CN109841868B

CN109841868B - Solid oxide fuel cell composite sealant and application thereof

Info

Publication number: CN109841868B
Application number: CN201711203638.5A
Authority: CN
Inventors: 区定容; 程谟杰; 王秀玲
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2017-11-27
Filing date: 2017-11-27
Publication date: 2021-06-18
Anticipated expiration: 2037-11-27
Also published as: CN109841868A

Abstract

The invention discloses a composite sealant of a solid oxide fuel cell, which comprises a solid glass component and a liquid glass componentWherein the weight ratio of the solid glass component is 50-80 percent, and the weight ratio of the liquid glass component is 20-50 percent. The solid glass component is made of SiO₂Is a formed body and contains one or more than one alkali metal elements and alkaline earth metal elements as modifiers; the liquid glass component is an aqueous solution of glass, and the glass for preparing the liquid glass component is SiO₂Is a formed body and contains one or more than one alkali metal element and alkaline earth metal element. The solid oxide fuel cell composite sealant is applied between a fuel cell unit and other components of a cell stack, and has the advantages of good sealing and high bonding strength. The sealing layer with higher density and strength can be formed after the composite sealing agent is dried, and the sealing layer does not need to be sintered under pressure, and is particularly suitable for sealing tubular solid oxide fuel cells.

Description

Solid oxide fuel cell composite sealant and application thereof

Technical Field

The invention relates to a solid oxide fuel cell, in particular to a composite sealant of the solid oxide fuel cell and application thereof.

Background

The Solid Oxide Fuel Cell (SOFC) is a power generation device which can directly convert chemical energy in fuel into electric energy cleanly and efficiently, and has the advantages of wide adaptability to various fuel gases, high waste heat utilization value and the like. The SOFC can provide a module close to an end user, solves the problems of high energy consumption, noise and the like in the electric energy transmission process, can be applied to the fields of mobile power sources, distributed power generation systems, embedded power generation devices, cogeneration power generation and the like, and is particularly suitable for important government and military departments.

Currently, SOFCs are mainly classified into plate type and tube type. The plate type SOFC cell stack is formed by laminating a plate type cell unit and a sheet bipolar plate, complete sealing of the plate type cell unit and the sheet bipolar plate under the high-temperature operation condition of the SOFC is required to be realized in order to isolate anode gas and cathode gas, and the requirements on thermal expansion matching, thermal stability, chemical stability and the like of a sealing material are very high. Currently, plate-type SOFC cell stacks mainly use silica glass or borosilicate glass as sealing materials with alkali metals and alkaline earth metals as modifiers. CaO-Al as disclosed in patent CN1494176A₂O₃-B₂O₃-SiO₂Glass, SiO disclosed in patent CN1746252A₂-Al₂O₃-B₂O₃-Na₂O-CaO glass, BaO-CaO-Al disclosed in patent CN1660954A₂O₃-La₂O₃-B₂O₃-SiO₂Glass, CaO-MgO-B disclosed in patent CN14699497A₂O₃-SiO₂Glass, and the like. Mixing glass powder or glass fiber with organic solvent and adhesive to form glass sealant, coating the glass sealant on the part to be sealed, and heating to the sealing temperature to realize bonding and sealing. In order to improve the mechanical strength and thermal expansion matching of the glass sealing material, a certain proportion of solid ceramic powder or high-melting glass powder can be added into the glass sealing material as a bone phase, such as glass sealing agents disclosed in patents CN1884423A, 101079476A, CN103570372A and CN 106277794A. In general, the sealing temperature of an SOFC is higher than the softening temperature of glass, but lower than the glass melting temperature. When sealing, the glass is a viscoelastic body, so certain pressure needs to be applied to promote the flow and extension of the glass in the sealing process so as to ensure the sealing effect.

