JP5146652B2 - Alloy negative electrode for lithium ion secondary battery, method for producing the same, and lithium ion secondary battery using the same - Google Patents
Alloy negative electrode for lithium ion secondary battery, method for producing the same, and lithium ion secondary battery using the same Download PDFInfo
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims description 42
- 229910001416 lithium ion Inorganic materials 0.000 title claims description 42
- 229910045601 alloy Inorganic materials 0.000 title claims description 38
- 239000000956 alloy Substances 0.000 title claims description 38
- 238000004519 manufacturing process Methods 0.000 title claims description 21
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims description 73
- 229910052707 ruthenium Inorganic materials 0.000 claims description 72
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 69
- 239000011863 silicon-based powder Substances 0.000 claims description 39
- 229910052710 silicon Inorganic materials 0.000 claims description 30
- 239000010703 silicon Substances 0.000 claims description 30
- 229910052744 lithium Inorganic materials 0.000 claims description 28
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 27
- 239000007789 gas Substances 0.000 claims description 20
- 238000000151 deposition Methods 0.000 claims description 17
- 239000007773 negative electrode material Substances 0.000 claims description 16
- 238000007772 electroless plating Methods 0.000 claims description 10
- 239000000758 substrate Substances 0.000 claims description 9
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 claims description 5
- 239000012159 carrier gas Substances 0.000 claims description 4
- 239000003638 chemical reducing agent Substances 0.000 claims description 4
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 3
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- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
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- SWAIALBIBWIKKQ-UHFFFAOYSA-N lithium titanium Chemical compound [Li].[Ti] SWAIALBIBWIKKQ-UHFFFAOYSA-N 0.000 description 2
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- 229910011458 Li4/3 Ti5/3O4 Inorganic materials 0.000 description 1
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- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
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- KLARSDUHONHPRF-UHFFFAOYSA-N [Li].[Mn] Chemical compound [Li].[Mn] KLARSDUHONHPRF-UHFFFAOYSA-N 0.000 description 1
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- MTAZNLWOLGHBHU-UHFFFAOYSA-N butadiene-styrene rubber Chemical compound C=CC=C.C=CC1=CC=CC=C1 MTAZNLWOLGHBHU-UHFFFAOYSA-N 0.000 description 1
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- CKFRRHLHAJZIIN-UHFFFAOYSA-N cobalt lithium Chemical compound [Li].[Co] CKFRRHLHAJZIIN-UHFFFAOYSA-N 0.000 description 1
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- SMBQBQBNOXIFSF-UHFFFAOYSA-N dilithium Chemical class [Li][Li] SMBQBQBNOXIFSF-UHFFFAOYSA-N 0.000 description 1
- KFIKNZBXPKXFTA-UHFFFAOYSA-N dipotassium;dioxido(dioxo)ruthenium Chemical compound [K+].[K+].[O-][Ru]([O-])(=O)=O KFIKNZBXPKXFTA-UHFFFAOYSA-N 0.000 description 1
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- 229910052742 iron Inorganic materials 0.000 description 1
- 150000002641 lithium Chemical class 0.000 description 1
- RSNHXDVSISOZOB-UHFFFAOYSA-N lithium nickel Chemical compound [Li].[Ni] RSNHXDVSISOZOB-UHFFFAOYSA-N 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
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- 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
Description
本発明は、リチウムイオン二次電池用合金負極、その製造方法及びそれを用いたリチウムイオン二次電池に関し、さらに詳しくは、リチウム二次電池負極として用いた際に、充放電容量が高く、かつ充放電サイクル特性に優れたリチウム二次電池とすることができる、新規なリチウム電池用合金負極と、その工業上効率的な製造方法と、これを用いた高性能のリチウム二次電池に関する。 The present invention relates to an alloy negative electrode for a lithium ion secondary battery, a method for producing the same, and a lithium ion secondary battery using the same, and more specifically, when used as a lithium secondary battery negative electrode, The present invention relates to a novel alloy negative electrode for a lithium battery that can be a lithium secondary battery having excellent charge / discharge cycle characteristics, an industrially efficient production method thereof, and a high-performance lithium secondary battery using the same.
近年、リチウム二次電池は、電子機器の駆動用電源として、その研究開発が盛んに行われている。このリチウム二次電池においては、使用する電極活物質により、充放電電圧、充放電サイクル寿命特性、保存特性などの電池特性が大きく左右される。
ところで、一般的には、リチウムイオン二次電池の負極活物質としては、天然黒鉛、人造黒鉛、フェノール樹脂等の有機化合物焼成体、コークス等の炭素物質の粉状体からなる黒鉛材料が主流であった。ところが、前記黒鉛材料は、例えば、単位質量当りの理論容量が３７２ｍＡｈ／ｇ であり、比重も２．２５ｇ／ｃｍ３と小さいので、単位体積当り容量は８３７ｍＡｈ／ｃｍ３と小さいため、電池の高容量化が難しいという課題があった。
In recent years, lithium secondary batteries have been actively researched and developed as power sources for driving electronic devices. In this lithium secondary battery, battery characteristics such as charge / discharge voltage, charge / discharge cycle life characteristics, and storage characteristics are greatly affected by the electrode active material used.
By the way, in general, as a negative electrode active material of a lithium ion secondary battery, a graphite material composed of a powdery body of a carbon substance such as natural graphite, artificial graphite, an organic compound fired body such as a phenol resin, or a coke is mainly used. there were. However, the graphite material has, for example, a theoretical capacity per unit mass of 372 mAh / g 2 and a specific gravity as small as 2.25 g / cm 3 , so that the capacity per unit volume is as small as 837 mAh / cm 3. There was a problem that capacity was difficult.
