A method for controlling the sintering temperature of a battery stack

Abstract

The present invention provides a method for controlling the sintering temperature of a battery stack, including a stage of moisture volatilization of the separator and ethanol volatilization of the electrolyte salt in the battery stack body, a stage of organic matter combustion and volatilization in the separator, a stage of Ni oxidation at the cathode of the battery stack, a stage of the electrolyte salt becoming molten, and a stage of anode electrode reduction. Among them, CO2 is introduced on the anode side in the stage of the electrolyte salt becoming molten, N2 is introduced on the anode side in the stage of Ni oxidation at the cathode of the battery stack. In the stage of organic matter combustion and volatilization, the temperature is raised from 136 - 140 °C to 238 °C - 242 °C within 17 - 19 h, and the temperature is maintained at 238 °C - 242 °C for 7 - 12 h. Then, the temperature is raised from 238 °C - 242 °C to 343 - 347 °C within 17 - 19 h, and the temperature is maintained at 343 - 347 °C for 5 - 9 h, which can remove the organic matter in the separator and form an internal pore structure, increase the amount of electrolyte salt infiltrating the separator, accelerate the ion conduction process, and improve the voltage response speed.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt fuel cells, and particularly to a method for controlling the sintering temperature of a battery stack. Background Art

[0002] A fuel cell is a power generation device that directly converts the chemical energy of a fuel into electrical energy through an electrochemical reaction without combustion. The energy conversion efficiency is not limited by the "Carnot cycle" and can reach as high as 50%-60%. When a fuel cell operates, hydrogen or other fuels are input into the anode, and an electrochemical reaction of oxidation of hydrogen or other fuels and reduction of oxygen occurs at the interface of the electrode and the electrolyte, generating an electric current and outputting electrical energy.

[0003] Since a molten carbonate fuel cell operates at 650°C and the electrolyte diaphragm is calcined during the temperature rise process of the battery stack, the temperature rise of the battery stack is particularly important. The quality of the calcination directly affects the performance output of the battery stack.

[0004] CN106935887B discloses a method for starting a molten carbonate fuel cell stack: (1) calculating the required air flow according to the power of the battery stack; (2) raising the temperature of the battery stack, and the temperature rise rate shall not be greater than 5°C / min; (3) from room temperature to 200°C, introducing a set amount of air from the cathode side of the battery stack to ensure a gas leakage rate of 20%-30% at the sealing surface of the battery stack; (4) from 200°C to 450°C, increasing carbon dioxide on the cathode side of the battery stack, and the gas volume is half of the air flow. When the temperature reaches 450°C, ensure that there is no gas leakage at the sealing surface; (5) from 450°C to 550°C, closing the cathode intake, and the battery stack enters the salt melting stage; (6) from 550°C to 650°C, introducing hydrogen into the anode to reduce the electrode; (7) after the temperature reaches 650°C, introducing air and carbon dioxide into the cathode to perform a discharge performance test; however, during the battery calcination process, the organic matter in the key material diaphragm of the battery is not completely discharged, which will cause a decrease in the porosity of the diaphragm, resulting in less infiltration of the subsequent electrolyte salt into the diaphragm, affecting the ion conduction process and the slow voltage response speed. Summary of the Invention

[0005] The present invention provides a method for controlling the sintering temperature of a battery stack. It includes the stage of moisture volatilization of the diaphragm and ethanol volatilization of the electrolyte salt in the battery stack body, the stage of combustion and volatilization of organic matter in the diaphragm, the stage of Ni oxidation on the cathode of the battery stack, the stage of the electrolyte salt becoming molten, and the stage of reduction of the anode electrode. Among them, CO2 is introduced on the anode side during the stage of the electrolyte salt becoming molten, N2 is introduced on the anode side during the stage of Ni oxidation on the cathode of the battery stack, and the following procedure is used for temperature rise during the stage of combustion and volatilization of organic matter;

[0006] Heat up from 136 - 140°C to 238 - 242°C within 17 - 19 h, and keep the temperature at 238 - 242°C for 7 - 12 h. Then heat up from 238 - 242°C to 343 - 347°C within 17 - 19 h, and keep the temperature at 343 - 347°C for 5 - 9 h.

