HK1144617B - Fuel cell stack - Google Patents

Description

Fuel cell stack

Technical Field

The present invention relates to a method of manufacturing a Solid Oxide Fuel Cell (SOFC) stack, wherein the fuel cell units and interconnect plates making up the stack are provided with a glass sealing gel having a TEC significantly lower than the rest of the fuel cells prior to operation. The glass sealant is a paste-like sheet or glass fiber composed of CaO-MgO-SiO₂-Al₂O₃-B₂O₃In the system of (1). More particularly, the present invention relates to a solid oxide fuel cell stack that can be manufactured by a method comprising the use of a glass sealant having the following composition: 50-70 wt% SiO₂0-20 wt% of Al₂O₃10-50 wt% of CaO, 0-10 wt% of MgO and 0-6 wt% of (Na)₂O+K₂O), 0 to 10 wt.%, preferably 3 to 6 wt.% of B₂O₃And 0-5 wt% of a material selected from TiO₂、ZrO₂、F、P₂O₅、MoO₃、Fe₂O₃、MnO₂La-Sr-Mn-O perovskite (LSM) and combinations thereof. The glass sealant is preferably a glass fiber sheet in the form of E-glass.

Background

SOFCs include an oxygen ion conducting electrolyte, a cathode at which oxygen is reduced and an anode at which hydrogen is oxidized. The overall reaction in a SOFC is the electrochemical reaction of hydrogen and oxygen to produce electrical energy, heat, and water. The SOFC operates at a temperature in the range of 600 to 1000 c, typically 650 to 1000 c, and more typically 750 to 850 c. SOFCs provide a voltage of about 0.75V under normal operating conditions. The fuel cells are thus assembled into a stack in which the fuel cells are electrically connected through the interconnect plate.

Generally, such fuel cells include a Y-stabilized zirconia (YSZ) electrolyte, a cathode and an anode, and layers in contact with an electronically conductive interconnect plate. The interconnect connects the cells in series and typically provides a gas supply path for the fuel cell. A gas-tight sealant is typically used to prevent air in the cathode region and fuel in the anode region from mixing with each other, and also to provide suitable adhesion between the fuel cell elements and the interconnect plate. Therefore, the sealant is important for the performance, life and safe operation of the fuel cell stack.

During operation, the SOFC is subjected to thermal cycling and may therefore be exposed to tensile stresses. If the tensile stress exceeds the tensile strength of the fuel cell, the fuel cell will rupture and the entire fuel cell stack will fail. One source of tensile stress in SOFCs is the difference in Thermal Expansion Coefficient (TEC) between cell stack components. The high operating temperatures and thermal cycling of SOFC stacks require that the interconnect plates be made of materials with similar TEC as the fuel cell units. It has now become possible to find suitable materials for the interconnect plate that have substantially the same TEC as the cells.

Another more difficult source of tensile stress to avoid is the TEC difference between the sealant (typically a glass sealant) and the interconnect plates and cells in the fuel cell stack it is generally believed that the coefficient of Thermal Expansion (TEC) of the sealant should be between 11 and 13 × 10^-6K^-1(25-900 c) to match the TEC of the interconnect plate and/or the fuel cell to eliminate the formation of cracks in the fuel cell assembly. In addition, the seal material must remain stable against reaction with other materials and/or ambient gases over a period of, for example, 40,000 hours.

Common materials for hermetic sealants are glasses having various compositions, and much research has been done in developing suitable glass compositions:

our EP-A-1010675 describes ｃA variety of glass sealing materials suitable for SOFCs, including alkali oxide silicate glasses, micｃA glass ceramics, alkaline earth oxide borosilicate/borosilicate glasses, and alkaline earth oxide aluminosilicates^-6K^-1Therefore, a filler material is added to increase the TEC of the final glass powder so that it is 9 to 13 × 10 with the TEC^-6K^-1Substantially matching the fuel cell unit.

EP-A-1200371 describes ｃA glass-ceramic composition which is Al in ｃA specific range₂O₃、BaO、CaO、SrO、B₂O₃And SiO₂The glass and the crystallized (after heat treatment) glass-ceramic show a value of from 7 × 10^-6K^-1To 13 × 10^-6K^-1The TEC of (1). However, a considerable amount of BaO is required in the glass-ceramic composition to obtain a high TEC. The TEC of the glass-ceramic is substantially matched (within 30%) to the TEC of other solid ceramic components prior to heat treatment.

