Unit cell of solid oxide fuel cell, stack using the unit cell, and methods of manufacturing the unit cell and the stack

Patent metadata

Field	Value
Publication number	US-2016064767-A1
Application number	US-201514838138-A
Country	US
Kind code	A1
Filing date	Aug 27, 2015
Priority date	Aug 27, 2014
Publication date	Mar 3, 2016
Grant date	—

Abstract

A unit cell includes an air inlet/outlet that is formed on a frame unit rather than being installed in a fuel electrode (anode) to simplify a sealing process, and accordingly, a continuous process using a tape casting technique may be performed. In addition, an electrolyte material that is in contact with an air electrode (cathode) in the frame unit is optimized to improve ion conductivity and a porosity of an upper layer material of the fuel electrode unit is optimized to increase fuel diffusion from a gas channel to an electrolyte layer. In addition, a sealing process performed inside the unit cell or between the unit cells of the stack is stabilized and strongly maintained, and thus a fuel cell using the unit cell and the stack disclosed herein may have excellent economic feasibility and high energy efficiency.

First claim

What is claimed is:

1 . A unit cell of a solid oxide fuel cell (SOFC), the unit cell comprising:
a fuel electrode unit having a gas channel formed therein for fuel flow; a frame formed of an electrolyte material and configured to cover and contacting the fuel electrode unit wherein the frame comprises an opening formed at a bottom portion thereof; an interconnector positioned at the opening whereby it covers and contact the fuel electrode; and an air electrode unit covering and contacting a top portion of the frame; wherein the frame comprises a fuel inlet/outlet and an air inlet/outlet, and wherein the fuel inlet/outlets are formed on each side of the front and the rear of frame penetrating the frame in a vertical direction to be connected with each end of the gas channel of the fuel electrode unit, and the air inlet/outlets are formed on each side of the right and left penetrating the frame in a vertical to supply an air to the air electrode unit.

2 . The unit cell of claim 1 , wherein the gas channel is a tube, lattice, or honeycomb form.

3 . The unit cell of claim 1 , wherein the frame is made of 3 mol % to 8 mol % of Y 2 O 3 -doped zirconia.

4 . The unit cell of claim 3 , wherein the top portion of the frame that contacts the air electrode unit is made of an electrolyte material that is different from the rest of the frame and selected from zirconia doped with scandium (Sc) or ytterbium (Yb), ceria doped with yttrium (Y), gadolinium (Gd), or samarium (Sm), and LaGaO 3 dope with strontium (Sr) and magnesium (Mg).

5 . The unit cell of claim 1 , wherein a material for forming the fuel electrode unit comprises a composite comprising an ion conductive electrolyte material and at least one selected from a nickel, a nickel alloy, and an iron-based alloy,
wherein the ion conductive electrolyte material comprises at least one selected from a group consisting of a yttria-stabilized zirconia (YSZ), a scandia-a stabilized zirconia (ScSZ), a Gd doped-ceria (GDC), a Sm doped-ceria, and a lanthanum gallates.

6 . The unit cell of claim 1 , wherein the interconnector is formed of a material selected from a ceramic or a composite of a ceramic and an ion conductive electrolyte material,
wherein the ceramic comprises at least one selected from a group consisting of a strontium titanium ferrite (STF), a lanthanum strontium ferrite (LSF), a LSF comprising Sc (LSFSc), a lanthanum calcium ferrite (LCF), a lanthanum strontium manganite (LSM), a lanthanum strontium cobatite (LSC), a lanthanum strontium chromite (LSCr), a lanthanum strontium cobalt ferrite (LSCF), a manganese ferrite (MnFe 2 O 4 ), and nickel ferrite (NiFe 2 O 4 ), and the ion conductive electrolyte material comprises at least one selected from a Gd doped-ceria (GDC) or a La doped-ceria.

7 . The unit cell of claim 1 , wherein the fuel electrode unit comprises a fuel diffusion layer and a fuel electrode support that have a different porosity from each other,
the fuel diffusion layer has a porosity of at least about 30%, and an upper surface of the fuel diffusion layer is in contact with an inner surface of the frame and a bottom surface of the fuel diffusion layer is in contact with the fuel electrode support, thereby form the fuel flow passage unit.

