JP2016131056A - Power storage device - Google Patents

Power storage device Download PDF

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JP2016131056A
JP2016131056A JP2013103498A JP2013103498A JP2016131056A JP 2016131056 A JP2016131056 A JP 2016131056A JP 2013103498 A JP2013103498 A JP 2013103498A JP 2013103498 A JP2013103498 A JP 2013103498A JP 2016131056 A JP2016131056 A JP 2016131056A
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negative electrode
active material
positive electrode
power storage
storage device
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亨 永浦
Toru Nagaura
亨 永浦
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NAGAURA ATSUKO
NAGAURA CHIEKO
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NAGAURA CHIEKO
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Priority to PCT/JP2014/061163 priority patent/WO2014175212A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

PROBLEM TO BE SOLVED: To overcome the problem of an internal resistance increased in a power storage device arranged so that an electron-insulating ceramics layer formed on an electrode surface serves as a separator.SOLUTION: In a power storage device according to the present invention, ceramic particles included in an electron-insulating ceramics layer are selected from electron insulating ceramics on which an electrochemical reductive reaction can progress in an organic electrolytic solution. Therefore, the ceramic particles in contact with a positive electrode remain electron insulating, and other ceramic particles are electrochemically reduced and end up having ion conductivity. Thus, the internal resistance is not increased even in the power storage device arranged to use the ceramics layer as a separator.SELECTED DRAWING: Figure 4

Description

本発明は、蓄電装置のセパレーターに関するものである。    The present invention relates to a separator for a power storage device.

これまで携帯電話やノート型パソコンなどの電子機器の電源として広く普及してきたリチウムイオン電池は、近年、ハイブリッド自動車や電気自動車や電力貯蔵用等の更に大型の蓄電装置（以下、二次電池およびキャパシタを総称して蓄電装置という。）への利用にも期待されており、リチウムイオン二次電池の安全性の向上が重要な課題となっている。    Lithium ion batteries, which have been widely used as power sources for electronic devices such as mobile phones and notebook computers, have recently become larger power storage devices (hereinafter referred to as secondary batteries and capacitors) for hybrid vehicles, electric vehicles, and power storage. Are collectively expected to be used for power storage devices), and improving the safety of lithium ion secondary batteries is an important issue.

リチウムイオン二次電池は正極の活物質中に存在するリチウムイオン（Ｌｉ＋）が充電によって負極に移動し、放電では再び正極に戻るという電池システムであるが、斯かる電池システムは１９８０年以前に既に提案されており、充電状態では特定のイオンが負極（又は正極）に偏り、放電状態では負極（又は正極）に偏ることから“ロッキングチェアー電池”とよばれていた。A lithium ion secondary battery is a battery system in which lithium ions (Li + ) present in the active material of the positive electrode move to the negative electrode by charging, and return to the positive electrode again by discharging. Such a battery system was used before 1980 Already proposed, specific ions are biased to the negative electrode (or positive electrode) in the charged state, and biased to the negative electrode (or positive electrode) in the discharged state, which is called a “rocking chair battery”.

本願発明者らは、正極にＬｉＣｏＯ２を使用し、負極にはカーボンを使用して、このロッキングチェアー電池を世界で初めて商品化し、これを、“リチウムイオン電池（二次電池）”と名付けて、１９９０年２月にプレスリリースした。同年３月にはフロリダで開かれた第３回二次電池セミナーで、本願発明者が初めてリチウムイオン電池（二次電池）の優れた性能を世界に紹介したという経緯がある（非特許文献１参照）。The inventors of the present application commercialized this rocking chair battery for the first time in the world using LiCoO 2 for the positive electrode and carbon for the negative electrode, and named it “Lithium ion battery (secondary battery)”. A press release was made in February 1990. In March of the same year, at the third secondary battery seminar held in Florida, the inventor of the present application first introduced the excellent performance of lithium ion batteries (secondary batteries) to the world (Non-patent Document 1). reference).

近年では、正極材料をＬｉＣｏＯ２からＬｉＮｉＯ２やＬｉＭｎ２Ｏ４やＬｉＦｅＰＯ４等の価格の安い材料に置き換えて、低価格タイプのロッキングチェアー電池が実用化されている。また、正極活物質だけでなく負極活物質も、カーボンからセラミックス材料（例えば、ＴｉＯ２−Ｂ、Ｌｉ４Ｔｉ５Ｏ１２、ＳｉＯ等）に置き換えて、ロッキングチェアー電池の安全性を高める提案がなされており、これ等の電池も今ではリチウムイオン電池と呼ばれている（非特許文献２〜７参照）。In recent years, low-cost rocking chair batteries have been put into practical use by replacing the positive electrode material with a low-priced material such as LiNiO 2 , LiMn 2 O 4, or LiFePO 4 from LiCoO 2 . Further, not only the positive electrode active material but also the negative electrode active material has been proposed to replace carbon with a ceramic material (for example, TiO 2 -B, Li 4 Ti 5 O 12 , SiO, etc.) to increase the safety of the rocking chair battery. These batteries are now also called lithium ion batteries (see Non-Patent Documents 2 to 7).

今日では、非金属鉱物の全般が一般にセラミックスと呼ばれているが、このセラミックス材料の中には、リチウムイオンのドーピング・脱ドーピングを伴って電気化学的な酸化還元反応が可逆的に進行しうる物質がかなり多く存在し、斯かるセラミックス材料はリチウムイオン電池の正極活物質や負極活物質に利用できる。従って今後、その組み合わせによって、数多くのリチウムイオン電池が出現する可能性がある。斯かるセラミックス材料には資源的に豊富なものもあり、今後のリチウムイオン電池の価格低減の鍵にもなる。    Today, non-metallic minerals are generally called ceramics, but in some ceramic materials, electrochemical redox reactions can proceed reversibly with lithium ion doping / dedoping. There are considerably many substances, and such a ceramic material can be used as a positive electrode active material or a negative electrode active material of a lithium ion battery. Therefore, in the future, many lithium ion batteries may appear depending on the combination. Some of these ceramic materials are abundant in resources, and will be the key to reducing the price of future lithium ion batteries.

蓄電装置における“活物質”とは蓄電反応に直接寄与する物質を意味する。蓄電装置における活物質は電気化学的な酸化還元反応に基づいて可逆的に化学変化するものと、化学変化はしないものに分けられる。電解液中で電気化学的な酸化還元反応に基づいて可逆的に化学変化する活物質を正極活物質にも負極活物質にも使用する蓄電装置が“二次電池（または単に電池ということもある。）”である。    An “active material” in a power storage device means a material that directly contributes to a power storage reaction. Active materials in power storage devices are classified into those that reversibly chemically change based on electrochemical redox reactions and those that do not change chemically. A power storage device that uses an active material that reversibly changes chemically based on an electrochemical redox reaction in an electrolyte solution as a positive electrode active material or a negative electrode active material is referred to as a “secondary battery (or simply a battery). .) ”.

一方、電気化学的な酸化還元反応に基づいて化学変化する活物質は正極か負極かの一方にだけ使用する蓄電装置は“キャパシタ”に分類される。キャパシタには少なくとも正極か負極かの一方には化学変化に基づかない活物質を用いるため、二次電池に比べて蓄電容量が少なく、電気自動車や電力貯蔵用等の大型の蓄電装置には不向きである。    On the other hand, a power storage device that uses only one of a positive electrode and a negative electrode as an active material that chemically changes based on an electrochemical redox reaction is classified as a “capacitor”. Since an active material that is not based on chemical change is used for at least one of the positive electrode and the negative electrode for the capacitor, the storage capacity is smaller than that of the secondary battery, and it is not suitable for large power storage devices such as electric vehicles and power storage. is there.

これまでの蓄電装置においては、一般的には、正極と負極はそれぞれの活物質層がそれぞれの集電体に密着して形成された電極であり、それぞれの活物質層中の活物質は集電体と電子的に導通する必要があるため、活物質層はカーボン等の伝導助材を混ぜて電子伝導性とされる。従って、対向する正極と負極の間にはセパレーターを介在させて、正極と負極の内部短絡を阻止する必要がある。    In conventional power storage devices, in general, the positive electrode and the negative electrode are electrodes in which each active material layer is formed in close contact with each current collector, and the active material in each active material layer is collected. Since it is necessary to be electrically connected to the electric body, the active material layer is made electronically conductive by mixing a conduction aid such as carbon. Therefore, it is necessary to prevent an internal short circuit between the positive electrode and the negative electrode by interposing a separator between the positive electrode and the negative electrode facing each other.

“正極と負極の内部短絡”とは一般には内部ショートともいわれるが、対向する正極と負極が直接電子伝導で導通することである。蓄電装置における“セパレーター”は対向する正極と負極の間に介在してセパレーター機能を有するものを言うが、“セパレーター機能”とは正極活物質と負極活物質との電子的な導通は断って、イオン電導は確保するという機能である。    “Internal short-circuit between positive electrode and negative electrode” is generally referred to as an internal short circuit, but is a direct conduction between the positive electrode and the negative electrode facing each other. “Separator” in a power storage device means a separator function that is interposed between the positive electrode and the negative electrode facing each other, but “separator function” means that electronic conduction between the positive electrode active material and the negative electrode active material is cut off, Ion conduction is a function to ensure.

また、蓄電装置における“活物質層”とは活物質で構成される多孔質体であり、蓄電反応に直接寄与する活物質が外部回路との電子の授受と、対極とのイオン伝達をスムーズに行うことができる成形体として、通常、集電体に密着して形成される。この“集電体”は活物質と外部回路との電子の授受を仲介する電子伝導体である。通常、活物質層には平均粒径５〜１０μｍ程度のグラファイト等が伝導助剤として混ぜられるので、セパレーター層の厚さを５〜１０μｍ程度以下とした場合には、斯かる伝導助剤が導電性異物として電極間に挟まって、蓄電装置を内部ショートに至らしめることが十分に考えられる。従って、セパレーター層の厚さは１５μｍ程度以上とすることが望ましい。    An “active material layer” in a power storage device is a porous body composed of an active material, and an active material that directly contributes to a power storage reaction smoothly transfers electrons to and from an external circuit and transmits ions to and from a counter electrode. The molded body that can be used is usually formed in close contact with the current collector. This “current collector” is an electron conductor that mediates the exchange of electrons between the active material and an external circuit. Usually, graphite or the like having an average particle size of about 5 to 10 μm is mixed in the active material layer as a conduction aid. Therefore, when the thickness of the separator layer is about 5 to 10 μm or less, such a conduction aid is conductive. It is sufficiently conceivable that the power storage device is short-circuited between the electrodes as a conductive foreign substance. Therefore, the thickness of the separator layer is desirably about 15 μm or more.

これまでのリチウムイオン電池では、セパレーターとしては厚さ２５μｍ程度以上のポリエチレン（ＰＥ）やポリプロピレン（ＰＰ）製のシート状セパレーターが使用されている。“シート状セパレーター”とは正極と負極の間に介在させるシート状の多孔質膜であるが、シート状の多孔質膜は電解液を含浸すれば、正極と負極のイオン電導は確保されてセパレーター機能が備わる。    In a conventional lithium ion battery, a sheet separator made of polyethylene (PE) or polypropylene (PP) having a thickness of about 25 μm or more is used as the separator. The “sheet separator” is a sheet-like porous film interposed between the positive electrode and the negative electrode. However, if the sheet-like porous film is impregnated with an electrolytic solution, the ion conduction between the positive electrode and the negative electrode is ensured and the separator. It has a function.

