# US 2010/0167156 A1 · Fuel cell stack having an integrated end plate assembly

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- Number: US 2010/0167156 A1
- Document ID: US20100167156A1
- Status: Published application
- Kind: A1
- Application number: 12/448,400
- Filed: 2006-12-21
- Published: 2010-07-01
- Earliest claimed: 2006-12-21
- Assignees: UTC Fuel Cells, LLC
- Inventors: Jeffrey G. Lake; Leonard A. Bach; Pedro Inigo; Evan C. Rege; Chris Vargas; Stephen P. Victor
- Web page: https://patentgrep.com/patent/US20100167156A1

## CPC

- H01M 8/248: Means for compression of the fuel cell stacks
- 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

A fuel cell stack (30) includes an integrated end plate assembly having a current collector (40) secured adjacent and end cell (36) of the stack, a pressure plate (42) secured adjacent the current collector (40), and a backbone (60) secured within a backbone-support plane (44) defined within the plate (42). Tie rod ends (62, 64, 66, 68) of the backbone (60) extend over a gap (84) defined between the backbone-support plane (44) and a deflection plane (50) defined within the pressure plate (42) so that the tie rod ends deflect within the gap (84) upon tightening of tie rods (78, 80). Deflection of the backbone enables the backbone (60) to permit limited expansion of the fuel cell stack (30) during operation, and the backbone (60) has adequate flexural strength to prohibit expansion of the stack (30) beyond operating dynamic limits of the stack (30).

## Claims

### Claim 1

A fuel cell stack (30) for producing electricity from reducing fluid and process oxidant reactant streams, the fuel cell stack (30) comprising:
a. a plurality of fuel cells (32) stacked adjacent each other to form a reaction portion (34) of the fuel cell stack (30), the plurality of fuel cells (32) including an end cell (36) at an outer end of the reaction portion (34) of the fuel cell stack (30);
b. an integrated end plate assembly (38) secured adjacent the end cell (36), the assembly including;
i. a current collector (40) secured adjacent and in electrical communication with the end cell (36);
ii. a pressure plate (42) secured adjacent the current collector and overlying the end cell (36), the pressure plate (42) defining a backbone-support plane (44) extending a distance from a center (46) of the pressure plate to between about thirty percent and about eighty percent of a distance between the center (46) of the pressure plate (42) and an exterior perimeter (48) of the pressure plate (42), and the pressure plate (42) defining a deflection plane (50) extending between the backbone-support plane (44) and the exterior perimeter (48) of the pressure plate (42), the deflection plane (50) also being between the backbone-support plane (44) and a contact surface (54) of the pressure plate (42) adjacent the current collector (40);
iii. a backbone (60) including a plurality of tie-rod ends (62, 64, 66, 68) defining throughbores (70, 72, 74, 76) configured to receive and secure tie rods (78, 80) adjacent a perimeter (48) of the pressure plate (42), the backbone (60) including at least one beam (82) extending between the tie-rod ends (62, 64, 66, 68), the backbone (60) being secured adjacent the backbone-support plane (60) and configured to contact and extend along the backbone-support plane (44), and the tie-rod ends (62, 64, 66, 68) of the backbone (60) configured to overlie the deflection plane (55) and define a gap (84) between the tie-rod ends (62, 64, 66, 68) and the deflection plane (50), the backbone (60) configured to have adequate flexibility to permit expansion of the fuel cell stack (30) within operating dynamic limits of the stack (30) and having predetermined flexural strength to prohibit expansion of the stack (30) beyond the operating dynamic limits of the stack (30); and,
iv. the deflection plane (55) being defined within the pressure plate (42) a predetermined distance from the backbone-support plane (44) to permit flexure of the backbone (60) within the gap (84).

### Claim 2 (depends on 1)

The fuel cell stack (30) of claim 1, wherein the backbone-support plane extends a distance from the center (46) of the pressure plate to between about fifty percent and about sixty percent of a distance between the center (46) of the pressure plate (42) and an exterior perimeter (48) of the pressure plate (42).

