JP4238230B2 - AB5 type hydrogen storage alloy powder - Google Patents

Description

The present invention relates to an AB ₅ type hydrogen storage alloy powder having a CaCu ₅ type crystal structure, and in particular, does not fall under the category of hazardous materials (flammable solids) stipulated by the Fire Service Act and is used as a negative electrode active material for batteries. about AB ₅ -type hydrogen absorbing alloy powder capable of realizing excellent low-temperature battery characteristics when.

  A hydrogen storage alloy is an alloy that reacts with hydrogen to form a metal hydride and can reversibly store and release a large amount of hydrogen near room temperature, so this property can be used, for example, in hybrid vehicles and digital still cameras. Practical use is being promoted in various fields such as nickel-hydrogen batteries to be installed.

As the hydrogen storage alloy, various alloys such as an AB ₅ type alloy typified by LaNi ₅ , an AB ₂ type alloy typified by ZrV _0.4 Ni _1.5 , and other AB type alloys and A ₂ B type alloys are known. Many of them have a relatively low affinity for hydrogen with element groups (Ca, Mg, rare earth elements, Ti, Zr, V, Nb, Pt, Pd, etc.) that have a high affinity for hydrogen and a large amount of hydrogen storage. Although the amount of occlusion is small, it is composed of a combination with an element group (Ni, Mn, Cr, Fe, etc.) that has a fast hydrogenation reaction and lowers the reaction temperature.

Among hydrogen storage alloys, AB ₅ type hydrogen storage alloy having a CaCu ₅ type crystal structure, for example, A site element is composed of a rare earth-based mixture Mm (Misch metal), and B site element is Ni, Al Mm-Ni-Mn-Al-Co alloy composed of 4 elements, Mn and Co, which can be manufactured at a relatively low cost, has a long cycle life, and has a low internal pressure increase due to the generated gas during overcharge. Features such as the ability to obtain a hydrogen storage battery (see Patent Documents 1 to 5).

As a method for producing such an AB ₅ type hydrogen storage alloy, conventionally, an alloy lump (ingot) cast by a mold casting method or the like is heat-treated in an inert gas atmosphere such as argon, and the heat-treated alloy has a predetermined particle size. The method of pulverizing was generally used. In this production, a contrivance for preventing oxidation during heat treatment as much as possible has been made by homogenizing the disorder of the structure during casting by heat treatment and heat-treating the alloy ingot.

  In addition, in order to obtain a hydrogen storage alloy having particularly excellent life characteristics, that is, a hydrogen storage alloy having a homogeneous structure and characteristics, the nickel-based hydrogen storage alloy raw material is melted, and the obtained molten metal is poured into a mold and rapidly cooled. A manufacturing method is disclosed in which the obtained alloy is pulverized into an alloy powder, the alloy powder is classified, and the classified alloy powder is heat-treated at a temperature of 1000 to 1200 ° C. in an inert gas atmosphere (Patent Document 6).

JP 2001-040442 A JP 2001-181763 A JP 2001-348636 A JP 2002-0775347 A JP 2002-146457 A JP 2002-212601 A

Conventionally, the AB ₅ type hydrogen storage alloy powder having a CaCu ₅ type crystal structure, which occupies 50% by weight or more of the mesh sieve having a mesh size of 150 μm, is basically classified as a hazardous material class 2 Therefore, the storage method, transport method, and other handling methods are strictly limited by the Fire Service Act, and there is a problem that labor and cost increase accordingly.

Accordingly, the present invention provides a dangerous substance defined by the Fire Service Act, even if it is an AB ₅ type hydrogen storage alloy powder having a CaCu ₅ type crystal structure that occupies 50% by weight or more through a mesh screen having a mesh size of 150 μm. It is not classified as a class (flammable solid), yet it is intended to provide a new AB ₅ type hydrogen storage alloy powder capable of realizing excellent low-temperature battery characteristics when used as a negative electrode active material for various batteries. is there.

