Impact of Initial Li Content on Kinetics and Stabilities of Layered Li1+x(Ni0.33Mn0.33Co0.33)1-xO₂

Structure, morphology, and performance of Li 1+ x (Ni 0.33 Mn 0.33 Co 0.33 ) 1- x O 2 cathode materials with stoichiometric ( x = 0) and excess Li ( x = 0.14) were compared on micron-sized, well-formed single crystals. The additional Li in the fresh overlithiated oxide facilitated the formation of a superstructure with a hex × a hex × c hex unit cells, decreased the cell volume change, and improved the initial O3 phase stability upon lithium extraction. Slower kinetics were observed at low Li content where oxide activation dominated, a process that induced significant structure rearrangements and particle damages. For the first time, morphological evaluation during delithiation was well captured on the micron-sized single crystals. An irreversible activation plateau at 4.4 V was only observed during the first charge of the overlithiated crystals. The oxide's higher discharge capacity and better cycling stability between 2.5 and 4.8 V were attributed to its enhanced O3 phase stability upon deep Li extraction.