JP4240030B2 - Alkaline zinc storage battery - Google Patents

Description

  The present invention relates to an alkaline zinc storage battery using zinc as a negative electrode and an alkaline aqueous solution as an electrolyte, such as a nickel-zinc storage battery, a silver oxide-zinc storage battery, a manganese-zinc storage battery, an air-zinc battery, etc. It is about improvement.

  Alkaline zinc storage battery uses zinc for the negative electrode, so it has high energy density, does not contain harmful substances such as cadmium and mercury, and has good characteristics such as being inexpensive, and is therefore practically used. Is strongly expected. However, due to the high solubility of zinc in an alkaline aqueous solution that is an electrolytic solution, there are problems such as negative electrode shape change and generation of dendrite in the negative electrode, which in turn has a short lifespan, and thus is widely put into practical use. The current situation has not yet been reached.

  By the way, in the conventional alkaline zinc storage battery, the separator which consists of cellophane and polyvinyl alcohol was used. And it was possible to prevent the short circuit by the dendrite of zinc during the period until a separator deteriorates with alkaline aqueous solution. In recent years, it has been proposed to use a separator obtained by subjecting a microporous membrane such as polyethylene or polypropylene to a surfactant treatment, and it is used as a separator that is hardly deteriorated by an alkaline aqueous solution.

On the other hand, the following is known as a technique for enhancing the effect of suppressing the generation of dendrite by the separator.
(a) In Patent Document 1, a metal having a low hydrogen overvoltage is applied or deposited on a microporous membrane separator.
(b) In Patent Document 2 and Patent Document 3, a selectively permeable membrane such as an ion exchange resin that is nickel-plated or nickel-attached is disposed between the microporous membrane separators.
(c) In Patent Document 4, a specific metal is uniformly dispersed in a microporous membrane separator.
(d) In Patent Document 5, a layer made of a metal having a low hydrogen overvoltage and a cellophane layer are provided on the negative electrode side of the microporous membrane separator.
Further, there is a prior document such as Patent Document 6.
JP-A-56-138864 JP 58-165243 A JP 58-165244 A JP-A-57-197758 JP-A-5-343096 JP 55-46243 A

  However, the separators (a) to (c) are intended to oxidize and dissolve dendrite on a metal having a low hydrogen overvoltage. However, in the separator, hydrogen is generated when the dendrite comes into contact with the metal. There was a problem that self-discharge was accelerated.

  In the separator (d), the cellophane layer can suppress the contact between the dendrite and the metal having a low hydrogen overvoltage. However, since the cellophane is easily decomposed in the alkaline aqueous solution, the sustainability of the suppression effect is lacking. There was a problem.

In order to solve the above problem, among the alkaline zinc storage batteries of the present invention, the invention according to claim 1 includes a separator having at least a first film facing the positive electrode and a second film facing the negative electrode, The first film is an alkali-resistant microporous film, the second film is a polyvinyl alcohol film, the first film is composed of nickel, iron, cobalt, platinum, palladium, indium, chromium, manganese, titanium, and the main components thereof. A metal arbitrarily selected from the alloys described above is included, and the first film has the metal on the surface facing the negative electrode in a layered state .

  In the invention according to claim 2, in addition to the structure of claim 1, the second film has a crosslinked structure.

  According to a third aspect of the invention, in addition to the configuration of the first aspect, the alkali-resistant microporous membrane is a polyethylene microporous membrane or a polypropylene microporous membrane.

In addition to the structure of Claim 1, the invention described in Claim 4 has a nonwoven fabric interposed between at least one of the first film and the positive electrode or the second film and the negative electrode.

According to a fifth aspect of the invention, in addition to the configuration of the first aspect, the second film is formed by applying a polyvinyl alcohol resin to one surface of the first film.

As described above, the alkaline zinc storage battery of the present invention has the following effects.
According to the first aspect of the invention, since the first film of the separators has a predetermined metal such as nickel, can oxide dissolved the precipitated zinc on the metal can be suppressed dendrite generation. In particular, according to the present invention, the metal layer formed on the first film of the separator can reliably oxidize and dissolve the precipitated zinc and suppress the formation of dendrites. Further, since it has a second film separators are made of polyvinyl alcohol film, dendrites and can be easily dissolved by miniaturization, it is possible to suppress dendrite growth, further dendrites from contacting directly to the metal of the first layer Therefore, self-discharge can be prevented. Therefore, the synergistic action of the first film and the second film can sufficiently prevent the occurrence of a short circuit due to dendrite and can extend the life.

According to the invention of claim 2 or 3, it can improve alkali resistance of separators, thus, can sufficiently prevent the occurrence of short circuit due to deterioration of the separators.

