Electrode ink manufacturing method and electrode ink manufacturing device

Abstract

To provide a method for producing an electrode ink capable of suppressing generation of air bubbles, even when a ratio of water in a solvent of an electrode paste is increased.SOLUTION: A method for producing electrode ink comprises, for each of a first material containing conductive particles, a second material containing a polymer material, and a solvent containing water and an organic solvent soluble in water, a degassing step S60 to remove soluble gases that dissolve more easily in alcohol than in nitrogen, and a kneading step in which the first material from which the soluble gas has been removed, the second material, and the solvent are mixed. The kneading step is carried out under an atmosphere of low-solubility gas that is less soluble in alcohol than in nitrogen.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a method and an apparatus for producing electrode ink used in the manufacture of electrodes for electrochemical cells. [Background technology]

[0002] Electrode ink is used in the manufacturing process of electrodes for electrochemical cells such as fuel cells and water electrolysis devices. Electrode ink is a paste-like coating liquid containing conductive particles such as carbon particles, and is used to form a catalyst layer or a diffusion layer by applying it to the surface of an electrolyte membrane and drying it.

[0003] For example, electrode ink for a catalyst used in a proton-conducting electrolyte membrane contains a carbon support carrying a platinum catalyst, an ionomer, and an appropriate solvent. The electrode ink is prepared by mixing the carbon support, an ionomer solution in which the ionomer is dispersed, and a solvent in a kneading process (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-66510 A Summary of the Invention [Problem to be solved by the invention]

[0005] The characteristics of electrodes are significantly affected by the solvent in the electrode ink. A mixture of water and a water-soluble organic solvent (e.g., alcohols) is used as the solvent for electrode ink. While organic solvents have the effect of increasing the dispersibility of polymeric materials such as ionomers, they also reduce the rate at which the polymeric material (e.g., ionomer) adheres to conductive particles (e.g., carbon support). Therefore, in the case of electrode ink for catalysts, increasing the concentration of organic solvent makes it difficult for the ionomer to adhere to the carbon support, reducing the proton transport pathways and tending to increase the proton resistance of the catalyst.

[0006] A similar problem occurs with electrode inks used in the manufacture of gas diffusion layers. Electrode inks for gas diffusion layers contain carbon particles as conductive particles, a water-repellent polymer material (e.g., fluororesin), and a solvent containing water and an organic solvent. Increasing the proportion of water in the solvent increases the adsorption of the polymer material that constitutes the water-repellent agent to the conductive particles.

[0007] Therefore, in order to improve the adsorption of polymer materials to conductive particles, the inventors of the present application have investigated reducing the concentration of organic solvents contained in the solvent in the electrode ink and increasing the proportion of water.

[0008] However, it was found that increasing the proportion of water in the solvent can result in the generation of large amounts of bubbles during the kneading process. Furthermore, increasing the proportion of water in the solvent tends to increase the viscosity of the electrode ink mixture up to an A / W ratio (the ratio of the alcohol mass divided by the water mass) of approximately 0.07. Therefore, once bubbles form in the electrode ink mixture (electrode paste), it is extremely difficult to remove them. When electrode ink containing such bubbles dries, the bubbles remain as large cavities, reducing the electrode's performance. Therefore, there is a need for a manufacturing method and an apparatus for manufacturing electrode ink that can suppress the generation of bubbles even when the proportion of water in the electrode paste solvent is increased.

[0009] An object of the present invention is to solve the above-mentioned problems. [Means for solving the problem]

[0010] A first aspect of the present disclosure is a method for producing an electrode ink, comprising: a degassing step for removing soluble gases that are more soluble in the organic solvent than nitrogen from each of a first raw material containing conductive particles, a second raw material containing a polymer material, and a solvent containing water and an organic solvent that is soluble in water; and a kneading step for mixing the first raw material from which the soluble gases have been removed, the second raw material, and the solvent, wherein the kneading step is carried out in an atmosphere of a low-solubility gas that is less soluble in the organic solvent than nitrogen.

