JP2015065184A - Si ALLOY POWDER FOR LITHIUM ION SECONDARY BATTERY NEGATIVE ELECTRODE, AND METHOD FOR MANUFACTURING THE SAME - Google Patents
Si ALLOY POWDER FOR LITHIUM ION SECONDARY BATTERY NEGATIVE ELECTRODE, AND METHOD FOR MANUFACTURING THE SAME Download PDFInfo
- Publication number
- JP2015065184A JP2015065184A JP2015002159A JP2015002159A JP2015065184A JP 2015065184 A JP2015065184 A JP 2015065184A JP 2015002159 A JP2015002159 A JP 2015002159A JP 2015002159 A JP2015002159 A JP 2015002159A JP 2015065184 A JP2015065184 A JP 2015065184A
- Authority
- JP
- Japan
- Prior art keywords
- phase
- alloy powder
- crsi
- negative electrode
- secondary battery
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
Description
本発明は、放電容量、サイクル寿命に優れる、微細組織を有するリチウムイオン二次電池負極用Ｓｉ合金粉末およびその製造方法に関するものである。 The present invention relates to a Si alloy powder for a lithium ion secondary battery negative electrode having a fine structure and excellent discharge capacity and cycle life, and a method for producing the same.
リチウム二次電池の負極活物質には従来より炭素材料からなる粉末が用いられているが、炭素材料は理論容量が３７２ｍＡｈ／ｇと低く、更なる高容量化には限界がある。これに対し、近年ではＳｎ、Ａｌ、Ｓｉなど炭素材料よりも理論容量の高い金属材料の適用が検討、実用化されている。特に、Ｓｉは４０００ｍＡｈ／ｇを超える理論容量があり、有望な材料である。これら炭素に変わる金属材料をリチウム二次電池の負極活物質として適用する際には、高容量は得られるものの、サイクル寿命が短いという課題がある。 Conventionally, a powder made of a carbon material has been used as a negative electrode active material of a lithium secondary battery. However, the theoretical capacity of the carbon material is as low as 372 mAh / g, and there is a limit to further increasing the capacity. On the other hand, in recent years, application of metal materials having higher theoretical capacity than carbon materials such as Sn, Al, and Si has been studied and put into practical use. In particular, Si has a theoretical capacity exceeding 4000 mAh / g and is a promising material. When a metal material that changes to carbon is used as a negative electrode active material of a lithium secondary battery, there is a problem that the cycle life is short although a high capacity is obtained.
この課題に対し、Ｓｉに種々の元素を添加し、純Ｓｉ粉末ではなくＳｉ合金粉末とし、微細組織を得ることで改善する方法が多く提案されている。例えば、特開２００１−２９７７５７号公報（特許文献１）では、共晶となる量、もしくはそれ以上の過共晶となる量のＣｏなどの元素を添加し、これを１００℃／ｓ以上の冷却速度で凝固させることによって、Ｓｉ相の短軸粒径が５μｍ以下となる合金粉末を得ている。このような微細Ｓｉ相を有するＳｉ合金粉末を用いることでサイクル寿命を改善している。すなわち、Ｌｉを吸蔵、放出しない珪化物を生成させることにより、微細なＳｉ相のＬｉ吸蔵、放出時の体積変化を抑制する効果を得ている。 In response to this problem, many methods have been proposed in which various elements are added to Si to form a Si alloy powder instead of pure Si powder to obtain a fine structure. For example, in Japanese Patent Application Laid-Open No. 2001-297757 (Patent Document 1), an element such as Co is added in an amount that becomes a eutectic or a hypereutectic amount higher than that, and this is cooled at 100 ° C./s or more. By solidifying at a speed, an alloy powder having a minor axis particle size of the Si phase of 5 μm or less is obtained. The cycle life is improved by using such an Si alloy powder having a fine Si phase. That is, by producing a silicide that does not occlude and release Li, an effect of suppressing volume change during Li occlusion and release of a fine Si phase is obtained.
しかしながら、実際に種々の添加元素によりＳｉ相と珪化物の共晶合金を作製すると、添加元素の種類により必ずしも微細な共晶組織は得られないことが分かった。例えば、図４は、Ｓｉ−ＦｅＳｉ2 系共晶合金の走査型電子顕微鏡写真による断面組織図で、図５は、Ｓｉ−ＶＳｉ2の共晶合金の光学顕微鏡写真によるミクロ組織図であり、この図に示す通り、共晶合金でも粗大な珪化物もしくはＳｉ相が生成してしまう課題がある。 However, it was found that when a eutectic alloy of Si phase and silicide was actually produced with various additive elements, a fine eutectic structure could not always be obtained depending on the kind of additive element. For example, FIG. 4 is a cross-sectional structure diagram of a Si—FeSi 2 eutectic alloy by a scanning electron micrograph, and FIG. 5 is a micro structure diagram of an optical micrograph of a Si—VSi 2 eutectic alloy. As shown in the figure, there is a problem that a coarse silicide or Si phase is generated even in an eutectic alloy.
