JP2009076373A - Non-aqueous secondary battery - Google Patents

Non-aqueous secondary battery Download PDF

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JP2009076373A
JP2009076373A JP2007245686A JP2007245686A JP2009076373A JP 2009076373 A JP2009076373 A JP 2009076373A JP 2007245686 A JP2007245686 A JP 2007245686A JP 2007245686 A JP2007245686 A JP 2007245686A JP 2009076373 A JP2009076373 A JP 2009076373A
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battery
negative electrode
electrode
lithium
siox
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JP5182477B2 (en
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Satoru Miyawaki
悟 宮脇
Hirofumi Fukuoka
宏文 福岡
Tetsuo Nakanishi
鉄雄 中西
Tsuguro Mori
嗣朗 森
Hisashi Satake
久史 佐竹
Shizukuni Yada
静邦 矢田
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Shin Etsu Chem Co Ltd
信越化学工業株式会社
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous secondary battery in which energy density is high and excellent cycle characteristics is possessed. <P>SOLUTION: In the non-aqueous secondary battery having a positive electrode, a negative electrode, and a non-aqueous electrolyte, the positive electrode is composed of a material capable of electrochemically storing and releasing lithium, and the negative electrode contains a material in which SiOx (0.3≤x≤1.6) is molded by a binder and the electrode unit is pressurized with a pressure of 3 kgf/cm<SP>2</SP>or more at the time of charge and discharge. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、非水系電解質を用いる二次電池に関し、特に負極にSiOxよりなる負極材料を用いる非水系二次電池に関する。   The present invention relates to a secondary battery using a non-aqueous electrolyte, and more particularly to a non-aqueous secondary battery using a negative electrode material made of SiOx for a negative electrode.
近年、携帯電話、ノート型パソコンに代表される小型携帯機器用の電源、家庭用分散型蓄電システム、電気自動車などに関連して、各種の高エネルギー密度電池の開発が精力的に行われている。特に、黒鉛を負極材料に用いたリチウムイオン電池は、高エネルギー密度を有すること、金属リチウムを負極として用いるリチウム二次電池に比べて、安全性、サイクル特性などの信頼性が優れることなどの理由により、小型携帯機器用の電源として、その市場が飛躍的に拡大している。   In recent years, various high energy density batteries have been vigorously developed in connection with power supplies for small portable devices typified by mobile phones and laptop computers, home-use distributed power storage systems, electric vehicles, etc. . In particular, lithium ion batteries using graphite as a negative electrode material have high energy density, and are superior in reliability such as safety and cycle characteristics compared to lithium secondary batteries using metal lithium as a negative electrode. As a result, the market is rapidly expanding as a power source for small portable devices.
リチウムイオン電池は、正極としてLiCoO2、LiMn24などに代表されるリチウム含有遷移金属酸化物を用い、負極として黒鉛に代表される炭素系材料を用いている。現在、リチウムイオン電池のより一層の高容量化が進められているが、正極酸化物及び負極炭素系材料の改良による高容量化は、ほぼ限界である500Wh/lに達したため、過度な活物質充填率の向上、セパレータの薄型化、充電電圧の高電圧化等により無理な高容量化を進めざるを得ない状況にある。この結果、リチウムイオン電池の特徴である安全性を脅かすこととなり、500Wh/lを超える電池は市販されているものの安全性が懸念される。 The lithium ion battery uses a lithium-containing transition metal oxide typified by LiCoO 2 or LiMn 2 O 4 as a positive electrode, and a carbon-based material typified by graphite as a negative electrode. Currently, further increase in capacity of lithium ion batteries is being promoted, but the increase in capacity by improving positive electrode oxide and negative electrode carbon-based material has reached almost the limit of 500 Wh / l, so an excessive active material It is in a situation where it is unavoidable to increase the capacity by increasing the filling rate, thinning the separator, and increasing the charging voltage. As a result, the safety characteristic of the lithium ion battery is threatened, and there is a concern about safety although batteries exceeding 500 Wh / l are commercially available.
リチウムイオン電池において、従来の材料系での高容量化が限界に達した今、高エネルギー密度化に向け、信頼性、安全性を有し、高エネルギー密度化が可能な新たな材料系が希求されている。   Lithium ion batteries have reached the limit of capacity increase in conventional material systems, and there is a need for new material systems that are reliable and safe and that can increase energy density in order to achieve higher energy densities. Has been.
負極材料においては、高容量材料として、黒鉛の理論容量であるC6Li(372mAh/g)を超える炭素材料、1000mAh/gを超えるリチウム吸蔵能を有するポリアセン系有機半導体に代表される多環芳香族系縮合ポリマー等が開発されている。また、別の方向性としてSi、SnとLiの合金系材料、Si、Sn等をベースとした酸化物系材料も高容量材料として注目されている。これら材料の中で合金系材料は、最も高い質量あたりの容量が期待されているが、充放電の繰り返しにおける材料自身の微粉化問題を本質的に有することから、実用化へのハードルは高い。一方、合金に比べ体積膨収が少ない酸化物系材料は、容量においては合金材料に比べ劣るものの、例えば、特許文献1(特開2006−62949号公報)に記載されているSi−C−O複合材料は、容量が900mAh/gと黒鉛系材料の3倍程度と大きな値を示し、かつ、50サイクル後容量も初期の95%程度と良好なサイクル特性が得られている。 In the negative electrode material, as a high-capacity material, a polycyclic aromatic typified by a carbon material exceeding the theoretical capacity of graphite, C 6 Li (372 mAh / g), and a polyacene-based organic semiconductor having a lithium storage capacity exceeding 1000 mAh / g. Group condensation polymers have been developed. As other directions, Si, Sn and Li alloy-based materials, and oxide-based materials based on Si, Sn and the like are also attracting attention as high-capacity materials. Among these materials, the alloy-based material is expected to have the highest capacity per mass, but the hurdle to practical use is high because it essentially has the problem of pulverization of the material itself in repeated charge and discharge. On the other hand, an oxide-based material whose volume expansion is smaller than that of an alloy is inferior to that of an alloy material in capacity. For example, Si—C—O described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-62949). The composite material has a capacity of 900 mAh / g, which is about three times as large as that of the graphite-based material, and the capacity after 50 cycles is about 95% of the initial capacity and good cycle characteristics are obtained.
