Room-temperature sodium–sulfur batteries (RT-NaSBs)
are
the evolving candidates for large-scale stationary storage because
of their major benefits including double-electron redox process and
the natural abundance of sodium and sulfur resources. However, their
practical applications have been hampered by the poor cycling stability
due to the shuttle effect. This work aims at understanding the role
of heteroatom-functionalized nanoporous graphene (NPG) in preventing
the shuttle effect. The density functional theory method was used
to unravel important properties associated with polysulfide–NPG
interactions, including binding energy, electronic density of states,
charge transfer mechanism, and dissociative energy barriers of the
polysulfides. The findings reveal that oxygen- and nitrogen-functionalized
NPG can effectively present the shuttle effect by chemically binding
to sodium polysulfides (Na2S
n
) with a binding energy stronger than that between Na2S
n
and the common electrolyte solvents.
The chemical adsorption of Na2S
n
on the functionalized NPG causes a semiconductor-to-metal transition,
benefiting the electrical conductivity. Moreover, the functionalized
NPG lowers the Na2S dissociation energy to substantially
form NaS and Na, which serves as a catalyst for enhancing the redox
reactions between Na and S.