JP2001084982A - Metal hydroxide-hydrogen storage battery - Google Patents

Abstract

(57) [Problem] To provide a metal hydroxide-hydrogen storage battery having excellent life characteristics and storage performance after charge / discharge cycles. SOLUTION: In a metal hydroxide-hydrogen storage battery comprising a positive electrode, a negative electrode mainly composed of a hydrogen storage alloy, a hydrophilized separator and an alkaline electrolyte, at least one layer of a polyolefin woven or nonwoven fabric is used. By using a separator having a multilayer structure with at least one polyolefin porous membrane layer having an average pore diameter smaller than that of a polyolefin woven or nonwoven fabric, metal hydroxide having excellent life characteristics and storage performance after charge / discharge cycles is provided. Article-hydrogen storage battery can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal hydroxide-hydrogen storage battery using a hydrogen storage alloy electrode as a negative electrode.

[0002]

2. Description of the Related Art Nickel-hydrogen storage batteries that have been put to practical use by using a hydrogen storage alloy have been widely used as power sources for various cordless devices and electronic devices as batteries having characteristics such as high energy density. In addition, they are also being used as power sources for electric vehicles, electric tools, and the like.

As a negative electrode material for nickel-hydrogen storage batteries, MmNi having a CaCu ₅ type crystal structure is generally used.
₅ (Mm is a mixture of rare earth elements) -based alloy in which a part of Ni is replaced by a metal such as Co, Mn, Al, or Cu is used. Various alloys are weighed so as to match the alloy composition, and a mixture of various metals is melted using a high-frequency melting furnace or the like and poured into a mold to produce an alloy having a desired composition. Recently, in order to further homogenize the alloy structure, an alloy is sometimes produced from a molten alloy obtained by high-frequency melting by a quenching method such as a roll quenching method or an atomizing method. This alloy is further pulverized, if necessary, to several tens.
A powder of about μm, a binder, a conductive agent, a thickener, etc. are added to the powder and kneaded so as to be uniform to form a paste, and an electrode support such as a punched metal, foamed metal porous body, etc. After being coated or pressurized, dried and pressed to form an electrode body. Using this hydrogen storage electrode as a negative electrode,
A metal hydroxide-hydrogen storage battery is configured by combining with a known nickel positive electrode or the like via a separator.

Further, as the separator, a non-woven fabric of polyolefin fibers, which has been rendered hydrophilic by a sulfonation treatment, an acrylic acid graft polymerization treatment, a surfactant treatment, or the like, is widely used.

[0005]

The preferred alloy for the hydrogen storage electrode is manufactured by a high-frequency melting method or the like, but the homogeneity of the alloy structure is important, and it is necessary to manufacture an alloy with even improved homogeneity. is there. However, this alloy has
Metal elements such as Mn, Al, and Co that dissolve in alkaline aqueous solutions are also included, and when they are not completely alloyed, some of these metals dissolve in alkaline solutions that are electrolytes. I do. In particular, when the temperature becomes high, the dissolution rate and the dissolution amount increase.

When used for power applications such as electric vehicles and electric tools, this battery is 50 A or sometimes 100 A.
It is discharged with a large current of A or more. At the time of such a large current discharge, a potential distribution is easily generated in the hydrogen storage electrode, and oxidation and dissolution of the constituent elements in the alloy are likely to occur at an electrode portion having a more noble potential.

[0007] The metal ions dissolved in the electrolytic solution are deposited in a metal state on the negative electrode and in an oxide or hydroxide state on the positive electrode due to the oxidation-reduction reaction and solubility on the positive and negative electrodes. Or Many of these fine precipitates adhere to and grow on the separator, deteriorating the insulation of the separator, and in the worst case, a short circuit occurs in the battery. Especially Mn and Co
The HMnO ₂ in alkaline electrolyte ^- and HCoO ₂ ^- easily move to the positive electrode precipitation to dissolve in the form of anions such as.

In order to solve the above-mentioned problems, the following contents can be raised. Mn, Al, which are alkali-soluble components in a hydrogen storage alloy, are as follows.
Do not contain Co or the like.

[0009] Soluble components are previously removed from the surface of the hydrogen storage alloy.

[0010] The eluted ions are trapped before a short circuit occurs in the battery.

[0011] Regarding Mn-free alloy, Co-free alloy, Al-free alloy, etc., many proposals have been made. However, in practice, there are various problems such as a decrease in hydrogen storage capacity, a decrease in discharge characteristics and a decrease in life characteristics. Not converted.

