JPH05326014A - Sealed square alkaline storage battery - Google Patents

Abstract

PURPOSE:To lower the inner resistance while retaining the advantages of an alkaline storage battery by forming a water repelling layer on the surface of a negative electrode. CONSTITUTION:A sealed alkaline storage battery is provided with electricity generating elements consisting of a positive electrode plate 4, a negative electrode plate 6, and a separator 5 which insulates the positive electrode 4 and the negative electrode 6 electrically, contains an electrolytic solution necessary for charge-discharge reaction, has proper space inside, and is chemically stable against alkali. The outer most sides in right and left of the electrode group of the electricity generating elements are composed of the negative electrode plate 6 and at the same time water repelling layer of fluororein, etc., is formed on the negative electrode plate 6 except the outside electrode faces of the negative electrode plate 6 in the right and left outer most sides. The outside electrode faces of the negative electrode plate in the right and left outer most sides directly touch a metal case 1 and the positive pole plate 4 is connected with a cover 2 made of a metal through a lead 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prismatic sealed alkaline storage battery, and more particularly to a prismatic sealed alkaline storage battery using hydrogen in a hydrogen storage alloy as an active material of a negative electrode.

[0002]

2. Description of the Related Art In recent years, various portable electronic devices such as AV devices and communication devices, which have become extremely popular, are becoming more and more compact and lighter and thinner. However, there is an increasing demand for higher energy density. In many cases, a sealed alkaline storage battery is mainly used as the power source, and there is a strong demand for the power source battery to have a high capacity density and space saving.

At present, a battery system that represents a sealed alkaline storage battery is a nickel-cadmium storage battery, and in order to meet these demands, this battery system has been rapidly increased in capacity in recent years. For the purpose of space saving,
Nickel-cadmium storage batteries whose outer shape has changed from a general cylindrical shape to a rectangular shape have also begun to be marketed.

The shape of the battery storage portion in various portable devices is often a rectangular parallelepiped space, and when a cylindrical battery is stored in this space and used, an extra space that cannot be used between adjacent batteries is used. Occurs. On the other hand, if a prismatic battery is used, almost no extra space is needed. Therefore, when a suitable prismatic battery is used, the mounting space can be reduced by about 30% as compared with the cylindrical battery.

The prismatic battery is also
It can be easily made smaller than a cylindrical battery, and is suitable for devices that require a thin battery storage space. From this point of view, nickel-cadmium storage batteries have begun to be put into practical use, but if the capacity density is to be further improved, a new battery system that uses a material that is expected to have a higher energy density than nickel-cadmium storage batteries Development is important.

Recently, since a hydrogen storage alloy negative electrode capable of storing hydrogen at a high density has a higher energy density than a cadmium electrode, attention has been paid to the development of a high capacity density metal oxide-hydride storage battery using the same. There is. Therefore, by applying this battery system to a prismatic battery, a battery with high capacity and high space efficiency has been developed. However, when it is applied to a power source for portable devices in recent years, it is strongly required to have higher charging efficiency and quick charging performance. In order to develop a new prismatic battery of a new battery system using a hydrogen storage alloy, it is necessary to add new battery construction methods and manufacturing methods of constituent materials in addition to the conventional battery construction technology to meet these needs. .. For that purpose, for example, the following two technical problems must be solved. 1) Problems Related to Negative Electrode Current Collection System In the case of a prismatic battery having high charging efficiency, it is preferable to stack a plurality of positive and negative electrodes to form an electrode plate group. However, when a lead for collecting current is welded to the hydrogen storage alloy electrode, there is a safety problem such as ignition by heat of the welded portion. In particular, when hydrogen is occluded in the alloy electrode, it tends to ignite more easily. In addition, if you take out the lead from the negative electrode one by one, weld them at one place and press the negative electrode outside the group and the outer metal case into pressure contact to collect current, the current can be applied to one welding point. Are concentrated, the electrical resistance is increased, and the internal resistance value of the battery is increased. As a result, the discharge performance is deteriorated especially at a high rate discharge. 2) Issues in performing rapid charging When charging with a large current of about 1 C for rapid charging, oxygen gas is generated from the positive electrode at the end of charging and the hydrogen storage rate of the negative electrode hydrogen storage alloy is insufficient. The internal pressure of the battery rises due to the generation of free hydrogen. In the case of a prismatic battery where the side surface of the sealed container is flat compared to the cylindrical shape,
The case is easily deformed by the internal pressure, and the metal container reaches the yield point at a low pressure. Therefore, the allowable battery internal pressure depends on the yield point of the container, specifically about 12 kg / cm ² , and the increase in the battery internal pressure must be suppressed below that.

