JPH08227707A - Nickel-metal hydride battery - Google Patents

Abstract

PURPOSE: To provide a nickel - metal hydride battery with excellent battery content in which an electrolyte retaining amount in a separator rarely reduces even if charge/discharge cycles are repeated and minor short circuit between a positive electrode and a negative electrode does not occur. CONSTITUTION: A nickel - metal hydride battery comprises a positive electrode containing nickel, a negative electrode containing a hydrogen storage alloy, a separator 10 placed between both electrodes, and an electrolyte. The separator 10 comprises a synthetic resin porous plate 1 having a large number of through holes 11 and a synthetic resin nonwoven fabric arranged on each side of the porous plate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-hydrogen compound battery, and more particularly to a separator used therein.

[0002]

2. Description of the Related Art As shown in FIG. 5 and FIG. 6, a nickel-hydrogen compound battery 90 is conventionally composed of a positive electrode 9 containing nickel.
1, a negative electrode 92 containing a hydrogen storage alloy, a separator 8 interposed between the two, and an electrolytic solution (JP-A-4-349349).

In manufacturing the nickel-hydrogen compound battery 90, as shown in FIG. 7, the upper and lower surfaces of the negative electrode 92 are covered with a separator 8 and a positive electrode 91 is superposed on the separator 8 and spirally wound to form a spiral electrode. Group. Next, this spiral electrolysis group is connected to a battery case 95 as shown in FIG.
Insert it and inject the electrolyte.

Conventionally, as the separator 8, for example, a nonwoven fabric of polyamide, a nonwoven fabric of polypropylene, a nonwoven fabric of a sulfonated polyolefin resin having a sulfone group or an alkali salt group, etc. has been used (for example, JP-A-64- 57568).

[0005]

However, in the conventional nickel-hydrogen compound battery, there is a problem that the amount of the electrolytic solution held in the separator decreases during use thereof, resulting in a decrease in battery capacity.

That is, in the conventional nickel-hydrogen compound battery, as shown in FIGS. 8A and 8B, the positive electrode 91 expands during repeated charging and discharging, and as shown in FIG. The separator 8 is compressed between the positive electrode 91 and the negative electrode 92, and its thickness is reduced.

Therefore, the electrolytic solution impregnated in the separator 8 is discharged to the outside, and the electrolytic solution in the separator 8 between the positive electrode 91 and the negative electrode 92 decreases. In addition, this increases the internal resistance, which adversely affects the battery performance and reduces the battery capacity. Further, since the thickness of the separator 8 is reduced, the distance between the positive electrode 91 and the negative electrode 92 is shortened, and an electrical micro short circuit occurs between both electrodes.

In view of the above conventional problems, the present invention is an excellent battery in which the amount of electrolyte retained in the separator hardly decreases even after repeated charging and discharging, and a minute short circuit between the positive electrode and the negative electrode does not occur. It is an object of the present invention to provide a nickel-hydrogen compound battery having a capacity.

[0009]

The present invention provides a nickel-hydrogen compound battery having a positive electrode containing nickel, a negative electrode containing a hydrogen storage alloy, a separator interposed between both electrodes, and an electrolytic solution. Is a synthetic resin perforated plate having a large number of through holes, and a synthetic resin non-woven fabric disposed on both sides of the perforated plate.
It is in a hydrogen compound battery.

What is most noticeable in the present invention is that the separator is composed of a synthetic resin porous plate and synthetic resin nonwoven fabrics arranged on both front and back surfaces thereof.
The porous plate and the non-woven fabric preferably have alkali resistance because the electrolyte is alkaline.

The synthetic resin used for the porous plate is preferably one or more selected from the group consisting of polypropylene, modified polyphenylene ether (PPE) and polyether sulfone. In this case, there is an effect that the alkali resistance is excellent and the initial performance can be maintained for a long time.

