We proposed a facile film treatment with formic acid to enhance the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by 4 orders of magnitude. The effect of formic acid concentration on conductivity was investigated; conductivity increased fast with increasing concentration up to 10 M and then increased slightly, the highest conductivity being 2050 S cm(-1) using 26 M concentration. Formic acid treated PEDOT:PSS films also exhibited very high transmittances. The mechanism of conductivity enhancement was explored through SEM, AFM, and XPS. Formic acid with its high dielectric constant screens the charge between PEDOT and PSS bringing about phase separation between them. Increased carrier concentration, removal of PSS from the film, morphology, and conformation change with elongated and better connected PEDOT chains are the main mechanisms of conductivity enhancement. ITO-free polymer solar cells were also fabricated using PEDOT:PSS electrodes treated with different concentrations of formic acid and showed equal performance to that of ITO electrodes. The concentrated acid treatment did not impair the desirable film properties as well as stability and performance of the solar cells.

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CitationBifunctional separator as a polysulfide mediator for highly stable Li-S batteries 2016 J. Graphical Abstract ABSTRACTThe shuttling process involving lithium polysulfides is one of the major factors responsible for the degradation in capacity of lithium-sulfur batteries (LSBs). Herein, we demonstrate a novel and simple strategy-using a bifunctional separator, prepared by spraying poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on pristine separator-to obtain long-cycle LSBs. The negatively charged SO 3 -groups present in PSS act as an electrostatic shield for soluble lithium polysulfides through mutual coulombic repulsion, whereas PEDOT provides chemical interactions with insoluble polysulfides (Li 2 S, Li 2 S 2 ). The dual shielding effect can provide an efficient protection from the shuttling phenomenon by confining lithium polysulfides to the cathode side of the battery. Moreover, coating with PEDOT:PSS transforms the surface of the separator from hydrophobic to hydrophilic, thereby improving the electrochemical performance. We observed an ultralow decay of 0.0364% per cycle when we ran the battery for 1000 cycles at 0.25 C-far superior to that of the pristine separator and one of the lowest recorded values reported at a low current density. We examined the versatility of our separator by preparing a flexible battery that functioned well under various stress conditions; it displayed flawless performance. Accordingly, this economical and simple strategy appears to be an ideal platform for commercialization of LSBs.

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In this study we prepared molybdenum trioxide (MoO3) nanorods having average lengths of 0.5-1.5 μm and widths of approximately 100-200 nm through a one-step mechanical break-down process involving favorable fracturing along the crystal direction. We controlled the dimensions of the as-prepared nanorods by applying various imposing times (15-90 min). The nanorods prepared over a reaction time of 90 min were, on average, much shorter and narrower relative to those obtained over 30 min. Evaluations of lithium-ion storage properties revealed that the electrochemical performance of these nanorods was much better than that of bulk materials. As cathodes, the nanorods could deliver a high specific capacity (>315 mA h g(-1)) with losses of less than 2% in the first cycle at a rate of 30 mA g(-1); as anodes, the specific capacity was 800 mA h g(-1) at a rate of 50 mA g(-1). Relative to α-MoO3 microparticles, these nanorods displayed significantly enhanced lithium-ion storage properties with higher reversible capacities and better rate performance, presumably because their much shorter diffusion lengths and higher specific surface areas allowed more-efficient insertion/deinsertion of lithium ions during the charge/discharge process. Accordingly, enhanced physical and/or chemical properties can be obtained through appropriate nanostructuring of materials.

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A one-step process for the preparation of NbSe2 nanostructures under the effects of mechanical forces to be used as Pt replacement CEs in DSSCs is reported.

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