In order to solve these problems, the present applicant has proposed a sealed alkaline storage battery in which a power generating element is first housed in a rectangular metal case and the case is sealed with a metal lid provided with a safety valve. A rectangular positive electrode plate composed of an active material mainly composed of a metal oxide, a hydrogen storage alloy powder and a conductive support as main constituent materials, and a water repellent composed of fluororesin, petroleum pitch, polybutene, etc. on the electrode surface. A rectangular negative electrode plate provided with a layer, an alkaline electrolyte, electrically insulates the positive electrode and the negative electrode, and has the above-mentioned electrolytic solution and a proper space necessary for the charge and discharge reaction inside, and with respect to alkali It comprises a power generating element consisting of a chemically stable separator, the left and right outermost parts of the electrode group in this power generating element are constituted by the negative electrode plate and are in direct contact with the metal case, and the positive electrode plate is through a lead, Metal lid It proposed a prismatic sealed alkaline storage battery which is connected to a terminal provided with insulating.

The formation of the water repellent layer on the electrode surface of the negative electrode plate is usually carried out by applying a fluororesin powder.

[0009]

However, it has been found that the alkaline storage battery having the above structure has a larger internal resistance than the conventional alkaline storage battery.

An object of the present invention is to provide a prismatic sealed alkaline storage battery with reduced internal resistance while maintaining the advantages of the alkaline storage battery proposed above.

[0011]

[Background of the Solution to the Problem and Means for Solving the Problem] The inventors of the present application have earnestly studied the problem that the internal resistance becomes large, and as a result, It was found that the electrical contact between the metal case and the outermost negative electrode plate is hindered by the influence of the water repellent layer formed on the negative electrode, which is a fluororesin having poor conductivity.

The present invention is based on the above findings,
A sealed alkaline storage battery in which a power generating element is housed in a rectangular metal case and the case is sealed with a metal lid provided with a safety valve, wherein a rectangular positive electrode plate composed of an active material mainly containing a metal oxide, and hydrogen. A rectangular negative electrode plate containing a storage alloy powder and a support having conductivity as a main constituent material, an alkaline electrolyte, and the positive electrode and the negative electrode are electrically insulated from each other, and the electrolytic solution necessary for a charge-discharge reaction. It has a power generating element having a suitable space inside and a separator that is chemically stable against alkali, and the left and right outermost sides of the electrode group in this power generating element are constituted by the negative electrode plate, The negative electrode plate has a water-repellent layer formed on the electrode surfaces except for the outer electrode surfaces of the left and right outermost negative electrode plates, and the outer electrodes of the left and right outermost negative electrode plates are formed. The surface is in direct contact with the metal case and the positive plate is the lead Through it, the metallic lid is characterized in that it is connected to a terminal provided with insulating.

As the water-repellent material, a fluororesin-based material,
It is desirable to use petroleum pitch or polybutene.

[0014]

By providing a water repellent layer on the surface of the negative electrode, a gas-liquid-solid three-phase interface is widely formed on the surface of the negative electrode, and the oxygen gas generated during overcharge and the occlusion reaction are delayed from the positive electrode. The hydrogen gas liberated from the negative electrode was promptly guided to the electrode surface for reaction, and the reaction of returning to water was promoted, and the rise in internal pressure during rapid charging could be suppressed. In addition, since the water repellent layer was not provided on the outer electrode surface of the outermost negative electrode plate, the electrode was brought into direct contact with the metal case, thus reducing the internal resistance of the battery.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A prismatic sealed alkaline storage battery according to a preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

An example of the prismatic nickel-hydrogen battery will be described. 1A, 1B, 1C show a prismatic sealed alkaline storage battery according to an embodiment of the present invention, in which 1 is an outer metal case, 2 is a metal lid, 3 is a positive electrode terminal, 4 is a positive electrode,
Reference numeral 5 denotes a bag-shaped separator including a positive electrode, 6 denotes a U-shaped negative electrode, and 7 denotes a positive electrode lead.

