JP2006092902A - Manufacturing method of electrode material for alkaline storage battery, treatment device of same, hydrogen storing alloy powder, and alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline storage battery excellent in a discharging property by easily removing oxide and hydroxide deposited on the surface of a hydrogen storage alloy at an alkaline treatment process. <P>SOLUTION: A manufacturing method of the electrode material comprises a first process stirring crushed hydrogen storage alloy powder in alkaline aqueous solution of high temperature; a second process draining waste fluid generated at the first process; and a third process pressurizing and filtrating the hydrogen storage alloy powder treated at the second process. At the second and third processes, before draining the waste fluid, alkaline aqueous solution is additionally supplemented so that an alkaline solid part becomes 10 to 30 wt.% to the hydrogen storage alloy powder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrode for an alkaline storage battery comprising a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen, and an alkaline storage battery using the same.

  A hydrogen storage alloy is an intermetallic compound capable of electrochemically storing and releasing hydrogen, and is mainly used as an electrode material for a negative electrode of an alkaline storage battery. This alloy is an intermetallic compound capable of electrochemically storing and releasing hydrogen, and is mainly used as a negative electrode material for alkaline storage batteries. Normally, this alloy is activated by repeated expansion and contraction of the volume during charge and discharge after the battery is produced, and hydrogen can be easily stored and released on the active material surface.

  Therefore, for the purpose of improving battery characteristics, attempts have been made to activate a hydrogen storage alloy at the time of manufacturing a battery to facilitate the storage and release of hydrogen from the beginning. In general, it is effective to activate the surface of the hydrogen storage alloy using an alkaline aqueous solution, an acidic aqueous solution, high-temperature water, or the like.

  A method (hereinafter referred to as alkali treatment) for activating a surface by eluting constituent elements of a hydrogen storage alloy using a high-concentration solution such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) is disclosed in Patent Document 1. And 2. According to this method, an appropriate amount (3% by weight or more of the hydrogen storage alloy) of a magnetic substance (nickel or cobalt which is a constituent element of the alloy) which is an active point of reaction can be formed on the surface of the hydrogen storage alloy. The discharge characteristics are improved. However, conventionally, the mixture is heated and mixed while stirring and mixing the hydrogen storage alloy powder and the alkaline aqueous solution, and the temperature is controlled to keep the mixture at a high temperature for a predetermined period of time. It was discharged to the next process. In this method, the constituent elements of the alloy eluted in the high-concentration alkaline aqueous solution reach the saturation point due to dilution or lowering of temperature when discharged to the next step, and become oxides and hydroxides. It adheres to the surface and inhibits the battery reaction.

In view of this, there has been proposed a method of eluting and removing oxides and hydroxides on the surface of the hydrogen storage alloy using an acidic aqueous solution such as hydrochloric acid (HCl) (see, for example, Patent Document 3). According to this method, the oxide and hydroxide described above can be removed from the surface of the hydrogen storage alloy, so that the discharge characteristics are improved.
JP-A 61-285658 JP 2002-256301 A Japanese Patent Laid-Open No. 7-73878

  However, even if the above-described method is used, it is difficult to remove oxides and hydroxides once adhered to the surface of the hydrogen storage alloy, and the discharge characteristics cannot be improved as expected because a factor for inhibiting the battery reaction remains.

  This invention is made | formed in view of the subject mentioned above, and provides the alkaline storage battery excellent in discharge characteristics by removing easily the oxide and hydroxide which precipitated on the hydrogen storage alloy surface in the alkali treatment process. For the purpose.

  In order to solve the above problems, a method for producing a hydrogen storage alloy powder for an alkaline storage battery according to the present invention includes a first step of stirring a hydrogen storage alloy into a powder form in a high-temperature alkaline aqueous solution. A second step of discharging the waste liquid generated in the first step, and a third step of pressure filtration of the hydrogen storage alloy powder subjected to the second step. In the process, before discharging the waste liquid, the alkaline aqueous solution is additionally charged so that the alkali solid content is 10 to 35% by weight with respect to the hydrogen storage alloy powder.

  After discharging the waste liquid generated in the first step in advance, a high-concentration aqueous alkali solution is additionally added, and by heating the aqueous alkali solution using the heat of dissolution of the oxide and hydroxide once precipitated, Since the deposited oxide and hydroxide are completely melted, the surface of the hydrogen storage alloy can be fundamentally activated.

