JP6241130B2 - Negative electrode active material for electricity storage devices - Google Patents
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Description
本発明は、携帯型電子機器、電気自動車、電気工具、バックアップ用非常電源等に用いられる蓄電デバイス用負極活物質に関する。 The present invention relates to a negative electrode active material for power storage devices used for portable electronic devices, electric vehicles, electric tools, backup emergency power supplies, and the like.
近年、携帯用パソコンや携帯電話の普及に伴い、リチウムイオン二次電池等の蓄電デバイスの高容量化と小サイズ化に対する要望が高まっている。蓄電デバイスの高容量化が進めば、電池の小サイズ化も容易となるため、蓄電デバイスの高容量化へ向けての開発が急務となっている。 In recent years, with the spread of portable personal computers and mobile phones, there is an increasing demand for higher capacity and smaller size of power storage devices such as lithium ion secondary batteries. If the capacity of the electricity storage device is increased, it will be easy to reduce the size of the battery. Therefore, there is an urgent need to develop the capacity of the electricity storage device.
リチウムイオン二次電池用の負極活物質には、一般に黒鉛質炭素材料、ピッチコークス、繊維状カーボン、高容量型のソフトカーボンなどの炭素材料が用いられている。しかしながら、炭素材料は、理論容量が約３７２ｍＡｈ／ｇであるため、電池の高容量化が困難であるという問題がある。 Generally, carbon materials such as graphitic carbon material, pitch coke, fibrous carbon, and high-capacity soft carbon are used as the negative electrode active material for lithium ion secondary batteries. However, since the theoretical capacity of the carbon material is about 372 mAh / g, there is a problem that it is difficult to increase the capacity of the battery.
リチウムイオンを吸蔵および放出することが可能であり、炭素材料からなる負極活物質を上回る高容量密度を有する負極活物質として、ＳｉやＳｎを含有する負極活物質が提案されている（例えば、特許文献１参照）。しかしながら、ＳｉやＳｎを含有する負極活物質は、初回充放電効率（初回の充電容量に対する放電容量の比率）に優れるものの、充放電時におけるリチウムイオンの吸蔵および放出反応に起因する体積変化が著しく大きいため、繰り返し充放電した際に負極活物質が構造劣化して亀裂が生じやすくなる。亀裂が進行すると、場合によっては負極活物質中に空洞が形成され、微粉化してしまうこともある。負極活物質に亀裂が生じると、電子伝導網が分断されるため、繰り返し充放電した後の放電容量（サイクル特性）が低下する問題がある。 A negative electrode active material containing Si and Sn has been proposed as a negative electrode active material that can occlude and release lithium ions and has a higher capacity density than a negative electrode active material made of a carbon material (for example, a patent) Reference 1). However, although the negative electrode active material containing Si or Sn is excellent in the initial charge / discharge efficiency (ratio of the discharge capacity to the initial charge capacity), the volume change due to the lithium ion occlusion and release reaction during charge / discharge is remarkable. Since it is large, the negative electrode active material is structurally deteriorated and repeatedly cracked when repeatedly charged and discharged. As cracks progress, in some cases, cavities are formed in the negative electrode active material and may be pulverized. When a crack occurs in the negative electrode active material, the electron conduction network is divided, so that there is a problem that the discharge capacity (cycle characteristics) after repeated charge and discharge is lowered.
さらに、高容量密度とサイクル特性の両方に優れた負極活物質として、ＳｎＯおよびＰ２Ｏ５からなるガラス材料が提案されている（例えば、特許文献２参照）。 Furthermore, a glass material made of SnO and P 2 O 5 has been proposed as a negative electrode active material excellent in both high capacity density and cycle characteristics (see, for example, Patent Document 2).
負極を製造するにあたり用いられる電極用水系ペーストは、上記ＳｎＯおよびＰ２Ｏ５からなるガラス材料を負極活物質として使用し、その負極活物質に対し、結着剤としてカルボキシメチルセルロース（以下、ＣＭＣ）やポリビニルアルコール（以下、ＰＶＡ）等の水系バインダを加えることにより、製造される。このペーストを長期間保管すると、ペースト中の水分により、ガラス材料中に望まない異種結晶（例えば、ＳｎＨＰＯ４等）が生じるために、ガラス材料中のＰ２Ｏ５ネットワークが切断され、リチウムイオンまたはナトリウムイオンを吸蔵および放出する際におけるＳｎＯの体積変化を緩和できず、結果として、サイクル特性が低下するという問題がある。 An aqueous paste for an electrode used for manufacturing a negative electrode uses the glass material composed of SnO and P 2 O 5 as a negative electrode active material, and carboxymethyl cellulose (hereinafter, CMC) as a binder for the negative electrode active material. And an aqueous binder such as polyvinyl alcohol (hereinafter referred to as PVA). When this paste is stored for a long period of time, unwanted heterogeneous crystals (for example, SnHPO 4 etc.) are generated in the glass material due to moisture in the paste, so that the P 2 O 5 network in the glass material is cut and lithium ions or There is a problem that the volume change of SnO during occlusion and release of sodium ions cannot be mitigated, resulting in a decrease in cycle characteristics.
