Intercalation Mechanism of Lithium Ions into Graphite Layers Studied by Nuclear Magnetic Resonance and Impedance Experiments

The intercalation mechanism of lithium ions into graphite layers has been studied in organic solvents employing nuclear magnetic resonance (NMR) and electrochemical impedance spectroscopy (EIS) experiments. The lithium ions solvated with these solvent molecules were shown to intercalate into the graphite lattices by NMR experiments, which is also supported by the EIS results. Association constants of the complexes formed between lithium ions and solvent molecules have been determined by 7 Li NMR spectroscopic experiments. The 7 Li and 13 C solid-state NMR and EIS results obtained from fully charged graphite electrodes clearly indicate that solvent or crown ether molecules are cointercalated into the graphite layers with the lithium ions. We conclude from these results that solvent and/or crown ether molecules are dragged into the graphite layers by lithium ions when they are intercalated.