The present invention relates to an AB ₅ type hydrogen storage alloy powder having a CaCu ₅ type crystal structure in which 50% by weight or more passes through a mesh sieve having an opening of 150 μm, and the Ce content in the alloy is 25% by weight or less. , and the oxygen content is not more than 0.12 wt% 0.04 wt% or more, a specific surface area in the volume-based particle size distribution is not more than 0.16 m ² / cc or more 0.27 m ² / cc, more, The volume average particle size in the volume-based particle size distribution is 41.0 μm or more and 69.0 μm or less, or the standard deviation (SD) in the volume-based particle size distribution is 24.0 μm or more and 42.0 μm or less, or Suggest AB ₅ -type hydrogen absorbing alloy powder wherein a volume average particle diameter and the standard deviation (SD) are both within the predetermined range.

In other words, the AB ₅ type hydrogen storage alloy powder having a CaCu ₅ type crystal structure that occupies 50% by weight or more passing through a mesh sieve having a mesh size of 150 μm is basically a dangerous substance class 2 ( Although it is classified as a flammable solid), it defines the Ce content, oxygen content, and specific surface area in the volume-based particle size distribution, and further, the volume average particle size in the volume-based particle size distribution or the standard deviation (SD) in the volume-based particle size distribution Alternatively, by specifying both of these, it is possible to prevent ignition within 10 seconds in the small gas flame ignition test, which is a judgment test for the second class of dangerous goods (flammable solids). According to the regulations, it became clear that it does not fall under the category of hazardous materials (combustible solids). In addition, it has been clarified that when used as a negative electrode active material for various batteries, excellent battery characteristics, particularly excellent low-temperature battery characteristics can be realized.

  Embodiments of the present invention will be described in detail below, but the scope of the present invention is not limited to the embodiments described below.

In the hydrogen storage alloy powder according to the present embodiment, 50% by weight or more passes through a mesh sieve having an opening of 150 μm, and the general formula MmNia Mnb Alc Cod (where Mm is a misch metal, a, b, c and d is a numerical value indicating the ratio of each element), which is a hydrogen storage alloy powder made of an AB ₅ type hydrogen storage alloy having a CaCu ₅ type crystal structure, and the Ce content in the alloy is less than a predetermined ratio The oxygen content is in a predetermined range, the specific surface area in the volume-based particle size distribution is in the predetermined range, and the volume average particle diameter in the volume-based particle size distribution or the standard deviation (SD) in the volume-based particle size distribution, or both Is an AB ₅ type hydrogen storage alloy powder characterized by having a predetermined range.
This will be described in detail below.

However, as long as the hydrogen storage alloy powder of the present invention is an AB ₅ type hydrogen storage alloy having a CaCu ₅ type crystal structure, other than the AB ₅ type hydrogen storage alloy that can be represented by the general formula MmNiaMnbAlcCod as in this embodiment. Even if it exists, there exists an effect similarly to this embodiment and it is thought that it is contained in this invention.

  In the general formula MmNia Mnb Alc Cod, the ratio of the total number of moles of the elements constituting the B site to the total number of moles of the elements constituting the A site in the ABx composition a + b + c + d (this ratio is also referred to as ABx) is 4.5 ≦ ABx It is preferred that ≦ 5.5. If it is ABx of this range, a battery life etc. can be maintained suitably, and also a hydrogen storage characteristic and an output characteristic can be maintained. From this point of view, the lower limit of ABx is preferably 4.9 or more, and the upper limit is more preferably 5.45 or less.

The proportion (a) of Ni is adjusted within the range of 3.2 ≦ a ≦ 4.8, preferably 3.7 ≦ a ≦ 4.7, and more preferably 4.2 ≦ a ≦ 4.5. Good.
The ratio (b) of Mn is adjusted within the range of 0.1 ≦ b ≦ 0.7, preferably 0.35 ≦ b ≦ 0.6.
The ratio (c) of Al is adjusted in the range of 0.05 ≦ c ≦ 0.6, preferably 0.2 ≦ c ≦ 0.4.
The ratio (d) of Co is adjusted in the range of 0.05 ≦ d ≦ 1.0, preferably 0.05 ≦ d ≦ 0.8.

In the above composition, “Mm” is a misch metal which is a rare earth-based mixture such as La, Ce, Pr, Nd, and Sm. For example, rare earths containing Ce (1 to 50%), La (20 to 98%), Pr and Nd as main constituent elements can be mentioned.
In addition, from the viewpoint of further suppressing the ignitability in the small gas flame ignition test, which is a judgment test for the hazardous material type 2 (flammable solid) stipulated by the Fire Service Act, the Ce content is 25% by weight or less with respect to the entire alloy. It is important that it is 20% by weight or less, and more preferably 15% by weight or less.