このため、負極活物質を改善することにより、電池特性を向上させることが図られている。例えば、負極活物質として金属リチウム（Ｌｉ）を用いることにより、重量当り、及び体積当りともに、高いエネルギー密度の電池を構成することができる。しかしながら、電池の充電時に、リチウムがデンドライト状に析出し内部短絡を引き起こすという問題がある。
この解決策として、充電に際して、電気化学的にリチウムと合金化するアルミニウム、シリコン、スズなどを負極材料として用いたリチウム二次電池が報告されている（例えば、非特許文献１参照。）。これらのうち、特に、シリコンは、理論容量が大きく高容量の電池用負極として有望であり、これを負極活物質とする種々の二次電池が提案されている（例えば、特許文献１、２、非特許文献２参照。）。しかしながら、これらの合金負極では、電極活物質である合金自体が、充放電により大きな体積変化を生じ、活物質粒子の割れ、又は微粉化された活物質と集電体との接触不良等を起こすため、集電特性が悪化することから、十分なサイクル特性が得られないという問題がある。
For this reason, it is intended to improve battery characteristics by improving the negative electrode active material. For example, by using metallic lithium (Li) as the negative electrode active material, a battery with a high energy density can be configured both by weight and by volume. However, when the battery is charged, there is a problem that lithium precipitates in a dendrite state and causes an internal short circuit.
As a solution, a lithium secondary battery using aluminum, silicon, tin or the like electrochemically alloyed with lithium as a negative electrode material during charging has been reported (for example, see Non-Patent Document 1). Among these, silicon is particularly promising as a negative electrode for a battery having a large theoretical capacity and a high capacity, and various secondary batteries using this as a negative electrode active material have been proposed (for example, Patent Documents 1 and 2; (Refer nonpatent literature 2.). However, in these alloy negative electrodes, the alloy itself as the electrode active material undergoes a large volume change due to charge and discharge, causing cracks in the active material particles, poor contact between the pulverized active material and the current collector, and the like. For this reason, there is a problem that sufficient cycle characteristics cannot be obtained because current collection characteristics deteriorate.
一方、代替負極材料として、リチウムの吸蔵及び放出能力を有する酸化物系負極材料を利用する多くの研究もなされている。例えば、リチウムの吸蔵と放出が可能な金属酸化物として、スズを主体とする酸化物（例えば、特許文献２、３参照。）、シリコンを主体とする酸化物（例えば、特許文献３参照。）、或いは、ＬｉＴｉ２Ｏ４又はＬｉ４／３Ｔｉ５／３Ｏ４で表されるリチウムチタンスピネル酸化物（例えば、非特許文献３参照。）などが提案されている。しかしながら、スズ又はシリコンを主体とする酸化物からなる負極では、サイクル特性が十分でなく、他方、リチウムチタンスピネル酸化物からなる負極では、比較的サイクル特性は良好であるが、電位が高いために電池にしたときの電圧を高くできないという問題がある。 On the other hand, as an alternative negative electrode material, many studies have been made on the use of an oxide negative electrode material having the ability to occlude and release lithium. For example, as a metal oxide capable of inserting and extracting lithium, an oxide mainly composed of tin (for example, see Patent Documents 2 and 3) and an oxide mainly composed of silicon (for example, refer to Patent Document 3). Alternatively, a lithium titanium spinel oxide represented by LiTi 2 O 4 or Li 4/3 Ti 5/3 O 4 (for example, see Non-Patent Document 3) has been proposed. However, in the negative electrode made of an oxide mainly composed of tin or silicon, the cycle characteristics are not sufficient. On the other hand, in the negative electrode made of lithium titanium spinel oxide, the cycle characteristics are relatively good, but the potential is high. There is a problem that the voltage cannot be increased when the battery is used.
本発明の目的は、上記の従来技術の問題点に鑑み、リチウム二次電池負極として用いた際に、充放電容量が高く、かつ充放電サイクル特性に優れたリチウム二次電池とすることができる、新規なリチウム電池用合金負極と、その工業上効率的な製造方法と、これを用いた高性能のリチウム二次電池を提供することにある。 An object of the present invention is to provide a lithium secondary battery having a high charge / discharge capacity and excellent charge / discharge cycle characteristics when used as a negative electrode for a lithium secondary battery in view of the above-mentioned problems of the prior art. An object of the present invention is to provide a novel alloy negative electrode for a lithium battery, an industrially efficient production method thereof, and a high-performance lithium secondary battery using the same.
本発明者らは、上記目的を達成するために、リチウムイオン二次電池用合金負極について、鋭意研究を重ねた結果、負極活物質として、特定の組成を有するルテニウム（Ｒｕ）で被覆したケイ素（Ｓｉ）を用いて，リチウムイオン二次電池用合金負極を形成したところ、充放電容量が高く、かつ充放電サイクル特性に優れたリチウム二次電池とすることができること、及びガスデポジション法を用いた製造方法により、工業上効率的に上記合金負極が得られることを見出し、本発明を完成した。 In order to achieve the above object, the present inventors have conducted extensive research on an alloy negative electrode for lithium ion secondary batteries, and as a result, silicon (Ru) coated with ruthenium (Ru) having a specific composition as a negative electrode active material. Si) was used to form an alloy negative electrode for a lithium ion secondary battery, so that a lithium secondary battery having high charge / discharge capacity and excellent charge / discharge cycle characteristics could be obtained, and a gas deposition method was used. It was found that the above alloy negative electrode can be obtained industrially efficiently by the production method described above, and the present invention was completed.
すなわち、本発明の第１の発明によれば、負極活物質としてルテニウムで被覆したケイ素を用いてなるリチウムイオン二次電池用合金負極であって、前記ルテニウムで被覆したケイ素は、ルテニウムを全量に対し０．１〜２５質量％含有することを特徴とするリチウムイオン二次電池用合金負極が提供される。 That is, according to the first aspect of the present invention, there is provided an alloy negative electrode for a lithium ion secondary battery using silicon coated with ruthenium as a negative electrode active material, and the silicon coated with ruthenium contains ruthenium in a total amount. The alloy negative electrode for lithium ion secondary batteries characterized by containing 0.1-25 mass% with respect to it is provided.
