JP2000012011A - Manufacture of nickel-hydrogen storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel-hydrogen storage battery which has no collapse of a conducting matrix of cobalt and no drop in battery capacity, even if the nickel-hydrogen storage battery having a non-sintered nickel positive electrode to which a cobalt compound is added is overdischarged during activation. SOLUTION: This manufacturing method contains a higher order cobalt compound forming process for forming a higher order cobalt compound layer higher than divalent, containing an alkali metal ion, having disordered crystal structure on the surface of a nickel hydroxide particle, an active material filling process for forming slurry of the nickel hydroxide on which the higher order cobalt compound layer is formed and for filling the slurry in an active material holding substrate having three-dimensional net structure, an electrode body forming process for forming an electrode body by winding or stacking a nickel positive electrode prepared in the active material filling process and a hydrogen storage alloy negative electrode through a separator, an activation process for repeating charging/discharging of the battery after a battery is assembled by putting the electrode body together with an alkaline electrolyte into an outer can, and an overdischarging process for overdischarging the battery until the voltage of the battery drops to 0.3 V or lower in the activation process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a nickel-hydrogen storage battery having a negative electrode containing a hydrogen storage alloy capable of reversibly storing and releasing hydrogen.

[0002]

2. Description of the Related Art In recent years, due to the rapid spread of portable devices, there has been a demand for higher performance storage batteries than ever. Against this background, a nickel-hydrogen storage battery using a hydrogen storage alloy electrode as a negative electrode has attracted attention as a lightweight and high energy density storage battery.

[0003] The hydrogen storage alloy electrode used as the negative electrode of this type of nickel-hydrogen storage battery has low electrochemical activity. Therefore, charge and discharge are repeated several times after assembling the battery, or gaseous hydrogen is removed before assembling the battery. Activation processing such as repeated occlusion / release is performed so that stable characteristics can be obtained. For example, the method proposed in Japanese Patent Application Laid-Open No. 4-6758 discloses a method for charging and discharging a battery after assembling, in which a discharge process for continuously reducing a discharge current and almost completely discharging the battery is performed in a short time. It is said that it becomes possible to improve the activity. By setting the discharge end voltage at the time of discharge to -0.3 V to 1.0 V, the effect of improving the activity becomes remarkable.

By the way, when the above-mentioned activation treatment is performed, when a non-sintered nickel positive electrode is used as the positive electrode of the nickel-hydrogen storage battery, the discharge end voltage at the time of activation becomes 1.0 V or less. When the battery is discharged, there is a problem that the battery capacity decreases as the overdischarge amount increases, that is, as the discharge end voltage approaches -0.3 V. On the other hand, when a sintered nickel positive electrode is used as the positive electrode of the nickel-hydrogen storage battery, the discharge end voltage at the time of activation is 1.
Even if the battery is discharged so as to have a voltage of 0 V or less, the battery capacity does not decrease.

[0005] When the above-mentioned non-sintered nickel positive electrode is used, the reason why the battery capacity is reduced due to overdischarge is considered as follows. That is, a non-sintered nickel positive electrode uses a nickel porous body (nickel foam) having a three-dimensional network structure as an active material holder, and this nickel foam is an active material holder of the sintered nickel positive electrode. Since the current collecting ability is lower than that of a certain nickel sintered body, a cobalt compound such as cobalt oxide is added to the positive electrode active material in order to increase the utilization rate of the positive electrode active material containing nickel hydroxide as a main component. . This cobalt compound changes to a higher-order cobalt compound (such as cobalt oxyhydroxide) upon charging. Since high-order cobalt compounds (such as cobalt oxyhydroxide) have high conductivity, a three-dimensional conductive matrix is formed in the non-sintered nickel positive electrode, and the utilization rate of the positive electrode active material is improved.

[0006]

However, in a sealed secondary battery, the positive electrode capacity is made smaller than the negative electrode capacity in order to achieve a sealed structure. For this reason, as described above, over-discharge is performed at the time of activation to reduce the discharge end voltage to 1.
When the voltage is reduced to 0 V or less, the positive electrode potential shifts to the negative electrode potential side (a lower direction). When the positive electrode potential shifts to the negative electrode potential side (a lower direction), higher-order cobalt compounds formed during charging (such as cobalt oxyhydroxide)
Is reduced to cobalt, and the cobalt diffuses into the nickel hydroxide particles.

[0007] Since the cobalt once diffused into the nickel hydroxide particles does not come out of the nickel hydroxide particles, higher cobalt compounds (such as cobalt oxyhydroxide) are used.
As a result, the charge / discharge efficiency is reduced and the battery capacity is reduced.