また、上記ガラス材料が高温高湿雰囲気下に長期間曝されると、ガラス材料中に望まない異種結晶が生じるために、ガラス材料中のＰ２Ｏ５ネットワークが切断され、リチウムイオンまたはナトリウムイオンを吸蔵および放出する際におけるＳｎＯの体積変化を緩和できず、結果として、サイクル特性が低下するという問題がある。 Further, when the glass material is exposed to a high temperature and high humidity atmosphere for a long period of time, an undesirable heterogeneous crystal is generated in the glass material, so that the P 2 O 5 network in the glass material is cut, and lithium ions or sodium ions There is a problem that the volume change of SnO during occlusion and release cannot be mitigated, and as a result, cycle characteristics deteriorate.
本発明は、上記従来技術の現状に鑑みてなされたものであり、その主な目的は、サイクル特性に優れた蓄電デバイス用負極活物質を提供することを目的とする。 The present invention has been made in view of the above-described state of the art, and a main object of the present invention is to provide a negative electrode active material for an electricity storage device having excellent cycle characteristics.
本発明の蓄電デバイス用負極活物質は、酸化物換算のモル％で、ＳｎＯ ４０〜７０％、Ｐ２Ｏ５ ５〜２５％、ＳｉＯ２ ５〜２２％、Ａｌ２Ｏ３ ２〜２０％を含有することを特徴とする。 Negative electrode active material for an electricity storage device of the present invention is the mole percent oxide equivalent, SnO 40~70%, P 2 O 5 5~25%, SiO 2 5~22%, the Al 2 O 3 2 to 20% It is characterized by containing.
また、本発明の蓄電デバイス用負極活物質は、ＳｎＯ／Ｐ２Ｏ５の値が酸化物換算のモル比で３．０〜５．０の範囲にあることが好ましい。 The negative electrode active material for an electricity storage device of the present invention, it is preferable that the value of SnO / P 2 O 5 is in the range of 3.0 to 5.0 in a molar ratio of oxide equivalent.
本発明の蓄電デバイス用負極活物質は、実質的に非晶質からなることが好ましい。 The negative electrode active material for an electricity storage device of the present invention is preferably substantially amorphous.
本発明によれば、サイクル特性に優れた蓄電デバイス用負極活物質を提供することが可能となる。 ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the negative electrode active material for electrical storage devices excellent in cycling characteristics.
本発明の蓄電デバイス用負極活物質は、酸化物換算のモル％で、ＳｎＯ ４０〜７０％、Ｐ２Ｏ５ ５〜２５％、ＳｉＯ２ ５〜２２％、Ａｌ２Ｏ３ ２〜２０％を含有することを特徴とする。各成分をこのように限定した理由を以下に説明する。 Negative electrode active material for an electricity storage device of the present invention is the mole percent oxide equivalent, SnO 40~70%, P 2 O 5 5~25%, SiO 2 5~22%, the Al 2 O 3 2 to 20% It is characterized by containing. The reason why each component is limited in this way will be described below.
ＳｎＯはリチウムイオンまたはナトリウムイオンを吸蔵および放出するサイトとなる活物質成分であり、その含有量は４０〜７０％である。ＳｎＯの含有量は４５〜６８％であることが好ましく、４８〜６５％であることがより好ましく、５０〜６３％であることがさらに好ましい。ＳｎＯの含有量が少なすぎると、負極活物質の単位質量当たりの放電容量が小さくなり、かつ、初回充放電時の充放電効率が低下する傾向がある。一方、ＳｎＯの含有量が多すぎると、負極活物質中の非晶質成分が相対的に少なくなるため、充放電時のリチウムイオンまたはナトリウムイオンの吸蔵および放出に伴う体積変化を緩和できずに、サイクル特性が低下する傾向がある。なお本発明において、ＳｎＯの含有量は、ＳｎＯ以外の酸化スズ成分（ＳｎＯ２等）もＳｎＯに換算して合算したものを指す。 SnO is an active material component that becomes a site for occluding and releasing lithium ions or sodium ions, and its content is 40 to 70%. The SnO content is preferably 45 to 68%, more preferably 48 to 65%, and still more preferably 50 to 63%. When there is too little content of SnO, the discharge capacity per unit mass of a negative electrode active material will become small, and there exists a tendency for the charge / discharge efficiency at the time of first time charge / discharge to fall. On the other hand, if the content of SnO is too large, the amorphous component in the negative electrode active material is relatively reduced, and the volume change associated with insertion and extraction of lithium ions or sodium ions during charge / discharge cannot be mitigated. , The cycle characteristics tend to deteriorate. In the present invention, the content of SnO is oxidized tin component other than SnO (SnO 2, etc.) also refers to that summed in terms of SnO.
