Factors influencing the chemical lithium extraction rate from layered LiNi1-y-zCoyMnzO2 cathodes

The rate of chemical lithium extraction from the layered LiNi1-y-zCoyMnzO2 has been investigated with the oxidizer NO2BF4 in acetonitrile medium. While all the lithium could be extracted in 30 min from the cobalt-rich LiNi1-yCoyO2 (0.5 less than or equal to y less than or equal to 1), it takes a longer time (6-48 h) to extract all the lithium from the nickel-rich LiNi1-yCoyO2 (0 less than or equal to y less than or equal to 0.5) and LiNi1-yMnyO2 (y = 0.25 and 0.5). In the case of LiNi0.5-0.5yMn0.5-0.5yCoyO2 samples, the time required to extract all the lithium decreases with increasing Co content. The slow lithium extraction rate in the nickel-rich LiNi1-yCoyO2, LiNi1-yMnzO2, and cobalt-poor LiNi0.5-0.5yMn0.5-0.5yCoyO2 systems is attributed to a considerable cation disorder as indicated by the Rietveld analysis of the X-ray diffraction data. In the LiNi1-yMnyO2 and cobalt-poor LiNi0.5-0.5yMn0.5-0.5yCoyO2 systems, a larger inter-slab space for lithium in the structure is found to help the lithium extraction. (C) 2004 Elsevier B.V. All rights reserved.