Unit cell for fuel cell

Abstract

Unit cell for a fuel cell, the unit cell comprising: a membrane electrode assembly (10); a gas diffusion layer (20, 30) arranged on a surface of the membrane electrode assembly (10); a separating plate (40, 50) arranged such that it is spaced apart from the gas diffusion layer (20, 30);and a helical spring (60) arranged between the gas diffusion layer and the partition plate (40, 50) to elastically mount the gas diffusion layer (20, 30) and the partition plate (40, 50), while electrically connecting the gas diffusion layer (20, 30) to the partition plate (40, 50) and providing a reaction gas passage (90) for transferring reaction gas, wherein the helical spring (60) comprises a plurality of helical springs (60), wherein the helical springs (60) are arranged to increase the porosity of the reaction gas passage (90) from an upstream side of the reaction gas passage (90) towards a downstream side of the reaction gas passage (90), wherein the helical springs (60) are arranged such that a helical spring (60) with a longer spring pitch is located among the helical springs (60) from the upstream side of the reaction gas passage (90) is positioned in the direction of the downstream side of the reaction gas passage (90).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Korean Patent Application No. 10-2018-0016449, filed on February 9, 2018, which is hereby incorporated by reference. TECHNICAL FIELD

[0002] The present disclosure relates to a unit cell for a fuel cell. BACKGROUND

[0003] A fuel cell stack is a device that generates electricity through a redox reaction of hydrogen and oxygen as a main power source of a fuel cell vehicle.

[0004] Generally, the fuel cell stack is formed by stacking a plurality of unit cells having a membrane electrode assembly (MEA) and separator plates arranged on both sides of the MEA.

[0005] The MEA includes a polymer electrolyte membrane, an anode electrode provided on one surface of the polymer electrolyte membrane, and a cathode electrode provided on an opposite surface of the polymer electrolyte membrane. The partition plate includes a hydrogen channel for supplying hydrogen to the anode electrode, an air channel for supplying air to the cathode electrode, and a coolant passage for supplying coolant.

[0006] The anode electrode receives high-purity hydrogen supplied from a hydrogen storage tank through the hydrogen channel of the partition plate. The cathode electrode receives air in the atmosphere supplied by an air supply device such as an air compressor through the air channel of the partition plate. Then, as the oxidation reaction of hydrogen proceeds, protons and electrons are generated in the anode electrode. The generated protons and electrons are moved to the cathode electrode through the polymer electrolyte membrane and the partition plate. In addition, the reduction reaction proceeds in the cathode electrode, involving the protons and electrons moved by the anode electrode and oxygen in the atmosphere supplied by the air supply device, thereby generating water and electrical energy resulting from the flow of electrons.

[0007] Meanwhile, a unit cell designed to transmit air through a formed porous body or a foamable porous body has recently been developed and used. It is designed to sandwich the formed porous body and the foamable porous body between a partition plate and a gas diffusion layer, rather than forming the air passage in the partition plate. When forming an air passage to transmit air using the formed porous body or the foamable porous body, the porosity of the formed porous body or the foamable porous body needs to be adjusted for the design purpose of the unit cell. However, since the foamable porous body has a random geometric shape, it may be difficult to precisely adjust the porosity for the design purpose. Furthermore, a mold is required due to the characteristics of the manufacturing process.to manufacture the molded porous body. Accordingly, the molded porous body has problems in requiring high costs when installing the mold and requiring additional costs to change the structure of the mold in the event that a shape change is required while optimizing the molded porous body for the design purpose. DESCRIPTION OF THE INVENTION

[0008] Embodiments of the present disclosure may solve problems encountered in the prior art while still maintaining advantages achieved by the prior art.

[0009] One aspect of the present disclosure provides a unit cell for a fuel cell having a structure improved to precisely adjust the porosity of a reaction gas passage for design purposes.

[0010] Another aspect of the present disclosure provides a unit cell for a fuel cell having a structure improved to adjust the porosity of a reaction gas passage differently depending on portions of the reaction gas passage.

[0011] Another aspect of the present disclosure provides a unit cell for a fuel cell having a structure improved to stably maintain the contact state between components in the unit cell.

[0012] The technical problems to be solved by the present disclosure are not limited to the above-mentioned problems, and any other technical problems not mentioned here will be clearly apparent to those skilled in the art from the present disclosure from the following description.

