Mutually-doped double-phase composite cathode material and preparation method thereof

Abstract

The invention provides a mutually-doped biphase composite cathode material and a preparation method thereof, and belongs to the technical field of solid oxide fuel cells. The invention provides a mutually doped double-phase composite cathode material, which comprises the following chemical components: (1-x) Sr (1-x) Sr (1-x) Ceax / (1-x) Co (0.8) Fe (0.2) O (3-delta-x) Ce (1-a) SraO (2-delta), and x is more than 0 and less than 1. The two-phase composition of the mutually-doped double-phase composite cathode material provided by the invention is synchronously prepared by adopting a'one pot ', the cobalt content of the mutually-doped double-phase composite cathode material provided by the invention is reduced, the thermal expansion coefficient of the cathode material is reduced, and the mutually-doped double-phase composite cathode material can be sintered with electrolyte more firmly, so that the electrochemical performance of the cathode material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid oxide fuel cells, and in particular relates to an inter-doped two-phase composite cathode material and a preparation method thereof. Background Art

[0002] Solid oxide fuel cells (SOFCs) are power generation devices that directly convert hydrocarbon fuels into electricity, offering advantages such as high efficiency, low pollution, and fuel flexibility. Traditional SOFCs operate at temperatures exceeding 1000°C, placing stringent demands on electrode materials, cell components, and ancillary equipment. This also increases the construction and operation and maintenance costs of the cells. Therefore, medium- and low-temperature technologies (operating at 800°C and below) have become a major focus of SOFC development.

[0003] In medium and low temperature SOFC, SrCo 0.8 Fe 0.2 O 3-δ (SCF82, among which, δ Oxygen vacancies (OVs) have attracted significant attention. This cathode material, with its excellent catalytic performance and high electrical conductivity, holds great promise as a medium- and low-temperature SOFC cathode material. However, due to the influence of the cobalt crystal field and electron spin state, this cathode material has a large thermal expansion coefficient, making it difficult to sinter with mainstream SOFC electrolytes, resulting in reduced electrochemical performance. Therefore, improving the electrochemical performance of cathode materials has become a pressing technical challenge in this field. Summary of the Invention

[0004] The object of the present invention is to provide a co-doped dual-phase composite cathode material and a preparation method thereof. The co-doped dual-phase composite cathode material provided by the present invention has excellent electrochemical properties.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a mutually doped dual-phase composite cathode material, the chemical composition of which is (1- x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ - x Ce 1-a Sr a O 2-δ , where 0< x <1; Said x The second phase Ce 1-a Sr a O 2-δ The amount of material in the inter-doped dual-phase composite cathode material; Saida is the co-doping concentration of Sr and Ce elements in the co-doped biphasic composite cathode material, a According to (1 - x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ and Ce 1-a Sr a O 2-δ varies according to the specific conditions of the composition ratio and synthesis temperature factors, 0 < a < 0.1; The δ is a general representation of lattice oxygen vacancies.

[0006] Preferably, the x is 0.15, 0.3, 0.45, 0.5, 0.6, 0.7, 0.8 or 0.9.

[0007] The present invention also provides a preparation method of the co-doped biphasic composite cathode material described in the above technical solution, including the following steps: (1) Mix strontium salt, cobalt salt, iron salt, cerium salt, a first solvent, a complexing agent and a second solvent to obtain a mixed solution; (2) Gel and dry the mixed solution obtained in step (1) in sequence to obtain a dry gel; (3) Calcine and anneal the dry gel obtained in step (2) in sequence to obtain a co-doped biphasic composite cathode material.

[0008] Preferably, the complexing agent in step (1) includes citric acid and ethylenediaminetetraacetic acid.

[0009] Preferably, the molar ratio of the total metal ions, citric acid and ethylenediaminetetraacetic acid in the strontium salt, cobalt salt, iron salt and cerium salt in step (1) is 1:(1~2):(1~2).

[0010] Preferably, the temperature of the gel in step (2) is 70~90°C.

[0011] Preferably, the temperature of the drying in step (2) is 150~180°C.

[0012] Preferably, the temperature of the calcination in step (3) is 400~450°C, and the calcination time is 5~10 h.

