JP2003229122A - Sealed metal oxide and hydrogen storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize high capacity and lightweight in a sealed storage battery using a metal oxide and a hydrogen storage alloy for use as a mobile power supply or the like. <P>SOLUTION: This is a sealed metal oxide-hydrogen storage battery and comprises a positive electrode having a metal oxide and a negative electrode having a hydrogen storage alloy, a separator, an alkaline electrolyte, a lid with a safety valve, and a battery case. The positive electrode contains either one or more kinds out of the group of yttrium oxide and a rare earth oxide and 0.05-3.0 wt.% of Co to the metal oxide is dissolved as a solid solution in the crystals of the metal oxide. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention uses a high-capacity, lightweight positive electrode using a metal oxide and a high-capacity, low hydrogen equilibrium pressure hydrogen storage alloy negative electrode, and is excellent in charging characteristics and reliability at high temperatures. Closed metal oxide / hydrogen storage battery.

[0002]

2. Description of the Related Art An electrode using a hydrogen storage alloy that reversibly absorbs and releases hydrogen at room temperature and atmospheric pressure is a cadmium electrode that has been known for a long time in terms of charge and discharge and energy density. Due to its superiority, it has attracted attention as a new negative electrode for alkaline storage batteries.

In particular, for the last 10 years, research and development in the battery industry has been extremely active, and as a result of research and development, it has been commercialized as a high-capacity secondary battery and used in various portable electronic devices in earnest. began.

This is a small sealed battery mainly represented by a cylindrical sealed type, which is a nickel-hydrogen storage battery using nickel oxide for the positive electrode and a hydrogen storage alloy for the negative electrode.

The structure is such that both plate electrodes of the nickel positive electrode and the hydrogen storage alloy negative electrode are spirally formed with a resin separator interposed therebetween, and then inserted into a metal cylindrical can, and then a safety valve is provided. The structure in which the lid is closed is common.

The nickel positive electrode is formed by impregnating a nickel sintered substrate, which is generally used in nickel-cadmium batteries, with a nickel salt solution, and then converting it into a hydroxide electrode, or a nickel hydroxide. The powder used as the main material is made into a paste with a small amount of additives such as cobalt and cobalt oxide, filled into a highly porous electrode substrate made of three-dimensional sponge nickel, and then dried and pressure-molded. Electrodes (hereinafter referred to as SME type, which are disclosed in U.S. Pat. Nos. 4,251,603, 4,935,318, and JP-A-62-290019). .

On the other hand, the hydrogen storage alloy negative electrode is an LnNi ₅ system (Ln is a rare earth metal (La, La, atomic number 57 to 71).
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
(y, Ho, Er, Tm, Yb, Lu) or a mixture thereof, a powder of a hydrogen storage alloy of misch metal (hereinafter referred to as Mm)), which is filled in a substrate made of a three-dimensional sponge-like nickel porous body. (U.S. Pat. No. 4,935,31
No. 8 specification. ) Or an electrode coated with a binder on a two-dimensional perforated plate or a powder of Ti-based TiNi-based alloy (disclosed in US Pat. No. 4,849,205). There is known an electrode coated with a binder on a metal plate and an electrode to which an operation of sintering after coating is applied. As another hydrogen storage alloy material,
There is also a proposal that a ZrNi-based alloy based on Zr is also a promising material in terms of high capacity (US Pat. No. 4,946,664).
No. 6 specification. ).

These negative electrodes are used in combination with any one of the above-mentioned positive electrodes and wound in a spiral shape through a separator. The capacity of the negative electrode is generally larger than that of the positive electrode.

As the separator material, it is usual to use a non-woven fabric made of a polyamide resin fiber which is generally used in nickel-cadmium batteries, but it has been subjected to a sulfonation treatment which is extremely effective in reducing self-discharge. The adoption of a non-woven fabric made of polyolefin resin fibers has already been proposed. (It is disclosed in U.S. Pat. No. 4,937,119 and Japanese Patent Application Laid-Open No. 64-57568). As the electrolytic solution, an aqueous caustic potash solution similar to that used in nickel-cadmium batteries is mainly used. .

In this battery system, when the hydrogen partial pressure in the battery drops below the hydrogen equilibrium pressure of the hydrogen storage alloy used, the hydrogen storage alloy releases hydrogen gas. Electrolyte decreases due to escape,
It causes deterioration of battery performance and increase of self-discharge.

Therefore, a sealed battery having a safety valve is constructed. The operating pressure of the safety valve of this battery is to increase the internal pressure of the battery due to oxygen and hydrogen gas during overcharge, and to increase the internal pressure of the battery due to the increase in hydrogen gas equilibrium pressure of the hydrogen storage alloy due to the temperature increase accompanying the reaction of oxygen and hydrogen gas. It is decided in consideration of such things.

