Lithium–sulfur
(Li–S) batteries have been widely
considered as the next-generation energy storage system but hindered
by the soluble polysulfide intermediate-induced shuttle effect. Doping
heteroatoms was confirmed to enhance the affinity of polysulfide and
the carbon host, release the shuttle effect, and improve the battery
performance. To enhance the Lewis acidity and reinforce the interaction
between polysulfide and the carbon skeleton, a novel covalent triazine
framework (CTFO) was designed and fabricated by copolymerizing 2,4,6-triphenoxy-s-triazine and 2,4,6-trichloro-1,3,5-triazine through Friedel–Crafts
alkylation. Polymerization led to triazine substitution on the para-position
of the phenoxy groups of 2,4,6-triphenoxy-triazine and produced two-dimensional
three-connected honeycomb nanosheets. These nanosheets were confirmed
to exhibit packing in the AB style through the intralayer π–π
interaction to form a three-dimensional layered network with micropores
of 0.5 nm. The practical and simulated results manifested the enhanced
polysulfide capture capability due to the abundant N and O heteroatoms
in CTFO. The unique porous polar network endowed CTFO with improved
Li–S battery performance with high Coulombic efficiency, rate
capability, and cycling stability. The S@CTFO cathode delivered an
initial discharge capacity of 791 mAh g–1 at 1C
and retained a residual capacity of 512 mAh g–1 after
300 charge–discharge cycles with an attenuation rate of 0.117%.
The present results confirmed that multiple heteroatom doping enhances
the interaction between the porous polar CTF skeleton and polysulfide
intermediates to improve the Li–S battery performance.