WO2022193551A1 - Method for adding electrolyte to molten carbonate fuel cell - Google Patents

Abstract

A method for adding an electrolyte to a molten carbonate fuel cell, comprising: mixing an electrolyte with water and ethanol, adding the mixture to the surface of an electrode, and heating at a high temperature to realize addition of the electrolyte. By means of the method, an electrolyte can be successfully added to an electrode of a molten carbonate fuel cell, such that the thickness of a bipolar plate is decreased in assembly of a cell stack; and in the cell test process, a nickel oxide cathode can effectively realize the lithiation process, such that the cell can maintain relatively high voltage and power density.

Description

A kind of molten carbonate fuel cell electrolyte adding method technical field

The present application relates to the field of molten carbonate fuel cells, in particular to a method for adding electrolytes to molten carbonate fuel cells.

Background technique

As a high-temperature fuel cell power generation technology, molten carbonate fuel cell power generation technology is widely used abroad because of its advantages of wide fuel sources, modularization and high power generation efficiency. In recent years, with the continuous development of technology in the domestic hydrogen energy field, fuel cell power generation technology has also entered the domestic field of vision. Especially in the preparation method of key fuel cell materials, the electrolyte of molten carbonate fuel cell is mainly carbonate, such as Li ₂ CO ₃ and K ₂ CO ₃ or LiCO ₃ and Na ₂ CO ₃ . In foreign countries, the electrolyte is prepared into a carbonate salt membrane, or the electrolyte and the diaphragm are prepared at the same time, or the electrolyte is put into the flow channel. This foreign electrolyte preparation technology is set for its molten carbonate structure, but has certain limitations for domestic fuel cells.

SUMMARY OF THE INVENTION

The purpose of this application is to provide a molten carbonate fuel cell electrolyte addition method to overcome the defects of the prior art. In this application, the electrolyte is added to the electrode to reduce the distribution of the electrolyte in the flow channel, which can effectively reduce the bipolar The thickness of the plate, and by adding an electrolyte to the cathode, the lithiation process of the cathode material can be quickly achieved, improving the performance of the fuel cell.

To achieve the above object, the application adopts the following technical solutions:

A method for adding molten carbonate fuel cell electrolyte, comprising the following steps:

Step 1: mix the electrolyte with water and ethanol, and stir to obtain an electrolyte mixed solution;

Step 2: Weigh the mass of the electrode and measure the porosity of the electrode, and calculate the theoretical required mass of the electrolyte inside the electrode;

Step 3: Put the electrode into the container, and add the electrolyte mixed solution;

Step 4: place the container under drying conditions until the water and ethanol are completely volatilized;

Step 5: Weigh the total mass of the electrode and the electrolyte attached to the electrode after drying, and then calculate the mass of the electrolyte attached to the electrode. If the electrolyte quality does not meet the actual required quality of the electrolyte inside the electrode, repeat steps 3 and 3 Fourth, if the quality of the electrolyte exceeds the actual required quality of the electrolyte inside the electrode, scrape off the excess electrolyte until the actual required quality range of the electrolyte inside the electrode is met. %;

Step 6: heating the electrode obtained in step 5, and cooling after the heating and heating, that is, the addition of the molten carbonate fuel cell electrolyte is completed.

Further, in the first step, the electrolyte is a mixture of Li ₂ CO ₃ and K ₂ CO ₃ , and the molar ratio between Li ₂ CO ₃ and K ₂ CO ₃ is 31:19.

Further, in step 1, the mass ratio of electrolyte to water and ethanol is 1:(1-2):(1.5-2).

Further, the stirring time in step 1 is 1.5-2h.

Further, the formula for calculating the theoretical required mass of the electrolyte inside the electrode in step 2 is:

Among them, _melectrolyte represents the theoretical demand mass of the electrolyte inside the electrode, ρelectrolyte represents the density of the _electrolyte , _Vpore represents the _electrode pore volume, Velectrode represents the volume of the _electrode , melectrode represents the mass of the electrode, and ρnickel represents the density of metallic _nickel .

Further, the drying conditions in step 4 are as follows: the temperature is 30°C, and the ventilation is carried out.

