FIELD OF THE INVENTION:
The present invention relates to the development of adhesive sealed gasket flow
field plate for low and high temperature proton exchange membrane (PEM) fuel
cells in which the gasket is bonded to graphite or metal alloy plate using an
adhesive material wherein the projected height of the gasket is relatively higher
than the total thickness of two electrodes. More particularly the present invention
relates to a system for providing better sealing and leak proof contact due to
defined boundaries given to the gas flow field plate which would enable leak
proof sealing of gas between graphite plate and membrane electrode assemblies
(MEA’s).
BACKGROUND OF THE INVENTION:
A PEM fuel cell is an electrochemical cell, comprises of a cathode and anode
separated by electrolyte medium (Ionic conductor). At the anode, hydrogen is
reacted to produce protons (H+) and electrons. The electrons produced are
allowed to travel outside through interconnects to the external circuit to form a
closed loop thereby generating current in the circuit. Protons are allowed to pass
through the electrolyte medium to cathode side where oxygen is reduced by
reacting with the protons to form water. In construction of a single PEM fuel cell
many components are required like Membrane Electrode Assembly (MEA), gas
circulating graphite plates, gaskets which may include fluoropolymers (e.g.
Teflon: PTFE, FEP etc.), elastomers (e.g., high temperature fluorosilicones, Viton
rubber), polyimides, polysulfones, phenolic resins, etc., Copper plates for
collecting the current, end plates to hold the functional parts together,
humidifying units, reheating plate in case of high temperature and tie rods.
Membrane electrode assembly consists of two electrodes and proton exchange
membrane (PEM) sandwiched together to form MEA. One side named anode and
cathode being on the other side of the MEA, whereas PEM is placed in between
these two electrodes. A single PEM fuel cell is formed by placing MEA between
two gas circulating graphite plates with good sealing materials which are able to
withstand under operating temperature range of 40oc – 200oc. A current collector

is placed between graphite plate and end plate on each side of the graphite plate
which is connected to external load. Provision for cooling (or heating) is provided
on the back face of the each graphite plate. In conventional PEM stack assembly,
sealing of hardware components and active cells for effective separation of
anode and cathode reactant-flows and prevention of their leakage and
intermixing, is a critical technical issue with direct impact on reliability, durability
and ease of manufacturing of the fuel cell stack. These factors have significant
bearing on the cost of the PEM stacks and in turn of the PEM fuel cell based
power devices. The sealing is very cumbersome work when it is done on stack
directly. Cost-effective manufacturing of PEM stacks is largely dependent on their
sealing process and relevant materials. In practice, the MEA is assembled
between the gas flow field plates of anode and cathode for allowing the
hydrogen and air at the respective sides. During the assembly, a sealing
materials is placed between the MEA and the gas flow field plates at each of
anode and cathode respectively for arresting gas leakage to external and to
avoid cross-over (inter mixing) of any gas from one side to the other. For this
purpose of sealing, various technologies are being used such as flat gaskets,
adhesive, gaskets, liquid injected sealants (wet sealing) and O-rings etc.
Patent WO2011103505A2 (2011), the integrated seal is applied and adhered to
each plate, as needed, either prior to or during production of the fuel cell stack.
The plates include a seal integrated with the support plates as needed, the seal
being suitable particularly for high temperature (e.g., 120oC – 250oC) and acidic
environments, such as those found in high temperature PEM fuel cell stack
assemblies. The capability to apply the seal prior to production of the fuel cell
stack enables production of the fuel cell stack without the cumbersome step of
applying the seal. With the removal of this step, production of the fuel cell stack
is substantially more efficient and cost effective because it can be completed
more quickly and results in an improved seal. Furthermore, because there is no
adhesive bonding between the plate and MEA interfaces, disassembly and
reassembly of the stack is efficient and does not require reapplication of
adhesive or new seals.

