JP7772673B2 - Hydrogen storage alloy and method for producing the same - Google Patents
Hydrogen storage alloy and method for producing the sameInfo
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- JP7772673B2 JP7772673B2 JP2022134208A JP2022134208A JP7772673B2 JP 7772673 B2 JP7772673 B2 JP 7772673B2 JP 2022134208 A JP2022134208 A JP 2022134208A JP 2022134208 A JP2022134208 A JP 2022134208A JP 7772673 B2 JP7772673 B2 JP 7772673B2
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Description
本開示は水素吸蔵合金およびその製造方法に関する。 This disclosure relates to hydrogen storage alloys and methods for producing them.
水素を２次エネルギーとするエネルギー供給社会を構築するために、水素貯蔵方法の開発が行われている。水素貯蔵方法として、高圧水素もしくは液体水素として貯蔵する方法、又は有機ハイドライドもしくは水素吸蔵合金（ＭＨ）を用いる方法等が考えられる。中でも安全性と体積充填効率に優れるＭＨを用いる貯蔵法が注目されている。 In order to build an energy supply society that uses hydrogen as a secondary energy source, hydrogen storage methods are being developed. Possible hydrogen storage methods include storing hydrogen as high-pressure hydrogen or liquid hydrogen, or using organic hydrides or hydrogen storage alloys (MH). Of these, MH storage methods are attracting attention due to their excellent safety and volumetric filling efficiency.
ＭＨは、高い水素吸蔵量を有することが求められる。ＭＨは一般的に、不純物が少ない方が好ましい。例えば特許文献１には、金属不純物の総量を１０００ｗｔｐｐｍ超（すなわち０．１０質量％超）にすると、水素吸蔵合金の水素吸蔵量が著しく低下することが開示されている。具体的には、金属不純物の総量を０．１０質量％以下にした実施例では、水素吸蔵量が７．５ｗｔ％以上であったのに対し、０．１０質量％超にした比較例では水素吸蔵量が３．０ｗｔ％以下となり、水素吸蔵量が４０％以下に低下している。また、非金属不純物（Ｓ、Ｃ、Ｎ）が特に水素吸蔵能を低下させるため、それぞれの含有量を１００ｗｔｐｐｍ以下にすべきことが開示されている。 MH is required to have a high hydrogen storage capacity. Generally, it is preferable for MH to have fewer impurities. For example, Patent Document 1 discloses that if the total amount of metallic impurities exceeds 1000 wtppm (i.e., exceeds 0.10 mass%), the hydrogen storage capacity of the hydrogen storage alloy significantly decreases. Specifically, in an example where the total amount of metallic impurities was 0.10 mass% or less, the hydrogen storage capacity was 7.5 wt% or more, while in a comparative example where the total amount of metallic impurities was more than 0.10 mass%, the hydrogen storage capacity was 3.0 wt% or less, meaning that the hydrogen storage capacity had decreased to 40% or less. It also discloses that non-metallic impurities (S, C, N) in particular reduce hydrogen storage capacity, and therefore their respective contents should be kept to 100 wtppm or less.
ＭＨは、通常純金属等を用いて製造され得る。しかし、純金属は高コストである。さらに近年、環太平洋地域でのステンレス鋼の需要増加等の要因で、純Ｎｉ等のコストが増大している。コスト低減のためには、純金属に代えてリサイクル材を用いること等によりＭＨを製造することが考えられる。しかしながら、リサイクル材を用いると不純物量が増大してしまい、その結果、例えば特許文献１に開示されるように、著しく水素吸蔵量が低下するおそれがある。 MHs are typically manufactured using pure metals, etc. However, pure metals are expensive. Furthermore, in recent years, the cost of pure Ni and other materials has been increasing due to factors such as increased demand for stainless steel in the Pacific Rim region. To reduce costs, it is possible to manufacture MHs using recycled materials instead of pure metals. However, using recycled materials increases the amount of impurities, which may result in a significant decrease in hydrogen storage capacity, as disclosed in Patent Document 1, for example.
本発明はこのような状況に鑑みてなされたものであり、その目的の１つは、従来技術に対して、水素吸蔵量を大きく低下させることなく、コスト低減可能な水素吸蔵合金、およびその製造方法を提供することである。 The present invention was made in light of these circumstances, and one of its objectives is to provide a hydrogen storage alloy and a method for producing the same that can reduce costs without significantly reducing the hydrogen storage capacity compared to conventional techniques.
