An accelerated calendar and cycle life study of Li-ion cells

The accelerated calendar and cycle life of lithium-ion cells was studied. U seful cell life was strongly affected by temperature, time, state-of-charge (SOC) and change in state-of-charge (Delta SOC). In calendar life experime nts, useful cell life was strongly affected by temperature and time. Temper ature accelerated cell performance degradation. The rates of area specific impedance (ASI) increase and power fade followed simple laws based on a pow er of time and Arrhenius, kinetics. The data have been modeled using these two concepts and the calculated data agree well with the experimental value s. The calendar life ASI increase and power fade data follow (time)(1/2) kinet ics. This behavior may be due to solid electrolyte interface layer growth. From the cycle life experiments, the ASI increase data follow (time)(1/2) k inetics also, but there is an apparent change in overall power fade mechani sm when going from 3 to 6% Delta SOC. Here, the power of time drops to belo w 1/2, which indicates that the power fade mechanism is more complex than l ayer growth. (C) 2001 Elsevier Science B.V. All rights reserved.