The Reaction of Charged Cathodes with Nonaqueous Solvents and Electrolytes: I. Li[sub 0.5]CoO[sub 2]

The thermal decomposition of was studied by accelerating rate calorimetry and X-ray diffraction. Oxygen loss from the material according to the reaction occurs at temperatures above By contrast, the reaction of with ethylene carbonate:diethyl carbonate (EC:DEC) solvent initiates at temperatures as low as which is much lower than the decomposition temperature of itself, and reduction to CoO occurs. We believe that this is caused by the reducing power of the solvent. The heat generated by this reaction is consistent with that expected from the combustion of the solvent by the oxygen liberated during the decomposition of the solid. The reaction of with electrolyte was also studied. As the salt concentration is increased, the solvent combustion reaction is suppressed, suggesting that increased concentration can slow the cathode/electrolyte reaction in practical Li-ion cells under conditions of electrical or mechanical abuse. © 2001 The Electrochemical Society. All rights reserved.