Studies on the cycle life of commercial lithium ion batteries during rapidcharge-discharge cycling

The impedance spectra of Li-ion batteries as a function of the number of ch arge-discharge cycles have been measured to study the cycle life of the com mercial Li-ion battery (prismatic Sanyo UF653467) during cycling at 1 C cha rge-discharge rate. The individual electrodes in the batteries have been ex amined using XRD, transmission electron microscopy (TEM) and SEM. The resul ts show that the Nyquist plots of commercial lithium-ion batteries are comp rised of an inductive tail at high frequency followed by two semicircles at medium and low frequencies. The size of the semicircles at low frequency i ncrease during cycling due to the increase in interfacial resistances of bo th cathode and anode. Thus, it may be used to predict the cycle life of the battery. XRD, TEM and SEM studies of the individual electrodes show that t he cation disorder, microcracks of the LiCoO2 particles in the cathode and the increase in thickness of the passive film on the anode due to the reduc tion of the electrolyte are linked to the capacity fade of the battery duri ng cycling. (C) 2001 Elsevier Science B.V. All rights reserved.