The patent US 8298714B2 2012-10-30 explains about the sealing around plate
manifold openings and MEAs within fuel cells, which includes framing the MEA
with a fluid-impermeable and resilient gasket, placing preformed gaskets in
channels in the electrode layers and/or separator plates, or moulding seals within
grooves in the electrode layer or separator plate, and circumscribing the
electrochemically active area and any fluid manifold openings. Again they
discussed two ways of forming gaskets cure-in-place and form-in-place methods,
to provide a seal between two or more components. It is clear from patent that it
is difficult to reliably meet tight gasket height tolerances (e.g., 1.050+0.10 mm).
The precursor (sealant) is dispensed on the surface of one or more components
and the components are then assembled while the precursor is still wet and
uncured. Once the precursor has cured, elastomeric cohesion provides sealing
between the components. This technique can be used where components are
assembled immediately on a production line and for parts that do not need to be
frequently disassembled. However, with form-in-place sealing, the metal bipolar
plates in a fuel cell may not be stiff and flat enough, making if difficult to control
the uncured and wet gasket thickness upon stack assembly. It is only applicable
to the stacks where disassembly is not required. But it is sometimes necessary to
disassemble the stack to replace MEAs or gaskets after long operations.
The present invention can bypass the method of adhesive sealing gasket on both
the plates, where both the plates are integrated with the gasket using adhesive
or gel based sealing (wet sealing). The current method involves an addition of
significant groove depth around the gas flow grooves of anode, cathode plates
and their respective inlet-outlet manifolds and the same groove is used for
gasket sealing application. Initially, significant depth of anode and cathode plate
gasket groove is filled with sealant material for groove width of defined
thickness. One such sealant filled groove is adhered with the gasket material and
allowed for air drying. The sealant possesses the property of anti-stick and
compressive. The plate having gasket is called male plate and the other is called
female plate having deep groove filled with sealant of defined thickness.

OBJECTS OF THE INVENTION:
It is therefore the object of the invention to develop an adhesive sealed gasket
flow field plate for low and high temperature proton exchange membrane (PEM)
fuel cells which improves the quality of sealing in Proton Exchange Membrane
Fuel Cell stacks of HTPEM and LTPEM.
Another object of the invention is to develop an adhesive sealed gasket flow field
plate for low and high temperature proton exchange membrane (PEM) fuel cells
that reduces the operating cost per Kwh by reducing the leakages.
A further object of the invention is to develop an adhesive sealed gasket flow
field plate for low and high temperature proton exchange membrane (PEM) fuel
cells that reduces the stack assembly cycle time as gasket and graphite plates
are adhered together to form a seal bonded gas flow field plate that lead to easy
of assembly.
A still another object of the invention is to reduce the cost by using sealing by
gasket on one side.
A still further object of the invention is to develop an adhesive sealed gasket flow
field plate for low and high temperature proton exchange membrane (PEM) fuel
cells that simplifies the manufacturing of PEM fuel cell stacks.
SUMMARY OF THE INVENTION:
A PEM fuel cell stack is shown in Figure 1, the stack comprises two end plates
(1A,1B) between which the components of the PEM fuel stack are tightened
using two internal tie rods (2) and eight external tie rods (3). The components of
Proton Exchange Membrane Fuel Cells (PEMFC) stack includes insulating plates
(4A,4B) to protect against thermal and electrical loses, cooper plates (5A,5B) for
collecting the electrons generated at the electrocatalyst sites of the membrane
electrode assemblies (6, as shown in Fig.7) through blank half bipolar plates
(one side groove and other side blank) of anode (7) and cathode (8, shown in

