FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, rule 13]
TITLE: “BIPOLAR PLATE FOR A FUEL CELL”
NAME AND ADDRESS OF THE APPLICANT:
TATA MOTORS LIMITED of Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001 Maharashtra, India.
Nationality: Indian
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
Present disclosure generally relates to a field of renewable energy. Particularly, but not exclusively, the present disclosure relates to a fuel cell. Further, embodiments of the present disclosure disclose a bipolar plate for the fuel cell.
BACKGROUND
A fuel cell is an electrochemical cell which converts chemical energy of a fuel into an electrical energy. the fuel cell produces electricity as long as fuel, in the form of hydrogen, and air are supplied thereto. A fuel cell system generally comprises a fuel cell stack for generating electricity. Further, the fuel cell system includes a fuel supply system for supplying fuel like hydrogen to the fuel cell stack and air supply system for supplying oxygen. The oxygen may act as an oxidizing agent required for an electrochemical reaction, within the fuel cell stack.
A significant part of the fuel cells are bipolar plates, which are designed to carry out functions, such as distribution of reactants uniformly over active areas, remove heat from the active areas, supply current from one fuel cell to another fuel cell and prevent leakage of reactants and coolant.
Typically, the bipolar plates are manufactured using metals which exhibit hight mechanical strength without requiring excessive structural dimensions. However, the metal bipolar plates are prone to corrosion which decreases the effectiveness of the fuel cell and the life of the bipolar plate. Generally, to increase the corrosion resistance of the metal bipolar plates, a protective material is laid on a metal substrate by spray-coating. However, the protective layer laid over the metal is porous in nature and does not have the required surface density to withstand the fuel cell environment for extended periods. Hence, multiple protective layers have to be laid over the metal to increase the life of the bipolar plate. Nevertheless, laying multiple protective layers over the metal renders the processing procedures for manufacturing the bipolar plate complicated, and also increases production cost, which is undesired. Alternatively, physical vapor deposition (PVD) process may also be employed for laying the protective layer over the metals. However, the protective layer laid by the PVD process is prone to chipping, thereby resulting in poor reliability, which leads to decreased life of the bipolar plate.

The present disclosure is directed to overcome one or more limitations stated above, or any other limitation associated with the prior arts.
SUMMARY
The one or more shortcomings of the prior art are overcome by a method as claimed and additional advantages are provided through the provision of the method as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.
In a non-limiting embodiment of the disclosure, a method of manufacturing a bipolar plate for a fuel cell is disclosed. The method includes steps of laying a graphite powder on a surface of a base material. Further, the graphite powder is subjected to a spark plasma process to form a graphite layer on the base material. Furthermore, upon formation of the graphite layer on the base material, a plurality of flow channels are machined on the graphite layer for flow of fluid on the bipolar plate. The method enables manufacturing of the bipolar plate which is resistant to corrosion and is mechanically durable by having the graphite layer over the base material.
In an embodiment, the spark plasma process comprises densifying the graphite powder by compacting and heating the graphite powder on the surface of the base material to form adhesion between graphite particles and the surface of the base material, and to form cohesion among each of the graphite particles in the graphite powder.
In an embodiment, the graphite powder is compacted at a compaction pressure in a range of 250 MPa to 350 MPa.
In an embodiment, the graphite powder is heated to a temperature range of 1100 Degree Celsius to 1250 Degree Celsius.
In another non-limiting embodiment of the disclosure, a bipolar plate for a fuel cell is disclosed. The bipolar plate includes a base material and a graphite layer, which is disposed on a surface of the base material. The graphite layer is directly adhered on the surface of the base material through a spark plasma process. Further, the bipolar plate includes a plurality of flow channels that are defined on the graphite layer for flow of fluid on the bipolar plate.
In an embodiment, the base material is a stainless steel.

In an embodiment, density of the graphite layer is in a range of 1g/cc to 3g/cc.
In another non-limiting embodiment of the disclosure, a fuel cell is disclosed. The fuel cell include a pair of bipolar plates. Each of the pair of bipolar plates include a base material and a graphite layer, which is disposed on a surface of the base material. The graphite layer is directly adhered on the surface of the base material through a spark plasma process. Further, each of the bipolar plates include a plurality of flow channels that are defined on the graphite layer for flow of fluid on the bipolar plate.
It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:
Fig. 1 illustrates a perspective view of a fuel cell having a bipolar plate, according to an embodiment of the present disclosure.
Fig. 2 illustrates a side view of the bipolar plate, according to an embodiment of the present disclosure.
Fig. 3 is a flowchart illustrating a method of manufacturing a bipolar plate, according to an exemplary embodiment of the present disclosure.

