Synthesis of sulfur-rich copolymers
using the inverse vulcanization
reaction is a practical approach to modify the sulfur active material
for enhanced stability in Li–S batteries. However, to effectively
design such polymers, a thorough understanding of the underlying redox
mechanisms is critical. Here, we study electrochemical behavior of
sulfur-rich copolymers using in operando FTIR spectroscopy
with attenuated total reflection. We used sulfur-diisopropenylbenzene
copolymers [poly(S-co-DIB)] as the active material
in Li–S batteries and monitored the evolution of the C–S
peak position and cyclic changes in the S–S bond stretching
at different potentials during discharge and charge. Moreover, we
synthesized various copolymers with sulfur wt % of 80 and 30 wt %
and compared the electrochemical behavior and their corresponding
IR response during cyclic voltammetry sweep. Our results indicated
that the C–S bond in sulfur copolymers is not active in the
voltage window of Li–S batteries. Moreover, we showed that
the shift in the C–S peak position becomes smaller with increase
in the monomer wt %. In addition, the S–S stretching peak at
∼500 cm–1 diminishes when the sulfur wt %
is decreased from 80 to 30 wt %, highlighting a significant change
in electrochemical behavior of the copolymers.
The role of mesoporous carbon nanofibers as a sulfur host is highlighted for the efficient use of a biphenyl-4,4′-dithiol electrolyte additive in Li–S batteries.
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