[0007] Further, the stage when the electrolyte salt becomes molten state is as follows: heat up from 403 - 407°C to 478 - 482°C, with a heating rate of 0.03 - 0.05°C / min; heat up from 478 - 482°C to 578 - 582°C, with a heating rate of 0.03 - 0.04°C / min.

[0008] Even further, detect the content of CO2 in the tail gas during the stage when the organic matter in the separator burns and volatilizes.

[0009] Further, the stage when the moisture in the separator of the battery stack body volatilizes and the ethanol in the electrolyte salt volatilizes is to heat up from room temperature to 136 - 140°C, and then keep the temperature at 136 - 140°C for 5 - 7 h.

[0010] Further, the stage when the Ni at the cathode of the battery stack oxidizes is to heat up from 343 - 347°C to 403 - 407°C, with a heating time of 17 - 19 h.

[0011] Further, the stage when the anode electrode is reduced is to heat up from 578 - 582°C to 668 - 672°C, with a heating time of 11 - 13 h, and then keep the temperature at 668 - 672°C.

[0012] Even further, the gas flow rate of CO2 introduced on the anode side during the stage when the electrolyte salt becomes molten state is 3 - 5 L / min.

[0013] Even further, the gas flow rate of N2 introduced on the anode side during the stage when the Ni at the cathode of the battery stack oxidizes is 13 - 17 L / min.

[0014] Even further, the battery stack obtained after being processed by the battery stack sintering temperature control method described above.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] In the present invention, CO2 is introduced on the anode side during the stage when the electrolyte salt becomes molten, which can avoid electrolyte loss; N2 is introduced on the anode side during the stage when Ni on the cathode of the battery stack is oxidized, which can maintain the internal pressure difference balance of the battery stack; during the stage of organic matter combustion and volatilization, the temperature is raised in a programmed manner, from 136 - 140 °C to 238 - 242 °C within 17 - 19 h, and kept at 238 - 242 °C for 7 - 12 h, then from 238 - 242 °C to 343 - 347 °C within 17 - 19 h, and kept at 343 - 347 °C for 5 - 9 h, which can remove the organic matter in the diaphragm and form an internal pore structure, accelerate the ion conduction process, and improve the voltage response speed. Detailed implementation mode

[0017] The temperature rise and roasting test of the battery stack body is only applicable to a single battery stack. Before roasting, both the cathode and anode are Ni electrodes. After the battery stack is roasted, before testing, the anode is a Ni electrode and the cathode is a NiO electrode. The flow rates of the inlet gases such as air, N2, H2, CO2, etc. required can be calculated according to the power of the battery stack. The following examples and comparative examples are all carried out with a 10-cell molten carbonate battery stack as an example for the temperature rise and roasting control method, and its effective battery area is 2 m 2 , and the power generation power is 1.2 KW; after roasting, the open circuit voltage is connected to an electronic load for real-time monitoring. If the open circuit voltage of a single cell is expected to be 1.0 V - 1.2 V, then the expected open circuit voltage of the 10-cell battery stack of the present invention is 10 - 12 V.

[0018] Example 1

[0019] This example provides a method for controlling the sintering temperature of a battery stack. The battery stack is in-situ roasted and heated by a heating furnace, and the heating program is set as follows:

[0020] (1) Stage of diaphragm moisture volatilization and ethanol volatilization in the electrolyte salt

[0021] The temperature is raised from room temperature to 138 °C in 12 h. During this period, the air flow rate introduced on the cathode side of the battery stack is 20 L / min;

[0022] It is kept at 138 °C for 6 h. During this period, the air flow rate introduced into the battery stack is 20 L / min.

