Electrochemistry-Mechanics Coupling in Intercalation Electrodes

Diffusion induced stress, due to repeated intercalation/deintercalation of lithium during cycling, causes mechanical degradation in graphite active particles used as an anode in lithium-ion batteries. The microcracks formed in the active particles hinder diffusion of lithium. On the other hand, flow of electrolyte through the accessible microcracks in the active particles leads to additional electrochemically active surfaces and effectively reduces the diffusion length. In this work, stochastic modeling of electrochemistry-mechanics interaction is presented which introduces the influence of electrochemically active microcracks on electrochemical reactions. Enhanced electrochemically active surface area further results in the formation of solid electrolyte interphase (SEI), which decreases the cell capacity due to the consumption of cyclable lithium. This stochastic model successfully predicts the formation of non-uniform and spanning cracks in active particles, which are typically observed in scanning electron micrographs. The impact of coupled electrochemical and mechanical interaction in graphite active particles on capacity fade is elucidated.