本発明の態様１は、
Ｌａ：１５～３０質量％、
Ｃｅ：５～１５質量％、
Ｐｒ：０～０．０５質量％、
Ｎｄ：０．０１～０．１５質量％、
Ｓｍ：０～０．０５質量％、
Ｃｏ：５～１５質量％、
Ｍｎ：２～８質量％、
Ａｌ：０～０．０５質量％、
Ｆｅ：０質量％以上３．００質量％未満、
Ｃｕ：０質量％以上３．００質量％未満、
Ｐ ：０質量％以上３．００質量％未満、
Ｃ ：０質量％以上３．００質量％未満、および
残部：Ｎｉおよび不可避不純物からなり、且つ下記式（１）および（２）を満たす水素吸蔵合金である。
４．５＜Ｂ／Ａ＜５．５ ・・・（１）
０．１０＜［Ｆｅ］＋［Ｃｕ］＋［Ｐ］＋［Ｃ］＜３．００ ・・・（２）
式（１）中のＡは、前記水素吸蔵合金中に含まれるＬａ、Ｃｅ、Ｐｒ、ＮｄおよびＳｍの合計モル数であり、Ｂは、前記水素吸蔵合金中に含まれるＮｉ、Ｃｏ、ＭｎおよびＡｌの合計モル数である。
式（２）中の［Ｆｅ］、［Ｃｕ］、［Ｐ］および［Ｃ］は、それぞれ、質量％で示したＦｅ、Ｃｕ、ＰおよびＣの含有量を示す。
Aspect 1 of the present invention is
La: 15 to 30% by mass,
Ce: 5 to 15% by mass,
Pr: 0 to 0.05% by mass,
Nd: 0.01 to 0.15% by mass,
Sm: 0 to 0.05% by mass,
Co: 5 to 15% by mass,
Mn: 2 to 8% by mass,
Al: 0 to 0.05% by mass,
Fe: 0% by mass or more and less than 3.00% by mass,
Cu: 0% by mass or more and less than 3.00% by mass,
P: 0% by mass or more and less than 3.00% by mass,
C: 0 mass % or more but less than 3.00 mass %, and the balance: Ni and unavoidable impurities, and the hydrogen storage alloy satisfies the following formulas (1) and (2).
4.5<B/A<5.5...(1)
0.10<[Fe]+[Cu]+[P]+[C]<3.00...(2)
In formula (1), A is the total number of moles of La, Ce, Pr, Nd, and Sm contained in the hydrogen storage alloy, and B is the total number of moles of Ni, Co, Mn, and Al contained in the hydrogen storage alloy.
In formula (2), [Fe], [Cu], [P] and [C] represent the contents of Fe, Cu, P and C, respectively, expressed in mass %.
本発明の態様２は、
下記式（３）を満たす、態様１に記載の水素吸蔵合金である。
［Ｐ］＋［Ｃ］≧０．１ ・・・（３）
式（３）中の［Ｐ］および［Ｃ］は、それぞれ、質量％で示したＰおよびＣの含有量を示す。
Aspect 2 of the present invention is
The hydrogen storage alloy according to aspect 1 satisfies the following formula (3):
[P]+[C]≧0.1...(3)
In formula (3), [P] and [C] represent the P and C contents, respectively, expressed in mass %.
本発明の態様３は、
リサイクル材を含む原料を用いることを特徴とする、態様１または２に記載の水素吸蔵合金の製造方法である。
Aspect 3 of the present invention is
The method for producing a hydrogen storage alloy according to aspect 1 or 2 is characterized in that raw materials containing recycled materials are used.
本発明の態様４は、
前記リサイクル材は、二次電池のリサイクル材である、態様３に記載の製造方法である。
Aspect 4 of the present invention is
Aspect 4. The method according to aspect 3, wherein the recycled material is a recycled material from a secondary battery.
本発明の態様５は、
前記二次電池は、リチウムイオン電池である、態様４に記載の製造方法である。
Aspect 5 of the present invention is
Aspect 5 is the method according to aspect 4, wherein the secondary battery is a lithium ion battery.
本発明の実施形態によれば、従来技術に対して、水素吸蔵量を大きく低下させることなく、コスト低減可能な水素吸蔵合金、およびその製造方法を提供することが可能である。 Embodiments of the present invention make it possible to provide a hydrogen storage alloy and a method for manufacturing the same that can reduce costs without significantly reducing the hydrogen storage capacity compared to conventional techniques.
