JPH09199160A - Sealed alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a rise of the internal pressure of a battery and make the reduction of the capacity of the battery hardly occur by specifying the ratio of an electrolyte allocated to separators at the time of assembling of the sealed alkaline storage battery. SOLUTION: An electrode group provided with separators between positive electrodes and negative electrodes is sealed in a can body together with an alkaline electrolyte to form this sealed alkaline storage battery. In assembling this alkaline battery, 50wt.% or above of the injected electrolyte is held by the separators, and the upper limit value is preferably set to 80wt.%. If 30wt.% or above of the electrolyte is allocated to the separators when the complete discharge of this battery is finished, the battery has more excellent internal pressure characteristic and life characteristic and is preferable. A nonwoven fabric made of polyolefin resin fibers applied with a sulfonation process on the surface is used for the separator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed alkaline storage battery, and more particularly to a sealed alkaline storage battery having excellent internal pressure characteristics and life characteristics.

[0002]

2. Description of the Related Art A sealed alkaline storage battery usually has an electrical insulation between a positive electrode plate having a current collector sheet supporting a positive electrode active material and a negative electrode plate having a current collector sheet supporting a negative electrode active material. And a liquid-retaining separator are interposed to form an electrode plate group, and the electrode plate group is housed in a conductive bottomed can that also serves as a negative electrode terminal, and a predetermined alkaline electrolyte solution is also placed therein. After the liquid is injected, the upper part of the can is sealed with a sealing plate which also serves as a positive electrode terminal.

For example, in the case of a nickel-hydrogen storage battery, the active material carried on the positive electrode plate is Ni (OH) having a predetermined particle size.
_Two powders, and the negative electrode plate carries a hydrogen storage alloy powder having a predetermined particle size. Therefore, in both the positive electrode plate and the negative electrode plate, voids exist in the layer of Ni (OH) ₂ powder and the layer of hydrogen storage alloy powder that are carried, and the electrolytic solution permeates there to realize the battery reaction. It will be. As the separator, a non-woven fabric composed of fibers of polyamide resin or fibers of polyolefin resin such as polypropylene resin is generally widely used.

When an electrolytic solution is poured into a bottomed can body accommodating the electrode plate group, the electrolytic solution is distributed at a predetermined ratio to the positive electrode plate, the negative electrode plate, and the separator, each of which has a porous structure. To be done. Then, the liquid is retained in a balanced state at a certain ratio. When the balance of the electrolytic solution is lost, it becomes difficult for the battery to exert its normal function.

By the way, in recent years, with the progress of miniaturization and weight reduction of electronic equipment, there is an increasing demand for miniaturization and high capacity of a battery as a driving source thereof. In order to meet such requirements, generally, the occupancy of the electrode plate group to be accommodated is increased by reducing the wall thickness of the can body and increasing the internal volume, and the thickness of the separator that does not contribute to the battery capacity is reduced. Measures have been taken to reduce the thickness to increase the occupancy of the positive electrode plate and the negative electrode plate in the electrode plate group.

However, if the latter measure is taken, that is, the separator is made thinner, the assembled battery will have the following problems. First, when the thickness of the separator is reduced, the amount of electrolytic solution held by the separator is reduced. Therefore, when the charge / discharge cycle of the battery is continued, the liquid depletion phenomenon in the separator occurs at a relatively early stage, and the battery function is stopped.

Particularly, in the case of a nickel-hydrogen secondary battery in which the positive electrode active material is Ni (OH) ₂ , the positive electrode plate is likely to expand or deform during the charging / discharging process, so that it is held by the separator. There is a problem that the electrolyte solution is squeezed out by the positive electrode plate and the liquid is likely to run out. This problem of deterioration of battery life can be solved by increasing the amount of electrolyte injected. However, if the amount of the electrolytic solution is increased, on the other hand, there is a problem that the internal pressure of the battery increases during charging / discharging, and the electrolytic solution easily leaks. Such a problem also impairs the balance of the electrolytic solution in the electrode plate group in the battery, and eventually leads to the deterioration of the battery life.

