Synthesis and Investigations on an O4-LiCoO[sub 2] Polytype

A polytype of has been synthesized through an ion-exchange reaction. By exchanging for ions from an -mixed cobaltite, a stacking is obtained. It alternatively combines O2- and polytypes and corresponds to an O4 stacking. The phase crystallizes in the hexagonal system with cell parameters and . As the O2 phase, the , is metastable; it transforms into the thermodynamically stable at around . The crystallographic data, the thermal properties, and the electrochemical behavior of this phase are presented.