本発明者らは、従来技術に対して、水素吸蔵量を大きく低下させることなく、コスト低減可能な水素吸蔵合金を実現するべく、様々な角度から検討した。その結果、特定の組成（ＭＡＮｉＢ－ｘ－ｙ－ｚＣｏｘＭｎｙＡｌｚ、ＭはＬａ、Ｃｅ等の特定のランタノイド、４．５＜Ｂ／Ａ＜５．５）の水素吸蔵合金に対して、Ｆｅ、Ｃｕ、ＰおよびＣという特定の不純物であれば、従来技術において水素吸蔵量を著しく低下させると考えられていた量（０．１０質量％超）を含有させても、水素吸蔵量があまり低下しない（例えば、従来技術に対して水素吸蔵量の低下が２０％以内である）ことを見出した。また、上記組成の水素吸蔵合金であれば、Ｆｅ、Ｃｕ、ＰおよびＣを含むリサイクル材を使用することができ、さらに、それらの元素を低減する工程を必要としないため、製造コストを低減できることを見出した。さらに、上記水素吸蔵合金は、上記リサイクル材を使用することができるので、資源循環に貢献できるという利点もある。 The present inventors have conducted extensive research to develop a hydrogen storage alloy that can reduce costs without significantly reducing the hydrogen storage capacity compared to conventional techniques. As a result, they have found that for a hydrogen storage alloy with a specific composition (MANiB- x -y- zCoxMnyAlz , where M is a specific lanthanide such as La or Ce, and 4.5<B/A<5.5) , the hydrogen storage capacity does not decrease significantly (for example, the decrease in hydrogen storage capacity is within 20% compared to conventional techniques) even when specific impurities such as Fe, Cu, P, and C are added in amounts (more than 0.10 mass%) that were previously thought to significantly reduce the hydrogen storage capacity in conventional techniques. Furthermore, they have found that a hydrogen storage alloy with this composition can use recycled materials containing Fe, Cu, P, and C, and furthermore, does not require a process for reducing these elements, thereby reducing manufacturing costs. Furthermore, because the hydrogen storage alloy can use recycled materials, it also has the advantage of contributing to resource recycling.
以下に、本発明の実施形態が規定する各要件の詳細を示す。 Below are details of each requirement stipulated in the embodiments of the present invention.
本発明の実施形態に係る水素吸蔵合金は、Ｌａ：１５～３０質量％、Ｃｅ：５～１５質量％、Ｐｒ：０～０．０５質量％、Ｎｄ：０．０１～０．１５質量％、Ｓｍ：０～０．０５質量％、Ｃｏ：５～１５質量％、Ｍｎ：２～８質量％、Ａｌ：０～０．０５質量％、Ｆｅ：０質量％以上３．００質量％未満、Ｃｕ：０質量％以上３．００質量％未満、Ｐ：０質量％以上３．００質量％未満、Ｃ：０質量％以上３．００質量％未満を含み、残部はＮｉおよび不可避不純物からなることが好ましい。さらに本発明の実施形態に係る水素吸蔵合金は、下記式（１）および（２）を満たす。
４．５＜Ｂ／Ａ＜５．５ ・・・（１）
０．１０＜［Ｆｅ］＋［Ｃｕ］＋［Ｐ］＋［Ｃ］＜３．００ ・・・（２）
式（１）中のＡは、前記水素吸蔵合金中に含まれるＬａ、Ｃｅ、Ｐｒ、ＮｄおよびＳｍの合計モル数であり、Ｂは、前記水素吸蔵合金中に含まれるＮｉ、Ｃｏ、ＭｎおよびＡｌの合計モル数である。
式（２）中の［Ｆｅ］、［Ｃｕ］、［Ｐ］および［Ｃ］は、それぞれ、質量％で示したＦｅ、Ｃｕ、ＰおよびＣの含有量を示す。
上記合金により、従来技術に対して水素吸蔵量を大きく低下させることなく、コスト低減できる。また、複数回（例えば２５回）水素の吸蔵および放出を繰り返しても、粉化することなく、所定の水素吸蔵量を維持できる。さらに、従来技術と比較して同等の水素吸蔵速度を示すことができる。
Preferably, the hydrogen storage alloy according to the present invention contains 15 to 30 mass% La, 5 to 15 mass% Ce, 0 to 0.05 mass% Pr, 0.01 to 0.15 mass% Nd, 0 to 0.05 mass% Sm, 5 to 15 mass% Co, 2 to 8 mass% Mn, 0 to 0.05 mass% Al, 0 to less than 3.00 mass% Fe, 0 to less than 3.00 mass% Cu, 0 to less than 3.00 mass% P, and 0 to less than 3.00 mass% C, with the balance being Ni and inevitable impurities. Furthermore, the hydrogen storage alloy according to the present invention satisfies the following formulas (1) and (2):
4.5<B/A<5.5...(1)
0.10<[Fe]+[Cu]+[P]+[C]<3.00...(2)
In formula (1), A is the total number of moles of La, Ce, Pr, Nd, and Sm contained in the hydrogen storage alloy, and B is the total number of moles of Ni, Co, Mn, and Al contained in the hydrogen storage alloy.
In formula (2), [Fe], [Cu], [P] and [C] represent the contents of Fe, Cu, P and C, respectively, expressed in mass %.
The alloy can reduce costs without significantly reducing the hydrogen storage capacity compared to conventional technologies. It can also maintain a predetermined hydrogen storage capacity without pulverization even after repeated hydrogen storage and desorption (e.g., 25 times). Furthermore, it can exhibit a hydrogen storage rate equivalent to that of conventional technologies.