Taniguchi et al, Journarof PowerSources90(2000)163-169 which describes the use of silica/alumina (52% SiO)₂、48％Al₂O₃；FIBERFRAXFFX paper #300, toshiba monoofrax, thickness 0.35mm) ceramic fiber as sealing material for solid oxide fuel cells. Such a sealant can suppress the fragmentation of the electrolyte in the fuel cell, but the gas sealant is not sufficient in performance because gas leakage is detected in the vicinity of the sealing material.

US-A-2003/0203267 discloses the use of A multilayer seal comprising the use of A seal containing 58% SiO₂About 9% of B₂O₃About 11% of Na₂O, about 6% Al₂O₃About 4% of BaO and ZnO, CaO and K₂And O, a glass material.

Disclosure of Invention

It is an object of the present invention to provide a solid oxide fuel cell stack comprising a gas-tight sealant which does not cause cell fragmentation and which has low reactivity with other stack components.

It is another object of the present invention to provide a solid oxide fuel cell stack comprising a gas-tight sealant that enables faster stack production and better thickness variation of the sealant throughout the stack.

It is a further object of the present invention to provide a solid oxide fuel cell stack comprising a gas-tight sealant that provides low electrical conductivity at stack operating temperatures.

These and other objects have been solved by the present invention.

We therefore provide a solid oxide fuel cell stack obtainable by a process comprising the steps of:

(a) forming a first fuel cell stack assembly by alternating at least one interconnect plate and at least one fuel cell unit, wherein each fuel cell unit comprises an anode, a cathode and an electrolyte disposed between the anode and the cathode, and providing a glass sealant between the interconnect plate and each fuel cell unit, wherein the glass sealant has the following composition:

50-70 wt% SiO₂0-20 wt% of Al₂O₃10-50 wt% of CaO, 0-10 wt% of MgO and 0-6 wt% of (Na)₂O+K₂O), 0 to 10 wt.% of B₂O₃And 0-5 wt% of a material selected from TiO₂、ZrO₂、F、P₂O₅、MoO₃、Fe₂O₃、MnO₂La-Sr-Mn-O perovskite (LSM) and combinations thereof;

(b) by heating said first component to a temperature of 500 ℃ or more and subjecting the stack to 2-20kg/cm²Converting said first fuel cell stack assembly into a second assembly having a glass sealant with a thickness of 5-100 μm;

(c) converting the second assembly of step (b) to a final fuel cell stack assembly by cooling the second assembly to a temperature lower than that in step (b).

Preferably, the glass sealant contains 3 to 6 wt% of B₂O₃。

Preferably, the temperature in step (b) is 800 ℃ or higher and the load pressure is 2 to 10kg/cm². Thus, in a preferred embodiment we provide a solid oxide fuel cell stack obtainable by a process comprising the steps of:

(a) forming a first fuel cell stack assembly by alternating at least one interconnect plate and at least one fuel cell unit, wherein each fuel cell unit comprises an anode, a cathode and an electrolyte disposed between the anode and the cathode, and providing a glass sealant between the interconnect plate and each fuel cell unit, wherein the glass sealant has the following composition:

50-70 wt% SiO₂0-20 wt% of Al₂O₃10-50 wt% of CaO, 0-10 wt% of MgO and 0-6 wt% of (Na)₂O+K₂O), 0 to 10 wt.%, preferably 3 to 6 wt.% of B₂O₃And 0-5 wt% of a material selected from TiO₂、ZrO₂、F、P₂O₅、MoO₃、Fe₂O₃、MnO₂La-Sr-Mn-O perovskite (LSM) and combinations thereof;

(b) by heating said first component to a temperature of 800 ℃ or higher and subjecting the stack to 2-10kg/cm²Converting said first fuel cell stack assembly into a second assembly of glass sealant having a thickness of 5-100 μm;

(c) converting the second assembly of step (b) to a final fuel cell stack assembly by cooling the second assembly to a temperature lower than that in step (b).

In this specification, the terms "glass sealant" and "hermetic sealant" are used interchangeably.

The stack of step (c) may for example be cooled to room temperature. Room Temperature (RT) means the ambient temperature at which the first fuel cell stack assembly is prepared, and is typically 20-30 ℃.

