Molecular structures of polymer/sulfur composites for lithium–sulfur batteries with long cycle life
2013
Xiao, Lifen | Cao, Yuliang | Xiao, Jie | Schwenzer, B. (Birgit) | Engelhard, Mark H. | Saraf, Laxmikant V. | Nie, Zimin | Exarhos, Gregory J. | Liu, Jun
Vulcanized polyaniline/sulfur (SPANI/S) nanostructures were investigated for Li–S battery applications, but the detailed molecular structures of such composites have not been fully illustrated. In this paper, we synthesize SPANI/S composites with different S content in a nanorod configuration. FTIR, Raman, XPS, XRD, SEM and elemental analysis methods are used to characterize the molecular structure of the materials. We provide clear evidence that a portion of S was grafted on PANI during heating and connected the PANI chains with disulfide bonds to form a crosslinked network and the rest of S was encapsulated within it. Polysulfides and elementary S nanoparticles are physically trapped inside the polymer network and are not chemically bound to the polymer. The performance of the composites is further improved by reducing the particle size. After 200 cycles, a capacity retention rate of 80.4, 80.5, 87.6, and 90.0% is observed at 0.1, 0.2, 0.5 and 1 C respectively in the SPANI/S composite with 55% S content.
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