Fuel cell with energy attenuation flanges

Abstract

A fuel cell system includes a plurality of stacked bipolar plate assemblies. Each of the plurality of stacked bipolar plate assemblies includes a first sub-gasket including a first peripheral edge. The first sub-gasket supports a first membrane electrode assembly (MEA). A second sub-gasket includes a second peripheral edge. The second sub-gasket supports a second MEA. A bipolar plate is disposed between the first sub-gasket and the second sub-gasket. The bipolar plate has a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first sub-gasket and the second sub-gasket. A seal flange extends around the bipolar plate. The seal flange abuts the first sub-gasket and the second sub-gasket. An energy attenuation flange extends around the bipolar plate and is spaced apart from the seal flange.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of fuel cells, and more particularly, to a fuel cell having energy attenuating flanges. BACKGROUND

[0002] Fuel cells are used to generate electrical energy in a variety of vehicles. The electrical energy can be stored in a battery and / or directed to an electric motor to provide power to the vehicle. In a typical fuel cell, such as a polymer electrolyte membrane fuel cell, an ion transport membrane is sandwiched between a pair of catalyzed electrodes, which are further sandwiched between two gas diffusion layers to form a membrane electrode assembly (MEA). An electrochemical reaction occurs when a first reactant in the form of a gaseous reducing agent, such as hydrogen gas, is introduced to the anode electrode through the first gas diffusion layer and ionized. The first reactant then passes through the ion transport material. Upon passing through the ion transport material, the first reactant combines with a second reactant in the form of a gaseous oxidizing agent, such as oxygen gas introduced to the cathode through the second gas diffusion layer. The reactants combine to form water. Electrons released in the ionization travel to the cathode in the form of a DC current via an external circuit, which typically includes a load such as an electric motor.

[0003] The MEA is typically formed into a stack to form a fuel cell. Adjacent MEAs are separated from each other by a series of reactant channels, which are typically in the form of gas-impermeable bipolar plates. The bipolar plates, in addition to facilitating the flow of reactants, provide support for the stack. Each bipolar plate includes one or more sealing flanges that prevent the reactants from exiting the MEA. In a crash event, the front side cell nearest the point of impact is subjected to an effective positive acceleration force, while the rear side cell farthest from the point of impact is subjected to an effective negative acceleration force. As a result, the front side cell tends to experience an increased sealing force, while the rear side cell tends to experience a decreased sealing force.

[0004] As the sealing force on the front side cell increases, the risk of exceeding the upper sealing limit also increases. Similarly, as the sealing force on the rear side cell decreases, the risk of falling below the minimum sealing force also decreases. Exceeding the upper limit or falling below the lower limit of the sealing force can result in deformation of the sealing flange. Deformation of the sealing flange can compromise the integrity of each cell and can result in leakage of the first reactant, the second reactant, and / or the coolant. Therefore, it is desirable to provide a fuel cell having energy attenuating sealing flanges to improve structural integrity and crashworthiness. SUMMARY

[0005] A fuel cell system including a plurality of stacked bipolar plate assemblies is disclosed. Each of the plurality of stacked bipolar plate assemblies includes a first sub-gasket including a first peripheral edge. The first sub-gasket supports a first membrane electrode assembly (MEA). A second sub-gasket includes a second peripheral edge. The second sub-gasket supports a second MEA. A bipolar plate is disposed between the first sub-gasket and the second sub-gasket. The bipolar plate has a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first sub-gasket and the second sub-gasket. A sealing flange extends around the bipolar plate. The sealing flange abuts the first sub-gasket and the second sub-gasket. An energy attenuation flange extends around the bipolar plate and is spaced apart from the sealing flange.

[0006] In addition to one or more features described herein, the energy attenuation flange includes a first portion extending around a first portion of the bipolar plate and a second portion extending around a second portion of the bipolar plate.

[0007] In addition to one or more features described herein, the first portion is not connected to the second portion.

[0008] In addition to one or more features described herein, the sealing flange is continuous around the bipolar plate.

