Capacity Fading Machanism for Both Electrodes in Prismatic Lithium Ion Batteries with Long Calendar Life

lithium-ion batteries have been produced on a large scale and used extensively in the commercial mobile devices, typically in the so-called 3C (cellular phones, camcorders, and computers) industry since they have high working voltage, large capacity, and no memory effect compared with other candidates such as metal-hydride batteries and nickel-cadmium batteries . [ 1 ] . Besides, lithium ion batteries are also good candidates in applications for electric vehicles (EV) and hybrid electric vehicles (HEV) if both electrodes are well matched in kinetic characteristics at high charge and discharge current rates. The first commercial lithium ion battery developed by Sony in 1991 was composed of LiCoO 2 as the cathode and carbon as the anode. One-dimensional lithium ion transport path means lower energy barriers and high ionic conductivity which makes layered-structure materials such as LiCoO 2, LiNi x Co y M 1-x-y O 2 ( M = Mn, Al, etc ), and some carbon materials attractive to the researchers as well as the business developers although they suffer from structure changes during cycling.[2,3,4,5] For a specific cell, the cathode and anode may contribute differently to the capacity fading since both electrodes possess different electrochemical properties. However, most literatural reports focused on one single electrode, i.e. either the cathode or the anode, when discussing the capacity fading machanism of a specific cell. Here, we monitor the EOCV(end of charge voltage) and EODV (end of the discharge voltage ) of the both elecrodes in one cell in-situ to figure out the main fading factor of a LiNi 0.8 Co 0.15 Al 0.05 O 2 / graphite prismatic cell at different calendar stages during cycling at the rate of 0.2C. And we find that, during the former 100 cylces, the cathode material is the controlling factor contributing to the capacity fading while the lateral 100 cycles see the controlling factor changing from cathode to the anode [1] Abraham K M. Directions in secondary lithium battery research and development[J]. Electrochimica Acta, 1993, 38(9): 1233-1248. [2] Muto S, Sasano Y, Tatsumi K, et al. Capacity-Fading Mechanisms of LiNiO2-Based Lithium-Ion Batteries II. Diagnostic Analysis by Electron Microscopy and Spectroscopy[J]. Journal of The Electrochemical Society, 2009, 156(5): A371-A377. [3] Zheng S, Huang R, Makimura Y, et al. Microstructural Changes in LiNi0. 8Co0. 15Al0. 05O2 Positive Electrode Material during the First Cycle[J]. Journal of The Electrochemic