Medium and high-temperature carbon-air cell

Abstract

The present invention relates to a medium and high-temperature carbon-air cell, which include a solid oxide fuel cell, a CO.sub.2 separation membrane and a carbon fuel. The solid oxide fuel cell is a tubular solid oxide fuel cell with one end closed, the carbon fuel is placed inside the tubular solid oxide fuel cell, and the CO.sub.2 separation membrane is sealed at the open end of the solid oxide fuel cell. In the carbon-air cell, with carbon as fuel and oxygen in the air as an oxidizing gas, electrochemical reactions occur. The carbon-air cell of the present invention has a novel structural design, and can achieve electricity generation with the solid oxide fuel cell without externally charging a gas, and at the same time, CO.sub.2 generated inside the solid oxide fuel cell can be discharged from the system through the CO.sub.2 separation membrane in time.

Claims

1. A medium and high-temperature carbon-air cell, comprising: a solid oxide fuel cell having a tubular structure with one end closed; a CO.sub.2 separation membrane sealing an open end of the tubular structure, the CO.sub.2 separation membrane being an inorganic material that is formed by pressing a mixture of a carbonate and a high-temperature oxygen ion conductor, wherein the mass fraction of the carbonate in the mixture is 20% to 80%; and a carbon fuel placed inside the tubular structure, wherein electrochemical reactions occur in response to carbon being supplied as fuel, and oxygen in the air being supplied as an oxidizing gas.

2. The carbon-air cell according to claim 1, wherein the solid oxide fuel cell has an anode-supported configuration, an electrolyte-supported configuration or a cathode-supported configuration; the solid oxide fuel cell comprises three layers that include an anode, an electrolyte and a cathode; and the anode is located inside a cell tube, the cathode is located outside the cell tube, and an electrolyte layer is located between the anode and the cathode.

3. The carbon-air cell according to claim 2, wherein the electrolyte layer of the solid oxide fuel cell is at least one or a combination of stabilized zirconia, doped ceria and doped lanthanum gallate; and the combination form is mixing or multi-layer stacking.

4. The carbon-air cell according to claim 2, wherein the anode of the solid oxide fuel cell is a mixture of an electrolyte material and at least one of: (i) an elemental metals Ni, Pt, Ag, Ru, Fe and Cu, or (ii) a perovskite material, and the mass fraction of the elemental metal in the mixture is 10% to 90%.

5. The carbon-air cell according to claim 2, wherein the cathode of the solid oxide fuel cell is a mixture of at least La.sub.0.8Sr.sub.0.2MnO.sub.3, La.sub.0.6Sr.sub.0.4Co.sub.0.2Fe.sub.0.8O.sub.3, Ba.sub.0.5Sr.sub.0.5Co.sub.0.8Fe.sub.0.2O, La.sub.2NiO.sub.4, PrBaCoO.sub.5, Pt, AgSm.sub.0.2Ce.sub.0.8 O.sub.1.9 or AgLa.sub.0.8Sr.sub.0.2MnO.sub.3 and an electrolyte material, and the mass fraction of the electrolyte material in the mixture is 0 to 90%.

6. The carbon-air cell according to claim 1, wherein an operating temperature of the carbon-air cell is 500 C. to 900 C.

7. The carbon-air cell according to claim 1, wherein the carbonate includes at least Li.sub.2CO.sub.3, NaCO.sub.3 or K.sub.2CO.sub.3; and a high-temperature oxygen ion conductor at least is SDC, GDC or YSZ.

8. The carbon-air cell according to claim 1, wherein the fuel carbon is at least one of charcoal, bamboo charcoal, activated carbon, coke, amorphous carbon, powdered coal or graphite, or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the disclosure, and wherein:

(2) FIG. 1 is a schematic diagram of a carbon-air cell according to the present invention, where 1 is a CO.sub.2 separation membrane, 2 is a solid oxide fuel cell, 3 is a carbon fuel, A is a negative pole (anode), and B is a positive pole (cathode);

(3) FIG. 2 is a schematic diagram of a CO.sub.2 separation membrane according to the present invention, where C is the inside of the cell, and D is the outside of the cell;

(4) FIG. 3 is a schematic structural diagram of a solid oxide fuel cell according to the present invention, where 2-1 is an anode, 2-2 is an electrolyte, and 2-3 is a cathode;

(5) FIG. 4 is a cross-section morphology of a single cell according to Embodiment 1 after test; and

(6) FIG. 5 is a performance chart of a single cell according to Embodiment 4 in test.