そこで、発明者は種々の元素における共晶付近の組成について詳細に検討した結果、（１）微細組織が得られる条件を見出し、本発明に至った。また、その検討の過程で、単なるミクロ組織のサイズだけでなく、（２）珪化物の構造制御により、更に充放電特性に優れる条件を見出したものである。 Therefore, as a result of detailed studies on the composition around the eutectic in various elements, the inventor found (1) conditions for obtaining a fine structure and led to the present invention. In addition, in the course of the study, the present inventors have found not only a simple microstructure size but also (2) conditions for further excellent charge / discharge characteristics by controlling the structure of silicide.
その発明の要旨とするところは、
（１）Ｓｉ合金粉末において、ａｔ％で、ＣｒとＴｉを合計で１６〜２１％含み、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）が０．１５〜１．００の範囲とし、かつＳｉ相とＣｒＳｉ2 相からなる共晶組織を有し、該Ｓｉ相とＣｒＳｉ2 相の各相における薄い幅方向の厚みの平均値が４μｍ以下であることを特徴とするリチウムイオン二次電池負極用Ｓｉ合金粉末。
The gist of the invention is that
(1) The Si alloy powder contains at least 16 to 21% of Cr and Ti in a total of Cr% / (Cr% + Ti%) in the range of 0.15 to 1.00, and the Si phase and CrSi Si alloy powder for a negative electrode of a lithium ion secondary battery having a eutectic structure consisting of two phases, and an average value of the thickness in the thin width direction of each of the Si phase and CrSi 2 phase being 4 μm or less .
（２）Ｓｉ合金粉末において、ａｔ％で、Ｃｒ，Ｔｉ，ＡｌおよびＳｎを合計１６〜２１％含み、Ｃｒ％／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）が０．１５〜１．００、かつ（Ａｌ％＋Ｓｎ％）／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）が０．４０以下の範囲とし、かつＳｉ相とＣｒＳｉ2 相からなる共晶組織を有し、該Ｓｉ相とＣｒＳｉ2 相の各相における薄い幅方向の厚みの平均値が４μｍ以下であることを特徴とするリチウムイオン二次電池負極用Ｓｉ合金粉末。
（３）前記（１）または（２）に記載のＳｉ合金粉末の溶解原料を冷却速度１００℃／ｓ以上で急冷凝固させる工程を含むことを特徴とするリチウムイオン二次電池負極用Ｓｉ合金粉末の製造方法にある。
(2) In the Si alloy powder, at%, Cr, Ti, Al and Sn are included in a total of 16 to 21%, Cr% / (Cr% + Ti% + Al% + Sn%) is 0.15 to 1.00, and (Al% + Sn%) / (Cr% + Ti% + Al% + Sn%) is in a range of 0.40 or less, and has a eutectic structure comprising Si phase and CrSi 2 phases, of the Si phase and the CrSi 2 phases An Si alloy powder for a negative electrode of a lithium ion secondary battery, wherein an average value of thicknesses in the thin width direction in each phase is 4 µm or less.
(3) A Si alloy powder for a negative electrode of a lithium ion secondary battery, comprising a step of rapidly solidifying the melting raw material of the Si alloy powder according to (1) or (2) at a cooling rate of 100 ° C./s or more. It is in the manufacturing method.
以上述べたように、本発明は放電容量が高く、サイクル寿命に優れるリチウムイオン二
次電池負極活物質用Ｓｉ合金粉末およびその製造方法を提供できる極めて優れた効果を奏するものである。
As described above, the present invention has an excellent effect of providing a Si alloy powder for a negative electrode active material for a lithium ion secondary battery having a high discharge capacity and excellent cycle life, and a method for producing the same.
以下、本発明について詳細に説明する。
本発明における第１の特徴は、共晶合金を得るための添加元素としてＣｒを用いたことである。図１は、本発明に係るＳｉ−ＣｒＳｉ2の共晶合金の走査型電子顕微鏡写真による断面組織図で、黒い相がＳｉ相、白い相がＣｒＳｉ2相である。この図１に示す通り、Ｓｉ相およびＣｒＳｉ2相ともに極めて微細であり、平均の短軸幅は１μｍ以下である。なお、ＦｅやＶなどの他の元素と比較し、Ｃｒ添加が極端に微細な共晶組織となり、充放電特性にも優れる原因については、以下のことが推測される。
Hereinafter, the present invention will be described in detail.
The first feature of the present invention is that Cr is used as an additive element for obtaining a eutectic alloy. FIG. 1 is a cross-sectional structure diagram of a Si—CrSi 2 eutectic alloy according to the present invention, which is a scanning electron micrograph, wherein the black phase is the Si phase and the white phase is the CrSi 2 phase. As shown in FIG. 1, both the Si phase and the CrSi 2 phase are extremely fine, and the average minor axis width is 1 μm or less. In addition, compared with other elements, such as Fe and V, the following is estimated about the cause by which Cr addition becomes an extremely fine eutectic structure and is excellent also in a charge / discharge characteristic.
