CN115775902A - Method for increasing density of fuel cell electrolyte layer and fuel cell - Google Patents

Abstract

The invention discloses a method for increasing the density of an electrolyte layer of a fuel cell and a fuel cell. The method for increasing the density of an electrolyte layer of a fuel cell includes: providing a metal support; forming a cathode layer on one side of the metal support; forming a cathode layer on the cathode A first electrolyte layer with a porosity of 5-10% is formed on the surface of the layer away from the metal support; the surface of the first electrolyte layer away from the metal support is in contact with the molten metal, and the The molten metal undergoes an electrochemical oxidation reaction in pores of the first electrolyte layer to obtain the electrolyte layer. The electrolyte layer prepared by the method has higher density and better stability, and can effectively reduce the internal resistance of the fuel cell.

Description

Method for increasing density of fuel cell electrolyte layer and fuel cell

technical field

The invention belongs to the field of fuel cells, and in particular relates to a method for increasing the density of an electrolyte layer of a fuel cell and a fuel cell.

Background technique

The solid oxide fuel cell belongs to the third generation of fuel cells. It is an all-solid-state chemical power generation device that directly converts the chemical energy stored in fuel and oxidant into electrical energy in an efficient and environmentally friendly manner at medium and high temperatures. Biofuel can improve the mechanical strength of the battery, increase the thermal shock resistance of the battery, and reduce the system cost. Therefore, metal-supported solid oxide fuel cells have gradually become a new research point in the field of fuel cells in recent years. The use of plasma spraying technology to prepare the metal-supported fuel cell electrolyte layer does not require long-term high-temperature sintering of the battery, and can avoid the problems of chromium poisoning of the electrode and high-temperature oxidation of the metal support caused by the high-temperature sintering of the electrolyte in the traditional sintering method. The electrolyte layer prepared so far is still not dense enough.

Therefore, the current method for increasing the density of the fuel cell electrolyte layer and the fuel cell still need to be improved.

Contents of the invention

In the present invention, it is based on the inventor's discovery of the following problems:

The inventors found that although the cost of preparing the electrolyte layer by atmospheric plasma spraying equipment is low, the density of the prepared electrolyte layer is poor, which will cause gas leakage on both sides of the cathode layer and the anode layer of the fuel cell, making the cathode layer and the anode layer The partial pressure of the gas in the anode layer decreases, thereby reducing the open circuit voltage of the fuel cell. Therefore, it is necessary to further densify the electrolyte layer to increase its density. The inventors further found that although the porosity of the electrolyte layer can be reduced by treating the electrolyte layer by impregnation in the related art, this process requires multiple impregnation processes, the process takes a long time, and it is difficult to eliminate the contact resistance of the electrolyte layer; related In the technology, the low melting point electrolyte composite method is used, such as antimony oxide and bismuth oxide with low melting points to form the electrolyte layer. During the operation of the fuel cell, the electrolyte layer is easily reduced to a simple metal, causing the battery to short circuit and fail.

The present invention aims to alleviate or solve at least one of the above-mentioned problems, at least to some extent.

In one aspect of the present invention, the present invention proposes a method for increasing the density of the electrolyte layer of a fuel cell, comprising the following steps: providing a metal support; forming a cathode layer on one side of the metal support; forming a cathode layer on the cathode layer A first electrolyte layer with a porosity of 5-10% is formed on the surface away from the metal support; the surface of the first electrolyte layer away from the metal support is in contact with the molten metal, and an external power supply is used to make the The molten metal undergoes an electrochemical oxidation reaction in pores of the first electrolyte layer to obtain the electrolyte layer. Thus, an electrolyte layer with higher density and good stability can be obtained.

According to an embodiment of the present invention, the molten metal includes at least one of metals aluminum, sodium, potassium and gallium. Therefore, the properties of the metal used are stable, and the oxide is not easy to be reduced, which improves the safety performance of the fuel cell.