The batteries that have been proposed so far are mainly small-sized, cylindrical, sealed batteries, and have excellent pressure resistance of the battery case and the sealing portion. Therefore, it is possible to adopt a high operating pressure of the safety valve that can maintain the sealing even when overcharging with a large current such as 1 C (the battery is charged at an hour rate). It is used by setting it to 10 to 30 kg / cm ² . This is also due to the excellent heat dissipation of small batteries.

The above is the outline of the prior art of the small nickel-hydrogen storage battery which has already been put into practical use.

[0014]

Recently, however, there has been a strong demand for a battery having a large capacity and a high power density for mobile power sources such as home electric appliances and electric vehicles, which has high energy density and high reliability.

In response to this demand, the metal oxide / hydrogen storage battery is considered to be a promising battery system. Considering economy, nickel oxide and manganese oxide are suitable as metal oxides. Among these, nickel-hydrogen storage batteries using nickel oxide have been reported to be trial-produced, but medium-capacity batteries (below Capacity is defined as 10 Ah to 100 Ah) and large capacity battery (hereinafter capacity is 100 Ah)
Defined as above. With regard to ()), there are currently few proposals for specific battery configurations.

Therefore, nickel-hydrogen storage battery is taken up as a battery system representing a metal oxide-hydrogen storage battery, and many technical problems are required to achieve a medium / large-capacity battery in consideration of characteristics of the small battery in this battery. , Which is explained below.

1. About high energy density and high reliability. Especially when used as a mobile power source, unlike a small battery, the energy density per weight (Wh / kg)
It is important to increase. Therefore, it is important to use a combination of lightweight and high capacity density electrodes. However, in medium- and large-capacity batteries, due to the temperature rise due to poor heat dissipation and the temperature rise in the high temperature atmosphere during use, if the conventional positive electrode is adopted as it is, the charge acceptance is lowered and the desired energy density is reduced. I can't get it.
Further, in order to obtain a highly reliable battery with a long life, it is necessary to improve the electrode structure that prevents the positive and negative electrode materials from falling off more than in a small battery.

2. About the structure of the sealed battery. Unlike small batteries, medium- and large-capacity sealed batteries have a large capacity, so it is difficult to adopt a cylindrical shape due to the manufacturing method.
For this reason, it is preferable to adopt a rectangular shape, but generally, the rectangular shape remarkably reduces the pressure resistance of the battery case. Therefore, it is necessary to make the battery internal pressure lower than before even at the end of charging when the battery internal pressure rises most during normal use. In addition, it is necessary to adopt a structure that makes the sealing of the poles and the like durable.

3. About low self-discharge. It is said that this battery system has extremely large self-discharge as compared with the nickel-cadmium battery. In applications such as mobile power sources where there is a high chance of being used at high temperatures or being left unattended, a battery with a large amount of self-discharge causes a significant decrease in capacity, which may hinder actual use. Therefore, it is necessary to reduce self-discharge.

4. About ensuring safety. Generally, as the capacity and capacity of a battery increase, the risk of heat generation when the positive and negative electrodes are short-circuited and the risk of explosion due to oxygen or hydrogen gas generated in the battery increases. Therefore, it is necessary to develop a battery with high safety by using a battery structure that does not easily cause a short circuit and that does not ignite even if a short circuit occurs or a battery structure that does not allow oxygen or hydrogen gas to come into contact with the fire.

As described above, there are many technical problems to be solved in order to put the nickel-hydrogen storage battery using the hydrogen storage alloy into practical use in a wide range from small capacity to medium and large capacity.

The present invention is intended to solve such a problem, and has high energy density (particularly Wh / kg) and high reliability in a wide temperature range from high temperature to low temperature, and has strength and It is an object of the present invention to provide a sealed metal oxide / hydrogen storage battery that is highly safe in terms of internal gas generation and has low self-discharge.

[0023]

In order to solve the above-mentioned problems, the present invention is designed to increase the energy density per unit weight (Wh / kg). The active material of both the positive electrode and the negative electrode was held on the electrode substrate having a three-dimensional structure.

Also, in order to reduce the temperature rise of the battery,
Co, Cd, Ca, Ag, Mn, Zn, Sr, V, B
The metal selected from the group consisting of a, Sb, Y and rare earth metals is added to the positive electrode active material as a solid solution or an oxide of the above metal as an additive. The rare earth metal here means La, Ce, Pr, Nd, which are well known to those skilled in the art.
Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
Indicates m, Yb, and Lu.

Further, the present invention uses MmNiα (4.5 ≦ α ≦ 5.
In 5), the amount of La in Mm and the amount of Mn and Co substituting for Ni are increased, and in ZrNiβ (1.9 ≦ β ≦ 2.4), the amount of Ti and V substituting for Zr and Ni is increased. Is.

Regarding the alkaline electrolyte, the present invention uses Na
Regarding the amount of OH and LiOH, NaOH is 3.5 mol /
The upper limit is liter, and LiOH is added up to 1.5 mol / liter.

Further, according to the present invention, a polyolefin resin such as polypropylene resin is used as a separator interposed between the positive and negative electrodes, and particularly a polypropylene sulfonated separator is used.

