Observation of Lithium Isotope Effects Accompanying Electrochemical Release from Lithium Cobalt Oxide

Change in the lithium isotope composition in a lithium cobalt oxide (LiCoO 2 ) cathode for lithium ion secondary batteries accompanying the electrochemical lithium release from the cathode into an organic electrolyte solution was observed. The 7 Li/ 6 Li isotopic ratios of the electrodes after the release of 37.2 to 55:4% lithium were 1.018 to 1.033 times smaller than that before the release. This means that the heavier isotope, 7 Li, is preferentially transferred to the electrolyte solution.