JPH0794164A - Alkaline battery separator and alkaline battery using the separator - Google Patents

Abstract

PURPOSE:To provide a separator almost free from the ingress of an electrolyte, while having the high capability for holding an electrolyte and almost ensuring freedom from short-circuit due to dendrite by forming the separator out of water flow leno nonwoven fabric containing the bridged state of polyvinyl alcohol having the specified constitutional unit. CONSTITUTION:An alkaline battery separator is constituted of water flow leno nonwoven fabric containing the bridged state of polyvinyl alcohol having a constitutional unit expressed by the general formula I, where R1 stands for a quaternary aromaticity complex cyclic residual group containing nitrogen, R2 for a hydrogen atom or an alkoxy group and R3 for a hydrogen atom or an acyl group. Also, (m) stands for 0 or 1, and (n) for a natural number between 1 and 6. For an alkaline battery, this separator is employed. The bridged polyvinyl alcohol has affinity with an electrolyte, and is excellent in holding the electrolyte. In addition, the fiber of the water flow leno nonwoven fabric is generally oriented toward a thicknesswise direction. Thus, a certain degree of thickness can be maintained against the expansion of an electrode or the like. Thus, the separator comes to have the higher capability of holding the electrolyte.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline battery separator and an alkaline battery using the same.

[0002]

2. Description of the Related Art Conventionally, a separator has been used so as to separate a positive electrode and a negative electrode of an alkaline battery to prevent a short circuit and to hold an electrolytic solution so that an electromotive reaction can be carried out smoothly.

A conventional alkaline secondary battery separator is
It is provided in the form of a woven fabric or a non-woven fabric, and the fibers that make up the woven fabric or the non-woven fabric are polyamide fibers, and it is common to use a potassium hydroxide solution as the electrolytic solution. There was a problem that the positive electrode and the negative electrode were short-circuited by being attacked.

Therefore, it has been considered to use a separator using a polyolefin fiber such as polypropylene fiber, but since the polyolefin fiber is hydrophobic and has a low affinity with the electrolytic solution, the electrolyte retaining property is low. There was a problem of being bad.

Further, the separator using the above polyamide-based fiber or polyolefin-based fiber has a shortened service life due to a so-called dendrite in which dendritic metal is deposited on the electrode plate during discharging and / or charging. There was also the problem of being short.

On the other hand, conventional separators for alkaline primary batteries are provided in the form of non-woven fabric, paper, etc. Vinylon fibers and polyvinyl alcohol fibers make up the non-woven fabric and paper, and potassium hydroxide solution is used as an electrolytic solution. However, there is a problem that the fiber is attacked by the electrolytic solution as it is used, and the positive electrode and the negative electrode are short-circuited.

[0007] Further, pulp such as mercerized pulp and linter pulp is used in order to improve the electrolyte retention of the separator. Impurities and / or impurities in these pulps are used.
Or, in order to suppress the generation of hydrogen in the electrolytic solution, due to the action of aluminum added to the zinc that constitutes the negative electrode, during discharge, a short circuit occurs due to dendrites in which dendritic zinc oxide is deposited on the electrode plate, There is also a problem that the service life is short, such as causing abnormal voltage drop.

[0008]

DISCLOSURE OF THE INVENTION The present invention is an alkaline battery which is not easily corroded by an electrolytic solution, is excellent in retaining the electrolytic solution, and is unlikely to cause a short circuit due to dendrites from which dendritic metal is deposited, and has a long service life. It is intended to provide a separator for batteries and an alkaline battery using the separator.

[0009]

Means for Solving the Problems Alkaline battery separator of the present invention (hereinafter sometimes referred to as "separator")
Is the general formula

[Chemical 2] (In the formula, R ₁ is a quaternized aromatic nitrogen-containing heterocyclic residue, R ₂ is a hydrogen atom or an alkoxy group, R ₃ is a hydrogen atom or an acyl group, m is 0 or 1, and n is 1 to 1. Polyvinyl alcohol having a structural unit represented by a natural number of 6) (hereinafter,
"PVA" is sometimes crosslinked (hereinafter,
It may be referred to as “crosslinked PVA”). When the ultrafine fibers are contained in the constituent fibers of the hydroentangled nonwoven fabric, the separator is more excellent in retaining electrolyte and preventing dendrite.

The alkaline battery of the present invention is an alkaline battery using the above separator.

[0011]

Since the separator of the present invention contains cross-linked PVA, it is not easily decomposed by an alkaline electrolyte such as potassium hydroxide, can be used for a long time, and has excellent heat resistance. Therefore, it can withstand use under high temperature conditions such as trickle charging.