  Hydrogen storage alloy powders that occupy 50% by weight or more of particles that pass through a mesh sieve with an opening of 150 μm are classified in principle as hazardous materials class 2 (flammable solids) stipulated by the Fire Service Act. The storage alloy powder defines the Ce content, the oxygen content, and the specific surface area in the volume-based particle size distribution, and further calculates the volume average particle diameter in the volume-based particle size distribution and / or the standard deviation (SD) in the volume-based particle size distribution By stipulating within the prescribed range, it is possible to prevent ignition within 10 seconds in the small gas flame ignition test, which is a judgment test for dangerous goods class 2 (flammable solids) stipulated by the Fire Service Act. According to the provisions of, it can be considered not to fall under the category of dangerous goods class 2 (flammable solids).

  Whether or not to pass through a screen sieve having an opening of 150 μm is determined, for example, by using a sieve shaker (Shintouki) by the RO-TAP method and using a JIS standard sieve screen made of SUS by the method described in JIS Z 2510. It is preferred to do so.

  It is important that the oxygen content in the hydrogen storage alloy powder of the present embodiment is 0.04 wt% or more and 0.12 wt% or less, preferably 0.05 wt% or more and 0.12 wt% or less, more preferably Is 0.05 wt% or more and 0.10 wt% or less.

The specific surface area in the volume-based particle size distribution of the hydrogen-absorbing alloy powder of the present embodiment, it is important that 0.16 m ² / cc or more 0.27m is ² / cc or less, preferably 0.19 m ² / cc or more 0 .26 m ² / cc or less.
In order to adjust the specific surface area, for example, pulverization conditions (number of rotations / feed amount), sieve opening at the time of classification, etc. may be adjusted.
The measurement of the specific surface area can be calculated from the following formula from the volume-based particle size distribution output by the laser diffraction method using Microtrac (Nikkiso Co., Ltd.).

Specific surface area (CS; m ² / cc) = 6 / MA
MA (Area average particle diameter; μm) = ΣVi / Σ (Vi / di)
In the above formula, Vi is frequency, and di is the median value of the particle size classification.

In the hydrogen storage alloy powder of this embodiment, the volume average particle size in the volume-based particle size distribution is 41.0 μm or more and 69.0 μm or less, particularly 41.0 μm or more and 65.0 μm or less, and particularly 41.0 μm or more and 60.0 μm or less. Is preferred.
In order to adjust the volume average particle diameter, for example, the pulverization conditions (the number of rotations and the feed amount), the sieve opening during classification, and the like may be adjusted.
The measurement of the volume average particle diameter can be calculated from the following formula from the volume reference particle size distribution output by the laser diffraction method using Microtrac (Nikkiso Co., Ltd.).

Volume average particle diameter (MV; μm) = Σ (Vi × di) / ΣVi
In the above formula, Vi is frequency, and di is the median value of the particle size classification.

Further, in the hydrogen storage alloy powder of this embodiment, it is important that the standard deviation in the volume-based particle size distribution is 24.0 μm or more and 42.0 μm or less, and 24.0 μm or more and 40.0 μm or less, particularly 24.0 μm. It is preferably 36.0 μm or less.
In order to adjust the standard deviation in the volume-based particle size distribution, for example, the pulverization conditions (number of rotations / feed amount), the sieve opening at the time of classification, etc. may be adjusted.
The standard deviation in the present invention is an index indicating the extent of the volume-based particle size distribution, and the measurement is performed from the volume-based particle size distribution output by the laser diffraction method using Microtrac (Nikkiso Co., Ltd.). It can be calculated from the formula.

