Multi-Scale Characterization Studies of Aged Li-Ion Large Format Cells for Improved Performance: An Overview

Among various electrical energy storage devices the recent advances in Li-ion battery technology has made this technology very promising for the electric vehicles. The advantage of these batteries is high energy and power density. Understanding the aging mechanisms of these batteries to improve the cycle life is critical for electrification of vehicles. Aging of the cells at the system level is quantified by the increase in internal resistance and drop in capacity. It is imperative to understand the degradation of the electrode materials of the battery related to these system level parameters. The degradation of the material is caused by several simultaneous physiochemical processes that occur within the batteries, which makes material characterization of the electrodes challenging. This review provides results of a systematic multi-scale characterization study to understand the degradation mechanisms in LiFePO4 cathode material. The study includes various techniques to understand the physical, morphological, electrical, chemical and structural changes in the cathode material. The review also presents an overview of the various modeling techniques used for Li-ion batteries. Simulation results of one of the models are presented using results of multi-scale characterization studies of the cathode material.