[0009] In addition to one or more features described herein, the sealing flange includes a first stiffness and the energy attenuation sealing flange includes a second stiffness different than the first stiffness.

[0010] In addition to one or more features described herein, the second stiffness is between about one-half to about five times greater than the first stiffness.

[0011] In addition to one or more features described herein, the bipolar plate is formed of a metal.

[0012] In addition to one or more features described herein, the bipolar plate is formed of a non-metal.

[0013] A power system is also disclosed, including an electric motor and a fuel cell system having a plurality of stacked bipolar plate assemblies. Each of the plurality of stacked bipolar plate assemblies includes a first subgasket including a first peripheral edge. The first subgasket supports a first membrane electrode assembly (MEA). A second subgasket includes a second peripheral edge. The second subgasket supports a second MEA. A bipolar plate is disposed between the first subgasket and the second subgasket. The bipolar plate has a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first subgasket and the second subgasket. A sealing flange extends around the bipolar plate. The sealing flange seals against the first subgasket and the second subgasket. An energy attenuation flange extends around the bipolar plate and is spaced apart from the sealing flange.

[0014] In addition to one or more of the features described herein, the energy attenuation flange includes a first portion extending around a first portion of the bipolar plate and a second portion extending around a second portion of the bipolar plate.

[0015] In addition to one or more of the features described herein, the first portion is not connected to the second portion.

[0016] In addition to one or more of the features described herein, the sealing flange includes a first stiffness and the energy attenuation sealing flange includes a second stiffness different from the first stiffness.

[0017] In addition to one or more of the features described herein, the second stiffness is between about one-half to about five times greater than the first stiffness.

[0018] In addition to one or more of the features described herein, the bipolar plate is formed of a metal.

[0019] A vehicle is also disclosed, including a vehicle body and a power system disposed in the vehicle body. The power system includes an electric motor and a fuel cell system including a plurality of stacked bipolar plate assemblies. Each of the plurality of stacked bipolar plate assemblies includes a first subgasket including a first peripheral edge. The first subgasket supports a first membrane electrode assembly (MEA). A second subgasket includes a second peripheral edge. The second subgasket supports a second MEA. A bipolar plate is disposed between the first subgasket and the second subgasket. The bipolar plate has a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first subgasket and the second subgasket. A sealing flange extends around the bipolar plate. The sealing flange seals against the first subgasket and the second subgasket. An energy attenuation flange extends around the bipolar plate and is spaced apart from the sealing flange.

[0020] The energy attenuation flange includes, in addition to one or more features described herein, a first portion extending around a first portion of the bipolar plate and a second portion extending around a second portion of the bipolar plate.

[0021] The first portion is not connected to the second portion, in addition to one or more features described herein.

[0022] The sealing flange includes a first stiffness, the energy attenuation sealing flange includes a second stiffness different from the first stiffness, in addition to one or more features described herein.

[0023] The second stiffness is between about one-half to about five times the first stiffness, in addition to one or more features described herein.

[0024] The bipolar plate is formed of a metal, in addition to one or more features described herein.

[0025] The above-mentioned and other features and advantages of the present disclosure will become apparent from the following detailed description, when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0026] Other features, aspects, and details of the present disclosure will become apparent from the following detailed description, the accompanying drawings, and the claims.

[0027] Figure 1 A vehicle including a power system having a fuel cell system with a plurality of stacked bipolar plate assemblies each having an energy attenuation flange is shown in accordance with non-limiting examples;

[0028] Figure 2 is a block diagram illustrating a power system of Figure 1 in accordance with non-limiting examples;

[0029] Figure 3 is a stacked bipolar plate assembly of the fuel cell system of Figure 1 in accordance with non-limiting examples;

[0030] Figure 4 is a partial exploded view of a portion of one of the stacked bipolar plate assemblies of Figure 3 in accordance with non-limiting examples;

[0031] Figure 5 is a top sectional view of a portion of the bipolar plate assembly of Figure 3 in accordance with non-limiting examples, taken along line 4-4. DETAILED DESCRIPTION

