Synthesis and characterization of tetrazole-derived solid polymeric electrolytes

In this work, N-alkylated tetrazole copolymers were prepared to produce the solid polymeric electrolytes StVTz-82, StVTz-82:4C, StVTz-82:6C, StVTz-82:8C and StVTz-82:sultone. The chemical structure was confirmed by FTIR, H NMR, C NMR and GPC. GPC thermal analysis showed that the membranes are thermally stable up to 160 °C. DSC was used to evaluate the structural effect on the Tg value. Water absorption (WU) and ion exchange capacity (IEC) were conducted for all electrolytes. We observed a decrease in the elastic modulus with the introduction of side alkyl chains linked to the tetrazole heterocycle. The ionic conductivity of these materials was studied by electrochemical impedance spectroscopy. We observed that the StVTz-82 and StVTz-82:sultone copolymers, in hydrated conditions and at room temperature, are the ones that present the best conductivity values 2.09 and 9.78 mS. cm, respectively. Relating to the hydration number (λ), the StVTz-82:sultone electrolyte has a higher λ value. It also has sulfonic acid group, which has a lower pKa value (~ 1.9) then tetrazole (~ 4.50). From the point of view of mechanical properties, the StVTz-82:sultone electrolyte has a rigidity modulus intermediate to that of StVTz-82, which is more rigid, and StVTz-82:8C, which is the most flexible. These characteristics provide suitable properties for use of StVTz-82:sultone as a solid electrolyte for power generation devices such as fuel cells and batteries.