JPH08250101A - Separator for electrochemical reacting device, and electrochemical reacting device using the same - Google Patents

Abstract

PURPOSE: To provide a separator excellent in chemical resistance, heat resistance and hydrophilic property, and free from wetting unevenness in which electrochemical reacting device characteristics (particularly, safety and reliability) can be improved, and an electrochemical reacting device using this separator. CONSTITUTION: This separator consists of a metal oxide composite polymer porous body in which at least the fine fiber.fine node or pore wall surface of a polymer porous body such as a fluorine resin porous body film is covered with a metal oxide consisting of the dried body of a metal oxide water- contained get formed by the gelating reaction of a hydrolytic metal-contained organic compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator used in an electrochemical reaction device such as a battery and a capacitor, and an electrochemical reaction device using the separator.

[0002]

2. Description of the Related Art In this type of electrochemical reactor, a separator is used for the purpose of interposing a positive electrode material and a negative electrode material to hold an electrolytic solution and to separate the two electrodes. There is.

As a battery which is one of the electrochemical reaction devices, there are a sulfuric acid electrolyte type lead storage battery, an alkaline aqueous solution electrolyte type alkaline storage battery, an organic solvent electrolyte type lithium battery, and the like. As a separator for use in the past, polymeric porous materials such as woven and non-woven fabrics of polyamide fibers and polyolefin fibers have been used for chemical resistance (alkali resistance,
It is appropriately selected and used in consideration of (such as oxidation resistance). In addition, various capacitors are available on the market, but electric double-layer capacitors are attracting attention because of their small size and large capacity, and their separators are porous non-woven fabrics and films such as films. Has been done.

However, in the case of a hydrophobic polymer porous material,
Since it lacks hydrophilicity, it cannot be applied to aqueous liquids. Therefore, in order to impart hydrophilicity to such a hydrophobic polymer porous body, the following methods have been proposed. (1) A method in which a porous body is impregnated with a suspension of metal oxide fine particles and then dried (JP-A-54-61081). (2) The porous body is impregnated with a precursor solution of a metal oxide,
A method of converting into a metal oxide by physical or chemical means (JP-A-49-81281 and JP-A-51-1373).
JP-A-52-127479 and JP-A-53-129.
No. 261). (3) A method of compounding a metal into a porous body by a metal vapor deposition method. However, none of these methods is still satisfactory and includes the following problems. In (1), since the metal oxide fine particles are not firmly bonded to the porous body, they easily fall off. In (2), a zirconium oxide or titanium oxide precursor solution is mainly used. In this method, however, since the hydrolysis reaction of the precursor solution occurs rapidly, the precursor solution firmly adheres to the porous body. Many metal oxide particles are not produced and easily fall off. Moreover, since most of the pores of the porous body are filled with the metal oxide particles, the porosity decreases, and when used as a separator or the like, the membrane resistance increases. In the case of (3), the metal oxide adheres only to the outer surface of the porous body, and a large amount of undeposited metal exists on the inner surfaces of the pores of the porous body, so that uniform hydrophilicity cannot be obtained.

Further, in recent years, the electrochemical reactors described above have been further improved in performance. And
With the increase in performance, the separator for electrochemical reaction device is required to have the following characteristics. (1) It must be able to withstand the temperature rise of the battery and the main body of the electrochemical reaction device when charged and discharged at high current density. (2) It must be possible to mount it on equipment used in a high temperature atmosphere (environment). (3) Solder heat resistance (flow resistance, reflow resistance) characteristics.

In order to meet such demands, there are increasing cases in which a fluororesin porous material which is a heat resistant material is used as a separator for an electrochemical reaction device. However, although the fluororesin porous material is excellent in chemical resistance and heat resistance, it lacks important requirements as a separator because it is water repellent. That is, in a separator for an electrochemical reaction device, ions present in an electrolytic solution (aqueous solution, organic solvent, etc.) pass through the separator's porosity or between fibers and are separated from one location by the separator to the other location. Must be movable. For that purpose, it is necessary that the separator be hydrophilic and the inside of the separator be wet with the electrolytic solution. However, since the porous fluororesin material is water repellent, it does not meet this requirement.

