Influence of chemical prehistory on the phase formation and electrochemical performance of LiCoO2 materials

Thermal decomposition of freeze-dried salt precursors leads to the formation of lows temperature (LT) modification of LiCoO2 at 350-450 degreesC. The conversion rate of LT into high-temperature (HT) modification at 850 C depends greatly on the anion composition of salt precursors and correlates quite well with the appearance of second step at thermogravimetric curves of their thermal decomposition related to the solid-state reaction between Li2CO3 and Co3O4. Relationship between the appearance of Co3O4 and preferential formation of LT/HT polymorphs at reduced temperatures is discussed. The consecutive formation of LT and HT modifications during solid-state reaction between Li2CO3 and Co3O4 at 75800 C was observed: LiCoO2 cathode materials with the domination of LT polymorph demonstrated a better initial discharge capacity while a greater amount of HT modification is accompanied by better reversibility of charge-discharge processes. (C) 2003 Elsevier Science B.V All rights reserved.