Fig.3) respectively. An half bipolar plate (7A) having a serpentine flow pattern
and the other plate having parallel interdigited (7B) flow pattern can be seen in
Fig.6 and Fig.3 respectively.
As the anode plate is facing towards down in the stack assembly its flow pattern
is invisible. In addition to this, number of bipolar plates (combination of 8 and 9
shown in Fig.1) having gas flow grooves both the sides and provided with
cooling channels (10) in between the plates. The bipolar plate is formed by
laminating the two half bipolar plates of anode (8) and cathode (9) using sealant
(11) adhered to four corners of anode half bipolar plate (8). The bipolar plate
has provision for reactant circulation on both the sides for air, hydrogen and
coolant circulation through cooling channels (10) in between the plates of anode
(8) and cathode (9) half bipolar plates. Multiple number of such bipolar units are
stacked one over the other consisting of MEA (6) in between the bipolar units,
sealing gasket (21, shown in Fig.4) placed on cathode plate which is shown in
figure (5), all three (6,8,9) together is called single cell (22) details are exploded
in Fig.2. It comprises one cathode plate (24), membrane electrode assembly (23)
and anode plate (25) having serpentine pattern at the bottom side (shown in
Fig 6) are aligned through a common circular duct of stack internal tie rods (2)
while assembling such single cells in a stack. The total assembled plates form a
common duct or manifold for air and hydrogen. The air inlet manifold (12A) is in
fluid communication with the air outlet manifold (12B) which are in fluid
communication with the air inlet (14) and out lets (15) provided for the stack
end plates (1A, 1B). Similarly, the hydrogen inlet manifold (13A) is in fluid
communication with the hydrogen outlet manifold (13B) which are in fluid
communication with the hydrogen inlet (16) and outlets (17) provided for the
stack end plates (1A, 1B). In case of conventional PEM fuel cell stack, the other
ends of each manifold of hydrogen and air are provided with dead end bolts
(18).

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: PEM Fuel Cell stack assembly
Figure 2: Complete assembly of single cell with male-female sealing method
Figure 3: Gas flow distribution plate provided with groove around the gas
distribution area for sealing application
Figure 4: Schematic of gasket used for leak proof sealing application
Figure 5: Gas flow distribution plate adhered with gasket in the sealing groove
(Male plate)
Figure 6: Gas flow distribution plate with partially adhesive filled groove of gasket
area (Female plate)
Figure 7: Membrane Electrode assembly (MEA)
DETAILED DESCRIPTION OF THE INVENTION:
The present method of sealing in fuel cell stacks is applicable for working
temperature up to 2000C, in which the reactants of hydrogen and air/oxygen
used in fuel cells have to be precisely sealed. To overcome the drawbacks of
surface leaks and intermixing of gases (hydrogen and air) between anode and
cathode, a cost effective sealing method is developed for fuel cell applications.
Details of the gasket (21) are shown in Fig.4.
In practice, graphite based composite material or special metal alloy plates are
used as the gas distribution plates for circulation of gases over the electrodes of
anode and cathode. One such gas distribution plate is shown in Fig.3, having
significant groove depth (26) for placement of gasket with outer (27) and inner
(28) boundary walls (non-grooved area) around the gasket placement groove
area. The plate consists of various gas flow path distribution channels (29)
connected through the respective gas inlet (30) of air which is in fluid
communication with the stack inlet gas manifold of air (12A) through which the
gas is supplied to cathode side of individual cells in a fuel cell stack. The excess

reactants or products exit from the individual cell are allowed to pass through the
air outlet (31) which is in fluid communication with the stack exit gas manifold of
air (12B). In similar way, on the other side, for anode plate as shown in Fig.6
having serpentine flow pattern for distribution of hydrogen received from
hydrogen inlet (33) which is in fluid communication hydrogen inlet manifold
(13A) and excess hydrogen exits through the outlet (34) of anode plate which in
fluid communication with the hydrogen outlet manifold (13B), number of such
plates are assembled in a stack using fixtures connected through the passage of
hole (32) of anode and cathode plates.
The method of sealing consists sequence of processes in which the groove
sealing depth is filled with adhesive Silicone/ Viton or any other compressible
material, which are compressive in nature under mechanical compressive load
conditions. Significant depth of groove (26) is filled with the adhesive material
over which the gasket (shown in Fig 4) is adhered under wet conditions. The
plates are allowed for air drying for about 24 hours, the plate having bonded
gasket in place of groove depth is called male part (26A) of the plate is shown in
Fig.5 as projected top and the other anode plate having partially filled adhesive
in the groove (34) is called female part of sealing shown in Fig.6 which is
bounded between the boundary walls (35) of serpentine gas flow field pattern
(33) and outermost boundary (36) which are non-machined.
There are two types of plates having gas distribution grooves of which one is
used for circulating hydrogen (Female plate) and other plate is used for air
circulation (Male plate). The extended portion of gasket (26A) above the gas
distribution grooves (29) acts as male part of sealing component as indicated in
Fig.5 having hatch pattern.
Besides this, the female part shown in Fig.6 having an addition of partial fill of
groove depth with adhesive material around the active area i.e the area of gas
flow distribution (33) of the plate. Finally, the modified gasket groove area (34)