According to an embodiment of the present invention, the method further includes: placing the metal support with the surface of the first electrolyte layer facing upwards, and disposing the surface of the first electrolyte layer away from the metal support A molten pool having molten metal therein. Thus, the density of the electrolyte layer can be further increased.

According to an embodiment of the present invention, the difference between the temperature of the molten metal and the melting point of the molten metal is not less than 50°C. Thereby, melting of the molten metal can be promoted, and the density of the electrolyte layer can be further increased.

According to an embodiment of the present invention, the melting process of the molten metal is performed under an inert gas. Thus, the oxidation of the metal during the melting process can be reduced, and the density of the electrolyte layer can be further improved.

According to an embodiment of the present invention, the liquid level of the molten metal in the molten pool is at least 2 cm. Thus, the density of the electrolyte layer can be further increased.

According to an embodiment of the present invention, one end of the external power supply is electrically connected to the molten metal, and the other end of the external power supply is electrically connected to the metal support. In this way, in-situ electrochemical oxidation of the molten metal can occur in the pores of the first electrolyte layer, further improving the density of the electrolyte layer.

According to an embodiment of the present invention, the current density of the electrochemical oxidation reaction is 0.01-0.05 A/cm ² . Thus, an electrolyte layer with higher density and better stability can be obtained.

According to an embodiment of the present invention, the method further includes: forming a molten metal oxide layer on the surface of the electrolyte layer, and removing the molten metal oxide layer. As a result, an electrolyte layer with higher density can be obtained.

In another aspect of the present invention, the present invention provides a fuel cell, comprising the electrolyte layer prepared by the aforementioned method. Therefore, the battery has all the features and advantages of the aforementioned electrolyte layer, which will not be repeated here.

Description of drawings

1 is a flowchart of a method for densifying a fuel cell electrolyte layer according to an embodiment of the present invention;

Fig. 2 is a partial structural schematic diagram of a fuel cell according to an embodiment of the present invention;

3 is a schematic diagram of the connection of an electrochemical oxidation reaction device according to an embodiment of the present invention;

Fig. 4 is a partial structural diagram of the fuel cell after the electrochemical oxidation reaction is completed according to an embodiment of the present invention;

Fig. 5 is a schematic structural view of a fuel cell according to an embodiment of the present invention;

Fig. 6 is a scanning electron microscope image of the electrolyte layer of Example 1 of the present invention.

Reference signs:

Metal support: 10; cathode layer: 20; first electrolyte layer: 30; first electrolyte layer pores: 310; molten metal: 40; molten metal oxide layer: 50; molten metal oxide: 320; molten pool: 70 ; Electrolyte layer: 80; Anode layer: 90.

Detailed ways

Embodiments of the present application are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary, and are only for explaining the present application, and should not be construed as limiting the present application.

In an invention of the present invention, the present invention proposes a method for improving the density of fuel cell electrolyte, specifically, referring to Fig. 1, the method may include the following steps:

S100: Provide metal support body

According to some embodiments of the present invention, the metal support body is the most basic feature of the metal support solid oxide fuel cell compared to the traditional solid oxide fuel cell. The metal support body has a higher thermal conductivity, which can greatly reduce the Thermal gradient and thermal stress, the metal support also has high electrical conductivity, which can improve the electrical performance of the solid oxide fuel cell. The preparation process of the metal support is not particularly limited, for example, the metal support can be obtained by thin-plate laser processing, chemical corrosion and powder metallurgy.

According to some embodiments of the present invention, the material of the metal support is not particularly limited. For example, the material of the metal support can be stainless steel. Stainless steel can better carry A cathode layer and an electrolyte layer on a metal support.

According to some embodiments of the present invention, since the solid oxide fuel cell needs to be ventilated with an atmosphere during operation, the metal support may have porosity, and the porosity of the metal support is not particularly limited, for example, it may be 15-30%.

According to some embodiments of the present invention, the thickness of the metal support is not particularly limited. For example, the thickness of the metal support can be 0.5-3mm. When the thickness of the metal support is greater than 0.5mm, it can effectively carry the cathode above it. layer, electrolyte layer and anode layer.

