Electrochromic Polymer Ink Derived from a Sidechain-Modified EDOT for Electrochromic Devices with Colorless Bright State

AbstractPrintable organic electrochromic materials are the key component of flexible low power and low weight displays and dynamic shading systems. A vast number of more or less well‐performing materials is reported in the literature, but only a very limited number of them have been tested in an industrially‐relevant environment so far. Upscaling requires simplicity of synthesis, overall sustainability, low cost and compatibility with simple and high throughput wet‐chemical deposition techniques, such as slot‐die coating or inkjet printing. In the present paper, an original process is described that enables the controlled oxidative polymerization of a water insoluble, functionalized 3,4‐ethylene dioxythiophene (EDOT) derivative. This process leads to the formation of an ink that consists solely of active polymeric material (no dispersing agents) and has suitable rheological properties for use in roll‐to‐roll slot‐die coating or ink‐jet printing. The straightforward deposition, followed by a simple thermal treatment, directly yields stable and homogeneous thin films with state‐of‐the‐art electrochromic performance

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

Relevance of ion clusters for Li transport at elevated salt concentrations in [Pyr12O1][FTFSI] ionic liquid-based electrolytes

In binary ionic liquid/Li salt mixtures with the novel asymmetric anion FTFSI, electrophoretic mobility μi values of all ion species were determined using electrophoretic NMR. Li was determined to migrate in negatively charged Li-anion clusters towards the anode. This vehicular transport mechanism was shown to have decreasing relevance at elevated salt concentrations

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