A high-performance, heat-cycle-resistant composite nano-air electrode and its preparation method

Abstract

The present invention discloses a high-performance, heat-resistant and cycle-resistant composite nano-air electrode and its preparation method, which is composed of La 1‑ x Sr x CoO 3‑δ and Co3O4, SrCO3, SrCoO 2.5 , LaSrCoO4. The preparation process is as follows: (1) dissolving La(NO3)3·6H2O, Sr(NO3)2, Co(NO3)3·6H2O, citric acid, and ethylenediaminetetraacetic acid in deionized water by adjusting the pH with ammonia water; heating and stirring until a gel is obtained; the gel is first dried and then calcined to obtain a composite nano-air electrode powder. (2) The powder is mixed with a binder to form an electrode slurry, which is then printed on the electrolyte surface of the battery; after drying, a high-performance, high-thermal cycle stability composite nano-air electrode is obtained. The present invention can prepare nano-sized composite air electrodes at low cost and exhibit outstanding electrochemical performance and thermal cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell catalytic material preparation, and in particular relates to a high-performance, heat-cycle-resistant composite nano air electrode and a preparation method thereof. Background Art

[0002] To address the global energy crisis and global warming, there is an urgent need to develop high-efficiency energy conversion devices to support the efficient utilization and regeneration of renewable energy. Solid oxide cells (SOCs) are highly efficient, all-solid-state electrochemical energy conversion devices that enable the efficient utilization and regeneration of renewable energy. SOCs consist of three components: a fuel electrode, an electrolyte, and an air electrode. The slow oxygen reduction / evolution reaction (ORR / OER) kinetics of the air electrode are a major obstacle to their commercialization.

[0003] Cobalt-containing perovskite air electrodes have mixed electron / ion conductivity and can extend the reaction active sites to the entire electrode area, thus having excellent catalytic performance. 1-x Sr x CoO 3-δ (LSC) has commercial prospects. However, LSC has a high thermal expansion coefficient, which is not compatible with commonly used electrolyte materials. During long-term operation and thermal cycling, interfacial delamination or electrode rupture is prone to occur, resulting in battery performance degradation. In order to improve the catalytic performance of LSC and solve the problem of high thermal expansion coefficient, the electrode catalytic activity can be improved by preparing a composite nanostructured electrode, and the thermal expansion coefficient can be balanced by introducing a material with low thermal expansion coefficient into the electrode, and the interaction between the two phases can be enhanced to suppress the adverse effects of thermal expansion coefficient mismatch (Song YS, ChenY B, Wang W, et al. Self-assembled triple-conducting nanocomposite as a superior protonic ceramic fuel cell cathode[J]. Joule, 2019, 3(11): 2842-2853). Therefore, how to obtain a composite nanoelectrode with fine structure and strong interaction is a major challenge to improve the performance and thermal cycling stability of LSC electrodes. Summary of the Invention

[0004] To address this issue, the present invention discloses a high-performance, heat-cycle-resistant composite nano-air electrode and its preparation method. This method is simple, and the resulting composite air electrode not only exhibits a fine structure but also exhibits strong interactions between its phases, enhancing the electrode's electrocatalytic performance and thermal cycling stability.

[0005] The electrode composition is La 1-x Sr xCoO 3-δ and Co3O4, SrCO3, SrCoO 2.5 , a complex of one or more of LaSrCoO4; wherein x is 0.2~1.

[0006] The preparation steps of the electrode are as follows:

[0007] (1) La(NO3)3·6H2O, Sr(NO3)2, Co(NO3)3·6H2O, citric acid, and ethylenediaminetetraacetic acid were dissolved in deionized water by stirring and adjusting the pH with ammonia water; then heated and stirred until a gel was obtained; the gel was dried at a certain temperature and then calcined at a temperature below t°C to obtain a composite nano-air electrode powder; where t is the temperature at which the single-phase La 1-x Sr x CoO 3-δ Minimum temperature required.

[0008] (2) The composite nano-air electrode powder is mixed with a binder to form an electrode slurry, which is then screen-printed on the electrolyte surface of the battery; after drying at a certain temperature without the need for traditional high-temperature sintering, the thermally cycle-stable solid oxide battery composite nano-air electrode is obtained.

[0009] Furthermore, in step (1), the pH value of the ammonia solution is adjusted to 2-10.

[0010] Furthermore, in step (1), the molar ratio of La(NO3)3·6H2O:Sr(NO3)2:Co(NO3)3·6H2O is (0.01~1):(0.01~1):(1~1.5).

[0011] Furthermore, in step (1), the molar ratio of citric acid to ethylenediaminetetraacetic acid is (0.1-2.5):(0.1-2).

[0012] Furthermore, in step (1), the molar ratio of EDTA to metal cations in the solution is (0.1-10):1.

[0013] Furthermore, in step (1), the heating and stirring temperature is 50-500°C.