Compared to plate-type SOFCs, the sealing structure of tubular SOFCs for stationary power station power supplies is relatively simple, and generally adopts a technical solution of no or incomplete sealing, for example, the incomplete sealing structure is adopted in the tubular SOFC cell stack of siemens-west house (US2002/0110716a 1). For small and medium-sized mobile power stations or power supplies, higher requirements are often placed on sealing in order to meet the mobile requirements. At present, the sealing of the tubular SOFC cell is mainly performed by using an inorganic adhesive (a silicate adhesive, a phosphate adhesive, or the like) or the like. The inorganic adhesive has higher bonding strength, but is difficult to meet the sealing requirement when used for sealing SOFC cells: on one hand, the inorganic adhesive can show a porous structure on a microscopic scale after being cured; on the other hand, since the thermal expansion coefficient of the inorganic adhesive is much lower than that of the battery material, the thermal stress during the temperature rise and fall process may cause the sealing layer to peel off or crack inside the sealing layer. The reaction gas on both sides of the cathode and anode can pass through the porous sealing layer or the crack, which not only reduces the open-circuit voltage of the battery, but also can cause the failure of the galvanic pile or accidents such as fire, explosion and the like in severe cases.

Compared with inorganic adhesives, SOFC glass sealing materials are thermal expansion matched and have good sealing performance, however, because the glass is in a viscoelastic state during sealing, pressurization is needed to promote the glass to extend so as to realize sealing. In tubular cells, it is difficult to achieve such pressure sealing, limiting the application of glass sealing materials in tubular SOFC cell stacks.

Disclosure of Invention

It is an object of the present invention to provide a glass sealant that does not require pressure sealing to achieve good sealing for tubular SOFC or other types of SOFC cells.

The composite sealant for the solid oxide fuel cell comprises a solid glass component and a liquid glass component, wherein the solid glass component is made of SiO₂Is a formed body and contains one or more than two alkali metal elements and/or alkaline earth metal elements as a modifier; the liquid glass component is an alkaline aqueous solution of glass, and the glass used for preparing the liquid glass component is SiO₂Is a formed body and contains one or two or more alkali metal elements and/or alkaline earth metal elements.

In the solid glass component and the liquid glass component, the alkali metal element serving as a modifier comprises one or two of K or Na, and the alkaline earth metal element serving as a modifier comprises one or more of Mg, Ca, Sr or Ba. The solid glass component comprises a glass intermediate and a glass modifier, wherein the glass intermediate is Al₂O₃The mass percentage of the glass in the solid glass component is 1-10%. The glass modifier is one or more than two of rare earth oxides. By controlling the modifier and intermediate content, the thermal expansion coefficient of the solid glass component is controlled between 9.0 and 12.0, so as to realize good thermal expansion matching between the sealing material and the battery. Other additives for adjusting physical properties such as viscosity, fluidity, glass transition temperature and the like of the glass can be added to the glass according to actual needs.

The liquid glass component is an alkaline aqueous solution of glass, obtained by reaction of initial glass with an alkaline solution of K, Na, Ba or Sr; the initial glass is made of SiO₂Is a formed body and contains one or more than two alkali metal elements and/or alkaline earth metal elements as a modifier.

In the composite sealant of the solid oxide fuel cell, the fluidity of the composite glass sealant is better along with the increase of the proportion of the liquid glass component, but the sealing strength and the high-temperature stability are reduced to a certain degree, and the composite sealant can be adjusted according to the required viscosity and fluidity in actual use. In the technical scheme of the invention, the optimized weight ratio of the solid glass component in the composite sealant is 50-80%, and the optimized weight ratio of the liquid glass component is 20-50%. Within the range, the glass sealant can achieve good sealing effect and can meet the sealing and strength requirements of common SOFCs.

In the composite sealant for a solid oxide fuel cell, the solid glass component contains one or more than two solid-phase glass powders or fibers. When the solid glass component contains two or more kinds of solid glass powders and fibers, the average thermal expansion coefficient of the two glasses should be 9.0 to 12.0X 10^-6and/K is between.

