Microstructural stability of nanocrystalline LiCo O2 in lithium thin-film batteries under high-voltage cycling

Abstract

The microstructural stability of nanocrystalline LiCo O2 cathodes in rechargeable thin-film batteries after high-voltage cycling was investigated by transmission electron microscopy. It was found that besides the trigonal- LiCo O2 phase, there are two other phases of Lix Co O2, spinel and H1-3, that form inside the nanocrystalline cathode after electrochemical cycling (charge cutoff voltages 4.5 V). The formation of the aforementioned secondary phases in the cathode material is irreversible and leads to capacity loss in lithium thin-film batteries. © 2007 American Institute of Physics.