[0013] According to one aspect of the present disclosure, a unit cell for a fuel cell includes: a membrane electrode assembly (MEA), a gas diffusion layer disposed on a surface of the MEA, a partition plate disposed to be spaced apart from the gas diffusion layer, and at least one coil spring disposed between the gas diffusion layer and the partition plate to elastically support the gas diffusion layer and the partition plate while electrically connecting the gas diffusion layer to the partition plate and providing a reaction gas passage for transferring reaction gas.

[0014] Preferably, the coil springs are arranged such that an axial direction of each coil spring is perpendicular to a thickness direction of the MEA.

[0015] Preferably, each coil spring is attached to the separator plate.

[0016] Preferably, each coil spring is welded to the separating plate.

[0017] Preferably, each coil spring is bonded to the separating plate by an adhesive.

[0018] Preferably, the partition plate has at least one locking projection to lock one of the coil springs.

[0019] Preferably, each coil spring is locked to the locking projections so that a spring pitch of the coil spring is varied depending on portions of the reaction gas passage.

[0020] Preferably, the coil springs are provided such that at least one of the pitches of the coil springs, the diameters of the coil springs, an overlap ratio between the coil springs, and the diameter of the spring wires of the coil springs is varied to vary the porosity of the reaction gas passage depending on portions of the reaction gas passage.

[0021] Preferably, the coil springs are arranged to increase the porosity of the reaction gas passage from upstream or an upstream side of the reaction gas passage toward downstream or a downstream side of the reaction gas passage.

[0022] Preferably, the coil springs are arranged such that the spring pitches of the coil springs are increased from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage.

[0023] Preferably, the coil springs are arranged such that a coil spring having a longer spring pitch is positioned among the coil springs from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage.

[0024] Preferably, the coil springs are arranged such that an overlap ratio between the coil springs is reduced from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage.

[0025] Preferably, the coil springs are arranged such that an arrangement distance between the coil springs is increased from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage.

[0026] Preferably, the coil springs are arranged such that a coil spring having a spring wire with a smaller diameter is positioned among the coil springs from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage.

[0027] Preferably, the coil springs are arranged such that a coil spring having a smaller diameter is positioned among the coil springs from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage.

[0028] Preferably, the coil springs are arranged such that an axial direction of each coil spring forms a specific angle with a flow direction of the reaction gas.

[0029] Preferably, at least some of the coil springs are arranged such that axial directions of the at least some of the coil springs are parallel to the flow direction of the reaction gas.

[0030] Preferably, at least some of the coil springs are arranged such that axial directions of the at least some of the coil springs are perpendicular to the flow direction of the reaction gas.

[0031] Preferably, the coil springs are arranged to reduce the porosity of the reaction gas passage towards a region with a higher current density.

[0032] As described above, the present disclosure relates to the unit cell for the fuel cell and has the following effects.

[0033] First, according to aspects of the present invention, the porosity of the reaction gas passage that transfers the reaction gas is adjusted using the coil spring, thereby precisely adjusting the porosity of the reaction gas passage for the design purpose of the unit cell and precisely adjusting the electrical resistance between the gas diffusion layer and the partition plate to be adjusted according to the current density.

[0034] Second, according to aspects of the present invention, the permanent shrinkage strain of the gas diffusion layer is compensated by the elastic restoring force of the coil spring, thereby stably maintaining the contact state between components in the unit cell. Character list

[0035] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings: Fig. 1 is a perspective view showing the stack structure of a unit cell for a fuel cell according to an exemplary embodiment of the present disclosure; Fig. 2 is a sectional view showing the stacking structure of an MEA; Fig. 3 is a view schematically showing the shape of the coil spring; Fig. 4 is a view illustrating the state of coil springs arranged in a plurality of rows; Fig. 5A is a view illustrating the state in which the Fig. 4 are arranged so that they are parallel to the flow direction of the reaction gas; Fig. 5B is a view illustrating the state in which the Fig. 4 are arranged so that they are perpendicular to the flow direction of the reaction gas; Fig. 6 is a view showing the arrangement state of a coil spring folded in a zigzag pattern; Fig. 7 is a view showing the arrangement state of a coil spring folded in a spiral shape; Fig. 8 is a view showing a coil spring welded to the first partition plate; Fig. 9A to Fig. 9C are views illustrating states in which a coil spring is locked to a locking projection of the first partition plate; Fig. 10A to Fig. 10C are views illustrating the states in which coil springs are arranged to overlap each other; and Fig. 11 to Fig. 14 are views illustrating ways of adjusting the porosity of the reaction gas passage using coil springs. DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0036] Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, like elements are assigned like reference numerals even though the elements are shown in different drawings. In addition, in the following description of an embodiment of the present disclosure, a detailed description of well-known features or functions is omitted in order not to unnecessarily obscure the gist of the present disclosure.

