JP2002042861A - Nickel-metal hydride storage battery and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a high-performance nickel-metal hydride storage battery having excellent self-discharge characteristics. SOLUTION: The negative electrode includes, as an active material, a hydrogen-absorbing alloy having a body-centered cubic structure in which a crystal structure of a main phase including at least Ti is an active material; a positive electrode, including nickel hydroxide as an active material; In an alkaline storage battery, at least one of manganese, manganese ions, and a manganese compound is contained in at least one of the negative electrode, the positive electrode, the separator, and the alkaline electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in characteristics of a nickel-metal hydride storage battery and a method of manufacturing the same.

[0002]

2. Description of the Related Art An electrode using, as an active material, a hydrogen storage alloy that reversibly absorbs and releases hydrogen has a theoretical capacity density higher than that of a cadmium electrode. In addition, since there is no deformation or dendrite formation unlike the zinc electrode, it has a long life and no pollution, and has a high energy density, so that future development is expected.

[0003] The hydrogen storage alloy used for such an electrode is usually produced by an arc melting method, a high-frequency induction heating melting method, or the like. Currently, hydrogen storage alloy that has been put to practical use as an electrode, AB ₅ type (A: La, Zr, affinity of large elements with hydrogen, such as Ti, B: Ni, Mn, and hydrogen and transition elements such as Cr Element with low affinity for La)
(Or Mm: misch metal-a mixture of rare earth elements)
It is a Ni-based multi-component alloy. However, since this alloy uses a capacity almost close to the theoretical value, and a large capacity increase cannot be expected in the future, a new hydrogen storage alloy material having a larger discharge capacity is desired.

[0004] As an alloy having a large hydrogen storage capacity than the AB ₅ alloys, there are Ti-V system hydrogen storage alloy. As an electrode using this alloy, for example, a Ti _x V _y Ni _z alloy is disclosed in JP-A-6-228699 or JP-A-7-268.
No. 513, Japanese Unexamined Patent Application Publication No. 7-268514, and the like. An example of increasing the capacity by sintering Ni on the surface of a TiVCr-based alloy is disclosed in JP-A-11-1447.
No. 28 is proposed.

[0005]

However, a nickel-metal hydride storage battery using a hydrogen storage alloy whose main phase is an alloy having a body-centered cubic structure containing Ti as described above has a large self-discharge during storage. There are issues.

[0006]

In order to solve the above-mentioned problems, a nickel-metal hydride storage battery according to the present invention comprises: a negative electrode comprising, as an active material, a hydrogen storage alloy containing at least Ti and having a main phase crystal structure of a body-centered cubic structure; A positive electrode having nickel hydroxide as an active material, a separator, and an alkaline storage battery having an alkaline electrolyte, wherein at least one of the negative electrode, the positive electrode, the separator or the alkaline electrolyte, manganese, manganese ions, or It is characterized by containing at least one manganese compound.

At this time, manganese or a manganese compound may be arranged on at least one of the surface of the positive electrode active material, the inside of the positive electrode, the outer surface of the positive electrode, the surface of the negative electrode active material, the inside of the negative electrode, and the outer surface of the negative electrode. It is valid.

Further, the amount of manganese contained in the battery is
It is desirable that the amount is 0.1 part by weight or more and 10 parts by weight or less based on the positive electrode active material.

The above-described method for producing a nickel-metal hydride storage battery includes:
The method includes a step of preparing a paste by mixing at least one of manganese and a manganese compound with a positive electrode material containing nickel hydroxide, and a step of applying or filling the paste to a conductive core material.

[0010] The method further comprises a step of impregnating the positive electrode obtained by applying or filling a positive electrode material containing nickel hydroxide on a conductive core material with a solution in which a manganese salt is dissolved and drying.

