Understanding redox mechanisms as well as interactions between redox species and electrolyte is critical for rational design of electrolyte/cathode systems for Li−S batteries. Here, we demonstrate in situ FT-IR with attenuated total reflection (ATR) to monitor both polysulfide (PS) speciation (S x 2− , 2 ≤ x ≤ 8) and triflate anion (electrolyte) coordination state while simultaneously discharging/charging a full battery coin cell. We report the concentration of various PS species as a function of voltage during cell discharge. In addition, we found that molecular-level changes occurred in the electrolyte salt anion in response to PS speciation. During discharge, PS dissolution increases total solute concentration, inducing anion interactions between low coordination state complexes ion pairs and free ionsto form aggregate complexes. Under fast cyclic voltammetry sweep, less progressive formation of all PSs, due to diffusion limitations, resulted in a higher concentration of aggregates and PSs even upon completion of discharge. This new application of in situ FT-IR offers direct insight into dynamic interactions between electrolyte salt and polysulfides fundamental in developing Li−S systems.
We demonstrate a facile methodology to fabricate binder-free porous carbon nanofiber electrodes for room temperature ionic-liquid supercapacitors. The device provides an energy density of 80 W h kg(-1) based on the mass of two electrodes while retaining the high rate capability of supercapacitors with near-ideal CV curves at a high scan rate of 200 mV s(-1).
We report the fabrication and self-assembly study of solution-cast films and electrospun nanofibers of poly(3-hexylthiophene)-block-poly(g-benzyl-L-glutamate) (P3HT-b-PBLG) rodrod diblock copolymer. X-ray scattering and transmission electron microscopy revealed hierarchical self-assembly in P3HT-b-PBLG with ordered structures at two length scales: block copolymer self-assembly between P3HT and PBLG (%11nm) and molecular ordering within each block (0.4-1.6 nm). Vapor pressure of the casting solvent was proven critical in both levels of assembly for films. However, as-spun nanofibers exhibit poorly developed structures, regardless of solvent, due to rapid evaporation during electrospinning. Upon annealing, molecular structures exhibited clear signatures of both blocks in nanofibers.
We report monoaxial electrospinning and self-assembly characterization of poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester (P3HT/PCBM) nanofibers. Nanofibers were directly compared to films (as made and annealed) to understand the effects of extensional forces and high evaporation rate inherent to electrospinning on nanoscale structure. X-ray scattering shows electrospinning can achieve improved crystallinity and reduced length scale of P3HT and PCBM phases. Due to extensional flow, co-continuous phases form along the fiber axis, as evident in transmission electron microscopy. To our knowledge, this is the first study to investigate monoaxially-spun, pure P3HT/PCBM nanofibers, a facile processing method with the potential to transform the field of wearable photovoltaics.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.