Gelatin Hydrogel Electrolytes and Their Application to Electrochemical Supercapacitors

Gelatin hydrogel electrolytes GHEs with varying NaCl concentrations have been prepared by cross-linking an aqueous solution of gelatin with aqueous glutaraldehyde and characterized by scanning electron microscopy, differential scanning calorimetry, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic chronopotentiometry. Glass transition temperatures \nfor GHEs range between 339.6 and 376.9 K depending on the dopant concentration. Ionic conductivity behavior of GHEs \nwas studied with varying concentrations of gelatin, glutaraldehyde, and NaCl, and found to vary between 10−3 and 10−1 S cm−1. \nGHEs have a potential window of about 1 V. Undoped and 0.25 N NaCl-doped GHEs follow Arrhenius equations with activation \nenergy values of 1.94 and 1.88 � 10−4 eV, respectively. Electrochemical supercapacitors �ESs� employing these GHEs in conjunction \nwith Black Pearl Carbon electrodes are assembled and studied. Optimal values for capacitance, phase angle, and relaxation \ntime constant of 81 F g−1, 75°, and 0.03 s are obtained for 3 N NaCl-doped GHE, respectively. ES with pristine GHE \nexhibits a cycle life of 4.3 h vs 4.7 h for the ES with 3 N NaCl-doped GHE.