Also, a negative electrode containing a hydrogen storage alloy having at least Ti and Mn and a main phase having a body-centered cubic crystal structure as an active material, a positive electrode containing nickel hydroxide as an active material, a separator, And at least one place of the negative electrode, the positive electrode, or the alkaline electrolyte,
Manganese, in a nickel-metal hydride storage battery containing at least one manganese ion or manganese compound, by storing or charging and discharging the nickel-metal hydride storage battery,
At least a part of manganese contained in the negative electrode is eluted.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to embodiments.

[0013]

EXAMPLES (Example 1) As nickel hydroxide as a positive electrode active material, spherical nickel hydroxide containing 2% by weight and 5% by weight of cobalt and zinc respectively as a solid solution was used. This powder was mixed with 7% by weight of cobalt powder, 5% by weight of cobalt hydroxide powder, and the additives shown in Table 1 and added to water to form a paste. This was used as a positive electrode.

Next, an alloy having a composition represented by Ti _0.32 V _0.33 Cr _0.33 La _0.02 (alloy 1) was prepared by an arc melting method.
The pulverized material was classified to 75 μm or less. Further, the surface of this alloy was plated with 10% by weight of Ni by electroless plating,
The powder heat-treated in a reduced-pressure atmosphere at 5 ° C. for 3 hours was filled into foamed nickel and pressed, and this was used as an electrode for a negative electrode.

The above positive electrode and negative electrode were swirled through a polypropylene separator and housed in an AA size case. Further, an electrolyte solution was charged and sealed to form a sealed battery. The electrolyte used was a solution in which 30 g / l of LiOH was dissolved in a 31% by weight KOH aqueous solution.

The nominal capacity of this battery is 1500 mAh. Using this battery, the self-discharge characteristics of the battery were studied. The evaluation process firstly charges the battery to 150% of the theoretical capacity of the positive electrode with a current corresponding to 0.1 CmA,
After a rest, the battery was discharged at 25 ° C. at a current equivalent to 0.2 CmA until the battery voltage reached 1.0 V. This charge / discharge cycle was repeated 20 times to sufficiently activate. Thereafter, the battery was charged at 150% under the same conditions as above, and then left at 45 ° C. for 2 weeks. And 0.2CmA
The discharge capacity at the time of discharging to 1.0 V was compared with the discharge capacity before storage, and the residual capacity ratio was determined from the following formula.

When the remaining capacity ratio (%) = remaining discharge capacity after storage / discharge capacity before storage × 100 or more was evaluated, as shown in Table 1, the non-added battery of Comparative Example was self-contained. It was found that the discharge was large. To verify this mechanism, deposits inside the separator of the battery of the comparative example were analyzed by characteristic X-ray analysis. As a result, it was presumed that a large amount of Ni or Co was precipitated, whereby the battery of the comparative example caused a micro short circuit inside and the battery capacity was reduced. Further, it is considered that Ni and Co were eluted from the positive electrode.

In addition, MmNi_3.55Mn_0.4Al_0.3Co
_0.75AB_FiveType alloy, ZrMn_0.6V _0.2Co_0.1Cr
_0.1Ni_1.2AB such as_TwoType alloys have a capacity
Has a body-centered cubic structure containing Ti
Batteries using a hydrogen storage alloy for the negative electrode show marked deterioration.
It is. This is because Ti eluted from the alloy acts on the positive electrode
However, it is considered to promote the elution of Ni and Co.

On the other hand, it was found that the battery of this example had a very small self-discharge. Many precipitates of Mn were found inside the separator of the battery of the present example, and the conductivity of the precipitate was small, so that the battery of the present example was suppressed from a micro short circuit, thereby suppressing self-discharge. Think of things.

As the addition form of Mn, metals, oxides,
Both halides and sulfates showed improvement effects.
When the amount of addition was in the range of 0.1 to 10 wt% in terms of Mn, a residual capacity ratio of 80% or more was obtained.

[0021]

[Table 1]

(Example 2) Next, an example in which the positive electrode is impregnated with a solution containing Mn ions will be described.

