# US 8,771,901 B2 · SOFC stack having a high temperature bonded ceramic interconnect and method for making same

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- Number: US 8,771,901 B2
- Document ID: US8771901B2
- Status: Granted
- Kind: B2
- Application number: 11/696,624
- Filed: 2007-04-04
- Published: 2007-10-11
- Granted: 2014-07-08
- Earliest claimed: 2006-04-05
- Assignees: Saint-Gobain Ceramics & Plastics, Inc.
- Applicants: William J. Donahue; Oh-Hun Kwon; F. Michael Mahoney; John D. Pietras
- Inventors: William J. Donahue; Oh-Hun Kwon; F. Michael Mahoney; John D. Pietras
- Web page: https://patentgrep.com/patent/US8771901B2

## CPC

- H01M 8/2425: High-temperature cells with solid electrolytes
- C04B 35/645: Pressure sintering
- C04B 37/005: {consisting of glass or ceramic material}
- H01M 4/8885: {Sintering or firing}
- H01M 4/9025: {Oxides specially used in fuel cell operating at high temperature, e.g. SOFC}
- H01M 4/9066: {of metal-ceramic composites or mixtures, e.g. cermets}
- H01M 8/0219: {Chromium complex oxides}
- H01M 8/0236: Glass; Ceramics; Cermets
- H01M 8/0241: Composites
- H01M 8/0297: Arrangements for joining electrodes, reservoir layers, heat exchange units or bipolar separators to each other (H01M8/0271 takes precedence)
- H01M 8/2404: Processes or apparatus for grouping fuel cells
- H01M 8/2432: Grouping of unit cells of planar configuration
- C04B 2237/06: Oxidic interlayers
- C04B 2237/066: based on rare earth oxides
- C04B 2237/068: based on refractory oxides, e.g. zirconia
- C04B 2237/708: of one or more of the interlayers
- H01M 8/1253: the electrolyte containing zirconium oxide
- H01M 2008/1293: {Fuel cells with solid oxide electrolytes}
- Y02E 60/50: Fuel cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The present disclosure is directed to an integrated SOFC stack including, a first cell having a cathode layer, an electrolyte layer overlying the cathode layer, and an anode layer overlying the electrolyte layer. The SOFC stack also includes a second cell having a cathode layer, an electrolyte layer overlying the cathode layer, and an anode overlying the electrolyte layer. The SOFC stack further includes a ceramic interconnect layer between the first cell and the second cell, the ceramic interconnect layer having a first high temperature bonding region along the interfacial region between the first cell and the ceramic interconnect layer. The ceramic interconnect layer also includes a second high temperature bonding region along the interfacial region between the second cell and the ceramic interconnect layer.

## Claims

### Claim 1

An integrated solid oxide fuel cell (SOFC) stack comprising:
a first cell having a cathode layer, an electrolyte layer overlying the cathode layer, and an anode layer overlying the electrolyte layer;
a second cell having a cathode layer, an electrolyte layer overlying the cathode layer, and an anode overlying the electrolyte layer, wherein the first cell and the second cell include gas delivery channels formed within the cathode layer or the anode layer; and
a planar ceramic interconnect layer having a thickness of not less than 1 micron and not greater than 15 microns between the first cell and the second cell, the ceramic interconnect layer having a first high temperature bonding region along an interfacial region between the first cell and the ceramic interconnect layer, and a second high temperature bonding region along an interfacial region between the second cell and the ceramic interconnect layer,
wherein the first and second high temperature bonding regions include a diffusion bond between the ceramic interconnect layer and the first cell and a diffusion bond between the ceramic interconnect layer and the second cell, and wherein the diffusion bonds have a diffusion region having a thickness not less than 10 microns and not greater than 300 microns.

### Claim 2 (depends on 1)

The integrated solid oxide fuel cell (SOFC) stack of claim 1, wherein the ceramic interconnect layer includes a percent porosity of less than 3.0 vol %.

