New Roll‐to‐Roll Processable PEDOT‐Based Polymer with Colorless Bleached State for Flexible Electrochromic Devices

Conjugated electrochromic (EC) polymers for flexible EC devices (ECDs) generally lack a fully colorless bleached state. A strategy to overcome this drawback is the implementation of a new sidechain-modified poly(3,4-ethylene dioxythiophene) derivative that can be deposited in thin-film form in a customized high-throughput and large-area roll-to-roll polymerization process. The sidechain modification provides enhanced EC properties in terms of visible light transmittance change, Δτv = 59% (ΔL* = 54.1), contrast ratio (CR = 15.8), coloration efficiency (η = 530 cm² C−1), and color neutrality (L* = 83.8, a* = −4.3, b* = −4.1) in the bleached state. The intense blue-colored polymer thin films exhibit high cycle stability (10 000 cycles) and fast response times. The design, synthesis, and polymerization of the modified 3,4-ethylene dioxythiophene derivative are discussed along with a detailed optical, electrochemical, and spectroelectrochemical characterization of the resulting EC thin films. Finally, a flexible see-through ECD with a visible light transmittance change of Δτv = 47% (ΔL* = 51.9) and a neutral-colored bleached state is developed

Dielectric spectroscopy of Pyr14TFSI and Pyr12O1TFSI ionic liquids

Due to the conductivity of ionic liquids (IL), the dipolar dynamics are covered by charge separation phenomenon, which leads to difficulties extracting necessary parameters, i.e. static dielectric permittivity. We suggest a procedure, which allows relatively easy extracting parameters of dipolar dynamics of IL. Our experiments were performed on Pyr14TFSI and Pyr12O1TFSI ILs. Obtained results allowed comparing the dipolar dynamics of both materials. The factor, which makes the static dielectric permittivity of Pyr12O1TFSI to be higher than that of Pyr14TFSI may be accounted for the permanent dipole of Pyr12O1+ cation

Evaluation of Carbon-Coated Graphite as a Negative Electrode Material for Li-Ion Batteries

Low-cost and environmentally-friendly materials are investigated as carbon-coating precursors to modify the surface of commercial graphite for Li-ion battery anodes. The coating procedure and final carbon content are tuned to study the influence of the precursors on the electrochemical performance of graphite. Thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area analysis are used to characterize the carbon coating content and the surface area, respectively, whereas X-ray diffraction (XRD) and Raman spectroscopy allow tracking of the graphite’s structural changes and surface amorphization. In general, the coating reduces the first cycle coulombic efficiency by 3%–10% compared to pristine graphite due to the increase of the surface area available for the continuous electrolyte decomposition. However, the use of citric acid as a carbon source (5 wt %) improves the rate capability of graphite, resulting in the specific delithiation capacity at 3C of 228 mAh g−1 vs. 211 mAh g−1 for the uncoated graphite. The attempt to reduce the coating amount from 5 wt % to 2 wt % results in a lower rate capability, but the first cycle coulombic efficiency is similar to that of pristine graphite

Interplay between Mechanical, Electrical, and Thermal Relaxations in Nanocomposite Proton Conducting Membranes Based on Na\ufb01on and a [(ZrO2)\ub7(Ta2O5)0.119] core-shell nanofiller

The thermal, mechanical and electric properties of hybrid membranes based on Nafion that contain a [(ZrO2) 19(Ta2O5)0.119] \u201ccore-shell\u201d nanofiller are elucidated. DSC investigations reveal the presence of four endothermic transitions between 50 and 300\ub0C. The DMA results indicate improved mechanical stability of the hybrid materials. The DSC and DMA results are consistent with our previous suggestion of dynamic R-SO3H 19 19 19[ZrTa] cross-links in the material. These increase the thermal stability of the \u2013SO3H groups and the temperature of thermal relaxation events occurring in hydrophobic domains of Nafion. The broadband electric spectroscopic analysis reveals two electric relaxations associated with the materials\u2019 interfacial (\u3c3IP) and bulk proton conductivities (\u3c3EP). The wet [Nafion/(ZrTa)1.042] membrane has a conductivity of 7.0 710 122 Scm 121 at 115\ub0C, while Nafion has a conductivity of 3.3 710 122 Scm 121 at the same temperature and humidification conditions. \u3c3EP shows VTF behaviour, suggesting that the long-range conductivity is closely related to the segmental motion of the Nafion host matrix. Long range conduction (\u3c3EP) occurs when the dynamics of the fluorocarbon matrix induces contact between different delocalization bodies (DB), which results in proton exchange processes between these DB

