JP7444366B1 - Electrode for non-aqueous electrolyte secondary battery and method for manufacturing the same - Google Patents
Electrode for non-aqueous electrolyte secondary battery and method for manufacturing the same Download PDFInfo
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- JP7444366B1 JP7444366B1 JP2023050161A JP2023050161A JP7444366B1 JP 7444366 B1 JP7444366 B1 JP 7444366B1 JP 2023050161 A JP2023050161 A JP 2023050161A JP 2023050161 A JP2023050161 A JP 2023050161A JP 7444366 B1 JP7444366 B1 JP 7444366B1
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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
Landscapes
- Battery Electrode And Active Subsutance (AREA)
Abstract
【課題】 ケイ酸塩やリン酸塩からなる無機バインダと活物質との接着性が十分に確保しにくい電極、あるいは膜厚や密度の高い活物質層を有する電極であっても、大幅にサイクル特性を向上させることができる電極の製造方法を提案する。【解決手段】 非水電解質二次電池の電極の製造方法であって、活物質と樹脂バインダを含んでなるスラリーを集電体に塗布または充填し、乾燥後、活物質層を製造する工程Ａと、温度３０℃以上１２０℃以下の無機バインダ水溶液に、前記活物質層を浸漬または塗布し、乾燥後、電極を製造する工程Ｂと、を備え、前記無機バインダ水溶液が、ケイ酸塩水溶液またはリン酸塩水溶液であり、前記ケイ酸塩水溶液は、Ａ2Ｏ・ｎＳｉＯ2で表されるケイ酸塩を水に溶解した液体であり、ＡがＬｉ、ＮａまたはＫの少なくともいずれか一種であり、ｎが１．７以上５以下であり、前記リン酸塩水溶液は、Ａｌ2Ｏ3・ｎＰ2Ｏ5で表されるリン酸塩を水に溶解した液体であり、ｎが１．７以上５以下である、電極の製造方法。【選択図】 なし[Challenge] Even for electrodes where it is difficult to ensure sufficient adhesion between an inorganic binder made of silicate or phosphate and an active material, or an electrode that has an active material layer with a high thickness or density, it is difficult to cycle We propose a manufacturing method for electrodes that can improve properties. [Solution] A method for manufacturing an electrode for a non-aqueous electrolyte secondary battery, which includes a step A of applying or filling a current collector with a slurry containing an active material and a resin binder, and manufacturing an active material layer after drying. and step B of immersing or applying the active material layer in an aqueous inorganic binder solution at a temperature of 30° C. to 120° C. and manufacturing an electrode after drying, wherein the inorganic binder aqueous solution is a silicate aqueous solution or The silicate aqueous solution is a liquid obtained by dissolving a silicate represented by A2O.nSiO2 in water, where A is at least one of Li, Na, or K, and n is 1.7 or more and 5 or less, the phosphate aqueous solution is a liquid obtained by dissolving a phosphate represented by Al2O3/nP2O5 in water, and n is 1.7 or more and 5 or less, a method for producing an electrode. . [Selection diagram] None
Description
本発明は、非水電解質二次電池の電極及びその製造方法に関する。 The present invention relates to an electrode for a non-aqueous electrolyte secondary battery and a method for manufacturing the same.
二次電池の利用分野は、電子機器から自動車、大型蓄電システムなどへと展開しており、その市場規模は１０兆円以上の産業に成長することが期待される。すでに、スマートフォン、タブレット型端末などの情報通信機器が、めざましい普及を遂げている。 Fields of use for secondary batteries are expanding from electronic equipment to automobiles and large-scale power storage systems, and the market size is expected to grow into an industry worth more than 10 trillion yen. Information and communication devices such as smartphones and tablet devices have already achieved remarkable popularity.
加えて、二次電池は、電気自動車（ＥＶ）、プラグインハイブリッド自動車（ＰＨＥＶ）等をはじめとする次世代自動車の電源へと応用範囲も広がっている。また、二次電池は、家庭用バックアップ電源、自然エネルギーの蓄電、負荷平準化などに用いられるようになっている。このように、二次電池は、省エネルギー技術や新エネルギー技術の導入においても不可欠な存在である。 In addition, the scope of application of secondary batteries is expanding to power sources for next-generation vehicles such as electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs). In addition, secondary batteries have come to be used for household backup power sources, natural energy storage, load leveling, and the like. In this way, secondary batteries are indispensable in the introduction of energy saving technology and new energy technology.
従来の二次電池としては、鉛蓄電池、ニッケル－カドニウム電池、ニッケル－水素電池などの電解質に水を含む蓄電池が主流であったが、小型、軽量、高電圧、メモリー効果なしという特徴から、近年では非水電解質二次電池の使用が増大している。非水電解質二次電池とは、水を主成分としない電解質を用いた電池系で、且つ充放電可能な蓄電デバイスの総称である。 Traditionally, secondary batteries that contain water as an electrolyte, such as lead-acid batteries, nickel-cadmium batteries, and nickel-metal hydride batteries, have been mainstream, but in recent years they have become popular due to their small size, light weight, high voltage, and no memory effect. The use of non-aqueous electrolyte secondary batteries is increasing. A non-aqueous electrolyte secondary battery is a general term for chargeable and dischargeable electricity storage devices that use an electrolyte that does not have water as a main component.
例えば、リチウムイオン電池、リチウムポリマー電池、リチウム全固体電池、リチウム空気電池、リチウム硫黄電池、ナトリウムイオン電池、ナトリウム硫黄電池、カリウムイオン電池、多価イオン電池、フッ化物イオン電池などが知られている。この非水電解質二次電池は、正極、負極、電解質、電槽（収納ケース）などから構成される。また、電解質が流動性を有する場合には正極と負極との間にさらにセパレータを介在させて構成される。 For example, lithium ion batteries, lithium polymer batteries, lithium all-solid-state batteries, lithium air batteries, lithium sulfur batteries, sodium ion batteries, sodium sulfur batteries, potassium ion batteries, multivalent ion batteries, fluoride ion batteries, etc. are known. . This nonaqueous electrolyte secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, a container (storage case), and the like. Further, when the electrolyte has fluidity, a separator is further interposed between the positive electrode and the negative electrode.
正極や負極などの電極は、活物質、導電助剤、樹脂系バインダおよび集電体から構成される。一般的に、電極は、活物質、導電助剤、樹脂系バインダを溶媒に混合してスラリー状にし、これを集電体上に塗工して乾燥することで活物質層を形成後、ロールプレスなどで調圧することによって製造される。 Electrodes such as positive electrodes and negative electrodes are composed of an active material, a conductive agent, a resin binder, and a current collector. Generally, electrodes are made by mixing an active material, a conductive additive, and a resin binder in a solvent to form a slurry, and then coating this onto a current collector and drying it to form an active material layer. Manufactured by regulating pressure using a press, etc.
ところで、上記非水電解質二次電池では、電池寿命（サイクル特性）の向上が求められている。そこで、特許文献１～３、および非特許文献１には、シロキサン結合を有するケイ酸塩を含む骨格形成剤を少なくとも活物質層の表面に存在させ、表面から内部に骨格形成剤を浸透させる技術が開示されている。これらの技術によれば、活物質層に強固な無機骨格を形成できるため、サイクル特性を向上できるとされる。 Incidentally, in the above-mentioned non-aqueous electrolyte secondary batteries, improvement in battery life (cycle characteristics) is required. Therefore, Patent Documents 1 to 3 and Non-Patent Document 1 disclose a technique in which a skeleton-forming agent containing a silicate having a siloxane bond is present at least on the surface of the active material layer, and the skeleton-forming agent permeates into the inside from the surface. is disclosed. According to these techniques, it is possible to form a strong inorganic skeleton in the active material layer, thereby improving cycle characteristics.
上記骨格形成剤は、活物質の種類によってサイクル特性の向上効果の度合いが異なり、骨格形成剤と活物質には相性がある。例えば、非特許文献１によれば、上記骨格形成剤（文献中では無機バインダと表記されている）をコートしたシリコン（Ｓｉ）電極とシリコン酸化物（ＳｉＯ）電極のサイクル特性を、上記骨格形成剤をコートしていない電極と比較した結果が示されている。Ｓｉ電極では、上記骨格形成剤を設けたことにより、サイクル特性が大幅に向上しているのに対し、ＳｉＯ電極では、骨格形成剤を設けたことにより、サイクル特性の向上は認められるものの、Ｓｉ電極と比べると向上効果が小さいことが示されている。 The degree of the effect of improving cycle characteristics of the above-mentioned skeleton-forming agent varies depending on the type of active material, and the skeleton-forming agent and the active material are compatible. For example, according to Non-Patent Document 1, the cycle characteristics of a silicon (Si) electrode and a silicon oxide (SiO) electrode coated with the skeleton forming agent (referred to as an inorganic binder in the literature) are Results are shown compared to electrodes without agent coating. In Si electrodes, the cycle characteristics are significantly improved by providing the above-mentioned skeleton forming agent, whereas in SiO electrodes, although the cycle characteristics are improved by providing the skeleton forming agent, Si It has been shown that the improvement effect is small compared to electrodes.
また、上記非水電解質二次電池では、エネルギー密度の向上が求められている。エネルギー密度の向上には、活物質層の厚さを大きくすることや、活物質層の高密度化が有効であると考えられている。 Furthermore, the non-aqueous electrolyte secondary battery is required to have improved energy density. It is believed that increasing the thickness of the active material layer and increasing the density of the active material layer are effective ways to improve the energy density.
そこで、本発明者らは、ケイ酸塩またはリン酸塩を含んでなる無機バインダ水溶液を用いて、さらなるサイクル特性とエネルギー密度を向上させる電極とその製造方法を検討し、本発明を完成するに至った。 Therefore, the present inventors investigated an electrode and its manufacturing method that further improves cycle characteristics and energy density using an inorganic binder aqueous solution containing silicate or phosphate, and completed the present invention. It's arrived.
特許文献１～３および非特許文献１の技術では、骨格形成剤と活物質との接着性が不十分である場合がある。特に、酸化物からなる活物質を含む電極である場合に、骨格形成剤と活物質との結着強度が十分に得られず、活物質層の膨潤や剥離、割れが発生し、安定した容量を維持しにくい。したがって、このような電極を用いた電池であっても、サイクル特性に優れた電池の実現が望まれる。 In the techniques disclosed in Patent Documents 1 to 3 and Non-Patent Document 1, the adhesion between the skeleton forming agent and the active material may be insufficient. In particular, in the case of electrodes containing active materials made of oxides, sufficient bonding strength between the skeleton forming agent and the active material may not be obtained, resulting in swelling, peeling, or cracking of the active material layer, resulting in a stable capacity. difficult to maintain. Therefore, it is desired to realize a battery with excellent cycle characteristics even when using such an electrode.
また、活物質層の厚さを大きくした電極や、高密度の活物質層を設けた電極では、無機バインダ水溶液が活物質層に浸透しにくくなるため、活物質層の骨格形成剤の分布が不均一になるという課題がある。 In addition, in electrodes with a thicker active material layer or electrodes with a high-density active material layer, it becomes difficult for the inorganic binder aqueous solution to penetrate into the active material layer, so the distribution of the skeleton forming agent in the active material layer is affected. There is a problem with unevenness.
本発明は、上記に鑑みてなされたものであり、従来に比べて電池のサイクル特性とエネルギー密度を向上できる非水電解質二次電池の電極とその製造方法を提供することを目的とする。 The present invention has been made in view of the above, and an object of the present invention is to provide an electrode for a non-aqueous electrolyte secondary battery and a method for manufacturing the same, which can improve the cycle characteristics and energy density of the battery compared to conventional ones.
