JPS6079674A - Manufacture of electrolyte tile for fuel cell - Google Patents

Abstract

PURPOSE:To obtain electrolyte tile for fuel cell having large porosity and fine pores by adding flocculation agent and surface active agent to slurry prepared by mixing gamma-lithium aluminate, wood pulpe, and thermoplastic resin, and making paper-like sheet and burning it. CONSTITUTION:Lithium hydroxide, lithium salt, and gamma-Al2O3 are heated at 1,000 deg.C for 1hr, cooled, and crushed to powder having a particle size of 1mu or less to prepare gamma-lithium aluminate. This aluminate is used as inorganic material. 3-40% Of wood pulpe as fiber material to total dry weight of sheet and 3-4% of thermoplastic resin are mixed to inorganic material to prepare slurry. The water slurry is adjusted to pH7, then flocculation agent and surface active agent are added to the slurry. After alocculation, it is prepared to a sheet by a paper making process. It is burned in such a condition that temperature is increased from room temperature at the rate of 30-8 deg.C/h, and kept at 500-700 deg.C for 1- 3hr, and increased at a rate of 100-300 deg.C/h, and kept at 1,000-1,300 deg.C for 1- 3hr. By this process, sheet-shaped electrolyte tiles having uniform thickness is continuously manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing electrolyte tiles for fuel cells.

Conventional ceramic porous bodies for electrolyte tiles for fuel cells include unglazed pottery, foamed glass ceramics, and ceramic foam, although each type has different pore properties.However, these are used as electrolyte tiles for fuel cells. As a ceramic, it lacks the hardness and precision required of ceramics. In addition, when filling the pores with various inorganic substances or electrolytes, Ion Co.
There are quite a few that are n-transparent and lack electron conductivity. In addition, even if the ion permeability and electron conductivity are satisfied, there are drawbacks such as the various inorganic substances and electrolytes filled in the pores being washed away from the pores, or the fact that the ceramic skeleton alone does not have sufficient strength. There were many things.

Furthermore, when producing ceramic sheets, there are injection molding methods, extrusion molding methods, and isostatic pressing methods that do not use papermaking methods. However, with these methods, 6
If a ceramic suture with a large area of 0 Crn square or more is made, the surface will be cracked or distorted and will not be uniform.

Conventionally, in the method of making electrolyte tiles for fuel cells, α-alumina is added as a sinterable material powder and 51 to 70% by weight of wood pulp is added as a fibrous material, and after wet kneading and agglomeration, There is a method of obtaining a thin and dense porous body by firing a sorted material obtained by papermaking. However, in this method, in order to obtain a high porosity, the content of wood pulp is high, and since α-alumina is used, it takes 1.500 to 1.50% to obtain a sintered material. 6
It was necessary to bake at a high temperature of 00°C.

The present invention uses a ceramic material that is sufficiently dense and strong, has high porosity, and has labyrinth-like pores to eliminate or compensate for the above-mentioned drawbacks. As a method for manufacturing a porous body, r-lithium aluminate with an average particle size of 1 μm or less is used as the sinterable inorganic material, and sintering is performed at a lower temperature than the method using alumina.
1, the amount of wood pulp added is as small as 3 to 15% by weight, and the resin is a thermosetting plastic, powder, preferably emulsion, is added to 3 to 40% by weight, and the porosity is reduced. , 40-80% of the total volume of the sintered product
This is a method for manufacturing electrolyte tiles for fuel cells.

As an electrolyte tile for fuel cells, alumina is dense and has excellent electrical insulation properties. However, among the carbonates used as electrolytes, alumina reacts particularly with lithium carbonate and turns into lithium aluminate. Therefore, in the present invention, r-lithium aluminate, which has the most stable structure among lithium aluminates, is produced in advance by reacting lithium hydroxide or lithium salts with alumina, and this is sintered. Use as an inorganic substance.

To explain in more detail below, in the production of sinterable inorganic materials, f, 10H5L L2 COs, Li C stone,
Lithium salts such as L12SO- are reacted with R-alumina, which has a small particle size among alumina (and surface active R-alumina), by baking at 1.000℃ for more than 1 hour, and then allowed to cool to form IJ lithium aluminate. A reaction calcined product is produced, and this cooled product is pulverized in a ball mill to obtain a particle size of 1 μm or less for use.

In a ball mill, the particle size of IJ thium aluminate was reduced to 1μ.
The following steps are the same as when sintering ceramics:
In electrolyte tiles for fuel cells as well, the sintering temperature is lowered as the particle size becomes finer to save energy and increase the strength of the sintered product. Further, when an electrolyte tile for a fuel cell is manufactured using IJ tium aluminate having a fine particle size, the tile must be impregnated with a carbonate such as L 12 COs or K 2 COa. In order for this tile to fill and retain carbonate in its pores, the pore diameter must be 0.
The pores must be about 1 to 1 μm in size. Making the particle size of the r-lithium aluminate finer makes the pores of the electrolyte tile finer.