[0032] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0033] According to the non-restrictive example, the vehicle in Figure 1 The vehicle 10 is generally designated as 10. The vehicle 10 includes a body 12 situated on a plurality of wheels, one of which is designated as 14. The vehicle 10 includes a passenger compartment 16. A power system 20 is operatively connected to one or more of the plurality of wheels 14. (Reference) Figure 2 The power system 20 includes an electric motor 24 connected to the fuel cell system 30. The fuel cell system 30 provides electricity to operate the electric motor 24 based on driver input. That is, a driver (not shown) sitting in the passenger compartment 16 can request power to be delivered from the electric motor 24 to the wheels 14. At this point, it should be understood that although the vehicle 10 is described as an automobile, by way of non-limiting example, the fuel cell system 30 can be used in a variety of vehicles, including locomotives, airplanes, ships, etc.

[0034] Now refer to Figure 3 and Figure 4 A fuel cell system 30 is described according to a non-limiting example. The fuel cell system 30 is formed of multiple stacked and interconnected bipolar plate assemblies, including a first bipolar plate assembly 34, a second bipolar plate assembly 36, and a third bipolar plate assembly 38. The number and arrangement of the bipolar plate assemblies can vary. Reference will be made to... Figure 5 And continue to refer to Figure 3 and 4 The first bipolar plate assembly 34, the second bipolar plate assembly 36, and the third bipolar plate assembly 38 are described as having similar structures.

[0035] The first bipolar plate assembly 34 includes a first sub-pad 41 having a first peripheral edge 43 and a first membrane electrode assembly (MEA) 45. The first bipolar plate assembly 34 also includes a second sub-pad 48 having a second peripheral edge 50. The second sub-pad 48 includes a second MEA 52. Figure 4 As shown, the second sub-shield 48 can define the surface of the second bipolar plate assembly 36 or the surface of the first bipolar plate assembly 34. A bipolar plate 56 is located between the first sub-shield 41 and the second sub-shield 48. The bipolar plate 56 includes a first side 58 defining a cathode side (not shown separately) and a second side 60 defining an anode side (also not shown separately). In a non-limiting example, the bipolar plate 56 can be formed of metal. In another non-limiting example, the bipolar plate 56 can be formed of non-metal.

[0036] The bipolar plate 56 includes a plurality of corrugations (not individually labeled) that form a first plurality of channels 62 on a first side 58. The first plurality of channels 62 can contain a first reactant or cathode fluid (not shown) that will be in contact with a surface (not individually labeled) of the first MEA 45. The corrugations also form a second plurality of channels 64 on a second side 60. The second plurality of channels 64 can contain a second reactant or anode fluid (not shown) that will be in contact with a surface (also not individually labeled) of the second MEA 52. The bipolar plate 56 also includes a plurality of coolant channels 69 that can contain a coolant that absorbs heat from the fuel cell system 30.

[0037] Further in accordance with non-limiting examples, the bipolar plate 56 includes a plurality of manifolds 70 that are in fluid communication with the first plurality of channels 62, the second plurality of channels 64, and the coolant channels 69. More specifically, the plurality of manifolds 70 includes a first reactant inlet 72 and a first reactant outlet 74. The plurality of manifolds 70 also includes a second reactant inlet 76 and a second reactant outlet 78. In addition, the plurality of manifolds can include a coolant inlet 80 and a coolant outlet 82.

[0038] The bipolar plate 56 is also shown to include a perimeter seal flange 90 that extends completely around the first MEA 45, the second MEA 52, and the first plurality of channels 62, the second plurality of channels 64, and the coolant channels 69. In addition, each of the plurality of manifolds 70 includes an associated manifold seal flange, as shown at 94, 96, and 98, that is connected to the first reactant inlet 72, the coolant inlet 80, and the second reactant inlet 76. For example, the seal flange 94 extends completely around the first reactant inlet 72, the seal flange 96 extends completely around the coolant inlet 80, and the seal flange 98 extends completely around the second reactant inlet 76. The seal flanges 90, 94, 96, and 98 are disposed between the first subgasket 41 and the second subgasket 48. The seal flange 90 extends around the first bipolar plate assembly 34. In this manner, the seal flange 90 fluidly isolates the bipolar plate assembly 34 from the environment. The seal flanges 90, 94, 96, and 98 ensure fluid isolation between the first reactant, the second reactant, and the coolant and / or the environment.

