JP3011394B2 - Method for manufacturing nickel-metal hydride storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a nickel-metal hydride storage battery.

[0002]

2. Description of the Related Art Recent advances in electronic technology have reduced power consumption,
2. Description of the Related Art Advances in packaging technology have made portable electronic devices that could not be expected in the past. In order to make electronic equipment portable, it is required to increase the capacity of a storage battery as a power supply incorporated therein. As a storage battery that can respond to such demands, a nickel cadmium storage battery having a non-sintered electrode filled with a paste containing an active material on a three-dimensional structure substrate,
Nickel-metal hydride storage batteries using a negative electrode containing a hydrogen storage alloy instead of a cadmium negative electrode have been developed and have been widely put on the market. In particular, the demand for nickel-metal hydride storage batteries equipped with a negative electrode containing a hydrogen storage alloy has been increasing in recent years because they can achieve a capacity approximately twice or more higher than nickel cadmium storage batteries and do not contain environmental pollutants such as cadmium. It is growing rapidly.

However, the above-mentioned nickel-metal hydride storage battery has not sufficiently satisfied the recent rapid progress of electronic equipment and the demands of electronic equipment users. In particular, in response to the demand for higher capacity, there is an urgent need to develop a device that responds to the demand for improving the pulse-like high-current discharge characteristics accompanying the progress of digital devices.

[0004] By the way, it is known to increase the amount of a cobalt compound added to a nickel positive electrode and to increase the porosity of the nickel positive electrode as typical conventional measures for improving large current characteristics. However, since all of these improvement measures involve a decrease in the capacity of the storage battery, it has been difficult to improve the large-current discharge characteristics without sacrificing a high capacity.

On the other hand, problems specific to recent electronic devices include, for example, continuous discharge due to a minute current after turning off a power switch such as an operating power supply of a memory built-in holding circuit of a portable small computer, and a long-lasting battery. There is also an urgent need to develop a solution to a decrease in battery capacity after being left unattended. However, such a problem has only recently become apparent, and no solution has been made at present.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the capacity after long-term storage without increasing the amount of the cobalt compound in the positive electrode, and to reduce the heat used in the first charging step. An object of the present invention is to provide a method for manufacturing a nickel-metal hydride storage battery that can effectively use energy.

[0007]

Method for manufacturing a nickel-metal hydride storage battery according to the present invention SUMMARY OF] is cobalt monoxide, hydroxide Koba
An electrode group is produced by interposing a non-sintered nickel positive electrode containing nickel oxide and a non-sintered nickel positive electrode containing nickel oxide and a negative electrode containing a hydrogen storage alloy with a separator made of a polymer nonwoven fabric interposed therebetween for insulation. A step of storing the electrode group in a closed container together with an alkaline electrolyte, a step of performing initial charging at a high temperature of 40 to 120 ° C., and a closed container after the first charging and the uncharged electrode group and Cooling the sealed container after the first charge by exchanging heat with the sealed container containing the alkaline electrolyte, and heating the not-yet-charged sealed container. is there.

The non-sintered nickel positive electrode has a structure containing nickel oxide and a cobalt compound. Such a non-sintered nickel positive electrode is prepared, for example, by kneading a nickel hydroxide powder, a cobalt compound powder, and a binder in the presence of water to prepare a paste, and filling the paste into a current collector. It is produced by pressing after drying.

The nickel hydroxide powder has an average particle size of 5
It is preferable that the tap density is 1.8 g / cm ³ or more and the specific surface area is 8 to 25 m ² / g. The nickel hydroxide powder preferably has a spherical shape or a shape similar thereto.

The above-mentioned cobalt compound means cobalt monoxide, cobalt hydroxide or metallic cobalt. Examples of the binder include carboxymethyl cellulose, polyacrylate, polytetrafluoroethylene,
Polyvinyl alcohol or the like can be used.