Ｐ２Ｏ５は網目形成酸化物であり、ＳｎＯにおけるリチウムイオンまたはナトリウムイオンの吸蔵および放出サイトを取り囲み、サイクル特性を向上させる作用があり、その含有量は５〜２５％である。Ｐ２Ｏ５の含有量は５．５〜２４％であることが好ましく、６〜２３％であることがより好ましい。Ｐ２Ｏ５の含有量が少なすぎると、充放電時のリチウムイオンまたはナトリウムイオンの吸蔵および放出に伴うＳｎＯの体積変化を緩和できず構造劣化を起こすため、サイクル特性が低下しやすくなる。一方、Ｐ２Ｏ５の含有量が多すぎると、耐水性が低下しやすくなり、また、水系電極ペーストを作製した際に、ガラス材料中に望まない異種結晶が生じるために、ガラス材料中のＰ２Ｏ５ネットワークが切断され、リチウムイオンまたはナトリウムイオンを吸蔵および放出する際におけるＳｎＯの体積変化を緩和できず、結果として、サイクル特性が低下しやすくなる。 P 2 O 5 is a network-forming oxide that surrounds lithium ion or sodium ion storage and release sites in SnO and has an effect of improving cycle characteristics, and its content is 5 to 25%. The content of P 2 O 5 is preferably 5.5 to 24%, and more preferably 6 to 23%. If the content of P 2 O 5 is too small, the volume change of SnO associated with insertion and extraction of lithium ions or sodium ions during charge / discharge cannot be alleviated, resulting in structural deterioration, and cycle characteristics are likely to deteriorate. On the other hand, if the content of P 2 O 5 is too large, the water resistance tends to decrease, and when a water-based electrode paste is produced, unwanted heterogeneous crystals are produced in the glass material. The P 2 O 5 network is cut, and the volume change of SnO when occlusion and release of lithium ions or sodium ions cannot be mitigated, and as a result, the cycle characteristics are likely to deteriorate.
ＳｉＯ２も網目形成酸化物であり、ＳｎＯにおけるリチウムイオンまたはナトリウムイオンの吸蔵および放出サイトを取り囲み、サイクル特性を向上させる作用があり、その含有量は５〜２２％である。ＳｉＯ２の含有量は５．５〜２１％であることが好ましく、６〜２０％であることがより好ましい。ＳｉＯ２の含有量が少なすぎると、充放電時のリチウムイオンまたはナトリウムイオンの吸蔵および放出に伴うＳｎＯの体積変化を緩和できず構造劣化を起こすため、サイクル特性が低下しやすくなる。一方、ＳｉＯ２の含有量が多すぎると、ＳｉＯ２やＳｉＰ２Ｏ７などの結晶が析出しやすくなり、サイクル特性が低下する傾向がある。 SiO 2 is also a network-forming oxide, has an effect of surrounding the lithium ion or sodium ion occlusion and release sites in SnO and improving cycle characteristics, and its content is 5 to 22%. The content of SiO 2 is preferably 5.5 to 21%, and more preferably 6 to 20%. If the content of SiO 2 is too small, the volume change of SnO accompanying the occlusion and release of lithium ions or sodium ions during charge / discharge cannot be relaxed, resulting in structural deterioration, so that the cycle characteristics are likely to deteriorate. On the other hand, when the content of SiO 2 is too large, crystals such as SiO 2 and SiP 2 O 7 tend to precipitate, and the cycle characteristics tend to be deteriorated.
Ａｌ２Ｏ３は耐水性を向上させる作用があり、その含有量は２〜２０％である。Ａｌ２Ｏ３の含有量は３〜１７％であることが好ましく、４〜１５％であることがより好ましい。Ａｌ２Ｏ３の含有量が少なすぎると、耐水性が低下しやすくなり、サイクル特性が低下しやすくなる。Ａｌ２Ｏ３の含有量が多すぎると、Ａｌ２Ｏ３やＡｌＰＯ４などの結晶が析出しやすくなり、サイクル特性が低下する傾向がある。 Al 2 O 3 has an effect of improving water resistance, and its content is 2 to 20%. The content of Al 2 O 3 is preferably 3 to 17%, more preferably 4 to 15%. When Al 2 content of O 3 is too small, it water resistance tends to decrease, the cycle characteristics are easily lowered. When the content of Al 2 O 3 is too large, Al 2 O 3 or AlPO 4 becomes crystals are likely to deposit, such as the cycle characteristics tend to decrease.
ＳｎＯ／Ｐ２Ｏ５（モル比）は、３．０〜５．０であることが好ましく、３．２〜４．８であることがより好ましく、３．３〜４．５であることがさらに好ましい。ＳｎＯ／Ｐ２Ｏ５が小さすぎると、ＳｎＯ２結晶やＳｎＰ２Ｏ７結晶、ＳｉＯ２結晶、Ａｌ２Ｏ３結晶が析出しやすく、均質なガラスが得られ難くなり、サイクル特性が低下する傾向がある。一方、ＳｎＯ／Ｐ２Ｏ５が大きすぎると、ＳｎＯの不均化反応が起こり、ＳｎＯ２結晶や金属Ｓｎが析出しやすくなり、サイクル特性が低下する傾向がある。 SnO / P 2 O 5 (molar ratio) is preferably 3.0 to 5.0, more preferably 3.2 to 4.8, and more preferably 3.3 to 4.5. Further preferred. When SnO / P 2 O 5 is too small, SnO 2 crystal, SnP 2 O 7 crystal, SiO 2 crystal, and Al 2 O 3 crystal are likely to precipitate, and it becomes difficult to obtain a homogeneous glass, and the cycle characteristics tend to be lowered. There is. On the other hand, if SnO / P 2 O 5 is too large, a disproportionation reaction of SnO occurs, SnO 2 crystals and metal Sn tend to precipitate, and the cycle characteristics tend to deteriorate.
