Role of preparation methods on the structural and dielectric properties of plasticized polymer blend electrolytes: Correlation between ionic conductivity and dielectric parameters

Analysis of Dielectric Parameters of Fe2O3-Doped Polyvinylidene Fluoride/Poly(methyl methacrylate) Blend Composites

In this paper, we report the effect of metal oxide (Fe2O3) loading in different weight ratios (0.5%, 1%, 2%, and 4%) on the structural and electrical parameters, viz., the complex dielectric constant, electric modulus spectra, and the AC conductivity, of polymeric composites of PVDF/PMMA (30/70 weight ratio) blend. The structural and geometric measurements have been analyzed with the help of peak location, peak intensity, and peak shape obtained from XRD as well as from FTIR spectra. The electrical properties have been investigated using an impedance analyzer in the frequency range 100 Hz to 1 MHz. The real parts of the complex permittivity and the dielectric loss tangent of these materials are found to be frequency independent in the range from 20 KHz to 1 MHz, but they increase with the increase in the concentration of nano-Fe2O3. The conductivity also increases with an increased loading of Fe2O3 in PVDF/PMMA polymer blends. The electric modulus spectra were used to analyze the relaxation processes associated with the Maxwell-Wagner-Sillars mechanism and chain segmental motion in the polymer mix.

Gradient H-Bonding Supports Highly Adaptable and Rapidly Self-Healing Composite Binders with High Ionic Conductivity for Silicon Anodes in Lithium-Ion Batteries

An ideal binder for high-energy-density lithium-ion batteries (LIBs) should effectively inhibit volume effects, exhibit specific functional properties (e.g., self-repair capabilities and high ionic conductivity), and require low-cost, environmentally friendly mass production processes. This study adopts a synergistic strategy involving gradient (strong-weak) hydrogen bonding to construct a hard/soft polymer composite binder with self-healing abilities and high battery cell environments adaptability in LIBs. The meticulously designed 3D network structure comprising continuous electron transport pathways buffers the mechanical stresses caused by changes in silicon volume and improves the overall stability of the solid electrolyte interphase film. The Si-based anode with a polymer composite binder poly(acrylic acid-g-ureido pyrimidinone_5% )/polyethylene oxide (Si/PAA-UPy_5% /PEO) achieves a reversible capacity of 1245 mAh g^-1 after 200 cycles at 0.5 C, which is 6.6 times higher than that of the Si/PAA anode. After 200 cycles at 0.2 A g^-1 , a half-cell comprising Si/C anode with a polymer composite binder (Si/C/PAA-UPy_5% /PEO) has a remaining specific capacity of 420 mAh g^-1 and a capacity retention rate of 79%. The corresponding full cell with a Li-based cathode (LiFePO₄ /Si/C/PAA-UPy_5% /PEO) has an initial area capacity of 0.96 mAh cm^-2 and retains an area capacity of 0.90 mAh cm^-2 (capacity retention rate = 93%) after 100 cycles at 0.2 A g^-1 .

Influence of the Polarity of the Plasticizer on the Mechanical Stability of the Filler Network by Simultaneous Mechanical and Dielectric Analysis

Four styrene butadiene rubber (SBR) compounds were prepared to investigate the influence of the plasticizer polarity on the mechanical stability of the filler network using simultaneous mechanical and dielectric analysis. One compound was prepared without plasticizer and serves as a reference. The other three compounds were expanded with different plasticizers that have different polarities. Compared with an SBR sample without plasticizer, the conductivity of mechanically unloaded oil-extended SBR samples decreases by an order of magnitude. The polarity of the plasticizer shows hardly any influence because the plasticizers only affect the distribution of the filler clusters. Under static load, the dielectric properties seem to be oil-dependent. However, this behavior also results from the new distribution of the filler clusters caused by the mechanical damage and supported by the polarity grade of the plasticizer used. The Cole–Cole equation affirms these observations. The Cole–Cole relaxation time τ  and thus, the position of maximal dielectric loss increases as the polarity of the plasticizer used is also increased. This, in turn, decreases the broadness parameter α implying a broader response function.