The composite sealant for a solid oxide fuel cell according to any of the above embodiments can be used for sealing and bonding between the SOFC fuel cell unit and other components in the stack. In specific applications, the composite sealant of the present invention can adopt different technical schemes to form the sealing layer. In the first scheme, the solid glass component and the liquid glass component of the composite sealant are uniformly mixed and then directly coated between the solid oxide fuel cell unit to be sealed and other components of the cell stack, and a glass sealing layer is formed after drying. Dispersing a solid glass component of the composite sealant in an organic solution, coating the organic solution between a solid oxide fuel cell unit to be sealed and other parts of a cell stack, drying, and pre-burning at the temperature of 400-800 ℃ to obtain a porous glass skeleton; and filling the liquid glass component into the pores of the porous glass skeleton, and drying to form a glass sealing layer. The dried liquid glass component forms glass gel around the solid glass component, and the air tightness of the sealing layer is ensured. When the SOFC electric pile is raised to the operation temperature, the glass gel formed after drying and the solid glass component are in a viscoelastic state and are fused to form a uniform glass sealing layer. In order to further improve the strength of the sealing layer in the assembly process, the solid oxide fuel cell unit and other components of the cell stack which need to be sealed are bonded and sealed by the composite sealant, then the solid oxide fuel cell unit and other components are dried and then heated at the temperature of 600-900 ℃, and the cell unit and other components after being heated are placed in the cell stack for assembly.

The composite sealant can be applied to the air-tight sealing between the SOFC battery unit and other components, and has the advantages of good sealing and high bonding strength. The sealing layer with higher density and strength can be formed after the composite sealant is fully dried, and the composite sealant does not need to be sintered under pressure, and is particularly suitable for sealing tubular solid oxide fuel cells.

Drawings

Fig. 1 is a schematic composition diagram of a solid oxide fuel cell composite sealant of the present invention.

In the figure, A1 and A2 represent solid glass components, and B represents liquid glass components

FIG. 2 is a scanning electron micrograph of the composite sealant of the present invention after sealing and heating.

Fig. 3 is a schematic view of the composite sealant according to the present invention applied to the sealing of a tube-type battery cell.

In the figure, 1 represents a solid oxide fuel cell unit requiring sealing, 2 represents a metal terminal, and 3 represents a glass sealing layer

Fig. 4 is a comparison of cell performance sealed with the composite sealant of the present invention and a conventional silicate adhesive.

Detailed Description

While the invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described in detail, certain embodiments and examples of the invention, with the understanding that the present disclosure is not intended to be limited to the specific embodiments and examples.

Example 1

The composite sealant for the tubular solid oxide fuel cell comprises a solid glass component (shown as A1 and A2 in figure 1) and a liquid glass component (shown as B in figure 1).

In this example, solid glass component A1 is SrO-Al₂O₃-SiO₂And (3) glass powder. A2 is SrO-K₂O-Al₂O₃-SiO₂And (3) glass powder. The glass preparation adopts the traditionThe melting method of (1). The oxide raw materials mixed according to the proportion are melted at 1300-1500 ℃ and then quenched to obtain glass frits, and the glass frits are dried and crushed to obtain glass powder. The liquid glass component B is a glass aqueous solution containing Sr and K, and is obtained by heating, pressurizing and hydrolyzing silicate glass in an alkaline solution containing Sr and K.

In this example, the weight ratio of the solid glass component was 80% and the weight ratio of the liquid glass component was 20%. Mixing the solid glass component and the liquid glass component, uniformly coating the mixture on a part to be sealed, drying at room temperature for more than 12h, drying at room temperature for 12-18h, and heating and sintering at 900 ℃. In order to accelerate the drying speed, the drying can be carried out for 4 to 6 hours at 60 ℃.