S200: forming a cathode layer on one side of the metal support

According to some embodiments of the present invention, the cathode layer is arranged on one side surface of the metal support, and the aforesaid cathode layer serves as the cathode of the metal-air battery in the subsequent electrochemical oxidation process, and oxygen is generated at the cathode to obtain electrons to generate oxygen ions Cathode reaction, specifically, the preparation process of the cathode layer is not particularly limited, for example, the cathode layer can be obtained by the atmospheric plasma spraying process, that is, the high-temperature and high-speed plasma flame flow generated by the powder supply system to send the cathode layer material powder into the spray gun The core, the powder will quickly turn into molten droplets and accelerate under the action of high-temperature and high-speed flame flow, and finally hit the metal support to cool and solidify, and the molten droplets will continuously deposit on the metal support to form a cathode layer. The cathode obtained by the plasma spraying process The layer can reduce the interface reaction between the metal support material and the cathode layer material, and improve the binding force between the cathode layer and the metal support.

According to some embodiments of the present invention, the first arc power of spraying the cathode layer by the atmospheric plasma spraying process is not particularly limited, for example, the first arc power can be 25-35kW, when the first arc power can be 25-35kW, The porosity of the cathode layer can be increased, which is conducive to the diffusion and migration of gas in the pores during the subsequent electrochemical oxidation process, thereby promoting the occurrence of subsequent electrochemical oxidation reactions, thereby obtaining a denser electrolyte layer.

According to some embodiments of the present invention, the porosity of the cathode layer is not particularly limited, for example, the porosity may be 20-30%. When the porosity of the cathode layer is less than 20%, the effective gas diffusion and migration channels of the cathode layer are reduced, which is not conducive to the subsequent electrochemical oxidation reaction, thereby affecting the density of the electrolyte layer; when the porosity of the cathode layer is greater than 30%. , the effective conductive volume of the cathode layer will decrease, thereby affecting the working voltage of the solid oxide fuel cell; when the porosity of the cathode layer is 20-30%, it is conducive to the diffusion and migration of gas in the pores of the cathode layer, thereby promoting the subsequent principle occurrence of electrochemical oxidation reactions.

S300: forming a first electrolyte layer on the surface of the cathode layer away from the metal support

According to some embodiments of the present invention, the electrolyte layer plays the role of isolating oxygen and fuel in the solid fuel cell. When the density of the electrolyte layer is low, it will cause gas leakage on both sides of the cathode layer and the anode layer of the fuel cell. , so that the partial pressure of the cathode layer and the anode layer gas is reduced, thereby reducing the open circuit voltage of the fuel cell. In this step, a first electrolyte layer with a porosity of 5-10% is formed on the surface of the cathode layer away from the metal support, and then an electrolyte with a higher density is formed by densifying the first electrolyte layer Referring to FIG. 2 , a cathode layer 20 is formed on one surface of the metal support 10 , and a first electrolyte layer 30 is formed on the surface of the cathode layer away from the metal support 10 , wherein the first electrolyte layer 30 has pores 310 .

According to some embodiments of the present invention, the preparation process of the first electrolyte layer is not particularly limited. For example, the first electrolyte layer can be obtained by using an atmospheric plasma spraying process, and the first electrolyte layer obtained by using the aforementioned process can reduce the material of the first electrolyte layer. The interface reaction with the material of the cathode layer increases the binding force between the cathode layer and the first electrolyte layer.

According to some embodiments of the present invention, the second arc power for spraying the first electrolyte layer by the atmospheric plasma spraying process is not particularly limited, for example, the second arc power can be 45-50kW, when the second arc power can be 45-50kW When , the degree of melting of the powder material of the first electrolyte layer during the spraying process can be improved, and after the powder droplets of the first electrolyte layer with a better melting degree are deposited on the surface of the cathode layer, the first electrolyte layer with a lower porosity can be formed. That is, the porosity of the first electrolyte layer sprayed by the aforementioned second arc power is 5-10%.

