3 ELECTRODE ELECTROCHEMICAL VOLTAGE SPECTROSCOPY (TEVS) - EVALUATION OF A MODEL LITHIUM ION SYSTEM

Lithium ion cells incorporate two intercalation type electrodes which each demonstrate voltage profiles which are directly dependent on their relative states-of-charge. A new electrochemical technique, Three Electrode Electrochemical Voltage Spectroscopy (TEVS) is described which allows detailed information to be derived for both intercalation electrodes within a single experiment. Only minor modifications to conventional two electrode electrochemical cell designs are necessary for implementation of this technique. During the experimental procedure, both the pseudo-open circuit voltage (ocv) profiles and the corresponding differential capacity plots for the two electrodes can be collected. A model lithium ion cell, namely the Li1-xMn2O4/Li1+xMn2O4 system, has been initially investigated using the new technique. This system can be cycled utilizing the approximate 3V and 4V vs. Li/Li+ voltage ranges. Around x = 0.68 in Li1-xMn2O4 and Li1+xMn2O4 was cycled in the cell under the prevailing TEVS test conditions. The collected TEVS data is directly compared to previously reported findings on two-electrode cells which utilized lithium counter electrodes.