The through hole of the perforated plate has a hole diameter of 1 to 2
It is preferably mm. If it is less than 1 mm, it is difficult to sufficiently retain the electrolytic solution. On the other hand, if it exceeds 2 mm, there is a possibility that the problem of not being able to achieve the purpose of maintaining the distance between the electrodes against the expansion of the electrodes may occur. The thickness of the perforated plate is preferably 0.1 to 0.2 mm.
If it is less than 0.1 mm, there is a possibility that the problem that the electrolyte holding space is small may occur. On the other hand, when it exceeds 0.2 mm, there is a possibility that there is a problem that it is not preferable in terms of improvement of the volume energy density.

The synthetic resin used for the non-woven fabric is preferably one or more selected from the group consisting of polyolefin and polypropylene. The porous plate and the non-woven fabric are preferably joined by heat fusion, an adhesive or the like. As a result, there is no separation between the two.

[0014]

FUNCTION AND EFFECT In the nickel-hydrogen compound battery of the present invention, the separator comprises the porous plate as described above and the non-woven fabric arranged on both surfaces thereof. The through hole of the perforated plate is surrounded by the non-woven fabric, and the electrolytic solution is retained in the through hole.

Therefore, even if the positive electrode expands due to repeated charging and discharging, the thickness of the porous plate at the center of the separator does not change. Therefore, even if the nonwoven fabrics on both sides of the porous plate are compressed by the expansion of the positive electrode, the through holes in the porous plate do not change at all, and the capacity is maintained as it is. Therefore, the amount of electrolyte retained in the separator hardly changes.

Further, due to the presence of the porous plate, the distance between the positive electrode and the negative electrode is kept at least equal to or larger than the thickness of the porous plate. Therefore, a minute short circuit does not occur between the positive electrode and the negative electrode. Therefore, an excellent battery capacity can be maintained.

As described above, according to the present invention, even if the charge and discharge are repeated, the amount of the electrolytic solution retained in the separator is hardly reduced, and a minute short circuit between the positive electrode and the negative electrode does not occur, and an excellent battery capacity is obtained. A nickel-hydrogen compound battery having the same can be provided.

[0018]

【Example】

Example 1 A nickel-hydrogen compound battery according to an example of the present invention will be described with reference to FIGS. As shown in FIG. 3, the nickel-hydrogen compound battery of this example includes a positive electrode 91 containing nickel, a negative electrode 92 containing a hydrogen storage alloy, a separator 10 interposed between both electrodes, an electrolytic solution (not shown). )
Have and. As shown in FIGS. 1 and 2, the separator 10 is composed of a synthetic resin porous plate 1 provided with a large number of through holes 11, and a synthetic resin nonwoven fabric 2 arranged on both sides of the porous plate 1.

The through holes 11 of the porous plate 1 are surrounded by the nonwoven fabrics 2 arranged on both sides of the through holes 11. Further, the contact surface between the plate portion 13 of the perforated plate 1 not provided with the through holes 11 and the nonwoven fabric 2 is heat-sealed as described later. Therefore, the porous plate 1 and the nonwoven fabric 2 are integrally formed to form the separator 10. Further, the positive electrode 91, the separator 10 and the negative electrode 92 are wound as shown in FIGS. 7 and 8 and placed in a battery case, and an electrolytic solution is injected to form a nickel-hydrogen compound battery.

In the nickel-hydrogen compound battery of this example, even if the positive electrode 91 expands due to repeated charging and discharging,
The perforated plate 1 in the separator 10 serves as a core material, and its thickness does not change at all. Therefore, even if the nonwoven fabric 2 is compressed due to the expansion, the through holes 11 in the porous plate 1 do not change at all, and the capacity is maintained as it is.

Therefore, the amount of the electrolytic solution held in the separator 10 hardly changes. Further, due to the presence of the porous plate 1, the distance between the positive electrode 91 and the negative electrode 92 is kept at least equal to or larger than the thickness of the porous plate 1. Therefore, a minute short circuit does not occur between the positive electrode 91 and the negative electrode 92.
Therefore, excellent battery capacity can be maintained.

