JP2012059380A - Fuel cell stack and deformation absorbing member used in fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a fuel cell stack, properly design a circulation layer which circulates gas for power generation and a cooling layer which circulates a cooling medium so as to be independent from each other, and reduce the heights of the circulation layer and the cooling layer.SOLUTION: According to the invention, a joined body 40 is formed by joining an electrolyte 43 so as to be sandwiched between an anode side electrode 41 and a cathode side electrode 42, and multiple unit cells 10, each of which is formed by sandwiching the joined body 40 with a pair of separators 30 and 31, are laminated. Two kinds of gases for power generation are respectively contacted with both the electrodes 41 and 42 of each unit cell 10 with the gases separated from each other, thereby generating power. The unit cells 10 are laminated so as to define a cooling layer S used for circulating a cooling medium between the two facing separators 30 and 31. Further, a conductive deformation absorbing member 50, which contacts with the separators 30 and 31 defining the cooling layer S so as to establish electric continuity and is used for absorbing expanding/contracting deformation of each unit cell 10, is inserted in the cooling layer S.

Description

  The present invention relates to a fuel cell stack using a solid polymer type or solid oxide type unit cell and a deformation absorbing member used for the fuel cell stack.

As this type of fuel cell stack, there is a configuration disclosed in Patent Document 1.
The fuel cell stack disclosed in Patent Document 1 includes a plurality of unit cells each having a joined body in which an electrolyte is interposed between an anode side electrode and a cathode side electrode, and a set of separators that sandwich the joined body. And at least one of the set of separators has a set of metal plates each having a portion where recesses and projections are alternately continuous, and between the set of metal plates. A leaf spring is interposed.
Further, the above-described plate spring is in contact with the top of each convex portion of the pair of metal plates, and the concave portion of one metal plate and the convex portion of the other metal plate are opposed to each other via the plate spring. It has become.
With the above configuration, it is intended to absorb the change in the unit cell dimensions due to thermal expansion, swelling of the electrolyte membrane, and the like during operation of the fuel cell by elastically deforming the leaf spring.

JP 2002-367665 A

However, in the conventional fuel cell stack, if the pitch of the unit cell is reduced while maintaining the power generation performance, the pitch of the cooling water passage is inevitably reduced together with the pitch of the gas passage.
For this reason, the pitch of the leaf springs is also reduced, and the rigidity of the leaf springs is increased so that a predetermined load and stroke cannot be secured, so that it is difficult to absorb the expansion / contraction deformation of the unit cells, and it is difficult to reduce the pitch of the unit cells. It is.

  Accordingly, the present invention provides a fuel cell stack that can be reduced in size by absorbing expansion / contraction deformation of the unit cells even when the stacking pitch of the unit cells is reduced, and a deformation absorbing member used for the fuel cell stack. It is aimed.

  In the fuel cell stack for achieving the above object, a plurality of unit cells in which a joined body in which an electrolyte is joined between an anode side electrode and a cathode side electrode are sandwiched between a pair of separators are laminated to each other. Power generation is performed by causing two types of power generation gas to flow separately from each other on both electrodes of each unit cell, and a cooling medium is circulated between the two separators facing each other in the unit cell. A conductive deformation absorbing member for partitioning and laminating a cooling layer for forming a conductive layer, and conductively contacting both separators for partitioning the cooling layer and absorbing expansion / contraction deformation of the unit cell, It is characterized by being inserted in the cooling layer.

  A deformation absorbing member used in a fuel cell stack for achieving the above object has a plurality of unit cells in which a joined body in which an electrolyte is joined between an anode side electrode and a cathode side electrode is interposed between a pair of separators. The unit cell is used for a fuel cell stack in which a cooling layer for circulating a cooling medium between the two opposing separators is formed and laminated, and the cooling layer is formed. It is characterized by being formed of a conductive material that is in conductive contact with both separators and absorbs expansion / contraction deformation of the unit cell.