[0013] Preferably, the holding temperature of the annealing in step (3) is 900~1200°C, and the holding time of the annealing is 8~15 h.

[0014] Preferably, in the step (3), the annealing holding temperature is 1000~1100°C, and the annealing holding time is 10 h.

[0015] The present invention provides a mutually doped biphasic composite cathode material, and its chemical composition is (1- x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ - x Ce 1-a Sr a O 2-δ , where 0< x <1; the x is the molar ratio of the second phase Ce 1-a Sr a O 2-δ in the mutually doped biphasic composite cathode material; the a is the mutual doping concentration of Sr and Ce elements in the mutually doped biphasic composite cathode material, a varies according to the composition ratio of (1- x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ and Ce 1-a Sr a O 2-δ and the specific situation of the synthesis temperature factor, 0< a <0.1; the δ is the general representation of lattice oxygen vacancies. Since the mutually doped biphasic composite cathode material provided by the present invention is biphasic, and one of the phases does not contain cobalt element, the two phases are combined together. Compared with the single-phase cathode material SrCo 0.8 Fe 0.2 O 3-δ , the cobalt content is reduced, the thermal expansion coefficient of the cathode material is reduced, and it can be sintered more firmly with the electrolyte, thereby improving the electrochemical performance of the cathode material. The experimental results show that the interface impedance between the mutually doped biphasic composite cathode material provided by the present invention and the electrolyte is 0.115~0.26Ω·cm 2 ; the single cell prepared with the mutually doped biphasic composite cathode material provided by the present invention as the cathode has a maximum output power of 435~630mW·cm -2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the SEM image of the mutually doped biphasic composite cathode material prepared in Example 1; Figure 2 XRD pattern and standard PDF card of the mutually doped biphasic composite cathode material prepared in Example 1; Figure 3 Electrochemical impedance spectrum of the mutually doped biphasic composite cathode material prepared in Example 1; Figure 4 Variation curves of operating voltage and power with current density of the single cell prepared with the mutually doped biphasic composite cathode material in Example 1 at 800 °C; Figure 5 SEM image of the mutually doped biphasic composite cathode material prepared in Example 2; Figure 6 XRD pattern and standard PDF card of the mutually doped biphasic composite cathode material prepared in Example 2; Figure 7 Electrochemical impedance spectrum of the mutually doped biphasic composite cathode material prepared in Example 2; Figure 8 Variation curves of operating voltage and power with current density of the single cell prepared with the mutually doped biphasic composite cathode material in Example 2 at 800 °C; Figure 9 Lattice atomic structure of the single-phase cathode material prepared in Comparative Example 1; Figure 10 SEM image of the single-phase cathode material prepared in Comparative Example 1; Figure 11 XRD pattern and standard PDF card of the single-phase cathode material prepared in Comparative Example 1; Figure 12 Electrochemical impedance spectrum of the single-phase cathode material prepared in Comparative Example 1; Figure 13 Variation curves of operating voltage and power with current density of the single cell prepared with the mutually doped biphasic composite cathode material in Comparative Example 1 at 800 °C; Figure 14 Lattice atomic structure of the electrolyte material CeO2 prepared in Comparative Example 2; Figure 15 SEM image of the electrolyte material CeO2 prepared in Comparative Example 2; Figure 16 XRD pattern and standard PDF card of the electrolyte material CeO2 prepared in Comparative Example 2; Figure 17 SEM image of the mutually doped biphasic composite cathode material prepared in Example 3; Figure 18 XRD pattern and standard PDF card of the mutually doped biphasic composite cathode material prepared in Example 3. Detailed implementation mode

[0017] The present invention provides a mutually doped biphasic composite cathode material, and its chemical composition is (1 - x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ - x Ce 1-a Sr a O 2-δ where 0 < x < 1. In the present invention, the x is the molar ratio of the second phase Ce 1- a Sr a O 2-δ in the mutually doped biphasic composite cathode material; the a is the mutual doping concentration of Sr and Ce elements in the mutually doped biphasic composite cathode material, a varies according to the specific conditions of the composition ratio, synthesis temperature, etc. of (1 - x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ and Ce 1- a Sr a O 2-δ , 0 < a < 0.1; the δ is a general representation of lattice oxygen vacancies.

