Synthesis and characterization of biopolymer pectin: zinc nitrate for primary zinc battery application

The application of biopolymer electrolytes instead of synthetic polymer electrolytes has been pursued for the development of environmentally friendly and safer electrochemical energy systems, owing to the biodegradability, biocompatibility, and non-toxic characteristics of biopolymer electrolytes. In this research, a membrane composed of pectin and Zn(NO₃)₂·6H₂O is fabricated using solution casting method and characterized through various techniques. The amorphous property of the biopolymer is studied using X-ray diffraction (XRD). The membrane with a composition of 50% pectin and 50% Zn(NO₃)₂·6H₂O shows the highest degree of amorphous nature. Fourier-transform infrared spectroscopy (FTIR) studies confirm the formation of a polymer-salt complex. The highest ionic conductivity of the pectin and Zn(NO₃)₂·6H₂O mixture at a 50:50 ratio is measured to be 7.29 × 10⁻³ S/cm using AC impedance spectroscopy. The membrane demonstrating the highest zinc ion conductivity shows the lowest glass transition temperature of 50.98 ℃, as determined by differential scanning calorimetry (DSC) technique. The electrochemical window of the highest ion conducting membrane is found to be 1.9 V, as assessed by linear sweep voltammetry (LSV). A primary zinc ion conducting battery is constructed, and the output voltage of the assembled battery is determined to be 1.86 V. The performance of the primary zinc ion battery is measured under various load conditions.