Novel insights into electrical transport mechanism in ionic‐polaronic glasses

Transformation of electrical transport from ionic to polaronic in glasses, which are a potential class of new cathode materials, has been investigated in four series containing WO₃/MoO₃ and Li⁺/Na⁺ ions, namely: xWO₃–(30?0.5x)Li₂O–(30?0.5x)ZnO–40P₂O₅, xWO₃–(30?0.5x)Na₂O–(30.5x)ZnO–40P₂O₅, xMoO₃–(30?0.5x)Li₂O–(30?0.5x)ZnO–40P₂O₅, and xMoO₃–(30?0.5x)Na₂O–(30?0.5x)ZnO–40P₂O₅, 0 ≤ x ≤ 60, (mol%). This study reports a detailed analysis of the role of structural modifications and its implications on the origin of electrical transport in these mixed ionic‐polaron glasses. Raman spectra show the clustering of WO₆ units by the formation of W–O–W bonds in glasses with high WO₃ content while the coexistence of MoO₄ and MoO₆ units is evidenced in glasses containing MoO₃ with no clustering of MoO₆ octahedra. Consequently, DC conductivity of tungstate glasses with either Li⁺ or Na⁺ exhibits a transition from ionic to polaronic showing a minimum at about 20‐30 mol% of WO₃ as a result of ion‐polaron interactions followed by a sharp increase for six orders of magnitude as WO₃ content increases. The formation of WO₆ clusters involved in W‐O‐W linkages for tungsten glasses plays a key role in significant increase in DC conductivity. On the other hand, DC conductivity is almost constant for glasses containing MoO₃ suggesting an independent ionic and polaronic transport pathways for glasses containing 10‐50 mol% of MoO₃.     

Electrospun poly(lithium 2‐acrylamido‐2‐methylpropanesulfonic acid) fiber‐based polymer electrolytes for lithium‐ion batteries

Novel single‐ion conducting polymer electrolytes based on electrospun poly(lithium 2‐acrylamido‐2‐methylpropanesulfonic acid) (PAMPSLi) membranes were prepared for lithium‐ion batteries. The preparation started with the synthesis of polymeric lithium salt PAMPSLi by free‐radical polymerization of 2‐acrylamido‐2‐methylpropanesulfonic acid, followed by ion‐exchange of H⁺ with Li⁺. Then, the electrospun PAMPSLi membranes were prepared by electrospinning technology, and the resultant PAMPSLi fiber‐based polymer electrolytes were fabricated by immersing the electrospun membranes into a plasticizer composed of ethylene carbonate and dimethyl carbonate. PAMPSLi exhibited high thermal stability and its decomposition did not occur until 304°C. The specific surface area of the electrospun PAMPSLi membranes was raised from 9.9 m²/g to 19.5 m²/g by varying the solvent composition of polymer solutions. The ionic conductivity of the resultant PAMPSLi fiber‐based polymer electrolytes at 20°C increased from 0.815 × 10^?5 S/cm to 2.12 × 10^?5 S/cm with the increase of the specific surface area. The polymer electrolytes exhibited good dimensional stability and electrochemical stability up to 4.4 V vs. Li⁺/Li. These results show that the PAMPSLi fiber‐based polymer electrolytes are promising materials for lithium‐ion batteries. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Theoretical investigations of electronic structure and charge transport properties in polythiophene‐based organic field‐effect transistors

Regioregular poly(3‐hexylthiophene) (P3HT) is a hole transport polymer material used in organic field‐effect transistors (OFETs) and can reach mobilities as high as 0.1 cm² V^?1 s^?1. Factors that affect the charge mobility and the transport mechanisms of P3HT‐based OFET systems are therefore of great importance. We use quantum mechanical methods to interpret the charge mobility and the transport properties of self‐assembled P3HT molecules along the intra‐chain and inter‐chain directions. Our approach is illustrated by a hopping transport model, in which we examine the variation of charge mobility with torsional angle and the intermolecular distance between two adjacent thiophene segments. We also simulate packed P3HT structures via molecular dynamics (MD) simulations. The MD results indicate that the resultant mobility along the π?π inter‐chain direction is significantly less than that along the intra‐chain direction. Accordingly, the main charge‐transfer route within the P3HT ordered domains is an intra‐chain rather than an inter‐chain one. The calculation result for the inter‐chain hole mobility is around 10^?2 cm² V^?1 s^?1, which is consistent with experimental data from P3HT single fibril. Copyright © 2009 Society of Chemical Industry     

Electropolymerization and characterization of ionic diffusion in poly(diphenyldithieno[3,2‐b;20,30‐d]thiophene)

