A cathode material for molten carbonate fuel cells, a cathode electrode sheet and a method for manufacturing the same

Abstract

The application belongs to the technical field of molten carbonate fuel cells, and particularly relates to a high-performance cathode material for a molten carbonate fuel cell, a cathode electrode sheet prepared based on the cathode material, and a fuel cell. The cathode material LiFeO2@GO for the molten carbonate fuel cell can replace traditional NiO as a cathode material for a molten carbonate fuel cell, has good conductivity and stable electrical properties, and has better stability in electrolyte salt than NiO, thereby effectively prolonging the service life of the cathode electrode sheet and the fuel cell and meeting the needs of large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of molten carbonate fuel cell technology, specifically relating to a high-performance cathode material for molten carbonate fuel cells, and further disclosing its preparation method, as well as cathode electrodes and fuel cells prepared based on the cathode material. Background Technology

[0002] Molten carbonate fuel cells (MCFCs), as a type of chemical device that directly converts the chemical energy of fuel into electrical energy, have advantages such as high efficiency, cleanliness, wide availability of fuel sources, and no need to use precious metals as catalysts, making them one of the most promising power generation devices.

[0003] In molten carbonate fuel cells, an ideal cathode material should possess good toughness and mechanical strength, as well as excellent resistance to deformation, dissolution, and electrochemical performance. Traditional molten carbonate fuel cells typically use nickel oxide (NiO) as the cathode material; however, nickel oxide is readily and slowly dissolved in molten carbonate electrolytes, leading to the formation of NiO in the electrolyte. 2+ Ni 2+ In the electrolyte, it is reduced to Ni metal by hydrogen at the anode. Ni metal particles accumulate in the electrolyte and eventually form electron channels, causing Ni short circuits. This has always been a major factor affecting the lifespan of molten carbonate fuel cells and hindering their further large-scale commercialization.

[0004] To address this issue, in traditional molten carbonate fuel cell manufacturing processes, Mg or Fe is typically added during cathode material synthesis to modify the cathode material, resulting in a composite cathode material that reduces the dissolution rate of NiO in the electrolyte. For example, Chinese patent CN105845887A discloses a solid-phase synthesis method for lithium-ion battery anode material γ-LiFeO2. This method uses Li2CO3 and Fe2O3 as raw materials, which are mixed, pressed into sheets, and then calcined at 550-650℃ to obtain the desired γ-LiFeO2. While this anode material avoids the problem of nickel oxide dissolving in the molten carbonate electrolyte, the poor conductivity of LiFeO2 somewhat affects battery performance.

[0005] Therefore, developing a cathode material with strong conductivity and good electrode stability is of great significance for the development and utilization of molten carbonate fuel cells. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a high-performance cathode material for molten carbonate fuel cells, wherein the cathode material uses LiFeO2@GO to replace the original NiO, and its stability in the electrolyte salt is better than that of NiO, thereby extending the service life of the fuel cell and meeting the needs of large-scale industrial production.

[0007] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned high-performance cathode material for molten carbonate fuel cells;

[0008] The third technical problem to be solved by the present invention is to provide a molten carbonate fuel cell cathode electrode and a fuel cell based on the above-mentioned cathode material.

[0009] To address the aforementioned issues, a method for preparing a cathode material for molten carbonate fuel cells includes a step of preparing LiFeO2 by calcining Li2CO3 and Fe2O3 as raw materials at 550-650℃, and a step of adding graphene oxide powder and carbonizing it at 800-900℃, thereby obtaining the desired cathode material LiFeO2@GO.

[0010] Specifically, the mass ratio of Li2CO3, Fe2O3, and GO is 1:0.3-0.7:2-3;

[0011] Preferably, the mass ratio of Li2CO3, Fe2O3, and GO is 1:0.5:2.5;

[0012] Preferably, the method further includes a step of synthesizing graphene oxide by hydrothermal oxidation using graphite as a raw material.

[0013] The present invention also discloses a cathode material for a fuel cell prepared by the above method.

