In-situ synthesis method for modified electrode of solid oxide battery

Abstract

The present invention discloses an in-situ synthesis method of a modified electrode for a solid oxide battery, and belongs to the technical field of solid oxide batteries and solid oxide electrolytic cells. The present invention adopts a tape casting method to prepare a fuel electrode support, and then screen prints a fuel electrode functional layer, an electrolyte and a porous air electrode skeleton composed of an electrolyte material, which is formed by a single sintering, and then a precursor mixed solution of the synthesized air electrode functional material and the modified material is impregnated into the air electrode skeleton to complete the preparation of a solid oxide battery. When the method of the present invention is used, the battery can complete the phase reaction of the air electrode functional component before reaching the operating temperature because the operating temperature is higher than the phase formation temperature of the precursor of the air electrode functional component during use. This process can simplify the three sintering processes required for the preparation of traditional batteries into a single sintering process, and the air electrode functional components are phased during the battery operation process, which greatly simplifies the battery preparation process.

Description

Technical Field

[0001] The invention belongs to the technical field of solid oxide batteries and solid oxide electrolytic cells, and particularly relates to an in-situ synthesis method for a modified electrode of a solid oxide battery. Background Art

[0002] A solid oxide cell is an all-solid-state electrochemical energy conversion device that can operate in a fuel cell mode, directly converting the chemical energy of the fuel gas into electrical energy through an electrochemical reaction, or using the reverse reaction electrolyzer mode to electrolyze water to produce hydrogen and oxygen. Its structure includes a support, a fuel electrode, an electrolyte, and an air electrode. Taking a common solid oxide cell with an oxygen ion conductor electrolyte as an example, the electrochemical reaction in the fuel cell mode occurs at the fuel electrode and the air electrode, the fuel molecules are oxidized and lose electrons in the fuel electrode, the oxygen in the air obtains electrons and is reduced at the air electrode, and the electrons are transmitted from the fuel electrode to the air electrode through an external circuit, thereby realizing the power generation process. The electrochemical reaction of the electrolyzer is that water obtains electrons at the fuel electrode and decomposes into hydrogen and oxygen ions, and the oxygen ions pass through the electrolyte and are reduced to oxygen and release electrons at the air electrode.

[0003] According to the characteristics of electrochemical reactions, the commonly used fuel electrode structure is porous nickel metal and electrolyte ceramics (such as yttria-stabilized zirconia YSZ), and the air electrode structure is electrolyte ceramics and high-temperature electronic conductive ceramics (such as doped lanthanum manganate LSM) or electronic / ion mixed conductive ceramics (such as doped lanthanum cobaltate LSCF). In order to obtain higher electrochemical stability and energy conversion rate, the electrode materials, especially the air electrode materials, are usually further modified, such as loading the modified substance nano PdO particles into the porous structure of the air electrode, and in order to prevent its particle growth, nano zirconium oxide particles are also loaded at the same time to form a LSM+YSZ+PdO / ZrO2 composite air electrode.

[0004] Since the battery involves the synthesis and molding of multiple materials, the battery preparation process is relatively complicated. The densification sintering temperature of the electrolyte is generally higher than 1400°C. The fuel electrode is usually composed of NiO + electrolyte ceramics, and the physical phase is relatively stable and can be co-sintered. However, in the air electrode, such as LSM, it will react with YSZ above 1200°C to generate high-resistance La2Zr2O7, so the preparation of the air electrode is usually carried out in steps. The typical battery preparation method is: first use the casting method to complete the preparation of the fuel electrode support, then screen print the fuel electrode and electrolyte, degrease and co-sinter to complete the preparation except the air electrode. Then synthesize the active ingredients of the air electrode, such as LSM, and mix them evenly with the YSZ powder mechanically to prepare a printing slurry and print it on the surface of the sintered electrolyte, and then perform low-temperature sintering. If the electrode needs to be modified, it is necessary to immerse the solution of the modification material in the air electrode, synthesize the active material precursor by sol-gel method or self-propagating combustion method, and then perform low-temperature calcination to form a phase. The battery preparation process requires multiple sintering and roasting processes at different temperatures. The process is complicated, the preparation process is long, and the energy consumption is high. Summary of the invention

[0005] In order to solve the complex battery preparation problems caused by the characteristics of the air electrode, the present invention provides an in-situ synthesis method for a solid oxide battery modified electrode. Using the method of the present invention, during the use of the battery, since the operating temperature is about 750°C, when the temperature rises to 400°C, the functional component precursors in the air electrode will begin to react to form a phase, and the phase reaction of LSM, PdO and ZrO2 can be completed before reaching the operating temperature. This process can simplify the three-time sintering process into one-time sintering, and the functional components of the air electrode form a phase during the battery operation process, which greatly simplifies the battery preparation process.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the purposes of the present invention is to provide an in-situ synthesis method for a modified electrode of a solid oxide battery, comprising the following steps: preparing a fuel electrode support by a tape casting method, then screen printing a fuel electrode functional layer, an electrolyte and a porous air electrode skeleton composed of an electrolyte material, sintering them once, and then impregnating a mixed solution of a precursor of a synthesized air electrode functional material and a modifying material into the air electrode skeleton to complete the preparation of a solid oxide battery.