According to the invention described in claim 4 , the electrode surface can be uniformly and sufficiently wetted with the electrolytic solution, and therefore the active material utilization rate can be improved, and the current distribution during charging and discharging can be made uniform. Shape change can be suppressed.

According to the fifth aspect of the invention, the manufacturing process can be simplified for separators.

FIG. 1 is a partial sectional view showing a power generation element of a prototype alkaline zinc storage battery belonging to one embodiment of the present invention. This power generation element is configured by the following arrangement: positive electrode 2 / nonwoven fabric 4 / separator 3 / nonwoven fabric 4 / negative electrode 1. This power generation element is actually arranged as shown in FIG. 2 to constitute a battery. In addition, FIG. 2 uses the separator 3 of Example 1 shown below.

The prototype battery has the following configuration.
The negative electrode 1 was formed by applying a mixture of 80 parts by weight of zinc oxide powder, 20 parts by weight of zinc powder and 3 parts by weight of polytetrafluoroethylene particles on both sides of a current collector made of copper punching metal having a thickness of 0.1 mm. Configured. The porosity is about 50% and the electrode plate dimensions are 3 cm × 3 cm.

  The positive electrode 2 is a sintered nickel electrode mainly composed of nickel hydroxide and has an electrode plate size of 3 cm × 3 cm.

As the electrolytic solution, an 8 mol / l potassium hydroxide aqueous solution was used and injected to 80 to 90% of the total voids. Also, the capacity density of the positive 2 and 30 mAh / cm ^2, the capacitance density of the negative electrode 1 was 120 mAh / cm ^2.

And as the separator 3, the thing of Example 1 shown below was used. In addition, for reference and comparison, the separators 3 of Reference Examples 1 to 5 and Comparative Examples 1 to 10 shown below were used, and an alkaline zinc storage battery having the same configuration as that in the case of using the separator 3 of Examples was made as a prototype. . The separator 3 of Example 1 , Reference Examples 1 to 5 and Comparative Examples 6 to 10 has a two-film structure including a first film 31 and a second film 32 as shown in FIG. 1 and Comparative Examples 6 and 7, as shown in FIG. 4, the first film 31 itself has a two-layer structure.

Reference examples, examples and comparative examples are shown below. In addition, as the 1st film | membrane 31 of Reference Examples 1-4, an alkali-resistant microporous film, such as a polyethylene microporous film and a polypropylene microporous film, is used instead of a polyvinyl alcohol film.

[Reference Example 1]
The first film 31 is a polyvinyl alcohol film (PVA film) containing nickel powder in a dispersed state and having a crosslinked structure. However, the crosslinking was performed by electron beam irradiation. The second film 32 is a simple polyvinyl alcohol film.

The first film 31 was formed as follows. That is, 10 parts by weight of a polyvinyl alcohol powder reagent having a polymerization degree of 1500 to 1800 (manufactured by Wako Pure Chemical Industries, Ltd.) is dissolved in 50 parts by weight of purified water, and a scale having an average particle diameter of 15 μm and an average thickness of 1 μm. 10 parts by weight of powdered nickel powder was uniformly dispersed and cross-linked by irradiation with an electron beam, so that the film resistance was 230 mΩ · cm ² .

  The second film 32 was formed as follows. That is, polyvinyl alcohol powder reagent (manufactured by Wako Pure Chemical Industries, Ltd.) having a polymerization degree of 1500 to 1800 is uniformly dispersed to form a film having a thickness of 15 μm, and is dissolved in alkali by heat treatment at a temperature of 180 ° C. for 10 minutes. It was hard to do.

[Reference Example 2]
The first film 31 is a polyvinyl alcohol film containing nickel powder in a dispersed state and having a crosslinked structure. However, crosslinking was performed by boric acid treatment. The second film 32 is the same polyvinyl alcohol film as the second film 32 of Reference Example 1.

The first film 31 was formed as follows. That is, 10 parts by weight of polyvinyl alcohol powder was dissolved in 50 parts by weight of purified water, and 10 parts by weight of flaky nickel powder having an average particle diameter of 15 μm and an average thickness of 1 μm was uniformly dispersed therein, and saturated boron was added thereto. 1 part by weight of an acid aqueous solution was added for crosslinking to form a membrane resistance of 230 mΩ · cm ² .

[Reference Example 3]
The first film 31 is a polyvinyl alcohol film containing nickel powder in a dispersed state. The second film 32 is the same polyvinyl alcohol film as the second film 32 of Reference Example 1.