Further, the heating and temperature increase program in step 6 is specifically as follows: firstly, the temperature is raised from room temperature to 450°C in a nitrogen atmosphere, then the temperature is raised from 450°C to 650°C in a hydrogen atmosphere, and finally, the temperature is kept at 650°C for 2 hours under a hydrogen atmosphere.

Further, the temperature was increased from normal temperature to 450° C. for 5 h.

Further, the temperature was increased from 450°C to 650°C for 10 h.

Compared with the prior art, the present application has the following beneficial technical effects:

In this application, the electrolyte is added to the electrode, because the electrode material is a porous structure, and more than 70% of the interior is porosity, which can be filled with a certain quality of electrolyte, while the electrolyte of conventional molten carbonate fuel cells is generally placed in the flow channel, through this method The electrolyte is immersed in the pores of the electrolyte by heating and heating to realize the addition of the electrolyte. This method of adding electrolyte can reduce the distribution of the electrolyte in the flow channel, which can effectively reduce the thickness of the bipolar plate, and the electrolyte is added to the cathode material. During the heating process, nickel can chemically react with lithium carbonate to generate LiNiO ₂ , so as to quickly realize the lithiation process of the cathode material and improve the performance of the fuel cell.

Further, the present application precisely controls the heating program. During the heating process from room temperature to 450 °C, the oxidation of the electrode is prevented under the protection of nitrogen gas. Under the protection of hydrogen gas from 450 °C to 650 °C, the electrolyte is melted and immersed in the electrode pores. The partially oxidized nickel electrode is reduced, and the heat preservation at 650°C can make the nickel react with lithium carbonate to form LiNiO ₂ , so as to quickly realize the lithiation process of the cathode material.

Description of drawings

FIG. 1 is a schematic diagram of adding electrolyte to the electrode of the present application.

Detailed ways

Embodiments of the present application are described in further detail below:

A method for adding molten carbonate fuel cell electrolyte, comprising the following steps:

1. Mix the electrolyte (Li ₂ CO ₃ and K ₂ CO ₃ , the molar ratio between the two is 31:19) with water and ethanol in a mass ratio of 1:(1-2):(1.5-2), And stir for 1.5-2h to obtain electrolyte mixed solution;

2. Weigh the electrode mass and measure the porosity of the electrode, and calculate the demand for electrolyte inside the electrode. The calculation formula is:

Among them, _melectrolyte represents the theoretical demand mass of the electrolyte inside the electrode, ρelectrolyte represents the density of the _electrolyte , _Vpore represents the _electrode pore volume, Velectrode represents the volume of the _electrode , melectrode represents the mass of the electrode, and ρnickel represents the density of metallic _nickel .

3. Put the electrode into the tray, and add the electrolyte mixed solution;

4. Put the tray into the oven, keep the temperature at 30℃ and ventilate until the water and ethanol evaporate completely;

5. Weigh the common mass of the electrode and the electrolyte, and then calculate the mass of the electrolyte attached to the electrode. If the mass of the electrolyte does not meet the actual demanded mass of the electrolyte inside the electrode, repeat steps 3 and 4. If the mass of the electrolyte exceeds that of the electrolyte inside the electrode If the actual demanded mass of the electrode is reached, scrape off the excess electrolyte until the actual demanded mass of the electrolyte inside the electrode is met, and the actual demanded mass of the internal electrolyte of the electrode is 60%-80% of the theoretical demanded mass of the internal electrolyte of the electrode;

6. Put the electrode and electrolyte into the heating furnace, the heating program is normal temperature to 450°C ( _N2 protection) for 5h, 450-650°C ( _H2 protection) for 10h, 650°C ( _H2 protection) for 2h, and cooling with the furnace ( _H2 protection), nitrogen and hydrogen atmospheres prevent the oxidation of the electrodes.

In this application, the electrolyte is mixed with water and ethanol to form a solution. The electrolyte is dissolved in water and ethanol. The addition of ethanol is conducive to the rapid volatilization of the solvent. The electrolyte is placed in the electrode by heating, which is different from the traditional electrolyte and electrode. Mixing preparation, heating process Gas protection is used to prevent the oxidation of nickel electrodes. The addition of catholyte needs to be strictly controlled according to the formula and the quality range of electrolyte requirements to ensure effective electrolyte in the electrode and prevent waste of electrolyte.