  Standard deviation (SD) = (D84% −D16%) / 2

(Method for producing hydrogen storage alloy powder)
As a method for producing the AB type ₅ hydrogen storage alloy powder of this embodiment, for example, each hydrogen storage alloy raw material is weighed and mixed so as to have a predetermined alloy composition, the mixture is cast, heat-treated, and then pulverized. Then, a method of performing oxygen fixation treatment and classification as necessary can be exemplified. At this time, the processes from casting to heat treatment and pulverization are performed in an inert gas atmosphere such as argon gas or nitrogen gas or in a low oxygen concentration atmosphere (for example, an oxygen concentration of 0.5% or less, preferably 0.1% or less, particularly preferably). 0.01% or less), and after that, it is preferable to carry out oxygen fixation treatment and package in a sealed state.
In some cases, however, the mixture may be cast, heat-treated, pulverized, classified, and then subjected to oxygen fixation treatment. In this case, the steps from casting to heat treatment, pulverization and classification are performed in an inert gas atmosphere or an atmosphere having a low oxygen concentration (for example, an oxygen concentration of 0.5% or less, preferably 0.1% or less, particularly preferably 0.01). Or the like, and the process from casting to heat treatment and pulverization may be performed in an inert gas atmosphere or in a low oxygen concentration atmosphere (for example, an oxygen concentration of 0.5% or less, Preferably, it is performed at 0.1% or less, particularly preferably 0.01% or less), followed by classification in air, followed by oxygen fixation treatment and packaging in a sealed state.

  In this production method, conditions such as casting conditions (casting method, molten metal temperature, mold shape), heat treatment conditions, grinding conditions (rotation speed / feed amount), classification method (including sieve openings), oxygen fixation treatment, etc. are appropriately selected. It is preferable to select and control. In particular, in the oxygen fixation treatment, after pulverization is completed, oxygen or air is introduced into the pulverizer to an oxygen concentration of 1% to 50%, and the alloy powder is held in this atmosphere for 30 minutes to 48 hours, preferably 30 minutes to 24 hours. By doing so, it is preferable to fix oxygen on the particle surface.

(Use of AB type ₅ hydrogen storage alloy powder)
The use of the hydrogen storage alloy powder of the present embodiment is not particularly limited, but can be suitably used as a negative electrode active material for various batteries. For example, the hydrogen storage alloy powder of the present embodiment is appropriately subjected to a surface treatment such as coating the alloy surface with a metal material or a polymer resin as necessary, or treating the surface with an acid or an alkali, if necessary. Therefore, it can be used as a negative electrode active material for various batteries. In this case, the battery negative electrode can be prepared by mixing and forming a binder, a conductive additive and the like in the negative electrode active material by a known method to produce a hydrogen storage alloy negative electrode.
The hydrogen storage alloy negative electrode obtained from the hydrogen storage alloy powder of the present embodiment can be used not only for secondary batteries but also for primary batteries (including fuel cells). For example, a nickel-MH (MH) metal secondary battery can be formed from a positive electrode using nickel hydroxide as an active material, an electrolytic solution made of an alkaline aqueous solution, and a separator.

  Hereinafter, the present invention will be specifically described based on examples.

<Hydrogen storage alloy powder A>
Mm (La 25%, Ce 5%) Al _0.40 Mn _0.30 Co _0.50 Ni _4.00 (ABx = 5.20, Mm is a misch metal which is a mixture of rare earth metals of La, Ce, Nd and Pr) In order to obtain an alloy, each raw material is Mm: 32.4%, Ni: 54.4%, Mn: 3.8%, Al: 2.5%, Co: 6.8% by weight% so that an alloy can be obtained. Weigh and mix the mixture into a crucible and fix it in a high-frequency melting furnace. After reducing the pressure to 10 ⁻⁴ to 10 ⁻⁵ Torr, the mixture is heated and dissolved in an argon gas atmosphere and poured into a water-cooled copper mold, Casting was performed at 1450 ° C. to obtain an alloy.
The obtained alloy was roughly crushed using a jaw crusher (Fuji Paudal: model1021-B) in an atmosphere with an oxygen concentration of 0.5% or less, and further horizontal brown under an atmosphere with an oxygen concentration of 0.5% or less. Using a pulverizer (Yoshida Seisakusho), pulverization was performed to a particle size that passed through a 500 μm sieve to obtain hydrogen storage alloy powder A.

(Comparative Example 1)
The above hydrogen storage alloy powder A5 kg was further pulverized at a rotational speed of 4000 rpm and a feed rate of 12 kg / hr using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) in an atmosphere having an oxygen concentration of 0.01% or less. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) with an opening of 180 μm in an air atmosphere, and the powder under the sieve is collected and sampled Got.