Further, dendrite-like precipitates are formed on the positive electrode plate or the negative electrode plate in the process of charging and discharging, but when the separator is thin, the positive electrode plate and the negative electrode plate are broken by the precipitates. It is easy for a situation where a short circuit occurs. When such an internal short circuit occurs, the self-discharge of the battery becomes large and the battery life is deteriorated.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in the conventional sealed alkaline storage battery, suppresses the increase in the internal pressure of the battery, and reduces the battery capacity even when the charge / discharge cycle is continued for a long time. It is an object of the present invention to provide a sealed alkaline storage battery that has excellent cycle life characteristics, in particular, a nickel-hydrogen storage battery.

[0010]

The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, the above-mentioned internal pressure characteristics and life characteristics of the electrolytic solution distributed to the separator during battery assembly were It was found that the amount and the amount of the electrolytic solution held by the separator at the time of complete discharge are affected.
Specifically, it is a finding that at the time of assembly, the distribution amount of the electrolytic solution to the separator needs to be 50% by weight with respect to the total amount of the injected electrolytic solution. Further, it is a finding that a battery in a state where the amount of the electrolyte solution distributed to the separator is 30% by weight or more at the end of complete discharge, the internal pressure characteristics and life characteristics are further improved.

The present invention was made based on the above findings. That is, the sealed alkaline storage battery of the present invention is a sealed alkaline battery in which an electrode group formed by interposing a separator between a positive electrode plate and a negative electrode plate is sealed in a can together with an alkaline electrolyte, at the time of assembling the battery. In the sealed alkaline storage battery, the ratio of the electrolytic solution distributed to the separator is 50% by weight or more with respect to the total amount of the electrolytic solution.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The sealed alkaline storage battery of the present invention, like the above-described conventional sealed alkaline storage battery, has an electrode plate group housed in a can body together with an electrolytic solution, and the whole is sealed by a sealing plate. It has a special structure. And, 50% by weight of the injected electrolyte solution when assembling the battery
The above is what is held by the separator.

In the case of a battery in which the amount of electrolytic solution distributed to the separator during assembly is less than 50% by weight based on the total amount of electrolytic solution, the internal pressure of the battery rises significantly, and the separator becomes relatively early in the charging / discharging cycle. It is difficult to say that the battery has excellent internal pressure characteristics and life characteristics because the liquid drainage phenomenon and internal short circuit easily occur. However, if the distribution amount becomes too large, the electrolytic solution must be replenished excessively, resulting in poor economic efficiency. Further, it becomes difficult for oxygen gas generated from the positive electrode plate to move to the negative electrode plate, and at the same time, when a relatively large amount of electrolyte is not absorbed, the active material powder that has fallen off is blown up by oxygen gas or hydrogen gas, and the separator In some cases, short circuit may occur by depositing on the bipolar lead portions that are not shielded by, and eventually the internal pressure of the battery will rise and the cycle life characteristics will also decrease, so the upper limit is preferably regulated to 80% by weight. A more preferable allocation is
It is 55 to 65% by weight.

Separation capable of ensuring the above-mentioned holding amount of electrolyte
The following items are suitable examples of data
Can be. That is, it is composed of fibers having an average diameter of 3 to 9 μm.
The basis weight is 60 to 70 g / m ^TwoDial dial
Thickness when measured with a Kness gauge (measuring force: 1.4N)
Is 140 to 250 μm, and 0.5 N NaO
Alkaline water consisting of H, 1N LiOH and 7N KOH
The liquid retention rate when immersed in the solution for 30 minutes is 300 by weight.
% Or more, preferably 350% or more.
Absorption rate of Lucari aqueous solution is 20mm / 30min, preferred
Specifically, it is a non-woven fabric showing a value of 25 mm / 30 min.