[0011] a low-solubility gas supply unit that supplies a low-solubility gas that is less soluble in the organic solvent than nitrogen to the first container to replace the atmosphere of the first raw material with the low-solubility gas; a first degassing device connected to the second container to remove gas from the second raw material; a second degassing device connected to the third container to remove gas from the organic solvent; a third degassing device connected to the fourth container to remove gas from the water; and an agitation container that mixes the first raw material, whose atmosphere has been replaced with the low-solubility gas, the second raw material from which the gas has been removed, the organic solvent from which the gas has been removed, and the water from which the gas has been removed, in the low-solubility gas atmosphere. [Effects of the Invention]

[0012] The above-described electrode ink manufacturing method and electrode ink manufacturing device can suppress the generation of bubbles by preventing the release of soluble gas that has become insoluble in the organic solvent, etc. due to mixing with water during the kneading process. As a result, the above-described electrode ink manufacturing method and electrode ink manufacturing device can increase the proportion of water in the solvent of the electrode ink, and improve the adsorption of the polymer material to the conductive particles. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a process diagram illustrating a method for producing a membrane electrode assembly according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing the reaction of the solvent (normal propanol) contained in the solvent in the electrode ink. [Figure 3] FIG. 3A is an explanatory diagram of the weight fraction of the electrode ink of the embodiment and the electrode ink of the comparative example, and FIG. 3B is an explanatory diagram of the weight fraction of the ionomer solution. [Figure 4] Figure 4 is a photograph of a catalyst ink with bubbles. [Figure 5] FIG. 5A is a diagram showing the amounts of oxygen, nitrogen, and helium dissolved in organic solvents, and FIG. 5B is a graph showing the relationship between the amount of dissolved oxygen relative to the composition ratio of normal propanol / water (solvent) and the amount of dissolved oxygen in an ionomer solution. [Figure 6] FIG. 6A is a diagram illustrating the steps of the method for producing an electrode ink according to the first embodiment, and FIG. 6B is a diagram illustrating the degassing step according to the second embodiment. [Figure 7] FIG. 7 is an explanatory diagram of an electrode ink (catalyst ink) manufacturing apparatus according to an embodiment. [Figure 8] FIG. 8 is an explanatory diagram of the degassing device of FIG. [Figure 9] FIG. 9 is an explanatory diagram of the stirring vessel of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] For example, electrochemical cells such as fuel cells and water electrolysis devices use a membrane electrode assembly (UEA) in which an electrolyte membrane is sandwiched between a pair of electrodes. The electrolyte membrane uses, for example, an ion exchange resin that allows protons (cations) or hydroxide ions (anions) to pass through. The electrodes have a catalyst layer laminated to cover the surface of the electrolyte membrane and a gas diffusion layer covering the catalyst layer. The catalyst layer is made of a porous material containing, for example, a carbon support supporting a catalyst such as platinum and an ionomer (ion exchange resin) adsorbed on the carbon support. The diffusion layer is made of a porous material containing conductive particles such as carbon particles and a polymer material such as a water repellent.

[0015] The membrane electrode assembly is manufactured by the manufacturing process shown in Figure 1. As shown in the figure, the manufacturing process for the membrane electrode assembly begins with a pre-mixing step S10 in which raw materials for the catalyst ink are mixed. In the pre-mixing step S10, for example, a catalyst (conductive particles), an ionomer (ion-conductive polymer material), a first solvent, and a dispersant are mixed.

[0016] The catalyst is, for example, a carbon support carrying catalyst particles such as platinum, and the carbon support portion forms the current passage path. The catalyst is used as a powdered first raw material. The ionomer is used as an ionomer solution (second raw material). The ionomer solution is a solution in which an ionomer such as an ion exchange resin is dissolved in an ionomer solvent containing alcohol and water. The first solvent is a mixture of alcohol such as normal propanol and water. A small amount of dispersant is added to improve the dispersibility of the catalyst and ionomer in the first solvent.