Regarding the method, a method has been proposed in which an alloy is immersed in an alkaline aqueous solution in a powder state or an electrode state to remove a soluble component from the alloy surface in advance (JP-A-61-285658). However, although this method can suppress the dissolution of the alloy at the beginning of charge and discharge, the alloy constituent elements elute from the exposed new surface because the alloy becomes finer and the new surface is exposed with the charge and discharge cycle of the battery. I do. Therefore, it cannot be a permanent measure.

As for the method, a method has been proposed in which an acid dissociation type complexing agent capable of forming a complex with a transition metal such as EDTA is added to an electrolytic solution (JP-A-4-167372). There is a problem in that the effect is small with the addition of, or the discharge performance decreases due to a change in the pH of the electrolytic solution when added in a large amount.

In a nickel-cadmium storage battery using cadmium for the negative electrode, which is a similar alkaline storage battery,
In order to prevent a short circuit in the battery due to the passage of the dissolved cadmium compound from the negative electrode to the positive electrode, a proposal has been made in which two types of separators having different pore sizes are used and a separator having a pore size of 1 μm or less is arranged on the positive electrode side (Japanese Patent Application Laid-Open No. Sho 51-12645). ) Has been made. However, when this method is applied to a metal hydride-hydrogen storage battery, as described later, the growth of precipitates due to elution of the alloy electrode can be suppressed by a separator having a pore diameter of 1 μm or less, but a polyamide nonwoven fabric is used as a main separator. The self-discharge characteristics of metal hydride-hydrogen storage batteries are reduced due to the adoption, and uneven distribution of the electrolyte solution occurs in the separator due to the combined use of a hydrophilic polyamide nonwoven fabric and a poorly hydrophilic film-like polypropylene. There is a problem that the discharge performance is easily lowered.

An object of the present invention is to provide a metal hydroxide-hydrogen storage battery having a long life and a stable quality by preventing the above-mentioned short-circuit phenomenon from occurring during a charge / discharge cycle. It is assumed that.

[0016]

In order to achieve the above object, the present invention provides a method for preventing the occurrence of a short circuit during a charge / discharge cycle by using the above metal, metal oxide, or hydroxide on a separator. At least one to reduce adhesion growth
A hydrophilized separator having a structure in which three or more polyolefin woven fabrics or nonwoven fabrics and at least one polyolefin porous membrane having an average pore diameter smaller than that of the polyolefin woven fabric or nonwoven fabric are laminated three or more times is used. Preferably, both surfaces of the polyolefin porous membrane had a superposed structure sandwiched between at least one polyolefin woven or nonwoven fabric, and the polyolefin porous membrane in the separator at a position closer to the positive electrode than the negative electrode An object of the present invention is to provide a metal hydroxide-hydrogen storage battery which is disposed, more preferably, subjected to a sulfonation treatment as a hydrophilic treatment of a separator, and which has excellent life characteristics and storage performance after charge / discharge cycles.

Similarly, the multilayer structure of at least one polyolefin woven or non-woven fabric layer and at least one polyolefin porous membrane layer having an average pore diameter smaller than that of the polyolefin woven or non-woven fabric layer is defined. Using a separator subjected to hydrophilization treatment, preferably having a multilayer structure in which both surfaces of a polyolefin porous membrane layer are sandwiched between at least one polyolefin woven or nonwoven fabric layer, and a polyolefin in the separator The porous membrane layer is arranged at a position close to the positive electrode, more preferably,
An object of the present invention is to provide a metal hydroxide-hydrogen storage battery which has been subjected to sulfonation treatment as hydrophilic treatment of a separator and has excellent life characteristics and storage performance after charge / discharge cycles.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention relates to a metal hydroxide comprising a positive electrode, a negative electrode mainly composed of a hydrogen storage alloy, a separator subjected to hydrophilic treatment, and an alkaline electrolyte. In the hydrogen storage battery, the separator includes:
A metal water having a structure in which at least one polyolefin woven fabric or nonwoven fabric and at least one polyolefin porous membrane having an average pore diameter smaller than that of the polyolefin woven fabric or nonwoven fabric are laminated three or more times. An oxide-hydrogen storage battery. By using this separator, without greatly reducing the discharge characteristics,
When the battery voltage drops during discharge in the charge / discharge cycle, the negative electrode dissolves in the electrolyte from the negative electrode in an ionic state, and the deposition of fine precipitates deposited on the positive and negative electrodes on the separator is suppressed. A sealed metal hydroxide-hydrogen storage battery having excellent storage performance after cycling can be manufactured. As a method of forming the superposed structure, the layers may be simply laminated at the time of use, or may be integrated by heat welding or embossing before use. Further, it is more preferable that the porous membrane has a large surface area such that it has fine irregularities on the membrane surface and a vein-like fiber layer inside by stretching uniaxially or biaxially.