Therefore, a proposal for imparting hydrophilicity to a fluororesin porous material to form a separator for an electrochemical reaction device is disclosed in Japanese Examined Patent Publication No. 55-24459 and Japanese Patent Laid-Open No. 2868863.
It is made in the official gazette etc. That is, Japanese Examined Japanese Patent Publication 55-2
Japanese Patent No. 4459 discloses that the pores of the fluororesin porous material are filled with an inorganic hydrophilizing material to such an extent that the air permeability is not significantly impaired, and the inorganic hydrophilizing material is not washed away or dropped, and has stable hydrophilicity for a long period of time. A technique for obtaining a separator for an electrochemical reactor is disclosed. However, the separator having this structure has problems that the manufacturing process is complicated and that the adhesion strength of the inorganic hydrophilizing material to the substrate is insufficient, so that it cannot withstand long-term use.

On the other hand, Japanese Patent Application Laid-Open No. 4-286863 discloses a technique for obtaining a separator for an electrochemical reaction device, which is made hydrophilic by subjecting a fluororesin porous body to plasma surface treatment. However, the separator with this configuration requires a large-scale device because it performs plasma surface treatment, and mechanical strength (tensile strength, compression strength) decreases at the stage of surface treatment, and uneven wetting occurs, resulting in uniform hydrophilicity. It is difficult to obtain processed products, and as a result,
The reaction effective area is reduced, which causes a problem that the internal resistance of the electrochemical reaction device is increased.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems found in the prior art in which a polymer porous body such as a fluororesin porous body is made hydrophilic and used as a separator for an electrochemical reaction device. Has excellent chemical resistance, heat resistance and hydrophilicity,
It is an object of the present invention to provide a separator capable of improving the characteristics of an electrochemical reaction device (in particular, improving safety and reliability) without uneven wetting.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the inventors of the present invention have developed a separator for an electrochemical reaction device of a hydrophilization technique such as fluororesin porous material, which has been extensively studied in the past. As a result of repeated studies on the adaptation of
Consisting of a dried body of a metal oxide hydrogel formed by a gelation reaction of a hydrolyzable metal-containing organic compound on at least the surface of fine fibers, fine nodules or pore walls of a polymer porous body having continuous pores By using a metal oxide composite polymer porous body coated with a metal oxide as a separator for an electrochemical reaction device, it has excellent wettability and is also suitable for charging / discharging at high current density, high temperature environment, and solder flow / reflow. They have found that a separator that can withstand is obtained, and completed the present invention.

That is, according to the present invention, firstly, at least the surface of the fine fibers / fine nodules or pore walls of the polymer porous body having continuous pores is subjected to the gelation reaction of the hydrolyzable metal-containing organic compound. There is provided a separator for an electrochemical reaction device, comprising a metal oxide composite polymer porous body coated with a metal oxide, which is a dried body of the metal oxide hydrogel formed by the above.

Secondly, in the first separator, there is provided a separator for an electrochemical reaction device, wherein the metal oxide hydrogel is silica gel, and third, in the first separator, the metal The oxide composite polymer porous body comprises a step of impregnating the polymer porous body with a gelled product formed by reacting a hydrolyzable metal-containing organic compound with water, and impregnating the polymer porous body. From the step of reacting the solution-like gelled product with water to convert it into a solid gelled product, and the step of heating and drying the solid gelled product thus formed in the polymer porous body. There is provided a separator for an electrochemical reactor manufactured by the method.

Fourthly, in the first separator, the polymer porous body is at least one selected from a fluororesin porous body and a polyolefin resin porous body.
Provided is a separator for electrochemical reaction device is a seed, further fifth, in the fourth separator, the fluororesin porous body, the separator for electrochemical reaction device is a polytetrafluoroethylene resin porous body. Provided,
Further, sixthly, there is provided an electrochemical reaction device using any one of the first to fifth separators.

The present invention will be described in detail below. As described above, the separator for an electrochemical reaction device of the present invention is a gel of a hydrolyzable metal-containing organic compound, at least the surface of fine fibers / fine nodules or pore walls of a polymer porous body having continuous pores. It is characterized by comprising a metal oxide composite polymer porous body coated with a metal oxide which is a dried body of a hydrogel of a metal oxide formed by a chemical reaction. That is, the separator of the present invention comprises a polymer porous body as a substrate, and a composite of the metal oxide precursor and the porous body.

