Adaption of kinetics to solid electrolyte interphase layer formation and application to electrolyte-soluble reaction products

During the electrochemical lithiation of a carbon electrode, carbonate-based electrolytes react with the electrode surface and undergo reductive decomposition to form a solid electrolyte interphase (SEI) layer that passivates the surface of the carbon electrode. In addition, reduction of the electrolyte also results in the generation of electrolyte-soluble products. Structural similarities between the soluble and insoluble products provide an opportunity to examine the formation kinetics of the SEI layer through an analysis of the kinetic behavior of the soluble products. In this work, the electrolyte-soluble products generated by reductive decomposition of a baseline electrolyte were analyzed at different stages and at different hold times during the initial lithiation of an amorphous carbon electrode. A statistical regression analysis of that data was used to produce a representative lithiation experiment from which was calculated the potential-dependent formation rates for the soluble decomposition products. The predicted formation rate data was fitted using an adapted rate equation that accounts for the effect of the SEI layer to obtain estimated formation rate constants and redox potentials.