Fig. 4 illustrates a side view of a base material of the bipolar plate, according to an embodiment of the present disclosure.
Fig. 5 illustrates a side view of a graphite powder laid on the base material for manufacturing the bipolar plate, according to an embodiment of the present disclosure.
Fig. 6 illustrates a side view of a graphite layer formed on the base material, according to an embodiment of the present disclosure.
The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other mechanism for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a system, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or method proceeded by “comprises… a” does not,

without more constraints, preclude the existence of other elements or additional elements in the system or apparatus or method.
Henceforth, a method of manufacturing a bipolar plate of the present disclosure is explained with the help of figures. However, such exemplary embodiments should not be construed as limitations of the present disclosure. A person skilled in the art can envisage various such embodiments without deviating from scope of the present disclosure.
Fig. 1 is a perspective view of a fuel cell (200). A plurality of fuel cells (200) may be positioned adjacent to each other or may be stacked one above the other to form a fuel cell stack. In an embodiment, the fuel cell (200) may include a membrane (12) which may facilitate electrochemical reactions. Further, the fuel cell (200) may include a gas diffusion layer (11) which may be positioned on either sides of the membrane (12). Additionally, the fuel cell (200) may include a pair of bipolar plates (10) which may be positioned adjacent to the gas diffusion layer (11) and on either sides of the membrane (12). The bipolar plate (10) may be configured to operate as either an anode or a cathode when positioned adjacent to the gas diffusion layer (11).
Further, Fig. 2 illustrates a schematic view of the bipolar plate (10) for the fuel cell (200). The bipolar plate (10) may include a base material (1). Further, the bipolar plate (10) may include a graphite layer (3) which may be disposed or laid on a surface of the base material (1). In an embodiment, the graphite layer (3) may be directly laid or adhered on each surface of the base material (1) through spark plasma process. In an embodiment, the density of the graphite layer (3) disposed on the surface of the base material (1) may be in a range of 1g/cc to 3g/cc. Additionally, the bipolar plate (10) may include a plurality of flow channels (4). The plurality of flow channels (4) may be defined on the graphite layer (3). The flow channels (4) defined on the graphite layer (3) facilitates flow of fuel and/or air over the surface of the bipolar plate (10). The base material (1) may be manufactured of stainless steel and may provide mechanical strength to the bipolar plate (10) without rendering the bipolar plate (10) to be bulky and heavy. Furthermore, the graphite layer (3) on the surface of the base material (1) may prevent corrosion of the base material (1) as direct interaction between the fuel and the gases with the base material involved in chemical reactions during fuel cell (200) operation is mitigated. The base material (1) may be a metal. In an embodiment, the base material (1) is a stainless steel.

Referring now to Fig. 3, which illustrates a flowchart depicting a method of manufacturing the bipolar plate (10) for the fuel cell (200). At block 101, the base material (1) [as seen in Fig. 4] of required dimension suitable for use as the bipolar plate (10) may be machined or selected. Further, graphite powder (2) may be laid on the surface of the base material (1) based on requirement [as seen in Fig. 5]. In an embodiment, the graphite powder (2) may be laid on each layer of the base material (1). Furthermore, at block 102, the method may include subjecting the graphite powder (2) laid on the base material (1) to the spark plasma process. In an embodiment, the base material (1) may be positioned within a spark plasma apparatus [not shown in Figs]. For example, the base material (1) may be positioned within a die of the spark plasma apparatus. In an embodiment, the spark plasma process may include subjecting a powder material to a predefined pressure in the presence of electric current to sinter the powder material.
Referring back to block 102, the graphite powder (2) that may be laid on the base material (1), upon being subjected to the spark plasma process may densify on the surface of the base material (1) to form the graphite layer (3) [as seen in Fig. 6]. The spark plasma process may include densifying the graphite powder (2) by compacting and heating the graphite powder (2) on the surface of the base material (1). In an embodiment, the compacting of the graphite powder (2) may be carried out by applying pressure on the graphite powder (2) by a compacting unit [not shown] of the spark plasma apparatus. In an embodiment, the graphite powder (2) may be compacted at a compaction pressure in a range of 250 MPa - 350 MPa. Further, heating of the graphite powder (2) under the compacting pressure may be carried out by supplying electric current onto the graphite powder (2). In an embodiment, the graphite powder (2) may be heated to a temperature in a range of 1100 Degree Celsius - 1250 Degree Celsius.
The compacting and the heating of the graphite powder (2) by the spark plasma process on the surface of the base material (1) may result in adhesion between graphite particles and the surface of the base material (1), and may form cohesion among graphite particles in the graphite powder (2). The adhesion between graphite particles and the surface of the base material (1) and the cohesion between each of the graphite particles may form the graphite layer (3) on the surface of the base material (1) [as seen in Fig. 6]. Additionally, the spark plasma process enables achieving high adhesion between the graphite particles and the base material (1). Therefore, a separate binder, such as glue, need not be used for achieving the adhesion. Thus, the bipolar plate (10) manufactured according to the present subject matter