The negative electrode 6 is manufactured as follows. First, about 40 wt% of cerium, about 30 wt% of lanthanum, and about 13 wt% of neodymium, misch metal (Mm), nickel, cobalt, aluminum, and manganese in atomic ratios of 1: 3.5: 0.8: 0, respectively. ．
After mixing so as to have a ratio of 3: 0.4, the mixture is melted in a high-frequency melting furnace in an inert gas atmosphere, transferred to a container provided with a cooling device with stirring, and rapidly cooled. The obtained alloy ingot is coarsely pulverized by mechanical means. Then, the alloy is placed in argon for 10
When heated to 50 ° C. and kept for 3 hours, a hydrogen storage alloy having an SF value of 2.5 or less can be obtained. Re-mill the alloy 3
The powder is 7 μm or less. Further, this powder is dipped in a potassium hydroxide aqueous solution (7N) at 80 ° C. for 30 minutes, washed with water and dried to obtain an alloy powder having innumerable irregularities in a portion of about 0.01 μm thickness near the surface layer.

0.5 wt% of polyvinyl alcohol was added to the obtained hydrogen storage alloy and kneaded into a paste with water to form a foamed nickel porous body (porosity about 98%, thickness about 0.7 mm, average spherical space). (Diameter 400 μm), dried, pressed, and then cut to obtain a negative electrode 6 shown in FIG. 4 having a negative electrode lead 8 which is a portion not filled with an active material in the central portion.
Further, a predetermined weight of fluororesin fine powder is uniformly applied to the surface of the negative electrode. Here, what is particularly important is to prepare two sheets of one battery, one of which is not coated with the fluorine resin fine powder on one electrode surface. The alloy composition is not particularly limited to the above composition. In use, a flat PTC curve is desirable, and the above SF value is 0.25 or less, and the alloy composition is
In the general formula Mm _1-X M _1X Ni _Y M _2Z , Mm is misch metal, M ₁ is any _one of Ca, Ti, Zr elements or a mixture thereof, and M ₂ is Co, Al, M
One or a combination of elements selected from the group consisting of n, Cu, Cr, Fe and V, and 1> x ≧ 0, y>
Those satisfying 3.0 and 4.7 ≦ y + z ≦ 5.3 are desirable. There is no problem with the surface roughening treatment of the alloy as long as it is a method for forming fine irregularities on the alloy surface, such as etching treatment with an acid, etching treatment with an acid or salt, or etching treatment with a physical method. Further, as the support of the alloy powder, a foamed nickel porous body having a three-dimensional network structure was used, but any support that has a three-dimensional network structure like metal fibers and alkali resistance can be used. Can also be used. Further, although the fluororesin is used for the water repellent treatment on the surface of the negative electrode, a polyolefin resin may be used in addition to this, and treatment with another substance having water repellency is also intended by the present invention. Further, the shape of the water-repellent resin is not limited to a granular shape as long as it can impart water repellency to the surface of the negative electrode.

In forming the lead portion 8 in the negative electrode 6, a portion not filled with the active material was formed by mechanical pressure prior to filling the active material into the porous body. There is no problem in forming the negative electrode lead portion by masking the unfilled portion or filling the active material and then removing the active material in that portion by some method.

The positive electrode 4 was prepared by mixing 100 parts by weight of nickel hydroxide powder with 6 parts by weight of cobalt oxide and 3 parts by weight of metallic cobalt, and adding water to the mixture to knead it to form a paste. , Foamed nickel porous body (porosity 98%,
Filled to a thickness of 0.7 mm and an average spherical space diameter of 400 μm,
After drying, pressure is applied to produce a metal foam nickel positive electrode 4.

A nickel lead 7 for current collection is spot-welded to the positive electrode 4, and a separator 5 having a thickness of 0.22 mm in which a sulfone group is introduced into a polypropylene non-woven fabric is welded in a bag shape and wrapped in the state shown in FIG. .. In this example, a mixture of nickel oxide as a main component and nickel added as the positive electrode active material was used, but other metals, such as manganese, can be used as long as they are metal salts capable of performing a redox reaction in an alkaline aqueous solution. It can be used as an additive.

