Fuel cell with elastic member

Abstract

A fuel cell having an elastic member is provided. The fuel cell includes: a cell stack having a plurality of unit cells stacked in a first direction; and an end plate provided on each of opposite side ends of the cell stack. The elastic member is provided in a portion of the end plate in a manner overlapping a lower region of the cell stack where condensed water remains in the first direction.

Description

Technical Field

[0001] The present invention relates to a fuel cell, and more particularly, to a fuel cell that prevents damage to a gas diffusion layer and a separator plate by using an elastic member. Background Art

[0002] Generally, as a byproduct of power generation using hydrogen and oxygen in a fuel cell, water (hereinafter referred to as generated water or condensed water) may be generated in each of a plurality of unit cells and remain therein. In particular, a vehicle including a fuel cell may be exposed to various external environmental factors. When the vehicle is exposed to low temperatures for a long time, the generated water remaining in each unit cell may freeze, and the expansion of the frozen generated water may increase the contact pressure of a specific area within the unit cell. Therefore, irreversible plastic deformation may occur in the gas diffusion layer and the separator in the constituent elements inside the unit cell, which may deteriorate the performance and durability of the battery stack composed of the unit cells. Summary of the invention

[0003] Therefore, the exemplary embodiments are directed to a fuel cell that substantially eliminates one or more problems caused by the limitations and disadvantages of the prior art. The exemplary embodiments provide a fuel cell with excellent performance and durability. Other advantages, objects, and features of the present disclosure will be set forth in part in the following description, and in part will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present disclosure. The objects and other advantages of the present disclosure can be realized and obtained by the structures particularly pointed out in the written description and claims thereof and the accompanying drawings.

[0004] According to an exemplary embodiment, a fuel cell may include: a cell stack having a plurality of unit cells stacked along a first direction; an end plate disposed on each of opposite side ends of the cell stack; and an elastic member overlapping a lower region of residual condensed water of the cell stack in the first direction, at least a portion of the elastic member being disposed in the end plate.

[0005] For example, the end plate may include: a main body formed with a recess; and a collector plate disposed between the battery stack and an inner side surface of the main body facing the battery stack, the elastic member being separated from the collector plate and disposed in the recess. The main body may include: a first region, in which the recess provided with the elastic member is located; and a second region where the elastic member is not provided, the second region being located above the first region.

[0006] In addition, in the gravity direction, a first length of the first area is equal to or less than a second length of the second area. The first length may correspond to a length from a bottom surface of the body to a first point at one third of the total height of the body, and wherein the second length may correspond to a length from the first point to a top surface of the body.

[0007] In addition, the elastic member may include a plurality of springs stacked in the direction of gravity and spaced apart from each other. The elastic force of the plurality of springs may enable the first region and the second region to have the same initial pressure in an initial state where the condensed water does not expand. The elastic force of each spring decreases as the distance from the bottom surface of the main body increases. The elastic force per unit length of all springs is the same, and the length of each spring may decrease as the distance from the bottom surface of the main body increases.

[0008] The elastic member may have a repulsive force equal to the pressure applied to the inner side of the body due to the expansion force of the condensed water. In particular, the repulsive force of the elastic member is in the range of about 0.8 MPa to 1.2 MPa. In addition, the elastic member has an elastic modulus such that the repulsive force is less than about 1.5 MPa when the displacement of the inner side due to the expansion force is about 1 mm.

[0009] Each unit cell may include: a membrane electrode assembly including a fuel electrode, an air electrode, and a polymer electrolyte membrane disposed between the fuel electrode and the air electrode; a gas diffusion layer disposed on both sides of the membrane electrode assembly; and a separator plate disposed on the outside of the gas diffusion layer. Each of the end plate and the separator plate may include an inlet communication portion for introducing a reaction gas and an outlet communication portion for discharging a reaction gas and condensed water, the outlet communication portion being located below the inlet communication portion, the inlet communication portions of the end plate and the separator plate may be communicated with each other, and the outlet communication portions of the end plate and the separator plate may be communicated with each other.

[0010] The fuel cell may further include: a stopper disposed between the collector plate and the elastic member. Each unit cell may further include a gasket disposed between the separator plate and the gas diffusion layer, and wherein the stopper may be disposed to overlap with the gasket in the first direction. In addition, a first length of the first region in the gravity direction corresponds to a length from a bottom surface of the separator plate to a first point at one third of a total height of the separator plate, and a second length of the second region in the gravity direction corresponds to a length from the first point to a top surface of the separator plate.

[0011] The elastic member may include: a first elastic member disposed in an end plate disposed on a first side end of the opposite side ends of the battery stack; and a second elastic member disposed in an end plate disposed on a second side end of the opposite side ends of the battery stack. The elastic force of the first elastic member is different from the elastic force of the second elastic member.

[0012] The reaction gas may be introduced or exhausted through a first side end of the opposite side ends of the battery stack, and the elastic force of the first elastic member may be greater than the elastic force of the second elastic member. The first elastic member and the second elastic member may have a cross-sectional shape that is symmetrical about the center of the battery stack in the first direction.

[0013] It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are exemplary and explanatory and are intended to provide further explanation of the disclosure as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this application. The accompanying drawings illustrate exemplary embodiments of the present disclosure and together with the description are used to explain the principles of the present invention. In the drawings:

[0015] Figure 1 is a perspective view showing the appearance of a fuel cell according to an exemplary embodiment of the present disclosure;

[0016] Figure 2 is a diagram showing an exemplary embodiment of the present disclosure Figure 1 A perspective view of another exemplary embodiment of a first end plate shown in;

[0017] Figure 3 is a cross-sectional view showing an end plate and a cell stack of a fuel cell according to an exemplary embodiment of the present disclosure;

[0018] Figure 4 is a diagram showing an exemplary embodiment of the present disclosure Figure 1 and Figure 3 A partial cross-sectional view of an exemplary embodiment of a fuel cell shown in FIG.

