The effects of different exchanging ions including Ag, Cu, and Sn on enhancing the photocatalytic activity of KNbTeO6 are investigated by means of experiments and calculations.
The formation of solid-electrolyte
interphase (SEI) layers which
results from the decomposition of organic solvents in the electrolyte
on the anode of sodium-ion batteries (SIBs) is crucial and must be
addressed to make SIBs well positioned in commercialization because
the SEI layer has profound effects on SIBs’ initial capacity
loss, life cycle, and safety. SEI properties such as chemical reactivity,
thermal reactivity, mechanical stability, and durability have an impact
on the overall performance of the batteries. Carbon-based anode materials
are commonly used in SIBs and usually contain many types of defects
and oxygenated functional groups. To gain insight into the influence
of oxygenated functional groups of carbon-based materials on solvent
decomposition mechanisms on the carbon surface, we perform density
functional theory (DFT) calculations to investigate the effect of
an epoxy group on decomposition mechanisms of ethylene carbonate (EC),
which is a common solvent used in SIBs. We find that the presence
of the epoxy group on the graphene surface diminishes EC decomposition
as evidenced by a significant increase of reaction energies and reaction
barriers. The EC decomposition mechanism yielding CO3 and
C2H4 is most kinetically favorable. A similar
effect of the epoxy group is also exhibited when the Na concentration
increases. However, the increase of Na concentration affects the reaction
barriers of each elementary step differently. More possible mechanisms
were found when the explicit solvent molecules in the first solvation
shell of Na are included. The additional pathway that an epoxy group
reacts with a solvent molecule is found to be the most energetically
favorable one. Thus, the epoxy group could promote EC decomposition
through these pathways.
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