DETAILED DESCRIPTION

(7) The method involved in the present invention includes, but not limited to, materials in the following embodiments.

(8) Embodiment 1:An NiO-YSZ anode support tube was prepared by a casting method, and the support tube was dried and then sintered at 1100 C. A layer of YSZ electrolyte film was prepared on the anode support surface by a spraying method, and the electrolyte film was sintered at 1400 C. to obtain a half-cell. The half-cell was subjected to high-temperature reduction (750 C.) for 2 hours under hydrogen atmosphere to obtain an anode reduced half-cell, and the mass fraction of YSZ in the reduced anode support tube was 50%. Next, a layer of LSM cathode was sprayed on the half-cell surface, and then sintered for 5 hours at 1100 C. under inert atmosphere to obtain an anode supported tubular solid oxide fuel cell. As shown in FIG. 1, activated carbon was filled inside the solid oxide fuel cell tube, and naturally stacked to a level about 1 cm from the tube orifice. Elargol was coated on the cathode surface of the solid oxide fuel cell as a current collector, and wires were respectively introduced from the cathode and the anode as the positive pole and the negative pole.

(9) YSZ and K.sub.2CO.sub.3 were mixed at a mass ratio of 2:1 (mass ratio), and then the mixture was subjected to isostatic pressing to prepare a sheet having a cross-section size the same as that of the tubular solid oxide fuel cell as the CO.sub.2 separation membrane, and the open end of the tubular solid oxide fuel cell was sealed with the CO.sub.2 separation membrane by elargol to obtain a carbon-air cell. The schematic diagram of the carbon-air cell after assembly is shown in FIG. 1. The microtopography of the cross-section of the solid oxide fuel cell is shown in FIG. 4, and it can be seen from FIG. 4 that, the electrolyte layer is compact, and the anode layer and the cathode layer are porous.

(10) The carbon-air cell works at 800 C., the open-circuit voltage is 0.86 V, the power density is up to 150 mWcm.sup.2, and the cell capacity is up to 4200 mAh g.sup.1,

(11) Embodiment 2: A GDC electrolyte support tube was prepared by a casting method, and the support tube was dried and then sintered at 1400 C. A layer of GDC-CuO anode film was prepared on the inner surface of the electrolyte support tube by an impregnation method, and then sintered at 1400 C. to obtain a half-cell. The half-cell was subjected to high-temperature reduction (750 C.) for 2 hours under hydrogen atmosphere to obtain an anode reduced half-cell, and the mass fraction of Cu in the reduced anode support tube was 30%. Next, a layer of LSCF electrode was sprayed on the half-cell surface, and then sintered for 5 hours at 1100 C. under inert atmosphere to obtain an electrolyte supported tubular solid oxide fuel cell. Activated carbon was filled inside the solid oxide fuel cell tube, elargol was coated on the cathode surface of the oxide fuel cell as a current collector, and wires were respectively introduced from the cathode and the anode as the positive pole and the negative pole.

(12) GDC and K.sub.2CO.sub.3 were mixed at a mass ratio of 1:1 (mass ratio), and then the mixture was subjected to isostatic pressing to prepare a sheet having a cross-section size the same as that of the tubular solid oxide fuel cell as the CO.sub.2 separation membrane, and the open end of the tubular solid oxide fuel cell was sealed with the CO.sub.2 separation membrane by elargol to obtain a carbon-air cell.

(13) The carbon-air cell works at 900 C., the open-circuit voltage is 0.72 V, the power density is up to 150 mWcm.sup.2, and the cell capacity is up to 2800 mAh g.sup.1.

(14) Embodiment 3: A cathode support tube was prepared by a casting method, and the support tube was dried and then sintered at 1000 C. A layer of YSZ electrolyte film was prepared on the inner surface of the cathode support tube by an impregnation method, and then sintered at 1300 C. to obtain a half-cell. A layer of SDC-NiO anode was prepared on the inner surface of the half-cell through impregnation, and then sintered for 5 hours at 1300 C. under air atmosphere to obtain an anode unreduced tubular solid oxide fuel cell. The tubular solid oxide fuel cell was subjected to high-temperature reduction (750 C.) for 2 hours under hydrogen atmosphere to obtain an anode reduced cathode supported tubular solid oxide fuel cell, and the mass fraction of Ni in the reduced anode support tube was 60%. Activated carbon was filled inside the solid oxide fuel cell tube, elargol was coated on the cathode surface of the solid oxide fuel cell cathode as a current collector, and wires were respectively introduced from the cathode and the anode as the positive pole and the negative pole.