すなわち、本発明の一の形態にかかる電極の製造方法によれば、ケイ酸塩やリン酸塩からなる無機バインダと活物質との接着性が十分に確保しにくかった電極、あるいは活物質層を膜厚化や高密度化した電極であっても、大幅にサイクル特性を向上させることができる。 That is, according to the method for manufacturing an electrode according to one embodiment of the present invention, an electrode or an active material layer in which it is difficult to ensure sufficient adhesion between an inorganic binder made of a silicate or a phosphate and an active material can be manufactured. Even with thicker and more dense electrodes, cycle characteristics can be significantly improved.
ケイ酸塩には、オルトケイ酸塩（Ａ4ＳｉＯ4）、メタケイ酸塩（Ａ2ＳｉＯ3）、ピロケイ酸塩（Ａ6Ｓｉ2Ｏ7）、二ケイ酸塩（Ａ2Ｓｉ2Ｏ5）、四ケイ酸塩（Ａ2Ｓｉ4Ｏ9）などの多ケイ酸塩や、Ａ2Ｓｉ2Ｏ5、Ａ2Ｓｉ3Ｏ7、Ａ2Ｓｉ4Ｏ9などの多岐の種類が存在し、これらは水和物としても存在することが知られている。 Silicates include orthosilicates (A 4 SiO 4 ), metasilicates (A 2 SiO 3 ), pyrosilicates (A 6 Si 2 O 7 ), and disilicates (A 2 Si 2 O 5 ). , polysilicates such as tetrasilicate (A 2 Si 4 O 9 ), and a wide variety of types such as A 2 Si 2 O 5 , A 2 Si 3 O 7 , A 2 Si 4 O 9 , It is known that these also exist as hydrates.
しかし、すべてのケイ酸塩が本発明に適用できるものではない。発明者らが種々のケイ酸塩を検討したところ、一般式Ａ2Ｏ・ｎＳｉＯ2で表されるケイ酸塩において、ＡがＬｉ、ＮａまたはＫの少なくともいずれか一種であり、ｎが１．７以上５以下である条件を満たす場合において、本発明の高い効果が得られることがわかった。なお、一般式Ａ2Ｏ・ｎＳｉＯ2で表されるケイ酸塩は水和物であってもかまわないが、電池を組む際には可能な限り水を取り除いていることが好ましい。 However, not all silicates are applicable to the present invention. The inventors studied various silicates and found that in the silicate represented by the general formula A 2 O.nSiO 2 , A is at least one of Li, Na, or K, and n is 1. It has been found that when the condition of 7 or more and 5 or less is satisfied, a high effect of the present invention can be obtained. Note that the silicate represented by the general formula A 2 O.nSiO 2 may be a hydrate, but it is preferable to remove as much water as possible when assembling a battery.
リン酸塩には、第一リン酸アルミニウム塩（Ａｌ（Ｈ2ＰＯ4）3）、リン酸水素アルミニウム塩（Ａｌ2（Ｈ2ＰＯ2）3）、メタリン酸アルミニウム（Ａｌ（ＰＯ3）3）、第一リン酸マグネシウム塩（Ｍｇ（Ｈ2ＰＯ4）3）、リン酸水素マグネシウム塩（ＭｇＨＰＯ4）、メタリン酸マグネシウム（Ｍｇ（ＰＯ3）2）、第一リン酸カルシウム塩（Ｃａ（Ｈ2ＰＯ4）3）、リン酸水素カルシウム塩（ＣａＨＰＯ4）、リン酸三カルシウム塩（Ｃａ3（Ｈ2ＰＯ4）2）、メタリン酸カルシウム（Ｃａ（ＰＯ3）2）などの多岐の種類が存在し、これらは水和物としても存在することが知られている。 Phosphates include primary aluminum phosphate (Al(H 2 PO 4 ) 3 ), aluminum hydrogen phosphate (Al 2 (H 2 PO 2 ) 3 ), and aluminum metaphosphate (Al(PO 3 ) 3 ). ), monobasic magnesium phosphate salt (Mg(H 2 PO 4 ) 3 ), magnesium hydrogen phosphate salt (MgHPO 4 ), magnesium metaphosphate (Mg(PO 3 ) 2 ), monobasic calcium phosphate salt (Ca(H 2 There are a wide variety of types such as PO 4 ) 3 ), calcium hydrogen phosphate (CaHPO 4 ), tricalcium phosphate (Ca 3 (H 2 PO 4 ) 2 ), and calcium metaphosphate (Ca(PO 3 ) 2 ). However, it is known that these also exist as hydrates.
しかし、すべてのリン酸塩が本発明に適用できるものではない。発明者らが種々のリン酸塩を検討したところ、一般式Ａｌ2Ｏ3・ｎＰ2Ｏ5で表されるリン酸塩において、ｎが１．７以上５以下である条件を満たす場合において、本発明の高い効果が得られることがわかった。なお、一般式Ａｌ2Ｏ3・ｎＰ2Ｏ5で表されるリン酸塩は水和物であってもかまわないが、電池を組む際には可能な限り水を取り除いていることが好ましい。 However, not all phosphates are applicable to the present invention. The inventors investigated various phosphates and found that in phosphates represented by the general formula Al 2 O 3 .nP 2 O 5 , when n satisfies the condition of 1.7 or more and 5 or less, It was found that high effects of the present invention can be obtained. Note that the phosphate represented by the general formula Al 2 O 3 .nP 2 O 5 may be a hydrate, but it is preferable to remove as much water as possible when assembling a battery.
電極は少なくとも活物質層と集電体から構成される。活物質層は、活物質と樹脂バインダを含んでなるスラリーを集電体に塗布または充填し、乾燥することで製造することができる。このようにして得られた活物質層は、さらにケイ酸塩やリン酸塩を水に溶解して得られた無機バインダ水溶液に浸漬または塗布され、乾燥することが好ましい。 The electrode is composed of at least an active material layer and a current collector. The active material layer can be manufactured by applying or filling a current collector with a slurry containing an active material and a resin binder, and drying the slurry. The active material layer thus obtained is preferably further dipped or coated in an aqueous inorganic binder solution obtained by dissolving a silicate or phosphate in water, and then dried.
ここで、後述する樹脂バインダに、酸性やアルカリ性の水溶液に接触して、バインダ成分が析出する性質を有する場合においては、スラリーを集電体に塗布後または充填後に乾燥工程を設けなくてもかまわない。しかし、バインダ成分が析出する際にバインダマイグレーション（樹脂の偏析）が発生しやすいため、どのような樹脂バインダを使用したとしても上記の活物質層は、スラリーを集電体に塗布後または充填後に乾燥することが好ましい。 Here, if the resin binder described later has a property that the binder component precipitates when it comes into contact with an acidic or alkaline aqueous solution, there is no need to provide a drying step after applying the slurry to the current collector or after filling the current collector. do not have. However, binder migration (resin segregation) is likely to occur when the binder component precipitates, so no matter what kind of resin binder is used, the above active material layer cannot be formed after applying the slurry to the current collector or filling it. Drying is preferred.
ここで、乾燥とは、加熱や減圧などによりスラリーに含まれる気化成分（水分や有機溶媒など）を除去し、乾いた状態にすることを意味している。乾燥させる手段は特に制限がなく、例えば、熱源による乾燥（加熱乾燥、熱風乾燥、遠赤外線乾燥等）や減圧乾燥などが例示される。熱源によって乾燥を行う場合には、温度は５０℃以上４００℃以下であることが好ましい。減圧乾燥を行う場合には、絶対圧力０．０５ＭＰａ以下まで減圧することが好ましい。なお、熱源による乾燥と減圧乾燥を組み合わせてもよい。 Here, drying means removing vaporized components (moisture, organic solvent, etc.) contained in the slurry by heating, reducing pressure, etc., and making the slurry dry. The means for drying is not particularly limited, and examples thereof include drying using a heat source (heat drying, hot air drying, far infrared drying, etc.) and reduced pressure drying. When drying is performed using a heat source, the temperature is preferably 50°C or more and 400°C or less. When drying under reduced pressure is performed, it is preferable to reduce the pressure to an absolute pressure of 0.05 MPa or less. Note that drying using a heat source and drying under reduced pressure may be combined.
上記の無機バインダ水溶液の濃度は、０．１質量％以上３５質量％以下であることが好ましい。０．１質量％未満では、骨格形成剤として機能する無機バインダの充填量が少なくなり、サイクル特性の向上効果が発揮されにくい。活物質の種類によっても異なるが、正極では０．１質量％以上、負極では３質量％以上が好ましい。いずれの電極であっても、３５質量％を超える場合は高粘度のため、浸透速度が遅くなり、また不均一に無機バインダが浸透した電極となりやすい。また、濃度は３０質量％以下がより好ましく、２５質量％以下が望ましい。 The concentration of the inorganic binder aqueous solution is preferably 0.1% by mass or more and 35% by mass or less. If it is less than 0.1% by mass, the filling amount of the inorganic binder that functions as a skeleton forming agent will be small, making it difficult to exhibit the effect of improving cycle characteristics. Although it varies depending on the type of active material, it is preferably 0.1% by mass or more for the positive electrode and 3% by mass or more for the negative electrode. In any electrode, if it exceeds 35% by mass, the viscosity is high, resulting in a slow penetration rate, and the electrode tends to be unevenly penetrated by the inorganic binder. Further, the concentration is more preferably 30% by mass or less, and desirably 25% by mass or less.
また、上記の無機バインダ水溶液の濃度を、０．１質量％以上３５質量％以下にすることで、前記活物質層の総量を１００％とした場合、無機バインダが０．１質量％以上３０質量％以下の範囲内に調整しやすい。無機バインダが０．１質量％未満では効果が得られにくく、３５質量％を超える場合では内部抵抗が大きくなる。 Further, by setting the concentration of the inorganic binder aqueous solution to 0.1% by mass or more and 35% by mass or less, when the total amount of the active material layer is 100%, the inorganic binder is 0.1% by mass or more and 30% by mass. Easy to adjust within a range of % or less. If the amount of inorganic binder is less than 0.1% by mass, it is difficult to obtain an effect, and if it exceeds 35% by mass, the internal resistance increases.
無機バインダ水溶液の温度は、３０℃以上１２０℃以下であることが好ましく、４０℃以上９５℃以下がより好ましい。３０℃以上にすることで、酸化物からなる活物質を含む電極であっても、無機バインダと活物質との結着強度が十分に得られ、サイクル特性に優れた電極が得られる。ただし、１２０℃を超える場合は、活物質の変質が活物質の内部にまで起こり、不可逆容量の増大、可逆容量の低下、サイクル特性の低下、内部抵抗の増大などを招く恐れがある。 The temperature of the inorganic binder aqueous solution is preferably 30°C or more and 120°C or less, more preferably 40°C or more and 95°C or less. By setting the temperature to 30° C. or higher, even if the electrode contains an active material made of an oxide, sufficient binding strength between the inorganic binder and the active material can be obtained, and an electrode with excellent cycle characteristics can be obtained. However, if the temperature exceeds 120° C., deterioration of the active material may occur to the inside of the active material, leading to an increase in irreversible capacity, a decrease in reversible capacity, a decrease in cycle characteristics, an increase in internal resistance, etc.