しかし、樹脂製のシート状セパレーターは、微小の導電性異物で軽度に内部短絡した場合でも、ショート箇所の部分的な温度上昇によって、セパレーターが部分的に熱収縮して、内部短絡が重度化して電池が熱暴走に至り、発火事故等に繋がる可能性がある。    However, even if a resin-made sheet-like separator is slightly short-circuited with a small amount of conductive foreign matter, the separator partially heat-shrinks due to a partial temperature rise at the short-circuited location, causing the internal short circuit to become severe. There is a possibility that the battery will run out of heat and lead to a fire accident.

従って、リチウムイオン電池の安全性の改善には、耐熱性の高いセパレーターの採用が望ましい。そこで、耐熱性の高いセパレーターとして、電極表面に非電子伝導性（電子絶縁性）のセラミックス層を形成するという方法が提案されている（非特許文献８参照）。提案されている従来技術では、アルミナ（Ａｌ２Ｏ３）等の電子絶縁性のセラミックス粒子をスラリーとして電極表面に塗布して乾燥するというものであり、電子絶縁性のセラミックス層（多孔質セラミックス層）を電極表面上に安価に形成することができる。Therefore, it is desirable to use a separator with high heat resistance to improve the safety of the lithium ion battery. Therefore, a method of forming a non-electron conductive (electronic insulating) ceramic layer on the electrode surface as a separator having high heat resistance has been proposed (see Non-Patent Document 8). In the proposed prior art, electronic insulating ceramic particles such as alumina (Al 2 O 3 ) are applied to the electrode surface as a slurry and dried, and the electronic insulating ceramic layer (porous ceramic layer) ) Can be formed on the electrode surface at low cost.

電極表面に形成される電子絶縁性のセラミックス層には空孔も存在するので、当該空孔が電解液で充満されれば、イオン伝導性が付加されて“セパレーター機能”が備わる。従って、従来のシート状セパレーターに代替可能であり、リチウムイオン電池の安全性の改善と同時にセパレーターコストの低減にも効果的である。    Since the electronic insulating ceramic layer formed on the electrode surface has pores, if the pores are filled with the electrolyte, ion conductivity is added and a “separator function” is provided. Therefore, it can be replaced with a conventional sheet-like separator, and is effective in improving the safety of the lithium ion battery and at the same time reducing the separator cost.

なお、一般に、電気伝導率が１０−１０Ｓ／ｃｍ未満の材料が絶縁体と言われており、本明細書で言う“電子絶縁性”または“非電子伝導性”とは電子伝導率が１０−１０Ｓ／ｃｍ未満を意味するものであり、電子伝導率が１０−１０Ｓ／ｃｍ以上は、通常半導体に分類される範囲（電子伝導率が１０３〜１０−１０Ｓ／ｃｍ程度）も含めて、本明細書では“電子伝導性”と言う。In general, a material having an electric conductivity of less than 10 −10 S / cm is said to be an insulator, and “electronic insulating” or “non-electron conductive” in this specification means an electronic conductivity of 10 It means less than −10 S / cm, and an electron conductivity of 10 −10 S / cm or more is usually classified as a semiconductor (electron conductivity is about 10 3 to 10 −10 S / cm). Including, it is referred to as “electron conductivity” in this specification.

Ｔ．Ｎａｇａｕｒａ、ＪＥＣ Ｂａｔｔｅｒｙ Ｎｅｗｓｌｅｔｔｅｒ Ｎｏ．２（Ｍａｒ．−Ａｐｒ．）１９９０T.A. Nagaura, JEC Battery Newsletter No. 2 (Mar.-Apr.) 1990 橘田晃宣、その他、第５３回電池討論会講演予稿集、Ｐ．２３８（２０１２）Yoshinori Tachida, et al., Proceedings of the 53rd Battery Discussion Meeting, 238 (2012) 渋川憲太、その他、第５３回電池討論会講演予稿集、Ｐ．２４０（２０１２）Kenta Shibukawa and others, Proceedings of the 53rd Battery Discussion Meeting, 240 (2012) 伊藤龍太、その他、第５３回電池討論会講演予稿集、Ｐ．２４１（２０１２）Ryuta Ito, et al., Proceedings of the 53rd Battery Conference, 241 (2012) 門磨義裕、その他、第５３回電池討論会講演予稿集、Ｐ．２４２（２０１２）Yoshihiro Kadoma and others, Proceedings of the 53rd Battery Conference 242 (2012) 中野善之、その他、第５３回電池討論会講演予稿集、Ｐ．２４５（２０１２）Yoshiyuki Nakano, et al., Proceedings of the 53rd Battery Discussion Meeting, p. 245 (2012) 古谷泰幸、その他、第５３回電池討論会講演予稿集、Ｐ．２４６（２０１２）Yasuyuki Furuya, et al., Proceedings of the 53rd Battery Discussion Meeting, p. 246 (2012) 豊田裕次郎、その他、第５３回電池討論会講演予稿集、Ｐ．２（２０１２）Yujiro Toyoda, et al., Proceedings of the 53rd Battery Conference, 2 (2012) 峰裕之、その他、第５３回電池討論会講演予稿集、Ｐ．１２２（２０１２）Hiroyuki Mine, et al., Proceedings of 53rd Battery Discussion Meeting, 122 (2012) 浅利祐介、その他、第５３回電池討論会講演予稿集、Ｐ．１２９（２０１２）Yusuke Asari, et al., Proc. 129 (2012)

しかしながら、電極表面に形成する前記セラミックス層は、その厚さを、正極と負極の内部短絡を阻止できる十分な厚さ（１５μｍ以上）で形成した場合には、蓄電装置の内部抵抗は高くなってしまう。また、蓄電装置の内部抵抗が満足な値に収まる厚さ（５μｍ程度）で前記セラミックス層を形成した場合には、セラミックス層だけでは正極と負極の内部短絡は十分に阻止することができない。    However, when the ceramic layer formed on the electrode surface is formed with a thickness (15 μm or more) sufficient to prevent the internal short circuit between the positive electrode and the negative electrode, the internal resistance of the power storage device increases. End up. In addition, when the ceramic layer is formed with a thickness (about 5 μm) at which the internal resistance of the power storage device falls within a satisfactory value, an internal short circuit between the positive electrode and the negative electrode cannot be sufficiently prevented with the ceramic layer alone.

本発明は、以上の課題に鑑みて成されたものであり、その目的は、蓄電装置の内部抵抗を満足な値に収め、且つ正極と負極の内部短絡は完璧に阻止できるセラミックス層を電極表面に形成せしめることを可能とするものである。    The present invention has been made in view of the above problems, and its object is to provide a ceramic layer that can keep the internal resistance of a power storage device at a satisfactory value and can completely prevent internal short circuit between the positive electrode and the negative electrode. Can be formed.

正極と負極が対向してなる蓄電装置において、前記正極と前記負極は何れも集電体に電子伝導性の活物質層が形成された電極であって、対向する正極と負極の内部短絡は対向する正極と負極の活物質層間に介在する電子絶縁性のセラミックス層によって阻止されており、当該セラミックス層を構成するセラミックス粒子は電気化学的な還元反応によって化学変化しうる電子絶縁性のセラミックスから選択されることを特徴とする。    In a power storage device in which a positive electrode and a negative electrode are opposed to each other, the positive electrode and the negative electrode are both electrodes in which an electron conductive active material layer is formed on a current collector, and an internal short circuit between the opposed positive electrode and the negative electrode is opposed. Selected from electronically insulating ceramics that can be chemically changed by an electrochemical reduction reaction, which is blocked by an electronically insulating ceramic layer interposed between the positive and negative electrode active material layers. It is characterized by being.

本発明に係る電極構造の蓄電装置では、対向する正極と負極の内部短絡は対向する正極と負極の活物質層間に介在する電子絶縁性のセラミックス層によって阻止されており、正極と負極のイオン電導は、基本的には、当該セラミックス層に含浸される電解液によって確保されるが、加えて、前記セラミックス層を構成するセラミックス粒子は電気化学的な還元反応によって化学変化しうる電子絶縁性のセラミックスから選択されるので、前記セラミックス層を構成しているセラミックス粒子のうち、正極と直接接触する以外のセラミックス粒子は電気化学的に還元されてイオン電導性のセラミックス粒子に変化するため、前記セラミックス層のイオン電導率は高くなる。その結果、内部抵抗が十分に低い、耐熱性の高い蓄電装置を実現することができる。    In the power storage device having the electrode structure according to the present invention, the internal short circuit between the positive electrode and the negative electrode facing each other is prevented by an electronic insulating ceramic layer interposed between the active material layers of the positive electrode and the negative electrode facing each other. Is basically secured by the electrolyte solution impregnated in the ceramic layer, but in addition, the ceramic particles constituting the ceramic layer can be chemically changed by an electrochemical reduction reaction. Among the ceramic particles constituting the ceramic layer, the ceramic particles other than those in direct contact with the positive electrode are electrochemically reduced to change into ion conductive ceramic particles. The ionic conductivity of becomes higher. As a result, a power storage device with sufficiently low internal resistance and high heat resistance can be realized.

上記した以外の課題やその解決手段と効果は、以下の実施の形態の説明により更に詳細に説明する。    Problems other than those described above and solutions and effects thereof will be described in more detail with reference to the following embodiments.

本発明の一実施形態に係る蓄電素子の斜視図である。  It is a perspective view of the electrical storage element which concerns on one Embodiment of this invention. 本発明の一実施形態に係る蓄電装置の斜視図である。  It is a perspective view of the electrical storage apparatus which concerns on one Embodiment of this invention. 本発明の一実施形態に係る蓄電素子の断面図である。  It is sectional drawing of the electrical storage element which concerns on one Embodiment of this invention. 本発明の一実施形態に係る蓄電素子の断面図である。  It is sectional drawing of the electrical storage element which concerns on one Embodiment of this invention. 本発明の一実施形態に係る蓄電装置のセラミック層断面の模式図である。  It is a schematic diagram of the ceramic layer cross section of the electrical storage apparatus which concerns on one Embodiment of this invention. 対向する電極間に介在するセラミック層の厚さと内部短絡の関係を示す模式図である。  It is a schematic diagram which shows the relationship between the thickness of the ceramic layer interposed between opposing electrodes, and an internal short circuit. 対向する電極間に介在するセラミック層の厚さと内部短絡の関係を示す模式図である。  It is a schematic diagram which shows the relationship between the thickness of the ceramic layer interposed between opposing electrodes, and an internal short circuit. 対向する電極間に介在するセラミック層の厚さと内部短絡の関係を示す模式図である。  It is a schematic diagram which shows the relationship between the thickness of the ceramic layer interposed between opposing electrodes, and an internal short circuit.