[0014] The present invention also discloses a cathode electrode for a fuel cell prepared by the above method, comprising the following steps:

[0015] (1) A mixed slurry was prepared using Li2CO3 and Fe2O3 as raw materials, and the mixed slurry was slit coated and dried to obtain an initial electrode sheet;

[0016] (2) The initial electrode sheet is calcined and annealed at 400-650℃ under a protective atmosphere to obtain a sample sheet for later use;

[0017] (3) Take graphene oxide powder to prepare GO slurry, and place the sample in the GO slurry for wetting treatment;

[0018] (4) The sample sheet after being soaked is dried and calcined at 800-900℃ in a high oxygen atmosphere to obtain the desired LiFeO2@GO electrode sheet;

[0019] (5) The LiFeO2@GO electrode is hot-pressed to obtain the desired cathode electrode.

[0020] Specifically, in step (1), the drying step includes drying at 40-50℃ for 6-10 hours and drying at 70-90℃ for 1-3 hours.

[0021] Specifically, in step (1), the mass concentration of the mixed slurry is 18-23 wt%.

[0022] Preferably, the mass concentration of the mixed slurry is 21 wt%.

[0023] Preferably, the process further includes the step of adding a dispersant to the Li2CO3 and Fe2O3 to prepare a mixed slurry and then fully dispersing it;

[0024] Preferably, the dispersant comprises sodium carboxymethyl cellulose;

[0025] The dispersant is added at a ratio of 1.5-2 wt% based on the total amount of the Li2CO3 and Fe2O3 raw materials;

[0026] More preferably, the dispersant is added at a ratio of 1.87 wt% based on the total amount of the Li2CO3 and Fe2O3 raw materials.

[0027] Specifically, the mixing step of the slurry and the dispersant can be carried out in one go or by adding the slurry to the dispersant system in batches. Based on conventional experience, different amounts of the mixture added will have a certain difference in slurry viscosity. Taking the system in this case as an example, the viscosity of the slurry obtained by adding the mixture in one go is about 10 cp higher than that obtained by adding it in batches. The viscosity of the slurry obtained by adding it in one go is about 73 cp, while the viscosity obtained by adding it in batches is about 63 cp. The control of the slurry viscosity value has a slight impact on the initial thickness of the electrode sheet, but does not affect the technical effect of the cathode electrode sheet. Therefore, the preferred method of this invention is to mix the slurry with the dispersant system in batches.

[0028] Preferably, in step (1), the coating thickness of the coating machine is set to 1.2-1.5 mm.

[0029] Specifically, in step (2), the calcination step includes calcining at 400-450°C for 0.5-2 hours under a protective atmosphere, and calcining at 550-650°C for 6-10 hours.

[0030] Specifically, in step (3), the solvent used to prepare the GO slurry includes isopropanol and / or ethanol;

[0031] Preferably, the mass concentration of the GO slurry is 10-14 wt%.

[0032] More preferably, the GO slurry has a mass concentration of 12 wt%.

[0033] Preferably, the method further includes the step of preparing the desired graphene oxide powder using graphite as a raw material;

[0034] Preferably, the preparation method of the graphene oxide is based on the Hummers method, which uses a strong oxidant to chemically oxidize graphite in a concentrated sulfuric acid system via an ice bath-warm water bath-hot water bath, followed by freeze drying to obtain the desired graphene oxide (GO).

[0035] The present invention also discloses a cathode electrode for a molten carbonate fuel cell, wherein the cathode electrode comprises the above-described cathode material, or the cathode electrode is prepared by the above-described method.

[0036] The present invention also discloses a molten carbonate fuel cell prepared by the above method, including the cathode electrode for the above molten carbonate fuel cell.

[0037] The high-performance cathode material for molten carbonate fuel cells described in this invention utilizes Li₂CO₃ and Fe₂O₃ as raw materials to prepare LiFeO₂ through calcination, and then adds graphene oxide and carbonizes it at high temperature to obtain LiFeO₂@GO. This composite material, LiFeO₂@GO, can replace traditional NiO as the cathode material for molten carbonate fuel cells. It not only has better conductivity and electrical stability, but also exhibits superior stability in electrolyte salts compared to NiO, effectively extending the service life of the fuel cell and meeting the needs of large-scale industrial production.

[0038] The high-performance cathode electrode for molten carbonate fuel cells described in this invention, based on traditional electrode preparation methods, involves preparing a LiFeO2 sample by coating and calcining Li2CO3 and Fe2O3, then impregnating and loading it onto graphene oxide, followed by calcination to form a LiFeO2@GO composite electrode. Using graphene oxide as a carrier, the prepared LiFeO2@GO composite electrode effectively improves electrode stability and high conductivity.

