New Opportunities for Lithium and Oxygen Spectroscopy in Working Batteries Using Inelastic X-ray Scattering

T. T. Fister, P. Fenter, M. Balasubramanian, N. Karan, M. Chan, and J. Greeley

Researchers at Argonne National Laboratory's Center for Electrochemical Energy Storage (CEES) are developing a new approach for studying lithium and oxygen spectroscopy in a working battery environment. Inelastic x-ray scattering (IXS) uses the energy lost by high energy x-rays to measure excited state spectroscopy from core electrons of light elements, such as a lithium. IXS is an element-specific probe of bonding and chemical structure. Unlike traditional methods (e.g., electron energy-loss spectroscopy [EELS] and x-ray absorption spectroscopy [XAS]), IXS uses high energy x-rays that can penetrate the in-situ conditions of a working battery.

IXS is particularly useful in the study of decomposition products in lithium-ion batteries. Early research within CEES has been devoted toward characterizing the well-known solid electrolyte interphase (SEI) compounds and lithium-oxygen reaction products. Both the lithium and oxygen IXS spectra are extremely sensitive to the differences of bonding and structure in these materials (Fig. 1).[1] Theoretical calculations systematically agree with the measured spectra and, in the case of lithium peroxide, were used to distinguish between two inconsistent crystal structures that had been proposed (Fig. 2).[2] Ongoing and future studies in CEES will build on these results to break down the composition of the SEI and to decouple decomposition reactions from actual discharge products in a Li-air battery.

Plot graphs showing (left) experimental and (right) theoretical lithium IXS from common SEI compounds plotted both as function of x-ray energy loss (x-axis) and momentum transfer (y-axis).

Fig. 1. Experimental (a) and theoretical (b) lithium IXS from common SEI compounds is plotted both as function of x-ray energy loss and momentum transfer (q). Such q-dependence is unique to IXS and was used to quantify the s-p hybridization of each material.

Plot graphs showing analogous IXS as measured on the left and as theoretically predicted by CEES researchers on the right.

Fig. 2. Analogous IXS was measured (a) and theoretically predicted (b) by members of CEES. Two candidate structures were calculated for lithium peroxide (Li2O2); the “Foppl” structure was found to systematically agree with Li and O IXS.

New Opportunities for Lithium and Oxygen Spectroscopy in Working Batteries Using Inelastic X-ray Scattering

T. T. Fister, P. Fenter, M. Balasubramanian, N. Karan, M. Chan, and J. Greeley

References