  According to the present invention, since the deformation absorbing member inserted in the cooling layer through which the cooling medium is circulated is deformed so as to absorb the expansion / contraction deformation of the unit cell, even when the stacking pitch of the unit cell is reduced, Expansion and contraction deformation can be absorbed, and downsizing can be achieved.

1 is an external perspective view of a fuel cell stack according to an embodiment of the present invention. It is a disassembled perspective view of the fuel cell stack which concerns on one Embodiment same as the above. It is a schematic front view of the unit cell which concerns on an example which makes a part of fuel cell stack same as the above. It is a cross-sectional perspective view for demonstrating the cooling layer divided and formed between the unit cells which concern on an example which adjoins. It is a fragmentary sectional view showing the cooling layer divided and formed between unit cells concerning an example which adjoins, and showing the state where the unit cell expanded and deformed. (A) is the side view of the deformation | transformation absorption member which concerns on 1st embodiment, (B) is the front view, (C) is the part which expands and shows the part shown by the surrounding line I shown to (A) It is an enlarged view. It is the partial expansion side view which expands and shows partially the deformation | transformation absorption member which concerns on 2nd embodiment, and the unit cell which concerns on an example which contacts this. It is a partial expanded side view which expands and shows partially the unit cell which concerns on the deformation | transformation absorption member which concerns on 1st embodiment, and the other example which contacts this. It is the partial expansion side view which expands and shows the deformation | transformation absorption member which concerns on 3rd embodiment, and the unit cell which concerns on the other example which contacts this partially. It is a fragmentary perspective view of the deformation | transformation absorption member which concerns on 4th embodiment. It is a front view of the deformation | transformation absorption member which concerns on 4th embodiment.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to drawings. FIG. 1 is an external perspective view of a fuel cell stack according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the fuel cell stack, and FIG. 3 is a unit according to an example forming a part of the fuel cell stack. FIG. 4 is a schematic front view of a cell, and FIG. 4 is a cross-sectional perspective view for explaining a cooling layer that is partitioned between unit cells according to an example adjacent to each other. In FIG. 4, one of the pair of separators is schematically shown.

As shown in FIG. 1, a fuel cell stack A according to an embodiment of the present invention is a case in which a rectangular parallelepiped cell stack B in which a plurality of unit cells 10 are stacked together is accommodated in a case 20.
As shown in FIG. 2, the unit cell 10 has a structure in which a joined body 40 is sandwiched between a pair of separators 30 and 31.

As shown in FIGS. 2 and 4, the separators 30 and 31 are formed in a rectangular shape in front view, for example, a metal plate such as stainless steel, aluminum, aluminum alloy, magnesium, copper, titanium, etc., to ensure electrical conductivity. Surface treatment is applied.
The separators 30 and 31 are formed with a plurality of rectifying portions 30a and 31a in a required region between the long edge portions 30b, 30b, 31b and 31b formed with a constant width between both end portions.
Also, at both ends, inflow holes 32I, 33I, and 34I, and outflow holes 32O, 33O, through which a hydrogen-containing gas that is one power generation gas, a cooling medium, and an oxygen-containing gas that is the other power generation gas are respectively circulated. The opening is formed by making 34O into a square shape.
In the present embodiment, hydrogen gas will be described as an example of hydrogen-containing gas, air as oxygen-containing gas, and cooling water as a cooling medium.

  The required region in which the rectifying units 30a and 31a are formed is a surface facing the cooling layer S, the details of which will be described later. In this embodiment, the rectifying units 30a and 31a are rectangular shapes having the same shape and the same size. The protrusions are formed at a constant pitch P1 in a direction perpendicular to the flow direction α.

  As shown in the present embodiment, by forming the rectifying portions 30a and 31a in a rectangular shape, the contact area with the deformation absorbing member 50, which will be described in detail later, can be increased, but the shape is not limited to that, Of course, other known shapes may be used. In short, what is necessary is just to be able to rectify the cooling water flowing through the cooling layer S.