In order to function as a reinforcing agent and obtain a porosity of 40 to 80%, wood pulp is selected from among various types of fibers, and the amount of wood pulp added is adjusted to the total weight of the sheet when dry before sintering. 6% to 15%. However, it is impossible to obtain pores of 01 to 1 μm with a porosity of 40 to 80% only by adding wood pulp. Therefore, a resin is added to achieve the desired porosity and pore size. The resin is a plastic resin of thermosetting resin 1, which may be in the form of a powder, but preferably in the form of an emulsion, and is added in an amount of 6 to 40% based on the total dry weight of the sheet material before firing.

It is necessary for the resin to maintain the shape of the paper-formed sheet without dissolving during drying and firing, and for this purpose, a thermosetting plastic resin is required. In addition, among thermosetting plastic resins, it is better to select one that is more likely to aggregate during the papermaking process (or one that has been emulsified to be suitable for papermaking). It is 6 to 40% of the total dry weight of the product.If this addition amount is 3% or less, the porosity of the sintered product will be 40%.
If the amount added is 40% or more, the porosity will be 80% or more, and the strength of the sintered product will decrease, and the shape of the sheet-like product will change (easily shift and warp. The amount of thermosetting plastic resin added is 3 to 40% by weight.

The method for producing the sintered material is as follows: 3~1'' 5% by weight of an aqueous phase bulb, 3~40% by weight of a thermosetting plastic resin, and a sinterable inorganic material, r-lithium aluminum with a particle size of 1μ or less. Water is added in an amount of about 10 to 50 times the weight of the solid content consisting of aluminate powder and wet-mixed to prepare an aqueous slurry suitable for papermaking.This aqueous slurry contains Excess lithium hydroxide or lithium salts are eluted, acidic or alkaline solution is added to adjust PIl to 7, and flocculant 1.9
Add surfactant and coagulate, make paper using a paper making machine,
Form into a sheet or plate.

The reason for adding the flocculant is that the fibers, resin, and sinterable inorganic substance coagulate together to facilitate paper-making. In addition, surfactants help fibers, resins, inorganic substances, and fibers, resins, and inorganic substances coagulate together, and the surface of paper-shaped or plate-shaped objects is uniform and smooth. Add to make it.

This molded product is placed in a firing furnace and fired in an oxidizing atmosphere. Firing is performed from room temperature to 60-8°C per hour (hereinafter simply [
30-80℃/abbreviated as II), raise the temperature to 500-700℃
Hold for 1 to 6 hours. This is because the wood pulp and thermosetting plastic resin are burned and vaporized, creating a labyrinth of pores. The heating rate is 3o'c
/II or more, it takes too much time to raise the temperature, and
o℃/I], the pulp and resin expand rapidly;
The paper-made sheet or plate shape will swell and lose its shape. Therefore, a temperature increase rate of 30' to 80' C/H is suitable. and to burn out the resin (IZ) <soo ~ 7
Hold at 00'C for 1-3 hours.

If the holding time is less than 1 hour, the burning and vaporization of the pulp and resin will not be completed, and if the holding time is more than 6 hours, the baking time will be too long, so 1 to 6 hours is appropriate. During this time, it is also effective to send air (oxygen) into the furnace to create an oxidizing atmosphere. After that, the IJ lithium aluminate is sintered, from 000 to 1,600 °C, from 10" to 30
The temperature is raised at 0'C/II and sintering takes place i, 00.0
~1, Perform baking at 300°C for 1 to 6 hours, baking at i
, 1. Sintering is completed below 000°C.
,! , 00'C or higher, sintering progresses too much and the pores that have been created are clogged, so the sintering temperature is 1.
000-i and 500°C are suitable. Also, 1,00
0 to 1. Holding at 300°C for 1 to 6 hours is 1.
In order to complete sintering at 000~1.300°CVC, a holding time is required; if the holding time is less than 1 hour, the strength will deteriorate and the shape will shift, and if it is held for more than 3 hours, the sintering will fail. The knot ends up going too far.

Therefore, 1 to 6 hours is appropriate.

As described above, by using IJ tium aluminate with a particle size of 1μ or less, it is possible to sinter at a lower temperature, and moreover, it is possible to sinter at a lower temperature, and it is possible to add wood pulp of about 3 to 15% and to make thermosetting plastics. A dense and strong electrolyte tile for fuel cells with a large porosity of 40 to 80% and a labyrinth-like pore structure by adding 3 to 40% of a resin, preferably in the form of an emulsion. becomes possible to manufacture.

Specific examples of the present invention will be described below.

<Example 1> (A) For the production of r-IJ thium aluminate, put 50 parts of r-alumina into a plastic bag of about 500 m1, shake it around by hand for about 10 minutes, dry mix it, and add it to about 300 m1+. Put it in a crucible and put it in an electric furnace. 1. In an oxidizing atmosphere, with air flowing if necessary, from room temperature to 200°C. OO'
Raise the temperature to 0°C. The mixture is held at 1.000°C for 2 hours to cause a reaction, and then allowed to cool in the furnace and cooled to room temperature.