On the other hand, in the case of the sintered nickel positive electrode, it is unnecessary to add a cobalt compound because the nickel sintered body before impregnation with the positive electrode active material has a sufficient current collecting ability. Even so, the influence of overdischarge is small because the amount is small. Therefore, the above-described problem does not occur.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a method of adding a cobalt compound to a non-sintered nickel positive electrode to cause overdischarge during activation. Even so, an object of the present invention is to provide a nickel-hydrogen storage battery in which a conductive matrix does not collapse and a battery capacity does not decrease.

Therefore, the method for manufacturing a nickel-hydrogen storage battery according to the present invention provides a method for forming a high-order cobalt compound layer containing alkali metal ions on a surface of nickel hydroxide particles and having a crystal structure disturbed and higher than divalent. A cobalt compound forming step and a nickel hydroxide formed with a higher cobalt compound layer containing alkali metal ions and having a disordered crystal structure in the higher cobalt compound forming step are formed into a slurry. An active material filling step of filling an active material holding body having a network structure, and a nickel positive electrode and a hydrogen storage alloy negative electrode formed by the active material filling step are wound or laminated via a separator to form an electrode body An electrode assembly forming process, and an activation process that repeats charging and discharging after forming the battery by filling the electrode assembly in an outer can with an alkaline electrolyte. With the door, in the activation step, so that provided the over-discharge step of over-discharge until the battery voltage reached 0.3V or less.

The higher-order cobalt compound layer containing alkali metal ions and having a disordered crystal structure is more difficult to reduce than the conventional crystalline higher-order cobalt compound (cobalt oxyhydroxide). It is difficult to dissolve in the electrolyte. When a layer of higher-order cobalt compound containing alkali metal ions and having a disordered crystal structure and higher than two valences is formed on the surface of the nickel hydroxide particles, a cobalt unevenly distributed layer is formed as a first layer from the surface, and a second layer is formed. Is formed as an integrated layer of cobalt and nickel hydroxide, and a nickel hydroxide layer is formed as a third layer.

[0012] Even if the nickel hydroxide provided with a layer of a higher-order cobalt compound having a crystal structure disordered and larger than 2 valences on the surface is over-discharged, the higher-order cobalt compound having a crystal structure disordered and larger than a 2 valued layer can be obtained. Is hardly reduced and hardly dissolved in an alkaline electrolyte, and the unified layer of cobalt and nickel hydroxide as a second layer acts as a barrier for cobalt diffusion. Also, the conductive matrix does not collapse. For this reason, since the charge / discharge efficiency does not decrease, the battery capacity does not decrease.

When any one selected from the compounds of yttrium, ytterbium, and bismuth is present on the surface of the higher-order cobalt compound layer, the compound of yttrium, ytterbium, and bismuth acts as a barrier for cobalt diffusion. Therefore, even after the non-sintered nickel positive electrode is over-discharged, the conductive matrix is not further collapsed, and a reduction in battery capacity can be prevented.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a non-sintered nickel positive electrode and a nickel-hydrogen storage battery according to the present invention will be described below. 1. Preparation of Nickel Hydroxide Powder A nickel hydroxide powder containing 2.5% by weight of zinc and 1% by weight of cobalt as a coprecipitating component is put into an aqueous solution of cobalt sulfate, and a 1M aqueous solution of sodium hydroxide is gradually added thereto while stirring. And the pH was maintained at 11 during the reaction to prepare a granular material having a nickel hydroxide particle as a nucleus and a 5% by weight coating layer of cobalt hydroxide formed on the surface thereof. The nickel hydroxide powder obtained by sorting, washing and drying the granules thus produced is referred to as powder X.

While stirring the above-mentioned powder X in a beaker (oxygen atmosphere), a 25% by weight aqueous solution of sodium hydroxide was added thereto at a 10-fold weight ratio to impregnate the powder X, and heated at 85 ° C. with stirring for 8 hours. An alkali heat treatment was performed by the treatment. By this alkali heat treatment step, the crystal structure of the cobalt compound is destroyed and the crystal structure is disturbed, and the oxidation of cobalt hydroxide is strongly promoted, and a part of the cobalt hydroxide has an average valence of more than 2 It becomes a large higher-order cobalt compound and contains sodium ions.

After this alkali heat treatment, this is fractionated,
After washing three times with pure water, dehydration and drying at 65 ° C. yielded composite particles containing 1% by weight of sodium ions in the cobalt hydroxide coating layer. The composite particles thus produced are referred to as powder Y.

