Raman Evidence for Late Stage Disproportionation in a Li–O2 Battery

• Published in: The journal of physical chemistry letters Vol. 5; no. 15; pp. 2705 - 2710
• Main Authors: Zhai, Dengyun, Wang, Hsien-Hau, Lau, Kah Chun, Gao, Jing, Redfern, Paul C, Kang, Feiyu, Li, Baohua, Indacochea, Ernesto, Das, Ujjal, Sun, Ho-Hyun, Sun, Ho-Jin, Amine, Khalil, Curtiss, Larry A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07.08.2014
• Subjects: Energy Conversion and Storage; Energy and Charge Transport; LiO2-like species; activated carbon; interface; spectroscopy; toroids
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/jz501323n

Raman spectroscopy is used to characterize the composition of toroids formed in an aprotic Li–O2 cell based on an activated carbon cathode. The trends in the Raman data as a function of discharge current density and charging cutoff voltage provide evidence that the toroids are made up of outer LiO2-like and inner Li2O2 regions, consistent with a disproportionation reaction occurring in the solid phase. The LiO2-like component is found to be associated with a new Raman peak identified in the carbon stretching region at ∼1505 cm–1, which appears only when the LiO2 peak at 1123 cm–1 is present. The new peak is assigned to distortion of the graphitic ring stretching due to coupling with the LiO2-like component based on density functional calculations. These new results on the LiO2-like component from Raman spectroscopy provide evidence that a late stage disproportionation mechanism can occur during discharge and add new understanding to the complexities of possible processes occurring in Li–O2 batteries.