JP4118991B2 - Manufacturing method of nickel metal hydride storage battery - Google Patents

Description

【００５０】
表１から明らかなように、実施例１の二次電池は、利用率、低温放電特性及び放置後の回復率を優れたものに維持しつつ、容量を向上できることがわかる。
これに対し、負極の合金に表面処理を施さずに室温を越える温度で初充電を行った比較例１の二次電池は、低温放電時の利用率が著しく低下することがわかる。また、負極の合金に表面処理を施したものの、初充電温度が室温である比較例２の二次電池は、放置後の回復率が実施例１に比べて劣ることがわかる。表面処理を行わずに室温で初充電を行った比較例３の二次電池は、容量、利用率、低温放電特性及び放置特性のいずれの特性も実施例１に比べて劣ることがわかる。
【００５１】
一方、正極理論容量に対するアルカリ電解液量（２５℃）の比が１．７ｃｍ³ ／Ａｈである比較例４の二次電池は、利用率、低温放電特性及び放置特性に優れるものの、容量が実施例１に比べて低いことがわかる。
（実施例２）
正極の導電剤を一酸化コバルト粉末にすること以外は、実施例１と同様な方法により円筒形ニッケル水素蓄電池を製造した。
【００５２】
得られた蓄電池の特性を前述したのと同様にして測定したところ、放電容量は３７２０ｍＡｈで、初期利用率が９３％で、低温放電時の利用率が３４％で、放置後の容量回復率が９９％であった。
【００５３】
【発明の効果】
以上詳述したように本発明によれば、導電剤の配合量を無駄に多くせずに、初期から高容量が得られ、更に低温放電特性及び過放電特性に優れ、電池特性のバランスが良好なニッケル水素蓄電池の製造方法を提供することができる。
【図面の簡単な説明】
【図１】本発明に係る方法で製造されるニッケル水素蓄電池の一例を示す部分切欠斜視図。
【符号の説明】
１…容器、
２…正極、
３…セパレータ、
４…負極、
７…封口板。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a nickel metal hydride storage battery.
[0002]
[Prior art]
In recent years, various electronic devices have become portable due to advances in electronic technology. Along with this, the storage battery as a power source is not only high in capacity, but it is desired to improve problems such as capacity reduction after standing, large current discharge characteristics from the beginning and discharge characteristics at low temperatures, Development for these requirements is urgent.
[0003]
Conventionally known measures for improving the large current discharge characteristics include an increase in the amount of cobalt compound added to the nickel positive electrode and an increase in the porosity in the battery. However, since all of these improvement measures are accompanied by a decrease in the capacity of the nickel metal hydride storage battery, it has been difficult to improve the large current discharge characteristics without sacrificing the increase in capacity.
[0004]
On the other hand, JP-A-8-236145 and JP-A-8-195218 propose charging at a high temperature until the cobalt compound added to the positive electrode is oxidized into a conductive cobalt high-order oxide. Yes. According to these, the cobalt compound added to the positive electrode is effectively converted into a conductive matrix without waste, and the amount of cobalt compound added can be reduced. An excellent nickel metal hydride storage battery is obtained.
[0005]
[Problems to be solved by the invention]
However, when a hydrogen-containing alloy containing Mn is used as the hydrogen storage alloy contained in the negative electrode, if the above-described high-temperature initial charge is performed, the Mn component in the alloy elutes into the electrolyte during the initial charge, and this is the positive electrode surface. Therefore, the negative electrode capacity and the charge / discharge reaction rate are reduced. Therefore, when a hydrogen storage alloy containing Mn is used, it is not preferable to set the atmosphere for manufacturing the nickel metal hydride storage battery to a high temperature.
[0006]
Moreover, the capacity of the active material increases as the capacity increases, and the space for the amount of electrolyte in the battery container has been limited as never before. For this reason, the consumption of the electrolytic solution (water) at the first charge is one factor that greatly affects the battery characteristics such as the cycle life later.
[0007]
In such an environment, it is difficult to sufficiently activate the positive electrode by initial charging without impairing the characteristics of the negative electrode. In addition, a manufacturing method that satisfies the other characteristics such as the leaving characteristics and the low-temperature discharge characteristics in a balanced manner while increasing the capacity has not been developed.