The current collector may be, for example, a three-dimensional substrate such as a foamed nickel substrate, a reticulated sintered metal fiber substrate, a felt-plated substrate prepared by plating a nonwoven fabric with nickel, a punched metal, an expanded metal, or the like. Can be used.

The negative electrode is manufactured by applying a paste containing, for example, a hydrogen storage alloy powder and a binder to a current collector. As the hydrogen storage alloy to be blended in the paste, for example, AB ₅ type, A ₂ B type, AB-type, AB ₂
All alloys referred to as molds can be used. However, RNi _5-xy Co _x A _y (where R is La, Y
At least one element selected from the rare earth elements containing or a misch metal, A is Al, Mn, Ti, Cu, Z
It is preferable to use a hydrogen storage alloy represented by at least one selected from n, Zr, and Cr, and x and y each represent x ≧ 0.4 and 0 ≦ y ≦ 2.0 in atomic ratio. .

Examples of the binder compounded in the paste include polyacrylates such as sodium polyacrylate and potassium polyacrylate, fluorine resins such as polytetrafluoroethylene (PTFE), and polyvinyl alcohol. Can be mentioned. Such a binder is used in an amount of 0.1 to 100 parts by weight of the hydrogen storage alloy.
It is preferable to mix 5 parts by weight.

The paste is allowed to contain a conductive material such as carbon black or graphite as necessary. Such a conductive material is preferably blended in an amount of 0.1 to 4 parts by weight based on 100 parts by weight of the hydrogen storage alloy powder.

As the current collector, for example, a three-dimensional substrate such as a foamed nickel substrate, a reticulated sintered metal fiber substrate, a felt-plated substrate produced by applying a nickel plating to a nonwoven fabric, a punched metal, an expanded metal, or the like. Can be used.

The separator is made of, for example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric, a nylon nonwoven fabric, or a nonwoven fabric obtained by mixing polypropylene fibers and nylon fibers. In particular, a polypropylene nonwoven fabric whose surface has been hydrophilized is suitable as a separator.

Examples of the alkaline electrolyte include sodium hydroxide (NaOH) and lithium hydroxide (LiO).
H), a mixed solution of potassium hydroxide (KOH) and LiOH, a mixed solution of NaOH, KOH and LiOH, or the like can be used.

The temperature at the time of the first charge is specified for the following reason. 40 ℃ at first charging
If it is less than the above range, it becomes difficult to improve the utilization rate of nickel oxide, which is the active material of the positive electrode, that is, to sufficiently achieve the effect of restoring the battery capacity after long-term storage. On the other hand, if the temperature at the time of the first charge exceeds 120 ° C., the vapor pressure of the electrolytic solution increases, which may cause the safety valve to operate or the battery components to be thermally degraded to lower the reliability. A more preferable temperature at the time of the first charge is 50 to
90 ° C.

The heat exchange between the sealed container after the first charge and the sealed container containing the electrode group and the alkaline electrolyte not yet charged may be performed, for example, by directly contacting each of the sealed containers.
A method of contacting each of the closed containers via a heat medium such as water or oil may be employed.

[0020]

According to the present invention, a nickel oxide and a cobalt compound (the above-mentioned cobalt compound is cobalt monoxide,
A non-sintered nickel positive electrode containing cobalt or metallic cobalt) and a negative electrode containing a hydrogen storage alloy are interposed and insulated from each other with a separator made of a polymer nonwoven fabric. After being stored in an airtight container together with the electrolyte, the initial charge is performed at a predetermined high temperature, which not only increases the capacity and improves the large current discharge characteristics, but also suppresses the decrease in capacity when recharging after long-term storage. A possible nickel-metal hydride storage battery can be manufactured. It is considered that the nickel-metal hydride storage battery having such characteristics is obtained by the following mechanism.