[0039] In a crash event, the integrity of the seal flanges can be compromised.

[0040] The change in sealing force in a crash event can be represented as:

[0041] Equation 1: AF leading ∝ (a N ma) / L; and

[0042] Equation 2: AF trailing ∝ - (a N ma) / L

[0043] where, AFleading is the change in sealing force in the front cell [N / mm];

[0044] AF trailing is the change in sealing force in the rear cell [N / mm];

[0045] N is the number of cells within the stack;

[0046] m is the mass of each cell [g];

[0047] a is the peak acceleration during a crash event [mm / s 2 ];

[0048] a is the mass fraction of the cell applied on the sealing area; and

[0049] L is the total sealing length.

[0050] To reduce the absolute value of AF trailing and AF leading , the product (aN ma) can be reduced or L can be increased. However, the quantity (aN ma) is typically a fixed value predetermined by the power and power density of the fuel cell stack, and increasing the sealing length L will increase the likelihood of sealing defects, which disadvantageously increases the risk of leaks. Based on an understanding of the sealing behavior in crash events, it is desirable to provide a fuel cell having an energy attenuation sealing flange that improves the sealing integrity and crashworthiness of the fuel cell seal by having the same effect of increasing L without actually changing the size and design of the fuel cell seal.

[0051] Accordingly, according to one non-limiting example, the bipolar plate assembly 34 further includes an energy attenuation flange 100 designed to absorb the acceleration forces so that the sealing flanges 90, 94, 96, and 98 maintain sealing integrity in, for example, a crash event. In the non-limiting example, the energy attenuation flange 100 can include a first portion 108 extending around a first portion of the first outer perimeter edge 43 (not separately labeled) and a second portion 110 extending around a second portion of the first outer perimeter edge 43 (also not separately labeled). In the non-limiting example, the first portion 108 is not connected to the second portion 110. However, it should be understood that the energy attenuation sealing flange 100 can extend around the entire perimeter of the bipolar plate assembly 34.

[0052] It should also be appreciated that while shown as being disposed outside of the sealing flanges 90, 94, 96, and 98, the specific location of the energy attenuation sealing flange 100 can vary. For example, the energy attenuation sealing flange 100 can be disposed inside of the sealing flange 90, or between any of the sealing flanges 90, 94, 96, and 98. It should also be appreciated that while shown as being integrally formed with the bipolar plate 56, the sealing flanges 90, 94, 96, and 98 can be formed of different materials. For example, the sealing flanges 90, 94, 96, and / or 98 can be formed of a metal, a non-metal, or any combination thereof. Thus, it should be appreciated that in non-limiting examples, the material used to form the sealing flanges 90, 94, 96, and 98 can be different than the material used to form the bipolar plate 56 and / or different than the material used to form each of the sealing flanges 90, 94, 96, and 98.

[0053] In one non-limiting example, the sealing flanges 90, 94, 96, and 98 are formed of a first material having a first stiffness, and the energy attenuation sealing flange 100 is formed of a second material having a second stiffness that is different than the first stiffness. Stiffness should be understood as the magnitude of vertically applied compressive force [N] required to displace a unit length [mm] of the sealing flange by a unit length [nm]. The second material can be the same as the first material, with the difference in stiffness due to manufacturing techniques, geometry, thickness, etc. In non-limiting examples, the second stiffness can be greater than the first stiffness by a factor of one-half to five. In non-limiting examples, the second stiffness can be greater than the first stiffness by a factor of one to two.

