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

To extend the lifetime of lithium-ion batteries, determining the side-reaction current (ISR) is essential because capacity fading is mainly caused by the state-of-charge imbalances of positive and negative electrodes. Among the three types of ISR (intrinsic, additional, and actual), the additional ISR 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 ISR was examined by measuring the three types of ISR in Li[Li1/3Ti5/3]O4/Li[Li0.1Al0.1Mn1.8]O4 cells with different capacity ratios of the positive and negative electrodes. The results indicate that additional ISR correlates with the weight of the opposing electrode, whereas intrinsic ISR depends on the weight of each electrode. These findings suggest that additional ISR is closely related to the amounts of side-reaction products generated at the opposing electrode owing to the intrinsic ISR. 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 ISR.