Structure of Lithium Peroxide

Abstract

The reliable identification of lithium oxide species, especially lithium peroxide (Li 2 O 2 ), is of vital importance to the study of Li-air batteries. Previous X-ray diffraction studies of Li 2 O 2 resulted in the proposal of two disparate structures by Féher and Föppl. In this Letter, we assess these competing Li 2 O 2 structures using a combination of the following X-ray and first-principles techniques: (i) high-energy X-ray diffraction (XRD), (ii) comparisons of the measured nonresonant inelastic X-ray scattering (NIXS) spectra with those computed from first principles using the Bethe-Salpeter equation (BSE), and (iii) comparison of thermochemistry data with the formation enthalpies obtained from density functional theory (DFT) calculations using a hybrid functional. All three approaches result in the identification of Föppl’s proposal as the more appropriate structure for Li 2 O 2 . The measured and computed spectra and data presented in this Letter are useful as benchmarks for future characterization of Li 2 O 2 .