Ceramic electrode material for solid oxide fuel cells and method for producing the same

Abstract

The application discloses a kind of ceramic electrode materials for solid oxide fuel cell, raw material includes nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1‑x O 2.75 And manganese oxide, the ratio of the nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1‑x O 2.75 And manganese oxide is (5-7) :(3-5);The nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1‑x O 2.75 It is perovskite phase, wherein 0 < x < 1;The manganese oxide is any one in Mn2O3, Mn3O4.The ceramic electrode material for solid oxide fuel cell of the application has high conductivity at low temperature, can make battery have lower operating temperature and considerable ion migration intensity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid oxide fuel cell material technology, in particular to a ceramic electrode material for solid oxide fuel cells and a preparation method thereof. BACKGROUND

[0002] Since the new century, the global energy supply situation is extremely nervous, the main energy coal and oil are non-renewable resources, and the degree of climate change is more and more severe. The energy conversion mode of fuel cell is very direct, is not restricted by the Carnot cycle, has small loss, and the efficiency can reach 50%. If the waste heat is recycled for power supply and water supply, the final efficiency can reach 80%. The fuel cell has less mechanical parts, good reliability and operability, small noise, and small occupation. Considering the above many advantages, and the irreversibility of energy shortage and environmental pollution, the fuel cell is widely concerned and researched.

[0003] According to the different methods of electrolyte, the fuel cell is divided into five categories, alkaline fuel cell (AFC, Alkaline Fuel Cell), phosphoric acid fuel cell (PAFC, Phosphorous Acid Fuel Cell), molten carbonate fuel cell (MCFC, Molten Carbonate Fuel Cell), proton exchange membrane fuel cell (PEMFC, Proton Exchange Membrane Fuel Cell) and solid oxide fuel cell (SOFC, Solid Oxide Fuel Cell). Among them, SOFC is favored by people because of high energy conversion rate, wide range of fuel selection and other advantages. The high temperature operation of SOFC at about 1000 DEG C will produce a series of problems, such as material decomposition, high temperature sealing difficulty, high energy consumption, high cost and the like. Lower operating temperature can reduce the difficulty of electrode material and auxiliary material selection and preparation, which is beneficial to cost reduction and prolonging the service life of the battery, slowing down the time of metal corrosion, and improving the durability of the battery. Developing electrode materials with high activity at low temperature has become the key to making the battery have lower operating temperature and considerable ion migration strength. SUMMARY

[0004] Based on the technical problems existing in the background art, the present application provides a ceramic electrode material for solid oxide fuel cells and a preparation method thereof.

[0005] The ceramic electrode material for solid oxide fuel cells provided by the present application has the advantages that the raw materials include nano metal oxides La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 And manganese oxide, the nano metal oxides La0.5 Ca 0.5 Fe x Mn 1-x O 2.75 and the molar ratio of the manganese oxide is (5-7):(3-5); the nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 is perovskite phase, wherein 0

[0006] The preparation method of the nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 may adopt a conventional method, for example, a sol-gel method. Preferably, the preparation method of the nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 includes:

[0007] S1, weighing lanthanum salt, calcium salt, iron salt and manganese salt according to a chemical formula, dissolving them in deionized water, then adding citric acid and ethylene glycol to fully dissolve, heating and stirring to react, then drying to obtain a dry gel;

[0008] S2, pre-burning the dry gel to obtain a powder;

[0009] S3, tabletting the powder, high-temperature calcining, and crushing to obtain.

[0010] Preferably, in S1, the number of moles of citric acid is (1-2.5) times the sum of the number of moles of metal ions, and the number of moles of ethylene glycol is (1-2.5) times the number of moles of citric acid.

[0011] Preferably, in S1, the heating and stirring reaction is at a pH of 3-6, a temperature of 50-90°C, and a time of 4-6h.

[0012] Preferably, in S2, the pre-burning is at a temperature of 650-1000°C for a time of 3-8h.

[0013] Preferably, in S3, the tabletting step is: first tabletting at a pressure of 3-4MPa for 20-40s, and then tabletting at a pressure of 10-20MPa for 2-10min; in S3, the high-temperature calcining is at a temperature of 1300-1550°C for a time of 1.5-5h.

[0014] The application discloses a preparation method of a ceramic electrode material for a solid oxide fuel cell. 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 and manganese oxide, and then adding a binder into the mixture and grinding uniformly, and then performing tabletting and sintering to obtain the ceramic electrode material.

[0015] Preferably, when the manganese oxide is Mn2O3, the sintering temperature is 500-600 DEG C and the sintering time is 1-3h; and when the manganese oxide is Mn3O4, the sintering temperature is 900-1100 DEG C and the sintering time is 1-3h.

