JP3404758B2 - Nickel-metal hydride storage battery and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-metal hydride storage battery in which the main active material of the positive electrode is nickel hydroxide and the main component of the negative electrode is a hydrogen storage alloy, and a method for producing the same.

[0002]

2. Description of the Related Art A hydrogen storage electrode used for a negative electrode of a nickel-metal hydride storage battery has a hydrogen storage alloy. This hydrogen storage alloy has intermetallic compounds such as LaNi ₅ and ZiNi _2, and by substituting some of the constituent elements of these alloys with other elements, or by changing the stoichiometry, Change the hydrogen storage capacity of these alloys,
It is used for electrodes by changing the equilibrium hydrogen pressure of these metal hydrides and improving the corrosion resistance of alloys in alkaline electrolytes.

In this hydrogen storage electrode, the powder of the above hydrogen storage alloy is held on a conductive support such as punching metal or foamed nickel, and an alkali resistant polymer such as polyvinyl alcohol, fluororesin or acrylic-styrene resin is used. There are things such as those that are bonded together and those that are obtained by sintering a hydrogen storage alloy.

For the positive electrode to be combined with this negative electrode, a nickel hydroxide electrode of the same sintering type or metal foam type as that of an alkaline battery such as a nickel-cadmium battery is used.

An aqueous solution containing potassium hydroxide or sodium hydroxide as a main component is used as the electrolytic solution.

[0006]

SUMMARY OF THE INVENTION Such nickel-
The metal hydride storage battery has a drawback that it has a higher self-discharge rate than the nickel-cadmium battery. This remarkably large self-discharge is caused by a self-discharging reaction in which, when a hydrogen storage alloy is used for the negative electrode, the hydrogen stored in this alloy is released and reaches the positive electrode to reduce and discharge the charge product of the positive electrode. It is speculated that

[0007] This self-discharge is caused by the content ratio of manganese in the alloy, especially in the case of a hydrogen storage alloy in which the constituent element of LaNi ₅ , which is an intermetallic compound having a CaCu _{5 type} crystal structure, is replaced with another element. It was known that the higher the value, the more effectively it was suppressed.

However, not only CaCu _{5 type} but also ZrNi ₂ and
Even with hydrogen storage alloys such as TiNi, the higher the content of manganese in the hydrogen storage alloy, the higher the rate of deterioration of the hydrogen storage alloy with the progress of charge / discharge cycles, and the shorter the charge / discharge cycle life of the battery. There is.

Therefore, the content of manganese in the hydrogen storage alloy of the negative electrode is low and the charge / discharge cycle life is long, and
A nickel-metal hydride storage battery with a low self-discharge rate has been desired.

[0010]

In order to solve the above-mentioned problems, the present invention has a main active material of a positive electrode made of nickel hydroxide and a main body of a negative electrode made of a hydrogen storage alloy. A nickel-metal hydride storage battery containing a solid manganese compound that is dissolved and precipitated in an electrolytic solution in a state of being in contact with a liquid, or a main active material of a positive electrode is nickel hydroxide,
A nickel-metal hydride storage battery in which the main component of the negative electrode is a hydrogen storage alloy containing no manganese, and the negative electrode contains a manganese compound consisting of at least one selected from the group consisting of manganese hydroxide, manganese sulfate, and manganese oxide. provide. Further, the main active material of the positive electrode is nickel hydroxide, the main component of the negative electrode is a hydrogen storage alloy, and the negative electrode is a manganese compound consisting of at least one selected from the group consisting of manganese hydroxide, manganese sulfate, and manganese oxide. A method for producing a nickel-metal hydride storage battery containing: a powder of the hydrogen storage alloy; and a powder of a manganese compound consisting of at least one selected from the group consisting of manganese hydroxide, manganese sulfate and manganese oxide. There is provided a method for producing a nickel-metal hydride storage battery, characterized in that

[0011]

In the present invention, by adopting the above-mentioned constitution, even when the content ratio of manganese in the hydrogen storage alloy of the negative electrode of the metal hydride storage battery is small, the self-discharge of the nickel-metal hydride storage battery is suppressed. . Therefore, it is possible to obtain a nickel-metal hydride storage battery in which the reduction of the life of the hydrogen storage alloy of the negative electrode due to the progress of the charge / discharge cycle is suppressed and the self-discharge rate is low.