That is, a storage battery assembled using a non-sintered nickel positive electrode containing a nickel oxide and a cobalt compound and a negative electrode containing a hydrogen storage alloy is initially charged at a high temperature of 40 to 120 ° C. Dissolution of the cobalt compound in the alkaline electrolyte, followed by redeposition on the nickel hydroxide surface, and oxidation of the redeposited cobalt compound (formation of cobalt oxyhydroxide) by the charging current is smooth and complete. Therefore, an effective amount of cobalt oxyhydroxide to contribute to conduction in the positive electrode is uniformly generated. As described above, the cobalt compound contained in the nickel positive electrode more effectively acts on nickel hydroxide, which is a positive electrode active material, thereby improving the utilization rate of the positive electrode and recharging after being stored or left for a long time. It is considered that the capacity reduction at the time is suppressed.

Further, heat exchange is performed between the sealed container after the first charge and the sealed container containing the electrode group and the alkaline electrolyte not yet charged to cool the sealed container after the first charge, and By heating the sealed container for charging,
Excessive rise in the production atmosphere temperature due to heat radiation from the airtight container after the initial charge can be suppressed. In addition, since the heating time for the uninitialized closed container can be reduced, the initial charging can be performed efficiently. In addition, it is possible to achieve a reduction in manufacturing cost due to energy saving.

That is, a temperature range of 70 to 90 ° C., which is an effective temperature range for producing cobalt oxyhydroxide serving as a conductive matrix of the nickel positive electrode in the initial charging step.
Is higher than normal temperature by 40 to 50 ° C or more. By the way, A
In an A-size nickel-metal hydride storage battery, about 18 cal of heat is required to raise the temperature by 1 ° C., so the temperature of the storage battery before the first charge is 25 ° C., and the temperature at the time of the first charge is 85 ° C. If so, the temperature must be increased by 60 ° C. Therefore, it requires 1080 cal of heat per one AA-size storage battery.
To heat a group of 10,000 batteries, about 10 ⁷ c
In order to cool the storage battery group after the initial charge to a temperature of 20 to 30 ° C., the same heat quantity needs to be released from the storage battery group.

Heating and cooling each time a plurality of storage batteries are charged for the first time requires extra energy and lowers efficiency. Therefore, as in the present invention, heat exchange between the storage battery or the storage battery group still in a high temperature state after the end of the initial charge and the sealed container or the plurality of sealed containers in which the electrode group and the alkaline electrolyte not yet charged are stored. By performing the above, unnecessary energy consumption can be eliminated, and furthermore, it is possible to avoid raising the manufacturing atmosphere temperature more than necessary.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, LmNi _4.0 Co _0.4 Mn _0.3 Al
_0.3 (Lm; lantern rich misch metal) (Lm;
0.125 parts by weight of sodium polyacrylate, 0.125 parts by weight of carboxymethyl cellulose,
A paste was prepared by adding 0.25 parts by weight of polytetrafluoroethylene, 1 part by weight of carbon black, and 60 parts by weight of water, mixing and kneading while applying shear stress. Thereafter, the paste was applied to punched metal, dried, and molded to produce a negative electrode.

On the other hand, 90 parts by weight of nickel hydroxide powder, 10 parts by weight of cobalt monoxide, 0.2% of sodium polyacrylate
A paste was prepared by kneading 5 parts by weight, 0.25 parts by weight of carboxymethyl cellulose, 3.0 parts by weight of polytetrafluoroethylene, and 30 parts by weight of water.
The paste was applied to a conductive core made of nickel fiber, filled, dried, and pressed to produce a non-sintered positive electrode.