[0017] Thereafter, the manufacturing process of the membrane electrode assembly proceeds to the main mixing step S20, in which the raw materials of the catalyst ink are further mixed to complete the electrode ink.

[0018] Thereafter, the manufacturing process of the membrane electrode assembly proceeds to the coating step S30. In the coating step S30, the catalyst ink is applied to the surface of the electrolyte membrane to form a coating film of the catalyst ink.

[0019] The membrane electrode assembly manufacturing process then proceeds to the drying step S40. In the drying step S40, the first solvent is removed from the coating film of the catalyst ink, completing the catalyst layer. Note that, since the catalyst layers are formed on both sides of the electrolyte membrane, the coating step S30 and the drying step S40 are performed on both sides of the electrolyte membrane, respectively.

[0020] When forming a gas diffusion layer, the electrode ink for the gas diffusion layer is also subjected to the above-mentioned preliminary stirring step S10, main stirring step S20, coating step S30, and drying step S40. In the electrode ink for the gas diffusion layer, carbon particles are used instead of the catalyst, a water-repellent fluorine-based polymer material is used instead of the ionomer, and a mixture of water and alcohol is used as the solvent.

[0021] Thereafter, the manufacturing process of the membrane electrode assembly proceeds to the assembly step S50. In the assembly step S50, a resin frame member is joined to the periphery of the electrolyte membrane to assemble the membrane electrode assembly (UEA).

[0022] The properties of the membrane electrode assembly manufactured through the above processes are significantly affected by the composition of the catalyst ink solvent. Reducing the concentration of alcohol (e.g., normal propanol) contained in the catalyst ink solvent increases the proportion of ionomer that is adsorbed onto the catalyst and contributes to the electrochemical reaction. For example, in the case of hydrogen fuel cells and electrochemical hydrogen pumps, proton-conductive ion-exchange resins are used as ionomers. In this case, adsorbing more ionomer near the catalyst increases the number of paths through which protons can pass, thereby reducing proton resistance.

[0023] Furthermore, when alcohol contained in the solvent of catalyst ink comes into contact with highly active catalysts such as platinum, it may react with oxygen in the air and produce various impurities. For example, as shown in Figure 2, normal propanol (NPA) contained in the solvent produces impurities such as propyl aldehyde, dipropoxypropane, propionic acid, and propyl propionate through oxidation and condensation reactions. These impurities may cover the surface of the catalyst and reduce its catalytic activity.

[0024] Therefore, the inventors attempted to prepare catalyst inks with lower alcohol concentrations by varying the composition of the catalyst ink, as shown in Figure 3A. In Figure 3A, the A / W ratio is the weight of alcohol contained in each sample divided by the weight of water. The smaller the A / W ratio, the higher the proportion of water. As shown in Figure 3B, the ionomer solution contains a certain amount of alcohol (ethanol, for example) to stably dissolve the ionomer.

[0025] 3A, the amounts of catalyst and ionomer solution are constant, and only the composition of the first solvent is different. The proportion of water in the first solvent increases in the order of Sample 1, Sample 2, and Sample 3.

[0026] Sample 1 in Figure 3A is a catalyst ink with a solvent A / W ratio of 3. Sample 2 is a catalyst ink with a solvent A / W ratio of 0.34. Sample 3 used a first solvent containing nearly 100% water. However, because Sample 1 contains alcohol derived from the ionomer solution, the A / W ratio was not 0, but 0.07.

[0027] The preliminary mixing step S10 and main mixing step S20 in Figure 1 were performed for each of Samples 1, 2, and 3. For Samples 1 and 2, catalyst inks were prepared without foaming. On the other hand, mixing the catalyst ink for Sample 3 resulted in the incorporation of a large amount of air bubbles, as shown in Figure 4. The catalyst ink for Sample 3 obtained in this manner was in the form of a highly viscous slurry, and it was difficult to remove the generated air bubbles later. Therefore, the catalyst ink for Sample 3 could not be used to form a catalyst layer.