### Claim 3 (depends on 1)

The fuel cell stack (30) of claim 1, wherein the beam (82) of the backbone (60) extends across the center (46) of the pressure plate (42).

### Claim 4 (depends on 1)

The fuel cell stack (30) of claim 1, wherein a maximum planar cross sectional area of the backbone (60) in a plane parallel to the contact surface (54) of the pressure plate (42) is no greater than about fifty percent of a planar cross sectional area of the pressure plate (42) in a plane parallel to the contact surface (54) of the pressure plate (42).

### Claim 5 (depends on 1)

The fuel cell stack (30) of claim 1, wherein the pressure plate (42) defines a plurality of walls (56A, 56B, 56C, 56D) adjacent the backbone (60) and arising in a direction away from the current collector (42), the plurality of walls (56A, 56B, 56C, 56D) configured to prohibit lateral motion of the backbone (60) in any direction about parallel to a plane defined by the contact surface (54) of the pressure plate (42).

### Claim 6

A method of dynamically securing fuel cells (32, 36) within a fuel cell stack (30), comprising the steps of:
a. defining a backbone-support plane (44) within a pressure plate (42), the backbone-support plane (44) configured to extend a distance from a center (46) of the pressure plate (42) to between about thirty percent and about eighty percent of a distance between the center (46) of the plate (42) and an exterior perimeter (48) of the plate (42), and defining a deflection plane (50) within the pressure plate (42) extending between the backbone-support plane (44) and the exterior perimeter (48) of the pressure plate (42) and between the backbone-support plane (44) and a contact surface (54) of the pressure plate (42);
b. securing the contact surface (54) of the pressure plate (42) adjacent a current collector (40);
c. securing the current collector (40) adjacent an end cell (36) of the stack (30);
d. securing a backbone (60) within the backbone-support plane (44) so that tie rod ends (62, 64, 66, 68) of the backbone (60) extend over the deflection plane (50) defined within the pressure plate (42); and,
e. deflecting the tie rod ends (62, 64, 66, 68) within a gap (84) defined between the tie rod ends (62, 64, 66, 68) and the deflection plane (50) by tightening tie rods (78, 80) within the tie rod ends (62, 64, 66, 68) of the backbone (60).

### Claim 7

A method of dynamically securing fuel cells (32) within a fuel cell stack (30), comprising the steps of:
a. integrating a backbone (60) within a multi-plane pressure plate (42) coupled to a current collector (40) secured adjacent an end cell (36) of the fuel cell stack (30) to form a low thermal mass integrated end plate assembly (38);
b. deflecting tie rod ends (62, 64, 66, 68) of the backbone (60) within a gap (84) adjacent a deflection plane (50) of the multi-plane pressure plate (42);
c. extending a beam (82) of the backbone (60) between opposed exterior perimeters (48) of the multi-plane pressure plate (42);
d. redistributing a clamping load from the tie-rod ends (62, 64, 66, 68) of the backbone (60) through the center (46) of the multi-plane pressure plate (42); and,
e. providing a load follow-up load wherein the tie-rod ends (62, 64, 66, 68) deflect within the gap (84) to a predetermined value in an absence of contacting the deflection plane (50).

### Claim 8 (depends on 7)

The method of claim 7, further comprising deflecting the tie rod ends (62, 64, 66, 68) into the gap (84) responsive to varying fuel cell temperatures, and permitting expansion of the fuel cell stack (32) within operating dynamic limits of the fuel cell stack (32).

### Claim 9 (depends on 7)

The method of claim 7, comprising the further step of configuring the backbone (60) with a predetermined flexural strength to prohibit expansion of the fuel cell stack (32) beyond operating dynamic limits of the fuel cell stack (32).

### Claim 10 (depends on 7)

The method of claim 7, comprising the further steps of gradually decreasing deflection of the tie rod ends (62, 64, 66, 68) of the backbone (60) responsive to thinning of the fuel cells (32) resulting from compressive creep, and maintaining the follow-up load responsive to the decreasing deflection of the tie rod ends (62, 64, 66, 68).