[0037] In the following description of elements according to an embodiment of the present disclosure, the terms "first," "second," "A," "B," "(a)," and "(b)" may be used. The terms are used only to distinguish relevant elements from other elements, and the type, order, or sequence of the relevant elements is not limited to the terms. Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those commonly understood by one of ordinary skill in the art to which this disclosure relates.Terms such as those defined in a commonly used dictionary are to be construed to have meanings that correspond to contextual meanings in the relevant field and are not to be interpreted as having ideal or overly formal meanings unless they are clearly defined as such in the present application.

[0038] Fig. 1 is a perspective view showing the stack structure of a unit cell for a fuel cell according to an exemplary embodiment of the present disclosure, and Fig. Figure 2 is a cross-sectional view showing the stack structure of an MEA.

[0039] Referring to Fig. 1, according to an embodiment of the present disclosure, a unit cell 1 for a fuel cell (hereinafter referred to as “unit cell 1 “) have: an MEA 10 , a first gas diffusion layer 20, which are on a surface of the MEA 10 is arranged, a second gas diffusion layer 30 located on an opposite surface of the MEA 10 is arranged, a first partition plate 40 , which is arranged so that it extends from a surface of the first gas diffusion layer 20 is separated, a second separating plate 50 , the bridge parts 52 (land parts) and canal parts 54 which are alternately formed in a specific direction and which are formed on a surface of the second gas diffusion layer 30 is arranged, and at least one coil spring 60 which is located between the first gas diffusion layer 20 and the first partition plate 40 is arranged.

[0040] First, as in Fig. As shown in Figure 2, the MEA 10 an electrolyte membrane 12 , one on a surface of the electrolyte membrane 12arranged cathode electrode 14 and one on an opposite surface of the electrolyte membrane 12 arranged anode electrode 16 Since the MEA 10 has the same structure as a MEA of a typical unit cell, the details of the MEA 10 omitted in the following description.

[0041] Furthermore, as in Fig. 1, the first gas diffusion layer is 20 on a surface of the cathode electrode 14 arranged such that the first gas diffusion layer 20 at an outer section of the unit cell 1 positioned as the cathode electrode 14 . As in Fig. 1, the second gas diffusion layer 30 on a surface of the anode electrode 16 arranged such that the second gas diffusion layer 30 at an outer part of the unit cell 1as the anode electrode 16 These gas diffusion layers 20 and 30 have the same structures as the gas diffusion layers of a typical unit cell, and therefore the details of the first gas diffusion layer 20 and the second gas diffusion layer 30 omitted in the following description.

[0042] As in Fig. 1, the first partition plate 40 arranged so that they are separated from a surface of the first gas diffusion layer 20 separated by a specific distance, so that the first partition plate 40 at an outer section of the unit cell 1 as the first gas diffusion layer 20 is positioned. The first partition plate 40 can take different forms. For example, as in Fig. 1, the first partition plate 40 have a flat plate shape.

[0043] Furthermore, the second partition plate 50 on a surface of the second gas diffusion layer 30 arranged such that the second partition plate 50 at an outer section of the unit cell 1 as the second gas diffusion layer 30 is positioned. The second partition plate 50 can the bridge parts 52 and the canal parts 54 which are alternately formed in a specific direction. The web parts 52 and the canal parts 54 can take different forms. For example, as in Fig. 1, the web parts can 52 valley shapes and the channel parts 54 can have mountain shapes.

[0044] As in Fig. 1, the second partition plate 50 on one surface of the second gas diffusion layer 30 be arranged so that the web parts 52on one surface of the second gas diffusion layer 30 sit and the channel parts 54 from one surface of the second gas diffusion layer 30 In this case, a separator plate channel fluid passage 70 between the channel part 54 and the second gas diffusion layer 30 be designed to transfer reaction gas and generated water. A coolant passage 80 can be placed between the bridge part 52 any unit cell 1 and the first partition plate 40 another unit cell 1 be formed which can be connected to any unit cell 1 in contact to transfer coolant C.