By heating the first fuel cell stack assembly to a temperature of 800 ℃ or higher, such as 850 ℃, 900 ℃, 950 ℃ or higher, while using 2-10kg/cm²Preferably 4 to 8kg/cm²The load pressure presses the stack, which may compress the sealant material to form a hermetic and dense sealant. However, the load pressure may be higher than 10kg/cm²E.g. up to 20kg/cm²For example 14 or 18kg/cm². Preferably, the temperature in step (b) is in the range of 800-900 ℃. However, rather than heating to 800 ℃ or higher, lower temperatures, such as 500-,700 or 750 deg.c. The resulting closed porous structure makes the sealant less prone to leakage. The resulting sealant has a thickness in the range of 5 to 100 μm, typically 5 to 50 μm, and more typically 10 to 35 μm.

In another preferred embodiment, the glass sealant has the following composition:

50-65 wt% SiO₂0-20 wt% of Al₂O₃15-40 wt% of CaO, 0-10 wt% of MgO and 0-6 wt% of (Na)₂O+K₂O), 3-6 wt% of B₂O₃And 0-5 wt% of a material selected from TiO₂、ZrO₂、F、P₂O₅、MoO₃、Fe₂O₃、MnO₂La-Sr-Mn-O perovskite (LSM) and combinations thereof.

It should be understood that the glass sealant composition may be free of Al₂O₃(0 wt.%), but it is preferred that it contains up to 20 wt.% Al₂O₃For example 10-15 wt% Al₂O₃. Similarly, the glass sealant composition may be free of MgO (0 wt%), but preferably it contains up to 10 wt% MgO, for example 0.5-4 wt% MgO. The composition of the glass sealant may be free of (0 wt%) Na₂O+K₂O, but preferably it contains up to 6 wt% Na₂O+K₂O, more preferably up to 2 wt% Na₂O, but not K₂O(0wt％K₂O), most preferably 0.25-2 wt% Na₂O, but not K₂And O. The glass sealant composition may be free of (0 wt%) B₂O₃But B is₂O₃The content of (B) may be up to 6 wt% or 10 wt%. The glass sealant may also have a composition which is free (0 wt%) of compounds selected from TiO₂、ZrO₂、F、P₂O₅、MoO₃、Fe₂O₃、MnO₂La-Sr-Mn-O perovskite (LSM) and combinations thereof, but they may also be present in amounts up to 5 wt%.

Preferably, SiO₂、Al₂O₃CaO and MgO in the glass85-95 wt% or 87-97 wt% of sealant composition, and Na₂O+K₂O and B₂O₃The content of the glass sealant is 3-8 wt% of the glass sealant, and the glass sealant is selected from TiO₂、F、ZrO₂、P₂O₅、MoO₃、Fe₂O₃、MnO₂La-Sr-Mn-O perovskite (LSM) and the combination thereof account for 0-5wt percent of the functional components.

Likewise, the invention includes the use of a glass having the following composition as a glass sealant for a solid oxide fuel cell stack: 50-70 wt% SiO₂0-20 wt% of Al₂O₃10-50 wt% of CaO, 0-10 wt% of MgO and 0-6 wt% of (Na)₂O+K₂O), 0 to 10 wt.%, preferably 3 to 6 wt.% of B₂O₃And 0-5 wt% of a material selected from TiO₂、ZrO₂、F、P₂O₅、MoO₃、Fe₂O₃、MnO₂La-Sr-Mn-O perovskite (LSM) and combinations thereof.

More specifically, the invention also includes the use of a glass having the following composition as a glass sealant in a solid oxide fuel cell stack: 52-56 wt% SiO₂12-16 wt% of Al₂O₃16-25 wt% of CaO, 0-6 wt% of MgO and 0-6 wt% of Na₂O+K₂O, 0-10 wt.%, preferably 3-6 wt.% of B₂O₃And 0-1.5 wt% TiO₂0-1 wt% of F.

Preferred glasses are E-glasses having the following composition: 52-62 wt% SiO₂10-15 wt% of Al₂O₃18-25 wt% of CaO, 0.5-4 wt% of MgO and 0.25-2 wt% of Na₂O, 3.5-5.5 wt% of B₂O₃Which corresponds to the low boron E-glass described in U.S. patent No.7,022,634. The invention therefore also includes the use of an E-glass having the above composition as a glass sealant in a solid oxide fuel cell stack.