  In order to embody the manufacturing method described above, the hydrogen storage alloy powder processing apparatus for an alkaline storage battery according to the present invention includes a first means for mixing and / or stirring the hydrogen storage alloy powder and an alkaline aqueous solution, A second means for heating the mixture of the occluded alloy powder and the aqueous alkaline solution, a third means for controlling the temperature of the aqueous alkaline solution in the second means, a fourth means for discharging the waste aqueous alkaline solution, hydrogen A fifth means for pressure-filtering the occluded alloy powder and a sixth means for introducing the stored alkaline aqueous solution into the first and / or fifth means are provided.

  Furthermore, the hydrogen storage alloy powder of the present invention is produced through the manufacturing method described above, and the oxygen concentration obtained by the oxygen concentration measurement method (infrared absorption method) described in JIS-Z-2613 is 0.9% by weight. It is characterized by the following. This oxygen concentration represents the amount of deposits from the waste liquid deposited on the hydrogen storage alloy powder. By reducing this value, it is possible to provide an alkaline storage battery having excellent discharge characteristics.

  As described above, according to the present invention, since most of oxides and hydroxides precipitated on the surface of the hydrogen storage alloy in the alkali treatment step can be removed, an alkaline storage battery having excellent discharge characteristics can be provided.

  This Embodiment demonstrates the manufacturing method and processing apparatus of the electrode material for alkaline storage batteries of this invention, and an alkaline storage battery.

  The method for producing an alkaline storage battery electrode according to the present invention comprises the first step (pulverizing the hydrogen storage alloy to form a powder in the production process of an alkaline storage battery electrode comprising a hydrogen storage alloy capable of storing and releasing hydrogen. At least a second step of discharging the waste liquid generated in the step of stirring the aqueous solution in a hot alkaline aqueous solution) and a third step of pressure filtering the hydrogen storage alloy powder subjected to the second step. In any step, it is essential to add an aqueous alkali solution to the hydrogen storage alloy powder so that the alkali solid content is 10 to 35% by weight. By passing through the process described above, the alkaline aqueous solution is heated to a high temperature using the heat of dissolution of the oxide and hydroxide once precipitated, and the precipitate is completely melted, so that the surface of the hydrogen storage alloy is fundamentally changed. It can be brought into an active state.

In the first step, as the hydrogen storage alloy surface area increases, a waste liquid in which a part of the elements constituting the alloy is eluted is generated. The eluate differs depending on the composition of the hydrogen storage alloy. For example, a general MmNi _5-X M _X (where Mm is a mixture of light rare earth metals, M = Co, Mn, Al, F)
e, Cu, etc.), light rare earth metal ions (eg, La ³⁺ , Nd ³⁺ etc.) and complex anions (eg, CoO ₂ ⁻ , AlO ₂ ^—, etc.). Here, when the waste liquid and the hydrogen storage alloy powder are sent to the step of pressure filtration at the same time, the precipitation of the ions starts due to the temperature drop or dilution (mixing with the water used for washing) of the waste liquid. Precipitates are mainly light rare earth metal hydroxides such as Ce (OH) ₃ and La (OH) ₃ , and complex oxides such as Mn, which are deposited on the hydrogen storage alloy powder. The alloy surface activated by the treatment is deactivated again.

  Here, after removing the waste liquid in advance, a high-concentration alkaline aqueous solution is newly added and the temperature is increased by the heat of dissolution, whereby the deposits deposited on the hydrogen storage alloy powder are re-dissolved, and the activity of the alloy surface is increased. Can keep. The amount of the aqueous alkali solution added at this time does not depend on the concentration if the alkali solid content is in the range of 10 to 35% by weight with respect to the hydrogen storage alloy powder. Here, when the alkali solid content is less than 10% by weight, the dissolution efficiency of the precipitate is lowered. On the other hand, if it exceeds 35% by weight, not only the dissolution of the precipitate but also the alkali treatment proceeds excessively, so that it becomes difficult to control the activation degree as designed, which is not preferable.

The alkali to be added is preferably NaOH and / or KOH. These alkali ionization degrees (degrees of generating OH ⁻ ) are as high as 0.89 and 0.84, respectively, and efficient alkali treatment is possible.