(Comparative Example 2)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 150 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

Example 1
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 125 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Example 2)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 106 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Example 3)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 8000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified in an air atmosphere using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having a mesh opening of 90 μm, and the powder under the sieve is collected to obtain a sample. Got.

(Example 4)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 8000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder was classified in an air atmosphere using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having openings of 75 μm and 90 μm, and a 75 μm sieve above a 90 μm sieve. The powder was collected to obtain a sample.

(Example 5)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 8000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an opening of 75 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Example 6)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotational speed of 12000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 63 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Example 7)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotational speed of 12000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having openings of 63 μm and 75 μm in an air atmosphere. The powder was collected to obtain a sample.

(Comparative Example 3)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotational speed of 12000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an opening of 45 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Comparative Example 4)
The hydrogen storage alloy powder A5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotational speed of 12000 rpm and a feed rate of 12 kg / hr. After the pulverization, argon gas was introduced into the pulverizer and held for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having openings of 63 μm and 75 μm in an air atmosphere. The powder was collected to obtain a sample.

<Hydrogen storage alloy powder B>
Mm (La 20%, Ce 9%) Al _0.60 Mn _0.10 Co _0.60 Ni _3.80 (ABx = 5.10, Mm is a misch metal which is a mixture of rare earth metals of La, Ce, Nd and Pr) In order to obtain an alloy, each raw material is Mm: 33.3%, Ni: 53.1%, Mn: 1.3%, Al: 3.9%, Co: 8.4% by weight%. Weigh and mix the mixture into a crucible and fix it in a high-frequency melting furnace. After reducing the pressure to 10 ⁻⁴ to 10 ⁻⁵ Torr, the mixture is heated and dissolved in an argon gas atmosphere and poured into a water-cooled copper mold, Casting was performed at 1450 ° C. to obtain an alloy.
The obtained alloy was roughly crushed using a jaw crusher (Fuji Paudal: model1021-B) in an atmosphere with an oxygen concentration of 0.5% or less, and further horizontal brown under an atmosphere with an oxygen concentration of 0.5% or less. Using a pulverizer (Yoshida Seisakusho), pulverization was performed to a particle size that passed through a 500 μm sieve to obtain hydrogen storage alloy powder B.

(Comparative Example 5)
The hydrogen storage alloy powder B5 kg is further pulverized in an atmosphere with an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 150 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Example 8)
The hydrogen storage alloy powder B5 kg is further pulverized in an atmosphere with an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 125 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Comparative Example 6)
The hydrogen storage alloy powder B5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 12000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an opening of 45 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

<Hydrogen storage alloy powder C>
Mm (La 19%, Ce 9%) Al _0.50 Mn _0.70 Co _0.05 Ni _4.20 (ABx = 5.45, Mm is Misch metal which is a mixture of rare earth metals of La, Ce, Nd and Pr) In order to obtain an alloy, each raw material is Mm: 31.7%, Ni: 55.9%, Mn: 8.7%, Al: 3.1%, Co: 0.7% by weight%. Weigh and mix the mixture into a crucible and fix it in a high-frequency melting furnace. After reducing the pressure to 10 ⁻⁴ to 10 ⁻⁵ Torr, the mixture is heated and dissolved in an argon gas atmosphere and poured into a water-cooled copper mold, Casting was performed at 1450 ° C. to obtain an alloy.
The obtained alloy was roughly crushed using a jaw crusher (Fuji Paudal: model1021-B) in an atmosphere with an oxygen concentration of 0.5% or less, and further horizontal brown under an atmosphere with an oxygen concentration of 0.5% or less. Using a pulverizer (Yoshida Seisakusho), pulverization was performed to a particle size that passed through a 500 μm sieve to obtain hydrogen storage alloy powder C.