(15) YSZ and K.sub.2CO.sub.3 were mixed at a mass ratio of 3:1 (mass ratio), and then the mixture was subjected to isostatic pressing to prepare a sheet having a cross-section size the same as that of the tubular solid oxide fuel cell as the CO.sub.2 separation membrane, and the open end of the tubular solid oxide fuel cell was sealed with the CO.sub.2 separation membrane by elargol to obtain a carbon-air cell.

(16) The carbon-air cell works at 500 C., the open-circuit voltage is 0.84 V, the power density is up to 40 mWcm.sup.2, and the cell capacity is up to 3800 mAh g.sup.1.

(17) Embodiment 4: NiO and YSZ were mixed, and the mixture was added with water and an adhesive, and then ball-milled for 1 hour; the mixture was added with 5% (mass fraction) Arabic gum and continuously ball-milled for 1 hour, to obtain slurry having a solid content of 70% (mass fraction). The slurry was casted into a construction mold to obtain an anode support tube, and the support tube was dried and then sintered at 1100 C. A layer of YSZ electrolyte film was prepared on the anode support surface by a spraying method, the electrolyte film was sintered at 1400 C., and then an SDC electrolyte layer was prepared on the YSZ electrolyte film by spraying and sintered at 1300 C. to obtain a half-cell. The half-cell was subjected to high-temperature reduction (750 C.) for 2 hours under hydrogen atmosphere to obtain an anode reduced half-cell, and the mass fraction of Ni in the reduced anode support tube was 20%. Next, a layer of BSCF electrode was prepared on the half-cell surface by spraying, and then sintered for 2 hours at 1000 C. under inert atmosphere to obtain an anode supported tubular solid oxide fuel cell. Graphite powder was filled inside the solid oxide fuel cell tube, elargol was coated on the cathode surface of the solid oxide fuel cell as a current collector, and wires were respectively introduced from the cathode and the anode as the positive pole and the negative pole.

(18) SDC and K.sub.2CO.sub.3 were mixed at a mass ratio of 1:1 (mass ratio), and then the mixture was subjected to dry pressing to prepare a sheet having a cross-section size the same as that of the tubular solid oxide fuel cell as the CO.sub.2 separation membrane, and the open end of the tubular solid oxide fuel cell was sealed with the CO.sub.2 separation membrane by elargol to obtain a carbon-air cell. Results of test of the single cell at 700 C., 750 C. and 800 C. are shown in FIG. 5, and it can be seen from FIG. 5 that, the open-circuit voltages of the carbon-air cell are respectively 0.71 V, 0.75 V and 0.78 V, and the maximal powers are respectively 0.17 W, 0.42 W and 0.48 W.

(19) Embodiment 5: The process was the same as that in Embodiment 4, except that the carbon fuel was changed from graphite powder into powered coal.

(20) The carbon-air cell works at 700 C., the open-circuit voltage is 0.88 V, the power density is up to 110 mWcm.sup.2, and the cell capacity is up to 4400 mAh g.sup.1.

(21) Embodiment 6: The process was the same as that in Embodiment 4, except that the CO.sub.2 separation membrane was prepared by Na.sub.2CO.sub.3 and SDC at a ratio of 1:2 (mass ratio) through mixing and dry pressing.

(22) The carbon-air cell works at 700 C., the open-circuit voltage is 0.85 V, the power density is up to 100 mWcm.sup.2, and the cell capacity is up to 3900 mAh g.sup.1.

(23) Embodiment 7: The process was the same as that in Embodiment 4, except that the CO.sub.2 separation membrane was prepared by Na.sub.2CO.sub.3, Li.sub.2CO.sub.3 and GDC at a ratio of 1:1:2 (mass ratio) through mixing and dry pressing.

(24) The carbon-air cell works at 700 C., the open-circuit voltage is 0.88 V, the power density is up to 130 mWcm.sup.2, and the cell capacity is up to 4300 mAh g.sup.1.