Patent Publication Number: US-2023145403-A1

Title: Fuel cell stack including a separator having a gas equal distribution structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0154927, filed on Nov. 11, 2021 and Korean Patent Application No. 10-2022-0038059, filed on Mar. 28, 2022, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a fuel cell stack, and more specifically, to a fuel cell stack including a separator having a gas equal distribution structure. 
     2. Discussion of Related Art 
     Fuel cells are devices directly convert chemical energy of sources into electrical energy through electrochemical reactions and have advantages that an energy efficiency is remarkably high compared to general thermal devices, and almost no pollutants are discharged. 
     SUMMARY 
     The present disclosure provides a fuel cell stack having a structure capable of uniformly distribute fuel and air to an entire region of a fuel cell in order to minimize degradation of the performance and durability of the fuel cell stack. 
     According to an aspect of the present disclosure, there is provided a fuel cell stack including a separator having a gas equal distribution structure, the fuel cell stack including a cell formed by sequentially stacking an air electrode, an electrolyte, and a fuel electrode, an air electrode current collector having one surface disposed at a side of the air electrode, an air electrode separator which is disposed at a side of the other surface of the air electrode current collector and in which an air path, along which air moves, is formed, a fuel electrode current collector having one surface disposed at a side of the fuel electrode, and a fuel electrode separator which is disposed at a side of the other surface of the fuel electrode current collector and in which a fuel path, along which fuel moves, is formed, wherein at least one of the air path and the fuel path includes a first channel through which the air or the fuel is introduced from the outside and which is formed to extend to a predetermined length, an auxiliary channel branched off from the first channel so that the air or the fuel moves from the first channel, and a second channel connected to an end portion of the auxiliary channel and formed to extend to a predetermined length so that the air or the fuel moved from the auxiliary channel is moved and discharged to the outside, and at least one of the air path and the fuel path is formed such that the air or the fuel moves in a direction toward the cell and is restricted from moving from the first channel toward the cell. 
     The first channel may be formed to linearly extend in one direction, and the auxiliary channel may be provided as a plurality of auxiliary channels spaced at predetermined intervals in an extending direction of the first channel. 
     The first channel and the second channel may be disposed in parallel. 
     The auxiliary channel may be provided as a plurality of auxiliary channels disposed in parallel. 
     The plurality of auxiliary channels may be disposed orthogonal to the first channel and the second channel. 
     The auxiliary channel may extend to a length smaller than an extension length of each of the first channel and the second channel. 
     The second channel may be disposed at each of two sides of the first channel, and the auxiliary channel may be disposed at each of the two sides of the first channel so that the air or the fuel is distributed in two side directions of the first channel. 
     The first channel may be provided as a plurality of first channels, the second channel may be provided as a plurality of second channels, and the plurality of first channels and the plurality of second channels may be alternately disposed. 
     The auxiliary channel may be formed to include a bent portion which changes an extending direction. 
     The air path or the fuel path may be formed so that an upper portion thereof facing the cell is open, and the fuel cell stack may further include a cover member disposed between the air electrode separator and the air electrode current collector or between the fuel electrode separator and the fuel electrode current collector to cover a region corresponding to the first channel in the upper portion. 
     The cover member may be formed in a plate shape manufactured separately from the air electrode separator or the fuel electrode separator, and a slit may be formed in the cover member so that the air or the fuel moves in a region corresponding to the auxiliary channel. 
     The slit may be formed in a shape corresponding to the auxiliary channel. 
     The air electrode separator and the cover member or the fuel electrode separator and the cover member may be integrally formed. 
     At least one of the air path and the fuel path may be formed so that the air or the fuel moves in the direction toward the cell though only the auxiliary channel. 
     The fuel cell stack may be a fuel cell stack for a solid oxide fuel cell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Not only detailed descriptions of example embodiments of the present disclosure described below but also the summary described above will be understood more easily when read with reference to the accompanying drawings. The example embodiments are illustrated in the drawings to illustrate the present disclosure. However, it should be understood that the present disclosure is not limited to the exact layout and method illustrated in the drawings, in which: 
         FIG.  1    is an exploded perspective view illustrating a fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure; 
         FIG.  2    is a view illustrating one example of a fuel path (or air path) formed in a fuel electrode separator (or air electrode separator) of the fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure; 
         FIG.  3    is a view visually illustrating a fuel concentration in a cross section in a height direction of the fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure; 
         FIG.  4    is a view illustrating an example of a fuel path (or air path) formed in a fuel electrode separator (or air electrode separator) of a fuel cell stack including a separator having a gas equal distribution structure according to another embodiment of the present disclosure; 
         FIGS.  5  and  6    are views illustrating an example of a fuel path (or air path) formed in a fuel electrode separator (or air electrode separator) of a fuel cell stack including a separator having a gas equal distribution structure according to still another embodiment of the present disclosure; 
         FIG.  7    is a view separately illustrating the fuel electrode separator (or air electrode separator) and a cover member of the fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure; and 
         FIG.  8    is a view visually illustrating a fuel concentration for each channel of the fuel path formed in the fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings in order for those skilled in the art to easily perform the present disclosure. The present disclosure may be implemented in several different forms and is not limited to the embodiments described herein. Parts irrelevant to descriptions are omitted in the drawings in order to clearly explain the present disclosure, and the same or similar parts are denoted by the same reference numerals throughout this specification. 
     Terms and words used in this specification and claims should not be interpreted as limited to commonly used meanings or meanings in dictionaries and should be interpreted with meanings and concepts which are consistent with the technological scope of the disclosure based on the principle that the inventors have appropriately defined concepts of terms in order to describe the disclosure in the best way. 
     Among various fuel cells, since a solid oxide fuel cell (SOFC) operates at high temperatures of 600 to 1000° C., the SOFC can freely use not only hydrogen-based fuel but also hydrocarbon-based fuel through internal reforming without using a reformer, a fuel conversion efficiency of the SOFC reaches 45 to 65%, a system efficiency of 85% or more can be obtained in a cogeneration system using waste heat, and thus the SOFC is attracting attention as a next-generation eco-friendly electricity generation method. 
     More specifically, the SOFC includes an oxygen ionic conducting electrolyte, an air electrode (positive electrode) positioned at one side of the oxygen ionic conducting electrolyte, and a fuel electrode (negative electrode) positioned at the other side thereof. 
     In this case, in the air electrode, oxygen ions generated by a reduction reaction of oxygen move to the fuel electrode through the electrolyte and react with hydrogen supplied from the fuel electrode to generate water, in this process, electrons are generated by the fuel electrode, the electrons are consumed by the air electrode, and thus electricity flows when two electrodes are connected. 
     In relation thereto, since power generated by a unit cell basically including the air electrode, the electrolyte, and the fuel electrode is very small, several unit cells can be stacked to form a fuel cell stack to increase an amount of output power. 
     In this case, an air electrode of one unit cell needs to be electrically connected to a fuel electrode of another unit cell, and to this end, separators are used. In addition, current collectors are provided between the air electrode and the separator and between the fuel electrode and the separator to assist uniform contact between the electrodes and the separators. 
     Meanwhile, it may be very important to uniformly distribute fuel and air into a region in which an electrochemical reaction occurs in order to improve the performance and durability of the fuel cell. 
     However, in the case of the foregoing technique, there may be complete consuming/converting gas (fuel and air) at an entrance as soon as the gas is introduced, and thus a concentration of the fuel gradually decreases while the fuel moves from one end portion through which the fuel is introduced to the other end portion at an opposite side through which the fuel is discharged, and the like. That is, in the distribution structure of the foregoing technique, all electrochemical/thermochemical reactions are extremely concentrated on the entrance, and accordingly, a reaction does not occur at an exit of the gas, and thus a real reaction area of the cell is reduced. Such non-uniform reaction distribution can cause not only performance degradation but also a serious long-term durability decrease. 
     When a direction is mentioned in the present specification, a longitudinal direction, a width direction, and a height direction of a fuel cell stack will be respectively referred to as an X-axis direction, a Y-axis direction, and a Z-axis direction based on coordinate axes illustrated in  FIG.  1   . In this case, the X-axis, the Y-axis, and the Z-axis are defined to be perpendicular to each other. 
       FIG.  1    is an exploded perspective view illustrating a fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure,  FIG.  2    is a view illustrating one example of a fuel path (or air path) formed in a fuel electrode separator (or air electrode separator) of the fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure, and  FIG.  3    is a view visually illustrating a fuel concentration in a cross section in a height direction of the fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure.  FIG.  4    is a view illustrating an example of a fuel path (or air path) formed in a fuel electrode separator (or air electrode separator) of a fuel cell stack including a separator having a gas equal distribution structure according to another embodiment of the present disclosure, and  FIGS.  5  and  6    are views illustrating an example of a fuel path (or air path) formed in a fuel electrode separator (or air electrode separator) of a fuel cell stack including a separator having a gas equal distribution structure according to still another embodiment of the present disclosure. 
     A fuel cell stack  100  including a separator having a gas equal distribution structure (hereinafter, fuel cell stack) according one embodiment of the present disclosure may be a unit cell forming a part of a fuel cell including a plurality of fuel cell stacks and may include a fuel electrode separator  60 , a fuel electrode current collector  50 , a cell  10 , an air electrode current collector  20 , and an air electrode separator  30  to may make fuel react with an oxidant to generate electrical energy. 
     In this case, as illustrated in  FIG.  1   , the fuel cell stack  100  according one embodiment of the present disclosure may be formed by sequentially stacking the separator  60 , the fuel electrode current collector  50 , the cell  10 , the air electrode current collector  20 , the air electrode separator  30  in the height direction, and fuel and air may be supplied through the fuel electrode separator  60  and the air electrode separator  30 . 
     In this case, in the fuel cell stack  100  according one embodiment of the present disclosure, a unique path structure may be formed in the fuel electrode separator  60  and the air electrode separator  30  to uniformly distribute the fuel and the air to an entire region of the fuel cell stack, and hereinafter, the path structure will be mainly described. 
     First, the cell  10  may be formed by sequentially stacking a fuel electrode, an electrolyte, and an air electrode and may be a cell used in, as an example, a fuel cell stack for a solid oxide fuel cell (SOFC). However, an application of the fuel cell stack  100  according one embodiment of the present disclosure is not limited to the SOFC, and the fuel cell stack  100  can be used as various types of fuel cell stack in addition thereto. 
     In this case, as an example, a sheet of the cell may be formed through a process in which all of the fuel electrode, the electrolyte, the air electrode are formed of ceramic materials and sintered at high temperatures. However, the above-described materials and the manufacturing method are only examples, and the cell  10  may be formed through various materials and methods in addition thereto. 
     Referring to  FIG.  1    again, next, the fuel electrode current collector  50  and the air electrode current collector  20  may be respectively disposed at a side of the fuel electrode and a side of the air electrode of the cell  10 . 
     In this case, it is considered that poor contact may occur due to generation of tolerances when the cell  10  and the fuel electrode separator (or air electrode separator), which will be described below, are in surface contact with each other, and in order to prevent this, the fuel electrode current collector  50  and the air electrode current collector  20  may be disposed between the cell  10  and the fuel electrode separator  60  or between the cell  10  and the air electrode separator  30  to implement uniform contact between the members. 
     As an example, each of the current collectors  20  and  50  may be formed as a mesh type current collector, a foam type current collector, or the like. In this case, the mesh type current collector may serve to secure stiffness of the current collector and may be formed of a material containing at least one of, for example, stainless steel, a Fe—Cr alloy, manganese (Mn), copper (Cu), nickel (Ni), cobalt (Co), silver (Ag), and platinum (Pt). In addition, the form type current collector is for securing a current collecting function of the current collector and may have a (Mn,Cr)3O4, (Ni,Cr)3O4, (Ni,Co)3O4, (Co,Cr)3O4 or (Co,Ni)3O4 type spinel structure. However, the current collectors  20  and  50  may be formed of various materials and in various shapes other than those. 
     The fuel cell stack  100  according one embodiment of the present disclosure may include the fuel electrode separator  60  and the air electrode separator  30  which are disposed on one surface of the fuel electrode current collector  50  and one surface of the air electrode current collector  20  which are opposite to the cell  10 . 
     In this case, in the fuel electrode separator  60 , a fuel path  70  serving as a path along which fuel moves may be formed, and in the air electrode separator  30 , an air path  40 , along which air moves after air is supplied, may be formed. 
     Meanwhile, since the fuel electrode separator  60  and the air electrode separator  30  only have a difference that a type of a fluid is fuel or air but have substantially the same structures and functions, in the description below, the fuel electrode separator  60  will be mainly described in order to avoid redundant descriptions. That is, a description for the air electrode separator  30  may be understood by replacing the fuel with the air in the description for the fuel electrode separator  60 , and thus most of the description of the air electrode separator  30  will be omitted. 
     In relation thereto, a cover member  80 , which will be described below, may be equally disposed at a side of the air electrode separator  30  as well as a side of the fuel electrode separator  60 , and in this case, it is clear that a function and a structure of a cover member  82  disposed at the side of the air electrode separator  30  are the same as or similar to those of a cover member  81  disposed at the side of the fuel electrode separator  60 . 
     In one embodiment of the present disclosure, the fuel path  70  may be a concave groove formed around a plurality of protrusions  76  by the protrusions  76  formed to protrude from one surface of the fuel electrode separator  60  toward the fuel electrode current collector  50 . In addition, the fuel path  70  may be a space formed in the fuel electrode separator  60  when the protrusions  76  and the cover member  80 , which will be described below, are disposed adjacent to each other. 
     Specifically, referring to  FIG.  2   , the fuel path  70  may include a first channel  71 , a second channel  72 , and an auxiliary channel  73 . 
     First, the first channel  71  is a channel extending to a predetermined length so that fuel is introduced from the side of the fuel electrode separator  60  and is moved, and as illustrated in  FIG.  2   , one end portion may be connected to an inlet  62  of the fuel electrode separator  60  through which the fuel is introduced. 
     In this case, in an end portion of the first channel  71  opposite to the inlet  62 , movement of a fluid may be blocked by the protrusion  76 . 
     In addition, as illustrated in the drawings, the first channel  71  may be linearly formed to extend in a straight line. In this case, the first channel  71  may be formed across the fuel electrode separator  60  so that the fuel may be distributed to an entire region of the fuel electrode separator  60 . 
     However, alternatively, the first channel  71  may be formed to include a bent portion having entirely or partially curved shape and may be formed in any shape. 
     Meanwhile, in  FIG.  2   , although one first channel  71  is illustrated as being disposed at a central portion of the fuel electrode separator  60 , the first channel  71  may have any shape, and the number of first channels  71  may vary in addition thereto as long as the first channel  71  can serve as a channel through which fuel is introduced. This will be described in more detail through embodiments which will be described below. 
     Referring to  FIG.  2    again, the fuel path  70  may include the auxiliary channel  73  formed to be branched off from the first channel  71 . 
     In this case, the auxiliary channel  73  may be formed to communicate with one side portion of the first channel  71 . Accordingly, the fuel introduced through the inlet  62  may move along the first channel  71  in a longitudinal direction, and at the same time, a part of the fuel may move in a width direction through the auxiliary channel  73  formed in a side portion. 
     In one embodiment of the present disclosure, the auxiliary channel  73  may have a length smaller than that of each of the first channel  71  and the second channel  72  which will be described below. For example, as in  FIG.  2   , the auxiliary channel  73  may be formed to have the extension length smaller than that of each of the first channel  71  and the second channel by arranging the auxiliary channel  73  to connect the first channel  71  and the second channel  72  which extend in one direction (in the drawing, a Y-axis direction). 
     When the auxiliary channel  73  having the smaller length than the first channel  71  is disposed as described above, as illustrated in  FIG.  3   , fuel diffusion of the fuel electrode current collector  50  or the cell  10  above the fuel electrode separator  60  may be expedited, and accordingly, uniformity of fuel concentration over the entire region of the fuel cell stack can be improved compared to when only the first channel  71  or the second channel  72  which has the relatively greater length is disposed. 
     As a specific example, as illustrated in the drawings, the auxiliary channel  73  may be disposed perpendicular to the first channel  71 . In this case, the extension length of the auxiliary channel  73  may be minimized compared to the first channel  71 . When the length of the auxiliary channel  73  is small as described above, there is an advantage that a fuel diffusion effect in the fuel electrode current collector  50  or the cell  10  above the auxiliary channel  73  can be maximized so that a distribution of the fuel is uniform. 
     However, as necessary, the auxiliary channel  73  may be branched off from the first channel  71  at a predetermined angle other than 90°. For example, the auxiliary channel  73  may be formed to obliquely extend from first channel  71  at 45° with respect to a direction in which the first channel  71  extends. 
     When the auxiliary channel  73  is obliquely disposed with respect to the first channel  71  as described above, the extension length of the auxiliary channel  73  may be sufficiently secured, a sufficient remaining time may be secured so that the fuel sufficiently moves in the height direction in the auxiliary channel  73 , and at the same time, a reaction region having a smaller length than the first channel  71  may be provided, and thus diffusion of the fuel in a region of the current collector  50  or the cell  10  can be expedited. 
     In one embodiment of the present disclosure, as illustrated in  FIG.  2   , a plurality of auxiliary channels  73  may be disposed at predetermined intervals in the extending direction of the first channel  71 . Accordingly, the fuel may be uniformly distributed in the longitudinal direction (for example, the Y-axis direction) of the fuel electrode separator  60  without being biased to any one region. 
     In embodiments, the plurality of auxiliary channels  73  may be disposed in parallel to uniformly distribute the fuel to the entire region of the fuel cell stack  100  as illustrated in  FIG.  2   . 
     Then, in one embodiment of the present disclosure, the fuel path  70  may include the second channel  72  connected to an end portion of the auxiliary channel  73 . That is, the second channel  72  may be a channel spaced apart from the first channel  71  and may communicate with the first channel  71  through the auxiliary channel  73 . 
     In this case, referring to  FIG.  2    again, in the second channel  72 , unlike the first channel  71 , one end portion may be connected to an outlet  64  through which the fuel is discharged to the outside from the fuel electrode separator  60 , and in the other end portion, movement of the fuel may be restricted by the protrusion  76 . 
     Accordingly, the fuel introduced through the first channel  71  may be branched off and moved to the auxiliary channel  73 , a part of the fuel may be moved to the cell  10  in the height direction and used for a reaction, and the remaining part may be ultimately moved to the second channel  72  and discharged to the outside of the fuel electrode separator  60  through the outlet  64 . 
     In one embodiment of the present disclosure, as an example, the second channel  72  may be disposed parallel to the first channel  71 . Accordingly, a distance between the first channel  71  and the second channel  72  may be uniformly maintained, and thus lengths of the plurality of auxiliary channels  73  disposed between the first channel  71  and the second channel  72  may also be uniformly maintained to improve uniformity of a fuel distribution in the entire region of the fuel cell stack  100 . 
     When the first channel  71  and the second channel  72  are disposed in parallel as described above, the auxiliary channel  73  may form the same angle with respect to the first channel  71  and the second channel. As an example, as the auxiliary channel  73  may be disposed perpendicular to both of the first channel  71  and the second channel  72 , the entirety of the fuel path  70  may form a lattice structure. 
     In various embodiments of the present disclosure, the fuel path  70  may be variously disposed as described below. 
     As a specific example, as illustrated in  FIG.  2    described above, any one first channel  71  is disposed in the central portion, and a pair of second channels  72  may be disposed at two sides of the one first channel  71  at positions spaced predetermined distances therefrom. In this case, the auxiliary channels  73  may be disposed at two sides of the first channel  71  so that the fuel is branched off in two side directions of the first channel  71 . In this case, there is an advantage that the fuel is branched off in the two side directions of the first channel  71  to increase a speed of fuel supply. 
     As another example, as illustrated in  FIG.  4   , a fuel path  70  may be formed as a dense lattice structure by alternately arranging a plurality of first channels  71  and a plurality of second channels  72  and arranging a plurality of auxiliary channels  73  to connect the first channels and the second channels  72  which are adjacent to each other. 
     In this case, in order to prevent fuel moved to a side of the second channels  72  from being introduced into the adjacent auxiliary channels  73 , a step having a predetermined height may be formed between the auxiliary channels  73  and the second channels  72 . 
     When the plurality of first channels  71  and the plurality of second channels  72  are alternately disposed, an extension length of each of the auxiliary channels  73  may be minimized, diffusion of the fuel in porous members such as a current collector  50  and a cell  10  may be expedited, and thus uniformity of a fuel concentration can be maximized. 
     However, when the auxiliary channel  73  is extremely short as described above, a sufficient remaining time for which the fuel moves in a height direction may not be secured. 
     In order to supplement this point, as illustrated in  FIG.  5   , an auxiliary channel  73  of a fuel path  70  may be formed to include bent portions  74 . 
     Specifically, the auxiliary channel  73  is not branched off from a first channel  71  to be directly connected to a second channel  72 , as illustrated in  FIG.  6   , an extending direction of the auxiliary channel  73  may be changed at a region close to the second channel  72  through a first bent portion  84   a , the auxiliary channel  73  may extend toward the first channel  71 , and the extending direction may be changed again at a region close to the first channel  71  through a second bent portion  84   b  and may ultimately meet the second channel  72 . 
     When the auxiliary channel  73  includes two bent portions  84   a  and  84   b  as described above, the auxiliary channel  73  may secure an extension length which is three times a distance a between the first channel and the second channel, and accordingly, a sufficient remaining time may be provided to allow fuel moving along the auxiliary channel  73  to move to a cell  10 . At the same time, since the length of the auxiliary channel extending in a width direction may be minimized, there is an effect of maximizing diffusion in a current collector  50  and the cell  10  formed of porous materials. 
     As described above, in a fuel cell stack  100  according to the various embodiments, a distribution of a fuel concentration can be uniformed by separately forming the first channel  71  through which the fuel is introduced and the second channel  72  through which the fuel is discharged, and connecting the first channel  71  and the second channel  72  using the auxiliary channel  73  having the relatively short length to maximize diffusion of the fuel in regions of the cell  10  and the current collector  50  formed of the porous materials. 
       FIG.  7    is a view separately illustrating the fuel electrode separator (or air electrode separator) and a cover member of the fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure, and  FIG.  8    is a view visually illustrating a fuel concentration for each channel of the fuel path formed in the fuel cell stack including a separator having a gas equal distribution structure according one embodiment of the present disclosure. 
     Meanwhile, in relation to the fuel path  70  in the fuel cell stack  100  according one embodiment of the present disclosure, fuel may move from the first channel  71  toward the cell  10  in the height direction, and the first channel  71  through which the fuel is introduced and moved may be formed so that the fuel is restricted from moving toward the cell  10 . 
     Specifically, in the fuel cell stack  100  according one embodiment of the present disclosure, as illustrated in  FIG.  7   , as the cover member  81  is provided on the fuel electrode separator  60  in which the fuel path  70  is formed, movement of the fuel in the height direction may be blocked in a region  85  corresponding to the first channel  71  and a region  86  corresponding to the second channel  72  in the fuel path  70 . 
     In this case, as an example, the cover member  81  may be formed so that an opening is formed in a region corresponding to the auxiliary channel  73  to allow movement of the fuel, and a region corresponding to the first channel  71  is covered. 
     More specifically, the fuel moved from the fuel path  70  to the cell  10  may generate water by reacting with air moved through the air electrode current collector  20  which will be described below, and in this case, the generated water may move into the fuel path  70  to reduce a concentration of the fuel. When the fuel of which the concentration is reduced is introduced through the auxiliary channel  73  as described above, the fuel concentration may be reduced over the entire region of the fuel cell stack  100  to cause degradation of the performance and durability of the fuel cell. 
     In the fuel cell stack  100  according one embodiment of the present disclosure, the fuel of the first channel  71  can be prevented from being diluted by water by arranging the cover member  81  between the fuel electrode separator  60  and the fuel electrode current collector  50  to prevent an upper portion of the first channel  71  from communicating with the current collector  50  and the cell  10 . 
     In addition, the cover member  81  may solve a phenomenon that the reaction mainly occurs and the fuel is consumed most at the entrance of the fuel electrode separator  60 . In other words, in the fuel cell stack  100  according one embodiment of the present disclosure, since electrical/thermal reaction may be prevented or allowed in some regions by the cover member  81 , there is an effect that an engineer may freely control a reaction region. 
     In this case, referring to  FIG.  8   , an effect of the cover member  80  of the fuel cell stack  100  according one embodiment of the present disclosure may be more clearly seen. 
     As illustrated in  FIG.  8   , in one embodiment of the present disclosure, the first channel  71  may secure a uniform fuel concentration of almost 100% at both of an upper portion  71 ′ close to the inlet  62  and a lower portion  71 ″ far away from the inlet  62 . This is because the upper portion of the first channel  71  may be spatially blocked by the cover member  81  to prevent water from being introduced from the cell  10 . 
     In the fuel cell stack  100  according one embodiment of the present disclosure, as the uniform concentration is maintained in the longitudinal direction of the first channel  71  as described above, there is an effect of maintaining a uniform fuel concentration in the plurality of auxiliary channels  73  branched off from the first channel  71  regardless of positions spaced apart from the upper portion of the first channel  71 . 
     Meanwhile, the cover member  81  may be formed to block the second channel  72  as well as the first channel  71  through which the fuel is introduced. In this case, the cover member  81  may effectively solve a phenomenon that the fuel concentration in the cell is diluted overall because the fuel diffuses from the second channel  72  through which fuel having a relatively low concentration flows. 
     As a specific example related to the cover member  81 , as illustrated in  FIG.  7   , the cover member  81  may be a plate member manufactured separately from the fuel electrode separator  60 . In this case, in the cover member  81  having the plate shape, slits  83  may be formed so that the fuel may move in a region corresponding to the auxiliary channel  73 . 
     In embodiments, the slits may be formed to have a shape corresponding to the auxiliary channel  73 . In addition, the cover member  81  having the plate shape may be coupled to the fuel electrode separator  60  by being inserted into an outer edge of the fuel electrode separator  60  so that the outer edge of the fuel electrode separator  60  and an outer edge of the cover member  81  are engaged with each other. 
     Meanwhile, unlike the example in which the fuel electrode separator  60  and the cover member  81  are separated from each other, the fuel electrode separator  60  and the cover member  81  may also be integrally formed. As an example, through a stacking manufacturing method using a three-dimensional (3D) printing, the fuel path  70  may be formed so that the upper portion of the first channel  71  is closed in the fuel electrode separator  60 , and at the same time, an upper portion corresponding to the auxiliary channel  73  is opened. 
     In the fuel cell stack  100  according one embodiment of the present disclosure, a uniform and high fuel concentration can be secured overall by blocking the movement of the fuel in the height direction in the first channel  71  or the second channel  72  using the unique cover member  81 . 
     Meanwhile, as described above, like the fuel electrode separator  60 , in the air electrode separator  30 , an air path  40  including a first channel  41  connected to an air inlet  32 , a second channel  42  connected to an air outlet  34 , and an auxiliary channel  43  connecting the first channel  41  and the second channel  42 , and a separate cover member  21  may be provided, and thus air can be blocked from being moved in a direction from the first channel  41  to the cell  10 . 
     According to embodiments, in a fuel cell stack including a separator having a gas equal distribution structure, a first channel through which fuel is introduced and a second channel through which the fuel is discharged are separately formed, and the first channel and the second channel are connected by an auxiliary channel having a relatively short length, and thus diffusion of the fuel in regions of a cell and a current collector which are formed of porous materials can be maximized. 
     Accordingly, in the fuel cell stack including a separator having a gas equal distribution structure according to the embodiment of the present disclosure, a distribution of a fuel concentration can be uniform in an entire region of the fuel cell stack. 
     In addition, in the fuel cell stack including a separator having a gas equal distribution structure according to the embodiment of the present disclosure, an electrochemical/thermochemical reaction can be induced or controlled to occur at a desired position in the fuel cell stack by blocking movement of fuel or air in a part of a channel through which the fuel or air moves using a unique cover member. 
     Accordingly, the fuel cell stack including a separator having a gas equal distribution structure according to the embodiment of the present disclosure can effectively solve a phenomenon that the electrochemical/thermochemical reaction is concentrated on one local region, which causes degradation of the performance and durability of the fuel cell stack. 
     Effects of the present disclosure are not limited to the above-described effects and should be understood to include all possible effects which may be inferred from the detailed description of the present disclosure or elements of the present disclosure described in the claims. 
     While embodiments of the present disclosure have been described above, the spirit of the present disclosure is not limited to the embodiments proposed in this specification, and other embodiments may be easily suggested by adding, changing and removing components by those skilled in the art and will fall within the spiritual range of the present disclosure.