Phase Relationships and Structural and Chemical Stabilities of Charged Li[sub 1−x]CoO[sub 2−δ] and Li[sub 1−x]Ni[sub 0.85]Co[sub 0.15]O[sub 2−δ] Cathodes

The structural and chemical stabilities of and cathodes have been investigated by chemically extracting lithium with an acetonitrile solution of The and systems maintain the initial O3-type structure, respectively, for and While begins to form a P3-type phase for begins to form a new O3-type phase, designated as phase, for The P3-type and the phases have smaller parameters than do the O3-type phase and oxygen contents of resulting in a loss of oxygen from the lattice for and respectively, for and The loss of oxygen is also confirmed for electrochemically charged samples. The formation of new phases with lower oxygen contents at different levels of charge, vs. for the two systems may play a role in limiting the practical capacities of the two systems (140 vs. 180 mAh/g). © 2003 The Electrochemical Society. All rights reserved.