[0008]
An object of the present invention is to provide a method for producing a nickel-metal hydride storage battery capable of obtaining a high capacity from the beginning even under a low liquid ratio and having excellent low-temperature discharge characteristics and overdischarge characteristics.
[0009]
[Means for Solving the Problems]
The method for producing a nickel metal hydride storage battery according to the present invention includes a step of immersing a negative electrode including a hydrogen storage alloy containing Mn with an aqueous sodium hydroxide solution having a concentration of 20 to 40 wt% and a temperature of 70 to 90 ° C. When,
The negative electrode, a positive electrode containing a conductive agent composed of at least one selected from cobalt and a cobalt compound in terms of cobalt element with respect to an active material containing nickel hydroxide, and a liquid volume ratio of 0.5 to a step Ru assembled nickel-metal hydride storage battery comprising an alkaline electrolyte is 1.6 cm ³ / Ah,
Applying the initial charge to the storage battery at 70-90 ° C .;
It is characterized by comprising .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the manufacturing method of the nickel hydride storage battery of this invention is demonstrated.
(First step)
A positive electrode comprising an active material containing nickel hydroxide, and a conductive agent comprising at least one selected from cobalt and a cobalt compound in an amount of 10% by weight or less of cobalt based on the active material; surface treatment is performed, and Mn A nickel hydride storage battery comprising: a negative electrode including a hydrogen storage alloy containing; an alkaline electrolyte having a liquid amount ratio of 0.5 to 1.6 cm ³ / Ah to a theoretical capacity of the positive electrode. This storage battery has a structure as shown in FIG. 1, for example.
[0011]
That is, the bottomed cylindrical container 1 accommodates an electrode group 5 produced by laminating the positive electrode 2, the separator 3, and the negative electrode 4 and winding them in a spiral shape. The negative electrode 4 is disposed on the outermost periphery of the electrode group 5 and is in electrical contact with the container 1. The alkaline electrolyte is accommodated in the container 1. A circular first sealing plate 7 having a hole 6 in the center is disposed in the upper opening of the container 1. A ring-shaped insulating gasket 8 is disposed between the periphery of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the sealing plate is attached to the container 1 by caulking to reduce the diameter of the upper opening to the inside. 7 is hermetically fixed through the gasket 8. The positive electrode lead 9 has one end connected to the positive electrode 2 and the other end connected to the lower surface of the sealing plate 7. A positive electrode terminal 10 having a hat shape is attached on the sealing plate 7 so as to cover the hole 6. The rubber safety valve 11 is disposed so as to close the hole 6 in a space surrounded by the sealing plate 7 and the positive electrode terminal 10. A circular presser plate 12 made of an insulating material having a hole in the center is arranged on the positive electrode terminal 10 so that the protruding portion of the positive electrode terminal 10 protrudes from the hole of the presser plate 12. The outer tube 13 covers the periphery of the pressing plate 12, the side surface of the container 1, and the bottom periphery of the container 1.
[0012]
Next, the positive electrode 2, the negative electrode 4, the separator 3 and the electrolytic solution will be described.
1) Positive electrode 2
The positive electrode 2 includes an active material mainly composed of nickel hydroxide and a conductive agent composed of at least one selected from cobalt and a cobalt compound in an amount of 10% by weight or less in terms of cobalt element with respect to the active material.
[0013]
As an active material mainly composed of nickel hydroxide, for example, nickel hydroxide particles or nickel hydroxide particles in which zinc and / or cobalt are eutectic can be used. The latter positive electrode containing nickel hydroxide particles can further improve the charging efficiency in a high temperature state.
[0014]
From the viewpoint of improving the charge / discharge efficiency of a nickel-metal hydride storage battery in which the alkaline electrolyte amount ratio is limited to the above range, the nickel hydroxide has a peak half of the (101) plane at 2θ of X-ray powder diffraction by Cu-Kα rays. The value width is preferably 0.8 ° or more. A more preferable half width of the peak is 0.9 to 1.1 ° / 2θ (Cu—Kα).
