JP2007165074A - Lithium secondary battery, electric vehicle using it, and power tool - Google Patents

Lithium secondary battery, electric vehicle using it, and power tool Download PDF

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JP2007165074A
JP2007165074A JP2005358639A JP2005358639A JP2007165074A JP 2007165074 A JP2007165074 A JP 2007165074A JP 2005358639 A JP2005358639 A JP 2005358639A JP 2005358639 A JP2005358639 A JP 2005358639A JP 2007165074 A JP2007165074 A JP 2007165074A
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secondary battery
lithium secondary
positive electrode
density
electrode mixture
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Masanori Yoshikawa
正則 吉川
Juichi Arai
寿一 新井
Yoshimi Yanai
吉美 矢内
Takenori Ishizu
竹規 石津
Akira Kojima
亮 小島
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Hitachi Ltd
Vehicle Energy Japan Inc
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Hitachi Vehicle Energy Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact lithium secondary battery having high output and high energy density. <P>SOLUTION: In the lithium secondary battery having high output and high energy density, the density of a mix of a positive electrode comprising a lithium transition metal composite oxide, a binder, and a conductor is 2.5-3.3 g/cm<SP>3</SP>, and the thickness of the mix layer is 50-110 μm. Especially when the thickness of the positive mix layer is 50-110 μm, the lithium secondary battery having high energy density and high output can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、リチウム二次電池、それを用いた電気自動車、電動工具に関するものであり、特に、出力密度、エネルギー密度を大幅に向上し、かつ長寿命なリチウム二次電池に関するものである。 The present invention relates to a lithium secondary battery, an electric vehicle using the same, and a power tool, and more particularly, to a lithium secondary battery that greatly improves output density and energy density and has a long life.

リチウム二次電池あるいはキャパシタなどの電源装置がハイブリッド車等への適用のため、その開発が盛んである。ハイブリッド車のような用途に適用するには、電源装置の高出力化、長寿命化、低コスト化が必要である。近年では、特に環境問題の観点から、ハイブリッド自動車、燃料自動車の補助電源等への電源装置の実用化の期待が高まっている。このような電気自動車分野への適用にはこれら電源装置のより一層の高出力化、長寿命化が重要である。燃料電池車の補助電源へ適用するには、燃料電池が起動するまでの間、電気だけで走行できることが望ましく、またハイブリッド車においても、都市部を電気だけで走行ができるデュアルモードの要望も近年出てきている状況である。   Power source devices such as lithium secondary batteries or capacitors have been actively developed for application to hybrid vehicles and the like. In order to be applied to applications such as hybrid vehicles, it is necessary to increase the output, extend the life, and reduce the cost of the power supply device. In recent years, in particular, from the viewpoint of environmental problems, there is an increasing expectation for practical use of a power supply device for an auxiliary power source of a hybrid vehicle and a fuel vehicle. For application to such an electric vehicle field, it is important to further increase the output and extend the life of these power supply devices. In order to apply to an auxiliary power source of a fuel cell vehicle, it is desirable that the fuel cell can be driven only by electricity until the fuel cell is started. In recent years, there is a demand for a dual mode in a hybrid vehicle that can be driven only by electricity in urban areas. It is a situation that has emerged.

このような要求に対応するには、出力だけではなくエネルギー密度のさらなる向上が不可欠である。例えばリチウム二次電池の高容量化、負荷特性の向上に関する技術が、特許文献１に開示されている。しかしながら、携帯用機器への適用を主とした電池に関するものであり、電気自動車分野や電動工具等の大電力用途への適用には、より大電流で良好な負荷特性、すなわち高出力を得ることが課題となる。一般的にこれら携帯用機器においては１／３時間率程度の負荷特性が要求されるが、電気自動車の分野においては１／１０〜１／２０の時間率、すなわち、携帯用機器に適用される電池の３〜７倍の大電流において高出力化とともに、高いエネルギー密度が要求される。   In order to meet such demands, it is essential to further improve not only the output but also the energy density. For example, Patent Document 1 discloses a technology relating to an increase in capacity and load characteristics of a lithium secondary battery. However, it is related to batteries that are mainly applied to portable devices. For application to high-power applications such as electric vehicles and power tools, a good load characteristic, that is, high output can be obtained with a larger current. Is an issue. In general, these portable devices require a load characteristic of about 1/3 hour rate, but in the field of electric vehicles, the time rate is 1/10 to 1/20, that is, applied to portable devices. A high energy density is required with high output at a large current 3 to 7 times that of a battery.

