Bulk-sensitive characterization of the discharged products in Li-O ₂ batteries by nonresonant inelastic X-ray scattering

Understanding the nature of discharged products is critical to identifying suitable electrolyte systems for Li-O ₂ batteries. We have employed nonresonant inelastic X-ray scattering (NIXS), which is a hard X-ray photon-in photon-out technique to monitor low energy core-shell excitations and to obtain bulk sensitive information on the solid discharged products in Li-O ₂ batteries using various electrolyte solvent/salt combinations. NIXS measurements were performed on cathodes after discharging the Li-O ₂ cells using low discharge current (∼25 mA/g of carbon). NIXS results reveal that, even in cells containing current state-of-the-art electrolytes, the oxygen in the discharged products is bound predominantly to species other than a peroxide or lithia. This finding shows that electrolyte decomposition is a significant pathway during discharge of Li-O ₂ batteries using ether and oligoether substituted silane based electrolytes.