以下、本発明の実施の形態を図面に基づきさらに詳細に説明する。    Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

図１は本発明の一実施形態に係る蓄電素子１０（以下、「電極積層体１０」ともいう。）の斜視図である。図２は本発明の一実施形態に係る蓄電装置１００の斜視図であり、図１に示す蓄電素子１０が、有機電解液（不図示）を含有してラミネートシート１１および１２に密封されてなる蓄電装置１００の斜視図である。    FIG. 1 is a perspective view of a power storage device 10 (hereinafter also referred to as “electrode laminate 10”) according to an embodiment of the present invention. FIG. 2 is a perspective view of a power storage device 100 according to an embodiment of the present invention, in which the power storage element 10 shown in FIG. 1 contains an organic electrolyte (not shown) and is sealed in laminate sheets 11 and 12. 1 is a perspective view of a power storage device 100. FIG.

図３は本発明の一実施形態に係る蓄電素子の断面図であり、図１に示す蓄電素子１０のＤ−Ｄ’の断面を、中央部は省略し、電極端部を拡大して示した断面図である。図４は本発明の一実施形態に係る蓄電装置の、初回の充電を終えた後の蓄電素子１０の断面図であり、同じく図１に示す蓄電素子１０のＤ−Ｄ’の断面を、中央部は省略し、電極端部を拡大して示した断面図である。    FIG. 3 is a cross-sectional view of a power storage device according to an embodiment of the present invention, in which the cross section DD ′ of the power storage device 10 shown in FIG. It is sectional drawing. FIG. 4 is a cross-sectional view of the power storage device 10 after the first charge of the power storage device according to the embodiment of the present invention, and a cross-section of DD ′ of the power storage device 10 shown in FIG. FIG. 5 is an enlarged cross-sectional view of an electrode end portion, with parts omitted.

なお、本発明の実施形態に係る蓄電装置では、対向する正極３１と負極３２の間には、電子絶縁性のセラミックス粒子で構成されるセラミックス層５が介在し、当該セラミックス層を構成する電子絶縁性のセラミックス粒子は有機電解液中で電気化学的な還元反応によって化学変化しうる電子絶縁性のセラミックスから選択されることを特長とする。    In the power storage device according to the embodiment of the present invention, the ceramic layer 5 made of electronic insulating ceramic particles is interposed between the positive electrode 31 and the negative electrode 32 facing each other, and the electronic insulation that constitutes the ceramic layer. The ceramic particles are selected from electronically insulating ceramics that can be chemically changed by an electrochemical reduction reaction in an organic electrolyte.

蓄電素子１０は、図３に示すように正極３１と負極３２が交互に積層されて構成されるが、正極３１は、正極活物質と伝導助剤で構成される電子伝導性の活物質層２（以下、「正極活物質層２」ともいう。）が集電体４（以下、「正極集電体４」ともいう。）に密着して形成された電極であり、活物質層２を構成する正極活物質は集電体４に電子的に導通している。また、負極３２も、負極活物質と伝導助剤で構成される電子伝導性の活物質層１（以下、「負極活物質層１」ともいう。）が集電体３（以下、「負極集電体３」ともいう。）に密着して形成された電極であり、活物質層１を構成する負極活物質は集電体３に電子的に導通している。しかし、正極活物質層２中の正極活物質と負極活物質層１中の負極活物質の間の電子的導通は、負極活物質層１の表面に形成されている電子絶縁性のセラミックス層５で断たれている。    As shown in FIG. 3, the power storage element 10 is configured by alternately stacking positive electrodes 31 and negative electrodes 32, and the positive electrode 31 is an electronically conductive active material layer 2 composed of a positive electrode active material and a conductive assistant. (Hereinafter also referred to as “positive electrode active material layer 2”) is an electrode formed in close contact with the current collector 4 (hereinafter also referred to as “positive electrode current collector 4”), and constitutes the active material layer 2 The positive electrode active material is electronically connected to the current collector 4. In addition, the negative electrode 32 also has an electron conductive active material layer 1 (hereinafter also referred to as “negative electrode active material layer 1”) composed of a negative electrode active material and a conduction aid, and a current collector 3 (hereinafter referred to as “negative electrode collector”). The negative electrode active material constituting the active material layer 1 is electronically connected to the current collector 3. However, the electronic continuity between the positive electrode active material in the positive electrode active material layer 2 and the negative electrode active material in the negative electrode active material layer 1 is the electronic insulating ceramic layer 5 formed on the surface of the negative electrode active material layer 1. It has been refused.

一方、正極活物質層２と、負極活物質層１と、セラミックス層５にはそれぞれ空孔が存在し、当該空孔に電解液が充満すれば、正極活物質層２と負極活物質層１はイオン電導では導通する。つまり、絶縁性のセラミックス層５は、正極活物質層２と負極活物質層１の電子的導通は断ってイオン電導では導通するので、セパレーター機能を有することになる。従って集電体４と集電体３に集電体４をプラスとする電圧が印加されれば、正極活物質層２を構成する正極活物質は電気化学的に酸化され、負極活物質層１を構成する負極活物質は電気化学的に還元される。    On the other hand, if the positive electrode active material layer 2, the negative electrode active material layer 1, and the ceramic layer 5 have pores, and the pores are filled with the electrolytic solution, the positive electrode active material layer 2 and the negative electrode active material layer 1. Are conductive in ion conduction. That is, the insulating ceramic layer 5 has a separator function because the positive electrode active material layer 2 and the negative electrode active material layer 1 are turned off by ionic conduction without being electrically connected. Therefore, when a voltage that makes the current collector 4 positive is applied to the current collector 4 and the current collector 3, the positive electrode active material constituting the positive electrode active material layer 2 is electrochemically oxidized, and the negative electrode active material layer 1 The negative electrode active material constituting is reduced electrochemically.

以上のように、図１に示す蓄電素子１０は電解液を含浸して、アルミニウムとポリプロピレンのラミネートシート１１と１２の間に納められて、周囲を熱融着して密封されれば、図２に示す本実施形態に係る蓄電装置１００が完成する。    1 is impregnated with an electrolytic solution, and is placed between aluminum and polypropylene laminate sheets 11 and 12 and sealed by heat-sealing the periphery. The power storage device 100 according to this embodiment shown in FIG.

図１に示すように、蓄電素子１０では負極３２は正極３１より縦・横寸法を２Ａだけ大きくし、負極３２の電極端が正極３１の電極端より寸法Ａだけ外側に位置するように積層すれば、負極３２の電極端部が正極３１とショートすることは避けられる。また正極３１に設けた正極集電体の露出部３４には絶縁部材８で被覆することで、負極３２の電極端と正極集電体の露出部３４のショートを防ぐことができる。    As shown in FIG. 1, in the electric storage element 10, the negative electrode 32 is stacked so that the vertical and horizontal dimensions are larger by 2 A than the positive electrode 31, and the electrode end of the negative electrode 32 is positioned outside the electrode end of the positive electrode 31 by the dimension A. For example, the electrode end of the negative electrode 32 can be prevented from short-circuiting with the positive electrode 31. Further, by covering the exposed portion 34 of the positive electrode current collector provided on the positive electrode 31 with the insulating member 8, it is possible to prevent a short circuit between the electrode end of the negative electrode 32 and the exposed portion 34 of the positive electrode current collector.

負極３２の各電極に設けた集電体の露出部３３はいずれも負極タブ６に溶接され、正極３１の各電極に設けた集電体の露出部３４はいずれも正極タブ７に溶接される。電極タブ６、７には予めプラスチックテープ９を熱圧着して貼り付けているので、蓄電素子１０が図２に示すように、ラミネートシート１１、１２で密封されるとき、当該プラスチックテープ９がラミネートシート１１、１２と一体化して熱融着されるので、蓄電素子１０の密封を妨げることなく、負極タブ６と正極タブ７は外部に取り出されて負極外部端子１３および正極外部端子１４になる。    Any exposed portion 33 of the current collector provided on each electrode of the negative electrode 32 is welded to the negative electrode tab 6, and any exposed portion 34 of the current collector provided on each electrode of the positive electrode 31 is welded to the positive electrode tab 7. . Since the plastic tape 9 is preliminarily bonded to the electrode tabs 6 and 7 by thermocompression bonding, the plastic tape 9 is laminated when the power storage element 10 is sealed with the laminate sheets 11 and 12 as shown in FIG. Since the sheet 11 and 12 are integrated and heat-sealed, the negative electrode tab 6 and the positive electrode tab 7 are taken out to become the negative electrode external terminal 13 and the positive electrode external terminal 14 without hindering the sealing of the electricity storage element 10.

図２に示される蓄電装置１００では、初回の充電がなされる前は、電極積層体（蓄電素子）１０は図３に示すように「負極活物質層１」、「電子絶縁性のセラミックス層５」、「正極活物質層２」の順番に配列されていて、いずれの層もその空孔は電解液で満たされているので、負極活物質層１の中の負極活物質と正極活物質層２の中の正極活物質はイオン電導では導通する。    In the power storage device 100 shown in FIG. 2, before the first charge, the electrode laminate (power storage element) 10 includes the “negative electrode active material layer 1” and the “electronic insulating ceramic layer 5” as shown in FIG. 3. ”,“ Positive electrode active material layer 2 ”are arranged in this order, and the vacancies of all the layers are filled with the electrolyte solution. Therefore, the negative electrode active material and the positive electrode active material layer in the negative electrode active material layer 1 The positive electrode active material in 2 conducts by ionic conduction.

従って、負極外部端子１３と正極外部端子１４に充電電圧が印加されれば、負極活物質は電気化学的に還元され、正極活物質は電気化学的に酸化されて、蓄電装置１００は充電される。    Therefore, when a charging voltage is applied to the negative electrode external terminal 13 and the positive electrode external terminal 14, the negative electrode active material is electrochemically reduced, the positive electrode active material is electrochemically oxidized, and the power storage device 100 is charged. .

十分長時間、充電電圧が印加されれば、電極積層体１０は図４に示すように、セラミックス層５を構成しているセラミックス粒子のうち、負極活物質層１と直接接触する粒子には負極の電位が印加されるので、当該セラミックス粒子は電気化学的に還元されて、イオン電導性と電子伝導性を有するセラミックス粒子に変質することとなる。更に、電子伝導性に変わった粒子を介して、負極活物質層１とは直接接触していないセラミックス粒子にも負極の電位が印加され、連鎖的に電気化学的還元反応が起こるため、セラミックス層５の大部分はイオン電導性と電子伝導性を有するセラミックス粒子で構成される、電導性セラミックス層５１に変わる。なお、以下、イオン電導性又はイオン電導性と電子伝導性に基づく場合には“電導性”と表記し、電子伝導性のみに基づく場合は“伝導性”と表記する。    If the charging voltage is applied for a sufficiently long time, the electrode laminate 10 is formed of the ceramic particles constituting the ceramic layer 5 among the particles directly contacting the negative electrode active material layer 1 as shown in FIG. Therefore, the ceramic particles are electrochemically reduced to be transformed into ceramic particles having ion conductivity and electron conductivity. Furthermore, since the potential of the negative electrode is applied to the ceramic particles that are not in direct contact with the negative electrode active material layer 1 through the particles that have changed to electron conductivity, an electrochemical reduction reaction occurs in a chained manner. Most of 5 is changed to a conductive ceramic layer 51 composed of ceramic particles having ion conductivity and electron conductivity. Hereinafter, when based on ion conductivity or ion conductivity and electron conductivity, it is expressed as “conductivity”, and when based on only electron conductivity, it is expressed as “conductivity”.