[0014] Furthermore, in step (1), the drying temperature of the gel is 50-500° C., and the drying time is 0.1-50 hours.

[0015] Furthermore, in step (1), a single-phase La is formed. 1-x Sr x CoO 3-δ The minimum temperature required is determined by the following criteria: when the powder is calcined above this temperature, only La 1-x Srx CoO 3-δ The XRD spectrum of the powder calcined below this temperature contains the diffraction peaks of the La phase. 1-x Sr x CoO 3-δ The diffraction peaks of the phase also exist, including Co3O4, SrCO3, SrCoO 2.5 , diffraction peaks of one or more phases in LaSrCoO4.

[0016] Furthermore, in step (2), the binder is terpineol dissolved with ethyl cellulose, wherein the ethyl cellulose accounts for 0.1% to 8% of the binder mass;

[0017] Furthermore, in step (2), the mass ratio of the composite nano air electrode powder to the binder is 1:(0.1~5).

[0018] Furthermore, in step (2), the drying temperature is 50-200° C., and the drying time is 0.1-12 hours.

[0019] The present invention has the following advantages:

[0020] 1. The composite nano-air electrode disclosed in the present invention not only has a fine structure, but also has strong interactions between the phases.

[0021] 2. The composite nano air electrode disclosed in the present invention has high performance and high thermal cycle stability.

[0022] 3. The preparation method of the composite nano-air electrode provided by the present invention has low equipment requirements, simple and stable process, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : This is the XRD pattern and Rietveld refinement result of the composite nano-air electrode powder obtained in this example;

[0024] Figure 2 is a SEM morphology of the surface of the composite nano-air electrode obtained in this example;

[0025] Figure 3 is a discharge curve diagram of an anode-supported battery having a composite nano-air electrode obtained in this embodiment at 750°C;

[0026] Figure 4 This is a thermal cycle stability diagram of an anode-supported battery having a composite nano-air electrode obtained in this embodiment;

[0027] Figure 5 is the SEM morphology of the single-phase LSC air electrode surface;

[0028] Figure 6is the discharge curve of the anode-supported cell with a single-phase LSC air electrode at 750°C;

[0029] Figure 7 Figure 2 is a thermal cycling stability diagram of an anode-supported cell with a single-phase LSC air electrode. DETAILED DESCRIPTION

[0030] The present invention is further described with reference to the following specific examples, but its protection scope is not limited to the following examples.

[0031] Embodiment 1:

[0032] (1) La(NO3)3·6H2O, Sr(NO3)2, Co(NO3)3·6H2O, citric acid, and ethylenediaminetetraacetic acid were placed in a beaker at a molar ratio of 0.6:0.4:1:3:2, deionized water was added, and the pH of the solution was adjusted to 6 with ammonia water. The raw materials were stirred continuously to completely dissolve.

[0033] (2) The solution obtained in step (1) was stirred continuously at 250°C until a gel was obtained. The gel was dried at 180°C for 12 hours and then calcined at 850°C for 3 hours to obtain a product having LSC, SrCoO 2.5 , SrCO3 three-phase composite nano air electrode powder.

[0034] (3) The composite nano-air electrode powder was mixed with a pine alcohol binder containing 4% ethyl cellulose in a mass ratio of 1:0.667 to prepare an electrode slurry.

[0035] (4) The electrode slurry is screen-printed on the electrolyte surface and dried at 150°C for 1 hour without the need for traditional high-temperature sintering to obtain a composite nano-air electrode.

[0036] Figure 1 The XRD pattern and Rietveld refinement results of the composite nano-air electrode powder obtained in this example are shown. XRD shows that LSC, SrCoO 2.5 The Rietveld refinement results show that the three phases account for 85%, 10.2% and 4.8% of the total mass of the powder, respectively.

[0037] Figure 2 This is a SEM image of the surface of the composite nano-air electrode obtained in this example. As shown in the figure, the average particle size of the electrode particles is only 75±21 nm.

[0038] Figure 3 The discharge curve of the anode-supported battery with the composite nano-air electrode obtained in this example at 750°C is shown in the figure. As shown in the figure, the maximum power density of the battery at 750°C reaches 1.56 W·cm-2 .

[0039] Figure 4 The thermal cycling stability of the anode-supported battery with the composite nano-air electrode obtained in this example is shown in the figure. -1 The attenuation rate of the heating and cooling rate is 0.57% after 24 cycles between 500-750℃.

[0040] Figure 5 This is the SEM morphology of the surface of the single-phase LSC air electrode. As shown in the figure, the average particle size of the electrode particles is only 116±43 nm, which is significantly higher than Figure 2 The average particle size shown in FIG. 4 illustrates that the method of the present invention can significantly refine the electrode structure.

