GB1318713A - Solid state electrochemical cells - Google Patents

Abstract

1318713 Solid state cell PHILIP MORRIS Inc 10 Nov 1970 [20 Nov 1969 12 June 1970 (2) 15 June 1970] 53331/70 Heading H1B [Also in Division G1] A solid state cell has an electrolyte consisting of a solid rare earth fluoride, i.e. the fluoride of scandium, yttrium, lanthanum and of the metals of the lanthanide series (atomic numbers 58-71). The cell may be used to determine the oxygen concentration of a sample (see Division G1). For use as a power supply producing extremely small currents the cell may have a gasimpermeable covering so that it is not oxygensensitive. Thus, for example, when it is connected to a load resistance of 1À0 x 10<SP>9</SP> ohms the cell has a voltage of 0À15 volts and gives a current of 1À5 x 10<SP>-10</SP> amps. The voltage decreases with increasing current so that the voltage eventually becomes zero to provide an inherent safeguard. In another application of the cell it is implanted in the body to receive oxygen from the blood and provide a modicum of power for use in biomedical electronics. The electrode requirements are that the anode forms stable fluorides and oxides and that the cathode is inert. Suitable anode metals are silver, zinc, bismuth, beryllium, cadmium, rubidium, lanthanum, iron, lead and suitable cathode metals are gold, platinum, rhodium, palladium. The cell is constructed by the forming of successive films on an insulative substrate by vapour deposition techniques. Thus the cell of Figs. 1, 2, 3 comprises an insulative support 10, a film 12 of anodic metal, a film 14 of solid electrolyte and a film 16 of cathodic metal. An overlying insulative film 18 is oxygen-permeable or oxygenimpermeable depending upon how the cell is to function. A permeable film 18 may be of P.T.F.E. or polyethylene and an impermeable film may be of silicon dioxide, tantalum oxide, aluminium oxide or silicon oxide. Anodic film 12 has a strip portion 12a extending through films 14, 16 to an anode terminal pad 12b, the strip portion being covered by an insulative film 20 of silicon dioxide. Cathodic film 16 has a strip portion 16a and terminal pad 16b. In another embodiment, Figs. 4, 5, a circular cathodic film 28 is coplanar with an anodic film 26 having a re-entrant portion 26e, 26f receiving the cathodic film. Anodic strip portions 26a, 26b have terminal pads 26c, 26d and a cathodic strip portion 28a having an overlying insulative film 30 is provided with a terminal pad 28b. In a modification (Fig. 6, not shown) the re-entrant portion of the anodic film and the cathodic film are rectangular-shaped.