2. Preparation of non-sintered nickel positive plate a. Example 1 95 parts by weight of the above-described powder Y (composite particles having a cobalt hydroxide coating layer containing 1% by weight of sodium ions on the surface of nickel hydroxide), 2 parts by weight of cobalt hydroxide, Powder mixed with 3 parts by weight of zinc powder (active material)
Then, 50 parts by weight of a 0.2% by weight aqueous solution of hydroxypropyl cellulose is added and mixed to prepare an active material slurry.

The thus prepared active material slurry is mixed with a nickel foam (nickel sponge) having a basis weight of 600 g / m ² , a porosity of 95% and a thickness of about 2 mm.
In addition, the active material packing density after rolling is about 2.9 g / cc-vo.
After filling and drying so as to be id (the amount of the active material with respect to the space volume of the nickel foam), the thickness was about 0.7 mm.
, And cut to a predetermined size to produce a nickel positive electrode plate a of Example 1.

B. Example 2 95 parts by weight of the powder Y (composite particles having a cobalt hydroxide coating layer containing 1% by weight of sodium ions on the surface of nickel hydroxide), 2 parts by weight of cobalt hydroxide, To a mixed powder (active material) of 2.5 parts by weight of zinc powder and 0.5 parts by weight of yttrium oxide (Y ₂ O ₃ ) was added a 50% by weight aqueous solution of hydroxypropyl cellulose.
The active material slurry is prepared by adding and mixing parts by weight.

The thus prepared active material slurry was mixed with a nickel foam (nickel sponge) having a basis weight of 600 g / m ² , a porosity of 95% and a thickness of about 2 mm.
In addition, the active material packing density after rolling is about 2.9 g / cc-vo.
After filling and drying so as to be id (the amount of the active material with respect to the space volume of the nickel foam), the thickness was about 0.7 mm.
, And cut to predetermined dimensions to produce a nickel positive electrode plate b of Example 2.

C. Example 3 95 parts by weight of the above powder Y (composite particles having a cobalt hydroxide coating layer containing 1% by weight of sodium ions on the surface of nickel hydroxide), 2 parts by weight of cobalt hydroxide, Mixed powder of 2.5 parts by weight of zinc powder and 0.5 part by weight of ytterbium oxide (Yb ₂ O ₃ ) (active material)
Then, 50 parts by weight of a 0.2% by weight aqueous solution of hydroxypropyl cellulose is added and mixed to prepare an active material slurry.

A nickel foam (nickel sponge) having a basis weight of 600 g / m ² , a porosity of 95% and a thickness of about 2 mm was prepared by mixing the active material slurry thus prepared.
In addition, the active material packing density after rolling is about 2.9 g / cc-vo.
After filling and drying so as to be id (the amount of the active material with respect to the space volume of the nickel foam), the thickness was about 0.7 mm.
, And cut to a predetermined size to produce a nickel positive electrode plate c of Example 3.

D. Example 4 95 parts by weight of the powder Y (composite particles having a cobalt hydroxide coating layer containing 1% by weight of sodium ions on the surface of nickel hydroxide), 2 parts by weight of cobalt hydroxide, and 2.5 parts by weight of zinc powder and bismuth oxide (B
50 parts by weight of a 0.2% by weight aqueous solution of hydroxypropylcellulose is added to and mixed with powder (active material) mixed with 0.5 parts by weight of i ₂ O ₃ ) to prepare an active material slurry.

A nickel foam (nickel sponge) having a base weight of 600 g / m ² , a porosity of 95% and a thickness of about 2 mm was prepared by mixing the active material slurry thus prepared.
In addition, the active material packing density after rolling is about 2.9 g / cc-vo.
After filling and drying so as to be id (the amount of the active material with respect to the space volume of the nickel foam), the thickness was about 0.7 mm.
, And cut to a predetermined size to produce a nickel positive electrode plate d of Example 4.

E. Comparative Example 90.25 parts by weight of nickel hydroxide powder containing 2.5% by weight of zinc and 1% by weight of cobalt as a coprecipitating component,
To a mixed powder (active material) of 6.75 parts by weight of cobalt hydroxide and 3 parts by weight of zinc oxide powder, 50 parts by weight of a 0.2% by weight aqueous solution of hydroxypropyl cellulose is added and mixed to prepare an active material slurry. .

The active material slurry thus prepared was used as a nickel foam (nickel sponge) having a basis weight of 600 g / m ² , a porosity of 95%, and a thickness of about 2 mm.
In addition, the active material packing density after rolling is about 2.9 g / cc-vo.
After filling and drying so as to be id (the amount of the active material with respect to the space volume of the nickel foam), the thickness was about 0.7 mm.
, And cut to a predetermined size to produce a nickel positive electrode plate e of a comparative example.