[0015]
Examples of the cobalt compound include dicobalt trioxide (Co ₂ O ₃ ), cobalt monoxide (CoO), and cobalt hydroxide {Co (OH) ₂ }. As said cobalt compound, 1 type, or 2 or more types chosen from the types mentioned above can be used. In particular, under a low electrolyte ratio that is conscious of high capacity, the solubility difference in alkaline electrolyte between room temperature and high temperature is large, excellent storage stability, and water is consumed when forming a conductive matrix during initial charging. In addition, cobalt hydroxide that is excellent in holding the electrolyte in the battery for a long period is preferable.
[0016]
The conductive agent is added to the active material in the above range in terms of cobalt element for the following reason. If the amount exceeds 10% by weight, the amount of active material in the positive electrode is insufficient, which is a disadvantageous factor in increasing the capacity. A more preferable range of the addition amount is 3 to 6% by weight.
[0017]
The positive electrode can be produced, for example, by the method described in the following (a) to (c).
(A) One or more particles selected from cobalt particles and cobalt compound particles, a binder, and water are added to particles containing nickel hydroxide as a main component, kneaded to prepare a paste, The positive electrode is produced by filling a paste into a current collector and drying and pressing the paste.
[0018]
(B) First, at least a part of the surface of particles mainly composed of nickel hydroxide is coated with at least one selected from cobalt and a cobalt compound to produce composite nickel hydroxide particles. The composite nickel hydroxide particles, the binder and water are kneaded to prepare a paste, and the paste is filled in a current collector, which is dried and pressure-molded to produce the positive electrode.
[0019]
(C) One or more kinds of particles selected from the composite nickel hydroxide particles, cobalt particles and cobalt compound particles, a binder and water are kneaded to prepare a paste, and the paste is filled in a current collector, The positive electrode is prepared by drying and pressure-molding.
[0020]
Examples of the current collector include those having a sponge-like, fibrous or felt-like porous structure made of a metal such as nickel or stainless steel or a resin plated with nickel.
[0021]
Examples of the binder include polytetrafluoroethylene, carboxymethylcellulose, methylcellulose, sodium polyacrylate, polyvinyl alcohol and the like.
[0022]
2) Negative electrode 4
The negative electrode 4 is subjected to a surface treatment and includes a hydrogen storage alloy containing Mn.
The surface treatment is performed for the purpose of suppressing elution of Mn in the alloy into the alkaline electrolyte. Examples of such surface treatment include metal (for example, metal having corrosion resistance such as nickel), addition of metal oxide (plating), alkali treatment, heat treatment, fluorine treatment, and the like. The surface treatment may be performed in an alloy state or in an electrode state.
[0023]
The negative electrode 4 is produced, for example, by the method described below. First, a hydrogen storage alloy powder, a conductive material, a binder and water are kneaded to prepare a paste, the conductive substrate is filled with the paste, dried, and then molded. Subsequently, the said negative electrode is obtained by surface-treating to the said alloy by immersing in alkaline aqueous solution.
[0024]
As the hydrogen-absorbing alloy, for example, the general formula _{(1); LmNi w Co x} Mn y Al z in (atomic ratio w, x, y, the total value of z is 5.00 ≦ w + x + y + z ≦ 5.50) Of the composition represented, general formula (2); AB _x (where A is Ti and / or Zr, B is composed of Mn alone, or Mn and Ni, V, Co, Cr, Al , Fe, Cu, Mo, La, Ce, Pr, and Nd, and x represents 1.8 ≦ x ≦ 2.5), and the main component of the alloy phase is Examples thereof include C14 or C15 Laves phase.
[0025]
Examples of the conductive material include carbon black and graphite.
Examples of the binder include polyacrylic acid salts such as sodium polyacrylate and potassium polyacrylate, fluorine resins such as polytetrafluoroethylene (PTFE), and carboxymethylcellulose (CMC).
[0026]
Examples of the conductive substrate include two-dimensional substrates such as punched metal, expanded metal, perforated rigid plate, nickel net, and three-dimensional substrates such as felt-like metal porous bodies and sponge-like metal porous bodies. Can do.
[0027]
By immersing the negative electrode in an alkaline aqueous solution, a component that is easily dissolved in an alkaline electrolyte such as Mn existing on the alloy surface is dissolved in the aqueous solution, and the surface state in which the elution of the Mn component is unlikely to occur. Therefore, elution of the Mn component into the electrolyte during initial charge and charge / discharge can be suppressed, and the total elution amount of Mn can be reduced.