一方、リチウムイオン電池あるいはキャパシタなどの蓄電デバイスにおいて、活物質にあらかじめリチウムイオンを担持させること(以下、プリドープと呼ぶ)により、蓄電デバイスの高容量化、高電圧化する技術が注目されている。プリドープは古くから実用化されている技術であり、例えば、非特許文献1(矢田静邦,工業材料,Vol.40,No.5,32(1992))、特許文献2(特開平3−233860号公報)には、リチウムを負極活物質であるポリアセン系骨格構造を含有する不溶不融性基体にプリドープさせた、高電圧かつ高容量な蓄電デバイスが開示されている。プリドープ法に関しては、あらかじめリチウムを担持させた電極を用いて蓄電デバイスに組み込む方法、リチウム金属などを電極成形時に混合する方法などが知られているが、簡便かつ実用的なプリドープ法に関しては、活物質を含有する電極にリチウム金属箔を接触させる方法があり、実際、コイン型電池で実用化されている。   On the other hand, in a power storage device such as a lithium ion battery or a capacitor, attention has been paid to a technology for increasing the capacity and voltage of the power storage device by previously supporting lithium ions on the active material (hereinafter referred to as pre-doping). Pre-doping is a technology that has been put into practical use for a long time. For example, Non-Patent Document 1 (Shiho Yada, Industrial Materials, Vol. 40, No. 5, 32 (1992)), Patent Document 2 (Japanese Patent Laid-Open No. 3-233860). Discloses a high-voltage and high-capacity electricity storage device in which lithium is pre-doped on an insoluble infusible substrate containing a polyacene skeleton structure which is a negative electrode active material. As for the pre-doping method, there are known a method of incorporating an lithium-supported electrode into an electricity storage device, a method of mixing lithium metal or the like at the time of electrode formation, and the like. There is a method of bringing a lithium metal foil into contact with an electrode containing a substance, and in fact, it has been put to practical use in a coin-type battery.
また、特許文献3(国際公開第98/33227号パンフレット)には、貫通孔を備えた集電体上に電極層を形成し、電池内に配置されたリチウム金属と負極を短絡することにより、リチウムイオンが集電体の貫通孔を通過し、すべての負極にプリドープする技術も開示されており、電極が巻回構造、積層構造をとる円筒型、角型電池等に有効な技術である。   Patent Document 3 (International Publication No. 98/33227 pamphlet) forms an electrode layer on a current collector provided with a through hole, and short-circuits a lithium metal and a negative electrode arranged in the battery, A technique in which lithium ions pass through the through-holes of the current collector and pre-dope all the negative electrodes is also disclosed, which is an effective technique for a cylindrical battery, a rectangular battery, etc. in which the electrode has a wound structure or a laminated structure.
上記のように酸化物系材料、特にSi系酸化物は質量あたりのリチウム吸蔵能は高く、電池の高エネルギー密度化において有望な材料であるが、リチウム吸蔵時に体積変化が炭素材料に比べて大きいことから、サイクル特性を確保するためには、バインダー量を増加するなどの必要があった。   As described above, oxide-based materials, particularly Si-based oxides, have a high lithium storage capacity per mass and are promising materials for increasing the energy density of batteries, but the volume change during lithium storage is larger than that of carbon materials. Therefore, in order to ensure cycle characteristics, it was necessary to increase the amount of binder.
特開2006−62949号公報JP 2006-62949 A 特開平3−233860号公報JP-A-3-233860 国際公開第98/33227号パンフレットInternational Publication No. 98/33227 Pamphlet
本発明は、上記事情に鑑みなされたもので、エネルギー密度が高く、かつ、優れたサイクル特性を有する非水系二次電池を提供することを目的とする。   The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-aqueous secondary battery having high energy density and excellent cycle characteristics.
本発明者らは、上記目的を達成するために鋭意検討を重ねた結果、正極、負極及び非水系電解質を備えた非水系二次電池において、正極としてリチウムを電気化学的に吸蔵及び放出し得る材料を用い、負極としてSiOx(0.3≦x≦1.6)を主成分とする活物質粒子とバインダーで成形されたものを用い、かつ、充放電時に電極ユニットを3Kgf/cm2以上で加圧することにより、得られた非水系二次電池は、サイクル特性が著しく向上することを見出し、本発明を完成するに至った。なお、本発明において、正極、負極とは、それぞれ正極活物質層(即ち、正極活物質を含む正極合材層)、負極活物質層(即ち、負極活物質を含む負極合材層)を意味し、集電体は含まない。 As a result of intensive studies to achieve the above object, the present inventors can electrochemically occlude and release lithium as a positive electrode in a nonaqueous secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte. The material is used, and the negative electrode is formed of active material particles mainly composed of SiOx (0.3 ≦ x ≦ 1.6) and a binder, and the electrode unit is 3 Kgf / cm 2 or more at the time of charge / discharge. The non-aqueous secondary battery obtained by pressurization was found to have significantly improved cycle characteristics, and the present invention was completed. In the present invention, the positive electrode and the negative electrode mean a positive electrode active material layer (ie, a positive electrode mixture layer containing a positive electrode active material) and a negative electrode active material layer (ie, a negative electrode mixture layer containing a negative electrode active material), respectively. However, the current collector is not included.
従って、本発明は、下記非水系二次電池を提供する。
〔1〕 正極、負極及び非水系電解質を備えた非水系二次電池において、正極がリチウムを電気化学的に吸蔵及び放出し得る材料からなり、負極がSiOx(0.3≦x≦1.6)をバインダーで成形したものを含み、かつ、充放電時に電極ユニットが3Kgf/cm2以上に加圧されていることを特徴とする非水系二次電池。
〔2〕 バインダーがポリイミド系樹脂であることを特徴とする〔1〕に記載の非水系二次電池。
〔3〕 バインダー量がSiOx(0.3≦x≦1.6)の質量に対し13%以下であることを特徴とする〔1〕又は〔2〕に記載の非水系二次電池。
〔4〕 負極中のSiOx(0.3≦x≦1.6)を主成分とする活物質粒子にリチウムをプリドーピングさせてなることを特徴とする〔1〕〜〔3〕のいずれかに記載の非水系二次電池。
〔5〕 電池形状が円筒型であることを特徴とする〔1〕〜〔4〕のいずれかに記載の非水系二次電池。
Accordingly, the present invention provides the following non-aqueous secondary battery.