上述のようなことから、高容量かつ高出力なリチウム二次電池技術はハイブリッド車、燃料電池車等の分野で電池の実用化を図る上で、極めて重要な課題となる。本発明のリチウム二次電池は電気自動車や電動工具等に適用するのに適する。   In view of the above, high capacity and high output lithium secondary battery technology is an extremely important issue in the practical application of batteries in the fields of hybrid vehicles, fuel cell vehicles and the like. The lithium secondary battery of the present invention is suitable for application to an electric vehicle, a power tool and the like.

特許文献１においては、正極合剤における活物質（ＬｉＣｏＯ２，ＬｉＮｉＯ２など）の密度が３．０〜４．０ｇ／ｃｍ３である、寿命が長く、高エネルギー密度で高出力の非水電解液電池が開示されている。ここで、正極合剤における活物質密度とは、単位体積（ｃｍ３）あたりの正極合剤に含まれる活物質の重量（ｇ）であると定義されている。その定義内容から判断すると、特許文献１の活物質密度は、活物質の充填密度であると言える。 In Patent Document 1, the density of the active material (LiCoO 2 , LiNiO 2, etc.) in the positive electrode mixture is 3.0 to 4.0 g / cm 3 , which has a long life, high energy density, and high output. A liquid battery is disclosed. Here, the active material density in the positive electrode mixture is defined as the weight (g) of the active material contained in the positive electrode mixture per unit volume (cm 3 ). Judging from the definition, the active material density in Patent Document 1 can be said to be the packing density of the active material.

また、特許文献２においては、正極活物質合剤の密度が３．４（ｇ／ｃｍ３）で、集電体の両面に１５０μｍの厚さに転写されたリチウム電池の正極が記載されている。更に特許文献３においては、正極活物質の充填密度が開示されているが、合剤の密度は不明である。 Patent Document 2 describes a positive electrode of a lithium battery in which the density of the positive electrode active material mixture is 3.4 (g / cm 3 ) and is transferred to both sides of the current collector to a thickness of 150 μm. . Furthermore, Patent Document 3 discloses the packing density of the positive electrode active material, but the density of the mixture is unknown.

特開２００２−５６８９６号公報JP 2002-56896 A 特開平１１−２４２９５６号公報Japanese Patent Laid-Open No. 11-242958 特開平０８−１３８６７８号公報Japanese Patent Laid-Open No. 08-138678

本発明は上述のような背景に鑑みてなされたものであり、電気自動車及び電動工具の補助電源に適用可能な高出力、高エネルギー密度、かつ長寿命なリチウム二次電池を提供することを目的としたものである。   The present invention has been made in view of the above-described background, and an object thereof is to provide a lithium secondary battery having a high output, a high energy density, and a long life that can be applied to an auxiliary power source of an electric vehicle and a power tool. It is what.

本発明によるリチウム二次電池は、非水電解液を用いたリチウム二次電池においては、正極合剤の密度がエネルギー密度に密接に関連し、また、正極合剤の厚さも重要な要因であることを見出した。即ち、本発明によるリチウム二次電池は、ＬｉＭＯ２（Ｍは１種以上の遷移金属元素）で表されるリチウム遷移金属複合酸化物、結着剤、および導電剤から構成される正極合剤、Ｌｉを吸蔵・放出する負極、およびリチウム塩を含む非水電解液で構成されたリチウム二次電池であって、上記正極合剤の密度が２．５〜３．３ｇ／ｃｍ３であることを特徴とするものである。 In the lithium secondary battery according to the present invention, the density of the positive electrode mixture is closely related to the energy density in the lithium secondary battery using the non-aqueous electrolyte, and the thickness of the positive electrode mixture is also an important factor. I found out. That is, the lithium secondary battery according to the present invention is a positive electrode mixture composed of a lithium transition metal composite oxide represented by LiMO 2 (M is one or more transition metal elements), a binder, and a conductive agent, A lithium secondary battery composed of a negative electrode that occludes and releases Li, and a non-aqueous electrolyte containing a lithium salt, wherein the density of the positive electrode mixture is 2.5 to 3.3 g / cm 3. It is a feature.

本発明により、エネルギー密度が高く、かつ高出力なリチウム二次電池が提供され、電気自動車に好適な高出力かつ高容量なリチウム二次電池が提供できる。さらには電動工具など高出力、高容量が必要とされる分野等へ幅広く適用できるリチウム二次電池の提供も可能となる。   According to the present invention, a lithium secondary battery with high energy density and high output is provided, and a high output and high capacity lithium secondary battery suitable for an electric vehicle can be provided. Furthermore, it is possible to provide a lithium secondary battery that can be widely applied to fields that require high output and high capacity such as electric tools.