[0018] In the present invention, the x is preferably 0.15, 0.3, 0.45, 0.5, 0.6, 0.7, 0.8 or 0.9.

[0019] In the present invention, the structure of Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ in the mutually doped biphasic composite cathode material is preferably a cubic perovskite structure; the space group of Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ is preferably Pm-3m (No.221); the Ce 1-a Sr a O 2-δThe structure is preferably a cubic fluorite structure; the Ce 1-a Sr a O 2-δ preferably has a space group of Fm-3m (No. 225).

[0020] Compared with the single-phase cathode material SrCo 0.8 Fe 0.2 O 3-δ (SCF82), Ce 1-a Sr a O 2-δ in the dual-phase composite cathode material provided by the present invention can improve the oxygen ion transport performance of the single-phase cathode material, refine the grains of the Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ phase, and make the particles more dispersed, so that the dual-phase composite cathode material exhibits better electrochemical performance; the cobalt content of the dual-phase composite cathode material provided by the present invention is lower, reducing the thermal expansion coefficient of the cathode material, enabling it to sinter more firmly with the electrolyte, thereby improving the electrochemical performance of the cathode material and making the battery prepared with this dual-phase composite cathode material operate more stably.

[0021] The present invention also provides a preparation method of the mutually doped dual-phase composite cathode material described in the above technical solution, including the following steps: (1) Mix a strontium salt, a cobalt salt, an iron salt, a cerium salt, a first solvent, a complexing agent, and a second solvent to obtain a mixed solution; (2) Gel and dry the mixed solution obtained in step (1) in sequence to obtain a dry gel; (3) Calcine and anneal the dry gel obtained in step (2) in sequence to obtain the mutually doped dual-phase composite cathode material.

[0022] The present invention has no special limitation on the sources of each raw material, and commercially available products well-known to those skilled in the art can be used.

[0023] The present invention mixes a strontium salt, a cobalt salt, an iron salt, a cerium salt, a first solvent, a complexing agent, and a second solvent to obtain a mixed solution.

[0024] In the present invention, the strontium salt is preferably a soluble strontium salt, more preferably strontium nitrate or strontium acetate; the cobalt salt is preferably a soluble cobalt salt, more preferably cobalt nitrate or cobalt acetate; the iron salt is preferably a soluble iron salt, more preferably iron nitrate or iron citrate; the cerium salt is preferably a soluble strontium salt, more preferably cerium nitrate. In the present invention, the strontium salt, cobalt salt, iron salt, and cerium salt are used to provide the metal ions required in the mutually doped dual-phase composite cathode material.

[0025] The present invention has no special limitation on the proportions of the strontium salt, cobalt salt, iron salt and cerium salt, and it can be determined according to the actual chemical composition required.

[0026] In the present invention, the first solvent is preferably an inorganic solvent, and more preferably deionized water. The present invention has no special limitation on the amount of the first solvent, as long as the strontium salt, cobalt salt, iron salt and cerium salt can be completely dissolved.

[0027] In the present invention, the complexing agent preferably includes citric acid and ethylenediaminetetraacetic acid. The present invention uses citric acid and ethylenediaminetetraacetic acid as the complexing agent, which has low cost and is easily available, and can improve the complexing effect.

[0028] In the present invention, the molar ratio of the total metal ions, citric acid and ethylenediaminetetraacetic acid in the strontium salt, cobalt salt, iron salt and cerium salt is preferably 1:(1 - 2):(1 - 2), and more preferably 1:1:1. Limiting the molar ratio of the total metal ions, citric acid and ethylenediaminetetraacetic acid in the strontium salt, cobalt salt, iron salt and cerium salt within the above range in the present invention can improve the complexing effect.

[0029] In the present invention, the second solvent is preferably concentrated ammonia water. The present invention has no special limitation on the concentration and amount of the concentrated ammonia water. Using the concentrated ammonia water well-known to those skilled in the art, as long as the ethylenediaminetetraacetic acid in the complexing agent can be dissolved to make the pH of the mixed solution within the range of 8 - 9.