[1] In a nonaqueous secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte, the positive electrode is made of a material capable of electrochemically inserting and extracting lithium, and the negative electrode is made of SiOx (0.3 ≦ x ≦ 1.6). ), And the electrode unit is pressurized to 3 kgf / cm 2 or more during charge and discharge.
[2] The nonaqueous secondary battery according to [1], wherein the binder is a polyimide resin.
[3] The nonaqueous secondary battery according to [1] or [2], wherein the binder amount is 13% or less with respect to the mass of SiOx (0.3 ≦ x ≦ 1.6).
[4] Any one of [1] to [3], wherein active material particles mainly composed of SiOx (0.3 ≦ x ≦ 1.6) in the negative electrode are predoped with lithium. The nonaqueous secondary battery as described.
[5] The nonaqueous secondary battery according to any one of [1] to [4], wherein the battery has a cylindrical shape.
上記構成によれば、サイクル特性に優れた非水系二次電池が得られ、特に、バインダーを結着強度の高いポリイミド系樹脂とし、更に、バインダー量を減少させた場合、電極ユニットを3Kgf/cm2以上で加圧した効果が大きい。また、SiOx(0.3≦x≦1.6)を主成分とする活物質粒子にリチウムをプリドーピングした場合、エネルギー密度の高い非水系二次電池が得られる。更に、円筒型電池は、角型、扁平型等の電池構造に比べ、圧力に対して強いことから、電極ユニットへの高い加圧力が得られ易い。 According to the above configuration, a non-aqueous secondary battery having excellent cycle characteristics can be obtained. In particular, when the binder is a polyimide resin having high binding strength and the amount of the binder is further reduced, the electrode unit is 3 kgf / cm. The effect of pressurizing at 2 or more is great. Moreover, when lithium is pre-doped into active material particles mainly composed of SiOx (0.3 ≦ x ≦ 1.6), a non-aqueous secondary battery having a high energy density can be obtained. Furthermore, since the cylindrical battery is strong against pressure as compared with a battery structure such as a square type or a flat type, it is easy to obtain a high applied pressure to the electrode unit.
本発明の非水系二次電池は、エネルギー密度が高く、かつ、優れたサイクル特性が得られるという効果を奏する。   The non-aqueous secondary battery of the present invention has an effect that energy density is high and excellent cycle characteristics can be obtained.
本発明による非水系二次電池は、正極、負極及び非水系電解質を備えた非水系二次電池において、正極がリチウムを電気化学的に吸蔵及び放出し得る材料からなり、負極がSiOx(0.3≦x≦1.6)を主成分とする活物質粒子をバインダーで成形したものを含む。   The non-aqueous secondary battery according to the present invention is a non-aqueous secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode is made of a material capable of electrochemically inserting and extracting lithium, and the negative electrode is made of SiOx (0. Including active material particles mainly composed of 3 ≦ x ≦ 1.6) formed with a binder.
本発明において、負極はSiOx(0.3≦x≦1.6)を主成分とする活物質粒子とバインダーで成形されたものである。SiOxにおけるxは0.3≦x≦1.6であり、xが下限値未満の時、Si比率が高いため充放電時の体積変化が大きくなりすぎ、サイクル特性が低下する傾向にあり、xが上限値を超える場合、Si比率が低下し、本発明の目的であるエネルギー密度向上効果を得にくくなる。この観点から、xは特に0.7≦x≦1.2が好ましい。SiOxの製造法は特に限定されるものではないが、例えば、特開2002−260651号公報に記載の方法で製造可能であり、製造時にSiOxに炭素、窒素等を複合することも可能である(以下の説明において、SiOxと記載した場合、このように他元素を複合させたものも含む。)。   In the present invention, the negative electrode is formed of active material particles mainly composed of SiOx (0.3 ≦ x ≦ 1.6) and a binder. X in SiOx is 0.3 ≦ x ≦ 1.6, and when x is less than the lower limit value, the Si ratio is high, so that the volume change during charge / discharge becomes too large, and the cycle characteristics tend to deteriorate. When the value exceeds the upper limit value, the Si ratio decreases, making it difficult to obtain the effect of improving the energy density, which is an object of the present invention. In this respect, x is particularly preferably 0.7 ≦ x ≦ 1.2. The production method of SiOx is not particularly limited. For example, it can be produced by the method described in JP-A-2002-260651, and it is possible to combine carbon, nitrogen, etc. with SiOx during production ( In the following description, the term “SiOx” includes such a composite of other elements).
また、負極に含まれるSiOxには、サイクル特性を向上させる目的でSiOxの表面に炭素材料をSiOxに対し1〜50質量%で複合させたものを用いることもできる。炭素材料はSiOxに対し5〜30質量%が好ましく、5〜20質量%が特に好ましい。複合させる炭素量が1質量%未満では、当該SiOxを単独で負極活物質として用いた場合、負極膜の導電性が少なく、炭素複合の意味がなく、50質量%を超えると、炭素の割合が多くなりすぎ、負極容量が減少してしまい、本発明の目的であるエネルギー密度向上効果を得にくくなる場合がある。複合方法については特に限定するものではないが、CVD等の手法を用いることができる(以下の説明において、SiOxと記載した場合、このように炭素材料を複合させたものも含む。)。   Moreover, what mixed the carbon material on the surface of SiOx at 1-50 mass% with respect to SiOx can also be used for SiOx contained in a negative electrode for the purpose of improving cycling characteristics. 5-30 mass% is preferable with respect to SiOx, and, as for a carbon material, 5-20 mass% is especially preferable. When the amount of carbon to be combined is less than 1% by mass, when the SiOx is used alone as a negative electrode active material, the conductivity of the negative electrode film is small, and there is no meaning of carbon composite. In some cases, the negative electrode capacity decreases and the energy density improvement effect that is the object of the present invention is hardly obtained. Although there is no particular limitation on the composite method, a technique such as CVD can be used (in the following description, the term “SiOx” includes a composite of carbon materials in this way).