In the second aspect of the present invention, the separator having the overlapping structure of the present invention preferably has a structure in which both surfaces of a polyolefin porous membrane are sandwiched between at least one polyolefin woven or nonwoven fabric. This is because the polyolefin woven or nonwoven fabric has a larger pore diameter than the polyolefin porous membrane, so the electrolyte has a high mass mobility,
This is because water and OH 2 ^- ions are not depleted on the electrode surface during a large current discharge, and a large decrease in discharge characteristics is not caused.

According to a third aspect of the present invention, the polyolefin porous membrane portion in the separator having the superposed structure of the present invention is arranged at a position closer to the positive electrode than to the negative electrode. This is effective in suppressing the adhesion growth of a compound of Mn or Co among the constituent elements of the negative electrode alloy, particularly on the separator. It, Mn and Co are HMnO ₂ in alkaline electrolyte ^- and HCoO ₂ ^- tends to move to the positive electrode precipitation to dissolve in the form of anions such, should there inhibit the growth of precipitates at the positive electrode near That's why.

In claim 4, it is preferable that the average pore diameter of the polyolefin porous membrane is 0.1 to 10 μm.
As a result of various studies, it was found that the size of the fine precipitate deposited on the positive and negative electrodes was about 10 to 20 μm. The average pore size of a nonwoven fabric made of polyolefin, which is a currently used nickel-hydrogen storage battery separator, is generally 15 to
It is about 30 μm. With this pore size, it is difficult to completely suppress the growth of fine precipitates. For this reason, the average pore diameter of the polyolefin porous membrane that plays a role in suppressing the growth of fine precipitates is preferably 10 μm or less. In addition, when the average pore diameter is small, the mass mobility of the electrolytic solution is reduced, so that the membrane resistance of the separator is increased, and the large-current discharge characteristics tend to be reduced. Therefore, the lower limit of the average pore diameter of the polyolefin porous membrane varies depending on the required performance for each application to the battery, but is preferably 0.1 μm.
More preferably, it is 1 μm or more.

In the present invention, it is preferable that the polyolefin porous membrane has a thickness of 10 to 50 μm. As the thickness of the polyolefin porous membrane is increased, the storage characteristics are improved, but the discharge characteristics are reduced. Generally, the thickness of a polyolefin nonwoven fabric, which is a currently used separator for a nickel-hydrogen storage battery, is about 100 to 200 μm. Since the size of the precipitate is about 10 μm,
In order to improve the storage performance without lowering the discharge performance as much as possible, the thickness of the polyolefin porous film should be 10 to 5 times.
It is required to be 0 μm, more preferably 10 to 30 μm.

In claim 6, a sulfonation treatment is preferable as a method for hydrophilizing a separator having an overlapping structure. Although the detailed reason is not clear, the separator employing the sulfonation treatment as the hydrophilic treatment method has a fine precipitate compared to the separator employing another hydrophilic treatment method such as acrylic acid graft polymerization treatment or corona discharge treatment. The effect of suppressing the growth was remarkable.

According to a seventh aspect of the present invention, there is provided a metal hydroxide-hydrogen storage battery comprising a positive electrode, a negative electrode mainly composed of a hydrogen storage alloy, a hydrophilized separator, and an alkaline electrolyte. The separator has a multilayer structure of at least one polyolefin woven or nonwoven fabric layer and at least one polyolefin porous membrane layer having an average pore size smaller than that of the polyolefin woven or nonwoven fabric layer. And a metal hydroxide-hydrogen storage battery. By using this separator, as in claim 1, without greatly reducing the discharge characteristics,
When the battery voltage drops during discharge in the charge / discharge cycle, the negative electrode dissolves in the electrolyte from the negative electrode in an ionic state, and the deposition of fine precipitates deposited on the positive and negative electrodes on the separator is suppressed. A sealed metal hydroxide-hydrogen storage battery having excellent storage performance after cycling can be manufactured. As a method for forming a multilayer structure, there is a method in which a porous film is prepared in advance, and a woven or non-woven fabric layer is formed on the surface of the porous film as a base material. Advantages when compared with the superimposed structure of claim 1 are that there is no shift in the separator at the time of battery production and the non-defective product rate is high, and this occurs in the case of the superimposed structure.
Since there is no so-called electrolyte solution pool between the separators, the electrolyte solution in the battery can be used effectively, and the discharge characteristics can be further improved.