[0030] In the present invention, the mixing of the strontium salt, cobalt salt, iron salt, cerium salt, first solvent, complexing agent and second solvent is preferably to mix the strontium salt, cobalt salt, iron salt, cerium salt and first solvent, and then sequentially add the complexing agent and the second solvent. The present invention can make the raw materials mix more evenly by using the stepwise feeding method.

[0031] The present invention has no special limitation on the operation of mixing the strontium salt, cobalt salt, iron salt, cerium salt and first solvent, and then sequentially adding the complexing agent and the second solvent, as long as they are mixed evenly.

[0032] After obtaining the mixed solution, the present invention gels and dries the mixed solution in sequence to obtain a dry gel.

[0033] In the present invention, the temperature of the gel is preferably 70 - 90 °C. As an implementation manner, the temperature of the gel can be 75 °C, 80 °C or 85 °C. The present invention has no special limitation on the time of the gel, as long as the gel state is achieved. Limiting the temperature of the gel within the above range in the present invention can prevent the gel from boiling due to too high temperature and causing the gel to be lost.

[0034] In the present invention, the drying temperature is preferably 150~180°C. As an embodiment, the drying temperature can be 160~170°C. The present invention has no special limitation on the drying time, and it can be dried to constant weight. By drying in the present invention, the gel can be further fully dried to obtain a xerogel.

[0035] After obtaining the xerogel, the present invention subjects the xerogel to roasting and annealing in sequence to obtain an inter-doped biphasic composite cathode material.

[0036] In the present invention, the roasting temperature is preferably 400~450°C; the roasting time is preferably 5~10 h. As an embodiment, the roasting temperature can be 410°C, 420°C, 430°C or 440°C; the roasting time can be 6 h, 7 h, 8 h or 9 h. By roasting in the present invention, the organic substances in the xerogel can be decomposed to form a precursor.

[0037] In the present invention, the roasting is preferably carried out in an air atmosphere; the roasting is preferably carried out in a muffle furnace. The present invention has no special limitation on the model of the muffle furnace, and any instrument and equipment well-known to those skilled in the art can be used.

[0038] After roasting is completed, the present invention preferably subjects the product obtained by roasting to grinding and drying in sequence. The present invention has no special limitation on the grinding operation, and it can be ground to an ink-like state.

[0039] The present invention has no special limitation on the drying operation, and it can be dried to constant weight.

[0040] In the present invention, the holding temperature for annealing is preferably 900~1200°C; the holding time for annealing is preferably 8~15 h. As an embodiment, the holding temperature for annealing can be 1000°C or 1100°C; the holding time for annealing can be 9 h, 10 h, 11 h, 12 h, 13 h or 14 h. By annealing in the present invention, the precursor can form a specific crystal structure.

[0041] In the present invention, the annealing is preferably carried out in an air furnace. The present invention has no special limitation on the model of the air furnace, and any instrument and equipment well-known to those skilled in the art can be used.

[0042] The present invention adopts a simple "one-pot" synchronous preparation method, which has a simple process flow, high material preparation efficiency, and is conducive to large-scale production and application; the "one-pot" synchronous preparation can enable Sr and Ce elements to dissolve in each other between the two phases, so as to achieve the effect of mutual doping, and further improve the ion and electron transport performance of the inter-doped biphasic composite cathode material, so that the inter-doped biphasic composite cathode material exhibits better electrochemical performance.

[0043] The technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Example 1 A mutually doped biphasic composite cathode material, the chemical composition is (1 - x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ - x Ce 1-a Sr a O 2-δ , where x is 0.15; The x is the molar ratio of the second phase Ce 1-a Sr a O 2-δ in the mutually doped biphasic composite cathode material; The a is the mutual doping concentration of Sr and Ce elements in the mutually doped biphasic composite cathode material, a According to (1 - x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ and Ce 1-a Sr a O 2-δ and the specific situation of the synthesis temperature factor, 0 < a < 0.1; The δ is the general representation of lattice oxygen vacancies; The preparation method of the mutually doped biphasic composite cathode material is as follows: (1) Mix strontium nitrate, cobalt nitrate, iron nitrate, cerium nitrate and deionized water to obtain a nitrate solution; (2) Add citric acid and ethylenediaminetetraacetic acid to the nitrate solution obtained in step (1), stir, and then add concentrated ammonia water to obtain a brownish-red mixed solution; wherein, the molar ratio of the total metal ions, citric acid and ethylenediaminetetraacetic acid is 1:1:1; the pH of the mixed solution is 8.5; (3) Put the mixed solution obtained in the step (2) into an oven, first carry out gelation at 80 °C, and then carry out drying at 150 °C to obtain a dry gel; (4) Put the dry gel obtained in the step (3) into a muffle furnace and calcine it at 450 °C for 5 h, then grind it into an ink-like state and dry it, and then anneal it at 1000 °C for 10 h in an air furnace to obtain an inter-doped biphasic composite cathode material.