また、本発明の効果を損なわない範囲で、上記成分に加えてさらに種々の成分を添加することができる。このような成分としては、例えばＣｕＯ、ＺｎＯ、Ｂ２Ｏ３、ＭｇＯ、ＣａＯ、Ｒ２Ｏ（ＲはＬｉ、Ｎａ、ＫまたはＣｓを示す）などが挙げられる。上記成分の含有量は、合量で０〜２０％であることが好ましく、０〜１５％であることがより好ましく、０．１〜１３％であることがさらに好ましい。 Further, various components can be added in addition to the above components within the range not impairing the effects of the present invention. Examples of such components include CuO, ZnO, B 2 O 3 , MgO, CaO, R 2 O (R represents Li, Na, K, or Cs). The total content of the above components is preferably 0 to 20%, more preferably 0 to 15%, and further preferably 0.1 to 13%.
本発明の蓄電デバイス用負極活物質の結晶化度は、充放電反応前において質量％で９５％以下であることが好ましく、８０％以下であることがより好ましく、７０％以下であることがさらに好ましく、５０％以下であることがなお好ましく、４０％以下であることがより一層好ましく、１０％以下であることが特に好ましい。また、負極活物質は実質的に非晶質からなることが好ましい。ここで、「実質的に非晶質からなる」とは、結晶化度が実質的に０％（具体的には、０．１％未満）であることを指し、後述の粉末Ｘ線回折測定において、結晶性回折線が検出されないものをいう。結晶化度が小さい（非晶質の割合が大きい）ほど、繰り返し充放電時の体積変化を緩和できるため、サイクル特性が向上する傾向がある。 The degree of crystallinity of the negative electrode active material for an electricity storage device of the present invention is preferably 95% or less, more preferably 80% or less, and more preferably 70% or less in mass% before the charge / discharge reaction. Preferably, it is 50% or less, more preferably 40% or less, and particularly preferably 10% or less. The negative electrode active material is preferably substantially amorphous. Here, “consisting essentially of amorphous” means that the crystallinity is substantially 0% (specifically, less than 0.1%), and will be described later by powder X-ray diffraction measurement. In which no crystalline diffraction line is detected. The smaller the degree of crystallinity (the greater the proportion of amorphous material), the more the change in volume during repeated charge / discharge can be alleviated, and the cycle characteristics tend to improve.
なお、結晶化度は、ＣｕＫα線を用いた粉末Ｘ線回折測定によって得られる２θ値で１０〜６０°の回折線プロファイルを、結晶性回折線と非晶質ハローとにピーク分離することで求められる。具体的には、回折線プロファイルからバックグラウンドを差し引いて得られた全散乱曲線から、１０〜４０°におけるブロードな回折線（非晶質ハロー）をピーク分離して求めた積分強度をＩａ、１０〜６０°において検出される各結晶性回折線をピーク分離して求めた積分強度の総和をＩｃとした場合、結晶化度Ｘｃは次式から求められる。
Ｘｃ＝[Ｉｃ／（Ｉｃ＋Ｉａ）]×１００（％）
The crystallinity is obtained by separating a diffraction line profile of 10 to 60 ° with a 2θ value obtained by powder X-ray diffraction measurement using CuKα ray into a crystalline diffraction line and an amorphous halo. It is done. Specifically, the integrated intensity obtained by peak-separating a broad diffraction line (amorphous halo) at 10 to 40 ° from the total scattering curve obtained by subtracting the background from the diffraction line profile is Ia, 10 When the total integrated intensity obtained by peak separation of each crystalline diffraction line detected at ˜60 ° is Ic, the crystallinity Xc can be obtained from the following equation.
Xc = [Ic / (Ic + Ia)] × 100 (%)
負極活物質が粉末状である場合、平均粒子径は０．１〜２０μｍであることが好ましく、０．２〜１５μｍであることがより好ましく、０．３〜１０μｍであることがさらに好ましく、０．５〜５μｍであることが特に好ましい。最大粒子径は１５０μｍ以下であることが好ましく、１００μｍ以下であることがより好ましく、７５μｍ以下であることがさらに好ましく、５５μｍ以下であることが特に好ましい。平均粒子径や最大粒子径が大きすぎると、充放電した際にリチウムイオンまたはナトリウムイオンの吸蔵および放出に伴う負極活物質の体積変化を緩和できず、集電体から剥れやすくなり、サイクル特性が著しく低下する傾向がある。一方、平均粒子径が小さすぎると、ペースト化した際に粉末の分散状態に劣り、均一な電極を製造することが困難になる傾向がある。また、比表面積が大きくなりすぎて、電極形成用のペーストを製造する際に負極活物質粉末が分散しにくくなるため、多量の結着剤や溶剤が必要となる。さらに、電極形成用ペーストの塗布性に劣り、均一な厚みを有する負極を形成しにくくなる。 When the negative electrode active material is in a powder form, the average particle size is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, still more preferably 0.3 to 10 μm, and 0 It is particularly preferably 5 to 5 μm. The maximum particle size is preferably 150 μm or less, more preferably 100 μm or less, further preferably 75 μm or less, and particularly preferably 55 μm or less. If the average particle size or the maximum particle size is too large, the volume change of the negative electrode active material due to the insertion and extraction of lithium ions or sodium ions during charge / discharge cannot be mitigated, and it becomes easy to peel off from the current collector, resulting in cycle characteristics. Tends to decrease significantly. On the other hand, if the average particle size is too small, the powder is in a poorly dispersed state when formed into a paste, and it tends to be difficult to produce a uniform electrode. In addition, since the specific surface area becomes too large and the negative electrode active material powder is difficult to disperse when producing a paste for forming an electrode, a large amount of binder and solvent are required. Furthermore, it is inferior to the applicability of the electrode forming paste, and it becomes difficult to form a negative electrode having a uniform thickness.