  Furthermore, in the second and / or third steps, by applying an ultrasonic wave having a frequency of 35 to 170 kHz, the precipitate deposited on the hydrogen storage alloy powder is easily detached from the alloy surface. Is more preferable. Regarding the frequency, application of vibrational energy is insufficient when the frequency is lower than 35 kHz, so that the remelting of the precipitate cannot be accelerated. On the other hand, if it exceeds 170 kHz, the energy becomes excessive and disperses, so that the re-dissolution of the precipitate cannot be accelerated similarly. Therefore, a preferable range is 35 to 170 kHz.

  Further, by providing a fourth step of washing the hydrogen storage alloy powder obtained in the third step with water, the alkaline aqueous solution that has undergone the treatment of the present invention can be completely washed away, so that new deposits can be attached. It is preferable in avoiding it.

  Furthermore, in the fourth step, it is more preferable to apply ultrasonic waves having a frequency of 35 to 170 kHz because precipitates deposited on the hydrogen storage alloy powder are easily detached from the alloy surface. Regarding the frequency, application of vibrational energy is insufficient when the frequency is lower than 35 kHz, so that the remelting of the precipitate cannot be accelerated. On the other hand, if it exceeds 170 kHz, the energy becomes excessive and disperses, so that the re-dissolution of the precipitate cannot be accelerated similarly. Therefore, a preferable range is 35 to 170 kHz.

  As a processing apparatus for establishing the above manufacturing method, the processing apparatus for hydrogen storage alloy powder for alkaline storage batteries of the present invention includes a first means for mixing and / or stirring the hydrogen storage alloy powder and an aqueous alkali solution, A second means for heating the mixture of the occluded alloy powder and the aqueous alkaline solution, a third means for controlling the temperature of the aqueous alkaline solution in the second means, a fourth means for discharging the waste aqueous alkaline solution, hydrogen A hydrogen storage alloy powder and an alkali comprising: a fifth means for pressure-filtering the storage alloy powder; and a sixth means for introducing the stored alkaline aqueous solution into the first and / or the fifth means. A first means for mixing and / or stirring the aqueous solution, a second means for heating the mixture of the hydrogen storage alloy powder and the alkaline aqueous solution, and discharging the waste aqueous solution of the alkaline aqueous solution. Third means, fourth means for stocking the heated alkaline aqueous solution, fifth means for controlling the temperature of the alkaline aqueous solution in the second and fourth means, and pressure-filtering the hydrogen storage alloy powder And sixth means.

  FIG. 1 is a schematic view of a processing apparatus of the present invention. The stirring tank 1 for storing the hydrogen storage alloy powder 4 and the alkaline aqueous solution 5 and the stirring blade 3 for mixing and stirring these correspond to the first means. The alkaline aqueous solution 5 is introduced into the stirring tank 1 by opening the valve 10 of the alkaline aqueous solution storage tank 9. A heating means 2 is provided to heat and maintain the mixture of the hydrogen storage alloy powder 4 and the alkaline aqueous solution 5 at a high temperature, and a temperature control means 8 is provided to control the temperature in the stirring tank 1. When the predetermined alkali treatment is completed, the alkaline aqueous solution 5 becomes a waste liquid and becomes a supernatant in the stirring tank 1. The waste liquid discharging means 6 discharges this.

  When the discharge of the waste liquid is completed, the alkaline aqueous solution 5 is continuously added as necessary. This alkaline aqueous solution is introduced into the stirring tank 1 by opening the valve 10 of the alkaline aqueous solution storage tank 9, and the deposits (oxides and hydroxides) deposited on the hydrogen storage alloy powder 4 are eluted with heat of dissolution. Thus, the effect of the present invention is exhibited.

  The hydrogen storage alloy powder 4 that has been subjected to the alkali treatment is put into the pressure filtration tank 12 by opening the valve 7. Here, the alkaline aqueous solution 5 is added as necessary. This alkaline aqueous solution 5 is put into the pressure filtration tank 12 by opening the valve 11 of the alkaline aqueous solution storage tank 9, and the deposits (oxides and hydroxides) deposited on the hydrogen storage alloy powder 4 are accompanied by heat of dissolution. The effect of the present invention is exhibited by elution.

  There are the following two types of hydrogen storage alloys used in the present invention, but the type (2) is more preferable.