Free-Radical Photopolymerization of Acrylonitrile Grafted onto Epoxidized Natural Rubber

The exploitation of epoxidized natural rubber (ENR) in electrochemical applications is approaching its limits because of its poor thermo-mechanical properties. These properties could be improved by chemical and/or physical modification, including grafting and/or crosslinking techniques. In this work, acrylonitrile (ACN) has been successfully grafted onto ENR- 25 by a radical photopolymerization technique. The effect of (ACN to ENR) mole ratios on chemical structure and interaction, thermo-mechanical behaviour and that related to the viscoelastic properties of the polymer was investigated. The existence of the –C≡N functional group at the end-product of ACN-g-ENR is confirmed by infrared (FT-IR) and nuclear magnetic resonance (NMR) analyses. An enhanced grafting efficiency (~57%) was obtained after ACN was grafted onto the isoprene unit of ENR- 25 and showing a significant improvement in thermal stability and dielectric properties. The viscoelastic behaviour of the sample analysis showed an increase of storage modulus up to 150 × 10³ MPa and the temperature of glass transition (T_g) was between −40 and 10 °C. The loss modulus, relaxation process, and tan delta were also described. Overall, the ACN-g-ENR shows a distinctive improvement in characteristics compared to ENR and can be widely used in many applications where natural rubber is used but improved thermal and mechanical properties are required. Likewise, it may also be used in electronic applications, for example, as a polymer electrolyte in batteries or supercapacitor.

A fully screen-printed potentiometric chloride ion sensor employing a hydrogel-based touchpad for simple and non-invasive daily electrolyte analysis

This is the first report demonstrating proof of concept for the passive, non-invasive extraction and in situ potentiometric detection of human sweat chloride ions (Cl^- ions) using a stable printed planar liquid-junction reference electrode-integrated hydrogel-based touch-sensor pad without activities such as exercise to induce perspiration, environmental temperature control, or requiring cholinergic drug administration. The sensor pad was composed entirely of a screen-printed bare Ag/AgCl-based chloride ion-selective electrode and a planar liquid-junction Ag/AgCl reference electrode, which were fully covered by an agarose hydrogel in phosphate-buffered saline (PBS). When human skin contacted the hydrogel pad, sweat Cl^- ions were continuously extracted into the gel, followed by in situ potentiometric detection. The planar liquid-junction Ag/AgCl reference electrode had a polymer-based KCl-saturated inner electrolyte layer to stabilize the potential of the Ag/AgCl electrode even with a substantial change in the chloride ion concentration in the hydrogel pad. We expect this fully screen-printed sensor to achieve the low-cost passive and non-invasive daily monitoring of human Cl^- ions in sweat in the future.

The role of nickel–iron based layered double hydroxide on the crystallinity, electrochemical performance, and thermal and mechanical properties of the poly(ethylene-oxide) solid electrolyte

The electrochemical performance and physical properties of PEO-based composite electrolytes were improved with the addition of a NILDH filler.

Copolymer Solid-State Electrolytes for 3D Microbatteries via Initiated Chemical Vapor Deposition

Reliable integration of thin film solid-state polymer electrolytes (SPEs) with 3D electrodes is one major challenge in microbattery fabrication. We used initiated chemical vapor deposition (iCVD) to produce a series of nanoscale copolymer films comprising hydroxyethyl methacrylate and ethylene glycol diacrylate. Conformal copolymer coatings were applied to a variety of patterned 3D electrodes and subsequently converted into ionic conductors by lithium salt doping. Broad tunability in ionic conductivity was achieved by optimizing the copolymer cross-linking density and matrix polarity, resulting in a room-temperature conductivity of (6.1 ± 2.7) × 10^-6 S cm^-1, the highest value reported for conformal, nanoscale SPEs.

Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte

In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO₈-NaPF₆+  x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times ([Formula: see text]) have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation ([Formula: see text]) was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole-Cole plot ([Formula: see text]) in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed.

