JP2001068147A - Nickel - hydrogen alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably improve a high-temperature characteristic and a cycle characteristic while preventing degradation of battery capacity. SOLUTION: In this nickel - hydrogen alkaline storage battery, a negative electrode containing a hydrogen storage alloy as a main constituent and a positive electrode containing a nickel oxide as a main constituent are installed in a battery can through a separator with an alkaline electrolytic solution impregnated. In this case, a rare-earth compound exceeding saturated concentration is dispersed in an ion state or molecule state in the alkaline electrolytic solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a nickel-based battery in which a negative electrode mainly composed of a hydrogen storage alloy and a positive electrode mainly composed of nickel are disposed in a battery can via a separator impregnated with an alkaline electrolyte. It relates to a hydrogen-alkaline storage battery.

[0002]

2. Description of the Related Art In recent years, hydrogen storage alloys capable of reversibly storing and releasing hydrogen have been actively developed.
Nickel using such a hydrogen storage alloy as a negative electrode material
Hydrogen-alkaline storage batteries are conventionally used lead storage batteries,
It is expected to occupy the mainstream of next-generation alkaline storage batteries because they are lighter in weight and higher in capacity than nickel-cadmium storage batteries and the like.

Here, the nickel-hydrogen alkaline storage battery has a problem that it has poor high-temperature characteristics and cycle characteristics. Then, in order to improve the above characteristics, the following batteries have been proposed.

(1) Japanese Patent Application Laid-Open No. 62-249364,
JP-A-10-21904, or JP-A-10-1
As disclosed in JP 06620 and the like, a battery in which a rare earth element (particularly, yttrium) is added to an electrolytic solution has been proposed. In such a battery, although the high temperature characteristics and the cycle characteristics can be improved to some extent, there is a problem that the effect of the improvement is insufficient because the amount of the rare earth element added is small.

(2) JP-A-63-166146,
JP-A-6-215765, USP 5,547,7
As shown at 84, a battery has been proposed in which a rare earth element is added to a positive electrode or a negative electrode. In such a battery, the amount of addition can be increased, so that high-temperature characteristics and cycle characteristics can be improved, but the amount of the positive electrode active material and the negative electrode active material is reduced by the amount of the rare earth element added to the positive electrode and the negative electrode. Therefore, new problems such as a decrease in battery capacity arise.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned conventional problems, and has a significant improvement in high-temperature characteristics and cycle characteristics while preventing a decrease in battery capacity. It is an object of the present invention to provide a nickel-hydrogen alkaline storage battery that can be used.

[0007]

In order to achieve the above object, a nickel-hydrogen alkaline storage battery according to the present invention comprises a negative electrode mainly composed of a hydrogen storage alloy and a positive electrode mainly composed of nickel oxide. In a nickel-hydrogen alkaline storage battery disposed in a battery can via a separator impregnated with a liquid, the alkaline electrolyte may have a rare earth compound exceeding a saturation concentration dispersed in an ionic state or a molecular state. Features.

As described above, if the rare earth compound exceeding the saturation concentration is dispersed in the alkaline electrolyte in the ionic state or molecular state, a large amount of the rare earth compound can be added, so that the high temperature characteristics and the cycle characteristics are reduced. It can be dramatically improved. In addition, since the rare earth compound is dispersed in the alkaline electrolyte, it is not necessary to reduce the amount of the positive electrode active material or the negative electrode active material, and as a result, it is possible to prevent problems such as a reduction in battery capacity.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, a dispersant is contained in the alkaline electrolyte. As described above, if the dispersant is contained in the alkaline electrolyte, the rare earth compound is more uniformly dispersed, so that the above-mentioned effect is further exhibited. The invention according to claim 3 is characterized in that, in the invention according to claim 2, a surfactant or a complexing agent is used as the dispersant.

[0010] The invention described in claim 4 is based on claim 1,
4. The invention according to the item 2 or 3, wherein an yttrium compound and / or an ytterbium compound is used as the rare earth compound. Since yttrium and ytterbium have low solubility in an alkaline electrolyte and are stably present in the alkaline electrolyte, the above-mentioned effects are further exhibited.

