Cathode/Electrolyte Interface-Dependent Changes in Stress and Strain in Lithium Iron Phosphate Composite Cathodes. Issue 12 (1st January 2019)

• Record Type: Journal Article
• Authors: Bassett, Kimberly L.; Özgür Çapraz, Ö.; Özdogru, Bertan; Gewirth, Andrew A.; Sottos, Nancy R.
• Is Part Of: Journal of the Electrochemical Society. Volume 166:Issue 12(2019)
• Page Start: A2707
• Page End: A2714
• Publication Date: 2019-01-01
• Subjects: Batteries - Lithium -- Battery -- Strain -- Stress; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.1391912jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Dynamic interactions between electrode and electrolyte species during electrochemical cycling have an impact on the interfacial kinetics and mechanical stability of the electrode materials. In this study, we employ in-situ stress and strain measurements to investigate potential-dependent mechanical changes in lithium iron phosphate (LiFePO4 ) cathodes during cyclic voltammetry in LiPF6 and LiClO4 -containing electrolytes. Analysis of the stress and strain derivatives in LiClO4 –containing electrolytes exhibits single peaks during both lithiation and delithiation that coincide with LiFePO4 phase transformations. An additional feature in the stress and strain derivatives is observed in LiPF6 -containing electrolytes at the onset of the delithiation process. The current peak splitting in LiPF6 is larger than in LiClO4, and electrochemical impedance spectroscopy measurements show higher impedances in LiPF6 versus LiClO4 -containing electrolytes in lithiated LiFePO4 . The larger current peak splitting and higher impedance in LiPF6 electrolytes suggest the potential-dependent growth of a thick and resistive cathode/electrolyte interface (CEI) layer on LiFePO4 cathodes. We hypothesize that kinetic limitations in Li + transport through the CEI leads to additional stress and strain development at the electrode surface.