having adhesive material partially filled will have net-depth of 30% to 40% of the
gasket thickness used for the purpose of sealing application shown in Fig.4.
Any fuel cell consists of half bipolar anode plate (7A), half bipolar cathode plate
(7B),MEA (6), copper plates (5A,5B), MEA sealing gaskets (21), lamination
gasket (11), end plates (1A,1B) and its fixtures/ tie rods (2,3) etc. All these
aforementioned components are assembled between end plates (1A,1B) with the
use of tie rods (2). The typical sequence of assembly follows as i) end plate
ii) copper plate iii) half bipolar anode plate iv) MEA v) bipolar plate (anode-
cathode) having cooling grooves in between the half bipolar plates and repetitive
sequence of iv & v as per the stack capacity requirements finally the end with
the MEA, half bipolar cathode plate and end plate followed by copper plate.
Gasket is an indispensable component in between every interface of MEA-plate &
plate-plate. Schematic of membrane electrode assembly is shown in Fig.7, where
the electrode (37) made of platinum or platinum alloy based materials of
required size is placed on both sides of the membrane (38) between which the
membrane is hot pressed to form MEA. The membrane possesses the properties
of electrically insulative and ionic conductive to assist in transfer of hydrogen
ions (H+). Fuel cell components such as anode, cathode, bipolar and cooling
plates of the fuel cell stack may be made of electrically conducting solid materials
including: (a) metals and metal alloys (including composites), (b) non-metals
(carbon, graphite and their composites) and (c) any combination of (a) and (b).
The plates may be treated for enhanced performance and may be fabricated by
machining, moulding, stamping, etching, or similar processes to create channels
on anode/cathode plates for supply of reactants and coolant flow, sealing surface
the remainder area outside of the sealing is applied with non-conducting material
(electrically inactive), there by separating the graphite plates electrically to avoid
short circuit.
Complete assembly with sealing of membrane electrode assembly (Fig.7)
between the cathode (Fig.5) and anode (Fig.6) plates is shown in Fig.2. The

mechanism of sealing method is that the male projected part (26A) of cathode
plate (Fig.5) comes in close contact with the female part (34) of anode plate
(Fig.6) and interface between these two plates is separated by the ionic
conducting membrane (38) whose through hole dimensions are equal as that of
the male or female plate manifolds of air or hydrogen. In addition to that, width
of the male plate gasket is relatively less than that of the width of the sealing
groove of the female plate. Excess sealing width in the female plate is provided
to ensure that the sufficient space is provided for the male gasket during
expansion which is inevitable while assembling the stack using tie rods (2,3)
while subjecting the total components for compressive load. In order to ensure
proper sealing under compressive conditions, the expansion of gasket is limited
by the boundary walls provided in the area of gasket sealing of male and female
plate which will ensure complete leak proof sealing against surface gas leaks and
cross leakage between anode (female plate) and cathode (male plate) sides. In
addition to that, four gaskets (11) are used at the four corners of the plates for
laminating the male-female plates to form a bipolar plate as one unit after
lamination which has through channels for coolant circulation, hydrogen and air
circulation over the gas distribution channels of female and male plates
respectively.

