Manoj K. Singh

In this paper, comparative performances of the supercapacitor based on different redox additives (vanadyl sulfate [VOSO ₄ ] and potassium iodide [KI]) incorporated gel polymer electrolytes (redox additive gel polymer electrolytes [RGPEs]) are reported. RGPEs were prepared by entrapping liquid electrolyte solution NaClO ₄ /ethylene carbonate (EC):propylene carbonate (PC) in host polymer PVdF‐HFP along with redox additives via conventional solution casting techniques. It is observed that the ionic conductivity of pristine gel polymer electrolyte (GPE) is dependent on the content of redox additives (VOSO ₄ and KI) and temperatures. It is improved by adding redox additive 0.1 wt% VOSO ₄ (RGPE‐1) and 0.3 wt% KI (RGPE‐2) with corresponding ionic conductivity values to ∼3.25 × 10 ⁻³ and ∼4.02 × 10 ⁻³ S cm ⁻¹ , respectively. Further, two quasi‐solid‐state supercapacitor cells are fabricated using the optimized GPEs RGPE‐1 and RGPE‐2 with honeycomb‐based activated carbon (HCAC) electrodes. The comparative performances of the supercapacitor cells are evaluated and analyzed in terms of different electrochemical characterization techniques such as impedance, electrochemical stability window (ESW), cyclic voltammetry (CV), linear sweep voltammetry (LSV), and galvanostatic charge discharge (GCD) characteristics.

The objective of this research is to synthesize and thoroughly investigate polymer electrolyte films for energy applications by blending biopolymer cellulose acetate (CA) with ionic liquid 1‐hexyl‐3‐methylimidazolium iodide (HMIMI). Polymeric films based on biopolymer cellulose acetate are produced by blending various amounts of ionic liquid (HMIMI) using the solution cast method. The structural, electrical, and dielectric properties of the synthesized films are evaluated using various characterization techniques, including XRD, FTIR, electrochemical impedance spectroscopy, linear sweep voltammetry, and Wagner polarization method. The film containing 1.8 g of HMIMI exhibits a peak conductivity of 5.60 × 10⁻⁴ S cm⁻¹ and an electrochemical stability range of 3.3 V. In addition, the dielectric characteristics of the CA–HMIMI polymeric films are investigated, including the dielectric constant (κ) and the variation of the real and imaginary components of the dielectric constant with frequency.

The present work is focused on the synthesis and detailed study of biopolymer phytagel and ionic liquid 1-ethyl-3-methylimidazolium tricyanomethanide (EMIm[TCM]) blended polymer electrolyte films for energy applications. Here, biopolymer phytagel-based polymeric films are synthesized with different concentrations of ionic liquid (EMIm[TCM]) using the solution cast technique. The synthesized films are characterized for their structural, electrochemical, and dielectric properties using different characterization tools i.e., XRD, FTIR, Electrochemical Impedance Spectroscopy, Linear Sweep Voltammetry, and Wagnor polarization technique. The film with 30wt% EMIm[TCM] shows a maximum conductivity of 3.64 × 10-4 S cm-1 and an electrochemical stability window of 3.1 V. The dielectric properties such as dielectric constant (κ), dielectric loss tangent (tanδ), relaxation time, and frequency are also studied for the prepared pure phytagel and phytagel/EMIm[TCM] polymeric films.

Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP)‐sodium thiocyanate (NaSCN) solid polymer electrolytes containing different weight ratios of ionic liquid (IL)—tributylmethylphosphonium iodide (TBMPI) were prepared using solution‐cast approach. Electrochemical impedance data indicates that increasing ionic liquid into polymer electrolyte matrix increases ionic conductivity and the maximum value of ionic conductivity was obtained at 150 wt% TBMPI, having conductivity value of 8.3 × 10⁻⁵ S cm⁻¹. The dielectric measurement supports our conductivity data. Ionic transference number measurement affirms this system to be predominantly ionic in nature, while electrochemical stability window (ESW) was found to be 3.4 V. Polarized optical microscopy (POM) along with differential scanning calorimetry (DSC) suggest suitability of TBMPI as plasticizer, while infrared spectroscopy (FTIR) confirms ion interaction, complexation, and composite nature. The thermogravimetric analysis (TGA) shows thermal stability of these ionic liquid‐doped polymer electrolytes (ILDPEs). Using maximum conducting ILDPE, a sandwiched supercapacitor has been fabricated which shows stable performance as high as 228 Fg⁻¹ using cyclic voltammetry (CV).

In this paper, quasi‐solid electrolytes (QSEs) “PEO + xwt.% BMIMPF₆” for x = 0–20 were prepared by the immobilization of ionic liquid (IL), 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆) to the PEO polymer matrix by solution casting technique. These quasi‐solid electrolytes (QSEs) are in the thin film form of good mechanical integrity. The QSEs are characterized by X‐ray diffraction (XRD), Attenuated total reflectance Infrared (ATR‐IR) spectroscopy, differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), impedance spectroscopy, and electrochemical techniques. XRD/DSC results confirm an increase in the flexibility (and hence polymer chain mobility) with the increasing amount of IL in the QSEs, as confirmed by the analysis of degree of crystallinity (X_c). The maximum room temperature ionic conductivity ~1.32 × 10⁻⁵ S. cm⁻¹ is obtained for the 20 wt.% IL (BMIMPF₆) added QSEs. The interaction/complexation between the dopant IL‐cation BMIM⁺ with the ether oxygen (i.e., COC bond of PEO) has been confirmed by FTIR spectroscopic analysis. FESEM results confirm the appearance of crystalline spherical grains (spherulites), whose size decreases with the increasing amount of IL in the membranes and shows overall semicrystalline microstructures. The TGA analysis confirmed that the onset decomposition temperature of the QSEs is found to be ~175°C, which is the sufficient temperature range of operation for the solid‐state electrochemical devices. The electrochemical performances of the QSEs were examined by fabricating the symmetrical electrical double‐layer capacitor (EDLC) device. The fabricated EDLC cell with optimized QSE “PEO + 20 wt.% BMIMPF₆” with biomass‐based honeycomb activated carbon (HCAC) electrodes offers specific energy ~5.8 Wh kg⁻¹ at power density ~ 79.9 W kg⁻¹. It also displays excellent cycling stability with 81.3% of the initial specific capacitance after 2500 charge–discharge cycles.