JPH06267584A - Secondary battery - Google Patents

Abstract

PURPOSE:To restrain reversible reaction at the time of charge/discharge from being degraded, and thereby lengthen the life of the battery by filling gel of gas permeability into the circumference of each electrode group, and thereby enabling electrolytes to be fed to each electrode. CONSTITUTION:Electrode groups 4 are housed in the container 2 of the secondary battery, so that a single cell is thereby formed. A gelling agent is filled up in the cavity section 3 at both the sides of the electrode groups 4. After that, a KOH electrolyte is adjusted in liquid measure so as to be added, the gelling agent is made to hold the KOH electrolyte so as to be swelled out, so that gel 1 is tightly closed with a cover 5, and a pressure regulating valve 6 is installed on the cover 5. By this constitution, a great amount of the electrolyte is held so as to allow the electrolyte to be fed to electrodes, and concurrently the decreasing rate of the electrolyte within the electrodes can be restrained from being degraded when charge/discharge is repeated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery used in an electric vehicle or the like, and more particularly to a secondary battery using a gel which can suitably hold an alkaline electrolyte and is excellent in gas permeability.

[0002]

2. Description of the Related Art In recent years, as the problem of environmental pollution such as acid rain becomes more serious, instead of a gasoline engine vehicle,
It has been considered to increase the proportion of electrically powered electric vehicles. In such an electric vehicle, a battery as a power source is one of the particularly important constituent elements, and a battery having a characteristic capable of discharging for a long time is desired, and various studies have been made.

However, the sealed lead-acid battery as a conventional battery has drawbacks that it has a heavy weight and a small energy density, and an electric vehicle using the lead-acid battery has power performance such as acceleration performance and load characteristics. There was a problem that it was inferior in terms of.

Therefore, a sealed nickel nickel alloy as an alkaline secondary battery having a large energy density and excellent load characteristics
Although a cadmium secondary battery (hereinafter referred to as a Ni / Cd secondary battery) has been tried, it is still unpractical because of its high manufacturing cost and large weight relative to its electric capacity.

Therefore, instead of the Ni.Cd secondary battery, for example, a sealed nickel-zinc secondary battery shown in FIG.
It was considered that Ni.Zn secondary battery) 12 was used as a secondary battery. The Ni / Zn secondary battery 12 has the advantages that it is lighter in weight than the lead storage battery, has a large energy density and excellent power characteristics, and can be made cheaper than the Ni / Cd secondary battery.

The Ni / Zn secondary battery 12 includes an electrode plate group 1
4, the electrode plate group 14 includes a nickel plate 14a as a positive electrode plate and a zinc plate 1 as a negative electrode plate.
4b, and a separator 14c that allows the ions of the electrolytic solution to pass therethrough, and a retainer 14d that contains the electrolytic solution in the form of a fiber mat laminated on both sides of the separator 14c. There is.

Since the retainer 14d is used by holding an alkaline electrolytic solution, for example, a 30% KOH aqueous solution, various hydrophilic surface treatments are applied to each fiber surface of the retainer 14d so that the electrolytic solution can be retained. Has been done. Further, the Ni / Zn secondary battery 12 is provided with a hermetically sealing portion 15 that can prevent leakage of the electrolyte solution on the top thereof, and the oxygen gas generated during overcharging is released to the outside to the hermetically sealing portion 15. A pressure control valve 16 is provided for this purpose.

In the Ni / Zn secondary battery 12, a plurality of the electrode plate groups 14 are stacked and accommodated according to a set capacity as shown in FIG. Hollow portions 17 are formed on both sides of the electrode plate group 14 in order to mitigate a pressure increase in the secondary battery when gas is generated.

The hollow portion 17 serves to mitigate the pressure rise, and has a minimum necessary capacity because of space saving. Further, the hollow portion 17 has a capacity for discharging the electrolyte to the outside. The electrolyte is not filled in to avoid problems due to leakage.

However, when the retainer 14d as shown in FIG. 7 is used, since the retainer 14d has a poor liquid retaining ability, the amount of the electrolytic solution in the upper portion becomes smaller than that in the lower portion.
The use of the electrode plates 14a and 14b becomes non-uniform, and the surface treatment agent of the retainer 14d and the substrate itself may be deteriorated by the electrolytic solution, and the electrolytic solution may not be retained. There are problems that the characteristics cannot be obtained and that the absolute amount of the electrolytic solution that can be filled in the secondary battery is small and it is difficult to extend the life.

Therefore, in order to improve the holding power of the electrolytic solution of the retainer as described above, it has been considered to use a gelling agent for the retainer in the sulfuric acid electrolytic solution of the lead storage battery, which is in a gel state (Japanese Patent Laid-Open No. Hei 10 (1999) -31977). No. 1-235155).