［Ｌａ：１５～３０質量％、Ｃｅ：５～１５質量％、Ｐｒ：０～０．０５質量％、Ｎｄ：０．０１～０．１５質量％、Ｓｍ：０～０．０５質量％］
ＬａＮｉ５系水素吸蔵合金において、Ｌａは、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍで所定量置換できる。本発明の実施形態において、Ｌａ以外にＣｅ、Ｐｒ、ＮｄおよびＳｍを上記範囲で含有させることができる。ＰｒおよびＳｍについては、含んでいても（すなわち０質量％超であっても）、含んでいなくても（すなわち０質量％であっても）よい。以上により、特定の不純物の影響を小さくできる。
[La: 15-30% by mass, Ce: 5-15% by mass, Pr: 0-0.05% by mass, Nd: 0.01-0.15% by mass, Sm: 0-0.05% by mass]
In the LaNi5 -based hydrogen storage alloy, La can be substituted with Ce, Pr, Nd, and Sm in predetermined amounts. In an embodiment of the present invention, in addition to La, Ce, Pr, Nd, and Sm can be contained within the above-mentioned ranges. Pr and Sm may be contained (i.e., greater than 0% by mass) or not (i.e., 0% by mass). This reduces the effects of specific impurities.
［Ｃｏ：５～１５質量％、Ｍｎ：２～８質量％、Ａｌ：０～０．０５質量％］
ＬａＮｉ５系水素吸蔵合金において、Ｎｉは、Ｃｏ、Ｍｎ、Ａｌで所定量置換できる。本発明の実施形態において、Ｎｉ以外にＣｏ、Ｍｎ、Ａｌを上記範囲で含有させることができる。Ａｌについては、含んでいても（すなわち０質量％超であっても）、含んでいなくても（すなわち０質量％であっても）よい。これにより、特定の不純物の影響を小さくできる。
[Co: 5 to 15% by mass, Mn: 2 to 8% by mass, Al: 0 to 0.05% by mass]
In the LaNi5 - based hydrogen storage alloy, Ni can be substituted with Co, Mn, or Al in a predetermined amount. In an embodiment of the present invention, Co, Mn, and Al can be contained in addition to Ni within the above ranges. Al may be contained (i.e., greater than 0% by mass) or not (i.e., 0% by mass). This can reduce the influence of specific impurities.
[Ｆｅ：０質量％以上３．００質量％未満]
Ｆｅは、リサイクル材を使用したとき等に混入し得る不純物であり得る。Ｆｅ含有量は好ましくは、０質量％超であり、より好ましくは０．０１質量％超であり、さらに好ましくは０．１０質量％超である。一方で、Ｆｅ含有量の上限は、式（２）を満たすように３．００質量％未満であり、２．００質量％以下または１．００質量％以下であってもよい。
[Fe: 0 mass% or more and less than 3.00 mass%]
Fe may be an impurity that may be mixed in when recycled materials are used, etc. The Fe content is preferably greater than 0 mass%, more preferably greater than 0.01 mass%, and even more preferably greater than 0.10 mass%. On the other hand, the upper limit of the Fe content may be less than 3.00 mass% so as to satisfy formula (2), and may be 2.00 mass% or less or 1.00 mass% or less.
[Ｃｕ：０質量％以上３．００質量％未満]
Ｃｕは、リサイクル材を使用したとき等に混入し得る不純物であり得る。Ｃｕ含有量は好ましくは、０質量％超であり、より好ましくは０．０１質量％超であり、さらに好ましくは０．１０質量％超である。一方で、Ｃｕ含有量の上限は、式（２）を満たすように３．００質量％未満であり、２．００質量％以下または１．００質量％以下であってもよい。
[Cu: 0 mass% or more and less than 3.00 mass%]
Cu may be an impurity that may be mixed in when recycled materials are used, etc. The Cu content is preferably greater than 0 mass%, more preferably greater than 0.01 mass%, and even more preferably greater than 0.10 mass%. On the other hand, the upper limit of the Cu content may be less than 3.00 mass%, or may be 2.00 mass% or less, or 1.00 mass% or less, so as to satisfy formula (2).
[Ｐ：０質量％以上３．００質量％未満]
Ｐは、リサイクル材を使用したとき等に混入し得る不純物であり得る。Ｐ含有量は好ましくは、０質量％超であり、より好ましくは０．０１質量％超であり、さらに好ましくは０．１０質量％超である。一方で、Ｐ含有量の上限は、式（２）を満たすように３．００質量％未満であり、２．００質量％以下または１．００質量％以下であってもよい。
[P: 0% by mass or more and less than 3.00% by mass]
P may be an impurity that may be mixed in when recycled materials are used, etc. The P content is preferably greater than 0 mass%, more preferably greater than 0.01 mass%, and even more preferably greater than 0.10 mass%. On the other hand, the upper limit of the P content may be less than 3.00 mass%, or may be 2.00 mass% or less, or 1.00 mass% or less, so as to satisfy formula (2).