Although the reason why the self-discharge rate of the battery is reduced by adopting the configuration of the present invention is not clear, the reason for this may be explained by the following hypothesis if an inference is made. unknown.

That is, as a self-discharging mechanism peculiar to the nickel-metal hydride storage battery, as described above, there is one in which a small amount of hydrogen generated from the negative electrode is oxidized at the positive electrode. Then, when the means of the present invention is adopted, the manganese compound separated from the electrode and in contact with the electrolytic solution, or the manganese compound added to the negative electrode is gradually dissolved in the electrolytic solution or the like, and the positive electrode active material or the positive electrode active material is gradually added. It seems that the self-discharge rate decreases as a result of moving to the surface of the current collector and decreasing the oxidation reaction rate of hydrogen on the surface of the positive electrode active material or the current collector.

[0014]

EXAMPLES The present invention will be described by way of preferred examples. [Rechargeable Battery A] (Example of the present invention) A sealed nickel-metal hydride storage battery, in which the negative electrode was mainly composed of a hydrogen storage alloy and which had an alkaline electrolyte and had a rectangular outer shape, was manufactured as follows.

As the negative electrode plate, five paste type plates having dimensions of 15 mm × 55 mm × 0.4 mm were used. This electrode was manufactured as follows.

The hydrogen storage alloy has an atomic composition of LmNi in atomic ratio.
The constituent elements were dissolved in a metal state in a high-frequency induction furnace in a vacuum so that _3.8 Co _0.7 Al _0.5 was obtained, cast, and then pulverized. Here, Lm is a lanthanum-rich misch metal which is a mixture of rare earth metals containing about 90% by weight of La. This alloy powder was immersed in a 1M concentration manganese sulfate aqueous solution, and then an equivalent amount or more of sodium hydroxide aqueous solution was added to precipitate manganese hydroxide on the surface of the hydrogen storage alloy powder. The addition rate of manganese hydroxide is 1 hydrogen storage alloy.
It was about 1 part by weight with respect to 00 parts by weight. Then, the hydrogen storage alloy was washed with water, dried, and then dispersed in an aqueous solution of polyvinyl alcohol that functions as a thickener and a binder to form a paste. Then, this paste was applied to both sides of a nickel-plated iron punching metal, dried, pressed, and cut to manufacture a hydrogen storage electrode.

The weight of the hydrogen storage alloy contained in 5 sheets of the negative electrode plate of this battery was about 5.3 g.

As the positive electrode, four known sintered nickel hydroxide electrodes (the size of one is 14 mm × 54 mm × 0.75 mm) are used, and the total weight of nickel hydroxide contained in the four electrodes is 1 It is 3.9 g per cell. Therefore, nickel hydroxide is 1
Assuming that the electron reaction is followed, the theoretical capacity of the positive electrode of one battery is about 1.1 Ah. To this electrode was added 0.04 grams of cobalt hydroxide per gram of nickel hydroxide.

In the test battery, the negative electrode and the positive electrode are alternately laminated through a separator in which polystyrene, which is a nonwoven fabric made of fibers of a mixture of polypropylene and polystyrene, is sulfonated to impart hydrophilicity, and the negative electrode and the positive electrode are alternately laminated. The plate group was housed in a rectangular closed metal battery case. For the conventional battery A, a 6M KOH aqueous solution in which 20 g / l of LiOH was dissolved was used as the electrolytic solution.