無機バインダと接触させる際には、１０秒以上５時間以下の時間をかけて、活物質層と無機バインダ水溶液を接触させることが好ましく、３０秒以上３時間以下がより好ましく、１分以上１時間以下がさらに好ましい。活物質層と無機バインダ水溶液の接触は、無機バインダ水溶液中に活物質層を浸漬または、活物質層に無機バインダ水溶液を塗布することで実現できる。 When bringing the active material layer into contact with the inorganic binder, it is preferable to bring the active material layer into contact with the inorganic binder aqueous solution for a time of 10 seconds or more and 5 hours or less, more preferably 30 seconds or more and 3 hours or less, and 1 minute or more and 1 hour. The following are more preferred. Contact between the active material layer and the inorganic binder aqueous solution can be achieved by immersing the active material layer in the inorganic binder aqueous solution or by applying the inorganic binder aqueous solution to the active material layer.
３０℃未満の無機バインダ水溶液と活物質層を接触後、加熱乾燥する場合は、所定温度範囲の無機バインダ水溶液が１０秒以上接触することにならず、直ちに乾燥が完了するため、活物質層と無機バインダ水溶液の接触時間を十分に確保できない。 When drying by heating after contacting the active material layer with an inorganic binder aqueous solution at a temperature of less than 30°C, the inorganic binder aqueous solution at a predetermined temperature range will not come into contact with each other for more than 10 seconds and drying will be completed immediately. It is not possible to ensure sufficient contact time for the inorganic binder aqueous solution.
接触時間を１０秒以上にすることで、活物質の表面に存在する酸化物がエッチングされ、表面が露わとなった活物質新面と無機バインダを強固に結合させることができる。ただし、接触時間が５時間を超える場合は、活物質が変質し、不可逆容量の増大や寿命特性の低下を招き、また活物質によっては機能を失う恐れがある。 By setting the contact time to 10 seconds or more, the oxide present on the surface of the active material is etched, and the exposed new surface of the active material can be firmly bonded to the inorganic binder. However, if the contact time exceeds 5 hours, the active material may change in quality, resulting in an increase in irreversible capacity and a decrease in life characteristics, and depending on the active material, there is a risk of loss of function.
また、無機バインダと接触する前に、絶対圧０．０３ＭＰａ（３０ｋＰａ）以下まで減圧し、活物質層内の空気や揮発成分を除去することが好ましい。活物質層と無機バインダ水溶液が接触している状態で、前記減圧状態を解除することにより、活物質層の空隙部分に無機バインダ水溶液を均一に充填することができる。活物質層の厚さを大きくした電極や、緻密な活物質層を有する電極であっても、予め減圧処理することで、無機バインダが集電体表面まで均一に浸透させることができる。 Further, before contacting with the inorganic binder, it is preferable to reduce the pressure to an absolute pressure of 0.03 MPa (30 kPa) or less to remove air and volatile components in the active material layer. By releasing the reduced pressure state while the active material layer and the inorganic binder aqueous solution are in contact with each other, the voids in the active material layer can be uniformly filled with the inorganic binder aqueous solution. Even in the case of an electrode with a thick active material layer or an electrode with a dense active material layer, the inorganic binder can be uniformly permeated to the surface of the current collector by performing a vacuum treatment in advance.
例えば、特許文献１では、活物質層の表面から内部に骨格形成剤を均一に浸透させるために、界面活性剤を含有させることが好ましいとしているが、この方法によれば、界面活性剤や消泡剤の添加を不要にすることもできる。 For example, Patent Document 1 states that it is preferable to contain a surfactant in order to uniformly infiltrate the skeleton forming agent from the surface to the inside of the active material layer. It is also possible to eliminate the need for adding a foaming agent.
また、無機バインダ水溶液を充填後、さらに絶対圧０．１２ＭＰａ以上で加圧することで充填速度を速めることができ、活物質新面と無機バインダを強固に結合させることができる。圧力を高めるにつれて、充填速度が速くなる傾向にあるが、１０ＭＰａを超える場合は活物質や集電体から、有価金属が溶出されて材料変質が起こる。また、耐圧容器が必要になり装置が大がかりなものとなる。 Further, after filling the aqueous inorganic binder solution, the filling speed can be increased by further applying pressure to an absolute pressure of 0.12 MPa or more, and the new surface of the active material and the inorganic binder can be firmly bonded. The filling rate tends to increase as the pressure increases, but if it exceeds 10 MPa, valuable metals are eluted from the active material and current collector, causing material deterioration. Moreover, a pressure-resistant container is required, making the apparatus large-scale.
二次電池に用いられる電極には、正極と負極があるが、平衡電位が高い（貴な）活物質を用いる場合は正極、平衡電位が低い（卑な）活物質を用いる場合は負極となる。 There are two types of electrodes used in secondary batteries: a positive electrode and a negative electrode.The positive electrode is used when an active material with a high equilibrium potential (noble) is used, and the negative electrode is used when an active material with a low equilibrium potential (base) is used. .
正極である場合には、非水電解質二次電池で用いられる正極活物質であれば特に限定されない。遷移金属酸化物系材料、バナジウム系材料、硫黄系材料、固溶体系（リチウム過剰系、ナトリウム過剰系、カリウム過剰系）材料、カーボン系材料、有機物系材料、ポリアニオン系材料等を含む公知の正極活物質が用いられる。 In the case of a positive electrode, it is not particularly limited as long as it is a positive electrode active material used in non-aqueous electrolyte secondary batteries. Known cathode active materials including transition metal oxide materials, vanadium materials, sulfur materials, solid solution materials (excessive lithium, excessive sodium, excessive potassium) materials, carbon materials, organic materials, polyanionic materials, etc. Substances are used.
例えば、ＡＮｉＯ2、ＡＮｉ0.6Ｃｏ0.2Ｍｎ0.2Ｏ2、ＡＮｉ0.8Ｃｏ0.1Ｍｎ0.1Ｏ2、ＡＮｉ0.8Ｃｏ0.15Ａｌ0.05Ｏ2、ＡＮｉ0.88Ｃｏ0.1Ａｌ0.02Ｏ2などの遷移金属酸化物系材料、ＡＶ2Ｏ5、ＡＶＯ2、Ａ3ＶＯ4などのバナジウム系材料、硫黄、硫化カーボン、ポリスルフィド、ポリ硫化カーボン、硫黄変性ポリアクリルニトリル、ジスルフィド化合物、硫化金属などの硫黄系材料、Ａ2ＭｎＯ3－ＡＮｉＯ2、Ａ2ＭｎＯ3－ＡＭｎＯ2、Ａ2ＭｎＯ3－ＡＣｏＯ2、Ａ2ＭｎＯ3－Ａ（Ｎｉ，Ｍｎ）Ｏ2、Ａ2ＭｎＯ3－Ａ（Ｎｉ，Ｃｏ）Ｏ2、Ａ2ＭｎＯ3－Ａ（Ｍｎ，Ｃｏ）Ｏ2、Ａ2ＭｎＯ3－Ａ（Ｎｉ，Ｍｎ，Ｃｏ）Ｏ2などの固溶体系材料、グラファイト、ソフトカーボン、ハードカーボン、グラッシーカーボンなどのカーボン系材料、キノン化合物、ラジアレン化合物、テトラシアキノジメタン、フェナジンオキシドなどの有機物系材料、ＡＦｅＰＯ4、ＡＭｎＰＯ4、ＡＦｅ0.2Ｍｎ0.8ＰＯ4、ＡＮｉＰＯ4、ＡＣｏＰＯ4、ＡＶＰＯ4、Ａ3Ｖ2（ＰＯ4）3、Ａ2ＦｅＳｉＯ4、Ａ2Ｆｅ0.5Ｍｎ0.5ＳｉＯ4、Ａ2ＭｎＳｉＯ4、Ａ2ＣｏＳｉＯ4、Ａ2ＮｉＳｉＯ4などのポリアニオン系材料である。 For example, transition metals such as ANiO 2 , ANi 0.6 Co 0.2 Mn 0.2 O 2 , ANi 0.8 Co 0.1 Mn 0.1 O 2 , ANi 0.8 Co 0.15 Al 0.05 O 2 , ANi 0.88 Co 0.1 Al 0.02 O 2 Oxide-based materials, AV Vanadium-based materials such as 2 O 5 , AVO 2 , A 3 VO 4 , sulfur-based materials such as sulfur, carbon sulfide, polysulfide, polysulfide carbon, sulfur-modified polyacrylonitrile, disulfide compounds, metal sulfide, A 2 MnO 3 - ANiO 2 , A 2 MnO 3 -AMnO 2 , A 2 MnO 3 -ACoO 2 , A 2 MnO 3 -A(Ni,Mn)O 2 , A 2 MnO 3 -A(Ni, Co)O 2 , A 2 MnO 3 - Solid solution materials such as A (Mn, Co) O 2 and A 2 MnO 3 - A (Ni, Mn, Co) O 2 , carbon materials such as graphite, soft carbon, hard carbon, glassy carbon, quinone compounds , radialene compounds, tetracyaquinodimethane, phenazine oxide and other organic materials, AFePO 4 , AMnPO 4 , AFe 0.2 Mn 0.8 PO 4 , ANiPO 4 , ACoPO 4 , AVPO 4 , A 3 V 2 (PO 4 ) 3 , These are polyanionic materials such as A 2 FeSiO 4 , A 2 Fe 0.5 Mn 0.5 SiO 4 , A 2 MnSiO 4 , A 2 CoSiO 4 and A 2 NiSiO 4 .
このうち、少なくともアルカリ金属と酸素を含む正極活物質が好ましい。なかでも、高容量でサイクル特性が安定しているという観点からは、シリケート系材料が好ましい。シリケート系材料は、一般式Ａ2-aＭbＳｉcＯ4-dで表される正極活物質である。ここで、ＡがＬｉ、ＮａまたはＫの少なくともいずれか一種であり、ＭがＦｅ、Ｎｉ、Ｍｎ、またはＣｏの少なくともいずれか一種であり、ａが０以上２以下であり、ｂが０．８以上１以下であり、ｃが０．８以上１以下であり、ｄが０以上０．２以下である。 Among these, a positive electrode active material containing at least an alkali metal and oxygen is preferred. Among these, silicate-based materials are preferred from the viewpoint of high capacity and stable cycle characteristics. The silicate-based material is a positive electrode active material represented by the general formula A 2-a M b Si c O 4-d . Here, A is at least one of Li, Na, or K, M is at least one of Fe, Ni, Mn, or Co, a is 0 or more and 2 or less, and b is 0.8 c is 0.8 or more and 1 or less, and d is 0 or more and 0.2 or less.
なお、シリケート系材料の結晶構造の安定化や、電池の高電位化を図るために、例えば、遷移金属元素の一部が、他の遷移金属元素に置換した化合物、またはシリコン元素の一部がリン元素やホウ素元素に置換した化合物、あるいはカルコゲン元素の一部が他のカルコゲン元素に置換した化合物であってもよい。この場合、置換率は元素比率で２０％以下であることが好ましい。 In addition, in order to stabilize the crystal structure of silicate-based materials and increase the potential of batteries, for example, compounds in which a part of a transition metal element is replaced with another transition metal element, or a part of a silicon element is used. It may be a compound in which phosphorus element or boron element is substituted, or a compound in which a part of a chalcogen element is substituted with another chalcogen element. In this case, the substitution rate is preferably 20% or less in terms of element ratio.
Ａ2-aＭbＳｉcＯ4-dはＳｉやＳｉＯと比べて充放電に伴う体積変化が小さいが、従来の無機バインダの塗布方法では活物質と無機バインダとの接着性が不十分となりやすい。しかし、本発明の方法によれば、酸化物であっても無機バインダと活物質の結合性を向上することができ、サイクル特性の悪化を抑制することができる。 A 2-a M b Si c O 4-d has a smaller volume change due to charging and discharging than Si or SiO, but the adhesion between the active material and the inorganic binder is insufficient with the conventional inorganic binder application method. Cheap. However, according to the method of the present invention, even if the inorganic binder is an oxide, it is possible to improve the bonding properties between the inorganic binder and the active material, and it is possible to suppress deterioration of cycle characteristics.