また、本発明の第２の発明によれば、第１の発明において、前記ルテニウムで被覆したケイ素は、無電解めっき法により製造したものであることを特徴とするリチウムイオン二次電池用合金負極が提供される。 According to a second aspect of the present invention, in the first aspect, the ruthenium-coated silicon is produced by an electroless plating method, and is an alloy negative electrode for a lithium ion secondary battery. Is provided.
また、本発明の第３の発明によれば、ガスデポジション法により、集電体上にルテニウムで被覆したケイ素粉末が堆積された電極を形成することを特徴とする第１又は２の発明のリチウムイオン二次電池用合金負極の製造方法が提供される。 According to a third invention of the present invention, the electrode in which the silicon powder coated with ruthenium is deposited on the current collector is formed by a gas deposition method. A method for producing an alloy negative electrode for a lithium ion secondary battery is provided.
また、本発明の第４の発明によれば、第３の発明において、前記ガスデポジション法は、表面を洗浄した集電体基板上に、ノズルから、窒素ガス又は希ガスからなるキャリアーガスとともに、ルテニウムで被覆したケイ素粉末を吐出させることを特徴とするリチウムイオン二次電池用合金負極の製造方法が提供される。 According to a fourth aspect of the present invention, in the third aspect, the gas deposition method includes a carrier gas composed of nitrogen gas or a rare gas from a nozzle on a current collector substrate whose surface has been cleaned. There is provided a method for producing an alloy negative electrode for a lithium ion secondary battery, wherein silicon powder coated with ruthenium is discharged.
また、本発明の第５の発明によれば、第３の発明において、前記ルテニウムで被覆したケイ素粉末は、無電解めっき法により、塩化ルテニウム水溶液中にケイ素粉末を添加し、次いで還元剤を添加してケイ素粉末の表面上にルテニウムを析出させたものであることを特徴とするリチウムイオン二次電池用合金負極の製造方法が提供される。 According to a fifth aspect of the present invention, in the third aspect, the silicon powder coated with ruthenium is added to the ruthenium chloride aqueous solution by an electroless plating method, and then a reducing agent is added. Thus, there is provided a method for producing an alloy negative electrode for a lithium ion secondary battery, characterized in that ruthenium is deposited on the surface of a silicon powder.
また、本発明の第６の発明によれば、第１又は２の発明のリチウムイオン二次電池用合金負極と、リチウム吸蔵可能な酸化物からなる正極と、非水系電解質とから構成されることを特徴とするリチウムイオン二次電池が提供される。 Further, according to the sixth invention of the present invention, the lithium ion secondary battery alloy negative electrode of the first or second invention, a positive electrode made of an oxide capable of occluding lithium, and a non-aqueous electrolyte are included. A lithium ion secondary battery is provided.
本発明のリチウムイオン二次電池用合金負極は、負極活物質としてルテニウムで被覆したケイ素を用いてなるものであり、これを用いて充放電容量が高く、かつ充放電サイクル特性に優れたリチウム二次電池を得ることができ、またその製造方法は、工業上効率的な方法であるので、その工業的価値は極めて大きい。 The alloy negative electrode for a lithium ion secondary battery according to the present invention is made of silicon coated with ruthenium as a negative electrode active material, and uses this lithium lithium having a high charge / discharge capacity and excellent charge / discharge cycle characteristics. Since the secondary battery can be obtained and the manufacturing method thereof is an industrially efficient method, its industrial value is extremely high.
以下、本発明のリチウムイオン二次電池用合金負極、その製造方法及びそれを用いたリチウムイオン二次電池を詳細に説明する。
１．リチウムイオン二次電池用合金負極
本発明のリチウムイオン二次電池用合金負極は、負極活物質としてルテニウムで被覆したケイ素を用いてなるリチウムイオン二次電池用合金負極であって、前記ルテニウムで被覆したケイ素は、ルテニウムを、全量に対し０．１〜２５質量％含有することを特徴とする。
Hereinafter, an alloy negative electrode for a lithium ion secondary battery of the present invention, a manufacturing method thereof, and a lithium ion secondary battery using the same will be described in detail.
1. An alloy negative electrode for a lithium ion secondary battery according to the present invention is an alloy negative electrode for a lithium ion secondary battery using silicon coated with ruthenium as a negative electrode active material and coated with the ruthenium. The silicon is characterized by containing 0.1 to 25% by mass of ruthenium with respect to the total amount.
本発明において、リチウムイオン二次電池用合金負極は、負極活物質として、所定の組成のルテニウムで被覆したケイ素を用いることが重要である。すなわち、ルテニウムが被覆されたケイ素はケイ素単体に比べ、容量は多少低下するものの、黒鉛より重量あたりの容量は大きいため、高容量のリチウムイオン二次電池が得られる。 In the present invention, it is important that the alloy negative electrode for a lithium ion secondary battery uses silicon coated with ruthenium having a predetermined composition as the negative electrode active material. That is, although the capacity of silicon covered with ruthenium is somewhat lower than that of silicon alone, the capacity per weight is larger than that of graphite, so that a high capacity lithium ion secondary battery can be obtained.
また、所定の組成のルテニウムで被覆したケイ素では、ケイ素単体の場合の乏しいサイクル特性を向上させることができる。すなわち、ルテニウムはその表面のみが活物質として働くが、内部は電極反応に関与しないため、充放電サイクルの間においてもケイ素粒子表面で安定に存在することができる。これにより、ケイ素粒子のリチウム化・脱リチウム化反応に伴う体積変化を抑制することが可能である。
さらに、上記合金負極において、ルテニウムは、ケイ素粒子間ではクッションの働きをするものと考えられる。すなわち、ルテニウムも電極反応によりわずかに体積変化するので、ケイ素粒子による大きな体積変化で生じる応力を緩和する働きをする。
In addition, silicon coated with ruthenium having a predetermined composition can improve poor cycle characteristics in the case of silicon alone. That is, only the surface of ruthenium functions as an active material, but the inside does not participate in the electrode reaction, so that it can stably exist on the surface of the silicon particles even during the charge / discharge cycle. Thereby, it is possible to suppress the volume change accompanying the lithiation / delithiation reaction of the silicon particles.