[0016] Preferably, the tabletting is performed under the condition of a pressure of 3-4MPa for 20-40s, and then the tabletting is performed under the condition of a pressure of 10-15MPa for 2-10min.

[0017] Preferably, the amount of the binder is 10-20% of the mass of the mixture.

[0018] The application has the following beneficial effects:

[0019] The application discloses a preparation method of a ceramic electrode material for a solid oxide fuel cell. 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 and manganese oxide, and then adding a binder into the mixture and grinding uniformly, and then performing tabletting and sintering to obtain the ceramic electrode material. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 XRD images of the nanometer metal oxides La 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 synthesized by high-temperature calcination at different temperatures.

[0021] Figure 2 SEM images of ceramic electrode material samples prepared in Embodiment 2 and having different doping ratios of LCFM and Mn2O3.

[0022] Figure 3 XRD images of ceramic electrode material samples prepared in Embodiment 2 and having different doping ratios of LCFM and Mn2O3.

[0023] Figure 4 The conductivity test results of the ceramic electrode material samples with different LCFM and Mn203 doping ratios prepared in Example 2.

[0024] Figure 5 The Arrhenius curves of the polarization resistance of the ceramic electrode material samples with different LCFM and Mn203 doping ratios prepared in Example 2.

[0025] Figure 6 The SEM images of the ceramic electrode material samples with different LCFM and Mn304 doping ratios prepared in Example 3.

[0026] Figure 7 The XRD images of the ceramic electrode material samples with different LCFM and Mn304 doping ratios prepared in Example 3.

[0027] Figure 8 The conductivity test results of the ceramic electrode material samples with different LCFM and Mn304 doping ratios prepared in Example 3.

[0028] Figure 9 The Arrhenius curves of the polarization resistance of the ceramic electrode material samples with different LCFM and Mn304 doping ratios prepared in Example 3. DETAILED DESCRIPTION

[0029] Hereinafter, the technical solutions of the present application will be described in detail through specific embodiments.

[0030] Example 1

[0031] Preparation of nano metal oxide La 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 :

[0032] S1, La (NO3) 3·6H2O, CaCl2, Fe (NO3) 3·9H2O and MnCl2·4H2O are weighed according to the chemical formula, dissolved in 100 mL of deionized water, then citric acid and ethylene glycol are added for sufficient dissolution, ammonia water is added to adjust the pH to 4, stirred at 80°C for 5h, then placed in an oven and dried at 120°C for 10h to obtain a dry gel, wherein the molar number of citric acid is 1.2 times the sum of the molar number of metal ions, and the molar number of ethylene glycol is 1.5 times the molar number of citric acid;

[0033] S2, the dry gel is pre-fired at 850°C for 5h to obtain a powder;

[0034] S3, the powder is first pressed into a tablet under a pressure of 3.5 MPa for 30 s, then pressed into a tablet under a pressure of 12 MPa for 3 min, and then calcined at a high temperature for 2 h, and then ground to obtain the product.

[0035] In S3, when the high-temperature calcination temperature is 1100℃, 1200℃, 1300℃ and 1450℃ respectively, the XRD patterns of the synthesized nanometer metal oxides are as shown in Figure 1 .

[0036] From Figure 1 it can be seen that the series of powders synthesized by the sol-gel method are single phases. Temperature change only affects the intensity of the peaks and does not cause peak shift, so there is no phase change. At 1300℃, the perovskite forms a pure phase, but the diffraction peak type is relatively wide and the peak intensity is relatively weak, which is not the most ideal temperature. At 1450℃, the diffraction peak intensity increases and the crystallization degree tends to be perfect. The increase in temperature increases the grain size and makes the crystal type more complete, indicating that the sintering effect of the sample powder is good at this temperature.

[0037] Example 2

[0038] Preparation of ceramic electrode material for solid oxide fuel cell:

[0039] The nanometer metal oxide La 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 (1450℃) and Mn2O3 prepared in Example 1 are mixed to obtain a mixture, and then 15% of polyvinyl alcohol binder based on the mass of the mixture is added to the mixture and ground uniformly. The mixture is first pressed into a tablet under a pressure of 3.5 MPa for 30 s, then pressed into a tablet under a pressure of 12 MPa for 3 min, and then sintered at 550℃ for 2 h to obtain the product.

[0040] According to the above method, samples with a La 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 and Mn2O3 ratio of 10:0, 7:3, 5:5, 3:7 and 0:10 are prepared.

