Lithium Isotope Effect Accompanying Chemical Insertion of Lithium into Graphite

Abstract

Lithiumwas chemically intercalated from 1-methoxybutane solution of lithiumand naphthalene into graphite and vice versa, and lithium isotope fractionation accompanying those intercalation and deintercalation processes was observed. 6Li was always preferentially fractionated into the graphite phase. The single-stage lithium isotope separation factor upon intercalation was about 1.023 at 25 ºC, nearly independent of the structure of the lithium-graphite intercalation compounds formed. A much smaller separation factor was observed for the deintercalation process, suggesting the existence of lithium sites (surface areas) other than the sites between graphene layers of the host graphite. Separation factor data were consistent with the following decreasing order of the 6Li-to-7Li reduced partition function ratio (RPFR): RPFR of 1-methoxybutane solution > RPFR of surface areas > RPFR of metal lithium > RPFR of graphene interlayer sites.