Lithium Isotope Effect Accompanying Electrochemical Intercalation of Lithium into Graphite

Abstract

Lithium has been electrochemically intercalated from a 1:2 (v/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1 M LiClO 4 into graphite, and the lithium isotope fractionation accompanying the intercalation was observed. The lighter isotope was preferentially fractionated into graphite. The single-stage lithium isotope separation factor ranged from 1.007 to 1.025 at 25 • C and depended little on the mole ratio of lithium to carbon of the lithium-graphite intercalation compounds (Li-GIC) formed. The separation factor inceased with the relative content of lithium. This dependence seems consistent with the existence of an equilibrium isotope effect between the solvated lithium ion in the EC/MEC electrolyte solution and the lithium in graphite, and with the formation of a solid electrolyte interfaces on graphite at the early stage of intercalation.

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

“…In passing, in this paper, we use technical terms such as anode, cathode, and charge and discharge reactions by following the conventions in the research field of lithium ion secondary batteries; lithium composite oxides are cathodes, graphite is the anode, and the charge reaction is defined as the reaction in which lithium is released from the lithium composite oxides cathode. We found that the lighter isotope 6 Li is preferentially inserted in graphite upon charge reactions at anodes from an organic electrolyte solution [3]. Our molecular orbital (MO) calculations assuming equilibrium isotope effects between the electrolyte and graphite phases support the experimental results in a qualitative fashion [8,9].…”

Observation of Lithium Isotope Effect Accompanying Electrochemical Insertion of Lithium into Zinc

“…Naturally occurring lithium consists of two stable isotopes, 6 Li and 7 Li, and they play important roles in nuclear science and industry. The largest demand for the isolated or enriched lighter isotope will be in DT fusion power reactors where lithium compounds rich in 6 Li will be required for the tritium breeder blanket.…”

Lithium Isotope Effects Accompanying Electrochemical Insertion of Lithium into Metal Oxides

“…Table 1 also includes the results of other non-electric current experiments using graphite electrodes made in the similar way described in the previous paper 5) and copper foils on which only the binder was daubed. In Fig.…”

“…2, is basically the same as the one used in experiments in the previous paper 5) where lithium was electrochemically intercalated into graphite. It was composed of a power supply (a Hokuto Denko Corporation HJ-201B battery charge/ discharge unit), a three-electrode cell (electrolytic cell) equipped with water jacket and a data acquisition unit consisting of an A/D converter and a personal computer.…”

“…Thus, if they show large lithium isotope effects, it may be possible to establish a system in which lithium isotopes are enriched by utilizing the charge-discharge cycles of lithium ion secondary batteries. In previous papers, 5,6) we investigated the lithium isotope effects accompanying electrochemical insertion of lithium from organic electrolyte solution to graphite and tin. As is well known, graphite is used as the cathode of lithium ion secondary batteries and tin is investigated as possible electrode material.…”