[0028] The generation of bubbles in the catalyst ink of Sample 3 is thought to be due to the influence of dissolved gases. That is, as shown in Figure 5A, organic solvents dissolve relatively large amounts of oxygen and nitrogen. In contrast, water dissolves only small amounts of oxygen and nitrogen compared to organic solvents.

[0029] It is believed that the bubbles in Sample 3 were generated when the oxygen and nitrogen dissolved in the ionomer solution were not completely dissolved during the preliminary stirring step S10 to the main stirring step S20. Specifically, as shown in FIG. 3B, the ionomer solution contains a relatively high concentration of alcohol (ethanol) as an organic solvent, and a relatively large amount of oxygen and nitrogen can be dissolved in the ionomer solution. When such an ionomer solution is mixed with a first solvent with a high water concentration, the alcohol concentration of the entire solvent decreases, as shown in FIG. 5B. It is believed that this results in the oxygen or nitrogen contained in the ionomer solution not being completely dissolved in the electrode ink, causing the bubbles to form.

[0030] (First embodiment) As shown in FIG. 6A, the method for producing an electrode ink according to the first embodiment includes a degassing step S60 prior to the preliminary stirring step S10.

[0031] One embodiment of the degassing step S60 includes a step of removing gas components from at least the ionomer solution. The degassing step S60 involves, for example, degassing the ionomer solution under reduced pressure to remove the gas components dissolved in the ionomer solution. To prevent changes in the solvent composition of the ionomer solution, degassing under reduced pressure using a membrane separator capable of removing only the gas components can be suitably used. The degassing step S60 of this embodiment reduces the amount of gas components dissolved in the ionomer solution to below the saturated solubility of the gas components in the electrode ink. Therefore, the electrode ink manufacturing method of this embodiment can prevent the generation of bubbles in the ionomer solution when the ionomer solution is mixed with the first solvent in the preliminary stirring step S10 and the main stirring step S20.

[0032] The degassing step S60 of this embodiment is not limited to vacuum degassing. A second aspect of the degassing step S60 may involve replacing gas components dissolved in the ionomer solution with other gas components whose solubility in organic solvents, such as alcohol, is lower than that of nitrogen. Examples of gases with low solubility in alcohol include helium and hydrogen. These gases have small molecular sizes and low solubility in organic solvents. Helium, in particular, has extremely low solubility in alcohol and water, effectively preventing the generation of bubbles. Hydrogen is more soluble in alcohol than helium, but its solubility in alcohol is lower than that of other gases, such as nitrogen. Furthermore, hydrogen is more inexpensive than helium and is therefore preferred. The ionomer solution in which the gas is replaced with helium or hydrogen in the degassing step S60 of this embodiment has a reduced amount of dissolved gas. Therefore, the degassing step S60 can effectively prevent the generation of bubbles in the catalyst ink during the subsequent preliminary stirring step S10 to main stirring step S20.

[0033] (Second embodiment) In the electrode ink manufacturing method according to the second embodiment, a degassing step S60 is performed on each of the ionomer solution, the water and alcohol solvents, and the dispersant. The degassing step S60 in this embodiment is performed by degassing under reduced pressure or by replacing the gas with a low-solubility gas, similar to the degassing step S60 described with reference to FIG. 6A. For a powdered catalyst, the atmospheric gas is replaced with a low-solubility gas whose solubility in alcohol is equal to or lower than nitrogen in a gas replacement step S70 shown in FIG. 6B. The low-solubility gas is, for example, hydrogen or helium. In the preliminary stirring step S10, the catalyst and water are mixed together. In the preliminary stirring step S10, the ionomer solution, alcohol, and dispersant are mixed separately from the catalyst. Then, in the main stirring step S20, the water and catalyst are mixed with the mixture of the ionomer solution, alcohol, and dispersant to prepare the electrode ink.