Building Ion-Conduction Highways in Polymeric Electrolytes by Manipulating Protein Configuration

Solid polymer electrolytes play a critical role in the development of safe, flexible, and all-solid-state energy storage devices. However, the low ion conductivity has been the primary challenge impeding them from practical applications. Here, we propose a new biotechnology to fabricate novel protein-ceramic hybrid nanofillers for simultaneously boosting the ionic conductivity, mechanical properties, and even adhesion properties of solid polymer electrolytes. This hybrid nanofiller is fabricated by coating ion-conductive soy proteins onto TiO₂ nanoparticles via a controlled denaturation process in appropriate solvents and conditions. It is found that the chain configuration and protein/TiO₂ interactions in the hybrid nanofiller play critical roles in improving not only the mechanical properties but also the ion conductivity, electrochemical stability, and adhesion properties. Particularly, the ion conductivity is improved by one magnitude from 5 × 10^-6 to 6 × 10^-5 S/cm at room temperature. To understand the possible mechanisms, we perform molecular simulation to study the chain configuration and protein/TiO₂ interactions. Simulation results indicate that the denaturation environment and procedures can significantly change the protein configuration and the protein/TiO₂ interactions, both of which are found to be critical for the ion conductivity and mechanical properties of the resultant solid composite electrolytes. This study indicates that biotechnology of manipulating protein configuration can bring novel and promising strategies to build unique ion channels for fast ion conduction in solid polymer electrolytes.

Experimental and Theoretical Study of Ionic Pair Dissociation in a Lithium Ion-Linear Polyethylenimine-Polyacrylonitrile Blend for Solid Polymer Electrolytes

Herein, we report the preparation and characterization of a novel polymeric blend between linear polyethylene imine (PEI) and polyacrylonitrile (PAN), with the purpose of facilitating the dissociation of lithium perchlorate salt (LiClO₄) and thus to enhance Li ion transport. It is a joint theoretical and experimental procedure for evaluating and thus demonstrating the lithium salt dissociation. The procedure implies the correlation between the theoretical pair distribution function (PDF) and conventional X-ray diffraction (XRD) by means of a molecular dynamics (MD) approach. Additionally, we correlated the experimental and theoretical Raman and infrared spectroscopy for vibrational characterization of the lithium salt after dissociation in the polymeric blend. We also performed confocal Raman microscopy analysis to evidence the homogeneity on the distribution of all components and the LiClO₄ dissociation in the polymer blend. The electrochemical impedance analysis confirmed that the Li-PAN-PEI blend presents a slightly better lithium conductivity of ∼8 × 10^-7 S cm^-1. These results suggest that this polymer blend material is promising for the development of novel fluorine-free solid polymer lithium ion electrolytes, and the methodology is suitable for characterizing similar polymeric systems.

Structural and Ionic Transport Properties of Protonic Conducting Solid Biopolymer Electrolytes Based on Carboxymethyl Cellulose Doped with Ammonium Fluoride

Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and transference number measurement (TNM) techniques were applied to investigate the complexation, structural, and ionic transport properties of and the dominant charge-carrier species in a solid biopolymer electrolyte (SBE) system based on carboxymethyl cellulose (CMC) doped with ammonium fluoride (NH₄F), which was prepared via a solution casting technique. The SBEs were partially opaque in appearance, with no phase separation. The presence of interactions between the host polymer (CMC) and the ionic dopant (NH₄F) was proven by FT-IR analysis at the C-O band. XRD spectra analyzed using Origin 8 software disclose that the degree of crystallinity (χ_c%) of the SBEs decreased with the addition of NH₄F, indicating an increase in the amorphous nature of the SBEs. Analysis of the ionic transport properties reveals that the ionic conductivity of the SBEs is dependent on the ionic mobility (μ) and diffusion of ions (D). TNM analysis confirms that the SBEs are proton conductors.

Novel fluorine-free 2,2′-bis(4,5-dimethylimidazole) additive for lithium-ion poly(methyl methacrylate) solid polymer electrolytes

In this report, we study the effect of the addition of fluorine-free 2,2′-bis(4,5-dimethylimidazole) (BDI) on lithium-ion solid polymer electrolytes based on lithium nitrate and poly(methyl methacrylate) (PMMA).