[0028]
Examples of the alkaline aqueous solution include a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and a lithium hydroxide aqueous solution.
The concentration of the alkaline aqueous solution is preferably in the range of 20 to 40 wt%. This is due to the following reason. If the concentration is less than 20 wt%, it may be difficult to suppress the dissolution of the Mn component in the alloy into the electrolyte, and the low-temperature discharge characteristics may be deteriorated. On the other hand, even if the concentration exceeds 40 wt%, there is not much change in the elution amount of the Mn component into the electrolyte. A more preferable range of the concentration is 25 to 35 wt%.
[0029]
The temperature of the alkaline aqueous solution is preferably 60 to 120 ° C. This is due to the following reason. If the temperature is less than 60 ° C., it may be difficult to reduce the amount of the Mn component dissolved in the alloy, and the low-temperature discharge characteristics may be deteriorated. On the other hand, even if the temperature exceeds 120 ° C., the elution amount of the Mn component into the electrolyte does not change much. A more preferable range of the temperature is 70 to 90 ° C.
[0030]
The immersion time in the alkaline aqueous solution is preferably 0.5 to 5 hours.
In addition, after the alkali treatment is performed on the hydrogen storage alloy, a paste containing the alloy is prepared, the conductive substrate is filled with the paste, dried, and pressure-molded to produce the negative electrode. good.
[0031]
3) Separator 3
Examples of the separator 3 include polyamide fiber nonwoven fabrics and polyolefin fiber nonwoven fabrics such as polyethylene and polypropylene provided with a hydrophilic functional group.
[0032]
4) Alkaline electrolyte As the alkaline electrolyte, for example, an aqueous solution of sodium hydroxide (NaOH), an aqueous solution of lithium hydroxide (LiOH), an aqueous solution of potassium hydroxide (KOH), a mixed solution of NaOH and LiOH, KOH and A mixed solution of LiOH, a mixed solution of KOH, LiOH, and NaOH can be used.
[0033]
The ratio of the amount of the alkaline electrolyte (25 ° C.) to the theoretical capacity of the positive electrode [{the amount of alkaline electrolyte (cm ³ )} at 25 ° C.} / {The theoretical capacity of positive electrode (Ah)}] is 0.5 to 1. The range is 6 cm ³ / Ah. This is due to the following reason. The ratio of the liquid amount exceeding 1.6 cm ³ / Ah is a disadvantageous factor for increasing the capacity. Although the smaller the liquid volume ratio is, the better the capacity is. However, when the liquid volume ratio is less than 0.5 cm ³ / Ah, the positive electrode utilization rate decreases, and satisfactory characteristics cannot be obtained. A more preferable range of the liquid volume ratio is 0.8 to 1.2 cm ³ / Ah.
(Second step)
The storage battery is initially charged at a temperature exceeding room temperature.
[0034]
The initial charging with the charging temperature set in such a range is preferably performed at least from the start until the charging of the conductive agent is completed. At least during such a period, by setting the charging temperature within the above range, a conductive matrix can be uniformly formed in the positive electrode, and the reduction resistance of the conductive matrix can be increased. It is possible to further improve the utilization factor and the standing characteristics when the amount of liquid is limited. In the initial charging step, the charging temperature may be set to a temperature exceeding room temperature over the entire period.
[0035]
The initial charging temperature is preferably in the range of 40 to 100 ° C. This is due to the following reason. If the initial charging temperature is less than 40 ° C., the high solubility of the conductive agent cannot be obtained. Therefore, when the amount of the electrolyte is small, it is difficult to form a conductive matrix uniformly in the positive electrode, and the initial utilization rate is reduced. There is a fear. On the other hand, even if the initial charging temperature exceeds 100 ° C., there is no significant change in the solubility of the conductive agent, and it is difficult to obtain an advantage in consideration of productivity. A more preferable initial charging temperature is in the range of 70 ° C to 90 ° C.
[0036]
The manufacturing method of the nickel metal hydride storage battery according to the present invention allows aging to be performed before the initial charge.