In the eighth aspect, the separator having a multilayer structure of the present invention preferably has a structure in which both surfaces of a polyolefin porous membrane layer are sandwiched between at least one polyolefin woven or nonwoven fabric layer. This is because, similarly to claim 2, the polyolefin woven or non-woven fabric layer has a larger pore diameter than the polyolefin porous membrane layer, so that the electrolyte has a high mass mobility, and water and OH on the electrode surface during large current discharge. ^- there is no depletion of ions occurs, because the do not slow down the large discharge characteristics.

In the ninth aspect, the polyolefin porous membrane layer in the separator having a multilayer structure of the present invention is arranged at a position closer to the positive electrode than to the negative electrode. This is the same as in claim 3, particularly among the constituent elements of the negative electrode alloy, particularly Mn and Co.
Is effective in suppressing the adhesion growth of the compound in the separator. Mn and Co are H in alkaline electrolyte.
MnO ₂ ^- or HCoO ₂ ^- tends to move to the positive electrode precipitation to dissolve in the form of anions such, because the need to suppress the growth of precipitates at the positive electrode vicinity there.

In the tenth aspect, for the same reason as in the fourth aspect, the average pore diameter of the polyolefin porous membrane layer is set to 0.1.
The thickness is preferably 1 to 10 μm. The size of the fine precipitate deposited on the positive and negative electrodes is about 10 to 20 μm, and it is difficult to completely suppress the growth of the fine precipitate in a polyolefin nonwoven fabric layer having an average pore diameter of about 15 to 30 μm. For this reason, the average pore diameter of the polyolefin porous membrane layer that plays a role in suppressing the growth of fine precipitates is 10 μm.
m or less is preferable. In addition, when the average pore diameter is small, the mass mobility of the electrolytic solution is reduced, so that the membrane resistance of the separator is increased, and the large-current discharge characteristics tend to be reduced. Therefore, the lower limit of the average pore diameter of the polyolefin porous membrane layer,
It varies depending on the required performance of the battery for each application,
It is preferably 0.1 μm, more preferably 1 μm.
m or more.

In the eleventh aspect, for the same reason as in the fifth aspect, the thickness of the polyolefin porous membrane layer is set to 10 to 10.
It is preferably 50 μm. As the thickness of the polyolefin porous membrane layer is increased, the storage characteristics are improved, but the discharge characteristics are reduced. Since the size of the precipitate is about 10 μm, the thickness of the polyolefin porous membrane layer is 10 to 50 μm, more preferably 10 to 30 μm, in order to improve the storage performance without lowering the discharge performance as much as possible.
It is required to be μm.

In the twelfth aspect, for the same reason as in the sixth aspect, a sulfonation treatment is preferable as a method for hydrophilizing a separator having a multilayer structure.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

(Example 1) In this example, a nickel-hydrogen storage battery using a sulfonated separator in which a polyethylene porous film is laminated on a polyolefin nonwoven fabric will be described as an example.

The separator was manufactured according to the following procedure.

First, PP / PE having a nominal fiber diameter of 4.7 μm
PP having a splittable conjugate fiber of 80 parts by weight and a nominal fiber diameter of 9 μm
/ PE core-sheath fiber was mixed with 20 parts by weight, and a nonwoven fabric made of polyolefin having an average pore diameter of 15 μm was prepared by a wet-type hydroentanglement method. This nonwoven fabric was subjected to a sulfonation treatment to impart hydrophilicity. First, it was immersed in Emulgen 709 manufactured by Kao Corporation, which is a nonionic surfactant, to impart wettability. Then, 10% in fuming sulfuric acid of 25% concentration at 60 ° C.
After immersion for a minute, the fuming sulfuric acid was removed, and alkali washing was performed with KOH, and excess alkali was washed off with water.

Next, a polyethylene porous membrane was prepared by a biaxial stretching method. When the pore size distribution of this film was measured, the average pore size was 1 μm. This film was also subjected to a sulfonation treatment in the same manner as the above nonwoven fabric.

These sulfonated polyolefin nonwoven fabrics and polyethylene porous membranes are prepared by changing the basis weight and thickness in various ways, and after superposing a plurality of them, a part thereof is prevented in order to prevent misalignment during group formation. Heat welded, combined weight 72g / m ² , thickness 0.18mm, width 51m
m, a separator having a superposed structure having a length of 1320 mm was produced.