ここで、平均粒子径と最大粒子径は、それぞれ一次粒子のメイジアン径でＤ５０（５０％体積累積径）とＤ９０（９０％体積累積径）を示し、レーザー回折式粒度分布測定装置により測定された値をいう。 Here, the average particle size and the maximum particle size are D50 (50% volume cumulative diameter) and D90 (90% volume cumulative diameter), respectively, in terms of the median diameter of primary particles, and were measured by a laser diffraction particle size distribution analyzer. Value.
本発明の蓄電デバイス用負極活物質において、所定サイズの粉末を得るためには、一般的な粉砕機や分級機が用いられる。例えば、乳鉢、ボールミル、振動ボールミル、衛星ボールミル、遊星ボールミル、ジェットミル、篩、遠心分離、空気分級などが用いられる。 In order to obtain a powder of a predetermined size in the negative electrode active material for an electricity storage device of the present invention, a general pulverizer or classifier is used. For example, a mortar, a ball mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a jet mill, a sieve, a centrifugal separator, an air classification, or the like is used.
本発明の蓄電デバイス用負極活物質は、例えば原料粉末を加熱溶融してガラス化することにより製造される。Ｓｎを含む酸化物材料は、溶融条件によってＳｎ原子の酸化状態が変化しやすく、大気中で溶融した場合、望まないＳｎＯ２やＳｎＰ２Ｏ７等の結晶がガラス融液表面やガラス融液中に形成されやすい。その結果、負極活物質の初回充放電効率およびサイクル特性が低下しやすくなる。そこで、還元雰囲気または不活性雰囲気中で溶融を行うことで、酸化物材料中のＳｎイオンの価数の増加を抑制し、望まない結晶の形成を抑制でき、初回充放電効率およびサイクル特性に優れた蓄電デバイスを得ることが可能となる。 The negative electrode active material for an electricity storage device of the present invention is produced, for example, by heating and melting raw material powder to vitrify it. Oxide material containing Sn, the oxidation state of Sn atoms is likely to vary with the melting conditions, when melted in the atmosphere, the crystal such as SnO 2 and SnP 2 O 7 is not desired glass melt surface or a glass melt in It is easy to be formed. As a result, the initial charge / discharge efficiency and cycle characteristics of the negative electrode active material are likely to deteriorate. Therefore, by performing melting in a reducing atmosphere or an inert atmosphere, it is possible to suppress an increase in the valence of Sn ions in the oxide material, to suppress formation of unwanted crystals, and to be excellent in initial charge / discharge efficiency and cycle characteristics. It is possible to obtain an electricity storage device.
還元雰囲気で溶融するには、溶融槽中へ還元性ガスを供給することが好ましい。還元性ガスとしては、体積％で、Ｎ２ ９０〜９９．５％およびＨ２ ０．５〜１０％を含有する混合気体を用いることが好ましく、Ｎ２ ９２〜９９％およびＨ２ １〜８％を含有する混合気体を用いることがより好ましい。 In order to melt in a reducing atmosphere, it is preferable to supply a reducing gas into the melting tank. The reducing gas, by volume%, it is preferable to use a mixed gas containing N 2 90 to 99.5% and H 2 0.5~10%, N 2 92~99 % and H 2 1 to 8 It is more preferable to use a mixed gas containing%.
不活性雰囲気で溶融する場合は、溶融槽中へ不活性ガスを供給することが好ましい。不活性ガスとしては、窒素、アルゴン、ヘリウムのいずれかを用いることが好ましい。 When melting in an inert atmosphere, it is preferable to supply an inert gas into the melting tank. As the inert gas, it is preferable to use any of nitrogen, argon, and helium.
還元性ガスまたは不活性ガスは、溶融槽において溶融ガラスの上部雰囲気に供給してもよいし、バブリングノズルから溶融ガラス中に直接供給してもよく、両手法を同時に行ってもよい。 The reducing gas or the inert gas may be supplied to the upper atmosphere of the molten glass in the melting tank, may be supplied directly from the bubbling nozzle into the molten glass, or both methods may be performed simultaneously.
また、上記負極活物質の製造方法において、出発原料粉末に複合酸化物を使用することにより、失透異物が少なく均質性に優れた負極活物質が得られやすくなる。当該負極活物質を用いれば、放電容量が安定した蓄電デバイスが得られやすくなる。このような複合酸化物としては、ピロリン酸第一錫（Ｓｎ２Ｐ２Ｏ７）等が挙げられる。 Moreover, in the manufacturing method of the said negative electrode active material, it becomes easy to obtain the negative electrode active material with few devitrification foreign materials and excellent uniformity by using composite oxide for starting raw material powder. If the negative electrode active material is used, an electricity storage device having a stable discharge capacity can be easily obtained. Examples of such complex oxides include stannous pyrophosphate (Sn 2 P 2 O 7 ).
以上、主にリチウムイオン二次電池及びナトリウムイオン二次電池用負極活物質について説明してきたが、本発明の負極活物質はこれに限定されるものではなく、他の非水系二次電池や、さらには、リチウムイオン二次電池及びナトリウムイオン二次電池用の負極活物質と非水系電気二重層キャパシタ用の正極材料とを組み合わせたハイブリットキャパシタ等にも適用できる。 As mentioned above, although the negative electrode active material for lithium ion secondary batteries and sodium ion secondary batteries has been mainly described, the negative electrode active material of the present invention is not limited to this, other non-aqueous secondary batteries, Furthermore, the present invention can be applied to a hybrid capacitor in which a negative electrode active material for a lithium ion secondary battery and a sodium ion secondary battery and a positive electrode material for a non-aqueous electric double layer capacitor are combined.
