Effect of Salt Concentration on Poly (Acrylic Acid) Hydrogel Electrolytes and their Applications in Supercapacitor

With rapidly rising demand of power in the field of flexible and wearable electronics, electrolytes being one of the influential components of the electrochemical energy storage devices and are getting more attention as their physical and chemical properties play vital role in device performance. Hydrogel electrolytes are emerging as novel materials for use in supercapacitors due to their diverse 3D porous network, bendable structure and tuneable properties. In the present work, Poly (acrylic acid) hydrogel has been synthesized using free-radical polymerization in the presence of chemical crosslinker N,N′-methylene bisacrylamide (MBA). The prepared hydrogels were soaked in four different molar concentration of lithium perchlorate (LiClO ₄ ) for 48 h to form double network hydrogel electrolytes. The structural and morphological characteristics of hydrogel electrolytes have been investigated using Fourier transform infrared-attenuated total reflectance (FTIR-ATR), X-ray diffraction and field emission scanning electron microscope (FESEM). In addition, the mechanical strength of hydrogel electrolytes was observed. The electrochemical studies including cyclic voltammetry (CV) and galvanic charge-discharge (GCD) investigated the performance of fabricated cells (AC/AA1/AC, AC/AA2/AC, AC/AA3/AC, and AC/AA4/AC) using hydrogel electrolytes in terms of specific capacitance, energy density and power density. Electrochemical studies show that AC/AA3/AC (activated carbon/acrylic acid (1.5 M LiClO ₄ )/activated carbon) is the optimised electrochemical cell among the fabricated cells of hydrogel electrolytes. AC/AA3/AC achieved maximum specific capacitance of 115 F g ⁻¹ at 3 mV s ⁻¹ and 132.20 F g ⁻¹ at 50 mA g ⁻¹ with energy density and power density of 18.36 Wh kg ⁻¹ and 1000 W kg ⁻¹ , respectively. All the results indicated significantly that poly (acrylic acid)/LiClO ₄ hydrogel electrolytes are competitive candidates for application in supercapacitors.