本発明の負極は、例えば、平均粒径0.5〜30μm、特に1〜20μm程度の上記SiOx粉末を、バインダーと混合して例えば集電体上に成形することにより得られる。なお、この平均粒径は、レーザー光回折法による粒度分布測定における質量平均値D50(即ち、累積質量が50%となるときの粒子径又はメジアン径)として測定した値である。
本発明の負極の成形は、所望の非水系二次電池の形状、特性などを考慮しつつ、公知の方法により行うことができる。
The negative electrode of the present invention can be obtained, for example, by mixing the SiOx powder having an average particle size of 0.5 to 30 μm, particularly about 1 to 20 μm, with a binder and molding it on a current collector, for example. The average particle diameter is a value measured as a mass average value D 50 (that is, a particle diameter or a median diameter when the cumulative mass is 50%) in the particle size distribution measurement by the laser light diffraction method.
The negative electrode of the present invention can be molded by a known method in consideration of the shape and characteristics of a desired nonaqueous secondary battery.
成形に用いるバインダー樹脂は特に限定されるものではなく、具体的には、ポリフッ化ビニリデン(PVdF)、ポリ四フッ化エチレンなどのフッ素系樹脂;フッ素ゴム、SBRなどのゴム系材料;ポリエチレン、ポリプロピレンなどのポリオレフィン;アクリル樹脂;ポリイミド系樹脂等が例示されるが、特にポリイミド系樹脂を用いることで良好なサイクル特性が得られる。   The binder resin used for molding is not particularly limited, and specifically, fluorine-based resins such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene; rubber-based materials such as fluorine rubber and SBR; polyethylene and polypropylene Examples of such polyolefins; acrylic resins; polyimide resins and the like are exemplified, but good cycle characteristics can be obtained particularly by using polyimide resins.
負極成形混合物におけるバインダー配合量は、本発明のSiOxの種類、粒径、形状、充放電時におけるSiOxのSi原子に対するリチウム量等に応じて適宜決定すれば良いが、電極ユニットを加圧しない場合、結着強度の高い樹脂(例えば、ポリイミド系樹脂:結着強度を高めるために電極形成後180℃以上に加熱処理したもの等)を用いても、サイクル特性を考慮した場合、SiOxの質量に対し15%以上(炭素材料に比べ2〜3倍量)用いる必要があった。本発明では、充放電時に電極ユニットを3Kgf/cm2以上で加圧することにより、このバインダー配合量を低下させることも可能であり、バインダー量をSiOxの質量に対し13%以下とした場合においても良好なサイクル特性が得られる。好ましいバインダー量はSiOxの質量に対し3〜10%、特に5〜10%である。 The binder compounding amount in the negative electrode molding mixture may be appropriately determined according to the type, particle size, shape, and the amount of lithium with respect to Si atoms of SiOx during charge / discharge, but the electrode unit is not pressurized. Even when using a resin with high binding strength (for example, polyimide resin: heat treated at 180 ° C. or higher after electrode formation in order to increase the binding strength) On the other hand, it was necessary to use 15% or more (2 to 3 times the amount of carbon material). In the present invention, it is possible to reduce the amount of the binder by pressurizing the electrode unit at 3 Kgf / cm 2 or more at the time of charging / discharging. Even when the amount of the binder is 13% or less with respect to the mass of SiOx. Good cycle characteristics can be obtained. A preferable binder amount is 3 to 10%, particularly 5 to 10%, based on the mass of SiOx.
また、本発明の負極に、必要に応じ、導電剤を添加することも可能である。本発明の負極に添加する導電剤の種類、量は特に限定されるものではなく、活物質の電子伝導性(炭素材料との複合の有無)、平均粒径、形状などにより適宜決定されるものであり、添加する場合、その量はSiOxの質量に対し1〜30%、特に1〜20%程度である。また、SiOx表面に炭素材料が複合されている場合などは導電剤を添加しなくてもよい。導電剤の種類としては、カーボンブラック、アセチレンブラック、黒鉛などの微粉状炭素材料、カーボン繊維や単層又は多層カーボンナノチューブ(例えば昭和電工(株)製のVGCF等)などの繊維状炭素材料や、銅、ニッケルなどの金属材料が例示される。   Moreover, it is also possible to add a electrically conductive agent to the negative electrode of this invention as needed. The kind and amount of the conductive agent added to the negative electrode of the present invention are not particularly limited, and are appropriately determined depending on the electronic conductivity of the active material (whether it is combined with the carbon material), the average particle diameter, the shape, or the like. When added, the amount is about 1 to 30%, particularly about 1 to 20% with respect to the mass of SiOx. Further, when a carbon material is composited on the SiOx surface, it is not necessary to add a conductive agent. As a kind of conductive agent, carbon fiber, acetylene black, fine carbon material such as graphite, carbon fiber and fibrous carbon material such as single-walled or multi-walled carbon nanotubes (for example, VGCF manufactured by Showa Denko KK), Examples of the metal material include copper and nickel.
本発明において、上記負極成形混合物を集電体上に成形し、電極を形成するに際し、使用する集電体は特に限定されるものではないが、銅箔、ステンレス鋼箔、チタン箔などが挙げられる。更に、多孔性集電体である、例えば、エキスパンドメタル、メッシュ、パンチングメタルなどを用いることもできる。   In the present invention, when forming the electrode by forming the negative electrode molding mixture on a current collector, the current collector to be used is not particularly limited, and examples thereof include copper foil, stainless steel foil, and titanium foil. It is done. Furthermore, a porous current collector, for example, expanded metal, mesh, punching metal, or the like can be used.
本発明の負極を構成するSiOxに、リチウムをプリドーピングすることも可能であり、該プリドーピングにより、更にエネルギー密度の高い電池を得ることができる。プリドーピングとは、正負極間での通常の充放電前にSiOxにリチウムを吸蔵・担持させることである。SiOxへのリチウムのプリドーピングは、電極を形成した後に行うのが実用的である。   It is possible to pre-dope lithium into the SiOx constituting the negative electrode of the present invention, and a battery having a higher energy density can be obtained by the pre-doping. Pre-doping means that SiOx is occluded / supported before normal charge / discharge between positive and negative electrodes. It is practical to pre-dope lithium into SiOx after the electrodes are formed.