The liquid retention of the above-mentioned non-woven fabric means that the weight of the whole non-woven fabric after immersing the non-woven fabric in the alkaline aqueous solution under the above-mentioned conditions is W _1, and the weight of the whole non-woven fabric before immersion is W ₀ . At this time, it means a value calculated based on the following formula: (W ₁ −W ₀ ) × 100 / W ₀ (%). The larger this value is, the better the non-woven fabric has in retaining the alkaline aqueous solution.

The liquid absorption rate is the height (mm) at the time when the lower end of the nonwoven fabric is dipped in the alkaline aqueous solution and the alkaline aqueous solution oozes out after 30 minutes. The larger the value of the nonwoven fabric, the more quickly the nonwoven fabric can absorb the alkaline aqueous solution. Such a non-woven fabric has excellent electrolytic solution retention performance and high tensile strength, and is therefore suitable for manufacturing an electrode plate assembly. In particular, a non-woven fabric satisfying the above specifications and manufactured by the melt blow method is suitable.

The fibers constituting this non-woven fabric are 6-
The surface of a fiber made of a polyamide resin such as nylon, 6,6-nylon or 4,6-nylon or a fiber made of a polyolefin resin such as polypropylene or polyethylene is treated with fuming sulfuric acid to be sulfonated to be hydrophilic. The modified fiber can be mentioned as a suitable example. However, although fibers of polyamide resin have a tendency to deteriorate the self-discharge characteristics of the battery although they are excellent in liquid retention, those of fibers of polyolefin resin having a sulfonated surface are more preferable. .

Further, in the case of the battery of the present invention, when 30% by weight or more of the electrolytic solution is distributed to the separator at the end of the complete discharge, the battery has further excellent internal pressure characteristics and life characteristics. It is suitable because it will become a problem. In that case, it is preferable that the remaining electrolytic solution is in a state of being distributed to the positive electrode plate in an amount of 15 to 25% by weight and in a state of being in an amount of being distributed to the negative electrode plate in an amount of 15 to 35% by weight.

[0019]

【Example】

Example 1 A positive electrode plate having a porosity of 30% and a thickness of 0.7 mm was manufactured by filling a sponge-like nickel sheet with 2.8 g / ml of an active material paste containing Ni (OH) ₂ as a main component. In addition, the composition by the arc melting method: MmNi _3.3 Co _1.0 Mn _0.4 Al
After producing a hydrogen storage alloy represented by _0.3 (Mm: misch metal), it is pulverized to an alloy powder under 150 mesh (Tyler sieve, 100 μm or less), and then
To 100 parts by weight of this alloy powder, 2 parts by weight of polyvinylidene powder and 10 parts by weight of nickel powder (conductive material) are mixed,
The mixed powder was added to 20 parts by weight of a 1% carboxymethyl cellulose (thickener) aqueous solution and then stirred to prepare various alloy powder slurries.

This alloy powder slurry has an opening ratio of 38%.
Punching nickel sheet (thickness 0.07mm, opening diameter
1.5mm), soak it up, and then dry it in the atmosphere.
Dried, 2 ton / cm^TwoRolling with the pressure of
A negative electrode plate having a size of 0.36 mm was manufactured. Furthermore, the separator
As for, the average diameter of the fiber is 6.2μm, and the basis weight is 60g.
/ M ^Two, 220 μm thick, 0.5N NaOH and 1N
The electrolyte retention rate of LiOH and 7N KOH is 3
75%, sulfo having a liquid absorption rate of 25 mm / 30 min
Prepared polypropylene non-woven fabric.

The negative electrode plate, the separator, and the positive electrode plate are superposed in this order and wound to form an electrode plate group, which is then housed in a cylindrical container, and 0.5 N NaOH and 1 N LiO 2 are contained.
Inject an alkaline electrolyte consisting of H and 7N KOH,
The whole is sealed with a sealing plate and the rated capacity is 1 at 4 / 5A size.
A 200 mAh battery was assembled. Various characteristics of the 200 batteries were measured according to the following specifications.