The first film 31 was formed as follows. That is, 10 parts by weight of polyvinyl alcohol powder was dissolved in 50 parts by weight of purified water, and 10 parts by weight of scaly nickel powder having an average particle diameter of 15 μm and an average thickness of 1 μm was uniformly dispersed therein, and the thickness of 40 μm was The film was heat treated at 180 ° C. for 10 minutes to make it difficult to dissolve in alkali, and the film resistance was set to 165 mΩ · cm ² .

[Reference Example 4]
The first film 31 and the second film 32 of Reference Example 3 are integrated.
This was formed as follows. That is, 10 parts by weight of polyvinyl alcohol powder was dissolved in 50 parts by weight of purified water, and 10 parts by weight of scaly nickel powder having an average particle diameter of 15 μm and an average thickness of 1 μm was uniformly dispersed therein, and the thickness of 40 μm was A film (first film 32) is formed, and a polyvinyl alcohol resin is applied to one surface of this film to form a 15 μm polyvinyl alcohol film (second film 32), and heat-treated at a temperature of 180 ° C. for 10 minutes. While making it hard to melt | dissolve with respect to an alkali, the film resistance was 180 mΩ · cm ² .

[Reference Example 5]
The first film 31 is a polyethylene microporous film (PE microporous film) containing nickel powder in a dispersed state. The second film 32 is the same polyvinyl alcohol film as the second film 32 of Reference Example 1.

The first film 31 was formed as follows. That is, 100 parts by weight of polyethylene powder and 10 parts by weight of carbonyl nickel powder (INCO # 255) were kneaded and roll-formed to form a film having a thickness of 50 μm, a porosity of 42%, and a membrane resistance of 200 mΩ · cm ² .

[Example 1]
The first film 31 is a polypropylene microporous film (PP microporous film) having a nickel coating layer 31a (FIGS. 2 and 4) on the second film 32 side. The second film 32 is the same polyvinyl alcohol film as the second film 32 of Reference Example 1.

  The first film 31 was formed as follows. That is, nickel particles were adhered to the surface of the 25 μm-thick polypropylene microporous film (Hoechst Celanese, Celgard # 3401) on the second film 32 side to form a nickel coating layer.

[Comparative Example 1]
It is made up of only one 25 μm thick polypropylene microporous membrane (Hoechst Celanese, Celgard # 3401).

[Comparative Example 2]
It is made of only one cellophane film having a thickness of 25 μm.

[Comparative Example 3]
It is made of only one polyvinyl alcohol film that is the same as the second film 32 of Reference Example 1.

[Comparative Example 4]
It is made of only the same polyvinyl alcohol film as the first film 31 of Reference Example 3.

[Comparative Example 5]
It is made only in the same polypropylene microporous membrane one first layer 31 of Example 1.

[Comparative Example 6]
The first film 31 is the same as the first film 31 of Example 1. The second film 32 is the same polypropylene microporous film as in Comparative Example 1.

[Comparative Example 7]
The first film 31 is the same as the first film 31 of Example 1. The second film 32 is the same cellophane film as in Comparative Example 2.

[Comparative Example 8]
Both the first film 31 and the second film 32 are the same polypropylene microporous film as in Comparative Example 1.

[Comparative Example 9]
The first film 31 is the same polypropylene microporous film as in Comparative Example 1. The second film 32 is the same cellophane film as in Comparative Example 2.

[Comparative Example 10]
The first film 31 is the same polypropylene microporous film as in Comparative Example 1. The second film 32 is the same polyvinyl alcohol film as in Comparative Example 3.

Above Reference Example 1-5, briefly showing the configuration of the first embodiment 及 beauty Comparative Examples 1 to 10, so the Table 1.

The A alkali zinc battery having a separator 3 of Example 1 and Reference Examples 1-5, the following operational effects are obtained.
(1) Since the first film 31 of the separator 3 has nickel in a dispersed state or a layered state, the deposited zinc is oxidized and dissolved on the nickel, and dendrite formation is suppressed. Further, since the separator 3 has the second film 32 made of the polyvinyl alcohol film, the dendrite is refined and easily dissolved, dendrite growth is suppressed, and the dendrite is directly applied to the nickel of the first film 31. Contact is prevented and thus self-discharge is prevented. Therefore, the dendrite generation suppressing action by the first film 31 and the dendrite growth suppressing action by the second film 32 act synergistically, and the occurrence of short circuit due to dendrite is sufficiently prevented, resulting in a long life.

  The above-mentioned action by the polyvinyl alcohol film is considered to be due to the alcohol group, which is a functional group of polyvinyl alcohol, and the aggregate structure of the polyvinyl alcohol molecules. The synthetic polyvinyl alcohol has a molecular weight, a saponification degree, and a crystallization. Since control of the degree and the like is easy, an excellent dendrite growth suppressing action can be obtained by setting optimum conditions.