Further, the crosslinked PVA has an affinity with the electrolytic solution and is excellent in retaining the electrolytic solution. Further, since the fiber orientation of the hydroentangled nonwoven fabric is mainly in the thickness direction,
Since the thickness can be maintained to some extent against the expansion of the electrode, the separator has more excellent electrolyte retention.

Further, since the crosslinked PVA has a hydroxyl group capable of forming a chelate with an ion before the dendritic metal is deposited on the electrode plate during discharging and / or charging, the crosslinked PVA is dendritic. It is difficult for metal to deposit and short circuit due to dendrite does not occur easily. In addition, forming a chelate with ions,
The trapping of ions has been confirmed by the experimental example described later.

The crosslinked PVA of the present invention has a structural unit represented by the following general formula.

[Chemical 3] In the formula, R ₁ is a quaternized aromatic nitrogen-containing heterocyclic residue, R ₂ is a hydrogen atom or an alkoxy group, R ₃ is a hydrogen atom or an acyl group, m is 0 or 1, and n is 1 Is a natural number of 6 to 6, and R ₁ is, for example, a pyridinium group, a quinolinium group, an isoquinolinium group, a pyrimidinium group, a thiazolium group, a benzothiazolium group, a benzoxazolium group, etc. May have a substituent such as an alkyl group, an alkoxyl group, an amino group and a carbamoyl group. R ₂ is, for example, a hydrogen atom or an alkoxy group such as a methoxy group, an ethoxy group, an n-propoxy group and an isopropoxy group. R ₃ is, for example, a hydrogen atom or an acyl group such as a formyl group, an acetyl group, a propionyl group, a butyryl group and an isobutyryl group.

More specifically, chemical formulas 4 to 7 in which R ₃ is a hydrogen atom and chemical formula 8 in which R ₃ is an acetyl group can be exemplified.

[Chemical 4]

[Chemical 5]

[Chemical 6]

[Chemical 7]

[Chemical 8]

The hydroxyl group of PVA is preferably present in an amount of 20 mol% or more, more preferably 40 mol% or more, and most preferably 80 mol, based on the monomer unit of PVA so as to easily form a chelate with an ion. % Or more. Further, although the aromatic nitrogen-containing heterocyclic residue is cross-linked with a side chain containing the nitrogen-containing heterocyclic residue, the aromatic nitrogen-containing heterocyclic residue is added to the monomer unit of PVA so as not to inhibit chelate formation between a hydroxyl group and an ion. , Preferably 20 mol% or less,
It is preferably 0.5 mol% or more so as not to impair the electrolytic solution resistance and heat resistance due to crosslinking. More preferably, it is 1 to 10 mol%.

The degree of polymerization of PVA is not less than 500, and the degree of saponification is not limited to 70 to 100%.

If a hydrophobic portion is partially formed on the PVA with an aldehyde compound such as butyraldehyde, flexibility is generated and the handleability of the separator can be improved.

The separator of the present invention has the above-mentioned crosslinked P
Hydro-entangled non-woven fabric containing VA, but cross-linked P on the fiber surface
It may be a non-woven fabric in which a fiber web containing fibers to which VA is attached is hydroentangled, or may be one in which crosslinked PVA is attached to a non-woven fabric in which the fiber web is hydroentangled, but like the latter, If the crosslinked PVA is attached after forming the nonwoven fabric, the crosslinked PVA will not be peeled off by the water flow.

Hereinafter, the case where the cross-linked PVA is attached after the nonwoven fabric is formed will be described based on the manufacturing method.

When the fiber constituting the hydroentangled nonwoven fabric of the present invention is a polyolefin fiber, it is more likely to be decomposed by an electrolytic solution and can be suitably used. Examples of the polyolefin fiber include polyethylene fiber and polypropylene. Polyolefin fiber such as fiber, core-sheath type, side-by-side type, eccentric type, or FIG.
One having a chrysanthemum-shaped fiber cross-section in which one component 1 is disposed between the other components 2 as shown in (d), and one component 1 and the other component 2 alternate as shown in FIG. 1 (e). Splittable or non-splittable polyethylene having a fiber cross section laminated in layers
Examples include polypropylene composite fibers. Incidentally, among the polyolefin fibers, ultrafine fibers obtained by the melt-blowing method and ultrafine fibers obtained by dividing the above-mentioned splittable conjugate fiber, the hydroentangled nonwoven fabric obtained has a large surface area and thus has an affinity for the electrolytic solution. Is easy to work, and the distance between the entanglement points of the fibers is short, and the voids are minute and dense.
It is a separator that can be used for a long period of time because it has a capillary effect, is excellent in retaining electrolyte, and can physically prevent a short circuit due to dendrite. Among these, if the splittable conjugate fiber is a divided ultrafine fiber, it can be split at the same time as entanglement by water flow, so not only is preferable in production, but the obtained hydroentangled nonwoven fabric is also excellent in strength. Therefore, it is excellent in workability when assembling a battery and can be used more preferably.

