Lithium-oxygen batteries offer extremely attractive theoretical energy densities and therefore represent a rapidly emerging area of research. Our research has focused on developing electrocatalytic materials that can lower the charge hysteresis and potentially impact the nature of the discharge products. Specifically we have synthesized and characterized transition metal oxide catalyst, a�MnO2 that is most widely recognized charge electrocatalyst in nonaqueous Li-O2 cells. However, the discharge/charge reaction mechanisms at work and catalytic efficacy retain a large degree of uncertainty. Herein we report in situ high energy X-ray diffraction experiments performed on Li-O2 cells at the Advanced Photon Source (APS) of Argonne National Laboratory. Electrochemical cycling has been performed using three different electrolyte solvents, two different MnO2-based electrocatalysts, and varying XRD conditions. The data provides evidence that the crystal structure of a-MnO2 undergoes irreversible changes in lattice parameters and strain during the first electrochemical cycle. Expansion/contraction tends to be reversible during the subsequent cycles after stabilization of MnO2 was established in the first cycle by insertion of Li+. Insights into reversible changes of tunnel structure of MnO2, as determined by first principles density functional theory calculations, are used to provide a possible explanation for osme of the observed results.

In situ investigation of a-MnO<sub>2</sub> electrocatalyst during electrochemical cycling probed by high-energy synchrotron X-ray diffraction

246th National Meeting (2013)

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In situ investigation of a-MnO2 electrocatalyst during electrochemical cycling probed by high-energy synchrotron X-ray diffraction

In situ investigation of a-MnO₂ electrocatalyst during electrochemical cycling probed by high-energy synchrotron X-ray diffraction