  Hydrogen gas, air, and cooling water flowing from the inflow holes 32I, 33I, and 34I toward the outflow holes 32O, 33O, and 34O are provided at the outer peripheral edges of the inflow holes 32I, 33I, and 34I and the outflow holes 32O, 33O, and 34O. A path forming wall (not shown) for projecting each of them along a required path is projected.

As shown in FIG. 4, the joined body 40 has a structure in which an electrolyte 43 is inserted and joined between an anode side electrode 41 and a cathode side electrode 42, and is attached to a frame 44. Note that the frame 44 may be disposed as necessary.
The joined body 40 is configured to generate power by causing the anode side electrode 41 and the cathode side electrode 42 to flow in contact with the two kinds of power generation gases described above.

The frame 44 is formed in a rectangular shape having the same shape and size as the separators 30 and 31, and the inflow holes 32I, 33I, and 34I and the outflow holes 32O, 33O, and 34O are provided at both ends of the frame 44, respectively. A rectangular opening is formed.
In this frame 44, a required region where the joined body 40 is disposed is also referred to as a “power generation area”.

The anode side electrode 41 and the cathode side electrode 42 are composed of a gas diffusion layer (not shown) made of carbon cloth, carbon paper, or the like, and porous carbon particles carrying a platinum alloy on the surface. The electrode catalyst layers (not shown) are applied to the solid polymer electrolyte membrane 43 so that the electrode catalyst layers face each other with the solid polymer electrolyte membrane 43 therebetween. Yes.
The gas diffusion layer may be a member that can reduce pressure loss even when gas is circulated, such as a porous substrate.

  The solid polymer electrolyte membrane 43 is formed, for example, by impregnating water into a perfluorosulfonic acid thin film.

The unit cell 10 described above is hermetically stacked via the sealing material 11 (FIG. 4) wound along the outer edges of the separators 30 and 31 adjacent to each other, so that the separators 30 and 31 facing each other. The cooling layer S for circulating the cooling water described above is defined in the middle.
The sealing material 11 is made of a material that can be elastically deformed in accordance with the expansion / contraction deformation of the unit cell 10.
“Expansion / contraction deformation of the unit cell 10” refers to a dimensional change accompanying expansion and contraction of the unit cell 10 mainly in the stacking direction.

  In the present embodiment, the conductive deformation absorbing member 50 according to the embodiment for absorbing the expansion / contraction deformation of the unit cells 10 in each cooling layer S partitioned and formed for each adjacent unit cell 10, 10. Is inserted into the separators 30 and 31 in conductive contact.

  FIG. 5 shows a cooling layer that is partitioned between unit cells according to an example adjacent to each other, and is a partial cross-sectional view showing a state where the unit cells are expanded and deformed. FIG. 6A is the first embodiment. The side view of the deformation | transformation absorption member which concerns on this, (B) is the front view, (C) is an enlarged view of the part shown by the surrounding line I shown to (A). In FIGS. 5 and 6A and 6C, the direction orthogonal to the drawings is the flow direction of the cooling water.

As shown in FIG. 6B, the deformation absorbing member 50 according to the first embodiment is a metal member formed in a rectangular shape in front view, and the flow direction α of the cooling water in the cooling layer S described above. A plurality of elastic deformation portions 51 orthogonal to each other are integrally coupled between the long side edge portions 52 and 52 having a required width so as to be an area equivalent to the above-described power generation area. The elastic deformation portion 51 having the above configuration does not hinder the cooling water flowing through the cooling layer S and is easy to manufacture.
The plurality of elastic deformation portions 51 are not limited to those formed so as to be orthogonal to the flow direction α of the cooling water in the cooling layer S, and may be formed so as to cross the flow direction α, for example.

  The elastic deformation portion 51 is in conductive contact with the separators 30 and 31 and elastically deforms according to the expansion / contraction deformation of the unit cell 10, and as shown in FIG. It has a shape.

  Adjacent elastic deformation portions 51 and 51 are formed at a predetermined pitch in a direction orthogonal to the flow direction α, and specifically, project at a constant pitch P2 in the direction orthogonal to the flow direction α. Yes.