(Comparative Example 7)
The hydrogen storage alloy powder C5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less by using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 150 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

Example 9
The hydrogen storage alloy powder C5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less by using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 125 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Comparative Example 8)
The hydrogen storage alloy powder C5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotational speed of 12000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an opening of 45 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

<Hydrogen storage alloy powder D>
Mm (La 16%, Ce 11%) Al _0.05 Mn _0.20 Co _0.10 Ni _4.80 (ABx = 5.15, Mm is a misch metal that is a mixture of rare earth metals of La, Ce, Nd, and Pr) In order to obtain an alloy, each raw material is Mm: 31.8%, Ni: 64.1%, Mn: 2.5%, Al: 0.3%, Co: 1.3% in terms of% by weight. Weigh and mix the mixture into a crucible and fix it in a high-frequency melting furnace. After reducing the pressure to 10 ⁻⁴ to 10 ⁻⁵ Torr, the mixture is heated and dissolved in an argon gas atmosphere and poured into a water-cooled copper mold, Casting was performed at 1450 ° C. to obtain an alloy.
The obtained alloy was roughly crushed using a jaw crusher (Fuji Paudal: model1021-B) in an atmosphere with an oxygen concentration of 0.5% or less, and further horizontal brown under an atmosphere with an oxygen concentration of 0.5% or less. Using a pulverizer (Yoshida Seisakusho), pulverization was performed to a particle size that passed through a 500 μm sieve to obtain hydrogen storage alloy powder D.

(Comparative Example 9)
The hydrogen storage alloy powder D5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 150 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Example 10)
The hydrogen storage alloy powder D5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 125 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Comparative Example 10)
The hydrogen storage alloy powder D5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotational speed of 12000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an opening of 45 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

<Hydrogen storage alloy powder E>
Mm (La 11%, Ce 15%) Al _0.30 Mn _0.40 Co _1.00 Ni _3.20 (ABx = 4.90, Mm is a misch metal which is a mixture of rare earth metals of La, Ce, Nd and Pr) In order to obtain an alloy, each raw material is Mm: 31.8%, Ni: 64.1%, Mn: 2.5%, Al: 0.3%, Co: 1.3% in terms of% by weight. Weigh and mix the mixture into a crucible and fix it in a high-frequency melting furnace. After reducing the pressure to 10 ⁻⁴ to 10 ⁻⁵ Torr, the mixture is heated and dissolved in an argon gas atmosphere and poured into a water-cooled copper mold, Casting was performed at 1450 ° C. to obtain an alloy.
The obtained alloy was roughly crushed using a jaw crusher (Fuji Paudal: model1021-B) in an atmosphere with an oxygen concentration of 0.5% or less, and further horizontal brown under an atmosphere with an oxygen concentration of 0.5% or less. Using a pulverizer (Yoshida Seisakusho), pulverization was performed to a particle size that passed through a 500 μm sieve to obtain hydrogen storage alloy powder E.

(Comparative Example 11)
The hydrogen storage alloy powder E5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 150 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Example 11)
The hydrogen storage alloy powder E5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a fine pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 6000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an aperture of 125 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

(Comparative Example 12)
The hydrogen storage alloy powder E5 kg is further pulverized in an atmosphere having an oxygen concentration of 0.01% or less using a pulverizer bantam mill (manufactured by Tokyo Atomizer: modelTAP-1WZ type) at a rotation speed of 12000 rpm and a feed rate of 12 kg / hr. After the pulverization was completed, air was introduced into the pulverizer to the atmospheric oxygen concentration (%) shown in the table, and kept in the atmosphere for 30 minutes, and then the alloy powder was taken out. This alloy powder is classified using an OCTAGON DIGITAL automatic classifier (manufactured by CSC SCIENTIFIC COMPANY) using a sieve (JIS Z 8801) having an opening of 45 μm in an air atmosphere, and the powder under the sieve is collected to obtain a sample. Got.

<Oxygen content measurement>
The oxygen content of the hydrogen-absorbing alloy powder was measured by adding 0.05 g of sample to a Ni capsule (0.3 g, 5φ × 10 L) and pressing the mouth of the Ni capsule with radio pliers so that the powder would not scatter. The air was removed and measurement was performed under the following conditions using the following analyzer.

Analyzer: Oxygen / nitrogen analyzer (Horiba, EMGA-520)
Carrier gas: He (purity 99.995% or more), gas pressure 3.5 ± 0.2 kg / cm ² G
Crucible: Graphite crucible Measurement conditions: Standard setting conditions described in the EMGA-520 instruction manual (ANALYZE (1) Melting conditions (1) 6.00, 6.00KW; changed to 30 seconds)
Measurement mode: STANDARD BLOCK operation mode in BLOCK mode

<Volume-based particle size distribution measurement>
Volume-based particle size distribution measurement is performed under the following setting conditions using the following measuring device, specific surface area (m ² / cc), volume average particle diameter (μm), number average particle diameter (μm), area average diameter ( μm) and standard deviation (μm) were obtained.

