JP2000030697A - Nickel-hydrogen storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel-hydrogen storage battery forming a negative electrode with a hydrogen storage alloy made of a polyphyletic alloy and excellent in both high-temperature storage characteristic and low-temperature discharge characteristic. SOLUTION: This nickel-hydrogen storage battery is provided with a positive electrode having an active material made of nickel hydroxide, a negative electrode made of a hydrogen storage alloy, an electrolyte made of an alkaline aqueous solution, and a separator. The hydrogen storage alloy is made of a polyphyletic alloy substituted with part of Ni of a MmNi5 alloy, (where Mm indicates misch metal,) by at least one kind of Co, Mn, Al, Mo, Cu, Cr. The negative electrode made of the hydrogen storage alloy contains a compound constituted of at least one kind of Nb, W, Y, Yb, Bi as an additive and at least one kind selected from B, B2O3 and H3BO3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel hydrogen storage battery using a hydrogen storage alloy electrode capable of reversibly storing and releasing hydrogen, and more particularly to the above nickel hydrogen storage battery used as a power source for portable terminal equipment. is there.

[0002]

2. Description of the Related Art With the development of portable terminal equipment, a nickel hydrogen storage battery has been known as a battery used as a power source for the portable terminal equipment. This battery operates with hydrogen as a negative electrode active material. A hydrogen storage alloy electrode in which a hydrogen storage alloy capable of storing and releasing hydrogen reversibly is supported on a conductive base material is used as a negative electrode, and usually, a positive electrode active material is used. A nickel electrode in which a nickel hydroxide that operates as a substrate is supported on a conductive base material is used as a positive electrode, and both positive and negative electrodes are arranged in an alkaline electrolyte via a separator.

[0003] A hydrogen storage alloy electrode used as a negative electrode is formed by molding an electrode mixture containing a hydrogen storage alloy powder, a conductive powder and a polytetrafluoroethylene powder into a sheet, and forming the mixture into a porous material serving as a conductive base material. The method of pressing to a metal plate, the hydrogen storage alloy powder, the conductive powder, and carboxymethyl cellulose
A paste-like electrode mixture is prepared by kneading a polymer binder such as sodium and polyacrylic acid soda and water, and this is used as a current collector such as a punched metal conductive base material. It is manufactured by a method of applying to the surface.

[0004] Here, the above-mentioned conductive powder is used to enhance the conductivity of the hydrogen storage alloy to improve the current collecting ability as a negative electrode. For example, nickel powder, cobalt powder,
Copper powder, carbon powder and the like are used, and the use of nickel powder is being studied in particular. JP-A-3-179664
No. 7-114922, the diameter of 1 μm
The following nickel powder is used to prevent an increase in internal pressure and improve cycle characteristics, and to use a nickel powder having an average particle size of 2 to 8 μm and a bulk density of 0.4 to 1 g / cm ³ to achieve charge-discharge characteristics. It has been proposed to improve. In addition, Japanese Patent Application Laid-Open
Publications such as No. 65826 and No. 7-37583 disclose that nickel powder contains a different element, for example, carbon, to prevent an increase in internal pressure, and that high-rate discharge characteristics are improved by using an alloy powder composed of nickel and cobalt. It has been proposed to.

[0005]

However, in recent nickel hydrogen storage batteries, a part of Ni of an MmNi ₅ alloy (Mm represents a metal mesh) is used as a hydrogen storage alloy in order to increase the capacity. A multi-element alloy substituted by such as is used. In this case, the replacement alloy causes corrosion to progress in the alkaline electrolyte during the charge / discharge cycle, and there is a problem that the battery capacity is reduced even if the above-described conductive powder is added to the negative electrode.