[0019] Figure 5 is a diagram showing an exemplary embodiment according to the present disclosure Figure 4 A cross-sectional view of an exemplary embodiment of a resilient member is shown;

[0020] Figure 6 It is used to illustrate the exemplary embodiment of the present disclosure. Figure 4 A cross-sectional view of another embodiment of the elastic member shown;

[0021] Figure 7is a diagram showing an exemplary embodiment according to the present disclosure Figure 4 A cross-sectional view of another embodiment of the elastic member shown;

[0022] Figure 8 is a graph showing the amount of condensed water of each unit cell according to an exemplary embodiment of the present disclosure; and

[0023] Fig.9A and Fig. 9B is a graph showing profiles of contact pressure on reaction surfaces of unit cells according to comparative examples and exemplary embodiments under various conditions. DETAILED DESCRIPTION

[0024] It should be understood that the term "vehicle" or "vehicle-related" or other similar terms used herein include general motor vehicles, such as passenger cars (including sports utility vehicles (SUVs)), buses, trucks, various commercial vehicles, watercraft (including various boats and ships), aircraft, etc., and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels obtained from resources other than petroleum). As mentioned herein, a hybrid vehicle is a vehicle having two or more power sources, for example, a vehicle that has both gasoline power and electric power.

[0025] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "one", "one / a kind of" and "the / said" are intended to also include plural forms, unless the context clearly indicates otherwise. It should also be understood that when used in this specification, the terms "include" and / or "comprise" indicate the presence of the described features, integers, steps, operations, elements and / or parts, but do not exclude the presence or increase of one or more other features, integers, steps, operations, elements, parts and / or their groups. As used herein, the term "and / or" includes any combination of one or more of the listed related items and all combinations.

[0026] Unless specifically stated or apparent from the context, as used herein, the term "about" is understood to be within the normal tolerance range in the art, e.g., within 2 standard deviations of the mean. "About" may be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the recited value. Unless clearly apparent from the context, all numerical values ​​provided herein are modified by the term "about."

[0027] Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings, so as to specifically describe the present disclosure and help understand the present disclosure. However, the exemplary embodiments disclosed herein can be changed into various other forms, and the scope of the present disclosure should not be interpreted as being limited to the exemplary embodiments. The exemplary embodiments disclosed herein are provided in order to more completely describe the present disclosure to those skilled in the art.

[0028] It should be understood that when an element is referred to as being formed "on" or "under" another element, it may be directly "on" or "under" the other element, or be formed indirectly with intervening elements therebetween. In addition, when expressed as "on (above)" or "under (below)", this includes not only the meaning of the upward direction based on the given element, but also the meaning of the downward direction.

[0029] In addition, relative terms used in the following description (e.g., "first", "second", "upper / upper part / above" and "lower / lower / below") may be used to distinguish any one substance or element from another substance or element without requiring or implying any physical or logical relationship or order between these substances or elements.

[0030] Hereinafter, a fuel cell 100 or 100A according to an exemplary embodiment will be described with reference to the accompanying drawings. For ease of description, a Cartesian coordinate system (x, y, z) will be used to describe the fuel cell 100 or 100A, but any other coordinate system may be used for description. In addition, in the Cartesian coordinate system, the x-axis, the y-axis, and the z-axis are orthogonal to each other, but the embodiment is not limited thereto. In other words, the x-axis, the y-axis, and the z-axis may obliquely cross each other.

[0031] Figure 1 1 is a perspective view showing the appearance of a fuel cell 100 according to an exemplary embodiment. The fuel cell 100 may be a polymer electrolyte membrane fuel cell (or proton exchange membrane fuel cell) (PEMFC) which is much studied as a power supply source for vehicle driving, but the exemplary embodiment is not limited to a specific form of the fuel cell 100.

[0032] The fuel cell 100 may include end plates (or pressurized plates or compression plates) 110A-1 and 110B and a battery stack 122. The battery stack 122 may include a plurality of unit cells stacked along a first direction (e.g., an x-axis direction). The end plates 110A-1 and 110B may be respectively disposed on opposite side ends of the battery stack 122, and may support and fix the unit cells. In other words, the first end plate 110A-1 may be disposed on a first side end of the opposite side ends of the battery stack 122, and the second end plate 110B may be disposed on a second side end of the opposite side ends of the battery stack 122.

[0033] In addition, the fuel cell 100 may further include a fastening member 130. The fastening member 130 may fasten the end plates 110A-1 and 110B and the unit cells together in a first direction (eg, an x-axis direction). Figure 1 As shown, the fastening member 130 may be formed as a rod, but the exemplary embodiment is not limited thereto. In other words, according to another exemplary embodiment, the fastening member 130 may be formed as an elongated bolt, a band, or a rigid rope to fasten the unit battery.

[0034] Now, an example of combining the fastening member 130 with the fuel cell 100 will be described. After the end plates 110A-1 and 110B are respectively provided at opposite side ends of the battery stack 122 in which the unit cells are repeatedly stacked, the structure can be loaded into the fastening device. Then, the battery stack 122 can be fastened to the end plates 110A-1 and 110B using the fastening member 130 in a state where an appropriate load is applied thereto. Therefore, the fastening pressure of the battery stack 122 can be maintained by the rigid end plates 110A-1 and 110B.

[0035] Figure 2 It is shown Figure 1 A perspective view of another exemplary embodiment 110A-2 of the first end plate 110A-1 is shown in FIG. Figure 1 The first end plate 110A-1 shown in FIG. 1 may include a plurality of inlets and outlets 160. Figure 1 As shown, the first end plate 110A-1 may include four inlet and outlet ports 160, and as shown in FIG. Figure 2 As shown, the first end plate 110A- 2 may include six inlet and outlet ports 160 , but the exemplary embodiment is not limited thereto.

[0036] in addition, Figure 1 The first end plate 110A-1 shown in FIG. Figure 2 In other words, the exemplary embodiments are not limited to a particular form of the first end plate 110A-1 or 110A-2 and the second end plate 110B. The inlet and outlet 160 will be described in more detail below.