  Furthermore, in this embodiment, the pitch P2 of the elastic deformation parts 51 and 51 is made larger than the pitch P1 of the rectification parts 30a and 31a. Thereby, it can prevent that the elastic deformation part 51 of the deformation | transformation absorption member 50 fits into the rectification | straightening parts 30a and 31a, and a required spring function is impaired.

Note that the pitch P2 of the elastic deformation portion 51 can be set wide and narrow in consideration of the circulation state of the cooling water, and the pitch may be changed regularly.
For example, the pitch is gradually narrowed from the long edge portions 52 and 52 to the central portion, and the pitch is gradually widened from the long edge portions 52 and 52 to the central portion.
As described above, the deformation absorbing member 50 is inserted in at least one cooling layer S in consideration of expansion / contraction deformation of the unit cell 10 without being inserted in all the cooling layers S. Good. Thereby, manufacturing cost can be reduced.

As described above, the following effects can be obtained by inserting the deformation absorbing member 50 in the cooling layer S formed between the unit cells 10 and 10.
First, by disposing the deformation absorbing member 50 only in the power generation area, it is possible to prevent the cooling water from flowing unnecessarily outside the power generation area where much heat is generated. That is, if there is a lot of useless amount of cooling water, the temperature variation in the unit cell 10 increases, and it becomes easy to dry out during power generation.

In addition, the stacking structure parts of the fuel cell stack A, and particularly the membrane / electrode catalyst layer and the gas diffusion layer disposed in the power generation area, are easily damaged when the stacking load is too high, while the gas diffusion layer is too low when the stacking load is too low. The contact resistance between the gas diffusion layer and the separator, between the gas diffusion layer and the separator, between the separator and the deformation absorbing member increases, the cell resistance during power generation increases, and the performance decreases.
That is, as shown in the present embodiment, the load absorption in the power generation area important for the performance of the fuel cell stack A can be appropriately performed by interposing and arranging the deformation absorbing member 50 corresponding to the power generation area. .

  Further, since the long side edge portion 52 described above is formed on both sides of the deformation absorbing member 50 and the long side edge portions 30b and 31b are formed on the separators 30 and 31, the deformation absorbing member 50 is compressed and laminated. Even when displaced in a direction orthogonal to the direction, the long side edge portions 52, 52 abut against the long side edge portions 30b, 31b of the separators 30, 31, and the amount of displacement is limited. The deformation absorbing member 50 can be kept at the position.

  Further, if the elasticity of the sealing material 11 is small, even when the separators 30 and 31 accompanying power generation are displaced, the deformation absorbing member 50 can be functioned without stretching the sealing material 11, while the elasticity of the sealing material 11 is large. If the surface rigidity of the separators 30 and 31 is low, the separators 30 and 31 can be bent and function as springs. Ideally, both the elasticity of the sealing material 11 and the surface elasticity of the separators 30 and 31 should be as small as possible.

Next, the case 20 will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the case 20 is formed in a rectangular parallelepiped shape having an internal volume that accommodates the cell stack B by fastening plates 21 and 21, reinforcing plates 22 and 22, and end plates 23 and 24.

  Current collector plates 60 and 61 are disposed between both end faces of the cell stack B and the end plates 23 and 24, and a spacer 62 is disposed between the one current collector plate 61 and the end plate 24. It is installed. “A” is a bolt.

  One end plate 23 has plate-side inflow holes 23 a, 23 b, approximately the same shape and size as the inflow holes 32 I, 33 I, 34 I and outflow holes 32 O, 33 O, 34 O of the unit cell 10. 23c and plate side outflow holes 23d, 23e, and 23f are formed.

  The current collecting plate 60 is formed in the same shape and size as the unit cell 10, and is substantially at positions facing the inflow holes 32I, 33I, 34I and the outflow holes 32O, 33O, 34O of the unit cell 10, respectively. Plate-side inflow holes 60a, 60b and 60c and plate-side outflow holes 60d, 60e and 60f having the same shape and size are formed.

