CN1239591A - Separator for battery and alkaline secondary battery using same - Google Patents

Abstract

A separator for batteries comprising exchangeable fine powder prevented from coming off by fixing the powder by using a binder resin which is placed in fine pores or narrow grooves formed in the surface of organic fibers constituting a porous sheet, having an excellent electrolyte holding property, and exhibiting an ion exchanging ability for a long period. The pores or grooves exist in the surface of olefin fibers. The pores or grooves are formed by etching the fibers with an organic solvent. In the pores or grooves, the binder resin is fixed, partially entering the pores or grooves and projecting outward from the pores or grooves. The ion-exchangeable fine powder is fixed to the ends of the projecting resin. It is preferable to use a styrene-entylene-butylene-styrene (SEBS) thermoplastic copolymer as the resin.

Description

Separator for battery and alkaline secondary battery using same

Technical field

The present invention relates to a battery separator and an alkaline secondary battery using the separator.

Background technique

Separators used in alkaline secondary batteries such as nickel-cadmium and nickel-hydrogen are generally required to have chemical stability such as alkali resistance and oxidation resistance at high temperatures, electrolyte retention, gas permeability, etc. In order to solve this problem due to various properties, olefin fibers have been mainly used as the constituent base material of the separator until now.

However, although the chemical stability of the olefin fiber separator is very good, its hydrophobicity is strong, its affinity with the electrolyte is poor, and the electrolyte retention is also poor. It is easy to cause the electrolyte to volatilize when it is repeatedly charged and discharged for a long time. Dry.

Therefore, in order to solve the problems of olefin fibers, various methods of applying hydrophilic treatments to nonwoven sheets have been proposed, including:

a. A method of post-treatment using a surfactant as a water-soluble wetting agent;

b. A method of graft-polymerizing acrylic acid, acrylate and other acrylic resin monomers or polymers by using ultraviolet rays or electron rays;

c. A method of oxidation treatment using oxygen or fluorine gas in an inert gas;

d. The method of sulfonation treatment using fuming sulfuric acid, concentrated sulfuric acid, chlorosulfonic acid, sulfurous acid gas, etc.

In addition, a solution proposed by someone is to use a binder to fix an inorganic micropowder (magnesium silicate) with metal ion adsorption on an alkali-resistant In order to prevent these micropowders from falling off from the surface of the diaphragm and entering the electrolyte, and use these micropowders to adsorb metal ions so as to prevent metal ions from transferring in the direction of reverse polarity (Special Publication No. 52 - Bulletin No. 37574).

In addition, a scheme proposed by others is to give a layer of ethylene-unsaturated carboxylic acid copolymer or ethylene-methacrylic acid copolymer as a matrix on a porous sheet made of olefinic resin fibers and melt it by adding An ionomer resin obtained by mixing metal cations (particularly zinc ions) (JP-A-4-232158).

In the prior art described above, the hydrophilic treatment-applied separator has the following problems. That is to say, in terms of the methods a and c above, due to long-term storage of the battery or repeated charging and discharging, the surfactants or oxides (-COOH, -OH) and the like are simply detached from the olefin fibers, Therefore, the electrolyte in the separator is gradually depleted, causing the internal resistance of the battery to rise, thereby reducing its discharge capacity.

For the separator of the method b above, since the acrylic resin lacks heat resistance and oxidation resistance, the battery life at high temperature is shortened. In addition, since ultraviolet rays or electron rays are used in the grafting reaction, deterioration of olefin-based fibers is caused, and there is a risk of minute short circuits. Furthermore, since a washing step for washing away by-products (homopolymers) generated during graft polymerization is required, there is a problem of high production cost.

In addition, for the separator of the above-mentioned method d, although its heat resistance, alkali resistance, and oxidation resistance are excellent, it lacks electrolyte retention. In order to improve its electrolyte retention, fuming sulfuric acid, etc. must be used. Strong acid is used to increase its sulfonation rate, thus causing deterioration of olefinic fibers, resulting in the risk of micro-short circuits. In addition, since a washing step for washing off unreacted sulfuric acid is required after the sulfonation treatment, there is a problem of high production cost.

In addition, for the separator that uses a binder to fix the inorganic fine powder, since the binder used is a water-based resin, and the alkali-resistant fiber is hydrophobic, there is a gap between the binder and the alkali-resistant fiber. The weak binding force makes the inorganic fine powder easy to fall off, and if a large amount of binder is used, the surface of the inorganic fine powder will be completely covered by the binder, making it difficult to exert its adsorption performance on metal ions. In addition, if using Water-based dispersion resin (emulsion) has a negative impact on battery performance due to the emulsification and dissolution in the electrolyte.

However, in recent years, with the high performance of products using alkaline secondary batteries (mobile electronic devices such as mobile phones and notebook personal computers), the performance of batteries (long life, large capacity, and miniaturization) etc.) put forward higher requirements, and the above-mentioned prior art cannot fully adapt to these requirements, which is the actual situation at present.

Disclosure of Invention

The purpose of the present invention is to solve the problems in the above-mentioned prior art, to provide a kind of electrolytic solution retention, ion exchange capacity and strength are high, alkali resistance and oxidation resistance are also excellent, can suppress self-discharge phenomenon and can A separator for a battery that can be manufactured at low cost while prolonging the life of the battery, and an alkaline secondary battery using the separator.

