XRD, DSC, and Dielectric Studies of MWNT-Doped Polymer Electrolytes for Supercapacitor Application

Recently, high ionic conducting composite polymer electrolytes have become of great interest on account of their probable applications in various electrochemical devices, such as batteries, supercapacitors, fuel cells, solar cells, etc. The aim of the present work is to cast a stable free-standing membrane of polyvinyl alcohol (PVA)-based nanocomposite polymer electrolyte (NCPE) gel membranes using ammonium acetate salt (NH4CH3COO) and multiwall carbon nanotube (MWNT) contents for supercapacitor applications. X-ray diffraction (XRD) studies revealed improvements in the amorphous nature. The average crystal size of the MWNT-doped NCPE system was found to lie in the range of 30-70 nm). The degree of crystallinity (chi(c)) in this case shows a decrease of up to 35 wt.% with the increase in filler concentrations. The differential scanning calorimetry (DSC) studies show better thermal response upon the addition of MWNTs. Thermo-gravimetric analysis (TGA) studies reveal that the mass of nanocomposite polymer electrolyte gel decreases continuously with the increase in the MWNT contents. Dielectric loss studies have also been used to understand the conduction process in the system. The presence of alpha-relaxation was evidenced during loss measurements. The source of polarizability decreases with an increase of frequency, and finally disappears due to the inertia of mobile ions. Optimum conductivity was achieved at 5.49 x 10(-4) Scm(-1) for 1 wt.% MWCNT-embedded NCPE gel membranes. The electrical conductivity response seems to follow the universal power law. The studies suggest the development of environmentally friendly H+ ion (proton) conducting-based supercapacitor applications.

Automated summary

Recently, the development of high ionic conducting composite polymer electrolytes has sparked great interest due to their potential applications in various electrochemical devices. In this study, a stable free-standing membrane of polyvinyl alcohol (PVA)-based nanocomposite polymer electrolyte (NCPE) gel was successfully prepared using ammonium acetate salt and multiwall carbon nanotube. The addition of multiwall carbon nanotube improved the amorphous nature and thermal response of the NCPE system. Furthermore, the inclusion of multiwall carbon nanotube led to a decrease in the degree of crystallinity and an enhancement in the electrical conductivity of the gel membranes.