Furthermore, in the alloy negative electrode, ruthenium is considered to act as a cushion between the silicon particles. That is, ruthenium also slightly changes in volume due to the electrode reaction, and thus works to relieve stress generated by a large volume change caused by silicon particles.
以上より明らかなように、上記リチウムイオン二次電池用合金負極は、単位重量当り充放電容量、サイクル特性において、リチウム二次電池のリチウム反応電極として好適であり、高容量でサイクル特性が良好なリチウムイオン二次電池を構成することができる。
なお、ケイ素に被覆する金属としたは、ルテニウム以外に、鉄、コバルト又はニッケルでも上記と同じような効果が得られる。
As apparent from the above, the alloy negative electrode for lithium ion secondary battery is suitable as a lithium reaction electrode of a lithium secondary battery in charge / discharge capacity and cycle characteristics per unit weight, and has high capacity and good cycle characteristics. A lithium ion secondary battery can be constituted.
In addition to the ruthenium, the same effect as described above can be obtained by using iron, cobalt, or nickel in addition to ruthenium.
上記合金負極に用いるルテニウムで被覆したケイ素は、ルテニウムを、全量に対し０．１〜２５質量％含有するものである。すなわち、ルテニウムはケイ素粉末全体を被覆しても、一部のみを被覆しても、体積変化を緩和する働きを持たせる効果はあるが、ルテニウムの含有割合が０．１質量％未満では、リチウム化・脱リチウム化反応に伴う体積変化が緩和できなくなり、サイクル特性の悪化につながる。一方、ルテニウムの含有割合が２５質量％を超えると、サイクル特性は良好だが、ケイ素に起因して充放電容量が小さくなり、全体としての充放電容量が小さくなる。 The silicon covered with ruthenium used for the alloy negative electrode contains 0.1 to 25% by mass of ruthenium with respect to the total amount. That is, ruthenium has the effect of reducing the volume change, even if it covers the entire silicon powder or only a part of it, but if the ruthenium content is less than 0.1% by mass, The volume change accompanying the lithiation / delithiation reaction cannot be mitigated, leading to deterioration of cycle characteristics. On the other hand, when the content ratio of ruthenium exceeds 25% by mass, the cycle characteristics are good, but the charge / discharge capacity decreases due to silicon, and the overall charge / discharge capacity decreases.
上記ルテニウムで被覆したケイ素に用いるケイ素としては、通常、電極反応に影響を与える程には不純物元素を含有しない純度のものが用いられるが、その他の目的に応じて、他の元素を添加して合金化したケイ素合金も用いることができる。また、ケイ素の粒径は０．１〜５０μｍであることが好ましい。また、必要に応じて機械的な方法などで粉砕したり、分級したりしたものでもよい。 The silicon used for the ruthenium-coated silicon is usually of a purity that does not contain an impurity element to the extent that it affects the electrode reaction, but other elements may be added depending on other purposes. Alloyed silicon alloys can also be used. Moreover, it is preferable that the particle size of silicon is 0.1-50 micrometers. Moreover, what was grind | pulverized and classified by the mechanical method etc. as needed may be used.
なお、上記ルテニウムで被覆したケイ素粉末は、熱処理すれば、充放電容量及びサイクル特性とも熱処理前に比べ向上するが、特に熱処理しなくても問題はない。 The silicon powder coated with ruthenium improves both the charge / discharge capacity and the cycle characteristics as compared with those before the heat treatment when heat-treated, but there is no problem even if it is not heat-treated.
２．リチウムイオン二次電池用合金負極の製造方法
本発明のリチウムイオン二次電池用合金負極の製造方法としては、特に限定されるものではなく、従来から行われているリチウムイオン二次電池用の合金負極の製造方法を採用することができる。例えば、所望割合のルテニウムで被覆したケイ素粉末を、所望割合の導電補助材及び所望割合のバインダと混合した後、混合物を圧延によりシート電極を形成する方法、混合物に適当な溶剤を加えてペースト状にして、銅等の金属箔集電体の表面に塗布、乾燥し、必要に応じて電極密度を高めるべく圧縮して電極形成したりする方法、或いはガスデポジション法により、集電体上にルテニウムで被覆したケイ素粉末からなる電極を形成する方法等が挙げられるが、この中で、特に、ガスデポジション法により、集電体上にルテニウムで被覆したケイ素粉末が堆積された電極を形成する方法が好ましい。
2. Manufacturing method of alloy negative electrode for lithium ion secondary battery The manufacturing method of the alloy negative electrode for lithium ion secondary battery of the present invention is not particularly limited, and a conventional alloy for lithium ion secondary battery is used. The manufacturing method of a negative electrode is employable. For example, a silicon powder coated with a desired ratio of ruthenium is mixed with a desired ratio of a conductive auxiliary material and a desired ratio of a binder, and then the mixture is formed into a sheet electrode by rolling. An appropriate solvent is added to the mixture to form a paste. Then, it is applied to the surface of a metal foil current collector such as copper and dried, and if necessary, the electrode is formed by compressing to increase the electrode density, or the gas deposition method on the current collector. Examples include a method of forming an electrode made of silicon powder coated with ruthenium. Among them, an electrode in which silicon powder coated with ruthenium is deposited on a current collector is formed by a gas deposition method. The method is preferred.