Regarding the alkaline electrolyte, it has also been proposed to use an active material and a gelling agent in the cathode of an alkaline primary battery (JP-A-1-231272, JP-A-2-11).
9053 publication). As such a gelling agent, a water-absorbing polymer containing a carboxylic acid group such as sodium polyacrylate or cross-linked and branched sodium polyacrylate or a water-absorbing polymer containing a sulfone group is used.

In addition, in order to enhance the liquid holding capacity, the space between the electrode group and the battery case is made of an acid resistant material such as acrylic wool, and
It has also been proposed to fill a spongy body having elasticity or a porous body (JP-A-63-19157).

On the other hand, as a measure for preventing the formation of a high resistance layer (so-called barrier layer) which is likely to occur between the lattice body and the surface of the active material at the time of over-discharge, a super absorbent resin for supplying sulfate ions is provided in the space. Filling is also considered (Japanese Patent Laid-Open No. 1-143158).

Further, in the storage battery of the above-mentioned Japanese Patent Laid-Open No. 63-19157, since the liquid holding capacity is insufficient, the battery size becomes large, and as the battery size becomes particularly high, the electrolyte solution becomes longer as the non-woven fabric. It could not be kept stable for a certain period of time, gradually causing inconveniences such as lower dripping. Further, the storage battery disclosed in JP-A-1-143158 is not suitable for a storage battery as a secondary battery because it does not consider release of gas generated by overcharging.

[0016]

Conventionally, a secondary battery using an alkaline electrolyte has a property that, when it is charged, the capacity does not recover unless it is overcharged with an amount of electricity that is higher than a normal charge capacity. . At this time, during charging, the battery is overcharged while generating oxygen from the positive electrode.

Most of the oxygen generated in the positive electrode is absorbed by the negative electrode, but a part of the oxygen that does not reach the negative electrode is provided in the Ni.Zn secondary battery 12 shown in FIG. The gas is released from the pressure control valve 16 to the outside as a gas. As a result, the generation of such oxygen gas reduces the amount of the electrolytic solution and deteriorates the characteristics of the secondary battery.

Therefore, an object of the present invention is to hold a large amount of electrolytic solution in a secondary battery to supply the electrolytic solution to the electrodes, and to rapidly supply the ions of the electrolytic solution to the electrodes for charge / discharge. It is intended to provide a secondary battery capable of suppressing a decrease in reversible reaction at the time and extending the life.

[0019]

In order to solve the above-mentioned problems, the secondary battery according to claim 1 is a gas in which the periphery adjacent to the electrode group absorbs and retains an alkaline electrolyte in a gelling agent. It is characterized in that it is filled with a gel that permeates through the electrolyte so that an alkaline electrolyte can be supplied to the electrode.

In order to solve the above problems, the secondary battery according to claim 2 is characterized in that, in the secondary battery according to claim 1, the gel has a gas permeability of 1% or more. There is.

In order to solve the above-mentioned problems, a secondary battery according to a third aspect of the present invention is the secondary battery according to the first or second aspect, wherein the gel is an aggregate of a large number of particles, and gas permeates through the gel. It is characterized in that voids are formed between the particles.

In order to solve the above problems, the secondary battery according to claim 4 is characterized in that, in the secondary battery according to claim 3, the void ratio of the voids is 3 to 45%.

In order to solve the above problems, the secondary battery according to claim 5 is the secondary battery according to claim 1, 2, 3 or 4, wherein the gel has a gel strength of 40 to 20.
It is characterized by being 0 g.

The base resin of the gelling agent may be a polymer having a three-dimensional network structure and containing acrylic acid and / or acrylate as a main constituent unit.

The gelling agent may be prepared by polymerizing and cross-linking a monomer compounding liquid containing a water-soluble copolymerizable cross-linking agent in a water-soluble polymerizable monomer, or a water-insoluble polymerizable monomer. Any method may be used in which a desired gelling agent is obtained by polymerizing and cross-linking a monomer-containing liquid containing a water-insoluble copolymerizable cross-linking agent and then hydrophilizing it by treatment such as hydrolysis.

As the salt of the acrylic acid salt, alkali metals such as sodium, potassium and lithium, ammonium salts such as methylamine, trimethylamine, triethanolamine and diethanolamine, and amine salts can be used.