Poly(diphenyldithieno[3,2‐b;20,30‐d]thiophene) was synthesized by electropolymerization on Pt quartz crystal and on an indium tin oxide electrode by cyclic voltammetry. Ionic diffusion through the electronic conducting film (for the p‐doping process) was studied by cyclic voltammetry coupled to a quartz crystal microbalance (E‐QCM) and electrochemical impedance spectroscopy (EIS), using different electrolyte salts such as LiTFSI, LiClO₄ or LiCF₃CO₂. The molar ratio of insertion/expulsion of anions and cations was estimated from E‐QCM. By comparison between E‐QCM and EIS, the intrinsic ionic diffusion mechanisms in the electronic conducting film were highlighted depending on the salts used in acetonitrile. Moreover, the different mechanisms are in good agreement with the molar ratio of anion/cation insertion/expulsion. © 2018 Society of Chemical Industry     

Effects of B‐site doped elements in the electronic‐conducting perovskite phase on the property of dual‐phase membranes

A series of dense oxygen permeable dual‐phase membranes with a composition of 60 wt% Ce_0.8Gd_0.2O_2?δ‐40 wt% Ba_0.95La_0.05Fe_0.9M_0.10O_3?δ (CGO‐ BLFM_0.10, M=Fe, Nb, Zr, Zn, Sc, Y) were successfully synthesized and evaluated as potential ceramic membranes for oxy‐fuel combustion. The effects of B‐site doped elements in electronic‐conducting phase (BLFM_0.10) on the crystal structure, microstructure, chemical compatibility, oxygen permeability, as well as chemical stability of CGO‐BLFM_0.10 were systematically investigated. All electronic‐conducting phase BLFM_0.10 oxides exhibited a pure cubic perovskite structure and showed good chemical compatibility with ionic‐conducting phase CGO. CGO‐BLFSc_0.10 showed the best oxygen permeation stability under a pure CO₂ atmosphere. CO₂‐corrosion on the perovskite phase is the main reason for the property deterioration of fluorite‐perovskite‐typed dual‐phase membrane materials. The stability of dual‐phase membrane materials can be effectively enhanced by reducing the basicity of electronic‐conducting phase of perovskite materials.     

Charge density in non‐isotropic electrolytes conducting current

This article presents applications of an electrochemical model that can predict concentrations and electric current distributions assuming neither electroneutrality nor negligible concentration gradients. This numerical model is used to analyse two cases: a liquid‐junction and a lithium‐ion cell. For both cases, it is shown how the inclusion of charge density effects on the electric field is beneficial. For the case of a liquid‐junction the predicted potential gradient is compared with values experimentally and numerically determined by other researchers. For the case of a charging lithium‐ion cell, a phenomenon seen experimentally (but not previously reported by other models) is predicted. © 2011 Canadian Society for Chemical Engineering     

Diffusion of mineral oil in styrene‐butadiene polymer films

Mineral oil diffusion in styrene‐butadiene polymer films was investigated with a simple gravimetric sorption method. Over the selected range of temperatures and film thicknesses for which sorption tests were performed, the diffusion process is described in terms of Fick's third law. Polymer dissolution was found to compete with the diffusion process especially at high temperature. Possible interference due to dissolution on data generated using a gravimetric method, resulted in an estimation of apparent activation energy using diffusion coefficient set calculated with Crank's half‐time relationship. The mineral oil diffusion activation energy was found to be relatively high compared with those of hydrocarbons diffusing in natural and synthesized rubbers or crosslinked polybutadiene as reported in the literature. The influence of polymer T_g, crosslinking density, and polarity on mineral oil ability to penetrate polymer film was evaluated in terms of percent weight increase over time. Maximum absorption after 60‐min sorption time linearly correlates with mineral oil absorption rate for polymers prepared with different structures. This linear relationship suggests that diffusion of solvent in styrene‐butadiene polymers reveals the macroscopic composition and structural polymer modification rather than local changes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Application of thermosetting organic solvent free polymer gel electrolyte in quasi‐solid‐state dye‐sensitized solar cell

A kind of thermosetting organic solvent free polymer gel electrolyte with oligomer ethylene glycol as liquid phase was prepared and applied in quasi‐solid‐state dye‐sensitized solar cell (QS‐DSSC). The viscosity and the ionic conductivity of the polymer gel electrolyte are sensitive to the changed temperature. The photovoltaic performance of QS‐DSSC is also improved with the increased temperature due to the increased ionic conductivity and diffusion coefficient of iodide in polymer gel electrolyte. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrosynthesis of free‐standing poly(para‐phenylene) films in mixed electrolytes of boron trifluoride diethyl etherate and trifluoroacetic acid on stainless steel electrode

Free‐standing poly(para‐phenylene) (PPP) films have been electrosynthesized by direct oxidation of benzene on stainless steel electrode in mixed e1ectrolytes of boron trifluoride diethy1 etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potential of the monomer in these media is lower than those in the neutral media. Increasing the content of TFA in the mixed electrolyte can effective1y decrease the oxidation potential and increase the coup1ing rate of the monomer. The films obtained from these media were very shiny and flexible, and could easily be processed into various shapes by conventional mechanical methods. The films had a 1inear chain structure, and their degree of polymerization could be improved by increasing the TFA content in the mixed electrolyte. Moreover, the films had a fairly good thermal stability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2462–2466, 2002