A New Kinetic Equation for Intercalation Electrodes

The kinetic equation used to predict the current being passed in an intercalation electrode depends on the overpotential and the composition of the intercalating species. The overpotential depends on the difference between the potential in the solid phase and in the solution phase, both of which depend on the composition of the intercalation species in the solid and solution phases, respectively. Furthermore, the overpotential depends on the local open circuit potential OCP of the intercalation electrode. Consequently, the kinetic equation and the OCP equation are coupled and must be written accordingly; that is, they must be written in a consistent way. In this work, a new kinetic equation, which is derived along with a thermodynamic OCP equation from the same reaction rate expression, is presented for intercalation electrodes. The thermodynamic equation is used to fit the OCP data of carbon MCMB-2528 and LiCoO2 electrodes. Comparison of the predictions from the new kinetic equation and the traditional Butler-Volmer equation used in the literature indicates that the new kinetic equation better describes the kinetic current–potential relationship for intercalation electrodes. © 2005 The Electrochemical Society. DOI: 10.1149/1.2142287 All rights reserved.