FIG. 2 is a scanning electron micrograph of the sealing layer after heat treatment, and it can be seen that after the composite sealant is used for sealing, two components in the sealant have reacted to form a whole, and a dense sealing layer can be obtained under the sealing condition without pressure.

Example 2

The difference from example 1 is that the solid glass component of the composite sealant is BaO-Al₂O₃-SiO₂The glass powder and the liquid glass component are silicate glass aqueous solution containing Na and Ba. In this example, the weight ratio of the solid glass component was 50%, and the weight ratio of the liquid glass component was 50%. Mixing the solid glass component and the liquid glass component, uniformly spreading on the part to be sealed, fully drying, and heating at 600 deg.C.

Example 3

The difference from example 2 is that the solid glass component of the composite sealant is BaO-Al₂O₃-SiO₂A mixture of glass powder and fibers. The mixture of the glass powder and the fiber is dispersed in an organic solution of PVB, coated between a solid oxide fuel cell unit 1 to be sealed and a metal terminal 2 (as shown in fig. 3), dried, and then pre-fired at 800 ℃ to obtain a porous glass skeleton, and then a liquid glass component is filled in the pores of the glass skeleton to form a glass sealing layer 3, and the glass sealing layer is dried and used.

Fig. 4 is a graph of the performance of a tube-type battery sealed with the composite sealant of the present invention. Compared with the battery sealed by the traditional silicate adhesive (high-temperature adhesive), the open-circuit potential and the power density of the battery are obviously improved due to the improvement of the sealing performance.

Claims

1. A solid oxide fuel cell composite sealant, characterized by:

the solid oxide fuel cell composite sealant comprises a solid glass component and a liquid glass component;

the solid glass component is made of SiO₂Is a formed body and contains one or more than two alkali metal elements and/or alkaline earth metal elements as a modifier;

the liquid glass component is an aqueous solution of glass, and the glass used for preparing the liquid glass component is SiO₂Is a formed body and contains one or more than two alkali metal elements and/or alkaline earth metal elements;

an alkaline aqueous solution for the liquid glass component being glass obtained by reaction of a starting glass with an alkaline solution of K, Na, Ba or Sr; the initial glass is made of SiO₂Is a formed body and contains one or more than two alkali metal elements and/or alkaline earth metal elements as a modifier.

2. The composite sealant according to claim 1, characterized in that: the weight ratio of the solid glass component is 50-80%, and the weight ratio of the liquid glass component is 20-50%.

3. The composite sealant according to claim 1, characterized in that: the solid glass component contains one or more than two solid glass powders and/or fibers.

4. The composite sealant according to claim 1, characterized in that: in the solid glass component modifier, the alkali metal element comprises one or two of K or Na, and the alkaline earth metal element comprises one or more of Mg, Ca, Sr or Ba.

5. The composite sealant according to claim 1, characterized in that: the solid glass component comprises Al₂O₃As an intermediate of the glass, the mass percentage of the intermediate in the solid glass component is 1-10%.

6. The use of the composite sealant for a solid oxide fuel cell according to claim 1, wherein: and after being uniformly mixed, the solid glass component and the liquid glass component are coated between a solid oxide fuel cell unit to be sealed and other components of the cell stack, and a glass sealing layer is formed after drying.

7. The use of the composite sealant for a solid oxide fuel cell according to claim 1, wherein: the solid glass component is dispersed in organic or inorganic solution, coated between the solid oxide fuel cell unit to be sealed and other parts of the cell stack, dried and then processed at 400-800-^oPre-sintering to obtain a porous glass skeleton; and filling the liquid glass component into the pores of the porous glass skeleton, and drying to form a glass sealing layer.

8. Use of a composite sealant according to any one of claims 6 to 7, wherein: and after the solid oxide fuel cell unit to be sealed and other parts of the cell stack are bonded and sealed by the composite sealant, heating at the temperature of 600 ℃ and 900 ℃.