負極である場合には、アルカリ金属イオン（リチウムイオン、ナトリウムイオン、カリウムイオンなど）を可逆的に吸蔵・放出することが可能な材料であれば特に限定されない。例えば、Ｃ、Ｍｇ、Ａｌ、Ｓｉ、Ｐ、Ｃａ、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｇａ、Ｇｅ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｐｄ、Ａｇ、Ｃｄ、Ｉｎ、Ｓｎ、Ｓｂ、Ｗ、Ｐｂ及びＢｉよりなる群から選ばれた少なくとも一種以上の元素、これらの元素を用いた合金、複合化物、酸化物、カルコゲン化物又はハロゲン化物であればよい。 In the case of a negative electrode, the material is not particularly limited as long as it is capable of reversibly intercalating and releasing alkali metal ions (lithium ions, sodium ions, potassium ions, etc.). For example, C, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Pd, Ag, It may be at least one element selected from the group consisting of Cd, In, Sn, Sb, W, Pb, and Bi, or an alloy, composite, oxide, chalcogenide, or halide using these elements.
高容量でサイクル特性が安定しているという観点からは、シリコン酸化物が好ましい。シリコン酸化物は、一般式ＳｉＯxで表される負極活物質である。活物質と無機バインダとの接合性は、ｘが大きくなるにつれて低下すると考えられる（例えば、特許文献４および非特許文献１を参照）。 Silicon oxide is preferred from the viewpoint of high capacity and stable cycle characteristics. Silicon oxide is a negative electrode active material represented by the general formula SiO x . It is thought that the bondability between the active material and the inorganic binder decreases as x increases (see, for example, Patent Document 4 and Non-Patent Document 1).
しかし、本発明の方法によれば、ｘが０．２以上１．８以下であることが好ましく、０．２２以上１．２以下がより好ましく、０．２５以上０．８５以下がさらに好ましい。ｘが小さくなるにつれて高容量で不可逆容量が小さい電極となるが、充放電に伴う体積変化が大きくなる。その反面、ｘが大きくなるとサイクル特性に優れた電極となるが、ｘが１．８を超える場合では、無機バインダと活物質の結合性が悪く、サイクル特性が悪化し、また容量が小さく、抵抗と不可逆容量が大きな電極となる。 However, according to the method of the present invention, x is preferably 0.2 or more and 1.8 or less, more preferably 0.22 or more and 1.2 or less, and even more preferably 0.25 or more and 0.85 or less. As x becomes smaller, the electrode has a higher capacity and a smaller irreversible capacity, but the volume change due to charging and discharging becomes larger. On the other hand, when x becomes large, the electrode has excellent cycle characteristics, but when x exceeds 1.8, the bond between the inorganic binder and the active material is poor, resulting in poor cycle characteristics, low capacity, and low resistance. This results in an electrode with a large irreversible capacity.
正極や負極を問わず、活物質はメディアン径（Ｄ50）０．０１μｍ以上５０μｍ以下が好ましい。また、活物質粒子の形状は特に限定されず、球状、楕円状、切子状、帯状、ファイバー状、フレーク状、ドーナツ状、中空状であってもよい。 Regardless of whether it is a positive electrode or a negative electrode, the active material preferably has a median diameter (D 50 ) of 0.01 μm or more and 50 μm or less. Further, the shape of the active material particles is not particularly limited, and may be spherical, elliptical, faceted, band-like, fibrous, flaky, donut-like, or hollow.
樹脂バインダは、水や有機溶媒に溶解または分散することの可能なバインダであればよく、例えば、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリイミド（ＰＩ）、ポリアミド、ポリアミドイミド、ポリアクリル、スチレンブタジエンゴム（ＳＢＲ）、エチレン－酢酸ビニル共重合体（ＥＶＡ）、スチレン－エチレン－ブチレン－スチレン共重合体（ＳＥＢＳ）、カルボキシメチルセルロース（ＣＭＣ）、キタンサンガム、ポリビニルアルコール（ＰＶＡ）、ポリビニルブチラール（ＰＶＢ）、エチレンビニルアルコール（ＥＶＯＨ）、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリアクリル酸、ポリアクリル酸リチウム、ポリアクリル酸ナトリウム、ポリアクリル酸カリウム、ポリアクリル酸アンモニウム、ポリアクリル酸メチル、ポリアクリル酸エチル、ポリアクリル酸アミン、ポリアクリル酸エステル、エポキシ樹脂、ポリエチレンテレフタレート（ＰＥＴ）、ポリブチレンテレフタレート（ＰＢＴ）、ナイロン、塩化ビニル、シリコーンゴム、ニトリルゴム、シアノアクリレート、ユリア樹脂、メラミン樹脂、フェノール樹脂、ラテックス、ポリウレタン、シリル化ウレタン、ニトロセルロース、デキストリン、ポリビニルピロリドン、酢酸ビニル、ポリスチレン、クロロプロピレン、レゾルシノール樹脂、ポリアロマティック、変性シリコーン、メタクリル樹脂、ポリブテン、ブチルゴム、２－プロペン酸、シアノアクリル酸、メチルメタクリレート、グリシジルメタクリレート、アクリルオリゴマー、２－ヒドロキシエチルアクリレート、ポリアセタール、アルギン酸、デンプン、ショ糖、うるし、にかわ、カゼイン、セルロースナノファイバー等の有機材料を１種単独で用いてもよく、２種以上を併用してもよい。なお、上述した酸性やアルカリ性の水溶液に接触して、バインダ成分が析出する性質を有する樹脂バインダとしては、例えばＰＶｄＦ、ポリアクリル、ＳＥＢＳ、ＥＶＡ、ＣＭＣ、キタンサンガム、ＰＶＡ、ＥＶＯＨ、ポリアクリル酸、ポリアクリル酸塩などが挙げられる。 The resin binder may be any binder that can be dissolved or dispersed in water or an organic solvent, such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamideimide, Polyacrylic, styrene-butadiene rubber (SBR), ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butylene-styrene copolymer (SEBS), carboxymethyl cellulose (CMC), chitan sun gum, polyvinyl alcohol (PVA), polyvinyl Butyral (PVB), ethylene vinyl alcohol (EVOH), polyethylene (PE), polypropylene (PP), polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, polymethyl acrylate , polyethyl acrylate, polyacrylic amine, polyacrylic ester, epoxy resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, vinyl chloride, silicone rubber, nitrile rubber, cyanoacrylate, urea resin, melamine Resin, phenolic resin, latex, polyurethane, silylated urethane, nitrocellulose, dextrin, polyvinylpyrrolidone, vinyl acetate, polystyrene, chloropropylene, resorcinol resin, polyaromatic, modified silicone, methacrylic resin, polybutene, butyl rubber, 2-propenoic acid , cyanoacrylic acid, methyl methacrylate, glycidyl methacrylate, acrylic oligomer, 2-hydroxyethyl acrylate, polyacetal, alginic acid, starch, sucrose, lacquer, glue, casein, cellulose nanofiber, etc. can be used alone. Often, two or more types may be used in combination. In addition, examples of resin binders having the property of precipitating binder components upon contact with the above-mentioned acidic or alkaline aqueous solutions include PVdF, polyacrylic, SEBS, EVA, CMC, chitansan gum, PVA, EVOH, polyacrylic acid, and polyacrylic acid. Examples include acrylates.
スラリーに含まれる固形分の総量を１００％とした場合、樹脂バインダが０．１質量％以上３０質量％以下で含有されていることが好ましい。無機バインダ水溶液を活物質層に浸透させた後、加熱により水分除去することによって、強固な活物質層が得られるが、水分除去後の活物質層と比して、水分除去前では脆い。 When the total amount of solids contained in the slurry is 100%, it is preferable that the resin binder is contained in an amount of 0.1% by mass or more and 30% by mass or less. A strong active material layer can be obtained by impregnating the active material layer with an aqueous inorganic binder solution and then removing water by heating, but the active material layer is more brittle before the water is removed than the active material layer after the water is removed.
無機バインダ水溶液に浸した程度で、活物質層が剥離や崩壊する場合には、長寿命な電極を得ることができないため、無機バインダ水溶液に浸しても活物質層の形状を維持する強度は最低限必要になる。このような理由から、樹脂バインダの含有が必須となる。ただし、３０質量％を超える場合は、無機バインダが浸透しにくくなるばかりか、電極のエネルギー密度が低下する。 If the active material layer peels off or collapses even after being immersed in the inorganic binder aqueous solution, it will not be possible to obtain a long-life electrode. It will be necessary for a limited time. For these reasons, it is essential to include a resin binder. However, if it exceeds 30% by mass, not only will it be difficult for the inorganic binder to penetrate, but the energy density of the electrode will decrease.
集電体上に活物質層を形成する他の手法として、スパッタリングや蒸着などの気相法が知られている。気相法の場合においては、樹脂バインダを使用していなくても、集電体から活物質層が剥離しにくい特徴を有する。しかし、活物質層は緻密で、本発明の製造方法を用いて、無機バインダ水溶液に浸しても集電体近傍にまで成分が浸透することがなく、厚みの大きな電極ではサイクル特性の改善効果が得られにくい。無機バインダ水溶液に浸して、高容量かつ長寿命な電池を実現するためには、活物質と樹脂バインダからなる多孔質の活物質層を形成することが好ましい。 Vapor phase methods such as sputtering and vapor deposition are known as other methods for forming an active material layer on a current collector. In the case of the gas phase method, the active material layer is difficult to peel off from the current collector even if a resin binder is not used. However, the active material layer is dense, and when the manufacturing method of the present invention is used, the components do not penetrate into the vicinity of the current collector even when immersed in an aqueous inorganic binder solution. Hard to obtain. In order to realize a battery with high capacity and long life by immersing it in an aqueous inorganic binder solution, it is preferable to form a porous active material layer consisting of an active material and a resin binder.
活物質層の導電性を高めるという観点から、上記スラリーには、さらに導電助剤が含有されていることが好ましい。スラリーに含まれる固形分の総量を１００％とした場合、導電助剤が０質量％以上２０質量％以下で含有されていることが好ましい。すなわち、導電助剤は必要に応じて含有される。 From the viewpoint of increasing the conductivity of the active material layer, it is preferable that the slurry further contains a conductive aid. When the total amount of solids contained in the slurry is 100%, it is preferable that the conductive additive is contained in an amount of 0% by mass or more and 20% by mass or less. That is, the conductive aid is contained as necessary.
導電助剤は、電子伝導性を有していれば特に制限はなく、例えば、金属、炭素材料、導電性高分子、導電性ガラス等が挙げられるが、高い電子伝導性と耐酸化・還元性の観点から、炭素材料が好ましい。具体的にはアセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）、ファーネスブラック（ＦＢ）、サーマルブラック、ランプブラック、チェンネルブラック、ローラーブラック、ディスクブラック、カーボンブラック（ＣＢ）、カーボンファイバー（例えば、登録商標であるＶＧＣＦという名称の気相成長炭素繊維）、カーボンナノチューブ（ＣＮＴ）、カーボンナノホーン、グラファイト、グラフェン、ガラス状炭素（例えば、登録商標であるグラッシーカーボンという名称の非黒鉛化炭素）、アモルファスカーボンなどが挙げられ、これらの一種又は二種以上を用いてもよい。電子伝導性に優れ、さらに活物質層の機械強度が高くなるという理由から、ＡＢとＶＧＣＦ、ＡＢとＣＮＴ、ＡＢとグラフェン、ＣＮＴとグラフェンの組み合わせで用いることが好ましい。 The conductive agent is not particularly limited as long as it has electronic conductivity, and examples include metals, carbon materials, conductive polymers, conductive glass, etc.; From this point of view, carbon materials are preferred. Specifically, acetylene black (AB), Ketjen black (KB), furnace black (FB), thermal black, lamp black, channel black, roller black, disc black, carbon black (CB), carbon fiber (e.g. registered carbon nanotubes (CNTs), carbon nanohorns, graphite, graphene, glassy carbon (e.g., non-graphitized carbon under the registered trademark Glassy Carbon), amorphous carbon etc., and one or more of these may be used. It is preferable to use combinations of AB and VGCF, AB and CNT, AB and graphene, and CNT and graphene because they have excellent electronic conductivity and further increase the mechanical strength of the active material layer.