Example 2 In this example, a charging / discharging test of the specific example of the nickel-hydrogen compound battery shown in Example 1 is shown together with a comparative example.
In the nickel-hydrogen compound battery of this example, the positive electrode 91
Is a known nickel sintered plate.

The negative electrode 92 was manufactured as follows. That is, first, Mm (Misch metal) -Ni-Al-Co-
A Mn-based MH alloy was used as a hydrogen storage alloy. This hydrogen storage alloy was mechanically pulverized into a powder of 100 mesh or less, and the powder was electroless copper plated. The amount of copper plating was 10% with respect to 100% of the powder (weight ratio, the same applies hereinafter).

15% of the above copper plating powder was added to 5% -PT
An aqueous FE (polytetrafluoroethylene) dispersion solution was added and kneaded to form a sheet. This sheet was sandwiched between nickel expands and pressure-bonded with a pressure of 300 kg / cm ² to produce a negative electrode 92. The negative electrode 92 has a thickness of 0.
The length is 6 mm, the width is 33 mm, and the length is 220 mm.

As the separator 10, a separator made of a perforated plate 1 made of polypropylene (PP) and a polypropylene short fiber non-woven fabric 2 on both sides of which the surfaces were lightly fused was used. The perforated plate 1 had a thickness of 0.1 mm, and 25 rectangular through holes 11 of 1 × 1 mm per 1 cm ² were punched and punched.

The PP porous plate 1 had a tensile strength of 700 kg / cm ² or more. On the other hand, non-woven fabric 2
Had a weight of 40 g / m ² and a thickness of 0.1 mm. The width and length of the positive electrode 91 are almost the same as those of the negative electrode 92, while the separator 10 is slightly larger than these.

The polypropylene used for the porous plate 1 and the nonwoven fabric 2 contains a small amount of polyethylene. As a result, the polyethylene acts as a bonding agent during heat fusion, and the heat fusion between the porous plate 1 and the nonwoven fabric 2 can be easily performed without causing deformation.
Note that an acrylic resin may be mixed in place of the polyethylene. Further, the porous plate 1 and the non-woven fabric 2 can be bonded together by using an alkali resistant adhesive other than the above heat fusion.

As the electrolytic solution, IN (normative) L
An iOH-5N.KOH aqueous solution was used. Then, the positive electrode 91, the separator 10 and the negative electrode 92 were combined with each other and an electrolytic solution was injected to form a cylindrical sealed nickel-hydrogen compound battery (see FIG. 6).

On the other hand, a comparative nickel-hydrogen compound battery was constructed using a polypropylene non-woven fabric as a separator. The non-woven fabric has a weight of 72 g / m ² and a thickness of 0.19.
mm. The positive electrode, the negative electrode, the electrolytic solution, etc. are the same as those of the nickel-hydrogen compound battery according to the above-mentioned embodiment.

Next, a charge / discharge cycle test was conducted using the nickel-hydrogen compound batteries of the present example and comparative example described above. This test is 120 ° C at 0.3 ° C at 50 ° C.
The charging and discharging were repeated under the conditions of% charge, 0.3 C discharge, and cut voltage 0.9 V.

The results are shown in FIG. 4 with the horizontal axis representing the number of charge / discharge cycles (times) and the vertical axis representing the discharge capacity ratio (%). The above test results are average values of three nickel-hydrogen compound batteries. Here, the discharge capacity ratio means the ratio of the discharge capacity in each charge / discharge cycle when the discharge capacity at the 10th charge / discharge cycle is 100%.

As is known from FIG. 4, the nickel-hydrogen compound battery of this example has a high discharge capacity even after 650 cycles of charging and discharging. On the contrary,
The conventional comparative nickel-hydrogen compound battery is 450
It can be seen that the discharge capacity drops sharply from near the cycle.