[0037] Figure 3 1 is a cross-sectional view showing the end plates 110A and 110B of the fuel cell 100 and the cell stack 122. For ease of description, Figure 1 The fastening member 130 shown in FIG. Figure 3 Omitted. Figure 3 The end plate 110A shown in FIG. 1 may correspond to Figure 1 or Figure 2 The end plate 110A-1 or 110-2 shown in FIG. Figure 3 The battery stack 122 shown in FIG. 1 may correspond to Figure 1An exemplary embodiment of a battery stack 122 is shown in FIG. The same components will be denoted by the same reference numerals, and repeated descriptions related to the same components will be omitted.

[0038] Reference Figure 3 , the battery stack 122 may include a plurality of unit cells 122-1 to 122-N stacked along a first direction (e.g., the x-axis direction). In particular, "N" is a positive integer equal to or greater than 1, and may be in the range of tens to hundreds. For example, "N" may be in the range of about 100 to 300, more specifically, 220, but the exemplary embodiment is not limited to the specific value of "N". Each unit cell 122-n may generate power in the range of about 0.6V to 1.0V, and an average of about 0.7V. It is worth noting that 1≤n≤N. Therefore, "N" may be determined according to the power intensity supplied from the fuel cell 100 to the load. The term "load" may refer to a part of a vehicle that requires power. Each unit cell 122-n may include a membrane electrode assembly (MEA) 210, a gas diffusion layer (GDL) 222 and 224, gaskets 232 and 234, and separators (or bipolar plates or separators) 242 and 244.

[0039] The membrane electrode assembly 210 may include a catalyst electrode layer where an electrochemical reaction occurs, and the catalyst electrode layer may be attached to opposite sides of an electrolyte membrane that allows hydrogen ions to move, with the electrolyte membrane interposed therebetween. Specifically, the membrane electrode assembly 210 may include a polymer electrolyte membrane (or proton exchange membrane) 212, a fuel electrode (or hydrogen electrode or anode) 214, and an air electrode (or oxygen electrode or cathode) 216.

[0040] The polymer electrolyte membrane 212 may be provided between the fuel electrode 214 and the air electrode 216. In the fuel cell 100, hydrogen as a fuel may be supplied to the fuel electrode 214 through the first separator 242, and air containing oxygen as an oxidant may be supplied to the air electrode 216 through the second separator 244.

[0041] The hydrogen supplied to the fuel electrode 214 can be decomposed into hydrogen ions (H+) (protons) and electrons (e-) by a catalyst. Among them, only hydrogen ions can be selectively passed through the polymer electrolyte membrane 212 and transmitted to the air electrode 216, and electrons can be transmitted to the air electrode 216 by separators 242 and 244 as conductors. For the above operation, a catalyst layer can be applied to each of the fuel electrode 214 and the air electrode 216. Therefore, due to the movement of electrons, an electron flow through an external wire occurs, thereby generating an electric current. In other words, the fuel cell 100 can be configured to generate electricity by an electrochemical reaction between hydrogen as a fuel and oxygen contained in the air.

[0042] The air electrode 216 causes a reaction in which hydrogen ions supplied through the polymer electrolyte membrane 212 and electrons transferred through the separators 242 and 244 meet oxygen in the air supplied to the air electrode 216 to generate water (hereinafter referred to as "condensed water" or "generated water"). Therefore, the condensed water generated in the air electrode 216 can permeate the polymer electrolyte membrane 212 and be transferred to the fuel electrode 214. In some cases, the fuel electrode 214 can be referred to as an anode and the air electrode 216 can be referred to as a cathode, or conversely, the fuel electrode 214 can be referred to as a cathode and the air electrode 216 can be referred to as an anode.

[0043] The gas diffusion layers 222 and 224 may uniformly distribute hydrogen and oxygen as reaction gases and may transfer the generated electricity. Therefore, the gas diffusion layers 222 and 224 may be disposed on opposite sides of the membrane electrode assembly 210, respectively. In other words, the first gas diffusion layer 222 may be disposed on the left side of the fuel electrode 214, and the second gas diffusion layer 224 may be disposed on the right side of the air electrode 216.

[0044] The first gas diffusion layer 222 may diffuse and uniformly distribute hydrogen as a reaction gas supplied through the first separator plate 242, and may be conductive. The second gas diffusion layer 224 may diffuse and uniformly distribute air as a reaction gas supplied through the second separator plate 244, and may be conductive. Each of the first gas diffusion layer 222 and the second gas diffusion layer 224 may be a microporous layer obtained by combining micro carbon fibers, but the exemplary embodiment is not limited to specific forms of the first gas diffusion layer 222 and the second gas diffusion layer 224.

[0045] The gaskets 232 and 234 can maintain air tightness of the reaction gas, water tightness of the cooling water, and appropriate tightening pressure to disperse stress when stacking the partition plates 242 and 244, and independently seal the flow path. By maintaining air tightness / water tightness through the gaskets 232 and 234, the flatness of the surface adjacent to the battery stack 122 that generates electricity can be managed, and thus, uniform contact pressure distribution can be achieved on the reaction surface of the battery stack 122.

[0046] The separators 242 and 244 may move the reaction gas and the cooling medium, and may also separate the unit cells from each other. In addition, the separators 242 and 244 may structurally support the membrane electrode assembly 210 and the gas diffusion layers 222 and 224. The separators 242 and 244 may also collect the generated current and transfer the current to the collector plate 112. In particular, the separators 242 and 244 may be disposed on the outside of each gas diffusion layer 222 and 224. In other words, the first separator 242 may be disposed on the left side of the first gas diffusion layer 222, and the second separator 244 may be disposed on the right side of the second gas diffusion layer 224.