Ｓｉ相と珪化物の共晶を得るために必要な添加元素量は元素の種類により決まっており
、例えばＦｅの場合は２６．５％、Ｖの場合は３％の添加が必要である。なお、これらはいずれもＳｉと添加元素の状態図から読み取ることができる。ここで、共晶を得るためにＦｅのように比較的多くの添加量が必要な場合は必然的に珪化物の量が多くなり粗大化しやすく、Ｌｉを吸蔵、放出するＳｉ相の割合が低下し、高い放電容量が得られない。
The amount of added element necessary to obtain a eutectic of Si phase and silicide is determined by the kind of element. For example, 26.5% for Fe and 3% for V are necessary. These can be read from the phase diagrams of Si and additive elements. Here, when a relatively large amount of addition is required, such as Fe, in order to obtain a eutectic, the amount of silicide is inevitably large and is likely to be coarsened, and the proportion of the Si phase that occludes and releases Li decreases. However, a high discharge capacity cannot be obtained.
一方、Ｖのように極端に少ない添加量で共晶となる場合、共晶組織中の珪化物の割合が少なく、必然的にＳｉ相が粗大化しやすくなり、充放電時のＳｉ相の体積変化を抑制する珪化物の効果が得られない。一方、Ｃｒは共晶となる添加量がこれらの中間であり、Ｓｉ相および珪化物の両者が微細となると考えられる。したがって、Ｓｉ−ＣｒＳｉ2共晶合金は高い放電容量と優れたサイクル寿命を兼備することができる。 On the other hand, when it becomes eutectic with an extremely small addition amount like V, the proportion of silicide in the eutectic structure is small, and the Si phase tends to be coarsened, and the volume change of the Si phase during charge / discharge The effect of the silicide which suppresses is not acquired. On the other hand, Cr is added in the middle of the eutectic amount, and it is considered that both the Si phase and the silicide become fine. Therefore, the Si—CrSi 2 eutectic alloy can have a high discharge capacity and an excellent cycle life.
本発明における第２の特徴は、Ｃｒの一部をＴｉで置換することにより、さらに、充放
電特性を改善できることである。発明者は、Ｓｉ−ＣｒＳｉ2共晶合金において、ＣｒをＴｉに置換する検討を詳細に行なった結果、ＴｉはＣｒＳｉ2のＣｒに置換され、その結晶構造を変化させることなく格子定数を増加させると考えられた。
The second feature of the present invention is that charge / discharge characteristics can be further improved by replacing a part of Cr with Ti. As a result of detailed study of substituting Cr with Ti in the Si—CrSi 2 eutectic alloy, the inventor has replaced Ti with Cr in CrSi 2 and increases the lattice constant without changing the crystal structure. It was considered.
図２は、Ｃｒ／Ｔｉ比を変化させたＳｉ−ＣｒＳｉ2共晶合金のＸ線回折を示す図である。この図に示すように、Ｃｒの一部をＴｉに置換することにより、ＣｒＳｉ2は結晶構造を変化させることなく回折ピーク位置が低角度側にシフトしており、格子定数が増加しているものと考えられる。ここで、特許文献１には、珪化物中を通過するＬｉによる、珪化物の体積変化によっても内部応力が発生し、サイクル寿命劣化の一因となる可能性について言及されている。 FIG. 2 is a diagram showing X-ray diffraction of a Si—CrSi 2 eutectic alloy with a changed Cr / Ti ratio. As shown in this figure, by replacing a part of Cr with Ti, CrSi 2 has a diffraction peak position shifted to a lower angle without changing the crystal structure, and the lattice constant is increased. it is conceivable that. Here, Patent Document 1 mentions the possibility that internal stress is generated due to a change in the volume of the silicide due to Li passing through the silicide, which may contribute to cycle life deterioration.
本発明におけるＣｒへのＴｉ置換によるＣｒＳｉ2の格子定数増加は、この珪化物中のＬｉの通過をスムーズにし、これに伴う体積変化を軽減する役割を果たしている可能性が推測される。このように、Ｓｉと珪化物の共晶系合金をリチウムイオン電池負極活物質に利用する検討で、珪化物の構造にまで踏み込んだ研究はこれまでにほとんど見られない。 The increase in the lattice constant of CrSi 2 due to Ti substitution with Cr in the present invention is presumed to play a role of smoothing the passage of Li in the silicide and reducing the volume change associated therewith. Thus, in the study of utilizing a eutectic alloy of Si and silicide as a negative electrode active material for a lithium ion battery, there has been almost no research so far that has gone into the structure of silicide.
更に、Ｃｒの一部をＴｉへ置換する効果については、詳細な原因は不明であるが、次のような意外な利点も見出された。通常の共晶組成は、添加元素量が一点の特異的な組成であり、少しでも添加量が前後に振れると、亜共晶もしくは過共晶合金となり、著しく粗大な初晶が晶出してしまうため、厳密に共晶組織を得るためには、高い製造技術を要する。しかしながら、Ｃｒの一部をＴｉに置換した本発明合金では、ＣｒとＴｉの合計が約１６〜２１％程度の広い範囲で微細な組織が得られ、製造ロットにより多少は添加量が前後に振れても極端な組織変化がない。なお、図３は、ＣｒとＴｉの合計量を変化させたＳｉ−ＣｒＳｉ2 系共晶合金の走査型電子顕微鏡写真による断面組織図である。なお、図３（ａ）はＣｒとＴｉの合計量が１７％の場合であり、図３（ｂ）はＣｒとＴｉの合計量が１９％の場合である。 Furthermore, although the detailed cause is unknown about the effect which substitutes a part of Cr to Ti, the following unexpected advantages were also discovered. The normal eutectic composition is a unique composition with a single additive element amount. If the added amount fluctuates back and forth, it becomes a hypoeutectic or hypereutectic alloy, and an extremely coarse primary crystal is crystallized. Therefore, a high production technique is required to obtain a eutectic structure strictly. However, in the alloy of the present invention in which a part of Cr is replaced with Ti, a fine structure is obtained in a wide range where the total of Cr and Ti is about 16 to 21%, and the added amount fluctuates back and forth depending on the production lot. But there is no extreme organizational change. FIG. 3 is a cross-sectional structure diagram of a scanning electron micrograph of a Si—CrSi 2 -based eutectic alloy in which the total amount of Cr and Ti is changed. FIG. 3A shows a case where the total amount of Cr and Ti is 17%, and FIG. 3B shows a case where the total amount of Cr and Ti is 19%.