[Ｃ：０質量％以上３．００質量％未満]
Ｃは、リサイクル材を使用したとき等に混入し得る不純物であり得る。Ｃ含有量は好ましくは、０質量％超であり、より好ましくは０．０１質量％超であり、さらに好ましくは０．１０質量％超である。一方で、Ｃ含有量の上限は、式（２）を満たすように３．００質量％未満であり、２．００質量％以下または１．００質量％以下であってもよい。
[C: 0% by mass or more and less than 3.00% by mass]
C may be an impurity that may be mixed in when recycled materials are used, etc. The C content is preferably greater than 0 mass%, more preferably greater than 0.01 mass%, and even more preferably greater than 0.10 mass%. On the other hand, the upper limit of the C content may be less than 3.00 mass%, or may be 2.00 mass% or less, or 1.00 mass% or less, so as to satisfy formula (2).
本発明の実施形態に係る水素吸蔵合金は、上記の成分組成を含み、本発明の１つの実施形態では、残部はニッケルおよび不可避不純物であることが好ましい。不可避不純物として、Ｓなど、原料、資材、製造設備等の状況によって持ち込まれる元素の混入が許容される。なお、例えば、Ｆｅ、Ｃｕ、ＰおよびＣのように、通常不可避不純物であり得るが、その組成範囲について上記のように別途規定している元素がある。このため、本明細書において、「不可避不純物」という場合は、別途その組成範囲が規定されている元素を除いた概念である。 The hydrogen storage alloy according to an embodiment of the present invention preferably contains the above-described component composition, with the balance being nickel and unavoidable impurities in one embodiment of the present invention. Affected impurities include elements such as S that are introduced depending on the conditions of raw materials, materials, manufacturing equipment, etc. Note that elements such as Fe, Cu, P, and C are typically considered unavoidable impurities, but their composition ranges are separately specified as above. Therefore, in this specification, the term "unavoidable impurities" excludes elements whose composition ranges are separately specified.
[４．５＜Ｂ／Ａ＜５．５ ・・・（１）]
本発明の実施形態に係る水素吸蔵合金は、従来技術に対して水素吸蔵特性を大きく低下させることなくコスト低減するための要件の１つとして、式（１）を満たす必要がある。Ｂ／Ａが４．５以下または５．５以上となると、水素吸蔵特性が大きく低下するおそれがある。
[4.5<B/A<5.5...(1)]
The hydrogen storage alloy according to the embodiment of the present invention must satisfy formula (1) as one of the requirements for reducing costs without significantly degrading the hydrogen storage characteristics compared to the prior art. If B/A is 4.5 or less or 5.5 or more, the hydrogen storage characteristics may be significantly degraded.
[０．１０＜［Ｆｅ］＋［Ｃｕ］＋［Ｐ］＋［Ｃ］＜３．００ ・・・（２）]
本発明の実施形態に係る水素吸蔵合金は、従来技術に対して水素吸蔵特性を大きく低下させることなくコスト低減するための要件の１つとして、式（２）を満たす必要がある。式（２）の下限値を満たすように、Ｆｅ、Ｃｕ、ＰおよびＣからなる群から選択されるいずれか１種以上の含有量が０．１０質量％超であり、例えば、Ｆｅ、Ｃｕ、ＰおよびＣからなる群から選択される１種単独、いずれか２種、いずれか３種、または４種全てを所定量含むことにより、式（２）の下限を満たしてもよい。例えば、ＦｅおよびＣｕのいずれか１種以上の含有量が０．１０質量％超であってもよい。式（２）の下限値を下回ると、例えばリサイクル材の使用がかなり制限されるため、従来技術と比較して実質的にコスト低減ができない。一方、式（２）の上限値を上回ると、水素吸蔵特性が大きく低下するおそれがある。
また、従来の水素吸蔵合金では水素吸蔵による膨張を繰り返すことで粉化してしまい、当該粉が、水素吸蔵合金を含む装置中のフィルターに詰まるという問題があった。本発明の実施形態に係る水素吸蔵合金は、式（２）を満たすことにより、水素吸蔵による膨張量が減少し、粉化が抑制され得る。
[0.10<[Fe]+[Cu]+[P]+[C]<3.00...(2)]
The hydrogen storage alloy according to the embodiment of the present invention must satisfy formula (2) as one of the requirements for reducing costs without significantly degrading hydrogen storage properties compared to conventional techniques. The content of one or more elements selected from the group consisting of Fe, Cu, P, and C is greater than 0.10 mass% so as to satisfy the lower limit of formula (2). For example, the lower limit of formula (2) may be satisfied by including a predetermined amount of one, two, three, or all four elements selected from the group consisting of Fe, Cu, P, and C. For example, the content of one or more elements of Fe and Cu may be greater than 0.10 mass%. Below the lower limit of formula (2), for example, the use of recycled materials is significantly limited, making it virtually impossible to achieve cost reductions compared to conventional techniques. On the other hand, above the upper limit of formula (2), hydrogen storage properties may be significantly degraded.