3 oom of cooled r-lithium aluminate
The mixture is placed in a ball mill of about 1.0 liters and pulverized for 24 hours to give an average particle size of about 0.8 parts.

(I3) Composition of the sample (C) Coagulant and surface active side Put 1,00 parts of water and 5 parts of wood pulp in a container with a size of about 24 cm, stir for 20 minutes to fully disperse it in the water, and then add Well, the tip was ground with a ball mill. Add 60 parts of baked IJ thium aluminate and 20 parts of phenol resin and stir for 1 minute to make an aqueous slurry.

This aqueous slurry becomes a strong alkali with a pH of 13 or more as excess lithium ions are eluted into water.

Therefore, we prepared dilute sulfuric acid (sulfuric acid: water: 20
:1) was added dropwise to bring the pH to 7. Add 20 parts of sulfuric acid band (15% aqueous solution) prepared in advance to the solution, stir for 2 minutes, and confirm with PH test paper that I) I-1 is 4 or less. .

A polyacrylamide polymer prepared in advance,
60 parts of agglomerate (0.2% aqueous solution of Sunpoly-N-5,00) and an amphoteric surfactant (Lipomin LA, 20%
Add 5 parts of the aqueous solution and stir for 1 minute to coagulate.

The sample agglomerated in the above manner is made into a paper using a paper making machine, and
Form into a 0cm square sheet with two thicknesses. After drying, it is placed in an electric furnace and heated from room temperature at a rate of 50°C/I-1 in an oxidizing atmosphere, with air flowing through the furnace if necessary, until the wood pulp and phenolic resin are burned off and vaporized. At a temperature of 600°C, a maze-like pore is formed.
'(:, held for 2 hours. Then 1. IJ tium aluminate is sintered 1. 200 °C / 200 °C
When the temperature of the electric furnace reaches 1.200℃ by increasing the temperature with H,
This temperature was maintained for 2 hours to sinter the r-lithium aluminate and produce an electrolyte tile for a fuel cell.

<Example 2> (B) Sample preparation (C) Flocculant and surfactant (Lion (ceramic product name: "Lipomi/", L+ 11 J
/The above composition (5) (131 (using Q,
The following is the same as in Example 1 for a sheet-shaped fuel 7L pond.
lJf IW quality metal was obtained.

The ceramic porous body thus obtained has excellent properties as an electrolyte tile used in fuel cells.
1. According to the present invention, a ceramic porous body which is excellent in durability, is thin, dense, has high porosity, and has continuous pores like a labyrinth. Ru.

The present invention incorporates the advantages of both the conventional method of making a thin, pore-free, dense metal oxide and the method of making a foamable porous material, and the porosity can also be adjusted using wood pulp and heat. (can be freely changed depending on the amount of curable plastic resin added). In addition, the present invention eliminates the complicated processing steps after foaming with polyurethane, which is a known problem in ceramic foam manufacturing, so the manufacturing process is simplified. In addition, by using r-lithium aluminate with a particle size of 1μ or less and adding wood pulp and thermosetting plastic resin, a dense and strong ceramic porous body can be obtained at lower temperatures, resulting in energy savings. Effects also occur.

In addition, it can be used in places where thermal stress does not repeatedly expand or contract due to heat, or places where stress is applied, and in particular, places where thermal stress, electrical stress, or mechanical stress is applied repeatedly, such as electrolyte tiles for fuel cells. It becomes fully possible to use it.

Furthermore, since papermaking technology is used to form sheet-like objects for firing, it is possible to continuously manufacture notebook-like objects of uniform thickness, and the thickness can also be varied within a variety of ranges. be.

patent applicant Toppan Printing Co., Ltd. Representative Kazuo Suzuki

Claims (1)

[Claims] Aqueous slurry is obtained by mixing an extraneous inorganic substance powder, fibrous material, and resin, and the sheet-like material obtained by agglomeration and papermaking is fired to burn off and vaporize the fibrous material and resin,
When producing a thin and dense porous body by sintering a powder of a sinterable inorganic substance, the inorganic substance is mixed with lithium hydroxide and/or lithium salts and r-Aff120. i,
o o o The baked product was baked at ℃ for more than 1 hour and then allowed to cool.The baked product was ground in a ball mill to reduce the average particle size to 1μ or less.
IJ thium aluminate is used, wood pulp is used as the fiber material, 3 to 15% of the total dry weight of the sheet before firing is used, and thermosetting plastic resin is used as the resin before firing. 3 to 4 for the total dry weight of the item
The pH of the mixed aqueous slurry IJ- is adjusted to 7 with an inorganic acid or alkaline aqueous solution, and then a flocculant and a surfactant are added to flocculate and form paper, and the firing starts from room temperature. Raise the temperature at 60-8'C/II, 500-700'
Hold at ℃ for 1-6 hours, then ioo~300°C/
A method for producing an electrolyte tile for a fuel cell, which comprises raising the temperature at I-I and holding it at 1.00 [ ] to 1.5 D 0°C for 1 to 3 hours.