The negative electrode of the hydrogen storage alloy was produced by the following procedure. The composition was MmNi _3.55 Mn _0.4 Al _0.3 Co _0.75 (M
m is a mixture of rare earth elements), and the hydrogen storage alloy was mechanically pulverized in water by a wet ball mill so as to have an average particle diameter of 30 μm. This powder was alkali-treated under the following conditions. The powder was immersed and stirred in a potassium hydroxide aqueous solution having a specific gravity of 1.30 and heated to 80 ° C. for the same weight for 60 minutes,
Water washing was performed until the pH of the washing water became 10 or less, followed by dehydration under pressure. Thereafter, an acid treatment was performed under the following conditions. The powder was immersed and stirred in an acetic acid aqueous solution having a pH of 3.0 at 60 ° C. for 30 minutes at the same weight as the powder, and washed with water until the pH of the washing water became 6 or more.
A hydrogen storage alloy powder slurry was obtained. 0.15 parts by weight of carboxymethyl cellulose as a thickener, 0.3 parts by weight of carbon black as a conductive agent, and a styrene-butadiene copolymer as a binder, based on 100 parts by weight of the alloy of the alloy powder slurry Was mixed with water as a dispersion medium to prepare an alloy paste. This paste was applied to a core material made of punching metal, dried and pressed to produce a hydrogen storage alloy electrode having a width of 49 mm, a length of 665 mm, a thickness of 0.27 mm, and a capacity of 11,000 mAh. As the positive electrode, a known sintered nickel positive electrode (width 49 mm, length 590 mm, thickness 0.53 mm,
A capacity of 6800 mAh) was used. The positive and negative electrodes were spirally wound through a separator. At this time, a spiral electrode group was formed so that the tips of the positive electrode plate and the negative electrode plate respectively protruded up and down, so that the electrodes were not short-circuited during the current collector welding. Next, after setting a disk-shaped current collector above and below the electrode group, the electrode group and the current collector were spot-welded and inserted into a D-size metal case, and then potassium hydroxide having a specific gravity of 1.20. 4 in aqueous solution
12 cc of an electrolyte solution in which 0 g / l of lithium hydroxide and 100 g / l of sodium hydroxide were dissolved was injected. Thereafter, the case was sealed to form a sealed battery as shown in FIG. The number of welding points between the electrode plate and the current collector was 50 for the positive electrode.
The point and the negative electrode were 70 points, and the distance between the collecting points was narrower in the negative electrode than in the positive electrode. This is because an attempt was made to minimize the polarization of the negative electrode because the negative electrode often caused the voltage drop during discharge. Regarding the number of current collecting points, the discharge performance was improved as the number of points increased up to 65 on the positive electrode side in the electrode length of the present invention.

Table 1 shows the batteries produced and the separators used. In addition, the separator was the first sheet from the negative electrode surface side. FIG. 2 shows a cross-sectional view of the arrangement of the electrodes and the separator of the battery B which is an example of the embodiment of the present invention.

[0038]

【table 1】

Using seven types of batteries A to G obtained by the above method, high-rate discharge characteristics and life characteristics were evaluated. The high-rate discharge characteristics are as follows.
The battery was charged for 2 hours, discharged after 1 hour rest at 100 A to 0.8 V, and evaluated by the ratio of the discharge capacity to the theoretical capacity. The life characteristics were as follows: in a 20 ° C. atmosphere, a cycle of charging 105% of the theoretical capacity at 6.5 A and discharging to 1.0 V at 30 A after a pause of 1 hour was repeated, and the discharge capacity was 60% in the first cycle. The number of cycles at that time was defined as the number of chargeable / dischargeable cycles of the battery. In each test, five batteries were subjected to the test.

Table 2 shows the average value of the discharge characteristics and the maximum value and the minimum value of the life characteristics of each battery, that is, the fluctuation range of the number of chargeable / dischargeable cycles.

[0041]

[Table 2]

From the life test results shown in Table 2, the batteries A to E and G can be charged / discharged for at least 1000 cycles or more under the above test conditions, and the variation width of the number of cycles of the five batteries is small. There was no problem in actual use. However, while the discharge capacity in the first cycle of the batteries A to E was 97% or more of the theoretical capacity of the positive electrode, the capacity decrease of the battery G due to the cycle was small.
It was as low as 85% of the theoretical capacity of the positive electrode. This was presumed to be because the pore diameter of the porous membrane used this time was 1 μm, which was as small as 1/15 of the pore diameter of the nonwoven fabric, so that the mobility of the electrolyte during discharge was small and the discharge polarization was increased. On the other hand, battery F
The number of chargeable / dischargeable cycles of each battery fluctuated greatly. 1
Although two batteries reached 000 cycles, the remaining three batteries decreased in capacity after 200 cycles,
One battery has 400 cycles and the remaining two batteries have 60
The discharge capacity was reduced to 60% of the initial capacity between 0 cycle and 700 cycles.