SiOxへのリチウムのプリドーピングの一例として、電極を形成した後、電気化学的に行う方法を具体的に説明する。この方法としては、電池組み立て前に、対極としてリチウム金属を用いる電気化学システムを組み立て、後述の非水系電解液中において、プリドーピングする方法、電解液を含浸した負極にリチウム金属を張り合わせる方法が挙げられる。また、電池組み立て後に、リチウムのプリドーピングを行うには、リチウム金属などのリチウム源と負極とを張り合わせる方法などにより電気的に接触させておき、電池内に電解液を注液することにより、リチウムをプリドーピングする方法があり、実用的には電池組み立て後にプリドーピングすることが好ましい。   As an example of lithium pre-doping into SiOx, a method of electrochemically forming an electrode will be described in detail. This method includes assembling an electrochemical system using lithium metal as a counter electrode before assembling the battery, pre-doping in a non-aqueous electrolyte described later, and attaching lithium metal to the negative electrode impregnated with the electrolyte. Can be mentioned. In addition, in order to perform lithium pre-doping after the battery is assembled, the lithium source such as lithium metal and the negative electrode are electrically contacted with each other by injecting the electrolyte into the battery. There is a method of pre-doping lithium, and it is practically preferable to pre-dope after battery assembly.
一般に負極材料に対するプリドーピングは、不可逆容量を補償する目的、あるいは、正極にリチウムを含まない材料を用いる場合において充放電に必要なリチウムを負極に持たせることを目的としている。しかし、プリドーピング技術の適用に関しては、負極個々の特性(充放電電位、充放電に伴う内部抵抗変化)、目的とする電池特性に応じて検討されるべきものである。例えば、プリドーピング量についても、不可逆容量分だけプリドーピングすれば良いというものではなく、正極リチウム量、正極効率、負極特性(充放電電位、充放電に伴う内部抵抗変化)により異なるものである。   In general, pre-doping of a negative electrode material is intended to compensate for irreversible capacity, or to provide the negative electrode with lithium necessary for charging and discharging when a material that does not contain lithium is used for the positive electrode. However, the application of the pre-doping technique should be examined according to the characteristics of each negative electrode (charge / discharge potential, change in internal resistance accompanying charge / discharge) and target battery characteristics. For example, the pre-doping amount is not limited to the pre-doping amount corresponding to the irreversible capacity, but differs depending on the positive electrode lithium amount, the positive electrode efficiency, and the negative electrode characteristics (charge / discharge potential, change in internal resistance associated with charge / discharge).
リチウムをプリドープしたSiOxを用いる場合、プリドープにより次の関係を満たす時、特に効果が大きい。すなわち、正極から放出され負極に吸蔵されるリチウムの負極Siに対する原子比をLpとし、負極へプリドーピングするリチウムの負極Siに対する原子比をLnとする時、0.3<Ln、かつ2.5<Ln+Lp<5.5とすることにより、エネルギー密度が高く、かつ、平均電圧、レート特性に優れた非水系二次電池を得ることができる。ここで、正極から放出され負極に吸蔵されるリチウムとは、正極に電気化学的に放出可能なリチウムを含む材料を用いる場合において初回充電量から算出されるリチウム量である。   When SiOx pre-doped with lithium is used, the effect is particularly great when the following relationship is satisfied by pre-doping. That is, when the atomic ratio of lithium released from the positive electrode and occluded in the negative electrode to the negative electrode Si is Lp, and the atomic ratio of lithium predoped to the negative electrode to the negative electrode Si is Ln, 0.3 <Ln and 2.5 By setting <Ln + Lp <5.5, a non-aqueous secondary battery having a high energy density and excellent average voltage and rate characteristics can be obtained. Here, the lithium released from the positive electrode and occluded by the negative electrode is the amount of lithium calculated from the initial charge amount when a material containing lithium that can be electrochemically released is used for the positive electrode.
負極へプリドーピングするリチウムの負極Siに対する原子比Lnは0.3<Lnであることが好ましい。正極に電気化学的に放出可能なリチウムを含む材料を用いる場合は、好ましくは0.8<Ln、更に好ましくは1.2<Lnである。また、正極に電気化学的に放出可能なリチウムを含まない材料を用いる場合は、好ましくは2.5<Ln、更に好ましくは3.5<Lnである。Lnの値が下限以下の場合、プリドープによる高エネルギー密度化、平均電圧の向上等の効果が得られない場合がある。   The atomic ratio Ln of lithium to be pre-doped into the negative electrode with respect to the negative electrode Si is preferably 0.3 <Ln. When a material containing lithium that can be electrochemically released is used for the positive electrode, preferably 0.8 <Ln, and more preferably 1.2 <Ln. When a material that does not contain lithium that can be electrochemically released is used for the positive electrode, preferably 2.5 <Ln, and more preferably 3.5 <Ln. When the value of Ln is less than the lower limit, effects such as higher energy density by pre-doping and improvement of average voltage may not be obtained.
本発明において使用する正極(正極活物質)としては、リチウムを電気化学的に吸蔵及び放出し得る材料であれば特に限定されず、例えば、電気化学的に放出可能なリチウムを含むものとして、リチウム複合コバルト酸化物、リチウム複合ニッケル酸化物、リチウム複合マンガン酸化物、あるいはこれらの混合物、更にはこれら複合酸化物に異種金属元素を一種以上添加した系などを用いることができる。また、電気化学的に放出可能なリチウムを含まないものとして、マンガン、バナジウム、鉄などの金属酸化物、ジスルフィド系化合物、ポリアセン系物質、活性炭などを用いることも可能である。本発明の正極は、上記正極活物質を公知の方法で電極とすれば良く、例えば、バインダー樹脂を用い、集電体上に成形される。また、必要に応じ、導電剤を添加することも可能である。   The positive electrode (positive electrode active material) used in the present invention is not particularly limited as long as it is a material capable of electrochemically occluding and releasing lithium. For example, lithium containing lithium that can be electrochemically released includes lithium. A composite cobalt oxide, a lithium composite nickel oxide, a lithium composite manganese oxide, or a mixture thereof, or a system in which one or more different metal elements are added to these composite oxides can be used. In addition, metal oxides such as manganese, vanadium, and iron, disulfide compounds, polyacene materials, activated carbon, and the like can be used as those that do not contain electrochemically releasable lithium. The positive electrode of the present invention may be obtained by forming the positive electrode active material into an electrode by a known method. For example, the positive electrode is formed on a current collector using a binder resin. Moreover, it is also possible to add a electrically conductive agent as needed.