The finer the fine fibers, the more capillary effect can be produced and the dendrites can be physically prevented. However, if the fine fibers are too fine, the separator will have no strength. 0.01-0.
It is preferably 4 denier.

Incidentally, in order to improve the dimensional stability of the separator and further improve the handleability, an adhesive fiber may be included. As this adhesive fiber, for example,
Polyolefin fibers such as all-melt type polyethylene fibers and polypropylene fibers, and partially melt-type core-sheath type, side-by-side type, and eccentric type polyolefin-based composite fibers are available. It is also possible to bond with a heat-bonding component generated from the splittable conjugate fiber having the heat-bonding component.

The fiber web is formed from the fibers as described above. Examples of the method for forming the fiber web include a dry method and a wet method such as a card method and an air lay method, but the method is not limited thereto.

When the fiber web is formed by the card method, the orientation direction of the fibers may be unidirectional, or the fibers may be oriented so as to cross each other by a cross layer or the like, or they may be laminated. Among these,
A fibrous web including a fibrous web oriented so that the fibers intersect with each other can easily be entangled with each other during the subsequent hydroentangling treatment, so that a hydroentangled nonwoven fabric having excellent strength can be obtained.

The fiber web thus obtained is subjected to hydroentangling treatment. By this hydroentangling treatment, the orientation direction of the fibers becomes substantially the thickness direction of the non-woven fabric, so that it can withstand the pressure when assembling the battery. When used in a secondary battery, when the electrode plate expands It is a separator that can withstand the pressure of, and has excellent electrolyte retention.

Further, if the entangled fibers are mainly composed of ultrafine fibers, a thin separator can be obtained, and therefore, the active material can be filled in the battery as much as it becomes thinner,
It is possible to increase the capacity of the battery.

As the hydroentangling treatment having such an excellent effect, for example, a nozzle plate having a nozzle diameter of 0.05 to 0.3 mm and a pitch of 0.2 to 3 mm and arranged in a row,
Use a nozzle plate with nozzles arranged in two or more rows,
Treat with a water pressure of 10 to 300 kg / cm ² . Such a hydroentangling treatment need not be performed once, and can be performed twice or more if necessary. Further, the water flow treated surface does not have to be only one side of the fiber web, and both sides may be treated.

If the support such as the net or mesh on which the fiber web is placed has large pores during the hydroentangling treatment, the resulting separator will also have large pores, and a short circuit will easily occur. Therefore, it is more preferable to use a fine plain weave net of 60 mesh or more, or a perforated plate having a hole distance of 0.4 mm or less.

The above-mentioned crosslinked PVA is attached to the hydroentangled nonwoven fabric thus obtained. As for this adhesion method, if another adhesive or the like is used to adhere the crosslinked PVA, the electrolyte retention and the dendrite prevention property of the crosslinked PVA will decrease, so the polyvinyl alcohol solution before crosslinking is sprayed. It is more preferable that self-crosslinking is carried out after the attachment by an impregnation method, a coating method or the like.

The crosslinked PVA is preferably contained in the separator in an amount of 0.5% by weight. This is because if it is less than 0.5% by weight, the ability of the crosslinked PVA to retain the electrolytic solution and the property of preventing dendrite are deteriorated. When this separator is used in a sealed secondary battery, the crosslinked PVA is preferably 10% by weight or less in the separator. This is because if it exceeds 10% by weight, the mobility of gas generated during charging to other electrodes deteriorates, the internal pressure rises, and there is a risk of explosion. When used in a sealed secondary battery, it is more preferable that the separator contains 1 to 5% by weight of crosslinked PVA.