The difference in the life characteristics is that a part of the metal contained in the hydrogen storage alloy negative electrode is dissolved, and the dissolved metal ions precipitate again on the surface and inside of the positive / negative electrode and the separator. The separator lost its insulation function due to the material, and the capacity was reduced due to the occurrence of a short circuit phenomenon.
It is also considered that the number of chargeable / dischargeable cycles of each battery fluctuated depending on the speed at which the short circuit occurred. As the charge and discharge were repeated, the metal gradually dissolved, and the number of chargeable and dischargeable cycles fluctuated due to the difference in the growth rate of the reprecipitated metal or metal hydroxide on the separator. When the battery H whose capacity was actually reduced was disassembled and investigated, black precipitates having a particle size of about 10 μm were attached to the surface and inside of the separator, and Mn and Co were detected when the elemental analysis was performed. Was.

On the other hand, batteries A to B, which are the batteries of the present invention,
When E was similarly disassembled and investigated, a black precipitate was attached to the surface and the inside of the nonwoven fabric separator, but almost no black precipitate was observed at the portion of the porous membrane separator. Further, in the case of a separator having a configuration in which the porous film is sandwiched by a nonwoven fabric, more precipitates were observed in the nonwoven fabric closer to the positive electrode than in the nonwoven fabric on the negative electrode side. Also,
In Comparative Example, even in the battery G using only the porous membrane as the separator, almost no black precipitate was observed in the portion of the porous membrane separator, and instead, a similar black precipitate could be confirmed on the positive electrode surface. Was.

From the above, regarding the life characteristics of the battery,
It can be guessed as follows.

Precipitates that are the main cause of the reduction in life are Mn and Co, and the precipitates are deposited and grown from the positive electrode side.

The size of the precipitate is about 10 μm in particle size, and it grows in a nonwoven fabric having an average pore diameter of 15 μm, but hardly grows in a porous film having an average pore diameter of 1 μm.

The precipitate grown in the separator lowers the insulating function of the separator and causes a short circuit phenomenon.

From the above, in order to prolong the life of the battery, it is preferable to use a separator having a small pore size such as a porous membrane as the separator. However, when only a porous film having a pore size of 1 μm is used as a separator as in the battery G, a significant adverse effect is caused on the discharge performance. Therefore, in order to improve the life characteristics without lowering the discharge performance of the battery, it is preferable to use a combination of a separator having a large pore size and a separator having a small pore size as in batteries A to E as the separator. As long as the pore size can be controlled, a porous membrane may be used as the large pore size separator, or a nonwoven fabric may be used as the small pore size separator.However, considering the manufacturing process, in the present invention, the nonwoven fabric is used as the large pore size separator, and the small pore size is used. A porous membrane was used as a separator. That is, the nonwoven fabric is easily made with a large pore size because it is made by making paper, and the porous membrane is easily made with a small pore size because it is made by stretching a small porous material.

When a battery using a separator having a porous film on one side is compared with a battery using a separator in which a middle porous film is sandwiched between nonwoven fabrics on both sides, such as batteries A to E, the life performances are almost the same. However, the discharge performance of the batteries A to E was better. This is because the polyolefin woven or nonwoven fabric has a larger pore diameter than the polyolefin porous membrane layer, so the electrolyte has a high mass mobility,
This is presumably because water and OH ^- ions are not depleted on the electrode surface during the large current discharge, and the large discharge characteristics do not deteriorate. For this reason, in a case where the discharge performance is more important, the separator preferably has a structure in which both surfaces of the polyolefin porous membrane are sandwiched between at least one polyolefin woven or nonwoven fabric.

In a battery in which reliability is more important, it is important to suppress the growth of fine precipitates deposited on the electrode plate in the vicinity of the electrode plate. As described above, most of the precipitate grows from the positive electrode side. Therefore, batteries A ~
Comparing the batteries using the three-layer stacked structure separator of C, the porous membrane is located at a position closer to the positive electrode,
The characteristics were good in the order of B, A, and C. From this,
It is preferable that the porous film is arranged at a position closer to the positive electrode than to the negative electrode.

(Example 2) A difference in battery characteristics due to a difference in pore diameter of a porous membrane was evaluated. By changing the stretching conditions at the time of producing the porous membrane, the average pore diameter of the porous membrane was set to 0.05 μm and 0.1 μm.
A battery using a three-layer laminated separator similar to Battery A, except that the thickness was changed to 1 μm, 1 μm (Battery A), 10 μm, and 15 μm. This was subjected to the same battery test as in (Example 1). The results are shown in (Table 3).

