JP2000348718A - Hydrogen storage alloy for alkaline storage battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a charge-discharge cycle characteristic and restrain the increase of the internal pressure of a battery by sticking a Zr compound to minute holes formed in the surfaces of hydrogen storage alloy particles. SOLUTION: This hydrogen storage alloy for a battery is formed by immersing hydrogen storage alloy particles 1 in an acidic solution with zirconium chloride added and thereafter extracting, washing and drying them. As a result, minute holes 2 are formed in the surfaces of the hydrogen storage alloy particles 1, and a Zr compound 3 is deposited on and stuck to the minute holes 2. Preferably, zirconium chloride is added by 0.3-5.0 wt.% with respect to the weight of the hydrogen storage alloy particles 1. The suitable initial pH of the acidic aqueous solution containing zirconium chloride is 0.7-2.0, and hydrochloric acid, nitric acid or phosphoric acid is used as the acid. In particular, the hydrogen storage alloy particles 1 produced by a gas atomization method is preferably used, and this increases the reaction area in the battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen storage alloy used as a negative electrode material for an alkaline storage battery. More specifically, the present invention relates to a hydrogen storage alloy electrode having excellent cycle characteristics and capable of suppressing an increase in the internal pressure of the battery. The present invention relates to improvement of a hydrogen storage alloy powder as an electrode material for the purpose of obtaining.

[0002]

2. Description of the Related Art In recent years, nickel-metal hydride storage batteries that are twice as high as nickel-cadmium storage batteries and have excellent environmental compatibility have attracted attention as new alkaline storage batteries. However, with the spread of various portable devices, this nickel-hydrogen storage battery is expected to have higher performance. Here, the hydrogen storage alloy used for the negative electrode of the nickel-hydrogen storage battery generally has a coating such as an oxide formed on its surface by natural oxidation or the like, and the hydrogen storage alloy is manufactured using such a hydrogen storage alloy. However, when this hydrogen storage alloy electrode is used as a negative electrode of a nickel-metal hydride storage battery, there are problems such that the activity of the hydrogen storage alloy in the initial stage is low and the battery capacity in the initial stage is low.

For this reason, in recent years, for example,
As disclosed in Japanese Patent No. 225975, a method has been proposed in which a hydrogen storage alloy is immersed in an acidic solution such as hydrochloric acid to remove an oxide film on the surface of the hydrogen storage alloy. here,
When the hydrogen storage alloy is immersed in an acidic solution to remove oxide films and the like on the surface of the hydrogen storage alloy, active metal nickel (Ni), metal cobalt (Co), etc. are formed on the surface of the hydrogen storage alloy. Appear.

However, the active sites on the surface are oxidized again, so that the initial activity of the hydrogen storage alloy is not sufficiently improved, the initial discharge capacity is still low, and the cycle characteristics are inferior. There is.

[0005] Further, by removing the oxide film by the above method, sites such as active metals Ni and Co appear on the surface,
Although the initial discharge capacity is improved, the oxidation resistance in the charge / discharge alkaline electrolyte is not improved and the increase in the internal pressure of the battery is not suppressed.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to improve the charge / discharge cycle characteristics and the internal pressure of a battery used in nickel-metal hydride storage batteries. An object of the present invention is to obtain a hydrogen storage alloy used for a hydrogen storage alloy electrode, which suppresses the rise of the hydrogen storage alloy.

[0007]

The present invention relates to a hydrogen storage alloy for an alkaline storage battery in which a zirconium compound is adhered to micropores formed on the surfaces of hydrogen storage alloy particles. The hydrogen storage alloy particles have a CaCu ₅ type crystal structure, and have a composition formula of MmNi _x Co _y Mn _z M _1-z [where M is aluminum (A
l), at least one element selected from copper (Cu), x
Is the abundance ratio of nickel (Ni), and 3.0 ≦ x ≦ 5.2, y
Is the abundance ratio of cobalt (Co) and 0 <y ≦ 1.2, z is the abundance ratio of manganese (Mn) and is 0.1 ≦ z ≦ 0.9, and the sum of x, y and z is 4.4 ≦ x + y + z ≦ 5.
4] can be exemplified as a typical example. When the composition is used as a hydrogen storage alloy in an alkaline storage battery in this composition range, corrosion in an alkaline electrolyte is suppressed, and an increase in the amount of hydrogen storage can be remarkably aimed at.