The separator of the present invention obtained as described above can be used for alkaline primary batteries or alkaline secondary batteries. For example, when it is used as a cylindrical alkaline manganese primary battery, the negative electrode portion is copper. Around the current collector of the negative electrode made of brass or brass rod, it is composed of an amalgamated zinc powder and a negative electrode mixture layer prepared by kneading an alkaline solution and a gelling agent such as carboxymethyl cellulose, and the positive electrode portion is made of manganese dioxide. A positive electrode mixture layer made of a mixture with carbon powder, and a nickel-plated steel plate that serves as both a positive electrode current collector and a terminal formed on the outside of the positive electrode mixture layer. The separator of the present invention is sandwiched and used so as to separate the layer and the positive electrode mixture layer. Even when zinc is used for the negative electrode as in this alkaline manganese primary battery, the use of the separator of the present invention can prevent a short circuit due to dendrite without using mercury to suppress the elution of zinc. As it can be prevented, it does not cause any environmental problems. Furthermore, since it is not necessary to use pure zinc so that mercury is not used, there is a labor saving of energy consumed for obtaining pure zinc, and a cost merit thereby arises.

On the other hand, for example, when it is used in a cylindrical nickel-cadmium sealed secondary battery, it is provided between a negative electrode composed of a porous body mainly composed of metal cadmium particles and a positive electrode having nickel hydroxide filled in the porous body. Then, the separator of the present invention is interposed, and the spirally wound cylindrical product is housed in a cylindrical nickel-plated steel case together with the electrolytic solution and hermetically sealed.

When the separator of the present invention is used in a nickel-hydrogen battery, self-discharge can be suppressed,
A battery with a long service life can be obtained. This is because the separator of the present invention can adsorb and suppress the migration of the metal eluted from the hydrogen storage electrode to the positive electrode, which is the main cause of self-discharge in the nickel-hydrogen battery. In addition, since the separator of the present invention can adsorb the eluted metal, the same effect can be obtained in other secondary batteries.

The alkaline primary battery of the present invention may have a cylindrical shape or a button shape, and the shape is not limited. On the other hand, the alkaline secondary battery may also be an open type or a closed type, and the shape may be a cylindrical shape, a flat shape, or a prismatic shape, and this point is not limited. The separator of the present invention is, for example, an alkaline manganese battery, a mercury battery, a silver oxide battery, a primary battery such as an air battery, a nickel-cadmium battery, a silver-zinc battery, a silver-cadmium battery, a nickel-zinc battery, a nickel-hydrogen battery. It can be used for secondary batteries such as.

Examples of the separator of the present invention will be described below, but the present invention is not limited to the following examples.

[0037]

【Example】

(Experiments 1 to 9) As shown in Table 1, 13% by weight of PVA (experiments 1 to 9) containing various styrylpyridinium-based residues and having a hydroxyl group capable of forming a chelate in an uncrosslinked state was dissolved in water. The PVA aqueous solution was applied on an acrylic plate with a metal coater and then dried at room temperature to obtain a film having a thickness of 100 μm. This was irradiated with ultraviolet rays for 10 minutes with a high pressure mercury lamp and self-crosslinked to obtain a crosslinked PVA film.

(Zinc ion adsorption test) 3 cm × 3 in a 30% potassium hydroxide solution having a zinc ion concentration of 0.1 mol / l
After immersing the films of Experiments 1 to 9 cut in cm and leaving them for 24 hours, each film was washed with pure water to remove zinc ions which were not attached to the surface but did not form a chelate. , Ash each film with a platinum crucible,
The adsorbed zinc ions were extracted and the zinc ion adsorption amount was measured by the atomic absorption method with a constant volume. The results are shown in Table 1.

[0039]

[Table 1]

(Cadmium ion adsorption test-1) Experiments 1 to 8 were conducted in an aqueous solution having a cadmium ion concentration of 0.1 mol / l.
The cadmium ion adsorption amount was measured in exactly the same manner as the zinc ion adsorption test except that each of the films was immersed. The results are also shown in Table 1.

(Cadmium ion adsorption test-2) Zinc ions except that the films of Experiments 1 to 3 were respectively immersed in a 30% potassium hydroxide solution having a cadmium ion concentration of 8.9 × 10 ^-5 mol / l. The cadmium ion adsorption amount was measured in exactly the same manner as the adsorption test. The results are also shown in Table 1.

As can be seen from Table 1, since the crosslinked PVA film can adsorb metal, it is considered that the deposition of dendritic metal can be suppressed and the short circuit due to dendrite can be prevented.

Examples 1 to 3 The styrylpyridinium-based residue as shown in Chemical formula 4 (a) is contained in an amount of 1.3 mol% based on the monomer unit of PVA, and a chelate-forming hydroxyl group is 98.7. It has a mol% of 1,700 and a saponification degree of 8
8% PVA dissolved in water, 13% by weight in uncrosslinked state
An aqueous PVA solution was obtained.