3. Preparation of hydrogen storage alloy negative electrode Misch metal (Mm: mixture of rare earth elements), nickel, cobalt, aluminum, and manganese
The mixture is mixed at a ratio of 3.4: 0.8: 0.2: 0.6, and this mixture is induction-heated in a high-frequency induction furnace in an argon gas atmosphere to form a molten alloy. The molten alloy is cooled by a known method to produce an ingot of a hydrogen storage alloy represented by a composition formula of Mm _1.0 Ni _3.4 Co _0.8 Al _0.2 Mn _0.6 .

After mechanically coarsely pulverizing the hydrogen storage alloy ingot, an average particle diameter of about 10 was obtained in an inert gas atmosphere.
Mechanically pulverize to 0 μm. A binder such as polyethylene oxide and an appropriate amount of water are added to the hydrogen storage alloy powder thus prepared, and mixed to prepare a hydrogen storage alloy slurry. This slurry was coated on both sides of an active material holder made of punched metal and the active material density after rolling was 5 g.
/ Cc, dried and rolled, and then cut to a predetermined size to produce a hydrogen storage alloy negative electrode.

4. Production of Nickel-Hydrogen Storage Battery Next, each of the non-sintered nickel positive plates a, b, c, d, and e produced as described above and the hydrogen storage alloy Each of the spirally wound electrode bodies is manufactured by spirally winding each of them through a separator made of a nonwoven fabric made of polypropylene having a thickness of 2 mm so that the outermost periphery becomes a negative electrode of the hydrogen storage alloy. Next, the spirally wound electrode body thus manufactured is inserted into a bottomed cylindrical metal outer can (AA size) also serving as a negative electrode terminal.

Thereafter, a negative electrode lead extending from the negative electrode is welded to the bottom of the metal outer can, and a positive electrode lead extending from the positive electrode is welded to a sealing body also serving as a positive electrode terminal. 8N KOH containing LiOH and NaOH) is poured into the metal outer can. Then
The sealing body was placed on the opening of the metal outer can via a gasket, and the opening of the metal outer can was swaged toward the sealing body to seal the opening, and each nickel-hydrogen storage battery A having a nominal capacity of 1300 mA was used. B, C, D, and E are manufactured.

5. Test a. Activation Conditions Next, each of the nickel-hydrogen storage batteries A, B, C, D, and E produced as described above is charged at room temperature with a charge current of 130 mA (0.1 C) for 16 hours, and then paused for 1 hour. Thereafter, discharge is performed at room temperature with a discharge current of 260 mA (0.2 C) until the final voltage reaches 1.0 V. Then, discharge is performed at room temperature with a discharge current of 130 mA (0.1 C) for the time shown in Table 1 below. This charge / discharge cycle was repeated at room temperature for two cycles, and each nickel-hydrogen storage battery A, B, C, D,
Activate E. After discharging for the time shown in Table 1 below, each of the nickel-hydrogen storage batteries A, B, C, D,
When the discharge end voltage of E (the battery voltage at the end of overdischarge) was measured, the results shown in Table 2 below were obtained.

[0032]

[Table 1]

B. Battery capacity test Each nickel-hydrogen storage battery A activated as described above,
B, C, D, and E are charged for 16 hours with a charging current of 130 mA (0.1 C) and then paused for 1 hour. Then 2
Final voltage of 1.0 V at 60 mA (0.2 C) discharge current
And the battery capacity was determined from the discharge time. The results were as shown in Table 2 below.

C. Low temperature discharge characteristic test Each of the nickel-hydrogen storage batteries A, B,
C, D, and E are charged at room temperature with a charge current of 130 mA (0.1 C) for 16 hours, and then left at 0 ° C. for 3 hours. Then, the battery was discharged in an atmosphere of 0 ° C. with a discharge current of 1300 mA (1 C) until the final voltage reached 1.0 V. The ratio between the discharge capacity at this time and the battery capacity obtained in the above-described battery capacity test was determined, and The discharge characteristics were as shown in Table 2 below.

[0035]

[Table 2]

In Table 2 above, No. The battery capacity and low-temperature discharge characteristics of the battery No. 3 are shown as 100.

As apparent from Table 2 above, Example 1
(Battery A using nickel positive plate a of Example 1), Example 2 (battery B using nickel positive plate b of Example 2),
No. 3 of Example 3 (battery C using nickel positive electrode plate c of Example 3) and Example 4 (battery D using nickel positive electrode plate d of Example 4). 3-No. When the battery is overdischarged until the battery voltage at the end of overdischarge at the time of activation becomes 0.3 V or less as in the battery of No. 9, the low-temperature discharge characteristics are improved,
It can be seen that the battery capacity has also been improved.

