Measurement of the electrochemical oxidation of organic electrolytes used in lithium batteries by microelectrode

The electrochemical oxidation of organic electrolytes was investigated usin g microelectrodes. The electrolytes we used were LiClO4/(EC + DEC) and LiPF 6(EC + DEC) which are widely employed in lithium ion batteries. We measured the oxidation current by the potential step method (the potential is maint ained until the current becomes constant) at potentials ranging from 4.5 to 5.5 V versus Li/Li+ The current density-potential relationship of the oxid ation of 1 M LiClO4/(EC + DEC) electrolyte on the carbon microelectrode sho ws good reproducibility and roughly fits exponential lines. We obtained a s imilar relationship regardless of the material and size of the microelectro des. Therefore, the electrochemical oxidation of organic electrolytes can b e compared using this method. The different oxidation behavior of LiPF6 sal t and LiClO4 salt electrolyte suggests that the salt anions may initiate th e electrolyte oxidation. (C) 2001 Elsevier Science B.V. All rights reserved .