[0023] (2) Stage of organic matter combustion and volatilization in the diaphragm

[0024] The temperature is raised from 138 °C to 240 °C in 18 h; at 240 °C: kept for 10 h; the temperature is raised from 240 °C to 345 °C in 18 h; at 345 °C: kept for 7 h;

[0025] During this period, the air flow rate into the cathode of the battery stack was 20 L / min, and the N2 flow rate into the anode side was 15 L / min. After the temperature rise was completed, the concentration of CO2 in the exhaust gas was detected. The results showed that the concentration of CO2 in the exhaust gas was 135 ppm, which was lower than 280 ppm, indicating that the organic matter in the diaphragm had been basically discharged.

[0026] (3) Cathode Ni oxidation stage of the battery stack

[0027] The temperature was raised from 345 °C to 405 °C over 18 h;

[0028] During this period, the air flow rate into the cathode of the battery stack was 20 L / min, and the N2 flow rate into the anode side was 15 L / min.

[0029] (4) Stage when the electrolyte salt becomes molten

[0030] The temperature was raised from 405 °C to 480 °C at a heating rate of 0.05 °C / min;

[0031] The temperature was raised from 480 °C to 580 °C at a heating rate of 0.035 °C / min;

[0032] During this period, the air intake of the cathode of the battery stack and the N2 intake of the anode were closed, and a small amount of CO2 was introduced into the anode at a flow rate of 3 L / min, which could reduce the loss of the molten electrolyte salt during the dialysis process.

[0033] (5) Anode electrode reduction stage

[0034] The temperature was raised from 580 °C to 670 °C over 12 h; then it was held at 670 °C;

[0035] During this period, the CO2 intake of the anode side of the battery stack was closed, and H2 was introduced for reduction at a H2 flow rate of 10 L / min.

[0036] After the temperature reached 670 °C, the H2 flow rate on the anode side was 13 L / min, the N2 flow rate was 20 L / min, the air flow rate was 37 L / min, and the CO2 flow rate was 12 L / min. After stabilizing for 10 min, an electronic load was connected for real-time voltage monitoring. The open-circuit voltage of the battery stack reached 11 V within 20 min; then, a discharge performance test was carried out at a given voltage. The corresponding current was measured to be 172 A at 7 V, and the discharge power reached 1.2 KW, and it could operate stably at this discharge power for 1 h. This indicates that the internal roasting effect of the battery stack is good, and the battery stack temperature sintering control method has achieved remarkable results.

[0037] Example 2

[0038] This example provides a method for controlling the sintering temperature of a battery stack. The battery stack is in-situ roasted and heated using a heating furnace, and the heating program is set as follows:

[0039] (1) Stage of moisture volatilization of the separator and ethanol volatilization in the electrolyte salt in the battery stack body

[0040] Heat up from room temperature to 136 °C over 11 h. During this period, the air flow rate into the cathode side of the battery stack is 20 L / min;

[0041] Keep warm at 136 °C for 7 h. During this period, the air flow rate into the battery stack is 20 L / min.

[0042] (2) Stage of combustion and volatilization of organic matter in the separator

[0043] Heat up from 136 °C to 238 °C over 19 h; keep warm at 238 °C for 12 h; heat up from 238 °C to 343 °C over 19 h; keep warm at 343 °C for 9 h;

[0044] During this period, the air flow rate into the cathode of the battery stack is 20 L / min, and the N2 flow rate into the anode side is 15 L / min. In the later stage of organic matter volatilization, the concentration of CO2 in the exhaust gas is detected. The result shows that the concentration of CO2 in the exhaust gas is 156 ppm, which is lower than 280 ppm, indicating that the organic matter in the separator has been basically discharged.

[0045] (3) Stage of Ni oxidation in the cathode of the battery stack

[0046] Heat up from 343 °C to 403 °C over 19 h;

[0047] During this period, the air flow rate into the cathode of the battery stack is 20 L / min, and the N2 flow rate into the anode side is 15 L / min.