有機電解液中における電気化学的な還元反応とは、結晶体へ電子と陽イオン（Ｌｉイオン）が継続（クーロン／ｓ）的に注入されることである。従って、電気化学的に還元されうる電子絶縁性の結晶体とは、電気化学的還元反応によって電子と陽イオン（Ｌｉイオン）が自由に移動出来る結晶体に変化しうる、つまり、電子伝導性で且つイオン伝導性の結晶体に変化しうることになる。もし、電気化学的還元反応によって、電子と陽イオン（Ｌｉイオン）が自由に移動出来る結晶体にならなければ、結晶体の中へは電子と陽イオン（Ｌｉイオン）は引き続き継続（クーロン／ｓ）的に進入していくことが出来ないため、結晶内部に向かって電気化学的還元反応が継続的に進むことは難しい。    The electrochemical reduction reaction in the organic electrolyte is that electrons and cations (Li ions) are continuously injected into the crystal body (Coulomb / s). Therefore, an electron-insulating crystal that can be electrochemically reduced can be changed to a crystal in which electrons and cations (Li ions) can move freely by an electrochemical reduction reaction. Moreover, it can be changed to an ion conductive crystal. If the crystal does not become a crystal in which electrons and cations (Li ions) can move freely by the electrochemical reduction reaction, electrons and cations (Li ions) continue into the crystal (coulomb / s). Therefore, it is difficult for the electrochemical reduction reaction to proceed continuously toward the inside of the crystal.

セラミックス層５を構成しているセラミックス粒子は電気化学的に還元されうる電子絶縁性のセラミックスから選択されるので、電気化学的還元によって、当該セラミックス粒子は電子伝導性で且つイオン電導性のセラミックスに変化するのである。    Since the ceramic particles constituting the ceramic layer 5 are selected from electronically insulating ceramics that can be reduced electrochemically, the ceramic particles are converted into electronically conductive and ionically conductive ceramics by electrochemical reduction. It will change.

一方、セラミックス層５を構成しているセラミックス粒子は電気化学的に還元されうる電子絶縁性のセラミックスとはいえ、セラミックス層５を構成しているセラミックス粒子のうち、正極活物質層２と直接接触する粒子には正極の電位が印加されるので、当該セラミックス粒子が電気化学的に還元されることはない。従って、正極活物質層２と直接接触する粒子は常に電子絶縁性のままであり、図４に示すように“非電子伝導性（電子絶縁性）のセラミックス層５０”として残る。    On the other hand, the ceramic particles constituting the ceramic layer 5 are in direct contact with the positive electrode active material layer 2 among the ceramic particles constituting the ceramic layer 5 although they are electronically insulating ceramics that can be reduced electrochemically. Since the positive electrode potential is applied to the particles, the ceramic particles are not electrochemically reduced. Therefore, the particles in direct contact with the positive electrode active material layer 2 always remain electronically insulating and remain as a “non-electron conductive (electronic insulating) ceramic layer 50” as shown in FIG.

有機電解液中で電気化学的に還元されうる非電子伝導性のセラミックスとしては、具体的にはＬｉ４Ｔｉ５Ｏ１２やＴｉＯ２−Ｂがある。近年、Ｌｉ４Ｔｉ５Ｏ１２やＴｉＯ２−Ｂはリチウムイオン電池やキャパシタの負極活物質として盛んに検討されている材料であるが（非特許文献２〜７参照）、セパレーター機能を持たせるためのセラミックス材料としての検討例はない。なお、スピネル構造のチタン酸リチウムは一般式Ｌｉ１／３＋ＸＴｉ２／３−ＸＯ４（０≦Ｘ≦１）で示されるものが存在するが、Ｘ＝１におけるＬｉ４Ｔｉ５Ｏ１２は電子絶縁性であり、且つ電気化学的に還元されやすい点から本発明の実施形態への利用に適したセラミックス材料である。Specific examples of non-electron conductive ceramics that can be electrochemically reduced in an organic electrolyte include Li 4 Ti 5 O 12 and TiO 2 —B. In recent years, Li 4 Ti 5 O 12 and TiO 2 —B are materials that have been actively studied as negative electrode active materials for lithium ion batteries and capacitors (see Non-Patent Documents 2 to 7), but have a separator function. There is no example of study as a ceramic material. Although there are those of lithium titanate having a spinel structure represented by the general formula Li 1/3 + X Ti 2 /3-X O 4 (0 ≦ X ≦ 1), Li 4 Ti 5 O 12 in X = 1 is It is a ceramic material suitable for use in the embodiment of the present invention because it is electronically insulating and easily reduced electrochemically.

図５は本発明の一実施形態に係る蓄電装置において、初回の充電前（図左）と充電後（図右）のセラミック層５の断面を模式図で示したものであり、セラミック層５を構成する非電子伝導性のセラミックス粒子として、具体的にＬｉ４Ｔｉ５Ｏ１２を使用する場合について示している。FIG. 5 is a schematic view showing a cross section of the ceramic layer 5 before the first charge (left in the figure) and after the charge (right in the figure) in the power storage device according to the embodiment of the present invention. Specifically, the case where Li 4 Ti 5 O 12 is used as the non-electron conductive ceramic particles is shown.

初回の充電前（図左）では、電子伝導性の負極活物質層１と電子伝導性の正極活物質層２は電子絶縁性のＬｉ４Ｔｉ５Ｏ１２で構成される電子絶縁性のセラミック層５で電子的導通は完璧に断たれており、初回の充電においては、負極活物質層１を構成する負極活物質は電気化学的に還元され、正極活物質層２を構成する正極活物質は電気化学的に酸化されて充電される。Before the first charge (left in the figure), the electronically conductive negative electrode active material layer 1 and the electronically conductive positive electrode active material layer 2 are electronically insulating ceramic layers composed of electronically insulating Li 4 Ti 5 O 12. 5, the electronic continuity is completely cut off, and in the first charge, the negative electrode active material constituting the negative electrode active material layer 1 is electrochemically reduced, and the positive electrode active material constituting the positive electrode active material layer 2 is It is electrochemically oxidized and charged.

初回の充電後（図右）では、正極活物質層２と直接接触するＬｉ４Ｔｉ５Ｏ１２粒子には正極電位がかかるので電気化学的に還元されることはなく、そのままＬｉ４Ｔｉ５Ｏ１２粒子として“非電子伝導性のセラミックス層５０”を構成しているが、負極活物質層１と直接又は間接的に電子的導通が可能なＬｉ４Ｔｉ５Ｏ１２粒子は負極電位がかかるので、電気化学的に還元されてＬｉ４＋ＸＴｉ＋４ ５−ＸＴｉ＋３ ＸＯ１２（０＜Ｘ≦３）となり、初回の充電後（図右）には、セラミックス層５１を構成する。After the first charge (right in the figure), the Li 4 Ti 5 O 12 particles that are in direct contact with the positive electrode active material layer 2 are not subjected to electrochemical reduction because of the positive electrode potential, and Li 4 Ti 5 O as it is. Although the “non-electron conductive ceramic layer 50” is configured as 12 particles, the Li 4 Ti 5 O 12 particles capable of direct or indirect electronic conduction with the negative electrode active material layer 1 have a negative electrode potential. Electrochemically reduced to Li 4 + X Ti +4 5−X Ti +3 X O 12 (0 <X ≦ 3), and the ceramic layer 51 is formed after the first charge (right side in the figure).

セラミックス層５１は結晶中の過剰のＬｉイオン（ＸＬｉ＋）により良好なイオン電導性となり、またＴｉ＋４とＴｉ＋３の自由な電子の授受に基づく良好な電子伝導性にもなる。良好なイオン電導性はセパレーター機能を高めるが、良好な電子伝導性はセパレーター機能を壊す可能性もある。しかし、負極活物質層１と正極活物質層２の電子的導通はセラミックス層５０によって完全に断たれるので、セラミックス層５１の電子電導性がセラミック層５のセパレーター機能を壊す心配はない。The ceramic layer 51 has good ionic conductivity due to excess Li ions (XLi + ) in the crystal, and also has good electron conductivity based on the exchange of free electrons of Ti +4 and Ti +3 . Good ionic conductivity enhances the separator function, but good electronic conductivity can also break the separator function. However, since the electronic conduction between the negative electrode active material layer 1 and the positive electrode active material layer 2 is completely interrupted by the ceramic layer 50, there is no concern that the electronic conductivity of the ceramic layer 51 breaks the separator function of the ceramic layer 5.

結局、本発明の一実施形態に係る蓄電装置においては、図５に示すように負極活物質層１と正極活物質層２の間に介在するセラミックス層５はその大部分がセラミックス層５１に変質してセパレーター機能、特にイオン電導性が高くなる分、蓄電装置の内部抵抗は低くなる。    After all, in the power storage device according to the embodiment of the present invention, the ceramic layer 5 interposed between the negative electrode active material layer 1 and the positive electrode active material layer 2 is mostly transformed into the ceramic layer 51 as shown in FIG. As a result, the internal resistance of the power storage device is lowered by the amount of the separator function, particularly the ion conductivity.

なお、図３に示した本発明の一実施形態に係る蓄電素子１０は、非電子伝導性のセラミックス層５を負極活物質層１の上に形成した場合について示したが、セラミックス層５を構成するセラミックス粒子が電気化学的に還元されて、イオン電導性に変わることを利用するものであり、セラミックス層５は負極活物質層１の上に形成される方が、セラミックス粒子が電気化学的な還元を受けやすいという点で有利である。    In addition, although the electrical storage element 10 which concerns on one Embodiment of this invention shown in FIG. 3 showed the case where the nonelectroconductive ceramic layer 5 was formed on the negative electrode active material layer 1, the ceramic layer 5 is comprised. The ceramic particles are electrochemically reduced to change to ionic conductivity, and the ceramic layer 5 is formed on the negative electrode active material layer 1 so that the ceramic particles are electrochemical. This is advantageous in that it is susceptible to reduction.

しかし、セラミックス層５を正極活物質層２の上に形成した場合でも、負極活物質層１と正極活物質層２が対向すれば、必然的にセラミックス層５は負極活物質層１と接触するので、負極活物質層１に接触するセラミックス粒子が電気化学的に還元される可能性はある。従って、セラミックス層５を正極活物質層２の上に形成することも否定するものではない。    However, even when the ceramic layer 5 is formed on the positive electrode active material layer 2, the ceramic layer 5 inevitably comes into contact with the negative electrode active material layer 1 if the negative electrode active material layer 1 and the positive electrode active material layer 2 face each other. Therefore, there is a possibility that the ceramic particles in contact with the negative electrode active material layer 1 are electrochemically reduced. Therefore, the formation of the ceramic layer 5 on the positive electrode active material layer 2 is not denied.

