Measurement of Side-Reaction Currents in Lithium-Ion Batteries with Different Capacity Ratios

Abstract

To extend the lifetime of lithium-ion batteries, determining the side-reaction current (I_SR) is essential because capacity fading is mainly caused by the state-of-charge imbalances of positive and negative electrodes. Among the three types of I_SR (intrinsic, additional, and actual), the additional I_SR resulting from crosstalk reactions exhibits complex behavior owing to its dependence on the opposing electrode. In this study, the effect of the opposing electrode on additional I_SR was examined by measuring the three types of I_SR in Li[Li_1/3Ti_5/3]O₄/Li[Li_0.1Al_0.1Mn_1.8]O₄ cells with different capacity ratios of the positive and negative electrodes. The results indicate that additional I_SR correlates with the weight of the opposing electrode, whereas intrinsic I_SR depends on the weight of each electrode. These findings suggest that additional I_SR is closely related to the amounts of side-reaction products generated at the opposing electrode owing to the intrinsic I_SR. The dependence of crosstalk reactions on the concentration of side-reaction products indicates that these concentrations must be considered to extend battery life by adjusting the actual I_SR.