For this reason, Japanese Patent Application Laid-Open No. Hei 3-280362 discloses that an alkaline electrolyte contains an alkaline earth metal ion such as strontium and barium, and hydrates the alkaline earth metal ion to cause corrosion of the alloy. It has been proposed to suppress. However, such a method has a small effect on a large amount of oxygen generated from the positive electrode in a high temperature state or in an overcharged state after the high temperature state, and it is difficult to suppress corrosion of the hydrogen storage alloy in an alkaline electrolyte. In particular, a sufficient recovery rate was not obtained after long-term storage. Further, when the alkaline earth metal ion concentration is increased, these hydroxides are deposited on the surface of the negative electrode, and there is a problem that the low-temperature discharge characteristics are reduced.

In view of such circumstances, the present invention provides a nickel hydrogen storage battery in which a negative electrode is formed using a hydrogen storage alloy made of a multiplexed alloy as described above, and which has excellent high-temperature storage characteristics and low-temperature discharge characteristics. It is intended to provide a storage battery.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, when forming a negative electrode using a hydrogen storage alloy made of a multi-element alloy as described above. It has been found that by adding two kinds of specific additives together with the above alloy to the negative electrode, a nickel hydrogen storage battery having both excellent high-temperature storage characteristics and low-temperature discharge characteristics can be obtained, and completed the present invention. Things.

That is, the present invention relates to a nickel hydrogen storage battery having a positive electrode containing nickel hydroxide as an active material, a negative electrode comprising a hydrogen storage alloy, an electrolyte comprising an alkaline aqueous solution, and a separator. MmNi ₅
Part of the Ni in the alloy (Mm represents the metal of the metal) is C
at least one of o, Mn, Al, Mo, Cu or Cr
Nb, as an additive, in a negative electrode using the hydrogen storage alloy.
A nickel hydrogen storage battery comprising: a compound composed of at least one element of W, Y, Yb or Bi; and at least one selected from B, B ₂ O ₃ or H ₃ BO ₃ ( According to claim 1).

Further, the present invention relates to the above-mentioned Nb, W, Y, Y
The compound composed of at least one element of b or Bi is 0.5 to 100 parts by weight of the hydrogen storage alloy.
The nickel hydrogen storage battery having the above-mentioned configuration, which is 2 parts by weight, and at least one selected from the group consisting of B, B ₂ O _{3, and} H ₃ BO ₃ are used in an amount of 0.1 part by weight with respect to 100 parts by weight of the hydrogen storage alloy. 1 to 3 parts by weight of the above nickel hydrogen storage battery (Claim 3), and Nb, W, Y, Yb or B
a compound composed of at least one element of i and at least one selected from the group consisting of B, B ₂ O _{3 and} H ₃ BO _{3 in} an atomic ratio of each of the former elements and boron of the latter. The present invention relates to a nickel hydrogen storage battery having the above-described configuration in which the ratio is 1: 0.5 to 1: 1.5.

[0011]

Hydrogen storage alloy used in the Detailed Description of the Invention The present invention is a part of Ni is Co of MmNi ₅ alloy (Mm represents Mitsushiyumetaru), Mn, Al, Mo, Cu or Cr
A ternary alloy substituted by at least one of the following,
Any of ternary or higher alloys such as quaternary, quinary, etc. can be used. Among them, a quinary alloy in which a part of Ni is replaced by Co, Mn and Al is particularly preferable since a high capacity alloy can be obtained. The particle diameter of the hydrogen storage alloy is preferably 100 μm or less, more preferably 20 to 100 μm.

Such a hydrogen storage alloy is, for example, M
m (Mesh metal which is a mixture of rare earth elements including La, Ce, Nd, Pr, etc.), Ni, Co, Mn,
At least one metal element selected from Al, Mo, Cu or Cr is melted in a high-frequency melting furnace or the like to form a molten alloy, which is rotated for about 200 to about
Rapidly solidifies at a cooling rate of 1,000 ° C./sec, evacuates in a pressure vessel, keeps it under hydrogen pressure, evacuates hydrogen, and heats it at 200 to 600 ° C. to completely alloy hydrogen. It can be synthesized by releasing from inside.

