Therefore, the present work focuses on developing protonconducting biopolymer electrolyte (BPE) by using natural biopolymer materials namely carboxymethyl cellulose as the host polymer while NH4Br has been chosen as the ionic dopant since ammonium
salts are considered as good proton donor to the biopolymer matrix [18]. The prepared BPE have been characterized by Fourier Transform Infra Red (FTIR), Thermo Gravimetric Analysis (TGA), Electrical Impedance Spectroscopy (EIS) and Transference Number
Measurement (TNM). In order to determine the potential of the highest proton conducting BPE as an electrolyte system in battery, it was used in the fabrication of Zn + ZnSO4·7H2O/BPE/MnO2 rechargeable proton battery. To the best of our knowledge there
are no systematic studies on rechargeable proton batteries basedon a CMC BPE.