上記シート電極又はペーストを用いた電極で用いられる導電補助材としては、黒鉛、カーボンブラック、アセチレンブラック、炭素繊維、金属粉末、金属繊維、その他導電性ポリマー等が用いられる。上記シート電極又はペーストを用いた電極で用いられるバインダとしては、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、エチレンプロピレンジエンゴム、フッ素ゴム、スチレンブタジエン、セルロース系樹脂、ポリアクリル酸などを用いることができる。 また、活物質粒子をつなぎ止める役割を果たすもので、例えば、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、フッ素ゴム等の含フッ素樹脂、ポリプロピレン、ポリエチレン等の熱可塑性樹脂等を用いることができる。 As the conductive auxiliary material used in the electrode using the sheet electrode or paste, graphite, carbon black, acetylene black, carbon fiber, metal powder, metal fiber, and other conductive polymers are used. As the binder used in the electrode using the sheet electrode or the paste, polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluorine rubber, styrene butadiene, cellulose resin, polyacrylic acid, or the like can be used. Moreover, it plays a role of holding the active material particles, and for example, fluorine-containing resins such as polytetrafluoroethylene, polyvinylidene fluoride, and fluorine rubber, and thermoplastic resins such as polypropylene and polyethylene can be used.
上記ガスデポジション法による電極形成方法では、例えば、集電体に上記ルテニウムで被覆したケイ素粉末を高速で吹き付け、集電体上に前記粉末を堆積して電極を形成することにより製造する。上記ガスデポジション法としては、特に限定されるものではなく、一般的な金属粉末の吹き付け方法が用いられるが、この中で、例えば、チャンバー中に取り付けた表面を洗浄した集電体基板上に、メタルマスクをおき円形電極を形成し、所定の距離に設定したノズルから、窒素ガス又は希ガスからなるキャリアーガスとともにルテニウムで被覆したケイ素粉末を吐出させる方法が好ましい。
ここで、上記集電体としては、圧延銅箔などの銅箔等の一般に用いられている銅系材料を使用することができるが、必要に応じて、ニッケル、ステンレス、モリブデン、タングステン、及びタンタルなど他の集電体材料を用いることができる。
In the electrode formation method by the gas deposition method, for example, the current collector is manufactured by spraying the ruthenium-coated silicon powder at a high speed and depositing the powder on the current collector to form an electrode. The gas deposition method is not particularly limited, and a general metal powder spraying method is used. Among these, for example, a surface mounted in a chamber is cleaned on a current collector substrate. A method of forming a circular electrode by placing a metal mask, and discharging a ruthenium-coated silicon powder together with a carrier gas made of nitrogen gas or a rare gas from a nozzle set at a predetermined distance is preferable.
Here, as the current collector, a commonly used copper-based material such as a copper foil such as a rolled copper foil can be used. However, if necessary, nickel, stainless steel, molybdenum, tungsten, and tantalum. Other current collector materials can be used.
上記ガスデポジション法による電極形成方法では、合金粉末同士の接合が生じるため、導電補助材、バインダ等を使用せずに、強固な電極を形成することができるという利点とともに、得られる電極には、粒子間に適度な空隙を有するので、良好なリチウム反応性を維持することができるという利点がある。 In the electrode formation method based on the gas deposition method, since the alloy powders are bonded to each other, the obtained electrode has the advantage that a strong electrode can be formed without using a conductive auxiliary material, a binder, or the like. In addition, since there are appropriate voids between the particles, there is an advantage that good lithium reactivity can be maintained.
上記ガスデポジション法による電極形成方法に用いるルテニウムで被覆したケイ素粉末を製造する方法としては、特に限定されるものではなく、無電解めっき法又は含浸法が挙げられるが、特に、ケイ素表面上に、強固に密着したリン、ホウ素を含んだルテニウム層を形成することができる無電解めっき法が好ましい。 The method for producing the ruthenium-coated silicon powder used in the electrode formation method by the gas deposition method is not particularly limited, and includes an electroless plating method or an impregnation method. An electroless plating method capable of forming a ruthenium layer containing phosphorus and boron that is firmly adhered is preferable.
上記無電解めっき法によるルテニウムで被覆したケイ素粉末としては、例えば、塩化ルテニウム水溶液中にケイ素粉末を添加し、次いで還元剤を添加してケイ素粉末の表面上にルテニウムを析出させたものである。その製造方法としては、例えば、まず、ケイ素粉末の表面上にルテニウムを析出させるためのルテニウム源として、塩化ルテニウム水和物、塩化ルテニウム酸、塩化ルテニウム酸カリウム等の塩化ルテニウム酸塩を、水に溶解させ、次いで、ケイ素粉末を添加する。続いて、これを十分に攪拌し、水素化ホウ素ナトリウム（ＮａＢＨ４）等の水素化ホウ素塩、アルデヒド、次亜リン酸塩、ヒドラジン等の還元剤を添加し、その後、ろ過してルテニウムで被覆したケイ素の粉末を得る。
ここで、ケイ素に対するルテニウム源の添加割合を所定の値に調整することによって、所定のルテニウム含有割合を有するルテニウムで被覆したケイ素の粉末を得ることができる。
As the silicon powder coated with ruthenium by the electroless plating method, for example, silicon powder is added to a ruthenium chloride aqueous solution, and then a reducing agent is added to deposit ruthenium on the surface of the silicon powder. As a production method thereof, for example, as a ruthenium source for precipitating ruthenium on the surface of silicon powder, ruthenium chloride hydrate, ruthenium chloride, ruthenium chloride, potassium ruthenate, etc. Dissolve and then add silicon powder. Subsequently, the mixture is sufficiently stirred, and a reducing agent such as borohydride such as sodium borohydride (NaBH 4 ), aldehyde, hypophosphite, hydrazine is added, and then filtered and covered with ruthenium. A silicon powder is obtained.
Here, a ruthenium-coated silicon powder having a predetermined ruthenium content ratio can be obtained by adjusting the addition ratio of the ruthenium source to silicon to a predetermined value.
