Lithium Isotope Effects upon Electrochemical Release from Lithium Cobalt Oxide to Non-Lithium Electrolyte Solution

Lithium was electrochemically released from a lithium cobalt oxide (LiCoO₂) cathode to an ethylene carbonate-based organic electrolyte solution containing no lithium ions, and the change in the lithium isotope composition of the cathode was measured. The ⁷Li/⁶Li isotopic ratio of the electrode was practically unchanged before and after the 45%–62% lithium release, which meant that the lithium release accompanied no isotope preference. This result is quite contrastive to the previous one; when lithium was released to an organic electrolyte solution containing lithium ions, the ⁷Li/⁶Li ratio of the cathode became 1.018 to 1.033 times smaller than that before the release. It was induced that the kind of electrolyte solution controlled the attainment of the lithium isotope exchange equilibrium between the cathode and the electrolyte solution.