[0045] Different types of gas can pass through the partition plate channel fluid passage 70 For example, the partition plate channel fluid passage 70be designed to transfer hydrogen. In this case, the entrance (not shown) of the separator plate channel fluid passage 70 be connected to a hydrogen supply line (not shown). The hydrogen supply line is provided to supply hydrogen, which is supplied from a hydrogen supply source (not shown), towards the entrance of the partition plate channel fluid passage 70 In this case, the hydrogen passing through the entrance of the partition plate channel fluid passage 70 is supplied to the anode electrode 16 through the second gas diffusion layer 30 transferred and then split into protons and electrons. In addition, the outlet of the separation plate channel fluid passage 70be connected to a hydrogen recirculation line (not shown). The hydrogen recirculation line is provided such that the fluid passage leading from the outlet of the partition plate channel 70 released hydrogen is transferred again to the hydrogen supply line. Then, remaining hydrogen that does not participate in the oxidation reaction in the anode electrode 16 participated, through the exit of the partition plate channel fluid passage 70 and the hydrogen recirculation line are transferred again to the hydrogen supply line.

[0046] Fig. 3 is a view schematically showing the shape of the coil spring.

[0047] As in Fig. 3, the coil spring is 60 by spiral winding of a spring wire 62 with a specific diameter D1 formed. The coil spring 60can be designed to have a specific spring pitch P and a specific diameter D2 for the design purpose of the unit cell 1 has.

[0048] The coil spring 60 is between a surface of the first gas diffusion layer 20 and the first partition plate 40 arranged to cover one surface of the first gas diffusion layer 20 and the first partition plate 40 elastically while forming the first gas diffusion layer 20 electrically with the first separating plate 40 connects. For example in Fig. 1, the coil spring can 60 between one surface of the first gas diffusion layer 20 and the first partition plate 40 be arranged such that the axial direction of the coil spring 60 perpendicular to a thickness direction of the MEA 10The coil spring 60 can prevent the reaction gas passage 90 to separate the reaction gas and the generated water between the first gas diffusion layer 20 and the first partition plate 40 by increasing the distance between the first gas diffusion layer 20 and the first partition plate 40 is kept at a specific distance.

[0049] Different types of gas can pass through the reaction gas passage 90 For example, the reaction gas passage 90 be designed to transfer air. In this case, the inlet (not shown) of the reaction gas passage 90 connected to a hydrogen supply line (not shown). An air compressor (not shown) may be installed on an air supply line to supply outside air to the inlet of the reaction gas passage 90In this case, oxygen is extracted from the air passing through the entrance of the reaction gas passage 90 is supplied through the first gas diffusion layer 20 to the cathode electrode 14 transferred and then with electrons passing through the first separator plate 40 transferred, and protons that pass through the electrolyte membrane 12 transferred. According to the reduction reaction in which protons, electrons, and oxygen participate, electrical energy and water can be generated. Furthermore, the entrance of the reaction gas passage 90 connected to an air discharge line (not shown). In this case, the remaining air and the generated water that are not used in the reduction reaction in the cathode electrode 14 participate, through the existence of the reaction gas passage 90 and the air discharge duct to the outside.

[0050] Fig. 4 is a view illustrating the state of coil springs arranged in a plurality of rows, Fig. 5A is a view illustrating the state in which the Fig. 4 are arranged parallel to the flow direction of the reaction gas, and Fig. 5B is a view illustrating the state in which the Fig. 4 are arranged perpendicular to the flow direction of the reaction gas.

[0051] Fig. 6 is a view showing the arrangement state of the coil spring folded in a zig-zag pattern, and Fig. 7 is a view showing the arrangement state of the coil spring folded in a spiral shape.

[0052] The coil spring 60 can be arranged in different ways.