The polymer porous material used as the substrate in the present invention may be formed of various conventionally known polymers. In this case, the polymer includes polyethylene, polypropylene, polyolefin resin such as ethylene / propylene copolymer, styrene resin such as polystyrene, polyester, polyamide, polyvinyl chloride, polysulfone, polyacrylonitrile, polyimide, polycarbonate, fluorine. Resin, silicone rubber, etc. can be mentioned. In particular, it is preferable to use a fluororesin in terms of heat resistance, chemical resistance and the like. The preferred fluororesin is polytetrafluoroethylene, but tetrafluoroethylene / hexafluoropropylene copolymer, polyvinyl fluoride, polyvinylidene fluoride, etc. may also be used. The fluororesin porous body used as the substrate as one embodiment of the present invention may be any one having continuous fine pores, and the means for forming the fine pores is not particularly limited, and various kinds can be used. . Among them, it is preferable to use porous polytetrafluoroethylene, particularly stretched porous polytetrafluoroethylene.

In the following description according to one embodiment of the present invention,
A fluororesin porous body is used as the polymer porous body used as the base material. The fluororesin porous material preferably used as the substrate in the present invention has a thickness of 1 to 1000 μm,
The maximum pore size is 0.01 to 10 μm, and the porosity is 5 to 95%. The above physical properties are extremely general physical properties,
Since it can be used regardless of the size of physical properties, almost all fluororesin porous materials can be preferably used as the substrate. Regarding such a substrate, Japanese Patent Publication No. 56-45773 and Japanese Patent Publication No. 56-17
No. 216, U.S. Pat. No. 4,187,390, and the like.

The separator according to the present invention is a composite of the above-mentioned fluororesin porous material and a metal oxide precursor. The metal oxide precursor used in the present invention is a hydrolyzable metal-containing organic metal. Any compound may be used, and such compounds include metal alkoxides and metal complexes. Examples of metals include lithium, beryllium, boron, carbon, magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, cesium,
Titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, ruthenium,
Rhodium, palladium, cadmium, indium, tin,
Antimony, Te, Cs, Barium, La, Ce, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H
o, Er, Tm, Yb, Lu, Th, Pa, U, Pu,
Hafnium, tantalum, tungsten, platinum, mercury,
Lead, bismuth, etc. are included. Specific examples of the metal alkoxide include, for example, tetramethoxy titanium, tetraethoxy titanium, tetraisopropoxy titanium, tetrabutoxy titanium, zirconium isopropylate, zirconium butyrate, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetratertiary titanium. Libutoxysilane and the like can be mentioned. Specific examples of the metal complex include metal acetylacetonates such as titanium tetraacetylacetonate and zirconium acetylacetonate. In the present invention, a silicone alkoxide such as tetraethoxysilane is preferably used.

In the present invention, the metal oxide precursor is brought into contact with water to be partially gelled before being complexed with the fluororesin porous material, thereby forming a solution-like gelation product. And This gelling reaction is a well-known reaction and includes a hydrolysis / polycondensation reaction. In order to partially gel the metal oxide precursor, the metal oxide precursor may be added to water and mixed with stirring. In this case, water can be mixed with a water-miscible organic solvent, for example, an alcohol such as methanol, ethanol, propanol, butanol, and further, if necessary, hydrochloric acid, sulfuric acid, nitric acid, acetic acid, hydrofluoric acid, etc. Acids and bases such as sodium hydroxide, potassium hydroxide and ammonia can also be added. The partial gelation reaction of the metal oxide precursor can also be carried out by adding water to an organic solvent solution of the metal oxide precursor and stirring and mixing. In this case, any organic solvent may be used as long as it can dissolve the metal oxide, and aliphatic and aromatic hydrocarbons as well as alcohols can be used. The gelling reaction is generally performed at a temperature of 0 to 100 ° C, preferably 60 to 80 ° C. The ratio of water used is 0.1 to 100 mol, preferably 1 to 10 mol, based on 1 mol of the metal oxide precursor. The gelling reaction is preferably carried out in a closed manner or under an inert gas stream, but it is also possible to allow the gelling reaction to proceed by the moisture in the outside air. A solution-like partially gelled product of the metal oxide precursor is obtained as described above. The partial gelation product of the metal oxide precursor referred to in the present specification is used in correspondence with a non-flowable solid metal oxide hydrogel which is a completely gelled product.

