Enhanced ionic conductivity of proton-conducting flaxseed gum based biopolymer electrolyte for energy storage

This work presents a facile and systematic way to prepare low resistive proton conducting biopolymer electrolyte (BPE) membranes from flaxseed gum (FG) via the solution casting technique. Ammonium fluoride (NH₄F) ionic salt has been added to the FG matrix and optimized the ionic conductivity of the BPE membrane. The structural and morphological investigations were done to comprehend the ion association phenomenon. The enhancement of amorphousity on doping is affirmed by x-ray diffraction (XRD). The complex formation and interactions between FG and proton (H⁺) have been characterized through fourier transform infrared (FTIR) spectroscopy. The flexibility of the prepared BPE membranes at low glass transition temperature T_g was confirmed by differential scanning calorimetry (DSC) thermal analysis. Electrochemical impedance spectroscopy (EIS) shows maximum ionic conductivity of 4.0 × 10^-3 S/cm at FGAF7 composition. The obtained surface topographic images from atomic force microscopy (AFM) confirms that the predominantly uneven amorphous surface with high rms roughness has transformed to a homogenous even surface on the addition of dopant. The TNM findings demonstrated that the ions were the predominant charge carriers. The linear sweep voltammetry (LSV) and cyclic voltammetry (CV) investigations were employed to confirm the electrochemical stability of the BPE membrane. An electrical double layer capacitor (EDLC) has been fabricated using the optimized utmost conducting BPE membrane as an electrolyte and characterized using cyclic voltammetry (CV). These outcomes indicates that the present electrolyte shows promising performance for application in energy storage devices.