One of the additives used in the present invention is N
It is a compound composed of at least one element of b, W, Y, Yb or Bi, for example, an oxide, a hydroxide and the like. Also,
Another of the additives is B, B ₂ O ₃ or H ₃ BO ₃
At least one of boron or a boron compound selected from
Is a seed. In the present invention, the combined use of the above-described corrosion inhibitor and boron or a boron compound gives good results in both high-temperature storage characteristics and low-temperature discharge characteristics. The reason is considered as follows. .

The above-mentioned corrosion-inhibiting compound is partially dissolved in an alkaline electrolyte, and precipitates as a complex or a hydroxide on the particle surface of the hydrogen-absorbing alloy to form a protective film. Sometimes suppresses corrosion of hydrogen storage alloy. On the other hand, this protective film reduces the activity of the hydrogen storage alloy activated by Co, Al, Mn, etc., and lowers the low-temperature discharge characteristics and the high-rate discharge characteristics. The compound dissolves in the electrolyte,
The hydrogen storage alloy particles generated during the charge / discharge cycle are deposited on the new surface and coexist with the above-mentioned protective film as an electrode active region to improve low-temperature discharge characteristics and high-rate discharge characteristics.
That is, it is considered that the coexistence of the above-mentioned protective film and the above-mentioned electrode active region on the surface of the particles of the hydrogen storage alloy results in both high-temperature storage characteristics and low-temperature discharge characteristics.

In the present invention, the above-mentioned corrosion-inhibiting compound is used in an amount sufficient to cover the alloy surface with a protective film while maintaining the activation of the hydrogen-absorbing alloy. The amount is preferably 0.5 to 2 parts by weight, more preferably 1 to 1.5 parts by weight. Further, the above-mentioned boron or boron compound is used in an amount of 0.1 to 3 parts by weight, preferably 0.5 to 1 part by weight, based on 100 parts by weight of the hydrogen storage alloy in order to allow the electrode active region to coexist with the protective film. It is preferable to use 5 parts by weight.

In the present invention, the proportion of the above-mentioned corrosion-inhibiting compound and the above-mentioned boron or boron compound in the negative electrode is determined by Nb, W, Y, and Nb in order to achieve both high-temperature storage characteristics and low-temperature discharge characteristics. The atomic ratio between each element of Yb or Bi and boron is 1: 0.5 to 1: 1.5, particularly 1: 1.
It is preferable that That is, with such an abundance ratio, the protective film and the electrode active region coexist well on the surface of the hydrogen storage alloy, and both the high-temperature storage characteristics and the low-temperature discharge characteristics are excellent.

In the present invention, the above-mentioned hydrogen storage alloy, an additive comprising the above-mentioned corrosion-inhibiting compound and the above-mentioned combination of boron or a boron compound, and a binder and the like are added in the presence of water or a solvent. To form a paste-like mixture, apply it to a conductive substrate made of porous metal such as punched metal, foamed metal, etc., fill it, dry it, and then press-mold it. And a negative electrode made of a hydrogen storage alloy. In addition, the above-mentioned paste-form mixture contains, as necessary, a compounding component such as various known conductive powders such as nickel powder, cobalt powder, copper powder, and cobalt oxide. Is also good.

Examples of the binder include polytetrafluoroethylene, sodium polyacrylate, polyvinyl alcohol, and a copolymer of styrene and an acrylic compound. Among these, a copolymer of a monomer mixture containing styrene and 2-ethylhexyl acrylate as main components has a high affinity for a hydrogen storage alloy and the like, and a good dispersibility can be obtained even in a small amount. ,preferable. The amount of these binders used is generally preferably 0.5 to 5 parts by weight based on 100 parts by weight of the hydrogen storage alloy.

A thickener such as carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, or polyoxyethylene may be added to the binder. Among these, polyoxyethylene is
It is particularly preferably used since the increase in viscosity when it is made into a strike is small. The compounding amount of these thickeners is usually preferably 1 to 5 parts by weight based on 100 parts by weight of the hydrogen storage alloy.