なお、この際、使用するケイ素としては、前述のように、通常、電極反応に影響を与える程には不純物元素を含有しない純度のものが用いられるが、その他の目的に応じて、他の元素を添加して合金化したケイ素合金も用いることができる。また、ケイ素の粒径は、０．１〜５０μｍであることが好ましい。また、必要に応じて機械的な方法などで粉砕したり、分級したりしたものでもよい。 In this case, as described above, silicon having a purity that does not contain an impurity element to the extent that it affects the electrode reaction is used as described above, but other elements may be used depending on other purposes. It is also possible to use a silicon alloy alloyed by adding. Moreover, it is preferable that the particle size of silicon is 0.1-50 micrometers. Moreover, what was grind | pulverized and classified by the mechanical method etc. as needed may be used.
３．リチウムイオン二次電池
本発明のリチウムイオン二次電池は、上記リチウムイオン二次電池用合金負極と、リチウム吸蔵可能な酸化物からなる正極と、非水系電解質とから構成されるものである。これにより、高容量でサイクル特性の良好なリチウムイオン二次電池が得られる。
3. Lithium ion secondary battery The lithium ion secondary battery of this invention is comprised from the said alloy negative electrode for lithium ion secondary batteries, the positive electrode which consists of an oxide which can occlude lithium, and a non-aqueous electrolyte. Thereby, a lithium ion secondary battery having a high capacity and good cycle characteristics can be obtained.
上記リチウム吸蔵可能な酸化物からなる正極としては、特に限定されるものではなく、リチウムコバルト複合酸化物（ＬｉＣｏＯ２）、リチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）或いはリチウムニッケル複合酸化物（ＬｉＮｉＯ２）、さらにこれらのＣｏ、Ｎｉを他の添加元素により置換したもの等が用いられる。 The positive electrode composed of the above-described lithium occlusion oxide is not particularly limited, and lithium cobalt composite oxide (LiCoO 2 ), lithium manganese composite oxide (LiMn 2 O 4 ), or lithium nickel composite oxide (LiNiO). 2 ) Further, those obtained by substituting these Co and Ni with other additive elements are used.
上記非水系電解質としては、支持塩としてのリチウム塩を有機溶媒に溶解したものが用いられる。上記有機溶媒としては、例えば、環状カーボネート、鎖状カーボネート、エーテル化合物等を用いることができる。上記支持塩としては、例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＮ（ＣＦ３ＳＯ２）２等、及びそれらの複合塩を用いることができる。 As the non-aqueous electrolyte, a solution obtained by dissolving a lithium salt as a supporting salt in an organic solvent is used. As said organic solvent, a cyclic carbonate, a chain carbonate, an ether compound etc. can be used, for example. Examples of the supporting salt include LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiN (CF 3 SO 2 ) 2 , and complex salts thereof.
以下に、本発明の実施例及び比較例によって本発明をさらに詳細に説明するが、本発明は、これらの実施例によってなんら限定されるものではない。なお、実施例及び比較例で用いた充放電特性の評価方法は、以下の通りである。
［充放電特性の評価方法］
三極式ビーカーセルを用いて、対極及び参照極として金属リチウム板（（株）レアメタリック製、厚さ１ｍｍ、純度９９．９％）、電解液として１ＭのＬｉＣｌＯ４支持塩とするプロピレンカーボネート（ＰＣ）溶液（（株）キシダ化学製）を用いた。電解液の温度としては、３０℃とした。なお、充放電測定装置（計測器センター（株）製、ＢＳ２５０６）により、電流値０．０５ｍＡで、０．００５〜３．４Ｖｖｓ．Ｌｉ／Ｌｉ＋の電位幅で充放電を繰り返し、１０００回までのサイクル特性を評価した。
Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the evaluation method of the charging / discharging characteristic used by the Example and the comparative example is as follows.
[Evaluation method of charge / discharge characteristics]
Using a tripolar beaker cell, metal lithium plate (made by Rare Metallic Co., Ltd., thickness 1 mm, purity 99.9%) as a counter electrode and a reference electrode, propylene carbonate (1M LiClO 4 supported salt as an electrolyte) ( PC) solution (manufactured by Kishida Chemical Co., Ltd.) was used. The temperature of the electrolyte was 30 ° C. In addition, with a charge / discharge measuring device (manufactured by Instrument Center Co., Ltd., BS2506), a current value of 0.05 mA and 0.005 to 3.4 Vvs. Charging / discharging was repeated with the potential width of Li / Li + , and cycle characteristics up to 1000 times were evaluated.
（実施例１）
まず、下記の［無電解めっき法によるルテニウム被覆ケイ素粉末の合成方法］により、ルテニウム被覆ケイ素粉末を作製し、下記の［ガスデポジション法による負極の作製方法］により、ルテニウム被覆ケイ素負極を作製した。
Example 1
First, a ruthenium-coated silicon powder was prepared by the following [Method of synthesizing ruthenium-coated silicon powder by electroless plating method], and a ruthenium-coated silicon negative electrode was prepared by the following [Method of preparing negative electrode by gas deposition method]. .