(Device used)
Micro Truck (Nikkiso Co., Ltd., HRA9320-X100)
(Setting conditions during measurement)
・ Particle Transparency: Refract
・ Spherical Particles: No
・ Particle Refractive Index: 1.51
・ Fluid Refractive index: 1.33 (water)
・ Flow Rate: 60mL / sec
(Microtrack measurement conditions)
・ Measurement time: 30 seconds ・ Number of measurements: once

<Charge / discharge test>
1 g of each sample obtained in the examples and comparative examples was mixed with 3 g of Ni as a conductive material and 0.12 g of polyethylene as a binder, and 0.3 g of the mixed powder was pressed on the foamed Ni to form a pellet electrode It was. Next, the pellet electrode was sandwiched by a positive electrode (nickel hydroxide) having a sufficient capacity through a separator, and immersed in a 30 wt% KOH aqueous solution to produce a model cell.

(Charge / discharge condition-activation)
・ Charge / discharge test equipment: TOSCAT (Toyo System Co., Ltd.)
・ Charging 0.2C-120%; discharging 0.2C-0.7V cut ・ Cycle: 15 cycles ・ Temperature: 20 ℃
(Low temperature cycle)
・ Charge: 1.0C-120%: Discharge 1.0C-0.7V cut ・ Cycle: 16th and 17th cycle ・ Temperature: 0 ° C

The cycle at low temperature was carried out after sufficient activation by repeating the 15-cycle charge / discharge test.
The low temperature characteristics were expressed by the maximum discharge capacity (15th cycle discharge capacity) measured at 20 ° C. divided by the low temperature discharge capacity (17th cycle discharge capacity).
Low temperature characteristic (%) = (17th cycle discharge capacity (0 ° C., 1C)) / (15th cycle discharge capacity (20 ° C., 0.2C)) × 100

However, in Tables 1 to 5, for each composition, that is, for the hydrogen storage alloy powder A (Examples 1 to 7, Comparative Examples 1 to 4), the relative low temperature characteristic (%) of Example 1 is 100. By value,
For the hydrogen storage alloy powder B (Example 8, Comparative Examples 5 and 6), the low temperature characteristic (%) of Example 8 is shown as a relative value of 100,
About the hydrogen storage alloy powder C (Example 9, Comparative Examples 7 and 8), the low temperature characteristic (%) of Example 9 is shown as a relative value with 100,
About the hydrogen storage alloy powder D (Example 10, Comparative Examples 9 and 10), the low temperature characteristic (%) of Example 10 is shown as a relative value with 100,
The hydrogen storage alloy powder E (Example 11, Comparative Examples 11 and 12) is shown as a relative value with the low temperature characteristic (%) of Example 11 as 100.

<Small gas flame ignitability test>
Each sample obtained in Examples and Comparative Examples was placed in a desiccator containing silica gel for drying, and stored at room temperature for 24 hours or more.
The test place was a place where the temperature was 20 ± 5 ° C., the humidity was 50 ± 10% RH, and it was in a state close to no wind under atmospheric pressure.

a. The collected test substance (sample) of about 3 cm ^{3 is} hemispherically deposited on an inorganic heat insulating plate with a thickness of 10 mm or more and a side of 15 cm square, and a diffusion flame (approx. 70 mm) was brought into contact with the test substance (sample) for 10 seconds.
b. The time from when the flame was brought into contact with the test substance until the test substance was ignited was measured to observe whether the test substance continued to burn.
c. In addition, after releasing the flame after ignition, the operation of a and b was repeated 10 times when the elapsed combustion for 10 seconds did not continue.

In the ignition judgment, those that ignited even once were judged as “ignition”, and those that never ignited were judged as “no ignition”.
In the continuous combustion determination, regardless of whether it is flammable combustion or nonflammable combustion (combustion that does not emit flame), the test substance The case where everything was burned out or the case where burning continued for 10 seconds or more after releasing the flame was judged as “continuous”, and the case where it was not burned was judged as “−”.

<Ignition time determination test>
In the same test as the above small gas flame ignition test, regardless of whether it is flammable combustion or non-flammable combustion, the flame is kept in contact without any time limit until the combustion starts, and the time from the contact of the flame to the start of the combustion is determined. Measured.
The continuous combustion determination was performed in the same manner as the small gas flame ignition test.