In order to composite the partially gelled product of the metal oxide precursor with the fluororesin porous body, the fluororesin porous body is dipped in the solution-like partially gelled product,
What kind of method can be used as long as it is a method of spraying or roll-coating the solution-like partially gelled product and filling the voids on the surface and inside of the fluororesin porous body with the partially gelled product? But it can be used. Thus, the fluororesin porous body in which the partially gelled product of the metal oxide precursor is composited is a solid gel which is a completely gelled product by further promoting the gelling reaction of the metal oxide precursor. Contact with excess water to form a hydrous metal oxide gel. For this complete gelation, it is preferable to use a method of immersing the fluororesin porous body in which the partially gelled product of the metal oxide precursor is composited, in water, but by spraying, etc. It is also possible to use a method of spraying, a method of spraying steam, and the like. In this case, the water used may contain an acid or an alkali in order to accelerate the gelling reaction. After the completion of this gelation reaction, a metal oxide hydrogel is formed in the form of a film on the inner surface of the pores of the fluororesin porous body, which is dried at 300 ° C or lower, preferably 200 ° C or lower. It is possible to form a thin and uniform metal oxide layer integrally attached to the inner surface of the pores. The thickness of this metal oxide layer is 0.01
To 0.2 μm, preferably 0.02 to 0.1 μm, and since the metal oxide is formed from the metal oxide hydrogel formed as described above, it is a continuous integral The film has excellent adhesion and is unlikely to peel from the fluororesin porous body. The metal oxide composite fluororesin porous material of one example of the present invention exhibits a high pore volume, and has 50% or more, preferably 70% or more of the pore volume of the original fluororesin porous material. Hold. Therefore, a separator having a small membrane resistance can be obtained.

The separator of the present invention is made of other materials,
For example, it may have a structure in which a polyolefin-based porous film is laminated and integrated. As the polyolefin porous body used here, a porous body made of a mixture of polyolefin and an inorganic fine powder (for example, calcium carbonate, barium sulfate, etc.) can be used, but more preferably, the inorganic fine powder is not included. The polyolefin porous body obtained by stretching in (1) and the polyolefin porous body obtained by removing the solvent from the polyolefin solution layer are used. As the polyolefin, various conventionally known ones are used, but more preferably polyethylene or polypropylene such as low-density polyethylene, high-density polyethylene, or ultra-high-molecular polyethylene is used alone or in combination. The maximum pore diameter of this polyolefin porous body is 0.01 to 15 μm, preferably 0.05 to 1 μm. When the maximum pore size is smaller than the above range, it is physically difficult for the electrolytic solution to penetrate into the porous body. On the other hand, if the maximum pore size exceeds the above range, it becomes difficult to prevent the diffusion of the active material and the reaction product. Further, the porosity of the polyolefin porous body is 5 to 95%,
It is preferably 20 to 80%. When the porosity is smaller than the above range, the amount of electrolyte solution that can be retained in the porous body becomes insufficient. On the other hand, when the porosity exceeds the above range, the mechanical strength of the porous body becomes insufficient.

Here, an embodiment of a method for manufacturing a separator for an electrochemical reaction device having a structure in which the other materials of the present invention are laminated and integrated will be described. First, a polyolefin solution is prepared by heating and dissolving the polyolefin in a good solvent. The solvent is not particularly limited as long as it sufficiently dissolves the polyolefin, and for example, xylene, decalin, nonane, decane, undecane and the like can be used. The heating dissolution is performed with stirring at a temperature at which the polyolefin is completely dissolved in the solvent. The temperature is
Depending on the polyolefin and solvent used, 80
The range of ˜250 ° C. is preferred. The concentration of the solution varies depending on the polyolefin used, but is 1 to 30% by weight, preferably 2 to 15% by weight. When the solution concentration is lower than the above range, the formation of the polyolefin porous body on the surface of the fluororesin porous body becomes insufficient and cracks may occur in the polyolefin porous body. On the other hand, if the solution concentration exceeds the above range, not only it becomes difficult to prepare a uniform solution, but also the thickness of the polyolefin porous film cannot be made as thin as necessary.

Next, the prepared polyolefin solution is brought into contact with one or both surfaces of the porous fluororesin substrate to form a polyolefin solution layer. As a method of contacting the fluororesin porous body substrate and the polyolefin solution here,
(A) a method of immersing the base material in a polyolefin solution,
(B) A method of supplying and coating the polyolefin solution on the surface of the substrate by a T-die extrusion method, (c) a method of coating the solution on the surface of the substrate by a spray method, a roll coater, a knife coater, or the like can be adopted.