[0048] (4) Stage of electrolyte salt becoming molten

[0049] Heat up from 403 °C to 478 °C: heating rate is 0.03 °C / min;

[0050] Heat up from 478 °C to 578 °C: heating rate is 0.04 °C / min;

[0051] During this period, close the air intake of the cathode of the battery stack and the N2 intake of the anode, and introduce CO2 into the anode with a gas flow rate of 3 L / min, which can reduce the loss of molten electrolyte salt during the dialysis process.

[0052] (5) Stage of anode electrode reduction

[0053] Heat up from 580 °C to 670 °C over 13 h; then keep warm at 670 °C;

[0054] During this period, close the CO2 intake of the anode side of the battery stack and introduce H2 for reduction with an H2 gas flow rate of 10 L / min.

[0055] After the temperature reaches 670 °C, H2 and N2 continue to be introduced on the anode side, and air and CO2 are introduced on the cathode side. The flow rate of H2 is 13 L / min, the flow rate of N2 is 20 L / min, the flow rate of air is 37 L / min, and the flow rate of CO2 is 12 L / min. After stabilizing for 10 min, an electronic load is connected for real-time voltage monitoring. The open-circuit voltage of the battery stack reaches 10.9 V within 18 min, and then the discharge performance test is carried out at a given voltage. The corresponding current is measured to be 170 A at 7 V, and the discharge power approximately reaches 1.2 KW. The fast voltage response indicates that the roasting effect inside the battery stack is good, and the battery stack temperature sintering control method has achieved significant results.

[0056] Example 3

[0057] This embodiment provides a method for controlling the sintering temperature of a battery stack. The battery stack is heated in situ by a heating furnace for temperature rise, and the temperature rise program is set as follows:

[0058] (1) Stage of moisture volatilization of the diaphragm in the battery stack body and ethanol volatilization in the electrolyte salt

[0059] The temperature is raised from room temperature to 140 °C over 13 h. During this period, the air flow rate introduced on the cathode side of the battery stack is 20 L / min;

[0060] It is kept at 140 °C for 5 h. During this period, the air flow rate introduced into the battery stack is 20 L / min.

[0061] (2) Stage of combustion and volatilization of organic substances in the diaphragm

[0062] The temperature is raised from 140 °C to 242 °C over 17 h; kept at 242 °C for 7 h; the temperature is raised from 242 °C to 347 °C over 17 h; kept at 345 °C for 5 h;

[0063] During this period, the air flow rate introduced on the cathode of the battery stack is 20 L / min, and the N2 flow rate introduced on the anode side is 15 L / min. In the later stage of organic matter volatilization, the concentration of CO2 in the tail gas is detected. The result shows that the concentration of CO2 in the tail gas is 130 ppm, which is lower than 280 ppm, indicating that the organic matter in the diaphragm has been basically discharged.

[0064] (3) Stage of Ni oxidation on the cathode of the battery stack

[0065] The temperature is raised from 347 °C to 407 °C over 17 h;

[0066] During this period, the air flow rate introduced on the cathode of the battery stack is 20 L / min, and the N2 flow rate introduced on the anode side is 15 L / min.

[0067] (4) Stage when the electrolyte salt becomes molten

[0068] Heat up from 407 °C to 482 °C: the heating rate is 0.03 °C / min;

[0069] Heat up from 482 °C to 582 °C: the heating rate is 0.035 °C / min;

[0070] During this period, close the cathode air intake and anode N2 intake of the battery stack, and introduce CO2 into the anode with a gas volume of 3 L / min, which can reduce the loss of molten electrolyte salt during the dialysis process.

[0071] (5) Anode electrode reduction stage

[0072] Heat up from 582 °C to 672 °C: heat up for 11 h; then keep the temperature at 670 °C;

[0073] During this period, close the CO2 intake on the anode side of the battery stack, introduce H2 for reduction, and the gas volume of H2 is 10 L / min.

