are critical for TiO 2 growth on NMC811.