Insight into the Effect of Glycerol on Dielectric Relaxation and Transport Properties of Potassium-Ion-Conducting Solid Biopolymer Electrolytes for Application in Solid-State Electrochemical Double-Layer Capacitor.

The increased interest in the transition from liquid to solid polymer electrolytes (SPEs) has driven enormous research in the area polymer electrolyte technology. Solid biopolymer electrolytes (SBEs) are a special class of SPEs that are obtained from natural polymers. Recently, SBEs have been generating much attention because they are simple, inexpensive, and environmentally friendly. In this work, SBEs based on glycerol-plasticized methylcellulose/pectin/potassium phosphate (MC/PC/K3PO4) are investigated for their potential application in an electrochemical double-layer capacitor (EDLC). The structural, electrical, thermal, dielectric, and energy moduli of the SBEs were analyzed via X-ray diffractometry (XRD), Fourier transforms infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS), transference number measurement (TNM), and linear sweep voltammetry (LSV). The plasticizing effect of glycerol in the MC/PC/K3PO4/glycerol system was confirmed by the change in the intensity of the samples' FTIR absorption bands. The broadening of the XRD peaks demonstrates that the amorphous component of SBEs increases with increasing glycerol concentration, while EIS plots demonstrate an increase in ionic conductivity with increasing plasticizer content owing to the formation of charge-transfer complexes and the expansion of amorphous domains in polymer electrolytes (PEs). The sample containing 50% glycerol has a maximal ionic conductivity of about 7.5 × 10-4 scm-1, a broad potential window of 3.99 V, and a cation transference number of 0.959 at room temperature. Using the cyclic voltammetry (CV) test, the EDLC constructed from the sample with the highest conductivity revealed a capacitive characteristic. At 5 mVs-1, a leaf-shaped profile with a specific capacitance of 57.14 Fg-1 was measured based on the CV data.

A Review of Current Trends on Polyvinyl Alcohol (PVA)-Based Solid Polymer Electrolytes.

Presently, the rising concerns about the fossil fuel crisis and ecological deterioration have greatly affected the world economy and hence have attracted attention to the utilization of renewable energies. Among the renewable energy being developed, supercapacitors hold great promise in broad applications such as electric vehicles. Presently, the main challenge facing supercapacitors is the amount of energy stored. This, however, does not satisfy the increasing demand for higher energy storage devices, and therefore, intensive research is being undertaken to overcome the challenges of low energy density. The purpose of this review is to report on solid polymer electrolytes (SPEs) based on polyvinyl alcohol (PVA). The review discussed the PVA as a host polymer in SPEs followed by a discussion on the influence of conducting salts. The formation of SPEs as well as the ion transport mechanism in PVA SPEs were discussed. The application and development of PVA-based polymer electrolytes on supercapacitors and other energy storage devices were elucidated. The fundamentals of electrochemical characterization for analyzing the mechanism of supercapacitor applications, such as EIS, LSV and dielectric constant, are highlighted. Similarly, thermodynamic transport models of ions and their mechanism about temperature based on Arrhenius and Vogel-Tammann-Fulcher (VTF) are analyzed. Methods for enhancing the electrochemical performance of PVA-based SPEs were reported. Likely challenges facing the current electrolytes are well discussed. Finally, research directions to overcome the present challenges in producing SPEs are proposed. Therefore, this review is expected to be source material for other researchers concerned with the development of PVA-based SPE material.

Effect of ZnO Nanofiller on Structural and Electrochemical Performance Improvement of Solid Polymer Electrolytes Based on Polyvinyl Alcohol-Cellulose Acetate-Potassium Carbonate Composites.

In this study, a solution casting method was used to prepare solid polymer electrolytes (SPEs) based on a polymer blend comprising polyvinyl alcohol (PVA), cellulose acetate (CA), and potassium carbonate (K2CO3) as a conducting salt, and zinc oxide nanoparticles (ZnO-NPs) as a nanofiller. The prepared electrolytes were physicochemically and electrochemically characterized, and their semi-crystalline nature was established using XRD and FESEM. The addition of ZnO to the polymer-salt combination resulted in a substantial increase in ionic conductivity, which was investigated using impedance analysis. The size of the semicircles in the Cole-Cole plots shrank as the amount of nanofiller increased, showing a decrease in bulk resistance that might be ascribed to an increase in ions due to the strong action of the ZnO-NPs. The sample with 10 wt % ZnO-NPs was found to produce the highest ionic conductivity, potential window, and lowest activation energy (Ea) of 3.70 × 10-3 Scm-1, 3.24 V, and 6.08 × 10-4 eV, respectively. The temperature-frequency dependence of conductivity was found to approximately follow the Arrhenius model, which established that the electrolytes in this study are thermally activated. Hence, it can be concluded that, based on the improved conductivity observed, SPEs based on a PVA-CA-K2CO3/ZnO-NPs composite could be applicable in all-solid-state energy storage devices.

