The stability of solvents is critical
for the efficiency and cyclability
of rechargeable aprotic lithium–oxygen (Li–O2) batteries. Here, we report a combined spectroscopic study on the
stability of tetraglyme (G4), which is one of the most commonly used
solvents in Li–O2 batteries, against superoxide
(O2
–) during oxygen reduction reaction
(ORR). Based on sum-frequency generation spectroscopy characterization,
we found that ORR induces significantly irreversible structural changes
in G4 molecules on the electrode surface in an O2-saturated
Li+-free solution. In the Li+-containing solution,
however, reversibility for the structural change in G4 molecules is
primarily improved. Furthermore, infrared reflectance absorption spectroscopy
and surface-enhanced Raman spectroscopy measurements confirmed that
G4 is extremely unstable during ORR in the Li+-free G4
solution. In addition, several decomposition products have been identified
during ORR. On the other hand, the decomposition of G4 during ORR
is significantly suppressed when Li+ is included in the
solution. These results indicate that O2
– plays a crucial role in the cathodic decomposition of the G4 solvent
during ORR. The decomposition mechanism and the inhibitory effect
of Li+ are discussed based on spectroscopic observations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.