[0047] The first separator plate 242 may supply hydrogen as a reaction gas to the fuel electrode 214 through the first gas diffusion layer 222. Therefore, the first separator plate 242 may include an anode plate (AP) formed with a channel (i.e., a flow channel or a flow path) through which hydrogen may flow. The second separator plate 244 may supply air as a reaction gas to the air electrode 216 through the second gas diffusion layer 224. Therefore, the second separator plate 244 may include a cathode plate (CP) formed with a channel through which air may flow.

[0048] In addition, each of the first partition plate 242 and the second partition plate 244 may be formed with a channel through which a cooling medium (e.g., cooling water) may flow. The partition plates 242 and 244 may be formed of a graphite-based, composite graphite-based, or metal-based material, but the exemplary embodiment is not limited to a specific material of the partition plates 242 and 244. Figure 3 The first end plate 100A shown in FIG. Figure 1 or Figure 2 When implemented as shown, each of the first partition plate 242 and the second partition plate 244 may include a Figure 1 or Figure 2 The inlets and outlets 160 shown in FIG. 1 are located at the same position and are formed in the same form.

[0049] Hydrogen and oxygen as the reaction gases required in the membrane electrode assembly 210 can be introduced into the cell stack 122 through the inlet. The gas or liquid to which the supplied humid reaction gas and the condensed water generated in the cell are added can be discharged to the outside of the fuel cell 100 through the outlet. The condensed water can be discharged from the lower part of the unit cells 122-1 to 122-N, or may remain in the lower part under the influence of gravity. In addition, the cooling medium can be introduced into the cell stack 122 from the outside through the inlet, and then can be discharged to the outside through the outlet.

[0050] Each of the first end plate 110A and the second end plate 110B may include a main body 111 and a collector plate 112. The main body 111 may be formed in such a way that the metal plug-in is surrounded by a plastic injection molded product. The metal plug-in of the main body 111 may be highly rigid to overcome the internal contact pressure of the metal plug-in, and may be achieved by machining a metal material. For example, the main body 111 may be formed by combining a plurality of plates, but the exemplary embodiment is not limited to a specific configuration of the main body 111. The collector plate 112 may be disposed between the battery stack 122 and an inner side 111A of the main body 111 facing the battery stack 122. The collector plate 112 may collect the electricity generated by the electron flow in the battery stack 122 and provide the electricity to a vehicle load using the fuel cell 100.

[0051] As described above, as a byproduct of power generation using oxygen and hydrogen in the fuel cell 100, condensed water may remain in each unit cell 122-1 to 122-N. In particular, when a vehicle including the fuel cell 100 is exposed to low temperatures for a long time, the condensed water remaining in each unit cell 122-n of the battery stack 122 may freeze, and the expansion of the frozen condensed water may increase the contact pressure in a specific area within the unit cells 122-1 to 122-N. Therefore, irreversible plastic deformation may occur in the gas diffusion layers 222 and 224 and the separators 242 and 244 of the unit cells 122-n, which may deteriorate the performance and durability of the battery stack 122. Therefore, in order to offset such a local increase in contact pressure, the fuel cell 100 according to an exemplary embodiment may include an elastic member.

[0052] Hereinafter, the configuration and operation of an exemplary embodiment 100A of a fuel cell 100 including an elastic member according to exemplary embodiments will be described with reference to the accompanying drawings.

[0053] Figure 4 It is shown Figure 1 and Figure 3 FIG. 1 is a partial cross-sectional view of an exemplary embodiment 100A of a fuel cell 100 shown in FIG. In particular, “IN” may indicate that a reactant gas or a cooling medium passes through the fuel cell 100A. Figure 1 or Figure 2 The direction of the inlet 160 shown in FIG. 1 , “OUT” may represent the direction in which the reaction gas or the cooling medium is introduced. Figure 1 or Figure 2 The direction of discharge from the outflow port 160 is shown.

[0054] For ease of description, Figure 1 The fastening member 130 shown in FIG. Figure 4 This is omitted in the fuel cell 100A shown. Figure 4, only the first end plate 110A and the first to third unit cells 122-1 to 122-3 located near the first end plate 110A are shown. However, the second end plate 110B and the Nth to N-2th unit cells 122-N, 122-(N-1), and 122-(N-2) located near the second end plate 110B may have the same Figure 4 The first end plate 110A and the first to third unit cells 122 - 1 to 122 - 3 are shown to have the same cross-sectional shape.

[0055] For example, in Figure 4 In the embodiment, the battery stack 122 may have a cross-sectional shape that is symmetrical about the N / 2th battery cell (122-(N / 2)) in a first direction (e.g., the x-axis direction). In addition, the elastic member (hereinafter referred to as the "first elastic member") 140 provided in the first end plate 110A and the elastic member (hereinafter referred to as the "second elastic member") (not shown) provided in the second end plate 110B may have a cross-sectional shape that is symmetrical about the center of the battery stack 122 in a first direction (e.g., the x-axis direction).

[0056] However, the exemplary embodiment is not limited thereto. According to another exemplary embodiment, Figure 4 In the embodiment, the battery stack 122 may have a cross-sectional shape that is asymmetric about the N / 2th battery cell (122-(N / 2)) in a first direction (e.g., the x-axis direction). In addition, the first elastic member and the second elastic member may have a cross-sectional shape that is asymmetric about the center of the battery stack 122 in the first direction (e.g., the x-axis direction).

[0057] Figure 4 The fuel cell 100A shown in FIG. 1 may include a first end plate 110A, first to third unit cells 122-1, 122-2, and 122-3, and an elastic member 140. The first end plate 110A and the first to third unit cells 122-1, 122-2, and 122-3 correspond to Figure 3 The first end plate 110A and the first to third unit cells 122 - 1 , 122 - 2 , and 122 - 3 are illustrated and perform the same functions therewith, and thus are denoted by the same reference numerals, and repeated descriptions thereof will be omitted.

[0058] exist Figure 4 In the embodiment, the first partition plate 242 may include a reaction channel (or a reaction flow path). In other words, the first partition plate 242 (242-1, 242-2, and 242-3) may include a channel P1 through which hydrogen as a reaction gas may flow. The cooling medium may flow through a groove P2 opposite to the channel P1.