[0034] In this embodiment, the preliminary mixing step S10 and the main mixing step S20 are preferably performed in an atmosphere of a low-solubility gas that has low solubility in alcohol and does not undergo an oxidation reaction with the alcohol even in the presence of a catalyst, and does not contain oxygen. For example, the helium or hydrogen used in the degassing step S60 may be used as the atmospheric gas for the preliminary mixing step S10, the main mixing step S20, and the coating step S30. By performing the preliminary mixing step S10, the main mixing step S20, and the coating step S30 in such an atmosphere of a low-solubility gas, oxidation of the alcohol can be prevented and the generation of impurities can be suppressed.

[0035] In the electrode ink manufacturing method of this embodiment, gas components that are likely to generate bubbles are removed from all of the substances introduced into the main stirring step S20 by the degassing step S60 and the gas substitution step S70. As a result, the electrode ink manufacturing method of this embodiment can more reliably reduce the generation of bubbles.

[0036] Next, an electrode ink manufacturing apparatus 10 for carrying out the degassing step S60, preliminary mixing step S10, main mixing step S20, and coating step S30 in the manufacturing method of the membrane electrode assembly of this embodiment will be described.

[0037] (Electrode ink manufacturing equipment) 7, the electrode ink manufacturing apparatus 10 includes a liquid raw material preparation unit 12, a powder raw material preparation unit 14, a first stirring vessel 16, a second stirring vessel 18, a third stirring vessel 20, and a low-solubility gas supply unit 22. The electrode ink manufacturing apparatus 10 may also include a coater 23 that applies the electrode ink to the electrolyte membrane, as necessary.

[0038] The liquid raw material preparation unit 12 has an alcohol tank 24 (third container), a dispersant tank 26, an ionomer tank 28 (second container), a water tank 30 (fourth container), a degassing device 32, a flow meter 34, and a valve 36. The alcohol tank 24 contains alcohol as the first component of the first solvent. The dispersant tank 26 contains a dispersant (liquid). The ionomer tank 28 contains an ionomer solution. The water tank 30 contains water as the second component of the first solvent.

[0039] The alcohol tank 24 is connected to the first agitator vessel 16 through a first flow path 40, and the dispersant tank 26 is connected to the first agitator vessel 16 through a second flow path 42. The ionomer tank 28 is connected to the first agitator vessel 16 through a third flow path 44. The water tank 30 is connected to the second agitator vessel 18 through a fourth flow path 46. The first flow path 40 is connected to a second degassing device 32B (degassing device 32) and a flow meter 34, and the second flow path 42 is connected to a fourth degassing device 32D (degassing device 32) and a flow meter 34. The third flow path 44 is connected to the first degassing device 32A (degassing device 32) and a flow meter 34, and the fourth flow path 46 is connected to a third degassing device 32C (degassing device 32) and a flow meter 34. A valve 36 is provided in each of the first flow path 40, the second flow path 42, the third flow path 44, and the fourth flow path 46.

[0040] As shown in FIG. 8 , the degassing device 32 is a vacuum degassing device and includes a resin membrane tube 48, a vacuum chamber 50, a vacuum pump 52, a pressure sensor 54, and a controller 56. The resin membrane tube 48 is formed of a gas-liquid separation membrane made of a gas-permeable resin. The resin membrane tube 48 is disposed inside the vacuum chamber 50. The resin membrane tube 48 communicates with the first flow path 40, the second flow path 42, the third flow path 44, or the fourth flow path 46, and separates gas components from the liquid flowing through these flow paths. The degassing device 32 maintains a negative pressure in the vacuum chamber 50 by driving the vacuum pump 52 under the control of the pressure sensor 54 and the controller 56.

[0041] 7, the flow meter 34 is, for example, a Coriolis flow meter. The flow meter 34 measures the flow rate (mass) of the liquid passing through. The valve 36 opens and closes at predetermined timings to supply a predetermined amount of liquid.