ハイブリットキャパシタであるリチウムイオンキャパシタ及びナトリウムイオンキャパシタは、正極と負極の充放電原理が異なる非対称キャパシタの１種である。リチウムイオンキャパシタ及びナトリウムイオンキャパシタは、リチウムイオン二次電池及びナトリウムイオン二次電池用の負極と電気二重層キャパシタ用の正極を組み合わせた構造を有している。ここで、正極は表面に電気二重層を形成し、物理的な作用（静電気作用）を利用して充放電するのに対し、負極は既述のリチウムイオン二次電池及びナトリウムイオン二次電池と同様にリチウムイオンまたはナトリウムイオンの化学反応（吸蔵および放出）により充放電する。 Lithium ion capacitors and sodium ion capacitors, which are hybrid capacitors, are one type of asymmetric capacitors that have different charge / discharge principles for the positive and negative electrodes. The lithium ion capacitor and the sodium ion capacitor have a structure in which a negative electrode for a lithium ion secondary battery and a sodium ion secondary battery and a positive electrode for an electric double layer capacitor are combined. Here, the positive electrode forms an electric double layer on the surface and is charged and discharged by utilizing a physical action (electrostatic action), whereas the negative electrode is a lithium ion secondary battery and a sodium ion secondary battery described above. Similarly, charging / discharging is performed by a chemical reaction (storage and release) of lithium ions or sodium ions.
リチウムイオンキャパシタ及びナトリウムイオンキャパシタの正極には、活性炭、ポリアセン、メソフェーズカーボンなどの高比表面積の炭素質粉末などからなる正極活物質が用いられる。一方、負極には、本発明の負極活物質を用いることができる。 A positive electrode active material made of a carbonaceous powder having a high specific surface area such as activated carbon, polyacene, or mesophase carbon is used for the positive electrode of the lithium ion capacitor and the sodium ion capacitor. On the other hand, the negative electrode active material of the present invention can be used for the negative electrode.
なお、本発明の蓄電デバイス用負極活物質を用いた蓄電デバイスを充放電した後は、当該蓄電デバイス用負極活物質はリチウム酸化物、ナトリウム酸化物、Ｓｎ−Ｌｉ合金、Ｓｎ−Ｎａ合金または金属スズを含有する場合がある。 In addition, after charging / discharging the electrical storage device using the negative electrode active material for electrical storage devices of this invention, the said negative electrode active material for electrical storage devices is lithium oxide, sodium oxide, Sn-Li alloy, Sn-Na alloy, or metal May contain tin.
以下、本発明の蓄電デバイス用負極活物質の一例として、非水二次電池の用途に適用した実施例について説明するが、本発明はこれらの実施例に限定されるものではない。 Examples of the negative electrode active material for an electricity storage device of the present invention will be described below with reference to examples applied to the use of a nonaqueous secondary battery, but the present invention is not limited to these examples.
（１）負極活物質の作製
表１に示す実施例１〜５および比較例１〜４の組成となるように、主原料としてスズとリンの複合酸化物（ピロリン酸第一錫：Ｓｎ２Ｐ２Ｏ７）を用い、各種酸化物、燐酸塩原料、炭酸塩原料、還元剤として金属粉末原料または炭素原料、などで原料粉末を調製した。原料粉末を石英ルツボに投入し、電気炉を用いて窒素雰囲気にて９５０℃、４０分間の溶融を行い、ガラス化した。
(1) Preparation of negative electrode active material Tin and phosphorus composite oxide (stannous pyrophosphate: Sn 2 P) as the main raw material so as to have the compositions of Examples 1 to 5 and Comparative Examples 1 to 4 shown in Table 1 2 O 7 ), raw material powders were prepared using various oxides, phosphate raw materials, carbonate raw materials, metal powder raw materials or carbon raw materials as a reducing agent. The raw material powder was put into a quartz crucible and melted at 950 ° C. for 40 minutes in a nitrogen atmosphere using an electric furnace to be vitrified.
次いで、溶融ガラスを一対の回転ローラー間に流し出し、急冷しながら成形し、厚み０．１〜２ｍｍのフィルム状のガラスを得た。このフィルム状ガラスを直径２０〜３０ｍｍのジルコニアボールを入れたボールミルを用いて１００ｒｐｍで３時間粉砕した後、目開き１２０μｍの樹脂製篩に通過させ、平均粒子径３〜１５μｍガラス粗粉末を得た。次いで、この粗粉末ガラスを空気分級することで平均粒子径３μｍかつ最大粒子径２８μｍのガラス粉末を得た。 Next, the molten glass was poured out between a pair of rotating rollers and molded while being rapidly cooled to obtain a film-like glass having a thickness of 0.1 to 2 mm. This film-like glass was pulverized at 100 rpm for 3 hours using a ball mill containing zirconia balls having a diameter of 20 to 30 mm, and then passed through a resin sieve having an opening of 120 μm to obtain a glass coarse powder having an average particle size of 3 to 15 μm. . Subsequently, this coarse powder glass was air classified to obtain a glass powder having an average particle size of 3 μm and a maximum particle size of 28 μm.