本発明における第３の特徴は、Ｃｒおよび／もしくはＴｉの一部をＡｌおよび／もしくはＳｎに置換できることである。Ａｌについては、ＣｒＳｉ2のＳｉに置換するものと考えられ、Ｔｉと同様にＣｒＳｉ2の格子定数を増加させるものと推測される。したがって、ＴｉによるＣｒＳｉ2の格子定数増加と概ね同様の効果が得られる。 The third feature of the present invention is that a part of Cr and / or Ti can be substituted with Al and / or Sn. Al is considered to be replaced by Si in CrSi 2 , and it is assumed that the lattice constant of CrSi 2 is increased in the same manner as Ti. Therefore, the same effect as the increase in the lattice constant of CrSi 2 by Ti can be obtained.
また、Ａｌ添加の場合は一部がＡｌ相としても残存することがＸ線回折で確認された。このＡｌ相はＳｉ相やＣｒＳｉ2相より延性があることから、充放電に伴う体積変化による粒子の崩壊を緩和する効果も得られると推測される。Ｓｎについては、合金中に主に単体で存在し、この相もＡｌ相と同様にＳｉ相やＣｒＳｉ2相より延性があることから、充放電に伴う体積変化による粒子の崩壊を緩和する効果が得られると推測される。 Further, in the case of Al addition, it was confirmed by X-ray diffraction that a part remained even as an Al phase. Since this Al phase is more ductile than the Si phase or CrSi 2 phase, it is presumed that the effect of alleviating the particle collapse due to the volume change accompanying charge / discharge can be obtained. Sn is mainly present alone in the alloy, and this phase is also more ductile than the Si phase or CrSi 2 phase, like the Al phase. Presumed to be obtained.
以下、本発明に係る条件を定めた理由について説明する。
４μｍ以下の薄い幅方向の厚みの平均値を有するＳｉ相およびＣｒＳｉ2相とした理由は、本発明合金においてＳｉ相はＬｉを吸蔵、放出し、充放電に寄与する相であり、ＣｒＳｉ2相は充放電時の体積変化を抑制し、サイクル寿命を改善する相である。これらの相は本発明における共晶合金の場合、図１に示すような複雑な微細混合組織として晶出する。この組織において、両相の薄い幅方向の厚みの平均が４μｍを超えるとサイクル寿命が劣化する。好ましくは１μｍ以下、より好ましくは５００ｎｍ以下である。
Hereinafter, the reason for determining the conditions according to the present invention will be described.
The reason why the Si phase and the CrSi 2 phase have an average thickness in the width direction of 4 μm or less is that the Si phase occludes and releases Li in the alloy of the present invention and contributes to charge and discharge, and the CrSi 2 phase Is a phase that suppresses volume changes during charge and discharge and improves cycle life. In the case of the eutectic alloy in the present invention, these phases are crystallized as a complicated fine mixed structure as shown in FIG. In this structure, when the average thickness in the thin width direction of both phases exceeds 4 μm, the cycle life is deteriorated. Preferably it is 1 micrometer or less, More preferably, it is 500 nm or less.
なお、本発明におけるＳｉ相はＳｉを主体としたＤｉａｍｏｎｄ構造の相であり、Ｌｉを吸蔵、放出する相である。したがって、Ｓｉ以外の添加元素を固溶したものも含む。また、本発明におけるＣｒＳｉ2相は六方晶型（Ｈｅｘａｇｏｎａｌ）の構造を持ち、空間群がＰ６2２２に属するものであり、充放電時のＳｉ相の体積変化を抑制する相である。したがって、その一部がＣｒ、Ｓｉ以外の添加元素と置換されたものを含む。 The Si phase in the present invention is a phase having a diamond structure mainly composed of Si, and is a phase that occludes and releases Li. Accordingly, a solution in which an additive element other than Si is dissolved is included. Further, CrSi 2 phase in the present invention has a structure of hexagonal (Hexagonal), it is those space group belongs to P6 2 22, which suppresses phase volume change of the Si phase during charging and discharging. Therefore, some of them are substituted with additive elements other than Cr and Si.