Furthermore, conventional hydrogen storage alloys suffer from the problem of being pulverized by repeated expansion due to hydrogen absorption, and the resulting powder clogs filters in devices containing the hydrogen storage alloy. By satisfying formula (2), the hydrogen storage alloy according to the embodiment of the present invention can reduce the amount of expansion due to hydrogen absorption and suppress pulverization.
Ｆｅ、Ｃｕ、ＰおよびＣのうち、特にＰおよびＣは、原子半径が比較的小さいため、原子半径が小さい水素を吸蔵する際に悪影響を及ぼし得る。さらに、Ｐ等は水素吸蔵合金の製造工程において除去することが困難であり得る。本発明の実施形態に係る水素吸蔵合金はＰおよび／またはＣを所定量含んでもよく、これにより従来技術に対するコスト低減効果が顕著となる。具体的には、本発明の実施形態は、下記式（３）を満たすことによりコスト低減効果が顕著となる。
［Ｐ］＋［Ｃ］≧０．１０ ・・・（３）
式（３）の下限値として０．１０質量％超であることがより好ましく、０．１２質量％超であることがさらに好ましく、０．１５質量％超であることがさらにより好ましい。なお、式（３）の上限値は、例えば式（２）を満たすように３．００質量％未満、２．００質量％以下または１．００質量％以下であってもよい。
Among Fe, Cu, P, and C, P and C in particular have relatively small atomic radii and may therefore have adverse effects when absorbing hydrogen, which has a small atomic radius. Furthermore, P and the like may be difficult to remove during the manufacturing process of the hydrogen storage alloy. The hydrogen storage alloy according to the embodiment of the present invention may contain a predetermined amount of P and/or C, which results in a significant cost reduction effect compared to conventional techniques. Specifically, the embodiment of the present invention achieves a significant cost reduction effect by satisfying the following formula (3):
[P]+[C]≧0.10...(3)
The lower limit of formula (3) is more preferably more than 0.10 mass%, even more preferably more than 0.12 mass%, and even more preferably more than 0.15 mass%. The upper limit of formula (3) may be, for example, less than 3.00 mass%, 2.00 mass% or less, or 1.00 mass% or less so as to satisfy formula (2).
本発明の実施形態に係る水素吸蔵合金は、上記のような化学成分組成を有していればよく、その製造方法も特に制限されず、公知の方法で製造することができる。本発明の実施形態に係る水素吸蔵合金の製造方法において、リサイクル材を含む原料を用いることが、コスト低減および地球環境保全の観点で好ましい。より好ましくは、リサイクル材として二次電池を含むことであり、さらに好ましくは、リサイクル材としてリチウムイオン電池を含むことである。これらの電池は、本発明の実施形態の構成元素であるＮｉ、Ｃｏ、ＭｎおよびＡｌ等を含み得ることに加え、Ｆｅ、Ｃｕ、ＰおよびＣを含み得る。例えばリチウムイオン電池において、正極材料にＮｉ、Ｃｏ、Ｍｎ、Ｆｅおよび／またはＰ、負極材料にＣ、正極集電体にＡｌ、負極集電体にＣｕ、電解質塩にＰが含まれ得る。従って、これらの電池のリサイクル材は、本発明の実施形態に係る製造方法に好適である。 The hydrogen storage alloy according to the embodiment of the present invention may have the above-described chemical composition. There are no particular limitations on its manufacturing method, and it can be manufactured by any known method. In the manufacturing method of the hydrogen storage alloy according to the embodiment of the present invention, it is preferable to use raw materials containing recycled materials, from the perspectives of cost reduction and global environmental conservation. It is more preferable that the recycled materials include secondary batteries, and even more preferable that the recycled materials include lithium-ion batteries. These batteries may contain Fe, Cu, P, and C in addition to the constituent elements of the embodiment of the present invention, such as Ni, Co, Mn, and Al. For example, in a lithium-ion battery, the positive electrode material may contain Ni, Co, Mn, Fe, and/or P, the negative electrode material may contain C, the positive electrode current collector may contain Al, the negative electrode current collector may contain Cu, and the electrolyte salt may contain P. Therefore, recycled materials from these batteries are suitable for the manufacturing method according to the embodiment of the present invention.
以下、実施例を挙げて本発明の実施形態をより具体的に説明する。本発明の実施形態は以下の実施例によって制限を受けるものではなく、前述および後述する趣旨に合致し得る範囲で、適宜変更を加えて実施することも可能であり、それらはいずれも本発明の実施形態の技術的範囲に包含される。 The following examples will explain the embodiments of the present invention in more detail. The embodiments of the present invention are not limited to the following examples, and may be implemented with appropriate modifications within the scope of the above-mentioned and below-mentioned aims, all of which are within the technical scope of the embodiments of the present invention.