[0053]

[Table 3]

From the results shown in Table 3, when the average pore diameter of the porous film was 0.1 to 10 μm, both characteristics of the discharge performance and the life performance were improved in a well-balanced manner. However, in the case of a battery using a porous membrane having an average pore diameter of
The battery characteristics were almost the same as those of the battery F, which is a separator made of only the nonwoven fabric, and no improvement in the life characteristics was observed. This is a reasonable result because the size of the precipitate is about 10 μm. Conversely, the average pore size of the porous membrane is 0.05 μm
Thus, even when a nonwoven fabric was used in combination, the discharge characteristics did not decrease to the level of Battery G using only the porous film as a separator, but greatly decreased. For this reason, the average pore size of the porous membrane needs to be smaller than the average pore size of the nonwoven fabric, and is preferably in the range of 0.1 to 10 μm in consideration of discharge characteristics.

Similarly, when the film thickness of the porous film layer was examined, it was found that the thickness was preferably set to 10 to 50 μm. As the thickness of the polyolefin porous membrane layer was increased, the storage characteristics were improved, but the discharge characteristics were lowered. Since the size of the precipitate is about 10 μm, a minimum film thickness of 10 μm is necessary so that a short circuit phenomenon does not occur even if the precipitate is deposited on the porous film. Conversely, the upper limit of the film thickness had to be set to 50 μm in order not to lower the discharge performance as much as possible.

With respect to the surface treatment for imparting hydrophilicity to the separator, an acrylic acid graft polymerization treatment, an immersion treatment in an aqueous solution of ethylene vinyl alcohol, and a corona discharge treatment were examined in addition to the above-mentioned sulfonation treatment. The life characteristics were the best when subjected to the sulfonation treatment. When the battery after the life test was disassembled and examined, the distribution of the black precipitate on the nonwoven fabric was different due to the difference in surface treatment, although the reason was not clear. In the case where the sulfonation treatment was performed, the black precipitate was uniformly distributed in the nonwoven fabric, whereas in the case where the other surface treatment was performed, the black precipitate was concentrated and grown on a part of the nonwoven fabric. In order to suppress the growth of the black precipitate and prevent the short circuit phenomenon, it is preferable to disperse the precipitation of the black precipitate. Therefore, a sulfonation treatment is preferable as the surface treatment of the separator.

(Embodiment 3) In this embodiment, a nickel-hydrogen battery using a separator obtained by laminating a polyolefin nonwoven fabric layer on a polyethylene porous membrane layer and performing sulfonation will be described as an example.

The separator was manufactured according to the following procedure.

First, a polyethylene porous membrane was prepared by a biaxial stretching method in the same manner as in (Example 1). When the pore size distribution of this film was measured, the average pore size was 1 μm.

Next, the above polyethylene porous membrane was used as a base material, and one side or both sides thereof were coated with a P of nominal fiber diameter of 4.7 μm.
80 parts by weight of P / PE splittable conjugate fiber and nominal fiber diameter of 9 μm
And 20 parts by weight of PP / PE core-sheath fiber, and a nonwoven fabric layer made of polyolefin having an average pore diameter of 15 μm is formed by a wet entanglement method, and a layer having a basis weight of 72 g / m ² and a thickness of 0.18 mm A separator having a structure was produced.
Then, the separator was subjected to a sulfonation treatment to impart hydrophilicity in the same manner as in (Example 1).

Using this separator, a battery similar to that of (Example 1) was produced and subjected to a battery test.

Table 4 shows the batteries produced and the separators used. The separator was the first layer from the negative electrode surface side.

[0063]

[Table 4]

Table 5 shows the average value of the discharge characteristics and the maximum value and the minimum value of the life characteristics of each battery, that is, the fluctuation range of the number of chargeable / dischargeable cycles.

[0065]

[Table 5]

The above-mentioned batteries HL are also the batteries A- (of the first embodiment).
The life characteristics were good as in E. Also, batteries J,
For K and L, the high-rate discharge performance was improved as compared with the batteries A, B, and C using the same configuration as the respective batteries and using the stacked separator. This is because the nonwoven fabric and the film have a layered structure, so that the electrolyte does not remain in the separator and the electrolyte distribution in the separator is more uniform than in the case of the superposed structure of the nonwoven and the film in Example 1. Because it became.

In the present embodiment, the alloy was melted by a high frequency melting method and cast into a water-cooled mold. Use of the alloy produced by the method further improved the life characteristics. The surface treatment of the hydrogen storage alloy was performed with an aqueous alkali solution and then with an acidic aqueous solution. The alkaline aqueous solution may be made of sodium or lithium other than potassium, and the acidic aqueous solution may be acetic acid / acetic acid. Similar effects can be obtained by treatment with an acidic buffer such as sodium. As the positive electrode material, in addition to nickel hydroxide, part of nickel of nickel hydroxide may be Co, Zn, Cd, M
The same effect can be obtained with other materials such as those substituted and dissolved with n, Al, Mg, and the like.
Needless to say, the same effect can be obtained even with a paste-type positive electrode in which a foamed metal is filled with nickel hydroxide powder in which various metal elements are dissolved.