Further, the gelling agent can have a function by forming a necessary copolymer according to the purpose, and methacrylic acid is used as a copolymerizable monomer in preparing the gelling agent. Unsaturated monocarboxylic acids or unsaturated polycarboxylic acids such as fumaric acid, itaconic acid, aconitic acid, citraconic acid and their anhydrides can be used, and further vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid. , Vinyltoluene sulfonic acid, styrene sulfonic acid, acrylic sulfonic acid, methacrylic sulfonic acid, acrylamido sulfonic acid, methacrylamide sulfonic acid, and other aliphatic or aromatic vinyl sulfonic acids, and further acrylamide, methacrylamide, N-methyl acrylamide, N-butyl acrylamide, N-methyl meta Acrylamides such as rilamide, N-alkylacrylamides, vinyl alcohols such as vinyl acetate, N-vinyllactams such as N-vinylpyrrolidone, vinylpyridines, aminoalkyl acrylic compounds, aminoalkylacrylamides, aminoalkyl Examples thereof include acrylates, vinyl ethers, acrylic acid esters, vinyl acrylates, olefins, olefinic polycarboxylic acid esters, and vinyl halides.

Further, as a copolymerizable cross-linking agent when preparing the above gelling agent, N, N'-methylenebisacrylamide, N, N'-methylenebismethacrylamide, N,
Examples thereof include N'-ethylenebisacrylamide, N, N'-ethylenebismethacrylamide, and 1,2-diacrylamideethylene glycol, and further ethylene glycol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene. Examples thereof include di- or tri-acrylic acid esters and methacrylic acid esters such as glycol, divinylbenzene, divinyltoluene, tetraallyloxyethane, diallyl phthalate, diallyl adipate and the like.

The method of polymerizing and crosslinking is not particularly limited, but when a radical polymerization initiator is used, an azo polymerization initiator such as azobiscyanovaleric acid or azobisamidinopropane dihydrochloride, ferrous sulfate or A redox initiator composed of a reducing agent such as dithionous acid and pyrosulfite, and a peroxide such as hydrogen peroxide and peroxodisulfate can also be used. These azo-based polymerization initiators and redox initiators may be used alone or as a mixture, if necessary. Further, the polymerization may be carried out by irradiation with radiation, electron beams, ultraviolet rays or the like.

Additives may be added during the polymerization,
Examples of such an additive include an extender, and as such an extender, organic powder, organic fiber or inorganic powder or inorganic fiber, gelling agent, water absorbent resin, or the like can be used. Further, the surface of the gelling agent particles can be given a function such as hydrophilicity by subjecting it to a secondary treatment required depending on the purpose.

The shape of the gelling agent is not particularly limited as long as it is a granular material having voids having gas permeability when it is filled adjacent to the periphery of the electrode group.
A flake shape or the like can be used, and the particle size of the gelling agent is
In the range of 10-150 mesh, i.e. particle size 0.1-1.
Within the range of 7 mm, the particle size after swelling is 0.2-5 mm
The particle size of the gelling agent is particularly preferably within the range of
Within the range of 16 to 42 mesh, that is, particle size is 0.4 to 1.0
mm, and the particle diameter after swelling in the liquid is in the range of 0.8 to 3 mm.

The gel filled as described above preferably has a gas permeability of 1% or more. If the gas permeability is less than 1%, the efficiency of absorbing oxygen gas generated in the electrode group at the negative electrode during overcharge is reduced, and the reversible reaction at the time of charge / discharge is hindered.

The porosity of the voids formed in the gel is preferably 3 to 45%. When the porosity is less than 3%, the gas permeability is deteriorated and the reversible reaction at the time of charging and discharging is hindered as described above, while when it exceeds 45%,
Since the amount of gel that holds the alkaline electrolyte decreases, the amount of alkali electrolyte that can be held decreases.

The gel strength of the above gel is 40 to 20.
0 g is desirable. When the gel strength is less than 40 g,
When the gel is filled, it collapses due to its own weight, gas permeability deteriorates and becomes non-uniform, which is not preferable because it interferes with the reversible reaction during charge and discharge as described above.
If the gel strength exceeds 400 g, the swelling upon absorption of the alkaline electrolyte is hindered and the amount of the alkaline electrolyte retained becomes unfavorable.

In the secondary battery, it is desirable that the gelling agent has the ability to retain the alkaline electrolyte within the range of 5 to 30 times. When the gelling agent is used, the gelling agent It is preferable to retain the liquid at about half the maximum liquid retention capacity of the agent. With a liquid retention capacity of less than 5 times, from the obtained gel,
The supply of the alkaline electrolyte to the electrode group is insufficient, which is not preferable, and when it exceeds 30 times, the gel strength is lowered and crushing due to its own weight is apt to occur, resulting in deterioration of gas permeability, which is not preferable.

[0036]

According to the structure of the above-mentioned claim 1, since the gel in which the gelling agent has absorbed and retained the alkaline electrolyte is filled in the periphery adjacent to the electrode, more alkaline electrolyte is retained. Since the alkaline electrolyte can be supplied to the electrode from the gel, the reduction rate of the alkaline electrolyte in the electrode when charging and discharging are repeated can be suppressed.