[0042] The powder raw material preparation unit 14 includes a catalyst container 55 (first container), an abrasive container 57, a weighing device 58, and a transport device 60. The catalyst container 55 contains a powdered catalyst such as a carbon support carrying platinum particles. The abrasive container 57 contains an abrasive for mixing the raw materials. The weighing device 58 weighs a predetermined amount of powder raw material in a low-solubility gas atmosphere. The transport device 60 introduces the powder raw material into the second stirring container 18 in the low-solubility gas atmosphere. The powder raw material preparation unit 14 is disposed in a first chamber 13 isolated from the atmosphere. A low-solubility gas supply unit 22 is connected to the first chamber 13, and a low-solubility gas is supplied. The powder raw material preparation unit 14 replaces the atmosphere surrounding the powder raw material with a low-solubility gas atmosphere.

[0043] The first stirred vessel 16, the second stirred vessel 18, the third stirred vessel 20, and the coater 23 are disposed in a second chamber 17. The second chamber 17 is isolated from the atmosphere and is filled with an inert gas. The second chamber 17 may be filled with a low-solubility gas supplied from a low-solubility gas supply unit 22. The first stirred vessel 16, the second stirred vessel 18, and the third stirred vessel 20 are connected to the low-solubility gas supply unit 22 via a supply passage 68 and an exhaust passage 70, and are filled with the low-solubility gas. The first stirred vessel 16 mixes alcohol, a dispersant, and an ionomer solution, and supplies the resulting mixture to the third stirred vessel 20. The second stirred vessel 18 mixes water, a catalyst, and an abrasive, and supplies the resulting mixture to the third stirred vessel 20.

[0044] The third agitator vessel 20 kneads a catalyst, an ionomer solution, a dispersant, alcohol, water, and an abrasive to prepare an electrode ink. The electrode ink prepared in the third agitator vessel 20 is supplied to the coater 23 while being maintained in a low-solubility gas atmosphere. The coater 23 applies the electrode ink to the surface of the electrolyte membrane to form an electrode layer (catalyst layer). The electrode ink manufacturing apparatus 10 may have a storage container instead of the coater 23. The electrode ink manufactured in the third agitator vessel 20 may be stored in a storage container while being maintained in a low-solubility gas atmosphere.

[0045] The low solubility gas supply unit 22 includes a low solubility gas tank 62, a supply / exhaust unit 64, and a gas recovery container 66. The low solubility gas supply unit 22 is connected to the first chamber 13 and the second chamber 17 through a supply flow path 68 and an exhaust flow path 70. The low solubility gas tank 62 contains a low solubility gas, such as helium or hydrogen. The low solubility gas tank 62 is connected to the supply / exhaust unit 64.

[0046] The supply and exhaust unit 64 sends the low-solubility gas to the supply flow path 68 and sends the low-solubility gas from the exhaust flow path 70 to the gas recovery container 66. The supply and exhaust unit 64 is equipped with valves for controlling the supply pressure. Specifically, as shown in FIG. 9 , the supply and exhaust unit 64 has a pressure reducing valve 72, a pressure gauge 74, a relief valve 76, and a resistance pipe 78 in the supply flow path 68. The supply and exhaust unit 64 also has an exhaust valve 80 in the exhaust flow path 70. The supply and exhaust unit 64 supplies the low-solubility gas at a predetermined pressure to the supply flow path 68 via the pressure reducing valve 72, the relief valve 76, and the resistance pipe 78. The supply and exhaust unit 64 also exhausts the low-solubility gas at a predetermined flow rate through the exhaust valve 80.

[0047] The gas recovery container 66 recovers the gas exhausted from the exhaust flow path 70. The gas recovery container 66 reduces gas loss by recovering an expensive gas such as helium. Note that if an inexpensive gas such as hydrogen is used as the low solubility gas, it is not necessary to recover the gas, and in that case, the gas recovery container 66 may be omitted from the low solubility gas supply unit 22.