[0041] Figure 6 The discharge curve of the anode-supported battery with a single-phase LSC air electrode at 750°C is shown in the figure. As shown in the figure, the maximum power density of the battery at 750°C reaches 0.91 W·cm -2 , significantly lower than Figure 3 The maximum power density shown in FIG1 indicates that the method of the present invention can significantly increase the electrode performance.

[0042] Figure 7 The thermal cycling stability of the anode-supported battery with a single-phase LSC air electrode is shown in the figure. -1 The attenuation rate of the heating and cooling rate was 2.54% after 24 cycles between 500-750℃, which was significantly higher than Figure 4 The decay rate shown indicates that the method of the present invention can significantly increase the thermal cycling stability of the electrode.

[0043] Example 2:

[0044] (1) La(NO3)3·6H2O, Sr(NO3)2, Co(NO3)3·6H2O, citric acid, and ethylenediaminetetraacetic acid were placed in a beaker at a molar ratio of 0.6:0.4:1:3:2, deionized water was added, and the pH of the solution was adjusted to 6 with ammonia water. The raw materials were stirred continuously to completely dissolve.

[0045] (2) The solution obtained in step (1) was stirred continuously at 250°C until a gel was obtained. The gel was dried at 180°C for 12 hours and then calcined at 750°C for 3 hours to obtain a composite material having LSC, SrCoO 2.5 , SrCO3 three-phase composite nano air electrode powder.

[0046] (3) The composite nano-air electrode powder was mixed with a pine alcohol binder containing 4% ethyl cellulose in a mass ratio of 1:0.667 to prepare an electrode slurry.

[0047] (4) The electrode slurry is screen-printed on the electrolyte surface and dried at 150°C for 1 hour without the need for traditional high-temperature sintering to obtain a composite nano-air electrode.

[0048] Example 3:

[0049] (1) La(NO3)3·6H2O, Sr(NO3)2, Co(NO3)3·6H2O, citric acid, and ethylenediaminetetraacetic acid were placed in a beaker at a molar ratio of 0.6:0.4:1:3:2, deionized water was added, and the pH of the solution was adjusted to 6 with ammonia water. The raw materials were stirred continuously to completely dissolve.

[0050] (2) The solution obtained in step (1) was continuously stirred at 250°C until a gel was obtained. The gel was dried at 180°C for 12 hours and then calcined at 650°C for 3 hours to obtain a composite nano-air electrode powder having three phases of LSC, SrCO3, and Co3O4.

[0051] (3) The composite nano-air electrode powder was mixed with a pine alcohol binder containing 4% ethyl cellulose in a mass ratio of 1:0.667 to prepare an electrode slurry.

[0052] (4) The electrode slurry is screen-printed on the electrolyte surface and dried at 150°C for 1 hour without the need for traditional high-temperature sintering to obtain a composite nano-air electrode.

[0053] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a high-performance, heat-cycle-resistant composite nano-air electrode, characterized by: a. The electrode composition is La 1-x Sr x CoO 3-δ and Co3O4, SrCO3, SrCoO 2.5 , LaSrCoO4 or more of the complex; wherein x is 0.2 to 1; b. Preparation steps: (1) La(NO3)3·6H2O, Sr(NO3)2, Co(NO3)3·6H2O, citric acid, and ethylenediaminetetraacetic acid were dissolved in deionized water by stirring and adjusting the pH with ammonia water; the mixture was then heated and stirred until a gel was obtained; the gel was first dried and then calcined at 650-850°C to obtain a composite nano-air electrode powder; (2) The composite nano-air electrode powder is mixed with a binder to form an electrode slurry, which is then screen-printed on the electrolyte surface of the battery; after drying, a high-performance, high-thermal cycle-stable composite nano-air electrode is obtained.

2. The preparation method according to claim 1, wherein: In step (1), the pH value of the ammonia solution is adjusted to 2-10.

3. The preparation method according to claim 1, wherein: In step (1), the molar ratio of La(NO3)3·6H2O:Sr(NO3)2:Co(NO3)3·6H2O is (0.01~1):(0.01~1):(1~1.5).

4. The preparation method according to claim 1, wherein: In step (1), the molar ratio of citric acid to ethylenediaminetetraacetic acid is (0.1-2.5):(0.1-2).

5. The preparation method according to claim 1, wherein: In step (1), the molar ratio of EDTA to metal cations in the solution is (0.1-10):

1.

6. The preparation method according to claim 1, wherein: In step (1), the heating and stirring temperature is 50~500℃.

7. The preparation method according to claim 1, wherein: In step (1), the drying temperature of the gel is 50-500°C, and the drying time is 0.1-50 h.

8. The preparation method according to claim 1, wherein: In step (2), the mass ratio of the composite nano air electrode powder to the binder is 1:(0.1~5); the drying temperature is 50~200℃, and the drying time is 1~12 h.

9. A high-performance, heat-cycle-resistant composite nano-air electrode prepared by the preparation method according to any one of claims 1 to 8.

Images