In addition, in the above constitution, the ions of the alkaline electrolyte and the water can be rapidly supplied from the gel to the electrode, so that the inhibition of the reversible reaction at the time of charging / discharging can be suppressed and the life can be extended and the discharge characteristics can be improved. be able to. Thereby, when the above configuration is applied to, for example, an electric vehicle,
Power characteristics such as acceleration characteristics and load characteristics of the electric vehicle can be improved.

On the other hand, in the above-mentioned constitution, since the alkaline electrolyte is retained in the gel, it is possible to prevent the alkaline electrolyte from leaking out, and to avoid the obstacle due to the leakage of the alkaline electrolyte.

Further, in the above structure, since the gel is permeable to gas, for example, oxygen gas generated during overcharging can be easily diffused / moved to the negative electrode and absorbed, and therefore, during discharge, It is possible to reduce the inhibition of the reversible reaction and suppress the decrease of the electrolytic solution due to the generation of oxygen gas.

[0040]

EXAMPLES First, each example of the method for producing the gelling agent used in the secondary battery of the present invention and the characteristics of the gelling agent obtained by each of the above examples will be described with reference to FIGS. 1 to 6. The parts used in the following examples are parts by weight, and%
Is% by weight.

Example 1 First, 500 parts of acrylic acid as a polymerizable monomer, 300 parts of water, 200 parts of sodium hydroxide as a neutralizing agent, and 0.45 part of N, N′-methylenebisacrylamide as a cross-linking agent were kept at room temperature. A monomer-blended solution was prepared by charging the mixture in a temperature-controllable reaction vessel and mixing and stirring the mixture.

After the liquid temperature of the above monomer-blended solution was adjusted to 20 ° C. in a nitrogen atmosphere, 25 parts of a 3% potassium persulfate aqueous solution was added to the above monomer-blended solution to maintain the reaction vessel at 60 ° C. The acrylic acid and N, N'-methylenebisacrylamide were polymerized and crosslinked.

After 1 hour from the initiation of polymerization, the reaction vessel was opened,
The gel-like water-containing crosslinked polymer produced in the reaction vessel was taken out. This gel-like water-containing crosslinked polymer was cut, dried with a dryer heated to 120 ° C., pulverized with a pulverizer, and then adjusted to a particle size of 42 to 100 mesh to obtain a gelling agent.

[Example 2] A gelling agent was obtained in the same manner as in Example 1 except that the particle size of 24 to 42 mesh was used instead of the particle size of 42 to 100 mesh in Example 1 above.

Example 3 A gelling agent was obtained in the same manner as in Example 1 except that the particle size of 16 to 24 mesh was used instead of the particle size of 42 to 100 mesh in Example 1 above.

Example 4 A gelling agent was prepared in the same manner as in Example 2 except that 0.55 part of N, N′-methylenebisacrylamide was used instead of 0.45 part of N, N′-methylenebisacrylamide in Example 1 above. Got

Example 5 A gelling agent was prepared in the same manner as in Example 2 except that 0.3 part of N, N′-methylenebisacrylamide was used instead of 0.45 part of N, N′-methylenebisacrylamide in Example 1. Got

Example 6 Next, another method for producing the gelling agent used in the secondary battery will be described. First, an aqueous solution prepared by dissolving 15 parts of partially saponified polyvinyl alcohol as a dispersion stabilizer in 1500 parts of water was prepared, and the aqueous solution was charged into the reaction vessel shown in Example 1 above. A mixture of 500 parts of methyl acidate, 0.75 parts of divinylbenzene as a cross-linking agent and 2.5 parts of benzoyl peroxide as a polymerization initiator was added and dispersed, and the temperature in the reaction vessel was kept at 70 ° C. under a nitrogen atmosphere. Suspension polymerization was carried out for an hour. The obtained crosslinked polymer was washed with water and then dehydrated.

Next, 500 parts of the above-mentioned polymerized crosslinked product was dispersed in 1500 parts of methyl alcohol, and 30% sodium hydroxide 640 was added.
Parts were added and saponification reaction was carried out at 80 ° C. for 4 hours. The saponified product after completion of the reaction was washed with methyl alcohol to remove free sodium hydroxide, dried under reduced pressure, and classified to 24 to 42 mesh to obtain a spherical gelling agent.

Example 7 In place of 0.75 part of divinylbenzene in Example 6 above, 0.
A gelling agent was obtained in the same manner as in Example 6 except that 40 parts were used.

Next, a gelling agent as a comparative control for the gelling agents of Examples 1 to 7 will be described.

Example 8 A gelling agent was prepared in the same manner as in Example 2 except that 0.05 part of N, N′-methylenebisacrylamide was used instead of 0.45 part of N, N′-methylenebisacrylamide in Example 1. Got

Example 9 A gelling agent was prepared in the same manner as in Example 2 except that 0.20 part of N, N′-methylenebisacrylamide was used instead of 0.45 part of N, N′-methylenebisacrylamide in Example 1. Got

[Example 10] As a gelling agent, a cross-linked branched sodium polyacrylate (trade name: Aquamate AQ-200B, manufactured by Sekisui Plastics Co., Ltd.), which is a general water-absorbing polymer, was used.

