Ionic Conductivity and Structural Analysis of 2-hyroxyethyl Cellulose Doped with Glycolic Acid Solid Biopolymer Electrolytes for Solid Proton Battery

Cellulose derivatives have high potential for use as solid biopolymer electrolytes in proton batteries because they are biodegradable, affordable, have good mechanical properties and their ionic conductivity can be enhanced with addition of ionic dopant. In this work, we developed a new type of solid biopolymer electrolytes (SBEs) based on 2-hydroxyethyl cellulose (2HEC) doped with glycolic acid (GA) as an ionic dopant. A solution casting technique was used to prepare the SBEs. The ionic conductivity and structural properties of the SBEs were analysed using Electrical Impedance Spectroscopy (EIS), Fourier Transform Infrared spectroscopy (FTIR) and an X-ray Diffractometer (XRD). The highest ionic conductivity achieved was 3.80 x10⁻⁴ S cm⁻¹ for the sample with 40 wt.% GA concentration at room temperature. FT-IR analysis showed that complexation occurred in the polymer system from the shifting of υC-O and υ _sCOO^- band of 2HEC and GA. FTIR deconvolution revealed the increasing pattern of percentage free mobile ions with the addition of GA concentration until 40 wt.% GA, which can be related to the high ionic conductivity of the sample. In XRD analysis, all SBEs shows amorphous nature. Based on the results obtained, GA is a good ionic dopant because it succeed in improve the ionic conductivity of the 2HEC film. (paper)