[Battery (B)] (Example of the present invention) In the battery (A), manganese hydroxide was added to 100 parts by weight of the hydrogen storage alloy powder instead of depositing manganese hydroxide on the surface of the hydrogen storage alloy powder. The nickel-metal hydride storage battery (B) of the present invention was manufactured in the same manner as the storage battery (A), except that 1 part by weight of the powder was added and mixed. [Battery (C)] (Example of the present invention) In the present invention, powder of manganese sulfate was used instead of the powder of manganese hydroxide of the negative electrode in the battery (B), and the other constitution was the same as that of the battery (B). Nickel-Metal Hydride Battery (C)
Was produced. [Storage Battery (D)] (Examples of the Present Invention) Manganese dioxide powder was used in place of the manganese hydroxide powder of the negative electrode in the storage battery (B), and the other configurations were the same as those of the storage battery (B). An inventive nickel-metal hydride storage battery (D) was made. [Storage Battery (E)] (Example of the Present Invention) Instead of adding the manganese hydroxide powder in the storage battery (B) to the hydrogen storage electrode, the manganese hydroxide powder is wrapped in the same separator as that of the battery, It was placed on the bottom of the battery so that it was in contact with the electrolyte. And the nickel-metal hydride storage battery (E) of the present invention was manufactured by making the other configurations the same as the storage battery (B). [Battery (F)] (Example of the present invention) Instead of the manganese hydroxide powder in the storage battery (E), manganese sulfate powder was used, and the other configurations were the same as those of the storage battery (E). -Metal hydride storage battery (F) was made. [Storage Battery (G)] (Examples of the Present Invention) Manganese dioxide powder was used in place of the manganese hydroxide powder in the storage battery (E), and the other configurations were the same as those of the storage battery (E). A nickel-metal hydride storage battery (G) was produced. [Battery (H)] (conventional example) Without adding manganese hydroxide in the battery (A), the other structure is the same as that of the battery (A). ) Was produced. [Battery (I)] (conventional example) As a hydrogen storage alloy for the negative electrode of the storage battery (H), the atomic ratio is LmNi _3.8 Co _0.7 Al _0.5.
Instead of using the composition of, the atomic ratio of LmNi _3.8 Co
_0.7 Al _0.2 Mn _0.3 is used, the other structure is the same as the storage battery (H), and the conventional rectangular sealed nickel-
A metal hydride storage battery (I) was manufactured.

These batteries were subjected to chemical charge and discharge under the condition that they were charged at a current of 10 hours rate for 15 hours and discharged at a current of 5 hours rate until the terminal voltage became 1 V, based on the theoretical capacity of the positive electrode. . Next, 15 hours at a current of 10 hours
The discharge capacity before standing was measured under the condition that the battery was charged for an hour and discharged with a current at a rate of 5 hours until the terminal voltage became 1V. Then, charge it for 15 hours with a current of 10 hours rate, and
The discharge capacity after standing was measured under the condition that the terminal was left for one day and then discharged at a current of 5 hours until the terminal voltage became 1V. Charge and discharge and leave after charging are all 25
Performed at ambient temperature of ° C.

In this test, the capacity retention rate after leaving is defined as the ratio of the discharge capacity after leaving to the discharge capacity before leaving, and the value of the capacity holding rate of each battery obtained in the above test is investigated. It was

Further, these batteries were charged at a current of 1 hour rate for 1.2 hours, and the terminal voltage was 1.0 at a current of 1 hour rate.
A charge / discharge cycle test was performed under the condition that the battery was discharged to V. Then, the number of charge / discharge cycles until the discharge capacity of the battery decreased to 70% of the initial discharge capacity of the charge / discharge cycle was examined. This charge / discharge cycle test was also performed at an ambient temperature of 25 ° C. The results of these tests are shown in Table 1.

[0024]

[Table 1] The following can be seen from Table 1.

That is, a battery (A) containing a manganese compound in the negative electrode and not containing manganese in the hydrogen storage alloy,
(B), (C), and (D), containing a manganese compound in a state of being separated from the electrode and in contact with the alkaline electrolyte,
A battery (E) in which the hydrogen storage alloy does not contain manganese,
(F) and (G) and the battery (I) which does not contain a manganese compound in the negative electrode and contains manganese in the hydrogen storage alloy, are separated from the electrode and contact the electrolytic solution.
Compared to the battery (H) in which the negative electrode does not contain a manganese compound and the hydrogen storage alloy does not contain manganese, the capacity retention rate when the battery in a charged state is left is large. Therefore, the self-discharge rate of the nickel-metal hydride storage battery decreases when the electrode is separated from the electrode and is in contact with the alkaline electrolyte, or when the negative electrode contains a manganese compound or the hydrogen storage alloy contains manganese.

On the other hand, batteries (A), (B), (C), (D) in which the hydrogen storage alloy of the negative electrode does not contain manganese.
(E), (F), (G), and (H) are compared with the battery (I) containing manganese in the hydrogen storage alloy of the negative electrode,
The number of charge / discharge cycles until the discharge capacity drops to 70% of the initial discharge capacity is large.