従来のシート状セパレーターは極めて多孔質な構造であるため、電解液の保持能力が高く、良好なイオン電導が確保される。一方、図３に示すように、対向する負極３２と正極３１の間にセラミックス層５を介在させる場合にも、当該セラミックス層に含有される電解液によって基本的に負極３２と正極３１のイオン電導が確保されるが、斯かるセラミックス層の空孔率は、一般的には現行のシート状セパレーターの１／２にも満たないため、セラミックス層５を相当薄くしないと蓄電装置の内部抵抗が大きくなってしまう。    Since the conventional sheet-like separator has a very porous structure, it has a high ability to hold an electrolytic solution and ensures good ion conduction. On the other hand, as shown in FIG. 3, when the ceramic layer 5 is interposed between the opposing negative electrode 32 and the positive electrode 31, the ionic conduction between the negative electrode 32 and the positive electrode 31 is basically determined by the electrolyte contained in the ceramic layer. However, since the porosity of such a ceramic layer is generally less than half that of the current sheet-like separator, the internal resistance of the power storage device is increased unless the ceramic layer 5 is made considerably thin. turn into.

つまり、従来の技術では、セラミックス層５はアルミナ（Ａｌ２Ｏ３）のような有機電解液中で電気化学的に酸化も還元もされない絶縁性のセラミックス粒子で構成されるので、充電状態に置かれてもセラミックス層５のイオン電導率が高くなるわけでもなく、シート状セパレーターと同じ厚さ（２５μｍ程度）では蓄電装置の内部抵抗が大きくなってしまう。In other words, in the conventional technique, the ceramic layer 5 is made of insulating ceramic particles that are not oxidized or reduced electrochemically in an organic electrolyte such as alumina (Al 2 O 3 ), so that it is placed in a charged state. Even if this is done, the ionic conductivity of the ceramic layer 5 does not increase, and the internal resistance of the power storage device increases at the same thickness (about 25 μm) as the sheet separator.

しかし、本発明の実施形態によれば、図４に示すように、少なくとも初回の充電を終えた後では、セラミックス層５では多くのセラミックス粒子が電気化学的に還元されてイオン伝導性となってセラミックス層５１を構成するため、負極３２と正極３１のイオン電導は、セラミックス層５（初回の充電を終えた後ではセラミックス層５１と５０である。）に含有される電解液のイオン電導性だけでなく、セラミックス層５１を構成するセラミックス粒子のイオン電導性によっても確保される。そのため、セラミックス層５は正極と負極の短絡を十分に阻止できる厚さで形成した場合でも、蓄電装置の内部抵抗は低く抑えられる。    However, according to the embodiment of the present invention, as shown in FIG. 4, at least after the first charge is completed, many ceramic particles are electrochemically reduced in the ceramic layer 5 to become ion conductive. In order to constitute the ceramic layer 51, the ionic conductivity between the negative electrode 32 and the positive electrode 31 is only the ionic conductivity of the electrolyte contained in the ceramic layer 5 (the ceramic layers 51 and 50 after the first charge is completed). It is ensured not only by the ionic conductivity of the ceramic particles constituting the ceramic layer 51. Therefore, even when the ceramic layer 5 is formed with a thickness that can sufficiently prevent a short circuit between the positive electrode and the negative electrode, the internal resistance of the power storage device can be kept low.

本発明の実施形態では、図４に示すように、初回の充電を終えた後では負極３２と正極３１の電子的短絡を阻止するのは、電子絶縁性のままのセラミックス粒子で構成されるセラミックス層５０であり、電子伝導性となっているセラミックス層５１には負極３２と正極３１の電子的短絡を阻止する能力はない。しかし、本発明の実施形態でも、やはり、最初に電極上に形成するセラミックス層５の厚さが、負極３２と正極３１の電子的短絡を阻止する能力に大きく関係してくる。    In the embodiment of the present invention, as shown in FIG. 4, after the first charge is completed, the electronic short circuit between the negative electrode 32 and the positive electrode 31 is prevented by ceramic particles composed of ceramic particles that remain electronically insulating. The ceramic layer 51, which is the layer 50 and is electronically conductive, does not have the ability to prevent an electronic short circuit between the negative electrode 32 and the positive electrode 31. However, also in the embodiment of the present invention, the thickness of the ceramic layer 5 initially formed on the electrode is greatly related to the ability to prevent the electronic short circuit between the negative electrode 32 and the positive electrode 31.

正極と負極の間に介在するセパレーター層の厚さが薄い場合には、正極と負極の間に極微小の導電性異物が挟まっても、蓄電装置が内部ショートに至る可能性は高くなる。もし、セパレーター層の厚さを５〜１０μｍ程度とした場合には、通常、活物質層に伝導助剤として混ぜられるグラファイト等（平均粒径でも５〜１０μｍ程度）が導電性異物として電極間に挟まって、蓄電装置が内部ショートに至ることも十分に考えられる。    In the case where the thickness of the separator layer interposed between the positive electrode and the negative electrode is small, the possibility that the power storage device will be short-circuited increases even if a very small amount of conductive foreign matter is sandwiched between the positive electrode and the negative electrode. If the thickness of the separator layer is about 5 to 10 μm, usually graphite or the like (average particle size of about 5 to 10 μm) mixed in the active material layer as a conduction aid is used as a conductive foreign substance between the electrodes. It is fully conceivable that the power storage device may be short-circuited due to being caught.

本発明の実施形態においても、セラミックス層５の厚さが薄い場合（５〜１０μｍ程度）では、蓄電装置が内部ショートに至る危険性は当然高い。    Also in the embodiment of the present invention, when the ceramic layer 5 is thin (about 5 to 10 μm), the risk of the power storage device reaching an internal short is naturally high.

図６には本発明の実施形態における、セラミック層５の厚さの違いによる内部短絡の発生の違いを電極の模式図で示した。図６Ａはセラミックス層５の厚さ（ｔ１）が薄い場合（５〜１０μｍ程度以下）である。図６ＢおよびＣはセラミックス層５の厚さ（ｔ２）が厚い場合（１５μｍ以上）であり、図６Ｂは初回の充電前であり、図６Ｃは初回の充電後である。FIG. 6 is a schematic diagram of electrodes showing the difference in occurrence of internal short circuit due to the difference in thickness of the ceramic layer 5 in the embodiment of the present invention. FIG. 6A shows the case where the thickness (t 1 ) of the ceramic layer 5 is thin (about 5 to 10 μm or less). 6B and C show the case where the thickness (t 2 ) of the ceramic layer 5 is thick (15 μm or more), FIG. 6B is before the first charge, and FIG. 6C is after the first charge.

図６Ａに示すように、負極活物質層１と正極活物質層２の間に介在するセラミックス層５の厚さが薄い（ｔ１）場合には、蓄電装置の内部抵抗は低くなるが、導電性異物６０が挟まって負極活物質層１と正極活物質層２が短絡されて、蓄電装置は内部ショートに至る危険性は高くなる。As shown in FIG. 6A, when the thickness of the ceramic layer 5 interposed between the negative electrode active material layer 1 and the positive electrode active material layer 2 is thin (t 1 ), the internal resistance of the power storage device is reduced, but the conductive There is a high risk that the negative electrode active material layer 1 and the positive electrode active material layer 2 are short-circuited with the conductive foreign matter 60 interposed therebetween, and the power storage device is short-circuited.

一方、図６Ｂに示すように、セラミックス層５の厚さが厚い（ｔ２）場合には、同じ大きさの導電性異物６０が挟まっても、負極活物質層１と正極活物質層２は導電性異物６０によって短絡されることはないので、蓄電装置は内部ショートには至らない。当然、この状態（初回の充電前）ではセラミックス層５の厚さに比例して蓄電装置の内部抵抗は大きくなってしまう。On the other hand, as shown in FIG. 6B, when the ceramic layer 5 is thick (t 2 ), the negative electrode active material layer 1 and the positive electrode active material layer 2 are Since the conductive foreign object 60 does not cause a short circuit, the power storage device does not cause an internal short circuit. Naturally, in this state (before the first charge), the internal resistance of the power storage device increases in proportion to the thickness of the ceramic layer 5.

しかし、初回の充電後では、図６Ｃに示すように、セラミックス層５を構成するセラミックス粒子のうち、正極活物質層２と導電性異物６０に直接接触するセラミックス粒子は正極電位がかかるために電気化学的に還元されることがなく電子絶縁性のままであり、当該電子絶縁性のままのセラミックス粒子は電子絶縁性のセラミックス層５０を構成する。    However, after the first charge, as shown in FIG. 6C, among the ceramic particles constituting the ceramic layer 5, the ceramic particles that are in direct contact with the positive electrode active material layer 2 and the conductive foreign material 60 are charged with the positive electrode potential. The ceramic particles that remain electronically insulating without being chemically reduced constitute the electronic insulating ceramic layer 50.

一方、正極活物質層２と導電性異物６０に直接接触しないセラミックス粒子は電気化学的に還元されてイオン伝導性のセラミックス層５１を構成するため、負極活物質層１と正極活物質層２の間のイオン電導は、セラミックス層５（初回の充電後以降ではセラミックス層５１と５０である。）に含有される電解液のイオン電導性だけでなく、セラミックス層５１を構成するセラミックス粒子のイオン電導性によっても確保される。そのため、セラミックス層５が正極と負極の短絡を十分に阻止できる厚さで形成される場合（図６Ｂ、Ｃ）でも、蓄電装置の内部抵抗は低く抑えられる。    On the other hand, since the ceramic particles that are not in direct contact with the positive electrode active material layer 2 and the conductive foreign material 60 are electrochemically reduced to form the ion conductive ceramic layer 51, the negative electrode active material layer 1 and the positive electrode active material layer 2 The ionic conduction between them is not only the ionic conductivity of the electrolyte contained in the ceramic layer 5 (after the first charge, the ceramic layers 51 and 50), but also the ionic conduction of the ceramic particles constituting the ceramic layer 51. Also secured by gender. Therefore, even when the ceramic layer 5 is formed with a thickness that can sufficiently prevent a short circuit between the positive electrode and the negative electrode (FIGS. 6B and 6C), the internal resistance of the power storage device can be kept low.

本発明の一実施形態に係る蓄電装置としては、Ｌｉ４Ｔｉ５Ｏ１２やＴｉＯ２等の、有機電解液中で電気化学的に還元可能な電子絶縁性のセラミックス粒子で、リチウムイオン電池の負極表面にセラミックス層を形成して、これに直接正極を重ねて積層することで、内部抵抗の十分に低い、安全性の高いリチウムイオン電池が実現できる。特にハイブリッド自動車や電気自動車や電力貯蔵用等の大型蓄電装置に内部抵抗の十分に低い、安全性の高い、安価なリチウムイオン電池が提供できるので、本実施形態に係る電極構造の工業的価値は大である。As a power storage device according to an embodiment of the present invention, there are electronic insulating ceramic particles such as Li 4 Ti 5 O 12 and TiO 2 that can be electrochemically reduced in an organic electrolyte, and a negative electrode of a lithium ion battery. By forming a ceramic layer on the surface and directly stacking a positive electrode on this, a lithium ion battery with sufficiently low internal resistance and high safety can be realized. The industrial value of the electrode structure according to the present embodiment is particularly high because a lithium ion battery with sufficiently low internal resistance, high safety, and low price can be provided for a large-scale power storage device such as a hybrid vehicle, an electric vehicle, or a power storage device. It ’s big.