[0045] Perform SEM morphology analysis on the inter-doped biphasic composite cathode material prepared in Example 1, and the results are as Figure 1 shown, Figure 1 which is the SEM image of the inter-doped biphasic composite cathode material prepared in Example 1.

[0046] It can be seen from Figure 1 that the characteristics of the two phases in the inter-doped biphasic composite cathode material are obvious, and one phase is uniformly attached to the other phase.

[0047] Perform XRD testing on the inter-doped biphasic composite cathode material prepared in Example 1, and the results are as Figure 2 shown, Figure 2 which is the XRD pattern of the inter-doped biphasic composite cathode material prepared in Example 1 and the standard PDF card.

[0048] It can be seen from Figure 2 that the sample of the inter-doped biphasic composite cathode material prepared in Example 1 is pure, and there are no impurity peaks of any third phase except for the two designed phases.

[0049] Perform electrochemical impedance spectroscopy measurement on the interface between the inter-doped biphasic composite cathode material prepared in Example 1 and La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 electrolyte, and the results are as Figure 3 shown, Figure 3 which is the electrochemical impedance spectrum of the inter-doped biphasic composite cathode material prepared in Example 1.

[0050] Combined with Figure 3 it is concluded that the interface impedance between the inter-doped biphasic composite cathode material prepared in Example 1 and La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 electrolyte is about 0.26 Ω·cm 2 .

[0051] A single cell was prepared with the mutually doped biphasic composite cathode material prepared in Example 1 as the cathode. Among them, the anode is Ni-Ce 0.8 Sm 0.2 O 2-δ (Ni-SDC), the electrolyte is La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 , the buffer layer between the anode and the cathode is SDC. The curves of the working voltage and power of the single cell varying with the current density at 800 °C are as Figure 4 shown. The maximum power of the single cell at 800 °C is approximately 435 mW·cm -2 .

[0052] Example 2 A mutually doped biphasic composite cathode material with a chemical composition of (1 - x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ - x Ce 1-a Sr a O 2-δ , where x is 0.3; The preparation method of the mutually doped biphasic composite cathode material is the same as that of Example 1.

[0053] The SEM morphology analysis was carried out on the mutually doped biphasic composite cathode material prepared in Example 2. The results are as Figure 5 shown, Figure 5 is the SEM image of the mutually doped biphasic composite cathode material prepared in Example 2.

[0054] It can be seen from Figure 5 that the characteristics of the two phases in the mutually doped biphasic composite cathode material are obvious, and one phase is uniformly attached to the other phase.

[0055] The XRD test was carried out on the mutually doped biphasic composite cathode material prepared in Example 2. The results are as Figure 6 shown, Figure 6 is the XRD pattern and the standard PDF card of the mutually doped biphasic composite cathode material prepared in Example 2.

[0056] It can be seen from Figure 6 that the mutually doped biphasic composite cathode material prepared in Example 2 is relatively pure and no impurity peaks appear.

[0057] For the mutually doped biphasic composite cathode material prepared in Example 2 and La0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 Electrochemical impedance spectroscopy measurements were carried out on the interface of the electrolyte, and the results are as Figure 7 shown, Figure 7 which is the electrochemical impedance spectrum of the co-doped biphasic composite cathode material prepared in Example 2.

[0058] Combined with Figure 7 it can be obtained that the co-doped biphasic composite cathode material prepared in Example 2 and La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 The interfacial impedance of the electrolyte is approximately 0.115 Ω·cm 2 .