Another preferred glass is E-glass having the following composition: 52-62 wt% SiO₂、12-16wt% of Al₂O₃16-25 wt% CaO, 0-5 wt% MgO, 0-2 wt% Na₂O+K₂O), 0 to 10 wt.% of B₂O₃0-1.5 wt% of TiO₂0.05-0.8 wt% of Fe₂O₃0-1.0 wt% of a fluoride corresponding to E-glass according to ASTM standard designation D578-05. The invention therefore also includes the use of an E-glass having the above composition as a glass sealant in a solid oxide fuel cell stack.

We have found that despite the very low TEC of the sealing material in the first fuel cell stack assembly of step (a), it is still possible to produce a final fuel cell stack in which the TEC of the assembly, including the sealing glue, operates properly together without leakage during normal operation and thermal cycling. It appears that the sealant is maintained under compression during the cooling of step (c) because of the greater shrinkage of the interconnect plate and cells at this stage. The calculation based on the mechanical model of elastic fracture shows that the maximum energy release rate of the glass layer is 20J/m²Close to the maximum release rate of the cell (18J/m)²) The model takes into account the non-linearity of the thermal expansion coefficient, and uses interconnection plates and cells with a TEC of 13.3 × 10^-6K^-1(RT-700 ℃ C.), the TEC of the glass sealant according to the invention, having a thickness of 11-33 μm and constituting 10% of the stack, is 6 × 10^-6K^-1. Thus, no chipping of the cell occurred due to the formation of a very thin glass sealant (11-33 μm).

In the heating step (b), the first fuel cell stack assembly is more preferably heated to 850-^-6K^-1。

The glass sealant may or may not be heated during step (b)Crystallization during any run at or above 800 ℃ after more than 100 hours, for example, after heat treatment at 800 ℃ for 168 hours, the sealant crystallizes with a composition similar to that obtained after 84 hours at 850 ℃, resulting in a TEC as high as 10 × 10, measured at 25-800 ℃, of up to 10 × 10^-6K^-1. The crystalline phase of the sealant, especially when using a sealant having an E-glass composition as described above, is diopside, varying in composition from diopside to wollastonite, anorthite and cristobalite, while B₂O₃May remain in the glass phase. (CaMg) Si when MgO is present in glass diopside₂O₆Possibly as the first phase of crystallization. Wollastonite/wollastonite (CaSiO)₃) The crystals are around the diopside nucleus. When Na is present₂When O is present in the melt, anorthite CaAl₂Si₂O₈With albite NaAlSi₃O₈A series of solid solutions is formed. A limited amount of K₂The surprisingly high TEC of the crystallized sealant appears to be due to the formation of diopside-wollastonite (TEC about 8 × 10)^-6K^-1) And cristobalite (TEC about 20 × 10)^-6K^-1) Which counteracts low TEC anorthite (TEC about 5 × 10)^-6K^-1) Is present.

The crystallized sealant exerts less tension on the ceramic cell and thus reduces the risk of cracking. Thus, the sealant is better matched to the rest of the fuel cell, particularly the interconnects, and the risk of cracking of the fuel cell during thermal cycling is further suppressed.

To ensure rapid crystallization of the sealant, nucleating components such as Pt, F, TiO may be added₂、ZrO₂、MoO₃LSM and Fe₂O₃。

The sealant is Na₂O+K₂The sum of O gives little alkaline component and no BaO. The low alkaline component content (≦ 2 wt%) of the conventional sealants is desirable because it ensures low conductivity. Also, a significant amount of alkaline elements is corrosive to the Cr-rich oxide surface layer of interconnects made of chromium-based alloys by forming Na with a melting point of 792 ℃₂CrO₄K having a melting point of 976 DEG C₂CrO₄Or (Na, K) with a minimum melting point of 752 DEG C₂CrO₄And occurs. These components become unstable at 800 ℃ and conduct electricity when operated at this temperature. However, to operate at temperatures closer to 800 ℃, higher Na levels in the glass sealant₂O or K₂O may be necessary because the alkali component tends to lower the softening point of the glass. The use of the alkaline earth BaO to increase TEC in the prior art may also be corrosive to the Cr oxide surface layer, forming BaCrO which may cause spalling₄。

In another embodiment of the present invention, the glass sealant in step (a) is provided in the form of a glass fiber sheet.