電池の高容量化を図るには、電極の高密度化、すなわち活物質を高密度に充填することが一般的である。しかしながら、高密度になるに従って、電極が保持できる電解液量が少なくなり、電解液と活物質表面とで形成される電極反応界面で起きる電極反応が阻害される心配がある。例えば、前記特許文献１や３では正極合剤中の正極活物質の密度を規定しているが、正極合剤は少なくとも正極活物質、導電剤及び結着剤を含み、この合剤がどのような状態で集電体上に形成されているかが重要である。正極合剤の密度とは、言い換えれば集電体上において、合剤がどの位空隙を残しているかと言うことである。非水電解液型リチウム二次電池においては、上記空隙に電解液が容易に浸透し、かつその電解液中でリチウムイオン等が容易に移動できなければならない。本発明の正極は、特許文献１における固体電解質型リチウム二次電池とは異なって、非水電解液を用いるものであって、電解液が浸透するための合剤間の空隙量が適切でなければならない。本発明における合剤の空隙率は、正極合剤中の正極活物質が７５〜９３重量％、導電剤が５〜１５重量％、結着剤が２〜８重量％であるとき、１５〜４３％が好ましい。   In order to increase the capacity of the battery, it is common to increase the density of the electrodes, that is, to fill the active material with a high density. However, as the density increases, the amount of electrolyte solution that can be held by the electrode decreases, and there is a concern that the electrode reaction occurring at the electrode reaction interface formed between the electrolyte solution and the active material surface may be hindered. For example, Patent Documents 1 and 3 specify the density of the positive electrode active material in the positive electrode mixture. The positive electrode mixture includes at least a positive electrode active material, a conductive agent, and a binder. It is important whether it is formed on the current collector in any state. The density of the positive electrode mixture is, in other words, how much void the mixture leaves on the current collector. In a non-aqueous electrolyte type lithium secondary battery, it is necessary that the electrolyte easily penetrates into the voids and that lithium ions and the like can easily move in the electrolyte. Unlike the solid electrolyte type lithium secondary battery in Patent Document 1, the positive electrode of the present invention uses a non-aqueous electrolyte, and the amount of voids between the mixture for allowing the electrolyte to permeate must be appropriate. I must. The porosity of the mixture in the present invention is 15 to 43 when the positive electrode active material in the positive electrode mixture is 75 to 93% by weight, the conductive agent is 5 to 15% by weight, and the binder is 2 to 8% by weight. % Is preferred.

電気自動車分野へリチウム二次電池を適用するには、高い出力特性が要求されるが、電極反応が阻害されると、この重要な出力特性が低下することが考えられる。高容量を保ちつつ、高い出力を得るには、電極反応を維持できる電解液量を保持できる電極構造の確保が重要であり、この点を考慮した高密度化が技術のポイントとなる。ＬｉＭＯ２（Ｍは１種以上の遷移金属）で表されるリチウム遷移金属複合酸化物の正極、結着剤、および導電剤から構成される正極の合剤密度を２．５〜３．３ｇ／ｃｍ３とすることにより、高容量かつ高出力のリチウム二次電池を提供することができる。 In order to apply a lithium secondary battery to the electric vehicle field, high output characteristics are required. However, if the electrode reaction is inhibited, it is considered that this important output characteristics deteriorate. In order to obtain a high output while maintaining a high capacity, it is important to secure an electrode structure capable of maintaining an amount of an electrolyte solution capable of maintaining an electrode reaction, and increasing the density in consideration of this point is a technical point. The mixture density of the positive electrode composed of a positive electrode of a lithium transition metal composite oxide represented by LiMO 2 (M is one or more transition metals), a binder, and a conductive agent is 2.5 to 3.3 g / By setting it to cm 3 , a high capacity and high output lithium secondary battery can be provided.