### Claim 3 (depends on 1)

The integrated solid oxide fuel cell (SOFC) stack of claim 1, wherein the diffusion bond between the ceramic interconnect layer and the first cell is disposed along the entire interfacial region between the first cell and the ceramic interconnect layer.

### Claim 4 (depends on 1)

The integrated solid oxide fuel cell (SOFC) stack of claim 1, wherein the diffusion bond between the ceramic interconnect layer and the second cell is disposed along the entire interfacial region between the second cell and the ceramic interconnect layer.

### Claim 5

A method for forming an integrated solid oxide fuel cell (SOFC) stack comprising:
forming a first cell structure, the first cell structure having a first electrode layer, an electrolyte layer overlying the first electrode layer, and a second electrode layer overlying the electrolyte layer;
forming a ceramic interconnect layer overlying the first cell structure;
forming a second cell structure, the second cell structure having a first electrode layer, an electrolyte layer overlying the first electrode layer, and a second electrode layer overlying the electrolyte layer; and
hot pressing the first cell structure, the ceramic interconnect layer, and the second cell structure together during a single hot pressing cycle to integrally bond the first cell structure, the ceramic interconnect layer and the second cell structure to form an integrated SOFC stack,
wherein the hot pressing is conducted at a temperature not less than 1200° C. and not greater than 1,800° C. and a pressure of not less than 0.5 MPa and not greater than 10 MPa,
wherein the ceramic interconnect layer of the integrated SOFC stack is planar and has a thickness of not less than 1 micron and not greater than 15 microns,
wherein the integrated SOFC stack includes a diffusion region along an interfacial region of the ceramic interconnect layer and the first cell structure, the second cell structure, or a combination thereof, and
wherein the first cell structure and the second cell structure include gas delivery channels formed within the first electrode layer or the second electrode layer.

### Claim 6 (depends on 5)

The method of claim 5, wherein hot pressing includes pressing the first cell structure, the ceramic interconnect layer, and the second cell structure together to form an integrally bonded structure in one thermal cycle.

### Claim 7 (depends on 5)

The method of claim 5, wherein the ceramic interconnect layer electrically connects the first cell structure and the second cell structure.

### Claim 8 (depends on 5)

The method of claim 5, wherein hot pressing includes forming a first high temperature bond region between the ceramic interconnect layer and an adjacent electrode layer in the first cell structure and a second high temperature bond region between the ceramic interconnect layer and an adjacent electrode layer in the second cell structure.

### Claim 9 (depends on 8)

The method of claim 8, wherein forming the first and second high temperature bond regions includes forming a diffusion bond region having a thickness not less than 10 microns and not greater than 300 microns.

### Claim 10 (depends on 5)

The method of claim 5, wherein the hot pressing is performed without the aid of a restraining die.

### Claim 11 (depends on 5)

The method of claim 5, wherein the forming of the first cell structure and the second cell structure is performed without the addition of pore formers.

### Claim 12

A method for forming an integrated, densified solid oxide fuel cell (SOFC) component comprising:
forming a first green cell structure having a first green electrode layer, a green electrolyte layer overlaying the first green electrode layer, and a second green electrode layer overlaying the green electrolyte layer;
forming a second green cell structure having a first green electrode layer, a green electrolyte layer overlaying the first green electrode layer, and a second green electrode layer overlaying the green electrolyte layer;
forming a green ceramic interconnect layer disposed between the first green cell structure and the second green cell structure; and
hot pressing the first green cell structure, the green ceramic interconnect layer, and the second green cell structure together during a single hot pressing cycle to integrally bond the first green cell structure, the green ceramic interconnect layer and the second green cell structure to form an integrated, densified SOFC component,
forming gas delivery channels within a resultant first electrode layer or a resultant second electrode layer of a resultant first or second cell structure of the integrated, densified SOFC component;
wherein a resultant interconnect layer of the integrated, densified SOFC component is planar and has a thickness of not less than 1 micron and not greater than 15 microns, and wherein the hot pressing is conducted at a temperature not less than 1200° C. and not greater than 1,800° C. and a pressure of not less than 0.5 MPa and not greater than 10 MPa.