The entropy and enthalpy of lithium intercalation into graphite

Measurements of open-circuit voltages (OCV) in half-cells with graphite electrodes were used to obtain the entropy and enthalpy of lithium intercalation into graphite. At low lithium concentrations, the entropy included a component identified as an entropy of mixing. The entropy of intercalation changed sign at higher lithium concentrations, suggesting a second component. Raman spectroscopy and prior work on inelastic neutron scattering indicate that this additional entropy is vibrational in origin. The enthalpy of intercalation into graphite is consistently negative, but becomes less so with higher lithium concentrations. (C) 2003 Elsevier Science B.V. All rights reserved.