# US 12,009,556 B2 · Fuel cell system and control method for fuel cell system

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- Number: US 12,009,556 B2
- Document ID: US12009556B2
- Status: Granted
- Kind: B2
- Application number: 17/807,107
- Filed: 2022-06-15
- Published: 2022-09-29
- Granted: 2024-06-11
- Earliest claimed: 2020-01-17
- Assignees: Panasonic Intellectual Property Management Co., Ltd.
- Applicants: Panasonic Intellectual Property Management Co., Ltd.
- Inventors: Takeshi Terayama; Tomohiro Kuroha; Kyohei Kawada
- Web page: https://patentgrep.com/patent/US12009556B2

## CPC

- H01M 8/04228: during shut-down
- H01M 8/04303: applied during shut-down
- H01M 8/04089: of gaseous reactants
- H01M 8/04238: {Depolarisation}
- H01M 8/0432: Temperature; Ambient temperature
- H01M 8/04544: {Voltage}
- H01M 8/04701: Temperature
- H01M 8/04753: {of fuel cell reactants}
- H01M 8/04865: {Voltage}
- H01M 8/04873: {of the individual fuel cell}
- H01M 8/0488: {of fuel cell stacks}
- H01M 8/04947: {of auxiliary devices, e.g. batteries, capacitors}
- H01M 8/04955: Shut-off or shut-down of fuel cells
- H01M 8/1004: characterised by membrane-electrode assemblies [MEA] (H01M8/12 takes precedence)
- H01M 8/1016: characterised by the electrolyte material (H01M8/12 takes precedence)
- H01M 8/1246: the electrolyte consisting of oxides
- H01M 8/126: the electrolyte containing cerium oxide
- H01M 2008/1293: {Fuel cells with solid oxide electrolytes}
- H01M 2300/0074: Ion conductive at high temperature
- Y02E 60/50: Fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

The fuel cell system of the present disclosure includes: a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas; a power source that applies a voltage to the fuel cell; and a controller. In a shutdown process, the controller controls the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell.

## Claims

### Claim 1

A fuel cell system comprising:
a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
a power source that applies a voltage to the fuel cell;
a temperature detector that detects a temperature of the fuel cell; and
a controller including a processing unit and a memory circuit storing a control program,
wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
wherein the electrolyte membrane has hole conductivity, and
wherein the control program, when executed by the processing unit, causes the controller to control the power source in the shutdown process such that the terminal voltage is equal to or higher than the open circuit voltage until the temperature detected by the temperature detector is determined to be equal to or lower than a temperature at which hole conduction in the electrolyte membrane decreases.

### Claim 2 (depends on 1)

The fuel cell system according to claim 1, wherein the control program, when executed by the processing unit, causes the controller to control the power source in the shutdown process such that the terminal voltage is equal to or higher than the open circuit voltage and lower than a voltage at which electrolysis of water starts at the cathode.

### Claim 3

A fuel cell system comprising:
a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
a power source that applies a voltage to the fuel cell;
a temperature detector that detects a temperature of the fuel cell; and
a controller including a processing unit and a memory circuit storing a control program,
wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell, and
wherein the control program, when executed by the processing unit, causes the controller to control the power source in the shutdown process such that the terminal voltage is equal to or higher than the open circuit voltage until the temperature detected by the temperature detector is determined to be equal to or lower than a temperature at which an oxidation-reduction reaction at the anode slows down.

### Claim 4 (depends on 1)

The fuel cell system according to claim 1, wherein the control program, when executed by the processing unit, causes the controller to control the power source in the shutdown process such that the terminal voltage is equal to or higher than the open circuit voltage until the temperature detected by the temperature detector is determined to be equal to or lower than 500° C.

### Claim 5 (depends on 1)

The fuel cell system according to claim 1, wherein the control program, when executed by the processing unit, causes the controller to control the power source in the shutdown process such that the terminal voltage is equal to or higher than the open circuit voltage until the temperature detected by the temperature detector is determined to be equal to or lower than 400° C.

### Claim 6 (depends on 1)

The fuel cell system according to claim 1, further comprising a voltage detector that detects a voltage of the fuel cell,
wherein the open circuit voltage is the voltage of the fuel cell that is detected by the voltage detector when no electric current is inputted/outputted to/from the fuel cell.