Battery internal pressure: A gas pressure gauge was attached to the battery and charged at 1200 mA for 2 hours at a temperature of 0 ° C.
Five cycles of charging and discharging with one cycle of discharging until the battery voltage reaches 1.0 V while connected to a constant resistance of 1Ω are performed, and the battery internal pressure is measured at the end of the five cycles. Life characteristics: Charge the battery for 1.5 hours at 1200mA, discharge the battery at 1200mA for 1.25 hours so that the battery voltage is 0V, and perform a cycle life test with 0.25 hours as one cycle. After 1000 cycles, the discharge capacity at that time was measured, and the ratio to the discharge capacity before the test was calculated as the capacity retention rate (%).

The larger this value is, the smaller the discharge capacity is, and the better the life characteristics are. Distributing amount of electrolyte to the separator during assembly: Before performing the charge / discharge test, disassemble 100 assembled batteries, take out the positive electrode plate, the negative electrode plate, and the separator, measure the weight of each, and distribute to each Measure the amount of electrolyte that has been filled, and calculate it as a percentage (%) with respect to the total amount of injected electrolyte. Amount of electrolyte distributed to the separator during complete discharge: 1200 m
A was discharged until the battery voltage became 1.0 V, and further discharged for 1 hour in a state of being connected to a constant resistance of 1 Ω, and the battery voltage was completely discharged to 0 V, then the battery was disassembled and the positive electrode plate, The negative electrode plate and the separator are taken out, the weight of the separator is measured to calculate the weight of the electrolytic solution retained, and the percentage of the total amount of the electrolytic solution is calculated.

The above results are shown in Table 1. Example 2 As a separator, the average fiber diameter was 5.1 μm, the basis weight was 70 g / m ² , the thickness was 175 μm, and 0.5 N NaOH was used.
A 6,6-nylon non-woven fabric having an electrolyte solution retention rate of 360% and a liquid absorption rate of 22 mm / 30 min was prepared from 1N LiOH and 7N KOH.

This separator was combined with the positive electrode plate and the negative electrode plate used in Example 1 to produce an electrode plate group. As an electrolytic solution, 0.5N NaOH, 1N LiOH and 7N were used.
A 4/5 A size battery having a rated capacity of 800 mAh was assembled using an alkaline aqueous solution containing KOH. The battery characteristics of the 200 batteries were measured according to the following specifications. Battery internal pressure: Measured in the same manner as in Example 1 except that the charging current was 800 mA and the constant resistance value was 1.5Ω. Lifetime characteristics: Charge current and discharge current until complete discharge is 8
Measured as in Example 1 except that it was 00 mA. Amount of electrolyte distributed to the separator during assembly: Measured in the same manner as in Example 1. Amount of electrolyte distributed to the separator during complete discharge: Measured in the same manner as in Example 1 except that the discharge current was 800 mA and the constant resistance value was 1.5Ω.

The above results are shown in Table 1. Example 3 As a material for a separator, the average fiber diameter was 5.0 μm,
The basis weight is 73 g / m ^TwoWith a thickness of 150 μm and 0.5 N
Electrode consisting of NaOH, 1N LiOH and 7N KOH
Liquid retention rate is 391%, liquid absorption rate is 26 mm / 30 m
described in Japanese Patent Application Laid-Open No. 1-132044
Prepared non-woven fabric of sulfonated polyolefin resin
did.

That is, the polyolefin resin is
As described in JP-A No. 1-132044, the outer layer is composed of a polyethylene layer which is easily sulfonated, and the inner layer is composed of a polyethylene-polypropylene copolymer layer. This non-woven fabric, temperature 35 ℃, concentration 2
The surface of the fiber was sulfonated by immersing it in 0% fuming sulfuric acid for 30 minutes to form a separator. The attached amount of sulfo group was 1 mg equivalent per 1 g of the total resin amount.

This separator was combined with the positive electrode plate and the negative electrode plate used in Example 1 to produce an electrode plate group. As an electrolytic solution, 0.5N NaOH, 1N LiOH and 7N were used.
A 4/5 A size battery having a rated capacity of 1200 mA was assembled using an alkaline aqueous solution composed of KOH. The battery characteristics of 200 batteries were measured under the same conditions as in Example 1.