ＣｒとＴｉを合計１６〜２１％含み、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）が０．１５〜１．００の範囲とした理由は、本発明合金においてＣｒはＳｉ相と微細共晶組織を形成するＣｒＳｉ2を生成する必須元素であり、ＴｉはＣｒに置換しＣｒＳｉ2の格子定数を増加させる有効な元素である。その合計量が１６％未満では亜共晶組織となり粗大な初晶Ｓｉ相を晶出し、２１％を超えると過共晶組織となり粗大なＣｒＳｉ2を晶出し、いずれもサイクル寿命を劣化させる。また、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）が０．１５未満ではＣｒＳｉ2相のほかにＴｉＳｉ2相が生成するとともに、Ｓｉ相を粗大化させサイクル寿命を劣化させる。ＣｒとＴｉの合計において、好ましい範囲は１７〜２０、より好ましくは１８〜１９である。また、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）の好ましい範囲は０．１５〜０．９０、より好ましくは０．２０〜０．８０である。 The reason why Cr and Ti are 16 to 21% in total and Cr% / (Cr% + Ti%) is in the range of 0.15 to 1.00 is that Cr forms a fine eutectic structure with the Si phase in the alloy of the present invention. It is an essential element that produces CrSi 2 , and Ti is an effective element that substitutes Cr and increases the lattice constant of CrSi 2 . If the total amount is less than 16%, a hypoeutectic structure is formed and a coarse primary Si phase is crystallized. If it exceeds 21%, a hypereutectic structure is formed and coarse CrSi 2 is crystallized, both of which deteriorate cycle life. If Cr% / (Cr% + Ti%) is less than 0.15, a TiSi 2 phase is generated in addition to the CrSi 2 phase, and the Si phase is coarsened to deteriorate the cycle life. In the total of Cr and Ti, the preferred range is 17-20, more preferably 18-19. Moreover, the preferable range of Cr% / (Cr% + Ti%) is 0.15-0.90, More preferably, it is 0.20-0.80.
Ｃｒ，Ｔｉ，ＡｌおよびＳｎを合計１６〜２１％含み、Ｃｒ％／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）が０．１５〜１．００、かつ（Ａｌ％＋Ｓｎ％）／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）が０．４０以下の範囲とした理由は、本発明合金においてＡｌはＴｉと同様にＣｒＳｉ2の格子定数を増加させると考えられる有効な元素であり、Ａｌ相も生成することから充放電時の体積変化による粒子の崩壊を抑制できるため、ＣｒもしくはＴｉと置換することができる。更に、ＳｎはＳｎ相を生成することから充放電時の体積変化による粒子の崩壊を抑制できるため、ＣｒもしくはＴｉと置換することができる。 Cr, Ti, Al and Sn are included in total 16 to 21%, Cr% / (Cr% + Ti% + Al% + Sn%) is 0.15-1.00, and (Al% + Sn%) / (Cr% + Ti%) + Al% + Sn%) is set to a range of 0.40 or less. In the alloy of the present invention, Al is an effective element that is considered to increase the lattice constant of CrSi 2 in the same manner as Ti, and an Al phase is also generated. From the above, it is possible to suppress the collapse of the particles due to the volume change at the time of charging / discharging, so that it can be replaced with Cr or Ti. Furthermore, since Sn generates a Sn phase, particle collapse due to a volume change during charge / discharge can be suppressed, so that it can be replaced with Cr or Ti.
ただし、Ｃｒ％／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）が０．１５未満では、ＣｒＳｉ2相のほかに，ＴｉＳｉ2相が生成するとともに、Ｓｉ相を粗大化させサイクル寿命を劣化させる。また、（Ａｌ％＋Ｓｎ％）／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）が０．４０を超えると微細組織が得られず、サイクル寿命が劣化する。Ｃｒ％／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）の好ましい範囲は０．１５〜０．９０、より好ましくは０．２０〜０．８０である。（Ａｌ％＋Ｓｎ％）／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）の好ましい範囲は、０．０３〜０．３０、より好ましくは０．０５〜０．２５である。 However, when Cr% / (Cr% + Ti% + Al% + Sn%) is less than 0.15, a TiSi 2 phase is generated in addition to the CrSi 2 phase, and the Si phase is coarsened to deteriorate the cycle life. On the other hand, if (Al% + Sn%) / (Cr% + Ti% + Al% + Sn%) exceeds 0.40, a fine structure cannot be obtained and the cycle life is deteriorated. A preferable range of Cr% / (Cr% + Ti% + Al% + Sn%) is 0.15 to 0.90, and more preferably 0.20 to 0.80. A preferable range of (Al% + Sn%) / (Cr% + Ti% + Al% + Sn%) is 0.03 to 0.30, and more preferably 0.05 to 0.25.
冷却速度１００℃／ｓ以上の凝固とした理由は、本発明合金はＳｉ−ＣｒＳｉ2系の共晶合金である。共晶合金のミクロ組織サイズは、一般に冷却速度により影響を受ける。したがって、１００℃／ｓ以上の冷却速度で凝固する方法として、ガスアトマイズ法、単ロール法などがあるが、本発明合金の製造工程において、好ましい工程はガスアトマイズ法による作製である。 The reason for the solidification at a cooling rate of 100 ° C./s or more is that the alloy of the present invention is a Si—CrSi 2 -based eutectic alloy. The microstructure size of eutectic alloys is generally affected by the cooling rate. Therefore, as a method of solidifying at a cooling rate of 100 ° C./s or more, there are a gas atomizing method, a single roll method, etc., but in the production process of the alloy of the present invention, a preferable step is production by a gas atomizing method.