[0053] For example, as in Fig. 4, a variety of coil springs 60 be arranged in a plurality of rows. In this case, the coil springs 60 be arranged so that the axial direction of the coil springs 60 forms a specific angle with the flow direction of the air passing through the reaction gas passage 90 For example, as in Fig. 5A, at least one of the coil springs 60 be arranged such that the axial direction of the at least one coil spring 60 parallel to the direction of air flow. For example, as in Fig. 5B, at least one of the coil springs 60 be arranged such that the axial direction of the at least one coil spring 60 perpendicular to the direction of air flow.

[0054] For example, as in Fig. 6, at least one coil spring 60 be arranged so that it is folded in a zigzag pattern.

[0055] For example, as in Fig. 7, at least one coil spring 60 be arranged so that it is folded in a spiral shape.

[0056] Fig. 8 is a view showing the coil spring welded to the first partition plate, and Fig. 9A to Fig. 9C are views illustrating states in which the coil spring is locked to a locking projection of the first partition plate.

[0057] The coil spring 60 is preferably on the first partition plate 40 fixed to maintain a specific position.

[0058] For example, as in Fig. 8, the coil spring is 60 at specific welding points W of the coil spring 60on a surface of the first partition plate 40 welded and fastened.

[0059] For example, as in the Fig. 9A and Fig. As shown in Figure 9B, the first partition plate 40 at least one locking projection 42 which is separated from one surface of the first partition plate 40 protrudes, and the coil spring 60 can be attached to the locking projections 42 locked and secured. In particular, as in Fig. As shown in Figure 9C, the coil spring 60 such on the locking projections 42 locked and secured so that the gradients P1 , P2 and P3 depending on sections of the coil spring 60 can be varied.

[0060] Fig. 10A to Fig. 10C are views illustrating the states in which the coil springs are arranged to overlap each other.

[0061] The coil springs 60 can be installed with different installation distances between them.

[0062] For example, as in the Fig. 10A to Fig. As shown in Figure 10C, coil springs 60 that are arranged side by side may be arranged to overlap with a specific overlap ratio, or they may be arranged to be spaced apart by a specific distance. The overlap between the coil springs 60 may refer to the condition in which the arrangement distance between the coil springs 60 smaller than the diameter D2 each coil spring 60 so that the coil springs 60 overlap.

[0063] Fig. 11 to Fig. 14 are views illustrating the manner of adjusting the porosity of the reaction gas passage using the coil springs.

[0064] The porosity of the reaction gas passage 90 is the ratio of the volume of a space not occupied by the coil springs 60 is taken up in the entire volume of the reaction gas passage 90 and is inversely proportional to the ratio of the volume absorbed by the coil springs 60 is taken up in the entire volume of the reaction gas passage 90 In other words, the porosity of the reaction gas passage 90 increases when the ratio of the volume absorbed by the coil springs 60 is taken up in the entire volume of the reaction gas passage 90 Accordingly, the porosity of the reaction gas passage 90 by adjusting the ratio of the volume released by the coil springs60 is taken up in the entire volume of the reaction gas passage 90 , can be set.

[0065] Therefore, the coil springs 60 be provided in such a way that the reaction gas passage 90 a specific porosity for the design purpose of the unit cell 1 The porosity of the reaction gas passage 90 can be used with the coil springs 60 can be adjusted in various ways. For example, at least one of the diameter D1 of the spring wire, the pitch P of the coil springs 60 , the diameter D2 the coil springs 60 and the overlap ratio of the coil springs 60 adjusted, whereby the porosity of the reaction gas passage 90 is precisely adjusted to a specific target porosity.

[0066] Meanwhile, the flow rate of air passing through the reaction gas passage 90 flows gradually from an upstream side 92 the reaction gas passage 90 towards a downstream side 94 the reaction gas passage 90 Accordingly, a dry-out phenomenon, in which humidity is reduced from a normal level, occurs more frequently towards the upstream side 92 the reaction gas passage 90 A flooding phenomenon, in which moisture is increased from the normal level, occurs more frequently towards the downstream side 94 the reaction gas passage 90 In this case, the upstream side refers 92 the reaction gas passage 90 to an area closer to the entrance of the reaction gas passage 90 and the downstream side94 the reaction gas passage 90 refers to an area closer to the exit of the reaction gas passage 90 .

[0067] To solve the problem, the coil springs 60 be arranged so that they reduce the porosity of the reaction gas passage 90 from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 Accordingly, the diffusivity of the air can be increased due to the lower porosity on the upstream side 92 the reaction gas passage 90 be reduced and can be achieved due to the higher porosity on the downstream side 94 the reaction gas passage 90 Accordingly, the coil springs can 60minimize the drying and flooding phenomena caused by the higher or lower flow rate of air.