上述のように電極の合剤の高密度化が、高容量化の１つの手段であるが、もう１つの手段としては、電極を厚くし、活物質をより多く充填する方法がある。電極を厚くすることにより高容量化は図れるが、その反面、電極が厚くなるに従って電極の抵抗が増大し、出力が低下する懸念がある。電極抵抗を増大させずに、高出力を確保できる厚さの電極が、自動車への電池の適用を図る上で技術上重要である。集電体箔の両面に設けた正極合剤層の両面の厚さの総和を５０〜１１０μｍとすることにより、高容量化と高出力化の両立が可能となる。すなわち、正極合剤層の厚さを５０〜１１０μｍとすることにより、高容量かつ高出力なリチウム二次電池を提供できる。合剤層が薄すぎると、電池の容量及び出力が不十分となる。   As described above, increasing the density of the electrode mixture is one of the means for increasing the capacity. As another means, there is a method of increasing the thickness of the electrode and filling the active material more. Although the capacity can be increased by increasing the thickness of the electrode, the resistance of the electrode increases and the output may decrease as the thickness of the electrode increases. An electrode having a thickness capable of ensuring a high output without increasing the electrode resistance is technically important in order to apply a battery to an automobile. By setting the total thickness of both surfaces of the positive electrode mixture layer provided on both surfaces of the current collector foil to 50 to 110 μm, both high capacity and high output can be achieved. That is, by setting the thickness of the positive electrode mixture layer to 50 to 110 μm, a high-capacity and high-power lithium secondary battery can be provided. If the mixture layer is too thin, the capacity and output of the battery will be insufficient.

本発明のリチウム二次電池の正極活物質にはＬｉＭＯ２（Ｍは１種以上の遷移金属）で表されるリチウム遷移金属複合酸化物を用いることができる。ニッケル酸リチウム、コバルト酸リチウムなどの正極活物質のＮｉ、Ｃｏなどの一部を１種あるいはそれ以上の遷移金属で置換して用いることができる。一方、負極材料としては、リチウム電池で一般的に用いられる非晶質系炭素材、黒鉛系材料などを用いることができる。 A lithium transition metal composite oxide represented by LiMO 2 (M is one or more transition metals) can be used as the positive electrode active material of the lithium secondary battery of the present invention. A part of a positive electrode active material such as lithium nickelate or lithium cobaltate, such as Ni or Co, can be substituted with one or more transition metals. On the other hand, as the negative electrode material, an amorphous carbon material, a graphite material, or the like generally used in lithium batteries can be used.

また、電解質としては、例えばプロピレンカーボネート、エチレンカーボネート、ブチレンカーボネート、ビニレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、メチルエチルカーボネート、テトラヒドロフラン、１，２−ジエトキシエタン等より選ばれた少なくとも１種の非水溶媒に、例えばＬｉＣｌＯ４、ＬｉＢＦ４、ＬｉＰＦ６等より選ばれた少なくとも１種のリチウム塩を溶解させた有機電解液あるいはリチウムイオンの伝導性を有する固体電解質あるいはゲル状電解質あるいは溶融塩など一般に炭素系材料などを負極活物質として用いた電池で使用される既知の電解質を用いることができる。また、電池の構成上の必要性に応じて微孔性セパレータを用いても本発明の効果は損なわれることはない。 Further, as the electrolyte, for example, at least one non-aqueous solvent selected from propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, tetrahydrofuran, 1,2-diethoxyethane, and the like. In addition, for example, an organic electrolytic solution in which at least one lithium salt selected from LiClO 4 , LiBF 4 , LiPF 6 or the like is dissolved, a solid electrolyte having a lithium ion conductivity, a gel electrolyte, or a molten salt is generally used. A known electrolyte used in a battery using a material or the like as a negative electrode active material can be used. Moreover, even if a microporous separator is used according to the structural requirements of the battery, the effect of the present invention is not impaired.

本発明のリチウム二次電池の用途としては、電気自動車などへの適用、さらには高出力が必要とされる電動工具などの電源としても適用可能である。なお、本発明で用いる電気自動車という用語は、リチウム二次電池で走行する純粋な電気自動車、エンジンとリチウム二次電池とが併用されるハイブリッド自動車および燃料電池車等を含む意味で用いる。   The use of the lithium secondary battery of the present invention can be applied to an electric vehicle or the like, and further to a power source such as an electric tool that requires high output. The term “electric vehicle” used in the present invention is used to include a pure electric vehicle that runs on a lithium secondary battery, a hybrid vehicle that uses an engine and a lithium secondary battery in combination, a fuel cell vehicle, and the like.

以下に実施例を挙げ、本発明を説明する。なお、本発明は以下に述べる実施例に限定されるものではない。   The following examples illustrate the invention. In addition, this invention is not limited to the Example described below.