Example 11 In place of 0.75 part of divinylbenzene in Example 6, divinylbenzene as a cross-linking agent
A gelling agent was obtained in the same manner as in Example 6 except that 3.5 parts was used.

Next, each of the above gelling agents was tested and evaluated for each of the following items. As the items, gel strength, liquid retention amount, porosity and gas permeability were used.

(1) Gel strength: 40 g of a 30% KOH aqueous solution was placed in a glass container having an inner diameter of 3.6 cmφ, 4 g of a gelling agent was added with stirring at 600 rpm, and the solution was uniformly absorbed to form a swollen gel. Created (sample height about 4 cm).

The gel was allowed to stand for 24 hours while being kept at 30 ° C., and then the rheometer (CR-2, manufactured by Sun Kagaku Co., Ltd.) was used.
(00 type) is equipped with a holding jig having a diameter of 10 mmφ, and this is applied to the center of the surface of the swollen gel, and a load is applied at a speed of 60 mm / min so as to enter downward from the surface of the swollen gel. Load value (g) at a position buried 10 mm from the gel surface
Was measured and taken as the gel strength (g).

(2) Liquid retention: relative to gelling agent (Ag)
The liquid retention amount (B / A times) of a 30% KOH aqueous solution (Bg) was measured by the tea bag method. In the tea bag method, after each gelling agent is weighed (Ag), it is enclosed in a tea bag-like bag (4 × 10 mm polypropylene nonwoven fabric), and the weight including the bag is weighed (Cg).

Next, the bag is immersed in a 30% KOH aqueous solution.
Then, after 10 minutes or 1 hour, the excess water in the bag is removed, and then the bag containing the absorbed gelling agent is weighed (D
g). Then, the liquid retention amount is calculated by setting D-C to B.
In addition, instead of the above 30% KOH aqueous solution, the amount of liquid retained using ion-exchanged water was similarly measured.

(3) Porosity: 100 g of 30% KOH aqueous solution was put into a 200 ml graduated cylinder having an inner diameter of 3.6 cmφ, the volume V ₁ (ml) was measured, and then the KOH aqueous solution was adjusted to 60%.
While stirring at 0 rpm, at least 5 g of the gelling agent was added to the above KOH aqueous solution to uniformly retain the solution, and a swollen gel without dripping was prepared in the above-mentioned graduated cylinder. The volume V ₂ (ml) is measured by the graduated cylinder. Then, (V ₂ -V ₁₎ /
V ₂ was calculated to determine the porosity of the gelling agent when swollen.

(4) Gas permeability: First, from the suction side, a gas consisting of a pressure reducing pump-pressure control valve-measuring cell-pressure gauge-precision needle valve (pressure loss 50 mmH ₂ O at -0.2 kgf / cm ² ). A device for measuring transmittance is produced, and first, in the device,
A measurement cell not filled with gel was attached, the decompression pump was operated, and the pressure control valve was set so that the pressure gauge value was always a negative pressure of −0.2 kgf / cm ² .

Next, a measuring cell filled with the gel to be measured (cell diameter 10 mm × filling height 60 mm) was attached, and a decompression pump was operated in the same manner to obtain the numerical value of the pressure gauge (kgf / cm 2). ² ) read. This numerical value was expressed as a percentage with respect to −0.2 kgf / cm ² described above, and was taken as the gas permeability.

The above-mentioned gel to be measured was prepared by adding each gelling agent to be tested to the above 30% KOH aqueous solution so as to be 9% with respect to the total weight of the 30% KOH aqueous solution and the above gelling agent. After swelling and uniformly gelling the whole inside of a cylindrical container with an inner diameter of 10 mm × 60 mm, fill each of the gas permeability measurement cells and leave it for one day, then each such measurement cell Was sequentially attached to the above-mentioned device, and the gas permeability was measured.

Next, each of the above test items was measured using each gelling agent in Examples 1 to 11 above, and the measurement results are shown in Table 1.

[0066]

[Table 1]

[Examples and Comparative Examples] Next, alkaline secondary batteries were prepared using the above gelling agents in which the alkaline electrolyte was retained. As the gelling agent used in each of the above Examples and Comparative Examples, the gelling agent of each of the above Examples having a tail number corresponding to the tail number of each Example and Comparative Example was used.

The above alkaline secondary battery was prepared in advance by using Zn.
And ZnO are mixed, and a sheet-shaped zinc active material layer is further prepared by the calender roll method, and the sheet is
It is pressure-molded on both sides of a copper punching metal current collector with 0.1 mm and 50% aperture ratio, thickness is 0.6 mm, width is 100 mm, height is 90 mm.
Zn plate was prepared.

