Xanthan and K-carrageenan based alkaline hydrogels as electrolytes for Al/air batteries

Xanthan and ?-carrageenan were used to prepare alkaline hydrogels to be used as electrolytes in aluminium air primary batteries. Two pasty gels were obtained starting from xanthan and KOH solutions (1 M and 8 M), while only the 8 M KOH solution permitted the formation of a stable, elastic and gumminess hydrogel with ?-carrageenan. Discharge tests, performed on three Al/air cells assembled with Al anodes, electrolyte gels and Pt based cathodes, evidenced that all hydrogels exhibited appreciable properties of Al ion conductivities, according to the following performance order: xanthan with KOH 1 M < xanthan with KOH 8 M < ?-carrageenan KOH 8 M. Characterization measurements (XRD, Ionic conductivity by EIS, SEM-EDS) were effected on hydrogels and galvanic cells to explain the behaviour differences detected between the hydrogels.