Below in conjunction with embodiment, this application is described in further detail:

Example 1

1. Mix electrolyte Li ₂ CO ₃ , K ₂ CO ₃ with water and ethanol in proportion (20:20:30, mass ratio), and stir for 1.5h;

2. Weigh the electrode mass of 33g and measure the porosity of the electrode to 77%, and calculate the theoretical demand for the electrolyte inside the electrode to be 25.3g;

3. Put the electrode that needs to be electrolyzed into the tray, and add the mixed solution of electrolyte and ethanol, the mass is 100g;

4. Put the tray into the oven at 30℃ and ventilate until the ethanol evaporates completely;

5. Weigh the common mass of the electrode and the electrolyte to 52g, which meets the required mass range of the electrolyte inside the electrode (75% of the theoretical requirement).

6. Put the electrode and electrolyte into the heating furnace, the heating program is normal temperature to 450°C (N ₂ protection) for 5h, 450-650°C (H ₂ protection) for 10h, 650°C for 2h (H ₂ protection), and cool down with the furnace ( _H2 protection), nitrogen and hydrogen atmospheres prevent the oxidation of the electrodes.

7. Weigh 50.9 g of the electrode and electrolyte after cooling, and calculate the mass of the added electrolyte to be 17.9 g.

8. Assemble the electrode into a single cell for performance testing. The single cell requires 50g of electrolyte, the electrode contains 17.9g of salt, and the rest of the electrolyte is placed in the flow channel. The open circuit voltage of a single cell is 1.3905V, and the current density of the battery is 93A/cm ² . Compared with the conventional method of adding 50g of electrolyte in the flow channel, the open circuit voltage is increased by 0.05V, and the current density is increased by 10A/cm ² .

Example 2

1. Mix electrolyte Li ₂ CO ₃ , K ₂ CO ₃ with water and ethanol in proportion (20:40:40, mass ratio), and stir for 1.8h;

2. Weigh the electrode mass of 30g and measure the porosity of the electrode to 77%, and calculate the theoretical demand for the electrolyte inside the electrode to be 24.1g;

3. Put the electrode that needs to be electrolyzed into the tray, and add the mixed solution of electrolyte and ethanol, the mass is 100g;

4. Put the tray into the oven at 30℃ and ventilate until the ethanol evaporates completely;

5. Weigh the common mass of the electrode and the electrolyte to 44.5g, which meets the required mass range of the electrolyte inside the electrode (60% of the theoretical electrode electrolyte mass).

6. Put the electrode and electrolyte into the heating furnace, the heating program is normal temperature to 450°C (N ₂ protection) for 5h, 450-650°C (H ₂ protection) for 10h, 650°C for 2h (H ₂ protection), and cool down with the furnace ( _H2 protection), nitrogen and hydrogen atmospheres prevent the oxidation of the electrodes.

7. The weight of the electrode and electrolyte after cooling is weighed to 43g, and the mass of the added electrolyte is calculated to be 13g.

8. Assemble the electrode into a single cell for performance testing. The single cell requires 50g of electrolyte, 13g of salt in the electrode, and the rest of the electrolyte is placed in the flow channel. The single cell open circuit voltage is 1.3885V, and the battery current density is 94A/cm ² . Compared with the conventional method of adding 50g of electrolyte in the flow channel, the open circuit voltage is increased by 0.04V, and the current density is increased by 9A/cm ² .

Example 3

1. Mix the electrolyte Li ₂ CO ₃ and K ₂ CO ₃ with water and ethanol in proportion (20:30:35, mass ratio), and stir for 2h;

2. Weigh the electrode mass of 35g and measure the porosity of the electrode to 77%, and calculate the theoretical demand for the electrolyte inside the electrode to be 27.1g;

3. Put the electrode that needs to be electrolyzed into the tray, and add the mixed solution of electrolyte and ethanol, the mass is 100g;

4. Put the tray into the oven at 30℃ and ventilate until the ethanol evaporates completely;

5. The common mass of the electrode and the electrolyte is weighed to 56.1g, which meets the required mass range of the electrolyte inside the electrode (78% of the theoretical electrode electrolyte requirement).