[0059] In addition, the second separator 244 may be a microporous structure (e.g., 244-1, 244-2, 244-3), but the exemplary embodiment is not limited thereto. In other words, instead of being formed into a microporous structure, the second separator 244 may have a reaction channel, similar to the first separator 242. Alternatively, instead of including a reaction channel, the first separator 242 may be formed into a microporous structure.

[0060] Reference Figure 4 , the microporous structure can uniformly compress the second gas diffusion layer 224 (e.g., 224-1, 224-2, 224-3) to uniformly distribute the contact pressure, and can improve the local diffusion of the reaction gas and the discharge of the generated water through the micropores. The microporous structure such as metal foam or metal wire mesh can have a high aperture ratio, and can also have a contact pressure distribution function of uniformly compressing the second gas diffusion layer 224. Metal foam has a structure in which a large number of bubbles are connected to each other in a metal material, provides a fluid passage, and has high rigidity and a high surface area ratio per unit volume, so it can be suitable as a separator material. For example, the microporous structure can be made of any one material selected from silver, copper, gold, aluminum, tungsten, zinc and a metal alloy, which has excellent electrical conductivity.

[0061] In addition, the fuel cell 100A may further include a dummy cell 122-0. In particular, the dummy cell 122-0 is a cell that does not perform a chemical reaction and is stacked for drainage. Figure 4 As shown in , the dummy cell 122-0 may be disposed between the first end plate 110A and the first unit cell 122-1. The dummy cell 122-0 may include at least one of a cathode plate CP, an anode plate AP, an end anode plate (EAP), or an end cathode plate (ECP). For example, the dummy cell 122-0 may include a plate 244-0, and the plate 244-0 may be a CP or an ECP. In particular, the EAP refers to a plate obtained by removing a hydrogen inlet and an outlet from a general AP, and the ECP refers to a plate obtained by removing an air inlet and an outlet from a general CP.

[0062] For example, in Figure 4 In the embodiment, the dummy unit 122-0 is shown as including the micro-hole structure 244-0, but the exemplary embodiment is not limited thereto. In some cases, the dummy unit 122-0 may be omitted. Figure 3 and 4 The elastic member 140 may be disposed to overlap a lower region of the battery stack 122 where condensed water W may remain in a first direction (eg, x-axis direction). The elastic member 140 may be disposed in a portion of at least one of the first end plate 110A and the second end plate 110B.

[0063] For example, the elastic member 140 may be disposed in a first recess H1 formed in the body 111 of each of the first end plate 110A and the second end plate 110B, as shown in FIG. Figure 3 The interior of the first recess H1 where the elastic member 140 is disposed may be filled with air, may be a vacuum, or may be filled with an insulating material, such as plastic.

[0064] The body 111 of at least one of the first end plate 110A and the second end plate 110B may include a first area A1 and a second area A2. In particular, the first area A1 is an area of ​​the body 111 where the elastic member 140 is disposed, and may be located at the lower portion of the body 111 in the direction of gravity (e.g., the z-axis direction). The second area A2 may be located at the upper portion of the body 111, that is, above the first area A1 in the direction of gravity, and the elastic member 140 may not be disposed in the second area A2. Figure 4 As shown in FIG. 1 , the first area A1 may be an area from the bottom surface 111B of the body 111 to the top surface of the first recess H1 and may be Figure 4 Different from the illustration, the first area A1 may be an area from the bottom surface 111B of the body 111 to the top surface of the elastic member 140 .

[0065] The first length of the first area A1 in the gravity direction (e.g., z-axis direction) may be smaller than the second length of the second area A2. In particular, the first length may correspond to the length from the bottom surface 240B of the partition plate 242 or 244 to the first point z1 at one third of the total height L of the partition plate 242 or 244. The second length may correspond to the length from the first point z1 to the top surface 240T of the partition plate 242 or 244.

[0066] Alternatively, the first length may correspond to a length from the bottom surface 111B of the body 111 of the first end plate 110A to a first point z1 that is one third of the total height L of the body 111 of the end plate 110A. The second length may correspond to a length from the first point z1 to the top surface 111T of the body 111. In other words, see Figure 4 , the first area A1 may be an area from z=0 to z=z1, and the second area A2 may be an area from z=z1 to z=L.

[0067] like Figure 4 As shown in FIG. 1 , condensed water W generated by the reaction of the reaction gas may remain in the lower regions of the first to third unit cells 122 - 1 to 122 - 3 . Figure 4As shown in , condensed water W may also remain in the lower region of the fourth to Nth unit cells 122-4 to 122-N. The elastic member 140 (or the first recess H1) may be separated from the collector plate 112 by a first distance g1. In addition, the elastic member 140 (or the first recess H1) may be separated from the bottom surface 111B of the main body 111 by a second distance g2. The elastic member 140 may be separated from the periphery 111A or 111B because the elastic member 140 may protrude from the main body 111 when there is no first gap g1 or second gap g2 (ie, g1=0 or g2=0). When there is no first gap g1 (ie, g1=0), the elastic member 140 may protrude from the main body 111, thereby causing damage to the unit cells 122-n of the battery stack 122.

[0068] As described above, the reason why the elastic member 140 is arranged to overlap with the lower region of the battery stack 122 where the condensed water W may remain in the first direction (e.g., the x-axis direction) is that when the condensed water W is frozen due to the low temperature around the fuel cell 100 or 100A, the elastic member 140 absorbs and offsets the expansion force of the condensed water W from the battery stack 122 toward the first end plate 110A, as shown in FIG. Figure 4 When the expansion force is offset by the elastic member 140, the contact pressure of the reaction surface can be maintained at a constant value instead of being locally increased due to the expansion of the condensed water W remaining in the lower region of the battery stack 122, thereby preventing damage to the partition plates 242 and 244 and the gas diffusion layers 222 and 224.