Next, a solvent removal treatment is performed on the polyolefin solution layer. As the desolvation treatment method, a method of drying and removing the solvent in the polyolefin solution layer, a porous fluororesin substrate having a polyolefin solution layer formed on the surface is immersed in a poor solvent to extract and remove the solvent, and then the poor solvent is dried. A method of removing it, a method of combining these, or the like can be considered. Here, in the process of drying and removing the solvent in the polyolefin solution layer, as a method for facilitating the formation of the porous material, it is possible to add a nonvolatile solvent having a high boiling point and being compatible with the main solvent in an appropriate ratio. preferable. In this case, the low boiling point volatile solvent is first removed during the drying process, but the removal rate of the high boiling point non-volatile solvent is extremely slow.
Therefore, the dissolved polyolefin easily aggregates in the high-boiling-point non-volatile solvent dispersed in the polyolefin solution layer to easily form a porous body. Xylene and DMS
The combination of O is one example. The poor solvent used for extracting the solvent includes hydrocarbons such as pentane, hexane and heptane; chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride; fluorinated hydrocarbons such as ethane trifluoride;
Ethers such as diethyl ether dioxane; other alcohols such as methanol, ethanol, propanol and the like. These solvents are appropriately selected depending on the solvent used for dissolving the polyolefin, and used alone or as a mixture. The subsequent method for compounding the metal oxide precursor is as described above. In the present invention, the metal oxide may be composited with the fluororesin porous body, and then the polyolefin porous body may be laminated by the method described above. By the above method, a separator of one embodiment of the present invention is obtained.

The separator of the present invention having the above-mentioned laminated structure is useful as a separator for an electrochemical reaction device such as a lithium battery which requires a safety mechanism called meltdown property. When the separator of one embodiment of the present invention having a laminated structure in which a polyolefin porous body is formed on the surface of a fluororesin porous body is used for a lithium battery, the battery generates heat due to an external short circuit, and the temperature is near the melting point of the polyolefin. Then, melting of the polyolefin causes clogging of the opening of the porous body, and the current shuts down. On the other hand, since the fluororesin porous body has higher heat resistance, the fluororesin porous body is not melted at the melting temperature of the polyolefin porous body, and the openings are not clogged.

In the case of a single separator made of a polyolefin porous body, when the melting progresses and the shrinkage becomes severe, the positive electrode and the negative electrode cannot be separated from each other, and the internal short circuit causes the danger to return to a dangerous state again. Cannot continue to maintain its function. On the other hand, when the fluororesin porous body is present in contact with the polyolefin porous body as in the present invention, clogging of the polyolefin porous body occurs near the melting point of the polyolefin, but the fluororesin porous body is higher. It has heat resistance and can withstand long-term use at around 200 ° C., and the fluororesin porous material acts as a support, whereby the shrinkage of the polyolefin porous material and the occurrence of cracks can be suppressed. As a result, the function of the separator can be maintained.

In one aspect of the present invention, the shutdown function depends on the polyolefin porous body, and the maintenance / continuation of the shutdown function by preventing the progress of shrinkage and cracks depends on the fluororesin porous body, and the advantages of both are utilized. Due to
A highly safe separator for an electrochemical reaction device and an electrochemical reaction device using the separator.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Tetraethoxysilane [manufactured by Shin-Etsu Silicone Co., Ltd.] 10
0 part, 52 parts of water, and 133 parts of ethanol were reacted at 80 ° C. for 24 hours under reflux in which the supply of water from the outside was blocked by a calcium chloride tube to prepare a partially gelled solution of the metal oxide precursor. A porous polytetrafluoroethylene membrane [Japan Gore-Tex Co., Ltd.]
Made, thickness 100 μm, pore diameter 0.5 μm, porosity 80%]
Then, it was immersed in warm water at 60 ° C. for 5 hours to complete gelation. This was dried in a constant temperature bath at 150 ° C. for 30 minutes to obtain a composite film in which the exposed surface including the inner surface of the porous body was covered with silica gel.

Next, activated carbon powder (specific surface area 1500 m ²
/ G) 80%, carbon black (specific surface area 950 m ²
/ G) 10% and PTFE 10% are kneaded and stretched to give a density of 0.
The sheet was 55 mm thick. This was dried at 100 ° C. for 3 hours or more, and then punched out to a diameter of 6.5 mm to prepare two polarizable electrodes. A separator made of the composite film prepared above was interposed between the two polarizable electrodes to form a graphite-based conductive adhesive on the inner surface of an outer container made of a stainless steel cap and a stainless steel can. Glued and stored. Next, an electrolytic solution obtained by dissolving 0.6 M tetraethylphosphonium tetrafluoroborate in propylene carbonate was placed in a container and impregnated therein, and then the cap and the can were closed via polypropylene (hereinafter sometimes referred to as PP) packing. It was tightly sealed and used as a capacitor cell.

The following measurements and tests were performed on 100 cells. First, the capacitance and internal resistance were measured. As for the capacity, after applying a voltage of 2.8 V to this cell at 20 ° C.,
It was calculated by performing constant current discharge at 0.2 mA up to 1.0 V. As the internal resistance of the cell, an equivalent DC resistance value measured by a 1 kHz constant current AC method using an LCR meter was used. Subsequently, a solder heat resistance test in which a heat load of 260 ° C. for 10 seconds was applied, and then the capacity and internal resistance were measured again by the same method. As a result, neither deterioration of capacity nor increase of internal resistance was observed.

Comparative Example 1 100 capacitor cells were prepared in the same manner as in Example 1, except that a 100 μm-thick PP non-woven fabric was used as the separator. This cell was subjected to a solder heat resistance test by the same method as in Example 1, and the capacity and internal resistance before and after the test were measured. As a result, those with deteriorated capacity,
There was a 5% increase in internal resistance. As a result of the analysis, it was confirmed that the cause was that the PP non-woven fabric as the separator was thermally deteriorated during the solder heat resistance test.

Comparative Example 2 In Example 1, a porous polytetrafluoroethylene membrane which was subjected to hydrophilic treatment by plasma treatment as a separator [manufactured by Japan Gore-Tex Co., Ltd., thickness 100 μm,
100 capacitor cells were prepared in the same manner except that the pore diameter was 0.5 μm and the porosity was 80%. Note that the plasma treatment was performed using argon gas at a treatment energy of 750 eV for 10 minutes.

This cell was subjected to a solder heat resistance test in the same manner as in Example 1 to measure the capacity and internal resistance before and after the test. As a result, 4% of defective capacity and defective internal resistance before the solder heat resistance test were observed. The cause of the failure before the solder heat resistance test is that, as a result of the analysis, due to poor hydrophilic treatment of the separator (unevenness of wetting), the liquid holding amount of the separator was decreased, or the effective separator area was decreased. confirmed.

From the above results, when the separator according to Example 1 is used as a separator for capacitors, the capacity deterioration and the internal resistance due to the thermal deterioration of the separator in a high temperature atmosphere (solder heat resistance test etc.) and the uneven wetting of the separator, etc. It can be seen that a reliable capacitor with no defects can be provided.

Example 2 A fluororesin porous material having a thickness of 15 μm was added to a 2% by weight polyethylene solution prepared by dissolving low density polyethylene in a 9: 1 mixed solvent of xylene and DMSO at a liquid temperature of 110 ° C.
m, maximum pore size 0.25 μm, porosity 60% polytetrafluoroethylene porous membrane was coated so that only one side was in contact with the solution, and then dried with hot air at 60 ° C. for 5 minutes to remove the solvent. went. Next, this porous body was immersed in ethanol to completely extract all the solvents, and then dried with hot air at 80 ° C. for 5 minutes to form a polyethylene porous film having a thickness of 10 μm on the surface of the fluororesin porous body. A laminated structure having a body was obtained. As subsequent hydrophilic treatment, 100 parts of tetraethoxysilane [produced by Shin-Etsu Silicone Co., Ltd.],
8 parts of 71 parts of water and 126 parts of ethanol were put under a reflux condition in which water supply from the outside air was blocked by a calcium chloride tube.
The reaction was carried out at 0 ° C for 24 hours to prepare a partially gelled solution of the metal oxide precursor. After impregnating the above-mentioned laminated film with this solution, it was immersed in warm water at 60 ° C. for 5 hours to complete gelation. This was dried in a constant temperature bath at 150 ° C. for 30 minutes to obtain a composite film in which the exposed surface including the inner surface of the porous body was covered with silica gel.

Here, manganese dioxide is used as the positive electrode active material, metallic lithium is used as the negative electrode active material, and the separator made of the above composite film is arranged as the separator so that the metallic lithium is in contact with the polyethylene porous body and the spirally structured electrode is formed. And LiClO ₄ 0.5M / PC: DME =
500 cylindrical lithium batteries using 1: 1 as an electrolytic solution were prepared.

First, the open circuit voltage and the internal resistance of the prepared battery were measured. The value of the internal resistance is 1 using the LCR meter.
The equivalent DC resistance value measured by the kHz constant current AC method was used. Then, as a safety test, the resistance at short circuit is 10
An external short circuit test was carried out in a test circuit with mΩ. As a result, the percentage of the batteries that did not maintain the shutdown state of the batteries and ruptured or ignited (shutdown breakdown) was 0%. This result is because the fluororesin porous material functions as a support, whereby the shrinkage of the polyethylene porous material and the occurrence of cracks are suppressed, and the function of the separator can be maintained.

Comparative Example 3 In Example 2, as a separator, P having a thickness of 25 μm was used.
500 cylindrical lithium batteries were produced in the same manner except that the P porous membrane (manufactured by Celanese) was used. First, the open circuit voltage and the internal resistance of the manufactured battery were measured. Subsequently, as a safety test, an external short-circuit test was conducted in a test circuit in which the resistance during short circuit was 10 mΩ. As a result, although the open circuit voltage and the internal resistance were not a problem, the ratio of the batteries that did not maintain the shutdown state of the battery and ruptured or ignited (shutdown breakdown) was 0.6%. As for this result, in the case of the separator made of the PP porous film alone, when the battery is shut down (melt down of the separator), the melting of the separator progresses and the shrinkage becomes severe,
This is because it became impossible to separate the positive and negative electrodes and the internal short circuit returned to the dangerous state again.

Comparative Example 4 500 cylindrical lithium batteries were produced in the same manner as in Example 2, except that plasma treatment was used as the hydrophilic treatment. Note that the plasma treatment was performed using argon gas at a treatment energy of 750 eV for 10 minutes. First, the open circuit voltage and the internal resistance of the manufactured battery were measured. Subsequently, as a safety test, an external short-circuit test was conducted in a test circuit in which the resistance during short circuit was 10 mΩ. As a result,
Although there was no problem in the safety test, the internal resistance of the battery was high and was 1.2 times that of the battery of Example 2. As a result of the analysis, it was confirmed that this result was due to a poor hydrophilic treatment (unevenness of wetting) of the separator, which resulted in a decrease in the amount of the liquid retained in the separator and a decrease in the area of the separator which worked effectively.

From the above results, by using the separator according to Example 2 as a battery separator, it is possible to achieve safety and reliability without internal resistance failure due to thermal deterioration of the separator under high temperature atmosphere and uneven wetting of the separator. It can be seen that a high battery can be provided.

[0041]

According to the present invention, because of the above-mentioned structure,
Provided is a separator having excellent wettability, small film resistance, high safety and reliability that can withstand charge / discharge at high current density, high temperature environment, solder flow / reflow, and an electrochemical reaction device using the separator. be able to.

Claims (6)

[Claims] 1. A metal oxide hydrogel formed by a gelation reaction of a hydrolyzable metal-containing organic compound on at least the surface of fine fibers / micronodules or pore walls of a polymer porous body having continuous pores. A separator for an electrochemical reaction device, comprising a metal oxide-composite polymer porous body coated with a metal oxide composed of the dried body. 2. The separator for an electrochemical reaction device according to claim 1, wherein the hydrous metal oxide gel is silica gel. 3. A step of impregnating the polymer porous body with a gelation product formed by reacting a hydrolyzable metal-containing organic compound with water, the metal oxide composite polymer porous body, A step of reacting a solution gelation product impregnated in a molecular porous body with water to convert it into a solid gelation product, and a solid gelation product thus formed in a polymer porous body The separator for an electrochemical reaction device according to claim 1, which is manufactured by a method including a step of heating and drying an object. 4. The separator for an electrochemical reaction device according to claim 1, wherein the polymer porous body is at least one selected from a fluororesin porous body and a polyolefin resin porous body. 5. The separator for an electrochemical reaction device according to claim 4, wherein the fluororesin porous body is a polytetrafluoroethylene resin porous body. 6. An electrochemical reaction device comprising the separator according to any one of claims 1 to 5.