[0068] The coil springs 60 can be arranged in different ways to increase the porosity of the reaction gas passage 90 from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 to increase as described above.

[0069] For example, as in Fig. 11, at least some of the coil springs 60 be arranged to adjust the overlap ratio between the coil springs from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 In other words, the coil springs can 60be arranged to adjust the arrangement distance between the coil springs 60 from the upstream side 92 the reaction gas passage 90 and from the downstream side 94 the reaction gas passage 90 to increase.

[0070] For example, as in Fig. 12, at least some of the coil springs 60 be arranged in such a way that a coil spring with a longer pitch P under at least some of the coil springs 60 from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 is positioned.

[0071] For example, as in Fig. 13, at least some of the coil springs 60 be arranged to ensure the overlap ratio between the coil springs 60from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 and arranged so that a coil spring with a longer pitch P under at least some of the coil springs 60 from the upstream side 92 towards the downstream side 94 is positioned.

[0072] For example, as in Fig. 14, at least some of the coil springs 60 be arranged so that they have gradients that run from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 are increased.

[0073] For example, at least some of the coil springs 60 be arranged so that a coil spring 60with a spring wire with a smaller diameter D1 under at least some of the coil springs 60 from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 is positioned.

[0074] For example, at least some of the coil springs 60 be arranged so that a coil spring 60 with a smaller diameter D2 under at least some of the coil springs 60 from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 is positioned.

[0075] Although the description regarding the coil springs 60 which are arranged to increase the porosity of the reaction gas passage 90from the upstream side 92 the reaction gas passage 90 towards the downstream side 94 the reaction gas passage 90 the present disclosure is not limited thereto. In other words, the coil springs 60 be arranged so that at least one of the diameter D1 of the spring wire, the pitch P of the coil springs 60 , the diameter D2 the coil springs 60 , and the overlap ratio of the coil springs 60 is varied to determine the porosity of the reaction gas passage 90 depending on the sections of the reaction gas passage 90 to vary.

[0076] For example, the coil springs 60 be arranged so that the porosity of the reaction gas passage 90decreases towards the area with higher current density. In other words, the coil springs 60 be arranged so that the ratio of the volume generated by the coil springs 60 in the entire volume of the reaction gas passage 90 increases towards the area with the higher current density. In this case, the contact surfaces between the coil springs 60 and the first gas diffusion layer 20 and the contact surfaces between the coil springs and the first separating plate 40 towards the area with the higher current density. Therefore, the coil springs reduce 60 the electrical resistance between the first gas diffusion layer 20 and the first partition plate 40 in the area having the higher current density, thereby minimizing the ohmic loss caused by the higher electrical resistance.

[0077] As described, the coil springs are 60 between the first gas diffusion layer 20 and the first partition plate 40 arranged, whereby the reaction gas passage 90 between the first gas diffusion layer 20 and the first partition plate 40 using the coil spring 60 is formed. In the unit cell 1 the ratio of the volume of the reaction gas passage 90 , which is provided by the coil spring in the entire area of ​​the reaction gas passage 90 is taken, whereby the porosity of the reaction gas passage 90 for the design purpose of the unit cell 1 is precisely adjusted and the electrical resistance between the first gas diffusion layer 20 and the first partition plate 40 is precisely adjusted according to the current density. Furthermore, in the case of the unit cell 1, if the gas diffusion layers 20 and 30 be permanently shrunk and deformed as long as time from the production of the unit cell 1 passes, the coil springs 60 which have been arranged so that they are elastically sandwiched between the first gas diffusion layer 20 and the first partition plate 40 by the coupling force acting on the unit cell 1 are elastically restored. Accordingly, in the case of the unit cell 1 , even if a long time has elapsed since the production of the unit cell 1 elapses, the permanent shrinkage deformation of the gas diffusion layers 20 and 30 due to the elastic restoring force of the coil spring 60 compensated, whereby the contact state between components in the unit cell 1is maintained stably.

[0078] Although the present disclosure has been described with reference to exemplary embodiments and the accompanying drawings, the present disclosure is not limited thereto, but may be variously modified and changed by those skilled in the art to which the present disclosure relates without departing from the spirit and scope of the present disclosure as claimed in the following claims.

