The effects of decomposition products of electrolytes on the thermal stability of bare and TiO2-coated delithiated Li1-xNi0.8Co0.2O2 cathode materials

In this work, the effects of decomposition products of electrolytes on the thermal stability of bare and TiO2-coated Li1-xNi0.8Co0.2O2 (1 > x >= 0) cathode material have been investigated by means of thermoanalytical, thermokinetic and temperature-programmed desorption-mass spectroscopy (TPD-MS) techniques. It is shown clearly that the decomposition products of the electrolytes such as carboxylates have distinctive effects on the thermal stability of the electrode materials. Firstly, the thermoanalytical and TPD-MS results indicate that surface coating can suppress the amount of oxygen release from the delithiated cathode material. The thermokinetic analytical results show that the reaction of oxygen release (i.e. oxygen loss) from delithiated Li1-xNi0.8Co0.2O2 material can be promoted by carboxylate salts supported on the electrode surface due to the decrease of initiated activation energy E-a of the reaction. Finally, the amount of carboxylate salts and length of carbon chains in carboxylates have different promotional effects on the thermal properties of the electrode materials. (c) 2006 Published by Elsevier Ltd.