We Claim
1. An adhesive sealed gasket flow field plate for low and high temperature
Proton Exchange Membrane (PEM) fuel cells comprising :
a multiple number of bipolar plates (8,9) stacked together with membrane
electrode assemblies, MEA (6) in between the bipolar plates forming each single
cell (22), the assembly being flanked by a further pair of MEA (6) on both sides;
a pair of half bipolar plates (7A) (Fig 1 & Fig 6) and (7B) (Fig 1 & Fig 3) covering
the assembly from two sides;
a further pair of copper plates (5A, 5B) covering the assembly from two sides for
collecting the electrons generated at electrocatalyst sides of membrane electrode
assembles (Fig.7);
a pair of insulating plates (4A, 4B) covering the assembly from two sides for
protecting against thermal and electrical losses;
a pair of end plates (1A, 1B) disposed from either side of the stack assembly for
tightening the stack assembly through bolts (18) wherein the internal tie rod (2)
and external tie rods (3) align the components characterized in that a sealing is
provided by the male projected part (26A) Fig.5 of gasket (21) (Fig.1) in the
groove depth (26) Fig.3 above gas distribution grooves (29) of cathode plate
(24) Fig.2 which comes in close contact with the female part (34) of anode plate
(25) (Fig.6) and the interface between these plates is separated by the ionic
conducting membrane (38) of membrane electrode assembly (6) to ensure
complete leak proof sealing against surface gas leaks as well as cross leakage
between anode female plate (25) and cathode male plate (24) sides.
2. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 1, wherein a sealing gasket (21) is placed over the
groove depth (26) having outer (27) and inner (28) boundary walls of gas

distribution plate (24) such that the protruding part (26A) Fig.5 above gas
distribution groove (29) Fig.3 fits into the female part (34) of the anode plate
(25).
3. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 1, wherein the bipolar plates (24,25) are formed by
laminating two half bipolar male female plates of anode (8) and cathode (9)
using sealing (11) adhered to four corners of anode/cathode half bipolar plates in
their respective corners of individual manifolds through which each single cell
receives the reactant gas of hydrogen or air oxygen as well as for the bipolar
plate which has through channels for coolant circulation, hydrogen and air
circulation over the gas distribution channels of female and male plates
respectively.
4. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell in which the Bipolar plates as claimed in claim 3, having gas distribution
patterns on each side around which one side of the plates is adhered with the
gasket (Figure 4) within the area (26) provided between the boundaries (27,28)
for placement of gasket (26A) being the male part, on the other side of the plate
whose gasket area (34) between the boundaries (35,36) is partially filled with a
compressible sealant material (11) being the female part.
5. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 1, wherein electrode (37) made of platinum or platinum
alloy based material of required size is placed on both sides of the membrane
(38) between which the membrane is hot pressed to form MEA (6).
6. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 5, wherein the MEA comprises electrodes of anode,
cathode and an ionic conducting membrane in which the size and dimension of
the membrane is higher than that of electrodes.

7. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 6, wherein the excess part of the membrane around the
electrodes is sealed with electrically insulative material for compression purpose.
8. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 1, wherein the non active area other than the gas flow
distribution profile area of male or female plate is spread with electrically
insulative material for compressive under mechanical load.
9. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 1, wherein the bonding material used for adhering the
gasket over the gasket groove of male or female plate is of compressive in
nature and thermally stable under fuel cell operating conditions upto an
operating temperature of 200oC.
10. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 1, wherein the bipolar plates are made by using four
single gaskets placed at the corners around the manifold of anode/ cathode plate
at the respective corners of individual manifolds through which each single cell
receives the reactant gas of hydrogen or air/oxygen.
11. The adhesive sealed gasket flow field plate for Proton Exchange membrane fuel
cell as claimed in claim 1, wherein each bipolar plate consists of one side gas
distribution channels for supply of air, other side of plate having different gas
distribution pattern for supply of hydrogen and straight cooling channels
provided between these two plates.