6. Put the electrode and electrolyte into the heating furnace, the heating program is normal temperature to 450°C (N ₂ protection) for 5h, 450-650°C (H ₂ protection) for 10h, 650°C for 2h (H ₂ protection), and cool down with the furnace ( _H2 protection), nitrogen and hydrogen atmospheres prevent the oxidation of the electrodes.

7. Weigh 55.1 g of the electrode and electrolyte after cooling, and calculate the mass of the added electrolyte to be 20.1 g.

8. Assemble the electrode into a single cell for performance testing. The single cell requires 50g of electrolyte, the electrode contains 20.1g of salt, and the rest of the electrolyte is placed in the flow channel. The single cell open circuit voltage is 1.401V, and the battery current density is 96A/cm ² . Compared with the conventional method of adding 50 g of electrolyte in the flow channel, the open circuit voltage is increased by 0.06V, and the current density is increased by 12A/cm ² .

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of the present application. within the scope of protection.

Claims (9)

A method for adding molten carbonate fuel cell electrolyte, comprising the following steps: Step 1: mix the electrolyte with water and ethanol, and stir to obtain an electrolyte mixed solution; Step 2: Weigh the mass of the electrode and measure the porosity of the electrode, and calculate the theoretical required mass of the electrolyte inside the electrode; Step 3: Put the electrode into the container, and add the electrolyte mixed solution; Step 4: place the container under drying conditions until the water and ethanol are completely volatilized; Step 5: Weigh the total mass of the electrode and the electrolyte attached to the electrode after drying, and then calculate the mass of the electrolyte attached to the electrode. If the electrolyte quality does not meet the actual required quality of the electrolyte inside the electrode, repeat steps 3 and 3 Fourth, if the quality of the electrolyte exceeds the actual required quality of the electrolyte inside the electrode, scrape off the excess electrolyte until the actual required quality range of the electrolyte inside the electrode is met. %; Step 6: heating the electrode obtained in step 5, and cooling after the heating and heating, that is, the addition of the molten carbonate fuel cell electrolyte is completed. A method for adding molten carbonate fuel cell electrolyte according to claim 1, wherein in step 1, the electrolyte adopts a mixture of Li ₂ CO ₃ and K ₂ CO ₃ , and Li ₂ CO ₃ and K ₂ CO ₃ The molar ratio between them is 31:19. A kind of molten carbonate fuel cell electrolyte adding method according to claim 1 is characterized in that, in step 1, the mass ratio of electrolyte to water and ethanol is 1:(1-2):(1.5-2). The method for adding molten carbonate fuel cell electrolyte according to claim 1, wherein the stirring time in step 1 is 1.5-2h. A kind of molten carbonate fuel cell electrolyte adding method according to claim 1, is characterized in that, in step 2, the formula for calculating the theoretical demand quality of the electrolyte inside the electrode is:

Among them, _melectrolyte represents the theoretical demand mass of the electrolyte inside the electrode, ρelectrolyte represents the density of the _electrolyte , _Vpore represents the _electrode pore volume, Velectrode represents the volume of the _electrode , melectrode represents the mass of the electrode, and ρnickel represents the density of metallic _nickel . The method for adding electrolyte of a molten carbonate fuel cell according to claim 1, wherein the drying conditions in step 4 are: a temperature of 30°C and ventilation. A method for adding molten carbonate fuel cell electrolyte according to claim 1, characterized in that, in step 6, the heating and temperature rise program is specifically as follows: firstly, the temperature is raised from normal temperature to 450°C in a nitrogen atmosphere, and then in a hydrogen atmosphere The temperature was raised from 450°C to 650°C, and finally, the mixture was kept at 650°C for 2h under the presence of hydrogen. The method for adding molten carbonate fuel cell electrolyte according to claim 7, wherein the temperature is increased from normal temperature to 450°C for 5 hours. The method for adding molten carbonate fuel cell electrolyte according to claim 8, wherein the temperature is increased from 450°C to 650°C for 10 hours.

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