Diagnostic studies on lithium-ion cells at Argonne National Laboratory: an overview

High-power and high-energy lithium-ion cells are being studied at Argonne National Laboratory (Argonne) as part of the U.S. Department of Energy's FreedomCar and Vehicle Technologies (FCVT) program. Cells ranging in capacity from 1 mAh to 1Ah, and containing a variety of electrodes and electrolytes, are examined to determine suitable material combinations that will meet and exceed the FCVT performance, cost, and safety targets. In this article, accelerated aging of 18650-type cells, and characterization of components harvested from these cells, is described. Several techniques that include electrochemical measurements, analytical electron microscopy, and x-ray spectroscopy were used to study the various cell components. Data from these studies were used to identify the most likely contributors to property degradation and determine mechanisms responsible for cell capacity fade and impedance rise.