The term "glass fibre sheet" as used herein is defined as a layer of glass fibres having a thickness of 0.10 to 1.0mm applied in step (a), which corresponds to a treated dense sealant layer according to the invention having a thickness of 5 to 100 μm. The glass fibre sheet is preferably a fibreglass paper, more preferably E-glass paper, for example containing or carrying fibres in an amount of from 20 to 200g/m²Preferably 30 to 100g/m²E.g. 50 to 100g/m²The fiber glass paper of (1).

Preferably, the glass fiber sheet contains 100 to 200g/m facing the battery cell²The fibers and the facing interconnect board of (1) comprise 20 to 50g/m²Or 60g/m²The fibers of (1). More preferably, the glass fiber sheet comprises 70 to 100g/m facing the battery²E.g. 100g/m²The fibers and the facing interconnect plate of (1) comprise 30 to 60g/m²For example 50g/m²Corresponding to a thickness of about 40 and 20 μm of the treated dense sealant layer according to the invention. Most preferably, the glass fiber sheet is E-cellophane and contains 70 to 100g/m facing the cell²E.g. 100g/m²And 30-60g/m facing the interconnection board²For example 50g/m²The fibers of (a) are,this corresponds to a dense sealant layer after treatment according to the invention of about 40 and 20 μm thickness. More specifically, 80g/m is used, for example, facing the battery²The amount of (b) produces a sealant thickness of about 30 μm facing the interconnect of 30g/m²The amount of (a) produced a thickness of about 10 μm. By providing different thicknesses of the cell-facing and interconnect-facing sheets of glass fibers, an advanced sealing of the SOFC cell stack is achieved.

Providing the sealant in the form of a fiberglass sheet, e.g., a fiberglass mat, such as E-fiberglass, results in better thickness variation than providing the sealant in the form of a powder and/or paste in a fuel cell stack. The sealant has a thickness in the final fuel cell stack of 5-100 μm, preferably 5-50 μm, more preferably 10-40 μm, which is kept within a specific narrow range, such as ± 5 μm. Thus, the difference in the thickness of the sealing glue between the fuel cell units of the final fuel cell stack is eliminated or at least significantly reduced compared to fuel cell stacks where the sealing glue is provided by conventional sputtering or by depositing a paste or paste made of e.g. powder. Also, the provision of the sealant in the form of a fiberglass sheet in step (a) enables solid oxide fuel cell stacks containing the sealant to be prepared by simply stamping commercially available E-fiberglass paper without resorting to much more expensive alternative processes, such as the implementation of process steps associated with the step of slurrying or pasting glass powder to prepare the sealant or adding filler material to increase the TEC of the sealant.

The glass fibre sheet may be chopped E-glass fibre, for example commercial E-glass in the form of a sheet of 0.10 to 1.0mm, preferably 0.3 to 1.0mm thick, corresponding to a sealant thickness in the final fuel cell stack of 5 to 50 μm, typically 10 to 40 μm, more typically 10 to 35 μm, for example 20 μm, especially 11 to 33 μm. E-glass fiber sheets are commercially available (e.g., 50 to 100 g/m)²E-glass) and its use is to provide a simple, inexpensive solution to the problem of suitable sealants in fuel cell stacks to inhibit fuel cell cracking during operation, to be gas tight, and to be electricalThe cells provide electrical insulation and a sealant with low reactivity with the interconnect board. When E-glass is used as the starting glass material, the E-glass is also preferably provided in the form of a glass fiber sheet, such as E-fiberglass paper. Since the E-glass can be made into a roll of glass fibers, the shape of the sealant with the holes corresponding to the respective passages of the fuel or the oxidizer can be efficiently and conveniently provided by a simple punching method.

In another embodiment, the sealant in step (a) is loaded with a filler material in the form of MgO, steel powder, quartz, leucite, and combinations thereof, the high TEC of the filler material enables to obtain a TEC corresponding to the interconnection board, i.e. 12-13 × 10^-6K^-1The composite glass sealant.

In another embodiment, the glass sealant is a paste formed by mixing a glass powder having the composition mentioned in claim 1 with a binder and an organic solvent. The paste is used for screen printing or as a paste in a dispenser (dispenser) for preparing a sealant.