### Claim 7 (depends on 1)

The fuel cell system according to claim 1, wherein the shutdown process is performed in a period from when the temperature of the fuel cell starts decreasing until the temperature of the fuel cell becomes lower than 200° C.

### Claim 8 (depends on 1)

The fuel cell system according to claim 1, further comprising:
a fuel gas feeder that feeds the fuel gas to the anode; and
an oxidant gas feeder that feeds the oxidant gas to the cathode.

### Claim 9 (depends on 8)

The fuel cell system according to claim 8, wherein the control program, when executed by the processing unit, causes the controller to control the fuel gas feeder in the shutdown process such that the amount of the fuel gas fed to the anode is larger than a fuel consumption of the fuel cell.

### Claim 10 (depends on 1)

The fuel cell system according to claim 1, wherein the power source is an electrical power system, a power generator, or a battery.

### Claim 11 (depends on 1)

The fuel cell system according to claim 1, wherein the fuel cell is a solid oxide fuel cell.

### Claim 12 (depends on 1)

The fuel cell system according to claim 1, wherein the electrolyte membrane contains an oxide.

### Claim 13

A fuel cell system comprising:
a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
a power source that applies a voltage to the fuel cell; and
a controller including a processing unit and a memory circuit storing a control program,
wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
wherein the electrolyte membrane contains a compound represented by BaCe1-xMxO3-α, BaZr1-x-yCexMyO3-α, or BaZr1-xMxO3-α, where M is a trivalent substituent element, x is 0<x<1, y is 0<y<1, and α is an oxygen deficiency and is 0<α<0.5.

### Claim 14

A fuel cell system comprising:
a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
a power source that applies a voltage to the fuel cell; and
a controller including a processing unit and a memory circuit storing a control program,
wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
wherein the electrolyte membrane contains a compound represented by BaZr1-xYbxO3-α, where x is 0<x<1, and α is an oxygen deficiency and is 0<α<0.5.

### Claim 15

A method for controlling a fuel cell system including:
a fuel cell that includes a membrane electrode assembly including a proton conducting electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
a power source that applies a voltage to the fuel cell;
a temperature detector that detects a temperature of the fuel cell; and
a controller including a processing unit and a memory circuit storing a control program,
wherein, in a shutdown process, the control program, when executed by the processing unit, causes the controller to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
wherein the electrolyte membrane has hole conductivity, and
wherein the control program, when executed by the processing unit, causes the controller to control the power source in the shutdown process such that the terminal voltage is equal to or higher than the open circuit voltage until the temperature detected by the temperature detector is determined to be equal to or lower than a temperature at which hole conduction in the electrolyte membrane decreases.

### Claim 16

A fuel cell system comprising:
a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
a power source that applies a voltage to the fuel cell; and
a controller including a processing unit and a memory circuit storing a control program,
wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell, and
wherein the electrolyte membrane contains a compound represented by BaCe1-xMxO3-α or BaZr1-x-yCexMyO3-α, where M is a trivalent substituent element, x is 0<x<1, y is 0<y<1, and α is an oxygen deficiency and is 0<α<0.5.

### Claim 17 (depends on 15)

The method for controlling a fuel cell system according to claim 15, wherein the proton conducting electrolyte membrane is a ceramic electrolyte membrane.

### Claim 18 (depends on 17)

The method for controlling a fuel cell system according to claim 17, wherein the ceramic electrolyte membrane contains a compound represented by BaCe1-xMxO3-α or BaZr1-x-yCexMyO3-α, where M is a trivalent substituent element, x is 0<x<1, y is 0<y<1, and α is an oxygen deficiency and is 0<α<0.5.

### Claim 19

A method for controlling a fuel cell system including:
a fuel cell that includes a membrane electrode assembly including a proton conducting electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
a power source that applies a voltage to the fuel cell; and
a controller including a processing unit and a memory circuit storing a control program,
wherein, in a shutdown process, the control program, when executed by the processing unit, causes the controller to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
wherein the proton conducting electrolyte membrane is a ceramic electrolyte membrane,
the ceramic electrolyte membrane contains a compound represented by BaCe1-xMxO3-α, or BaZr1-x-yCexMyO3-α, where M is a trivalent substituent element, x is 0<x<1, y is 0<y<1, and α is an oxygen deficiency and is 0<α<0.5.