Two U-shaped negative electrodes 6 and three positive electrodes 4 are used to form the electrode plate group shown in FIG. At this time, the left and right outermost electrodes of this electrode group are arranged such that the negative electrode 6 having no water-repellent layer formed on the one electrode surface 6a faces outward, that is, this electrode surface 6a faces outward. When the group is inserted into the outer metal case 1 as described later, the electrode surface 6a comes into direct contact with the inner surface of the outer metal case 1 which acts as a current collecting element for the negative electrode. Thereby, the electrical connection between the negative electrode 6 and the exterior metal case 1 becomes good. Reference numeral 8 in the drawing denotes a negative electrode lead that forms a bottom when bent. This electrode plate group is housed in the exterior metal case 1. Next, a nylon vacuum body 22 with an oxygen-reducing catalyst inserted therein is inserted into the upper portion of the electrode plate group.

Any material can be used as the material of the wax body 22 as long as it has alkali resistance and electric insulation, and for example, polypropylene, polyethylene, polyvinyl chloride, fluororesin, etc. can be used. Further, as the oxygen-reducing catalyst, in the present embodiment, a carbon carrier was used to carry palladium, and a water-repellent treatment with Teflon resin was used, but the carrier can be used without any problem as long as it has alkali resistance. For example, alumina, magnesia, zirconia, sintered nickel porous body, etc. can be used. As the catalyst, a platinum group catalyst other than palladium can be used, and as the water repellent treatment method, a paraffin treatment, a silicone water repellent treatment agent, or the like can be used in addition to the fluororesin.

The lid 2 is manufactured as follows (see FIGS. 5A, 5B and 5C). First, a nickel-plated steel plate is cut into a rectangle of 5.2 × 16.5 mm, and a hole of 3 mm is opened in the center to form a washer 13 portion. Next, a nylon resin is molded to form an upper gasket 12 and a lower gasket 1.
Get 4. Separately from this, a nickel-plated steel plate is punched with a die to obtain the cap 9 and the positive electrode current collecting washer 15.

Next, rubber is molded to obtain the valve body 10. Then, prone asphalt as a water-repellent material is applied to the top and bottom of the opening of the washer 13, and the upper gasket 12 and the lower gasket 14 are stacked from above and below. Further upper gasket 1
Pron asphalt is applied to the hole 2 and the hollow rivet 11 having a seat substantially corresponding to the recessed shape of the washer is inserted. Further, the positive electrode current collecting washer 15 is inserted from the lower part, and the whole is pressed in the vertical direction to expand and crimp the leg tips of the hollow rivet. Next, after applying polypten as a liquid sealant to the hollow rivet hole portion, the rubber valve body 10 is placed on the hollow rivet hole, and the cap 9 and the seat of the hollow rivet 11 are spot-welded while pressing the cap 9 from above. A lid is obtained by the above processing. In this embodiment, the upper and lower gaskets are made of nylon, but any of polyethylene resin, polypropylene resin, and fluororesin may be used. Further, as the water repellent material, pron asphalt and polypten were used, but other petroleum pitches and fluororesins can be used without any problem. The tip of the positive electrode lead 7 extending upward from the previously prepared electrode plate group was spot-welded to the positive electrode current collecting washer 15 of the lid thus obtained, and a small amount of lithium hydroxide was added to the potassium hydroxide aqueous solution. 1.5 ml of the electrolytic solution is injected, the lid and the mouth of the metal outer case 1 are fitted together, and this portion is sealed with a laser seam welder.

The prismatic sealed alkaline storage battery of FIG. 1 is manufactured as described above. Experimental Example Next, in order to confirm the effect of the present invention, an experiment as described below was conducted.

The positive electrode has the above structure and a width of 1
4.5, height 37.5 (filling part = 36), thickness 0.56
mm, capacity 180 mAh, three positive electrodes were prepared, and total capacity was 540 mAh.

The negative electrode has the above structure and a width of 15 mm.
The height was 75 mm, the thickness was 0.46 mm, and two pairs of pieces folded at the central unfilled portion were prepared. Total capacity is 1000m
Ah. The surface of the negative electrode is coated with fluorine resin fine powder, and depending on the amount and the portion to be coated, A to G is applied.
A variety of negative electrodes were created.

The separator has a thickness of 0.15 mm,
A non-woven fabric made of polypropylene having a basis weight of 66 g / m ² and having the above structure was used, whereby the positive electrode was wrapped in a bag as described above.