(1) AB type ₂ (Laves phase)
A Laves phase alloy whose main alloy phase is mainly composed of zirconium or nickel. This is an alloy (intermetallic compound) having an atomic diameter ratio of 1.225 or a close packed structure close to this. The main ones are Ti-Mn, Ti-Cr, Zr-Mn, and the like. For example _{(Ti z - x Zr x V} 4 - y Ni y) 1 - z, Cr 2 ZrV 0.41 Ni 1.6, and the like ZrMn _0.6 Cr _0.2 Ni _1.2.

(2) AB ₅ type (rare earth)
CaCu ₅ type structure, which uses rare earth, niobium, zirconium, etc. for the A site, nickel, cobalt, aluminum, etc. for the B site. The alloy actually used is an alloy having MmNi ₅ as a basic composition. Mm is a misch metal, which is a rare earth mixture containing Ce (40 to 50%), La (20 to 40%), Pr and Nd as main constituent elements. For example _{La 0.8 Nb 0.2 Ni 2.5 Co 2.4} Al 0.1, La 0.8 Nb 0.2 Zr 0.03 Ni 3.8 Co 0.7 Al 0.5, MmNi 3.65 Co 0.75 Mn 0.4 Al 0.3, MmNi 2.5 Co 0.7 Al 0.8, Mm 0.85 Zr 0.15 Ni 1.0 Al 0.8 V There is _0.2 mag.

  These hydrogen storage alloy powders were subjected to the treatment of the present invention using the above-described treatment apparatus, whereby the oxygen concentration determined by the oxygen concentration measurement method (infrared absorption method) described in JIS-Z-2613 was 0.9% by weight. Less than. The oxygen concentration mentioned here corresponds to an oxide / hydroxide as a deposit deposited on the hydrogen storage alloy powder. By using the production method of the present invention, the oxygen concentration can be reduced to the above-described range, and the discharge characteristics can be improved.

Using this alloy powder, a conductive agent, a thickener and a binder are added to prepare a negative electrode for a nickel-hydrogen battery. The conductive agent used for the negative electrode is not particularly limited as long as it is a material having electronic conductivity. For example, graphite such as natural graphite (such as flake graphite), artificial graphite, expanded graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber Conductive fibers such as metal fibers, metal powders such as copper, and organic conductive materials such as polyphenylene derivatives may be used. Among them, artificial graphite, ketjen black, and carbon fiber are preferable, but these materials may be mixed and used. Further, these materials may be mechanically coated on the electrode material. The addition amount of the said electrically conductive agent to a negative electrode is not specifically limited, For example, it is the range of 1 weight part-50 weight part with respect to 100 weight part of electrode materials, and the range of 1 weight part-30 weight part is preferable.

  As the thickener used for the negative electrode, those capable of imparting viscosity to the electrode mixture paste can be used. Examples include carboxymethylcellulose (hereinafter abbreviated as CMC) and modified products thereof, polyvinyl alcohol, methylcellulose, polyethylene oxide, and the like.

As the binder used for the negative electrode, any of a thermoplastic resin and a thermosetting resin may be used as long as the electrode mixture can maintain the state of being bound to the current collector. For example, styrene-butadiene copolymer rubber (hereinafter abbreviated as SBR), polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer , Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene , Vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-he Sa hexafluoropropylene - tetrafluoroethylene copolymer, vinylidene fluoride - perfluoromethyl vinyl ether - tetrafluoroethylene copolymer, ethylene - acrylic acid copolymer, ethylene - acrylic acid copolymer Na ⁺ ion crosslinking body, an ethylene - Methacrylic acid copolymer, ethylene-methacrylic acid copolymer Na ⁺ ion crosslinked product, ethylene-methyl acrylate copolymer, ethylene-methyl acrylate copolymer Na ⁺ ion crosslinked product, ethylene-methyl methacrylate copolymer Ethylene-methyl methacrylate copolymer Na ⁺ ion cross-linked body can be used alone or in combination.

  Next, a specific example of the present invention will be described with reference to FIG.