The operation of the fuel cell stack A having the above configuration will be described with reference to FIGS.
When each unit cell 10 shown in FIG. 4 expands due to heat and the solid polymer electrolyte membrane 43 swells, the separators 30 and 31 facing each other in the adjacent unit cells 10 and 10 are separated by a distance L1 shown in FIG. To the interval L2 shown in FIG.

  When the interval between the separators 30 and 31 facing each other in the adjacent unit cells 10 and 10 decreases, the deformation absorbing member 50 in the cooling layer S is elastically deformed as shown in FIG. 5 to prevent an increase in stacking load. To do.

On the other hand, when a displacement occurs in the direction in which the lamination load is removed due to heat shrinkage during operation, drying of the solid polymer electrolyte membrane 43, creep of components, etc., the deformation absorbing member 50 is lowered following the displacement. Prevent too much.
The “direction in which the stacking load is released” is synonymous with an increase in the distance between the separators 30 and 31, in other words, the height dimension of the cooling layer S.

  As a result, even if the conventional disc spring or gas diffusion layer displacement absorption is removed, the unit cell 10 during operation will absorb the increase / decrease displacement, the laminating load required for power generation (the upper limit is determined by the strength of the component, The lower limit side can be stably held (determined by the load necessary to ensure contact resistance).

Further, by inserting the deformation absorbing member 50 in the cooling layer S, the height of the circulating layer through which the hydrogen gas and air are circulated and the height of the cooling layer S can be optimally designed independently of each other.
Therefore, both the height (interval) of the flow layer and the cooling layer S can be reduced, and the size of the unit cell 10 in the stacking direction can be reduced, so that the fuel cell stack A itself can be downsized.

Furthermore, since the flow layer and the cooling layer S can be formed independently of each other, the flow direction of the cooling water and the flow direction of the air and hydrogen gas can be made different from each other, thus increasing the degree of freedom in design. be able to.
For example, the inflow direction of the cooling water and the rectifying units 30a and 31a are formed in a direction intersecting with the flow direction of air and hydrogen gas.

  Next, the deformation | transformation absorption member which concerns on 2nd embodiment is demonstrated with reference to FIG. FIG. 7 is a partially enlarged side view showing the deformation absorbing member according to the second embodiment and a unit cell according to an example in contact with the deformation absorbing member partially enlarged. In addition, about the thing equivalent to what was demonstrated in embodiment mentioned above, the code | symbol same as them is attached | subjected and description is abbreviate | omitted.

  The deformation absorbing member 70 according to the second embodiment is a metal member formed in a rectangular shape in a front view, and includes a plurality of elastic deformation portions 71 orthogonal to the flow direction α of the cooling water in the cooling layer S described above. , And integrally formed on a rectangular substrate (not shown).

  The elastic deformation portion 71 is in conductive contact with the separators 30 and 31 and in FIG. 7 and elastically deforms according to the expansion / contraction deformation of the unit cell 10. In this embodiment, the elastic deformation portion 71 contacts the separators 30 and 31. It has a substantially sinusoidal cross-sectional shape in which a flat surface contact portion 71a is formed so as to increase the area.

  The adjacent elastic deformation portions 71, 71 are formed at a predetermined pitch in a direction orthogonal to the flow direction α, and project at a constant pitch in the direction orthogonal to the flow direction α as described above. It is the same.

In this embodiment, the surface roughness of the contact surface on the separator 30, 31 side or the deformation absorbing member 70 side is increased. That is, when the surface roughness increases, the contact area increases, so the contact resistance decreases, and a certain point tends to increase again as a minimum value.
Further, by making the surface contact portion 71a flat (planar), it becomes surface contact, the contact area similarly increases and the contact resistance decreases, and therefore the power generation performance can be improved.

  A unit cell according to another example will be described with reference to FIG. FIG. 8 is a partially enlarged side view showing a partially enlarged deformation absorbing member according to the first embodiment and a unit cell according to another example in contact therewith. In addition, about the thing equivalent to what was demonstrated in embodiment mentioned above, the code | symbol same as them is attached | subjected and description is abbreviate | omitted.