Further, according to the present invention, a safety valve is provided on an exterior body such as a battery lid or a battery case, and the operating pressure of the safety valve is such that the pressure difference between the inside and the outside is in the range of ² to 5 kg / cm ² .

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has the above-described structure. First, since the positive and negative electrodes are made to hold their active materials respectively on the electrode substrate having a three-dimensional structure, unlike the electrode substrate having a two-dimensional structure, it is lightweight and high in its own right. It has retentivity and can achieve high packing density of active material and weight reduction. For example, the metal oxide that is the active material in the positive electrode is preferably composed mainly of a nickel oxide, a manganese oxide, a mixture of these, and a solid solution of both of them, as a main material. The packing density of the oxide powder is preferably 580 mAh / cm ³ or more on average in one-electron reaction between nickel oxide and manganese oxide. In the electrodes, Co, Cd, Ca, Ag, Mn,
By adding a solid solution of any one of Zn, Sr, V, Ba, Sb, Y, a rare earth metal or the like, or an oxide of the above metal as an additive, the oxygen gas generation overvoltage of the positive electrode active material is increased to increase the overcharge voltage at the end of charging. It delays the generation of oxygen. Therefore, at the end of charging, oxygen gas generated from the positive electrode reacts with hydrogen gas in the battery or hydrogen in the negative electrode to rapidly increase the amount of heat generation and raise the temperature of the battery, thereby reducing the charge acceptability of the positive electrode. The decrease in capacity can be reduced.

Further, in MmNiα (4.5 ≦ α ≦ 5.5) used as a hydrogen storage alloy for the negative electrode, the amount of La in Mm, the amounts of Mn and Co substituting with Ni, and ZrNi
In β (1.9 ≦ β ≦ 2.4), T replacing Zr or Ni
By increasing the amount of i and V, the hydrogen equilibrium pressure is reduced,
It is possible to reduce the increase in the internal pressure of the battery, and to improve the protection and safety of the battery components such as the battery case.

Next, the electrolytic solution has a specific gravity at 20 ° C. of 1.1.
A KOH-based aqueous solution of 5 to 1.35 is used. Further, preferably, the amount of NaOH or LiOH is Na
OH is 3.5 mol / l, LiOH is 1.5 mol / l
By adding liter as the upper limit, the utilization factor of the battery is improved and the high rate discharge characteristics are not deteriorated.

As the separator, a hydrophilic polyolefin-based separator is used. In particular, by using a polypropylene-based non-woven fabric or a woven fabric resin separator, the battery capacity can be maintained for a long period of time as compared with a conventional polyamide-based separator.

Further, a safety valve is provided on the battery lid or the battery case,
The operating pressure of the safety valve is set so that the pressure difference between the inside and outside of the battery is 2 to 5
By setting it in the range of kg / cm ² , the battery case will not be broken due to the pressure resistance of the battery case.

[0034]

EXAMPLES Examples of the present invention will be described below.

Example 1 A mixed solution of nickel sulfate (NiSO ₄ ) aqueous solution having a concentration of 0.6 mol / liter and cobalt sulfate added so as to be 0.5% by weight in terms of metal amount with respect to Ni and a concentration of 0. An aqueous sodium hydroxide (NaOH) solution of 0.65 mol / liter is prepared. Put the former mixed solution in a cylindrical container and stir well. Add the latter from the lower part of the center and the former from the upper part of the center little by little.
Make H a constant value of 11.3. The liquid temperature is kept around 35 ° C. The particle size of Ni (OH) _{2 in} which Co is solid-dissolved is grown to an average of about 20 μm and then continuously taken out.
The main active material for the positive electrode. Cobalt (Co) powder having an average particle diameter of 5 μm, calcium hydroxide (Ca (OH) ₂ ) powder having a purity of 99.5% or more, and graphite powder having a purity of 99.5% or more were added to the above Ni (OH) ₂ respectively.
5% by weight, 2% by weight and 3% by weight to obtain a uniform mixed powder. A paste of this mixed powder and water was filled in a foamed nickel substrate as an electrode substrate having a thickness of 1.6 mm and a porosity of 95%, dried and pressure-molded to a thickness of 0.9 m.
A nickel positive electrode plate having a filling density of m, Ni (OH) ₂ of about 600 mAh / cc is obtained. This is cut into 60 × 70 mm to obtain a nickel positive electrode having a theoretical capacity of 2.3 Ah. The schematic sectional view is shown in FIG. In the figure, 11 is a mixture of an active material and an additive, 12 is nickel foam, 13 is a space, and 2
Indicates a positive electrode. This electrode substrate will be described below.