  In addition, the dendrite production | generation suppression effect by the 1st film | membrane 31, the dendrite growth suppression effect | action by the 2nd film | membrane 32, and the synergistic effect | action by those effect | actions are proved by [Test 1]-[Test 3] shown below.

(2) Especially in the batteries using the separators 3 of Reference Examples 1 and 2 and Example 1 , the alkali resistance of the separator 3 is improved, and therefore the occurrence of a short circuit due to the deterioration of the separator 3 is sufficiently prevented.

(3) In particular, in the battery using the separator 3 of Example 1 , the nickel layer formed on the first film 31 of the separator 3 reliably oxidizes and dissolves precipitated zinc and suppresses dendrite generation.

(4) Since the non-woven fabric 4 is used, the surfaces of the electrodes 1 and 2 are uniformly and sufficiently wetted with the electrolyte solution. Therefore, the active material utilization rate is improved, and the current distribution during charge and discharge is uniform. Zinc negative electrode shape change is suppressed.

(5) Especially in the battery using the separator 3 of Reference Example 4, the manufacturing process of the separator 3 is simplified.

  The metal used in the first film 31 is a metal arbitrarily selected from nickel, iron, cobalt, platinum, palladium, indium, chromium, manganese, titanium, and alloys containing these as main components. It is not limited to nickel.

In the separator 3 of Example 1 , the nickel coating layer 31a is formed on the first film 31, but instead, the nickel coating layer is formed on the surface of the second film 32 on the first film 31 side. Also good.

  Moreover, in the said battery, although nickel is used as a positive electrode active material, you may use silver oxide and manganese. An air electrode may be used as the positive electrode.

  Furthermore, although the nonwoven fabric 4 is arrange | positioned in the said battery, if the negative electrode 1 and the positive electrode 2 will get wet uniformly and fully to electrolyte solution, the nonwoven fabric 4 will not be especially required.

[Test 1]
Example 1 An alkaline zinc storage battery having the above-described configuration including the separators 3 of Reference Examples 1 to 5 and Comparative Examples 1 to 10 was made on a trial basis, and the following test was performed. That is, each battery was charged at a current density of 300 mA / cm ² in an atmosphere of 60 ° C., and the amount of electricity at the time when the voltage during charging began to decrease was determined as the amount of charged electricity generated by short circuit. The results are shown in Table 2. A large amount of short-circuit generated charge electricity indicates high short-circuit resistance. In addition, when the prototype battery was disassembled after the test, it was confirmed that both were short-circuited.

Table 2 shows the following. First, comparing Comparative Examples 1 to 3 which are separators having a single membrane structure, the polypropylene microporous film has the lowest short-circuit resistance, and the short-circuit resistance is improved in the order of the cellophane film and the polyvinyl alcohol film. When comparing Comparative Examples 1 to 3 and Comparative Examples 8 to 10, the short-circuit resistance of Comparative Examples 8 to 10, which is a separator having a two-film structure, is the sum of the amount of electric charge generated by a short circuit of the separator having a single-film structure. ing. However, when Comparative Example 1 and Comparative Example 5 are compared, the short-circuit resistance is greatly improved by forming the nickel coating layer even in the case of the separator having the same single film structure. This can be seen by comparing Comparative Examples 6 and 7 and Example 1 with Comparative Examples 8 to 10. That is, the separator having a two-film structure formed by forming the nickel coating layer 31a on the polypropylene microporous film as the first film 31 has improved short-circuit resistance as compared with a separator having a simple two-film structure.

On the other hand, even in the case of the separator having the same two-film structure formed by forming the nickel coating layer, the short-circuit resistance of Example 1 is significantly improved as compared with Comparative Examples 6 and 7. This is considered due to the fact that the second film 32 is a polyvinyl alcohol film. That is, in the separator using the polyvinyl alcohol film as the second film 32, the dendrite is more easily made finer than the separator using the second film 32 as a polypropylene microporous film and a cellophane film, and the dendrite reaches the nickel coating layer. Is easily oxidized and dissolved, and is considered to have improved short-circuit resistance.

Further, in Reference Examples 1 to 5, even when nickel powder is contained in a dispersed state instead of forming the nickel coating layer 31a in the first film 31, short-circuit resistance is the same as in the case of Example 1 . Has improved.

