Raman Evidence for Late Stage Disproportionation in a Li-O2 Battery.
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.
†Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Dengyun
D
Zhai
‡Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Hsien-Hau
HH
Wang
‡Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Kah Chun
KC
Lau
∥Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
Jing
J
Gao
†Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Paul C
PC
Redfern
§Engineering Laboratory for Next Generation Power and Energy Storage Batteries, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China.
Feiyu
F
Kang
§Engineering Laboratory for Next Generation Power and Energy Storage Batteries, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China.
Baohua
B
Li
∥Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
Ernesto
E
Indacochea
‡Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Ujjal
U
Das
‡Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Ho-Hyun
HH
Sun
‡Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Ho-Jin
HJ
Sun
†Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Khalil
K
Amine
‡Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Larry A
LA
Curtiss
LiO2-like species; activated carbon; interface; spectroscopy; toroids