Quantification analysis and kinetic modeling of crosstalk reactions in lithium-ion batteries using a four-electrode cell

Crosstalk reactions in Li-ion batteries play an important role in the capacity fading caused by imbalance of the states-of-charge between positive and negative electrodes. A quantitative understanding of these reactions can enable estimation of battery life. Because crosstalk reactions are complex phenomena in which chemical species produced by a side reaction at one electrode react at the other electrode, a generator–collector-type electrochemical cell is required to investigate these reactions. Therefore, a new four-electrode cell was constructed in this study, in which oxidative decomposition of an electrolyte was achieved by constant-current electrolysis at one Al2O3 electrode, and the reduction of the generated oxidants was detected by cyclic voltammetry (CV) at the other Al2O3 electrode. CV indicated that the cathodic current due to the crosstalk reaction increased during electrolysis, and that two cathodic peaks appeared at 1.3 and 1.8 V. The cathodic current eventually stabilized and decreased to zero after electrolysis. A kinetic equation that expressed the crosstalk-reaction-induced cathodic current provided a decent fit to the observed current via kinetic parameters. This kinetic equation is remarkably useful for quantitatively understanding the electrochemical nature of crosstalk reactions and can help predict the side-reaction currents in actual batteries through the derived kinetic parameters, which can determine battery life.