本発明において、正極、負極の間に絶縁、電解液保持の目的でセパレータが配置される場合、このセパレータは特に限定されるものではなく、ポリエチレン微多孔膜、ポリプロピレン微多孔膜、あるいはポリエチレンとポリプロピレンの積層膜、セルロース、ガラス繊維、アラミド繊維、ポリアクリルニトリル繊維などからなる織布、あるいは不織布などがあり、その目的と状況に応じ、適宜決定することが可能である。   In the present invention, when a separator is disposed between the positive electrode and the negative electrode for the purpose of insulation and electrolyte holding, the separator is not particularly limited, and is a polyethylene microporous film, a polypropylene microporous film, or polyethylene and polypropylene. Laminated film, cellulose, glass fiber, aramid fiber, polyacrylonitrile fiber, woven fabric or non-woven fabric, etc., which can be appropriately determined according to the purpose and situation.
本発明において使用する非水系電解質としては、リチウム塩を含む非水系電解液、ポリマー電解質、ポリマーゲル電解質などの公知の非水系電解質を用いることが可能であり、正極材料の種類、負極材料の性状、充電電圧などの使用条件などに対応して、適宜決定される。リチウム塩を含む非水系電解液としては、例えば、LiPF6、LiBF4、LiClO4などのリチウム塩を、プロピレンカーボネート、エチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、ジメトキシエタン、γ−ブチロラクトン、酢酸メチル、蟻酸メチルなどの1種又は2種以上からなる有機溶媒に溶解したものを用いることができる。また、電解液の濃度は、特に限定されるものではないが、一般的に0.5〜2mol/l程度が実用的である。電解液は、当然のことながら、水分が100ppm以下のものを用いることが好ましい。なお、本明細書で使用する「非水系電解質」という用語は、非水系電解液及び有機電解液を含む概念を意味するものであり、また、ゲル状及び固体の電解質を含む概念をも意味するものである。 As the non-aqueous electrolyte used in the present invention, a known non-aqueous electrolyte such as a non-aqueous electrolyte containing a lithium salt, a polymer electrolyte, and a polymer gel electrolyte can be used. The type of the positive electrode material and the property of the negative electrode material It is determined appropriately according to the use conditions such as the charging voltage. As the non-aqueous electrolyte containing a lithium salt, for example, lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, γ-butyrolactone, What was melt | dissolved in the organic solvent which consists of 1 type (s) or 2 or more types, such as methyl acetate and methyl formate, can be used. The concentration of the electrolytic solution is not particularly limited, but generally about 0.5 to 2 mol / l is practical. As a matter of course, it is preferable to use an electrolytic solution having a water content of 100 ppm or less. As used herein, the term “non-aqueous electrolyte” means a concept including a non-aqueous electrolyte and an organic electrolyte, and also includes a concept including gelled and solid electrolytes. Is.
本発明においては、上記正極、上記負極及び上記非水系電解液を備えた非水系二次電池において、充放電時に電極ユニットを3Kgf/cm2以上で加圧する。電極ユニットとは上記正極、負極と集電体及び正極、負極の間に介在する非水系電解質(セパレータ)より構成される。電極ユニットは巻回構造、積層構造などをとるが、この電極ユニットを充放電時に3Kgf/cm2以上で加圧する。加圧方法は特に限定するものではないが、実用的には円筒型電池において電極巻回ユニットの充電終了状態の巻回径の寸法に対して、円筒型電池電槽の内径を小さくすることにより、3Kgf/cm2以上の力をかけるように設計することも可能である。また、角型、扁平型電池、箱型電池等電槽自身が3Kgf/cm2の圧力に耐えられない場合は、直接電池を外部から3Kgf/cm2以上の力を印加しても良い。 In the present invention, in the non-aqueous secondary battery including the positive electrode, the negative electrode, and the non-aqueous electrolyte solution, the electrode unit is pressurized at 3 kgf / cm 2 or more during charge / discharge. The electrode unit is composed of the positive electrode, the negative electrode and the current collector, and the non-aqueous electrolyte (separator) interposed between the positive electrode and the negative electrode. The electrode unit has a wound structure, a laminated structure, and the like, and this electrode unit is pressurized at 3 kgf / cm 2 or more during charge / discharge. The pressurizing method is not particularly limited, but practically by reducing the inner diameter of the cylindrical battery case relative to the dimension of the winding diameter of the electrode winding unit in the end state of charging in the cylindrical battery. It is also possible to design to apply a force of 3 kgf / cm 2 or more. Also, square, flat battery, if the box-type battery such as the battery case itself can not withstand a pressure of 3 kgf / cm 2 may be applied to 3 kgf / cm 2 or more force from the outside directly battery.
本発明での電極ユニットの加圧は、SiOxを主成分とする負極の充電時における体積変化(厚み増加)を利用することが可能である。例えば、円筒型電池において、巻回された電極ユニットは充電によりその外径が大きくなるが、缶内径よりも大きくなろうとする場合、円筒缶により拘束され電極ユニットには圧力が加わることになる。0.3mm厚の円筒缶の場合、20Kgf/cm2の圧力でも変形はほとんどないことから、この原理を用いて電極ユニットを加圧するのが容易である。 The pressurization of the electrode unit in the present invention can utilize volume change (thickness increase) during charging of the negative electrode mainly composed of SiOx. For example, in a cylindrical battery, the outer diameter of the wound electrode unit is increased by charging, but when it is going to be larger than the inner diameter of the can, it is restrained by the cylindrical can and pressure is applied to the electrode unit. In the case of a cylindrical can having a thickness of 0.3 mm, there is almost no deformation even at a pressure of 20 Kgf / cm 2 , so that it is easy to pressurize the electrode unit using this principle.
本発明での電極ユニットは3Kgf/cm2以上で加圧され、好ましくは5Kgf/cm2以上であり、実用的には50Kgf/cm2以下である。加圧力が下限値未満の場合、サイクル特性が低下する、あるいは、多量のバインダー、導電剤等が必要となりエネルギー密度が低下する。 Electrode unit of the present invention is pressurized at 3 kgf / cm 2 or more, preferably 5 Kgf / cm 2 or more, practically is 50 kgf / cm 2 or less. When the applied pressure is less than the lower limit value, the cycle characteristics are deteriorated, or a large amount of binder, conductive agent and the like are required, and the energy density is reduced.