以下実施例により本発明をさらに詳しく説明する。    Hereinafter, the present invention will be described in more detail with reference to examples.

本実施例では正極活物質としてスピネル系リチウムマンガン酸化物（ＬｉＭｎ２Ｏ４）を使用し、負極活物質としてはスピネル系リチウムチタン酸化物（Ｌｉ４Ｔｉ５Ｏ１２）を使用するロッキングチェアー電池（一般にはリチウムイオン電池と呼ばれている。）において、図３に示す電極構造を適用して実施する。In this example, a rocking chair battery using spinel lithium manganese oxide (LiMn 2 O 4 ) as a positive electrode active material and spinel lithium titanium oxide (Li 4 Ti 5 O 12 ) as a negative electrode active material ( In general, the electrode structure shown in FIG. 3 is applied.

本実施例では、図３に示すように正極３１と負極３２を交互に、シート状のセパレーターは介在させずに積層して電極積層体（蓄電素子）１０を構成する。正極３１は活物質と伝導助剤で構成される電子伝導性の活物質層２が正極集電体４に密着して形成された電極であり、負極３２も活物質と伝導助剤で構成される電子伝導性の活物質層１が負極集電体３に密着して形成された電極とする。負極３２は電子伝導性の負極活物質層１の表面に電子絶縁性のセラミックス層５を形成しておくので、電極積層体１０において対向する正極３１と負極３２が電子的に導通することはない。    In this embodiment, as shown in FIG. 3, the positive electrode 31 and the negative electrode 32 are alternately laminated without interposing a sheet-like separator to constitute the electrode laminate (electric storage element) 10. The positive electrode 31 is an electrode in which an electron conductive active material layer 2 composed of an active material and a conduction aid is formed in close contact with the positive electrode current collector 4, and the negative electrode 32 is also composed of an active material and a conduction aid. An electrode having an electron conductive active material layer 1 in close contact with the negative electrode current collector 3. In the negative electrode 32, the electronic insulating ceramic layer 5 is formed on the surface of the electron conductive negative electrode active material layer 1, so that the positive electrode 31 and the negative electrode 32 facing each other in the electrode stack 10 are not electrically connected. .

本実施例では、負極３２の電極表面に形成する電子絶縁性のセラミックス層５は前記負極活物質と同じＬｉ４Ｔｉ５Ｏ１２をその構成材料とする。Ｌｉ４Ｔｉ５Ｏ１２は電子伝導率（１０−１３Ｓ／ｃｍ程度）の小さい完全な電子絶縁性であり、且つ有機電解液中では還元されて良好な電子伝導性とイオン伝導性を併せ持つＬｉ７Ｔｉ５Ｏ１２へと変化するので、特に本発明の一実施形態には極めてよく適合するセラミックス材料である。In this embodiment, the electronic insulating ceramic layer 5 formed on the electrode surface of the negative electrode 32 is composed of Li 4 Ti 5 O 12 which is the same as the negative electrode active material. Li 4 Ti 5 O 12 is a completely electronic insulating material having a small electronic conductivity (about 10 −13 S / cm), and is reduced in an organic electrolytic solution to have both good electronic conductivity and ionic conductivity. Since it changes to 7 Ti 5 O 12 , it is a ceramic material that is particularly well suited to one embodiment of the present invention.

先ず、Ｌｉ４Ｔｉ５Ｏ１２は水酸化リチウム（ＬｉＯＨ）と二酸化チタン（ＴｉＯ２）を４：５のモル比でよく混合し、ペレット状に加圧成形し、ニッケルフォイルを敷き詰めたアルミナの容器に入れ、ヘリウム雰囲気中８００℃で焼成して合成した。合成物のＸＲＤパターンには未反応のＴｉＯ２はなく、Ｌｉ４Ｔｉ５Ｏ１２単層であり、合成物のＳＥＭ写真（倍率６６００）では０．２〜１ミクロン程度の１次粒子が集まって１〜１５ミクロン程度の２次粒子を形成していることが確認できた。なおＬｉ４Ｔｉ５Ｏ１２の粒径は９０％が６．７８μｍ以下で、１．１４μｍ以下が１０％に粒度調整した。First, Li 4 Ti 5 O 12 is a container of alumina in which lithium hydroxide (LiOH) and titanium dioxide (TiO 2 ) are mixed well in a molar ratio of 4: 5, pressed into a pellet, and nickel foil is spread. And synthesized by firing at 800 ° C. in a helium atmosphere. There is no unreacted TiO 2 in the XRD pattern of the composite, and it is a Li 4 Ti 5 O 12 monolayer. In the SEM photograph (magnification 6600) of the composite, primary particles of about 0.2 to 1 micron are gathered. It was confirmed that secondary particles of about 1 to 15 microns were formed. The particle size of Li 4 Ti 5 O 12 was adjusted such that 90% was 6.78 μm or less and 1.14 μm or less was 10%.

調整したＬｉ４Ｔｉ５Ｏ１２の８９重量部に、電導助材として２重量部のアセチレンブラックと３重量部のグラファイトを混ぜ、結着材とするＰＶＤＦ（ポリフッ化ビニリデン）６重量部を溶かした溶剤と湿式混合してスラリーを用意する。このスラリーを幅２００ｍｍ、厚さ０．０２ｍｍのアルミニウム箔の片面に、両端に１５ｍｍの未塗布部を残して、塗布幅１７０ｍｍで均一に塗布して乾燥し、その後、もう一方の面にも同じ塗布幅で塗布して乾燥した後、ローラープレス機で厚さを０．１５〜０．１６ｍｍになるように加圧して、負極活物質層１が集電体３に密着してなる帯状の負極を作製する。89 parts by weight of the adjusted Li 4 Ti 5 O 12 was mixed with 2 parts by weight of acetylene black and 3 parts by weight of graphite as a conductive aid, and 6 parts by weight of PVDF (polyvinylidene fluoride) as a binder was dissolved. A slurry is prepared by wet mixing with a solvent. This slurry was uniformly applied with a coating width of 170 mm and dried on one side of an aluminum foil having a width of 200 mm and a thickness of 0.02 mm, leaving uncoated portions of 15 mm on both ends, and then the same on the other side. After coating with a coating width and drying, a belt-shaped negative electrode in which the negative electrode active material layer 1 is in close contact with the current collector 3 by pressing with a roller press so that the thickness is 0.15 to 0.16 mm. Is made.

斯かる帯状の負極には更に電極表面に電子絶縁性のセラミックス層５を形成するが、絶縁性セラミックス層５を構成するセラミックス粒子にも上記調整のＬｉ４Ｔｉ５Ｏ１２を使用した。上記調整のＬｉ４Ｔｉ５Ｏ１２をＣＭＣ系の水系バインダーを用いて水系のスラリーとし、このスラリーを前記帯状負極の両面に、片面のセラミックス層の厚さが２５μｍ程度となるように、また負極活物質層１を完全に覆うように塗布して乾燥し、帯状負極の電極表面上に電子絶縁性のセラミックス層５を形成した。In such a strip-shaped negative electrode, an electronic insulating ceramic layer 5 is further formed on the electrode surface. Li 4 Ti 5 O 12 prepared as described above was also used for the ceramic particles constituting the insulating ceramic layer 5. The adjusted Li 4 Ti 5 O 12 is made into an aqueous slurry using a CMC aqueous binder, and this slurry is formed on both sides of the belt-like negative electrode so that the thickness of the ceramic layer on one side is about 25 μm. The active material layer 1 was applied so as to completely cover and dried to form an electronic insulating ceramic layer 5 on the electrode surface of the strip-shaped negative electrode.

次に、絶縁性セラミックス層５を形成した帯状負極は集電体の未塗布部を１０×２０ｍｍで電極タブの取り付け部３３として残し、セラミックス層の塗布面積で１７０×１１０ｍｍのサイズにカットして最終的な負極３２ａを用意した。    Next, the strip-shaped negative electrode on which the insulating ceramic layer 5 is formed leaves the uncoated portion of the current collector as 10 × 20 mm as the electrode tab mounting portion 33, and is cut into a size of 170 × 110 mm in the ceramic layer coating area. A final negative electrode 32a was prepared.

正極活物質とするＬｉＭｎ２Ｏ４は二酸化マンガンと炭酸リチウムの混合物を空気中８５０℃で焼成して、従来の合成法で調整した。ただしここで合成したＬｉＭｎ２Ｏ４はＸ線回折ではスピネル型ＬｉＭｎ２Ｏ４の回折パターンとよく一致するものであるが、マンガンの価数分析から判断して、正確にはマンガンの一部がリチウムで置換されたＬｉ１．０５Ｍｎ１．９５Ｏ４と考えられる。ＬｉＭｎ２Ｏ４の粒径は９０％が１２．９４μｍ以下で、３．５２μｍ以下が１０％に粒度調整した。LiMn 2 O 4 used as the positive electrode active material was prepared by firing a mixture of manganese dioxide and lithium carbonate in air at 850 ° C. and then using a conventional synthesis method. However, the LiMn 2 O 4 synthesized here agrees well with the diffraction pattern of spinel type LiMn 2 O 4 in X-ray diffraction. It is thought that Li 1.05 Mn 1.95 O 4 substituted with lithium. The particle size of LiMn 2 O 4 was adjusted so that 90% was 12.94 μm or less and 3.52 μm or less was 10%.

調整したＬｉＭｎ２Ｏ４の９０重量部に、電導助材としてアセチレンブラック３重量部とグラファイト４重量部および結着材としてＰＶＤＦ３重量部とともに溶剤であるＮ−メチルー２−ピロリドンと湿式混合してスラリーとする。このスラリーを集電体とする厚さ０．０２０ｍｍ、幅２００ｍｍのアルミニウム箔の片面に、両端に２０ｍｍのアルミニウム箔の未塗布部を残して塗布幅１６０ｍｍで均一に塗布して乾燥し、その後、もう一方の面にも同じ塗布幅で塗布して乾燥する。その後、ローラープレス機で、厚さ０．１９０〜０．２１０ｍｍに加圧して、正極活物質層２が集電体４に密着してなる帯状の正極を作製する。90 parts by weight of the prepared LiMn 2 O 4 was wet-mixed with N-methyl-2-pyrrolidone as a solvent together with 3 parts by weight of acetylene black and 4 parts by weight of graphite as a conductive aid and 3 parts by weight of PVDF as a binder. And Applying and drying uniformly with a coating width of 160 mm, leaving an uncoated portion of the aluminum foil of 20 mm on both ends on one side of an aluminum foil having a thickness of 0.020 mm and a width of 200 mm using the slurry as a current collector, Apply to the other side with the same coating width and dry. Then, it pressurizes to thickness 0.190-0.210mm with a roller press machine, and produces the strip | belt-shaped positive electrode by which the positive electrode active material layer 2 closely_contact | adheres to the electrical power collector 4.