電極に用いられる集電体は、電子伝導性を有し、保持した活物質に通電し得る材料であればよい。充放電によって集電体が崩壊しない場合においては、電極の軽量化と低コスト化の観点から、アルミニウムまたはアルミニウム合金が好ましい。 The current collector used in the electrode may be any material as long as it has electronic conductivity and can conduct electricity through the held active material. In the case where the current collector does not collapse due to charging and discharging, aluminum or an aluminum alloy is preferable from the viewpoint of reducing the weight and cost of the electrode.
ここで、アルミニウムとは、Ａｌ純度が９９％以上のものを意味する。アルミニウム合金には、Ａｌ－Ｃｕ系合金、Ａｌ－Ｃｕ－Ｍｇ系合金、Ａｌ－Ｍｎ系合金、Ａｌ－Ｓｉ系合金、Ａｌ－Ｍｇ系合金、Ａｌ－Ｍｇ－Ｓｉ系合金、Ａｌ－Ｚｎ系合金、Ａｌ－Ｚｎ－Ｍｇ系合金、Ａｌ－Ｚｎ－Ｍｇ－Ｃｕ系合金、Ａｌ－Ｆｅ系合金、Ａｌ－Ｆｅ－Ｓｉ系合金、Ａｌ－Ｆｅ－Ｍｎ系合金、Ａｌ－Ｍｇ－Ｓｉ－Ｆｅ系合金などが該当する。 Here, aluminum means aluminum having an Al purity of 99% or more. Aluminum alloys include Al-Cu alloys, Al-Cu-Mg alloys, Al-Mn alloys, Al-Si alloys, Al-Mg alloys, Al-Mg-Si alloys, and Al-Zn alloys. , Al-Zn-Mg alloy, Al-Zn-Mg-Cu alloy, Al-Fe alloy, Al-Fe-Si alloy, Al-Fe-Mn alloy, Al-Mg-Si-Fe alloy etc. apply.
ただし、リチウムイオンをキャリアとし、且つ負極として使用する場合においては、集電体の材質は、銅またはニッケル、ステンレス鋼、カーボンが好ましい。 However, when using lithium ions as a carrier and as a negative electrode, the material of the current collector is preferably copper, nickel, stainless steel, or carbon.
しかし、両性金属であるアルミニウムでは、酸やアルカリと接触することによって腐食や溶解が起こる。ただし、例外的に特定のケイ酸塩水溶液やリン酸塩水溶液では反応しない。すなわち、一般式Ａ2Ｏ・ｎＳｉＯ2で表されるケイ酸塩において、ＡがＬｉ、ＮａまたはＫの少なくともいずれか一種であり、ｎが１．７以上５以下である条件を満たす場合、または一般式Ａｌ2Ｏ3・ｎＰ2Ｏ5で表されるリン酸塩において、ｎが１．７以上５以下である条件を満たす無機バインダにおいては、腐食反応が進行しない。 However, aluminum, which is an amphoteric metal, corrodes and dissolves when it comes into contact with acids and alkalis. However, as an exception, it does not react with specific silicate or phosphate aqueous solutions. That is, in the silicate represented by the general formula A 2 O.nSiO 2 , A is at least one of Li, Na or K, and n is 1.7 or more and 5 or less, or In the phosphate represented by the general formula Al 2 O 3 .nP 2 O 5 , the corrosion reaction does not proceed in an inorganic binder that satisfies the condition that n is 1.7 or more and 5 or less.
ケイ酸塩では、ｎが１．７未満である場合、ｐＨ値は１０以上であり、アルミニウムやアルミニウム合金に対する腐食抑制効果が発揮されず、むしろ腐食を促進する。ｎが５を超える場合、スラリー塗工後の乾燥工程でゲル状の皮膜が形成されやすく、電極抵抗を増大させる要因になる。また、ｎが５を超える場合、ポットライフが短く、ケイ酸塩水溶液を大気中で放置していると白濁や沈殿を起こし、変質しやすいという難点をもつ。また、ｎが５を超える場合、ｐＨ値が１０未満であり、活物質の可逆容量が低下する。 In silicates, when n is less than 1.7, the pH value is 10 or more, and the corrosion inhibiting effect on aluminum and aluminum alloys is not exhibited, but rather the corrosion is accelerated. When n exceeds 5, a gel-like film is likely to be formed in the drying process after slurry coating, which becomes a factor that increases electrode resistance. In addition, when n exceeds 5, the pot life is short, and if the silicate aqueous solution is left in the atmosphere, it becomes cloudy and precipitates, and there are disadvantages in that it is easily deteriorated. Moreover, when n exceeds 5, the pH value is less than 10, and the reversible capacity of the active material decreases.
集電体の形状には、線状、棒状、板状、箔状、多孔状、繊維状があり、このうち充填密度を高めることができることと、無機バインダが活物質層に浸透させる工程で活物質層の剥離を抑制できることから多孔状または繊維状であることが好ましい。また、多孔状または繊維状であれば、樹脂バインダの使用量の低減や、結着力に劣る樹脂バインダを用いても、無機バインダ水溶液と接触させても剥離しにくくなる。あわせて、無機バインダ水溶液が活物質層に浸透しやすくなる効果もあり、活物質層の無機バインダの分布が均一になりやすい。 The shape of the current collector is linear, rod-like, plate-like, foil-like, porous, and fibrous. Porous or fibrous materials are preferable because peeling of the material layer can be suppressed. Moreover, if it is porous or fibrous, the amount of resin binder used can be reduced, and even if a resin binder with poor binding strength is used, it will be difficult to peel off even if it is brought into contact with an aqueous inorganic binder solution. In addition, there is an effect that the inorganic binder aqueous solution easily permeates into the active material layer, and the distribution of the inorganic binder in the active material layer tends to become uniform.
多孔状には、メッシュ、織布、不織布、エンボス体、パンチング体、エキスパンド、又は発泡体などが挙げられ、このうち、集電体の形状は、出力特性が良好なことからエンボス体または発泡体が好ましい。さらに、貫通孔を有することが好ましい。繊維状としては、単繊維でもよいし、複数の単繊維を集合させたものも有効である。具体的には、直径３～５０μｍの単繊維を１０～１０００本を集合させ１束となった状態のものが好ましく、これを用いて織布や不織布の状態としてもよい。 Examples of the porous shape include mesh, woven fabric, non-woven fabric, embossed body, punched body, expanded body, and foamed body. Among these, the shape of the current collector is preferably embossed body or foamed body because it has good output characteristics. is preferred. Furthermore, it is preferable to have a through hole. The fibrous material may be a single fiber, or an aggregate of a plurality of single fibers is also effective. Specifically, it is preferable to use a bundle of 10 to 1000 single fibers with a diameter of 3 to 50 μm, and this may be used to form a woven or nonwoven fabric.
このようにして得られた電極には、活物質とケイ酸塩またはリン酸塩が反応した変性材料を含むこととなる。この変性した材料は、少なくとも活物質と無機バインダの間に存在しており、活物質と無機バインダを強固に結合させる仲介的な機能を有する。この変性した材料が存在することで、活物質層の機械強度が高く、集電体と活物質層との剥離が起こりにくい電極にすることができる。 The electrode thus obtained contains a modified material in which the active material and the silicate or phosphate have reacted. This modified material exists at least between the active material and the inorganic binder, and has an intermediary function to firmly bond the active material and the inorganic binder. The presence of this modified material allows the active material layer to have high mechanical strength, making it possible to provide an electrode in which peeling between the current collector and the active material layer is less likely to occur.
上記の変性材料は、活物質とケイ酸塩またはリン酸塩が反応して生成されるものであるため、過剰に生成させると活物質の機能が喪失し、電極容量の低下を招く。逆に、生成量が不十分だと活物質層の機械強度の低下や、集電体と活物質層との剥離が起こりやすくなる。 The above-mentioned modified material is produced by a reaction between an active material and a silicate or phosphate, so if it is produced in excess, the active material loses its function, leading to a decrease in electrode capacity. On the other hand, if the amount produced is insufficient, the mechanical strength of the active material layer decreases, and separation between the current collector and the active material layer tends to occur.
上記の変性材料は、ケイ酸塩とリン酸塩で異なり、ケイ酸塩を使用した場合では、Ａ2ＳｉＯ3、Ａ4ＳｉＯ4、Ｎａ2Ｓｉ2Ｏ5、Ｎａ2Ｓｉ4Ｏ9、Ｈ2ＳｉＯ3、ＳｉＯ2などが、リン酸塩を使用した場合では、ＡｌＰＯ4、Ａｌ（ＰＯ3）3、Ａｌ2Ｐ4Ｏ13、Ａｌ（Ｈ2ＰＯ4）3、Ｈ3ＰＯ4、Ｐ4Ｏ10、Ａｌ2Ｏ3などから構成され、これらは水和物および結晶性の低い状態も含まれる場合がある。 The above modified materials differ between silicates and phosphates, and when silicates are used, A 2 SiO 3 , A 4 SiO 4 , Na 2 Si 2 O 5 , Na 2 Si 4 O 9 , H 2 SiO 3 , SiO 2 , etc., when phosphates are used, AlPO 4 , Al(PO 3 ) 3 , Al 2 P 4 O 13 , Al(H 2 PO 4 ) 3 , H 3 PO 4 , P It is composed of 4 O 10 , Al 2 O 3 and the like, and these may also include hydrates and states with low crystallinity.
上記の変性材料の比重は、１．５以上３．５以下の範囲内であることが好ましく、１．８以上３．２以下がより好ましい。比重が１．５未満だと水を多く含有しており、電池の早期サイクル劣化や電池膨れなどを引き起こす可能性が高くなる。３．５を超える場合は、電池の重量当たりのエネルギー密度の向上が困難になる。 The specific gravity of the modified material is preferably in the range of 1.5 or more and 3.5 or less, more preferably 1.8 or more and 3.2 or less. If the specific gravity is less than 1.5, it contains a lot of water, which increases the possibility of early cycle deterioration of the battery and battery swelling. If it exceeds 3.5, it becomes difficult to improve the energy density per weight of the battery.
上記の変性材料の厚さは、１ｎｍ以上５００ｎｍ以下であることが好ましい。変性材料の厚さがこの範囲内であることにより、活物質と無機バインダとの結着性が向上する。厚さが１ｎｍ未満だと活物質層の機械強度の低下や、集電体と活物質層との剥離が起こりやすく、５００ｎｍを超える場合は、活物質の機能が喪失し、電極容量の低下を招く。 The thickness of the above-mentioned modified material is preferably 1 nm or more and 500 nm or less. When the thickness of the modified material is within this range, the binding property between the active material and the inorganic binder is improved. If the thickness is less than 1 nm, the mechanical strength of the active material layer decreases, and separation between the current collector and the active material layer tends to occur. If the thickness exceeds 500 nm, the function of the active material is lost and the electrode capacity decreases. invite
本製造方法で得られた電極は、非水電解質二次電池の正極または負極として使用することができる。非水電解質二次電池とは、正極、負極、及び前記正極と前記負極との間に介在する非水電解質を備え、例えば、リチウムイオン電池、ナトリウムイオン電池、カリウムイオン電池、リチウムイオンキャパシタ、ナトリウムイオンキャパシタ、カリウムイオンキャパシタなどが該当する。 The electrode obtained by this manufacturing method can be used as a positive electrode or negative electrode of a nonaqueous electrolyte secondary battery. A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a nonaqueous electrolyte interposed between the positive electrode and the negative electrode, and includes, for example, a lithium ion battery, a sodium ion battery, a potassium ion battery, a lithium ion capacitor, and a sodium ion battery. This includes ion capacitors, potassium ion capacitors, etc.
