Microfocused X-ray Study on Precipitate Formation in the Separator Region of Nonaqueous Li-O2 Batteries

• Published in: ChemSusChem Vol. 5; no. 12; pp. 2421 - 2426
• Main Authors: Shui, Jiang-Lan, Okasinski, John S., Zhao, Dan, Almer, Jonathan D., Liu, Di-Jia
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.12.2012; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Diffraction; electrochemistry; energy conversion; lithium; sustainable chemistry; X-ray diffraction; X-rays
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201200555

Using a microfocused synchrotron X‐ray diffraction (μ‐XRD) method, we systematically investigated the distributions of insoluble lithium precipitates, which formed through electrolyte decomposition, separately in all three regions (cathode, separator, and anode) of failed batteries with a spatial resolution of 20 μm. We found unexpectedly that there was a significantly higher concentration (almost twice as much) of precipitates in the separator than in the cathode. SEM revealed that the precipitates grew on the separator fiber surface, ultimately obstructing the pores serving as the ion‐transport channel. A “refurbished” battery, which was composed of a spent separator from a failed battery, showed a much higher overpotential and shorter cycle life than that found in a new battery. Rejuvenation: Unexpectedly high concentrations of precipitates (mainly Li2CO3) with unique spatial and morphological distributions are detected in the separator region of Li–O2 batteries by microfocused XRD and SEM techniques, revealing the need for a stable electrolyte to minimize the deleterious effect of insoluble lithium salt (see picture).