[0048] The electrode ink manufacturing apparatus 10 configured as above can carry out the electrode ink manufacturing method shown in FIG. 6B.

[0049] Although the electrode ink manufacturing method and electrode ink manufacturing apparatus 10 have been described above using catalyst ink as an example, the present embodiment is not limited to this. For example, a diffusion layer ink for manufacturing a gas diffusion layer is manufactured by mixing carbon powder (conductive particles), a water-repellent solution (polymer material), a solvent, and a dispersant. The water-repellent solution contains a water-repellent resin such as a fluorine-containing polymer as the polymer material. In this process, to prevent the generation of bubbles, the ambient gas surrounding the raw carbon powder may be replaced with a gas with low solubility in alcohol, and the water-repellent solution and solvent may be degassed. This prevents the generation of bubbles.

[0050] The following additional notes are further disclosed regarding the above embodiment.

[0051] (Appendix 1) The method for producing an electrode ink of the present disclosure includes a degassing step (S60) for removing soluble gases that are more soluble in the organic solvent than nitrogen from each of a first raw material containing conductive particles, a second raw material containing a polymer material, and a solvent containing water and an organic solvent that is soluble in water, and a kneading step for mixing the first raw material from which the soluble gases have been removed, the second raw material, and the solvent, wherein the kneading step is carried out in an atmosphere of a low-solubility gas that is less soluble in the organic solvent than nitrogen.

[0052] The above-described method for producing an electrode ink can prevent the generation of bubbles during the kneading step and can increase the proportion of water in the solvent.

[0053] (Appendix 2) In the method for producing an electrode ink according to Appendix 1, at least oxygen is removed in the degassing step, and the low-solubility gas used in the kneading step may be oxygen-free. In this method for producing an electrode ink, the catalyst contained in the electrode ink can prevent the generation of impurities that would otherwise be produced by the reaction between the organic solvent and oxygen, thereby suppressing a decrease in power generation performance due to impurities.

[0054] (Appendix 3) In the method for producing an electrode ink according to Supplementary Note 1, the degassing step may be carried out by degassing under reduced pressure. This method for producing an electrode ink can efficiently remove gas components from the solvent under mild conditions.

[0055] (Appendix 4) In the method for producing an electrode ink according to Supplementary Note 3, the degassing under reduced pressure may be performed using a gas-liquid separation membrane. This method for producing an electrode ink can suppress fluctuations in the solvent composition by preventing the volatilization of the solvent components.

[0056] (Appendix 5) In the method for producing an electrode ink according to Appendix 1, the degassing step may be performed by replacing the soluble gas contained in the first raw material, the second raw material, and the solvent with the low-solubility gas. This method for producing an electrode ink can prevent the generation of bubbles in the kneading step.

[0057] (Appendix 6) In the method for producing an electrode ink according to Appendix 1, the solvent may have an A / W ratio, obtained by dividing the mass A of the organic solvent by the mass W of the water, of approximately 0.07 or less. This method for producing an electrode ink can prevent the generation of bubbles in the kneading step even in a high water concentration range where bubbles are significantly more likely to be generated.

[0058] (Appendix 7) In the method for producing an electrode ink according to any one of Supplementary Notes 1 to 6, the first raw material may contain a catalyst as the conductive particles, and the second raw material may contain an ionomer containing an ion-conductive polymer as the polymer material. This method for producing an electrode ink can produce a catalyst ink that contains almost no bubbles.

[0059] (Appendix 8) In the method for producing an electrode ink according to any one of Supplementary Notes 1 to 6, the first raw material may contain carbon particles as the conductive particles, and the second raw material may contain a water-repellent resin as the polymer material. This method for producing an electrode ink can produce a diffusion layer ink that contains almost no air bubbles.