リチウムイオン電池を焼却、破砕した後に、還元雰囲気でＣｏ、ＮｉおよびＭｎを金属化し、その後金属とスラグを分離して回収することにより、表１に示す成分組成のリサイクル合金を得た。表１に示すように、上記分離回収により、例えばＬｉ等は除去できるが、本発明の実施形態に係る特定の不純物（Ｆｅ、Ｃｕ、ＰおよびＣ）は完全に除去することはできず、リサイクル合金中にある程度残留していた。なお、表１において、「＜０．０１」は、該当の成分が含まれていないか、検出限界以下であったことを示す。 After incinerating and crushing lithium-ion batteries, Co, Ni, and Mn were metallized in a reducing atmosphere, and then the metals and slag were separated and recovered, yielding a recycled alloy with the composition shown in Table 1. As shown in Table 1, while the above separation and recovery process can remove elements such as Li, it cannot completely remove certain impurities (Fe, Cu, P, and C) according to an embodiment of the present invention, and some of these impurities remain in the recycled alloy. In Table 1, "<0.01" indicates that the corresponding element was not present or was below the detection limit.
所定の希土類元素（Ｌａ、Ｃｅ、Ｐｒ、ＮｄおよびＳｍ）および純金属（Ｎｉ、Ｃｏ、Ｍｎ）を、所定の割合で配合し、高周波誘導炉等一般的な炉を用いて溶製することにより、試験Ｎｏ．１の水素吸蔵合金を得た。
試験Ｎｏ．２～４の水素吸蔵合金については、純金属のそれぞれ約１０質量％、約１５質量％および約２０質量％をリサイクル合金に代える以外は、試験Ｎｏ．１と同様の方法で得た。具体的には、例えば試験Ｎｏ．２は、試験Ｎｏ．１の純金属（Ｎｉ：５４．３４質量部、Ｃｏ：９．４１質量部、Ｍｎ：４．４２質量部）の約１０質量％（Ｎｉ：約５．４３質量部、Ｃｏ：約０．９４質量部、Ｍｎ：約０．４４質量部）を、リサイクル合金約６．８１質量部に置き換えて作製した。試験Ｎｏ．１～４の成分組成を表２に示す。なお、表２において、「＜０．０１」は、該当の成分が含まれていないか、検出限界以下であったことを示す。「－」は、該当の成分が含まれていないか検出限界以下と考えられたために、分析していないことを示す。また、試験Ｎｏ．１のＬａ～Ｓｍの各含有量は、試験Ｎｏ．２～４のＬａ～Ｓｍの各含有量と同等であり、表２には、試験Ｎｏ．１のＬａ～Ｓｍにつき、それらの合計含有量のみ記載した。
Predetermined rare earth elements (La, Ce, Pr, Nd, and Sm) and pure metals (Ni, Co, and Mn) were blended in predetermined proportions and melted in a general furnace such as a high-frequency induction furnace to obtain a hydrogen storage alloy of Test No. 1.
The hydrogen storage alloys of Test Nos. 2 to 4 were obtained in the same manner as Test No. 1, except that approximately 10 mass%, approximately 15 mass%, and approximately 20 mass% of the pure metals were replaced with recycled alloys. Specifically, for example, Test No. 2 was prepared by replacing approximately 10 mass% (approximately 5.43 mass% Ni, approximately 0.94 mass% Co, and approximately 0.44 mass% Mn) of the pure metals of Test No. 1 (54.34 mass% Ni, 9.41 mass% Co, and 4.42 mass% Mn) with approximately 6.81 mass% recycled alloys. The component compositions of Test Nos. 1 to 4 are shown in Table 2. In Table 2, "<0.01" indicates that the corresponding component was not present or was below the detection limit. "-" indicates that the corresponding component was not analyzed because it was considered not present or below the detection limit. The contents of La to Sm in Test No. 1 were equivalent to the contents of La to Sm in Test Nos. 2 to 4, and Table 2 lists only the total contents of La to Sm in Test No. 1.
試験Ｎｏ．１～４の水素吸蔵合金に対して、以下の水素吸蔵特性評価を行った。
各合金１００ｇを容器内に封入し、ゲージ圧０．９ＭＰａＧ下、－１０℃にて、水素を１．５ＮＬ／分で導入することで各合金に水素を吸蔵させた後、ゲージ圧０．０ＭＰａＧ下、８０℃にて、各合金から水素を放出させる動作を１サイクルとし、これを２５サイクル繰り返した。
The hydrogen storage alloys of Test Nos. 1 to 4 were subjected to the following hydrogen storage characteristic evaluation.
100 g of each alloy was sealed in a container, and hydrogen was absorbed into each alloy by introducing hydrogen at a rate of 1.5 NL/min under a gauge pressure of 0.9 MPaG at −10°C. Hydrogen was then released from each alloy under a gauge pressure of 0.0 MPaG at 80°C. This cycle was repeated 25 times.