以下、本発明について実施例によって具体的に説明する。
表１に示す組成のＳｉ系合金粉末をガスアトマイズ装置にて作製した。溶解量１０００ｇの母材をアルミナ性耐火坩堝中で、Ａｒ雰囲気にて誘導溶解し、坩堝下部の細孔ノズルより溶湯を出湯した。出湯直後に噴霧ガスによりアトマイズした。得られた粉末を６３μｍ以下に分級し、各相の薄い幅方向の厚みの平均値および充放電特性を以下の方法で評価した。
Hereinafter, the present invention will be specifically described with reference to examples.
Si-based alloy powders having the compositions shown in Table 1 were produced with a gas atomizer. A base material having a dissolution amount of 1000 g was induction-dissolved in an Ar-based refractory crucible in an Ar atmosphere, and the molten metal was discharged from a pore nozzle at the bottom of the crucible. Immediately after the hot water was atomized with spray gas. The obtained powder was classified to 63 μm or less, and the average thickness and charge / discharge characteristics of each phase in the thin width direction were evaluated by the following methods.
各相の薄い幅方向の厚みの平均値については、供試粉末を樹脂埋め研磨し、その断面において、直径が４０μｍ以上の粉末をＳＥＭのＣｏｍｐｏ像にて４０００倍で無作為に５個撮影した。この写真１枚から無作為に５つのＳｉとＣｒＳｉ2の薄い幅方向の厚みを読取り、合計２５の読取値の平均をＳｉとＣｒＳｉ2 の薄い幅方向の厚みの平均値（これを平均短軸幅と記す）とした。なお本粉末は、図１に示す通り複雑な混合組織となっているが、図１中の矢印で示すように、各相における薄い幅方向の厚みを短軸幅としている。 About the average value of the thickness of each phase in the thin width direction, the test powder was resin-filled and polished, and in the cross section, five powders having a diameter of 40 μm or more were randomly photographed at 4000 times with a SEM Compo image. . Randomly read the thickness of 5 Si and CrSi 2 in the thin width direction from this photo, and average the total of 25 readings in the thin width direction of Si and CrSi 2 (this is the average minor axis) Width). The present powder has a complex mixed structure as shown in FIG. 1, but as indicated by arrows in FIG. 1, the thickness in the thin width direction of each phase is the short axis width.
また、粉末の断面写真では、各相の形状は紡錘状や棒状の粒もあれば不規則形状の粒状も多く含む。紡錘状や棒状の粒であれば「各相における薄い幅方向の厚み」の測定は簡単である。しかし、不規則形状の粒状では容易ではない。そこで、これらの不規則形状の粒状については、各粒を長径と短径がほぼ近似する楕円に見立て、そのときの短径に相当する長さを「各相における薄い幅方向の厚み」として評価することにした。 Moreover, in the cross-sectional photograph of the powder, the shape of each phase includes many spindle-shaped and rod-shaped grains and many irregular-shaped grains. In the case of spindle-shaped or rod-shaped grains, measurement of “thickness in the thin width direction in each phase” is easy. However, it is not easy with irregularly shaped particles. Therefore, regarding these irregularly shaped grains, each grain is regarded as an ellipse whose major axis and minor axis are approximately approximate, and the length corresponding to the minor axis at that time is evaluated as “thickness in the thin width direction in each phase”. Decided to do.
なお、図１で白色に写ったＣｒＳｉ2 相では、所々に、２個以上の紡錘状の結合しているように見える粒が存在する。これらについては個々の粒に分離した状態を仮想して短径相当部の幅を測定し評価した。また、図１で黒色に写ったＳｉ相については、黒色のため２個以上の層が連続して見えるところがあるが、その部位については、便宜上測定の対象外とした。 In the CrSi 2 phase shown in white in FIG. 1, there are two or more spindle-like grains that appear to be combined. About these, the width | variety of a minor axis equivalent part was measured and evaluated imagining the state isolate | separated into each grain. In addition, the Si phase shown in black in FIG. 1 is black and there are places where two or more layers can be seen continuously.
充放電特性については、供試粉末に、ポリフッ化ビニリデン（結着材）を１０ｍａｓｓ％、Ｎ−メチルピロリドン（溶媒）１０ｍａｓｓ％、アセチレンブラック（導電材）を１０ｍａｓｓ％添加し、これを乳鉢で混ぜ合わせスラリー状とした。このスラリーを銅箔（集電体）に塗布し、乾燥させた後、ハンドプレス機にてプレスした。更に、これを直径１０ｍｍに打ち抜いて負極とした。 For charge / discharge characteristics, 10% by mass of polyvinylidene fluoride (binder), 10% by mass of N-methylpyrrolidone (solvent), and 10% by mass of acetylene black (conductive material) are added to the test powder and mixed in a mortar. A combined slurry was obtained. This slurry was applied to a copper foil (current collector), dried, and then pressed with a hand press. Further, this was punched out to a diameter of 10 mm to obtain a negative electrode.