この電極を二次電池の正極として用いる場合、この電極の充放電電位よりも卑の電極と組みわせることで二次電池を作製できる。一方、この電極を二次電池の負極として用いる場合、この電極の充放電電位よりも貴の電極と組み合わせることで二次電池を作製できる。 When this electrode is used as a positive electrode of a secondary battery, the secondary battery can be produced by combining it with an electrode that is less noble than the charging/discharging potential of this electrode. On the other hand, when this electrode is used as a negative electrode of a secondary battery, a secondary battery can be produced by combining it with an electrode whose charging/discharging potential is higher than that of this electrode.
例えば、本開示の電極を正極として用いる場合、対極（負極）は、二次電池に用いられる負極として用いられる電極であれば特に限定されない。 For example, when using the electrode of the present disclosure as a positive electrode, the counter electrode (negative electrode) is not particularly limited as long as it is an electrode used as a negative electrode used in a secondary battery.
二次電池に用いる電解質は、正極から負極、又は負極から正極にアルカリ金属イオンやフッ素化合物アニオンを移動させることのできる液体又は固体であればよい。すなわち、公知の非水電解質を用いた二次電池に用いられる電解質と同じものが使用可能である。例えば、電解液、ゲル電解質、固体電解質、イオン性液体、溶融塩などが挙げられる。ここで、電解液とは、電解質が溶媒に溶けた状態のものをいう。 The electrolyte used in the secondary battery may be any liquid or solid that can move alkali metal ions and fluorine compound anions from the positive electrode to the negative electrode or from the negative electrode to the positive electrode. That is, the same electrolyte as used in secondary batteries using known non-aqueous electrolytes can be used. Examples include electrolytes, gel electrolytes, solid electrolytes, ionic liquids, and molten salts. Here, the electrolytic solution refers to a state in which an electrolyte is dissolved in a solvent.
二次電池の構造としては、特に限定されないが、積層式、捲回式などの既存の形態・構造を採用できる。すなわち、正極と負極とがセパレータを介して対向して積層又は捲回された電極群を、電解液内に浸漬した状態で密閉化され、二次電池となる。あるいは、正極と負極とが固体電解質を介して対向して積層又は捲回された電極群を密閉化して二次電池となる。 The structure of the secondary battery is not particularly limited, but existing forms and structures such as a stacked type and a wound type can be adopted. That is, an electrode group in which a positive electrode and a negative electrode are stacked or wound facing each other with a separator interposed therebetween is immersed in an electrolytic solution and sealed, thereby forming a secondary battery. Alternatively, a secondary battery is obtained by sealing an electrode group in which a positive electrode and a negative electrode are stacked or wound facing each other with a solid electrolyte interposed therebetween.
本発明の製造方法によれば、ケイ酸塩やリン酸塩からなる無機バインダと活物質との接着性が十分に確保しにくい電極、あるいは膜厚や密度の高い活物質層を有する電極であっても、大幅にサイクル特性を向上させることができる。また、本製造方法で得られた電極は、活物質の表面がケイ酸塩やリン酸塩で変性した材料を含んでなる。この変性した材料を介して無機バインダと活物質が一体化していることで、強度が高い電極になり、サイクル特性にすぐれた電極になる。 According to the manufacturing method of the present invention, it is difficult to ensure sufficient adhesion between the inorganic binder made of silicate or phosphate and the active material, or the electrode has an active material layer with a high thickness or density. However, the cycle characteristics can be significantly improved. Further, the electrode obtained by the present manufacturing method includes a material in which the surface of the active material is modified with a silicate or a phosphate. The inorganic binder and active material are integrated through this modified material, resulting in an electrode with high strength and excellent cycle characteristics.
以下、本発明の一の態様にかかる実施形態、実施例について説明するが、本発明はこの実施形態、実施例に限定されるものではない。 Hereinafter, embodiments and examples according to one aspect of the present invention will be described, but the present invention is not limited to these embodiments and examples.
本実施形態の非水電解質二次電池の製造方法としては、一例として、活物質、樹脂バインダ、導電助剤などからなるスラリーを集電体に塗工後または充填後、これを所定温度のケイ酸塩またはリン酸塩を含んでなる無機バインダ水溶液に接触し、乾燥して電極を作製する。なお、具体的な電極材料などは後述する。 As an example of the method for manufacturing the non-aqueous electrolyte secondary battery of this embodiment, after coating or filling a current collector with a slurry consisting of an active material, a resin binder, a conductive agent, etc. An electrode is produced by contacting with an aqueous inorganic binder solution containing an acid salt or a phosphate and drying. Note that specific electrode materials and the like will be described later.
そして、後述のとおり、この製造方法により得られた電極を用いてリチウムイオン電池を作製し、試験を行った。なお、リチウムイオンキャパシタは、主に対極の動作が異なる以外はリチウムイオン電池と同様にして作製できる。 Then, as described below, a lithium ion battery was manufactured using the electrode obtained by this manufacturing method and tested. Note that a lithium ion capacitor can be manufactured in the same manner as a lithium ion battery, except that the operation of the counter electrode is different.
具体的には、例えば、正極として、本実施形態の電極を、負極として従来のリチウムイオンキャパシタ用負極を用いる以外は、後述の電池と同様にして作製できる。リチウムイオン電池以外のアルカリ金属イオン電池は、主にリチウムイオン電池の電荷担体であるＬｉをＮａやＫに置き換えた以外はリチウムイオン電池と同様にして作製できる。 Specifically, for example, the electrode of this embodiment can be produced in the same manner as the battery described below, except that the electrode of this embodiment is used as the positive electrode and the conventional negative electrode for a lithium ion capacitor is used as the negative electrode. Alkali metal ion batteries other than lithium ion batteries can be produced in the same manner as lithium ion batteries, except that Li, which is a charge carrier in lithium ion batteries, is replaced with Na or K.
具体的には、ナトリウムイオン電池では、正極として本実施形態の電極を、負極として従来のナトリウムイオン電池用負極を、電解液としてナトリウム支持塩を用いる以外は、後述の電池と同様にして作製できる。カリウムイオン電池では、正極として本実施形態の電極を、負極として従来のカリウムイオン電池用負極を、電解液としてカリウム支持塩を用いる以外は、後述の電池と同様にして作製できる。 Specifically, a sodium ion battery can be produced in the same manner as the battery described below, except that the electrode of this embodiment is used as the positive electrode, a conventional negative electrode for sodium ion batteries is used as the negative electrode, and a sodium supporting salt is used as the electrolyte. . The potassium ion battery can be produced in the same manner as the battery described below, except that the electrode of this embodiment is used as the positive electrode, the conventional negative electrode for potassium ion batteries is used as the negative electrode, and the potassium supporting salt is used as the electrolyte.
［ＳｉＯ電極］
（実施例１、実施例２）
ＳｉＯx（ｘ＝０．７５、メディアン径Ｄ50＝５μｍ）、スチレンブタジエンゴム（ＪＳＲ製、ＴＤＲ２００１）、カルボキシメチルセルロース（ダイセル製、２２６０）、アセチレンブラック（デンカ製、デンカブラック）、カーボンファイバー（昭和電工製、ＶＧＣＦ－Ｈ）からなる水系スラリー（固形比９２：３：１：３：１質量％）を厚さ１３０μｍに調圧した発泡ニッケル（住友電工製、セルメット＃８）に充填し、８０℃で３０分間乾燥することで、単位面積当たりの電極容量が６ｍＡｈ／ｃｍ2のＳｉＯ電極を作製した。
[SiO electrode]
(Example 1, Example 2)
SiO x (x = 0.75, median diameter D 50 = 5 μm), styrene-butadiene rubber (JSR, TDR2001), carboxymethyl cellulose (Daicel, 2260), acetylene black (Denka, Denka Black), carbon fiber (Showa A water-based slurry (solid ratio 92:3:1:3:1 mass %) consisting of VGCF-H (manufactured by Denko) was filled into foamed nickel (Celmet #8, manufactured by Sumitomo Electric Industries, Ltd.) whose pressure was adjusted to a thickness of 130 μm. By drying at ℃ for 30 minutes, a SiO electrode having an electrode capacity of 6 mAh/cm 2 per unit area was produced.
表１に記載の条件で、ＳｉＯ電極を温度４０℃のケイ酸ナトリウム水溶液（Ｎａ2Ｏ・３．０ＳｉＯ2 ａｑ．、濃度１０質量％）に浸漬後、仮乾燥（８０℃、１時間）し、次いで真空乾燥（１５０℃、１０時間）することで、試験電極を作製した。含浸前後の電極の重量変化は、含浸前の電極（集電体を除く）に対して、含浸後の電極（集電体を除く）が１５％増加していた。なお、ＳｉＯ電極は完全に浸るまでケイ酸ナトリウム水溶液に浸漬された後、電極表面に残った余剰のケイ酸ナトリウム水溶液は紙製シート（キンバリー・クラーク製、キムワイプ）で吸い取って除去した。 Under the conditions listed in Table 1, the SiO electrode was immersed in a sodium silicate aqueous solution (Na 2 O 3.0 SiO 2 aq., concentration 10% by mass) at a temperature of 40°C, and then temporarily dried (80°C, 1 hour). Then, a test electrode was prepared by vacuum drying (150° C., 10 hours). Regarding the weight change of the electrode before and after impregnation, the electrode after impregnation (excluding the current collector) increased by 15% compared to the electrode before impregnation (excluding the current collector). Note that after the SiO electrode was immersed in the sodium silicate aqueous solution until it was completely immersed, the excess sodium silicate aqueous solution remaining on the electrode surface was removed by absorbing it with a paper sheet (Kimwipe, manufactured by Kimberly-Clark).
（実施例３～７）
表１に記載の条件で、ＳｉＯ電極を温度６０℃のケイ酸ナトリウム水溶液（Ｎａ2Ｏ・３．０ＳｉＯ2 ａｑ．、濃度１０質量％）に浸漬した他、実施例１と同様である。
(Examples 3 to 7)
The conditions described in Table 1 were the same as in Example 1 except that the SiO electrode was immersed in an aqueous sodium silicate solution (Na 2 O.3.0 SiO 2 aq., concentration 10% by mass) at a temperature of 60°C.
（実施例８～１１）
表１に記載の条件で、ＳｉＯ電極を温度８０℃のケイ酸ナトリウム水溶液（Ｎａ2Ｏ・３．０ＳｉＯ2 ａｑ．、濃度１０質量％）に浸漬した他、実施例１と同様である。
(Examples 8 to 11)
The conditions described in Table 1 were the same as in Example 1 except that the SiO electrode was immersed in an aqueous sodium silicate solution (Na 2 O.3.0 SiO 2 aq., concentration 10% by mass) at a temperature of 80°C.