On the other hand, a sintering type N having the same dimensions as the Zn electrode plate
An electrode group was prepared by alternately stacking 6 i electrode plates and 7 Zn electrode plates through a liquid retaining layer made of a nonwoven fabric and a microporous film.

Next, as shown in FIG. 1, the above electrode group 4 was housed in a container 2 of a secondary battery to form a single cell having a discharge capacity of 10 Ah. In the container 2, a space portion 3 having a sufficient size is provided at a position facing each of the liquid retaining layers on both sides of the electrode 4 group.
Was formed, and the space 3 was filled with 5 g of the gelling agent.

Thereafter, 3.5 mol / liter of KOH electrolytic solution was added to the container 2 while adjusting the amount of the solution so that there was no free solution, and the gelling agent was allowed to retain the KOH electrolytic solution to swell it. To prepare gel 1.

Next, the lid 5 made of epoxy resin or the like was attached to the top of the container 2 to seal the container 2. Subsequently, the lid 5 has a pressure control valve 6 for preventing the internal pressure from excessively rising due to oxygen gas or the like generated during overcharge.
Was attached, and an alkaline secondary battery using the gelling agent of each of the above examples was produced.

Next, the secondary battery performance (liquid retention test, liquid leakage test, weight reduction test, output test,
And cycle test). First, each of the above test methods will be described.

(5) Liquid holding power test: The state of the electrolytic solution held in the gel was visually confirmed after one month for each of the prepared secondary batteries. ◯: The electrolytic solution was uniformly retained in the upper and lower parts. Δ: The electrolytic solution was slightly accumulated in the lower part. X: The electrolytic solution was accumulated in the lower part.

(6) Leakage Test The leakage of the electrolytic solution was visually confirmed after one month with the terminal side of the prepared secondary battery as the lower surface. ◯: Electrolyte does not leak from the terminal. B: The electrolytic solution slightly leaks from the terminal portion. X: Electrolyte leaks from the terminal part.

(7) Weight reduction test Each of the above alkaline secondary batteries was charged with 0.1 C (1 A).
After charging for 10.5 hours, charging / discharging at 0.5C (5A) to 1 volt is defined as one cycle, and when the above cycle is repeated 50 times, the weight reduction of the alkaline secondary battery after 50 cycles is The reduction rate divided by the initial addition amount of the electrolytic solution was shown in percent.

(8) Output test In order to investigate the output characteristics of rapid discharge at low temperature, 0
It was discharged at 1 C (10 A) at 1 ° C. until it became 1 V, and the discharge duration was measured.

The measured discharge duration of the secondary battery was expressed as a percentage with respect to the discharge duration when the electrode group was immersed in an electrolytic solution bath for discharging without using a gelling agent. The comparison with the case where the electrode group is immersed in the electrolytic solution tank as described above is because the comparative discharge duration can be stabilized most.

(9) Cycle test The above charge / discharge cycle was repeated for each secondary battery,
The number of charge / discharge cycles until each of the secondary batteries fell below a specified discharge capacity, for example, 6 Ah was measured. On the other hand, as a comparison, the charging / discharging cycle number of a conventional alkaline secondary battery was similarly measured, which was not filled with a gelling agent, and the others were similarly measured. The ratio of the number of cycles is shown in percent.

Next, each of the above-mentioned first, second, third, fourth,
The test items were measured for each of the secondary batteries of Examples 6 and 7 and Comparative Examples 8 to 11, and the measurement results are shown in Table 2.

[0081]

[Table 2]

The above Examples 2, 4, 5 and Examples 8 to 1
The gelling agents obtained in 1 differ in the amount of the crosslinking agent with respect to the monomer. The relationship between each gas permeability of these gelling agents and the amount of the crosslinking agent with respect to the monomer is shown in FIG.

From FIG. 2, it can be seen that as the amount of the cross-linking agent in the gelling agent is increased, the gas permeability increases and the amount of electrolyte absorbed decreases. This is because by increasing the gel strength, the voids between the gelling agent particles can be maintained and the binding force between the polymer molecules is increased to inhibit the swelling of the gelling agent.

Next, the relationship between the gas permeability and the average particle size of the gelling agent is shown in FIG. 3, using the gelling agents of Examples 1 to 3 having the same composition but different particle sizes. From FIG. 3, it can be seen that as the average particle size of the gelling agent increases, the porosity between the gelling agent particles increases and the gas permeability increases.

