Microfocused X-ray study on precipitate formation in the separator region of nonaqueous Li-O(2) batteries

Abstract

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.