[0069] In order to counteract the expansion force, the elastic member 140 may have the following various characteristics. First, the elastic member 140 may have a repulsive force that is the same as the pressure applied to the inner side 111A of the body 111 due to the expansion of the condensed water W remaining in the battery stack 122. For example, the repulsive force of the elastic member 140 may range from about 0.8 MPa to 1.2 MPa, but exemplary embodiments are not limited thereto.

[0070] In addition, the elastic modulus of the elastic member 140 can be determined so that when the displacement of the inner side 111A due to the expansion force is about 1 mm, the repulsive force is less than about 1.5 MPa. The elastic force of the elastic member 140 disposed on the first end plate 110A can be greater than the elastic force of the elastic member 140 disposed on the second end plate 110B. The reason is as follows.

[0071] As will be referenced below Figure 8As described above, the amount of condensed water that may remain in the first unit cell 122-1 is greater than the amount of condensed water that may remain in the Nth unit cell 122-N. The greater the amount of condensed water, the greater the expansion force caused by freezing. Therefore, the first expansion force applied to the first end plate 110A from the unit cell disposed near the first end plate 110A is greater than the second expansion force applied to the second end plate 110B from the unit cell disposed near the second end plate 110B. Therefore, in order to offset the first expansion force that is greater than the second expansion force, the elastic force of the elastic member 140 disposed in the first end plate 110A needs to be greater than the elastic force of the elastic member 140 disposed in the second end plate 110B.

[0072] In the following, reference will be made to Figures 5 to 7 Various exemplary embodiments of the elastic member 140 are described. Figure 5 It is shown Figure 4 A cross-sectional view of an exemplary embodiment 140A of the elastic member 140 is shown in FIG. Figure 6 It is shown Figure 4 A cross-sectional view of another exemplary embodiment 140B of the elastic member 140 is shown in FIG. Figure 7 It is shown Figure 4 A cross-sectional view of another exemplary embodiment 140C of the elastic member 140 is shown in FIG.

[0073] In such Figures 5 to 7 In each of the above, the battery stack 122 may be as follows: Figure 4 The illustrated implementation, however, is not limited to a particular cross-sectional shape for the battery stack 122. Figure 5 and Figure 6 In FIG. 1 , the graph shows the contact pressure at each position in the direction of gravity (eg, the z-axis direction). Figures 5 to 7 In each of the figures, each of the elastic members 140A, 140B and 140C may include a plurality of springs SP1, SP2, SP3, SP4 and SP5, which are stacked in the gravity direction (e.g., z-axis direction) and spaced apart from each other in the body 111 of the first end plate 110A.

[0074] The following factors can be considered to determine Figures 5 to 7 The elastic force, quantity and position of each of the springs SP1, SP2, SP3, SP4 and SP5 included in each elastic member 140A, 140B and 140C shown. First, the elastic force, quantity and position of the springs SP1, SP2, SP3, SP4 and SP5 can be determined so that the first area A1 and the second area A2 of the side 111A of the body 111 have the same initial pressure in the initial state where the condensed water W does not expand.

[0075] In addition, since the elastic member 140A, 140B or 140C can be provided only in the first area A1, the elastic force, quantity and position of the springs SP1, SP2, SP3, SP4 and SP5 can be determined, for example, to prevent the change in contact pressure at the boundary of the first area A1 and the second area A2. Hereinafter, examples of the elastic force, quantity and position of the springs SP1, SP2, SP3, SP4 and SP5 can be determined.

[0076] exist Figures 5 to 7 In FIG. 1 , the number of springs included in each of the elastic members 140A, 140B, and 140C is shown as five, but this is given only as an example, and the exemplary embodiment is not limited to a specific number of springs included in each of the elastic members 140A, 140B, and 140C. Figures 5 to 7 , the first area A1 where the elastic member 140A, 140B or 140C is provided is an area from the bottom surface 111B of the body 111 (ie, z=0) to the first point (z=z1), because in each unit cell 122-n, condensed water may remain from z=0 to the first point (z=1).

[0077] In addition, the elastic force of the springs SP1, SP2, SP3, SP4, and SP5 may decrease as the distance from the bottom surface 111B of the body 111 increases. In other words, among the springs SP1, SP2, SP3, SP4, and SP5, the first spring SP1 closest to the bottom surface 111B may have the largest elastic force, and the fifth spring SP5 farthest from the bottom surface 111B may have the smallest elastic force. In particular, the elastic forces of the first spring SP1 to the fifth spring SP5 may be expressed by the following formula 1.

[0078] Formula 1

[0079] F5 <F4<F3<F2<F1

[0080] Among them, F1, F2, F3, F4 and F5 represent the elastic forces of the first spring SP1, the second spring SP2, the third spring SP3, the fourth spring SP4 and the fifth spring SP5 respectively.

[0081] As described above, the reason why the elastic force of springs SP1, SP2, SP3, SP4 and SP5 increases as the distance from the bottom surface 111B decreases is that, in each unit cell 122-n included in the battery stack 122, the closer to the bottom of the unit cell 122-n, the more condensed water W may remain.

[0082] In addition, it is assumed that all springs SP1, SP2, SP3, SP4 and SP5 have the same elastic force per unit length, such as Figure 6As shown, the springs SP1, SP2, SP3, SP4, and SP5 may be shorter as the distance from the bottom surface 111B in the gravity direction (e.g., in the x-axis direction) increases. When the springs SP1, SP2, SP3, SP4, and SP5 have the same elastic force per unit length and have the same length, as shown in FIG. Figure 5 As shown, the change in the contact pressure K1 may occur locally at a boundary point (z=z1) between the first area A1 and the second area A2.

[0083] However, if Figure 6 As shown, when the springs SP1, SP2, SP3, SP4 and SP5 have the same elastic force per unit length and become shorter as the distance from the bottom surface 111B increases, no change in the contact pressure K2 is detected at the boundary point (z=z1) between the first area A1 and the second area A2.