As in Example 1, 7% by weight of cobalt powder and 5% of cobalt hydroxide powder were added to spherical nickel hydroxide powder.
% By weight, and water was added thereto to form a paste. This paste was filled in foamed nickel, dried and pressed to form an electrode.

This electrode was treated with potassium permanganate for 30 minutes.
For 1 minute in an aqueous solution in which
A battery dried at ℃ was used as a positive electrode, and a battery formed using this positive electrode was referred to as Example 2-1. A battery constituted by a positive electrode which was not impregnated with the above aqueous solution was designated as Comparative Example 2-2. In the above battery configuration, the same negative electrode as in Example 1 was manufactured using the same negative electrode as in Example 1, and the self-discharge characteristics were examined.

As a result, those impregnated with the Mn solution had an increased capacity retention rate and improved storage characteristics. The remaining capacity ratio was 82% in Example 2-1 and Comparative Example 2-.
In No. 2, the value was as low as 27%.

Example 3 In this example, a sealed battery was manufactured in the same manner as in Example 1, and an Mn compound was added to the electrolyte. In this example, no Mn compound was added to the positive electrode.

Adding potassium permanganate to the electrolyte,
A battery using a component dissolved in such a manner that the Mn content was 5% by weight with respect to the positive electrode active material was referred to as Example 3-1. A battery in which potassium permanganate was not added to the electrolyte was Comparative Example 3. -2. Then, the self-discharge characteristics of each battery were measured in the same manner as in Example 1.

As a result, it was found that the battery of this example in which potassium permanganate was added to the electrolytic solution had improved self-discharge characteristics. Comparing the remaining capacity ratios as in Example 1, the value of Example 3-1 was 84%, while that of Comparative Example 3-2 was a low value of 27%.

Example 4 In this example, a sealed battery was manufactured in the same manner as in Example 1, and the case where a Mn metal powder or a manganese compound was added to the negative electrode was examined.

The alloy used as the active material for the negative electrode was the same as that used in Example 1. Mn powder or potassium permanganate was added to this alloy, and a mixture obtained by mixing so that the Mn content was 5% by weight with respect to the positive electrode active material was filled in foamed nickel, and then dried and pressed to form a negative electrode. An electrode was used.

As described above, a battery prepared by using a material obtained by adding Mn powder to a negative electrode as a constituent element is referred to as Example 4-1.
Example 4 also containing potassium permanganate
-2 and Comparative Example 4-3 in which neither Mn powder nor potassium permanganate was added. The self-discharge characteristics of the battery thus prepared were measured in the same manner as in Example 1.

As a result, it was found that the self-discharge characteristics of the battery of this embodiment to which Mn powder and potassium permanganate were added were improved. When compared with the remaining capacity ratio in the same manner as in Example 1, the value was 85% in Example 4-1 and 83% in 4-2, whereas the value in Comparative Example 4-3 was as low as 27%.

Example 5 A sealed battery was manufactured in the same manner as in Example 1, and the self-discharge characteristics when the negative electrode contained Mn were examined.

The negative electrode is a hydrogen storage alloy containing Mn.
_{Ti 0.2 V 0.4 Cr 0.2 Mn 0.1} Ni 0. 1 to (alloy 2), M
Ti-free alloy containing Ti _0.2 V _0.5 Cr _0.2 Ni
_0.1 (alloy 3) was used. These alloys are mainly Ti,
The alloy has a form in which an alloy having a body-centered cubic structure made of V, Cr (, Mn) is used as a main phase, and a second phase mainly made of Ti and Ni is precipitated in a network.

A battery using the above-mentioned alloy 2 was prepared in Example 5-
1. A battery using alloy 3 was designated as Comparative Example 5-2. The self-discharge characteristics of these batteries were measured in the same manner as in Example 1. Comparing the capacity retention ratio in the same manner as in Example 1, it was 80% in Example 5-1 and 23% in Comparative Example 5-2.
Met.