得られたガラス粉末について粉末Ｘ線回折測定することにより構造を同定した。実施例１〜５のガラス粉末は、結晶化度が２．１％以下であり、特に実施例１、および３〜５のガラス粉末は非晶質であり、結晶は検出されなかった。比較例１〜４の試料は、結晶化度が１１．３％以上であり、結晶を多く含有した構造であった。 The structure of the obtained glass powder was identified by powder X-ray diffraction measurement. The glass powders of Examples 1 to 5 had a crystallinity of 2.1% or less. In particular, the glass powders of Examples 1 and 3 to 5 were amorphous, and no crystals were detected. The samples of Comparative Examples 1 to 4 had a crystallinity of 11.3% or more and a structure containing many crystals.
（２）リチウムイオン二次電池用負極の作製
ガラス粉末に対し、結着剤としてカルボキシメチルセルロース、導電助剤として物質名ＳｕｐｅｒＣ６５（Ｔｉｍｃａｌ社製）を、ガラス粉末：結着剤：導電助剤＝８３：１２：５（質量比）となるように秤量し、これらを純水に分散した後、自転・公転ミキサーで十分に撹拌してスラリー化した。次に、隙間７５μｍのドクターブレードを用いて、負極集電体である厚さ２０μｍの銅箔上に、得られたスラリーをコートし、乾燥機にて７０℃で減圧乾燥後、一対の回転ローラー間に通してプレスすることにより電極シートを得た。電極シートを電極打ち抜き機で直径１１ｍｍに打ち抜き、減圧しながら１６０℃で８時間乾燥させて円形の負極を得た。
(2) Production of Negative Electrode for Lithium Ion Secondary Battery For glass powder, carboxymethyl cellulose as a binder, substance name SuperC65 (manufactured by Timcal) as a conductive aid, glass powder: binder: conductive aid = 83 : Weighed so as to be 12: 5 (mass ratio) and dispersed them in pure water, and then sufficiently stirred with a rotation / revolution mixer to form a slurry. Next, using a doctor blade with a gap of 75 μm, the obtained slurry was coated on a copper foil having a thickness of 20 μm as a negative electrode current collector, dried under reduced pressure at 70 ° C. with a dryer, and then a pair of rotating rollers An electrode sheet was obtained by pressing in between. The electrode sheet was punched to a diameter of 11 mm with an electrode punching machine and dried at 160 ° C. for 8 hours while reducing the pressure to obtain a circular negative electrode.
（３）試験電池（リチウムイオン二次電池）の作製
次に、得られた負極を、銅箔面を下に向けてコインセルの下蓋に載置し、その上に７０℃で８時間減圧乾燥した直径１６ｍｍのポリプロピレン多孔質膜（ヘキストセラニーズ社製 セルガード＃２４００）からなるセパレータ、および、対極である金属リチウムを積層し、試験電池を作製した。電解液としては、１Ｍ ＬｉＰＦ６溶液／ＥＣ：ＤＥＣ＝１：１（ＥＣ＝エチレンカーボネート、ＤＥＣ＝ジエチルカーボネート）を用いた。なお試験電池の組み立ては露点温度−４０℃以下の環境で行った。
(3) Production of test battery (lithium ion secondary battery) Next, the obtained negative electrode was placed on the lower lid of the coin cell with the copper foil surface facing down, and dried under reduced pressure at 70 ° C. for 8 hours. A test battery was manufactured by laminating a separator made of a polypropylene porous membrane having a diameter of 16 mm (Celguard # 2400 manufactured by Hoechst Celanese) and metallic lithium as a counter electrode. As the electrolytic solution, 1M LiPF 6 solution / EC: DEC = 1: 1 (EC = ethylene carbonate, DEC = diethyl carbonate) was used. The test battery was assembled in an environment with a dew point temperature of −40 ° C. or lower.
（４）充放電試験
上記試験電池に対し、３０℃で１Ｖから０ＶまでＣＣ（定電流）充電（負極活物質へのリチウムイオン吸蔵）を行い、負極活物質の単位質量中に充電された電気量（充電容量）を求めた。次に、０Ｖから１ＶまでＣＣ放電（負極活物質からのリチウムイオン放出）させ、負極活物質の単位質量中に放電された電気量（放電容量）を求めた。なお、Ｃレートは０．５Ｃとした。表１に、充放電特性の結果を示す。なお、放電容量維持率は、初回放電容量に対する１００サイクル目の放電容量の割合をいう。
(4) Charging / discharging test The test battery was charged at a unit mass of the negative electrode active material by performing CC (constant current) charge (lithium ion occlusion to the negative electrode active material) from 1 V to 0 V at 30 ° C. The amount (charge capacity) was determined. Next, CC discharge (lithium ion release from the negative electrode active material) was performed from 0 V to 1 V, and the amount of electricity (discharge capacity) discharged in the unit mass of the negative electrode active material was determined. The C rate was 0.5C. Table 1 shows the results of the charge / discharge characteristics. The discharge capacity retention rate is the ratio of the discharge capacity at the 100th cycle to the initial discharge capacity.