The glass powder can be produced to have a particle size of 12-13 × 10 by mixing with a filler material in the form of MgO, steel powder, quartz, leucite, and combinations thereof^-6K^-1The TEC glass of (1).

Again, regardless of whether the glass is provided in the form of a fiberglass sheet or paste, the starting fiberglass material can be converted by the present invention into a thin glass sealant, i.e., 5-100 μm, typically 5-50 μm, preferably 11-33 μm, which is dense and thus also gas tight, i.e., sealed, in the final fuel cell stack. This is highly desirable because the sealed sealant helps prevent mixing of the fuel in the anode and the oxidant in the cathode of the adjacent fuel cell unit. This tightness appears to be due to the complete bonding between the individual fibres pressed together by the load applied to the stack in the heating step (b) and the temperature used in this step, which is generally at least equal to the softening point of the glass sealant (greater than 800 ℃). Thereby making closedA porous structure or dense glass. The relatively high softening temperature of the sealant (above about 800 deg.C) allows the sealant to maintain a high viscosity, e.g., 10 deg.C, at the operating temperature of the fuel cell stack, e.g., 750 deg.C and 800 deg.C⁹-10¹¹Pa-s。

Drawings

Figure 1 shows a window of 21 thermal cycles (in two days) during a total run of a 10 cell stack prepared according to the invention over a period of 26 days.

Fig. 2 shows a graph (in 5 days) representing OCV (open circuit voltage) as an average over a period of 40 days.

Detailed Description

Example 1:

a 300 μm thick anode supported cell with internal feed and vent holes has unmasked the contact layer in the manifold area to minimize leakage through these porous structures. A metal gasket frame, covered on both sides with punched E-glass fiber paper of the same shape, was placed on both sides of the cell in such a way that: air from the manifold hole is allowed to pass through the cathode and a fuel gas is allowed to pass through the anode side. Interconnecting plates with manifold holes are placed above and below the cell and gasket assembly. The E-cellophane face to cell contained 100g/m²The fibers and the facing interconnect plate of (1) contain 50g/m²Corresponding to 40 and 20 μm thick fibers according to the invention at a temperature of about 880 ℃ and about 6kg/cm, respectively²The loaded pressure of (a). Stacks with 5 cells were prepared and the cross-leak between the anode and cathode sides in the two stacks over one complete thermal cycle was determined to be as low as 0.05 and 0.09% at RT. The method uses 2xN in oxygen on cathode side, as measured by gas chromatography₂Concentration step and measurement of N during operation on the anode side₂Molar concentration, we double the N in the anode in each step by the same gas pressure on the anode and cathode sides₂mole%, which shows that there is leakage and is diffusion controlled, probably due to diffusion through the porous structure of the cell (mainly the anode support). The increased gas pressure on the cathode side does not have any effect on the cross leak on the anode side.

The XRD spectrum of the E-glass shows wollastonite and CaSiO₃(diopside, (Ca, Mg) SiO₃Also in agreement with the spectrum, its presence depends on the MgO content in the glass) and anorthite (CaAl)₂Si₂O₈It may contain up to 10 mole% of NaAlSi₃O₈) And cristobalite (SiO), (si θ)₂) Is present.

As can be seen by OCV (open circuit voltage) (fig. 2), 21 thermal cycles during operation or removal of the ten cell stack to other test equipment (fig. 1) did not have any significant effect on the fuel side and air side cross leakage in the cell. The flat curve of the OCV in fig. 2 shows that the present invention enables the preparation of a final fuel cell stack in a simple manner (using E-fiberglass paper as a precursor to the glass sealant) where the components of the stack including the sealant work well together without creating leaks during normal operation and thermal cycling. Also, no decay reaction occurred between the oxide layer and the E-glass.

A similar flat OCV curve can also be obtained by the following examples:

example 2:

similar to example 1, but the E-glass sealant was infiltrated (by dipping or sputtering) or carried with a slurry containing 20-50 vol% MgO particles 1-5 μm in size, 3% PVA and 67 vol% ethanol.

Example 3:

analogously to example 2; wherein the slurry contains 20-50 vol% of AISI316L powder with a size of 1-3 μm.

Example 4:

analogously to example 2; wherein the slurry contains 20-50 vol% leucite.