[0084] In addition, if Figure 7 As shown, the fuel cell 100A may further include a stopper 150 disposed between the collector plate 112 and the elastic member 140A. Therefore, the body 111 may further have a second recess H2 disposed between the first recess H1 and the collector plate 112 and accommodating the stopper 150 therein. When the fastening force of the fuel cell 100 or 100A deteriorates later, the stopper 150 may prevent the elastic member 140C from protruding from the body 111 to the collector plate 112. In addition, the stopper 150 may be disposed to overlap with the gaskets 232 and 234 in a first direction (e.g., in the x-axis direction), but exemplary embodiments are not limited to a specific position of the stopper 150.

[0085] Hereinafter, a fuel cell according to a comparative example and a fuel cell according to an embodiment are compared with each other and described. It can be assumed that the fuel cell according to the comparative example has the same configuration as the fuel cell according to the exemplary embodiment except that the elastic member 140: 140A, 140B, or 140C is not included. In each of the fuel cells according to the comparative example and the exemplary embodiment, as a byproduct of power generation using hydrogen and oxygen, condensed water may be generated in each of the unit cells 122-1 to 122-N as described above.

[0086] Figure 8 is a graph showing the amount of condensed water W of each unit cell 122-n, wherein the horizontal axis represents the position of the unit cell and the vertical axis represents the amount of condensed water. Figure 8As shown in , in the unit cells closer to each of the first end plate 110A and the second end plate 110B, a larger amount of condensed water W remains, rather than being removed from the lower end of the unit cells. In other words, the amount of condensed water W remaining in the first unit cell closest to the first end plate 110A (at the point where x is 1) and the amount of condensed water W remaining in the Nth unit cell closest to the second end plate 110B (at the point where x is N) are greater than the amount of condensed water remaining in the other unit cells.

[0087] Fig.9A and Fig. 9B Graphs showing the distribution of contact pressure on the reaction surface of the unit cell 122-n according to the comparative example and the exemplary embodiment under various conditions, respectively. In each graph, the vertical axis represents the position in the gravity direction in each unit cell 122-n, and the horizontal axis represents the contact pressure. When the vehicle including the fuel cell 100 is exposed to low temperature for a long time, the condensed water W remaining in each unit cell 122-n of the battery stack 122 freezes, and therefore, the contact pressure in a specific area of ​​the unit cell may increase due to the expansion force of the condensed water.

[0088] In accordance with Fig.9A The comparison examples shown in Fig. 9B In the fuel cell of the exemplary embodiment shown, the contact pressure CP1 at the initial time (hereinafter referred to as "t1") when the cell stack 122 is tightened may be approximately 1 MPa, and the contact pressure CP2 at the operating time (hereinafter referred to as "t2") when the cell stack 122 operates may become greater than the initial contact pressure CP1. The contact pressure CP3 at the time (hereinafter referred to as "t3") after the durability of the cell stack 122 in each fuel cell increases may be reduced to less than the initial contact pressure CP1. In particular, t3 refers to the time after the cell stack 122 operates during a constant period (e.g., about 5,000 hours), and t2 refers to the time between t1 and t3. In other words, the temperature of the cell stack 122 is room temperature at time t1, and the temperature of the cell stack 122 after time t1 and before time t3 may be a high temperature greater than room temperature. Therefore, t3 corresponds to the time after room temperature and high temperature are repeated.

[0089] like Fig.9A As shown, for the fuel cell according to the comparative example, when the condensed water W freezes, the contact pressure CP4 increases in the lower region of the unit cell 122-n. When the contact pressure CP4 increases, irreversible plastic deformation may occur in the gas diffusion layers 222 and 224 and the separators 242 and 244 in the internal constituent elements of the unit cell 122-n. As a result, the performance and durability of the battery stack 122 may be deteriorated.

[0090] On the other hand, for the fuel cell 100 or 100A according to the exemplary embodiment, the elastic member 140: 140A, 140B or 140C may be disposed in a portion of the first region A1 of the end plate 110A or 110B, overlapping with the lower region of each unit cell 122-n in the first direction (e.g., the x-axis direction), thereby offsetting the increase in contact pressure on the reaction surface. Fig. 9B As shown, in the fuel cell 100 or 100A according to the exemplary embodiment, when the condensed water W is frozen, the contact pressure CP4 on the reaction surface may be maintained at a constant value.

[0091] In addition, when the condensed water W freezes and expands in volume, stress may be concentrated on the lower region of the unit cell 122-n. In particular, stress may be concentrated on the lower region of the first unit cell 122-1. In this case, when the stress is not offset, the condensed water W may flow along the Figure 4 The microporous structure (e.g., 244-1, 244-2, or 244-3) can expand in the direction indicated by the arrow, so that the microporous structure (e.g., 244-1, 244-2, or 244-3) can penetrate into the second gas diffusion layer (e.g., 224-1, 224-2, or 224-3), and the first channel P1 of the first separator (e.g., 242-1, 242-2, or 242-3) can penetrate into the first gas diffusion layer (e.g., 222-1, 222-2, or 222-3).

[0092] The microporous structure (e.g., 244-1, 244-2, or 244-3) may repeatedly penetrate into the second gas diffusion layer (e.g., 224-1, 224-2, or 224-3), and may cause damage to the membrane. In addition, when the channel P1 of the first separator (e.g., 242-1, 242-2, or 242-3) repeatedly penetrates into the first gas diffusion layer (e.g., 222-1, 222-2, or 222-3), in the lower area of ​​the first separator 242-n of each unit cell 122-n, the cross-sectional area of ​​the channel P1 through which hydrogen can flow may be reduced. Therefore, an area where the reaction deteriorates due to blockage of condensed water W may occur, which may cause degradation of the catalyst.

[0093] By providing the elastic member 140: 140A, 140B or 140C, the fuel cell 100 or 100A according to the exemplary embodiment can prevent damage to the gas diffusion layers 222 and 224 and the separators 242 and 244, can prevent reduction in the cross-sectional area of ​​the channel P1, and can prevent damage to the membrane. Therefore, the performance and durability of the cell stack 122 of the fuel cell 100 or 100A can be improved.