この負極と対極、参照極に金属Ｌｉ箔を用いたコイン型セルにて充放電特性を評価した。電解液はエチレンカーボネートにジメトキシエタンを同量混合したものを用い、電解質としてＬｉＰＦ6を１モル濃度添加した。充電は１／１０Ｃの電流値で０Ｖ（対参照極）まで行い、その後１／１０Ｃで２Ｖ（対参照極）まで放電した。これを１サイクルとし、５０サイクル繰り返した。放電容量として、１サイクル目の放電容量を評価し、寿命特性として５０サイクル目の放電容量を１サイクル目の放電容量で割り、１００（％）をかけた放電容量の維持率で評価した。 The charge / discharge characteristics were evaluated in a coin-type cell using a metal Li foil as the negative electrode, the counter electrode, and the reference electrode. The electrolytic solution was a mixture of ethylene carbonate and dimethoxyethane in the same amount, and LiPF 6 was added at a molar concentration of 1 as the electrolyte. Charging was performed at a current value of 1/10 C up to 0 V (vs. reference electrode), and then discharged to 1 V at 2 V (vs. reference electrode). This was defined as one cycle and repeated 50 cycles. As the discharge capacity, the discharge capacity at the first cycle was evaluated, and as the life characteristics, the discharge capacity at the 50th cycle was divided by the discharge capacity at the first cycle, and the maintenance rate of the discharge capacity multiplied by 100 (%) was evaluated.
表１に示す比較例Ｎｏ．１３は、Ｃｒ，Ｔｉの合計量が少なく、かつＳｉ平均短軸幅が大きいために、容量維持率が劣る。比較例Ｎｏ．１４は、Ｃｒ，Ｔｉの合計量が多く、かつＣｒＳｉ2 平均短軸幅が大きいために、容量維持率が低い。比較例Ｎｏ．１５は、Ｃｒ％（Ｃｒ％＋Ｔｉ％）の比が小さく、かつＳｉ平均短軸幅が大きいために、容量維持率が低い。比較例Ｎｏ．１６は、Ｃｒ，Ｔｉ，ＡｌとＳｎの合計量が少なく、かつＳｉ平均短軸幅が大きいために、容量維持率が劣る。 Comparative Example No. 1 shown in Table 1 No. 13 is inferior in capacity retention because the total amount of Cr and Ti is small and the Si average minor axis width is large. Comparative Example No. No. 14 has a low capacity retention rate because the total amount of Cr and Ti is large and the CrSi 2 average minor axis width is large. Comparative Example No. No. 15 has a low capacity maintenance ratio because the ratio of Cr% (Cr% + Ti%) is small and the Si average minor axis width is large. Comparative Example No. No. 16 is inferior in capacity retention because the total amount of Cr, Ti, Al and Sn is small and the Si average minor axis width is large.
比較例Ｎｏ．１７は、Ｃｒ，Ｔｉ，ＡｌとＳｎの合計量が多く、かつＣｒＳｉ2 平均短軸幅が大きいために、容量維持率が低い。比較例Ｎｏ．１８は、Ｃｒ％／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）の比が小さく、かつＳｉ平均短軸幅が大きいために、容量維持率が低い。比較例Ｎｏ．１９は、Ｃｒ％／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）の比が小さく、かつ（Ａｌ％＋Ｓｎ％）／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）の比が大きく、Ｓｉ平均短軸幅が大きいために、容量維持率が低い。 Comparative Example No. 17 has a large total amount of Cr, Ti, Al and Sn and a large average minor axis width of CrSi 2, so that the capacity retention rate is low. Comparative Example No. No. 18 has a low capacity retention ratio because the ratio of Cr% / (Cr% + Ti% + Al% + Sn%) is small and the Si average minor axis width is large. Comparative Example No. 19 has a small ratio of Cr% / (Cr% + Ti% + Al% + Sn%) and a large ratio of (Al% + Sn%) / (Cr% + Ti% + Al% + Sn%), and the Si average minor axis width is Since it is large, the capacity maintenance rate is low.
これに対して、本発明例Ｎｏ．１〜４、Ｎｏ．７〜９は、Ｃｒ，Ｔｉの合計量およびＣｒ％／（Ｃｒ％＋Ｔｉ％）の比率条件を満たしている。また、本発明例Ｎｏ．５〜６は、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）の比率条件およびＳｉ平均短軸幅、ならびにＣｒＳｉ2 平均短軸幅の条件を満たしている。また、本発明例Ｎｏ．１０〜１２は、Ｃｒ，Ｔｉ，ＡｌおよびＳｎの合計量およびＣｒ％／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）、ならびに（Ａｌ％＋Ｓｎ％）／（Ｃｒ％＋Ｔｉ％＋Ａｌ％＋Ｓｎ％）の比率条件を満たしていることから、いずれも放電容量と容量維持率の高い値を示していることが分かる。 On the other hand, the present invention example No. 1-4, no. 7 to 9 satisfy the total amount of Cr and Ti and the ratio condition of Cr% / (Cr% + Ti%). In addition, Invention Example No. 5-6 meets the Cr% / (Cr% + Ti %) in ratio conditions and Si average minor axis width, and CrSi 2 average minor axis width condition. In addition, Invention Example No. 10 to 12 are the total amount of Cr, Ti, Al and Sn and the ratio of Cr% / (Cr% + Ti% + Al% + Sn%) and (Al% + Sn%) / (Cr% + Ti% + Al% + Sn%) Since the conditions are satisfied, it can be seen that both show high values of discharge capacity and capacity retention rate.
