In Situ Measurements of Strains in Composite Battery Electrodes during Electrochemical Cycling
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The cyclic stress in lithium-ion battery electrodes induced by repeated charge and discharge cycles causes electrode degradation and fracture, resulting in reduced battery performance and lifetime. To investigate electrode mechanics as a function of electrochemical cycling, we utilize digital image correlation (DIC) to measure the strains that develop in lithium-ion battery electrodes during lithiation and delithiation processes. A composite graphite electrode is cycled galvanostatically (with constant current) in a custom battery cell while optical images of the electrode surface are captured in situ. The strain in the electrode is computed using an in-house DIC code. On average, an unconstrained composite graphite electrode expands 1.41 % during lithiation and contracts 1.33 % during delithiation. These strain values compare favorably with predictions based on the elastic properties of the composite electrode and the expansion of graphite-lithium intercalation compounds (G-LICs). The establishment of this experimental protocol will enable future studies of the relationship between electrode mechanics and battery performance.
KeywordsLithium-ion battery Graphite composite electrode Digital image correlation Electrode mechanics In situ strain measurement
This work was supported as part of the Center for Electrical Energy Storage - Tailored Interfaces, an Energy Frontier Research Center funded by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number 919 DOE ANL 9F-31921NS. The authors would like to acknowledge the Imaging Technology Group at the Beckman Institute for Advanced Science and Technology for use of microscopy equipment, Dr. Andrew Gewirth at the University of Illinois for insightful discussions, and Dr. Joseph Lyding for use of spot welding equipment. E. Jones was supported by the National Science Foundation Graduate Research Fellowship, and M. Silberstein was supported by the Arnold and Mabel Beckman Foundation Postdoctoral Fellowship.
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