S400: Bring the surface of the first electrolyte layer away from the metal support into contact with the molten metal, and make the molten metal undergo an electrochemical oxidation reaction in the pores of the first electrolyte layer through an external power supply.

According to some embodiments of the present invention, in this step, the surface of the first electrolyte layer away from the metal support is brought into contact with the molten metal, that is, the surface of the first electrolyte layer away from the metal support acts as the bottom surface of the molten pool, and is connected to the molten pool by an external power supply. Make the molten metal undergo an electrochemical oxidation reaction in the pores of the first electrolyte layer, so that the molten metal is oxidized into metal oxides in the pores of the first electrolyte layer and undergo volume expansion, thereby realizing effective oxidation in the pores of the first electrolyte layer. filling.

According to some embodiments of the present invention, the material of the molten metal is not particularly limited, for example, the material of the molten metal may include at least one of metals aluminum, sodium, potassium and gallium. The melting points of aluminum, sodium, potassium and gallium are relatively low, which is conducive to melting the metal at a lower temperature, so that the electrochemical oxidation reaction can be carried out at a lower temperature, and the oxides of the aforementioned metals are more difficult to be reduced to The metal, the metal oxide of the aforementioned metal can stably exist in the pores of the first electrolyte layer during the operation of the fuel cell.

According to some embodiments of the present invention, in this step, the surface of the metal support with the first electrolyte layer can be placed upward, and a molten pool is provided on the surface of the first electrolyte layer away from the metal support, and there is molten metal in the molten pool. . Referring to FIG. 3 , a molten pool 70 may be provided on the surface of the first electrolyte layer 30 away from the metal support 10 , and the molten pool 70 is filled with molten metal 40 .

According to some embodiments of the present invention, placing a molten pool on the surface of the first electrolyte layer away from the metal support can reduce the overflow of molten metal that is spread on the surface of the first electrolyte layer. The material of the molten pool is not particularly limited, for example , The material of the molten pool can be quartz, corundum, etc. When the material of the molten pool is quartz or corundum, the material of the molten pool will not chemically react with the molten metal during the process of metal melting and electrochemical oxidation reaction.

According to some embodiments of the present invention, the difference between the temperature of the molten metal and the melting point of the molten metal may be not less than 50°C. When the difference between the temperature of the molten metal and the melting point of the molten metal is maintained at not less than 50°C, the metal can be melted better and thus Oxidation reaction occurs in the pores of the first electrolyte layer to effectively fill the pores of the first electrolyte layer. For example, the melting point of aluminum is 660°C, and the corresponding temperature of molten aluminum is at least 710°C.

According to some embodiments of the present invention, the metal melting process is carried out under an inert gas, and the aforementioned inert gas can be selected from at least one of nitrogen, helium, neon, argon, krypton, xenon, and radon, The chemical properties of the aforementioned inert gas are relatively stable, and can protect the metal well during the metal melting process and prevent the metal from being oxidized.

According to some embodiments of the present invention, the amount of metal added is not particularly limited. For example, the amount of metal added can be such that after the metal is melted, the liquid level height of the molten metal in the molten pool is not less than 2 cm. When the liquid level of the molten metal in the molten pool When the surface height is not less than 2 cm, a sufficient amount of molten metal can enter the pores of the first electrolyte layer and undergo an oxidation reaction, so that the pores of the first electrolyte layer can be effectively filled.

According to some embodiments of the present invention, the connection mode of the external power supply is not particularly limited. For example, one end of the external power supply can be electrically connected to the molten metal, and the other end of the external power supply can be electrically connected to the metal support. Specifically, refer to FIG. 3 , the positive pole of the external power supply 60 is connected to the metal support body 10 through a metal wire, and the negative pole of the external power supply 60 is connected to the molten metal 40 through a stone grinding rod embedded in the molten metal 40 in advance, thus, the molten metal and air form a molten In a metal-air battery, when the power supply is discharged, a cathodic reaction occurs at the interface between the cathode layer 20 and the first electrolyte layer 30, and an anodic reaction occurs at the interface between the pores 310 of the first electrolyte layer and the contact interface between the first electrolyte layer 30 and the molten metal 40, Further, the densification treatment of the first electrolyte is completed.