[0059] A single cell was prepared with the co-doped biphasic composite cathode material prepared in Example 2 as the cathode. Among them, the anode is Ni-SDC, and the electrolyte is La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 . The curves of the working voltage and power of the single cell varying with the current density at 800 °C are as Figure 8 shown. The maximum power of the single cell at 800 °C is approximately 630 mW·cm -2 , which is higher than the electrochemical performance of the single-phase cathode SrCo 0.8 Fe 0.2 O 3-δ .

[0060] Comparative Example 1 The chemical composition of the single-phase cathode material is SrCo 0.8 Fe 0.2 O 3-δ , that is, on the basis of Example 1, x is set to 0, and a is 0; The preparation method of the single-phase cathode material is as follows: (1) Mix strontium nitrate, cobalt nitrate, iron nitrate and deionized water to obtain a nitrate solution; (2) Add citric acid and ethylenediaminetetraacetic acid to the nitrate solution obtained in step (1), stir, and then add concentrated ammonia water to obtain a brownish-red mixed solution; among them, the molar ratio of the total metal ions, citric acid and ethylenediaminetetraacetic acid is 1:1:1; the pH of the mixed solution is 8.5; (3) Put the mixed solution obtained in the step (2) into an oven, first gel at 80 °C, and then dry at 150 °C to obtain a dry gel; (4) Put the dry gel obtained in the step (3) into a muffle furnace and calcine at 450 °C for 5 h, then grind it into an ink-like state and dry it, and then anneal it at 1000 °C for 10 h in an air furnace to obtain a single-phase cathode material.

[0061] The lattice atomic structure of the single-phase cathode material prepared in Comparative Example 1 is as Figure 9 shown. In the figure, 8 vertices represent CoFe, the small ball in the middle represents Sr +2 , and the remaining large balls represent O -2 .

[0062] From Figure 9 it can be seen that the single-phase cathode material SrCo 0.8 Fe 0.2 O 3-δ is a cubic perovskite structure.

[0063] Perform SEM morphology analysis on the single-phase cathode material prepared in Comparative Example 1, and the results are as Figure 10 shown. Figure 10 It is the SEM image of the single-phase cathode material prepared in Comparative Example 1.

[0064] From Figure 10 it can be seen that SrCo 0.8 Fe 0.2 O 3-δ particles are very easy to sinter and agglomerate at high temperature. It can be seen that the grains are thick and the grain boundaries are obvious, which is not conducive to expanding the catalytic surface.

[0065] Perform XRD test on the single-phase cathode material prepared in Comparative Example 1, and the results are as Figure 11 shown. Figure 11 It is the XRD pattern and standard PDF card of the single-phase cathode material prepared in Comparative Example 1.

[0066] From Figure 11 it can be seen that the sample of the single-phase cathode material prepared in Comparative Example 1 is pure and there are no impurity peaks.

[0067] Perform electrochemical impedance spectroscopy measurement on the interface between the single-phase cathode material prepared in Comparative Example 1 and the La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 electrolyte, and the results are as Figure 12 shown. Figure 12 It is the electrochemical impedance spectrum of the single-phase cathode material prepared in Comparative Example 1.

[0068] Combined with Figure 12 it is obtained that the interfacial impedance between the single-phase cathode material prepared in Comparative Example 1 and La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 electrolyte is approximately 0.28 Ω·cm 2 .

[0069] Using the single-phase cathode material prepared in Comparative Example 1 as the cathode to prepare a single cell, where the anode is Ni-SDC, the electrolyte is La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 , the buffer layer between the anode and the cathode is SDC. The curves of the working voltage and power of the single cell varying with the current density at 800 °C are as Figure 13 shown. The maximum power of the single cell at 800 °C is approximately 402 mW·cm -2 .

[0070] Comparative Example 2 On the basis of Example 1, x is set to 1 to obtain the electrolyte material CeO2, which is not suitable to be used as a cathode alone.

[0071] The lattice atomic structure of the electrolyte material CeO2 prepared in Comparative Example 2 is as Figure 14 shown, where the small balls in the figure represent Ce +4 , and the large balls represent O -2 .

[0072] From Figure 14 it can be seen that the single-phase CeO2 has a fluorite structure.