In FIG. 1 described above, a separator is interposed between the positive electrode and the negative electrode, and the electrode group produced by winding the separator in a spiral shape is housed in the container. You may store the laminated body produced by interposing a separator in the meantime in the meantime in the container of a bottomed rectangular cylinder shape.
[0037]
As described above, the method for producing a nickel-metal hydride storage battery according to the present invention is an active material containing nickel hydroxide, and one type selected from cobalt and cobalt compounds of 10% by weight or less in terms of cobalt element with respect to the active material. A positive electrode including a conductive agent composed of the above; a negative electrode including a hydrogen storage alloy that has been surface-treated and contains Mn; a ratio of a liquid amount to a theoretical capacity of the positive electrode is 0.5 to 1.6 cm ³ / Ah. A step of assembling a nickel-metal hydride storage battery comprising an alkaline electrolyte; and a step of first charging the storage battery at a temperature exceeding room temperature.
[0038]
According to such a method, since the hydrogen storage alloy contained in the negative electrode can be subjected to a surface treatment so that Mn in the alloy does not elute into the alkaline electrolyte before performing the initial charge at a temperature exceeding room temperature. The amount of Mn eluted into the electrolyte during the initial charge can be reduced. As a result, the initial charge at a temperature exceeding room temperature is possible without impairing the characteristics of the negative electrode, so the positive electrode utilization rate when the amount of electrolyte is regulated by high capacity while maintaining excellent low temperature discharge characteristics It is possible to improve the capacity and to suppress a decrease in capacity due to being left in a high temperature environment or being left for a long time. Therefore, it is possible to manufacture a nickel-metal hydride storage battery that has been maintained with excellent low-temperature discharge characteristics, positive electrode utilization rate, leaving characteristics, and charge / discharge cycle life, and has an increased capacity.
[0039]
When the peak half-value width of the (101) plane at 2θ of X-ray powder diffraction of Cu-Kα ray of nickel hydroxide is 0.8 ° or more, the alkaline electrolyte amount ratio is limited to the above range. The positive electrode utilization rate can be further improved.
[0040]
In addition, by using cobalt hydroxide as the conductive agent, it is possible to reduce the alkaline electrolyte consumption during the initial charge, so the positive electrode utilization rate and charge / discharge cycle life when the alkaline electrolyte volume ratio is regulated Can be further improved.
[0041]
By setting the temperature of the initial charge to 40 to 100 ° C., even when the amount of the electrolyte is small, the formation reaction of a conductive cobalt compound such as cobalt oxyhydroxide can be uniformly generated over the entire positive electrode. Therefore, a high utilization factor can be ensured and an alkaline storage battery having a high discharge capacity can be provided. Furthermore, since the cobalt oxyhydroxide formed by such initial charging is difficult to be reduced after being left for a long period of time and after being left at a high temperature, a decrease in capacity after being left can be suppressed. Therefore, the positive electrode utilization factor and the leaving characteristics of the nickel-metal hydride storage battery can be further improved.
[0042]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Example 1)
<Preparation of positive electrode>
Cobalt hydroxide powder is used as a conductive agent for cobalt hydroxide powder as a conductive agent against 90% by weight of nickel hydroxide powder having a peak half-value width of (101) plane of 1.0 ° / 2θ (Cu-Kα) by X-ray powder diffraction method. In addition, 5.0% by weight is added, and further a binder (0.25% by weight of carboxymethyl cellulose, 0.25% by weight of sodium polyacrylate and 3.0% by weight of polytetrafluoroethylene) and water are added. The paste was prepared by kneading. The paste was filled in a nickel-plated fiber substrate having a thickness of 1.1 mm as a current collector and having a porosity of 95%, dried, and then roller-pressed to form a paste type positive electrode.
<Production of negative electrode>
A hydrogen storage alloy having a composition of LmNi _4.0 Co _0.4 Mn _0.3 Al _0.3 was prepared by a high frequency furnace using lanthanum-rich misch metal Lm and Ni, Co, Mn, and Al. The hydrogen storage alloy was mechanically pulverized, and 100 parts by weight of the obtained alloy powder was solidified with 0.5 parts by weight of sodium polyacrylate, 0.125 parts by weight of carboxymethylcellulose (CMC), and a polytetrafluoroethylene dispersion. A paste was prepared by adding 1.5 parts by weight, 1 part by weight of carbon powder and 50 parts by weight of water and kneading. This paste was applied to a punched metal, dried, and then subjected to pressure molding to produce a paste-type negative electrode.
