Low Temperature Electrolytes for Solid Oxide Cells Having High Ionic Conductivity

Example 1

[0213]FIG. 3 depicts one embodiment of the invention in the form of a solid oxide cell having a metal oxide electrolyte 380 positioned between a first electrode 310 and a second electrode 320. The metal oxide electrolyte 380 comprises a powder 350 together with a metal oxide 360. In some cases, the powder 350 can be mixed with one or more metal compounds to form a slurry that is then applied by spin coating, brushing, or other suitable method onto the first electrode 310 (or second electrode 320). Then, the metal compound is converted to form the metal oxide 360, for example, by heating the atmosphere about the metal compound, or by inductively heating the first electrode 310. Optionally, once a layer of the metal oxide electrolyte 380 has been formed, additional powder-metal compound slurry can be applied and heated to form a thicker metal oxide electrolyte 380. The cell is assembled by placing the second electrode 320 onto the metal oxide electrolyte 380, or, optionally, additional metal compound (or powder-metal compound slurry) is converted to metal oxide while contacting the metal oxide electrolyte 380 and the second electrode 320, to provide better contact between the metal oxide electrolyte 380 and the second electrode 320. In certain cases, the powder 350 is strontium titanate, and the metal oxide 360 is yttria-stabilized zirconia.

[0214]In operation, for example, air or other oxygen-containing gas is supplied to the first electrode 310, which acts as the cathode to reduce diatomic oxygen to O2−. O2− (shown as O═) then diffuses through the metal oxide electrolyte 380 to the second electrode 320, where the O2− joints H+ to form water (not shown). The H+ results from the oxidation of, for example, hydrogen gas at the second electrode 320, which acts as an anode. Circuitry (not shown) transmits electrons from the anode (second electrode 320) to the cathode (first electrode 310).

Example 2

[0215]FIG. 4 depicts another embodiment of the present invention, in which a first metal oxide 450 and a second metal oxide 460, disposed in interpenetrating domains of metal oxides, form a metal oxide electrolyte between two electrodes 410, 420. To form such domains, a first metal compound composition is applied to the first electrode 410 and converted to a first metal oxide 450, such as, for example, strontium titanate. Then, a second metal compound composition is applied to the first metal oxide 450 and allowed to accumulate in pores, imperfections, and defects in the first metal oxide so formed. The second metal oxide composition is converted to form a second metal oxide 460, such as, for example, yttria-stabilized zirconia. Six alternating layers of the first metal oxide 450 and the second metal oxide 460 are formed in this embodiment.

[0216]In operation, for example, air or other oxygen-containing gas is supplied to the first electrode 410, which acts as the cathode to reduce diatomic oxygen to O2−. O2− (shown as O═) then diffuses through the metal oxide electrolyte 480 to the second electrode 420, where the O2− joints H+ to form water (not shown). The H+ results from the oxidation of, for example, hydrogen gas at the second electrode 420, which acts as an anode. Circuitry (not shown) transmits electrons from the anode (second electrode 420) to the cathode (first electrode 410).

Example 3

[0217]FIG. 5 depicts a solid oxide cell according to one embodiment of the present invention. A nanobar 540 and a metal oxide 560, disposed so that the nanobars 540 orient substantially perpendicularly to a first planar electrode 510, form a metal oxide electrolyte 580 between two electrodes 510, 520. The nanobar 540 can be, for example, a multi-walled carbon nanotube of semiconductor characteristic, oriented in metal oxide 560 which can be, for example, yttria-stabilized zirconia. To make the cell of FIG. 5, chosen nanobars 540 are combined with at least one metal compound in a metal compound composition, that is then applied to the first electrode 510. An orienting force is then applied. Optionally, the first electrode with the metal compound composition is placed in a magnetic field, at least a portion of the nanobars orient due to the magnetic field, and the metal compound composition is converted to form the metal oxide 560. Or, an electric field is applied to orient at least a portion of the nanobars 540, and the metal compound composition is converted to form the metal oxide 560. In some cases, the second electrode 520 is placed over the metal compound composition on the first electrode 510, and an electric field is established between the first electrode 510 and the second electrode 520, thereby orienting at least a portion of the nanobars 540. Then the metal compound composition is converted, such as, for example, by heating, thereby forming the metal oxide 560 and the metal oxide electrolyte 580.

[0218]In operation, for example, air or other oxygen-containing gas is supplied to the first electrode 510, which acts as the cathode to reduce diatomic oxygen to O2−. O2− (shown as O═) then diffuses through the metal oxide electrolyte 580 to the second electrode 520, where the O2− joints H+ to form water (not shown). The H+ results from the oxidation of, for example, hydrogen gas at the second electrode 520, which acts as an anode. Circuitry (not shown) transmits electrons from the anode (second electrode 520) to the cathode (first electrode 510).