  For these reasons, forming the nickel coating layer 31a in the first film 31 or containing nickel powder in a dispersed state, and using the polyvinyl alcohol film as the second film 32 contributes to the improvement of short circuit resistance. You can see that

[Test 2]
An alkaline zinc storage battery having the above-described configuration including the separators of Example 1 , Reference Examples 1 to 5 and Comparative Examples 1, 7, and 9 was made as a prototype, and the following test was performed on this battery. The battery capacity was 2 Ah. That is, the initial discharge capacity, the change in open circuit voltage when left in a constant temperature bath at 60 ° C. for 40 days after charging, and the discharge capacity after returning to room temperature after standing were obtained. Table 3 shows the initial discharge capacity and the discharge capacity after standing, and FIG. 5 shows the change in the open circuit voltage. After the test, when the prototype battery was disassembled, it was short-circuited in Comparative Examples 1 and 9, and in Comparative Example 7, the nickel coating layer 31a and the zinc of the negative electrode 1 were in contact with each other to promote self-discharge. confirmed.

Table 3 shows the following. In Comparative Examples 1, 7, and 9, the discharge capacity after standing is decreased with respect to the initial discharge capacity, but not decreased in Example 1 and Reference Examples 1 to 5 . Further, as can be seen from FIG. 5, in Comparative Examples 1, 7, and 9, the open circuit voltage suddenly drops after 30 days have passed after being left. In particular, when Example 1 and Comparative Example 7 are compared, it can be seen that it is effective to use a polyvinyl alcohol film as the second film 32. This is because the separator in which the second film 32 is a polyvinyl alcohol film has better alkali resistance than the separator in which the second film 32 is a cellophane film.

  Therefore, it is considered that forming the nickel coating layer 31a in the first film 31 or containing nickel powder in a dispersed state and using the polyvinyl alcohol film as the second film 32 contributes to the improvement of the discharge characteristics.

[Test 3]
An alkaline zinc storage battery having the above-described configuration including the separators of Example 1 , Reference Examples 1 to 5 and Comparative Examples 1, 7, and 9 was made as a prototype, and the following test was performed on this battery. The battery capacity was 2 Ah. That is, a pattern consisting of one 2C charge / discharge cycle, one 0.2C charge / discharge cycle, and 50 heat cycles from -10 ° C to 60 ° C was repeated, and the discharge capacity after each pattern was determined. The results are shown in Table 4. In Table 4, the initial discharge capacity indicates the discharge capacity immediately after battery assembly.

Table 4 shows the following. In Comparative Example 1, short-circuited by 2C charge before 1 pattern of heat cycle, in Comparative Example 7 self-discharged by charge of 2C before 2 patterns of heat cycle, and in Comparative Example 9 2C of 2C before heat cycle of 2 patterns Shorted by charging. On the other hand, in Example 1 and Reference Examples 1 to 5 , the discharge capacity hardly decreased even after 6 patterns were completed, and no short circuit was observed. That is, Example 1 and Reference Examples 1 to 5 have high short-circuit resistance.

  Since the present invention can sufficiently prevent the occurrence of a short circuit due to dendrites and can prolong the service life, the industrial utility value is great.

It is a fragmentary sectional view showing the power generation element of the trial manufacture alkaline zinc storage battery which belongs to one embodiment of the present invention. It is sectional drawing which shows an example of the practical alkaline zinc storage battery of this invention. It is an expanded sectional fragmentary view which shows the separator of Example 1, Reference Examples 1-5, and Comparative Examples 6-10. FIG. 4 is an enlarged partial cross-sectional view showing separators of Example 1 and Comparative Examples 6 and 7 among the separators of FIG. 3. It is a figure which shows the change of the open circuit voltage in the test 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Positive electrode 3 Separator 31 1st film | membrane 31a Nickel coating layer 32 2nd film | membrane 4 Nonwoven fabric

Claims (5)

A separator having at least a first film facing the positive electrode and a second film facing the negative electrode;
The first film is an alkali-resistant microporous film, the second film is a polyvinyl alcohol film, the first film is composed of nickel, iron, cobalt, platinum, palladium, indium, chromium, manganese, titanium, and the main components thereof. and alloys, have arbitrarily selected metal from among,
The alkaline zinc storage battery , wherein the first film has the metal in a layer state on a surface facing the negative electrode .   The alkaline zinc storage battery according to claim 1, wherein the second film has a crosslinked structure.   The alkaline zinc storage battery according to claim 1, wherein the alkali-resistant microporous membrane is a polyethylene microporous membrane or a polypropylene microporous membrane.   The alkaline zinc storage battery according to claim 1, wherein a nonwoven fabric is interposed between at least one of the first film and the positive electrode or between the second film and the negative electrode.   The alkaline zinc storage battery according to claim 1, wherein the second film is formed by applying a polyvinyl alcohol resin to one surface of the first film.

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