（実施例１２、実施例１３）
表１に記載の条件で、ＳｉＯ電極を温度９５℃のケイ酸ナトリウム水溶液（Ｎａ2Ｏ・３．０ＳｉＯ2 ａｑ．、濃度１０質量％）に浸漬した他、実施例１と同様である。
(Example 12, Example 13)
The conditions described in Table 1 were the same as in Example 1 except that the SiO electrode was immersed in an aqueous sodium silicate solution (Na 2 O.3.0 SiO 2 aq., concentration 10% by mass) at a temperature of 95°C.
（実施例１４）
ＳｉＯ電極をステンレス製の密閉容器に入れ、該容器内を真空ポンプにて絶対圧１０ｋＰａまで減圧した。容器内の圧力が１０ｋＰａに達した後、減圧状態を維持しながら、６０℃のケイ酸ナトリウム水溶液（Ｎａ2Ｏ・３．０ＳｉＯ2 ａｑ．、濃度１０質量％）を電極が完全に浸るまで容器内に入れて、１分間経過後、エアパージにより、減圧状態を解除して、浸漬させた他、実施例３と同様である。
(Example 14)
The SiO electrode was placed in a stainless steel airtight container, and the pressure inside the container was reduced to an absolute pressure of 10 kPa using a vacuum pump. After the pressure inside the container reaches 10 kPa, while maintaining the reduced pressure state, add a 60°C sodium silicate aqueous solution (Na 2 O 3.0 SiO 2 aq., concentration 10% by mass) to the container until the electrode is completely immersed. The process was the same as in Example 3 except that after 1 minute had passed, the reduced pressure state was released by air purge and immersion was performed.
（実施例１５）
容器内の圧力が１０ｋＰａに達した後、減圧状態を維持しながら、６０℃のケイ酸ナトリウム水溶液（Ｎａ2Ｏ・３．０ＳｉＯ2 ａｑ．、濃度１０質量％）を電極が完全に浸るまで容器内に入れて、１分間経過後、加圧ポンプを用いて圧縮空気を容器内に入れ、絶対圧０．３ＭＰａまで加圧し、エアパージにより、加圧状態を解除して、浸漬させた他、実施例１４と同様である。
(Example 15)
After the pressure inside the container reaches 10 kPa, while maintaining the reduced pressure state, add a 60°C sodium silicate aqueous solution (Na 2 O 3.0 SiO 2 aq., concentration 10% by mass) to the container until the electrode is completely immersed. After 1 minute had elapsed, compressed air was introduced into the container using a pressurizing pump to pressurize the container to an absolute pressure of 0.3 MPa, and the pressurized state was released using an air purge. This is similar to Example 14.
（比較例１、比較例２）
表１に記載の条件で、ＳｉＯ電極を温度２５℃のケイ酸ナトリウム水溶液（Ｎａ2Ｏ・３．０ＳｉＯ2 ａｑ．、濃度１０質量％）に浸漬した他、実施例１と同様である。
(Comparative example 1, comparative example 2)
The conditions described in Table 1 were the same as in Example 1 except that the SiO electrode was immersed in an aqueous sodium silicate solution (Na 2 O.3.0 SiO 2 aq., concentration 10% by mass) at a temperature of 25°C.
（比較例３）
表１に記載の条件で、ＳｉＯ電極を温度０℃のケイ酸ナトリウム水溶液（Ｎａ2Ｏ・３．０ＳｉＯ2 ａｑ．、濃度１０質量％）に浸漬した他、実施例１と同様である。
(Comparative example 3)
The conditions described in Table 1 were the same as in Example 1 except that the SiO electrode was immersed in an aqueous sodium silicate solution (Na 2 O.3.0 SiO 2 aq., concentration 10% by mass) at a temperature of 0°C.
（比較例４）
ケイ酸ナトリウム水溶液に浸漬していないＳｉＯ電極である。
(Comparative example 4)
This is a SiO electrode that is not immersed in a sodium silicate aqueous solution.
（電池特性）
実施例１～１３及び比較例１～４で得られた試験電極と、金属リチウム対極（本城金属製、厚さ５００μｍのリチウム箔）、ポリプロピレン（ＰＰ）／ポリエチレン（ＰＥ）／ポリプロピレン（ＰＰ）の三層微多孔膜（セルガード社製、２３２５）、ガラスフィルタ（アドバンテック製、ＧＡ１００）、１ｍｏｌ／Ｌ ＬｉＰＦ6／エチレンカーボネート（ＥＣ）：ジエチルカーボネート（ＤＥＣ）＝１：１ｖｏｌ．，＋ビニレンカーボネート（ＶＣ）１質量％を用いて電池を作製した。
(Battery characteristics)
Test electrodes obtained in Examples 1 to 13 and Comparative Examples 1 to 4, metallic lithium counter electrode (manufactured by Honjo Metals, 500 μm thick lithium foil), polypropylene (PP) / polyethylene (PE) / polypropylene (PP) A three-layer microporous membrane (manufactured by Celgard, 2325), a glass filter (manufactured by Advantech, GA100), 1 mol/L LiPF 6 /ethylene carbonate (EC): diethyl carbonate (DEC) = 1:1 vol. , + 1% by mass of vinylene carbonate (VC).
充放電サイクル試験は、３０℃環境にて、カットオフ電圧０．０１～０．９Ｖ、充電電流０．０５ｍＡ／ｃｍ2、放電電流０．１ｍＡ／ｃｍ2で充放電を繰り返す条件で行った。 The charge/discharge cycle test was conducted in an environment of 30° C. under the conditions of repeating charging and discharging at a cutoff voltage of 0.01 to 0.9 V, a charging current of 0.05 mA/cm 2 , and a discharging current of 0.1 mA/cm 2 .
表２に、ＳｉＯ電極のサイクル特性（１～３サイクル目における放電容量、容量維持率、クーロン効率）を示す。 Table 2 shows the cycle characteristics of the SiO electrode (discharge capacity, capacity retention rate, and coulombic efficiency in the 1st to 3rd cycles).
実施例１～１５の４０℃以上のケイ酸ナトリウム水溶液に含浸した電極である場合には、比較例４の未処理の電極よりも放電容量が大きく、比較例１～３の２５℃以下のケイ酸ナトリウム水容器に含浸した電極よりも容量維持率が高い値を示している。また、いずれの実施例であっても比較例１～４よりも高いクーロン効率を示している。なかでも、実施例２の４０℃で１０分間浸漬した電極、実施例４～７の６０℃で５～６０分間浸漬した電極、実施例８と実施例９の８０℃で１～１０分間浸漬した電極は、初回の放電容量が８５％以上を示し、且つ３サイクル目における容量維持率も９０％以上と大きい。 In the case of the electrodes impregnated with the sodium silicate aqueous solution at 40°C or higher in Examples 1 to 15, the discharge capacity was larger than that of the untreated electrode in Comparative Example 4, and the electrodes impregnated with the sodium silicate aqueous solution at 25°C or lower in Comparative Examples 1 to 3 had The capacity retention rate is higher than that of the electrode impregnated in a sodium chloride water container. Furthermore, all of the examples show higher coulombic efficiency than Comparative Examples 1 to 4. Among them, the electrodes were immersed at 40°C for 10 minutes in Example 2, the electrodes were immersed at 60°C for 5 to 60 minutes in Examples 4 to 7, and the electrodes were immersed at 80°C for 1 to 10 minutes in Examples 8 and 9. The electrode exhibits an initial discharge capacity of 85% or more, and a high capacity retention rate of 90% or more in the third cycle.
このように、ケイ酸ナトリウム水溶液の温度が高い場合には、浸漬時間が短く、低い場合には浸漬時間を長くすることが好ましい傾向が認められる。また、ケイ酸ナトリウム水溶液の含浸工程の前に、減圧して活物質層内の空気を除去することにより、浸漬時間を短縮することができることが示唆される。また、含浸工程は大気圧よりも高圧環境で行う方が浸漬時間を短縮することができることが示唆される。ただし、温度が２５℃以下のケイ酸ナトリウム水溶液では処理時間を長くしても本発明の効果は得られなかった。 As described above, there is a tendency that when the temperature of the sodium silicate aqueous solution is high, it is preferable to shorten the immersion time, and when the temperature is low, it is preferable to lengthen the immersion time. It is also suggested that the immersion time can be shortened by reducing the pressure and removing air within the active material layer before the step of impregnating the aqueous sodium silicate solution. It is also suggested that the immersion time can be shortened by performing the impregnation step in a high pressure environment rather than atmospheric pressure. However, in a sodium silicate aqueous solution at a temperature of 25° C. or lower, the effects of the present invention could not be obtained even if the treatment time was increased.
［Ｌｉ2ＦｅＳｉＯ4電極］
Ｌｉ2ＦｅＳｉＯ4（メディアン径Ｄ50＝１２μｍ）、アセチレンブラック（デンカ製、デンカブラック）、アクリル系バインダ（ＪＳＲ製、ＴＲＤ２０２Ａ）からなる水系スラリー（固形比９４：３：３質量％）を厚さ１００μｍに調圧した発泡アルミニウム（住友電工製、Ａｌセルメット）に充填し、８０℃で３０分間乾燥後、ロールプレスにて調圧することで、単位面積当たりの電極容量が０．５ｍＡｈ／ｃｍ2のＬｉ2ＦｅＳｉＯ4電極を作製した。Ｌｉ2ＦｅＳｉＯ4は、ロータリーキルン処理（７００℃）により、１０質量％のカーボンが被覆複合されている。
[Li 2 FeSiO 4 electrode]
Aqueous slurry (solid ratio 94:3:3 mass %) consisting of Li 2 FeSiO 4 (median diameter D 50 = 12 μm), acetylene black (manufactured by Denka, Denka Black), and acrylic binder (manufactured by JSR, TRD202A) was made into a The electrode capacity per unit area was 0.5 mAh/cm 2 by filling foamed aluminum (Al Celmet, manufactured by Sumitomo Electric Industries, Ltd.) with a pressure of 100 μm and drying it at 80°C for 30 minutes, and then regulating the pressure with a roll press. A Li 2 FeSiO 4 electrode was produced. Li 2 FeSiO 4 is coated and composited with 10% by mass of carbon by rotary kiln treatment (700° C.).
（実施例１６）
Ｌｉ2ＦｅＳｉＯ4電極を温度４０℃のケイ酸リチウム水溶液（Ｌｉ2Ｏ・３．５ＳｉＯ2 ａｑ．、濃度１質量％）に１分間浸漬後、仮乾燥（８０℃、１時間）し、次いで真空乾燥（１４０℃、１０時間）することで、試験電極を作製した。含浸前後の電極の重量変化は、含浸前の電極（集電体を除く）に対して、含浸後の電極（集電体を除く）が１～３％増加していた。なお、ＳｉＯ電極は完全に浸るまでケイ酸リチウム水溶液に浸漬された後、電極表面に残った余剰のケイ酸ナトリウム水溶液は紙製シート（キンバリー・クラーク製、キムワイプ）で吸い取って除去した。
(Example 16)
The Li 2 FeSiO 4 electrode was immersed in a lithium silicate aqueous solution (Li 2 O.3.5SiO 2 aq., concentration 1% by mass) at a temperature of 40° C. for 1 minute, then temporarily dried (80° C., 1 hour), and then vacuumed. A test electrode was prepared by drying (140° C., 10 hours). Regarding the weight change of the electrode before and after impregnation, the electrode after impregnation (excluding the current collector) increased by 1 to 3% compared to the electrode before impregnation (excluding the current collector). Note that after the SiO electrode was immersed in the lithium silicate aqueous solution until it was completely immersed, the excess sodium silicate aqueous solution remaining on the electrode surface was removed by absorbing it with a paper sheet (Kimwipe, manufactured by Kimberly-Clark).
（比較例５）
Ｌｉ2ＦｅＳｉＯ4電極を温度１２０℃のホットプレート上に置き、スプレーガンによりケイ酸リチウム水溶液を噴霧して作製されたＬｉ2ＦｅＳｉＯ4電極である。なお、ケイ酸リチウム水溶液は電極と接触すると直ちに乾燥したため、ケイ酸リチウム水溶液が液体の状態として活物質層に接触している時間はわずか１秒に満たない。
(Comparative example 5)
The Li 2 FeSiO 4 electrode was prepared by placing the Li 2 FeSiO 4 electrode on a hot plate at a temperature of 120° C. and spraying a lithium silicate aqueous solution with a spray gun. Note that since the lithium silicate aqueous solution dried immediately upon contact with the electrode, the time that the lithium silicate aqueous solution was in contact with the active material layer in a liquid state was only less than 1 second.
（比較例６）
ケイ酸リチウム水溶液に浸漬していないＬｉ2ＦｅＳｉＯ4電極である。
(Comparative example 6)
This is a Li 2 FeSiO 4 electrode that is not immersed in a lithium silicate aqueous solution.
（電池特性）
実施例１６及び比較例５、比較例６で得られた電極を試験電極とし、金属リチウム対極（本城金属製、厚さ５００μｍのリチウム箔）、ＰＰ／ＰＥ／ＰＰの三層微多孔膜（セルガード社製、２３２５）、ガラスフィルタ（アドバンテック製、ＧＡ１００）、１ｍｏｌ／Ｌ ＬｉＰＦ6／エチレンカーボネート（ＥＣ）：ジエチルカーボネート（ＤＥＣ）＝１：１ｖｏｌ．，＋ビニレンカーボネート（ＶＣ）１ｗｔ．％を用いてコイン型電池（Ｒ２０３２）を作製した。
(Battery characteristics)
The electrodes obtained in Example 16, Comparative Example 5, and Comparative Example 6 were used as test electrodes, and a metallic lithium counter electrode (manufactured by Honjo Metals, 500 μm thick lithium foil), a three-layer microporous membrane of PP/PE/PP ( (manufactured by Celgard, 2325), glass filter (manufactured by Advantech, GA100), 1 mol/L LiPF 6 /ethylene carbonate (EC): diethyl carbonate (DEC) = 1:1 vol. ,+vinylene carbonate (VC) 1wt. A coin type battery (R2032) was produced using %.
充放電サイクル試験は、３０℃環境にて、カットオフ電圧４．８～１．５Ｖ、０．１Ｃ率充放電を１サイクル行った後、カットオフ電圧４．５～１．５Ｖ、０．２Ｃ率充放電を繰り返す条件で行った。 In the charge/discharge cycle test, one cycle of charge/discharge at a cutoff voltage of 4.8 to 1.5V and a rate of 0.1C was performed in a 30°C environment, and then a cutoff voltage of 4.5 to 1.5V and a rate of 0.2C was performed. The test was carried out under conditions of repeated charging and discharging.
表３に、ＬｉＦｅ2ＳｉＯ4電極のサイクル特性（１サイクル目、２サイクル目、５０サイクル目における放電容量、容量維持率、クーロン効率）を示す。 Table 3 shows the cycle characteristics (discharge capacity, capacity retention rate, and coulombic efficiency at the 1st cycle, 2nd cycle, and 50th cycle) of the LiFe 2 SiO 4 electrode.
実施例１６の４０℃のケイ酸リチウム水溶液に１分間浸漬した場合には、０．２Ｃ率で５０サイクル後でも、放電容量が１００ｍＡｈ／ｇ程度を有し、安定したサイクル特性を示している。 When immersed in the 40° C. lithium silicate aqueous solution of Example 16 for 1 minute, the discharge capacity was approximately 100 mAh/g even after 50 cycles at a rate of 0.2 C, showing stable cycle characteristics.
一方、比較例５のケイ酸リチウム水溶液が液体の状態として活物質層に接触している時間は１秒に満たない場合と、比較例６のケイ酸リチウム水溶液に浸漬しなかった場合には、初回から放電容量が低い。比較例５と比較例６を比べると、若干ではあるものの比較例５の方が高容量となっている。しかし、比較例５と実施例１６を比べると容量差は明確であることがわかる。 On the other hand, when the lithium silicate aqueous solution of Comparative Example 5 was in contact with the active material layer in a liquid state for less than 1 second, and when the lithium silicate aqueous solution of Comparative Example 6 was not immersed in the active material layer, Discharge capacity is low from the first time. Comparing Comparative Example 5 and Comparative Example 6, Comparative Example 5 has a higher capacity, albeit slightly. However, when comparing Comparative Example 5 and Example 16, it can be seen that there is a clear difference in capacity.
以上のとおり、本発明の好適な実施形態、実施例について説明したが、本発明の趣旨を逸脱しない範囲で、種々の追加、変更または削除が可能である。したがって、そのようなものも本発明の範囲に含まれる。また、本明細書において、化合物の一般式に記載された数字は、単なる表現上に整数で表していることがあるが、電気的中性を満たす数で、実質的に同一である場合は本発明の権利範囲に含まれる。 As described above, the preferred embodiments and examples of the present invention have been described, but various additions, changes, or deletions can be made without departing from the spirit of the present invention. Therefore, such materials are also included within the scope of the present invention. In addition, in this specification, the numbers described in the general formula of the compound may be expressed as integers for mere expression, but if they are numbers that satisfy electrical neutrality and are substantially the same, then Included in the scope of invention rights.
Claims (10)
活物質と第１バインダを含んでなるスラリーを集電体に塗布または充填し、乾燥後、活物質層を製造する工程Ａと、
温度３０℃以上１２０℃以下の第２バインダ水溶液を製造する工程Ｂと、
温度３０℃以上１２０℃以下の前記第２バインダ水溶液に前記活物質層を浸漬し、または前記第２バインダ水溶液を前記活物質層に塗布し、第２バインダ水溶液と活物質層を１秒以上接触させ、乾燥後、電極を製造する工程Ｃと、を備え、
前記第２バインダ水溶液が、ケイ酸塩水溶液またはリン酸塩水溶液であり、
前記ケイ酸塩水溶液は、Ａ2Ｏ・ｎＳｉＯ2で表されるケイ酸塩を水に溶解した液体であり、ＡがＬｉ、ＮａまたはＫの少なくともいずれか一種であり、ｎが１．７以上５以下であり、
前記リン酸塩水溶液は、Ａｌ2Ｏ3・ｎＰ2Ｏ5で表されるリン酸塩を水に溶解した液体であり、ｎが１．７以上５以下である、
電極の製造方法。 A method for manufacturing an electrode for a non-aqueous electrolyte secondary battery, the method comprising:
A step A of applying or filling a current collector with a slurry containing an active material and a first binder, and manufacturing an active material layer after drying;
Step B of producing a second binder aqueous solution at a temperature of 30° C. or higher and 120° C. or lower ;
The active material layer is immersed in the second aqueous binder solution at a temperature of 30° C. or more and 120° C. or less, or the second aqueous binder solution is applied to the active material layer, and the second aqueous binder solution and the active material layer are brought into contact for 1 second or more. and a step C of manufacturing an electrode after drying .
the second binder aqueous solution is a silicate aqueous solution or a phosphate aqueous solution,
The silicate aqueous solution is a liquid obtained by dissolving a silicate represented by A 2 O.nSiO 2 in water, where A is at least one of Li, Na, or K, and n is 1.7 or more. 5 or less,
The phosphate aqueous solution is a liquid in which a phosphate represented by Al 2 O 3 .nP 2 O 5 is dissolved in water, and n is 1.7 or more and 5 or less.
Method of manufacturing electrodes.
請求項１記載の電極の製造方法。 The first binder is a resin binder, and the second binder aqueous solution is an inorganic binder aqueous solution.
A method for manufacturing an electrode according to claim 1.
請求項１に記載の電極の製造方法。 In step C, dipping or coating is performed over a period of 10 seconds or more and 5 hours or less.
A method for manufacturing the electrode according to claim 1 .
予め絶対圧３０ｋＰａ以下まで減圧し、活物質層内の空気を除去する工程を有し、
前記第２バインダ水溶液に活物質層内の空気が除去された前記活物質層を浸漬し、または前記第２バインダ水溶液を活物質層内の空気が除去された前記活物質層に塗布し、乾燥後、電極を製造する工程である、
請求項１に記載の電極の製造方法。 The step C is
It has a step of reducing the pressure to an absolute pressure of 30 kPa or less in advance and removing air in the active material layer,
The active material layer from which air has been removed is immersed in the second aqueous binder solution, or the second aqueous binder solution is applied to the active material layer from which air has been removed, and the active material layer is dried. After that, the process of manufacturing the electrode,
A method for manufacturing the electrode according to claim 1.
前記第２バインダ水溶液に前記活物質層を浸漬し、または前記第２バインダ水溶液を
前記活物質層に塗布する工程において、絶対圧０．１２ＭＰａ以上１０ＭＰａ以下まで加圧する、
請求項１に記載の電極の製造方法。 The step C is
In the step of immersing the active material layer in the second aqueous binder solution or applying the second aqueous binder solution to the active material layer, pressurizing to an absolute pressure of 0.12 MPa or more and 10 MPa or less,
A method for manufacturing the electrode according to claim 1 .
予め絶対圧３０ｋＰａ以下まで減圧し、活物質層内の空気を除去する工程と、
減圧した状態で、前記第２バインダ水溶液に活物質層内の空気が除去された前記活物質層を浸漬し、または前記第２バインダ水溶液を活物質層内の空気が除去された前記活物質層に塗布し、減圧状態から絶対圧０．１２ＭＰａ以上１０ＭＰａ以下まで加圧する工程と、を有する、
請求項１に記載の電極の製造方法。 The step C is
A step of previously reducing the pressure to an absolute pressure of 30 kPa or less and removing air within the active material layer;
The active material layer from which air within the active material layer has been removed is immersed in the second aqueous binder solution under reduced pressure, or the active material layer from which air within the active material layer has been removed is immersed in the second aqueous binder solution. and pressurizing from a reduced pressure state to an absolute pressure of 0.12 MPa or more and 10 MPa or less,
A method for manufacturing the electrode according to claim 1.
請求項１に記載の電極の製造方法。 The electrode after the step C contains an inorganic binder in an amount of 0.1% by mass or more and 30% by mass or less, when the total amount of the active material layer is 100%.
A method for manufacturing the electrode according to claim 1.
ＡがＬｉ、ＮａまたはＫの少なくともいずれか一種であり、ＭがＦｅ、Ｎｉ、Ｍｎ、またはＣｏの少なくともいずれか一種であり、ａが０以上２以下であり、ｂが０．８以上１以下であり、ｃが０．８以上１以下であり、ｄが０以上０．２以下であり、ｘが０．２以上１．８以下である、
請求項１に記載の電極の製造方法。 The active material includes a material represented by the general formula A 2-a M b Si c O 4-d or the general formula SiO x ,
A is at least one of Li, Na, or K, M is at least one of Fe, Ni, Mn, or Co, a is 0 or more and 2 or less, and b is 0.8 or more and 1 or less. , c is 0.8 or more and 1 or less, d is 0 or more and 0.2 or less, and x is 0.2 or more and 1.8 or less,
A method for manufacturing the electrode according to claim 1.
請求項１に記載の電極の製造方法。 The current collector is a conductor made of a porous body or a group of fibers,
A method for manufacturing the electrode according to claim 1.
請求項１に記載の電極の製造方法。 The material of the current collector is aluminum or an aluminum alloy.
A method for manufacturing the electrode according to claim 1.
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