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Hexagonal to Cubic Spinel Transformation in Lithiated Cobalt Oxide

Gabrisch, Heike and Yazami, Rachid and Fultz, Brent (2004) Hexagonal to Cubic Spinel Transformation in Lithiated Cobalt Oxide. Journal of the Electrochemical Society, 151 (6). A891-A897. ISSN 0013-4651. http://resolver.caltech.edu/CaltechAUTHORS:GABjes04

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Abstract

A transmission electron microscopy (TEM) investigation was performed on LiCoO2 before and after it had been subjected to charge/discharge cycling in electrochemical cells, as well as on delithiated Li(1–x)CoO2 before and after thermal aging. Turbostratic disorder involving small rotations of the O-Co-O slabs was found in as-received material, and in material subjected to a few cycles. In LiCoO2 subjected to extensive charge/discharge cycling, it was found that increasing amounts of the trigonal O3 phase had transformed to H1-3 phase and to the cubic spinel phase. The transformation appears to initiate on the surfaces of trigonal crystals. The orientation relationship between the trigonal and spinel phases was determined from diffraction patterns to be {0001}trigonal parallel {111}cubic and <112-bar 0>trigonal parallel <110>cubic. The difference in unit cell dimensions leads to transformation stresses when spinel crystals are formed, and spallation of surface layers was observed. The formation of a spinel phase could suppress electrochemical performance of LiCoO2 cathodes in heavily cycled cells. Aging in the charged state also can alter particle surfaces and therefore the performance.


Item Type:Article
Additional Information:©2004 The Electrochemical Society. Manuscript submitted June 25, 2003; revised manuscript received January 10, 2004. Available electronically May 4, 2004. The authors thank Yasunori Ozawa for preparing the thermally aged specimen, Dr. Jason Graetz for preparing the chemically delithiated specimen, Enax Co. (Japan) for providing virgin and heavily cycled LiCoO2. This work was supported by the U.S. DOE through Basic Energy Sciences grant DE-FG03-00ER15035. California Institute of Technology assisted in meeting the publication costs of this article.
Subject Keywords:lithium compounds; solid-state phase transformations; ageing; internal stresses; electrochemistry; electrochemical electrodes; crystal orientation; transmission electron microscopy
Record Number:CaltechAUTHORS:GABjes04
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:GABjes04
Alternative URL:http://dx.doi.org/10.1149/1.1738677
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3039
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:11 May 2006
Last Modified:26 Dec 2012 08:52

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