<Examination 1. Additional alkaline aqueous solution>
Example 1
The hydrogen storage alloy powder 4 is obtained by using a hydrogen storage alloy represented by the composition formula MmNi _3.55 Co _0.75 Mn _0.4 Al _0.3 (Mm is a mixture of light rare earths) and pulverizing it to an average particle size of 30 μm in water by a wet ball mill. It was. After 10 kg of this powder was put into the stirring tank 1, 10 kg of a 20 wt% aqueous sodium hydroxide solution (alkaline aqueous solution 5) stored in the alkaline aqueous solution storage tank 9 was put into the stirring tank 1 by opening the valve 10. Thereafter, the temperature of the mixture of the hydrogen storage alloy powder 4 and the alkaline aqueous solution 5 is controlled by the heating means 2 so that the temperature is kept constant at 90 ° C., and the mixture is stirred for 15 minutes using the stirring blade 3. Then, alkali treatment was performed.

  After draining the waste liquid generated after the alkali treatment, the waste liquid discharge means 6 discharges the waste liquid, and 5 kg of the alkaline aqueous solution 5 is newly added to the stirring tank 1 from the alkaline aqueous solution storage tank 9 by opening the valve 10. I put it in. The newly added alkali solid content is 10% by weight with respect to the hydrogen storage alloy powder 4. At this time, a clear temperature increase of the mixture was recognized from the temperature display attached to the stirring tank 1.

Subsequently, by opening the valve 7, the mixture is introduced into the pressure filtration tank 12, the alkaline aqueous solution 5 is discharged at a pressure of 5 kgf / cm ² , and washed with water using a large amount of water. A hydrogen storage alloy powder was obtained.

  By adding 1 kg of 1.5 wt% CMC aqueous solution and 40 g of ketjen black to 10 kg of hydrogen storage alloy powder after alkali treatment and kneading, 175 g of SBR aqueous solution having a solid content ratio of 40% is added and stirred, A negative electrode mixture paste was prepared.

  This paste was applied to both sides of a nickel-plated iron punching metal having a thickness of 60 μm, a punching hole diameter of 1 mm, and a hole area ratio of 42%, dried and pressed, and a width of 35 mm, a thickness of 0.4 mm, and a capacity of 2200 mAh. A hydrogen storage alloy negative electrode was produced.

  This negative electrode and a known sintered nickel positive electrode having an electric capacity of 1500 mAh and a nonwoven fabric separator made of polypropylene are combined and wound in a spiral shape to form an electrode group. After inserting this electrode group into a metal case, the specific gravity A nickel-hydrogen solution in which 40 g / l of lithium hydroxide is dissolved in a 1.30 aqueous potassium hydroxide solution is poured, the upper part of the case is sealed with a sealing plate, and the nominal capacity is 1500 mAh in a 4 / 5A size. A storage battery was constructed. This is referred to as the battery of Example 1.

(Comparative Example 1)
In Example 1, 5 kg of a new alkaline aqueous solution 5 was added to the stirring tank 1, but no new alkaline aqueous solution 5 was added here. A battery manufactured in the same manner as in Example 1 except for the above is referred to as a battery of Comparative Example 1.

(Examples 2 and 4, Comparative Examples 2-3)
In Example 1, 5 kg of a new alkaline aqueous solution 5 was added to the stirring tank 1, but here, the input amount was changed to 2.5, 10, 17.5, and 20 kg, and the solid content of the input alkali was changed to hydrogen storage alloy powder. 4, 20, 35, 40% by weight. Except for this, batteries manufactured in the same manner as in Example 1 are referred to as Comparative Example 2, Example 2, Example 4, and Comparative Example 3, respectively. In addition, when the new alkaline aqueous solution 5 was added to the stirring tank 1, from the temperature display attached to the stirring tank 1, in the case of Examples 3 to 4 and Comparative Example 3, a clear temperature increase of the mixture was recognized. In the case of Comparative Example 2, the temperature rise was slight.

(Example 3)
In Example 1, 10 kg of a new alkaline aqueous solution 5 was introduced into the stirring tank 1, but here it was introduced into the pressure filtration tank 12 by opening the valve 11. A battery manufactured in the same manner as in Example 2 is referred to as the battery of Example 3. In addition, when the new alkaline aqueous solution 5 was thrown into the pressure filtration tank 12, the clear temperature increase of the mixture was recognized from the temperature display attached to the pressure filtration tank 12.