[0039] The method for preparing high-performance electrodes for molten carbonate fuel cells described in this invention, on the one hand, uses LiFeO2@GO to replace the original NiO, avoiding battery failure caused by cathode material dissolution and extending the service life of the fuel cell; on the other hand, it uses graphene oxide as a carrier, which improves the stability and conductivity of the electrode and meets the needs of large-scale industrial production.

[0040] The method for preparing high-performance electrodes for molten carbonate fuel cells described in this invention utilizes an alloy-supported graphite carrier, which has a relatively simple preparation process, can save on the cost of active ingredients, and can be mass-produced, thus having high industrial application value. Attached Figure Description

[0041] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the Li dissolution process described in Comparative Example 1;

[0043] Figure 2 The curves show the change of current density over time at 0.7V for different electrodes in the experimental example.

[0044] Figure 3 The figures show the voltage versus current density curves for different electrodes in the experimental example.

[0045] Figure 4 The result is the NiO electrode described in the experimental example after Li treatment;

[0046] Figure 5 The result is the LiFeO2@GO electrode described in the experimental example after Li treatment. Detailed Implementation

[0047] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0048] Where specific experimental steps or conditions are not specified in the examples, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Materials or instruments whose manufacturers are not specified are all conventional products that can be purchased.

[0049] Preparation Example 1

[0050] Using graphite powder as raw material, the method is improved based on the common Hummers process. The graphite is chemically oxidized in a concentrated sulfuric acid system by first using potassium permanganate as a strong oxidant in an ice bath at -5 to 0°C, then in a warm water bath at 30 to 40°C, and finally in a hot water bath at 90 to 110°C. After centrifuging the aqueous solution, it is dried in a freeze dryer to obtain the desired graphene oxide (GO).

[0051] The preparation method of LiFeO2@GO described in this example includes the following steps:

[0052] Li2CO3 and Fe2O3 were used as raw materials. After being mixed evenly, they were placed in a quartz boat and calcined at 600℃ for 48 hours in a tube furnace under a saturated nitrogen atmosphere. After annealing, LiFeO2 was obtained. Then, graphene oxide powder was added and carbonized again at 850℃ for 2 hours to obtain the desired cathode material LiFeO2@GO. The mass ratio of Li2CO3, Fe2O3 and GO was 1:0.5:2.5.

[0053] Preparation Example 2

[0054] Using graphite powder as raw material, the method is improved based on the common Hummers process. The graphite is chemically oxidized in a concentrated sulfuric acid system by first using potassium permanganate as a strong oxidant in an ice bath at -5 to 0°C, then in a warm water bath at 30 to 40°C, and finally in a hot water bath at 90 to 110°C. After centrifuging the aqueous solution, it is dried in a freeze dryer to obtain the desired graphene oxide (GO).

[0055] The preparation method of LiFeO2@GO described in this example includes the following steps:

[0056] Li2CO3 and Fe2O3 were used as raw materials. After being mixed evenly, they were placed in a quartz boat and calcined at 550°C for 48 hours in a tube furnace under a saturated nitrogen atmosphere. After annealing, LiFeO2 was obtained. Then, graphene oxide powder was added and carbonized again at 800°C for 2 hours to obtain the desired cathode material LiFeO2@GO. The mass ratio of Li2CO3, Fe2O3 and GO was 1:0.3:3.

[0057] Preparation Example 3

[0058] Using graphite powder as raw material, the method is improved based on the common Hummers process. The graphite is chemically oxidized in a concentrated sulfuric acid system by first using potassium permanganate as a strong oxidant in an ice bath at -5 to 0°C, then in a warm water bath at 30 to 40°C, and finally in a hot water bath at 90 to 110°C. After centrifuging the aqueous solution, it is dried in a freeze dryer to obtain the desired graphene oxide (GO).

[0059] The preparation method of LiFeO2@GO described in this example includes the following steps:

[0060] Li2CO3 and Fe2O3 were used as raw materials. After being mixed evenly, they were placed in a quartz boat and calcined at 650°C for 48 hours in a tube furnace under a saturated nitrogen atmosphere. After annealing, LiFeO2 was obtained. Then, graphene oxide powder was added and carbonized again at 900°C for 2 hours to obtain the desired cathode material LiFeO2@GO. The mass ratio of Li2CO3, Fe2O3 and GO was 1:0.7:2.