本発明の非水系二次電池の形状、大きさなどは特に限定されるものではなく、それぞれの用途に応じて、円筒型、角型、扁平型、箱型などの任意の形状及び寸法のものを選択すればよいが、円筒型電池は角型、扁平型等の電池構造に比べ圧力に対して強いことから、電極ユニットへの高い加圧力が得られ易い。   The shape, size, etc. of the non-aqueous secondary battery of the present invention are not particularly limited, and are of any shape and size such as a cylindrical shape, a square shape, a flat shape, a box shape, etc., depending on each application. However, since the cylindrical battery is strong against pressure as compared with the battery structure such as the square type and the flat type, it is easy to obtain a high pressure applied to the electrode unit.
高容量材料であるSiOxを負極材料として用い、充放電時に電極ユニットを加圧する本発明の非水系二次電池は、例えば、携帯機器用分野において希求される電池の大幅な高エネルギー密度化に応えることができ、かつ、良好なサイクル特性を有する。   The non-aqueous secondary battery of the present invention that uses SiOx, which is a high-capacity material, as a negative electrode material and pressurizes the electrode unit during charge / discharge responds to the drastic increase in energy density of batteries that are required in the field of portable equipment And has good cycle characteristics.
以下に実施例を示し、本発明の特徴とするところを更に明確化するが、本発明は下記の実施例により何ら限定されるものではない。   EXAMPLES Examples will be shown below to further clarify the features of the present invention, but the present invention is not limited to the following examples.
(SiOx負極の試作)
下記の物性を有するSiOx炭素複合体(信越化学工業製:KSC801)を用いて、負極を作製した。
SiOx:x=1.0
SiOxの炭素複合量:SiOxに対し5質量%
SiOx炭素複合体の粒径(D50%):7.0μm
(Trial manufacture of SiOx negative electrode)
A negative electrode was produced using a SiOx carbon composite (manufactured by Shin-Etsu Chemical Co., Ltd .: KSC801) having the following physical properties.
SiOx: x = 1.0
Carbon composite amount of SiOx: 5% by mass with respect to SiOx
Particle size of SiOx carbon composite (D 50% ): 7.0 μm
バインダーにはポリイミド樹脂(宇部興産社製:U−ワニスA、NMP(N−メチル−2−ピロリドン)溶液、固形分18.1質量%)を用いた。上記SiOxとバインダーを質量比で90:10(固形分量)の配合比にて混練し、NMPで粘度調整をしてスラリーを得た。集電体であるCu箔(厚み:18μm)に、該スラリーを塗布後乾燥して、厚み38μm、密度が1.00g/cm3の負極を得た。負極の電気伝導度は1.9×10-1S/cmであり、リチウムイオン電池用負極として十分な伝導度を有していた。また強度については、軸芯巻付け(4mmφ軸)及びアセトン浸漬に対しても剥れ・脱落等は見られず、以下の電気化学的評価に対し、十分な強度を持つことを確認した。 As the binder, polyimide resin (Ube Industries, Ltd .: U-Varnish A, NMP (N-methyl-2-pyrrolidone) solution, solid content 18.1% by mass) was used. The SiOx and the binder were kneaded at a mass ratio of 90:10 (solid content), and the viscosity was adjusted with NMP to obtain a slurry. The slurry was applied to a Cu foil (thickness: 18 μm) as a current collector and dried to obtain a negative electrode having a thickness of 38 μm and a density of 1.00 g / cm 3 . The electric conductivity of the negative electrode was 1.9 × 10 −1 S / cm, which was sufficient as a negative electrode for a lithium ion battery. In addition, the strength was confirmed to be sufficient for the following electrochemical evaluation without peeling or dropping off even when wound around the shaft core (4 mmφ axis) and acetone immersion.
(SiOx負極を用いた非水系二次電池の試作及び評価)
Ni系正極材料であるLiNi0.8Co0.22を活物質とし、正極を作製した。正極活物質、アセチレンブラック(導電剤)、PVdF(バインダー)を92/4/4(質量比)にてNMP溶液中で混合し、正極合剤スラリーを得た。該スラリーをAl集電箔上(厚さ20μm)に塗工して乾燥後、プレスにより、密度3.05g/cm3、厚さ107μmの正極を得た。この正極単極の初期充放電特性は4.3V−2.7Vで175mAh/gの容量を有し、初期充放電効率は82%であった。
(Trial manufacture and evaluation of non-aqueous secondary battery using SiOx negative electrode)
A positive electrode was prepared using LiNi 0.8 Co 0.2 O 2 , which is a Ni-based positive electrode material, as an active material. A positive electrode active material, acetylene black (conductive agent), and PVdF (binder) were mixed in an NMP solution at 92/4/4 (mass ratio) to obtain a positive electrode mixture slurry. The slurry was applied onto an Al current collector foil (thickness 20 μm), dried, and then pressed to obtain a positive electrode having a density of 3.05 g / cm 3 and a thickness of 107 μm. The initial charge / discharge characteristics of this positive electrode single electrode were 4.3V-2.7V, a capacity of 175 mAh / g, and the initial charge / discharge efficiency was 82%.
上記で作製した厚み38μmのSiOx電極(SiOx負極を集電体上に形成した電極)(200℃真空下、10時間乾燥)と上記Ni系正極(上記の厚さ107μmの正極を集電体上に形成した電極)(170℃真空下、10時間乾燥)を組み合わせて、非水系二次電池を試作した。なお、SiOxへのプリドーピングは、厚さ20μmのLi金属をSiOx電極上に貼り付け、セル組み立て後、電解液を注入し、60時間放置することにより電池内で実施した。   The 38 μm-thick SiOx electrode prepared above (electrode in which the SiOx negative electrode was formed on the current collector) (dried at 200 ° C. under vacuum for 10 hours) and the Ni-based positive electrode (the above-mentioned 107 μm-thick positive electrode on the current collector) In addition, a non-aqueous secondary battery was manufactured by combining the electrode formed in (1) and (under a vacuum at 170 ° C. for 10 hours). The SiOx pre-doping was carried out in the battery by attaching Li metal having a thickness of 20 μm on the SiOx electrode, injecting an electrolytic solution after cell assembly, and allowing to stand for 60 hours.