On the other hand, in the comparative example (the nickel positive electrode plate e of the comparative example)
No. of battery E) using 13-No. In the battery No. 15, when the battery was overdischarged until the battery voltage at the end of overdischarge at the time of activation became 0.3 V or less, the low-temperature discharge characteristics were improved, but the battery capacity was reduced.

This is because the higher-order cobalt compound layer containing alkali metal ions and having a disordered crystal structure is more difficult to reduce than the conventional crystalline higher-order cobalt compound (cobalt oxyhydroxide). In addition, it becomes difficult to dissolve in the alkaline electrolyte. When a higher-order cobalt compound layer having a disordered crystal structure containing alkali metal ions and having a valence of more than 2 is formed on the surface of the nickel hydroxide particles, a cobalt unevenly distributed layer is formed as a first layer from the surface,
An integrated layer of cobalt and nickel hydroxide is formed as a second layer, and a nickel hydroxide layer is formed as a third layer.

[0040] Even if the nickel hydroxide provided with a layer of a higher-order cobalt compound having a disordered crystal structure and larger than 2 valences on the surface is over-discharged, the higher-order cobalt compound having a disordered crystal structure with a charge of more than 2 valences is obtained. Is not easily reduced and hardly dissolved in an alkaline electrolyte, and the unified layer of cobalt and nickel hydroxide as a second layer acts as a barrier for cobalt diffusion. The conductive matrix of the positive electrodes a, b, c, and d does not collapse even after overdischarge. Therefore, it is considered that the charge / discharge efficiency does not decrease and the battery capacity does not decrease.

In the nickel-hydrogen batteries B, C and D using the non-sintered nickel positive electrodes b, c and d, the higher cobalt compound layer is selected from the compounds of yttrium, ytterbium and bismuth. When any one of them is present, these yttrium, ytterbium and bismuth compounds act as barriers for cobalt diffusion,
It is considered that even after the non-sintered nickel positive electrodes b, c, and d are overdischarged, the conductive matrix is not further collapsed, and a decrease in battery capacity can be prevented.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Nobuyuki Matsushita 2-5-5 Keihanhondori, Moriguchi City, Osaka Prefecture Inside Sanyo Electric Co., Ltd. (72) Takayuki Murakami 2-5-5 Keihanhondori, Moriguchi City, Osaka Prefecture No. 5 Sanyo Electric Co., Ltd. F-term (reference) 5H003 AA02 BA00 BA01 BA03 BA07 BB04 BC01 BC05 BD00 5H016 AA02 AA06 BB01 BB06 BB08 BB09 BB11 BB12 BB15 EE01 EE05 HH04 5H028 AA01 BB03 CC05 BB05 BB05 BB05 BB05 BB05 CC

Claims (3)

[Claims] An electrode body obtained by winding or laminating a non-sintered nickel positive electrode having nickel hydroxide as a main active material and a hydrogen storage alloy negative electrode via a separator is filled in an outer can together with an alkaline electrolyte. A method for producing a nickel-hydrogen storage battery to be formed, comprising: forming a higher-order cobalt compound layer containing alkali metal ions on a surface of the nickel hydroxide particles and having a disordered crystal structure larger than divalent. And forming a slurry of the nickel hydroxide on which the higher cobalt compound layer containing alkali metal ions and having a disordered crystal structure containing more than two valences is formed in the higher cobalt compound forming step, and forming the slurry into a three-dimensional network. An active material filling step of filling the active material holding body having a structure; and a nickel positive electrode formed by the active material filling step and a hydrogen absorbing compound. An electrode body forming step of forming an electrode body by winding or laminating a gold negative electrode with a separator interposed therebetween, and charging and discharging are repeated after the battery is formed by filling the electrode body together with an alkaline electrolyte in an outer can. An activation step, wherein the activation step includes an overdischarge step of overdischarging until the battery voltage becomes 0.3 V or less. 2. The high-order cobalt forming step is an alkali heat-treating step of subjecting nickel hydroxide particles provided with a coating layer of cobalt hydroxide to a heat treatment in an environment where oxygen and alkali coexist. 3. The method for producing a nickel-hydrogen storage battery according to claim 1. 3. The nickel alloy according to claim 1, wherein at least one selected from the group consisting of yttrium, ytterbium, and bismuth is present on the surface of the higher-order cobalt compound layer. Manufacturing method of hydrogen storage battery.