[0008] Furthermore, the fuel electrode support is composed of an electrolyte and a metal; the fuel electrode functional layer has the same composition as the fuel electrode support; the electrolyte is a dense solid ceramic ion conductor; and the porous air electrode skeleton is obtained by adding a pore-forming agent to the electrolyte.

[0009] Furthermore, the pore-forming agent is starch or carbon powder.

[0010] Furthermore, the fuel electrode support, the fuel electrode functional layer, the electrolyte and the porous air electrode skeleton together constitute a battery green body, which is formed by high-temperature sintering to obtain a solid oxide battery matrix composed of a porous fuel electrode support, a porous fuel electrode functional layer, a dense electrolyte layer and a porous air electrode skeleton.

[0011] Furthermore, the porous air electrode skeleton, the air electrode functional material (having electronic conductivity) and the modifying material (enhancing the catalytic ability of the air electrode or stabilizing the air electrode structure) together constitute an air modified electrode.

[0012] Furthermore, the air electrode functional material and the modifying material are synthesized by a sol-gel method, and the solution used for the synthesis is composed of precursors that can generate functional material components and modifying material components, which are fully mixed in a solution state.

[0013] Furthermore, the impregnation is to inject the mixed solution into the porous air electrode skeleton.

[0014] Furthermore, after the impregnation is completed, the mixture is allowed to stand or is heated to dry, so that the mixed solution is transformed into a gel.

[0015] Furthermore, the temperature at which the precursor mixed solution chemically reacts to generate the air electrode functional material and the modified material is lower than the operating temperature of the solid oxide battery.

[0016] Furthermore, when the solid oxide battery is in a prepared state, the air modified electrode does not contain components of air electrode functional materials and modifying materials, and is only composed of precursor materials that can generate these components through chemical reactions. When the battery is in use, during the process of heating from room temperature to operating temperature, the precursor undergoes a chemical reaction to generate components of electrode functional materials and modifying materials in situ.

[0017] The most commonly used air electrode material for solid oxide cells SOFC is LSM. In order to improve the electrochemical performance of LSM air electrode materials at medium and low temperatures, precious metal catalysts are doped into them. PdO, as a metal oxide catalyst, can increase the rate of oxygen reduction reaction at the air electrode, thereby improving the electrochemical performance of the air electrode. At the same time, because PdO is prone to agglomeration and growth at high temperatures, ZrO2 is added as a stabilizer.

[0018] The present invention can complete the battery preparation by impregnating the mixed solution without sintering, and at this time, the functional components in the air electrode have not formed a phase. During the use of the battery, since the working temperature is about 750°C, when the temperature rises to 400°C, the functional component precursors in the air electrode begin to react and form a phase, and the phase reaction of LSM, PdO and ZrO2 can be completed before reaching the working temperature.

[0019] Beneficial effects of the present invention:

[0020] The fuel electrode support of the present invention is prepared by a casting method, and the fuel electrode functional layer and the electrolyte are prepared by a screen printing method. After the electrolyte printing is completed, a layer of electrolyte material with a pore-forming agent added is printed, and a porous air electrode skeleton is obtained by high-temperature co-sintering. Subsequently, the air electrode is impregnated with a solution for synthesizing air electrode active substances and modifying substances, and can be injected multiple times after drying to increase its content. After the impregnation is completed, the battery production process is completed and can be used for stack assembly without sintering or roasting. The operating temperature of the stack is usually 650-750°C, which is higher than the phase formation temperature of the air electrode active substance. Therefore, during the heating process of the battery, the active substance of the air electrode can complete the phase synthesis process. This method can be used for the phase formation of a single type of active substance, or for the common phase formation of multiple active substances. The air electrode active component prepared by the in-situ phase formation method is usually a nano-scale particle, and the morphology will further change during the working process, including particle growth and migration, until a stable state is reached, and the electrochemical performance will also change accordingly.

[0021] The method for preparing the battery avoids multiple sintering and roasting during the electrode synthesis process, and only requires one high-temperature sintering, which can greatly shorten the preparation process, reduce the time and energy consumption of the preparation process, and thus reduce costs. Compared with the traditional preparation method, the electrolyte skeleton of the air electrode of the present invention is more closely combined with the dense electrolyte, which can reduce the resistance of oxygen ion conduction, and the air electrode is not easy to delaminate during operation.