(Example 5)
In Example 1, 5 kg of 20 wt% sodium hydroxide aqueous solution was added to the stirring tank 1, but here 5 kg of 20 wt% potassium hydroxide aqueous solution was added to the stirring tank 1. A battery manufactured in the same manner as in Example 1 except for the above is referred to as the battery of Example 5. When the aqueous potassium hydroxide solution was added to the stirring tank 1, a clear temperature increase of the mixture was observed from the temperature display attached to the stirring tank 1.

  The following evaluation was performed on each of the examples described above.

(Oxygen concentration measurement)
For the hydrogen storage alloy powder after alkali treatment, the gas extracted from the sample (hydrogen storage alloy powder) is sent to the infrared absorption cell in accordance with the oxygen concentration measurement method described in JIS-Z-2613. Was measured to determine the amount of oxygen. The value obtained is expressed as% by weight in the hydrogen storage alloy powder.
As shown in (Table 1).

(Low temperature discharge characteristics)
The produced battery was charged to 120% of the theoretical capacity at 20 ° C. and a current value of 1.5 A (1 CA), and the capacity until the battery voltage dropped to 1.0 V at 20 ° C. and a current value of 3.0 A (2 CA) ( Initial discharge capacity) was measured. Furthermore, the battery is charged to 120% of the theoretical capacity at 20 ° C. and a current value of 1.5 A (1 CA), and the capacity (low temperature) until the battery voltage drops to 1.0 V at 0 ° C. and a current value of 3.0 A (2 CA). Discharge capacity) was measured. The value obtained by dividing the low-temperature discharge capacity by the initial discharge capacity is used as an index of the low-temperature discharge characteristics, and the percentage is shown in (Table 1).

  From Table 1, Examples 1 to 5 and Comparative Examples 2 to 3 in which the novel alkaline aqueous solution, which is the gist of the present invention, was added, compared to Comparative Example 1 in which the addition was not performed, a decrease in oxygen concentration. The improvement of the low temperature discharge characteristics was noticeable. In these examples, a clear temperature increase of the mixture was confirmed when a new aqueous alkali solution was added. As described above, this is the heat of dissolution generated when the deposit deposited on the front surface of the hydrogen storage alloy powder after discharging the waste liquid is redissolved. This heat generation warms the aqueous alkaline solution and promotes further dissolution of precipitates that inhibit the battery reaction. Therefore, in Examples 1 to 5 in which a clear temperature increase was confirmed when a new alkaline aqueous solution was added, the low temperature discharge characteristics were remarkably improved.

  In contrast to these examples, Comparative Example 2 in which the alkali solid content was less than 10% by weight with respect to the hydrogen storage alloy powder did not have the desired effect because the precipitates were not sufficiently dissolved. Moreover, the desired effect was not acquired also in the comparative example 3 whose alkali solid content exceeded 35 weight% with respect to the hydrogen storage alloy powder. The reason for this is that the increase in the alkali solid content promotes the excessive alkali treatment not only for the dissolution of the precipitate, but also a new precipitate is generated correspondingly. Therefore, in order to fully exhibit the effects of the present invention, it is necessary to add an aqueous alkali solution so that the alkali solid content is 10 to 35% by weight with respect to the hydrogen storage alloy powder.

<Study 2. Ultrasonic treatment>
(Examples 6 to 12)
In Example 2, 10 kg of a new alkaline aqueous solution 5 was only added to 1, but at this time, ultrasonic waves were applied at frequencies of 20, 35, 40, 72, 104, 170, and 200 kHz. Except for this, batteries produced in the same manner as in Example 2 are referred to as batteries of Examples 6 to 12, respectively.

(Example 13)
In Example 3, only 10 kg of the new alkaline aqueous solution 5 was introduced into the pressure filtration tank 12, but here, ultrasonic waves were applied at a frequency of 40 kHz at the time of introduction. A battery manufactured in the same manner as in Example 3 except for the above is referred to as the battery of Example 13.

(Example 14)
In Example 2, the hydrogen storage alloy powder 4 was filtered under pressure and then washed with a large amount of water, but here, ultrasonic waves were applied at a frequency of 40 kHz during washing. A battery manufactured in the same manner as in Example 2 is referred to as the battery of Example 14.

  The following evaluation was performed on each of the examples described above.

(Oxygen concentration measurement)
It carried out like examination 1. The results are shown in (Table 2).

