CN114709457B - Double-doped medium-temperature solid oxide fuel cell electrolyte and preparation method thereof - Google Patents

Abstract

The invention provides a double-doped medium-temperature solid oxide fuel cell electrolyte and a preparation method thereof, wherein the medium-temperature solid oxide fuel cell electrolyte with high structural stability and excellent conductivity is prepared by adopting a sol-gel-combustion method, and the chemical formula of the medium-temperature solid oxide fuel cell electrolyte is Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23‑δ . The electrolyte has excellent structural stability in medium-high temperature environment, and the ionic conductivity reaches 0.013S/cm at 800 ℃ in air atmosphere, so that the requirement of the medium-temperature solid oxide fuel cell on electrolyte materials is met.

Description

A double-doped intermediate temperature solid oxide fuel cell electrolyte and its preparation method

technical field

The invention belongs to the technical field of fuel cell electrolytes, and in particular relates to a double-doped intermediate temperature solid oxide fuel cell electrolyte and a preparation method thereof.

Background technique

An urgent problem to be solved in today's society is to develop sustainable energy in order to deal with the environmental crisis caused by global warming and the exploitation of limited natural mineral resources. Advanced energy conversion and storage technologies, such as: fuel cells, lithium batteries, solar cells, etc. are being urgently developed. Fuel cell is one of the most advanced technologies in the future energy output system. It attracts attention due to its high power generation efficiency, no corrosion, and low pollution. It is regarded as one of the best green energy solutions.

Solid oxide fuel cells (SOFCs) have the characteristics of high energy conversion efficiency, low cost, and good long-term stability. SOFC can use various carbon-containing fossil fuels as fuel, and the fuel is not directly burned during the energy conversion process, which greatly improves the energy conversion efficiency and avoids or reduces the generation of toxic gases and dust and other pollutants. The working temperature of SOFC is 500°C~1000°C, and its by-products are high-quality heat and water vapor. In the case of combined heat-power supply, the energy utilization rate can be as high as about 80%, which is clean and efficient.

At present, the operating temperature of SOFC that has been commercially used is generally 1000 ° C. The long-term operation of the battery at such a high temperature will inevitably cause the electrolyte and the electrode to react to form a high-resistance interface, and the conductivity will decrease; the electrode sintering, porosity and catalytic performance. Decrease; due to the inconsistency of thermal expansion coefficients between the various components, stress will be generated at the interface and cracks will greatly reduce the safety and stability of the battery. Therefore, reducing the operating temperature of SOFC can effectively reduce its system cost and improve its stability. The electrolyte material of the invention can obtain excellent structural stability and high electrical conductivity at medium and high temperatures, and meets the requirements of medium-temperature SOFC electrolyte materials.

Contents of the invention

The object of the present invention is to provide a double-doped intermediate temperature solid oxide fuel cell electrolyte and a preparation method thereof.

To achieve the above object, the present invention adopts the following technical solutions:

A double-doped intermediate temperature solid oxide fuel cell electrolyte, the chemical formula of which is Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ , 0≤δ≤1.1.

The preparation method comprises the following steps:

Preparation method of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte powder:

1) Weigh Ta ₂ O ₅ , Sr(NO ₃ ) ₂ , LiNO ₃ , (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O according to the stoichiometric ratio of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ , And take ethylene glycol and citric acid as 1:2:2 by the mol ratio of metal cation and ethylene glycol, citric acid;

2) Add Sr(NO ₃ ) ₂ , LiNO ₃ , (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and citric acid to distilled water for dissolution;

3) Pour the Sr(NO ₃ ) ₂ solution, LiNO ₃ solution, (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O solution obtained in step 2) into the citric acid solution in sequence, and then add Ta ₂ O to the solution ₅ , and then drop ethylene glycol;

4) Add ammonia water with a mass concentration of 15%-20% dropwise to the solution to adjust the pH value of the solution to 7-8;

5) Heat the mixed solution obtained in step 4) to 80°C in a constant temperature magnetic stirrer, and then keep stirring continuously at 80°C until a gel is formed;

6) Move the gel into an evaporating dish and heat it on an electric furnace until fluffy oxide powder is formed;

7) Heat the obtained oxide powder to 800±10°C, keep it for 2±0.1 hours to eliminate residual organic matter, then keep it at 1100±10°C for 12±0.1 hours and cool it with the furnace to form Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _{23 - delta} powder;

The preparation method of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte sheet:

The prepared Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ powder was ball milled for 10 hours, dried, and an appropriate amount of PVB (10wt.%) was added as a binder. , to make a disc with a diameter of 12±0.1mm and a thickness of 1±0.1mm, heat the disc at a rate of 3°C/min to 500°C±10°C for 1h, and then heat it at a rate of 3°C/min to Incubate at 1300±10° C. for 12±0.1 hours to obtain a dense Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte disc.