[0074] After the temperature reaches 670 °C, continue to introduce H2 and N2 on the anode side, and introduce air and CO2 on the cathode side. Among them, the gas volume of H2 is 13 L / min, the gas volume of N2 is 20 L / min, the gas volume of air is 37 L / min, and the gas volume of CO2 is 12 L / min. After stabilizing for 10 min, connect the electronic load for real-time voltage monitoring. The open-circuit voltage of the battery stack reaches 11.2 V within 21 min, and then perform the discharge performance test at the given voltage. The corresponding current is 171 A at 7 V, and the discharge power approximately reaches 1.2 KW. The fast voltage response indicates that the baking effect inside the battery stack is better, and the battery stack temperature sintering control method has achieved significant results.

[0075] Comparative Example 1

[0076] The heating method of this comparative example is carried out according to CN106935887B, and the steps are as follows:

[0077] (1) Heat up from room temperature to 200 °C, adjust the assembly pressure of the battery stack so that the exhaust gas flow rate of the battery stack is 14.4 L, and 18 L / min of air leaks through the sealing surface to ensure the baking at the sealing surface;

[0078] (2) Heat up from 200 °C to 450 °C, and then introduce 9 L / min of CO2 into the cathode side of the battery stack to eliminate the carbon deposition during the baking process of the electrolyte diaphragm. At the same time, as the baking temperature rises, slowly increase the assembly pressure and gradually reduce the air leakage at the sealing surface. When the temperature reaches 450 °C, the cathode exhaust gas volume is basically equal to the intake gas volume;

[0079] (3) Heat up from 450 °C to 550 °C, close the intake on the cathode side to ensure the smooth immersion of the internal electrolyte of the battery stack into the electrolyte diaphragm;

[0080] (4) Heat up from 550 °C to 650 °C, and introduce H2 on the anode side of the battery stack for reduction;

[0081] After the temperature reaches 650 °C, the flow rate of H2 introduced into the anode is 6 L / min, the flow rate of air introduced into the cathode is 18 L / min, and the flow rate of CO2 is 7.2 L / min;

[0082] Result: Connect an electronic load for real-time voltage monitoring. The open-circuit voltage of the battery stack reaches 9.8 V in 45 min, and then the discharge performance test is carried out at a constant voltage. The corresponding current is 155 A at 7 V, and the discharge power approximately reaches 1.08 KW. Although the problem of internal carbon deposition is excluded, the organic matter in the electrolyte diaphragm cannot be completely discharged, and the loss of electrolyte salt leads to a relatively low open-circuit voltage value and a relatively low discharge power, indicating that the internal roasting of the battery stack needs to be improved, and the method for controlling the sintering temperature of the battery stack needs to be improved.

[0083] Comparative Example 2

[0084] This comparative example provides a method for controlling the sintering temperature of a battery stack, which is basically the same as that of Example 1, except that the temperature increase program in the stage of combustion and volatilization of organic matter in the diaphragm is as follows:

[0085] Heat up from 138 °C to 345 °C for 35 h; after the temperature increase is completed, detect the concentration of CO2 in the tail gas. The result shows that the concentration of CO2 in the tail gas is 420 ppm.

[0086] Result: Connect an electronic load for real-time voltage monitoring. The open-circuit voltage of the battery stack reaches 9.0 V in 50 min, and the voltage no longer rises with time. This indicates that the internal roasting of the battery stack is incomplete, and the method for controlling the sintering temperature of the battery stack needs to be improved.

[0087] Comparative Example 3

[0088] This comparative example provides a method for controlling the sintering temperature of a battery stack, which is basically the same as that of Example 1, except that N2 is not introduced in the stage of Ni oxidation at the cathode of the battery stack.

[0089] Result: Connect an electronic load for real-time voltage monitoring. The open-circuit voltage of the battery stack reaches 8.8 V in 48 min, and the voltage no longer rises with time. This indicates that the internal roasting of the battery stack is incomplete, and the method for controlling the sintering temperature of the battery stack needs to be improved.

[0090] Comparative Example 4

[0091] This comparative example provides a method for controlling the sintering temperature of a battery stack, which is basically the same as that of Example 1, except that CO2 is not introduced in the stage when the electrolyte salt becomes molten.