Innovative Methylcellulose-Polyvinyl Pyrrolidone-Based Solid Polymer Electrolytes Impregnated with Potassium Salt: Ion Conduction and Thermal Properties.

In this research, innovative green and sustainable solid polymer electrolytes (SPEs) based on plasticized methylcellulose/polyvinyl pyrrolidone/potassium carbonate (MC/PVP/K2CO3) were examined. The MC/PVP/K2CO3 SPE system with five distinct ethylene carbonate (EC) concentrations as a plasticizer was successfully designed. Frequency-dependent conductivity plots were used to investigate the conduction mechanism of the SPEs. Electrochemical potential window stability and the cation transfer number of the SPEs were studied via linear sweep voltammetry (LSV) and transference number measurement (TNM), respectively. Additionally, the structural behavior of the SPEs was analyzed using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), and differential scanning calorimetry (DSC) techniques. The SPE film complexed with 15 wt.% EC measured a maximum conductivity of 3.88 × 10-4 Scm-1. According to the results of the transference number examination, cations that record a transference number of 0.949 are the primary charge carriers. An EDLC was fabricated based on the highest conducting sample that recorded a specific capacitance of 54.936 Fg-1 at 5 mVs-1.

Substantial Proton Ion Conduction in Methylcellulose/Pectin/Ammonium Chloride Based Solid Nanocomposite Polymer Electrolytes: Effect of ZnO Nanofiller.

In this research, nanocomposite solid polymer electrolytes (NCSPEs) comprising methylcellulose/pectin (MC/PC) blend as host polymer, ammonium chloride (NH4Cl) as an ion source, and zinc oxide nanoparticles (ZnO NPs) as nanofillers were synthesized via a solution cast methodology. Techniques such as Fourier transform infrared (FTIR), electrical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) were employed to characterize the electrolyte. FTIR confirmed that the polymers, NH4Cl salt, and ZnO nanofiller interact with one another appreciably. EIS demonstrated the feasibility of achieving a conductivity of 3.13 × 10-4 Scm-1 for the optimum electrolyte at room temperature. Using the dielectric formalism technique, the dielectric properties, energy modulus, and relaxation time of NH4Cl in MC/PC/NH4Cl and MC/PC/NH4Cl/ZnO systems were determined. The contribution of chain dynamics and ion mobility was acknowledged by the presence of a peak in the imaginary portion of the modulus study. The LSV measurement yielded 4.55 V for the comparatively highest conductivity NCSPE.

State of the Art and New Directions on Electrospun Lignin/Cellulose Nanofibers for Supercapacitor Application: A Systematic Literature Review.

Supercapacitors are energy storage devices with high power density, rapid charge/discharge rate, and excellent cycle stability. Carbon-based supercapacitors are increasingly attracting attention because of their large surface area and high porosity. Carbon-based materials research has been recently centered on biomass-based materials due to the rising need to maintain a sustainable environment. Cellulose and lignin constitute the major components of lignocellulose biomass. Since they are renewable, sustainable, and readily accessible, lignin and cellulose-based supercapacitors are economically viable and environmentally friendly. This review aims to systematically analyze published research findings on electrospun lignin, cellulose, and lignin/cellulose nanofibers for use as supercapacitor electrode materials. A rigorous scientific approach was employed to screen the eligibility of relevant articles to be included in this study. The research questions and the inclusion criteria were clearly defined. The included articles were used to draw up the research framework and develop coherent taxonomy of literature. Taxonomy of research literature generated from the included articles was classified into review papers, electrospun lignin, cellulose, and lignin/cellulose nanofibers for use as supercapacitor electrode materials. Furthermore, challenges, recommendations, and research directions for future studies were equally discussed extensively. Before this study, no review on electrospun lignin/cellulose nanofiber-based supercapacitors has been reported. Thus, this systematic review will provide a reference for other researchers interested in developing biomass-based supercapacitors as an alternative to conventional supercapacitors based on petroleum products.