[0061] Example 1

[0062] The method for preparing the high-performance cathode sheet of the molten carbonate fuel cell described in this embodiment includes the following steps:

[0063] (1) Take 16g of Li2CO3 and Fe2O3 in a mass ratio of 2:1 and grind them in a ball mill at 800rpm for 2h to fully mix the raw materials. Then, add 4g of the mixture to 60g of 0.5% sodium carboxymethyl cellulose aqueous solution in 4 portions and stir and disperse in a disperser for 8h to obtain a mixed slurry with a mass concentration of 21wt%. The dispersant sodium carboxymethyl cellulose is added at a ratio of 1.87wt% based on the total amount of Li2CO3 and Fe2O3 raw materials.

[0064] The mixed slurry was uniformly coated on a slit coating plate with a thickness of 1.2 mm, and then placed in a drying oven to dry at 45°C for 8 hours and 80°C for 2 hours to obtain the initial electrode sheet. The thickness of the dried cathode electrode was 0.45 mm.

[0065] (2) The sample was then placed flat on a quartz boat and transferred into a tube furnace. It was calcined in a saturated nitrogen atmosphere, with the temperature rising from room temperature to 425°C and held for 1 hour. The temperature was then raised from 425°C to 600°C and held for 8 hours. The electrode sample was then annealed to obtain the sample.

[0066] (3) Prepare a GO slurry with a mass concentration of 12wt% by mixing graphene oxide and isopropanol, and immerse the above electrode sample in the GO slurry for 2 hours;

[0067] (4) After the sample is soaked, it is placed in a vacuum drying oven at 70°C for drying, and then transferred to a tube furnace and calcined at 850°C for 4 hours in a high oxygen atmosphere. After annealing, the cathode electrode LiFeO2@GO is obtained.

[0068] (5) The cathode LiFeO2@GO electrode sheet was held at 2MPa for 3 minutes in a hot press to obtain an electrode sheet with good flatness.

[0069] Example 2

[0070] The method for preparing the high-performance cathode sheet of the molten carbonate fuel cell described in this embodiment includes the following steps:

[0071] (1) Take 16g of Li2CO3 and Fe2O3 in a mass ratio of 2:1 and grind them in a ball mill at 800rpm for 2h to fully mix the raw materials. Then, divide the mixture into 4 portions, 5g for the first two portions and 3g for the last two portions, and add them to 60g of 0.4% sodium carboxymethyl cellulose aqueous solution. Stir and disperse in a disperser for 8h to obtain a mixed slurry with a mass concentration of 21wt%. The dispersant sodium carboxymethyl cellulose is added at a ratio of 1.5wt% based on the total amount of the Li2CO3 and Fe2O3 raw materials.

[0072] The mixed slurry was uniformly coated on a slit coating plate with a thickness of 1.3 mm, and then placed in a drying oven to dry at 40°C for 10 h and 70°C for 3 h to obtain the initial electrode sheet. The thickness of the dried cathode electrode was 0.4 mm.

[0073] (2) The sample was then placed flat on a quartz boat and transferred into a tube furnace. It was calcined in a saturated nitrogen atmosphere, with the temperature rising from room temperature to 400°C and held for 2 hours. Then the temperature was raised from 400°C to 550°C and held for 10 hours. The sample was then annealed to obtain the electrode sample.

[0074] (3) Prepare a GO slurry with a mass concentration of 10wt% by taking graphene oxide and isopropanol, and immerse the above electrode sample in the GO slurry for 2 hours;

[0075] (4) After the sample is soaked, it is placed in a vacuum drying oven at 70°C for drying, and then transferred to a tube furnace and calcined at 800°C for 3 hours in a high oxygen atmosphere. After annealing, the cathode electrode LiFeO2@GO is obtained.

[0076] (5) The cathode LiFeO2@GO was held at 2MPa for 3 minutes using a hot press to obtain a novel electrode sheet with good flatness.

[0077] Example 3

[0078] The method for preparing the high-performance cathode sheet of the molten carbonate fuel cell described in this embodiment includes the following steps:

[0079] (1) Take 16g of Li2CO3 and Fe2O3 in a mass ratio of 2:1 and grind them in a ball mill at 800rpm for 2h to fully mix the raw materials. Then, divide the mixture into 4 portions, 5g for the first two portions and 3g for the last two portions, and add them to 60g of ultrapure water. Stir and disperse the mixture in a disperser for 8h to obtain a mixed slurry with a mass concentration of 21wt%.