[0043]
(surface treatment)
The obtained negative electrode was housed in a heat-resistant container, immersed in a 30 wt% sodium hydroxide aqueous solution heated to 80 ° C. for 1 hour, washed with water, and dried to give an alkali treatment to the surface of the alloy. Mn in the alloy is dissolved by this alkali treatment, and the surface of the alloy is coated with Ni or Co, so that Mn in the alloy elutes into the alkaline electrolyte during initial charge and charge / discharge. Can be suppressed.
[0044]
Next, a separator made of a polypropylene nonwoven fabric subjected to a hydrophilic treatment was interposed between the positive electrode and the negative electrode, and wound into a spiral shape to produce an electrode group. The electrode group is housed in a bottomed cylindrical metal container, and an alkaline electrolyte mainly composed of potassium hydroxide has a liquid ratio (25 ° C.) of 1.0 cm ³ / Ah with respect to the theoretical capacity of the positive electrode. Then, using a member such as a metal lid, a 4 / 3A size, nominal capacity of 4000 mAh, and an uncharged cylindrical nickel-metal hydride battery were assembled.
[0045]
The obtained storage battery is charged at 0.1 C for 1 hour in an atmosphere of 90 ° C., then charged to 0.5 C until it reaches 150%, and then discharged to 0.2 V at 1 C to obtain nickel hydride. A storage battery was manufactured.
(Comparative Example 1)
After assembling the uncharged cylindrical nickel-hydrogen secondary battery in the same manner as in Example 1 except that the hydrogen storage alloy of the negative electrode was not subjected to alkali treatment, the initial charge / discharge was performed under the same conditions as in Example 1. And manufactured a nickel metal hydride storage battery.
(Comparative Example 2)
The uncharged cylindrical nickel-metal hydride storage battery assembled in the same manner as in Example 1 was charged at 25 ° C. for 1 hour at 0.1 C, and then charged to 150% at 0.5 C. Thereafter, the nickel hydride storage battery was manufactured by discharging to 0.2 V at 0.2 C.
(Comparative Example 3)
After assembling the uncharged cylindrical nickel-hydrogen secondary battery in the same manner as in Example 1 except that the hydrogen storage alloy of the negative electrode was not subjected to alkali treatment, the initial charge / discharge was performed under the same conditions as in Comparative Example 2. And manufactured a nickel metal hydride storage battery.
(Comparative Example 4)
A separator made of a polypropylene non-woven fabric subjected to a hydrophilic treatment is interposed between a positive electrode obtained in the same manner as in Example 1 and a negative electrode obtained in the same manner as in Comparative Example 1, and the electrode group is wound in a spiral shape. Was made. This electrode group is housed in a cylindrical metal container with a bottom, and an alkaline electrolyte having the same composition as in Example 1 has a liquid ratio (25 ° C.) of 1.7 cm ³ / Ah with respect to the theoretical capacity of the positive electrode. Then, using a member such as a metal lid, a 4 / 3A size, nominal capacity of 3000 mAh, and an uncharged cylindrical nickel-metal hydride battery were assembled.
[0046]
The obtained storage battery was subjected to initial charge / discharge under the same conditions as in Example 1 to produce a nickel metal hydride storage battery.
About the secondary battery of Example 1 and Comparative Examples 1-4, after charging 1.5 hours at 1C at room temperature, the charge / discharge cycle which discharges to battery voltage 1V at 1C was repeated 3 times. The discharge capacity at the third cycle was measured, the initial utilization rate was determined from the theoretical capacity, and the obtained discharge capacity (initial capacity) and the initial utilization rate are shown in Table 1 below.
[0047]
These secondary batteries were charged for 12 hours at 1 C at 25 ° C., then discharged to 1 V at 1 C in an atmosphere of −20 ° C., and the discharge capacity at this time was measured. The utilization rate at the time of low temperature discharge is calculated by dividing the obtained discharge capacity by the previous initial capacity, and the results are also shown in Table 1 below.