Next, using the gelling agent of Example 3, the gas swelling ratio was measured by changing the swelling ratio depending on the addition amount of the electrolytic solution, and the relationship between each swelling ratio and the gas permeability is shown in FIG. .
As shown in FIG. 4, since it is necessary to secure gas permeability, the swelling ratio by the electrolytic solution is 5 times the maximum liquid holding capacity of the electrolytic solution of each gelling agent.
It can be seen that 0 to 70% is preferable.

That is, if it is less than 50%, the particle size is small because the swelling ratio is small, and the fluidity of the gel 1 is small due to the small wetting of the surface. No void can be formed between them, which impairs gas permeability.

When the swelling ratio of the gel 1 approaches the maximum liquid retention amount of the gelling agent, an electrolytic solution layer is formed on the surface of the particles of the gel 1, and the voids between the particles of the gel 1 are reduced. Permeability decreased. However, even in the gel 1 prepared by adjusting the swelling ratio to 20 times, which is close to 21 times, which is the maximum liquid holding amount of the gelling agent of Example 3, the gas permeability was sufficiently maintained.

Further, the results of the cycle tests are shown for each of the secondary batteries of Examples 1 to 4, and for comparison, the secondary battery of Comparative Example 9 and the conventional secondary battery not filled with a gelling agent. 5 shows. From this, it is understood that the secondary batteries of Examples 1 to 4 can have a longer life.

This is because more electrolytic solution can be held in the container 2 and the electrolytic solution can be uniformly supplied to the electrode group 4 for a long period of time, so that the decrease of the electrolytic solution in the electrode group 4 is suppressed, Inhibition of reversible reaction at the time of charging / discharging in the electrode group 4 is prevented, and further, oxygen generated at the time of overcharging can be efficiently absorbed by the negative electrode, and the decrease of the electrolytic solution is suppressed. It is considered that this is because the gas permeation in Example 2 was sufficient and the inhibition of the reversible reaction during charge / discharge due to the retention of oxygen gas in the electrode group 4 was prevented. The reversible reaction is an electrochemical reaction that occurs on the surface of each electrode 4 group, and is a reaction that is in the opposite direction between charging and discharging.

Next, for comparison, each of the secondary batteries of Examples 1 to 4 was compared with the secondary battery using the gelling agent of Comparative Example 9 and the conventional secondary battery not filled with the gelling agent. The result of the output test at a low temperature with respect to is shown in FIG. From this, it is understood that the discharge time of each of the secondary batteries of Examples 1 to 4 is long.

By the way, in the conventional secondary battery, when performing rapid discharge, particularly when performing rapid discharge at a low temperature, OH ⁻
The smooth diffusion of is suppressed and the reversible reaction at the time of discharge is suppressed, so that the discharge duration is reduced.

However, in the secondary batteries of the above-mentioned respective examples, since the OH ⁻ ions necessary for the reversible reaction can be rapidly supplied from the gel 1 which is filled so as to be adjacent to the periphery of the electrode group 4 and retained, The inhibition of the reversible reaction at the time of discharge is reduced, and the discharge characteristics can be greatly improved.

As described above, from the results shown in Table 2, FIG. 5 and FIG. 6, the sealed nickel-zinc secondary batteries of Examples 1 to 4, 6 and 7 can have a long discharge duration, and It can be seen that even if charging and discharging are repeated, the decrease in discharge capacity can be suppressed and the life can be extended.

This can be explained by the mechanism described below.
That is, the gel 1 which is filled in the space 3 and holds the electrolytic solution and which is adjacent to the electrode group 4 has the electrolytic solution layer on the surface thereof, and the electrolytic solution or the electrolytic solution is provided between the particles of the adjacent gel 1. Ions can be moved and diffused to each other.

As a result, the gel 1 can rapidly supply ions, for example, OH ⁻ ions, to the reaction active material between the electrodes 4, so that the OH ⁻ ions in the electrolytic solution at each electrode 4 at the time of charging / discharging. The ion concentration in the low concentration area can be rapidly increased.

Since the gel 1 has gas permeability, the oxygen gas released from between the four electrode groups can be moved quickly,
It is possible to avoid the inhibition of the reversible reaction due to the retention of the oxygen gas in the electrode group 4.

As a result, the gelling agents of Examples 1 to 4, 6 and 7 described above were used in a sealed nickel-zinc secondary battery to suppress the reduction of reversible reaction during charging and discharging, and Since it is possible to suppress the decrease in capacity and discharge capacity, it is possible to improve the secondary battery performance such as the output characteristics of the sealed nickel-zinc secondary battery. Therefore, when the sealed nickel-zinc secondary battery is used in an electric vehicle, power performance such as acceleration performance and load performance of the electric vehicle can be improved.

In addition, by holding the electrolytic solution in the gel 1, it is possible to increase the holding amount of the electrolytic solution as compared with the conventional one, and further to form the space portion 3 in which a large amount of the gelling agent can be filled to hold the electrolytic solution. Since the amount can be further increased, the life of the sealed nickel-zinc secondary battery can be further extended.