Further, when the nickel-hydrogen compound battery was disassembled and observed after the above test, in the comparative example in which the capacity deterioration occurred, almost no electrolytic solution remained in the separator. On the other hand, in the nickel-hydrogen compound battery of this example, a considerable amount of the electrolytic solution remained in the separator. From this, it is understood that the capacity deterioration of the comparative battery is caused by the dryout of the electrolytic solution.

It is considered that the reason why the electrolytic solution in the separator is extruded is that the positive electrode expands as the activation progresses and the separator receives a pressure higher than that at the time of winding. Another reason is that the positive electrode becomes easier to suck up the electrolytic solution in the separator as the activation progresses. In the battery of the comparative example, no measures are taken against this pressure, but in the case of this example, the porous plate is relatively hard, so that it resists the pressure from the electrode and retains the electrolytic solution. To maintain. Therefore, the nickel-hydrogen compound battery of this example has an excellent battery capacity.

Next, 100 nickel-hydrogen compound batteries were prepared for each of the present embodiment and the comparative example. Then, each of the above charging and discharging is performed 20 times,
It was confirmed whether or not there was a minute short circuit thereafter. as a result,
In the nickel-hydrogen compound battery of this example, there was no occurrence of micro short circuit. On the other hand, in the comparative example, a minute short circuit occurred in 4 out of 100 pieces.

The reason is considered as follows. That is, as described above, when the positive electrode, the separator, and the negative electrode are wound, tension is applied to the separator to ensure the winding. However, the separator of the comparative example does not have sufficient mechanical strength because it is made of only nonwoven fabric.
Therefore, it is considered that the separator partially expands during the above-mentioned winding to reduce the thickness, and the positive electrode and the negative electrode come close to each other to cause a minute short circuit. On the other hand, since the separator of this embodiment uses the perforated plate, it hardly expands during the winding. Therefore, the minute short circuit does not occur.

[Brief description of drawings]

FIG. 1 is a perspective view of a separator according to a first embodiment.

FIG. 2 is a cross-sectional view of the separator according to the first exemplary embodiment.

FIG. 3 is a cross-sectional view of a combined state of a positive electrode, a separator and a negative electrode in Example 1.

FIG. 4 is a diagram of a charge / discharge cycle test in Example 2.

FIG. 5 is a perspective view of a positive electrode, a separator, and a negative electrode in a conventional example.

FIG. 6 is an explanatory view of a nickel-hydrogen compound battery in a conventional example.

FIG. 7 is a perspective view showing a state before winding a positive electrode, a separator, and a negative electrode in a conventional example.

FIG. 8 is an explanatory diagram showing (A) a combination state of a positive electrode, a separator, and a negative electrode, and (B) a problem thereof in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Perforated plate, 10 ... Separator, 11 ... Through hole, 2 ... Nonwoven fabric, 91 ... Positive electrode, 92 ... Negative electrode,

Claims (6)

[Claims] 1. A nickel-hydrogen compound battery comprising a positive electrode containing nickel, a negative electrode containing a hydrogen storage alloy, a separator interposed between both electrodes, and an electrolytic solution, wherein the separator has a plurality of penetrating holes. A nickel-hydrogen compound battery comprising a perforated plate of synthetic resin having holes, and a non-woven fabric of synthetic resin arranged on both sides of the perforated plate. 2. The nickel-hydrogen compound according to claim 1, wherein the synthetic resin used for the porous plate is at least one selected from the group consisting of polypropylene, modified polyphenylene ether (PPE) and polyether sulfone. battery. 3. The nickel-hydrogen compound battery according to claim 1, wherein the through hole of the porous plate has a hole diameter of 1 to 2 mm. 4. The method according to claim 1, wherein
The nickel-hydrogen compound battery, wherein the porous plate has a thickness of 0.1 to 0.2 mm. 5. The method according to any one of claims 1 to 4,
The nickel-hydrogen compound battery, wherein the synthetic resin used for the non-woven fabric is one or more selected from the group of polyolefin and polypropylene. 6. The method according to any one of claims 1 to 5,
A nickel-hydrogen compound battery, wherein the porous plate and the non-woven fabric are bonded together.