That is, since the nickel oxide used for the positive electrode is poor in both the binding property and the conductivity, it is difficult to adopt the construction method in which the nickel oxide is applied to the two-dimensional core material. For this reason, it is appropriate to use a three-dimensional metal substrate having excellent active material retention and electron conductivity as the positive electrode. In this substrate, it is preferable to use a sponge-like nickel or nickel fiber felt, which has a high porosity and is lightweight, instead of the conventional sintered substrate for the substrate to increase the capacity density and weight of the electrode. For example, a sintered substrate (having a porosity of 77 to 80%).
Instead of sponge-like nickel (porosity 93 to 95
%. ) Using a foam metal nickel positive electrode,
Due to the reduction of the theoretical filling amount of the active material and the used material, the capacity can be increased by about 30% and the weight can be reduced by about 20%. However,
Since the utilization rate of the active material filled in the three-dimensional reticulated substrate having such a large pore size is low, cobalt or cadmium is dissolved in nickel hydroxide as a solid solution, or the powder of cobalt or its oxide is used as an additive. It is effective to add powder such as nickel, graphite or graphite as a conductive material. In that case, the addition amount of one or more of cobalt, nickel, and graphite is preferably 0.1 to 10.0% by weight with respect to the positive electrode active material.

As the negative electrode, an electrode in which a hydrogen storage alloy having a high capacity and robustness is filled in a light substrate as described above, and in this case, since the hydrogen storage alloy is excellent in electronic conductivity, a binder or the like is used for the electrode substrate. It is possible to adopt a coating type electrode that is coated together with it. However, in the latter case, if the amount of the binder is too large, the electrode reaction is hindered. Therefore, it is necessary to select a material having excellent binding properties in the smallest possible amount. The electrode substrate is preferably a perforated plate or expanded metal, and most of the perforated plate or expanded metal is preferably nickel. As a binder,
In addition to polytetrafluoroethylene and polystyrene,
It is preferable to use an appropriate amount of polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, polystyrene, and the like that swell with an electrolytic solution, in some cases, in combination. These amounts are preferably in the range of 1 to 5% by weight with respect to the hydrogen storage alloy powder, and when the amount exceeds 5% by weight, the electrode reaction is remarkably reduced.

Next, the solid solution-formed product will be described. Although examples of Co have been shown above, Cd, Zn, C may be used instead of Co.
The salts of a, Ag, Mn, Sr, V, Ba, Sb, Y and rare earth metals may be used alone or in combination. Of these, Cd was slightly superior to Co in high-temperature charge acceptance, but was rather inferior in utilization factor of the active material at room temperature, and thus Co solid solution was used as a representative example.

Although graphite powder is shown as the conductive agent, nickel (Ni) powder having a small particle size may be used. However, when a high energy density per weight is specifically aimed at, graphite powder, which can be slightly reduced in weight, was used as a representative example of the embodiment. Co and Ca (OH) ₂ (symbol g) are shown as typical examples of powder additives.
o, Cd, Mn, Ag, Zn, Sr, V, Ba, Sb,
Y and oxides of rare earth metals also have an effect of improving high temperature charge acceptance.

Of these, the addition of Co and Ca (OH) ₂ was one of the most excellent combinations. For comparison, C
Two examples of similar structures with 5% by weight of o, 3% by weight of CdO and 5% by weight of Co, 1% by weight of Ca (OH) ₂ and 2% by weight of ZnO, respectively (f) and (h) )
A nickel positive electrode (d) having the same structure as the above nickel positive electrode of No. 1 and having no addition other than graphite and a nickel positive electrode (e) obtained by adding only Co to graphite were produced. Also, although it is a general-purpose, the packing density is about 400 mAh /
A sinter type nickel positive electrode (n) having the same size as cc was also prepared.

A misch metal (Mm) containing 48% by weight of cerium and 28% by weight of lanthanum, nickel, cobalt, manganese, and aluminum were mixed at a predetermined ratio and melted at about 1500 ° C. in a high-frequency melting furnace. copper container (space thickness is thin) at once flowed elaborate in composition obtained MmNi _3.8 Co _0.5 Mn _0.4 Al _0.3 alloy in a water-cooled to produce as an example. After mechanically crushing an ingot of this alloy, it was immersed in a KOH aqueous solution of 7.2 mol / l at 80 ° C. for 30 minutes while stirring, then washed with water and dried to obtain a powder having an average particle diameter of about 20 μm. . A foamed nickel substrate having a thickness of 1.0 mm and a porosity of 93% was filled with the paste of the powder and water, dried, and then pressure-molded to have a thickness of 0.6 mm and a packing density of about 1280 mAh / cc. To get This is cut into 60 × 70 mm, and the theoretical capacity is 3.
A 2 Ah hydrogen storage alloy negative electrode is used.

In addition to the alloy examples shown here, ZrMn
_Since alloys such as _0.6 V _0.1 Ni _1.3 Ti _0.2 have a large hydrogen storage capacity and a low equilibrium pressure, they are excellent as high energy density alloys. However, only cooling the molten metal in a conventional alumina vessel either case, when the hydrogen concentration is high, i.e. increase of the hydrogen equilibrium pressure when the storage amount is increased significantly, the preferred 1 kg / cm ² in this cell There was a case to exceed. These PCT curve diagrams at 60 ° C. are shown in FIG.
It was shown to. For both alloys, the effect of reducing the hydrogen equilibrium pressure by the rapid cooling (a-1, b-1) is clearer than that of the slow cooling (a, b), and a battery using the latter is expected to have a low battery internal pressure at the end of charging. it can. The hydrogen storage alloy will be described below.