（実施例１）
以下の実施例において用いられた正極活物質の真密度は５．０ｇ／ｃｍ３，導電剤（黒鉛系）の真密度は２．２ｇ／ｃｍ３、結着剤の真密度は１．８ｇ／ｃｍ３である。また、正極活物質、導電剤及び結着剤の量はそれぞれ８５重量％、１０重量％及び５重量％である。上記組成の正極合剤の真密度は４．１１ｇ／ｃｍ３である。 Example 1
The true density of the positive electrode active material used in the following examples is 5.0 g / cm 3 , the true density of the conductive agent (graphite type) is 2.2 g / cm 3 , and the true density of the binder is 1.8 g / cm 3 . cm 3 . The amounts of the positive electrode active material, the conductive agent, and the binder are 85% by weight, 10% by weight, and 5% by weight, respectively. The true density of the positive electrode mixture having the above composition is 4.11 g / cm 3.

正極活物質としてＬｉＭｎ０．５Ｎｉ０．５Ｏ２を用い、正極活物質、導電剤としての黒鉛、結着剤のポリフッ化ビニリデンを８５：１０：５の重量比で混練機を用い、３０分間混練し正極合剤を得た。正極合剤を厚さ２０μｍのアルミニウム箔（集電体）に塗布した。一方、負極材料には非晶質炭素を、結着剤にはポリフッ化ビニリデンを用い、９０：１０の重量比で混練し、得られた負極合剤を厚さ２０μｍの銅箔に塗布した。作製した正負電極は、プレス機で圧延成型した後、１５０℃で５時間真空乾燥した。 LiMn 0.5 Ni 0.5 O 2 was used as a positive electrode active material, a positive electrode active material, graphite as a conductive agent, and polyvinylidene fluoride as a binder were kneaded in a weight ratio of 85: 10: 5, 30 The mixture was kneaded for minutes to obtain a positive electrode mixture. The positive electrode mixture was applied to an aluminum foil (current collector) having a thickness of 20 μm. On the other hand, amorphous carbon was used as the negative electrode material and polyvinylidene fluoride was used as the binder, and the mixture was kneaded at a weight ratio of 90:10, and the obtained negative electrode mixture was applied to a copper foil having a thickness of 20 μm. The produced positive and negative electrodes were roll-formed with a press machine and then vacuum-dried at 150 ° C. for 5 hours.

なお、プレス、乾燥後の正極合剤層の密度は２．３ｇ／ｃｍ３、２．５ｇ／ｃｍ３、２．８ｇ／ｃｍ３、３．１ｇ／ｃｍ３、３．３ｇ／ｃｍ３、および３．６ｇ／ｃｍ３であった。また合剤層の厚さは、それぞれ、８８μｍ、９２μｍ、９０μｍ、９１μｍ、９１μｍ、および８９μｍであった。正極合剤の密度が２．３ｇ／ｃｍ３のときの空隙率は４４％であった。同様に、合剤密度２．５ｇ／ｃｍ３のとき、空隙率は３９％、２．８ｇ／ｃｍ３のとき３２％、３．１ｇ／ｃｍ３のとき２５％、３．３ｇ／ｃｍ３のとき２０％、３．６ｇ／ｃｍ３のとき１２％であった。 The density of the positive electrode mixture layer after pressing and drying is 2.3 g / cm 3 , 2.5 g / cm 3 , 2.8 g / cm 3 , 3.1 g / cm 3 , 3.3 g / cm 3 , and It was 3.6 g / cm 3 . The thickness of the mixture layer was 88 μm, 92 μm, 90 μm, 91 μm, 91 μm, and 89 μm, respectively. The porosity when the density of the positive electrode mixture was 2.3 g / cm 3 was 44%. Similarly, when the mixture density 2.5 g / cm 3, the porosity is 39%, 32% when the 2.8 g / cm 3, 25% when the 3.1 g / cm 3, of 3.3 g / cm 3 20% and 3.6 g / cm 3 at 12%.

正極合剤の密度ないし空隙率は、合剤組成だけでは決まらず、集電体に塗布した合剤を乾燥した後の圧延条件によっても変わる。しかし、前述したような、合剤の好ましい範囲で、前記の好ましい空隙率が得られるような圧力下で乾燥合剤を圧延して、前記のような空隙率となるような条件を選ぶ。   The density or porosity of the positive electrode mixture is not determined only by the composition of the mixture, but also varies depending on the rolling conditions after drying the mixture applied to the current collector. However, as described above, the dry mixture is rolled under a pressure that provides the above-mentioned preferable porosity in the preferable range of the mixture, and the conditions are selected so as to achieve the above-described porosity.