斯かる帯状の正極は集電体の未塗布部を１５×２０ｍｍで電極タブの取り付け部３４として残し、正極活物質層２の塗布面積で１６０×１００ｍｍのサイズにカットして最終的な正極３１ａを用意した。    In such a strip-like positive electrode, the uncoated portion of the current collector is left as an electrode tab attachment portion 15 × 20 mm, and is cut into a size of 160 × 100 mm in the coated area of the positive electrode active material layer 2 to obtain a final positive electrode 31a. Prepared.

以上のように用意した正極３１ａと負極３２ａは、図３に示すように、負極３２の３枚と正極３１の２枚とを負極３２ａの電極端が寸法Ａ（ここでは５ｍｍ）だけ正極３１ａの電極端より外側に位置するように積層し、図１に示すように、正極３１に設けた正極集電体の露出部３４と、負極３２に設けた負極集電体の露出部３３をそれぞれ正極タブ７と負極タブ６にまとめて溶接すれば、図１に示した蓄電素子１０となる。    As shown in FIG. 3, the positive electrode 31 a and the negative electrode 32 a prepared as described above are composed of three negative electrodes 32 and two positive electrodes 31 with the electrode end of the negative electrode 32 a having a dimension A (here, 5 mm). As shown in FIG. 1, the exposed portion 34 of the positive electrode current collector provided on the positive electrode 31 and the exposed portion 33 of the negative electrode current collector provided on the negative electrode 32 are respectively connected to the positive electrode 31 as shown in FIG. When the tab 7 and the negative electrode tab 6 are welded together, the power storage element 10 shown in FIG. 1 is obtained.

蓄電素子１０は、図２に示すように、ラミネートシート１１と１２に挟んでラミネートシートの周囲１１２ａを熱融着する。この時にはラミネートシートの周囲の一部１１２ｂは熱融着しないので、蓄電素子１０はラミネートシート１１と１２の袋の中に納まった状態となる。当該袋の中には、当該袋の未封じ部分１１２ｂを上にして１モル／ＬのＬｉＰＦ６を溶解したエチレンカーボネイト（ＥＣ）とジエチルカーボネイト（ＤＥＣ）の混合溶液を電解液として注入し、真空含浸法にて袋の中の蓄電素子１０に電解液を含浸させる。その後、ラミネートシートの未封じ部分１１２ｂを真空下で封じて、図２に示す構造のリチウムイオン電池Ａを外形寸法２１０ｍｍ×１４０ｍｍ×１．４ｍｍで作製した。As shown in FIG. 2, the power storage element 10 is heat-sealed around the laminate sheet 112 a while being sandwiched between the laminate sheets 11 and 12. At this time, since the portion 112b around the laminate sheet is not heat-sealed, the power storage element 10 is in a state of being placed in the bag of the laminate sheets 11 and 12. Into the bag, a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) in which 1 mol / L LiPF 6 is dissolved is injected as an electrolyte with the unsealed portion 112b of the bag facing up, The storage element 10 in the bag is impregnated with the electrolytic solution by an impregnation method. Thereafter, the unsealed portion 112b of the laminate sheet was sealed under vacuum, and a lithium ion battery A having a structure shown in FIG. 2 was produced with an outer dimension of 210 mm × 140 mm × 1.4 mm.

蓄電素子１０は図１に示すように、電極タブ６と７には予めプラスチックテープ９を熱圧着して貼り付けているので、当該プラスチックテープ９がラミネートシート１１、１２と一体化して熱融着するので、電極タブ６、７が蓄電素子１０の密封に妨げになることはなく、負極タブ６と正極タブ７は外部に取り出されてそれぞれ負極外部端子１３および正極外部端子１４となる。    As shown in FIG. 1, the power storage element 10 is preliminarily bonded with the plastic tape 9 on the electrode tabs 6 and 7 so that the plastic tape 9 is integrated with the laminate sheets 11 and 12 and heat-sealed. Therefore, the electrode tabs 6 and 7 do not hinder the sealing of the electric storage element 10, and the negative electrode tab 6 and the positive electrode tab 7 are taken out to be the negative electrode external terminal 13 and the positive electrode external terminal 14, respectively.

完成したリチウムイオン電池Ａは２４時間のエイジングの後、最初の充電では０．１Ａの電流で、充電電圧の上限を３．０Ｖに設定して２０時間かけて充電を行い、０．２Ａの定電流で放電を行った結果、約１．５Ａｈの放電容量が得られた。    The completed lithium ion battery A was aged for 24 hours, then charged at 0.1 A for the first charge, set the upper limit of the charge voltage to 3.0 V, and charged for 20 hours. As a result of discharging with current, a discharge capacity of about 1.5 Ah was obtained.

一方、完成したリチウムイオン電池Ａの内部抵抗は、最初の充電を行う前では周波数１ｋＨｚで測定した交流インピーダンスでは約１８０ｍΩであったが、最初の充電を行った後では周波数１ｋＨｚで測定した交流インピーダンスは約３６ｍΩにまで減少し、その後の充放電においても、充放電状態（ＳＯＣ：Ｓｔａｔｅ ｏｆ Ｃｈａｒｇｅ）の如何に関わらず、３６ｍΩ程度の内部抵抗が維持された。    On the other hand, the internal resistance of the completed lithium ion battery A was about 180 mΩ at the AC impedance measured at a frequency of 1 kHz before the first charge, but the AC impedance measured at a frequency of 1 kHz after the first charge. Decreased to about 36 mΩ, and the internal resistance of about 36 mΩ was maintained during the subsequent charge / discharge regardless of the state of charge (SOC).

因みに従来の樹脂性セパレーター（厚さ２５μｍ程度）を使用する場合では、その内部抵抗は７０ｍΩ程度であり、実施例１における電池の優位性が分かった。    Incidentally, when a conventional resin separator (thickness of about 25 μm) was used, the internal resistance was about 70 mΩ, and the superiority of the battery in Example 1 was found.

本実施例で作製したリチウムイオン電池Ａでは、図４に示すように、負極３２の電極表面に形成されたセラミックス層５は、最初の充電が終了した時点で絶縁性セラミックス層５０と電導性セラミックス層５１に分離し、絶縁性セラミックス層５０が実質的なセパレーターとして機能する。    In the lithium ion battery A produced in the present example, as shown in FIG. 4, the ceramic layer 5 formed on the electrode surface of the negative electrode 32 is composed of the insulating ceramic layer 50 and the conductive ceramic when the first charging is completed. The insulating ceramic layer 50 is separated into the layer 51 and functions as a substantial separator.

一方、負極活物質層１中の負極活物質であるＬｉ４Ｔｉ５Ｏ１２は充電終了時点では電気化学的に還元（充電）されてＬｉ７Ｔｉ５Ｏ１２となっているが、電導性セラミックス層５１においてもＬｉ４Ｔｉ５Ｏ１２が電気化学的に還元されて電導性（電子伝導性であり、イオン電導性でもある。）のＬｉ７Ｔｉ５Ｏ１２となっており、セラミックス層５１は実質的には負極活物質層として機能することができる。On the other hand, Li 4 Ti 5 O 12 which is the negative electrode active material in the negative electrode active material layer 1 is electrochemically reduced (charged) to Li 7 Ti 5 O 12 at the end of charging, but the conductive ceramics. Also in the layer 51, Li 4 Ti 5 O 12 is electrochemically reduced to become conductive (electron conductive and ion conductive) Li 7 Ti 5 O 12 , and the ceramic layer 51 It can function substantially as a negative electrode active material layer.

従って、負極活物質層１を構成する活物質が、本実施例のようにセラミックス層５を構成するセラミックス粒子と同じ物質である場合やセラミックス層５を構成するセラミックス粒子と同じ程度の酸化還元電位（充放電電位）を有する物質である場合には、電導性セラミックス層５１の充放電容量が負極活物質層１の充放電容量に加算されることによって蓄電装置の充放電容量が大きくなる利点もある。    Therefore, when the active material constituting the negative electrode active material layer 1 is the same material as the ceramic particles constituting the ceramic layer 5 as in this embodiment, or the redox potential of the same level as the ceramic particles constituting the ceramic layer 5. In the case of a substance having (charge / discharge potential), the charge / discharge capacity of the power storage device is increased by adding the charge / discharge capacity of the conductive ceramic layer 51 to the charge / discharge capacity of the negative electrode active material layer 1. is there.

比較例１Comparative Example 1

本比較例では負極の電極表面に形成するセラミックス層を一般的なセラミックスであるアルミナ（Ａｌ２Ｏ３）粒子で構成してリチウムイオン電池Ｂを作製し、実施例１の電池と比較する。In this comparative example, a ceramic layer formed on the electrode surface of the negative electrode is composed of alumina (Al 2 O 3 ) particles, which are general ceramics, to produce a lithium ion battery B, which is compared with the battery of Example 1.

本比較例では、正極は実施例１で用意した正極３１ａをそのまま使用するが、負極は、実施例１で作成した帯状の負極を使用して、これにアルミナ（Ａｌ２Ｏ３）粒子をＣＭＣ系の水系バインダーを用いて水系のスラリーとし、このスラリーを用いて絶縁性のセラミックス層５ｂを実施例１と同じように、同じ厚さ（２５μｍ程度）で形成し、実施例１と同じ寸法にカットして負極３２ｂとした。In this comparative example, the positive electrode 31a prepared in Example 1 is used as it is as the positive electrode. However, the negative electrode uses the strip-shaped negative electrode prepared in Example 1, and alumina (Al 2 O 3 ) particles are used as CMC. An aqueous ceramic binder is used to form an aqueous slurry, and using this slurry, the insulating ceramic layer 5b is formed with the same thickness (about 25 μm) as in Example 1 and has the same dimensions as in Example 1. The negative electrode 32b was cut.

用意した負極３２ｂの３枚と実施例１で用意した正極３１ａの２枚とを積層し、実施例１と同じようにして蓄電素子１０を組み立て、そのほか全て実施例１と同じにして、図２に示す構造のリチウムイオン電池Ｂを外形寸法２１０ｍｍ×１４０ｍｍ×１．４ｍｍで作製した。    Two of the prepared negative electrodes 32b and two of the positive electrodes 31a prepared in Example 1 are stacked, and the electricity storage device 10 is assembled in the same manner as in Example 1, and all the others are the same as in Example 1, and FIG. A lithium ion battery B having the structure shown in FIG. 2 was produced with an outer dimension of 210 mm × 140 mm × 1.4 mm.

完成したリチウムイオン電池Ｂも２４時間のエイジングの後、０．１Ａの電流で、充電電圧の上限を３．０Ｖに設定して２０時間の充電を行い、０．２Ａの定電流で放電を行った結果、約１．３Ａｈの放電容量が得られたが、この電池の内部抵抗は、最初の充電を行った後でも周波数１ｋＨｚで測定した交流インピーダンスでは１８０ｍΩ程度であり、その後の充放電においても、充放電状態（ＳＯＣ：Ｓｔａｔｅ ｏｆ Ｃｈａｒｇｅ）の如何に関わらず、内部抵抗が１８０ｍΩ以下となることはなかった。    The completed lithium-ion battery B is also subjected to aging for 24 hours, charging with 0.1 A current, charging voltage at the upper limit of 3.0 V, charging for 20 hours, and discharging with constant current of 0.2 A. As a result, a discharge capacity of about 1.3 Ah was obtained, but the internal resistance of this battery was about 180 mΩ in AC impedance measured at a frequency of 1 kHz even after the first charge, and in the subsequent charge / discharge Regardless of the charge / discharge state (SOC: State of Charge), the internal resistance did not become 180 mΩ or less.