The hydrogen storage alloy may be either CaCu ₅ type or MgCu ₂ type crystal alloy as long as it has appropriate charge / discharge efficiency and oxidation resistance (robustness). In order to make it more robust, the alloy powder is subjected to an alkali treatment to remove elements that are likely to be eluted in advance from the surface to form a large number of irregularities on the surface layer or to increase the amount of Ni in the surface layer.
It is also important to prevent oxidation of the alloy matrix by coating it with a material having a catalytic property or an electrolytic solution resistance and conductivity. Carbon powder is preferable as the conductive material having electrolytic solution resistance.

The CaCu ₅ type crystal structure is an ABα type alloy (4.5 ≦ α ≦ 5.5), and A of the structural formula is a rare earth metal or a misch metal which is a mixture thereof,
Alternatively, a part thereof is substituted with one or more metals selected from the group of Ca, Mg, V, Ti and Zr in an atomic weight of 0.1 to 0.3, and B is mainly Ni and a part thereof. Co, Al, Mn, Cu, Fe, V, Cr, S
One or more metals selected from the group of i and having a total atomic weight of 0.5 to 2.0. Also MgCu
_{The 2} type (ABβ type of C15 type Label crystal structure) crystal alloy (1.9 ≦ β <2.4) has Zr as a main component in its structural formula, and a part thereof is Ti, V, a rare earth metal and Ca
0.1 to 0.4 in atomic weight by substitution with one or more metals selected from the group B, Ni is the main component, and Co, Al, Mn, Cu, Fe, V,
One or more metals selected from the group of Cr and having an atomic weight of 0.3 to 1.2. And, as the material for imparting the catalytic property and the conductivity to the powder of the hydrogen storage alloy, Ni, Cu, Co, Ag, Cr and S in the form of fine powder are used.
It is possible to use a metal selected from the group consisting of n and white metal, and it is preferable that some of these metals are fused with the hydrogen storage alloy powder.

By combining such electrodes, a high packing density of the active material and a weight reduction can be achieved.

However, when a large number of electrodes are stacked and used in a medium / large capacity battery, the heat radiation is inferior, so that the temperature of the electrode group is particularly high. Therefore, it was also effective to insert a metal plate between the separators in the electrode group and let the heat escape to the outside through the poles. In this case, the metal plate to be inserted is preferably a metal plate at least the surface of which is covered with nickel,
Further, the metal plate is preferably a perforated plate or an expanded metal. However, even if the metal plate is inserted, the temperature rise of the electrode group at the end of charging is remarkable. The reason for this is that the oxygen gas generated from the positive electrode at the end of charging reacts with the hydrogen gas in the battery or the hydrogen in the negative electrode and the amount of heat generation increases sharply. This tendency of higher temperature is larger in the nickel / hydrogen (Ni · MH) storage battery than in the nickel / cadmium battery. As a result, in the nickel-hydrogen storage battery, the charge acceptability of the positive electrode is significantly reduced, and the battery capacity is reduced. Naturally, it becomes more remarkable when charging in a high temperature atmosphere.
Therefore, it is necessary to increase the oxygen gas generation overvoltage of the positive electrode active material and delay the oxygen generation until the charging is almost completed. To improve this, the solid solution-forming product (C
o, Cd), Ca, Ag, Mn, Zn, Sr, V,
The solid solutions of Ba, Sb, Y and the rare earth metal were effective in improving the oxygen gas generation overvoltage. To maintain high energy density, it is important to be effective with a small amount of material used. Co that is effective in improving charging efficiency even with a small amount is 0.05
The amount of Cd and the above-mentioned elements from Ca to the rare earth metal is suitably 5% by weight or less. For the same purpose, as a powder additive to the positive electrode, in addition to the above additives (Co, Co oxide), Ca, S
It has been found that oxides of r, Ba, Sb, Y, Zn, and rare earth metals are effective. In order not to significantly reduce the packing density of the active material, the addition amount of each is 0.1
It is suitable to be up to 5% by weight. It is more effective if a solid solution and a powder additive are combined. Positive electrode 1 in Table 1
Atmosphere temperatures of 45 ° C. and 60 ° C. in a sealed battery of 30 Ah composed of 3 sheets (30 Ah) and 14 sheets of negative electrode (45 Ah)
The utilization rate in

[0047]

[Table 1]

Any solid solution forming material on the positive electrode active material is powdered.
The powder additive is also added in an amount of 3% by weight.
8% by weight was added. Charged at 3A for 12 hours
The result is 5 cells each with 9A and a final voltage of 1.0V.
Is. Utilization rate of all solid solutions and powder additives at high temperature
The effect of increasing the Y in the above (Table 1)₂O₃To
Although shown as being used alone, two or more powder additives
When adding, the ratio of each addition amount is
3% by weight, so that Y₂O₃And rare earth metal oxides
Can be used in combination, for example, Y₂O₃: Ce (OH)₃
Is 1: 1 or Y₂O ₃: Ce (OH)₃Is appropriately selected such as 1: 2
You can choose.