[0080] The mixed slurry was uniformly coated onto a slit coating plate with a thickness of 1.4 mm, and then dried in a drying oven at 48°C for 9 hours and 75°C for 2 hours to obtain the initial electrode sheet. The thickness of the dried cathode electrode was 0.5 mm.

[0081] (2) The sample was then placed flat on a quartz boat and transferred into a tube furnace. It was calcined in a saturated nitrogen atmosphere from room temperature to 440°C and held at that temperature for 1.5 hours. Then it was calcined from 440°C to 630°C and held at that temperature for 8 hours to obtain the annealed electrode sample.

[0082] (3) Prepare a GO slurry with a mass concentration of 11wt% by mixing graphene oxide and ethanol, and immerse the above electrode sample in the GO slurry for 2 hours;

[0083] (4) After the sample is soaked, it is placed in a vacuum drying oven at 70°C for drying, and then transferred to a tube furnace and calcined at 900°C for 2 hours in a high oxygen atmosphere. After annealing, the cathode electrode LiFeO2@GO is obtained.

[0084] (5) The cathode LiFeO2@GO was held at 2MPa for 3 minutes using a hot press to obtain a novel electrode sheet with good flatness.

[0085] Example 4

[0086] The method for preparing the high-performance cathode sheet of the molten carbonate fuel cell described in this embodiment includes the following steps:

[0087] (1) Take 16g of Li2CO3 and Fe2O3 in a mass ratio of 2:1 and grind them in a ball mill at 800rpm for 2h to fully mix the raw materials. Then, add 4g of the mixture to 60g of ultrapure water in 4 portions and stir and disperse in a disperser for 8h to obtain a mixed slurry with a mass concentration of 21wt%.

[0088] The mixed slurry was uniformly coated onto a slit coating plate with a thickness of 1.5 mm, and then placed in a drying oven to dry at 50°C for 6 hours and 90°C for 1 hour to obtain the initial electrode sheet. The thickness of the dried cathode electrode was 0.4 mm.

[0089] (2) The sample was then placed flat on a quartz boat and transferred into a tube furnace. It was calcined in a saturated nitrogen atmosphere from room temperature to 450°C and held at that temperature for 0.5 h. Then it was calcined from 450°C to 650°C and held at that temperature for 6 h to obtain the annealed electrode sample.

[0090] (3) Prepare a GO slurry with a mass concentration of 14wt% by mixing graphene oxide and ethanol, and immerse the above electrode sample in the GO slurry for 2 hours;

[0091] (4) After the sample is soaked, it is placed in a vacuum drying oven at 70°C for drying, and then transferred to a tube furnace for high-temperature calcination at 870°C for 4 hours in a high-oxygen atmosphere. After annealing, the cathode electrode LiFeO2@GO is obtained.

[0092] (5) The cathode LiFeO2@GO was held at 2MPa for 3 minutes using a hot press to obtain a novel electrode sheet with good flatness.

[0093] Example 5

[0094] The method for preparing the high-performance cathode sheet of the molten carbonate fuel cell described in this embodiment includes the following steps:

[0095] (1) Take 16g of Li2CO3 and Fe2O3 in a mass ratio of 2:1 and grind them in a ball mill at 800rpm for 2h to fully mix the raw materials. Then, add the mixture in 4 portions, 5g for the first two portions and 3g for the last two portions, to a 60g aqueous solution of 0.54% sodium carboxymethyl cellulose and disperse it in a disperser for 8h to obtain a mixed slurry with a mass concentration of 21wt%. The dispersant sodium carboxymethyl cellulose is added at a ratio of 2wt% based on the total amount of Li2CO3 and Fe2O3 raw materials.

[0096] The mixed slurry was uniformly coated on a slit coating plate with a thickness of 1.3 mm, and then placed in a drying oven to dry at 43°C for 7 hours and 73°C for 2 hours to obtain the initial electrode sheet. The thickness of the dried cathode electrode was 0.4 mm.

[0097] (2) The sample was then placed flat on a quartz boat and transferred into a tube furnace. It was calcined in a saturated nitrogen atmosphere from room temperature to 420°C and held for 1 hour. Then it was calcined from 420°C to 570°C and held for 7 hours to obtain the annealed electrode sample.