[0068]

According to the present invention, at least one sheet of a metal hydroxide-hydrogen storage battery comprising a positive electrode, a negative electrode mainly composed of a hydrogen storage alloy, a hydrophilized separator, and an alkaline electrolyte is provided. A separator having a laminated structure of three or more polyolefin woven or nonwoven fabrics and at least one polyolefin porous membrane having an average pore size smaller than that of the polyolefin woven or nonwoven fabric, or a one-layer polyolefin woven fabric or By using a separator having a multilayer structure of a nonwoven fabric and a polyolefin woven fabric layer or at least one polyolefin porous membrane layer having an average pore diameter smaller than that of the nonwoven fabric layer, the life characteristics, storage performance after charge / discharge cycles, and storage characteristics And a metal hydroxide-hydrogen storage battery having excellent heat resistance.

[Brief description of the drawings]

FIG. 1 is a sectional structural view showing a configuration of a metal hydroxide-hydrogen storage battery according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an arrangement of electrodes and separators of a battery B which is an example of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Separator 4 Positive electrode current collector plate 5 Negative electrode current collector plate 3a Negative side first layer separator (nonwoven fabric) of battery D 3b Negative side second layer separator of battery D (porous membrane) 3c Negative electrode of battery B Side third layer separator (nonwoven fabric)

(72) Inventor Fumihiko Yoshii 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 4F074 CB91 CD14 CD17 DA03 DA20 DA49 4L035 CC20 DD07 DD14 FF01 FF05 MA01 MA10 5H021 CC00 CC02 CC04 EE04 EE18 HH03 5H028 AA05 BB10 EE01 EE05 EE06 HH05

Claims (12)

[Claims] 1. A metal hydroxide-hydrogen storage battery comprising a positive electrode, a negative electrode mainly composed of a hydrogen storage alloy, a hydrophilized separator and an alkaline electrolyte, wherein the separator is made of at least one sheet of polyolefin. A metal hydroxide-hydrogen storage battery having a structure in which three or more woven or nonwoven fabrics and at least one polyolefin porous membrane having an average pore diameter smaller than that of the polyolefin woven or nonwoven fabric are stacked. . 2. The metal hydroxide-hydrogen storage battery according to claim 1, wherein a separator having an overlapping structure in which both surfaces of the polyolefin porous membrane are sandwiched between at least one woven or nonwoven fabric of polyolefin is used. 3. The polyolefin porous membrane in the separator is located closer to the positive electrode than the negative electrode.
A metal hydroxide-hydrogen storage battery as described in the above. 4. The metal hydroxide-hydrogen storage battery according to claim 1, wherein a separator having a superposed structure in which the polyolefin porous membrane layer has an average pore size of 0.1 to 10 is used. 5. A polyolefin porous membrane having a thickness of 10 to 10.
The metal hydroxide-hydrogen storage battery according to any one of claims 1 to 3, wherein a separator having an overlapping structure of 50 µm is used. 6. The metal hydroxide-hydrogen storage battery according to claim 1, wherein the method for hydrophilizing the separator is a sulfonation treatment. 7. A metal hydroxide-hydrogen storage battery comprising a positive electrode, a negative electrode mainly composed of a hydrogen storage alloy, a hydrophilized separator and an alkaline electrolyte, wherein the separator comprises at least one layer of polyolefin. A metal hydroxide-hydrogen storage battery having a multilayer structure of a woven or nonwoven fabric layer and at least one polyolefin porous membrane layer having an average pore size smaller than that of the polyolefin woven or nonwoven fabric layer. 8. The metal hydroxide-hydrogen storage battery according to claim 7, wherein a separator having a multilayer structure in which both surfaces of the polyolefin porous membrane layer are sandwiched between at least one polyolefin woven or nonwoven fabric layer is used. 9. The metal hydroxide-hydrogen storage battery according to claim 7, wherein the polyolefin porous membrane layer in the separator is located closer to the positive electrode than to the negative electrode. 10. The metal hydroxide according to any one of claims 7 to 9, wherein a separator having a multilayer structure in which the polyolefin porous membrane layer has an average pore size of 0.1 to 10 µm is used.
Hydrogen storage battery. 11. The polyolefin porous membrane layer having a thickness of 1
The metal hydroxide-hydrogen storage battery according to any one of claims 7 to 9, wherein a separator having a multilayer structure of 0 to 50 µm is used. 12. The metal hydroxide-hydrogen storage battery according to claim 7, wherein the hydrophilizing treatment of the separator is a sulfonation treatment.