実施例１〜５の初回放電容量は４５８ｍＡｈ／ｇ以上、放電容量維持率８１．０％以上と、高容量であり、かつサイクル性も良好であった。一方、比較例１〜４は、４７９ｍＡｈ／ｇ以上と高容量であったが、放電容量維持率が５９．９％以下といずれも低かった。 In Examples 1 to 5, the initial discharge capacity was 458 mAh / g or more, the discharge capacity retention rate was 81.0% or more, the capacity was high, and the cycle performance was also good. On the other hand, Comparative Examples 1 to 4 had a high capacity of 479 mAh / g or more, but the discharge capacity retention rate was 59.9% or less, both of which were low.
（５）ナトリウムイオン二次電池用負極の作製
表１の実施例１または２のガラス粉末に対し、結着剤として熱硬化性ポリイミド樹脂、導電助剤として物質名ＳｕｐｅｒＣ６５（Ｔｉｍｃａｌ社製）を、ガラス粉末：結着剤：導電助剤＝８３：１２：５（質量比）となるように秤量し、これらをＮ−メチルピロリドン（ＮＭＰ）に分散した後、自転・公転ミキサーで十分に撹拌してスラリー化した。次に、隙間１００μｍのドクターブレードを用いて、負極集電体である厚さ２０μｍの銅箔上に、得られたスラリーをコートし、乾燥機にて７０℃で減圧乾燥後、一対の回転ローラー間に通してプレスすることにより電極シートを得た。電極シートを電極打ち抜き機で直径１１ｍｍに打ち抜き、減圧しながら３００℃で３時間乾燥させて円形の負極を得た。
(5) Production of negative electrode for sodium ion secondary battery For the glass powder of Example 1 or 2 in Table 1, a thermosetting polyimide resin as a binder and a substance name SuperC65 (manufactured by Timcal) as a conductive auxiliary agent, Glass powder: Binder: Conductive aid = 83: 12: 5 (mass ratio) Weighed so that these were dispersed in N-methylpyrrolidone (NMP), and then sufficiently stirred with a rotation / revolution mixer To make a slurry. Next, using a doctor blade with a gap of 100 μm, the obtained slurry was coated on a 20 μm thick copper foil as a negative electrode current collector, dried under reduced pressure at 70 ° C. in a dryer, and then a pair of rotating rollers An electrode sheet was obtained by pressing in between. The electrode sheet was punched to a diameter of 11 mm with an electrode punching machine and dried at 300 ° C. for 3 hours while reducing the pressure to obtain a circular negative electrode.
（６）試験電池（ナトリウムイオン二次電池）の作製
次に、得られた負極を、銅箔面を下に向けてコインセルの下蓋に載置し、その上に７０℃で８時間減圧乾燥した直径１６ｍｍのポリプロピレン多孔質膜からなるセパレータ、および、対極である金属ナトリウムを積層し、試験電池を作製した。電解液としては、１Ｍ ＮａＰＦ６溶液／ＥＣ：ＤＥＣ＝１：１を用いた。なお試験電池の組み立ては露点温度−７０℃以下の環境で行った。
(6) Production of test battery (sodium ion secondary battery) Next, the obtained negative electrode was placed on the bottom lid of the coin cell with the copper foil surface facing down, and dried under reduced pressure at 70 ° C. for 8 hours. A test battery was manufactured by laminating a separator made of a polypropylene porous film having a diameter of 16 mm and metallic sodium as a counter electrode. As the electrolytic solution, 1M NaPF 6 solution / EC: DEC = 1: 1 was used. The test battery was assembled in an environment with a dew point temperature of −70 ° C. or lower.
（７）充放電試験
上記試験電池に対し、３０℃で１Ｖから０ＶまでＣＣ（定電流）充電（負極活物質へのナトリウムイオン吸蔵）を行い、負極活物質の単位質量中に充電された電気量（充電容量）を求めた。次に、０Ｖから１ＶまでＣＣ放電（負極活物質からのナトリウムイオン放出）させ、負極活物質の単位質量中に放電された電気量（放電容量）を求めた。なお、Ｃレートは０．１Ｃとした。表２に、充放電特性の結果を示す。なお、放電容量維持率は、初回放電容量に対する２５サイクル目の放電容量の割合をいう。
(7) Charge / Discharge Test The above test battery was charged at a unit mass of the negative electrode active material by performing CC (constant current) charge (sodium ion occlusion in the negative electrode active material) from 1 V to 0 V at 30 ° C. The amount (charge capacity) was determined. Next, CC discharge (sodium ion release from the negative electrode active material) was performed from 0 V to 1 V, and the amount of electricity (discharge capacity) discharged in the unit mass of the negative electrode active material was determined. The C rate was 0.1C. Table 2 shows the results of the charge / discharge characteristics. The discharge capacity retention rate is the ratio of the discharge capacity at the 25th cycle to the initial discharge capacity.
実施例１、２の初回放電容量は２９３ｍＡｈ／ｇ以上、放電容量維持率９１％以上と、高容量であり、かつサイクル性も良好であった。 In Examples 1 and 2, the initial discharge capacity was 293 mAh / g or more, the discharge capacity retention rate was 91% or more, the capacity was high, and the cycle performance was also good.
本発明の蓄電デバイス用負極活物質は、携帯型電子機器、電気自動車、電気工具、バックアップ用非常電源等に用いられる蓄電デバイス用負極活物質として好適である。
The negative electrode active material for power storage devices of the present invention is suitable as a negative electrode active material for power storage devices used for portable electronic devices, electric vehicles, electric tools, backup emergency power supplies, and the like.
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