(Low temperature discharge characteristics)
It carried out like examination 1. The results are shown in (Table 2).

  From Table 2, Examples 7 to 11, 13 and 14 having an ultrasonic frequency of 35 to 170 kHz have a lower oxygen concentration and improved low-temperature discharge characteristics than Example 3 without application of ultrasonic waves. I understand that. On the other hand, in Example 6 in which the ultrasonic frequency is 20 kHz, since the frequency is too low, the effect of applying ultrasonic waves is small. Further, in Example 12 where the ultrasonic frequency is 200 kHz, the frequency is excessive, so that the vibration energy is dispersed and not only the efficiency of the precipitate removal is lowered, but also the precipitate suspended in the solution can be reattached. There is sex. This is apparent from a comparison between FIG. 2 (corresponding to Example 11) and FIG. 3 (corresponding to Example 12). Needle-like precipitates that are hardly seen in FIG. Many can be confirmed on the surface.

  From the above results, it is understood that when ultrasonic treatment is performed, it is preferable to perform the ultrasonic frequency in the range of 35 to 170 kHz.

  According to the present invention, since the discharge characteristics can be improved more than ever, it is particularly useful as an electrode for a high output type alkaline storage battery such as a power tool or an electric vehicle.

Schematic diagram of the processing apparatus of the present invention SEM photograph of hydrogen storage alloy powder surface of Example 11 of the present invention (applying ultrasonic waves with a frequency of 170 kHz) SEM photograph of hydrogen storage alloy powder surface of Example 12 of the present invention (applying ultrasonic waves with a frequency of 200 kHz)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stirring tank 2 Heating means 3 Stirring blade 4 Hydrogen storage alloy powder 5 Alkaline aqueous solution 6 Waste liquid discharge means 7, 10, 11 Valve 8 Temperature control means 9 Alkaline aqueous solution storage tank 12 Pressure filtration tank

Claims (9)

A method for producing a hydrogen storage alloy powder for an alkaline storage battery, comprising:
A first step of stirring the hydrogen storage alloy into a powder form in a high-temperature alkaline aqueous solution;
A second step of discharging the waste liquid generated in the first step;
A third step of pressure filtering the hydrogen storage alloy powder subjected to the second step,
In the second and / or third step, before discharging the waste liquid, the hydrogen storage alloy for an alkaline storage battery, in which an alkaline aqueous solution is additionally charged so that the alkali solid content is 10 to 35% by weight with respect to the hydrogen storage alloy powder Powder manufacturing method. The method for producing a hydrogen storage alloy powder for an alkaline storage battery according to claim 1, wherein the alkaline aqueous solution is sodium hydroxide and / or potassium hydroxide. The method for producing a hydrogen storage alloy powder for an alkaline storage battery according to claim 1, wherein an ultrasonic wave having a frequency of 35 to 170 kHz is applied in the second and / or the third step. The method for producing a hydrogen storage alloy powder for an alkaline storage battery according to claim 1, comprising a fourth step of washing the hydrogen storage alloy powder obtained in the third step with water. 5. The method for producing a hydrogen storage alloy powder for an alkaline storage battery according to claim 4, wherein an ultrasonic wave having a frequency of 35 to 170 kHz is applied in the fourth step. A hydrogen storage alloy powder processing apparatus for alkaline storage batteries,
A first means for mixing and / or stirring the hydrogen storage alloy powder and the alkaline aqueous solution;
A second means for heating the mixture of the hydrogen storage alloy powder and the alkaline aqueous solution;
A third means for controlling the temperature of the alkaline aqueous solution in the second means;
A fourth means for discharging the alkaline aqueous solution;
A fifth means for pressure filtering the hydrogen storage alloy powder;
An apparatus for processing a hydrogen storage alloy powder for an alkaline storage battery, comprising: sixth means for introducing a stored alkaline aqueous solution into the first and / or fifth means. The hydrogen storage alloy powder obtained by the manufacturing method in any one of Claims 1-5. The hydrogen storage alloy powder according to claim 7, wherein the oxygen concentration obtained by an oxygen concentration measurement method (infrared absorption method) described in JIS-Z-2613 is 0.9% by weight or less based on the hydrogen storage alloy powder. An alkaline storage battery using a negative electrode plate containing the hydrogen storage alloy powder according to claim 7 and / or 8.

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