Further, the problem of high temperature at the end of charging extends to the hydrogen storage alloy. That is, the hydrogen equilibrium pressure rises as the temperature rises, increasing the internal pressure of the battery. For medium- and large-capacity batteries, the pressure resistance is not so large as long as a resin battery or metal battery having a common thickness is used. In the case of a resin battery case having a thickness of 1.5 to 3 mm, even when reinforced, the deformation was remarkable when the pressure difference from the outside was 5 kg / cm ² or more, and in some cases, it was destroyed. Therefore, the internal pressure of the battery (pressure difference from the outside) is 5 kg / cm ² or less at the maximum, preferably 2 kg / c.
It is necessary to keep it to about m ² . That is, it is appropriate that the increase in the hydrogen equilibrium pressure due to the temperature increase and the increase in the battery internal pressure due to the gas generated after the last stage of charging be each increased by 1 kg / cm ² (total 2 kg / cm ² ).

In order to reduce the hydrogen equilibrium pressure, a method of improving the composition of the alloy and a method of devising the manufacturing method can be considered. Regarding the former, increasing the amount of La in Mm, the amount of Mn and Co substituting for Ni with MmNiα (4.5 ≦ α ≦ 5.5), and increasing ZrNiβ (1.9 ≦ β ≦ 2.4) with Zr And Ni
It is effective to increase the amount of Ti or V to be replaced with. MmNiα
An example of is shown in Table 2.

[0051]

[Table 2]

The amount of La in Mm of MmNiα is 55% by weight or less in consideration of the decrease in the oxidation resistance of the alloy.
Considering the decrease in energy density, the total number of elements substituting for is preferably 2.0 or less. One Zr
Considering the deterioration of crystallinity, the Ti amount in Niβ is 0.4 or less in atomic weight, the V amount is 0.4 or less for the same reason, and 1.2 or less in total with other substituting elements.

The improvement of the manufacturing method was extremely effective in reducing the hydrogen equilibrium pressure. When the composition is made uniform in any alloy, the plateau region of the PCT curve becomes flat as shown in a-1 and b-1 of FIG. 2, and the equilibrium pressure in the state of absorbing hydrogen at the end of charging is particularly low. . For homogenizing the composition, a method of pouring the molten alloy into a container having excellent cooling property and quenching it was suitable.

Further, a non-woven fabric having a weight per unit area of 75 g / m ² and a thickness of about 0.15 mm, which is obtained by heat-welding and integrating polypropylene fibers whose surfaces are coated with polyethylene, is prepared. This is immersed in an acid having a concentration of 95% at 100 ° C. for 5 minutes to be sulfonated, then sequentially dipped in sulfuric acid having a low concentration, washed with water at the end, and then dried with a separator, and the positive electrode and the negative electrode are each heat-welded. To wrap it in a bag. Only the part above the electrode lead was welded. This is illustrated in FIG. In the figure, 3 is an electrode lead, 4 is a separator, and 4-1 is its welded portion. Here, the separator will be described below.

In other words, in order to reduce self-discharge, it is effective to use a polypropylene-based separator in a polyolefin-based separator instead of a polyamide-based one even in a medium or large capacity battery. A battery capacity change of 30 Ah having the same structure as described above, which is obtained by converting this separator into a sulphone, and fully charged, and stored at 45 ° C., shows the capacity change g. For comparison, a case of a battery using a conventional polyamide 6 nylon is shown in g-1. The latter lost capacity in two weeks, while the former lost 55% after four weeks.
Maintained its capacity. As shown in FIG. 7, it can be seen that the one using the conventional separator has a small charge / discharge cycle.

However, as the electrode size increases, the active material or the like is likely to drop off during charging / discharging, which cannot withstand severe use for a long period of time and causes an increase in self-discharge due to a minute short circuit. Therefore, it is most certain to wrap the positive electrode and the negative electrode in a bag shape with the separator. FIG. 1 (D),
A schematic view of the electrode wrapped in a bag shape is shown in (E). here,
This is because the unsealed part is left in a part of the upper part, which is effective for degassing when the electrolytic solution is injected. Further, when the fiber has a directional property, it is more preferable to make it vertical for this purpose.

13 positive electrodes and 1 negative electrode wrapped in a separator
An electrode plate group in which four leads are welded to the poles through a metallic auxiliary plate to form a power generation element for a sealed nickel-metal hydride storage battery with a capacity of 30 Ah
It is inserted into a polypropylene battery container having a meat pressure of mm. After welding the predetermined lid to the battery case, 1 mol of LiOH was added to 5 mol / liter KOH and 2 mol / liter NaOH aqueous solution.
60 cc of the electrolytic solution in which was dissolved was inserted, and then the safety valve body was inserted to close the injection port to produce a sealed nickel-hydrogen storage battery. The electrolytic solution will be described below.