[0048]
Further, another secondary battery whose initial capacity and initial utilization were calculated was discharged at 1 C until 1 V, and stored in this discharged state at 65 ° C. for one month. Then, after charging at 25 ° C. for 12 hours at 0.1 C, the charge / discharge cycle in which the battery voltage is discharged at 1 C until the battery voltage reaches 100 mV is repeated three times, and the discharge capacity at the third cycle is divided by the initial capacity. Thus, the recovery rate is calculated, and the result is also shown in Table 1 below.
[0049]
[Table 1]

[0050]
As is apparent from Table 1, the secondary battery of Example 1 can be improved in capacity while maintaining excellent utilization, low temperature discharge characteristics, and recovery rate after being left.
On the other hand, it can be seen that the secondary battery of Comparative Example 1 in which the first charge was performed at a temperature exceeding room temperature without subjecting the negative electrode alloy to surface treatment, the utilization rate during low-temperature discharge was significantly reduced. In addition, although the negative electrode alloy was surface-treated, the secondary battery of Comparative Example 2 in which the initial charge temperature was room temperature was found to have a lower recovery rate than that of Example 1 after being left. It can be seen that the secondary battery of Comparative Example 3 that was initially charged at room temperature without surface treatment was inferior to Example 1 in terms of capacity, utilization, low-temperature discharge characteristics, and storage characteristics.
[0051]
On the other hand, the secondary battery of Comparative Example 4 in which the ratio of the amount of alkaline electrolyte (25 ° C.) to the positive electrode theoretical capacity is 1.7 cm ³ / Ah is excellent in utilization rate, low-temperature discharge characteristics, and storage characteristics, but the capacity is It can be seen that it is lower than Example 1.
(Example 2)
A cylindrical nickel-metal hydride storage battery was produced in the same manner as in Example 1 except that the conductive agent for the positive electrode was changed to cobalt monoxide powder.
[0052]
When the characteristics of the obtained storage battery were measured in the same manner as described above, the discharge capacity was 3720 mAh, the initial utilization rate was 93%, the utilization rate during low-temperature discharge was 34%, and the capacity recovery rate after standing was 99%.
[0053]
【The invention's effect】
As described above in detail, according to the present invention, a high capacity can be obtained from the initial stage without unnecessarily increasing the blending amount of the conductive agent, and further excellent in low temperature discharge characteristics and overdischarge characteristics, and a good balance of battery characteristics. A method for producing a nickel-metal hydride storage battery can be provided.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view showing an example of a nickel metal hydride storage battery manufactured by a method according to the present invention.
[Explanation of symbols]
1 ... container,
2 ... positive electrode,
3 ... Separator,
4 ... negative electrode,
7 ... Sealing plate.

Claims (4)

A step of immersing a negative electrode containing a hydrogen storage alloy containing Mn with an aqueous sodium hydroxide solution having a concentration of 20 to 40 wt% and a temperature of 70 to 90 ° C .;
The negative electrode, a positive electrode containing a conductive agent composed of at least one selected from cobalt and a cobalt compound in terms of cobalt element with respect to an active material containing nickel hydroxide, and a liquid volume ratio of 0.5 to a step Ru assembled nickel-metal hydride storage battery comprising an alkaline electrolyte is 1.6 cm ³ / Ah,
Applying the initial charge to the storage battery at 70-90 ° C .;
The manufacturing method of the nickel hydride storage battery characterized by comprising .   The nickel-hydride storage battery according to claim 1, wherein the nickel hydroxide has a peak half-value width of (101) plane at 2θ of X-ray powder diffraction by Cu-Kα rays of 0.8 ° or more. Method. The conductive agent according to claim 1 or 2 method for producing a nickel-metal hydride storage battery wherein it is a cobalt hydroxide. The hydrogen storage alloy is LmNi _w Co _x Mn _y Al _z (Lm is a lanthanum-rich misch metal, and the total value of atomic ratios w, x, y, z is 5.00 ≦ w + x + y + z ≦ 5.50). The method for producing a nickel-metal hydride storage battery according to any one of claims 1 to 3, wherein

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