A nickel hydrogen storage battery according to the present invention is characterized in that a hydrogen storage alloy electrode having the above structure is used as a negative electrode with respect to a positive electrode comprising a nickel electrode. The nickel electrode is usually prepared by mixing and dispersing nickel hydroxide powder, a conductive additive and a binder in the presence of water to form a paste, filling the paste into an alkali-resistant porous metal body, After drying and rolling, it is manufactured by cutting to a predetermined size.

The nickel hydrogen storage battery of the present invention comprises, for example, a positive electrode comprising the above-mentioned nickel electrode and a negative electrode comprising the above-mentioned hydrogen-absorbing alloy electrode laminated via a separator.
It can be manufactured by inserting this into a battery can and then injecting an alkaline electrolyte. Here, as the above separator, a non-woven fabric made of polyolefin fibers having a hydrophilic group is used. As the above-mentioned alkaline electrolyte, an aqueous potassium hydroxide solution alone or an alkaline aqueous solution in which additives such as sodium hydroxide and zinc oxide are dissolved are used.

[0022]

Next, an embodiment of the present invention will be described in more detail. In the following, “parts” means “parts by weight”.

Example 1 Mission metal Mm (La, Ce, Nd, Pr), N
i, Co, Mn, Al and Mo (all with a purity of 99.
9% by weight or more) of each sample in atomic ratio of Mm (La: 0.
32, Ce: 0.48, Nd: 0.15, Pr: 0.0
4), Ni: 3.55, Co: 0.75, Mn: 0.
4, Al: 0.3 and Mo: 0.04 were heated and melted by a high frequency melting furnace to obtain a hydrogen storage alloy. This hydrogen storage alloy is evacuated to 10 ⁻³ Torr in a pressure vessel, and then kept at a hydrogen pressure of 14 kg / cm ² for 24 hours, evacuated of hydrogen, and further heated at 400 ° C. to completely remove hydrogen. By releasing, a hydrogen storage alloy powder of 20 to 100 μm was obtained.

With 100 parts of this hydrogen storage alloy powder, N
b ₂ O ₅ powder, 1 part of boron powder 1 part, carbonyl Ni powder, 4 parts of aqueous solution of polyethylene oxide (solid content concentration of 6 wt%) as a thickener 20 parts was added, styrene and 2-ethylhexyl acrylate further as a binder 1.7 parts of an aqueous dispersion (solids concentration: 42.5% by weight) of a copolymer with a latex (styrene unit: 35 mol%, 2-ethylhexyl acrylate unit: 65 mol%) was added and mixed and dispersed. And pa
The mixture was in the form of a strike. The Nb ₂ O ₅ powder and the boron powder in this mixture had an atomic ratio of Nb to B of 1: 1. This paste-form mixture was applied to a punched metal in which Ni plating was applied to iron, filled and dried, and then compression-molded.
Thereafter, the resultant was cut into a predetermined size to produce a negative electrode sheet.

The positive electrode was prepared by dry-mixing 2 parts of nickel powder with 100 parts of nickel hydroxide powder, and then 10 parts of cobalt powder, 5 parts of carboxymethyl cellulose aqueous solution (solid content concentration 5% by weight), and polytetrafluorocarbon. 5 parts of an ethylene dispersant solution (solid content: 60% by weight) was mixed to obtain a paste mixture. This paste-form mixture is applied to a nickel foam base material, filled and dried at 80 ° C. for 2 hours.
It was compression molded at 1 ton / cm ² . Then, it was washed with warm water of 80 ° C. for 2 hours, dried at 80 ° C. for 1 hour, and compression-molded. Thereafter, the sheet was cut into a predetermined size to produce a positive electrode sheet.