The above electrode plate constituent materials were inserted into a predetermined metal case, an electrolytic solution containing potassium hydroxide as a main component was injected, and a sealing plate was attached to form a battery. Further, the batteries are classified into A to G corresponding to the types A to G of the negative electrodes inserted in the battery. Table 1 shows the classification of batteries and the contents of the negative electrodes.

The batteries A to G thus obtained were charged at a current of 500 mA for 5 hours, the pressure rise inside the batteries at that time was measured, and then the final voltage of 1.0 V was applied at a current of 500 mA.
Discharged up to.

After the discharge was completed, the internal resistance of the battery was measured.
The results are shown in Table 2. As is clear from the results shown in FIGS. 6 and 7 and Table 2, in the battery in which the fluorine resin is uniformly applied to the entire surface of the negative electrode plate, the internal pressure of the battery decreases as the amount of application increases, but the internal pressure of the battery decreases. The resistance rises, especially when the negative electrode plate surface is coated with 1.2 mg / cm ² and the internal resistance is 58 mΩ.
And the discharge voltage dropped to 1.191V. On the other hand, a battery in which the surface of the negative electrode plate, excluding the case contact surface, is uniformly coated with fluorine resin is similar to a battery in which the entire surface of the negative electrode plate is coated with fluorine resin. The rise of is small and suppressed. It is presumed that this is due to the effect of keeping good electrical conductivity between the negative electrode and the metal case because the fluorine resin was not applied to the surface of the negative electrode plate in contact with the case.

Regarding the rapid charging performance, by appropriately adjusting the amount of the electrolytic solution, a proper gas-liquid-solid three-phase interface is secured in the separator and on the surface of the negative electrode, and the negative electrode surface is treated to be water repellent. As a result, the effect was further improved, and by providing a catalyst for reacting free hydrogen with oxygen generated from the positive electrode, it was possible to satisfactorily eliminate the gas and prevent the deformation of the case.

[Brief description of drawings]

1A, 1B, 1C are perspective views of a battery according to an embodiment of the present invention and cross-sectional views taken along line BB ′ and line CC ′ of FIG.

FIG. 2 is an enlarged perspective view showing a configuration of an electrode plate group in the above embodiment.

FIG. 3 is a view showing a positive electrode wrapped with the separator.

FIG. 4 is a diagram showing a negative electrode before being folded in two.

5A, 5B, and 5C are a perspective view, a cross-sectional view, and a component diagram of a lid body according to an embodiment.

FIG. 6 is a graph showing the relationship between the coating state of fluororesin on the electrode surface of the negative electrode and the internal resistance of the battery.

FIG. 7 is a graph showing the relationship between the coating state of fluororesin on the electrode surface of the negative electrode and the internal pressure of the battery.

[Explanation of symbols]

 1 Exterior Metal Case 2 Lid 3 Positive Electrode Terminal 4 Positive Electrode 5 Separator 6 Negative Electrode 7 Positive Electrode Lead 8 Negative Electrode Lead

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Tsuda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A power generating element is housed in a rectangular metal case,
A sealed alkaline storage battery in which the case is sealed with a metal lid provided with a safety valve, a rectangular positive electrode plate made of an active material mainly containing a metal oxide, a hydrogen storage alloy powder, and a support having conductivity. A rectangular negative electrode plate having as a main constituent material, an alkaline electrolyte, and electrically insulates the positive electrode and the negative electrode,
It has a power generation element consisting of a separator that is chemically stable against alkali and has the above-mentioned electrolytic solution necessary for charge / discharge reaction and an appropriate space inside, and the left and right outermost sides of the electrode group in this power generation element are Along with the negative electrode plate,
In the negative electrode plate, a water repellent layer is formed on the electrode surfaces except for the outer electrode surfaces of the left and right outermost negative electrode plates,
The outer electrode surfaces of the left and right outermost negative electrode plates are in direct contact with the metal case, and the positive electrode plate is connected via leads to terminals provided so as to be insulated from the metal lid. The feature is a prismatic sealed alkaline storage battery. 2. The prismatic sealed alkaline storage battery according to claim 1, wherein the water repellent material is selected from the group consisting of fluororesin, petroleum pitch, and polybutene.