Separators each made of a hydrophilic non-woven polypropylene nonwoven fabric are placed between the obtained positive electrode and negative electrode, and these positive electrode groups are stored in a metal container. Then, an electrolytic solution containing potassium hydroxide as a main component is placed in the container. Housed in
A having the structure shown in FIG. 1 using each member such as a metal lid
An A-size cylindrical nickel-metal hydride battery was assembled. FIG.
1, the negative electrode 1 is spirally wound with a separator 3 interposed between the negative electrode 1 and the non-sintered positive electrode 2, and is housed in a bottomed cylindrical container 4. The alkaline electrolyte is contained in the container 4. A circular sealing plate 6 having a hole 5 in the center
Are arranged in the upper opening of the container 4. The ring-shaped insulating gasket 7 is disposed between the peripheral edge of the sealing plate 6 and the inner surface of the upper opening of the container 4, and the sealing plate is formed on the container 4 by caulking to reduce the diameter of the upper opening inward. 6 is hermetically fixed via the gasket 7. One end of the positive electrode lead 8 is connected to the positive electrode 2, and the other end is connected to the lower surface of the sealing plate 6. A positive electrode terminal 9 having a hat shape is mounted on the sealing plate 4 so as to cover the hole 5. A rubber safety valve 10 is disposed in a space surrounded by the sealing plate 4 and the positive electrode terminal 9 so as to close the hole 5.

A plurality of the nickel-metal hydride batteries B thus assembled were housed in a battery case 11 for initial charging shown in FIG. The case 11 includes a case body 12 having an open upper surface and made of an insulating material such as a heat-resistant resin, and four cases 11 disposed in the body 12 to partition the inside of the body 12 into five elongated spaces. Support plate 13 and the main body 12
A terminal portion 14 formed on the inner bottom surface of the main body 12 and connected to the negative electrode of the storage battery B, a heated water flow port 15 respectively opened at a lower portion of the opposite side wall of the main body 12, and attached to the main body 12. And a lid 17 made of an insulating material such as a heat-resistant resin and having an elastic terminal portion 16 connected to each of the B positive electrodes. The terminal portion 14 and the elastic terminal portion 16 are connected to a power source (not shown) disposed outside.

FIG. 3 is a plan view showing the initial charge processing device. In FIG. 3, reference numeral 21 denotes a first constant temperature bath set to a temperature of 45 ° C., 22 denotes a second constant temperature bath which is disposed adjacent to the left side of the first constant temperature bath 21 and is set to a temperature of 65 ° C. This is a third constant temperature bath which is arranged adjacent to the left side of the second constant temperature bath 22 and is set at a temperature of 85 ° C. The first to third thermostats 21 to 23 contain hot water as a heat medium.
The first and second thermostats 21 and 22 have a space for accommodating two cases 11, and the third thermostat 23 has a space for one case 11. A plurality of nickel-metal hydride batteries B in the above-described initial charging battery case 11 shown in FIG. 2 were initially charged at a high temperature by such an initial charging processing device.

That is, the battery case 11 for initial charging, in which a plurality of nickel-metal hydride batteries B are stored, is transported into the first constant temperature bath 21 as shown by an arrow A ₁ , and the heated water in the constant temperature bath 21 is transferred to the case body. The plurality of storage batteries were heated to 45 ° C. by flowing through the main body through the flow ports. Then, the second constant-temperature bath 22, as shown the case 11 in the arrow A ₂
And a plurality of storage batteries B in the case 11
Heated to 5 ° C. Subsequently, the case 11 of the arrow A ₃
Is transported to the third constant temperature bath 23 as shown in FIG. 3, and when heated to 85 ° C., a voltage of a predetermined current value is applied to the plurality of storage batteries B in the case 11 through the terminal portion 14 and the elastic terminal portion 16. And did the first charge. The case 11 in which the storage battery after the initial charge is stored is sequentially transported to the second constant temperature bath 22 and the first constant temperature bath 21 as shown by arrows C ₁ and C ₂ , and further transported outside as shown by the arrow C ₃ . . In the process of transporting the second thermostat 22 and the first thermostat 21 of such a case 11,
The storage battery after the first charge in the case 11 exchanges heat with the uninitialized storage battery in the case 11 transported to the first constant temperature bath 21 and the second constant temperature bath 22 as shown by arrows A ₁ and A _2. Therefore, the storage battery after the first charge in the case 11 is 65 ° C.
The storage battery, which was sequentially cooled to 45 ° C. and was not initially charged in the case 11, was sequentially heated to 45 ° C. and 65 ° C.