[0060] (Appendix 9) The electrode ink manufacturing apparatus (10) of the present disclosure includes a first container (55) containing a first raw material including conductive particles, a second container (28) containing a second raw material including a polymer material, a third container (24) containing an organic solvent soluble in water, a fourth container (30) containing water, a low-solubility gas supply unit (22) that supplies a low-solubility gas that is less soluble in the organic solvent than nitrogen to the first container to replace the atmosphere of the first raw material with the low-solubility gas, and a low-solubility gas supply unit (22) that is connected to the second container and replaces the atmosphere of the second raw material with the low-solubility gas. The system includes a first degassing apparatus (32A) that removes gas from the raw material, a second degassing apparatus (32B) that is connected to the third container and that removes gas from the organic solvent, a third degassing apparatus (32C) that is connected to the fourth container and that removes gas from the water, and a stirring container (16, 18, 20) that mixes the first raw material that has been replaced with the low-solubility gas atmosphere, the second raw material from which the gas has been removed, the organic solvent from which the gas has been removed, and the water from which the gas has been removed in the low-solubility gas atmosphere.

[0061] The above-described electrode ink manufacturing apparatus can prevent the generation of bubbles during the kneading process and can increase the proportion of water in the solvent.

[0062] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments. [Explanation of symbols]

[0063] 10... Manufacturing equipment 22... Low solubility gas supply unit 32... Degassing device 32A... First degassing device 32B... Second degassing device 32C... Third degassing device

Claims

1. a degassing step of removing soluble gases that are more easily soluble in the organic solvent than nitrogen from each of a first raw material containing conductive particles, a second raw material containing a polymer material, and a solvent containing water and an organic solvent soluble in water, wherein an A / W ratio obtained by dividing a mass A of the organic solvent by a mass W of the water is 0.07 or less; a kneading step of mixing the first raw material from which the dissolved gas has been removed, the second raw material, and the solvent, The method for producing an electrode ink, wherein the kneading step is carried out in an atmosphere of a low-solubility gas that is less soluble in the organic solvent than nitrogen.

2. 2. The method for producing an electrode ink according to claim 1, wherein at least oxygen is removed in the degassing step, and the low-solubility gas used in the kneading step does not contain oxygen.

3. 2. The method for producing an electrode ink according to claim 1, wherein the degassing step is performed by degassing under reduced pressure.

4. 4. The method for producing an electrode ink according to claim 3, wherein the decompression and degassing are performed using a gas-liquid separation membrane.

5. 2. The method for producing an electrode ink according to claim 1, wherein the degassing step is performed by replacing the soluble gas contained in the first raw material, the second raw material, and the solvent with the low-solubility gas.

6. A method for producing the electrode ink according to any one of claims 1 to 5, comprising: the first raw material contains a catalyst as the conductive particles, The second raw material includes an ionomer containing an ion-conductive polymer as the polymer material.

7. A method for producing the electrode ink according to any one of claims 1 to 5, comprising: the first raw material contains carbon particles as the conductive particles, The method for manufacturing an electrode ink, wherein the second raw material contains a water-repellent resin as the polymer material.

8. a first container containing a first raw material including conductive particles; a second container containing a second ingredient including a polymeric material; a third container containing a water-soluble organic solvent; a fourth container containing water; a low-solubility gas supply unit that supplies a low-solubility gas that is less soluble in the organic solvent than nitrogen to the first container and replaces an atmosphere of the first raw material with the low-solubility gas; a first degasser connected to the second vessel for removing gas from the second feedstock; a second degasser connected to the third vessel for removing gas from the organic solvent; a third degasser connected to the fourth vessel for removing gas from the water; an agitation vessel that mixes the first raw material, which has been replaced with an atmosphere of the low-solubility gas, the second raw material from which the gas has been removed, the organic solvent from which the gas has been removed, and the water from which the gas has been removed, in the atmosphere of the low-solubility gas, wherein the organic solvent and the water are supplied to the agitation vessel in an A / W ratio value obtained by dividing a mass A of the organic solvent by a mass W of the water is 0.07 or less.

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