本明細書において、正極合剤の密度は、上記のようにして、集電体の両面に正極合剤（正極活物質、導電剤、決着剤）を塗布し、乾燥した後、圧延したものについて、所定の大きさの正極試料を切り出し、その重量を測り、マイクロメータで合剤厚さ及び幅を測定し、正極重量から集電体重量を差し引いて、合剤重量を求め、それを合剤体積で除して求めた。   In this specification, the density of the positive electrode mixture is applied to the positive electrode mixture (positive electrode active material, conductive agent, fixing agent) applied to both sides of the current collector as described above, dried, and then rolled. Cut out a positive electrode sample of a predetermined size, measure its weight, measure the mixture thickness and width with a micrometer, subtract the current collector weight from the positive electrode weight, determine the mixture weight, and mix it Calculated by dividing by volume.

乾燥後、正極板と負極板とをセパレータを介して捲回し、電池缶に挿入した。負極集電リード片６はニッケルの負極集電リード部８に集めて超音波溶接し、集電リード部を缶底に溶接した。一方、正極集電リード片５はアルミニウムの集電リード部７に超音波溶接した後、アルミニウムのリード部を蓋９に抵抗溶接した。電解液（１ＭＬｉＰＦ６／ＥＣ：ＤＥＣ＝１：１）を注入後、蓋を缶４にカシメにより封口し、電気化学素子を得た。また、缶の上端と蓋の間にガスケット１２を挿入した。このようにして製造した電気化学素子の概略図を図１に示す。 After drying, the positive electrode plate and the negative electrode plate were wound through a separator and inserted into a battery can. The negative electrode current collecting lead piece 6 was collected on the nickel negative electrode current collecting lead portion 8 and ultrasonically welded, and the current collecting lead portion was welded to the bottom of the can. On the other hand, the positive electrode current collector lead piece 5 was ultrasonically welded to the aluminum current collector lead portion 7 and then the aluminum lead portion was resistance welded to the lid 9. After injecting the electrolytic solution (1M LiPF 6 / EC: DEC = 1: 1), the lid was sealed in the can 4 by caulking to obtain an electrochemical element. A gasket 12 was inserted between the upper end of the can and the lid. A schematic view of the electrochemical device thus produced is shown in FIG.

充電終止電圧４．２Ｖ、放電終止電圧２．７Ｖ、充放電レート１Ｃ（定格電気容量の１時間率）で充放電し、電池容量を求めた。ＳＯＣ（ｓｔａｔｅ ｏｆ ｃｈａｒｇｅ）５０％の状態で、１０秒間、１Ｃ、５Ｃ、１０Ｃ、２０Ｃの電流を印加し、１０秒目の電圧を測定し、出力性能を調べた。電池の放電終止電圧（Ｖ）と電流電圧特性の直線を放電終止電圧まで外挿したときの電流値（Ｉ）を用いて、式Ｐ＝Ｖ×Ｉより出力を求めた。出力測定結果を図２に示す。密度が高くなるに従って出力密度が若干低下する傾向があるが、３．６ｇ／ｃｍ３では、出力密度が、１７７０Ｗ／ｋｇとなり、２０００Ｗ／ｋｇに満たない出力密度となった。電池容量の測定結果を図３に示す。いずれの電池も６０Ｗｈ／ｋｇを超える値となった。 The battery capacity was determined by charging and discharging at a charge end voltage of 4.2 V, a discharge end voltage of 2.7 V, and a charge / discharge rate of 1 C (1 hour rate of the rated electric capacity). In a state of SOC (state of charge) 50%, a current of 1C, 5C, 10C, and 20C was applied for 10 seconds, a voltage at 10 seconds was measured, and output performance was examined. Using the current value (I) obtained by extrapolating the discharge end voltage (V) of the battery and the current-voltage characteristic line to the discharge end voltage, the output was obtained from the formula P = V × I. The output measurement results are shown in FIG. The output density tends to decrease slightly as the density increases, but at 3.6 g / cm 3 , the output density was 1770 W / kg, which was less than 2000 W / kg. The measurement results of the battery capacity are shown in FIG. All the batteries exceeded 60 Wh / kg.