As described above, the battery case 11 for initial charging shown in FIG. 2 in which a plurality of storage batteries are stored is transferred stepwise to the first to third constant temperature baths 21 to 23, and the initial charging at a high temperature is performed. Thereafter, the second and first constant temperature baths 22 and 21 are moved in the opposite directions.
By transporting the battery to the outside and taking it out after cooling, the temperature of the environmental atmosphere for the first charge does not rise, the storage battery before the first charge can be efficiently heated, and energy can be used effectively. In addition, the storage battery that was initially charged had a capacity recovery rate of 90% or more, which is desirable as long-term storage characteristics.

In the above-described embodiment, the high-temperature initial charging of the storage battery was performed using the initial charge processing device having three constant temperature baths shown in FIG. 3, but the initial charge processing device having four or more constant temperature baths was used. The battery may be initially charged at high temperature. By using such an initial charge processing device, it is possible to more efficiently cool the storage battery after the initial charge and heat the storage battery not yet initially charged.

In the above-described embodiment, a cylindrical nickel-metal hydride storage battery which is spirally wound with a separator interposed between a negative electrode and a non-sintered positive electrode and accommodated in a bottomed cylindrical container has been described as an example. The present invention can be similarly applied to a nickel-metal hydride storage battery in which a separator is interposed between a plurality of negative electrodes and a plurality of positive electrodes to form a laminate, and the laminate is housed in a bottomed rectangular cylindrical container.

[0034]

As described in detail above, according to the present invention, it is possible to suppress the capacity reduction after long-term storage without increasing the amount of the cobalt compound in the positive electrode, and to reduce the amount of the cobalt compound in the first charging step. It is possible to effectively utilize the heat energy to be used, and to provide a method for efficiently producing a high performance nickel-metal hydride storage battery.

[Brief description of the drawings]

FIG. 1 is a partially exploded perspective view showing a nickel-metal hydride secondary battery according to the present invention.

FIG. 2 is a partially cutaway front view showing a battery case for initial charging used in an embodiment of the present invention.

FIG. 3 is a plan view showing an initial charge processing device used in the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Negative electrode, 2 ... Positive electrode, 4 ... Container, 6 ... Sealing plate, 7 ... Insulating gasket, 9 ... Positive electrode terminal, 11 ... Battery case for initial charge, 12 ... Case main body, 15 ... Distribution port, 21-23 ... Constant temperature bath, B: storage battery.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Ken Omiyama 3-4-1-10 Minamishinagawa, Shinagawa-ku, Tokyo Inside Toshiba Battery Corporation (72) Inventor Hidekazu Ohata 3-4-1-10 Minamishinagawa, Shinagawa-ku, Tokyo No. Within Toshiba Battery Co., Ltd. (72) Inventor Hiroyuki Hasebe 1 at Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside of Toshiba R & D Center Co., Ltd. No. 1 Toshiba R & D Center Co., Ltd. (72) Inventor Shinji Tsuruta No. 1 Komukai Toshiba-cho, Yuki-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba R & D Center (72) Inventor Hideki Yoshida Komukai, Yuki-ku, Kawasaki-shi, Kanagawa No. 1, Toshiba Town Inside R & D Center, Toshiba Corporation (56) References JP-A-5-151990 (JP, A) JP-A-5-198302 (JP, ) Patent flat 5-314983 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) H01M 10/30 H01M 4/32 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. Cobalt monoxide, cobalt hydroxide and gold
A step of producing an electrode group by interposing and insulating a separator made of a polymer nonwoven fabric between a non-sintered nickel positive electrode containing nickel oxide and one selected from the group consisting of cobalt and a negative electrode containing a hydrogen storage alloy; A step of housing the electrode group together with an alkaline electrolyte in a closed container; a step of performing initial charge at a high temperature of 40 to 120 ° C .; a closed container after the first charge; Cooling the sealed container after the first charge by exchanging heat with the sealed container containing the liquid, and heating the not-yet-charged sealed container. Production method.