The unit cell 80 according to another example employs separators 81 and 81 that do not form a rectification unit, in other words, have both surfaces formed flat.
In this case, the pitch P2 of the elastic deformation portion 51 of the deformation absorbing member 50 can be set regardless of the pitch of the rectifying portions 30a and 31a, and the separators 81 and 81 can be provided without providing a surface contact portion. Can be easily slid.

  FIG. 9 is a partially enlarged side view showing the deformation absorbing member according to the third embodiment and a unit cell according to another example in contact therewith, partially enlarged. In addition, about the thing equivalent to what was demonstrated in the said FIG. 8, the code | symbol same as them is attached | subjected and description is abbreviate | omitted.

The deformation absorbing member 90 according to the third embodiment includes a plurality of elastic deformation portions 91 that are orthogonal to the flow direction α of the cooling water in the cooling layer S described above, on a substrate (not shown) formed in a rectangular shape in front view. It is formed by projecting together.
In the present embodiment, the elastic deformation portions 91 are formed at equal intervals in a direction orthogonal to the coolant flow direction α.

The elastic deformation portion 91 is in conductive contact with the separator and elastically deforms according to the expansion / contraction deformation of the unit cell 80. In the present embodiment, the stress distribution portion 92 for dispersing the stress generated in the unit cell 80 is provided as a contact portion. It has a substantially sinusoidal cross-sectional shape formed on both sides of 91a.
The stress dispersion portion 92 has a bent portion 92a protruding upward and a bent portion 92b protruding downward, but may have one or three or more bent portions.
By providing such a stress dispersion portion 92, the number of deformed portions (spring elements) increases and the number of sites that store strain energy increases. That is, the stroke with respect to the load can be increased by dispersing the stress.

  The adjacent elastic deformation portions 91, 91 are formed at a predetermined pitch in the direction orthogonal to the flow direction α, and project at a constant pitch in the direction orthogonal to the flow direction α as described above. It is the same.

  FIG. 10 is a partial perspective view of the deformation absorbing member according to the fourth embodiment, and FIG. 11 is a front view of the deformation absorbing member according to the fourth embodiment. In addition, about the thing equivalent to what was demonstrated in each embodiment mentioned above, the code | symbol same as them is attached | subjected and description is abbreviate | omitted.

The deformation absorbing member 100 according to the fourth embodiment is provided with a plurality of elastic deformation portions 101 corresponding to the partial expansion / contraction deformation of the unit cell 10 described above.
In the present embodiment, an elastic band 103 in which a plurality of elastically deforming portions 101 are formed at a constant pitch P2 between the long edge portions 102, 102 having a constant width and orthogonal to the circulation direction α of the cooling water, They are constructed with a certain distance T from each other.

According to this configuration, variations in surface pressure can be made uniform, and a predetermined load and stroke can be secured as a spring displacement absorbing function.
The “stroke” is a dimension capable of being displaced in the stacking direction of the unit cells 10.
Further, by putting a constant interval T between each other, the spring reaction force for a certain stroke is reduced by the area (the number of spring peaks × the spring length) in the interval T. For this reason, the target lamination load can be shifted to a low region.

The present invention is not limited to the above-described embodiments, and the following modifications can be made.
In the embodiment described above, the elastic deformation portion is described as an example having a substantially sinusoidal waveform, but may be formed in a rectangular wave, a triangular wave, a sawtooth shape, or the like.

The deformation absorbing member 90 according to the fourth embodiment shown in FIGS. 10 and 11 includes elastic bands 93 each having a plurality of elastic deformation portions 91 formed at a constant pitch so as to be orthogonal to the coolant flow direction α. Although an example in which the unit cell 10 is installed at a constant interval T has been described as an example, the elastically deformable portion 91 may be disposed in correspondence with partial expansion / contraction deformation of the unit cell 10.
For example, in the direction orthogonal to the flow direction α of the cooling water, the pitch of the elastic deformation portions 91 and 91 is increased from the long edge portions 92 and 92 toward the center portion, and the pitch is decreased.
Further, in the direction along the flow direction α of the cooling water, the pitch of the elastic deformation portions 91 and 91 is increased from both end portions toward the central portion, and the pitch is decreased.