Next, the above-mentioned negative electrode sheet and positive electrode sheet were wound through a separator made of nylon non-woven fabric to form a single sheet.
Electrode (30% by weight KO)
An aqueous alkaline solution in which 17 g of LiOH was dissolved in 1 liter of an aqueous H solution was injected. The positive electrode tab was spot-welded to the sealing member with the reversible valve provided with the resin packing, and the outermost peripheral portion of the negative electrode was brought into contact with the side surface of the can, followed by sealing. Then, this was stored at 60 ° C. for 17 hours, and 0.25 C (13
After charging at 8 mA) for 6 hours, the battery was discharged to 1.0 V at 0.2 C (110 mA). This charge / discharge cycle was repeated until the discharge capacity became constant, thereby producing a nickel hydrogen storage battery.

Example 2 In preparing a negative electrode sheet, Nb ₂ in the paste mixture was used.
A nickel hydrogen storage battery was produced in the same manner as in Example 1, except that the amount of the O ₅ powder was changed from 1 part to 2 parts.
The Nb ₂ O ₅ powder and the boron powder in the paste mixture of the negative electrode sheet had an atomic ratio of Nb to B of 2: 1.

Example 3 A nickel hydrogen storage battery was manufactured in the same manner as in Example 1 except that the amount of the boron powder in the paste mixture was changed from 1 part to 2 parts in producing a negative electrode sheet. Was prepared. The Nb ₂ O ₅ powder and the boron powder in the paste mixture of the negative electrode sheet had an atomic ratio of Nb to B of 1: 2.

Example 4 In preparing a negative electrode sheet, Nb ₂ in the paste mixture was used.
A nickel hydrogen storage battery was produced in the same manner as in Example 1, except that 1 part of WO ₃ powder was used instead of 1 part of O ₅ powder. The WO ₃ powder and the boron powder in the paste mixture of the negative electrode sheet had an atomic ratio of W to B of 1: 1.

Example 5 In preparing a negative electrode sheet, Nb ₂ in the paste mixture was used.
A nickel hydrogen storage battery was produced in the same manner as in Example 1, except that 2 parts of WO ₃ powder was used instead of 1 part of O ₅ powder. The WO ₃ powder and the boron powder in the paste mixture of the negative electrode sheet had an atomic ratio of W to B of 2: 1.

Example 6 In preparing a negative electrode sheet, Nb ₂ in the paste mixture was used.
A nickel hydrogen storage battery was produced in the same manner as in Example 1, except that 1 part of WO ₃ powder was used instead of 1 part of O ₅ powder, and the amount of the boron powder was changed from 1 part to 2 parts. The WO ₃ powder and the boron powder in the paste mixture of the negative electrode sheet had an atomic ratio of W to B of 1: 2.

Comparative Example 1 In preparing a negative electrode sheet, Nb ₂ in the paste mixture was used.
A nickel hydrogen storage battery was fabricated in the same manner as in Example 1, except that one part of O ₅ powder and one part of boron powder were omitted.

Comparative Example 2 In preparing a negative electrode sheet, Nb ₂ in the paste mixture was used.
The amount of O ₅ powder used was changed from 1 part to 2 parts,
A nickel hydrogen storage battery was fabricated in the same manner as in Example 1, except that one part of the boron powder was omitted.

Comparative Example 3 In preparing the negative electrode sheet, the amount of the boron powder in the paste mixture was changed from 1 part to 2 parts, and Nb was added.
_A nickel hydrogen storage battery was produced in the same manner as in Example 1, except that one part of ₂ O ₅ powder was omitted.

The nickel hydrogen storage batteries of Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated for high-temperature storage characteristics according to the following method. The results were as shown in Table 1.

<High temperature storage characteristics> 6 ° C. at 145 mA at 20 ° C.
After charging for an hour, the battery was discharged at 110 mA, and the discharge capacity until the battery voltage reached 1.0 V was measured (discharge capacity before high-temperature storage). After storage in a high-temperature bath at 80 ° C. for 14 days, a charge / discharge test was performed in the same manner as above to measure the discharge capacity (discharge capacity after high-temperature storage). The recovery rate was determined from the discharge capacity before storage at high temperature and the discharge capacity after storage at high temperature.

[0037]

Further, the above Examples 1 to 6 and Comparative Example 1
The low-temperature discharge characteristics of each of the nickel hydrogen storage batteries of Nos. 1 to 3 were evaluated according to the following method. This result is shown in Table 2
The results were as shown in FIG.

<Low-Temperature Discharge Characteristics>
After charging for an hour, 550 mA discharge was performed, and the discharge capacity until the battery voltage became 1.0 V was measured. After the above charging, the battery was kept in a constant temperature bath at −10 ° C. for 4 hours, and 550 m
A discharge was performed, and the discharge capacity until the battery voltage reached 1.0 V was measured. The low-temperature discharge characteristics were evaluated from both discharge capacities.

[0040]

As is clear from Tables 1 and 2 above, each of the nickel hydrogen storage batteries of Examples 1 to 6 of the present invention
It can be seen that it has excellent high-temperature storage characteristics of a recovery rate after storage at high temperatures of 90% or more, and also has excellent low-temperature discharge characteristics. On the other hand, the nickel hydrogen storage batteries of Comparative Examples 1 to 3 are inferior in high-temperature storage characteristics,
It is clear that the low-temperature discharge characteristics are inferior.

In the above embodiment, N was used as an additive.
Although an example using b ₂ O ₅ or WO ₃ and boron is shown, a compound composed of Y, Yb or Bi is used as another corrosion inhibitor, and B ₂ is used as a boron compound.
It has been confirmed that even when O ₃ or H ₃ BO ₃ is used, substantially the same effects as described above are exerted.

[0043]

As described above, in the present invention, the above-mentioned specific corrosion inhibitor and boron or a boron compound are used as additives in a negative electrode using a hydrogen storage alloy made of a ternary alloy. Thus, a nickel hydrogen storage battery having excellent high-temperature storage characteristics and low-temperature discharge characteristics can be provided.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Ryu Nagai 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell, Ltd. (Reference) 5H003 AA03 BB02 BB04 BC01 BD00 BD03 BD04 5H016 AA02 EE01 EE04 EE05 HH01 5H028 AA01 AA05 EE01 EE04 EE05 HH01

Claims (4)

[Claims] 1. A nickel hydrogen storage battery comprising a positive electrode containing nickel hydroxide as an active material, a negative electrode comprising a hydrogen storage alloy, an electrolytic solution comprising an aqueous alkali solution, and a separator.
In the above hydrogen storage alloy, a part of Ni of the MmNi ₅ alloy (Mm represents a metal mesh) is Co, Mn, Al, M
o, Cu, or Cr, which is composed of a ternary alloy substituted with at least one of Nb, W, Y, Yb or Bi as an additive in a negative electrode using the hydrogen storage alloy. A compound composed of the elements of
A nickel hydrogen storage battery comprising at least one selected from the group consisting of B, B ₂ O _{3 and} H ₃ BO ₃ . 2. The composition according to claim 1, wherein the compound composed of at least one element of Nb, W, Y, Yb or Bi is 0.5 to 2 parts by weight based on 100 parts by weight of the hydrogen storage alloy. The nickel-metal hydride storage battery according to any one of the preceding claims. 3. The nickel according to claim 1, wherein at least one selected from the group consisting of B, B ₂ O _{3 and} H ₃ BO ₃ is 0.1 to 3 parts by weight based on 100 parts by weight of the hydrogen storage alloy. Hydrogen storage battery. 4. A compound comprising at least one element of Nb, W, Y, Yb or Bi, and B, B ₂ O ₃
Alternatively, at least one selected from H ₃ BO ₃ means that the atomic ratio of the former element to boron is 1: 0.5.
The nickel hydrogen storage battery according to claim 1, wherein the ratio is で 1: 1.5.