Dendrite growth in Mg metal cells containing Mg(TFSI)2/Glyme electrolytes

One advantage of Mg batteries, which is often reported in the literature without further qualification such as the electrolyte system, is the high safety due to dendrite-free Mg deposition. Here we report results of a study on the possibility for dendrite growth in Mg metal cells using Mg(TFSI)2/glyme electrolytes. Dendrite growth and the subsequent internal short-circuit were proven electrochemically via cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and galvanostatic cycling. In addition, the structure and chemical composition of the globular dendrites were investigated by scanning electrode microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and in situ optical microscopy. The dendrites are structured in interconnected spherical deposits consisting of Mg metal, MgO, MgF2, and MgS. The results demonstrate the necessity of considering dendrite growth when developing new electrolyte systems for Mg metal batteries

In and out – new ionic mesogens based on a cyanoborate building block and lipophilic or hydrophilic counter ions

Abstract. New ionic mesogens have been prepared based on a cyanoborate head group, which is tethered to a lipophilic periphery via a short flexible spacer. As counter ions, either tetra-n-butyl ammonium cations or sodium and potassium cations stabilized by 18-crown-6 have been used. Although all compounds realise SmA enantiotropic mesomorphism, X-ray diffraction, modelling and solid-state NMR uncover distinct self-assembly of the LC materials in double layers. While the ammonium ions are located in-between the borate anions and are in contact with spacers and aromatic units, the crown ethers with the coordinated alkali metal cations are completely nanosegregated between two borate anion layers. Homogenous and homeotropic alignment has been achieved. Electrical impedance studies confirm two to three orders of magnitude higher conductivity of the correctly-aligned samples in the single-ion conductor. Values of ca. 10-4 Scm-1 in the SmA phase at 85 °C and 10-5 Scm-1 at 40 °C have been obtained

Insights into the Structure and Transport of the Lithium, Sodium, Magnesium, and Zinc Bis(trifluoromethansulfonyl)imide Salts in Ionic Liquids

Details of the lithium (Li+), sodium (Na+), magnesium (Mg2+), and zinc (Zn2+) cation coordination and electrolyte transport properties are examined using molecular dynamics (MD) simulations for the N-butyl-N-methylpyrrolidinium bis(trifluoromethansulfonyl)imide (pyr14TFSI) ionic liquid (IL) doped with LiTFSI, NaTFSI, Mg(TFSI)2, and Zn(TFSI)2 salts. MD simulations are performed as a function of temperature using a polarizable force field (APPLE&P) that yields the Li+, Na+, Mg2+, and Zn2+ cation binding energies to the TFSI– anions in excellent agreement with quantum chemistry results. At 333 K, 4.7–4.8 TFSI– oxygen atoms from approximately three TFSI– anions coordinate Li+ and Na+, while Zn2+ and Mg2+ cations are instead coordinated by approximately six TFSI– oxygen atoms. Significant Na+ coordination with the fluorine atoms of the TFSI– anions is observed, unlike for Li+, Mg2+ and Zn2+. The cation–TFSI– binding motifs and the propensity of the salts to form large aggregates are temperature dependent with opposite trends noted for the electrolytes containing the Li and Na salts vs Mg salts. The MD simulations accurately predicted electrolyte transport properties including ionic conductivity, viscosity, and self-diffusion coefficients. A connection between the metal cation coordination, transport properties, and transport mechanisms is established for the different cations. The much longer cation–anion residence times for the divalent Zn2+- and Mg2+-containing electrolytes, as compared to those with monovalent Na+ and Li+, indicate the significantly slower desolvation kinetics of the divalent salts and the dominance of the vehicular cation transport mechanism relative to the anion exchange mechanism

Characterization of sulfated-zirconia/Nafion\uae composite membranes for proton exchange membrane fuel cells

An interesting new material based on a Nafion\uae membrane doped with a sulfated-zirconia filler is presented. This filler is unique in that the filler itself can contribute to the proton conductivity due to the presence of acidic functionalities on the surface of the filler. The presence of the filler in the membrane results in the deprotonation of Nafion\uae\u2019s acid moieties as indicated by the absence of the acid mode at 1475 cm 121 in the FTIR spectrum. Spectra from DSC, DMA and broadband electric spectroscopy (BES) show the presence of several molecular transitions, two of which are detected in the BES permittivity profiles. The membrane exhibits a reasonably high conductivity (3 7 10 123 S/cm at 120 \ub0C) even in completely dry conditions, which makes it a promising material for an anhydrous fuel cell. The conductivity behaviour exhibits a mix of Arrhenius and VTF behaviours and is closely tied to the dielectric relaxations