[0094] In addition, by providing the elastic member 140: 140A, 140B, or 140C in the end plate 110A or 110B, the fuel cell 100 or 100A according to the exemplary embodiment may have no negative impact on the function (i.e., the air tightness, water tightness, insulation, and rigidity of other constituent elements of the fuel cell 100 or 100A). For example, since the elastic member 140: 140A, 140B, or 140C may be locally provided in the first area A1 of the end plate 110A or 110B, the deterioration of the rigidity of the end plate 110A or 110B may be minimized, and the weight increase of the fuel cell 100 may be minimized.

[0095] As is apparent from the above description, the fuel cell according to the exemplary embodiment can use the elastic member to prevent damage to the gas diffusion layer and the separator, can prevent the reduction of the cross-sectional area of ​​the channel, and can prevent damage to the membrane, whereby the fuel cell can achieve enhanced performance and durability. In addition, since the elastic member can be provided in a local area inside the end plate, the rigidity degradation of the end plate can be minimized and the weight increase of the fuel cell can be minimized without negatively affecting the air tightness, water tightness, insulation or rigidity of other constituent elements of the fuel cell.

[0096] Without departing from the purpose of the present disclosure, the above exemplary embodiments may be combined with each other unless they conflict with each other. In addition, when the constituent elements of any exemplary embodiment of the above various exemplary embodiments are not described in detail, the description related to the constituent elements with the same reference numerals as other exemplary embodiments may be adopted.

[0097] Although the exemplary embodiments have been described above, the above description is given only as an example and is not intended to limit the present disclosure, and it is obvious to those skilled in the art that various replacements, modifications and changes can be made within the spirit and scope of the exemplary embodiments. For example, the various constituent elements described in the exemplary embodiments can be modified in various ways. In addition, the differences associated with these modifications and changes should be interpreted as being included in the scope of the present disclosure defined by the appended claims.

Claims

1. A fuel cell, include: A battery stack having a plurality of unit batteries stacked along a first direction; an end plate disposed on each of opposite side ends of the battery stack; and an elastic member overlapping with a region of the battery stack where condensed water remains in the first direction, at least a portion of the elastic member being disposed in the end plate, Wherein, the end plate comprises: a main body having a recess, a bottom surface of the main body being opposite to a top surface of the main body in a second direction, and the second direction is perpendicular to the first direction; and a collector plate disposed between the battery stack and an inner side surface of the main body facing the battery stack, wherein the elastic member is separated from the collector plate, Wherein, the subject includes: a first region provided with the recess, wherein the elastic member is provided in the recess; and A second region of the elastic member is not provided, the second region being adjacent to the first region in the second direction, and The first area is closer to the bottom surface of the main body than the second area, and the second area is closer to the top surface of the main body than the first area.

2. The fuel cell according to claim 1, in, In the second direction, a first length of the first region is equal to or smaller than a second length of the second region.

3. The fuel cell according to claim 2, in, The first length corresponds to a length from a bottom surface of the body to a first point located at one third of a total height of the body, and wherein the second length corresponds to a length from the first point to a top surface of the body.

4. The fuel cell according to any one of claims 1 to 3, in, The elastic member includes a plurality of springs stacked along the second direction and spaced apart from each other.

5. The fuel cell according to claim 4, in, The elastic forces of the plurality of springs enable the first region and the second region to have the same initial pressure in an initial state where condensed water does not expand.

6. The fuel cell according to claim 4, in, The elastic force of each spring decreases as the distance from the bottom surface of the main body increases.

7. The fuel cell according to claim 4, in, The elastic force per unit length of the plurality of springs is the same, and the farther each spring is arranged from the bottom surface of the main body, the shorter the length of each spring is.

8. The fuel cell according to any one of claims 1 to 3, in, The elastic member has a repulsive force equal to a pressure applied to an inner side surface of the body due to an expansion force of condensed water.

9. The fuel cell according to claim 8, in, The repulsive force of the elastic member is in the range of 0.8 MPa to 1.2 MPa.

10. The fuel cell according to claim 8, in, The elastic member has an elastic modulus such that the repulsive force is less than 1.5 MPa when the displacement of the inner side surface due to the expansion force is about 1 mm.

11. The fuel cell according to claim 1, in, Each unit battery includes: A membrane electrode assembly, comprising a fuel electrode, an air electrode and a polymer electrolyte membrane disposed between the fuel electrode and the air electrode; Gas diffusion layers are disposed on both sides of the membrane electrode assembly; and A separator plate is arranged on the outer side of the gas diffusion layer.

12. The fuel cell according to claim 11, further comprising: include: A stopper is arranged between the collector plate and the elastic member.

13. The fuel cell according to claim 12, in, Each of the unit cells further includes a gasket disposed between the separator plate and the gas diffusion layer, and wherein the stopper is disposed to overlap the gasket in the first direction.

14. The fuel cell according to claim 11, in, A first length of the first region in the second direction corresponds to a length from a bottom surface of the partition plate to a first point at one third of a total height of the partition plate, and a second length of the second region in the second direction corresponds to a length from the first point to a top surface of the partition plate.

15. The fuel cell according to claim 1, in, The elastic member comprises: A first elastic member is disposed in an end plate disposed on a first side end of opposite side ends of the battery stack; and The second elastic member is disposed in an end plate disposed on a second side end of the opposite side ends of the battery stack.

16. The fuel cell according to claim 15, in, The elastic force of the first elastic member is different from the elastic force of the second elastic member.

17. The fuel cell according to claim 16, in, The reaction gas is introduced or exhausted through a first side end of opposite side ends of the cell stack, and an elastic force of the first elastic member is greater than an elastic force of the second elastic member.

18. The fuel cell according to claim 15, in, The first elastic member and the second elastic member have cross-sectional shapes that are symmetrical about a center of the battery stack in the first direction.

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