On the other hand, as shown in FIG. 1 (c), polypropylene component (symbol 2 in the figure, circular polypropylene component: 0.04 denier, petal-shaped polypropylene component:
0.12 denier) and polyethylene component (symbol 1 in the figure,
0.12 denier) having a cross-sectional shape of chrysanthemum and having a fineness of 2 denier and a fiber length of 38 mm was opened with a card machine to obtain a fiber web in which fibers were crossed with a cross layer. . This fibrous web was placed on an 80 mesh plain weave net with a nozzle diameter of 0.13 mm,
From the nozzle plate with a pitch of 0.6 mm, the water pressure is 120 kg / cm
² water flow, entangled by the action increments twice from both sides, basis weight 55 g / m ^2, to obtain a thickness of 0.15mm of hydroentangled nonwoven fabric.

For this hydroentangled nonwoven fabric, the PVA
The aqueous solution was impregnated with a solid content of 0.6, 1.7, and 2.9 g / m ² (Examples 1, 2, and 3 in that order), dried, and then irradiated with ultraviolet rays for 3 minutes with a high-pressure mercury lamp to perform PVA self treatment. It crosslinked and the separator of this invention was obtained.

(Comparative Example) A hydroentangled nonwoven fabric having a basis weight of 55 g / m ² and a thickness of 0.15 mm, which was obtained in the same manner as in Example 1 and was free of crosslinked PVA, was used as a separator.

(Measurement of liquid retention under pressure) Weight (W) of the separators of Examples 1 to 3 and Comparative Example cut into a diameter of 50 mm.
After the measurement of ₀ ), it is immersed in a potassium hydroxide solution having a specific gravity of 1.3 for 1 hour so that the air in the separator is replaced with the potassium hydroxide solution, and the potassium hydroxide solution is held. After that, this separator is sandwiched between three upper and lower filter papers (diameter 50 mm), and 1 ton of force is applied to 30 by a pressure pump.
After acting for 2 seconds, the weight (W ₁ ) of the separator is measured. Then, the liquid retention under pressure is calculated by the following formula. As a result, the pressurized liquid retention rates of Examples 1 to 3 and Comparative Example were 18.8%, 23.0%, 24.1%, and 15.9%, respectively.

[0048]

Since the alkaline battery separator of the present invention contains the crosslinked PVA, it is not easily decomposed by an alkaline electrolyte such as potassium hydroxide and can be used for a long period of time.

In addition to the fact that the crosslinked PVA has an affinity with the electrolytic solution and is excellent in the retention of the electrolytic solution, the hydroentangled nonwoven fabric has the fibers oriented in the thickness direction, so that the electrode Since the separator can maintain a certain thickness against swelling and the like, it is a separator excellent in retaining electrolyte.

Furthermore, since the crosslinked PVA has a hydroxyl group capable of forming a chelate with the ion before the dendritic metal is deposited on the electrode plate during discharging and / or charging, the crosslinked PVA has a dendritic shape. It is difficult for metal to deposit and short circuit due to dendrite does not occur easily.

When ultrafine fibers are contained in the constituent fibers of the hydroentangled nonwoven fabric of the present invention, the electrolyte retaining property is excellent,
A separator with excellent dendrite prevention properties.

As described above, since the separator of the present invention is not easily attacked by the electrolytic solution, has an excellent retaining property for the electrolytic solution, and has an excellent dendrite preventing property, the alkaline primary battery and the alkaline secondary battery using this separator are used. Has a long service life.

[Brief description of drawings]

FIG. 1 (a) is a schematic sectional view of a splittable conjugate fiber of the present invention (b) is a schematic sectional view of another splittable conjugate fiber of the present invention (c) is another splittable conjugate fiber of the present invention (D) A schematic cross-sectional view of another splittable conjugate fiber of the present invention (e) A schematic cross-sectional view of another splittable conjugate fiber of the present invention

[Explanation of symbols]

 1 one component 2 other component

Claims (3)

[Claims] 1. A general formula: (In the formula, R ₁ is a quaternized aromatic nitrogen-containing heterocyclic residue, R ₂ is a hydrogen atom or an alkoxy group, R ₃ is a hydrogen atom or an acyl group, m is 0 or 1, and n is 1 to 1. A separator for an alkaline battery, which is composed of a hydroentangled nonwoven fabric containing a crosslinked state of polyvinyl alcohol having a structural unit represented by a natural number of 6). 2. The separator for an alkaline battery according to claim 1, wherein ultrafine fibers are contained in the constituent fibers of the hydroentangled nonwoven fabric. 3. An alkaline battery comprising the separator according to claim 1 or 2.