Since the gel 1 has gas permeability, the oxygen gas generated during overcharge can be easily diffused / moved to the negative electrode and absorbed by the negative electrode. While reducing the inhibition of reversible reaction during charging,
It is possible to suppress the decrease in the electrolytic solution due to the generation of oxygen gas, and it is possible to extend the service life.

The gelling agents of Examples 1 to 7 have a slightly lower liquid retention amount than the gelling agents of Examples 8 to 10, but such reduction does not cause any problems in practical use. It is a thing. Moreover, the gelling agent of Example 11 was not suitable for a sealed nickel-zinc secondary battery because of its insufficient liquid retention capacity.

Further, in each of the above embodiments, an example of a sealed nickel-zinc secondary battery is given, but there is no particular limitation as long as it is a secondary battery using an electrolytic solution. For example, nickel-cadmium secondary battery It can also be applied to secondary batteries and the like.

[0102]

As described above, in the secondary battery of the present invention, the periphery adjacent to the electrode group is filled with a gas-permeable gel that absorbs and retains the alkaline electrolyte, and the electrode is exposed to the alkaline electrolyte. It is a structure that can be supplied.

Therefore, in the above structure, by filling the gel in which the alkaline electrolyte is retained, it is possible to prevent the alkaline electrolyte from leaking to the outside and to retain a larger amount of the alkaline electrolyte.

Therefore, since the alkaline electrolyte can be supplied to the electrode from the gel, the reduction rate of the alkaline electrolyte in the electrode during repeated charging / discharging can be suppressed, and the gel can be retained. Since the ions necessary for the reversible reaction at the time of charging / discharging can be replenished to the electrode from the liquid alkaline electrolyte, inhibition of the reversible reaction at the time of charging / discharging is suppressed and discharge characteristics can be improved. As a result, when the above configuration is applied to, for example, an electric vehicle, there is an effect that power characteristics such as acceleration characteristics and load characteristics of the electric vehicle can be improved.

Further, in the above constitution, since the gel permeates the gas, for example, the oxygen gas generated during overcharge can be easily moved to and absorbed by the negative electrode, so that the inhibition of the reversible reaction is reduced. It is possible to suppress the decrease of the alkaline electrolyte.

As a result, the above-mentioned structure can hold the alkaline electrolyte in the electrode for a longer period of time than the conventional one, and
Since the inhibition of the above reversible reaction can be reduced, there is an effect that the life can be extended.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a secondary battery of the present invention.

FIG. 2 is a graph showing the relationship between each gelling agent in which the amount of the cross-linking agent with respect to the monomer in preparing the gelling agent is changed and the gas permeability thereof.

FIG. 3 is a graph showing the relationship between the gelling agents having different average particle sizes and their gas permeability.

FIG. 4 is a graph showing the relationship between the gelling agents having different swelling ratios and their gas permeability.

FIG. 5 is a graph showing the results of a cycle test for each of the secondary batteries of Examples 1 to 4, the secondary battery of Comparative Example 9, and a conventional secondary battery not filled with a gelling agent. .

FIG. 6 is a graph showing the results of an output test for each of the secondary batteries of Examples 1 to 4, the secondary battery of Comparative Example 9, and a conventional secondary battery not filled with a gelling agent. .

FIG. 7 is an explanatory diagram illustrating a power generation mechanism of a conventional alkaline secondary battery.

FIG. 8 is an explanatory diagram showing a structure of the alkaline secondary battery.

[Explanation of symbols]

 1 Gel 3 Space part (surroundings) 4 Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiki Ikeda 3-25-8 Seta, Otsu City, Shiga Prefecture (72) Inventor ▲ Yoshi ▼ Kazuhiro Kawa 388 Yamanobo Town, Kashihara City, Nara Prefecture (72) Inventor Yoshi Kobayashi Wa 4-201-1 611, Nanjing Town, Nara City, Nara Prefecture (72) Inventor Shuichi Sasahara 4-27, Kudo, Oji Town, Kitakatsuragi-gun, Nara Prefecture

Claims (5)

[Claims] 1. A periphery of an electrode group is filled with a gas-permeable gel in which a gelling agent absorbs and retains an alkaline electrolyte so that the electrode can be supplied with the alkaline electrolyte. Secondary battery characterized by. 2. The secondary battery according to claim 1, wherein the gel has a gas permeability of 1% or more. 3. The gel is an aggregate of a large number of particles,
The secondary battery according to claim 1 or 2, wherein voids through which gas permeates are formed between the particles. 4. The secondary battery according to claim 3, wherein the void ratio of the voids is 3 to 45%. 5. The gel has a gel strength of 40 to 200.
The secondary battery according to claim 1, 2, 3 or 4, wherein g is g.