Claims (14)

1. A solid oxide fuel cell stack obtained by a method comprising the steps of:

(a) forming a first fuel cell stack assembly by alternating at least one interconnect plate and at least one fuel cell unit, wherein each fuel cell unit comprises an anode, a cathode and an electrolyte disposed between the anode and the cathode, and providing a glass sealant between the interconnect plate and each fuel cell unit, wherein the glass sealant has the following composition:

50-70 wt% SiO₂0-20 wt% of Al₂O₃10-50 wt% of CaO, 0-10 wt% of MgO and 0-6 wt% of (Na)₂O+K₂O), 3-6 wt% of B₂O₃And 0-5 wt% of a material selected from TiO₂、ZrO₂、P₂O₅、MoO₃、Fe₂O₃、MnO₂La-Sr-Mn-O perovskite and functional components in combination thereof;

(b) by heating said first fuel cell stack assembly to a temperature of 500 ℃ or more and subjecting the stack to 2-20kg/cm²Converting said first fuel cell stack assembly into a second assembly having a glass sealant with a thickness of 5-100 μm;

(c) converting the second assembly of step (b) to a final fuel cell stack assembly by cooling the second assembly to a temperature lower than that in step (b).

2. The solid oxide fuel cell stack of claim 1, wherein in step (b), the temperature is 800 ℃ or more and the load pressure is 2-10kg/cm²。

3. The solid oxide fuel cell stack of claim 1, wherein SiO₂、Al₂O₃CaO and MgO in 85-95 wt% of the glass sealant, and Na₂O+K₂O and B₂O₃Is selected from TiO in an amount of 3-8 wt% based on the glass sealant composition₂、ZrO₂、P₂O₅、MoO₃、Fe₂O₃、MnO₂And the functional components in the La-Sr-Mn-O perovskite and the combination thereof account for 0-5 wt%.

4. The solid oxide fuel cell stack of claim 1, wherein the glass sealant is a glass having the following composition: 52-62 wt% SiO₂10-15 wt% of Al₂O₃18-25 wt% of CaO, 0.5-4 wt% of MgO and 0.25-2 wt% of Na₂O, 3.5-5.5 wt% of B₂O₃。

5. The solid oxide fuel cell stack of claim 1, wherein the glass sealant is a glass having the following composition: 52-62 wt% SiO₂12-16 wt% of Al₂O₃16-25 wt% CaO, 0-5 wt% MgO, 0-2 wt% Na₂O+K₂O), 3-6 wt% of B₂O₃0-1.5 wt% of TiO₂0.05-0.8 wt% of Fe₂O₃。

6. The solid oxide fuel cell stack of claim 1, wherein the glass sealant in step (a) is provided in the form of a glass fiber sheet.

7. The solid oxide fuel cell stack of claim 6, wherein the glass fiber sheet facing the cell comprises 70-100g/m²The fibers and the facing interconnect plate of (1) comprise 30 to 60g/m²The fibers of (1).

8. The solid oxide fuel cell stack of claim 1, wherein the glass sealant in step (a) is loaded with a filler material in the form of MgO, steel powder, quartz, leucite, and combinations thereof.

9. A solid oxide fuel cell stack wherein said glass sealant is a paste formed by mixing a glass powder having the composition of claim 1 with a binder and an organic solvent.

10. The solid oxide fuel cell stack of claim 9, wherein the glass powder is mixed with a filler material in the form of MgO, steel powder, quartz, leucite, and combinations thereof.

11. Use of a glass having the following composition as a glass sealant in a solid oxide fuel cell stack: 52-56 wt% SiO₂12-16 wt% of Al₂O₃16-25 wt% of CaO, 0-6 wt% of MgO and 0-6 wt% of Na₂O+K₂O, 3-6 wt% of B₂O₃0-1.5 wt% of TiO₂。

12. Use of E-glass as a glass sealant in a solid oxide fuel cell stack having the following composition: 52-62 wt% SiO₂10-15 wt% of Al₂O₃18-25 wt% of CaO, 0.5-4 wt% of MgO and 0.25-2 wt% of Na₂O, 3.5-5.5 wt% of B₂O₃。

13. Use according to claim 11 or 12, wherein the glass is provided in the form of a glass fibre sheet.

14. The use according to claim 13, wherein the glass fiber sheet contains 70 to 100g/m facing the battery²The fibers and the facing interconnection plate of (1) contain 30-60g/m²The fibers of (1).