The advantages of the present invention are:

The double-layer perovskite oxide Sr ₁₁ Mo ₄ O ₂₃ exhibits high oxygen ion mobility due to its defective framework, which can be used as an electrolyte for solid oxide fuel cells. However, the phase structure of Sr ₁₁ Mo ₄ O ₂₃ is unstable, and the transformation of Sr ₁₁ Mo ₄ O ₂₃ → SrMoO ₄ will occur at 400°C, accompanied by a sharp drop in electrical conductivity, which greatly limits the application of this type of material. Aiming at the shortage of this material, the present invention prepares a novel Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte double-doped with lithium and tantalum through a sol-gel-combustion method. The electrolyte material operates at a temperature of 600°C-800°C The phase transition does not occur within the range, and the double perovskite structure is still maintained, and the electrical conductivity is higher than that of Sr ₁₁ Mo ₄ O ₂₃ (8.72×10 ^-3 S/cm at 800°C). Under air atmosphere, the ionic conductivity of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ reaches 0.013 S/cm at 800°C. Therefore, the Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte has the characteristics of good structural stability and excellent electrical conductivity, and is a potential medium-temperature SOFC oxygen ion conductor electrolyte.

Advantages: The Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte is a pure oxygen ion conductor, and at the operating temperature of SOFC, it always maintains the perovskite structure of Sr ₁₁ Mo ₄ O ₂₃ , and no Sr ₁₁ Mo ₄ O The transformation of ₂₃ → SrMoO ₄ has the characteristics of stable structure and high electrical conductivity, which is suitable for application in intermediate temperature solid oxide fuel cells.

Uses: Used as an electrolyte for medium temperature solid oxide fuel cells.

Description of drawings

Fig. 1 is a comparison of XRD patterns of Sr ₁₁ Mo ₄ O ₂₃ tablets before and after holding at 800°C for 24 hours. After ₂₃ pieces of Sr ₁₁ Mo ₄ O were kept at 800°C for 24 hours, they had completely transformed into SrMoO ₄ ;

Fig. 2 is a comparative XRD pattern of the Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ sheet prepared by the present invention before and after holding at 800°C for 24 hours. The Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte of the present invention still maintains its original structure after being kept at 800°C for 24 hours;

Figure 3 is a diagram of the total conductivity of Sr ₁₁ Mo ₄ O ₂₃ and Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolytes at different test temperatures. The conductivity of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte is significantly higher than that of Sr ₁₁ Mo ₄ O ₂₃ electrolyte. At 800℃, the electrical conductivity of the Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte reaches 0.013 S/cm.

Detailed ways

In order to make the above-mentioned features and advantages of the present invention more comprehensible, specific embodiments are given below for detailed description. The methods of the present invention are conventional methods in the art unless otherwise specified.

Example 1

1. Preparation method of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte powder:

1) Weigh Ta ₂ O ₅ , Sr(NO 3 ) ₂ , LiNO ₃ , (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O according to _the stoichiometric ratio of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ , And take ethylene glycol and citric acid as 1:2:2 by the mol ratio of metal cation and ethylene glycol, citric acid;

2) Add Sr(NO ₃ ) ₂ , LiNO ₃ , (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and citric acid to distilled water for dissolution;

3) Pour the Sr(NO ₃ ) ₂ solution, LiNO ₃ solution, (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O solution obtained in step 2) into the citric acid solution in sequence, and then add Ta ₂ O to the solution ₅ , and then drop ethylene glycol;

4) Add ammonia water with a mass concentration of 15%-20% dropwise to the solution to adjust the pH value of the solution to 7-8;

5) Heat the mixed solution obtained in step 4) to 80°C in a constant temperature magnetic stirrer, and then keep stirring continuously at 80°C until a gel is formed;

6) Move the gel into an evaporating dish and heat it on an electric furnace until fluffy oxide powder is formed;

7) Heat the obtained oxide powder to 800±10°C, keep it for 2±0.1 hours to eliminate residual organic matter, then keep it at 1100±10°C for 12±0.1 hours and cool it with the furnace to form Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _{23 - delta} powder;

2. Preparation method of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte sheet:

The prepared Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ powder was ball milled for 10 hours, dried, and an appropriate amount of PVB (10wt.%) was added as a binder. , make a disc with a diameter of 12±0.1mm and a thickness of 1±0.1mm, heat the disc at a rate of 3°C/min to 500°C±10°C for 1h, then raise the temperature at 3°C/min to 1300± Incubate at 10°C for 12±0.1 hours to obtain a dense Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte disc.

