# US 2014/0154607 A1 · Fuel cell

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- Number: US 2014/0154607 A1
- Document ID: US20140154607A1
- Status: Published application
- Kind: A1
- Application number: 13/823,982
- Filed: 2012-04-06
- Published: 2014-06-05
- Earliest claimed: 2011-04-06
- Assignees: Nissan Motor Co., Ltd.
- Inventors: Toshikazu Kotaka; Yuichiro Tabuchi; Yosuke Fukuyama
- Web page: https://patentgrep.com/patent/US20140154607A1

## CPC

- H01M 8/1007: with both reactants being gaseous or vaporised (H01M8/12 takes precedence)
- H01M 4/8605: {Porous electrodes}
- H01M 4/8807: {Gas diffusion layers}
- H01M 8/026: characterised by grooves, e.g. their pitch or depth
- H01M 2008/1095: {Fuel cells with polymeric electrolytes}
- 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

Provided is a fuel cell including: a membrane electrode assembly; a pair of gas diffusion layers holding the membrane electrode assembly therebetween; and a pair of separators holding the membrane electrode assembly and the pair of gas diffusion layer therebetween. The separators have ribs on surfaces facing the gas diffusion layers, the ribs forming channels which are gas flow paths. A thickness t (μm) of each of the gas diffusion layers and an area occupation ratio SC (−) of the channels on the surface facing the gas diffusion layer satisfy the relationship represented by the following formula (1): 0.9>SC≧55(t−103)2/1000000+0.3 (1).

## Claims

### Claim 1

A fuel cell comprising:
a membrane electrode assembly;
a pair of gas diffusion layers holding the membrane electrode assembly therebetween; and
a pair of separators holding the membrane electrode assembly and the pair of gas diffusion layers therebetween, wherein
each of the pair of separators has ribs on a surface facing a corresponding one of the gas diffusion layers, the ribs forming channels which are gas flow paths, and
a thickness t (μm) of each of the pair of gas diffusion layers and an area occupation ratio SC (−) of the channels on the surface facing the gas diffusion layer satisfy a relationship represented by the following formula (1):
0.9>SC≧55(t−103)2/1000000+0.3 (1).

### Claim 2 (depends on 1)

The fuel cell according to claim 1, wherein a width WC (mm) of the channels, a width WR (mm) of the ribs, an electrical conductivity σ (S/m) of the gas diffusion layer, and a thickness t (μm) of the gas diffusion layer satisfy the relationship represented by the following formula (2):
[
Math
.

1
]
W
C
(
W
C
+
W
R
)
<
min

(
(
0.0755

ln

(
σ
·
t
8000
)
-
0.1525
)

W
R
+
0.9611
,
0.9
)
(
2
)

### Claim 3 (depends on 2)

The fuel cell according to claim 2, wherein, when the electrical conductivity of the gas diffusion layer is anisotropic, an electrical conductivity in a width direction of the ribs is employed as the electrical conductivity a of the gas diffusion layer in Formula (2).

### Claim 4 (depends on 2)

The fuel cell according to claim 2, wherein, when shapes of the channels in a cross-section approximately perpendicular to a gas flow direction in the separator are trapezoidal shapes, a width of portions of the ribs in contact with the gas diffusion layer is employed as the rib width WR in Formula (2), and a width of portions of the channels facing the gas diffusion layer is employed as the channel width WC.

### Claim 5 (depends on 2)

The fuel cell according to claim 2, wherein, when the gas diffusion layer has an n-layer structure in which n layers are stacked on each other in a thickness direction, an electrical conductivity σlayered calculated from the following formula (3) is employed as the electrical conductivity a of the gas diffusion layer in Formula (2):
[
Math
.

2
]
σ
layered
=
∑
i
=
1
n

σ
i

t
i
t
(
3
)
where
σlayered: the electrical conductivity (S/m) of the gas diffusion layer having the n-layer structure,
t: the thickness (μm) of the gas diffusion layer,
σi: an electrical conductivity (S/m) of an i-th layer in the gas diffusion layer, and
ti: a thickness (μm) of the i-th layer in the gas diffusion layer.

### Claim 6 (depends on 2)

The fuel cell according to claim 2, wherein, when the gas diffusion layer is sensitive to a surface pressure in a thickness direction, an electrical conductivity of the gas diffusion layer in a state where the fuel cell is formed is employed as the electrical conductivity a of the gas diffusion layer in Formula (2).

### Claim 7 (depends on 2)

The fuel cell according to claim 2, wherein
when a gas flows in more than one direction in the separator,
a direction accounting for a highest ratio among gas flow directions in the separator is defined as a main flow direction,
a width of the ribs in a cross-section approximately perpendicular to the main flow direction is employed as the rib width WR in Formula (2), and
a width of the channels in the cross-section approximately perpendicular to the main flow direction is employed as the channel width WC in Formula (2).

### Claim 8 (depends on 2)

The fuel cell according to claim 2, wherein,
when a rib arrangement pattern in a cross-section approximately perpendicular to a thickness direction of the ribs is a dot-like or island-like arrangement pattern,
a value obtained by calculating gravity center positions of the ribs and gravity center positions of triangles which are formed by connecting the gravity center positions of the ribs and which are not overlapped with each other, and multiplying one of distances between the gravity center positions of the ribs and intersections of outlines of the ribs and line segments connecting the gravity center positions of the ribs and the gravity center positions of the triangles by 2 is employed as the rib width WR in Formula (2), and
a value obtained by multiplying one of distances between the intersections and the gravity center positions of the triangles by 2 is employed as the channel width WC in Formula (2).

### Claim 9 (depends on 2)

The fuel cell according to claim 2, wherein
when a rib arrangement pattern in a cross-section approximately perpendicular to a thickness direction of the ribs is a dot-like or island-like arrangement pattern,
gravity center positions of the ribs and gravity center positions of triangles which are formed by connecting the gravity center positions of the ribs and which are not overlapped with each other are calculated,
rib widths WRcg are obtained by multiplying distances between the gravity center positions of the ribs and intersections between outlines of the ribs and line segments connecting the gravity center positions of the ribs and the gravity center positions of the triangles by 2,
channel widths WCcg are obtained by multiplying the distances between the intersections and the gravity center positions of the triangles by 2, and
among the rib widths WRcg and the channel widths WCcg, those which give a smallest WCcg/(WCcg+WRcg) are employed as the rib width WR and the channel width WC in Formula (2).

### Claim 10 (depends on 1)

The fuel cell according to claim 1, wherein
the gas diffusion layer includes a gas diffusion layer-backing layer positioned on a side close to the membrane electrode assembly and a gas diffusion layer substrate layer positioned on a side close to the separator,
the gas diffusion layer-backing layer contains carbon and a water-repellent material, and
the gas diffusion layer substrate layer contains a porous metal material.