It is the graph which plotted the relationship between the specific surface area (CS value) in a volume reference | standard particle size distribution and a low-temperature characteristic about the sample obtained in Examples 1-7, Comparative Examples 1-3, and Comparative Example 4. FIG. The graph which plotted the relationship between the specific surface area (CS value) in a volume reference | standard particle size distribution and the ignition time in a small gas flame ignitability test about the sample obtained in Examples 1-7, Comparative Examples 1-3, and Comparative Example 4. It is. It is the graph which plotted the relationship between the volume average particle diameter in a volume reference | standard particle size distribution, and the low temperature characteristic about the sample obtained in Examples 1-7, Comparative Examples 1-3, and Comparative Example 4. FIG. It is the graph which plotted the relationship between the volume average particle diameter in a volume reference | standard particle size distribution and the ignition time in a small gas flame ignitability test about the sample obtained in Examples 1-7, Comparative Examples 1-3, and Comparative Example 4. . It is the graph which plotted the relationship between the standard deviation in a volume reference | standard particle size distribution and a low-temperature characteristic about the sample obtained in Examples 1-7, Comparative Examples 1-3, and Comparative Example 4. FIG. It is the graph which plotted the relationship between the standard deviation in a volume reference | standard particle size distribution, and the ignition time in a small gas flame ignitability test about the sample obtained in Examples 1-7, Comparative Examples 1-3, and Comparative Example 4. FIG.

Claims (6)

In an AB ₅ type hydrogen storage alloy powder for a battery having a CaCu ₅ type crystal structure in which 50% by weight or more passes through a 150 μm mesh screen,
Ce content in the alloy is 25 wt% or less,
The oxygen content is 0.04 wt% or more and 0.12 wt% or less,
The specific surface area in the volume-based particle size distribution is not more than 0.16 m ² / cc or more 0.27 m ² / cc,
The volume average particle size in the volume-based particle size distribution is 41.0 μm or more and 69.0 μm or less,
AB ₅ type hydrogen storage alloy powder for batteries, wherein standard deviation (SD) in the volume-based particle size distribution is 24.0 μm or more and 42.0 μm or less. In an AB ₅ type hydrogen storage alloy powder for a battery having a CaCu ₅ type crystal structure in which 50% by weight or more passes through a 150 μm mesh screen,
Ce content in the alloy is 25 wt% or less,
The oxygen content is 0.04 wt% or more and 0.12 wt% or less,
The specific surface area in the volume-based particle size distribution is not more than 0.16 m ² / cc or more 0.27 m ² / cc,
Battery AB ₅ -type hydrogen absorbing alloy powder wherein a volume average particle diameter in the volume-based particle size distribution is less than 69.0μm or 41.0μm. In an AB ₅ type hydrogen storage alloy powder for a battery having a CaCu ₅ type crystal structure in which 50% by weight or more passes through a 150 μm mesh screen,
Ce content in the alloy is 25 wt% or less,
The oxygen content is 0.04 wt% or more and 0.12 wt% or less,
The specific surface area in the volume-based particle size distribution is not more than 0.16 m ² / cc or more 0.27 m ² / cc,
AB ₅ type hydrogen storage alloy powder for batteries, wherein standard deviation (SD) in the volume-based particle size distribution is 24.0 μm or more and 42.0 μm or less. MmNi _a Mn _b Al _c Co _d (where Mm is Misch metal, 3.2 ≦ a ≦ 4.8, 0.1 ≦ b ≦ 0.7, 0.05 ≦ c ≦ 0.6, 0.05 ≦ d ≦ 1.0,4.5 ≦ a + b + c + d ≦ 5.5) battery AB ₅ -type hydrogen absorbing alloy powder according to claim 1 which is characterized by an alloy composition represented by . The battery according to any one of claims 1 to 4, wherein the gas is not ignited within 10 seconds in a small gas flame ignition test, which is a judgment test for a hazardous material class 2 (flammable solid) defined by the Fire Service Act . AB type ₅ hydrogen storage alloy powder. A battery comprising the AB ₅ type hydrogen storage alloy powder for a battery according to any one of claims 1 to 5 as a negative electrode active material.

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