[0079] Therefore, embodiments of the present disclosure are not intended to limit the technical scope of the present disclosure, but are provided for illustrative purposes only. The scope of the present disclosure should be interpreted by the appended claims, and all equivalents thereof should be construed as being included within the scope of the present disclosure. List of reference symbols 1: UNIT CELL 10: MEA 12: ELECTROLYTE MEMBRANE 14: CATHODE ELECTRODE 16: Anode Electrode 20: FIRST GAS DIFFUSION LAYER 30: SECOND GAS DIFFUSION LAYER 40: FIRST PARTITION PLATE 42: LOCKING PROJECTIONS 50: SECOND PARTITION PLATE 60: COIL SPRING 62: SPRING WIRE 70: Separator plate channel fluid passage 80: COOLANT PASSAGE 90: REACTION GAS PASSAGE 92: UPSTREAM SIDE 94: DOWNSTREAM OR DOWNSTREAM SIDE

Claims

[1] Unit cell for a fuel cell, the unit cell comprising: a membrane electrode assembly (MEA); a gas diffusion layer disposed on a surface of the MEA; a partition plate arranged to be spaced from the gas diffusion layer; and a coil spring disposed between the gas diffusion layer and the partition plate to elastically support the gas diffusion layer and the partition plate while electrically connecting the gas diffusion layer to the partition plate and providing a reaction gas passage for transferring reaction gas. [2] The unit cell according to claim 1, wherein the coil spring includes a plurality of coil springs. [3] The unit cell according to claim 1 or 2, wherein the coil spring is arranged such that an axial direction of the coil spring is perpendicular to a thickness direction of the MEA. [4] The unit cell according to any one of claims 1 to 3, wherein the coil spring is fixed to the partition plate. [5] The unit cell according to claim 4, wherein the coil spring is welded to the partition plate. [6] The unit cell according to claim 4, wherein the coil spring is bonded to the partition plate by an adhesive. [7] The unit cell according to claim 2, wherein the partition plate has a locking projection for locking one of the coil springs. [8] The unit cell according to claim 7, wherein each coil spring is locked to the locking projection such that a spring pitch of the coil spring is varied depending on portions of the reaction gas passage. [9] The unit cell according to claim 2, wherein the coil springs are provided such that at least one property of the coil springs is varied to vary the porosity of the reaction gas passage depending on portions of the reaction gas passage, the property being selected from the group consisting of: pitches of the coil springs, diameters of the coil springs, overlap ratio between the coil springs, and diameters of spring wires of the coil springs. [10] The unit cell according to claim 2, wherein the coil springs are arranged to increase the porosity of the reaction gas passage from an upstream side of the reaction gas passage toward a downstream side of the reaction gas passage. [11] The unit cell according to claim 10, wherein the coil springs are arranged such that the spring pitches of the coil springs are increased from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage. [12] The unit cell according to claim 10, wherein the coil springs are arranged such that a coil spring having a longer spring pitch is positioned among the coil springs from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage. [13] The unit cell according to claim 10, wherein the coil springs are arranged such that an overlap ratio between the coil springs is reduced from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage. [14] The unit cell according to claim 10, wherein the coil springs are arranged such that an arrangement distance between the coil springs is increased from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage. [15] The unit cell according to claim 10, wherein the coil springs are arranged such that a coil spring having a spring wire with a smaller diameter is positioned among the coil springs from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage. [16] The unit cell according to claim 10, wherein the coil springs are arranged such that a coil spring having a smaller diameter is positioned among the coil springs from the upstream side of the reaction gas passage toward the downstream side of the reaction gas passage. [17] The unit cell according to claim 2, wherein the coil springs are arranged such that an axial direction of each coil spring forms a specific angle with a flow direction of the reaction gas. [18] The unit cell according to claim 17, wherein at least some of the coil springs are arranged such that axial directions of the at least some of the coil springs are parallel to the flow direction of the reaction gas. [19] The unit cell according to claim 17, wherein at least some of the coil springs are arranged such that axial directions of the at least some of the coil springs are perpendicular to the flow direction of the reaction gas. [20] The unit cell according to claim 2, wherein the coil springs are arranged to reduce the porosity of the reaction gas passage toward a region of higher current density.

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