[0011]

DETAILED DESCRIPTION OF THE INVENTION (Preparation of Negative Electrode) First, commercially available misch metal (Mm; a mixture of rare earth elements such as La, Ce, Nd, Pr), nickel (Ni), cobalt (C
o), aluminum (Al), and manganese (Mn) as raw materials, each having an element ratio of 1: 3.7: 0.55:
After mixing at a ratio of 0.3: 0.5, the mixture was melted at 1500 ° C. using a high-frequency induction heating melting furnace, and the molten metal was further cooled on a water-cooled copper roll to obtain a composition formula of MmNi _3.7 Co. A hydrogen storage alloy represented by _0.55 Al _0.3 Mn _0.5 was produced. Next, the hydrogen storage alloy was pulverized to obtain a hydrogen storage alloy powder having an average particle size of 60 μm.

Next, the hydrogen storage alloy powder (1 kg)
Then, a treatment of adding an acidic solution (1 kg) having a pH of 1 and mixing and stirring was performed for 10 minutes to perform a surface treatment of the hydrogen storage alloy powder. Thereafter, the hydrogen storage alloy powder was sufficiently washed with pure water. Thereafter, 99 parts by weight of the hydrogen storage alloy powder were mixed with PEO (polyethylene oxide) as a binder.
After 1 part by weight and water were added and kneaded to prepare a slurry, the slurry was applied on a punching metal, dried and rolled to produce a hydrogen storage alloy negative electrode.

(Preparation of Positive Electrode) 100 parts by weight of nickel hydroxide, 7 parts by weight of metal cobalt as a conductive agent, 5 parts by weight of cobalt hydroxide, and 20 parts by weight of an aqueous solution containing 1% by weight of methylcellulose as a binder Then, the slurry was prepared by kneading the mixture and a slurry, and the slurry was filled in a porous substrate made of foamed metal, and then dried and pressed to produce a non-sintered nickel positive electrode.

(Preparation of electrolytic solution) In a KOH aqueous solution having a specific gravity of 1.30, 40 g of LiOH.H ₂ O and 10 g of NaOH were added.
After dissolving g, an electrolyte solution was prepared, and yttrium oxide was added to the electrolyte solution at a rate of 25 mg / l and dispersed with a homogenizer.

(Production of Battery) The above-mentioned hydrogen storage alloy negative electrode and non-sintered nickel positive electrode were wound around a separator made of polypropylene to produce a power generating element, and this power generating element was housed in a battery can. After the electrolyte containing the yttrium oxide was injected into the battery can, the outer can was sealed to produce a nickel-hydrogen alkaline storage battery having a theoretical capacity of 1000 mAh. The electrolyte was injected immediately after the yttrium was dispersed.

In the above embodiment, when dispersing yttrium oxide, a dispersant is not contained in the alkaline electrolyte, but a dispersant comprising a surfactant or a complexing agent may be contained. It is. In this case, it is possible to disperse with a homogenizer, but it is also possible to disperse with an ordinary mixer.
As the surfactant, an ionic surfactant may be used in addition to a neutral surfactant.
Besides, HEDTA, DOTA, crown ether and the like can also be used.

The rare earth compound is not limited to the above yttrium oxide, but may be lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, ytterbium oxide, scandium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, terbium oxide, or the like. Dysprosium, holmium oxide, erbium oxide,
Thulium oxide, lutetium oxide, or the like may be used. However, in order to improve both high-temperature charging characteristics and cycle characteristics, it is desirable to use yttrium oxide or ytterbium oxide. Further, the rare earth compound is not limited to oxides such as yttrium oxide, and the same effects can be obtained by using hydroxides or chlorides.

In addition, the hydrogen storage alloy used in the present invention is not limited to the above rare earth hydrogen storage alloys, but may be a Zr—Ni hydrogen storage alloy such as ZrNi, TiF
e, Ti—Fe-based hydrogen storage alloy, Zr such as ZrMn ₂
-Mn-based hydrogen storage alloy, it is also possible to use a TiMn-based hydrogen-absorbing alloy such as TiMn _1.5 or Mg-Ni based hydrogen absorbing alloy such as Mg ₂ Ni, and the like.

[0019] Nickel - hydrogen storage alloy having a particularly preferred CaCu ₅ type crystal structure in the hydrogen alkaline storage battery is represented by the general formula _{MmNi a Co b Al c Mn d} . Here, Mm in this equation is La, Ce, P
r, Nd, Sm, Eu, Sc, Y, Pm, Gd, Tb,
It is a mixture of rare earth elements selected from Gy, Ho, Er, Tm, Yb, and Lu. In particular, La, Ce, Pr, N
Preferably, the main component is a mixture of d and Sm.
a> 0, b> 0, c> 0, d ≧ 0 and 4.4 ≦ a + b +
c + d ≦ 5.4.