8 . The unit cell of claim 1 , wherein the fuel electrode unit is formed of a composite comprising nickel (Ni) and YSZ, and
a Ni-GDC composite layer is further comprised between the fuel electrode unit and the interconnector.

9 . A method of manufacturing a unit cell of a solid oxide fuel cell (SOFC), the method comprising:
preparing an upper layer of a frame, upper/intermediate/bottom layers of a fuel electrode unit, and an interconnecting layer, wherein the upper layer of the frame is formed of a same material with an electrolyte material; the upper/intermediate/bottom layers of the fuel electrode unit are surrounded by the frame that includes a first border as a portion of the frame formed of the same material with the electrolyte material and the fuel electrode unit positioned inside the first border; and the interconnecting layer is surrounded by the frame that includes a second border as a portion of the frame formed of the same electrolyte material with the electrolyte material and a ceramic interconnector positioned inside the second border, processing a space for a fuel flow passage unit, the gas channels being extended from a predetermined position on a portion of the first border with respect to the intermediate layer of the fuel electrode unit to a predetermined position on another portion opposite to the one portion of the same first border by penetrating the upper/intermediate/bottom layers of the fuel electrode unit; laminating the interconnecting layer surrounded by the frame, the bottom/intermediate/upper layers of the fuel electrode unit surrounded by the frame, and the upper surface of the frame sequentially in the stated order; processing an air inlet/outlet and a fuel inlet/outlet, wherein the air inlet/outlet penetrates both side surfaces of the laminated frame and the fuel inlet/outlet penetrates front and rear parts of the frame to be connected with the gas channels; manufacturing a half-cell by performing heat treatment on the laminated structure comprising the air inlet/outlet and the fuel inlet/outlet; applying a coating of a material for forming an air electrode unit to a central part of an upper surface of the upper layer of the frame that constitutes the half-cell, thereby manufacturing a coated structure; and heat-treating the coated structure.

10 . The method of claim 9 , wherein the upper layer of the frame, the upper/intermediate/bottom layers of the fuel electrode unit, and the interconnecting layer are prepared according to a tape casting technique,
the air electrode unit material layer is coated according to a screen printing technique, the material for forming the frame comprises 3 mol % Y 2 O 3 -doped zirconia, the material for forming a part of the frame that is in contact with the upper surface, which is coated with the air electrode unit, of the fuel electrode comprises at least one selected from zirconia comprising Sc or Yb, ceria comprising Y, Gd, or Sm, and LaGaO 3 comprising both Sr and Mg, and the upper layer of the fuel electrode unit has a porosity different from that of the intermediate/bottom layers of the fuel electrode unit, wherein the upper layer of the fuel electrode unit has a porosity of at least about 30%.

11 . A stack of a solid oxide fuel cell (SOFC) using the unit cell, the stack comprising:
a plurality of unit cells, each of which comprises a fuel inlet/outlet and an air inlet/outlet formed inside a frame, wherein the plurality of the unit cells are sequentially laminated to dispose an airflow layer between an air electrode unit comprised in one unit cell of the plurality of the unit cells and an interconnector comprised in another unit cell of the plurality of the unit cells, the airflow layer comprises a frame border comprising a fuel inlet/outlet and an air inlet/outlet, and the air inlet/out and the fuel inlet/outlet is connected with the plurality of the unit cells, and each of the plurality of the unit cells is the unit cell of claim 1 .

12 . The stack of claim 11 , wherein the airflow layer comprised in the stack is in a tube, lattice, or honeycomb type.

13 . The stack of claim 11 , wherein the gas channel is a tube, lattice, or honeycomb form.

14 . The stack of claim 11 , wherein the frame is made of 3 mol % to 8 mol % of Y 2 O 3 -doped zirconia, wherein the top portion of the frame that contacts the air electrode unit is m

Assignees

• Korea Energy Research Inst

Inventors

• Yu Ji Haeng
• Joo Jong Hoon
• Yoo Chung-Yul

Classifications

• H01M2008/1293

  Fuel cells with solid oxide electrolytes · CPC title

• H01M2300/0077

  based on zirconium oxide · CPC title

• H01M4/8652 Primary

  as mixture · CPC title

• H01M8/2485 Primary

  Arrangements for sealing external manifolds; Arrangements for mounting external manifolds around a stack · CPC title

• H01M4/905

  specially used in fuel cell operating at high temperature, e.g. SOFC · CPC title