[0098] (3) Prepare a GO slurry with a mass concentration of 13wt% by mixing graphene oxide and ethanol, and immerse the above electrode sample in the GO slurry for 2 hours;

[0099] (4) After the sample is soaked, it is placed in a vacuum drying oven at 70°C for drying, and then transferred to a tube furnace and calcined at 830°C for 2 hours in a high oxygen atmosphere. After annealing, the cathode electrode LiFeO2@GO is obtained.

[0100] (5) The cathode LiFeO2@GO was held at 2MPa for 3 minutes using a hot press to obtain a novel electrode sheet with good flatness.

[0101] Comparative Example 1

[0102] The method for preparing the high-performance electrode of the molten carbonate fuel cell described in this comparative example is the same as that in Example 1, except that NiO is directly used as the cathode material to prepare the cathode electrode.

[0103] like Figure 1 As shown, NiO is slightly dissolved in molten carbonate electrolyte and becomes Ni in the electrolyte. 2+ Ni 2+ In the electrolyte, it is reduced to Ni metal by hydrogen gas at the anode. Ni metal particles accumulate in the electrolyte and eventually form an electron channel, causing a Ni short circuit.

[0104] Comparative Example 2

[0105] The preparation method of the cathode electrode in this comparative example is the same as that in Example 1, except that the impregnation and calcination composite steps of the graphene oxide are not performed.

[0106] The study found that without the addition of graphene oxide as a carrier, the conductivity of the electrode material and the initial performance of the battery were both lower than those of the product in Example 1.

[0107] Experimental Example

[0108] The performance of the LiFeO2@GO composite materials prepared in Example 2 and Comparative Example 1 were tested respectively.

[0109] 1. Performance Testing

[0110] (1) Electrochemical stability tests were conducted on NiO and LiFeO2@GO under the following conditions: anode H2 flow rate of 1.5 L / min, cathode CO2 flow rate of 1.0 L / min, O2 flow rate of 0.5 L / min, and voltage of 0.7 V. The results are as follows: Figure 2 As shown in the figure. The results showed that the initial current density of the LiFeO2@GO electrode was 120 mA / cm². 2 The initial current density of the NiO electrode is 80 mA / cm². 2 40mA / cm 2 From the overall trend of the curve, the LiFeO2@GO electrode showed almost no current decay in the first 10 minutes. After 50 minutes, the current density began to decrease slightly, and after 80 minutes, the current density was still 118 mA / cm². 2 The current density decreased by 1.6% compared to the initial value; the NiO electrode had a current density of 76 mA / cm² in the first 10 minutes. 2 Compared to the initial value, the current density decreased by 5%. As time increased, the current density continued to decrease, reaching 67 mA / cm² after 80 minutes. 2 The value decreased by 16.25% compared to the initial value; compared with the NiO electrode, LiFeO2@GO showed better stability.

[0111] (2) Under the conditions of H2 flow rate at the anode being 1.5 L / min, CO2 flow rate at the cathode being 1.0 L / min, and O2 flow rate being 0.5 L / min, the current density ranged from 0 to 140 mA / cm². 2 Ten sampling points were used to test the electrochemical performance of NiO and LiFeO2@GO. The results are as follows: Figure 3 As shown. The results showed that the onset voltage of NiO was higher than that of LiFeO2@GO, starting from 20 mA / cm². 2Subsequently, the NiO electrode voltage initially fell below that of LiFeO2@GO. With increasing current density, the NiO electrode voltage decreased significantly, while the LiFeO2@GO electrode voltage decreased slowly, reaching a low of 100 mA / cm². 2 At that time, the LiFeO2@GO electrode voltage was still higher than 0.8V, and at 140mA / cm 2 At that time, the NiO electrode voltage dropped too much and was not tested. Overall, the LiFeO2@GO electrode showed better performance.

[0112] 2. Solubility of molten carbonates in Lithium oxide

[0113] This experiment verifies whether the prepared LiFeO2@GO electrode material and the original NiO electrode material will be dissolved by molten carbonate Li.

[0114] A simulated molten carbonate fuel cell was operated at 650°C with oxygen introduced into the cathode, followed by annealing to observe the surface morphology of two catalytic electrodes. The results are shown in the appendix. Figure 4-5 As shown, where, Figure 4 NiO electrode, Figure 5 For LiFeO2@GO. It can be observed that... Figure 4 The shape shown has obvious cracks. Figure 5 The surface remains intact. The results show that the LiFeO2@GO electrode can overcome the Li-induced dissolution defects of existing NiO electrodes.