図１にサイクル数に対する水素吸蔵量評価結果を示す。従来技術に係る、不純物量が少ない試験Ｎｏ．１の水素吸蔵合金に対して、Ｆｅ、Ｃｕ、ＰおよびＣの合計不純物量が０．１０質量％超（３．００質量％未満）の試験Ｎｏ．２～４は、いずれも２０％以内の水素吸蔵量の低下に留まっており、水素吸蔵量が大きく低下しなかった。また、いずれの合金も、粉化することなく、１サイクル目と比較して、２～２５サイクル試験後であっても水素吸蔵量を維持できるがわかった。 Figure 1 shows the results of evaluating hydrogen storage capacity versus cycle number. Compared to Test No. 1, a hydrogen storage alloy with a low impurity content according to conventional technology, Tests Nos. 2 to 4, which contain a total impurity content of Fe, Cu, P, and C of more than 0.10 mass% (less than 3.00 mass%), showed a decrease in hydrogen storage capacity of less than 20%, meaning no significant decrease in hydrogen storage capacity. Furthermore, it was found that all alloys were able to maintain their hydrogen storage capacity after 2 to 25 cycles of testing without pulverizing, compared to the first cycle.
図２に、１サイクル目の水素吸蔵速度評価結果を示す。いずれの合金も、約５～１０分で水素吸蔵量がほぼ飽和しており、例えばＦｅ、Ｃｕ、ＰおよびＣの合計不純物量が０．１０質量％超（３．００質量％未満）であっても、水素吸蔵速度を維持できることがわかった。 Figure 2 shows the results of the hydrogen absorption rate evaluation for the first cycle. For all alloys, the amount of hydrogen absorbed was nearly saturated in approximately 5 to 10 minutes, and it was found that the hydrogen absorption rate could be maintained even when the total impurity content of Fe, Cu, P, and C was greater than 0.10 mass% (less than 3.00 mass%).
Claims (4)
Ｃｅ：５～１５質量％、
Ｐｒ：０～０．０５質量％、
Ｎｄ：０．０１～０．１５質量％、
Ｓｍ：０～０．０５質量％、
Ｃｏ：５～１５質量％、
Ｍｎ：２～８質量％、
Ａｌ：０～０．０５質量％、
Ｆｅ：０質量％以上３．００質量％未満、
Ｃｕ：０質量％以上３．００質量％未満、
Ｐ ：０質量％以上０．０９４質量％以下、
Ｃ ：０質量％以上０．４質量％以下、および
残部：Ｎｉおよび不可避不純物からなり、且つ下記式（１）、（２）及び（３）を満たす水素吸蔵合金。
４．５＜Ｂ／Ａ＜５．５ ・・・（１）
０．１０＜［Ｆｅ］＋［Ｃｕ］＋［Ｐ］＋［Ｃ］＜３．００ ・・・（２）
［Ｐ］＋［Ｃ］≧０．１ ・・・（３）
式（１）中のＡは、前記水素吸蔵合金中に含まれるＬａ、Ｃｅ、Ｐｒ、ＮｄおよびＳｍの合計モル数であり、Ｂは、前記水素吸蔵合金中に含まれるＮｉ、Ｃｏ、ＭｎおよびＡｌの合計モル数である。
式（２）中の［Ｆｅ］、［Ｃｕ］、［Ｐ］および［Ｃ］は、それぞれ、質量％で示したＦｅ、Ｃｕ、ＰおよびＣの含有量を示す。
式（３）中の［Ｐ］および［Ｃ］は、それぞれ、質量％で示したＰおよびＣの含有量を示す。 La: 15 to 30% by mass,
Ce: 5 to 15% by mass,
Pr: 0 to 0.05% by mass,
Nd: 0.01 to 0.15% by mass,
Sm: 0 to 0.05% by mass,
Co: 5 to 15% by mass,
Mn: 2 to 8% by mass,
Al: 0 to 0.05% by mass,
Fe: 0% by mass or more and less than 3.00% by mass,
Cu: 0% by mass or more and less than 3.00% by mass,
P: 0% by mass or more and 0.094 % by mass or less ,
A hydrogen storage alloy comprising: C: 0 mass % or more and 0.4 mass % or less ; and the balance: Ni and inevitable impurities, and satisfying the following formulas (1) , (2) , and (3) .
4.5<B/A<5.5...(1)
0.10<[Fe]+[Cu]+[P]+[C]<3.00...(2)
[P]+[C]≧0.1...(3)
In formula (1), A is the total number of moles of La, Ce, Pr, Nd, and Sm contained in the hydrogen storage alloy, and B is the total number of moles of Ni, Co, Mn, and Al contained in the hydrogen storage alloy.
In formula (2), [Fe], [Cu], [P] and [C] represent the contents of Fe, Cu, P and C, respectively, expressed in mass %.
In formula (3), [P] and [C] represent the P and C contents, respectively, expressed in mass %.
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