以上のように、本発明によるＳｉ相とＣｒＳｉ2 相からなる共晶組織は、極めて微細で、かつ４μｍ以下の薄い幅方向の厚みの平均値を有し、高い放電容量と優れたサイクル寿命を兼備すると共に、Ｃｒの１部をＴｉで置換することにより、充電特性をさらに改善することが出来る。さらに加えて、Ａｌ，Ｓｎとも置換して、充放電に伴う体積変化による粒子の崩壊を緩和し、サイクル寿命を延長することが出来る等極めて優れた効果を有するものである。
特許出願人 山陽特殊製鋼株式会社
代理人 弁理士 椎 名 彊
As described above, the eutectic structure composed of the Si phase and the CrSi 2 phase according to the present invention is extremely fine and has an average value of the thickness in the thin width direction of 4 μm or less, and has a high discharge capacity and an excellent cycle life. In addition, the charging characteristics can be further improved by substituting a part of Cr with Ti. In addition, Al and Sn are both substituted to relieve particle collapse due to volume changes accompanying charging and discharging, and have extremely excellent effects such as extending the cycle life.
Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015002159A JP5913645B2 (en) | 2015-01-08 | 2015-01-08 | Si alloy powder for negative electrode of lithium ion secondary battery and manufacturing method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015002159A JP5913645B2 (en) | 2015-01-08 | 2015-01-08 | Si alloy powder for negative electrode of lithium ion secondary battery and manufacturing method thereof |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2011006910A Division JP5766445B2 (en) | 2011-01-17 | 2011-01-17 | Si alloy powder for negative electrode of lithium ion secondary battery and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2015065184A true JP2015065184A (en) | 2015-04-09 |
| JP5913645B2 JP5913645B2 (en) | 2016-04-27 |
Family
ID=52832868
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2015002159A Active JP5913645B2 (en) | 2015-01-08 | 2015-01-08 | Si alloy powder for negative electrode of lithium ion secondary battery and manufacturing method thereof |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP5913645B2 (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001297757A (en) * | 2000-04-14 | 2001-10-26 | Sumitomo Metal Ind Ltd | Negative electrode material for nonaqueous electrolyte secondary cell and its manufacturing method |
-
2015
- 2015-01-08 JP JP2015002159A patent/JP5913645B2/en active Active
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001297757A (en) * | 2000-04-14 | 2001-10-26 | Sumitomo Metal Ind Ltd | Negative electrode material for nonaqueous electrolyte secondary cell and its manufacturing method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP5913645B2 (en) | 2016-04-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP5766445B2 (en) | Si alloy powder for negative electrode of lithium ion secondary battery and manufacturing method thereof | |
| JP6322362B2 (en) | Si alloy negative electrode material | |
| TWI639268B (en) | Si-based alloy for negative electrode material of power storage device, negative electrode of power storage device, power storage device, and method for manufacturing negative electrode material of power storage device | |
| JP5696863B2 (en) | Si negative electrode material | |
| JP6371504B2 (en) | Si-based alloy negative electrode material for power storage device and electrode using the same | |
| JP6808988B2 (en) | Negative electrode active material for lithium-ion batteries and lithium-ion batteries | |
| JPWO2009060666A1 (en) | Nickel metal hydride storage battery and method for producing hydrogen storage alloy | |
| JP2016062660A (en) | Silicon-based alloy negative electrode material for power storage device, and electrode arranged by use thereof | |
| KR101356988B1 (en) | Negative active material and rechargeable lithium battery comprising same | |
| JP2017168362A (en) | Negative electrode for alkali storage battery, method for manufacturing the same, and alkali storage battery | |
| KR102165659B1 (en) | Si-ALLOY POWDER FOR LITHIUM-ION SECONDARY BATTERY NEGATIVE ELECTRODE ACTIVE MATERIAL AND METHOD FOR MANUFACTURING SAME | |
| JP5913645B2 (en) | Si alloy powder for negative electrode of lithium ion secondary battery and manufacturing method thereof | |
| JP6726798B2 (en) | Negative electrode for alkaline storage battery, manufacturing method thereof, and alkaline storage battery | |
| US20160315318A1 (en) | Negative active material for lithium secondary battery | |
| JP5594731B2 (en) | Sn alloy powder for negative electrode of lithium ion battery and method for producing the same | |
| JP5769578B2 (en) | Method for producing negative electrode active material for lithium secondary battery | |
| JP7146710B2 (en) | Negative electrode for alkaline storage battery, manufacturing method thereof, and alkaline storage battery | |
| JP6045879B2 (en) | Sn alloy powder used as a raw material of the negative electrode active material of a lithium ion secondary battery, and its manufacturing method. | |
| JP2007056309A (en) | Hydrogen storage alloy, its manufacturing method and nickel hydrogen secondary battery | |
| JP2002146458A (en) | Low-cost rare earth-based hydrogen storage alloy and its use | |
| JPH03254064A (en) | Battery with organic electrolytic solution |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20150109 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20151009 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20151110 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20151117 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20160329 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20160401 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 5913645 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |