JP2000149956A - Hydride secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydride secondary battery having a high utilization factor and excellent in a storage characteristic. SOLUTION: At least, one kind of metal species selected from the group comprising molybdic acid, chromium species and tungsten species, and zinc species are contained in a negative electrode 2, in a hydride secondary battery having a positive elctrode 1 with nickel hydroxide serving as a positive active material, the negative electrode 2 with a hydrogen storage alloy serving as a negative active material, an electrolyte comprising an aqueous alkaline solution and a separator 3. A compound such as an oxide, a chloride and a complex is used as the metal species and the zinc species, instead of metal and zinc themselves. A content of the zinc species in the negative electrode 2 is preferably 0.1-5 pts.wt. in terms of zinc oxide per 100 pts.wt. the hydrogen storage alloy, and a content of the metal species is preferably 10-90 wt.% with respect to the content of the zinc species.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydride secondary battery, and more particularly to a hydride secondary battery having a high utilization rate of a positive electrode active material,
The present invention also relates to a hydride secondary battery having excellent storage characteristics.

[0002]

2. Description of the Related Art A hydride secondary battery uses a nickel hydroxide as a positive electrode active material, and has a LaNi5 type or T type having the ability to electrochemically store and release hydrogen in an alkaline aqueous solution.
A hydrogen storage alloy such as i-Ni is used as a negative electrode active material, and a positive electrode is prepared in an alkaline aqueous solution containing potassium hydroxide (KOH), lithium hydroxide (LiOH), sodium hydroxide (NaOH) or the like as a main component. And the negative electrode cause a battery reaction represented by the following formula. In the reaction formula of the negative electrode, M is a hydrogen storage alloy.

[0003]

[0004]

In the reaction formula of the positive electrode and the negative electrode, in charging, the reaction proceeds to the right, and the hydrogen storage alloy M of the negative electrode electrolyzes water in the electrolytic solution, stores hydrogen, and is represented by M (H). And a hydroxyl group (OH ⁻ ) is generated.
^- ) Reacts with Ni (OH) of the positive electrode to form NiOOH, generating water. In the case of electric discharge, the reaction proceeds to the left, which is the reverse of the above. That is, in the negative electrode, hydrogen is absorbed by the hydrogen storage alloy during charging, and hydrogen is released during discharging.

[0006] The positive electrode in the above-mentioned hydride secondary battery is generally called a nickel electrode.
Instead of a conventional sintered nickel electrode, a conductive porous substrate having a porosity of 95% or more and a pore size of about several μm to 100 μm has recently been disclosed as disclosed in Japanese Patent Application Laid-Open No. 1-227363. A so-called paste-type nickel electrode, which is used and carries an active material-containing paste mainly composed of nickel hydroxide, has been widely used because of its high capacity and low price.

[0007] The negative electrode is generally called a hydrogen storage alloy electrode. Recently, a nickel-plated conductive porous substrate formed by perforating a steel plate having a thickness of 0.5 to 0.1 mm is also used for the hydrogen storage alloy electrode. And a so-called paste-type hydrogen storage alloy electrode in which an active material-containing paste mainly composed of a hydrogen storage alloy is supported.

[0008]

However, since the paste-type nickel electrode has a larger pore diameter of the base material than the sintered nickel electrode, the skeleton portion of the base material serving as a current collector and the active material are not used. However, there is a problem that the utilization rate of the active material and the load characteristics are poor. Therefore, it has been proposed to add a conductive aid such as cobalt powder or a cobalt compound powder into the positive electrode to form a conductive network of cobalt on the surface of nickel hydroxide, thereby improving utilization and load characteristics. ("Yuasa Tokiho", No. 65, page 28 (1988), "Electrochemistry" Vol 54, No. 2 (1986), etc.).

However, the paste type nickel electrode is more susceptible to the metal eluted from the counter electrode hydrogen storage alloy electrode than the sintered type nickel electrode. In the case of containing, there is a problem that the metal ion eluted from the hydrogen storage alloy electrode destroys the above-mentioned conductive network of cobalt, so that the utilization rate of the positive electrode active material is reduced.

In order to increase the capacity of a hydrogen storage alloy used as a negative electrode active material of recent hydride secondary batteries, a part of Ni of the MmNi ₅ alloy is replaced with Co, Mn,
Multi-element alloys substituted with Al etc. are used, but these added metals corrode in the alkaline electrolyte during the charge / discharge cycle and elute in the electrolyte or precipitate on the positive electrode surface to improve storage characteristics. There was a problem of lowering. Therefore,
In order to prevent the dissolution of these added metals into the electrolyte and the deposition on the surface of the positive electrode, there has been proposed a method in which the alloy is preliminarily treated with an alkaline solution at a high temperature for a long time before producing the electrode. And the cost increases, and also a problem arises in disposal of the processing solution.

The present invention solves the above-mentioned problems in the conventional hydride secondary battery and provides a hydride secondary battery having a high utilization rate of the positive electrode active material and excellent storage characteristics. Aim.

[0012]

SUMMARY OF THE INVENTION The present invention provides a hydride secondary battery having a positive electrode using nickel hydroxide as a positive electrode active material, a negative electrode using a hydrogen storage alloy as a negative electrode active material, an electrolytic solution comprising an aqueous alkaline solution, and a separator. In the negative electrode, by containing at least one metal species selected from the group consisting of molybdenum species, chromium species and tungsten species and zinc species, the utilization rate of the positive electrode active material is high, and the storage characteristics are excellent Thus, a hydride secondary battery can be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, at least one metal selected from the group consisting of molybdenum, chromium, and tungsten and zinc are contained in a negative electrode. Explaining first,
In the present invention, as the zinc species contained in the negative electrode,
For example, in addition to zinc metal, compounds in the form of zinc oxide, chloride, complex, and the like can be mentioned. The content of this zinc species in the negative electrode (the amount added to the negative electrode) is not particularly limited, but is 0.1 to 5 parts by weight in terms of zinc oxide with respect to 100 parts by weight of the hydrogen storage alloy. preferable. By making the content of the zinc species in the negative electrode 0.1 part by weight or more as described above, the effect of reducing the corrosion of the hydrogen storage alloy during storage becomes remarkable, and 5 parts by weight or less. Thereby, the hydrogen storage / release of the hydrogen storage alloy can be favorably maintained.

In the present invention, the molybdenum species, chromium species, and tungsten species contained in the negative electrode include:
In addition to these metals, compounds in the form of oxides, chlorides, complexes and the like can be mentioned. The content of these metal species in the negative electrode (the amount added to the negative electrode) is not particularly limited, but is preferably smaller than the zinc species in terms of each metal. That is, zinc in the negative electrode exists in a divalent ionic state, but the valence of the metal species varies in the negative electrode. Therefore, when forming a compound with zinc, the effect is exhibited with a smaller amount than the zinc species. More specifically, the content is preferably 10 to 90%, more preferably 30 to 80% by weight based on the content of zinc species in the negative electrode (in terms of zinc oxide).

In the present invention, the utilization rate of the positive electrode active material is improved by including at least one metal species selected from the group consisting of molybdenum, chromium and tungsten in the negative electrode and zinc. It is not always clear at this time why this can be done and the storage properties can be improved,
It is considered as follows. First, when only zinc is contained in the negative electrode, zinc dissolves in the electrolytic solution, so that the effect of suppressing the elution of the added metal from the hydrogen storage alloy cannot be sufficiently obtained. It dissolves in and precipitates on the surface of the positive electrode, destroying the conductive network of cobalt in the positive electrode, lowering the utilization factor and lowering the storage characteristics, but the above molybdenum, chromium, tungsten and other metals When the seed is contained in the negative electrode, zinc and these metals form a complex compound on the surface of the hydrogen storage alloy, thereby suppressing the elution of the added metal in the hydrogen storage alloy into the electrolytic solution. In addition, it is considered that the dissolution of zinc itself can be reduced.

In the present invention, for example, a paste is prepared by kneading nickel hydroxide powder and a conductive additive with a binder such as carboxymethylcellulose, polytetrafluoroethylene, or styrene-butadiene rubber in the presence of water. This paste is supported on a conductive porous substrate such as a nickel foam, dried, and compression-molded to form a sheet. In this case, the conductive assistant is preferably a cobalt metal powder or a cobalt compound powder having an average particle size of 1 to 10 μm, and examples of the cobalt compound powder include a cobalt oxide powder and a cobalt hydroxide powder. Further, as another conductive aid, the average particle diameter is 3 μm.
The following nickel powder can be used in combination.

In the present invention, the positive electrode is immersed in an aqueous alkaline solution at 40 to 100 ° C. for 5 to 120 minutes after the above-mentioned compression molding, and then the positive electrode is subjected to 40 to 100 ° C. with the alkaline aqueous solution attached.
It is preferable to dry at 100 ° C. for 5 to 120 minutes, wash with water and dry.

By the above alkali immersion, dissolution and precipitation of cobalt or a cobalt compound in the positive electrode occurs, and a cobalt network is formed on the surface of nickel hydroxide in the positive electrode. When heat treatment is performed in this state, the cobalt network becomes a strong and high-order oxide. as a result,
It has excellent conductivity and can maintain a high utilization rate.

In the present invention, the hydrogen storage alloy used as the active material of the negative electrode includes Mm (La, Ce, Nd, Pd).
r) -Ni, Ti-Ni, Ti-NiZr (Ti
_2-x Zr _x V _4-y Ni _y ) _1-z Cr _z system (x = 0 to 1.
5, y = 0.6 to 3.5, z = 0.2 or less), Ti-M
Various hydrogen storage alloys such as n-based and Zr-Mn-based alloys may be mentioned, and among them, the above-mentioned Mm (La, Ce, Nd,
Part of Ni in a Pr) -Ni-based alloy, Mn, Co, A
1, an alloy substituted with at least one selected from the group consisting of Mg, Cu and Cr, wherein La in Mm is 33-7.
Those containing 0 atomic% are preferred. Such a hydrogen storage alloy can be expected to have a high capacity at a low hydrogen equilibrium pressure, and is preferable as a hydrogen storage alloy.However, a large amount of added metal exists on the surface, a large amount of the added metal is eluted, and the positive electrode active material Utilization rate tends to decrease. However, according to the present invention, the elution of the additional metal as described above can be prevented, and thus the present invention is particularly useful for such a hydrogen storage alloy.

In the present invention, the negative electrode comprises a hydrogen storage alloy as described above, at least one or more metal species selected from the group consisting of molybdenum, chromium and tungsten and zinc, and water. In the presence, these and, for example, carboxymethylloose, a thickener such as polyethylene oxide and a binder such as polytetrafluoroethylene, styrene butadiene rubber to prepare a paste, to prepare a paste, nickel-plated steel sheet perforated the paste or After being supported on a conductive porous base material such as a nickel foam, dried, and then subjected to compression molding, it is produced in a sheet shape.

In the hydride secondary battery of the present invention, the positive electrode and the negative electrode produced as described above and a separator made of nylon nonwoven fabric and the like for separating them are loaded into a battery can, and sodium hydroxide is used as an electrolyte. It is manufactured through a step of injecting an alkaline aqueous solution in which an electrolyte such as lithium hydroxide is dissolved in an aqueous solution such as potassium hydroxide or potassium hydroxide.

In the manufacture of the hydride secondary battery according to the present invention, after injecting the electrolytic solution, a temperature of 10 to 100
It is preferable to perform time aging and then charge. By performing such a treatment, the above-mentioned metal species and zinc species contained in the anode can easily form a complex compound on the surface of the hydrogen storage alloy, and the corrosion and inertness of the hydrogen storage alloy during storage can be facilitated. Can be more effectively prevented.

[0023]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples. In the following examples and the like, percentages indicating concentrations and the like are percentages by weight unless otherwise indicated.