  In the above-described embodiment, the example in which the deformation absorbing member is disposed in the power generation area where the combined body is disposed has been described. However, the deformation absorbing member may be disposed in a wide region including the power generation area.

  As described above in detail, in any case, each configuration described in each of the above embodiments is not limited to being applied only to each of the above embodiments, but the configuration described in one embodiment is replaced by another embodiment. It can be applied mutatis mutandis or applied to it, and it can be arbitrarily combined.

10 Unit cells 30, 31 Separator 30a, 31a Rectifier 40 Assembly 41 Anode side electrode 42 Cathode side electrode 43 Electrolyte 50, 90, 100 Deformation absorbing member 51, 91 Elastic deformation part 92 Stress dispersion part A Fuel cell stack S Cooling layer α Flow direction of cooling medium

Claims (11)

A plurality of unit cells in which an electrolyte is joined between an anode side electrode and a cathode side electrode are sandwiched between a pair of separators, and two types of power generation are provided on both electrodes of each unit cell. In a fuel cell stack that generates power by flowing gas separately from each other,
The unit cell is formed by laminating and laminating a cooling layer for circulating a cooling medium between the two separators facing each other.
A fuel cell characterized in that a conductive deformation absorbing member that is in conductive contact with both separators defining the cooling layer and absorbs expansion / contraction deformation of the unit cell is interposed in the cooling layer. stack.   The fuel cell stack according to claim 1, wherein the deformation absorbing member is elastically deformed by expansion / contraction deformation of the unit cell.   The fuel cell stack according to claim 2, wherein the deformation absorbing member has an elastic deformation portion that elastically deforms due to expansion / contraction deformation of the unit cell.   The deformation absorbing member is interposed in at least any one of the cooling layers formed between adjacent unit cells, according to any one of claims 1 to 3. Fuel cell stack.   The fuel cell stack according to any one of claims 1 to 4, wherein the deformation absorbing member is disposed at least in a power generation area in which the combined body is disposed. The elastically deforming portions of the deformation absorbing member protrude from each other at a predetermined pitch, and on the separator, a rectifying portion for rectifying the cooling medium is formed at a predetermined pitch on the surface facing the cooling layer,
The fuel cell stack according to any one of claims 3 to 5, wherein the pitch of the elastically deforming portion is made larger than the pitch of the rectifying portion.   The fuel cell stack according to any one of claims 3 to 6, wherein the elastically deforming portion is formed so that an area in contact with the separator is increased.   The fuel cell stack according to any one of claims 1 to 7, wherein the deformation absorbing member is formed with a stress dispersion portion for dispersing stress generated in the deformation absorbing member.   The fuel cell stack according to any one of claims 3 to 8, wherein an elastically deforming portion of the deformation absorbing member is disposed corresponding to partial expansion / contraction deformation of the unit cell.   The deformation absorbing member is characterized in that elastic bands in which a plurality of elastically deforming portions are arranged in a direction intersecting with the flow direction of the cooling medium are arranged at predetermined intervals along the flow direction of the cooling medium. Item 10. The fuel cell stack according to Item 9. Having a plurality of unit cells in which a joined body in which an electrolyte is joined between an anode side electrode and a cathode side electrode is interposed between a pair of separators;
A deformation absorbing member for use in a fuel cell stack in which the unit cell is formed by laminating and laminating a cooling layer for circulating a cooling medium between the two separators facing each other,
A deformation absorbing member used for a fuel cell stack, wherein the deformation absorbing member is formed of a conductive material so as to be in conductive contact with both separators forming the cooling layer and absorb expansion / contraction deformation of a unit cell.

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