Studies of Ozone-Sensitized Low- and High-Temperature Oxidations of Diethyl Carbonate

Diethyl
carbonate (DEC) oxidation with different levels of O3 addition
was performed in an atmospheric laminar flow reactor
from 400 to 850 K. Experimental results showed that, without O3 addition, the oxidation of DEC began from 650 K with no low-temperature
reactivity, while with O3 addition the low-temperature
chemistry of DEC was observed from 450 K. A DEC/O3 kinetic
model was developed, and the model predictions agreed with the experimental
data reasonably well with a slight overprediction of DEC oxidation
between 550 and 750 K. The low-temperature chemistry of DEC with O3 addition was described in the reaction pathway of DEC. It
was found that O3 assisted the low-temperature oxidation
of DEC mainly through the production of the active O: atom instead
of the direct reaction with the fuel molecule. The present work indicated
that the Li-ion battery degradation at 400–500 K might result
from the low-temperature chemistry of DEC with active oxygen supplies
from the cathode metal oxide materials or from singlet O2 during the battery discharge process. This article used O3 to mimic the oxidizing environment in the Li-ion battery by providing
active atomic oxygen. It provided insights into the chemically sensitized
gas-phase low-temperature chemistry of DEC and explained the mechanism
of battery degradation involving the low-temperature oxidation at
the electrolyte solvent and the cathode interface from 400 to 500
K.