That is, the electrolytic solution is related to the charging efficiency of the positive electrode at high temperature and the battery internal pressure. Suitable amount of NaOH or LiOH
Is extremely effective for the former. In Figure 3, KOH and N
An example of the utilization rate of a battery having a capacity of 30 Ah similar to the above under an atmosphere of 45 ° C. when the number of moles of aOH was constant (7 mol / liter) was shown. The utilization rate increases as the amount of NaOH increases, but if it is too large, the high-rate discharge characteristics deteriorate, so 3.5 mol / liter or less is appropriate. L
The addition of iOH was uniformly effective even in the above mixed composition, and 1.5 mol / liter or less was suitable. The amount of electrolyte is related to the scavenging ability of oxygen and hydrogen gas generated after the end of charging, and in the above 30 Ah battery, 2.8 cc or less per 1 Ah of positive electrode capacity was effective for erasing gas, that is, reducing internal pressure. However, if 1.3 cc or less, the electrode reaction is hindered, so 1.3 to 2.8 cc is an appropriate amount.

In the figure, 1 and 2 are a negative electrode and a positive electrode, 3 is an electrode lead, 5 is an electrolytic solution, 6 is a pole, 7 is a space, 9 is a battery case, 10
Indicates the safety valve body. In addition, 8 is a porous body in which a plurality of separators are stacked, and is for the purpose of preventing sparks between electrodes from catching fire in oxygen and hydrogen gas in the space 7. Here, a separator is used for 8, but sponge-like synthetic resin, synthetic resin woven cloth, or synthetic resin non-woven cloth is preferable. Also,
The seal between the pole 6 and the battery case 9 was obtained by applying petroleum pitch to both and then pressing it with O-rings from both the upper and lower sides of the battery case, and the O-ring was fixed with a flat washer-shaped resin. The O-ring is preferably made of any one of ethylene / propylene copolymer, neoprene and fluorine resin.

The operating pressure of the safety valve body 10 was 2.0 to 2.5 kg / cm 2 by adjusting the position of the spring. A schematic sectional view of the safety valve body is shown in FIG. 1
Reference numeral 0a is a polypropylene frame main body, 14 is a stainless steel spring, 15 is an ethylene / propylene copolymer rubber stopper, 15-1 is a fixing part to the spring, and 16 is a spring whose position can be freely changed. A polypropylene bolt 17 is a vent hole. The safety valve will be described below.

That is, the power generating element structure of a medium / large capacity battery which has a high energy density even in a wide temperature range, has a long life and a low self-discharge, and keeps a low battery pressure until full charge has been described so far. However, in order to be evaluated as a practical battery, it is necessary to adopt a highly reliable safety valve and a battery configuration considering safety.

In order for the operating pressure of the safety valve to be unaffected by temperature changes, it was appropriate to use a metal spring to adjust the pressing of rubber. The operating pressure is preferably in the range of ² to 5 kg / cm ² in consideration of the pressure resistance of the battery case.

The above (d), (f), (g), (h),
A battery of 30 Ah in which (n) was used for each positive electrode (however, in the case of the sintering type of n, the packing density was small, so
h) Fig. 4 shows the relationship between the energy density and the cycle when 5 cells were made as prototypes and charged and discharged in an atmosphere of 20 ° C.
Here, the curve in the figure shows the average value of 3 cells excluding 1 cell above and below the energy density. Charging at 0.2C for 6 hours,
The discharge was up to 1.0V at 0.5C. As a result,
(Wh) 71Wh / kg, (g), (h) 72Wh / kg
An energy density of kg was maintained up to 1000 cycles. On the other hand, (d) has an energy density of 65 Wh /
It was as low as kg, and the decrease was remarkable after 500 cycles. (N) has an energy density of 52 to 53 Wh /
Although it was as low as kg, there was almost no capacity decrease due to cycling. It is considered that the difference in energy density between (d), (f), (g), and (h) is due to charge acceptability due to the oxygen generation overvoltage of the positive electrode. This is supported by the fact that the charging voltage rises quickly in (d), but the rising voltage is low, and the battery temperature rises accordingly. Further, it is considered that the capacity deterioration of (d) is caused by the operation of the safety valve due to the high temperature caused by the increase of the overcharge amount. The energy density of (n) is low due to the difference in the packing density of the positive electrode, and the decrease in capacity is small because the capacity of the negative electrode relative to the positive electrode is too large and the increase in hydrogen equilibrium pressure is small even when the temperature rises. it is conceivable that.
FIG. 5 shows similar test results at an ambient temperature of 45 ° C. However, the charging time was adjusted so that the amount of electricity charged was 120% of the initial capacity. As is clear from this result, it is found that the tendency at 20 ° C. is further increased. From these results, the nickel-hydrogen storage battery using the positive electrode of the present invention has a large energy density in a wide ambient temperature range and a cycle life of 1000 cycles or more.

