FACTORS AFFECTING THE INTERNAL RESISTANCE OF SILVER SILVER MOLYBDATE IODINE CELLS

A silver molybdate glass with the mol% stoichiometry of 60AgI-20Ag2.O-20MoO3 is prepared by liquid nitrogen temperature quenching of the melt. The glassy nature of the phase has been confirmed by powder X-ray diffraction. The conductivity of the glass from impedance spectroscopy is of the order 10(-3) S cm-1 at 300 K. The phase is an electrolyte and has been used to fabricate several iodine/silver electrochemical cells in which silver is mixed in different proportions with the solid electrolyte for the anode of the cells. The cathode consists of a fixed ratio of iodine, electrolyte and carbon. It is found that, if the cathode disc is placed over the electrolyte surface of the anode/electrolyte disc and clamped between two copper current collectors, the cell with a 1:1 weight ratio of silver powder and the electrolyte shows the lowest internal resistance. A second cell has been fabricated with this anode composition, but the anode, electrolyte and cathode are pressed together to form a single solid disc so as to eliminate cathode/electrolyte interfacial resistance that also contributes to the total internal resistance of the cell. For the cells with a composition of 1:1 silver powder and electrolyte weight ratio, the internal resistance of the cell decreases from 2.3 kOMEGA when the cathode and anode/electrolyte layers of the cell are pressed separately to 0.15 kOMEGA for a cell with the anode, electrolyte and cathode pressed together. The value of 0.15 kOMEGA is in reasonable agreement with the bulk resistance of the electrolyte as obtained from the impedance plot.