[0092] Results: The electronic load was connected for real-time voltage monitoring. The open-circuit voltage of the battery stack reached 8.5V in 50 minutes, and the voltage no longer increased with time. This indicates that the internal baking of the battery stack has failed, and the temperature sintering control method of the battery stack needs to be improved.

[0093] Comparative Example 5

[0094] This comparative example provides a method for controlling the sintering temperature of a battery stack, which is basically the same as Example 1, with the only difference being that: during the combustion and volatilization stage of organic matter in the diaphragm, the temperature is raised according to the following procedure: from 138°C to 240°C for 12 hours; 240°C: keep warm for 2 hours; 240°C to 345°C for 12 hours; 345°C, keep warm for 2 hours; after the heating is completed, the concentration of CO2 in the exhaust gas is detected, and the result shows that the concentration of CO2 in the exhaust gas is 380ppm.

[0095] Results: The electronic load was connected for real-time voltage monitoring. The open-circuit voltage of the battery stack reached 9.2V in 50 minutes, and the voltage no longer increased with time. This indicates that the internal baking of the battery stack has failed, and the temperature sintering control method of the battery stack needs to be improved.

[0096] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for controlling the sintering temperature of a battery stack, including the stage of moisture volatilization of the separator and ethanol volatilization of the electrolyte salt in the battery stack body, the stage of organic matter combustion and volatilization in the separator, the stage of Ni oxidation at the cathode of the battery stack, the stage of the electrolyte salt becoming molten, and the stage of anode electrode reduction, wherein, During the stage when the electrolyte salt becomes molten, CO2 is introduced on the anode side. During the stage when the Ni at the cathode of the battery stack is oxidized, N2 is introduced on the anode side. During the stage when the organic matter burns and volatilizes, the temperature is increased using the following procedure; The temperature is increased from 136 - 140 °C to 238 - 242 °C within 17 - 19 h, and held at 238 - 242 °C for 7 - 12 h. Then the temperature is increased from 238 - 242 °C to 343 - 347 °C within 17 - 19 h, and held at 343 - 347 °C for 5 - 9 h.

2. The method for controlling the sintering temperature of a battery stack according to claim 1, characterized in that, The stage when the electrolyte salt becomes molten is as follows: The temperature is increased from 403 - 407 °C to 478 - 482 °C at a heating rate of 0.03 - 0.05 °C / min; The temperature is increased from 478 - 482 °C to 578 - 582 °C at a heating rate of 0.03 - 0.04 °C / min.

3. The battery stack sintering temperature control method according to claim 1 or 2, characterized in that During the stage when the organic matter in the separator burns and volatilizes, the content of CO2 in the exhaust gas is detected.

4. The method for controlling the sintering temperature of the battery stack according to claim 1 or 2, characterized in that, The stage when the moisture in the separator of the battery stack body volatilizes and the ethanol in the electrolyte salt volatilizes is to increase the temperature from room temperature to 136 - 140 °C, and then hold at 136 - 140 °C for 5 - 7 h.

5. The battery stack sintering temperature control method according to claim 1 or 2, characterized in that The stage when the Ni at the cathode of the battery stack is oxidized is to increase the temperature from 343 - 347 °C to 403 - 407 °C over 17 - 19 h.

6. The battery stack sintering temperature control method according to claim 1 or 2, characterized in that The stage when the anode electrode is reduced is to increase the temperature from 578 - 582 °C to 668 - 672 °C over 11 - 13 h, and then hold at 668 - 672 °C.

7. The method for controlling the sintering temperature of the battery stack according to claim 1 or 2, characterized in that, During the stage when the electrolyte salt becomes molten, the gas flow rate of CO2 introduced on the anode side is 3 - 5 L / min.

8. The battery stack sintering temperature control method according to claim 1 or 2, characterized in that During the stage when the Ni at the cathode of the battery stack is oxidized, the gas flow rate of N2 introduced on the anode side is 13 - 17 L / min.

9. A battery stack obtained by treating according to the battery stack sintering temperature control method described in any one of claims 1 - 8.