Zinc—iodine secondary cell using 6-nylon or poly(ether) based electrode. Basic research for industrial use of the secondary cell

Abstract Porous 6-nylon—carbon composite was made, and a button type battery, Zn|ZnI2 + NH4Cl| cation exchanging membrane |ZnI2 + NH4Cl|I2-porous 6-nylon—carbon composite, having inner volume of 2.7 cm3 and electrode area of 3 cm2 was prepared. Most part of internal resistance of the battery originated from the membrane and the electrical resistance of the membrane was strongly decreased with increase in NH4Cl concentration. When an aqueous solution containing 2 M of ZnI2 and 6 M of NH4Cl and Selemion CMV with thickness of 0.13 mm were used as the electrolytic solution and the cation exchanging membrane, respectively, the battery had energy density of 72 W h dm−3, current efficiency of almost 100%, and energy efficiency of 88%. The battery was rechargeable more than 380 times with decrease in the discharging capacity to about 80% and 75% of that of early cycles at 200th and 380th cycles, respectively. Self-discharging rate of the battery was about 10% per month. Open circuit voltage of the battery after charging showed slight dependence on temperature (dV/dT=0.0005), and the battery showed good charging—discharging behaviour in a temperature range of 5–50°C.