次に、定電流パルスサイクル試験を実施した。入出力（充放電）はいずれも電流値は１０Ｃ（１／１０時間率）、入出力時間は２０秒とし、休止時間は３０秒とした。ＳＯＣ５０％でパルスサイクル試験を１０万回行い、試験前後での電池内部抵抗を出力試験の電流電圧特性の直線勾配から求めた。表１にパルス試験前後の電池内部抵抗上昇率の結果を示す。正極合剤密度２．３ｇ／ｃｍ３および３．６／ｃｍ３では上昇率が大きい結果となった。特に密度が低い電池１−１では上昇率は２０％近い値となった。電池１−１は電極成型時のプレス圧が低いため、正極活物質粒子間のメカニカルな接触が弱く、そのためサイクル試験後の抵抗上昇が大きいものと推定される。 Next, a constant current pulse cycle test was performed. As for input / output (charge / discharge), the current value was 10 C (1/10 hour rate), the input / output time was 20 seconds, and the rest time was 30 seconds. The pulse cycle test was conducted 100,000 times at 50% SOC, and the battery internal resistance before and after the test was determined from the linear slope of the current-voltage characteristics of the output test. Table 1 shows the results of the battery internal resistance increase rate before and after the pulse test. When the positive electrode material mixture density was 2.3 g / cm 3 and 3.6 / cm 3 , the rate of increase was large. In particular, the increase rate of the battery 1-1 having a low density was close to 20%. Since the press pressure at the time of electrode shaping | molding of the battery 1-1 is low, the mechanical contact between positive electrode active material particles is weak, Therefore It is estimated that the resistance rise after a cycle test is large.

Figure 2007165074
Figure 2007165074

（実施例２）
正極活物質にはＬｉＭｎ１／３Ｎｉ１／３Ｃｏ１／３Ｏ２を用い、実施例１と同様に電池を作製した。正極合剤の密度は２．９ｇ／ｃｍ３であった。なお、電極厚さは、２８μｍ、４９μｍ、７０μｍ、８８μｍ、１１１μｍ、および１２５μｍであった。電池容量、出力を実施例１と同様に試験し求めた。出力試験結果を図４に、電池容量試験結果を図５に示す。合剤層厚さが１２５μｍと厚い電池は出力密度が１７７０Ｗ／ｋｇと低い値となった。一方、エネルギー密度は、合剤層厚さが２８μｍと薄い正極の電池では４９Ｗｈ／ｋｇと低い値となった。次に負荷率試験をレート２０Ｃで（１／２０時間率）実施した。表２には１Ｃ（１時間率）での容量を基準に容量維持率でその結果を示す。最も合剤層の厚い正極の電池２−６は容量維持率が、５１．２％と低い値であった。 (Example 2)
LiMn 1/3 Ni 1/3 Co 1/3 O 2 was used as the positive electrode active material, and a battery was fabricated in the same manner as in Example 1. The density of the positive electrode mixture was 2.9 g / cm 3 . The electrode thickness was 28 μm, 49 μm, 70 μm, 88 μm, 111 μm, and 125 μm. The battery capacity and output were tested and determined in the same manner as in Example 1. The output test results are shown in FIG. 4, and the battery capacity test results are shown in FIG. The battery with a thick mixture layer thickness of 125 μm had a low output density of 1770 W / kg. On the other hand, the energy density was as low as 49 Wh / kg in the positive electrode battery having a thin mixture layer thickness of 28 μm. Next, a load factor test was performed at a rate of 20C (1/20 hour rate). Table 2 shows the results of the capacity retention rate based on the capacity at 1C (1 hour rate). The positive electrode battery 2-6 having the thickest mixture layer had a capacity retention rate as low as 51.2%.

Figure 2007165074
Figure 2007165074

（実施例３）
正極活物質にはＬｉＮｉ０．８Ｃｏ０．２Ｏ２を、負極活物質に黒鉛を用い、実施例１と同様に電極を作製し、積層型の角形電池を作製した。なお、合剤密度は３．０ｇ／ｃｍ３、合剤層の厚さは８３μｍであった。実施例１と同様に電池容量、出力を試験し求めた。出力密度は２６３０Ｗ／ｋｇ、エネルギー密度は８１Ｗｈ／ｋｇであった。 (Example 3)
Using LiNi 0.8 Co 0.2 O 2 as the positive electrode active material and graphite as the negative electrode active material, an electrode was produced in the same manner as in Example 1 to produce a stacked prismatic battery. The mixture density was 3.0 g / cm 3 and the thickness of the mixture layer was 83 μm. The battery capacity and output were tested and determined in the same manner as in Example 1. The power density was 2630 W / kg, and the energy density was 81 Wh / kg.

本発明の実施例によるリチウム二次電池を示す側面断面図。1 is a side sectional view showing a lithium secondary battery according to an embodiment of the present invention. 本発明の実施例によるリチウム二次電池の正極合剤密度と出力密度との関係を示すグラフ。The graph which shows the relationship between the positive mix ratio and output density of the lithium secondary battery by the Example of this invention. 本発明の実施例によるリチウム二次電池の正極合剤密度とエネルギー密度との関係を示すグラフ。The graph which shows the relationship between the positive mix density and energy density of the lithium secondary battery by the Example of this invention. 本発明の実施例によるリチウム二次電池の正極合剤厚さと出力密度との関係を示すグラフ。The graph which shows the relationship between the positive mix thickness and the power density of the lithium secondary battery by the Example of this invention. 本発明の実施例によるリチウム二次電池の正極合剤厚さとエネルギー密度との関係を示すグラフ。The graph which shows the relationship between the positive mix thickness and the energy density of the lithium secondary battery by the Example of this invention.

