An autocatalytic mechanism for the reaction of LixCoO2 in electrolyte at elevated temperature

Accelerating rate calorimetry (ARC) is used to study the reaction between LixCoO2 and electrolyte. The reacttion is found to be autocatalytic, that is, the reaction initially proceeds slowly, but accelerates rapidly as reaction products that promote the reaction itself are formed. An autocatalytic model of the reaction kinetics is used to reproduce accurately the experimental. self-heating rate vs. temperature results for samples of LixCoO2 charged to 4.1, 4.2, and 4.3 V. Two different samples of LixCoO2 were studied, and one was found to be much more reactive than the other, showing that the choice of electrode material is an important consideration in the manufacture of practical cells. The power vs. time or power vs. temperature generated by the reaction between LixCoO2 and electrolyte can also be calculated using the autocatalytic model, and compared to differential scanning calorimetry experiments, for example. These expressions can also be used to predict the heat evolved due to cathode-electrolyte reactions in practical Li-ion cells exposed to high temperature. Coupled with similar models for the anode-electrolyte reaction kinetics (that we have presented earlier), the response of full Li-ion cells to thermal abuse can be predicted accurately. (C) 2000 The Electrochemical Society. S0013-4651(99)08-045-3. Ail rights reserved.