Quantifying lithium concentration gradients in the graphite electrode of Li-ion cells using operando energy dispersive X-ray diffraction. Issue 2 (9th January 2019)

• Record Type: Journal Article
• Authors: Yao, Koffi P. C.; Okasinski, John S.; Kalaga, Kaushik; Shkrob, Ilya A.; Abraham, Daniel P.
• Is Part Of: Energy & environmental science. Volume 12:Issue 2(2019)
• Page Start: 656
• Page End: 665
• Publication Date: 2019-01-09
• Subjects: Energy conversion -- Periodicals; Fuel switching -- Periodicals; Environmental sciences -- Periodicals; Environmental chemistry -- Periodicals; 333.79
• DOI: 10.1039/c8ee02373e
• Languages: English
• ISSNs: 1754-5692

Abstract

Abstract : Spatial distribution of lithium cations in the graphite electrode of a lithium-ion battery is quantified using operando energy dispersive X-ray diffraction. Abstract : Safe, fast, and energy efficient cycling of lithium ion batteries is desired in many practical applications. However, modeling studies predict steep Li + ion gradients in the electrodes during cycling at the higher currents. Such gradients introduce heterogeneities in the electrodes, which make it difficult to predict cell lifetimes as different portions of the cell age at different rates. There is a dearth of experimental methods to probe these concentration gradients across the depth of the electrode. Here we use spatially resolved energy dispersive X-ray diffraction to obtain a "movie" of lithiation and delithiation in different sections of the cell and quantify lithium gradients that develop in a porous graphite electrode during cycling at a 1C rate. Inhomogeneity in the total Li content, and in the individual ordered Li x C6 phases formed during lithium insertion into (and extraction from) the graphite, has been observed in an operando fashion. The complex dynamics of lithium-staging in graphite with the distinct front propagation of phase changes have been characterized and new features of these dynamics are highlighted here. As large Li + ion gradients contribute to cell polarization, our results suggest that Li plating conditions can be met near the graphite electrode surface, even when the cell is charged at a moderate (1C) rate.