The hydrogen storage alloy having the above composition can satisfy the basic performance such as cycle characteristics and discharge characteristics of an alkaline secondary battery. Further, elements of Si, C, W, B, Cu, Zr, and Fe may be added as long as the hydrogen storage properties of the hydrogen storage alloy are not changed.

In the above composition formula, preferably, the amount a of nickel is 2.8 ≦ a ≦ 5.2, the amount b of cobalt is 0 <b ≦ 1.4, and the amount c of aluminum is 0 <c ≦ 1. .
2. It is preferable that the amount d of manganese be d ≦ 1.2. Furthermore, in order to increase the capacity of the battery, the amount c of aluminum is c ≦ 1.0, and the amount d of manganese is d ≦ 1.
Preferably, it is set to zero.

In addition, the core used for the hydrogen storage alloy electrode is not limited to the above-mentioned punched metal, but nickel foam, nickel fiber sintered body, or the like can also be used.

[0023]

EXAMPLES [First Example] (Example 1) In Example 1, the battery described in the above embodiment of the present invention was used. The battery fabricated in this manner is hereinafter referred to as Battery A1 of the invention.

(Examples 2 to 5) The addition ratio of yttrium oxide to the electrolytic solution was 50 mg / l and 10 mg / l, respectively.
A battery was fabricated in the same manner as in Example 1 except that the amounts were 0 mg / l, 500 mg / l, and 1000 mg / l. The batteries fabricated in this manner are hereinafter referred to as Batteries A2 to A5 of the invention, respectively.

Example 6 The procedure of Example 1 was repeated except that the addition ratio of yttrium oxide to the electrolyte was 500 mg / l and a surfactant (nonionic) as a dispersant was added to the electrolyte. A battery was manufactured in the same manner. The battery fabricated in this manner is hereinafter referred to as Battery A6 of the invention.

(Example 7) The addition ratio of yttrium oxide to the electrolyte was 500 mg / l, and a complexing agent (EDTA) as a dispersant was added to the electrolyte.
A battery was manufactured in the same manner as in Example 1. The battery fabricated in this manner is hereinafter referred to as Battery A7 of the invention.

(Comparative Example 1) The addition ratio of yttrium oxide to the electrolytic solution was 20 mg / l (saturated, about 1
A battery was fabricated in the same manner as in Example 1 except that the content was 2 ppm). Specifically, yttrium oxide was added to the alkaline aqueous solution at a rate of 5 g / l, and the filtered solution was used as an electrolytic solution. The battery fabricated in this manner is hereinafter referred to as Comparative Battery X1.

Comparative Example 2 A battery was fabricated in the same manner as in Example 1 except that the addition ratio of yttrium oxide to the electrolyte was 8.5 mg / l (in a dissolved state, about 5 ppm). The battery fabricated in this manner is hereinafter referred to as Comparative Battery X2.

Comparative Example 3 A battery was manufactured in the same manner as in Example 1 except that yttrium oxide was not added to the electrolytic solution. The battery fabricated in this manner is hereinafter referred to as Comparative Battery X3.

(Experiment) In the batteries A1 to A7 of the present invention and the comparative batteries X1 to X3, the following condition (1) (temperature:
After activating each battery by performing 5 cycles of charging / discharging at room temperature), charging / discharging was performed under the following conditions (2) to examine charge / discharge cycle characteristics, and charging / discharging was performed under the following conditions (3). Table 1 shows the high-temperature charge characteristics (active material utilization rate).

Charge / discharge conditions (1) Charging conditions: charge at 100 mA for 16 hours, pause for 1 hour Discharge conditions: discharge at 200 mA until the discharge end voltage becomes 1 V, pause for 1 hour (2) Charge conditions: charge for 48 minutes at 1500 mA Discharge condition: 1500 mA, discharge until the discharge end voltage became 1 V. When the battery capacity reached 500 mA, the battery life was determined.

(3) Charging condition: Charging at 100 mA for 16 hours (60 ° C.), rest for 1 hour Discharging condition: Discharging at 1000 mA until the discharge end voltage becomes 1 V (room temperature) And the capacity of nickel hydroxide was changed to 288 mA / g. Was calculated as the active material utilization rate.

[0033]

[Table 1]

As is clear from Table 1, the battery A1 of the present invention
It is recognized that the cycle characteristics of the batteries A7 to A7 are improved while the high-temperature charging characteristics (active material utilization rate) are improved as compared with the comparative batteries X1 to X3. This is because the comparative battery X3 did not contain yttrium oxide, and the comparative battery X3
In 1 and X2, yttrium oxide is added, but it only exists in a dissolved state or a saturated state in the electrolytic solution, respectively. Therefore, the addition amount of yttrium oxide is insufficient, and the effect of the addition is not sufficiently exhibited. On the other hand, in the batteries A1 to A7 of the present invention, since the amount of yttrium oxide exceeding the saturation concentration is dispersed in the electrolytic solution, the amount of yttrium oxide added is large, and the effect of the addition is sufficiently exhibited. It depends on the reason.

In order to confirm the above effects, the battery A1 of the present invention was used.
When A7 was decomposed after charging and discharging for 500 cycles and the amount of yttrium in each part of the separator was analyzed,
It was confirmed that yttrium was uniformly distributed in the separator. This is because, in a dispersion of yttrium, yttrium normally precipitates (when there is no separator), but when it is injected into a battery, it adsorbs to a separator or the like, so after the charge / discharge cycle has elapsed. This is considered to be because the dispersion state of yttrium is maintained.

Among the batteries A1 to A7 of the present invention, the battery A6 of the present invention to which a surfactant as a dispersant was added and the battery A7 of the present invention to which EDTA was added as a dispersant were particularly high-temperature charging characteristics and cycle characteristics. It is recognized that the number has improved. This is because the surfactant has the effect of dispersing yttrium oxide in the solid state, and EDTA has the effect of stabilizing yttrium as a complex in the ionic state, so that the dispersion of yttrium in the electrolyte is more uniform. It is considered that this is because

[Second Example] (Examples 1 to 5) Lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, etc. were used as the rare earth compounds to be contained in the electrolyte instead of yttrium oxide, respectively.
Use ytterbium oxide and reduce its content to 10
A battery was fabricated in the same manner as in Example 1 of the first example, except that the concentration was set to 00 mg / l. The batteries fabricated in this manner are hereinafter referred to as Batteries B1 to B5 of the present invention, respectively.

(Experiment) The batteries B1 to B5 of the present invention were charged and discharged under the same conditions as in the experiment of the first embodiment (condition (1)) to activate each battery, and then the first battery was charged.
Conditions similar to those in the experiment of the example [conditions of (2) and (3)]
Table 2 shows the results of the charge / discharge cycle and charge / discharge cycle characteristics and high-temperature charge characteristics (active material utilization rate). Table 2 also shows comparative batteries X1 to X3 for comparison.

[0039]

[Table 2]

As is clear from Table 2, the battery B5 of the present invention
It was recognized that the cycle characteristics were improved while improving the high-temperature charge characteristics (active material utilization rate). Although the batteries B1 to B4 of the present invention did not show an improvement in the high-temperature charge characteristics (active material utilization rate), It can be seen that the cycle characteristics have been improved.

[0041]

According to the present invention as described above,
An excellent effect is obtained such that high-temperature characteristics and cycle characteristics can be drastically improved while preventing the battery capacity from decreasing.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor ▲ Yohei Ta Hiro 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Toruyuki Murata Keihanhondori, Moriguchi-shi, Osaka 2-5-5 Sanyo Electric Co., Ltd. (72) Inventor Koji Miki 2-5-5 Sanyo Electric Co., Ltd. (72) Inventor Kozo Nogami Keihan Moriguchi, Osaka 2-5-5 Hondori F-term (reference) in Sanyo Electric Co., Ltd. 5H028 AA06 EE05 FF03 FF04

Claims (4)

[Claims] 1. A nickel-hydrogen alkaline storage battery in which a negative electrode mainly composed of a hydrogen storage alloy and a positive electrode mainly composed of nickel oxide are disposed in a battery can via a separator impregnated with an alkaline electrolyte. 3. The nickel-hydrogen alkaline storage battery according to claim 1, wherein a rare earth compound exceeding a saturation concentration is dispersed in an ionic state or a molecular state in the alkaline electrolyte. 2. The nickel-hydrogen alkaline storage battery according to claim 1, wherein the alkaline electrolyte contains a dispersant. 3. The nickel-hydrogen alkaline storage battery according to claim 2, wherein a surfactant or a complexing agent is used as the dispersant. 4. An yttrium compound and / or an ytterbium compound is used as the rare earth compound.
The nickel-hydrogen alkaline storage battery according to claim 1, 2 or 3.