[0041] The prepared samples are characterized by morphology, and the obtained SEM images are as shown in Figure 2 . Among them, Figure 2 (a), Figure 2 (b), Figure 2 (c), Figure 2 (d), Figure 2 (e) are La 0.5 Ca 0.5 Fe0.5 Mn 0.5 O 2.75 SEM images of samples with Mn2O3 ratios of 10:0, 7:3, 5:5, 3:7, and 0:10. It can be seen that the samples have a certain degree of porosity and are relatively uniformly distributed, allowing gas and ions to diffuse and migrate between sample particles.

[0042] Figure 3 La nano metal oxide 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 XRD patterns of ceramic electrode materials prepared with different ratios of LCFM and Mn2O3 are shown. The upper and lower spectra are provided as references for pure LCFM and Mn2O3, respectively, sintered at 550℃. The figures show that the Mn2O3-doped spectra exhibit similar diffraction peak shapes. All peaks are characteristic superpositions of LCFM and Mn2O3, without any impurity peaks. This is because LCFM and Mn2O3 do not chemically react at 550℃, exhibiting the good chemical compatibility required for fuel cells.

[0043] A layer of silver paste was evenly applied to both sides of the sample, and then it was placed in an oven to dry for 20 minutes. After that, it was taken out and calcined in a muffle furnace at 700℃ for 30 minutes. Then, conductivity and electrochemical impedance spectroscopy were performed at a temperature range of 400-800℃.

[0044] The conductivity test results are shown in Table 1 and Figure 4 As shown:

[0045] Table 1. Conductivity σ of ceramic electrode materials synthesized with different ratios of LCFM and Mn2O3

[0046]

[0047] Table 1 and Figure 4The test results show that within the temperature range of 400℃ to 800℃, the conductivity of all components increases with increasing temperature, reaching its maximum at 800℃. Before 500℃, the conductivity gradually decreases with increasing Mn2O3 content. After 550℃, the conductivity of all ceramic electrode materials increases at a faster rate than before. The LCFM to Mn2O3 ratios of 7:3 and 5:5 show significantly increased conductivity, both higher than that of pure LCFM ceramic electrode material without Mn2O3 doping. The ratios of 3:7 and 0:10 show relatively slower increases, with conductivity lower than that of pure LCFM ceramic electrode material without Mn2O3 doping. The ceramic electrode material with an LCFM to Mn2O3 ratio of 7:3 exhibits the highest conductivity, which is more conducive to effective current concentration and reduces resistance loss during electron transport, resulting in excellent electrochemical performance; this is the optimal composition in this series.

[0048] The results of electrochemical impedance spectroscopy are shown in Table 2 and Figure 5 As shown:

[0049] Table 2 Activation energies of ceramic electrode materials synthesized with different ratios of LCFM and Mn2O3

[0050]

[0051] Table 2 and Figure 5 The test results show that lnσT and 1 / T have a good linear relationship. The activation energy is the smallest when the ratio of LCFM to Mn2O3 is 10:0, which is 0.35 eV. The activation energy of the component with the ratio of LCFM to Mn2O3 is the second largest.

[0052] In summary, when LCFM:Mn2O3 = 7:3, the conductivity is the highest and the activation energy is relatively low, making it the group with the best performance of ceramic electrode materials among all components.

[0053] Example 3

[0054] Preparation of ceramic electrode materials for solid oxide fuel cells:

[0055] The nano-metal oxide La prepared in Example 1 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 Mix (1450℃) and Mn3O4 to obtain a mixture. Then add 15% of polyvinyl alcohol binder by mass of the mixture and grind it evenly. First, press it into tablets for 30s under a pressure of 3.5MPa, then press it into tablets for 3min under a pressure of 12MPa, and then sinter it at 1000℃ for 2h to obtain the final product.

[0056] La 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 and Mn3O4 ratio of 10:0, 7:3, 5:5, 3:7, 0:10 samples.

[0057] The prepared samples were characterized by morphology, and the obtained SEM images are shown in Figure 6 , wherein, Figure 6 (a), Figure 6 (b), Figure 6 (c), Figure 6 (d), Figure 6 (e) are La 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 and Mn3O4 ratio of 10:0, 7:3, 5:5, 3:7, 0:10 samples SEM images. As can be seen from the figure, with the increase of Mn3O4 content, the particles are more and more clear, and the grain shape is regular.

[0058] Figure 7 XRD patterns of ceramic electrode materials prepared with different ratios of nano-metal oxide La 0.5 Ca 0.5 Fe 0.5 Mn 0.5 O 2.75 (LCFM) and Mn3O4, the upper and lower two spectra respectively show the pure LCFM and Mn3O4 phase formed at 1000℃ sintering temperature reference. It can be observed from the figure that the XRD pattern of the mixed powder has one more diffraction peak than the pure LCFM phase, which shows that the two cannot be completely physically superimposed. In addition, other diffraction peaks only change in strength, and there is no position shift.