電極対向面積は1.4×2.0cm2とし、セパレータには厚さ25μmの多孔性ポリエチレンを介してSiOx電極(Li金属貼り付け)とNi系電極を対向させ、電解液としてエチレンカーボネートとメチルエチルカーボネートを3:7体積比で混合し、溶媒に1mol/lの濃度にLiPF6を溶解した溶液を含浸させた。60時間放置後、試作したセルの内1セルを解体したところ、リチウム金属は負極表面から消失しており、SiOx負極表面にリチウムを張り合わせることにより電池内で電気化学的に接触させ、リチウムをプリドーピングすることが、SiOxにおいて可能であることを確認した。この時の負極へプリドーピングしたリチウムの負極Siに対する原子比Lnは1.8であった。 The electrode facing area is 1.4 × 2.0 cm 2, and a SiOx electrode (Li metal affixed) and a Ni-based electrode are opposed to each other through a 25 μm thick porous polyethylene on the separator, and ethylene carbonate and methyl are used as the electrolyte. Ethyl carbonate was mixed at a volume ratio of 3: 7 and impregnated with a solution of LiPF 6 dissolved in a solvent at a concentration of 1 mol / l. After leaving for 60 hours, one of the prototype cells was disassembled, and the lithium metal had disappeared from the negative electrode surface. By attaching lithium to the SiOx negative electrode surface, the lithium metal was brought into electrochemical contact within the battery. It was confirmed that pre-doping is possible in SiOx. At this time, the atomic ratio Ln of the lithium pre-doped into the negative electrode to the negative electrode Si was 1.8.
上記で作製した電池を3mAの電流で4.3Vまで充電し、その後4.3Vの定電圧を印加する定電流定電圧充電を8時間行った。続いて、3mAの定電流で2.0V(負極電圧がリチウム電位に対し0.7V程度に相当)まで放電した。充電容量は18.0mAhであり、放電容量は14.9mAhであった。正極から放出され負極に吸蔵されるリチウムの負極Siに対する原子比Lpは2.7であり、Ln+Lp=4.5である。初期充放電効率は82.8%であり、正極の効率とほぼ等しくなり、負極SiOxに関してはプリドープにより、特性の優れるLi金属電位に対し、0.7Vまでの領域内で利用することが可能となった。   The battery fabricated as described above was charged to 4.3 V with a current of 3 mA, and then a constant current and constant voltage charge in which a constant voltage of 4.3 V was applied was performed for 8 hours. Subsequently, the battery was discharged at a constant current of 3 mA to 2.0 V (negative electrode voltage corresponding to about 0.7 V with respect to the lithium potential). The charge capacity was 18.0 mAh and the discharge capacity was 14.9 mAh. The atomic ratio Lp of lithium released from the positive electrode and occluded by the negative electrode with respect to the negative electrode Si is 2.7, and Ln + Lp = 4.5. The initial charge / discharge efficiency is 82.8%, which is almost equal to the efficiency of the positive electrode, and the negative electrode SiOx can be used in a region up to 0.7 V with respect to the Li metal potential having excellent characteristics by pre-doping. became.
(サイクル試験評価)
上記で作製した電池(アルミラミネート外装)をラミネートセルの外側から板で挟みながら所定の荷重(重り)を加えることによって、外部から加圧することにより、電極ユニット(積層)に対し、1Kgf/cm2、6Kgf/cm2、9Kgf/cm2の圧力で加圧してサイクル特性を評価した。サイクル条件は、3mAの電流で4.3Vまで充電し、その後4.3Vの定電圧を印加する定電流定電圧充電を8時間行い、続いて、3mAの定電流で2.0Vまで放電を繰り返した。1Kgf/cm2の場合、10サイクル目で容量が初期に対し63%となったが、6Kgf/cm2、9Kgf/cm2では、それぞれ98.2%、97.7%となり、電極ユニットを加圧することにより、顕著な効果が得られた。
(Cycle test evaluation)
By applying a predetermined load (weight) while sandwiching the battery (aluminum laminate exterior) produced above with a plate from the outside of the laminate cell, by applying pressure from the outside, 1 kgf / cm 2 with respect to the electrode unit (lamination) , 6 Kgf / cm 2 and 9 Kgf / cm 2 were pressurized to evaluate cycle characteristics. The cycle condition is charging to 4.3 V with a current of 3 mA, and then performing constant current and constant voltage charging for applying a constant voltage of 4.3 V for 8 hours, and then repeatedly discharging to 2.0 V with a constant current of 3 mA. It was. For 1 kgf / cm 2, the capacity at the 10th cycle becomes 63% of the initial, the 6Kgf / cm 2, 9Kgf / cm 2, respectively 98.2%, becomes 97.7%, the electrode unit pressure The remarkable effect was acquired by pressing.

Claims (5)

  1. 正極、負極及び非水系電解質を備えた非水系二次電池において、正極がリチウムを電気化学的に吸蔵及び放出し得る材料からなり、負極がSiOx(0.3≦x≦1.6)をバインダーで成形したものを含み、かつ、充放電時に電極ユニットが3Kgf/cm2以上に加圧されていることを特徴とする非水系二次電池。 In a non-aqueous secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, the positive electrode is made of a material capable of electrochemically occluding and releasing lithium, and the negative electrode is a binder of SiOx (0.3 ≦ x ≦ 1.6) A non-aqueous secondary battery characterized in that the electrode unit is pressed to 3 kgf / cm 2 or more during charging and discharging.
  2. バインダーがポリイミド系樹脂であることを特徴とする請求項1に記載の非水系二次電池。   The non-aqueous secondary battery according to claim 1, wherein the binder is a polyimide resin.
  3. バインダー量がSiOx(0.3≦x≦1.6)の質量に対し13%以下であることを特徴とする請求項1又は2に記載の非水系二次電池。   The non-aqueous secondary battery according to claim 1 or 2, wherein the binder amount is 13% or less with respect to the mass of SiOx (0.3≤x≤1.6).
  4. 負極中のSiOx(0.3≦x≦1.6)を主成分とする活物質粒子にリチウムをプリドーピングさせてなることを特徴とする請求項1〜3のいずれか1項に記載の非水系二次電池。   The non-active material according to any one of claims 1 to 3, wherein the active material particles mainly composed of SiOx (0.3≤x≤1.6) in the negative electrode are predoped with lithium. Water-based secondary battery.
  5. 電池形状が円筒型であることを特徴とする請求項1〜4のいずれか1項に記載の非水系二次電池。   The nonaqueous secondary battery according to any one of claims 1 to 4, wherein the battery shape is cylindrical.
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