負極の電極表面にアルミナ粒子で絶縁性のセラミックス層を形成する場合では、実施例１に比べて内部抵抗は５倍であり、従来の樹脂製のセパレーターを使用する電池と比べても、内部抵抗の値は２．５倍となる。    In the case where an insulating ceramic layer is formed of alumina particles on the electrode surface of the negative electrode, the internal resistance is 5 times that of Example 1, and the internal resistance is higher than that of a battery using a conventional resin separator. The value of is 2.5 times.

本実施例では正極活物質としてスピネル系リチウムマンガン酸化物を使用し、負極活物質としてはカーボンを使用するリチウムイオン電池において、図３に示す電極構造を適用して実施する。本実施例においても、負極３２の電極表面に形成する絶縁性のセラミックス層５は実施例１と同じくＬｉ４Ｔｉ５Ｏ１２をその構成セラミックス粒子とした。In this embodiment, spinel lithium manganese oxide is used as the positive electrode active material and carbon is used as the negative electrode active material, and the electrode structure shown in FIG. 3 is applied. Also in the present example, the insulating ceramic layer 5 formed on the electrode surface of the negative electrode 32 is composed of Li 4 Ti 5 O 12 as its constituent ceramic particles as in Example 1.

先ず、負極活物質として２８００℃で熱処理を施したメソカーボンマイクロビーズ（ｄ００２＝３．３６Å）の８８重量部に２重量部のアセチレンブラックを混ぜ、結着材とするＰＶＤＦ（ポリフッ化ビニリデン）１０重量部を溶かした溶剤と湿式混合してスラリーを用意する。このスラリーを幅２００ｍｍ、厚さ０．０１ｍｍの銅箔の片面に、両端に１５ｍｍの未塗布部を残して塗布幅１７０ｍｍで均一に塗布して乾燥し、その後、もう一方の面にも同じ塗布幅で塗布して乾燥した後、厚さ０．１３〜０．１５ｍｍにローラープレス機で加圧して帯状のカーボン負極を作製した。    First, PVDF (polyvinylidene fluoride) 10 used as a binder by mixing 2 parts by weight of acetylene black with 88 parts by weight of mesocarbon microbeads (d002 = 3.36 mm) heat-treated at 2800 ° C. as a negative electrode active material. A slurry is prepared by wet mixing with a solvent in which parts by weight are dissolved. Apply this slurry uniformly on one side of a 200 mm wide and 0.01 mm thick copper foil with a coating width of 170 mm, leaving 15 mm uncoated parts at both ends, and then apply the same to the other side. After coating with a width and drying, a belt-like carbon negative electrode was produced by pressing with a roller press to a thickness of 0.13 to 0.15 mm.

帯状のカーボン負極表面への絶縁性のセラミックス層の形成は、実施例１と同じくＬｉ４Ｔｉ５Ｏ１２の水系バインダーを用いたスラリーを使用する。このスラリーを帯状のカーボン負極の両面に、片面のセラミックス層の厚さが２５μｍ程度となるように、またカーボン塗布層を完全に覆うように塗布して乾燥し、帯状カーボン負極の表面上に絶縁性のセラミックス層５を形成した。The formation of the insulating ceramic layer on the surface of the belt-like carbon negative electrode uses a slurry using a Li 4 Ti 5 O 12 aqueous binder as in Example 1. This slurry is applied to both sides of the band-shaped carbon negative electrode so that the thickness of the ceramic layer on one side is about 25 μm and the carbon coating layer is completely covered and dried, and is insulated on the surface of the band-shaped carbon negative electrode The characteristic ceramic layer 5 was formed.

電極表面に絶縁性セラミックス層５を形成した帯状カーボン負極は実施例１と同じように、集電体の未塗布部を電極タブ取り付け部３３として残し、セラミックス層の面積で１７０×１１０ｍｍのサイズにカットして負極３２ｃを用意した。    In the same manner as in Example 1, the strip-shaped carbon negative electrode having the insulating ceramic layer 5 formed on the electrode surface leaves the uncoated portion of the current collector as the electrode tab mounting portion 33, and the size of the ceramic layer is 170 × 110 mm. The negative electrode 32c was prepared by cutting.

用意した負極３２ｃと実施例１で作成した正極３１ａは実施例１と同じ要領で図２に示す電池構造でリチウムイオン電池Ｃを外形寸法２１０ｍｍ×１４０ｍｍ×１．４ｍｍで作製した。    The prepared negative electrode 32c and the positive electrode 31a prepared in Example 1 were manufactured in the same manner as in Example 1, with the battery structure shown in FIG. 2 having a lithium ion battery C with outer dimensions of 210 mm × 140 mm × 1.4 mm.

完成したリチウムイオン電池Ｃの内部抵抗も、最初の充電を行う前では周波数１ｋＨｚで測定した交流インピーダンスでは１８０ｍΩ程度であった。最初の充電では０．１Ａの電流で、充電電圧の上限を４．２Ｖに設定して２０時間かけて充電を行い、０．２Ａの定電流で放電を行った結果、約１．５Ａｈの放電容量が得られた。最初の充電を行った後では周波数１ｋＨｚで測定した交流インピーダンスでは約３６ｍΩに減少し、その後の充放電においても、充放電状態（ＳＯＣ：Ｓｔａｔｅ ｏｆ Ｃｈａｒｇｅ）には殆ど関係なく、３６ｍΩ程度の内部抵抗が維持され、やはり、従来のリチウムイオン電池の内部抵抗の半分程度である。    The internal resistance of the completed lithium ion battery C was about 180 mΩ in AC impedance measured at a frequency of 1 kHz before the first charge. The initial charge is 0.1A, and the upper limit of the charge voltage is set to 4.2V. The battery is charged for 20 hours and discharged at a constant current of 0.2A. Capacity was obtained. After the first charge, the AC impedance measured at a frequency of 1 kHz decreases to about 36 mΩ, and even in subsequent charge / discharge, the internal resistance is about 36 mΩ regardless of the state of charge (SOC). Is still about half of the internal resistance of a conventional lithium ion battery.

一般にリチウムイオン電池に使用される樹脂製のセパレーターは耐熱性に乏しく、電池の安全性を低下させている要因である。また価格も高いために、電池の材料費を大きく引き上げている。本発明の一実施形態よれば、斯かる樹脂製のセパレーターは不要であり、良好なセパレーター機能を有する耐熱性の高いセラミック層が電極表面に安価に形成可能なので、安価で安全性の高いリチウムイオン電池を提供できる。    In general, a resin separator used in a lithium ion battery is poor in heat resistance, and is a factor that decreases the safety of the battery. In addition, due to the high price, the material cost of the battery is greatly increased. According to an embodiment of the present invention, such a resin separator is unnecessary, and a highly heat-resistant ceramic layer having a good separator function can be formed on the electrode surface at low cost. Battery can be provided.

以上、実施例１および２では、正極活物質としてＬｉＭｎ２Ｏ４を使用し、負極活物質にはＬｉ４Ｔｉ５Ｏ１２およびカーボンをそれぞれ使用したリチウムイオン電池について、その一実施形態を示したが、正極活物質や負極活物質はこれに限定されるものではないし、上記実施形態は本発明の適用例の一つを示したものであり、本発明の技術的範囲を上記実施形態の具体的構成に限定する趣旨ではない。本発明の要旨を逸脱しない範囲において種々変更可能である。As described above, in Examples 1 and 2, one embodiment of the lithium ion battery using LiMn 2 O 4 as the positive electrode active material and using Li 4 Ti 5 O 12 and carbon as the negative electrode active material is shown. However, the positive electrode active material and the negative electrode active material are not limited thereto, and the above embodiment shows one example of application of the present invention, and the technical scope of the present invention is specific to the above embodiment. It is not intended to be limited to a specific configuration. Various modifications can be made without departing from the scope of the present invention.

１ 負極活物質層
２ 正極活物質層
３ 負極集電体
４ 正極集電体
５ セラミックス層
６ 負極タブ
７ 正極タブ
８ 絶縁部材
９ プラスチックテープ
１０ 蓄電素子
１１、１２ ラミネートシート
１３ 負極外部端子
１４ 正極外部端子
３１ 正極
３２ 負極
５０ 非電子伝導性のセラミックス層
５１ 電導性のセラミックス層
６０ 導電性異物DESCRIPTION OF SYMBOLS 1 Negative electrode active material layer 2 Positive electrode active material layer 3 Negative electrode current collector 4 Positive electrode current collector 5 Ceramic layer 6 Negative electrode tab 7 Positive electrode tab 8 Insulating member 9 Plastic tape 10 Power storage element 11, 12 Laminate sheet 13 Negative electrode external terminal 14 Positive electrode outside Terminal 31 Positive electrode 32 Negative electrode 50 Non-electron conductive ceramic layer 51 Conductive ceramic layer 60 Conductive foreign matter

Claims (4)

正極と負極が対向してなる蓄電装置において、前記正極と前記負極は何れも集電体に電子伝導性の活物質層が形成された電極であって、対向する正極と負極の内部短絡は対向する正極と負極の活物質層間に介在する電子絶縁性のセラミックス層によって阻止されており、当該セラミックス層を構成するセラミックス粒子は電気化学的な還元反応で化学変化しうる電子絶縁性のセラミックスから選択されることを特徴とする蓄電装置。    In a power storage device in which a positive electrode and a negative electrode are opposed to each other, the positive electrode and the negative electrode are both electrodes in which an electron conductive active material layer is formed on a current collector, and an internal short circuit between the opposed positive electrode and the negative electrode is opposed. The ceramic particles are blocked by an electronic insulating ceramic layer interposed between the positive and negative active material layers, and the ceramic particles constituting the ceramic layer are selected from electronic insulating ceramics that can be chemically changed by an electrochemical reduction reaction. A power storage device. 前記セラミックス層が負極の電極表面に形成されていることを特徴とする請求項１記載の蓄電装置。    The power storage device according to claim 1, wherein the ceramic layer is formed on a negative electrode surface. 前記セラミックス層を構成するセラミックス粒子が化学式Ｌｉ４Ｔｉ５Ｏ１２で示されるスピネル構造のチタン酸リチウムであることを特徴とする請求項１記載の蓄電装置。2. The power storage device according to claim 1, wherein the ceramic particles constituting the ceramic layer are lithium titanate having a spinel structure represented by a chemical formula Li 4 Ti 5 O 12 . 負極の活物質層を構成する活物質が前記セラミックス層を構成するセラミックス粒子と同じ物質であることを特徴とする請求項１記載の蓄電装置。    The power storage device according to claim 1, wherein the active material constituting the active material layer of the negative electrode is the same material as the ceramic particles constituting the ceramic layer.
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