[0059] A layer of silver paste was evenly applied on both sides of the sample, then placed in an oven for 20 min to dry, then taken out and calcined in a muffle furnace at 700℃ for 30 min, and then tested for conductivity and electrochemical impedance spectroscopy in the temperature range of 400-800℃.

[0060] The conductivity test results are shown in Table 3 and Figure 8 .

[0061] Table 3 Conductivity σ of ceramic electrode materials synthesized with different ratios of LCFM and Mn3O4

[0062]

[0063] Table 3 and Figure 8The test results show that in the temperature range of 400-800℃, the temperature rise of all components is proportional to the increase of conductivity. The conductivity of ceramic electrode materials with LCFM and Mn3O4 ratio of 7:3 and 5:5 is higher than that of pure LCFM ceramic electrode material without doping Mn3O4, and the conductivity of ceramic electrode materials with LCFM and Mn3O4 ratio of 3:7 and 0:10 is lower than that of pure LCFM ceramic electrode material without doping Mn3O4. The conductivity of the component with LCFM and Mn3O4 ratio of 7:3 is optimal among the five components, and the conductivity increases with the increase of temperature, and reaches the maximum at 800℃.

[0064] The electrochemical impedance spectroscopy test results are shown in Table 4 and Figure 9

[0065] Table 4 Activation energy of ceramic electrode materials synthesized with different ratios of LCFM and Mn3O4

[0066]

[0067] The test results of Table 4 and Figure 9 show that the linear relationship between lnσT and 1 / T is good. The activation energy value of the component with LCFM and Mn3O4 ratio of 7:3 is the smallest, which is 0.13eV, and the conductivity of this component is the highest, which meets the requirements of solid oxide battery on ceramic electrode materials. Compared with the optimal component of the series of Mn2O3 doped components, the conductivity of this component is higher and the activation energy is lower.

[0068] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.​

Claims

1. A ceramic electrode material for solid oxide fuel cells, characterized by, The raw material includes nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 and manganese oxide, the molar ratio of the nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 and manganese oxide is (5-7):(3-5); the nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 is perovskite phase, wherein 0 The preparation method of the ceramic electrode material for solid oxide fuel cell is as follows: mixing nano metal oxides La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 and manganese oxide to obtain a mixture, then adding a binder to the mixture and grinding uniformly, and then pressing and sintering to obtain the product; when the manganese oxide is Mn2O3, the sintering temperature is 500-600 DEG C and the sintering time is 1-3h; when the manganese oxide is Mn3O4, the sintering temperature is 900-1100 DEG C and the sintering time is 1-3h.

2. The ceramic electrode material for solid oxide fuel cells according to claim 1, characterized by, The nano metal oxide La 0.5 Ca 0.5 Fe x Mn 1-x O 2.75 The preparation method comprises the following steps: S1, according to chemical formula, lanthanum salt, calcium salt, iron salt, manganese salt is dissolved in deionized water, then citric acid and ethylene glycol are added and fully dissolved, heated and stirred, then dried to obtain dry gel; S2, the dry gel is pre-fired to obtain powder; S3, the powder is tableted, high-temperature calcined, and crushed to obtain.

3. The ceramic electrode material for solid oxide fuel cells according to claim 2, characterized by In S1, the mole number of citric acid is (1-2.5) times of the sum of the mole number of metal ions, and the mole number of ethylene glycol is (1-2.5) times of the mole number of citric acid.

4. The ceramic electrode material for solid oxide fuel cells according to claim 2, characterized by, In S1, the pH of the heated and stirred reaction is 3-6, the temperature is 50-90℃, and the time is 4-6h.

5. The ceramic electrode material for solid oxide fuel cells according to claim 2, characterized by, In S2, the pre-firing temperature is 650-1000℃, and the time is 3-8h.

6. The ceramic electrode material for solid oxide fuel cells according to claim 2, characterized by, In S3, the tableting step is: first tableting under the condition of 3-4MPa for 20-40s, and then tableting under the condition of 10-20MPa for 2-10min; In S3, the high-temperature calcining temperature is 1300-1550℃, and the time is 1.5-5h.

7. The ceramic electrode material for solid oxide fuel cells according to claim 1, characterized by, The tableting step is: first tableting under the condition of 3-4MPa for 20-40s, and then tableting under the condition of 10-15MPa for 2-10min.

8. The ceramic electrode material for solid oxide fuel cells according to claim 1, characterized by, The amount of the binder is 10-20% of the mass of the mixture.

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