Example 2 A positive electrode plate and a negative electrode plate obtained in the same manner as in Example 1 were each 14.4 mm in length and 10 in width.
13 mm nickel electrode and hydrogen storage alloy negative electrode 1
A 100 Ah nickel-hydrogen storage battery was produced by combining four sheets. The other constituent materials and structures were the same as in Example 1. However, the amount of electrolytic solution was 210 cc / cell.
As a result of the same charge / discharge test as in Example 1 for the 5 cells of this battery, the energy density at 20 ° C. was 78 Wh / kg, 45
It showed 60 Wh / kg at 0 ° C. and little cycle degradation was observed up to at least 500 cycles. It was found that even in a large capacity battery of 100 Ah, the battery of the present invention exhibits excellent characteristics and reliability.

(Example 3) In the same manner as in Example 1, while adding a mixed aqueous solution of nickel sulfate and cobalt sulfate and manganese sulfate having a concentration of 0.6 mol / liter in equal amounts, the pH was adjusted to 11.5 with NaOH. A eutectic oxide powder having an atomic weight ratio of nickel and manganese of approximately 1: 1 is prepared.
The retention time in the liquid was adjusted so that the average particle diameter was 20 μm. Using this powder, 3 cells of 30 Ah battery were trial-produced in the same manner as in Example 1 and charged and discharged in the same manner. As a result, the voltage dropped by about 50 mV, but the capacity of all three cells remained small even after 500 cycles. For the nickel-metal hydride storage battery of Example 1,
Although it is not particularly superior in terms of characteristics, it is considered that Mn can be used for the low cost of the material.

It is possible to further increase the Mn ratio, but in that case it is important to raise the pH value to precipitate the oxide.

[0067]

As described above, according to the present invention, it is possible to provide a highly reliable sealed nickel-hydrogen storage battery having a wide temperature range, a high energy density, a small self-discharge.

[Brief description of drawings]

FIG. 1A is a schematic cross-sectional view of a positive electrode in one embodiment of the present invention, FIG. 1B is an internal front view of the same cell, and FIG. 1C is a cross-sectional view of the same side. Figure (E) Same side sectional view (F) Enlarged sectional view of the same safety valve body

FIG. 2 is a diagram showing a PCT curve of a hydrogen storage alloy having a low hydrogen equilibrium pressure for a negative electrode in Example 1 of the present invention.

[Fig. 3] Utilization rate of the battery at 45 ° C and N in the electrolytic solution
Diagram showing the relationship of aOH amount

FIG. 4 is a diagram showing the relationship between the energy density at 20 ° C. and the charge / discharge cycle of the battery.

FIG. 5 is a diagram showing the relationship between the energy density at 45 ° C. and the charge / discharge cycle of the battery.

FIG. 6 is a diagram showing a relationship between a separator type and self-discharge of the battery.

FIG. 7 is a diagram showing a relationship between a method of forming a separator and charge / discharge cycle life of the battery.

[Explanation of symbols]

1 negative electrode 2 positive electrode 3 electrode lead 4 separator 10 Safety valve body

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 10/30 H01M 10/30 Z (72) Inventor Morishita Nobuyasu 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshinori Toyokuchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Hiromu Matsuda 1006 Kadoma, Kadoma City, Osaka F Term (Matsushita Electric Industrial Co., Ltd.) Reference) 5H028 AA02 EE05 FF03 FF05 HH01 5H050 AA05 AA06 AA09 AA15 BA14 CA02 CB17 EA03 EA09 EA23 EA24 FA02 HA01

Claims (3)

[Claims] 1. A sealed metal oxide / hydrogen storage battery having a positive electrode having a metal oxide, a negative electrode having a hydrogen storage alloy, a separator, an alkaline electrolyte, and a lid portion provided with a safety valve and a battery case, wherein the positive electrode is a positive electrode. Contains at least one selected from the group consisting of yttrium oxide and oxides of rare earth metals, and Co is 0.05 to 3.0% by weight solid solution with respect to the metal oxide in the crystal of the metal oxide. Sealed metal oxide / hydrogen storage battery. 2. The hydrogen storage alloy is an ABα alloy mainly having a CaCu ₅ type crystal structure (4.5 ≦ α ≦ 5.5), wherein A is misch metal and B is Ni. The main component is Co, Al, Mn, Cu, Fe, V, C
The sealed metal oxide / hydrogen storage battery according to claim 1, which contains one or more metals selected from the group of r and Si, and the amount of La in the misch metal is 25 to 55% by weight. 3. A positive electrode having a metal oxide, a negative electrode having a hydrogen storage alloy, a separator, an alkaline electrolyte, and a lid portion provided with a safety valve and a battery case, and the lid portion and the battery case are made of synthetic resin. The sealed metal oxide / hydrogen storage battery according to claim 1 or 2, wherein both are integrated by heat welding or an adhesive.