Lithium-ion conductors of the system LiCo1-xFexO2:: a first electrochemical investigation

LiCo1-xFexO2 compounds (0 less than or equal to x less than or equal to 1) with ordered rock salt structure of alpha -NaFeO2 type were prepared by ion exchange reaction in a molten eutectic mixture from the corresponding Na compounds. The Li compounds are investigated by galvanostatic and potentiostatic cycling experiments. The new form, ion-exchanged LiCoO2 (IE-Li-CoO2), is compared in its electrochemical behaviour with the known high temperature HT-LiCoO2. A different behaviour at cycling up to 4.8 V versus Li/Li+ is evidenced. Galvanostatic and potentiostatic cycling experiments were also carried out on the iron-containing compounds. Charge voltage increases and electrochemical capacity decreases with increasing iron content and reaches a low value for LiFeO2 with an iron content of x = 0.6. Reasons that may account for this behaviour are discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.