According to some embodiments of the present invention, the molten metal undergoes an electrochemical oxidation reaction in the pores of the first electrolyte layer through an external power supply, specifically, through an external power supply, oxygen occurs at the interface between the cathode layer and the first electrolyte layer to generate electrons Oxygen ion cathodic reaction, that is, O ² +4e ^- → 2O ^2- , anodic reaction occurs in the pores of the first electrolyte layer and at the interface between the first electrolyte layer and the molten metal, and the molten metal loses electrons and combines with oxygen ions to form metal oxides , to achieve electrochemical oxidation of molten metal. Taking metal aluminum as an example, the molten metal aluminum has anodic reaction in the pores of the first electrolyte layer and the interface between the first electrolyte layer and the molten metal aluminum, and aluminum loses electrons, that is, 2Al-6e ^- +3O ^2- → Al ₂ O ₃ .

According to some embodiments of the present invention, the diffusion and migration of oxygen ions in the first electrolyte layer will oxidize the liquid metal that preferentially infiltrates into the pores of the first electrolyte layer and cause volume expansion to realize the effective filling of the pores of the first electrolyte layer. Electrolyte layer with high density and good stability.

According to some embodiments of the present invention, the current density of the electrochemical oxidation reaction is not particularly limited, for example, the current density can be 0.01-0.05A/cm ² , when the current density is 0.01-0.05A/cm ² , it is beneficial to The chemical oxidation reaction proceeds smoothly, the electrochemical oxidation reaction of molten metal in the pores of the first electrolyte layer is promoted, and a dense electrolyte layer is obtained.

According to some embodiments of the present invention, the type of the power supply is not particularly limited, for example, the power supply may include one of an electrochemical workstation and an electronic load.

According to some embodiments of the present invention, the aforementioned electrochemical oxidation reaction can be extended until a molten metal oxide layer is formed on the surface of the electrolyte layer to ensure that the pores inside the electrolyte layer are filled with metal oxides, and the excess metal oxide can be removed through subsequent treatment. Referring to Fig. 4, the pores of the first electrolyte layer 30 are filled with molten metal oxide 320 to form a highly dense electrolyte layer 80. When the molten metal oxide layer is formed on the surface of the electrolyte layer 80, the power supply stops working , the molten pool is removed from the surface of the electrolyte layer, and the surface of the electrolyte layer is polished with sandpaper to complete the densification treatment of the electrolyte layer. Using the method proposed by the invention to increase the density of the electrolyte layer of the fuel cell can obtain an electrolyte layer with a density of more than 99%, which can meet the requirements of the fuel cell for the density of the electrolyte layer and effectively reduce the internal resistance of the solid oxide fuel cell . Specifically, the thickness of the molten metal oxide layer formed on the surface of the electrolyte layer is not particularly limited, for example, the thickness of the oxide layer may be at least 1 cm.

In another aspect of the present invention, the present invention also proposes a fuel cell, which includes the electrolyte layer prepared by the aforementioned method, so the fuel cell has all the features and advantages of the electrolyte layer prepared by the aforementioned method.

According to some embodiments of the present invention, a fuel cell includes a metal support, a cathode layer, an electrolyte layer, and an anode layer. Referring to FIG. The anode layer 90 is located on the side surface of the electrolyte layer 80 away from the cathode layer 20, wherein the electrolyte layer 80 is prepared by the aforementioned method.

According to some embodiments of the present invention, the preparation process of the anode layer is not particularly limited. For example, the anode layer can be obtained by using an atmospheric plasma spraying process. The anode layer obtained by the aforementioned process can reduce the interface reaction between the anode layer material and the electrolyte layer material and Improve the binding force between the anode layer and the electrolyte layer.

According to some embodiments of the present invention, the preparation process of the anode layer and the cathode layer may also include one of magnetron sputtering, chemical vapor deposition, vacuum plasma spraying, supersonic flame spraying and cold spraying.