may be devoid of binder, which ensures high electrical and thermal conductivity of the bipolar plate (10).
The densification of the graphite powder (2) on the surface of the base material (1), which forms the graphite layer (3), requires less time duration due to spark plasma process. Therefore, manufacturing time and the costs involved are reduced. Additionally, the spark plasma process enables formation of the graphite layer (3) with high precision without altering shape and structure of the base material (1). Further, the spark plasma process enables the density of the graphite layer to be high, such as in the range of 1-3g/cc, which reduces the permeability of the bipolar plate (10) thereby increasing the efficiency.
In an embodiment, the amount or volume of the graphite powder (2) laid on the surface of the base material (1) may be determined based on the required thickness of the graphite layer (3) to be formed.
Further, at block 103, the graphite layer (3) that may be formed on the surface of the base material (1) may be subjected to machining. The machining may be carried out to define the plurality of flow channels (4) in the graphite layer (3) to manufacture the bipolar plate (10) [as seen in Fig. 2]. In an embodiment, the machining may include but not limited to grinding, carving, groove cutting, drilling, turning, boring and the like. Further, the number of flow channels (4) that may be machined on the graphite layer (3) may be selected based on the fuel cell (200) requirement.
In an embodiment, graphite layer (3) may be formed on the surface of the base material (1) without use of binder material which enhances efficiency of the bipolar plate (10).
In an embodiment, the bipolar plate (100) manufactured as per the method described in blocks 101-103, exhibit high mechanical strength exhibited due to the base material (1) and high resistance to corrosion due to the graphite layer (3) over the base material (1), which in-turn increases the life of the bipolar plate (10), without requirement of regular maintenance.
It should be imperative that the method and any other elements described in the above detailed description should not be considered as a limitation with respect to the figures. Rather, variation to such method should be considered within the scope of the detailed description.
Equivalents:

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B

and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope.

Referral Numerals:

Reference Number Description
200 Fuel cell
10 Bipolar plate
11 Gas diffusion layer
12 Membrane
1 Base material
2 Graphite powder
3 Graphite layer
4 Flow channels

We claim:
1. A method of manufacturing a bipolar plate (10) for a fuel cell (200), the method
comprising:
laying, graphite powder (2) on a surface of a base material (1);
subjecting, the graphite powder (2) to a spark plasma process to form a graphite layer (3) on the base material (1); and
machining, a plurality of flow channels (4) on the graphite layer (3) for flow of fluid on the bipolar plate (10).
2. The method as claimed in claim 1, wherein the spark plasma process comprises:
densifying the graphite powder (2) by compacting and heating the graphite powder (2) on the surface of the base material (1) to form adhesion between graphite particles and the surface of the base material (1), and to form cohesion among graphite particles in the graphite powder (2).
3. The method as claimed in claim 2, wherein the graphite powder (2) is compacted at a compaction pressure in a range of 250 MPa to 350 MPa.
4. The method as claimed in claim 2, wherein the graphite powder (2) is heated to a temperature range of 1100 Degree Celsius to 1250 Degree Celsius.
5. A bipolar plate (10) for a fuel cell (200), comprising:
a base material (1);
a graphite layer (3), disposed on a surface of the base material (1), wherein the graphite layer (3) is adhered directly on the surface of the base material (1); and
a plurality of flow channels (4) defined on the graphite layer (3) for flow of fluid on the bipolar plate (10).
6. The bipolar plate (10) as claimed in claim 5, wherein the base material (1) is a stainless steel.
7. The bipolar plate (10) as claimed in claim 5, wherein density of the graphite layer (3) is in a range of 1g/cc to 3g/cc.

8. A bipolar plate (10) manufactured by a method, wherein the method comprising:
laying, graphite powder (2) on the surface of the base material (1);
subjecting, the graphite powder (2) to a spark plasma process to form the graphite layer (3) on the base material (1); and
machining, the plurality of flow channels (4) on the graphite layer (3).
9. A fuel cell (200), comprising:
a pair of bipolar plates (10), each of the pair of bipolar plates (10) comprising:
a base material (1);
a graphite layer (3), disposed on a surface of the base material (1), wherein the graphite layer (3) is adhered directly on the surface of the base material (1); and
a plurality of flow channels (4) defined on the graphite layer (3) for flow of fluid on the bipolar plate (10).