Since the amount of manganese ions eluted from the alloy varies greatly depending on the alloy composition, not all alloy compositions can be mentioned here. However, if the amount eluted into the electrolyte is at the same level as in Example 3, It is considered that a similar effect can be obtained.

Example 6 A sealed battery was manufactured in the same manner as in Example 1, and the self-discharge characteristics when the separator contained a Mn compound were examined.

The separator was impregnated with an aqueous solution in which 30% by weight of potassium permanganate was dissolved, for 1 minute.
A battery prepared as a component by drying in Example 6-1 was referred to as Example 6-1 and a battery using a battery not subjected to the above impregnation was referred to as Comparative Example 6-2.

The same positive and negative electrodes as in Example 1 were used.
The same sealed battery as in Example 1 was manufactured, and the self-discharge characteristics were examined. As a result, when the separator was impregnated with the Mn solution, the residual capacity ratio was increased, and the storage characteristics were improved. The residual capacity ratio was 80% in Example 6-1 and 27% in Comparative Example 6-2.

[0040]

According to the above results, in a nickel-metal hydride storage battery using a hydrogen-absorbing alloy having a body-centered cubic structure containing Ti for a negative electrode, the self-discharge characteristics are improved by adding manganese or a manganese compound to the inside of the battery. I was sure that.

It is considered that the effect of the present invention is due to the fact that an insulating precipitate is deposited inside the separator. In the present invention, an example using manganese is shown. It is considered that similar effects can be obtained with other elements as long as they form.

Also, in a method other than the embodiment, if manganese or a manganese compound is present inside the battery,
It is considered that a similar effect can be obtained.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01M 4/38 H01M 4/38 A 4/62 4/62 C // C22C 14/00 C22C 14/00 A (72) Inventor Miho Kayama 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. GA23 HA01 HA13

Claims (6)

[Claims] 1. A negative electrode comprising a hydrogen storage alloy containing at least Ti as an active material and having a body phase cubic crystal structure of a main phase as an active material, a positive electrode comprising nickel hydroxide as an active material, a separator, and an alkaline electrolyte. A nickel-metal hydride storage battery comprising: at least one of manganese, manganese ions, or a manganese compound in at least one of the negative electrode, the positive electrode, the separator, and the alkaline electrolyte. 2. A manganese or manganese compound is disposed on at least one of the surface of the positive electrode active material, the inside of the positive electrode, the outer surface of the positive electrode, the surface of the negative electrode active material, the inside of the negative electrode, and the outer surface of the negative electrode. The nickel-metal hydride storage battery according to claim 1, wherein 3. The nickel-metal hydride storage battery according to claim 1, wherein the amount of manganese contained in the battery is 0.1 part by weight or more and 10 parts by weight or less based on the positive electrode active material. 4. A process for producing a paste by mixing at least one of manganese and a manganese compound with a positive electrode material containing nickel hydroxide, and applying or filling the paste to a conductive core material. The method for producing a nickel-metal hydride storage battery according to claim 1, 2, or 3. 5. The method according to claim 1, further comprising a step of impregnating a positive electrode material coated or filled with a positive electrode material containing nickel hydroxide on a conductive core material with a solution in which a manganese salt is dissolved and drying. 5. The method for producing a nickel-metal hydride storage battery according to 2, 3, or 4. 6. A negative electrode containing at least Ti and Mn and using a hydrogen storage alloy having a body-centered cubic crystal structure of a main phase as an active material, a positive electrode containing nickel hydroxide as an active material, a separator, and an alkaline electrolytic solution. A manganese, a manganese ion or a manganese compound in at least one place of the negative electrode, the positive electrode, or the alkaline electrolyte, wherein the nickel-hydrogen storage battery is stored or charged / discharged. Thereby elute at least a part of the manganese contained in the negative electrode.