Embodiments of the present invention are described in detail below. The embodiments described below are exemplary only for explaining the present invention and should not be construed as limiting the present invention. If no specific technique or condition is indicated in the examples, it shall be carried out according to the technique or condition described in the literature in this field or according to the product specification. The reagents or instruments used were not indicated by the manufacturer, and they were all commercially available conventional products.

Example 1

The cathode layer is sprayed on the surface of the metal support by a plasma spraying process with a first arc power of 30kW, and then the first electrolyte layer is sprayed on the surface of the cathode layer by a second plasma spray process with an arc power of 47kW.

Place the molten pool above the first electrolytic layer, fill the molten pool with metal aluminum powder, bury a graphite rod in the aluminum powder, and then connect the electrochemical workstation, wherein the positive electrode of the electrochemical workstation passes through the wire and the stone grinding rod Connection, the negative electrode of the electrochemical workstation is connected to the metal support body through a wire. Heat the molten pool, the first electrolyte layer, the cathode layer and the metal support to 710°C to completely melt the aluminum powder and keep it warm. The electrochemical workstation discharges at a current density of 0.03A/cm ² to cause an electrochemical oxidation reaction to occur on the surface of the first electrolyte layer and in the pores, and the discharge stops when an aluminum oxide layer with a thickness of 1cm appears on the surface of the first electrolyte layer, and the molten metal is removed. pool and clean and polish the surface of the electrolyte layer to obtain a denser electrolyte layer.

Examples 2-9, Comparative Examples 1-6 are the same as Example 1, the difference is the current density, the type of metal, the molten metal level and the melting temperature, see Table 1 for details.

Table 1

For Examples 1-9, and Comparative Examples 1-6, the electrolyte layers after the densification treatment were assembled into full cells, worked and tested under a hydrogen atmosphere, see Table 2 for details.

Table 2

From Table 2 combined with Figure 6, it can be concluded that the in-situ electrochemical oxidation of molten metal can significantly increase the density of the electrolyte layer, and the open circuit voltage of the battery can be significantly increased when hydrogen is used as fuel.

In the description of the present invention, it should be understood that the terms "first" and "second" are used for description purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, the first feature may be in direct contact with the first feature or the first and second feature may be in direct contact with the second feature through an intermediary. touch. Moreover, "above", "above" and "above" the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "beneath" and "beneath" the first feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is less horizontally than the second feature.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (10)

1. A method of increasing the density of an electrolyte layer of a fuel cell, comprising the steps of:

providing a metal support;

forming a cathode layer on one surface of the metal support:

forming a first electrolyte layer with the porosity of 5-10% on the surface of one side, away from the metal support, of the cathode layer;

and enabling the surface of the first electrolyte layer far away from the metal support body to be in contact with molten metal, and enabling the molten metal to generate electrochemical oxidation reaction in the holes of the first electrolyte layer through an external power supply so as to obtain the electrolyte layer.

2. The method of claim 1, wherein the molten metal comprises at least one of the metals aluminum, sodium, potassium, and gallium.

3. The method of claim 1, further comprising: the surface of the metal support body having the first electrolyte layer is placed face up and a molten pool having molten metal therein is provided on the surface of the first electrolyte layer on the side away from the metal support body.

4. The method of claim 3, wherein the temperature of the molten metal differs from the melting point of the molten metal by no less than 50 ℃.

5. The method of claim 4, wherein the melting of the molten metal is performed under an inert gas.

6. The method of claim 3, wherein the level of the molten metal in the molten bath is at least 2cm.

7. The method of claim 1, wherein one end of the external power source is electrically connected to the molten metal and the other end of the external power source is electrically connected to the metal support.

8. The method of claim 7, wherein the electrochemical oxidation reaction has a current density of 0.01 to 0.05A/cm ² 。

9. The method of claim 1, further comprising: forming a molten metal oxide layer on the surface of the electrolyte layer,

and removing the molten metal oxide layer.

10. A fuel cell comprising an electrolyte layer produced by the method according to any one of claims 1 to 9.

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