Nature of the Oxygen-Loss-Induced Rocksalt Layer and Its Impact on Capacity Fade in Ni-Rich Layered Oxide Cathodes
Nickil Shah, Galo J. Páez Fajardo, Hrishit Banerjee, Gaurav C. Pandey, Ashok S. Menon, Muhammad Ans, Veronika Majherova, Gerard Bree, Satish Bolloju, David C. Grinter, Pilar Ferrer, P. Thakur, Tien-Lin Lee, Melanie Loveridge, Andrew J. Morris, Clare P. Grey, Louis F. J. Piper
Abstract
High Resolution Image Download MS PowerPoint Slide In Ni-rich layered oxide cathodes, cycling above the oxygen-loss threshold voltage (∼4.3 V vs Li + /Li) promotes structural transformations at the cathode surface. These transformations can result in various thermodynamically favorable rocksalt-like (RSL) structures (NiO, NiO x, and/or Li y Ni z O) that have different Li + transport properties. Elucidating the precise phase type in the RSL can help determine design strategies to improve Li + kinetics and identify design rules to suppress capacity fade in Ni-rich cathodes. This study utilizes surface-sensitive X-ray absorption spectroscopy in combination with first-principles simulations and distinguishes the layered oxide spectroscopic features from those of surface-reduced layers of pure NiO and Li x Ni 1– x O. The transport of lithium ions through this oxygen-loss-induced surface-reconstructed layer is studied with operando X-ray diffraction in a pouch cell as a function of cycling aging and constant voltage protocols.