specific:

(a) Preparation of 1 mole Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte powder:

1) Weigh 2306.771g (10.9mol) Sr(NO ₃ ) ₂ , 6.895g (0.1mol) LiNO ₃ , 529.654g (0.42mol) (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O, 220.990g (0.5 mol) _Ta2O5 , 1862.100g (30mol) ethylene glycol and _6304.200g (30mol) citric acid;

2) Add Sr(NO ₃ ) ₂ , LiNO ₃ , (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and citric acid to distilled water for dissolution;

3) Pour the Sr(NO ₃ ) ₂ solution, LiNO ₃ solution, (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O solution obtained in step 2) into the citric acid solution in sequence, and then add Ta ₂ O to the solution ₅ , and then drop ethylene glycol;

4) Add ammonia water with a concentration of 15wt% dropwise to the solution to adjust the pH value of the solution to 7;

5) Heat the mixed solution obtained in step 4) to 80°C in a constant temperature magnetic stirrer, and then keep stirring continuously at 80°C until a gel is formed;

6) Move the gel into an evaporating dish and heat it on an electric furnace until fluffy oxide powder is formed;

7) Heat the obtained oxide powder to 800°C, keep it warm for 2 hours to eliminate residual organic matter, then keep it at 1100°C for 12 hours, and cool with the furnace to form Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ powder;

(2) Preparation method of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte sheet:

The prepared Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ powder was ball milled for 10 hours, dried, and an appropriate amount of PVB (10wt.%) was added as a binder. , to make a disc with a diameter of 12 mm and a thickness of 1 mm. The disc was heated at a rate of 3 °C/min to 500 °C for 1 hour, and then heated at a rate of 3 °C/min to 1300 °C for 12 hours to obtain a dense Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte disc.

Conductivity test method:

The AC conductance of the electrolyte was measured by the two-terminal method. The Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ electrolyte disc obtained after sintering at 1300°C for 12 hours was coated with silver paste on both sides, and then fired at 400°C for 2 hours to obtain a silver electrode. Connect the silver electrodes at both ends to the AC impedance meter with silver wires. The AC impedance meter used is Interface 1000 electrochemical workstation of American Gamry Company, the disturbance potential is 30mV, the measurement frequency range is 0.1Hz-1MHz, the test temperature is 450-800°C, and it is measured every 50°C in the air atmosphere. Conductivity was calculated using the following formula:

In the formula, σ is the conductivity of the electrolyte, S/cm;

h is the thickness of the electrolyte sheet, in cm;

R is the electrolyte resistance, unit Ω;

S is the cross-sectional area of the electrolyte sheet, in cm ² .

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (3)

1. A method for preparing a double-doped intermediate temperature solid oxide fuel cell electrolyte, characterized in that, comprising the following steps: 1) Weigh Ta ₂ O ₅ , Sr(NO 3 ) ₂ , LiNO ₃ , (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O according to _the stoichiometric ratio of Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ , And weigh ethylene glycol and citric acid according to the molar ratio of metal cation to ethylene glycol and citric acid as 1:2:2, 0≤δ≤1.1; 2) Add Sr(NO ₃ ) ₂ , LiNO ₃ , (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and citric acid to distilled water for dissolution; 3) Pour the Sr(NO ₃ ) ₂ , LiNO ₃ , (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O solution obtained in step 2) into the citric acid solution in sequence, and then add Ta ₂ O ₅ into the solution, Add ethylene glycol dropwise; 4) Add ammonia water with a mass concentration of 15%-20% dropwise to the solution to adjust the pH value of the solution to 7-8; 5) Heat the mixed solution obtained in step 4) to 80°C in a constant temperature magnetic stirrer, and then keep stirring continuously at 80°C until a gel is formed; 6) Transfer the gel into an evaporating dish and heat until a fluffy oxide powder is formed; 7) Heat the obtained oxide powder to 800±10°C, keep it for 2±0.1 hours to eliminate residual organic matter, then keep it at 1100±10°C for 12±0.1 hours and cool it with the furnace to form Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _{23 - Delta} electrolyte powder. 2. A double-doped intermediate temperature solid oxide fuel cell electrolyte prepared by the method according to claim 1, characterized in that, the chemical formula of the fuel cell electrolyte is Sr _10.9 Li _0.1 Mo ₃ Ta _1.0 O _23-δ , 0≤δ≤1.1. 3. The application of the electrolyte according to claim 2, characterized in that it is used in a solid oxide fuel cell, and the operating temperature of the cell is 800°C±10°C.