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Calendar aging of lithium metal batteries, in which cells' components degrade internally due to chemical reactions while no current is being applied, is a relatively unstudied field. In this work, a model to predict calendar aging of lithium metal cells is developed using two sets of readily obtainable data: solid electrolyte interphase (SEI) layer composition (measured via X‐ray photoelectron spectroscopy) and SEI stability (measured as a degradation rate using a simple constant current–constant voltage charging protocol). Electrolyte properties such as volume and salt concentration are varied in order to determine their effect on SEI stability and composition, with subsequent impacts to calendar aging. Lower salt concentrations produce a solvent‐based, more soluble SEI, while the highest concentration produces a salt‐based, less soluble SEI. Higher electrolyte volumes promote dissolution of the SEI and thus decrease its stability. The model predicts that lithium metal would be the limiting factor in calendar aging, depleting long before the electrolyte does. Additionally, the relative composition of the electrolyte during aging is modeled and found to eventually converge to the same value independent of initial salt concentration.

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 LiFePO 4 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.

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