By filling the conductive core with the hydrogen storage alloy, a hydrogen storage alloy electrode for an alkaline storage battery is formed. Using these electrodes, an alkaline storage battery is formed.

Further, the present invention provides a first step of preparing hydrogen storage alloy particles capable of reversibly storing and releasing hydrogen, and converting the alloy particles prepared in the first step to zirconium chloride (ZrCl _4). A) immersing it in an acidic solution to which the hydrogen storage alloy is added, and washing the alloy particles after the second step with water, and drying the alloy particles to form a hydrogen storage alloy. ,
The alloy particles are characterized in that zirconium compounds are precipitated in micropores on the surface.

Here, the particles of the hydrogen storage alloy are CaCu
_FiveHaving a type crystal structure and a composition formula of MmNi_xCo _yMn_zM_1-z[Where M is
At least selected from aluminum (Al) and copper (Cu)
A kind of element, x is the abundance ratio of nickel (Ni).
0 ≦ x ≦ 5.2, y is the abundance ratio of cobalt (Co)
<Y ≦ 1.2, z is the abundance ratio of manganese (Mn) and is 0.1
≦ z ≦ 0.9, and the total value of the x, y, and z is 4.4 ≦
x + y + z ≦ 5.4].

In the second step, zirconium chloride is added in an amount of 0.3 to 5.0% by weight based on the weight of the alloy particles.

Furthermore, in the second step, the acidic solution has a pH of 0.7 to 2.0.

On the other hand, the first step may be performed by gas atomizing to prepare particles of a hydrogen storage alloy.

By filling a conductive core with the hydrogen storage alloy obtained by the method for producing a hydrogen storage alloy for an alkaline storage battery, a hydrogen storage alloy electrode for an alkaline storage battery can be provided.

In the second step, the particles of the hydrogen storage alloy are immersed and treated in an acidic solution to which zirconium chloride is added. A zirconium compound precipitates in the micropores. Precipitation of the zirconium compound is preferentially performed in micropores on the surface of the hydrogen storage alloy as compared with other sites. Add zirconium chloride in an amount of 0.3
The reason for setting the content to ~ 5.0% by weight is that if the content is less than 0.3% by weight, the precipitated zirconium compound is small, and if the content is more than 5.0% by weight, the deposited zirconium compound becomes excessive and inhibits the electrochemical reaction on the alloy surface. .

Further, in the second step, a suitable initial pH of the acidic aqueous solution is in the range of 0.7 to 2.0. If the pH is lower than 0.7, the oxidation of the alloy particles occurs rapidly, and the inside of the hydrogen storage alloy is melted.
This is because if it is higher, the oxide film is not sufficiently removed. Examples of the acidic aqueous solution used in the second step include hydrochloric acid, nitric acid, and phosphoric acid.

Thus, the hydrogen storage alloy according to the present invention having the structure shown in FIG. 1 is obtained. FIG. 1 is an explanatory view schematically showing the state of the hydrogen storage alloy of the present invention. As shown in FIG. 1, on the surface of the hydrogen storage alloy particles 1, there are micropores 2 formed in step 2, and the zirconium compound 3 precipitates and adheres to the micropores 2.

These effects can be expected not only for alloy particles produced and pulverized by an arc furnace in an argon atmosphere and alloy particles produced by a roll quenching method but also for alloy particles produced by a gas atomizing method.
In particular, the particles of the hydrogen storage alloy formed by the gas atomization method have a smooth surface and a small number of fine pores, so that by performing immersion treatment with an acidic aqueous solution, the specific surface area of the alloy particles is increased, and the reaction area in the battery is increased. It can be said that it can be increased and is suitable.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail together with comparative examples. However, the present invention is not limited to the following embodiments, and the present invention is carried out by appropriately changing the scope of the present invention. It is possible. (Experiment 1) In Experiment 1, the effect of zirconium chloride on the battery characteristics was examined for the presence or absence of zirconium chloride when the hydrogen storage alloy particles were treated in an acidic aqueous solution. The result will be described below. The description will be made in the order of preparation of alloy particles, preparation of each sample, assembly of an alkaline storage battery, evaluation conditions of characteristics, and detailed results. [Preparation of MmNi _3.1 Co _0.9 Mn _0.6 Al _0.4 alloy particles] Mm (Misch metal Mm is a mixture of rare earth elements, La: 25% by weight, Ce: 50% by weight, Pr: 7% by weight, Nd: 18% by weight %), N
i, Co, Mn, Al (each elemental material is a simple metal with a purity of 99.9%) mixed in a molar ratio of 1.0: 3.1: 0.9: 0.6: 0.4, and roll quenched in an argon atmosphere to form a composition Formula MmNi
An alloy represented by _3.1 Co _0.9 Mn _0.6 Al _0.4 was produced. This alloy was mechanically pulverized in air to obtain alloy particles adjusted to an average particle size of 80 μm. . [Samples A1 to A10] Using the above alloy particles, zirconium chloride (ZrCl ₃ ) was contained in an amount of 0% by weight (no addition) to 10.0% by weight based on the alloy particles, and 30% in a hydrochloric acid aqueous solution adjusted to pH = 1.0. It was immersed for a minute and stirred. Thereafter, suction filtration, washing with water and drying were performed to obtain Samples A1 to A10. As a result,
Zirconium chloride precipitates and adheres as a zirconium compound in which zirconium hydroxide and zirconium oxide are mixed.

On the other hand, as a comparative example, as shown in Japanese Patent Application Laid-Open No. 5-225975, a treatment solution containing a hydrochloric acid aqueous solution prepared at 0.5 N (pH = 0.3) and maintained at 25 ° C. Inside, the alloy particles were immersed and stirred for 30 minutes. Thereafter, suction filtration, washing with water and drying were performed to obtain Comparative Sample X. [Assembly of Alkaline Storage Battery] A paste was prepared by mixing 100 parts by weight of each of the hydrogen storage alloys prepared above and 20 parts by weight of an aqueous solution of 5% by weight of PEO (polyethylene oxide) as a binder. This paste was applied (filled) on both surfaces of a conductive core made of punched metal plated with nickel and dried at room temperature. Thereafter, the resultant was cut into a predetermined size to prepare a hydrogen storage alloy electrode for an alkaline storage battery.

Using this hydrogen storage alloy electrode as a negative electrode,
AA-size positive electrode-dominated alkaline storage battery (battery capacity 1000
mAh). A conventionally known sintered nickel electrode as a positive electrode, an alkali-resistant nonwoven fabric as a separator,
In addition, a 30% by weight aqueous solution of potassium hydroxide was used as an electrolyte.

FIG. 2 is a schematic sectional view of the assembled alkaline storage battery. The positive electrode 11 and the negative electrode 12, the separator 13, the positive electrode lead 14, the negative electrode lead 15, the positive external terminal 16, the negative electrode can 17,
It consists of a sealing lid 18 and the like.

The positive electrode 11 and the negative electrode 12 are accommodated in a negative electrode can 17 while being spirally wound through a separator 13. The positive electrode 11 is connected to a sealing lid 18 via a positive electrode lead 14, and Numeral 12 is connected to a negative electrode can 17 via a negative electrode lead 15. An insulating packing 20 is attached to the joint between the negative electrode can 17 and the sealing lid 18 to hermetically seal the battery. A coil spring 19 is provided between the positive electrode external terminal 16 and the sealing lid 18 so that when the battery internal pressure rises abnormally, the battery is compressed and the gas inside the battery can be released to the atmosphere. [Characteristic Evaluation Conditions] The charge / discharge cycle characteristics of each battery described above were determined. The condition at this time is that after the battery activation is completed, each battery is charged at room temperature at a current value of 1.5 C for 0.8 hours, and the current value is 1.5
The cycle of discharging to 1.0 V at C is repeated, and the number of cycles when the discharge capacity reaches 75% of the designed capacity (1000 mAh) is actually measured.

The internal pressure characteristics of each battery were determined. The condition at this time is that after the activation of the battery is completed, the battery is continuously charged at a current value of 1.0 C and the internal pressure of the battery is measured. Note that the internal pressure characteristic is a charging time (mi) until the internal pressure of the battery becomes 10 kgf / cm ^2.
n). [Detailed results] The above-mentioned samples A1 to A10 and comparative sample X
Table 1 shows the amount of zirconium chloride used, the initial discharge capacity of each battery, and the internal pressure characteristics (min) in each battery using.

[0025]

[Table 1]

Samples A1 to A10 which had been treated in an aqueous hydrochloric acid solution to which no zirconium chloride (ZrCl ₄ ) had been added or which had been added at 10.0 wt% or less had larger charge / discharge cycle characteristics and inner pressure characteristics than the comparative sample X. Value.

[0027] In particular, 142Min in each cell zirconium chloride (ZrCl ₄₎ were used samples A2~ sample A8 is 0.3 wt% to 5.0 wt%, 832 cycles charge-discharge cycle characteristics 790 cycles, the internal pressure characteristics of 134min It showed a high value. Therefore, it is understood that the addition amount of zirconium chloride (ZrCl ₄ ) is particularly preferably in the range of 0.3% by weight to 5.0% by weight.

In Experiment 1, in step 2 which is a process for preparing a hydrogen storage alloy, an aqueous hydrochloric acid solution was used as the acidic aqueous solution. However, the same tendency is observed with nitric acid and phosphoric acid. (Experiment 2) In Experiment 2, the pH of the acidic solution used in the second step of producing the hydrogen storage alloy was changed to examine the relationship with the battery characteristics.

Using the alloy particles prepared in Experiment 1 above, zirconium chloride (ZrCl ₄ ) was contained at 3.0% by weight and pH = 0.3.
The mixture was immersed and stirred in a hydrochloric acid aqueous solution adjusted to ~ 3.0 for 30 minutes, filtered by suction, washed with water and dried. Thereafter, samples were washed with water and dried to obtain a hydrogen storage alloy, and samples B1 to B6 were prepared. Then, in the same manner as in Experiment 1, a battery was manufactured using Samples B1 to B6.

Table 2 shows the measurement results of the initial discharge capacity and the measurement result of the high rate discharge capacity of the batteries using the samples B1 to B6. The conditions for producing the battery and the conditions for measuring the capacity were the same as those in Experiment 1 described above.

[0031]

[Table 2]

After adding 3.0% by weight of zirconium chloride (ZrCl ₄ ), treating with a hydrochloric acid aqueous solution having a pH of 0.3 to 3.0, washing with water and drying, the batteries using the samples B1 to B6 according to the present invention include: The charge-discharge cycle characteristics showed values from 767 cycles to 830 cycles, and the internal pressure characteristics also showed values from 130 min to 142 min.

In the batteries using the samples B3 to B5 treated at pH = 0.7 to 2.0, the charge / discharge cycle characteristics were from 820 cycles to 8 cycles.
In 30 cycles, the internal pressure characteristics also showed particularly high values from 138 min to 142 min. Therefore, as the pH of the acidic solution, particularly 0.7 to 2.0
Is preferable.

In Experiment 2, a hydrochloric acid aqueous solution was used as the acidic aqueous solution in Step 2 which is a manufacturing process of the hydrogen storage alloy. A similar tendency is observed with nitric acid and phosphoric acid.

In the examples, the alloy particles prepared by the roll quenching method are shown, but the same effect can be obtained by the alloy particles produced by the gas atomizing method.

[0036]

As described in detail above, according to the hydrogen storage alloy for an alkaline storage battery and the method of manufacturing the same according to the present invention,
The charge / discharge cycle characteristics are improved, and an increase in battery internal pressure can be suppressed. By forming an electrode using this alloy and using it for the negative electrode of a nickel-metal hydride storage battery, the charge / discharge cycle characteristics and battery internal pressure characteristics are improved, and its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a hydrogen storage alloy of the present invention.

FIG. 2 is a schematic sectional view of an alkaline storage battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydrogen storage alloy particle 2 Micropore 3 Zirconium compound 11 Positive electrode 12 Negative electrode 13 Separator 14 Positive electrode lead 15 Negative electrode lead 16 Positive external terminal 17 Negative can 18 Sealing lid 19 Coil spring 20 Packing

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshihiro Masuda 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Kikuko Kato 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Nobuyuki Higashiyama 2-5-5, Keihanhondori, Moriguchi-shi, Osaka Pref. Sanyo Electric Co., Ltd. (72) Mamoru Kimoto Keihan-hondori, Moriguchi-shi, Osaka 2-5-5 Sanyo Electric Co., Ltd. (72) Inventor Yasuhiko Ito 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 4K017 AA01 BA08 BB05 BB06 BB07 BB09 CA01 EB17 4K018 AA11 BC01 BD07 KA38 5H003 AA04 BA01 BA02 BB02 BC05 BC06 BD00 BD04 BD06 5H016 AA05 BB09 EE01 HH01 HH08 5H028 EE01 FF02 FF04

Claims (10)

[Claims] 1. A hydrogen storage alloy for an alkaline storage battery in which a zirconium compound is attached to fine pores formed on the surface of hydrogen storage alloy particles capable of reversibly storing and releasing hydrogen. Wherein said hydrogen absorbing alloy particles have a CaCu ₅ type crystal structure, a composition formula _{MmNi x Co y Mn z M 1} -z [ wherein M is selected from aluminum (Al), copper (Cu) X is an abundance ratio of nickel (Ni), and 3.0 ≦ x
≦ 5.2, y is the abundance ratio of cobalt (Co), and 0 <y ≦
1.2, z is the abundance ratio of manganese (Mn), and 0.1 ≦ z ≦
0.9, and the total value of the x, y, and z is 4.4 ≦ x + y +
2. The hydrogen storage alloy according to claim 1, wherein z ≦ 5.4]. 3. A hydrogen storage alloy electrode for an alkaline storage battery, wherein the conductive core is filled with the hydrogen storage alloy for an alkaline storage battery according to claim 1. 4. An alkaline storage battery using the hydrogen storage alloy electrode for an alkaline storage battery according to claim 3. 5. A first step of preparing hydrogen storage alloy particles capable of reversibly storing and releasing hydrogen, and adding zirconium chloride (ZrCl ₄ ) to the alloy particles prepared in the first step. A second step of immersing the alloy particles in an acidic solution; and a method of manufacturing a hydrogen storage alloy for an alkaline storage battery, wherein the alloy particles after the second step are washed with water and dried to form a hydrogen storage alloy, Is a method for producing a hydrogen storage alloy for an alkaline storage battery, wherein a zirconium compound is precipitated in micropores on the surface. Wherein particles of the hydrogen absorbing alloy has a CaCu ₅ type crystal structure, a composition formula _{MmNi x Co y Mn z M 1} -z [ wherein M is selected from aluminum (Al), copper (Cu) X is the abundance ratio of nickel (Ni), and 3.0 ≦
x ≦ 5.2, y is the abundance ratio of cobalt (Co), and 0 <y
≦ 1.2, z is the abundance ratio of manganese (Mn) and 0.1 ≦ z
≦ 0.9, and the sum of the x, y, and z is 4.4 ≦ x + y
+ Z ≦ 5.4], wherein the method for producing a hydrogen storage alloy for an alkaline storage battery according to claim 5 is provided. 7. In the second step, zirconium chloride (ZrCl ₄ ) is added in an amount of 0.3 to 0.3 wt.
6. The method for producing a hydrogen storage alloy for an alkaline storage battery according to claim 5, wherein 5.0% by weight is added. 8. In the second step, an acidic solution is used.
The method for producing a hydrogen storage alloy for an alkaline storage battery according to claim 5, wherein the pH is 0.7 to 2.0. 9. The method for producing a hydrogen storage alloy for an alkaline storage battery according to claim 5, wherein said first step is a gas atomization method. 10. A hydrogen storage alloy for an alkaline storage battery, characterized in that a conductive core is filled with the hydrogen storage alloy obtained by the method for producing a hydrogen storage alloy for an alkaline storage battery according to any one of claims 5 to 9. Manufacturing method of electrode.