Effect of temperature on the performance of proton batteries based on chitosan–NH4NO3–EC membrane

Membranes of chitosan-based proton conductor polymer electrolyte were prepared by dissolving chitosan powder, ammonium nitrate (NH4NO3) salt and ethylene carbonate (EC) plasticizer in acetic acid solution. The temperature dependence of the chitosan-based membrane system was found to obey the Arrhenius relationship. The sample with the highest conductance, 18 wt.% CA + 12 wt.% NH4NO3 + 70 wt.% EC (CA40N70E), also possesses the lowest activation energy. From linear sweep voltammetry (LSV) results, the membrane is electrochemically stable at a potential of 1.6–1.8 V and a temperature of 298–353 K. The cells were fabricated using zinc powder (Zn) + zinc sulfate heptahydrate (ZnSO4·7H2O) + acetylene black (AB) + polytetrafluoroethylene (PTFE)|CA40N70E|manganese (IV) oxide (MnO2) + AB + PTFE. The open circuit voltages of the cells are decreases as temperature increases, the same trend as that obtained by LSV. The cell performance is excellent at 333 K, with discharge capacity of 42.7 mAh, internal resistance of 16.8 Ω, maximum power density of 14.6 mW cm−2 and a short-circuit current density of 31.0 mA cm−2. However, at temperatures above 333 K, decomposition of the membrane degraded the electrochemical properties of the cells.