[0115] Obviously, the above embodiments and comparative examples are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a cathode material for a molten carbonate fuel cell, characterized in that, The process includes the steps of preparing LiFeO2 by calcining Li2CO3 and Fe2O3 at 550-650℃, and adding graphene oxide powder and carbonizing it at 800-900℃, thus obtaining the desired cathode material LiFeO2@GO. The mass ratio of Li2CO3, Fe2O3, and GO is 1:0.3-0.7:2-3.

2. The method for preparing the cathode material for a molten carbonate fuel cell according to claim 1, characterized in that, The mass ratio of Li2CO3, Fe2O3, and GO is 1:0.5:2.

5.

3. The method for preparing the cathode material for a molten carbonate fuel cell according to claim 1, characterized in that, The method also includes a step of synthesizing graphene oxide by hydrothermal oxidation using graphite as a raw material.

4. A cathode material for a molten carbonate fuel cell, characterized in that, The cathode material is prepared according to the method described in any one of claims 1-3.

5. A method for preparing a cathode electrode for a molten carbonate fuel cell, characterized in that, Includes the following steps: (1) A mixed slurry was prepared by adding water to Li2CO3 and Fe2O3 as raw materials, and the mixed slurry was applied by slit coating and dried to obtain an initial electrode sheet; (2) The initial electrode sheet is calcined at 400-650℃ under a protective atmosphere and annealed to obtain a sample sheet for later use; (3) Take graphene oxide powder to prepare GO slurry, and place the sample in the GO slurry for wetting treatment; (4) The sample sheet after impregnation is dried and calcined at 800-900℃ in a high oxygen atmosphere to obtain the desired LiFeO2@GO electrode sheet; (5) The LiFeO2@GO electrode is hot-pressed to obtain the desired cathode electrode; The mass ratio of Li2CO3, Fe2O3, and GO is 1:0.3-0.7:2-3.

6. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 5, characterized in that, In step (1), the drying step includes drying at 40-50℃ for 6-10 hours and drying at 70-90℃ for 1-3 hours.

7. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 5, characterized in that, In step (1), the mass concentration of the mixed slurry is 18-23 wt%.

8. The method for preparing a cathode electrode for a molten carbonate fuel cell according to claim 5 or 7, characterized in that, The mass concentration of the mixed slurry is 21 wt%.

9. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 5, characterized in that, It also includes the step of adding a dispersant to the Li2CO3 and Fe2O3 to prepare a mixed slurry and then dispersing it thoroughly.

10. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 9, characterized in that, The dispersant includes sodium carboxymethyl cellulose; The dispersant is added in a ratio of 1.5-2 wt% based on the total amount of Li2CO3 and Fe2O3 raw materials.

11. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 10, characterized in that, The dispersant is added at a ratio of 1.87 wt% based on the total amount of the Li2CO3 and Fe2O3 raw materials.

12. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 5, characterized in that, In step (1), the coating thickness of the coating machine is set to 1.2-1.5 mm.

13. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 5, characterized in that, In step (2), the calcination step includes calcining at 400-450°C for 0.5-2 hours under a protective atmosphere, and calcining at 550-650°C for 6-10 hours.

14. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 5, characterized in that, In step (3), the solvent used to prepare the GO slurry includes isopropanol and / or ethanol.

15. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 14, characterized in that, The mass concentration of the GO slurry is 10-14 wt%.

16. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 15, characterized in that, The GO slurry has a mass concentration of 12 wt%.

17. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 5, characterized in that, The method also includes the step of preparing the desired graphene oxide powder using graphite as a raw material.

18. The method for preparing the cathode electrode for a molten carbonate fuel cell according to claim 17, characterized in that, The method for preparing graphene oxide is based on the Hummers process, which uses a strong oxidant to chemically oxidize graphite in a concentrated sulfuric acid system via an ice bath-warm water bath-hot water bath, followed by freeze drying to obtain the desired graphene oxide.

19. A cathode electrode for a molten carbonate fuel cell, characterized in that, The cathode electrode comprises a cathode material prepared by the preparation method according to any one of claims 1-3 or the cathode material according to claim 4, or the cathode electrode is prepared by the method according to any one of claims 5-18.

20. A molten carbonate fuel cell, characterized in that, Includes the cathode electrode for a molten carbonate fuel cell as described in claim 19.

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