［無電解めっき法によるルテニウム被覆ケイ素粉末の合成方法］
塩化ルテニウム水和物（ＲｕＣｌ３・ｎＨ２Ｏ、ｎ：１〜３、キシダ化学製、品番：０２０−６８６０２）０．２ｇを、１００ｍｌの水に溶解させ、これに、ケイ素粉末（和光純薬製、品番：１９１−０５５８２、平均粒径：１μｍ）０．１２５ｇを添加した。次いで、十分に攪拌し、水素化ホウ素ナトリウム（ＮａＢＨ４、和光純薬製、品番：１９２−０１４７２）０．５ｇを添加し、その後、ろ過してルテニウムで被覆したケイ素の粉末を合成した。得られたルテニウム被覆ケイ素粉末の定量分析をしてルテニウムの含有割合を求めた。ルテニウムの含有割合は、６．２５質量％であった。なお、ＳＥＭ観察により、被覆厚みを調べたところ、約０．５μｍであった。
[Method of synthesizing ruthenium-coated silicon powder by electroless plating]
Ruthenium chloride hydrate (RuCl 3 · nH 2 O, n: 1-3, manufactured by Kishida Chemical Co., Ltd., product number: 020-68602) 0.2 g was dissolved in 100 ml of water, and silicon powder (Wako Pure Chemical Industries, Ltd.) was dissolved therein. Manufactured, product number: 191-05582, average particle size: 1 μm) 0.125 g was added. Next, the mixture was sufficiently stirred, 0.5 g of sodium borohydride (NaBH 4 , Wako Pure Chemicals, product number: 192-01472) was added, and then filtered to synthesize silicon powder coated with ruthenium. The obtained ruthenium-coated silicon powder was quantitatively analyzed to determine the ruthenium content. The content ratio of ruthenium was 6.25% by mass. When the coating thickness was examined by SEM observation, it was about 0.5 μm.
［ガスデポジション法による負極の作製方法］
集電体基板として、圧延銅箔（ニラコ製、厚さ２０μｍ、純度９９％）を、アセトン脱脂し、次に硝酸による酸洗を行い、水洗後、再度アセトンで超音波洗浄したものを用いた。この集電体基板をチャンバー中に取り付け、集電体基板上にメタルマスクをおき、６ｍｍφの円形電極を形成した。ガスデポジションは、基板／ノズル間距離を１０ｍｍ、ノズル径０．８ｍｍに設定して、アルゴンガスをキャリアーガス（０．６ＭＰａ）として用いて、約５０ｍｇのルテニウム被覆ケイ素粉末を吐出させて、負極を作製した。
[Production method of negative electrode by gas deposition method]
As the current collector substrate, a rolled copper foil (manufactured by Nilaco, thickness 20 μm, purity 99%) was degreased with acetone, then pickled with nitric acid, washed with water, and then ultrasonically washed again with acetone. . The current collector substrate was mounted in a chamber, a metal mask was placed on the current collector substrate, and a 6 mmφ circular electrode was formed. In the gas deposition, the substrate / nozzle distance was set to 10 mm, the nozzle diameter was set to 0.8 mm, argon gas was used as a carrier gas (0.6 MPa), and about 50 mg of ruthenium-coated silicon powder was discharged to form a negative electrode. Was made.
次いで、得られた負極を用いて、上記［充放電特性の評価方法］により、１サイクル目と、５００サイクル目の放電容量を求めた。結果を表１に示す。なお、図１は、放電容量（Ｄｉｓｃｈａｒｇｅ ｃａｐａｃｉｔｙ）のサイクル回数（Ｃｙｃｌｅ ｎｕｍｂｅｒ）への依存性を表す図である。 Next, using the obtained negative electrode, the discharge capacities of the first cycle and the 500th cycle were determined by the above [Method for evaluating charge / discharge characteristics]. The results are shown in Table 1. FIG. 1 is a diagram illustrating the dependency of the discharge capacity on the cycle number.
（実施例２）
［ルテニウム被覆ケイ素粉末の合成］において、塩化ルテニウム水和物０．６４ｇを溶解して、ルテニウム被覆ケイ素粉末のルテニウムの含有割合が２０．０質量％となるようにしたこと以外は、実施例１と同様にして得られた負極を用いて、上記［充放電特性の評価方法］により、１サイクル目と、５００サイクル目の放電容量を求めた。結果を表１に示す。
(Example 2)
Example 1 except that in the synthesis of ruthenium-coated silicon powder, 0.64 g of ruthenium chloride hydrate was dissolved so that the ruthenium content in the ruthenium-coated silicon powder was 20.0% by mass. Using the negative electrode obtained in the same manner as described above, the discharge capacities at the first cycle and the 500th cycle were determined by the above [Method for evaluating charge / discharge characteristics]. The results are shown in Table 1.
（実施例３）
［ルテニウム被覆ケイ素粉末の合成］において、塩化ルテニウム水和物０．１ｇを溶解して、ルテニウム被覆ケイ素粉末のルテニウムの含有割合が３．８５質量％となるようにしたこと以外は、実施例１と同様にして得られた負極を用いて、上記［充放電特性の評価方法］により、１サイクル目と、５００サイクル目の放電容量を求めた。結果を表１に示す。
(Example 3)
Example 1 except that 0.1 g of ruthenium chloride hydrate was dissolved so that the ruthenium content in the ruthenium-coated silicon powder was 3.85% by mass in [Synthesis of ruthenium-coated silicon powder]. Using the negative electrode obtained in the same manner as described above, the discharge capacities at the first cycle and the 500th cycle were determined by the above [Method for evaluating charge / discharge characteristics]. The results are shown in Table 1.
（実施例４）
［無電解めっき法によるルテニウム被覆ケイ素粉末の合成方法］において、塩化ルテニウム水和物を水に溶解させた後に、ＫＯＨ１．１２ｇを添加して、ｐＨを１２に調整し、アルカリ性に保持した後に還元剤を添加したこと以外は、実施例１と同様にして得られた負極を用いて、上記［充放電特性の評価方法］により、１サイクル目と、５００サイクル目の放電容量を求めた。結果を表１に示す。
Example 4
In [Method of synthesizing ruthenium-coated silicon powder by electroless plating method], after dissolving ruthenium chloride hydrate in water, 1.12 g of KOH is added to adjust the pH to 12, and then reduced to alkaline. Using the negative electrode obtained in the same manner as in Example 1 except that the agent was added, the discharge capacities of the first cycle and the 500th cycle were determined by the above [Evaluation method of charge / discharge characteristics]. The results are shown in Table 1.