From the above experiment, the main active material of the positive electrode was nickel hydroxide, and the main component of the negative electrode was a hydrogen storage alloy,
The nickel-metal hydride storage battery of the present invention containing a manganese compound in a state where it is separated from the electrode and is in contact with an electrolytic solution, or the negative electrode contains a manganese compound, has a low self-discharge rate and also has the effect of a long charge / discharge cycle life. Is clear.

In the above examples, the case where the manganese compound contains a hydroxide, an oxide, and a sulfate has been described. However, in addition to this, chalcogenides, metal compounds, and various salts are also included. Even when it contains, the same effect is obtained.

In the above embodiments, the case where a rare earth alloy having a specific composition is used as the hydrogen storage alloy for the negative electrode has been described. However, not only these alloys but also La alloy
Even when the constituent metal of the hydrogen storage alloy such as Ni ₅ , ZrNi ₂ , TiNi, and Ti ₂ Ni is replaced with another element, the same effects as those of the above-described embodiment can be obtained.

In the above embodiment, the case of using the sintering type nickel hydroxide electrode as the positive electrode has been described. In addition to this, foamed nickel, a sintered body of metallic nickel fibers, nickel plated iron, etc. Similar effects are obtained in the case of a non-sintered nickel hydroxide electrode using such a perforated plate of an alkali resistant metal, a nickel net, and an expanded metal of nickel as the active material support.

Further, in the above embodiment, the case where the paste type hydrogen storage electrode is used for the negative electrode has been described.
In addition, the same effect can be obtained in the case of a sintered hydrogen storage electrode in which a hydrogen storage alloy is sintered into a porous body. In this case, a method of filling the manganese compound powder into the pores of the sintered porous body of the hydrogen storage alloy, or a solution of a manganese salt such as an aqueous solution of manganese sulfate is filled into the pores of the hydrogen storage electrode. Then, the manganese salt is reacted with an alkaline aqueous solution or the like to deposit a manganese compound such as manganese hydroxide in the pores of the hydrogen storage electrode. .

Further, in the above-mentioned embodiment, the prismatic closed type battery has been described, but the same operational effects as those of the above-mentioned embodiment can be obtained also in the case of the cylindrical type or the open type battery.

Further, in the storage battery (A), the hydrogen-absorbing alloy powder was first immersed in a solution of manganese salt, and then an aqueous alkaline solution was added to precipitate manganese hydroxide. Even if the method of adding the solution of manganese salt after first immersing the above in the alkaline aqueous solution is performed, the same operation and effect as those in the above-described embodiment can be obtained.

[0034]

As described above, the nickel-metal hydride storage battery of the present invention has the effects of a long charge / discharge cycle life and a low self-discharge rate.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-2-253558 (JP, A) JP-A-2-256161 (JP, A) JP-A-62-249364 (JP, A) JP-A-62- 296365 (JP, A) JP-A-62-295352 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/24-10/30 H01M 4/00-4/62

Claims (3)

(57) [Claims] 1. The main active material of the positive electrode is nickel hydroxide,
A nickel-metal hydride storage battery characterized in that the negative electrode mainly comprises a hydrogen storage alloy, and contains a solid manganese compound which is separated from the electrode and dissolved and deposited in the electrolytic solution in contact with the electrolytic solution . 2. The positive electrode main active material is nickel hydroxide,
The negative electrode is mainly composed of a hydrogen storage alloy containing no manganese, and the negative electrode contains manganese hydroxide, manganese sulfate, and manganese oxide.
Nickel containing at least one manganese compound selected from the group consisting of
Metal hydride storage battery. 3. The main active material of the positive electrode is nickel hydroxide,
The main component of the negative electrode is a hydrogen storage alloy, and the negative electrode is
Gangan, manganese sulfate, manganese oxide
Contains at least one manganese compound selected
Is a method of manufacturing a nickel-metal hydride storage battery.
The hydrogen storage alloy powder and the manganese hydroxide, sulfur
A small amount selected from the group consisting of manganese acid and manganese oxide.
Mix with at least one manganese compound powder
Manufacture of nickel-metal hydride storage batteries characterized by
Build method.