符号の説明Explanation of symbols

１…正極、２…負極、３…セパレータ、４…電池缶、５…正極集電リード片、６…負極集電リード片、７…正極集電リード部、８…負極集電リード部、９…電池蓋、１０…破裂弁、１１…正極端子部、１２…ガスケット。
DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 2 ... Negative electrode, 3 ... Separator, 4 ... Battery can, 5 ... Positive electrode current collection lead piece, 6 ... Negative electrode current collection lead piece, 7 ... Positive electrode current collection lead part, 8 ... Negative electrode current collection lead part, 9 ... Battery cover, 10 ... Rupture valve, 11 ... Positive terminal, 12 ... Gasket.

Claims (9)

ＬｉＭＯ２（Ｍは１種以上の遷移金属元素）で表されるリチウム遷移金属複合酸化物、結着剤、および導電剤から構成される正極合剤、Ｌｉを吸蔵・放出する負極、およびリチウム塩を含む非水電解液で構成されたリチウム二次電池であって、上記正極合剤の密度が２．５〜３．３ｇ／ｃｍ３であることを特徴とするリチウム二次電池。 A positive electrode mixture composed of a lithium transition metal composite oxide represented by LiMO 2 (M is one or more transition metal elements), a binder, and a conductive agent, a negative electrode that absorbs and releases Li, and a lithium salt A lithium secondary battery comprising a non-aqueous electrolyte solution containing a positive electrode mixture having a density of 2.5 to 3.3 g / cm 3 . 請求項１に記載のリチウム二次電池において、集電体箔の両面に設けられた正極合剤層の両面の合計厚さが５０〜１１０μｍであることを特徴とするリチウム二次電池。   2. The lithium secondary battery according to claim 1, wherein the total thickness of both surfaces of the positive electrode mixture layer provided on both surfaces of the current collector foil is 50 to 110 [mu] m. 前記正極合剤の空隙率が１５〜４３％であることを特徴とする請求項１記載のリチウム二次電池。   The lithium secondary battery according to claim 1, wherein a porosity of the positive electrode mixture is 15 to 43%. 請求項１に記載のリチウム二次電池において、Ｍは２種以上の遷移金属元素であることを特徴とするリチウム二次電池。   2. The lithium secondary battery according to claim 1, wherein M is two or more transition metal elements. 集電体箔の両面に設けられた、ＬｉＭＯ２（Ｍは２種以上の遷移金属元素）で表されるリチウム遷移金属複合酸化物、結着剤、および導電剤から構成される正極合剤、Ｌｉを吸蔵・放出する負極、およびリチウム塩を含む非水電解液で構成されたリチウム二次電池であって、上記正極合剤の密度が２．５〜３．３ｇ／ｃｍ３であり、前記集電体箔の両面に設けられた正極合剤層の両面の合計厚さが５０〜１１０μｍであることを特徴とするリチウム二次電池。 A positive electrode mixture comprising a lithium transition metal composite oxide represented by LiMO 2 (M is two or more transition metal elements), a binder, and a conductive agent, provided on both surfaces of the current collector foil; A lithium secondary battery composed of a negative electrode that occludes and releases Li and a non-aqueous electrolyte containing a lithium salt, wherein the positive electrode mixture has a density of 2.5 to 3.3 g / cm 3 , A lithium secondary battery, wherein the total thickness of both surfaces of a positive electrode mixture layer provided on both surfaces of a current collector foil is 50 to 110 μm. 前記正極合剤の空隙率が１５〜４３％であることを特徴とする請求項１又は５記載のリチウム二次電池。   The lithium secondary battery according to claim 1, wherein a porosity of the positive electrode mixture is 15 to 43%. １０Ｃ以上の大電流放電用に使用される請求項１、５又は６に記載のリチウム二次電池。   The lithium secondary battery according to claim 1, 5 or 6 used for discharging a large current of 10 C or more. 請求項１〜７のいずれかに記載のリチウム二次電池を備えた電気自動車。   The electric vehicle provided with the lithium secondary battery in any one of Claims 1-7. 請求項１〜７のいずれかに記載のリチウム二次電池を備えた電動工具。   The electric tool provided with the lithium secondary battery in any one of Claims 1-7.
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