（比較例１）
［ガスデポジション法による負極の作製方法］において、負極活物質として、ルテニウム被覆ケイ素粉末の代わりに、ケイ素粉末を用いたことこと以外は、実施例１と同様にして得られた負極を用いて、上記［充放電特性の評価方法］により、１サイクル目と、５００サイクル目の放電容量を求めた。結果を表１に示す。なお、図１は、放電容量のサイクル依存性を表す図である。
(Comparative Example 1)
In [Method for producing negative electrode by gas deposition method], the negative electrode obtained in the same manner as in Example 1 except that silicon powder was used as the negative electrode active material instead of ruthenium-coated silicon powder. The discharge capacities of the first cycle and the 500th cycle were determined by the above [Method for evaluating charge / discharge characteristics]. The results are shown in Table 1. FIG. 1 is a diagram showing the cycle dependency of the discharge capacity.
（比較例２）
［ルテニウム被覆ケイ素粉末の合成］において、塩化ルテニウム水和物０．９１ｇを溶解して、ルテニウム被覆ケイ素粉末のルテニウムの含有割合が２８．５質量％となるようにしたこと以外は、実施例１と同様にして得られた負極を用いて、上記［充放電特性の評価方法］により、１サイクル目と、５００サイクル目の放電容量を求めた。結果を表１に示す。
(Comparative Example 2)
[Synthesis of ruthenium-coated silicon powder] Example 1 except that 0.91 g of ruthenium chloride hydrate was dissolved so that the content of ruthenium in the ruthenium-coated silicon powder was 28.5% by mass. Using the negative electrode obtained in the same manner as described above, the discharge capacities at the first cycle and the 500th cycle were determined by the above [Method for evaluating charge / discharge characteristics]. The results are shown in Table 1.
表１より、実施例１〜４では、負極活物質としてルテニウムで被覆したケイ素を用いてリチウムイオン二次電池用合金負極を形成し、製造方法としてガスデポジション法を用いて、本発明の方法に従って行われたので、充放電容量が高く、かつ充放電サイクル特性に優れたリチウム二次電池とすることができることが分かる。これに対して、比較例１又は２では、負極活物質がこれらの条件に合わないので、充放電容量において満足すべき結果が得られないことが分かる。 From Table 1, in Examples 1-4, the alloy negative electrode for lithium ion secondary batteries is formed using silicon coated with ruthenium as the negative electrode active material, and the method of the present invention is performed using the gas deposition method as the manufacturing method. Therefore, it can be seen that a lithium secondary battery having high charge / discharge capacity and excellent charge / discharge cycle characteristics can be obtained. On the other hand, in Comparative Example 1 or 2, since the negative electrode active material does not meet these conditions, it can be seen that satisfactory results in charge / discharge capacity cannot be obtained.
より詳しくは、実施例１では、図１に示すように、充放電の初期には放電容量はケイ素単体に比べ容量は小さいが、サイクルを重ねても、放電容量の減少率は小さく、５００サイクルを経過しても５００ｍＡｈ／ｇの放電容量を示しており、良好なサイクル特性を示す。
また、実施例３では、充放電の初期には放電容量が高く、かつ５００サイクル目においても高い放電容量を示している。また、実施例４では、充放電の初期には放電容量が高く、かつ５００サイクル目においても７７０ｍＡｈ／ｇと特に高い放電容量を示している。
More specifically, in Example 1, as shown in FIG. 1, the discharge capacity is smaller than that of silicon alone in the initial stage of charge and discharge, but the reduction rate of the discharge capacity is small even after repeated cycles, and 500 cycles. Even after elapse of time, a discharge capacity of 500 mAh / g is shown and good cycle characteristics are exhibited.
In Example 3, the discharge capacity is high at the initial stage of charge / discharge, and the discharge capacity is high even at the 500th cycle. In Example 4, the discharge capacity is high at the initial stage of charge and discharge, and a particularly high discharge capacity of 770 mAh / g is shown even at the 500th cycle.
一方、比較例１では、ごく初期には２０００ｍＡｈ／ｇの極めて高い容量を示すが、図１に示すように、数〜１０サイクルまでに大きな容量の低下を示す。なお、第１サイクルの充電時に、すでに電極活物質の基板からの剥離が観察され、これにより放電容量が低下したと見られる。また、数十サイクル以後、放電容量の継続的減少が生じ、数百サイクル後には５０ｍＡｈ／ｇまで容量が低下してしまう。これは第一サイクルで活物質の基板からの剥離が観察されたことによるものと見られる。 On the other hand, Comparative Example 1 shows a very high capacity of 2000 mAh / g at the very beginning, but shows a large capacity drop by several to 10 cycles as shown in FIG. In addition, peeling of the electrode active material from the substrate was already observed at the time of charging in the first cycle, and it is considered that the discharge capacity was reduced due to this. Further, after several tens of cycles, the discharge capacity continuously decreases, and after several hundred cycles, the capacity decreases to 50 mAh / g. This is considered to be due to the observation of the peeling of the active material from the substrate in the first cycle.
以上より明らかなように、本発明のリチウムイオン二次電池用合金負極は、特に、単位体積当り容量、サイクル特性、電極の内部抵抗等の諸特性において、リチウム二次電池のリチウム反応電極として好適であり、黒鉛材料等の従来材料に代わって、リチウムイオン二次電池用負極として好適に用いられる。特に、高容量でサイクル特性が良好であることから、車載用電池等幅広い応用が期待できる。 As is clear from the above, the alloy negative electrode for lithium ion secondary batteries of the present invention is particularly suitable as a lithium reaction electrode for lithium secondary batteries in terms of various characteristics such as capacity per unit volume, cycle characteristics, and internal resistance of the electrodes. In place of conventional materials such as graphite materials, they are suitably used as negative electrodes for lithium ion secondary batteries. In particular, since it has a high capacity and good cycle characteristics, a wide range of applications such as in-vehicle batteries can be expected.
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