In order to achieve the above objects, the battery separator of the present invention is characterized in that fine voids or fine grooves are formed on the surface of the organic fibers constituting the porous sheet, and a binder resin soluble in an organic solvent is used. After impregnating and filling the above-mentioned gaps or fine grooves, an ion-exchange fine powder is fixed on the surface of the above-mentioned organic fiber and at least a part of the fiber interweaving region. According to this structure, since organic fiber, binder resin, and ion-exchange fine powder all have excellent alkali resistance and oxidation resistance, and these materials are firmly bonded to each other by anchoring, so The physical shedding or chemical decomposition of the ion-exchange fine powder is completely avoided, so that the electrolyte retention and ion exchange capacity can be exerted for a long time. In addition, compared with hydrophilization treatments such as sulfonation or acrylic acid graft polymerization in the prior art, according to the present invention, the ion exchange capacity can be greatly improved only by controlling the attachment amount of the ion exchange resin, and the Function to improve electrolyte retention. In addition, when the diaphragm of this structure is used in an alkaline secondary battery, the adsorption capacity of the diaphragm to harmful ions in the electrolyte can be improved, and at the same time, the self-discharge of the battery can be suppressed due to the reciprocating effect, and the electrolyte is not easily generated. The phenomenon of depletion, therefore, can seek to prolong the life of the battery.

In addition, the binder resin fixed as above can also exert a great reinforcing effect on the bonding of the fibers constituting the base material of the separator, so that it is possible to prevent breakage accidents or A short circuit phenomenon caused by long-term charging and discharging cycles.

In the battery separator of the present invention described above, the mixing weight ratio of the binder resin to the ion-exchange fine powder is preferably in the range of binder resin: ion-exchange fine powder = 1:0.3 to 1:10, more preferably Binder resin: ion-exchange fine powder = 1:0.5 to 1:6.

In addition, it is preferable to immobilize the ion-exchangeable fine powder on the battery separator of the present invention so that it can absorb and capture harmful ions in the electrolyte and at the same time maintain the alkaline electrolyte. That is to say, the surface of the ion-exchange fine powder body is not completely covered by the binder resin but a part of the surface is exposed, or is covered with a binder resin having many micropores and substantially in the shape of a spider web. Covering, so that it can fully exert the ion exchange function of the ion exchange fine powder. The so-called harmful ions in the electrolyte in this paper refer to those chemical ions such as ammonium ions, chloride ions, and nitrate ions that enter the electrolyte, as well as manganese ions, iron ions, aluminum ions, etc., when they are precipitated on the positive electrode. Metal ions that degrade battery performance.

In addition, the binder resin in the battery separator of the present invention is preferably selected from alkali-resistant and oxidation-resistant styrene-based thermoplastic polymers, olefin-based polypropylene resins or polyethylene resins, halogenated polyolefins, etc. At least one resin selected from the class of polytetrafluoroethylene resins. As styrene-based thermoplastic polymers, block copolymers of styrene-ethylene-butylene-styrene (abbreviated as SEBS), block copolymers of styrene-ethylene-propylene-styrene (abbreviated as SEPS), styrene Ethylene-isoprene-styrene block copolymer (SIS for short), styrene-butadiene-styrene block copolymer (SBS), etc.

In addition, among the above-mentioned binder resins, a thermoplastic copolymer of styrene-ethylene-butylene-styrene (SEBS) in which a part or all is styrene is particularly preferable.

In addition, the ion-exchange fine powder in the above-mentioned battery separator of the present invention is preferably cation exchange resin of styrene or acrylic, anion exchange resin of styrene, acrylic or phenol, styrene or pyridine At least one resin selected from the class of chelating resins. In addition, from the viewpoint of improving electrolyte retention, the ion-exchange group of the ion-exchange fine powder is preferably at least one group selected from sulfonic acid groups, sulfonate groups, carboxylic acid groups, or carboxylate groups. .

In addition, the ion-exchange fine powder in the battery separator of the present invention preferably contains metal oxides, hydroxides, and inorganic salts thereof that have alkali resistance and can exhibit ion exchange properties in alkaline electrolytes. At least one compound selected from .

In addition, the ion-exchange fine powder in the battery separator of the present invention preferably contains at least one compound selected from titanium oxide, aluminum oxide, antimony oxide, potassium titanate, and zirconium oxide.

In addition, the shape of the ion-exchange fine powder in the battery separator of the present invention is preferably a granular, flake, whisker or scale shape having fine voids on its surface. The ion-exchange fine powder can be obtained by at least one method selected from freeze pulverization, mechanical pulverization, and spraying, among which the preferred method is freeze pulverization. In addition, the average particle diameter of the ion-exchange fine powder is preferably 100 μm or less (pass), more preferably 50 μm or less.

In addition, the organic-based fiber in the above separator for batteries of the present invention is preferably a polymer-based fiber having alkali resistance and oxidation resistance. In addition, it is preferable that some or all of the organic fibers in the battery separator of the present invention are olefin fibers.

In addition, the battery separator of the present invention is preferably a separator for an alkaline secondary battery.

Furthermore, the battery separator of the present invention has a structure suitable for those alkaline secondary batteries using the above separator. Utilizing this structure, it is possible to provide a battery that is excellent in electrolyte retention, ion exchange capacity, and strength, and is also excellent in alkali resistance and oxidation resistance, can suppress self-discharge phenomenon, can achieve long life of the battery, and can be inexpensive. Separators for batteries and alkaline secondary batteries using the separators.

As mentioned above, the present invention first utilizes the method of organic solvent etching to make the surface part of the olefinic fiber (from the fiber surface to the surface layer part inside the fiber) porous, and then utilizes the anchoring effect to make an alkali-resistant, resistant The oxidative and organic solvent-soluble binder resin is firmly fixed on the olefin fiber, and finally the firmly fixed binder resin is used to absorb and capture harmful ions in the electrolyte, and at the same time The ion-exchangeable fine powder having the function of retaining the alkaline electrolyte is firmly fixed to the olefin fiber by anchoring. The ion-exchange fine powder obtained in this way does not physically fall off during the manufacturing process of the separator or during the operation of installing the separator into the battery, and has excellent electrolyte retention and can perform ion exchange function for a long time . In addition, as mentioned above, the fixed binder resin can exert a reinforcing effect, which greatly improves the bonding force between the fibers constituting the base material of the separator and improves the strength of the separator itself, so that it can prevent the A rupture accident that occurs when the separator is installed in the battery or a short circuit phenomenon caused by long-term charging and discharging cycles.

      A brief description of the accompanying drawings

Fig. 1 is an enlarged view of a model showing an example of a battery separator of the present invention.

Fig. 2 is an enlarged model view showing another example of the battery separator of the present invention.

Fig. 3 is a graph showing the relationship between the mixing weight ratio of the binder resin and the ion-exchangeable fine powder to the ion-exchange capacity according to an embodiment of the present invention.

Fig. 4 is a graph showing the relationship between the mixing weight ratio of the adhesive resin and the ion-exchange fine powder in one embodiment of the present invention and the retention rate of the electrolyte.

FIG. 5 is a graph showing a comparison of the electrolyte retention rates of the separators of the examples of the present invention, comparative examples, and prior art examples when pressurized.

Fig. 6 is a graph showing a comparison of the ion exchange capacities of Examples of the present invention with Comparative Examples and Prior Art Examples.

Fig. 7 is a graph showing a comparison of utilization ratios of high-rate discharge of sealed nickel-hydrogen batteries using separators of Examples of the present invention and Examples of the prior art.

Fig. 8 is a graph showing a comparison of capacity retention rates of sealed nickel-hydrogen batteries using the separators of Examples of the present invention and Examples of the prior art and stored at 45°C for 2 weeks after charging.

Fig. 9 is a graph showing a comparison of battery capacity with the number of cycles in sealed nickel-hydrogen batteries using the separators of Examples of the present invention and Examples of the prior art.

                                         

The following description will be made using the drawings. Fig. 1 is an enlarged view of a model showing one embodiment of the battery separator of the present invention. In Fig. 1, 1 is an olefin-based fiber as a base. Fine voids 2 or fine grooves exist on the surface of the above-mentioned olefin fiber 1 . The above-mentioned fine voids 2 or fine grooves can be formed by etching the above-mentioned olefin-based fibers with an organic solvent. The binder resin 3 is fixed to the above-mentioned olefin fibers in a structure in which a part is immersed in the above-mentioned fine voids 2 or fine grooves and the other part protrudes outward, and the ion-exchange fine powder 4 is fixed on the front end of the protruding part of the binder resin 3 within the area. In addition, a part of the ion-exchange fine powder body 4 has an exposed portion 5 .

Fig. 2 is an enlarged view of a model showing another embodiment of the present invention, in which there are many fine voids 2 or fine grooves formed due to being etched by an organic solvent on the surface of the olefinic fiber 1 as a base, and the adhesive The resin 3 is fixed in a form that a part thereof is immersed in the above-mentioned fine voids 2 or fine grooves, and at the same time, the ion-exchange fine powder is fixed by the porous portion 6 having many micropores on its surface.

In the present invention, numerous microscopic voids or fine grooves are first formed on the surface of the organic fibers constituting the porous sheet, and then a binder resin which has alkali resistance and oxidation resistance and is soluble in organic solvents is used to The above-mentioned gaps or fine grooves are soaked and filled, and then the binder resin that has soaked and filled the above-mentioned gaps or fine grooves is used to fix an ion-exchange fine powder on at least the surface of the above-mentioned organic fibers and the fiber interweaving region. On a part of the surface, most of the ion-exchange fine powder body is exposed to a part of the surface.

The mixing weight ratio of the above-mentioned binder resin to the ion-exchange fine powder is generally in the range of 1:0.3 to 1:10, preferably in the range of 1:0.5 to 1:6, when the mixing weight ratio is less than 1:0.3 , the surface of the ion-exchange fine powder is completely covered by the binder resin, so sufficient electrolyte retention and ion exchange capacity cannot be obtained. In addition, when the above-mentioned mixing ratio is greater than 1:10, the binder resin has a negative effect on the ion exchange rate. The retentivity of the exchangeable fine powder is insufficient, so that the ion-exchange fine powder physically falls off during the manufacturing process of the separator and when the separator is incorporated into a battery.

In order to confirm the above point of view, use a kind of adhesive resin (SEBS) and ion exchange fine powder (styrene sulfonic acid type strong acidic cation exchange resin fine powder) in the mixing weight ratio of 1:0.2～1:12 The solution (organic solvent: mixed xylene) formed by changing within a certain range is made into a test piece on a non-woven fabric made of polypropylene fiber, and then the test piece is used to measure the mixing weight ratio and ion exchange rate according to the following test method. Capacity relationship, the results shown in Figure 3 were obtained. In addition, the relationship between the mixing weight ratio and the electrolyte retention rate was measured, and the results shown in FIG. 4 were obtained. From these results, it can be seen that when the mixing weight ratio of the binder resin and the ion-exchange fine powder body is less than 1:0.3, the ion exchange capacity and electrolyte retention rate are insufficient, and when it exceeds 1:10, it will cause The ion-exchangeable fine powder body fell off, and it was confirmed that both the ion exchange capacity and the electrolyte retention rate at this time were lowered.

As the binder resin soluble in organic solvents, those having excellent alkali resistance and oxidation resistance, styrene-based thermoplastic copolymers, olefin-based polypropylene resins or polyethylene resins, halogenated polyolefin-based Any one or more than one of the polytetrafluoroethylene resins, especially from the adhesive aspects of polyolefin fibers and ion-exchange fine powders, preferably use styrene-ethylene-butylene-styrene (SEBS ) type copolymer as part or all of the binder resin.

As the ion-exchange fine powder, those cationic exchange resins with an ion exchange capacity of 0.5-4.5eq/liter in water and styrene or acrylic resin as the matrix are suitable, and styrene, acrylic or phenol Anion exchange resins based on resinous resins, chelating resins based on styrenes or pyridines; or metal oxides of zirconium, titanium, aluminum or antimony with an ion exchange capacity of 0.4-10.0meq/g compounds, hydroxides or inorganic salts thereof, among which titanium oxide, potassium titanate, antimony oxide, aluminum oxide or zirconium oxide are particularly suitable.

As an organic ion exchange resin, a strong acid type cation exchange resin obtained by sulfonating a polystyrene resin formed by three-dimensional crosslinking of divinylbenzene or a metal salt thereof, or a polystyrene resin formed by divinylbenzene The polyacrylate resin formed by three-dimensional cross-linking is obtained by hydrolysis, the weak acid type cation exchange resin or its metal salt, or the mixture obtained by proper combination of them.

The above-mentioned ion-exchange fine powder refers to those ion-exchange fine powders whose shape is granular (including spherical, microporous granular or particulate), flake-like, whisker-like or scale-like, and they can be used alone or in combination. . Among them, it is particularly preferable to use those micropowders having a microporous (void) shape on their surface. At this time, these micropowders are fixed due to the anchoring effect with the resin, and can fully Exert its ion exchange capacity in alkaline electrolyte.

In addition, the average particle size of the above-mentioned ion-exchange fine powder is generally below 100 μm, preferably below 50 μm. Since the surface area of the resin is large, the ion exchange capacity of the resin can be fully exerted, thereby improving its electrolyte retention. And thus the membrane resistance (internal resistance) can be reduced.

However, if the aforementioned metal salt is in the form of a potassium or sodium salt, fine powder can be easily obtained by mechanical pulverization.

In addition, as a manufacturing method of ion exchange resin fine powder, a spherical or crushed ion exchange resin with a moisture content of 35 to 75% and a particle size distribution of 0.3 to 1.2 mm can be dried to volatilize the moisture therein. dropped, and then frozen and pulverized using liquid nitrogen.

As commercially available ion exchange resins, "Sumikilet (registered trademark)" manufactured by Sumitomo Chemical Co., Ltd., "Day Yain (registered trademark)" manufactured by Mitsubishi Chemical Co., Ltd., and "Dyuzai (registered trademark)" manufactured by Mitsubishi Chemical Co., Ltd. can be used.ライット (registered trademark)", "Douex (registered trademark)" manufactured by Dou Chemical, etc.

In addition, as the ion-exchangeable porous inorganic fine powder, various metal oxides, hydroxides or metal salts of zirconium, antimony or aluminum that have alkali resistance can be used, and titanium oxide is particularly preferably used. Or potassium titanate, antimony oxide, aluminum oxide, zirconium oxide, etc.

Yes, among these solvent-based binder resins and ion-exchange fine powders, it is particularly preferred to use a combination of styrene-ethylene-butylene-styrene-based thermoplastic copolymers and strong-acid cation exchange resins or their metal salts as the basic Separator for secondary batteries.

As the organic fiber suitable for the present invention, it must be a polymer fiber with alkali resistance and oxidation resistance, preferably a part or all of which uses olefin fiber, and as olefin fiber, except for polypropylene and polyethylene Or in addition to split-film fibers composed of polymethylpentene and polyethylene, olefinic polyethylene, polypropylene, polymethylpentene fibers, or a class of polypropylene-based fibers with polyethylene as the core can also be used. Core-skin polyolefin fibers with sheath, or porous polyethylene or polypropylene fibers.

As an example of the manufacturing method of the separator for alkaline batteries having the above-mentioned structure, an aromatic hydrocarbon solvent that can swell the olefin fiber and form many voids or fine grooves on its surface is prepared, and the bonded agent resin is dissolved in the above-mentioned solvent and the ion-exchange fine powder is dispersed therein to form a slurry, which is impregnated, spread or coated on a nonwoven sheet made of olefin fibers, It was then dried with hot air to evaporate the solvent, thereby producing a separator for batteries.

However, in the above-mentioned method, by changing the method of attaching the slurry to the method of dipping, spreading or coating, the ion-exchangeable fine powder can be dispersed substantially uniformly inside the nonwoven sheet, or from the surface part. To the inside or vice versa, a layer of high-density area dispersed by finer particle size ion-exchange fine powder and a layer of low-density area dispersed by larger particle size ion-exchange fine powder are formed, thereby A density gradient-type structure is obtained. With such a density gradient structure, when the separator is installed in a battery, its high-density side faces the negative electrode and its low-density side faces the positive electrode, which can further improve its gas permeability.

As an organic solvent suitable for the above-mentioned production method, any one or more of them can be appropriately selected from xylene, toluene, methylcyclohexane, tetralin, and decahydronaphthalene.

In the case of using aromatic hydrocarbon solvents such as benzene or cyclohexane with a fast evaporation rate, once the heating temperature is too high, before voids or fine grooves are formed on the surface of the fiber through the dissolution of the solvent, If the solvent is evaporated, the adhesion between the olefin fiber and the binder resin will deteriorate, and the ion-exchange fine powder will easily fall off, which is not preferable.

In the case according to the present invention, firstly, a solvent capable of dissolving when heated is used to form innumerable fine voids or fine grooves in the surface portion of the olefin fiber, and then a binder resin is allowed to penetrate into the above-mentioned voids. Or fine grooves and firmly fixed here, and then use this binder resin with an anchoring effect to firmly fix the ion-exchange fine powder on at least the fiber surface or fiber interweaving area of the porous sheet A part of the surface exposes most of the ion-exchange fine powder.

Here, the so-called most of the ion-exchange fine powder with a part of its surface exposed means that the entire surface of the dispersed ion-exchange fine powder is not completely covered by the binder resin, but is completely covered. The fine powder and part of the covered fine powder are mixed together, and the part of the covered fine powder accounts for more than half of the state.

In addition, the partially covered state refers to the state where there is an exposed portion on a part of the surface of each ion-exchange fine powder, but it is preferable that the ratio of at least one-third or more of the surface area of the ion-exchange fine powder is one with many The spider web-like state of the microporous part.

In addition, by adjusting the mixing weight ratio and the adhesion amount of the binder resin and the ion-exchange fine powder and using the cation-exchange fine powder and the anion-exchange fine powder in combination as the above-mentioned ion-exchange fine powder, the Battery performance Freely control electrolyte retention, ion exchange performance, and the like.

Hereinafter, the present invention will be described more specifically using examples. Example 1

Use split-film polyolefin fibers made of polyethylene and polypropylene (manufactured by Yamato Textile Co., Ltd., trade name DF-72, fineness 2d, fineness after splitting 0.2d), after making thin sheets according to the usual pulping method, the It was subjected to water jet processing and hot calendering processing to produce a non-woven sheet with a weight per unit area of 30 g/m ² and a thickness of 100 μm.

Then the above-mentioned non-woven fabric sheet is placed in the slurry (solvent: mixed xylene, solid content concentration 10%) that is prepared according to the following matching conditions and dipped, followed by hot air drying at 80° C. for 5 minutes to make the The solvent was volatilized, and in order to adjust the thickness of the sheet, calendering was performed using a hot roll (temperature 125° C.) to produce a separator a with an adhesion amount of 6 g/m ² , a weight per unit area of 36 g/m ² , and a thickness of 100 μm.

Coordination condition 1 Mixing weight ratio SEBS resin (manufactured by Shell, trade name Kraton 100G-1652) styrene sulfonic acid type strong acid cation exchange resin 300 fat micropowder (manufactured by Rome and Hass, trade name DuoliteC-20 below 100 μm) Mechanical pulverization implementation Example 2

Using the nonwoven sheet of Example 1, it is placed in the slurry prepared according to the following matching condition 2 (solvent and solid content concentration are the same as Example 1) and soaked in the same way as Example 1. A separator b with an adhesion weight of 6 g/m ² , a weight per unit area of 36 g/m ² , and a thickness of 100 μm.

Coordination condition 2 Mixing weight ratio SEBS resin (manufactured by Shell, trade name Kraton 100G-1652) styrene sulfonic acid type strongly acidic cation exchange resin 100 lipid micropowder (manufactured by Rome and Hass, trade name DuoliteC-20 below 100 μm) Mechanical pulverization implementation Example 3

Using the nonwoven sheet of Example 1, it is placed in the slurry prepared according to the following matching condition 3 (solvent and solid content concentration are the same as Example 1) and soaked in the same way as Example 1. A separator c with an adhesion weight of 6 g/m ² , a weight per unit area of 36 g/m ² , and a thickness of 100 μm.

Compounding condition 3 Mixing weight ratio SEBS resin (manufactured by Shell, trade name Kraton 100G-1652) Potassium tetratitanate Whisker shape (manufactured by Otsuka Chemicals, 300 trade name TISMO) mechanically pulverized Below 50 μm

The structures of the various separators in Examples 1, 2, and 3 above have numerous voids 2 on the surface of the olefin fiber 1 as shown in FIG. and the solvent-based binder resin 3 firmly fixes the ion-exchange fine powder body 4 on the surface of the fiber and at least a part of the surface of the fiber interweaving region and makes the This ion-exchange fine powder has exposed parts 5 on most of its surface. Example 4

Use a core-sheath polyolefin fiber (Dawa Textile, trade name NBF, fineness 0.9d/1.5d, mixing ratio 1: 1) whose core is polypropylene and skin is polyethylene, and card it according to the conventional method. After the interwoven fabric sheet was produced, it was subjected to hot calendering to obtain a nonwoven fabric sheet with a weight per unit area of 50 g/m ² and a thickness of 170 μm.

Then use the slurry prepared according to the following matching condition 4 (the solvent and solid content concentration are the same as in Example 1) to make the above-mentioned slurry penetrate into the inside of the non-woven fabric sheet, and perform coating processing on the above-mentioned non-woven fabric sheet to produce A battery separator d having an adhesion amount of 6 g/m ² , a weight per unit area of 56 g/m ² and a thickness of 170 μm was obtained.

Coordination condition 4 Mixing weight ratio SEBS resin (manufactured by Shell, trade name Kraton 100G-1652) styrene sulfonic acid type strongly acidic cation exchange resin 100 lipid micropowder (manufactured by Rome and Hass, trade name DuoliteC-20 below 100 μm) freeze and pulverize implementation Example 5

Using the same nonwoven fabric sheet as in Example 4, the slurry of the following matching condition 5 (solvent and solid content concentration is the same as in Example 1) was soaked into the inside of the above-mentioned sheet in the same manner as in Example 4 to obtain a nonwoven sheet. A battery separator e with an adhesion amount of 6 g/m ² , a weight per unit area of 56 g/m ² , and a thickness of 170 μm.

Compounding condition 5 Mixing weight ratio SEBS resin (manufactured by Shell, trade name Kraton 100G-1652) styrene acrylic type weakly acidic cation exchange 100 resin micropowder (manufactured by Rome and Hass, trade name DuoliteC-433 below 100 μm) freeze pulverization Example 6

Using the same nonwoven sheet as in Example 4, the slurry of the following matching condition 6 (the same solvent and solid content concentration as in Example 1) was soaked into the inside of the above-mentioned sheet in the same manner as in Example 4 to obtain a nonwoven sheet. A battery separator f having an adhesion amount of 6 g/m ² , a weight per unit area of 56 g/m ² , and a thickness of 170 μm.

Coordination condition 6 Mixing weight ratio SEBS resin (manufactured by Shell, trade name Kraton 100G-1652) styrene quaternary ammonium salt strong basic cation exchange resin 100 fat micropowder (manufactured by Rome and Hass, trade name DuoliteA-133 below 100 μm) freeze and pulverize Example 7

Using the same non-woven fabric sheet as in Example 4, the slurry of the following matching condition 7 (solvent and solid content concentration is the same as in Example 1) was soaked into the inside of the above-mentioned sheet in the same manner as in Example 4, and a A battery separator g with an adhesion amount of 6 g/m ² , a weight per unit area of 56 g/m ² , and a thickness of 170 μm.

Mixing condition 7 Mixing weight ratio SEBS resin (manufactured by Shell, trade name Kraton 100G-1652) Potassium tetratitanate whisker shape (manufactured by Otsuka Chemicals, 300 trade name TISMO) mechanically pulverized Below 50 μm

The structures of the various separators of the above-mentioned Examples 4, 5, 6, and 7 are as shown in FIG. 2 which is an enlarged view of the model, and there are many holes formed by the attack of the organic solvent on the surface of the olefin fiber 1 as the matrix. The binder resin 3 penetrates into these fine voids or fine grooves and is fixed there, and the resin 3 firmly fixes the ion-exchange fine powder body 4 on the surface thereof. In addition, the binder resin 3 has a microporous portion 6 in which many pores are formed, and the ion-exchange fine powder body 4 is in a state capable of directly contacting external liquid. Comparative example 1

Using the slurry with the following matching condition 8 (solvent: water, solid content concentration 10%), according to the same method as Example 1, a kind of adhesion amount 6g/m ² , unit area weight 36g/m ² , thickness 100μm was prepared The diaphragm h.

Coordination condition 8 Mixing weight ratio PP emulsion (manufactured by Mitsui Petrochemical, Chemipa-100ルWP100, active ingredient 40%) styrene sulfonic acid type strongly acidic cation exchange resin 300 fat micropowder (manufactured by Rome and Hass, commercial name DuoliteC below 100 μm -20) Mechanical Pulverization Comparative Example 2

Use a slurry made of SEBS resin and ion exchange resin micropowder in a weight ratio of 100:20 to process the nonwoven sheet of Example 1, and obtain a kind of adhesion amount 6g/m ² , weight per unit area 56g/m ² , Separator i with a thickness of 170 μm. Comparative example 3

Use a kind of slurry that is made by SEBS resin and ion exchange resin micropowder by weight ratio 100:1200 to process the nonwoven sheet of embodiment 4, make a kind of adhesion amount 6g/m ² , weight per unit area 36g/m ² , Separator j with a thickness of 100 μm. Prior Art Example 1

According to the known method, use fuming sulfuric acid and concentrated sulfuric acid respectively to a kind of non-woven sheet with weight per unit area 30g/m ² , thickness 100μm and a kind of nonwoven sheet according to the same method as in Example 4 Non-woven sheets with a weight per unit area of 50 g/m ² and a thickness of 170 μm prepared by the same method were subjected to sulfonation treatment to prepare separators k and l respectively. Prior art example 2

According to the known method, use acrylic acid to prepare a kind of 30g/m ² per unit area and 100μm thickness and a 50g/m ² per unit area and 170μm thickness prepared by the same method as Example 1 and Example 4 respectively. The nonwoven sheets were grafted and polymerized to fabricate separators m and n, respectively.

Then, use totally 14 kinds of separators a, b, c, d, e, f, g, h, i, j, k, l, m, n, measure the alkali resistance, oxidation resistance, electrolyte retention rate, ion exchange capacity and strength of these diaphragms according to the following test methods, The results shown in Table 1 were obtained.

Table 1 Strength ratio (%) Alkali resistance (%) Oxidation resistance (%) Electrolyte retention rate (%) Ion exchange capacity (meq/m ² ) Example a 130 -0.15 -0.25 45 7.2 Example b 150 -0.22 -0.27 33 5.2 Example c 130 -0.13 -0.21 43 6.9 Example d 150 -0.12 -0.21 38 11.2 Example e 130 -0.22 -0.35 32 20.5 Example f 150 -0.21 -0.25 40 8.9 Example g 150 -0.11 -0.23 35 10.7 comparative example h 105 -1.5 -5.84 38 6.8 comparative example i 210 -0.10 -0.20 19 0.9 Comparative example j 110 -0.21 -0.26 82 22.3 Prior art example k 80 -0.35 -0.94 twenty four 0.24 Example of prior art 85 -0.31 -0.95 15 0.8 Example of prior art 90 -0.21 -1.05 twenty two 0.18 Example of prior art 95 -0.44 -1.75 17 0.25

The test methods for the physical property values in Examples, Comparative Examples and Prior Art Examples are as follows.

Strength test: use a tensile testing machine to clamp the two ends of the test piece (2cm wide) according to the distance between the two clamps as 10cm, and then stretch it to measure the strength of the test piece when it breaks. The intensity ratio was calculated according to the following formula.

Strength ratio (%) = strength of test piece after treatment / strength of test piece before treatment × 100

Alkali resistance: Make the test piece reach the water equilibrium state, measure its weight (W), then immerse it in a potassium hydroxide solution with a specific gravity of 1.30, and immerse it at 100°C for 1 hour. Then, it was washed with water and dried, and its weight (W ₁ ) was measured when it reached a water balance state, and its alkali resistance was obtained according to the following formula.

Alkali resistance (%)=(WW ₁ )/W×100

Oxidation resistance: Make the test piece reach the water balance state, measure its weight (W), and then immerse it in a 1% by weight potassium permanganate solution 250cc by adding 30% potassium hydroxide solution 500cc to form In the mixed solution, immerse at 50 degreeC for 1 hour. Then, it was washed with water and dried, and its weight (W ₁ ) was measured when it reached a water balance state, and its oxidation resistance was obtained according to the following formula.

Oxidation resistance (%)=(WW ₁ )/W×100(%)

Electrolyte retention rate: make the test piece (5cm square) reach the water balance state, measure its weight (W), and then use the potassium hydroxide solution with a specific gravity of 1.30 to replace the air in the test piece in an amount of 0.025g/ ^cm2 , In order to keep the potassium hydroxide solution in the test piece. Then, clamp the test piece from the upper and lower sides with two pieces of filter paper (diameter 20cm), apply a weight of 5 kg from above and pressurize it for 10 minutes, then measure the weight (W ₁ ) of the test piece according to the following Formula to find the electrolyte retention rate.

Electrolyte retention rate (%)=(WW ₁ )/W×100

Ion exchange capacity: The test piece was brought to a water balance state, and its weight (W) was measured. After immersing this test piece in 200 cc of 5N hydrochloric acid for 3 hours, it was taken out, washed sufficiently with distilled water, and dried at 100° C. for 1 hour. Then, place the test piece in 50 cc of 0.05 N potassium hydroxide solution, soak it at 60° C. for 5 hours, carefully draw 10 cc of supernatant, add bromocresol green indicator therein, use 0.05 N hydrochloric acid (titration degree f _c1 ) for titration. Taking the consumed amount of 0.05 N hydrochloric acid at this time as Xcc, the ion exchange capacity was obtained by the following formula.

Ion exchange capacity (meq/m ² )=(10f _K -f _Cl ×X)/4W

Then, use up to 14 kinds of diaphragms a, b, c, d, e, f, g, h, i, j, k, l, m, n, use the paste Ni pole as the positive pole, and use the paste MH pole as the negative pole , and use an alkaline electrolyte to produce sub-C size (SubC series) sealed nickel-metal hydride batteries A, B, C, D, E with a capacity of 2.1 to 2.5A (charge and discharge within 0.1 hour) , F, G, H, I, J, K, L, M, N, and then measure the utilization rate of these batteries during high-speed discharge, the capacity retention rate after self-discharge, and the charge-discharge cycle life. Perform a performance evaluation. The measurement results are shown in Table 2.

Table 2 Utilization rate during high-speed discharge (%) (2.0C/0.1C) Capacity retention after self-discharge (%) (45℃×2 weeks) Capacity retention after 500 cycles (%) Example A 91.5 52.3 100 Example B 90.3 52.5 100 Example C 91.2 51.5 100 Example D 91.0 52.7 100 Example E 82.7 48.1 100 Example F 90.0 50.8 100 Example G 90.8 51.8 100 Comparative Example H 89.0 32.5 80 Comparative Example I 89.5 40.2 80 Comparative Example J - - - Prior Art Example K 87.0 39.0 82 Prior Art Example L 86.3 39.5 82 Prior Art Example M 86.5 30.4 75 Example of prior art N 87.8 32.8 82

Test methods for various physical property values in Examples, Comparative Examples, and Prior Art Examples are as follows.

Initial activation conditions: temperature 30°C, charge 0.1C rate (290mA) x 12 hours, rest 0.5 hour, charge 0.1C rate (termination voltage 1.0V) for 10 cycles.

High-speed discharge test: temperature 30°C, charge 0.2C rate (290mA) x 6 hours, rest for 0.5 hours, then discharge 0.1C rate (end voltage 0.8V), measure the discharge capacity at this time, and then charge according to the same conditions, and then Discharge at a rate of 2.0C (end voltage 0.8V), measure the discharge capacity at this time, and finally find the ratio of the latter’s discharge capacity to the former’s discharge capacity, and use this ratio as the utilization rate (%) during high-speed discharge.

Self-discharge test: temperature 30°C, charge 0.1C rate × 12 hours, rest for 0.5 hours, then discharge 0.1C rate (end voltage 1.0V), measure the discharge capacity at this time, and then charge according to the same conditions, and then place it in the Place it at 45°C for two weeks, measure the remaining capacity at this time (0.1C rate discharge, end voltage 1.0V), find the ratio of the remaining capacity to the above discharge capacity, and use this ratio as the capacity retention rate after self-discharge (% ).

Cycle life characteristics: at a temperature of 30°C, perform 500 cycles according to the system of charging 0.2C rate × 5 hours, resting time 0.5 hours, and discharging 0.2C rate (end voltage 1.0V), then measure and obtain the capacity retention rate .

In addition, in Comparative Example J, the ion-exchange resin fine powder fell off and could not be incorporated into a battery.

The comparison of electrolyte solution retention rates at the time of pressurization listed in Table 1 above was plotted in the graph of FIG. 5 . In addition, a comparison of the ion exchange capacities listed in this table was made into the graph of FIG. 6 . In addition, the comparison of utilization factors at the time of high-speed discharge in the above-mentioned Table 2 is shown in the graph of FIG. 7 . The comparison of the capacity retention rates after self-discharge in this table is plotted in the graph of FIG. 8 . Furthermore, the graph of FIG. 9 was made for the comparison of the change of the battery capacity with the number of cycles in this table.

As can be seen from the above Tables 1-2 and Figures 5-9, compared with the diaphragms k-n and the sealed nickel-hydrogen batteries K-N of the prior art examples, the diaphragms a-g and the sealed nickel-hydrogen batteries of the embodiments of the present invention Nickel-hydrogen batteries A to G have greatly improved the electrolyte retention rate, ion exchange capacity and strength. In addition, it has been confirmed that in the battery performance test, especially the capacity retention rate after the self-discharge test and 500 times There is a dramatic improvement in the capacity retention rate after cycling.

In the above-mentioned examples, as the olefin fibers, split-type fibers composed of polyethylene and polypropylene were used and made into sheets by the papermaking method. In addition, core-sheath fibers may be used and made into sheets by a conventional carding method. into sheets, but it is also possible to use other organic fibers other than the above-mentioned fibers and form them into sheets.

Possibility of industrial use

As mentioned above, according to the present invention, firstly, countless fine voids or fine grooves are formed on the surface of the olefin fiber, and then the binder resin is impregnated and bonded in these voids or fine grooves, and then the ions are anchored. The exchangeable fine powder is firmly fixed on the surface of the olefinic fiber and at least a part of the surface of the fiber interweaving region, so its electrolyte retention, ion exchange capacity and strength are very good, and its alkali resistance and oxidation resistance are also very good. Since it is excellent, it is possible to control self-discharge and prolong the life of the battery.

In addition, the binder resin is fixed on the surface of the olefin fiber by anchoring, so it has a reinforcing effect on the mutual bonding between the fibers, and even if the fiber with a fine denier value is used, the strength of the fiber will not be reduced. There will be no fracture accident when it is installed in the battery, and there will be no fiber degradation due to repeated charging and discharging, so there will be no micro short circuit, so that it can achieve a thinner film for the battery separator and can adapt to the high capacity of the battery change.

Furthermore, it does not require a washing and removal process for unreacted substances unlike conventional acrylic acid graft polymerization or sulfonation treatment, so it can be manufactured at low cost. In addition, since ultraviolet rays, electron beams, or strong acids are not used, the olefin-based fibers constituting the fiber base of the separator are not degraded, and there is no risk of micro-short circuits.

In addition, electrolyte retention, ion exchange performance, and the like can be easily adjusted by changing the mixing weight ratio or adhesion amount of the binder resin and the ion-exchange fine powder.

An alkaline secondary battery using such a separator has excellent discharge characteristics, and can have a high capacity retention rate even when charge and discharge cycles are repeated.

Claims (22)

1. alkaline secondary cell barrier film, it is characterized in that, on the surface of the organic fibrid that constitutes the porousness thin slice, be formed with fine space or rill, use a kind of adhesive resin that dissolves in the organic solvent to soak into and fill up above-mentioned space or rill, more a kind of ion exchangeable powder body is fixed at least a portion in the surface of above-mentioned organic fibrid and fiber interweaving district.

2. battery separator as claimed in claim 1, wherein, the mixed weight of adhesive resin and ion exchangeable powder body is than being binder resin: the scope of ion exchangeable powder body=1: 0.3～1: 10.

3. battery separator as claimed in claim 2, wherein, the mixed weight of adhesive resin and ion exchangeable powder body is than being binder resin: the scope of ion exchangeable powder body=1: 0.5～1: 6.

4. battery separator as claimed in claim 1, wherein, the ion exchangeable powder body has absorption and catches the function of harmful ion in the electrolyte and the function of maintenance alkaline electrolyte.

5. battery separator as claimed in claim 1, wherein, adhesive resin is at least a resin of selecting from the polyflon of the acrylic resin of styrene analog thermoplastic polymer with alkali resistance, oxidative resistance, olefines or polyvinyl resin, halogenated polyolefin class.

6. battery separator as claimed in claim 1, wherein, part or all of adhesive resin is styrene-ethylene-butylene-styrene class (SEBS) thermoplastic polymer of phenylethylene.

7. battery separator as claimed in claim 5, wherein, part or all of adhesive resin is styrene-ethylene-butylene-styrene class (SEBS) thermoplastic polymer of phenylethylene.

8. battery separator as claimed in claim 1, wherein, the ion exchangeable powder body contains from the cation exchange resin of phenylethylene or acrylic compounds, the anion exchange resin of phenylethylene, acrylic compounds or phenol, at least a resin of selecting in the chelating resin of phenylethylene or pyridines.

9. battery separator as claimed in claim 8, wherein, the ion exchange substrate of ion exchangeable powder body is at least a group of selecting in sulfonic group, sulphonate-base, carboxylic acid group and the carboxylate group.

10. battery separator as claimed in claim 1, wherein, the ion exchangeable powder body contains from having alkali-proof and can bring into play at least a compound of selecting in metal oxide, hydroxide and the inorganic salts thereof of ion exchangeable alkaline electrolyte.

11. battery separator as claimed in claim 4, wherein, the ion exchangeable powder body contains from having alkali-proof and can bring into play at least a compound of selecting in metal oxide, hydroxide and the inorganic salts thereof of ion exchangeable alkaline electrolyte.

12. battery separator as claimed in claim 11, wherein, the ion exchangeable powder body contains at least a compound of selecting from titanium oxide, aluminium oxide, antimony oxide, potassium titanate, zirconia.

13. battery separator as claimed in claim 1, wherein, the ion exchangeable powder body is a kind of granular, laminar, whisker shape or flakey that has fine voids from the teeth outwards.

14. battery separator as claimed in claim 5, wherein, the ion exchangeable powder body is a kind of granular, laminar, whisker shape or flakey that has fine voids from the teeth outwards.

15. battery separator as claimed in claim 1, wherein, the average grain diameter of ion exchangeable powder body is below 100 μ m.

16. battery separator as claimed in claim 5, wherein, the average grain diameter of ion exchangeable powder body is below 100 μ m.

17. as claim 15 or 16 described battery separators, wherein, the average grain diameter of ion exchangeable powder body is below 50 μ m.

18. battery separator as claimed in claim 1, organic fibrid wherein are a kind of polymer class fibers with alkali resistance and oxidative resistance.

19. battery separator as claimed in claim 1, wherein, part or all of organic fibrid is olefine fibre.

20. battery separator as claimed in claim 18, wherein, part or all of organic fibrid is olefine fibre.

21. battery separator as claimed in claim 1, this battery separator are the alkaline secondary cell barrier films.

22. alkaline secondary cell that uses the described barrier film of claim 1.

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