[0022] When using this method to prepare batteries, the phase-forming temperature of the active substances in the electrodes is not higher than the battery operating temperature or the maximum temperature that the battery stack can withstand. For example, if the operating temperature of the battery stack is set to 750°C, the temperature may reach 800°C due to the heat release of the electrochemical reaction during operation. The operating temperatures of other components of the battery stack will match this temperature. Exceeding this temperature may cause problems such as sealing failure or metal deformation. Therefore, the applicable active substance phase-forming temperature should not be higher than 800°C. For active substances with a phase-forming temperature higher than the operating temperature of the battery stack, a phase-forming roasting process can be added to the production process to complete the synthesis process of multiple active substances in the electrode through a single phase-forming roasting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1This is a microscopic morphology image of Example 1 after the mixed solution is injected into the phase;

[0025] Figure 2 This is the XRD characterization diagram of the solid oxide battery of Example 1. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with embodiments.

[0027] Example 1

[0028] The NiO+YSZ fuel electrode support was prepared by the tape casting method, and then the NiO+YSZ fuel electrode functional layer and YSZ electrolyte were screen printed, and then a layer of porous YSZ air electrode skeleton was printed (a porous YSZ cathode skeleton was obtained by adding starch to the YSZ electrolyte), and sintered at 1400°C for 2h to complete the preparation of the solid oxide battery matrix.

[0029] According to (La 0.75 Sr 0.25 ) 0.8 Weigh lanthanum nitrate hexahydrate, strontium nitrate and manganese nitrate in a beaker, add ethylenediaminetetraacetic acid (EDTA), ammonia water and citric acid, the molar ratio of EDTA: NH3H2O: citric acid is 1:1:2, and then add ammonia water to adjust the pH of the solution to about 8, thereby preparing LSM solution. Take aqua regia and place it in a beaker, weigh palladium chloride and zirconium nitrate pentahydrate in a ratio of LSM: Pd: Zr = 1:1:1 and dissolve them in aqua regia. Then, measure the solution containing LSM and the solution containing Pd / Zr in a molar ratio of 10:1, mix them in a beaker, and mix them evenly in a magnetic stirrer. Inject the sol-gel precursor solution into the porous air electrode skeleton, and complete the battery preparation after drying.

[0030] Figure 1 This is a microscopic morphology of the embodiment after the air electrode precursor mixed solution is injected into the phase forming work. The coarse skeleton is YSZ, and the particles are a mixture of LSM, PdO and ZrO2.

[0031] Figure 2 This is the XRD characterization diagram of the solid oxide battery of this embodiment. It can be seen from the figure that all components have successfully formed phases without any impurities. The ZrO2 signal cannot be detected in the XRD due to its too small content.

[0032] Table 1 shows the ohmic impedance obtained by electrochemical testing of the solid oxide battery prepared by this method compared with the traditional mechanically mixed LSM+YSZ air electrode battery.

[0033] Table 1

[0034]

[0035] Example 2

[0036] The solid oxide cell matrix and air electrode precursor solution were prepared in the same manner as in Example 1, and the solution was injected into the air electrode skeleton and dried, and then injected and dried for a second time to electrochemically test its power output performance as a fuel cell working mode. Table 2 compares the performance of the solid oxide cell with a conventional mechanically mixed LSM+YSZ air electrode, the solid oxide cell with a single injection in Example 1, and the solid oxide cell with a double injection in Example 2.

[0037] Table 2

[0038]

[0039] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An in-situ synthesis method for a solid oxide battery modified electrode, characterized in that: The method comprises the following steps: preparing a fuel electrode support by a tape casting method, then screen printing a fuel electrode functional layer, an electrolyte and a porous air electrode skeleton composed of an electrolyte material, sintering the porous air electrode skeleton once, and then impregnating a mixed solution of a precursor of a synthetic air electrode functional material and a modifying material into the air electrode skeleton to complete the preparation of a solid oxide battery; The air electrode functional material is doped with a precious metal catalyst, the precious metal catalyst is a PdO metal oxide catalyst, and ZrO2 is added as a stabilizer; The air electrode functional material and the modified material are synthesized by a sol-gel method.

2. The in-situ synthesis method of a solid oxide battery modified electrode according to claim 1, characterized in that: The fuel electrode support is composed of an electrolyte and a metal; the fuel electrode functional layer has the same composition as the fuel electrode support; the electrolyte is a dense solid ceramic ion conductor; and the porous air electrode skeleton is prepared by adding a pore-forming agent to the electrolyte.

3. The in-situ synthesis method of a solid oxide battery modified electrode according to claim 1, characterized in that: The impregnation is to inject the mixed solution into the porous air electrode skeleton.

4. The in-situ synthesis method of a solid oxide battery modified electrode according to claim 1, characterized in that: After the impregnation is completed, the mixed solution is allowed to stand or is heated to dry, so that the mixed solution is transformed into a gel.

5. The in-situ synthesis method of a solid oxide battery modified electrode according to claim 1, characterized in that: The reaction temperature of the precursor mixed solution is lower than the operating temperature of the solid oxide battery.

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