[0054] The magnitude of the stiffness can determine the extent to which the energy attenuation sealing flange 100 extends around the first bipolar plate assembly 34. The greater the stiffness, the shorter the length of the energy attenuation sealing flange 100 that extends around the first bipolar plate assembly 34. The energy attenuation sealing flange 100 is designed and positioned to realize the acceleration forces before the sealing flanges 90, 94, 96, and 98. In this manner, the energy attenuation sealing flange 100 can deform and deflect, thereby absorbing those acceleration forces, in order to protect the sealing flanges 90, 94, 96, and 98, and ensure the overall integrity of the fuel cell system 30. It should be appreciated that the energy attenuation sealing flange 100 is designed to be under compression prior to a crash event. The compression establishes an unloading force range that accommodates the decrease in sealing forces in the rear-side cell units during a crash event, and a loading force range that accommodates the increase in sealing forces in the front-side cell units during a crash event.

[0055] It should be appreciated that, in accordance with one non-limiting example, the sealing flanges 90, 94, 96, and 98 actually seal the first subgasket 41 and the second subgasket 48 and prevent the flow of reactants therefrom. In contrast, the energy attenuating flange 100, which applies force to the first subgasket 41 and the second subgasket 48, is not designed to perform a sealing function. Moreover, it should be appreciated that the energy attenuating flange 100 applies force to the first subgasket 41 and the second subgasket 48 both during normal operation and during a crash event.

[0056] While the foregoing disclosure has been described in reference to illustrative embodiments, those skilled in the art will appreciate that various changes can be made without departing from the scope of the disclosure, and equivalents can be substituted for elements thereof. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from its central scope. Therefore, it is intended that the disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope of the disclosure.

Claims

1. A fuel cell system comprising: a plurality of stacked bipolar plate assemblies, each of the plurality of stacked bipolar plate assemblies comprising: a first sub-gasket comprising a first peripheral edge, the first sub-gasket supporting a first membrane electrode assembly (MEA); a second sub-gasket comprising a second peripheral edge, the second sub-gasket supporting a second membrane electrode assembly (MEA); a bipolar plate disposed between the first sub-gasket and the second sub-gasket, the bipolar plate having a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first sub-gasket and the second sub-gasket; a seal flange that is at least partially hollow and extends around the bipolar plate, the seal flange abutting to seal the first sub-gasket and the second sub-gasket; and an energy attenuation flange that is at least partially hollow, extends at least partially around the bipolar plate in a non-continuous manner, and is spaced apart between the seal flange and a peripheral edge of the bipolar plate; wherein the seal flange has a first stiffness and the energy attenuation flange has a second stiffness that is two to five times greater than the first stiffness, wherein the seal flange and the energy attenuation flange are made of the same material and the difference between the first stiffness and the second stiffness is due to the geometry of the seal flange and the energy attenuation flange.

2. The fuel cell system according to claim 1, wherein the energy attenuation flange comprises a first portion extending around a first portion of the bipolar plate and a second portion extending around a second portion of the bipolar plate.

3. The fuel cell system of claim 2, wherein, the first portion is not connected to the second portion.

4. The fuel cell system of claim 1, wherein, the seal flange is continuous around the bipolar plate.

5. The fuel cell system according to claim 1, wherein, the bipolar plate is formed of a metal.

6. The fuel cell system according to claim 1, wherein, the bipolar plate is formed of a non-metal.

7. A power system comprising: an electric motor; and a fuel cell system comprising a plurality of stacked bipolar plate assemblies, each of the plurality of stacked bipolar plate assemblies comprising: a first sub-gasket comprising a first peripheral edge, the first sub-gasket supporting a first membrane electrode assembly (MEA); a second sub-gasket comprising a second peripheral edge, the second sub-gasket supporting a second membrane electrode assembly (MEA); a bipolar plate disposed between the first sub-gasket and the second sub-gasket, the bipolar plate having a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first sub-gasket and the second sub-gasket; a seal flange that is at least partially hollow and extends around the bipolar plate, the seal flange abutting to seal the first sub-gasket and the second sub-gasket; and an energy attenuation flange that is at least partially hollow, extends at least partially around the bipolar plate in a non-continuous manner, and is spaced apart between the seal flange and a peripheral edge of the bipolar plate; wherein the seal flange has a first stiffness and the energy attenuation flange has a second stiffness that is two to five times greater than the first stiffness, wherein the seal flange and the energy attenuation flange are made of the same material and the difference between the first stiffness and the second stiffness is due to the geometry of the seal flange and the energy attenuation flange.