[0073] Performing SEM morphology analysis on the electrolyte material CeO2 prepared in Comparative Example 2, the results are as Figure 15 shown, Figure 15 which is the SEM image of the electrolyte material CeO2 prepared in Comparative Example 2.

[0074] From Figure 15 it can be seen that due to the poor conductivity of the electrolyte material CeO2 prepared in Comparative Example 2, the imaging is distorted to a certain extent.

[0075] Performing XRD testing on the electrolyte material CeO2 prepared in Comparative Example 2, the results are as Figure 16 shown, Figure 16 which is the XRD pattern of the electrolyte material CeO2 prepared in Comparative Example 2 and the standard PDF card.

[0076] From [[ID=6,4]]Figure 16It can be seen that the electrolyte material CeO2 sample prepared in Comparative Example 2 is pure and no impurity peaks appear.

[0077] Example 3 On the basis of Example 1, x is set to 0.45, and other conditions remain unchanged, obtaining an inter-doped biphasic composite cathode material.

[0078] Perform SEM morphology analysis on the inter-doped biphasic composite cathode material prepared in Example 3. The results are as Figure 17 shown. Figure 17 Figure

[0079] From Figure 17 it can be seen that the characteristics of the two phases in the inter-doped biphasic composite cathode material are obvious, and one phase is uniformly attached to the other phase.

[0080] Perform XRD testing on the inter-doped biphasic composite cathode material prepared in Example 3. The results are as Figure 18 shown. Figure 18 Figure

[0081] From Figure 18 it can be seen that the composition phase of the inter-doped biphasic composite cathode material prepared in Example 3 is pure and no impurity peaks appear.

[0082] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A mutually doped biphasic composite cathode material, characterized in that, The chemical composition is (1 - x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ - x Ce 1-a Sr a O 2-δ , where 0 < x < 1; The x is the molar ratio of the second-phase Ce 1-a Sr a O 2-δ in the inter-doped two-phase composite cathode material; The a is the inter-doping concentration of Sr and Ce elements in the inter-doped biphasic composite cathode material, a According to (1 - x )Sr 1-ax / (1-x) Ce ax / (1-x) Co 0.8 Fe 0.2 O 3-δ and Ce 1-a Sr a O 2-δ varies according to the specific conditions of the composition ratio and synthesis temperature factors, 0 < a < 0.1; The above-mentioned δ is a general representation of lattice oxygen vacancies.

2. The inter-doped biphasic composite cathode material according to claim 1, wherein The said x is 0.15, 0.3, 0.45, 0.5, 0.6, 0.7, 0.8 or 0.

9.

3. A preparation method of an inter-doped biphasic composite cathode material, applying an inter-doped biphasic composite cathode material as described in claim 1 or 2, characterized in that, comprises the following steps: (1) Mixing a strontium salt, a cobalt salt, an iron salt, a cerium salt, a first solvent, a complexing agent and a second solvent to obtain a mixed solution; (2) Subjecting the mixed solution obtained in step (1) to gelation and drying in sequence to obtain a xerogel; (3) Subjecting the xerogel obtained in step (2) to calcination and annealing in sequence to obtain an inter-doped biphasic composite cathode material.

4. The preparation method according to claim 3, characterized in that, In step (1), the complexing agent includes citric acid and ethylenediaminetetraacetic acid.

5. The preparation method according to claim 4, characterized in that, In step (1), the molar ratio of the total metal ions in the strontium salt, cobalt salt, iron salt and cerium salt, citric acid and ethylenediaminetetraacetic acid is 1:(1-2):(1-2).

6. The preparation method according to claim 3, characterized in that, In step (2), the temperature for gelation is 70-90 °C.

7. The preparation method according to claim 3, characterized in that, In step (2), the temperature for drying is 150-180 °C.

8. The preparation method according to claim 3, characterized in that, In step (3), the temperature for calcination is 400-450 °C, and the calcination time is 5-10 h.

9. The preparation method according to claim 3, characterized in that, In step (3), the holding temperature for annealing is 900-1200 °C, and the holding time for annealing is 8-15 h.

10. The preparation method according to claim 9, wherein, In step (3), the holding temperature for annealing is 1000-1100 °C, and the holding time for annealing is 10 h.

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