The results are shown in Table 1. Comparative Example 1 As a separator, the average fiber diameter was 20 μm, the basis weight was 80 g / m ² , the thickness was 230 μm, and 0.5 N NaOH was used.
A 6-nylon non-woven fabric having an electrolyte retention rate of 236% and an absorption rate of 16 mm / 30 min consisting of 1N LiOH and 7N KOH and having a liquid absorption rate of 16 mm / 30 min was sulfonated under the same conditions as in Example 3. Prepared.

This separator was combined with the positive electrode plate and the negative electrode plate used in Example 1 to produce a plate group, and the same alkaline aqueous solution as in Example 1 was used as the electrolytic solution.
A / 5 A size battery having a rated capacity of 1200 mAh was assembled. The battery characteristics of 200 batteries were measured under the same conditions as in Example 1. The results are shown in Table 1.

Comparative Example 2 As a separator, the average fiber diameter was 24.3 μm, the basis weight was 83 g / m ² , the thickness was 210 μm, and 0.5 N NaO was used.
Sulfonation of 6,6-nylon non-woven fabric having electrolyte retention rate of 263% and absorption rate of 18 mm / 30 min consisting of H, 1N LiOH and 7N KOH under the same conditions as in Example 3 The processed material was prepared.

This separator was combined with the positive electrode plate and the negative electrode plate used in Example 1 to produce an electrode plate group, and the alkaline aqueous solution of Example 3 was used as an electrolytic solution for 4/5.
A size A battery having a rated capacity of 1200 mAh was assembled.
The battery characteristics of 200 batteries were measured under the same conditions as in Example 1. The results are shown in Table 1.

[0033]

[Table 1]

As is clear from Table 1, when the distribution amount of the electrolytic solution to the separator at the time of assembly is more than 50% by weight, the increase in the internal pressure of the battery is small, and the capacity retention rate is remarkably large, which leads to the deterioration of the life characteristics. Improvements have been realized.
When the amount of the electrolytic solution distributed to the separator at the end of complete discharge is less than 30% by weight, the battery undergoes a liquid depletion phenomenon, and both internal pressure characteristics and life characteristics are deteriorated.

[0035]

As is clear from the above description, the sealed alkaline storage battery of the present invention uses the separator in which 50% by weight or more of the electrolyte injected at the time of assembly is distributed. The increase in the internal pressure of the battery is suppressed without increasing the amount of injected liquid, and the separator liquid is unlikely to run out, so that its cycle life characteristics are very excellent.

Therefore, this structure is particularly useful when applied to a sealed nickel-hydrogen secondary battery. In the case of the above battery in which the positive electrode active material is made of Ni (OH) ₂ , the positive electrode plate is likely to swell or deform in the process of charging / discharging, so that the electrolyte balance is lost and the separator is easily drained. Is.

Claims (3)

[Claims] 1. A sealed alkaline battery in which an electrode group consisting of a separator interposed between a positive electrode plate and a negative electrode plate is sealed in a can together with an alkaline electrolyte, and distributed to the separator at the time of assembling the battery. A sealed alkaline storage battery, characterized in that the proportion of the electrolytic solution is 50% by weight or more based on the total amount of the electrolytic solution. 2. The sealed alkaline storage battery according to claim 1, wherein the amount of the electrolytic solution held in the separator is 30% by weight or more based on the total amount of the electrolytic solution at the time of complete discharge. 3. The positive electrode plate comprises a current collector carrying an active material mixture mainly composed of nickel hydroxide, the negative electrode plate comprises a current carrier carrying a hydrogen storage alloy, and the separator comprises: The sealed alkaline storage battery according to claim 1, which is made of a non-woven fabric of polyolefin resin fibers whose surface is subjected to a sulfonation treatment, and wherein the electrolytic solution contains potassium hydroxide, lithium hydroxide and sodium hydroxide at the same time.