8. A vehicle comprising: a vehicle body; a power system disposed in the vehicle body, the power system comprising: an electric motor; and a fuel cell system comprising a plurality of stacked bipolar plate assemblies, each of the plurality of stacked bipolar plate assemblies comprising: a first sub-gasket comprising a first peripheral edge, the first sub-gasket supporting a first membrane electrode assembly (MEA); a second sub-gasket comprising a second peripheral edge, the second sub-gasket supporting a second membrane electrode assembly (MEA); a bipolar plate disposed between the first sub-gasket and the second sub-gasket, the bipolar plate having a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first sub-gasket and the second sub-gasket; a seal flange that is at least partially hollow and extends around the bipolar plate, the seal flange abutting to seal the first sub-gasket and the second sub-gasket; and an energy attenuation flange that is at least partially hollow, extends at least partially around the bipolar plate in a non-continuous manner, and is spaced apart between the seal flange and a peripheral edge of the bipolar plate; wherein the seal flange has a first stiffness and the energy attenuation flange has a second stiffness that is two to five times greater than the first stiffness, wherein the seal flange and the energy attenuation flange are made of the same material and the difference between the first stiffness and the second stiffness is due to the geometry of the seal flange and the energy attenuation flange. A fuel cell system comprising a plurality of stacked bipolar plate assemblies, each of the plurality of stacked bipolar plate assemblies comprising: a first sub-gasket comprising a first peripheral edge, the first sub-gasket supporting a first membrane electrode assembly MEA; a second sub-gasket comprising a second peripheral edge, the second sub-gasket supporting a second membrane electrode assembly MEA; a bipolar plate disposed between the first sub-gasket and the second sub-gasket, the bipolar plate having a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first sub-gasket and the second sub-gasket; a sealing flange that is at least partially hollow and extends around the bipolar plate, the sealing flange abutting the first sub-gasket and the second sub-gasket; and an energy attenuation flange that is at least partially hollow, extends at least partially around the bipolar plate in a discontinuous manner, and is spaced apart between the sealing flange and the peripheral edge of the bipolar plate; wherein the sealing flange has a first stiffness and the energy attenuation flange has a second stiffness that is two to five times greater than the first stiffness, wherein the sealing flange and the energy attenuation flange are made of the same material, and the difference between the first stiffness and the second stiffness is due to the geometry of the sealing flange and the energy attenuation flange. A fuel cell system comprising a plurality of stacked bipolar plate assemblies, each of the plurality of stacked bipolar plate assemblies comprising: a first sub-gasket comprising a first peripheral edge, the first sub-gasket supporting a first membrane electrode assembly MEA; a second sub-gasket comprising a second peripheral edge, the second sub-gasket supporting a second membrane electrode assembly MEA; a bipolar plate disposed between the first sub-gasket and the second sub-gasket, the bipolar plate having a first side defining a first plurality of channels to receive cathode fluid, a second side defining a second plurality of channels to receive anode fluid, and a plurality of coolant channels defined between the first sub-gasket and the second sub-gasket; a sealing flange that is at least partially hollow and extends around the bipolar plate, the sealing flange abutting the first sub-gasket and the second sub-gasket; and an energy attenuation flange that is at least partially hollow, extends at least partially around the bipolar plate in a discontinuous manner, and is spaced apart between the sealing flange and the peripheral edge of the bipolar plate; wherein the sealing flange has a first stiffness and the energy attenuation flange has a second stiffness that is two to five times greater than the first stiffness, wherein the sealing flange and the energy attenuation flange are made of the same material, and the difference between the first stiffness and the second stiffness is due to the geometry of the sealing flange and the energy attenuation flange.

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