Example 1 Commercially available Mm (La: 33 at%, Ce: 48 at%, N
d: 5 atomic%, Pr: 4 atomic%), Ni, Mo,
After melting Co, Mn and Al in an argon gas atmosphere using a high-frequency melting furnace, about 800 ° C./sec.
The alloy is quenched at a cooling rate of
Heat treated at 00 ° C for 6 hours to obtain a composition of MmNi _3.55 Mo _0.04
A hydrogen storage alloy represented by Co _0.75 Mn _0.4 Al _0.3 was obtained. This hydrogen storage alloy is evacuated in a pressure vessel,
After purging three times with argon gas, hydrogen pressure 14
By holding at 24 kg / cm ² for 24 hours, evacuating hydrogen, and further heating at 400 ° C. to completely release hydrogen,
A powder of 20-100 μm was obtained.

1 part by weight of the hydrogen storage alloy powder
10% by weight of 0% carboxymethylcellulose aqueous solution, 5
1 part by weight of a 0% styrene butadiene rubber dispersion, 3 parts by weight of zinc oxide and 2 parts by weight of lithium molybdate were added and kneaded to prepare a paste. The paste was filled and supported on a substrate made of a perforated steel sheet plated with nickel, dried, and compression-molded. Thereafter, the sheet was cut into a predetermined size to obtain a sheet-shaped negative electrode. 2 parts by weight of the above-mentioned lithium molybdate was 35% by weight based on the content of zinc species as molybdenum (in terms of zinc oxide).

Separately, nickel hydroxide powder 100
10 parts by weight of nickel powder (1 μm in average particle size)
m), 10 parts by weight of cobalt oxide powder (average particle size 3 μm)
m) 10 parts by weight of a 10% carboxymethylcellulose aqueous solution and 60% polytetrafluoroethylene dispersion 5
A part by weight was added and kneaded to prepare a paste. This paste was filled in a substrate made of a nickel foam, supported, dried at 80 ° C. for 2 hours, and then compression-molded at 1 ton / cm ² to form a sheet. This was immersed in an alkaline aqueous solution at 70 ° C. for 60 minutes, then dried at 70 ° C. for 60 minutes with the alkaline aqueous solution attached, washed with water, dried, and cut into a predetermined size to obtain a sheet-shaped positive electrode.

As the electrolytic solution, an alkaline aqueous solution obtained by dissolving 17 g / l of lithium hydroxide (LiOH) in a 30% aqueous potassium hydroxide solution was used. The above sheet-shaped negative electrode and sheet-shaped positive electrode were made of nylon nonwoven fabric. After being wound through a separator and inserted into an AA size battery can, the above-mentioned electrolytic solution was injected, and the battery can was sealed and sealed in a conventional manner, and then stored at 40 ° C. for 7 hours. , 0.1C (120m
Charge for 15 hours at A) and 1. at 0.2 C (220 mA).
Discharged to 0V. This charge / discharge cycle was repeated until the discharge capacity became constant, to produce a hydride secondary battery of AA size having the structure shown in FIG.

Now, the hydride secondary battery shown in FIG. 1 will be described. The positive electrode 1 is composed of a paste-type nickel electrode using the above-mentioned nickel hydroxide as an active material, and the negative electrode 2 is composed of the above-mentioned hydrogen storage alloy as an active material. It is composed of a paste-type hydrogen storage alloy containing lithium molybdate as a molybdenum species and zinc oxide as a zinc species. In FIG. 1, the positive electrode 1 and the negative electrode 2 are not shown in detail, and the base material and the like are not shown. It is omitted and shown as a single configuration. And
The separator 3 is made of a non-woven nylon fabric, and the positive electrode 1 and the negative electrode 2 are overlapped with each other via the separator 3, spirally wound and inserted into the battery can 5 as a wound electrode body 4. An insulator 14 is disposed on the upper part. An insulator 13 is provided on the bottom of the battery can 5 before the electrode body 4 is inserted.

The annular gasket 6 is made of nylon 66, and the battery lid 7 is composed of a terminal plate 8, a sealing plate 9, a metal spring 10 and a valve body 11 arranged in an internal space formed by the terminal plate 8, a sealing plate 9, and a battery can. The opening 5 is sealed with the battery cover 7 or the like. That is, after inserting the wound electrode body 4 and the insulators 13 and 14 into the battery can 5, an annular groove 5 a having a bottom protruding inward is formed in the vicinity of the open end of the battery can 5. The annular gasket 6 and the battery lid 7 are arranged in the opening of the battery can 5 by supporting the lower portion of the annular gasket 6 by the inner peripheral side protruding portion of the groove 5a. The opening of the battery can 5 is sealed by being tightened inward. The terminal plate 8 is provided with a gas discharge hole 8a, the sealing plate 9 is provided with a gas detection hole 9a, and a metal spring 10 and a valve body 11 are arranged between the terminal plate 8 and the sealing plate 9. ing. Then, the outer peripheral portion of the sealing plate 9 is bent to sandwich the outer peripheral portion of the terminal plate 8, thereby fixing the terminal plate 8 and the sealing plate 9.

Under normal circumstances, this battery is a metal spring 1
Since the valve body 11 closes the gas detection hole 9a by the pressing force of 0, the inside of the battery is kept in a sealed state, but gas is generated inside the battery and the pressure inside the battery rises abnormally. , The metal spring 10 contracts to form a gap between the valve body 11 and the gas detection hole 9a, and gas inside the battery passes through the gas detection hole 9a and the gas discharge hole 8a and is discharged to the outside of the battery. As a result, when the battery internal pressure decreases and the battery internal pressure returns to normal, the metal spring 10 is restored to the original state,
The pressing force causes the valve body 11 to close the gas detection hole 9a again to keep the inside of the battery in a sealed structure. As described above, the metal spring 10 and the valve element 11 are the main members of the safety valve. However, the safety valve is not composed of only the metal spring 10 and the valve element 11, but includes the terminal plate 8, the sealing plate 9, and the like. It is composed of members having other functions.

The positive electrode lead body 12 is made of a nickel ribbon, one end of which is spot-welded to an exposed portion of the base material at the outermost periphery of the positive electrode 2, and the other end is spot-welded to the lower end of the sealing plate 9. And the terminal plate 8 is connected to the sealing plate 9.
And can function as a positive electrode terminal. As described above, the base material is exposed on the outer surface of the outermost peripheral portion of the negative electrode 2, and the base material contacts the inner wall of the battery can 5, whereby the battery can 5 functions as a negative electrode terminal. .

Example 2 A hydride secondary battery was produced in the same manner as in Example 1, except that the negative electrode contained 2 parts by weight of potassium chromate instead of lithium molybdate. 2 parts by weight of this potassium chromate was 28% by weight based on the content of zinc as chromium (in terms of zinc oxide).

Example 3 A hydride secondary battery was manufactured in the same manner as in Example 1, except that the negative electrode contained 2 parts by weight of potassium tungstate instead of lithium molybdate. 2 parts by weight of this potassium tungstate was 38% by weight based on the content of zinc as zinc (in terms of zinc oxide).

Example 4 A hydride secondary battery was manufactured in the same manner as in Example 1 except that the negative electrode contained 2 parts by weight of lithium molybdate and 2 parts by weight of potassium chromate. 2 parts by weight of this lithium molybdate is 35% by weight based on the content of zinc species as molybdenum (in terms of zinc oxide), and 2 parts by weight of potassium chromate contains the content of zinc species as chromium (zinc oxide). (In terms of conversion) was 28% on a weight basis.

Example 5 A hydride secondary battery was manufactured in the same manner as in Example 1 except that the negative electrode contained lithium molybdate and potassium tungstate in an amount of 2 parts by weight each. 2 parts by weight of this lithium molybdate is 35% by weight based on the content of zinc species as molybdenum (in terms of zinc oxide), and 2 parts by weight of potassium tungstate is the content of zinc species as tungsten (zinc oxide). 3 on a weight basis for
8%.

Example 6 A hydride secondary battery was produced in the same manner as in Example 1 except that the negative electrode contained 2 parts by weight of lithium chromate and 2 parts by weight of potassium tungstate, respectively. 2 parts by weight of this lithium chromate is 28% by weight based on the content of zinc species as chromium (calculated as zinc oxide), and 2 parts by weight of potassium tungstate is the content of zinc species as tungsten (calculated as zinc oxide). ) Was 38% by weight.

Example 7 A hydride secondary battery was manufactured in the same manner as in Example 1 except that the negative electrode contained 0.5 part by weight of lithium molybdate, lithium chromate and potassium tungstate, respectively. 0.5 parts by weight of this lithium molybdate is 8.5% by weight based on the content of zinc species as molybdenum (in terms of zinc oxide), and 0.5 parts by weight of lithium chromate is zinc species as chromium. The content (in terms of zinc oxide) is 7% on a weight basis, and 0.5 parts by weight of potassium tungstate is 9.4% in terms of the weight of zinc species as tungsten (in terms of zinc oxide). Met.

Example 8 A hydride secondary battery was produced in the same manner as in Example 1, except that the content of zinc oxide in the negative electrode was changed to 1.2 parts by weight. As a result, 2 parts by weight of lithium molybdate became 85% by weight based on the content of zinc species (in terms of zinc oxide) as molybdenum.

Example 9 Except that the content of zinc oxide in the negative electrode was changed to 5 parts by weight,
A hydride secondary battery was produced in the same manner as in Example 1. As a result, 2 parts by weight of lithium molybdate became 20% by weight based on the content of zinc species (in terms of zinc oxide) as molybdenum.

Comparative Example 1 A hydride secondary battery was produced in the same manner as in Example 1, except that the negative electrode contained 4 parts by weight of zinc oxide and did not contain lithium molybdate.

Comparative Example 2 A hydride was prepared in the same manner as in Example 1 except that the positive electrode contained 3 parts by weight of zinc oxide, the alkali treatment was not performed, and the negative electrode contained neither zinc oxide nor lithium molybdate. A secondary battery was manufactured.

With respect to the hydride secondary batteries of Examples 1 to 9 and Comparative Examples 1 and 2, the utilization factor and storage characteristics of the positive electrode active material were examined. Note that the utilization rate of the positive electrode active material is 0.1%.
The battery was charged at 1 C for 15 hours and discharged at 0.2 C to 1.0 V. This charge / discharge cycle was repeated until the discharge capacity became constant, and the discharge capacity when the discharge capacity became constant was divided by the charge capacity. [(Discharge capacity / filling capacity) × 100], and the storage characteristics of the battery after the discharge were stored at 60 ° C. × 60 days, charged at 0.1 C (120 mA) for 15 hours, and 3 charge / discharge cycles for discharging to 1.0 V at 2 C (220 mA) are set as the discharge capacity after storage, and the same charge / discharge cycle as above is repeated 3 times before storage, Using the third discharge capacity as the discharge capacity before storage, the capacity retention after storage was determined by the following equation.

Capacity retention after storage (%) = (discharge capacity before storage / discharge capacity after storage) × 100

Table 1 shows the utilization factor of the positive electrode active material and the capacity retention ratio after storage as determined above.

[0045]

[Table 1]

As is clear from the results shown in Table 1, the batteries of Examples 1 to 9 have higher utilization rates of the positive electrode active material and the capacity retention after storage than the batteries of Comparative Examples 1 and 2. And the storage characteristics were excellent.

[0047]

As described above, according to the present invention, a hydride secondary battery having a high utilization rate of the positive electrode active material and excellent storage characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a hydride secondary battery of the present invention.

[Explanation of symbols]

 1 positive electrode 2 negative electrode 3 separator

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Ryu Nagai 1-88 Ushitora, Ibaraki-shi, Osaka F-term within Hitachi Maxell, Ltd. (Reference) 5H003 AA02 AA03 BB02 BB04 5H016 AA02 EE01 EE05 5H028 AA05 AA06 AA08 EE01 EE05 EE09

Claims (2)

[Claims] 1. A hydride secondary battery comprising a separator having a positive electrode having nickel hydroxide as a positive electrode active material, a negative electrode having a hydrogen storage alloy as a negative electrode active material, an electrolytic solution comprising an aqueous alkali solution, and a separator. , At least one selected from the group consisting of chromium species and tungsten species
A hydride secondary battery comprising at least two kinds of metal species and zinc species. 2. The hydride secondary battery according to claim 1, wherein the positive electrode contains cobalt metal or a cobalt compound.